Mechanochemical Process Enhanced Cobalt and Lithium Recyclingfrom Wasted Lithium-Ion BatteriesJie Guan,† Yaguang Li,† Yaoguang Guo,*,† Ruijing Su,† Guilan Gao,*,†,‡ Haixiang Song,§ Hao Yuan,†

Bo Liang,† and Zhanhu Guo*,§

†Shanghai Cooperative Center for WEEE Recycling, School of Environmental and Materials Engineering, Shanghai PolytechnicUniversity, Shanghai 201209, China‡School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China§Integrated Composites Laboratory (ICL), Department of Chemical & Bimolecular Engineering, University of Tennessee, Knoxville,Tennessee 37996, United States

*S Supporting Information

ABSTRACT: Cobalt (Co) and lithium (Li), rare and valuableelements, are mainly used to prepare lithium cobalt oxide(LiCoO2) for applications in lithium-ion batteries (LIBs).Developing an effective method to recover Co and Li from thewaste LIBs is of great significance. In the present study, Coand Li were extracted from pure LiCoO2 powders and theextracted cathode materials powders from the waste LIBs afteracid dissolution via a mechanochemical reduction processwith iron powders. For pure LiCoO2 powders, the effects of Feto LiCoO2 mass ratio, rotation speed, and mechanochemicalreduction time were examined. These parameters influencedpositively the extraction of Co, while they showed negligibleeffects on the leaching of Li. The X-ray diffraction (XRD) andscanning electron microscope (SEM) analyses indicated a promoted extraction of Li arising from the reduction of particle sizes,magnification of specific surface area, and change of the crystal structure of particles. For high-efficiency leaching of Co by themechanochemical reduction process with iron powders, X-ray photoelectron spectroscopy (XPS) analysis indicated the changesin the valence state of Co. The actual cathode materials disassembled from the wasted LIBs pretreated by this novel mech-anochemical reduction process were also explored. The results indicated that the leaching ratios of Li, Co, Mn, and Ni couldreach 77.15%, 91.25%, 100%, and 99.9%, respectively. This novel mechanochemical process would be of great importance for therecovery of valuable metals from waste LIBs.

KEYWORDS: Valuable metals, Wasted lithium-ion batteries, Mechanochemical reduction, Hydrometallurgy

■ INTRODUCTION

Lithium-ion batteries (LIBs) have captured increasing attentionfor around 16 years, and LIBs outperformed nickel−cadmiumand nickel metal−hydride rechargeable batteries, owing toexcellent features of small size, high power density, no memoryeffect, long cycle life, high voltage, low self-discharge, etc.1−4

Therefore, LIBs are widely used in a multitude of portableelectronics, especially mobile phones, personal computers, cam-eras, etc.5 As such, the LIBs are expanding their market share inthe area of rechargeable batteries. The quantity and weight ofLIBs in 2020 can surpass 25 billion units and 500 thousandtons, respectively.6 With extensive applications of LIBs inportable electronics, it is evident that an ocean of spent LIBswill be produced after the ∼1−3 years of lifetime service ofthe LIBs.7 If the spent LIBs are simply disposed, a seriousenvironmental concern of soil contamination would be causedby the leaked organic electrolytes as well as toxic metals (Co,Li, Cu, Mn, Ni, etc.) contained in the LIBs.8 Furthermore, the

spent LIBs can be used to recover valuable metals (Co, Li, Mn,Ni, etc.) or their compounds.9 For instance, lithium cobaltoxide (LiCoO2), a shared cathode active material for com-mercial LIBs, accounts for 27.5 wt % in a quintessential lithium-ion secondary rechargeable battery, with a metal content of 5−20 wt % Co and 5−7 wt % Li.10,11 Therefore, the recovery ofthe valuable metals, especially Co and Li from the spent LIBs, isconsidered to be highly desirable.Recently, several studies have been reported for the recycling

of Co and Li from the spent LIBs, focusing on pyrometallurgy,hydrometallurgy, or biohydrometallurgy processes.6,12,13 Incomparison to the pyrometallurgical technology with the disad-vantages of emission of toxic gases and consumption of inten-sive energy, the biohydrometallurgical approach is more favorable,

Received: September 27, 2016Revised: October 28, 2016Published: November 8, 2016

Research Article

pubs.acs.org/journal/ascecg

© 2016 American Chemical Society 1026 DOI: 10.1021/acssuschemeng.6b02337ACS Sustainable Chem. Eng. 2017, 5, 1026−1032

This is an open access article published under an ACS AuthorChoice License, which permitscopying and redistribution of the article or any adaptations for non-commercial purposes.

and involves higher efficiency, lower costs, and quite a fewindustrial requirements.14,15 However, the treatment period ofbiohydrometallurgical process is too long, and the requiredmicrobes are arduous to incubate effectively.14,15 By contrast,for the recovery of metals from spent LIBs, the broad hydro-metallurgical processes, involving higher metal recovery rateswith good purity, low energy consumption, and minimal gasemission, are considered to be more superior, and mainlyconsist of acid leaching, chemical precipitation, chemical dis-placement reaction, solvent extraction, hydrothermal reaction,crystallization and electrochemical accumulation, etc.6,12,13

Generally, the cathode active materials, separated by a seriesof pretreatment steps, such as mechanical separation, andthermal processes,10,11 are leached by an acidic solution inorder to transfer the target metals into the solution, and fol-lowed by the treatment of the acid leachate and final wastes torecover the metals of interest by means of chemical precipita-tion, chemical displacement, solvent extraction, electrochemicalaccumulation, etc. As such, acid leaching is a key step for therecovery of valuable metals. The leaching of LiCoO2 from spentLIBs is usually carried out by using inorganic acids, such assulfuric, hydrochloric, and nitric acids as leachants,16−22 amongwhich higher extractions of Co and Li were obtained with thehydrochloric and nitric acids as the leaching media.23 However,for the leaching process of LiCoO2 in the hydrochloric acidmedia, special antisepticizing equipment needs to be installedto treat chlorine (Cl2) generating from HCl oxidation, leadingto much greater recycling cost or serious environmental prob-lems if this kind of equipment is not available.12 Furthermore,the hydrogen peroxide is generally used as a reductant duringacid leaching, for the purpose that additional H2O2 easilyreduces Co(III) to Co(II) present in the spent LIBs, which aremore favorably solubilized than the unreduced moieties; other-wise, more concentrated acids are necessary to obtain com-parative dissolutions.10,11,22,24 For instance, Lee et al.22 indi-cated that the leaching efficiency was increased by 45% for Coand 10% for Li in the nitric acid leaching process with theaddition of H2O2 as a reducing agent, compared with the nitricacid leaching process without reducing agents. Moreover,whether H2O2 is contained in the nitric acid leaching media ornot, a temperature higher than 75 °C is needed.12 However, theaddition of H2O2 or high temperature might be regarded aspromoting or activating processes for nitric acid extraction,and might result in a higher average costs and operationalenvironmental risk. Therefore, an economic and safe recoveryprocess of Co and Li from waste LIBs is highly desirable.The mechanochemical approach has attracted more atten-

tion for potential applications in wide ranges based on the trig-gered physicochemical changes, including phase transfor-mations, structural defects, strain, amorpholization, and evendirect reaction under normal temperature and pressure.25 Thisapproach can also make technically feasible the environmentallyfriendly recycling of metals from some specific wastes, such ascathode ray tube funnel glass,26 tin-doped indium oxidecontaining waste,27,28 and waste fluorescent lamps,29 while sig-nificantly improving the recycling efficiency. As mentionedbefore, with the traditional hydrometallurgical acid leaching ofspent LIBs, little extraction of valuable metals can be obtainedat room temperature without the addition of other enhancedsolvents. Herein, a mechanochemical process to pretreat thespent LIBs might be supposed to be a promoting or activa-ting method for nitric acid extraction of valuable metals Coand Li.

Therefore, the aim of the present study is to examine thefeasibility of a mechanochemical process to enhance the acidleaching of Co and Li at room temperature from the spentLIBs. Metallic iron powders served as grinding aids. Purelithium cobalt oxide (LiCoO2) powders were selected to studythe influences of mechanochemical parameters on the Co andLi extraction, such as the Fe/LiCoO2 powder mass ratio, rota-tional speed, and mechanochemical milling time. The physico-chemical changes established by X-ray diffraction (XRD),scanning electron microscopy (SEM), and X-ray photoelectronspectroscopy (XPS) gave insights into the mechanism of themechanochemical method. Ultimately, the actual scrap sampleseparated and concentrated from the cathode materials in thewaste LIBs was examined to verify the behavior of this novelprocess.

■ EXPERIMENTAL SECTIONMaterials. Lithium cobalt oxide (LiCoO2, 99.8% metals basis)

powder reagent was purchased from Aladdin Industrial Co. Ltd.,Shanghai, China. Iron powder (Fe, ≥98% in purity), and nitric acid(HNO3, AR) were obtained from Sinopharm Chemical Reagent Co.,Ltd., Shanghai, China. Ultrapure water (18.2 MΩ cm) was used forall of the experiments. The spent LIBs were used in mobile phoneswhich were collected from Samsung Electronics Co. Ltd. (modelAB463446BC and capacity 800 mAh).

Experimental Procedure and Analysis. A planetary ball mill(DECO-PBM-V-0.4L, DECO, China) was used for the experiments.Stainless steel pots with a volume of 100 mL and balls with a diameterof 10.0 mm were used as grinding bodies for the ball milling experi-ments. Prior to each experiment, certain aliquots were transferred tothe reactor vessel to obtain the desired amounts. The rotation speed ofthe planetary disk was set as a certain value, and the rotation direc-tion changed automatically every 30 min. After the milling, all of thesamples were collected for characterization as well as acid leaching. Toavoid the interference of other substances and exactly elucidatethe mechanochemical mechanism, pure LiCoO2 powders were firstselected to study the influences of mechanochemical parameters onthe Co and Li extraction and physicochemical changes established byXRD, SEM, and XPS. Ultimately, the leaching of Co and Li in thewaste cathode materials from spent LIBs after mechanochemicalprocess was also examined. Prior to mechanochemical treatment, thespent LIBs were pretreated by discharging, dismantling, and separatingof cathode materials, which were followed by heat treatment to realizethe separation of the cathode materials and the aluminum foil, and

Figure 1. Extraction of Co and Li from different samples (raw sample,pure LiCoO2; activated sample, pure LiCoO2 after ground; mech-anochemical sample, ground samples of LiCoO2 and Fe with massratio of 1:1). Conditions: grinding time = 250 min, rotation speed =650 rpm.

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removal of the polyvinylidene fluoride (PVDF) binder and acetyleneblack conductive agent. The detailed pretreatment was presented inthe Supporting Information (SI).All the batch leaching experiments were performed in 100 mL of

HNO3 solution with the concentration of 1 mol/L in a conical flaskwith a 200 mL capacity immersed in a constant temperature bath at

25 ± 2 °C under magnetic stirring. Briefly, a 0.3 g portion of a groundsample was added into 1 mol/L HNO3 solution. After immersion for2 h, the samples were centrifuged. A 1 mL leaching sample was dilutedin a 50 mL colorimetric tube with ultrapure water. After that, thesample solutions were detected with an inductively coupled plasma-atomic emission spectrometry (ICP-AES) instrument (iCAP-6300,THERMO). Briefly, the solution was diluted 50 times with ultrapurewater before testing. The detection limits of Co and Li were 0.005 and0.002 μg/mL, respectively.

The metal leaching efficiency was calculated according to eq 1.

=×

××R

C Vm w%

100%0 0(1)

Here, the following abbreviations apply: R is the metal leaching effi-ciency; C0 is the mass concentration of metal ions in the leachate; V0 isthe volume of leachate; m is the mass of samples; and w% is the metalmass fraction.

Characterization of the Samples. Besides the ICP determi-nations above, the chemical composition changes of the solid sam-ples during the mechanochemical process were also characterized.XRD was conducted using an X-ray diffractometer (D8 ADVANCE,BRUKER-AXS Corporation) with Cu Kα radiation at a scan speed of8° (2θ) per minute ranging 2θ = 10−80°. The SEM observations werecarried out on a JSM 6400, JEOL, from Japan. XPS was conductedusing X-ray photoelectron spectrometry (ESCALAB 250Xi, Thermo-VG Scientific), and operated via a monochromatic Al Kα X-ray source(1486.6 eV) at 150 W.

Figure 3. Influence of rotation speed on Co and Li leaching (a) and XRD pattern change (b). Conditions: grinding time = 250 min, Fe/LiCoO2mass ratio = 1:1.

Figure 4. Influence of mechanochemical reduction time on Co and Li leaching (a) and XRD pattern change (b). Conditions: rotation speed =650 rpm, Fe/LiCoO2 mass ratio = 1:1.

Figure 2. Influence of Fe/LiCoO2 mass ratio on Co and Li leaching.Conditions: grinding time = 250 min, rotation speed = 650 rpm.

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■ RESULTS AND DISCUSSION

Evaluation of the Performance of the Mechanochem-ical Process. To evaluate the performance of the leachingefficiency of the samples, the powders pretreated by themechanochemical process were tested. The results show thatless than 23% of Co and 39% of Li can only be released frompure LiCoO2 powders after leaching for 2 h (Figure 1).However, even with leaching for 4 h, only less than 31% of Coand 55% of Li can be extracted (Figure S1), indicating thatdirect acid leaching is not an effective approach for the extra-ction of Co and Li. In a comparison with direct leaching of theraw sample, the Li extraction of both the activated sample (pureLiCoO2 pretreatment by milling) and the mechanochemicalsample (LiCoO2 and Fe with the mass ratio at 1:1 pretreatmentby milling) was increased significantly after leaching for 2 h.However, the dissolution of Co from pure LiCoO2 powderafter being ground for 250 min cannot be increased signifi-cantly by acid leaching. By comparison, the leaching efficiencyof Co was increased to around 80% as the reductive metalliciron was added during the mechanochemical pretreatmentprocess, showing a good performance for extraction of valuablemetals.Influence of Fe/LiCoO2 Mass Ratio. The Fe/LiCoO2

mass ratio was potentially critical for the extraction of Coand Li, since the leaching efficiency changed when the reductivemetallic iron was added. Figure 2 shows that the leaching effi-ciency of Li stays almost the same for both the activated sam-ples and the mechanochemical reduction samples of differentmass ratios. However, the extraction of Co was increased from23% to 80% with the addition of Fe, and the maximum dis-solution rate of Co (80%) was obtained when the Fe/LiCoO2mass ratio was above 1:1. When the Fe/LiCoO2 mass ratioswere above 1:1, the leaching of Co was almost constant. There-fore, Fe/LiCoO2 mass ratio of 1:1 was chosen to explore thesubsequent research.

Influence of Rotation Speed. Figure 3a represents theleaching rates of the Co and Li dissolved from the powdersground at different rotation speeds. In the milling processconducted by the planetary ball mill, different rotation speedsprovided different energies, which significantly affected thereaction rate of the mechanochemical reduction. The extractionof Co increased with an increase in the rotation speed, andaround 80% Co was obtained at rotation speeds over 450 rpm.However, the Li extraction was not increased significantly, andthis might be related to the crystal structure change. Figure 3bdemonstrates the dramatic change of the crystal structure of theground sample powders. The results show that the XRDpattern intensity decreased and the full width at half-maximum(fwhm) of all peaks was also broadened with the increase ofrotation speed, and ultimately the peaks of LiCoO2 disap-peared.

Influence of Mechanochemical Reduction Time. Figure 4ashows the mechanochemical reduction time ranging from0 to 250 min. The leaching rate of Co and Li increased moregreatly with prolonged mechanochemical reduction time. Theextraction of Co and Li was increased from 23% to 80% andfrom 39% to 63%, respectively, when the reaction time wasextended from 0 to 100 min, and the recovery ratio of Co andLi was stable at a high level when the reaction time was over100 min. Furthermore, the XRD pattern intensity decreasedwith an increase in the grinding time, and the peaks ofLiCoO2 disappeared after the material was ground for 100 min(Figure 4b), indicating that the higher leaching of Li and Comight arise from the amorphous LiCoO2 crystal.

Characterization Analysis and Mechanism Discussion.To elucidate the reaction mechanism in detail, physicochemicalchanges were also investigated. As shown in Figures 3b and 4b,for the samples pretreated by mechanochemical process withthe addition of Fe, the XRD pattern intensity decreased, andthe fwhm of all peaks was also broadened with the increases in

Figure 5. SEM images of LiCoO2 powders: (a) raw materials, (b) activated samples (grinding time = 150 min, rotation speed = 650 rpm),(c) activated samples (grinding time = 250 min, rotation speed = 650 rpm), (d) mechanochemical reduction samples (grinding time = 100 min,rotation speed = 650 rpm, Fe/LiCoO2 mass ratio = 1:1), (e) mechanochemical reduction samples with metallic iron (grinding time = 250 min,rotation speed = 650 rpm, Fe/LiCoO2 mass ratio = 1:1).

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both rotation speed and grinding time. When the rotationspeed and grinding time were over 550 rpm and 100 min,respectively, the peaks of LiCoO2 could disappear. In addition,the peaks of the activated samples ground without Fe are alsodecreased slowly (Figure S2). According to the previous studiesrelated to the mechanically activated process,30,31 the crystalstructure of the particles was destroyed and gradually trans-formed to an amorphous state due to the friction and impactduring the grinding process. Meanwhile, the internal stress ofthe crystal lattice would also increase with the progress ofgrinding.Figure 5 shows the morphologies of mechanically activated

samples and mechanochemically reduced LiCoO2 powdersobserved by SEM. For the raw materials of pure LiCoO2 withrelatively larger particle sizes, whether mixed with reductivemetallic iron or not, a significant reduction of the sizes could beobserved after the grinding process. Furthermore, the surfacesof the particles became much rougher with the increased

grinding time for both mechanically activated and mechano-chemical reduction samples (Figure 5b,c−e). As such, thereduction of particle size and the increase in specific surfacearea of particles could improve the leaching process, and achange in the crystal structure of particles also could be areason for the significant reduction of the apparent activationenergy of the leaching process. Hence, an obviously increasedextraction ratio of Li from acid solution could be achieved.However, Co was hardly extracted from the activated samplesby acid leaching even when the crystal structure had beendisordered, due to the stable chemical bonds between the Coatoms and O atoms (the states of Co in the activated samplewere not changed as discussed by the following XPS analysis,Figure 6a,b).In order to gain more evidence for the enhanced leaching

mechanism of Co during the mechanochemical reduction pro-cess with reductive metallic iron, XPS was performed to deter-mine the valence states of metals in the examined samples.Calibration was conducted using the C 1s peak of 284.8 eV.The photoelectron spectra of O 1s, Co 2p, and Fe 2p in LiCoO2powders were analyzed by XPS (Figure 6). The binding energy(BE) of Co 2p3/2 in activated samples is at 779.86 eV (Figure 6a),very consistent with that of 779.9 eV reported for LiCoO2.

32,33

Meanwhile, the BE of the O 1s spectrum in activated samples(Figure 6b) is at 529.45 eV, which can also be in goodagreement with the values of 529.0 and 529.6 eV reported forLiCoO2 by Elp et al.33 As shown in Figure 6a, the Co 2pspectrum in the mechanochemically reduced samples showed asatellite structure. Herein, the intense satellite structures havebeen about 5−6 eV above the Co 2p3/2 and the Co 2p1/2 transi-tions, in the case of high-spin Co2+ (S = 3/2) compounds.34

However, the satellites in activated samples were very weak, andlocated about 10 eV above the core level lines, in the case ofdiamagnetic Co3+ (S = 0).35 The Co 2p3/2−Co 2pl/2 separationcould increase with more unpaired electrons.36 Also, theseparation was 15.0 eV for diamagnetic Co3+, 15.4 eV for low-spin Co2+, and 16.0 eV for high-spin Co2+ ions.35 In this work,the Co 2p spectrum of the mechanochemically reduced samplesin Figure 6a shows satellite structure about 6 eV above the mainCo 2p transition, and the Co 2p3/2−Co 2p1/2 separation wasfound to be 15.6 eV. The Co 2p spectrum of activated samplesshows a satellite structure about 10 eV above the main Co 2ptransition, and the Co 2p3/2−Co 2p1/2 separation is found to beat 15.1 eV. These results indicate that the valence state of Cowas not changed after the activated process without Fe, i.e.,Co(III), while the oxidation state of Co was changed fromCo(III) to Co(II) after a mechanochemical reduction processwith Fe. This might be responsible for the difficult extraction ofCo from the activated sample but easy extraction from themechanochemical reduction sample by acid leaching.The Fe 2p spectra for the mechanochemical reduction sam-

ple are shown in Figure 6c. The BEs of Fe 2p1/2 and Fe 2p2/3were measured as 724 and 710.76 eV. According to the hand-book of X-ray photoelectron spectroscopy,37 the peaks of Fe(III)in Fe2O3 are located at 724.3 eV for Fe 2p1/2, and 710.7 eV forFe 2p3/2 respectively. That is to say that Fe2O3 appeared after themechanochemical reduction process with Fe. Two resolvedpeaks can be observed in each spectrum of the O ls in Figure 6b.The larger binding energy peak is broader in the mechanochem-ical reduction samples than that on the activated samples, whichis caused by the formation of Fe2O3 and the break of LiCoO2.Therefore, the change of valence state in Co was proposed forthe mechanochemical reduction process (eq 2).

Figure 6. XPS core level spectra of Co, O, and Fe in different samples.

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+ → +3Co(III) Fe(0) 3Co(II) Fe(III) (2)

On the basis of these prior observations, the destroyed crys-tal structure, amorphous state, and much rougher surfaces ofLiCoO2 were the reasons that leaching efficiency of Li wasimproved. Also, the high leaching efficiency of Co was improvedby the valence state change of Co in the LiCoO2 in the mech-anochemical reduction process with iron powders.Cobalt and Lithium Extraction from the Wasted LIBs.

To verify the effectiveness of the novel mechanochemical reduc-tion process for the pretreatment of valuable metals leachingfrom spent LIBs in acidic solutions, the actual cathode materialsdisassembled from waste LIBs were also examined, and theexperimental conditions were the same. The metal contents ofthe cathode materials are shown in Table S1. In a comparisonwith pure materials, the extractions of Li, Co, Mn, and Ni wereall obviously increased after 2 h leaching in a 1 mol/L HNO3solution at room temperature, and these observations were ingood agreement with the aforementioned results. It is worthmentioning that the extraction of Co, Mn, and Ni was signifi-cantly higher than that of activated samples. The yields of Coincreased from 20.43% to 91.25%, and the yields of Mn and Nialso increased from 33.19% and 38.67% to 100% and 99.9%,respectively, between actual material and mechanochemicalreduction samples (Figure 7a). In addition, over 99% of Fe canbe leached out by this mechanochemical reduction process inacid solutions. Figure 7b shows the XRD patterns of differentsamples. The crystal structure changed dramatically, and the XRDpattern intensity was decreased; the peaks nearly disappearedin both the activated and mechanochemical reduction samples.In a comparison with many other studies, the leaching effi-

ciency is relatively higher. For example, the leaching efficiencyof Co is 70% under the conditions of 2 mol/L H2SO4 + 5%H2O2 with a leaching time of 1 h at 75 °C,38 and 90% of Counder the conditions of 1.5 mol/L DL-malic acid (C4H5O6) +2.0% H2O2 with a leaching time of 40 min at 90 °C,14 and also45% of Co by bioleaching using Aspergillus niger.39 In a com-parison with these present conditions of 1 mol/L HNO3 withleaching time of 2 h at room temperature, the aforementionedconditions in the previous studies38,14,39 need higher acid con-centrations and higher temperature, which might result in moreenvironmental risk and operational difficulties. Therefore, theresults of cathode materials disassembled from waste LIBs fur-

ther illustrate that the mechanochemical reduction process withFe is an effective pretreatment approach.

■ CONCLUSIONSAn enhanced leaching for valuable metals in dilute acid solutionfrom wasted LIBs via a mechanochemical reduction processwith Fe is examined. The mass ratios of Fe/LiCoO2, rotationspeed, and mechanochemical reduction time have positiveinfluences on the leaching of Co, while they have almost noeffects on the extraction of Li. On the basis of the charac-terization analysis conducted by XRD, SEM, and XPS, themechanochemical mechanism was proposed. The reduction ofparticle sizes, increase of specific surface area, and changesof the crystal structure of particles by mechanical activationenhance the leaching of Li. However, for high-efficiency extrac-tion of Co, besides for the aforementioned reasons for Li, themechanochemical reduction by Fe to change the valence stateof Co played a dominant role. Ultimately, over 77% of Li, 91%of Co, 100% of Mn, and 99% of Ni can be extracted from actualwasted LIBs pretreated by this novel mechanochemical reduc-tion process in dilute acid solutions. The present study presentsa promising technology for cyclic regeneration of valuable metalsfrom waste LIBs.

■ ASSOCIATED CONTENT*S Supporting InformationThe Supporting Information is available free of charge on the ACSPublications website at DOI: 10.1021/acssuschemeng.6b02337.

Pretreatment of the waste cathode materials, metal con-tents, influence of direct leaching time, and XRD patternsof activated sample (PDF)

■ AUTHOR INFORMATIONCorresponding Authors*E-mail: ygguo@sspu.edu.cn.*E-mail: glgao@sspu.edu.cn.*E-mail: nanomaterials2000@gmail.com or zguo10@utk.edu.ORCIDYaguang Li: 0000-0003-3230-7771NotesThe authors declare no competing financial interest.

Figure 7. Yields of Li, Co, Mn, and Ni extracted from different samples (a) and XRD pattern of the different samples (b). Conditions: grinding time= 250 min, rotation speed = 550 rpm, Fe/LiCoO2 mass ratio = 1:1.

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■ ACKNOWLEDGMENTSWe gratefully appreciate the financial support from NaturalScience Foundation of China (51678353), Shanghai SailingProgram (15YF1404300), Shanghai “Chenguang” Program(15CG60), Shanghai Natural Science Foundation (No.15ZR1416800), Shanghai University Youth Teacher FundingProgram (ZZZZEGD15011), Cultivate Discipline Fund of Shang-hai Polytechnic University (XXKPY1601), and Eastern ScholarProfessorship Grant. The authors also acknowledge the GraduateStudent Funding Program of Shanghai Polytechnic University(A01GY16F030), Project Supported by Shanghai CooperativeCentre for WEEE Recycling (ZF1224), Shanghai Pudong NewArea of Science and Technology Development Fund (PKJ2015-C07 & PKJ2015-C14), and Qingpu “Industry-University-Institute”Cooperation Development Fund (Qing 2015-9).

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ACS Sustainable Chemistry & Engineering Research Article

DOI: 10.1021/acssuschemeng.6b02337ACS Sustainable Chem. Eng. 2017, 5, 1026−1032

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