Journal of Materials Chemistry Amezhao/pdf/303.pdf · Journal of Materials Chemistry A Review. synthesized via chemical vapor deposition (CVD) (such as sili-cene, germanene, borophene

Journal ofMaterials Chemistry A

REVIEW

Recent advances

LtASpibrpas

Department of Mechanical and Aerospace E

Science and Technology, Clear Water Bay

[email protected]; Tel: +86 852 2358 8647

Cite this: J. Mater. Chem. A, 2017, 5,3735

Received 14th November 2016Accepted 16th January 2017

DOI: 10.1039/c6ta09831b

www.rsc.org/MaterialsA

This journal is © The Royal Society of C

in inorganic 2Dmaterials and theirapplications in lithium and sodium batteries

Le Shi and Tianshou Zhao*

Two-dimensional inorganic materials, such as exfoliated graphene, have been under much research

attention as of late, for their high surface-to-mass ratio and unique physical and chemical properties.

Many of these properties are highly sought after in Li/Na-based batteries. In this paper, we review recent

advances in inorganic 2D materials and summarize their applications as: (i) the electrode materials or

additives for Li/Na-ion batteries; (ii) the scaffold or interfacial layer for lithium–metal anodes; (iii) the

cathode for Li/Na–O2 batteries; and (iv) the anchoring material for lithium polysulfides for Li–S batteries.

The challenges of employing 2D materials in these Li/Na-based batteries to improve performance are

discussed and possible solutions are proposed.

1. Introduction

Li-ion batteries based on the lithium ion intercalation mecha-nism (as illustrated in Fig. 1a) have been widely adopted inmodern day electronics, working as the main power sources forportable electronics and electric vehicles.1–3 However, under theever-increasing demand for energy storage devices with greateremphasis on high energy density and efficiency as well as lowcost, conventional lithium-ion batteries based on graphiteanodes and traditional cathode materials (with stable layeredstructures such as layered lithium metal phosphates andlithium transition metal oxides) are being outgrown.4–8 Next-generation energy storage devices which are able to outputa larger capacity, higher rate capability and longer cycle life are

e Shi is a Ph.D. candidate athe Department of Mechanical &erospace Engineering, HKUST.he received her B.S. degree inhysics from Peking Universityn 2013. She is now supervisedy Prof. Tianshou Zhao and heresearch is focused on rst-rinciples modeling ofdvanced energy storageystems.

ngineering, The Hong Kong University of

, Kowloon, Hong Kong, China. E-mail:

hemistry 2017

urgently needed and thus much effort has been placed ondeveloping new electrode materials to satisfy these needs.Li-alloy based anode materials such as silicon, tin and tin oxidehave been shown to demonstrate high capacity,9–15 but lithiuminsertion and extraction could cause severe volume expansionor contraction of the electrode materials, resulting in eventualelectrode pulverization and performance decay. Recent cathodematerial development has also experienced a stall. A majority ofemerging cathode materials are semiconductors with poorelectric conductivity that require further exploration.16 Thus,energy storage concepts based on pure lithium metal anodes,such as non-aqueous lithium–oxygen (Li–O2) batteries (asshown in Fig. 1b) and lithium–sulfur (Li–S) batteries (as shownin Fig. 1c), have been explored in recent years, reaching capac-ities unprecedented in Li-ion batteries.17–22 However, lithiumanodes suffer from dendrite growth, a long-standing issue thatposes severe safety concerns for users and has hindered thecommercialization of these energy storage systems.23–27 In non-

Professor Tianshou Zhao iscurrently the Chair Professor ofMechanical & Aerospace Engi-neering at HKUST, the Directorof the HKUST Energy Institute,and a Senior Fellow of theHKUST Institute for AdvancedStudy. He is an elected Fellow ofthe American Society Mechan-ical Engineers (ASME), a Fellowof the Royal Society of Chemistry(RSC), and a Highly CitedResearcher in Engineering byThomson Reuters (2014–2016).

J. Mater. Chem. A, 2017, 5, 3735–3758 | 3735

http://crossmark.crossref.org/dialog/?doi=10.1039/c6ta09831b&domain=pdf&date_stamp=2017-02-15

Fig. 1 Illustration and working principles of (a) Li/Na-ion batteries (M represents the anode material and N represents the cathode material), (b)non-aqueous Li/Na–O2 batteries and (c) Li–S batteries.

Journal of Materials Chemistry A Review

aqueous Li–O2 batteries, an insulated solid state dischargeproduct of Li2O2 slows down reaction kinetics and createsanomalously high overpotentials,28 calling for effective catalyststo promote reactions.29–32 Li–S batteries exhibit intermediatedischarge products, lithium polysuldes, that are soluble andcan dissolve into the electrolyte, thereby migrating to the anodeside, passivating the lithium metal surface and decayingperformance.33,34 Moreover, the cathode of Li–S batteries alsosuffers from low electronic/ionic conductivity of sulfur andlithium suldes as well as a large volume expansion of sulfurduring the lithiation process. New cathode and membranematerials should be designed to address these issues.

Na-based batteries (Na-ion, non-aqueous Na–O2) are alsocheap and promising alternatives to Li-based batteries.35 Whilethis is true, the size of a sodium ion is much larger than that ofa lithium ion, creating more specic requirements for electrodematerials than those of Li-ion batteries.36,37 The same problemof dendrite growth on sodiummetal anodes also plagues Na–O2

batteries, and likewise, the cathode faces sluggish reactionkinetics.38,39

Since Novoselov et al.'s success in exfoliating graphene in2004,40 there has been an increase in enthusiasm toward thedevelopment of inorganic two-dimensional materials (2D). Assuch, a slew of 2D materials have been exfoliated or synthesizedsuccessfully, with examples such as transition metal oxides(TMOs), transition metal dichalcogenides (TMDs), transitionmetal carbides/nitrides (Mxenes) and elemental analogues ofgraphene (silicene, phosphorene, and borophene).41–50 These2D materials have the unique ability to provide large surfaceareas with abundant active sites, while maintaining lowdimensions which help them to outperform their bulk coun-terparts, making them promising choices for Li/Na-basedbatteries in many aspects. As 2D materials are stackable viaweak van der Waals forces, volume changes are alleviatedduring the intercalation and de-intercalation processes oflithium/sodium atoms when being used as electrode materialsfor Li/Na-ion batteries. The large surface area would intuitivelyprovide higher theoretical capacity compared to that of the bulkform. Thus, 2D materials with high electronic conductivity have

3736 | J. Mater. Chem. A, 2017, 5, 3735–3758

been shown to be excellent Li/Na electrode materials with largecapacity and good structural stability.45 The electronic proper-ties of known 2Dmaterials range from wide band gap insulatorsto superior electron conductors. For instance, the insulated 2Dmaterial, h-BN, has been proposed to be used as an interfaciallayer to suppress dendritic growth of lithium metal anodes,27

while the conductive 2D material, graphene, has been used asan additive in the cathode of Li/Na-ion batteries to enhanceelectronic conductivity.16 Activated graphene-based materialsand some 2D TMOs show good catalytic activity towards theoxygen reduction reaction (ORR)/oxygen evolution reaction(OER), and have been used as catalytic materials in Li/Na–O2

batteries.51–56 With moderate adsorption towards lithium poly-suldes, certain 2D materials have been predicted to be goodanchoring materials in Li–S batteries to alleviate the shuttleeffect.57,58

In this article, we will give a comprehensive review of recentadvances in 2D materials and their applications in Li/Na-basedbatteries from both theoretical and experimental points of view.An overview of the basic properties and commonly employedsynthesis procedures of different categories of 2D materials isprovided. Then we will introduce their proposed and reportedapplications in Li/Na-ion batteries, non-aqueous Li/Na–O2

batteries and Li–S batteries successively.

2. Overview of 2D materials2.1 Basic properties of representative 2D materials

The inorganic 2D materials with applications in Li/Na-basedbatteries that have been reported thus far can be classiedinto the following categories: graphene and graphene deriva-tives (graphene oxide and reduced graphene oxide), elementalanalogues of graphene (silicene, germanene, phosphorene,borophene and stanene), transition metal oxides (TMOs),transition metal dichalcogenides (TMDs), transition metalcarbides/nitrides (MXenes), and other 2D structures such as h-BN and emerging new 2D materials. Many of these 2D struc-tures can be exfoliated from their bulk counterparts via micro-mechanical exfoliation or liquid exfoliation, while others are

This journal is © The Royal Society of Chemistry 2017

Review Journal of Materials Chemistry A

synthesized via chemical vapor deposition (CVD) (such as sili-cene, germanene, borophene and stanene).43–45 In practicalapplications, the obtained 2D materials in most cases are notexact monolayers but consist of several layers with nanosheetmorphology.

2.1.1 Graphene, graphene oxide (GO) and reduced gra-phene oxide (rGO). Graphene and its derivatives have beenstudied most extensively among reported 2D materials. Theatomic structure of pristine graphene is shown in Fig. 2a, wherethe sp2 hybridized carbon atoms are arranged in an ordered,at, honeycomb lattice. Pure graphene has an extremely largesurface area (2630 m2 g�1) as well as extraordinarily highintrinsic charge carrier mobility (2.5 � 105 cm2 V�1 s�1),thermal conductivity (5000 W mK�1), and Young's modulus (1TPa).40,59 The homogeneous sp2 hybridized electron distributionallows graphene to be chemically stable, and has been employedas a promising barrier material in numerous applications. Intro-duction of heteroatoms such as nitrogen or boron into graphenevia doping techniques can activate the electrons in the basal planeof graphene and turn graphene into a chemically reactivematerial.Layered graphene sheets can be obtained mainly from micro-mechanical exfoliation,40 CVD or liquid exfoliation.42 Micro-mechanical exfoliation creates higher quality graphene layers butlower yield, whereas CVD produces large-scale graphene that ishigh quality, but depends on substrate properties and the processis high in cost. Pure graphene is hydrophobic and shows poordispersion in aqueous environments. Hence, in liquid exfoliation,graphite is rstly oxidized and exfoliated into graphene oxide (GO)which can be dispersed in aqueous solutions uniformly, and thenreduced to reduced graphene oxide (rGO). This method is cheapand can deliver a higher yield of rGO sheets, but is relativelyunrened and results in defects in its atomic structure, whichtranslates to irregular physical/chemical properties compared tothose of pristine graphene.

GO is commonly produced by intercalation and oxidation ofgraphite through Hummer's method.60–62 The chemical reac-tions during the preparation process of GO introduce manyfunctional groups arranged in the at honeycomb structure of

Fig. 2 Top and side view of the atomic structure of 2D single layered(a) graphene, (b) silicene, (c) phosphorene, (d) borophene, (e) TiO2, (f)MoS2, (1H) (g) Ti3C2 and (f) h-BN.


graphene and severely disrupt its electronic structure; unlikegraphene, GO is an insulator with poor electronic conductivity.Due to the introduction of functional groups, GO also showsgood chemical reactivity. Generally, the main functional groupsin the basal plane are hydroxyl and epoxy, while at the edges,carboxylic groups dominate.63,64 These introduced functionalgroups are mainly hydrophilic, which give GO its amphiphilicproperty, and allow it to easily disperse into aqueous solutions.Thermal, chemical or light treatment of GO can change it torGO.

Removal of the functional groups in GO makes rGO restoredwith high electronic conductivity.65,66 The high electronicconductivity and facile preparation method also make rGO themost widely used form of graphene in the applications of Li/Na-based batteries. Transmission electron microscopy (TEM)reveals that the rGO atomic structure is comprised of bothdefect-free graphene areas and defective areas dominated byclustered pentagons and heptagons.67 The existence of defectsallows rGO to be more chemically reactive than pristinegraphene.

2.1.2 Elemental graphene analogues: silicene, germanene,stanene, phosphorene and borophene. Encouraged by theresults of graphene exfoliation, other IVA group elements havebeen explored for their 2D structures, namely silicon, germa-nium and stannum. Unlike carbon, silicon, germanium orstannum does not have allotropic layered structures that can beexfoliated into monolayers. Early studies mainly concentratedon rst-principles predictions.68–71 Calculations show that theseelements are thermodynamically stable at a slightly buckledconguration, known as the “low-buckled” structure (shown inFig. 2b), which differs from graphene's honeycomb structure,and lattice parameters varied for different elements.71 The 2Dstructures of these elements are predicted to be conductive andare suitable for electrode materials for Li/Na-based batteries.Experimentally, silicene, germanene and stanene have beensuccessively synthesized via CVD on metal substrates in 2012,72

2014 (ref. 73) and 2015.74 The observed atomic structures ofthese materials deposited on substrates are in agreement withtheoretical predictions. However, as there are intimate inter-actions between substrates and deposited atomic layers, theintrinsic properties of silicene, germanene and stanene may beperturbed, and free-standing forms of these materials still donot exist in nature.

Adjacent to the IVA group elements, phosphorus in group VAhas also been investigated for its possible 2D structures. Phos-phorous has a stable allotrope in the layered fashion calledblack phosphorus, which is energetically more stable than themore common white and red phosphorus. Monolayer phos-phorene (a-P) can be obtained via mechanical or liquid exfolia-tion. As shown in Fig. 2c, phosphorene has an orthogonalstructure with strong structural anisotropy. It exhibits an armchairconguration along the x direction and a zigzag congurationalong the y direction, giving it anisotropic mechanical, electronic,optical and thermal properties.75 Theoretical and experimentalinvestigations show that phosphorene is a semiconductor witha bandgap ranging from 0.76 to 2.1 eV, according to differentreports.75–78 In addition to a-P, other possible structures of

J. Mater. Chem. A, 2017, 5, 3735–3758 | 3737


monolayer phosphorus with higher formation energies, such asb-P, g-P and d-P, have been proposed.76–79

2D structures of boron in group IIIA have been explored.80–83

Mannix et al.84 reported the successful synthesis of boropheneon an Ag(111) substrate. Their experiments show that bor-ophene exists in the structure shown in Fig. 2d with a slightlypuckered lattice, which is also anisotropic, indicating corre-sponding anisotropic physical properties. Unlike bulk boron,this structure is conductive. According to the phonon calcula-tions, free-standing borophene shows a small imaginaryfrequency near the G point along the ZA branch, indicating itsinstability against long-wavelength transversal waves. Thisinstability can be xed by defects, but limit the size of theborophene sheet. Feng et al. subsequently reported successfullysynthesizing 2D boron on an Ag(111) surface.85 Unlike Mannixet al., however, they observed two phases, namely b12 sheet andc3 sheet, both of which exhibited a triangular lattice but withdifferent hole arrangements. Follow-up rst-principles calcula-tions showed three energetically favorable 2D boron monolayerstructures on Ag(111), justifying the coexistence of differentphases observed in experiments.86 Similar to the cases of sili-cene, germanene and stanene, these experimentally synthesized2D boron sheets have only existed in the form of substratedeposition and do not exist in free-standing form.

2.1.3 2D transition metal oxides (TMOs). In nature, there isa large group of layered transition metal oxide compounds withcation-exchange capability. These compounds are commonlycomposed of stacked negatively charged slabs made up ofcorner- or edge-shared MO6 (M ¼ Ti, Nb, Mn, Ta, Ru, W, andMo) octahedral units; alkali metal cations (K+, Rb+, and Cs+)reside between the layers. Treating these layered compounds inacid solution can turn them into a hydrated protonic form. Theprotons between the negative charge-bearing TMO layers canthen be further substituted by bulky organic ions such as tet-rabutylammonium (TBA+), thus exfoliating the stacked TMOlayers into 2D nanosheets. Fig. 2e gives an example of theatomic structure of the exfoliated TiO2 monolayer. Otherbottom-up methods such as CVD and wet-chemical one-potsynthesis have also been proposed to obtain 2D TMOs. Theelectronic properties of TMO monolayers show a large variety,ranging from metallic to insulated, and some 2D TMOs showfavorable catalytic activities towards certain reactions. The fullyexposed surface and diverse electronic, optical and catalyticproperties bring them versatile applications in energy harvest-ing and storage.41,87–89

2.1.4 2D transition metal dichalcogenides (TMDs). Tran-sition metal dichalcogenides (TMDs) are another large group ofcompounds which can be naturally layered. TMDs can be rep-resented by a general formula MX2, where M represents a tran-sition metal element from group 4 to group 10, and X representsa chalcogen element (S, Se and Te). Thus far, more than 40kinds of TMDs have been reported.90 TMDs with M from 4–7groups are predominantly found in a layered structure, whilethose with M from 8–10 groups are found in a non-layeredstructure.91 Metal atoms in the layered TMDs are sandwichedbetween two layers of chalcogen atoms via covalent bonding,where the metal coordination can be either trigonal prismatic

3738 | J. Mater. Chem. A, 2017, 5, 3735–3758

or octahedral, while the interaction between layers is mainlycomposed of van der Waals force. For bulk TMDs, three phasesexist, namely 1T, 2H and 3R, where T, H and R representtrigonal, hexagonal and rhombohedral congurations, and thedigital number represents the number of X–M–X units in theunit cell. Aer exfoliation, TMDs only have two polymorphs, thetrigonal prismatic (1H) phase and the octahedral phase (1T).For different TMDs, different phases are thermodynamicallypreferred. Fig. 2f shows the stable 1H structure of monolayerMoS2. Monolayer TMDs can be either exfoliated from the bulklayered TMDs or synthesized via bottom-up approaches likeCVD growth and the wet chemical method. 2D TMDs also showversatile electronic properties ranging from metals (NbS2, VSe2)to insulators (HfS2),92 where some of which are promisingsensing or catalytic materials.93 TMDs have since found broadapplications in batteries, solar cells, supercapacitors and elec-trochemical catalysis.94–97

2.1.5 2D transition metal carbides/nitrides (MXene). Inrecent years, a new family of 2D materials, MXenes, haveemerged from the successful exfoliation of the MAX phases.98

The MAX phases are composed of alternatively arranged MXand A layers, where MX denotes transition metal carbides/nitrides, and A refers to mainly group IIIA or IVA elements.For some time, it has been generally agreed that the MAX phasecannot be exfoliated, since the forces conjoining the MX and Alayers are not van der Waals, but are joined with high energychemical bonds. However, as the A layers in MAX phases aregenerally more reactive than the MX layers, it has been foundthat a portion of A atoms can be substituted with other elementsto form a substitutional solid solution.43,98,99 These solutions areknown as the “activated MAX phase” and can be more easilyisolated into layers. For example, Ti3AlC2, a widely studied MAXphase, can be etched with aqueous HF. The Al atoms willsubsequently be replaced by O, OH or F, allowing the activatedphase to be easily exfoliated into 2D Ti3C2 layers by sonication.Following this exfoliation procedure, the surfaces of MXenes arecommonly captioned with functional groups like –F, –O and–OH. These functional groups will signicantly inuence thephysical and chemical properties of MXenes.99 The exact surfaceterminations of exfoliated MXenes are still under investigation,and a general formula of Mn+1XnTx has been proposed torepresent the MXenes with surface terminations, where Tstands for the surface terminating functional groups. Fig. 2gshows the atomic structure of bare Ti3C2, where two layers ofcarbon atoms are sandwiched by three layers of titanium atoms.Most of the obtained MXenes are electronically conductive orsemi-conductive, making them promising materials for theelectrode of Li/Na-ion batteries and supercapacitors.100

2.1.6 2D h-BN. Being composed of two elements closest tocarbon in the periodic table, hexagonal boron nitride (h-BN)shares a similar lattice structure to graphite.101 Aer exfolia-tion, one can obtain monolayer h-BN as shown in Fig. 2h, whereboron and nitrogen atoms are alternately positioned in thehexagonal honeycomb lattice. The h-BN nanosheets can also beprepared via CVD and chemical synthesis.102 As the atomicstructure of h-BN is similar to that of graphene but witha slightly larger lattice parameter, h-BN is also known as “white



graphene”.103 Contrary to the excellent electronic conductivity ofgraphene, h-BN has a wide band gap of around 5.9 eV.104 Itsinsulating property and superb chemical stability make itpromising as a charge leakage barrier layer as well as a substratematerial for graphene in electronic devices.105,106

2.1.7 Emerging new 2D materials. In recent years,researchers have devoted much attention to identifying newmembers of inorganic 2D materials. Single layer III–V mate-rials107 and 2D group IV –mono chalcogenides108 are among thecontenders via rst-principles predictions. Possible new mate-rials such as SiGe109 and SiS2 (ref. 110) have also been proposedfor their promising applications in electronic and optoelec-tronic devices. The existence of these possible 2D structures andother unknown 2D materials still needs further investigations.Discovery of these 2D materials will undoubtedly enlarge thelibrary of potential materials for Li/Na-based batteries.

2.2 Preparation methods of 2D materials

Generally speaking, the preparation methods of the abovementioned 2D materials can be classied into two categories:the top-down strategies and the bottom-up strategies. For thetop-down strategies, the preparation starts from 3D bulkmaterials, and goes through various kinds of exfoliationprocedures to obtain the 2D materials. While for the bottom-upstrategies, the preparation starts form the building blocks of 2Dmaterials and goes through various kinds of synthesis proce-dures to obtain the 2D materials.43–45,47

2.2.1 Top-down strategies. As many of the reported 2Dmaterials have 3D bulk counterparts in a layered fashion, mostof them can be obtained from the top-down strategies.Mechanical exfoliation via scotch tape can result in 2D mono-layers with high quality, which are suitable for fundamentalstudies.40,111 However, the yield of this kind of mechanicalexfoliation is quite low, making it unsuitable for mass produc-tion. Another kind of mechanical exfoliation is ball milling,which has been successfully applied to the synthesis of gra-phene, h-BN, MoS2 andWS2 2D nanosheets.112,113 Different fromthe scotch tape-based exfoliation, ball milling is cheap andeffective, thus promising for large scale production. But theresulting 2D nanosheets via ball milling usually contain impu-rities. By adding chemicals such as dry ice during the ballmilling process, functional groups can be introduced into the2D matrix.114

According to the solubility theory, nanomaterials can bebetter dispersed in solvent with matched surface energy. Thusmany kinds of 2D materials can also be obtained via liquidexfoliation, where lamellar bulk materials are exfoliated underultrasonication in appropriate solvents.44,91,115 The efficiency ofliquid exfoliation can be further enhanced when combined withchemical intercalations. For example, lithium intercalationmethods have been widely used in the preparation process of2D TMDs, where 3D bulk TMDs rst go through a lithiumintercalation process to form lithium-intercalated compounds,and then be exfoliated in solvents under ultrasonication.116–118

Other chemicals such as gas molecules119 and formamide120

have also been employed to facilitate the exfoliation process by


intercalation. For 3D lamellar materials with different physicaland chemical properties, oxidation,64 ion-exchange41 andchemical etching121,122 can be used to pretreat the layered bulkmaterials (such as graphite, bulk TMOs and MAX) before theliquid exfoliation process to improve the exfoliation efficiencyrespectively. Liquid exfoliation methods are cheap and facile,and thus suitable for large scale production. However, the sameas the ball milling method, the introduction of functionalgroups and defects into the pristine 2D structures is unavoid-able during the exfoliation process, lowering the quality of theprepared 2D materials.

2.2.2 Bottom-up strategies. CVD is an effective and impor-tant method to prepare graphene and other 2D materials.123–126

During the CVD process, gas phase precursors are fed intoreactors and go through reactions and/or decompositions toform desired depositions on metal or metal oxides substrates.123

This method can achieve large area 2D materials with desiredquality, and is particularly important for the synthesis of 2Dmaterials without 3D bulk counterparts, such as silicene,72 bor-ophene84,85 and stanene.74However, operation conditions of CVDare harsh, and the isolation of synthesized 2Dmaterials from thesubstrates is nontrivial, both of which limited its broaderapplications.

The wet chemical hydrothermal/solvothermal method isanother important bottom-up strategy to synthesize 2D mate-rials. 2D materials including graphene,127 TMOs128 and TMDs129

have already been successfully synthesized via hydrothermal/solvothermal processes. These wet chemical approaches havemany advantages compared with other preparation methods,such as high yield, simple operation and low cost, making themfeasible for the mass production of 2D materials.

For the applications in Li/Na-based batteries, liquid exfolia-tion and wet chemical hydrothermal/solvothermal methods arethe most frequently employed methods to prepare required 2Dmaterials.

3. 2D materials in Li/Na-ion batteries

As discussed in Section 1, conventional electrode materials forLi/Na-ion batteries, such as graphite and transition metaloxides, suffer from low capacity and/or poor electronicconductivity.4–8,36,37 Newly developed anode materials that havethe capability to output larger capacities based on their alloymechanisms, such as silicon, tin and tin oxide, undergo largevolume uctuation during the insertion and extraction processof Li/Na ions, which will inevitably lead to the pulverization ofelectrode materials and cause severe capacity decay. With anextremely large surface area and weak interlayer interactions, 2Dmaterials are excellent alternatives that address these issues.45

2D materials can be either directly used as the electrode mate-rials to provide large capacity, good rate capability and stablecycle performance, or can composite with other active materialssuch as silicon nanoparticles to accommodate volume expan-sion and protect nanoparticles from pulverization. 2D materialswith good electric conductivity such as graphene can also beused as additives in the electrode materials to enhance theelectronic conductivity.

J. Mater. Chem. A, 2017, 5, 3735–3758 | 3739


As adjacent elements in the 1A group, lithium and sodiumshare similar chemical properties. And for Li-ion and Na-ionbatteries, the working principles are also identical as illus-trated in Fig. 1a. However, since the size of sodium atoms (1.02A) is much larger than that of lithium atoms (0.76 A), thedetailed requirements of these two elements towards the elec-trode materials are somewhat different, where the electrodematerials for Na-ion batteries are required to possess largerchannels and/or interstitial sites.36,37 An electrode material thatwork well for Li-ion batteries may not suitable for Na-ionbatteries, and vice versa.130

3.1 2Dmaterials as an anode material for Li/Na-ion batteries

3.1.1 Graphene and its derivatives. As the most widely usedanode material for Li-ion batteries, the theoretical capacity ofgraphite is about 372 mA h g�1 (LiC6), which is not high enoughto satisfy the increasing demand nor does it satisfy the ratecapability.59 When using graphite as the anode for sodium-ionbatteries, the utilization of graphite is as low as 1/8 becausethe size of sodium ions is much larger than that of lithiumions.35–37 Exfoliated from graphite, graphene has a larger surfacearea and exhibits an expanded interlayer spacing comparedwith graphite, resulting in much investigation of its feasibilityas an anode material for Li/Na-ion batteries.131

Fig. 3 (a) Illustrations of pure graphene (G) and N-doped graphene (Gdirections, (b) comparison of the total stored charge distribution for GN aand (d) cycle performance and coulombic efficiency of G and GN at C(Copyright 2014, American Chemical Society).

3740 | J. Mater. Chem. A, 2017, 5, 3735–3758

As both sides of graphene are able to adsorb lithium/sodiumions, its capacity is expected to be doubled compared withgraphite when being used as the anode material for Li/Na-ionbatteries. However, from density functional theory (DFT) calcu-lations, pristine graphene shows very weak adsorption towardsboth lithium and sodium.132–134 This is a problem becauseeffective anchoring of lithium and sodium atoms cannot beachieved, which would result in lithium/sodium clustering anddendrite growth. Introduction of edges or vacancies has beenpredicted to be an effective strategy to enhance the lithium/sodium binding strength.133,135–137 Another solution is hetero-atom doping, where graphitic B-doping, and pyridinic N-dopinghave been identied to be benecial to graphene's performanceas an anodematerial for Li/Na-ion batteries.132,138,139 Zhou et al.140

studied the conditions of graphene with paired B and N dopants,and found that the paired B dopants showed an adsorptionenergy 1.84 eV larger than that of pristine graphene towardlithium. Ling and Mizuno141 proposed that the B-doped gra-phene with an atomic ratio of BC3 can be used as a promisinganode material for Na-ion batteries, with a theoretical capacityas high as Na1.125BC3 and diffusion energy barriers ranging from0.16 to 0.22 eV.

Experimentally, Li-ion batteries installed with monolayergraphene anodes142 and all-graphene-batteries installed with

N) nanosheets for Li-insertion viewed from the edge and basal planend G, (c) TEM image of the nano-LIB and GN before and after lithiation/5 between 3.0 and 0.05 V versus Li+/Li.147 Reproduced from ref. 147



rGO anodes and functionalized graphene cathodes143 have beendemonstrated to show that the concept of graphene electrodesis feasible. It has also been shown that when graphene layersoriented parallel to the ux of lithium ions, the stress distri-bution is highly anisotropic and higher performance can beachieved in comparison to that of graphene layers that areperpendicular to direction of the lithium ion ux.144

To explore the inuence of edges, defects and doping, Liet al.145 fabricated graphene nanosheets (GNSs) with varyingsizes, edge sites, defects and layer numbers, and concluded thatthe GNS with fewer layer numbers, smaller size, more edge sitesand defects results in higher electrochemical performance forlithium intercalation. Reddy et al.146 synthesized N-doped gra-phene using CVD on the current collector, and concluded thatthe reversible capacity as a lithium anode was doubledcompared with pristine graphene, which agreed with theoret-ical predictions. Later, Wang et al.147 explored the reasons forthe ultrafast lithium storage property and high capacity of N-doped graphene (GN) using in situ TEM and DFT calculationsas shown in Fig. 3, and concluded that the enlarged edge {0002}spacing and surface defects are responsible for the improve-ments in surface capacitive effects and better batteryperformance.

Graphene with various morphologies has been synthesizedto pursue better performance as the anode for Li/Na-ionbatteries. Shu et al.148 prepared a porous graphene paper bypressing a graphene cryogel followed by thermal reduction at220 �C. When used as the anode of Li-ion batteries, the porousgraphene paper showed a discharge capacity higher than400 mA h g�1 at a current density of 2000 mA g�1. Cohn et al.149

Table 1 Electrochemical performance of the selected graphene-based

Battery Year Composite

Li-ion156 2012 Si@crumpled grapheneLi-ion157 2013 FeS@reduced graphene oxideLi-ion158 2013 Sn@N-doped reduced graphene oxideLi-ion159 2013 Cobalt suldes/graphene nanosheetLi-ion160 2013 Si–rGO stratum structureLi-ion161 2013 NiCo2O4/graphene nanosheetsLi-ion162 2013 Silicon nanowire@graphene sheath@reduced

graphene overcoatLi-ion163 2013 Co3Sn2@Co–N-doped grapheneLi-ion164 2014 Carbon nanobers/silicon nanoparticles@redu

graphene oxideLi-ion165 2014 Sn@porous graphene networksLi-ion166 2014 Si/reduced graphene oxideLi-ion167 2014 TiO2 nanotube/N-doped grapheneLi-ion168 2014 Defect-free graphene/Co3O4

Li-ion155 2015 Si/templated carbon-bridgedoriented graphene

Li-ion169 2015 Graphene–SiLi-ion170 2016 Fe2O3/g-C3N4–grapheneNa-ion171 2013 SnO2–reduced graphene oxideNa-ion172 2014 Phosphorus/graphene hybridNa-ion173 2014 SbOx–reduced graphene oxideNa-ion174 2015 NaTi2(PO4)3 embedded in 3D graphene networkNa-ion175 2015 Sb/multi-layer graphene


fabricated a 3D freestanding foam of a hybrid graphene-single-walled CNT nano-manufactured material and achieveda reversible capacity of 2640 mA h g�1 at 0.186 A g�1 and 236mA h g�1 at 27.9 A g�1 for Li-ion batteries. Ji et al.150 synthesizeda 3D free-standing N-doped porous graphene/graphite foam byin situ activation of N-doped graphene on highly conductivegraphite foam for Li-ion batteries, and achieved a capacity of643 mA h g�1 accounting for both the active material andcurrent collector. Hassoun et al.151 fabricated an advancedlithium-ion battery based on a graphene ink anode anda LiFePO4 cathode. The battery provided a capacity as high as165 mA h g�1 and an energy density of 190 W h kg�1. Zhouet al.152 reported a graphene-templated carbon (GTC) hybridprepared via a facile two-step approach. They achieveda capacity of 205 mA h g�1 and a capacity retention of 92% aer2000 cycles at 200 mA g�1 when used as a Na-ion anode. Xuet al.153 prepared 3D N-doped graphene foams (N-GF) witha high 6.8 atom% nitrogen content and used them as the anodefor Na-ion batteries. A high initial reversible capacity of 852.6mA h g�1 at a current density of 1C (500 mA g�1) was obtained.Aer 150 cycles, the N-GF could still maintain a charge capacityof 594 mA h g�1 with 69.7% retention of the initial chargecapacity.

Efforts have also been devoted to fabricating graphene-basedcomposites with other active anode materials that can poten-tially reach higher capacities.154 By wrapping the nanostructuredactive materials, graphene can effectively protect the activematerials from being exposed directly to the electrolyte, whichcircumvents the formation of an excessive solid electrolyteinterface (SEI). The presence of a graphene sheet simultaneously

composite anode material for Li/Na-ion batteries

Capacity(mA h g�1)

Current density(mA g�1) Cycles

Voltagewindow (V)

940 1000 250 0.02–2.0978 100 40 0.005–3.0481 100 100 0.005–2.0950 100 50 0.005–3.01500 1350 100 0.005–3.01267 100 10 0.01–3.01650 840 50 0.002–2.0

1615 250 100 0.005–3.0ced 1048 890 200 0.005–2.5

682 2000 1000 0.005–3.0780 7200 300 0.01–2.0369 100 180 1.0–3.0900 1000 200 0.01–3.01390 2000 200 0.02–1.0

1989 100 200 0.01–1.5980 50 50 0.1–3.0330 100 150 0.005–2.51706 260 60 0.0–2.0409 1000 100 0.0–2.0

s 77 1330 1000 1.5–3.0405 100 200 0.01–2.0

J. Mater. Chem. A, 2017, 5, 3735–3758 | 3741


accommodates the volume expansion of active materials duringthe Li/Na insertion process and enhances the structural stability.Graphene itself can also serve as an anode material during theworking process and provide additional capacity and electronicconductivity. Several different combinations of active materials(Si, Sn, SnO2, etc.) and graphene wrapping (with/without doping/defects) have been explored and are listed in Table 1. Thesestudies demonstrated enhanced performance using compositematerials compared with the use of pristine ones. For example,Fig. 4a and b show the morphology of a templated carbon-bridged oriented graphene composite with Si nanoparticles(TCG-Si). It can be seen that the silicon nanoparticles arehomogeneously deposited in the networks of templated carbon-bridged oriented graphene. Fig. 4c and d show the correspond-ing extraordinary rate capability and cycle performance of thiscomposite as the anode material of lithium-ion batteries.155

3.1.2 2D transition metal oxides (TMOs). Transition metaloxides (TMOs) that are layered are promising candidates forelectrode materials of Li/Na-ion batteries. They provide poten-tially high capacity, good chemical stability and cost-effectivity.TiO2–B, a polymorph of TiO2 with a monoclinic C2/m structureconsisting of edge- and corner-sharing TiO6 octahedral unitswith open channels parallel to the b-axis,176 is one of the mostinvestigated ones among layered TMOs that exhibit appropriatevoltages to be used as anode materials. The layered structureprovides more open channels and the characteristic pseudoca-pacitive behavior allows TiO2–B to reach the highest theoretical

Fig. 4 (a) The TEM image and (b) high-resolution TEM image of TCG-Si, (c28 mm), as well as a 5 mm thick G-Si electrode and (d) gravimetric capacitSiNP). The current rate is 0.2 A g�1 for the first cycle and 2 A g�1 for later celectrode weight.155 Reproduced from ref. 155 (Copyright 2015, America

3742 | J. Mater. Chem. A, 2017, 5, 3735–3758

capacity among all of its polymorphs. When exfoliated orsynthesized into morphology with few atomic layers, largercapacity and higher rate capability are expected. Arrouvelet al.177 and Dalton et al.178 investigated the lithium insertionsites and diffusion pathways in TiO2–B using DFT calculationsand Monte Carlo simulations. Their calculations show that thehighest thermodynamically favorable Li/Ti ratio during thelithium intercalation process could reach 1.25. Dylla et al.179

investigated the lithium intercalation behavior in TiO2–B withmorphologies of nanoparticles and nanosheets, and found thatwhile the 3D and 2D architectures of TiO2–B have essentially thesame capacity when lithiated at 1.0 V under slow chargingconditions, the inherent lithiation mechanisms are quitedifferent. Experimentally, Prochazka et al.180 proposed a two-step synthesis procedure to prepare TiO2–B mesoporous thinlms. The obtained thin lms show fast lithium ion insertion/extraction at a formal potential of 1.5 V vs. Li/Li+ as well asexcellent cycle stability with 20% decay aer 800 cycles. Later,Beuvier et al.181 synthesized TiO2–B nanoribbons with thethickness of about 6 nm, and obtained a capacity of 200 mA hg�1 at C/3 rate and a capacity of 100 mA h g�1 at 15C rate.Cycling stability was shown to be excellent at a rate of 5% decayover 500 cycles at 3C. Liu et al.182 proposed a one-step prepa-ration method for porous TiO2–B constructed by nanosheetswith 5–10 nm thickness and petal-like morphology. A capacityas high as 216 mA h g�1 at 10C has been achieved, and wasreduced to 200 mA h g�1 aer 200 cycles. Layered MoO2 is

) rate capabilities for the TCG-Si electrodes of different thicknesses (6–y and coulombic efficiency of the TCG-Si and control electrodes (G-Si,ycles; all the gravimetric capacities reported are on the basis of the totaln Chemical Society).



another promising anode material for lithium-ion batterieswith moderate discharge/charge voltages.183 Ni et al.184 synthe-sized a composite of ultrathin MoO2 nanosheets encapsulatedwith the carbon matrix. When employing this composite as theanode material of lithium-ion batteries, a capacity as high as1051 mA h g�1 over 100 cycles at a current density of 0.5 A g�1

has been delivered. Nb2O5 nanosheets have also been synthe-sized experimentally and tested as the anode of Li-ion batteries.A lithium capacity of 184 mA h g�1 was delivered together withgood rate capability at intermediate discharge/charge voltagesranging from 1.0 to 2.5 V.185

3.1.3 2D transition metal dichalcogenides (TMDs). 2Dtransition metal dichalcogenides (TMDs) are a growing familyof 2D materials. In recent years, there has been a surge of theemergence and synthesis of new 2D TMDs with varying electricproperties for their applications in Li/Na-ion batteries as elec-trode materials, either in their pristine 2D forms, forming het-erostructures with other 2D TMDs or composited with carbonmaterials.95,186,187

As the most studied TMD, semi-conductive MoS2 hasattracted the most attention from researchers. Li et al.188 rstsystematically investigated the adsorption and diffusion oflithium in the MoS2 bulk structure, on the 2D MoS2 nanosheetand on the 1D zigzag MoS2 nanoribbon via DFT calculations.Their calculations show that compared with the MoS2 bulkstructure, both the 2D MoS2 nanosheet and the 1D zigzag MoS2nanoribbon exhibit a lower diffusion energy barrier towardlithium, and the 1D zigzag MoS2 nanoribbon also provideshigher lithium binding energy. Recently, Shu et al.189

Fig. 5 (a) The concept of the rational design of the MoS2/m-C nanosheetlithium ion storage, (b) the capacity retention of the MoS2/m-C nanosheethe annealedMoS2 nanosheets at current densities from 200 to 6400mAat the MoS2/G interface, in which green indicates the electron accumulat2015, John Wiley and Sons).


investigated the thermodynamic phase diagrams and the lith-iation dynamics of MoS2-based nanostructures with the inter-calation of lithium ions using rst-principles calculation and abinitio molecular dynamics (AIMD). They found that continuousintercalation of lithium ions can induce structural destructionof 2H phase MoS2 nanosheets in the discharge process. Tosuppress the dissociation of MoS2, a sandwich-like graphene/MoS2/graphene structure was proposed.

In 2010, Xiao et al.190 fabricated a MoS2/PEO composite witha PEO/MoS2 ratio of 0.05, where PEO was used to stabilize thedisordered structure. When being used as the anode of Li-ionbatteries, this PEO/MoS2 composite showed a capacity as highas 1000 mA h g�1. Later, Hwang et al.191 prepared MoS2 nano-plates consisting of disordered graphene-like layers with aninterlayer distance of 0.69 nm and achieved excellent ratecapability (a capacity of 700 mA h g�1 at 50C). More efforts havebeen devoted to the fabrication of MoS2–carbon composites,where carbon is expected to provide better electric conductivityand mechanical strength as well as to prevent MoS2 nanosheetsfrom restacking. Zhang et al.192 synthesized morphologycontrolled MoS2 nanosheets with the aid of graphene/acid bya one-pot hydrothermal approach. The obtained MoS2 nano-sheets were self-assembled into a cockscomb-like structurecomposed of 3 wt% graphene, and demonstrated a batterycapacity of 709 mA h g�1 at 9420 mA g�1. Liu et al.193 prepareda graphene-like MoS2/graphene nanocomposite by hydrolysis oflithiated MoS2 and achieved a capacity of 1351 mA h g�1 aer200 cycles at 100 mA g�1. Most recently, Jiang et al.194 designedand synthesized a novel 2D hybrid nanosheet superstructure

superstructure for creating ideal MoS2/C atomic interfaces to enhancet superstructure, MoS2/graphene composites, exfoliated graphene, andg�1 and (c) 3D contour plot of charge density difference in Li adsorptionion and dark red for depletion.194 Reproduced from ref. 194 (Copyright

J. Mater. Chem. A, 2017, 5, 3735–3758 | 3743


consisting of the alternative layer-by-layer inter-overlappedsingle-layer MoS2 and mesoporous carbon as shown in Fig. 5.Excellent battery performance as shown in Fig. 5b has beenachieved with the use of this hybrid material. Their DFTcalculations also suggested that lithium will prefer to interca-late into the interface between MoS2 and graphene rst asshown in Fig. 5c with higher binding energy. Other combina-tions for the MoS2-based composite Li-ion anode, such as N-doped graphene/porous g-C3N4 nanosheets/layered MoS2hybrid,195 CNTs@MoS2 (ref. 196) and MoS2@CMK-3 carbonmatrix,197 have been synthesized and have also delivered goodbattery performance.

It should be noted that the experimentally observed capac-ities of MoS2 and MoS2-based composites are well above thetheoretical expectations (167 mA h g�1 for bulk MoS2 and 334mA h g�1 for MoS2 monolayers). It is now widely agreed thatduring the initial discharge process, lithium and MoS2 willinitially go through an ion/electron transfer topotactic reactionwhich can induce a phase transition of MoS2 from trigonalprismatic to octahedral phase when the voltage is above1.1 V.189,198 Along with the subsequent discharge process whenthe voltage drops below 1.1 V, MoS2 could further react withlithium and decompose into Li2S and Mo.186,199 This decompo-sition process is irreversible,200 and the electrode may work justas the cathode of Li–S batteries in the following cycles, wherethe product of Mo nanoparticles can provide better electronicconductivity and prevent the dissolution of lithium poly-suldes. In addition to MoS2, other TMDs with better electronicconductivity and lower price have been explored as the anodematerial for Li-ion batteries. Jing et al.201 predicted a VS2monolayer to be a likely anode material for Li-ion batteries witha capacity of 466 mA h g�1, an average discharge voltage of0.93 V and a lithiummigration energy barrier of 0.25 eV via DFTcalculations. Their calculations showed no obvious structuralchanges during lithiation. Liu et al.202 studied the intercalationand diffusion of lithium in pristine and modied SnS2 inter-layer using DFT calculations, and revealed a two-stage lithiationbehavior similar to that of MoS2, where SnS2 may decomposeinto Li2S and Sn when an excess amount of lithium was inter-calated. Wang et al.203 studied the feasibility of MX2 (M ¼Mo, W; X ¼ S, Se) single-layer and double layered hetero-structures as Li-ion anode materials via rst-principles calcu-lations and predicted that the MoS2/WS2 heterostructure caneffectively reduce the bandgap, improve the lithium ion bindingand maintain a high lithium ion mobility. Experimentally,Bhandavat et al.204 successfully exfoliated WS2 into layers usingstrong acid, and showed a capacity of 118 mA h g�1 aer 50cycles at a current density of 25 mA g�1 in a lithium half-celltest. Much attention has been given to fabricating SnS2 andgraphene composites,205–210 and high capacities ranging from760 to 1005 mA h g�1 have been reported. The reaction mech-anism for SnS2 is even more complicated than that of MoS2,where SnS2 will rst decompose into Sn and Li2S at the initialdischarge process. Lithium then alloys with Sn particles in thefollowing cycles.

Bulk layered MoS2 has also been predicted to be a promisinganode material for Na-ion batteries, with a theoretical capacity

3744 | J. Mater. Chem. A, 2017, 5, 3735–3758

of 146 mA h g�1 and voltages ranging from 0.75 V to 1.25 V.211

Exfoliation into 2D structures is expected to enhance perfor-mance. Other 2D TMDs such as TiS2, VS2, CrS2, CoTe2, NiTe2,ZrS2 and NbS2 have been explored for their feasibility assodium-ion anodes.212,213 According to the DFT calculations,TiS2, ZrS2 and NbS2 are suitable choices, with capacities rangingfrom 260 to 339 mA h g�1 and voltages ranging from 0.49 to0.85 V. Among them, TiS2 and NbS2 show low sodiummigrationenergy barriers of 0.22 eV and 0.07 eV, expected to provide goodrate capability. A Na–MoS2 battery was rst assembled by Parket al.214 in 2012, where an initial discharge capacity of 190 mA hg�1 was obtained, and dropped to 85 mA h g�1 aer 100 cycles.Similar to that in Li-ion batteries, researchers also attempted touse MoS2 and graphene composite layers for Na-ion batteryanodes,215,216 where a reversible capacity as high as 702mA h g�1

was achieved. SnS2 nanosheets are another popular candidateto form composites with graphene.217–219 Qu et al.217 showed thatthe SnS2/rGO composite can deliver a sodium capacity as highas 630 mA h g�1 at 200 mA g�1 and 544 mA h g�1 at 2A g�1. Thecycle test showed that a capacity of 500 mA h g�1 at a currentdensity of 1 A g�1 can be maintained aer 400 cycles. Thedetailed reaction mechanism responsible for the high capac-ities of MoS2/SnS2-based composites in Na-ion batteries is stillunclear. For cases that use the SnS2 composite as the anode, theformation of a ternary amorphous phase of Na–Sn–S has beensuggested.218

3.1.4 2D transition metal carbides/nitrides (MXene).Transition metal carbides/nitrides that were exfoliated byforming substitutional solid solutions from MAX phase havebeen explored for their unique physical/chemical properties.Bare MXenes have been reported to be conductive or semi-conductive, allowing them to be likely choices for anode mate-rials of Li/Na-ion batteries. Typically, the surface of MXenespossesses functional groups such as –F, –OH and –O, which cansignicantly alter the physical and chemical properties of bareMXenes during preparation, and should be taken into consid-eration when attempting to employ MXenes in realapplications.

In 2012, Tang et al.220 rst investigated the electronic prop-erties and lithium storage capabilities of bare Ti3C2 and Ti3C2

terminated with different functional groups (–F and –OH). Fromtheir DFT calculations, bare metallic Ti3C2 is the most prom-ising lithium anode material exhibiting a theoretical capacity of320 mA h g�1 and an ultralow lithium migration energy barrierof 0.07 eV. Surface functional groups were found to blocklithium transport and decrease lithium storage capacity. Ber-diyorov221 studied the effect of lithium and sodium adsorptionon the electric properties of bare Ti3C2 and Ti3C2 terminatedwith –O, –OH and –F functional groups. The author reportedthat ion adsorption impaired the electric conductivity of bareTi3C2, while improvements were shown in the case of oxygentermination. Sun et al.222 synthesized 2D Ti3C2 and tested itsperformance as a lithium ion anode. A capacity of 123.6 mA hg�1 at a rate of 1C was reported, along with a coulombic effi-ciency of 47%. Xie et al.223 systematically investigated thesurface structure and Li-ion storage capability of a number offunctionalized MXenes using combined experimental and



theoretical methods. They found that aer aqueous HF etching,Mxenes are generally terminated with –OH groups as shown inFig. 6a, which can be removed by high temperature annealing.Different surface functional groups can lead to differentcapacities as shown in Fig. 6b, where –OH groups correspond toa low lithium capacity and –O groups can effectively adsorb twolayers of lithium atoms and result in a much higher capacity.Based on these results, the authors proposed that bare or –Oterminated Mxenes are recommended for lithium ion batteries,which can be achieved through a more streamlined synthesisprocedure. Recently, researchers also fabricated Ti3C2Tx/CNTcomposites successfully and attempted to apply the compositeas the electrode in hybrid Mg2+/Li+ batteries224 and Li-ionbatteries,225 reporting satisfactory performances.

Other kinds of MXenes have been extensively investigated asthe anode material for Li-ion batteries. In 2013, Naguib et al.226

successfully synthesized V2C and Nb2C and measured theirperformance. Reversible capacities were obtained at 260 and170 mA h g�1 for V2C and Nb2C at 1C, and 125 and 110 mA h g�1

at 10C. Subsequent theoretical studies explored the propertiesof using monolayer V2C/Nb2C and V2C/Nb2C functionalized by–F and –OH as lithium anode materials,227,228 and the calcula-tions showed that bare V2C and Nb2C monolayers providedtheoretical capacities as high as 940mA h g�1 and 542mA h g�1,along with low lithium migration energy barriers. –F or –OHtermination tends to impede the lithium diffusion and reduce

Fig. 6 (a) Snapshots at 0, 0.5, and 5 ps of AIMD simulations of a bare Ti3Cmolecules close to the surfaces are shown. In all cases the surfaces of bSide and top views of lithiatedmonolayers of: (b1) Ti3C2(OH)2 and (b2) Ti3CTi3C2O2Li2, monolayers. (c) Variation of Ti edge energy (at half height of n(c1) combined with the corresponding voltage profiles (c2).223 Reproduc


the theoretical capacity. Byeon et al.229 fabricated an Nb2CTx–

CNT composite and used it as the electrode material in threetypes of hybrid cells, reporting satisfactory results. In 2016,Mo2C has been predicted to be a good anode material for bothLi- and Na-ion batteries, with theoretical capacities of 526 and132 mA h g�1 and diffusion energy barriers of 0.14 and 0.015 eVfor the cases of lithium and sodium respectively.230 In the sameyear, 2D Mo2CTx was synthesized by selectively etching galliumfrom Mo2Ga2C, and a Mo2CTx/CNT composite (CNT 8 wt%) wasfabricated. Stable capacities of 250 and 76 mA h g�1 were ach-ieved at 20 and 131C cycling rates aer 1000 cycles.231 Sunet al.232 further investigated lithium storage properties of eight2D M2CO2 (M ¼ V, Cr, Ta, Sc, Ti, Zr, Nb and Hf) via DFTcalculations and predicted that the V-type MXenes (V2CO2,Cr2CO2, and Ta2CO2) show reversible structural transformationduring the lithiation/delithiation processes which is benecialfor further lithium adsorption. Recently, Ashton et al.233 pre-dicted reversible capacities and other battery-related propertiesof six of the most promising members of the MXene family (-Ofunctionalized Ti- and V-based carbide MXenes) in bilayerstructures and found that the results from the bilayer model ofV2CO2 and Ti2CO2 were in better agreement with experimentsthan those that were obtained using monolayer models. Thecalculated lithium migration energy barriers for the bilayersituation are also higher than those for the monolayers.

2 monolayer in 50% HF (a1), 25% HF (a2), and water (a3) solutions. Onlyare Ti3C2 monolayers were rapidly covered with functional groups. (b)

2O2; and (b3) an extra metallic Li layer adsorbed on top of lithiated viz.,ormalized XANES spectra) vs. capacity during lithiation and delithiationed from ref. 223 (Copyright 2014, American Chemical Society).

J. Mater. Chem. A, 2017, 5, 3735–3758 | 3745


With the success achieved in Li-ion batteries, increasingresearch attention has been focused on applying MXenes inNa-ion batteries. Theoretical predictions show that bare Ti3C2

as well as Ti3C2Tx (T ¼ F, O, OH) could be used as the anodematerial for Na-ion batteries with acceptable capacities and lowsodium migration energy barriers.234,235 Employing combinedexperimental and theoretical methods, Xie et al.236 demon-strated the feasibility of Na and K ions' intercalation intoO-terminated MXenes. Yang et al.237 studied the sodium storageand migration properties of M2C-type MXenes (M ¼ Ti, V, Sr,Mn, Fe, Co, Ni, Nb, and Mo) via DFT calculations and suggestedthat the cases when M ¼ Ti, V, Cr, Mn and Mo are suitable forNa-ion battery anodes. In 2013, Lukatskaya et al.238 experimen-tally demonstrated the spontaneous intercalation of cations(Na+, K+, NH4

+, Mg2+, and Al3+) from aqueous salt solutionbetween 2D Ti3C2 MXene layers. In 2016, Kajiyama et al.239

revealed that Ti3C2Tx in a non-aqueous Na+ electrolyte exhibitsreversible Na+ intercalation/deintercalation into the interlayerspacing with the aid of solid state 23Na magic spinning NMRand DFT calculations. Recently, Xie et al. fabricated a porousTi3C2 MXene/CNT composite paper electrode and observeda high volumetric capacity of 421 mA h cm�3 at 20 mA g�1 aswell as high rate performance and cycling stability when testedas a sodium anode.240

3.1.5 Phosphorene. With a layered structure similar to thatof graphite, black phosphorus was studied as the anode mate-rial for Li/Na-ion batteries. According to Hembram et al.241

calculation results on the lithiation, sodiation and magnesia-tion processes of black phosphorus, at low ion concentrations,the metal ions will intercalate into the interlayer spacingbetween phosphorene layers as that in graphite, while at highion concentrations, black phosphorus can form alloys withthese metals. The highest atomic ratio of these ions towardsblack phosphorus is Li4.5P, Na4P and Mg2P. Similar to otheranode materials that are based on the alloy mechanism, blackphosphorus will undergo signicant size expansion during thelithium insertion process, which changes the lattice structure ofblack phosphorus and eventually lead to the pulverization of thematerial.242 As a consequence, researchers began to investigatewhether exfoliated phosphorene could be used as the anodematerial for Li/Na-ion batteries in substitution of black phos-phorus to address the structural instability.

From rst-principles calculations,243–245 phosphorenedemonstrates strong binding toward lithium and can reacha capacity as high as 432.79 mA h g�1 without altering its latticestructure. Lithium diffusion on the phosphorene is highlyanisotropic, with an energy barrier as low as 0.08 eV along thezigzag direction and an energy barrier as high as 0.68 eV alongthe armchair direction. Similar anisotropic diffusion behaviorhas also been reported for sodium ions.246 During the lithiation/sodiation process, the semi-conductive phosphorene willbecome more conductive.245,246 Zhang et al.247 investigated theinuence of intrinsic point defects (vacancy and Stone–Walesdefects) toward phosphorene's performance as a lithium anodematerial. They found that the presence of defects will blockdirectional ultrafast lithium diffusion and increase open circuitvoltage, suggesting that defects should be avoided during the

3746 | J. Mater. Chem. A, 2017, 5, 3735–3758

preparation process of phosphorene. Both h-BN and graphenehave been proposed to be potential candidates to form hybridstructures with phosphorene, which can enhance bindingenergies and simultaneously preserve low anisotropic Li/Namigration energy barriers.248,249 In addition, a polymorph ofphosphorene with a slightly higher formation energy, bluephosphorene, has also been predicted to be a promising anodematerial for Li-ion batteries as a hybrid with TMDs.250

Xu et al. reported for the rst time using in situ TEM toconstruct a nanoscale phosphorene Li-ion battery.251 Theyobserved that the use of several layers of phosphorene circum-vented the problem of decomposition. Sun et al.252 fabricateda phosphorene/graphene hybrid as shown in Fig. 7 and usedthis hybrid structure as the anode material for Na-ion batteries.Here, graphene is expected to act as the electron highway as wellas a mechanical backbone during the sodiation process. Asshown in Fig. 7c, extra-large capacity and high rate capabilityhave been demonstrated. Moreover, from the cycling test, thecapacity retention is 83% aer 100 cycles.

3.1.6 Silicene, germanene, borophene and stanene. Inaddition to phosphorene, other elemental analogues of gra-phene, silicene, germanene, borophene and stanene have beensynthesized in recent years.72–74 However, as these materials donot exhibit stable polymorphs in the layered structure forma-tion in nature, unlike in graphite or black phosphorus, reportedsynthesis procedures have relied on CVD, and structures aredeposited on substrates like Ag(111) or Au(111) surfaces. Thusfar, explorations into the feasibility of using these materials asthe anode for Li/Na-ion batteries have remained largelytheoretical.

Sharing the same lattice structure, silicene, germanene andstanene have been predicted to be likely anode materials for Li/Na-ion batteries with theoretical capacities of 954, 369 and 226mA h g�1 respectively.253–256 Before the successful synthesis ofborophene, Banerjee et al.83 investigated the possibility of 2Dboron sheets as an anode material for Li-ion batteries usingDFT and AIMD simulations, and three congurations, a, a1 andh4/28, have been studied. Aer the successful synthesis of bor-ophene by Mannix et al.,84 our group studied the possibility ofusing the reported 2D structure as the anode for both Li-ion257

and Na-ion batteries.258 We found that in both cases borophenecan provide large capacities (1860 mA h g�1 for Li and 1218mA h g�1 for Na) and anisotropic ultralow diffusion energybarriers along the valley direction (2.6 meV for Li and 1.9 meVfor Na).

While the aforementioned analogues of graphene have beenpredicted to be potential anode materials, they do not exist infree-standing form, which hinders their applications. Metalsubstrates are commonly found to signicantly alter the elec-tronic structure of thesematerials, which leads to unpredictableproperties. Zhu et al.259 proposed that the 2D MgX2 (X ¼ Cl, Brand I) shares a similar lattice structure to silicene and germa-nene and could be used as a new substrate for silicene andgermanene. The resulting van der Waals heterostructure canpreserve the intrinsic properties of silicene/germanene and canbe adopted as the anode material for Li-ion batteries. Recently,our group found that graphene could also be used as a substrate


Fig. 7 (a) Schematic of the structural evolution of the sandwiched phosphorene–graphene structure during sodiation; (b1) TEM image of thephosphorene–graphene hybrid. Scale bar, 2 mm. (b2) HRTEM image of the cross-section of the phosphorene–graphene hybrid (the turned-upright edge in (b1)). Scale bar, 2 nm (c) volumetric andmass capacities at different current densities (from0.05 to 26 A g�1).252 Reproduced from ref.252 (Copyright 2015, Nature Publishing Group).


as well as a protective layer for silicene, as shown in Fig. 8. Thisgraphene layer could provide extra electric conductivity andmechanical strength and simultaneously maintain high capac-ities and low lithium/sodium migration energy barriers of sili-cene, making the hybrid structure a promising candidate forlithium/sodium anode materials.260

3.2 2D materials in the cathode of Li/Na-based batteries

The cathode materials currently used in Li/Na-ion batteriessuffer from low energy density and poor electronic conductivity.As a 2D material with excellent electric conductivity and largesurface area, graphene has been explored as a conductiveadditive or framework for the cathode of Li/Na-ion batteries toimprove electric conductivity.16 With high discharge/charge

Fig. 8 Illustration of using silicene and graphene heterostructure asthe anode material for Li/Na-ion batteries.260 Reproduced from ref.260 (Copyright 2016, Royal Society of Chemistry).


voltages, large surface area, good chemical stability and lowcost, some 2D TMOs have also been proposed to be used as newcathode materials for Li/Na-ion batteries.

3.2.1 2D materials as an additive or framework in thecathode of Li/Na-ion batteries. Due to the extraordinaryconductivity and large surface area, graphene has been exploredextensively as a conductive additive or framework in the cathodeof Li/Na-ion batteries. In 2012, Su et al.261 studied the effect ofusing graphene as a conducting network for the electron andion transport in the cathode system. They found that althoughthe addition of graphene effectively enhanced the electricconductivity, it also showed a signicant steric effect, whichblocked lithium ion transport, resulting in heavy polarization,as shown in Fig. 9. Wei et al.262 later proposed that partial gra-phene wrapping of LiFePO4 provided a balance between theelectron transport and ion diffusion. Hu et al.263 coated LiFePO4

with 2 wt% of electrochemically exfoliated graphene layers, andachieved a capacity of 208 mA h g�1. Graphene has also beenadded in the cathode material of Na-ion batteries to enhancethe electric conductivity. As reported by Rui et al.,264 a cathode ofcarbon coated Na3V2(PO4)3 (NVP) in a porous graphene networkdelivered a rate capability of 86mA h g�1 at a rate of 100C as wellas a cycling performance of 64% retention aer 10 000 cycles at100C.

3.2.2 2D materials as the cathode material for Li/Na-ionbatteries. With a layered structure and a strong adsorptionenergy towards lithium, MoO3 has been explored for its prop-erties as a Li-ion cathode with different dimensions: the 3Dbulk, 2D double-layer, 2D monolayer and 1D nanoribbon.265

From DFT calculations, lowering the dimension of MoO3 couldeffectively increase the theoretical capacity (from 186 mA h g�1

J. Mater. Chem. A, 2017, 5, 3735–3758 | 3747

Fig. 9 EIS of the graphene nanosheet induced cell (GN) and commercial cells. Top: EIS of the two cells (the experimental profiles are fitted usingthe equivalent circuit inset). Bottom: Schematics of Li+ ion transport in the cathode sheet (Left: GN cell; Right: commercial cell).261 Reproducedfrom ref. 261 (Copyright 2012, Elsevier).


for 3D bulk to 434 mA h g�1 for 1D nanoribbons) and decreasethe lithium migration energy barrier. V2O5 is another popularchoice for the cathode material of Li/Na-ion batteries. Fromrst-principles calculations, it has been predicted that whenexfoliated into monolayers, V2O5 can provide a capacity as highas 274 mA h g�1 (Li2V2O5) for lithium ions and 235 mA h g�1

(Na2V2O5) for sodium ions, with an average voltage of 2.06 V forlithium ions and 1.86 V for sodium ions, respectively. Moreimportantly, it has been found that the sodium ion migrationenergy barrier can be reduced from 1.17 eV in V2O5 bulk to0.44 eV on the V2O5 monolayer, making the V2O5 monolayer anattractive choice for the cathode of Na-ion batteries.266 Leonget al.267 explored other possible 2D TMOs, MnO2, CoO2 and NiO2

as cathode materials for Li/Na-ion batteries using DFT calcu-lations and found that all of these materials provided largecapacities, good rate capabilities and high discharge voltages.

Experimentally, Menoza-Sanchez et al.268 synthesized 2D-MoO3 nanosheets via liquid-phase exfoliation successfully, andfabricated a 2D-MoO3/SWCNT (single-wall CNT) composite (85wt%/15 wt%) to be used as the cathode of Li-ion batteries. Acapacity of 123.0 mA h g�1 at 100 mA g�1 has been delivered. By

3748 | J. Mater. Chem. A, 2017, 5, 3735–3758

liquid exfoliation, Rui et al.120 fabricated few-layered V2O5

nanosheets with a thickness of 2.1–3.8 nm as shown in Fig. 10b.When being used as the cathode of Li-ion batteries, as shown inFig. 10c and d, the exfoliated V2O5 nanosheets exhibited muchbetter electrochemical performance compared with the V2O5

bulk cathode. Li et al.269 synthesized a leaf-like V2O5 nanosheetcathode for lithium-ion batteries, and achieved a capacity of294 mA h g�1 under a current density of 50 mA h g�1. V2O5

nanosheets have also been prepared successfully via the sol–gelmethod, and demonstrated improved performance serving asthe lithium ion cathode compared with commercial V2O5

powders.270 The performance of 2D V2O5 as the cathode of Na-ionbatteries has as well been investigated. Su andWang271 synthesizedsingle-crystalline bi-layered V2O5 nanobelts with enlarged d-spacing of the {001} planes. When applied as the cathode materialin Na-ion batteries, the V2O5 nanobelts delivered a capacity of 231.4mA h g�1 at a current density of 80 mA g�1. Zhu et al.272 fabricateda sponge-like V2O5 cathode material self-assembled by V2O5

nanosheets for Na-ion batteries, and a capacity of 216 mA h g�1 at20 mA g�1 has been achieved. To improve the electronic conduc-tivity, various kinds of V2O5/carbon composites have been


Fig. 10 (a) A schematic of lithiation processes for bulk V2O5 versus {001}-oriented few-layer V2O5 nanosheets; (b) TEM image of ultrathin V2O5

nanosheets; (c) initial galvanostatic charge–discharge voltage profiles of ultrathin V2O5 nanosheets and bulk V2O5 cathode at a current density of59 mA g�1 (0.2C); (d) rate capability of ultrathin V2O5 nanosheets and bulk V2O5 cathode at various charge and discharge rates.120 Reproducedfrom ref. 120 (Copyright 2013, Royal Society of Chemistry).


fabricated as the cathode of Li/Na-ion batteries. Different carbonmaterials such as rGO,273,274 CNT,275,276 carbon nanosheets277 andnanoporous carbon278 have been tested to composite with 2D V2O5

to serve as the cathode of Li/Na-ion batteries, and all of which havedemonstrated enhanced electrochemical performance comparedwith pristine 2D V2O5. Chao et al.279 fabricated a 3D hierarchicalstructure by growing V2O5 nanobelt arrays on 3D ultrathin graphitefoam, and then coated the V2O5 with a mesoporous thin layer ofconducting PEDOT. Extraordinary rate capability (265 mA h g�1 at5C and 168 mA h g�1 at 60C) and cycle stability (98% capacityretention aer 1000 cycles) have been demonstrated when usingthis 3D hierarchical structure as the cathode of Li-ion batteries. 2DVO2(B), a metastable monoclinic phase of vanadium oxide, hasalso been explored as the cathode of Li/Na-ion batteries. Nethra-vathi et al.280 fabricated a N-doped graphene–VO2(B) nanosheetbuilt 3D ower hybrid, which exhibited a capacity of 419 mA h g�1

at 0.05 A g�1 when being tested as the cathode of Li-ion batteries.Yang et al.281 synthesized a VO2 ribbon and graphene composite viaa simple hydrothermal and chemical reduction procedure. Excel-lent rate capability and cycle stability (90% capacity retention aer1000 cycles at 190C rate) have been achieved when using thiscomposite as the cathode of Li-ion batteries. Chao et al.282 designeda new structure by growing biface VO2 arrays on the graphenenetwork and coating graphene quantum dots on the VO2 surfaces.Excellent electrochemical performances have been observed when


employing the composite as the cathode of both Li-ion and Na-ionbatteries.

4. 2D materials in Li/Na–O2 batteries4.1 2D materials for lithium metal anodes

Lithiummetal anodes have long been regarded as the holy grailof anode materials for their highest theoretical capacity andlowest electrochemical potential. However, the application oflithium metal anodes has been severely hindered by the long-standing problem of dendrite growth, causing poor cyclestability and safety concern for real applications. To suppressdendrite formation, different strategies have been proposedsuch as building a lithium deposition scaffold,26,283 addingselected cations to provide an electrostatic shield24 and addinginterfacial layers to avoid direct contact between lithium andthe electrolyte.27,284–286

2D materials have been proposed to be used as both thelithium deposition scaffold and the interfacial layer, owing totheir large surface areas. Lin et al.283 fabricated a composite ofa lithium metal anode with 7 wt% lithiophilic layered rGO andnanoscale gaps to act as the host. The dimension variationduring the cycling process was effectively reduced to 20%. Kimet al.284 tried to coat multilayered graphene (MLG) on thesurface of the lithium metal anode to separate the SEI

J. Mater. Chem. A, 2017, 5, 3735–3758 | 3749

Fig. 11 Schematic diagrams of lithium deposition. (a) Deposition of Limetal on a bare copper substrate. A large number of Li dendrites wouldgrow because of the lack of confinement. Spontaneously formed SEIlayers with certain weak spots trigger ramified growth of lithiumdendrite, resulting in significant consumption of the electrolyte as wellas safety issues. (b) The sub-nanometer defects in the h-BN film grownon copper serve as channels for lithium ions during lithium deposition.Lithium is deposited between h-BN and copper. The stiff B–N bondand chemical stability prevent dendrite formation and lithium corro-sion, respectively.27 Reproduced from ref. 27 (Copyright 2014, Amer-ican Chemistry Society).


formation from lithium dendrites. Similarly, Yan et al.27

proposed a concept of using 2D atomic crystal layers as aninterfacial layer to suppress dendrite growth, as shown inFig. 11. Several atomic layers of h-BN were deposited on thecurrent collector, which effectively separated the electrolyte andlithium metal while lithium ions were able to diffuse into theinterface between h-BN and copper via the atomic defects. Thehigh stiffness as well as the insulating nature and chemicalstability of h-BN signicantly prevented dendrite growth andcorrosion. Luo et al.285 subsequently developed a h-BN nano-sheet coated separator, where the h-BN nanosheet was addi-tionally found to be a good thermal conductor, effectivelydissipating heat generated during the reactions. Shin et al.287

fabricated N- and S-codoped graphene coated on a polyethyleneseparator, which also effectively suppressed dendrite formation.

4.2 2D materials as the catalytic cathode for Li/Na–O2

batteries

At the cathode of Li/Na–O2 batteries, oxygen will obtain elec-trons and combine with lithium or sodium ions to form thesolid state discharge product Li2O2 or NaO2/Na2O2. The exis-tence of these discharge products slows down reaction kineticsof Li/Na–O2 batteries, and efforts have been focused on identi-fying effective catalysts. Graphene is the rst 2D material thathas been explored as a catalytic cathode for Li/Na–O2 batteries.In 2014, Ren et al.54 predicted that the B-doped grapheneeffectively lowered the overpotential during the OER process ofnon-aqueous Li–O2 batteries by enhancing the charge transferfrom Li2O2 to the cathode. Jing and Zhou55 investigated the ORRand initial Li2O2 nucleation processes on the surfaces of

3750 | J. Mater. Chem. A, 2017, 5, 3735–3758

pristine and N-doped graphene in Li–O2 batteries using DFTcalculations and revealed that the in-plane pyridinic N-dopedgraphene is more effective in facilitating the nucleation ofLi2O2 clusters than pristine or graphitic N-doped graphene. Ourgroup288 further considered the situations of B-doped, N-dopedand B-, N-co-doped graphene as the catalytic cathode for non-aqueous Li–O2 batteries and found that the B-doped caseshowed the best catalytic activity. Experimentally, Wu et al.51

synthesized N-doped graphene with a sheet-like structure underthe catalysis of a cobalt species using MWCNTs as the sup-porting template. This composite substantially improved theORR catalytic activity in non-aqueous Li–O2 batteries. Our groupalso studied the inuence of defects in graphene structurestoward its catalytic activity for the ORR and OER in both Li–O2

(ref. 289) and Na–O2 (ref. 290) batteries, and the calculationsindicate that the intrinsic defects play a positive role in theORR/OER process. Liu et al.52 experimentally demonstrated thatgraphene nanosheets were viable as the catalytic oxygen elec-trode for Na–O2 batteries, showing good electrochemicalperformance.

In 2014, silicene was predicted to be an effective catalyticmaterial in Li–O2 batteries without doping or the addition ofdefects via rst-principles calculations.291 In 2015, Liao et al.56

prepared 2D conductive RuO2 nanosheets via exfoliation of thelamellar NaRuO2 as shown in Fig. 12a. When using the obtainednanosheets as the cathode material for non-aqueous Li–O2

batteries, low charge overpotential at high current density andgood cycle performance were achieved as shown in Fig. 12b.Subsequent to this work, our group investigated the catalyticmechanism of the RuO2 monolayer toward the ORR and OER innon-aqueous Li–O2 batteries. We found that the strongadsorption between the RuO2 monolayer and Li2O2 attractedremaining Li2O2 to the catalytic surface during the OER processand was responsible for enhanced catalytic activity.292 Liuet al.293 proposed that the d-MnO2 monolayer can act as aneffective catalyst toward the ORR in non-aqueous Li–O2

batteries and create a thin lm morphology of the dischargeproduct.

5. 2D materials in Li–S batteries

Similar to the concept of Li–O2 batteries, Li–S batteries also relyon a lithium metal anode. At the cathode, sulfur reduces intoLi2S where the energy is stored. While both sulfur and Li2S aresolid state, a chain of soluble intermediate lithium polysuldeswill be generated during the reactions. The dissolution of thesepolysuldes into the electrolyte will cause severe capacity decay.Effective anchoring materials that conne lithium polysuldesin the cathode are indispensable.294,295 Thus, 2D materials thatexhibit a large surface area have become a popular choice. In2015, Zhang et al.58 systematically investigated the adsorption ofLi2Sn on various 2D layered materials (oxides, suldes andchlorides) as shown in Fig. 13. They found that the anchoring ofLi2Sn was always accompanied by soening of the Li–S bond,and if the binding strength is too strong, the structure of Li2Snwill be destroyed. Thus anchoring materials with moderatebinding strengths are preferred. Zhao et al.296 studied the


Fig. 12 (a) SEM images of the cell with a RuO2 nanosheet cathode,56 (b) the first cycle discharge–charge behavior of the RuO2 nanosheetcathode at a current density of 200 mA g�1 (ref. 56) and (c) proposed catalytic mechanism of RuO2 nanosheets during the OER process of non-aqueous Li–O2 batteries.292 Reproduced from ref. 56 (Copyright 2015, Royal Society of Chemistry) and ref. 291 (Copyright 2016, AmericanChemistry of Society).

Fig. 13 (a) Binding energies for Li–S composites at four different lithiation stages (S8, Li2S6, Li2S4, and Li2S2) on different anchoring materialsselected. (b) Li–S clusters' conformations on TiS2 with vdW functional.58 Reproduced from ref. 58 (Copyright 2015, American Chemistry Society).


adsorption of Li2Sn on phosphorene, and found that phos-phorene is suitable to be used as an anchoring material for Li–Sbatteries with intermediate adsorption energies.

Graphene-based materials have been tested as anchoringmaterials experimentally. In 2011, Wang et al.297 coated sub-micrometer sulfur particles with polyethylene glycol (PEG)and then wrapped it using mildly oxidized GO sheets decoratedby carbon black particles, where graphene and PEGwere used toaccommodate the volume changes of sulfur particles, trap thepolysuldes and enhance the electric conductivity. Many othergraphene-based materials such as GO,298,299 rGO,300–303 and gra-phene doped with B-304 and N-305 were explored as anchoringmaterials thereaer. Results have shown enhanced batteryperformance. Seh et al.57 also attempted to use 2D TMDs to


encapsulate the Li2S cathode, and found that cathodes wrappedwith TiS2 were able to deliver a high specic capacity.

6. Summary and outlook

In this article, we comprehensively reviewed recent progress ofapplying 2D materials in Li/Na-based batteries. With theoutstanding surface-to-mass ratio and unique physical/chemical properties, 2D materials are able to provide anextensive library of additional candidates for broad applicationsin Li/Na-based batteries. Studies using these materials as theelectrodes or additives for Li/Na-ion batteries, the hostingscaffold or interfacial layer for the lithium metal anode, thecatalytic material for the Li/Na–O2 cathode and the anchoringmaterials for Li–S batteries have been summarized in this

J. Mater. Chem. A, 2017, 5, 3735–3758 | 3751


review. Signicant improvements in battery performances havebeen reported with the employment of these 2D materials.

Although great progress has been made in the area ofproducing 2D materials and applying them to Li/Na-basedbatteries, many critical challenges still remain. Until now, reli-able mass production method to prepare 2D materials withhigh quality is still lacking. For some new 2D materials, such assilicene, borophene and stanene, the isolation of free-standing2D structures is still a big challenge. Facile liquid exfoliationand wet chemical approaches may provide solution for futurelarge scale production of 2D materials. Scalable optimizedsynthesis procedures to provide 2D materials with desiredquality and morphology are urgently needed.

When employing 2D materials in the Li/Na-based batterysystem, some detailed chemistries, such as the surface chem-istries of MXenes and the reaction mechanisms when employ-ing TMDs as the anode material for Li/Na-ion batteries, are stillfar from clear. Fundamental understanding on the structure–electrochemical property relationship and the interfacial reac-tions is still lacking. Efforts from both experimental andcomputational aspects, such as in situ atomic scale observationsand massive atomic/electronic scale simulations, are expectedto elucidate the detailed physical/chemical processes and toprovide guidance for future material design.

Although 2D materials possess high surface areas, theytypically show a high volume-to-mass ratio, which will lead toa low volumetric energy density when being used as the elec-trode material for Li/Na-ion batteries. During operation, 2Dmaterials are easily restacked or agglomerated, thus resulting ininferior cycling stability. In addition, the large surface areacould cause the signicant formation of a solid electrolyteinterphase (SEI), which will passivate the active sites and result inperformance decay. Rational design of hybrid nanostructuresmayprovide solutions to these problems. Much success has beenachieved in designing and fabricating graphene-based nano-composites to be used as the electrode materials for Li/Na-ionbatteries, where graphene can provide better electric conduc-tivity and mechanical strength, and simultaneously preventnanoparticle/nanosheet agglomeration or restacking. The forma-tion of a hybrid structure will also reduce the contact area betweenthe active materials and electrolyte, effectively inhibiting theformation of an excess SEI. Recently, emerging research interestshave been focused on the area of van der Waals heterostructures,which are composed of different kinds of 2D materials stackedtogether.306–309 Thismay provide new insights into the applicationsof 2D materials in Li/Na-based batteries.

In conclusion, the application of 2Dmaterials in Li/Na-basedbatteries is still at an early stage, and the current laboratoryresearches are still far from industrial manufacturing. Thecontinuous discovery of 2D materials provided new choices forthe building components of Li/Na-based batteries and hasdemonstrated their potential to contribute to better batteryperformance. In the future, by addressing the challengesmentioned above, Li/Na-based batteries with larger capacity,higher rate capability, longer cycle life and lower price can beexpected.

3752 | J. Mater. Chem. A, 2017, 5, 3735–3758

Acknowledgements

The work described in this paper was fully supported by a grantfrom the Research Grants Council of the Hong Kong SpecialAdministrative Region, China (Project No. 16213414).

References

1 V. Etacheri, R. Marom, R. Elazari, G. Salitra and D. Aurbach,Energy Environ. Sci., 2011, 4, 3243–3262.

2 S. Goriparti, E. Miele, F. De Angelis, E. Di Fabrizio,R. P. Zaccaria and C. Capiglia, J. Power Sources, 2014, 257,421–443.

3 P. Harks, F. Mulder and P. Notten, J. Power Sources, 2015,288, 92–105.

4 J. W. Fergus, J. Power Sources, 2010, 195, 939–954.5 S. B. Chikkannanavar, D. M. Bernardi and L. Liu, J. PowerSources, 2014, 248, 91–100.

6 Y. Deng, L. Wan, Y. Xie, X. Qin and G. Chen, RSC Adv., 2014,4, 23914.

7 B. Xu, D. Qian, Z. Wang and Y. S. Meng, Mater. Sci. Eng., R,2012, 73, 51–65.

8 M. Reddy, G. Subba Rao and B. Chowdari, Chem. Rev., 2013,113, 5364–5457.

9 H. Wu and Y. Cui, Nano Today, 2012, 7, 414–429.10 M. Ge, X. Fang, J. Rong and C. Zhou, Nanotechnology, 2013,

24, 422001.11 M. T. McDowell, S. W. Lee, W. D. Nix and Y. Cui, Adv. Mater.,

2013, 25, 4966–4985.12 M. Noh, Y. Kwon, H. Lee, J. Cho, Y. Kim and M. G. Kim,

Chem. Mater., 2005, 17, 1926–1929.13 A. R. Kamali and D. J. Fray, Rev. Adv. Mater. Sci., 2011, 27,

14–24.14 W. J. Zhang, J. Power Sources, 2011, 196, 13–24.15 P. Meduri, C. Pendyala, V. Kumar, G. U. Sumanasekera and

M. K. Sunkara, Nano Lett., 2009, 9, 612–616.16 G. Kucinskis, G. Bajars and J. Kleperis, J. Power Sources,

2013, 240, 66–79.17 Y. C. Lu, B. M. Gallant, D. G. Kwabi, J. R. Harding,

R. R. Mitchell, M. S. Whittingham and Y. Shao-Horn,Energy Environ. Sci., 2013, 6, 750–768.

18 G. Girishkumar, B. McCloskey, A. Luntz, S. Swanson andW. Wilcke, J. Phys. Chem. Lett., 2010, 1, 2193–2203.

19 P. G. Bruce, S. A. Freunberger, L. J. Hardwick andJ. M. Tarascon, Nat. Mater., 2012, 11, 19–29.

20 Y. X. Yin, S. Xin, Y. G. Guo and L. J. Wan, Angew. Chem., Int.Ed., 2013, 52, 13186–13200.

21 A. Manthiram, Y. Fu, S. H. Chung, C. Zu and Y. S. Su, Chem.Rev., 2014, 114, 11751–11787.

22 D. Bresser, S. Passerini and B. Scrosati, Chem. Commun.,2013, 49, 10545–10562.

23 W. Xu, J. Wang, F. Ding, X. Chen, E. Nasybulin, Y. Zhangand J. G. Zhang, Energy Environ. Sci., 2014, 7, 513–537.

24 F. Ding, W. Xu, G. L. Graff, J. Zhang, M. L. Sushko, X. Chen,Y. Shao, M. H. Engelhard, Z. Nie, J. Xiao and X. Liu, J. Am.Chem. Soc., 2013, 135, 4450–4456.



25 J. Qian, W. A. Henderson, W. Xu, P. Bhattacharya,M. Engelhard, O. Borodin and J. G. Zhang, Nat. Commun.,2015, 6, 6362.

26 G. Zheng, S. W. Lee, Z. Liang, H. W. Lee, K. Yan, H. Yao,H. Wang, W. Li, S. Chu and Y. Cui, Nat. Nanotechnol.,2014, 9, 618–623.

27 K. Yan, H. W. Lee, T. Gao, G. Zheng, H. Yao, H. Wang, Z. Lu,Y. Zhou, Z. Liang, Z. Liu and S. Chu, Nano Lett., 2014, 14,6016–6022.

28 L. Shi and T. Zhao, Sci. Bull., 2014, 60, 281–282.29 L. Shi, T. Zhao, A. Xu and Z. Wei, ACS Catal., 2016, 6, 6285–

6293.30 E. Yilmaz, C. Yogi, K. Yamanaka, T. Ohta and H. R. Byon,

Nano Lett., 2013, 13, 4679–4684.31 J. Zhu, F. Wang, B. Wang, Y. Wang, J. Liu, W. Zhang and

Z. Wen, J. Am. Chem. Soc., 2015, 137, 13572–13579.32 M. D. Radin, C. W. Monroe and D. J. Siegel, Chem. Mater.,

2015, 27, 839–847.33 Y. V. Mikhaylik and J. R. Akridge, J. Electrochem. Soc., 2004,

151, A1969–A1976.34 A. Manthiram, Y. Fu and Y. S. Su, Acc. Chem. Res., 2012, 46,

1125–1134.35 B. L. Ellis and L. F. Nazar, Curr. Opin. Solid State Mater. Sci.,

2012, 16, 168–177.36 M. D. Slater, D. Kim, E. Lee and C. S. Johnson, Adv. Funct.

Mater., 2013, 23, 947–958.37 N. Yabuuchi, K. Kubota, M. Dahbi and S. Komaba, Chem.

Rev., 2014, 114, 11636–11682.38 C. Xia, R. Black, R. Fernandes, B. Adams and L. F. Nazar,

Nat. Chem., 2015, 7, 496–501.39 H. Yadegari, M. N. Banis, B. Xiao, Q. Sun, X. Li,

A. Lushington, B. Wang, R. Li, T. K. Sham, X. Cui andX. Sun, Chem. Mater., 2015, 27, 3040–3047.

40 K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang,Y. Zhang, S. V. Dubonos, I. V. Grigorieva and A. A. Firsov,Science, 2004, 306, 666–669.

41 R. Ma and T. Sasaki, Adv. Mater., 2010, 22, 5082–5104.42 R. Mas-Balleste, C. Gomez-Navarro, J. Gomez-Herrero and

F. Zamora, Nanoscale, 2011, 3, 20–30.43 X. Zhang and Y. Xie, Chem. Soc. Rev., 2013, 42, 8187–8199.44 V. Nicolosi, M. Chhowalla, M. G. Kanatzidis, M. S. Strano

and J. N. Coleman, Science, 2013, 340, 1226419.45 Y. Jing, Z. Zhou, C. R. Cabrera and Z. Chen, J. Mater. Chem.

A, 2014, 2, 12104–12122.46 H. Wang, H. Feng and J. Li, Small, 2014, 10, 2165–2181.47 X. Zhang, L. Hou, A. Ciesielski and P. Samorı, Adv. Energy

Mater., 2016, 6, 1600671.48 B. Mendoza-Sanchez and Y. Gogotsi, Adv. Mater., 2016, 28,

6104–6135.49 P. Kumar, H. Abuhimd, W. Wahyudi, M. Li, J. Ming and

L. J. Li, ECS J. Solid State Sci. Technol., 2016, 5, Q3021–Q3025.

50 C. Huo, Z. Yan, X. Song and H. Zeng, Sci. Bull., 2015, 60,1994–2008.

51 G. Wu, N. H. Mack, W. Gao, S. Ma, R. Zhong, J. Han,J. K. Baldwin and P. Zelenay, ACS Nano, 2012, 6, 9764–9776.


52 W. Liu, Q. Sun, Y. Yang, J. Y. Xie and Z. W. Fu, Chem.Commun., 2013, 49, 1951–1953.

53 D. Higgins, Z. Chen, D. U. Lee and Z. Chen, J. Mater. Chem.A, 2013, 1, 2639–2645.

54 X. Ren, J. Zhu, F. Du, J. Liu and W. Zhang, J. Phys. Chem. C,2014, 118, 22412–22418.

55 Y. Jing and Z. Zhou, ACS Catal., 2015, 5, 4309–4317.56 K. Liao, X. Wang, Y. Sun, D. Tang, M. Han, P. He, X. Jiang,

T. Zhang and H. Zhou, Energy Environ. Sci., 2015, 8, 1992–1997.

57 Z. W. Seh, J. H. Yu, W. Li, P. C. Hsu, H. Wang, Y. Sun,H. Yao, Q. Zhang and Y. Cui, Nat. Commun., 2014, 5, 5017.

58 Q. Zhang, Y. Wang, Z. W. Seh, Z. Fu, R. Zhang and Y. Cui,Nano Lett., 2015, 15, 3780–3786.

59 V. Chabot, D. Higgins, A. Yu, X. Xiao, Z. Chen and J. Zhang,Energy Environ. Sci., 2014, 7, 1564–1596.

60 W. S. Hummers Jr and R. E. Offeman, J. Am. Chem. Soc.,1958, 80, 1339.

61 D. C. Marcano, D. V. Kosynkin, J. M. Berlin, A. Sinitskii,Z. Sun, A. Slesarev, L. B. Alemany, W. Lu and J. M. Tour,ACS Nano, 2010, 4, 4806–4814.

62 J. Chen, B. Yao, C. Li and G. Shi, Carbon, 2013, 64, 225–229.63 J. Kim, L. J. Cote and J. Huang, Acc. Chem. Res., 2012, 45,

1356–1364.64 D. R. Dreyer, S. Park, C. W. Bielawski and R. S. Ruoff, Chem.

Soc. Rev., 2010, 39, 228–240.65 C. Gomez-Navarro, R. T. Weitz, A. M. Bittner, M. Scolari,

A. Mews, M. Burghard and K. Kern, Nano Lett., 2007, 7,3499–3503.

66 O. C. Compton and S. T. Nguyen, Small, 2010, 6, 711–723.67 C. Gomez-Navarro, J. C. Meyer, R. S. Sundaram, A. Chuvilin,

S. Kurasch, M. Burghard, K. Kern and U. Kaiser, Nano Lett.,2010, 10, 1144–1148.

68 M. Houssa, A. Dimoulas and A. Molle, J. Phys.: Condens.Matter, 2015, 27, 253002.

69 J. Zhao, H. Liu, Z. Yu, R. Quhe, S. Zhou, Y. Wang, C. C. Liu,H. Zhong, N. Han, J. Lu and Y. Yao, Prog. Mater. Sci., 2016,83, 24–151.

70 N. J. Roome and J. D. Carey, ACS Appl. Mater. Interfaces,2014, 6, 7743–7750.

71 S. Balendhran, S. Walia, H. Nili, S. Sriram andM. Bhaskaran, Small, 2015, 11, 640–652.

72 P. Vogt, P. De Padova, C. Quaresima, J. Avila,E. Frantzeskakis, M. C. Asensio, A. Resta, B. Ealet andG. Le Lay, Phys. Rev. Lett., 2012, 108, 155501.

73 M. Davila, L. Xian, S. Cahangirov, A. Rubio and G. Le Lay,New J. Phys., 2014, 16, 095002.

74 F. F. Zhu, W. J. Chen, Y. Xu, C. L. Gao, D. D. Guan, C. H. Liu,D. Qian, S. C. Zhang and J. F. Jia, Nat. Mater., 2015, 14,1020–1025.

75 L. Kou, C. Chen and S. C. Smith, J. Phys. Chem. Lett., 2015, 6,2794–2805.

76 Y. Jing, X. Zhang and Z. Zhou, WIREs ComputationalMolecular Science, 2016, 6, 5–19.

77 P. Li and I. Appelbaum, Phys. Rev. B: Condens. Matter Mater.Phys., 2014, 90, 115439.

J. Mater. Chem. A, 2017, 5, 3735–3758 | 3753


78 H. Liu, A. T. Neal, Z. Zhu, Z. Luo, X. Xu, D. Tomanek andP. D. Ye, ACS Nano, 2014, 8, 4033–4041.

79 G. Schusteritsch, M. Uhrin and C. J. Pickard, Nano Lett.,2016, 16, 2975–2980.

80 Z. A. Piazza, H. S. Hu, W. L. Li, Y. F. Zhao, J. Li andL. S. Wang, Nat. Commun., 2014, 5, 3113.

81 W. L. Li, Q. Chen, W. J. Tian, H. Bai, Y. F. Zhao, H. S. Hu,J. Li, H. J. Zhai, S. D. Li and L. S. Wang, J. Am. Chem. Soc.,2014, 136, 12257–12260.

82 Y. Liu, E. S. Penev and B. I. Yakobson, Angew. Chem., Int.Ed., 2013, 52, 3156–3159.

83 S. Banerjee, G. Periyasamy and S. K. Pati, J. Mater. Chem. A,2014, 2, 3856–3864.

84 A. J. Mannix, X. F. Zhou, B. Kiraly, J. D. Wood, D. Alducin,B. D. Myers, X. Liu, B. L. Fisher, U. Santiago, J. R. Guestand M. J. Yacaman, Science, 2015, 350, 1513–1516.

85 B. Feng, J. Zhang, Q. Zhong, W. Li, S. Li, H. Li, P. Cheng,S. Meng, L. Chen and K. Wu, Nat. Chem., 2016, 8, 563–568.

86 H. Shu, F. Li, P. Liang and X. Chen, Nanoscale, 2016, 8,16284–16291.

87 M. Osada and T. Sasaki, J. Mater. Chem., 2009, 19, 2503–2511.

88 M. Osada and T. Sasaki, ECS Trans., 2013, 50, 111–116.89 L. Wang and T. Sasaki, Chem. Rev., 2014, 114, 9455–9486.90 R. Lv, J. A. Robinson, R. E. Schaak, D. Sun, Y. Sun,

T. E. Mallouk and M. Terrones, Acc. Chem. Res., 2014, 48,56–64.

91 M. Chhowalla, H. S. Shin, G. Eda, L. J. Li, K. P. Loh andH. Zhang, Nat. Chem., 2013, 5, 263–275.

92 H. Wang, H. Yuan, S. S. Hong, Y. Li and Y. Cui, Chem. Soc.Rev., 2015, 44, 2664–2680.

93 A. Y. S. Eng, A. Ambrosi, Z. Sofer, P. Simek and M. Pumera,ACS Nano, 2014, 8, 12185–12198.

94 D. Jariwala, V. K. Sangwan, L. J. Lauhon, T. J. Marks andM. C. Hersam, ACS Nano, 2014, 8, 1102–1120.

95 M. Pumera, Z. Sofer and A. Ambrosi, J. Mater. Chem. A, 2014,2, 8981–8987.

96 X. Chia, A. Y. S. Eng, A. Ambrosi, S. M. Tan and M. Pumera,Chem. Rev., 2015, 115, 11941–11966.

97 H. Li, Y. Shi, M. H. Chiu and L. J. Li, Nano Energy, 2015, 18,293–305.

98 M. Naguib, V. N. Mochalin, M. W. Barsoum and Y. Gogotsi,Adv. Mater., 2014, 26, 992–1005.

99 J. C. Lei, X. Zhang and Z. Zhou, Front. Phys., 2015, 10, 276–286.

100 M. Khazaei, M. Arai, T. Sasaki, C. Y. Chung,N. S. Venkataramanan, M. Estili, Y. Sakka andY. Kawazoe, Adv. Funct. Mater., 2013, 23, 2185–2192.

101 Y. Lin and J. W. Connell, Nanoscale, 2012, 4, 6908–6939.102 A. Nag, K. Raidongia, K. P. Hembram, R. Datta,

U. V. Waghmare and C. Rao, ACS Nano, 2010, 4, 1539–1544.103 H. Zeng, C. Zhi, Z. Zhang, X. Wei, X. Wang, W. Guo,

Y. Bando and D. Golberg, Nano Lett., 2010, 10, 5049–5055.104 L. Liu, Y. Feng and Z. Shen, Phys. Rev. B: Condens. Matter

Mater. Phys., 2003, 68, 104102.105 C. R. Dean, A. F. Young, I. Meric, C. Lee, L. Wang,

S. Sorgenfrei, K. Watanabe, T. Taniguchi, P. Kim,

3754 | J. Mater. Chem. A, 2017, 5, 3735–3758

K. Shepard and J. Hone, Nat. Nanotechnol., 2010, 5, 722–726.

106 J. M. Garcia, U. Wurstbauer, A. Levy, L. N. Pfeiffer,A. Pinczuk, A. S. Plaut, L. Wang, C. R. Dean, R. Buizza,A. M. Van Der Zande and J. Hone, Solid State Commun.,2012, 152, 975–978.

107 H. L. Zhuang, A. K. Singh and R. G. Hennig, Phys. Rev. B:Condens. Matter Mater. Phys., 2013, 87, 165415.

108 A. K. Singh and R. G. Hennig, Appl. Phys. Lett., 2014, 105,042103.

109 H. Zhou, M. Zhao, X. Zhang, W. Dong, X. Wang, H. Bu andA. Wang, J. Phys.: Condens. Matter, 2013, 25, 395501.

110 J. H. Yang, Y. Zhang, W. J. Yin, X. Gong, B. I. Yakobson andS. H. Wei, Nano Lett., 2016, 16, 1110–1117.

111 D. Lembke, S. Bertolazzi and A. Kis, Acc. Chem. Res., 2015,48, 100–110.

112 Y. Yao, Z. Lin, Z. Li, X. Song, K. S. Moon and C. P. Wong, J.Mater. Chem., 2012, 22, 13494–13499.

113 Z. Wu, B. Fang, A. Bonakdarpour, A. Sun, D. P. Wilkinsonand D. Wang, Appl. Catal., B, 2012, 125, 59–66.

114 I. Y. Jeon, H. J. Choi, S. M. Jung, J. M. Seo, M. J. Kim, L. Daiand J. B. Baek, J. Am. Chem. Soc., 2012, 135, 1386–1393.

115 G. Cunningham, M. Lotya, C. S. Cucinotta, S. Sanvito,S. D. Bergin, R. Menzel, M. S. Shaffer and J. N. Coleman,ACS Nano, 2012, 6, 3468–3480.

116 X. Fan, P. Xu, D. Zhou, Y. Sun, Y. C. Li, M. A. Nguyen,M. Terrones and T. E. Mallouk, Nano Lett., 2015, 15,5956–5960.

117 Z. Zeng, C. Tan, X. Huang, S. Bao and H. Zhang, EnergyEnviron. Sci., 2014, 7, 797–803.

118 A. H. Loo, A. Bonanni, Z. Sofer andM. Pumera, Electrochem.Commun., 2015, 50, 39–42.

119 J. Feng, X. Sun, C. Wu, L. Peng, C. Lin, S. Hu, J. Yang andY. Xie, J. Am. Chem. Soc., 2011, 133, 17832–17838.

120 X. Rui, Z. Lu, H. Yu, D. Yang, H. H. Hng, T. M. Lim andQ. Yan, Nanoscale, 2013, 5, 556–560.

121 M. Naguib, M. Kurtoglu, V. Presser, J. Lu, J. Niu, M. Heon,L. Hultman, Y. Gogotsi and M. W. Barsoum, Adv. Mater.,2011, 23, 4248–4253.

122 M. Naguib, O. Mashtalir, J. Carle, V. Presser, J. Lu,L. Hultman, Y. Gogotsi and M. W. Barsoum, ACS Nano,2012, 6, 1322–1331.

123 Y. Zhang, L. Zhang and C. Zhou, Acc. Chem. Res., 2013, 46,2329–2339.

124 J. C. Shaw, H. Zhou, Y. Chen, N. O. Weiss, Y. Liu, Y. Huangand X. Duan, Nano Res., 2014, 7, 511–517.

125 D. Kong, H. Wang, J. J. Cha, M. Pasta, K. J. Koski, J. Yao andY. Cui, Nano Lett., 2013, 13, 1341–1347.

126 Y. Zhan, Z. Liu, S. Najmaei, P. M. Ajayan and J. Lou, Small,2012, 8, 966–971.

127 S. Eigler, M. Enzelberger-Heim, S. Grimm, P. Hofmann,W. Kroener, A. Geworski, C. Dotzer, M. Rockert, J. Xiao,C. Papp and O. Lytken, Adv. Mater., 2013, 25, 3583–3587.

128 C. Tan and H. Zhang, Nat. Commun., 2015, 6, 7873.129 C. Altavilla, M. Sarno and P. Ciambelli, Chem. Mater., 2011,

23, 3879–3885.



130 S. W. Kim, D. H. Seo, X. Ma, G. Ceder and K. Kang, Adv.Energy Mater., 2012, 2, 710–721.

131 J. Liu, Nat. Nanotechnol., 2014, 9, 739–741.132 D. Wu, Y. Li and Z. Zhou, Theor. Chem. Acc., 2011, 130, 209–

213.133 X. Fan, W. Zheng and J. L. Kuo, ACS Appl. Mater. Interfaces,

2012, 4, 2432–2438.134 O. I. Malyi, K. Sopiha, V. V. Kulish, T. L. Tan, S. Manzhos

and C. Persson, Appl. Surf. Sci., 2015, 333, 235–243.135 C. Uthaisar, V. Barone and J. E. Peralta, J. Appl. Phys., 2009,

106, 113715.136 C. Uthaisar and V. Barone, Nano Lett., 2010, 10, 2838–2842.137 L. J. Zhou, Z. Hou and L. M. Wu, J. Phys. Chem. C, 2012, 116,

21780–21787.138 Y. X. Yu, Phys. Chem. Chem. Phys., 2013, 15, 16819–16827.139 X. K. Kong and Q. W. Chen, Phys. Chem. Chem. Phys., 2013,

15, 12982–12987.140 L. Zhou, Z. Hou, B. Gao and T. Frauenheim, J. Mater. Chem.

A, 2016, 4, 13407–13413.141 C. Ling and F. Mizuno, Phys. Chem. Chem. Phys., 2014, 16,

10419–10424.142 D. Wei, S. Haque, P. Andrew, J. Kivioja, T. Ryhanen,

A. Pesquera, A. Centeno, B. Alonso, A. Chuvilin andA. Zurutuza, J. Mater. Chem. A, 2013, 1, 3177–3181.

143 H. Kim, K. Y. Park, J. Hong and K. Kang, Sci. Rep., 2014, 4,5278.

144 A. Mukhopadhyay, F. Guo, A. Tokranov, X. Xiao, R. H. Hurtand B. W. Sheldon, Adv. Funct. Mater., 2013, 23, 2397–2404.

145 X. Li, Y. Hu, J. Liu, A. Lushington, R. Li and X. Sun,Nanoscale, 2013, 5, 12607–12615.

146 A. L. M. Reddy, A. Srivastava, S. R. Gowda, H. Gullapalli,M. Dubey and P. M. Ajayan, ACS Nano, 2010, 4, 6337–6342.

147 X. Wang, Q. Weng, X. Liu, X. Wang, D. M. Tang, W. Tian,C. Zhang, W. Yi, D. Liu, Y. Bando and D. Golberg, NanoLett., 2014, 14, 1164–1171.

148 K. Shu, C. Wang, M. Wang, C. Zhao and G. G. Wallace, J.Mater. Chem. A, 2014, 2, 1325–1331.

149 A. P. Cohn, L. Oakes, R. Carter, S. Chatterjee, A. S. Westover,K. Share and C. L. Pint, Nanoscale, 2014, 6, 4669–4675.

150 J. Ji, J. Liu, L. Lai, X. Zhao, Y. Zhen, J. Lin, Y. Zhu, H. Ji,L. L. Zhang and R. S. Ruoff, ACS Nano, 2015, 9, 8609–8616.

151 J. Hassoun, F. Bonaccorso, M. Agostini, M. Angelucci,M. G. Betti, R. Cingolani, M. Gemmi, C. Mariani,S. Panero, V. Pellegrini and B. Scrosati, Nano Lett., 2014,14, 4901–4906.

152 X. Zhou, X. Zhu, X. Liu, Y. Xu, Y. Liu, Z. Dai and J. Bao, J.Phys. Chem. C, 2014, 118, 22426–22431.

153 J. Xu, M. Wang, N. P. Wickramaratne, M. Jaroniec, S. Douand L. Dai, Adv. Mater., 2015, 27, 2042–2048.

154 B. Luo and L. Zhi, Energy Environ. Sci., 2015, 8, 456–477.155 M. Zhou, X. Li, B. Wang, Y. Zhang, J. Ning, Z. Xiao,

X. Zhang, Y. Chang and L. Zhi, Nano Lett., 2015, 15, 6222–6228.

156 J. Luo, X. Zhao, J. Wu, H. D. Jang, H. H. Kung and J. Huang,J. Phys. Chem. Lett., 2012, 3, 1824–1829.


157 L. Fei, Q. Lin, B. Yuan, G. Chen, P. Xie, Y. Li, Y. Xu, S. Deng,S. Smirnov and H. Luo, ACS Appl. Mater. Interfaces, 2013, 5,5330–5335.

158 X. Zhou, J. Bao, Z. Dai and Y. G. Guo, J. Phys. Chem. C, 2013,117, 25367–25373.

159 G. Huang, T. Chen, Z. Wang, K. Chang and W. Chen, J.Power Sources, 2013, 235, 122–128.

160 F. Sun, K. Huang, X. Qi, T. Gao, Y. Liu, X. Zou, X. Wei andJ. Zhong, Nanoscale, 2013, 5, 8586–8592.

161 Y. Chen, J. Zhu, B. Qu, B. Lu and Z. Xu, Nano Energy, 2014,3, 88–94.

162 B. Wang, X. Li, X. Zhang, B. Luo, M. Jin, M. Liang,S. A. Dayeh, S. Picraux and L. Zhi, ACS Nano, 2013, 7,1437–1445.

163 N. Mahmood, C. Zhang, F. Liu, J. Zhu and Y. Hou, ACSNano, 2013, 7, 10307–10318.

164 J. Shin, K. Park, W. H. Ryu, J. W. Jung and I. D. Kim,Nanoscale, 2014, 6, 12718–12726.

165 J. Qin, C. He, N. Zhao, Z. Wang, C. Shi, E. Z. Liu and J. Li,ACS Nano, 2014, 8, 1728–1738.

166 J. Chang, X. Huang, G. Zhou, S. Cui, P. B. Hallac, J. Jiang,P. T. Hurley and J. Chen, Adv. Mater., 2014, 26, 758–764.

167 Y. Li, Z. Wang and X. J. Lv, J. Mater. Chem. A, 2014, 2, 15473–15479.

168 K. H. Park, D. Lee, J. Kim, J. Song, Y. M. Lee, H. T. Kim andJ. K. Park, Nano Lett., 2014, 14, 4306–4313.

169 I. H. Son, J. H. Park, S. Kwon, S. Park, M. H. Rummeli,A. Bachmatiuk, H. J. Song, J. Ku, J. W. Choi, J. M. Choiand S. G. Doo, Nat. Commun., 2015, 6, 7393.

170 M. Shi, X. Song, J. Liu, L. Zhao, P. Zhang and L. Gao, J.Mater. Chem. A, 2016, 4, 10666–10672.

171 Y. X. Wang, Y. G. Lim, M. S. Park, S. L. Chou, J. H. Kim,H. K. Liu, S. X. Dou and Y. J. Kim, J. Mater. Chem. A,2014, 2, 529–534.

172 J. Song, Z. Yu, M. L. Gordin, S. Hu, R. Yi, D. Tang, T. Walter,M. Regula, D. Choi, X. Li and A. Manivannan, Nano Lett.,2014, 14, 6329–6335.

173 X. Zhou, X. Liu, Y. Xu, Y. Liu, Z. Dai and J. Bao, J. Phys.Chem. C, 2014, 118, 23527–23534.

174 C. Wu, P. Kopold, Y. L. Ding, P. A. van Aken, J. Maier andY. Yu, ACS Nano, 2015, 9, 6610–6618.

175 L. Hu, X. Zhu, Y. Du, Y. Li, X. Zhou and J. Bao, Chem. Mater.,2015, 27, 8138–8145.

176 A. G. Dylla, G. Henkelman and K. J. Stevenson, Acc. Chem.Res., 2013, 46, 1104–1112.

177 C. Arrouvel, S. C. Parker and M. S. Islam, Chem. Mater.,2009, 21, 4778–4783.

178 A. S. Dalton, A. A. Belak and A. Van der Ven, Chem. Mater.,2012, 24, 1568–1574.

179 A. G. Dylla, P. Xiao, G. Henkelman and K. J. Stevenson, J.Phys. Chem. Lett., 2012, 3, 2015–2019.

180 J. Prochazka, L. Kavan, M. Zukalova, O. Frank, M. Kalbac,A. Zukal, M. Klementova, D. Carbone and M. Graetzel,Chem. Mater., 2009, 21, 1457–1464.

181 T. Beuvier, M. Richard-Plouet, M. Mancini-Le Granvalet,T. Brousse, O. Crosnier and L. Brohan, Inorg. Chem.,2010, 49, 8457–8464.

J. Mater. Chem. A, 2017, 5, 3735–3758 | 3755


182 S. Liu, H. Jia, L. Han, J. Wang, P. Gao, D. Xu, J. Yang andS. Che, Adv. Mater., 2012, 24, 3201–3204.

183 H. Sugaya, K. Fukuda, M. Morita, H. Murayama,E. Matsubara, T. Kume and Y. Uchimoto, Chem. Lett.,2015, 44, 1595–1597.

184 J. Ni, Y. Zhao, L. Li and L. Mai, Nano Energy, 2015, 11, 129–135.

185 M. Liu, C. Yan and Y. Zhang, Sci. Rep., 2015, 5, 8326.186 T. Stephenson, Z. Li, B. Olsen and D. Mitlin, Energy Environ.

Sci., 2014, 7, 209–231.187 X.Wang, Q. Weng, Y. Yang, Y. Bando and D. Golberg, Chem.

Soc. Rev., 2016, 45, 4042–4073.188 Y. Li, D. Wu, Z. Zhou, C. R. Cabrera and Z. Chen, J. Phys.

Chem. Lett., 2012, 3, 2221–2227.189 H. Shu, F. Li, C. Hu, P. Liang, D. Cao and X. Chen,

Nanoscale, 2016, 8, 2918–2926.190 J. Xiao, D. Choi, L. Cosimbescu, P. Koech, J. Liu and

J. P. Lemmon, Chem. Mater., 2010, 22, 4522–4524.191 H. Hwang, H. Kim and J. Cho, Nano Lett., 2011, 11, 4826–

4830.192 K. Zhang, H. J. Kim, X. Shi, J. T. Lee, J. M. Choi, M. S. Song

and J. H. Park, Inorg. Chem., 2013, 52, 9807–9812.193 Y. C. Liu, Y. P. Zhao, L. F. Jiao and J. Chen, J. Mater. Chem. A,

2014, 2, 13109–13115.194 H. Jiang, D. Ren, H. Wang, Y. Hu, S. Guo, H. Yuan, P. Hu,

L. Zhang and C. Li, Adv. Mater., 2015, 27, 3687–3695.195 Y. Hou, J. Li, Z. Wen, S. Cui, C. Yuan and J. Chen, Nano

Energy, 2014, 8, 157–164.196 Q. Qu, F. Qian, S. Yang, T. Gao, W. Liu, J. Shao and

H. Zheng, ACS Appl. Mater. Interfaces, 2016, 8, 1398–1405.197 X. Zhou, L. J. Wan and Y. G. Guo, Nanoscale, 2012, 4, 5868–

5871.198 L. Wang, Z. Xu, W.Wang and X. Bai, J. Am. Chem. Soc., 2014,

136, 6693–6697.199 J. Xiao, X. Wang, X.-Q. Yang, S. Xun, G. Liu, P. K. Koech,

J. Liu and J. P. Lemmon, Adv. Funct. Mater., 2011, 21,2840–2846.

200 X. Fang, X. Guo, Y. Mao, C. Hua, L. Shen, Y. Hu, Z. Wang,F. Wu and L. Chen, Chem.–Asian J., 2012, 7, 1013–1017.

201 Y. Jing, Z. Zhou, C. R. Cabrera and Z. Chen, J. Phys. Chem. C,2013, 117, 25409–25413.

202 Z. Liu, H. Deng and P. P. Mukherjee, ACS Appl. Mater.Interfaces, 2015, 7, 4000–4009.

203 D. Wang, L. M. Liu, S. J. Zhao, Z. Y. Hu and H. Liu, J. Phys.Chem. C, 2016, 120, 4779–4788.

204 R. Bhandavat, L. David and G. Singh, J. Phys. Chem. Lett.,2012, 3, 1523–1530.

205 L. Ji, H. L. Xin, T. R. Kuykendall, S.-L. Wu, H. Zheng,M. Rao, E. J. Cairns, V. Battaglia and Y. Zhang, Phys.Chem. Chem. Phys., 2012, 14, 6981–6986.

206 Q. Wang, Y. X. Nie, B. He, L. L. Xing and X. Y. Xue, SolidState Sci., 2014, 31, 81–84.

207 K. Chang, Z. Wang, G. Huang, H. Li, W. Chen and J. Y. Lee,J. Power Sources, 2012, 201, 259–266.

208 L. Zhuo, Y. Wu, L. Wang, Y. Yu, X. Zhang and F. Zhao, RSCAdv., 2012, 2, 5084–5087.

3756 | J. Mater. Chem. A, 2017, 5, 3735–3758

209 B. Luo, Y. Fang, B. Wang, J. Zhou, H. Song and L. Zhi,Energy Environ. Sci., 2012, 5, 5226–5230.

210 Q. Zhang, R. Li, M. Zhang, B. Zhang and X. Gou,Electrochim. Acta, 2014, 115, 425–433.

211 M. Mortazavi, C. Wang, J. Deng, V. B. Shenoy andN. V. Medhekar, J. Power Sources, 2014, 268, 279–286.

212 D. B. Putungan, S. H. Lin and J. L. Kuo, ACS Appl. Mater.Interfaces, 2016, 8, 18754–18762.

213 E. Yang, H. Ji and Y. Jung, J. Phys. Chem. C, 2015, 119,26374–26380.

214 J. Park, J. S. Kim, J. W. Park, T. H. Nam, K. W. Kim,J. H. Ahn, G. Wang and H. J. Ahn, Electrochim. Acta, 2013,92, 427–432.

215 L. David, R. Bhandavat and G. Singh, ACS Nano, 2014, 8,1759–1770.

216 X. Xie, Z. Ao, D. Su, J. Zhang and G. Wang, Adv. Funct.Mater., 2015, 25, 1393–1403.

217 B. Qu, C. Ma, G. Ji, C. Xu, J. Xu, Y. S. Meng, T. Wang andJ. Y. Lee, Adv. Mater., 2014, 26, 3854–3859.

218 P. V. Prikhodchenko, Y. Denis, S. K. Batabyal, V. Uvarov,J. Gun, S. Sladkevich, A. A. Mikhaylov, A. G. Medvedevand O. Lev, J. Mater. Chem. A, 2014, 2, 8431–8437.

219 Y. Zhang, P. Zhu, L. Huang, J. Xie, S. Zhang, G. Cao andX. Zhao, Adv. Funct. Mater., 2015, 25, 481–489.

220 Q. Tang, Z. Zhou and P. Shen, J. Am. Chem. Soc., 2012, 134,16909–16916.

221 G. Berdiyorov, Appl. Surf. Sci., 2015, 359, 153–157.222 D. Sun, M. Wang, Z. Li, G. Fan, L. Z. Fan and A. Zhou,

Electrochem. Commun., 2014, 47, 80–83.223 Y. Xie, M. Naguib, V. N. Mochalin, M. W. Barsoum,

Y. Gogotsi, X. Yu, K. W. Nam, X. Q. Yang, A. I. Kolesnikovand P. R. Kent, J. Am. Chem. Soc., 2014, 136, 6385–6394.

224 A. Byeon, M. Q. Zhao, C. E. Ren, J. Halim, S. Kota,P. Urbankowski, B. Anasori, M. W. Barsoum andY. Gogotsi, ACS Appl. Mater. Interfaces, 2016, DOI:10.1021/acsami.6b04198.

225 N. C. Osti, M. Naguib, A. Ostadhossein, Y. Xie, P. R. Kent,B. Dyatkin, G. Rother, W. T. Heller, A. C. van Duin,Y. Gogotsi and E. Mamontov, ACS Appl. Mater. Interfaces,2016, 8, 8859–8863.

226 M. Naguib, J. Halim, J. Lu, K. M. Cook, L. Hultman,Y. Gogotsi and M. W. Barsoum, J. Am. Chem. Soc., 2013,135, 15966–15969.

227 J. Hu, B. Xu, C. Ouyang, S. A. Yang and Y. Yao, J. Phys. Chem.C, 2014, 118, 24274–24281.

228 J. Hu, B. Xu, C. Ouyang, Y. Zhang and S. A. Yang, RSC Adv.,2016, 6, 27467–27474.

229 A. Byeon, A. M. Glushenkov, B. Anasori, P. Urbankowski,J. Li, B. W. Byles, B. Blake, K. L. Van Aken, S. Kota,E. Pomerantseva, et al., J. Power Sources, 2016, 326, 686–694.

230 Q. Sun, Y. Dai, Y. Ma, T. Jing, W. Wei and B. Huang, J. Phys.Chem. Lett., 2016, 7, 937–943.

231 J. Halim, S. Kota, M. R. Lukatskaya, M. Naguib, M. Q. Zhao,E. J. Moon, J. Pitock, J. Nanda, S. J. May, Y. Gogotsi andM. W. Barsoum, Adv. Funct. Mater., 2016, 26, 3118–3127.

232 D. Sun, Q. Hu, J. Chen, X. Zhang, L. Wang, Q. Wu andA. Zhou, ACS Appl. Mater. Interfaces, 2015, 8, 74–81.



233 M. Ashton, R. G. Hennig and S. B. Sinnott, Appl. Phys. Lett.,2016, 108, 023901.

234 D. Er, J. Li, M. Naguib, Y. Gogotsi and V. B. Shenoy, ACSAppl. Mater. Interfaces, 2014, 6, 11173–11179.

235 Y. X. Yu, J. Phys. Chem. C, 2016, 120, 5288–5296.236 Y. Xie, Y. Dall'Agnese, M. Naguib, Y. Gogotsi,

M. W. Barsoum, H. L. Zhuang and P. R. Kent, ACS Nano,2014, 8, 9606–9615.

237 E. Yang, H. Ji, J. Kim, H. Kim and Y. Jung, Phys. Chem.Chem. Phys., 2015, 17, 5000–5005.

238 M. R. Lukatskaya, O. Mashtalir, C. E. Ren, Y. Dall'Agnese,P. Rozier, P. L. Taberna, M. Naguib, P. Simon,M. W. Barsoum and Y. Gogotsi, Science, 2013, 341, 1502–1505.

239 S. Kajiyama, L. Szabova, K. Sodeyama, H. Iinuma,R. Morita, K. Gotoh, Y. Tateyama, M. Okubo andA. Yamada, ACS Nano, 2016, 10, 3334–3341.

240 X. Xie, M. Q. Zhao, B. Anasori, K. Maleski, C. E. Ren, J. Li,B. W. Byles, E. Pomerantseva, G. Wang and Y. Gogotsi,Nano Energy, 2016, 26, 513–523.

241 K. P. Hembram, H. Jung, B. C. Yeo, S. J. Pai, H. J. Lee,K. R. Lee and S. S. Han, Phys. Chem. Chem. Phys., 2016,18, 21391–21397.

242 W. Xia, Q. Zhang, F. Xu, H. Ma, J. Chen, K. Qasim, B. Ge,C. Zhu and L. Sun, J. Phys. Chem. C, 2016, 120, 5861–5868.

243 S. Zhao, W. Kang and J. Xue, J. Mater. Chem. A, 2014, 2,19046–19052.

244 Q. Yao, C. Huang, Y. Yuan, Y. Liu, S. Liu, K. Deng andE. Kan, J. Phys. Chem. C, 2015, 119, 6923–6928.

245 W. Li, Y. Yang, G. Zhang and Y. W. Zhang, Nano Lett., 2015,15, 1691–1697.

246 V. V. Kulish, O. I. Malyi, C. Persson and P. Wu, Phys. Chem.Chem. Phys., 2015, 17, 13921–13928.

247 R. Zhang, X. Wu and J. Yang, Nanoscale, 2016, 8, 4001–4006.248 C. Chowdhury, S. Karmakar and A. Datta, ACS Energy Lett.,

2016, 1, 253–259.249 G. C. Guo, D. Wang, X. L. Wei, Q. Zhang, H. Liu, W. M. Lau

and L. M. Liu, J. Phys. Chem. Lett., 2015, 6, 5002–5008.250 Q. Peng, Z. Wang, B. Sa, B. Wu and Z. Sun, ACS Appl. Mater.

Interfaces, 2016, 8, 13449–13457.251 F. Xu, B. Ge, J. Chen, A. Nathan, L. L. Xin, H. Ma, H. Min,

C. Zhu, W. Xia, Z. Li and S. Li, 2D Mater., 2016, 3, 025005.252 J. Sun, H. W. Lee, M. Pasta, H. Yuan, G. Zheng, Y. Sun, Y. Li

and Y. Cui, Nat. Nanotechnol., 2015, 10, 980–985.253 G. A. Tritsaris, E. Kaxiras, S. Meng and E. Wang, Nano Lett.,

2013, 13, 2258–2263.254 S. M. Seyed-Talebi, I. Kazeminezhad and J. Beheshtian,

Phys. Chem. Chem. Phys., 2015, 17, 29689–29696.255 J. Zhu and U. Schwingenschlogl, 2DMater., 2016, 3, 035012.256 B. Mortazavi, A. Dianat, G. Cuniberti and T. Rabczuk,

Electrochim. Acta, 2016, 213, 865–870.257 H. Jiang, Z. Lu, M. Wu, F. Ciucci and T. Zhao, Nano Energy,

2016, 23, 97–104.258 L. Shi, T. Zhao, A. Xu and J. Xu, Sci. Bull., 2016, 61, 1138–

1144.259 J. Zhu, A. Chroneos and U. Schwingenschlogl, Nanoscale,

2016, 8, 7272–7277.


260 L. Shi, T. Zhao, A. Xu and J. Xu, J. Mater. Chem. A, 2016, 4,16377–16382.

261 F. Y. Su, Y. B. He, B. Li, X. C. Chen, C. H. You, W.Wei, W. Lv,Q. H. Yang and F. Kang, Nano Energy, 2012, 1, 429–439.

262 W. Wei, W. Lv, M. B. Wu, F. Y. Su, Y.-B. He, B. Li, F. Kangand Q. H. Yang, Carbon, 2013, 57, 530–533.

263 L. H. Hu, F. Y. Wu, C. T. Lin, A. N. Khlobystov and L. J. Li,Nat. Commun., 2013, 4, 1687.

264 X. Rui, W. Sun, C. Wu, Y. Yu and Q. Yan, Adv. Mater., 2015,27, 6670–6676.

265 F. Li, C. R. Cabrera and Z. Chen, J. Mater. Chem. A, 2014, 2,19180–19188.

266 X. Zhao, X. Zhang, D. Wu, H. Zhang, F. Ding and Z. Zhou, J.Mater. Chem. A, 2016, 4, 16606–16611.

267 C. C. Leong, H. Pan and S. K. Ho, Phys. Chem. Chem. Phys.,2016, 18, 7527–7534.

268 B. Mendoza-Sanchez, D. Hanlon, J. Coelho, S. O'Brien,H. Pettersson, J. Coleman and V. Nicolosi, 2D Mater.,2016, 4, 015005.

269 Y. Li, J. Yao, E. Uchaker, J. Yang, Y. Huang, M. Zhang andG. Cao, Adv. Energy Mater., 2013, 3, 1171–1175.

270 S. Liang, M. Qin, Y. Tang, Q. Zhang, X. Li, X. Tan andA. Pan, Met. Mater. Int., 2014, 20, 983–988.

271 D. Su and G. Wang, ACS Nano, 2013, 7, 11218–11226.272 K. Zhu, C. Zhang, S. Guo, H. Yu, K. Liao, G. Chen, Y. Wei

and H. Zhou, ChemElectroChem, 2015, 2, 1660–1664.273 J. Cheng, B. Wang, H. L. Xin, G. Yang, H. Cai, F. Nie and

H. Huang, J. Mater. Chem. A, 2013, 1, 10814–10820.274 N. Xu, J. Liang, T. Qian, T. Yang and C. Yan, RSC Adv., 2016,

6, 98581–98587.275 X. Chen, H. Zhu, Y. C. Chen, Y. Shang, A. Cao, L. Hu and

G. W. Rubloff, ACS Nano, 2012, 6, 7948–7955.276 R. Yu, C. Zhang, Q. Meng, Z. Chen, H. Liu and Z. Guo, ACS

Appl. Mater. Interfaces, 2013, 5, 12394–12399.277 X. Wang, W. Jia, L. Wang, Y. Huang, Y. Guo, Y. Sun, D. Jia,

W. Pang, Z. Guo and X. Tang, J. Mater. Chem. A, 2016, 4,13907–13915.

278 V. Raju, J. Rains, C. Gates, W. Luo, X. Wang, W. F. Stickle,G. D. Stucky and X. Ji, Nano Lett., 2014, 14, 4119–4124.

279 D. Chao, X. Xia, J. Liu, Z. Fan, C. F. Ng, J. Lin, H. Zhang,Z. X. Shen and H. J. Fan, Adv. Mater., 2014, 26, 5794–5800.

280 C. Nethravathi, C. R. Rajamathi, M. Rajamathi,U. K. Gautam, X. Wang, D. Golberg and Y. Bando, ACSAppl. Mater. Interfaces, 2013, 5, 2708–2714.

281 S. Yang, Y. Gong, Z. Liu, L. Zhan, D. P. Hashim, L. Ma,R. Vajtai and P. M. Ajayan, Nano Lett., 2013, 13, 1596–1601.

282 D. Chao, C. Zhu, X. Xia, J. Liu, X. Zhang, J. Wang, P. Liang,J. Lin, H. Zhang, Z. X. Shen and H. J. Fan, Nano Lett., 2014,15, 565–573.

283 D. Lin, Y. Liu, Z. Liang, H. W. Lee, J. Sun, H. Wang, K. Yan,J. Xie and Y. Cui, Nat. Nanotechnol., 2016, 11, 626–632.

284 J. S. Kim, D. W. Kim, H. T. Jung and J. W. Choi, Chem.Mater., 2015, 27, 2780–2787.

285 W. Luo, L. Zhou, K. Fu, Z. Yang, J. Wan, M. Manno, Y. Yao,H. Zhu, B. Yang and L. Hu, Nano Lett., 2015, 15, 6149–6154.

286 L. Shi, A. Xu and T. S. Zhao, ACS Appl. Mater. Interfaces,2016, DOI: 10.1021/acsami.6b14560.

J. Mater. Chem. A, 2017, 5, 3735–3758 | 3757


287 W. K. Shin, A. G. Kannan and D. W. Kim, ACS Appl. Mater.Interfaces, 2015, 7, 23700–23707.

288 H. Jiang, T. Zhao, L. Shi, P. Tan and L. An, J. Phys. Chem. C,2016, 120, 6612–6618.

289 H. Jiang, P. Tan, M. Liu, Y. Zeng and T. Zhao, J. Phys. Chem.C, 2016, 120, 18394–18402.

290 H. Jiang, M. Wu, X. Zhou, X. Yan and T. Zhao, J. PowerSources, 2016, 325, 91–97.

291 L. Shi, A. Xu and T. Zhao, J. Phys. Chem. C, 2016, 120, 6356–6362.

292 Y. Hwang, K. H. Yun and Y. C. Chung, J. Power Sources,2015, 275, 32–37.

293 Z. Liu, L. R. De Jesus, S. Banerjee and P. P. Mukherjee, ACSAppl. Mater. Interfaces, 2016, 8, 23028–23036.

294 Z. Lin, Z. Liu, W. Fu, N. J. Dudney and C. Liang, Angew.Chem., Int. Ed., 2013, 125, 7608–7611.

295 L. Ma, K. E. Hendrickson, S. Wei and L. A. Archer, NanoToday, 2015, 10, 315–338.

296 J. Zhao, Y. Yang, R. S. Katiyar and Z. Chen, J. Mater. Chem. A,2016, 4, 6124–6130.

297 H.Wang, Y. Yang, Y. Liang, J. T. Robinson, Y. Li, A. Jackson,Y. Cui and H. Dai, Nano Lett., 2011, 11, 2644–2647.

3758 | J. Mater. Chem. A, 2017, 5, 3735–3758

298 L. Ji, M. Rao, H. Zheng, L. Zhang, Y. Li, W. Duan, J. Guo,E. J. Cairns and Y. Zhang, J. Am. Chem. Soc., 2011, 133,18522–18525.

299 W. Zhou, H. Chen, Y. Yu, D. Wang, Z. Cui, F. J. DiSalvo andH. D. Abruna, ACS Nano, 2013, 7, 8801–8808.

300 Z. Wang, Y. Dong, H. Li, Z. Zhao, H. B. Wu, C. Hao, S. Liu,J. Qiu and X. W. D. Lou, Nat. Commun., 2014, 5, 5002.

301 X. Wang, Z. Wang and L. Chen, J. Power Sources, 2013, 242,65–69.

302 H. Li, X. Yang, X. Wang, M. Liu, F. Ye, J. Wang, Y. Qiu, W. Liand Y. Zhang, Nano Energy, 2015, 12, 468–475.

303 C. Wang, X. Wang, Y. Yang, A. Kushima, J. Chen, Y. Huangand J. Li, Nano Lett., 2015, 15, 1796–1802.

304 Y. Xie, Z. Meng, T. Cai and W.-Q. Han, ACS Appl. Mater.Interfaces, 2015, 7, 25202–25210.

305 J. Shan, Y. Liu, Y. Su, P. Liu, X. Zhuang, D.Wu, F. Zhang andX. Feng, J. Mater. Chem. A, 2016, 4, 314–320.

306 A. K. Geim and I. V. Grigorieva, Nature, 2013, 499, 419–425.307 T. Niu and A. Li, Prog. Surf. Sci., 2015, 90, 21–45.308 H. Wang, F. Liu, W. Fu, Z. Fang, W. Zhou and Z. Liu,

Nanoscale, 2014, 6, 12250–12272.309 Y. Liu, N. O. Weiss, X. Duan, H.-C. Cheng, Y. Huang and

X. Duan, Nature Reviews Materials, 2016, 1, 16042.


Documents

Journal of Materials Chemistry Amezhao/pdf/303.pdf · Journal of Materials Chemistry A Review. synthesized via chemical vapor deposition (CVD) (such as sili-cene, germanene, borophene