Article Electrochemistry, 84(11), 836–841 (2016)

A Simple Preparation of Polyaniline-coated Sulfur Compositesfor use as Cathodes in Li–S BatteriesJungeun HYUN,a,b Pyoung-Chan LEE,b Myoung-Jo JUNG,c and Tatsumi ISHIHARAa,d,*a Department of Automotive Science, Graduate School of Integrated Frontier Sciences, Kyushu University,Motooka 744, Nishi-ku, Fukuoka 819-0395, Japan

b Department of Environmental Materials and Components R&D Center, Korea Automotive Technology Institute 74,Yongjung-ri, Pungse-myeon, Chonan-si, Chungnam 330-912, Korea

c Elpani Co., 732-6 Yangno-ri, Bibong-myeon, Hwasung-si, Gyeonggi-do, Koread International Institute for Carbon Neutral Research Center (WPI-I2CNER), Kyushu University,Motooka 744, Nishi-ku, Fukuoka 819-0395, Japan

*Corresponding author: ishihara@cstf.kyushu-u.ac.jp

ABSTRACTA polyaniline (PANi)-coated sulfur cathode was prepared by in-situ polymerization to improve the performanceof Li–S batteries and prevent polysulfide dissolution. Because PANi polymerization requires only the addition ofsulfur powder, the polymerization method was simple. Battery performance testing was conducted using varioussulfur ratios, with the best performance being exhibited by the 31wt% sulfur PANi composite (approximately500mAhg−1S after 50 cycles from an initial capacity of 903mAhg−1S). Transmission electron microscopy imagesconfirmed that sulfur was coated by an approximately 10-nm-thick layer of PANi. Cycle testing was conducted at arate of 0.2C with an electrode loading of 2mgcm−2 of sulfur. Thus, a highly homogenous distribution of sulfurparticles in PANi was achieved, resulting in sulfur-coated composite materials and allowing for the preparation of aconductive polymer by a relatively simple sulfur distribution method.

© The Electrochemical Society of Japan, All rights reserved.

Keywords : Polyaniline, Composite, Lithium–sulfur, In-situ

1. Introduction

Electric vehicles (EVs) are expected to become the next-generation ground transportation vehicles because their batteriesgenerate less CO2 than gasoline-fueled vehicles. In addition, theenergy storage system (ESS) market is rapidly expanding owingto increasing public interest in environmental issues and energymanagement. To satisfy the resulting expectations, research onLi–S batteries has been focused on achieving performance close toa high theoretical energy capacity of 1675mAhg¹1.1 AlthoughEV and ESS battery systems do not require as much power as thehybrid electric vehicle (HEV) battery system, they still require highenergy densities. In this respect, sulfur cathodes are very promisingmaterials. It is known that sulfur cathode materials possess hightheoretical energy, but their cyclability and power characteristicsare low because of the shuttle effect, i.e., the transport of solublepolysulfides between both electrodes, including the charge “shuttle”that accompanies this mass transport.2

Researchers have addressed this issue by coating the sulfurcathode with a carbon material or a conductive polymer to suppressthe dissolution of polysulfides. Graphene,3–6 carbon nanotubes(CNTs),7–9 and carbon10–12 have been investigated as sulfur-based cathode materials. Carbon-conductive polymer compositematerials13–19 and conductive polymer matrices20–29 have also beenwidely tested for their ability to improve battery performance.Huang et al. showed that graphene-coated sulfur composites couldbe used to improve cycling performance.3 Moon et al. researchedpolyaniline-coated graphene oxide–sulfur composites and achievedgood performance up to 500 cycles.18 Liu et al. synthesizednanosulfur/polyaniline/graphene composites via one-pot in-situsynthesis, and they showed an energy capacity of 600mAhg¹1 at100 cycles with a 0.1C-rate.19 Graphene is a very good materialfor improving the electric conductivity of a material, but in terms of

price and processibility, PANi itself is a common and good materialfor improving the performance by preventing polysulfide dissolution.Xiao et al. reported improved cycling performance using sulfur-coated nanotube-type polyaniline.21 Wei et al. synthesized hollowpolyaniline sphere/sulfur composites using an etching method, andthe composites showed good performance.28 Sun et al. synthesized aternary polyaniline with acetylene black sulfur with a liquid phase,and it showed good performance, with an energy capacity of600mAhg¹1 sulfur at 100 cycles with a 100mAcm¹2 current rate.29

Various other approaches such as the electrolyte30–32 and electrolytesalt33 selected and electrode loading34–36 have also been consideredfor their impact on lithium sulfur battery performance.

In this study, PANi, a conductive polymer, was evaluated as acoating layer matrix in the presence of sulfur during polymersynthesis. We used the sulfur powder itself in the polymerizationprocess and synthesized the polymer matrix on the sulfur powdersurface, which simplifies the synthesis method and preventspolysulfide dissolution, thus providing improved lithium sulfurbattery performance.

2. Experimental

2.1 Synthesis and analysis of PANi composite materialsPANi–sulfur cathodes were prepared as follows (Fig. 1A). A

2-L double-jacketed reactor was equipped with a reflux condenserand the temperature was set to 0°C. Appropriate amounts of2-Acrylamido-2-methylpropane sulfonic acid (AMPSA, 99%,Aldrich), 2-phenoxyaniline (99%, Aldrich), purified aniline(99.5%, Aldrich), and sulfur (Aldrich, 100 mesh, pulverized for30min) were added to the reactor and stirred overnight at 0°C. Themass ratio of AMPSA and purified aniline was 1.5:1. Also, the 2-phenoxy aniline is added 1wt% of aniline. After stirring overnight,a 30wt% ammonium persulfate (98%, Aldrich) solution in AMPSA

Electrochemistry Received: December 13, 2015Accepted: July 13, 2016Published: November 5, 2016

The Electrochemical Society of Japan http://dx.doi.org/10.5796/electrochemistry.84.836

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was added dropwise over 3 h using an addition funnel. Once all thereagents were added and the reaction proceeded for 2 h, the resultantPANi was filtered through a 2-µm filter paper and washed withmethanol until the filtrate showed no color. The obtained solid wasthen dried at 50°C in a vacuum oven for 24 h. Three types ofcomposite materials were prepared by controlling the amount ofadded sulfur (19wt%, 31wt%, and 54wt%) with the in-situ method.

In order to compare the adsorption effects on the PANi powder,PANi powder was prepared with the above method, and the PANipowder and sulfur powder were mixed (using a ball mill) andreacted at 150°C for 3 h in vacuum, at which point the sulfur meltedand surrounded the PANi particles (Fig. 1B). Sulfur’s melting pointis 112°C, and so it melts at 150°C and especially in vacuum status ithas its vapor pressure. The sulfur powders adsorbed onto the PANiparticle surfaces were compared to the in-situ preparation method.Because the sulfur:PANi ratio affects the adsorption, to compare theperformance with the 54wt% PANi-coated sulfur composite, weadjusted the mixture ratio of the sulfur and PANi raw material to4:2 (g) and synthesized 55wt% of the sulfur composite, which wasattached to the surface after evaporation.

The surface characterization of the PANi–sulfur composite wascarried out using field emission scanning electron microscopy(FESEM; JEOL JSM-6701F). The particle distribution of thecomposite was investigated using a particle-size analyzer (PSA,Beckman Coulter LS-100Q). The morphology and energy dispersivespectroscopy (EDS) mapping of the samples were obtained withtransmission electron microscopy (TEM, JEM, ARM 200F at anaccelerating voltage of 200 kV), and X-ray photoelectron spec-troscopy (XPS) (AXIS NOVA) was carried out with a mono-chromatic Al KA (1486.6 eV) X-ray source and sputtering with anAr+ ion gun (2 kV power). The samples were sputtered four times.The crystal structure was analyzed by X-ray diffraction (XRD,Rigaku D/MAX 1400) with CuKA radiation. Thermal gravimetricanalysis (TGA, NETZSCH) was performed from 30°C to 650°Cin 10°Cmin¹1 increments to determine the sulfur content of the

composite. We measure the Brunauer–Emmett–Teller (BET) surfacearea with Quadrasorb station 6 by N2 gas sorption.

2.2 Formation of electrodes and electrochemical analysisFor the sulfur cathode, 70wt% sulfur (Aldrich, 100 mesh),

20wt% vapor-grown carbon fiber (VGCF, Showa Denko), 8wt%polyvinylidene fluoride (PVDF, Kynar 761), and 2wt% poly-ethylene glycol (PEO) binder (Aldrich) were used as referencesamples with an electrode loading of 2mg of sulfur. For the PANi–sulfur composite cathode electrode via in-situ polymerizationmethod and via adsorption method, the sulfur composite cathodeelectrode was prepared as 70wt% PANi–sulfur, 20wt% VGCF(Showa Denko), 8wt% PVDF (Kynar 761), and 2wt% PEO binder(Aldrich) with an electrode loading of 2mg of sulfur.

These experiments were performed using a homogenizer (ACE,20-mL cup) for all mixing steps with N-methyl-2-pyrrolidone(NMP, Dae-Jung) as the solvent, and a film applicator was used ona carbon-coated foil for coating the electrode. After the coatedelectrode was dried for 12 h at 50°C, the film was punched with a1.1 cm2 hole. 2-mm-thick lithium metal (HOSEN, Japanese) wasused as the anode with Celgard 2400 as the separation layer.The electrolyte used was 20 uL of a solution of 1M lithiumbis(trifluoromethanesulfonyl)imide (LiTFSI) dissolved in 5,5-di-methoxyethane and 1,3-dioxolane (1:1 in volume). Coin half-cellswere prepared in a glove box with the moisture content limited towithin 0.3 ppm. Galvanostatic charge–discharge cycling of the coincells were tested with a Wonatech 3000 battery performance testerwithin 1.5–2.65V and a 0.2C-rate. The 0.2C-rate corresponds toan equivalent current density of 335mAg¹1 based on the theoreticalcapacity of sulfur of 1675mAhg¹1. Cyclic voltammetry (CV)measurements of the coin cells were carried out with a Wonatech3000 battery performance tester within 1.5–3V and a scan speedof 0.1mV s¹1. The impedance was analyzed by electrochemicalimpedance spectroscopy (Wonatech, Zive-1000) in the frequencyrange of 1MHz to 100mHz with an AC signal amplitude of 10mV.

3. Results and Discussion

The sample surfaces were characterized by SEM to determine thesize and morphology of the PANi raw material [Fig. 2A(a)] and thePANi–sulfur composites [Figs. 2A(b–e)]. The primary particles ofthe PANi raw material were relatively small, approximately 100–200 nm in size [Fig. 2A(a)], thus providing a large surface area toreact. The size distribution of the secondary particles was 30–40 µm(Fig. 2B), which consisted of clusters of primary particles with asurface area of 90m2 g¹1. Larger primary particles were observed[Figs. 2A(b, c, d)] when aniline was polymerized with the sulfurpowder by the in-situ method. The secondary particle-sizedistribution of 30–40 µm is shown in Fig. 2B. The BET surfaceareas of the samples were 18.2m2 g¹1 for 19wt%S, 14.63m2 g¹1

for 31wt%S, and 16.5m2 g¹1 for 54wt%S, each with three differentPANi–sulfur composites. It is assumed that the primary particlesreached 200–400 nm in size by reacting with sulfur. Themorphology of the sulfur-coated PANi composite fabricated usingthe adsorption method is shown in Fig. 2A(e). This composite wasprepared by ball milling a mixture of the sulfur and PANi powders.The melted sulfur moved onto the PANi powder surfaces and coatedthe particles. The PANi powder surfaces were coated with sulfur,and so the pores seen for the PANi raw materials [Fig. 2A(a)] werenot detected in sulfur-coated PANi composite fabricated throughadsorption [Fig. 2A(e)].

We believe that the in-situ reaction of PANi with sulfur causedthe size of the primary particles to increase. We expected that thePANi-coated sulfur composite would prevent polysulfides fromdissolving in the electrolyte because of the presence of thephysically conductive polymer layer and the strong adhesion to

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Figure 1. (Color online) (A) Synthesis process of PANi–sulfurcomposite via in-situ reaction. (B) Synthesis process of PANi–sulfurcomposite via adsorption.

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the hydrophilic sulfonic group of PANi. As a dopant of PANi,AMPSA has a hydrophilic sulfonic group, which is expected tocreate ionic bonds (–O–S–) with polysulfides. Hence, we prepared acomposite via the adsorption reaction of sulfur and PANi, which wasexpected to result in only ionic bonding to prevent polysulfidedissolution on the PANi powder surface. The performance of thiscomposite was then compared to that of the coated sample. Thissimple adsorption reaction of sulfur and PANi showed that sulfurparticles were adsorbed onto the PANi surface [Fig. 2A(e)], whichgenerated a thin coating.

TGA analysis was conducted to confirm the ratio of sulfur in thecomposites. As shown in Fig. 3, the sulfur content was analyzed byTGA for both pure sulfur and the sulfur–PANi composites, and theresults confirmed that the composites contained 19, 31, and 54wt%

of sulfur. The simple adsorption process resulted in 55wt% sulfur.Pure sulfur vaporizes completely below 350°C. At approximately100°C, there was weight loss due to the evaporation of waterbecause hydrophilic AMPSA, which contained water, was includedin the PANi composites. It was assumed that the sublimatingtemperature decreased as the PANi content increased. In the caseof adsorption, the sulfur was distributed on the surfaces of thenano-sized PANi powder particles, which decreased the sublimatingtemperature.

The distribution of sulfur and the coating thickness of the in situ-generated PANi-coated composite were confirmed through TEMand XPS analysis. As shown in Fig. 4, TEM analyses wereconducted to investigate the distribution of sulfur and PANi withinthe composite particles. Analysis of the sulfur (green dots in Fig. 4)showed the presence of some sulfur from the external boundary ofthe particle to its interior. The homogeneous distribution of sulfurduring the PANi production process showed that PANi coated thesulfur surface. The changes in sulfur content from the surface to theinterior were further analyzed using XPS with internal sputtering(Fig. 5) with the 31wt% composite material. Figure 5 shows theXPS spectra of the S 2p region. Polymerization occurred on thesurface of the sulfur powder, and so we measured the XPS in thedepth direction after the fourth sputtering. The peak at approx-imately 163–164 eV represents the binding energy of sulfurcorresponding to S 2p3/2, whereas the sulfite peak was observed at166–170 eV.37 The sulfite peak is from the dopant AMPSA of PANi.If the sulfur content from the surface to the interior is equal, theS 2p peak in the XPS spectra with sputtering would be the same.However, the sulfur peak increased toward the inside of the

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Figure 2. (Color online) (A) SEM images of (a) PANi raw materials, PANi-coated sulfur composites with (b) 19wt%S, (c) 31wt%S, and(d) 54wt%S, and (e) sulfur-coated PANi composite via adsorption on the PANi surface. (B) Particle-size distribution data of (a)–(d).

Figure 3. (Color online) Thermogravimetric analyses of samples.

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particles, whereas the sulfite peak strength decreased, and so it isconfirmed that the sulfur powder was coated by a few-nm-thicklayer of PANi.

Figure 6 shows the collected XRD data. Raw sulfur, the PANi–sulfur composites, and raw PANi were analyzed in order to comparethe peak differences. A high-intensity peak was observed at2H = 23° for sulfur, whereas the composite material showed reducedintensity. PANi showed broad patterns typical of polymers. For the19wt% sulfur composite, the sulfur intensity was significantlyreduced and showed a broad PANi peak at 20–30°.

The discharging process begins with sulfur because of a changein the polysulfide structure (Li2Sn, 4 ¯ n ¯ 8), which generates

the final lithium sulfide form (Li2S2, Li2S). The solubility ofpolysulfides is high in electrolytes, as mentioned above, inducingthe deterioration of the sulfur cathode and lowering the cycleperformance. The final form of lithium sulfide is insoluble in theelectrolyte if it remains in the cathode as a solid adsorbed on thesulfur surface, serving as an insulating layer. If the dissolvedpolysulfide crosses the separation layer, it also forms lithiumsulfide and is adsorbed on the anode surface, reducing the cycleperformance. To circumvent these problems and improve the cycleperformance, a thin PANi coating (a few nanometers) was employedto block polysulfide movement.

Figure 7A(a) shows the cycle performance of the sulfur–PANicomposites. The composite with 31wt% sulfur showed the bestperformance, with an initial capacity of 903mAhg¹1 S andapproximately 500mAhg¹1 S after 50 cycles. The 54wt% and19wt% sulfur composites showed approximately 300mAhg¹1 Sand 190mAhg¹1 S after 50 cycles, respectively. AC impedancemeasurements carried out before the cycling experiments showedthat the 31wt% sulfur composite exhibited the lowest resistance[Fig. 7A(b)], which is in accordance with the cycle performance[Fig. 7A(a)]. Moreover, the voltage–capacity profile showed astable discharge at 2.0V for the 31wt% sample [Fig. 7A(c)]. InFig. 7A(a), the parameter of the PANi-coated sulfur composite is thequantity of the included sulfur to control the characteristics of thecomposite and prevent polysulfide dissolution. The following arepotential reasons for the poor performance of the 54wt% sampleas compared to the 31wt% sample: (1) The large quantity ofsulfur (54wt%) cannot be sufficiently covered with the conductivepolymer. (2) The hydrophilic group of PANi is expected to matchthe wetting characteristics of the electrolyte and sulfur electrode. Ifthere is an insufficient quantity of polymer, the wetting characteristicof electrode would be poor, which would result in an increase inthe impedance of the cell. The thicknesses of the electrodes were310µm for 19wt%S, 293 µm for 31wt%S, and 261µm for54wt%S, which are somewhat thick, and this may have affectedthe wettability.

In contrast, the composite containing 19wt% sulfur resulted inthe thickest electrode with an irregular surface structure that formedcracks during electrode synthesis, which resulted in the inferiorelectrical conductivity of the electrode, although the resistance ofthe PANi–sulfur composite powder was as low as 0.099³ cm for the19wt%S composite as compared to 0.178³ cm for 31wt% S and0.219³ cm for 54wt%S. It is assumed that this is the key reason forthe reduced cycle performance.

Figure 4. (Color online) TEM images of PANi-coated sulfur composites with (a) 19wt%S, (b) 31wt%S, and (c) 54wt%S.

Figure 5. (Color online) XPS data for the PANi-coated sulfurcomposite with 31wt%S.

Figure 6. (Color online) XRD patterns of samples.

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The cycle performance [Fig. 7A(d)] was studied using samplesprepared by the adsorption of sulfur. The effect of the simpleadsorption of sulfur onto the PANi surface as compared to the in-situpolymerization coating process was investigated. The sulfur–PANicomposite, by which sulfur was adsorbed via vapor reactions ontothe PANi surfaces, showed better cycle performance than the rawsulfur material [Fig. 7A(d)]. However, the sulfur-adsorbed samplesshowed inferior cycle performance as compared to the in situ-generated PANi-coated sulfur samples. For the samples with sulfuradsorbed onto the surface of PANi, it was expected also thatthe dissolution of polysulfides in the electrolyte solution would beprevented by chemical adsorption via ionic bonding between thehydrophilic group of PANi and the ionized polysulfide mentionedabove and by relatively weak physical adsorption via van der Waalsforces resulting from the large surface areas. These samples showedbetter performance as compared to the raw sulfur electrode.However, the PANi-coated sulfur composite still provided the bestperformance.

The SEM images in Figs. 7B(a, b) show the 31wt% sulfurelectrode before and after cycling. Byproducts (e.g., lithium sulfide)from the charge and discharge reactions were adsorbed onto thecomposite surface. However, the specific morphology of primary

and secondary particles is changed but primary and secondaryparticles are “still classified” not united. If the sulfur is not coated byPANi, we’re assumed the primary and secondary particle boundarywould disappear due to the united sulfur powders. It is assumed thatthe electrochemical reaction occurred on the primary particle surfacethrough the polymer matrix. Figure 8(a) shows the current changesthat occurred during the charge–discharge process for the 31wt%sulfur sample. The two obvious cathodic peaks at approximately2V indicate that sulfur (S8) was transformed into a long-chainpolysulfide (Li2Sn, 4 ¯ n ¯ 8), whereas the polysulfides weretransformed to the final solid form of lithium sulfide (Li2S, Li2S2).CV [Fig. 8(b)] measurements were conducted in the range of 1.5–3V to determine the reactivity of PANi in the Li–S battery system.There was almost no cathodic reaction with the raw PANi material.

4. Conclusion

In this study, to prevent polysulfide dissolution efficiently, wesynthesized PANi-coated sulfur composites and fabricated sulfurcathode electrodes with 2mg cm¹2 S loading. We have shown thata highly homogenous distribution of sulfur particles during PANipolymerization can generate PANi-coated sulfur materials. A

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Figure 7. (Color online) (A) (a) Cycle performance of PANi-coated sulfur composites and sulfur. (b) AC impedance data of PANi-coatedsulfur composites and sulfur. (c) Voltage–capacity profile of PANi-coated sulfur composite with 31wt%S. (d) Cycle performance of sulfur-coated PANi composite with adsorption on the PANi surface. (B) Electrode SEM image of PANi-coated sulfur composite with 31wt%S (a)before and (b) after cycling.

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31wt% sulfur composite showed superior performance as comparedto that shown by materials containing 19wt% and 54wt% sulfur.Thus, 31wt% is considered the optimal sulfur content. It is assumedthat polysulfide dissolution could not be prevented in the electrodeswith 54wt% sulfur owing to their higher sulfur content, whereasthe 19wt% sample showed unsatisfactory electrical conductivity.Polyaniline-coated sulfur also showed a significant improvement inperformance as compared to the sample fabricated with a simplephysical adsorption process.

References

1. J. R. Akridge, Y. V. Mikhaylik, and N. White, Solid State Ionics, 175, 9821(2004).

2. C. Lin, W. Chen, Y. Song, C. Wang, L. Tsai, and N. Wu, J. Power Sources, 263, 98(2014).

3. J. Huang, X. Liu, Q. Zhang, C. Chen, M. Zhao, S. Zhang, W. Zhu, W. Qian, and F.Wei, Nano Energy, 2, 314 (2013).

4. J. Wang, L. Lu, M. Choucair, J. A. Stride, X. Xu, and H. Liu, J. Power Sources,196, 7030 (2011).

5. G. Zhou, S. Pei, L. Li, D. Wang, S. Wang, K. Huang, L. Yin, F. Li, and H. Cheng,Adv. Mater., 26, 625 (2014).

6. X. Wang, Z. Zhang, Y. Qu, Y. Lai, and J. Li, J. Power Sources, 256, 361 (2014).7. X. Z. Ma, B. Jin, P. M. Xin, and H. H. Wang, Appl. Surf. Sci., 307, 346 (2014).8. Y. Wu, M. Gao, X. Li, Y. Liu, and H. Pan, J. Alloys Compd., 608, 220 (2014).9. Y. Li, R. Mi, S. Li, X. Liu, W. Ren, H. Liu, J. Mei, and W. Lau, Hydrogen Energy,

1 (2014).10. J. Zhang, H. Ye, Y. Yin, and Y. Guo, J. Energy Chemistry, 23, 308 (2014).11. Q. Li, Z. Zhang, Z. Guo, Y. Lai, K. Zhang, and J. Li, Carbon, 78, 1 (2014).12. L. Li, Y. Chen, and B. Zhong, Composites, Part A, 62, 26 (2014).13. X. Zhaoa, J. Kim, H. Ahn, K. Cho, and J. Ahn, Electrochim. Acta, 109, 145

(2013).14. J. Jin, Z. Wen, G. Ma, Y. Lu, and K. Rui, Solid State Ionics, 262, 170 (2014).15. Y. Lim, M. Park, S. Lee, W. Lee, and N. Jo, Trans. Nonferrous Met. Soc. China,

22, s717 (2012).

16. Z. Wei, M. Wan, T. Lin, and L. Dai, Adv. Mater., 15, 136 (2003).17. T. Chi, H. Li, X. Li, H. Bao, and G. Wang, Electrochim. Acta, 96, 206 (2013).18. S. Moon, Y. H. Jung, and D. K. Kim, J. Power Sources, 294, 386 (2015).19. Y. Liu, J. Zhang, X. Liu, J. Guo, L. Pan, H. Wang, Q. Su, and G. Du, Mater. Lett.,

133, 193 (2014).20. L. Duan, J. Lu, W. Liu, P. Huang, W. Wang, and Z. Liu, Colloids Surf., A, 414, 98

(2012).21. E. M. Genies and S. Picart, Synth. Met., 69, 165 (1995).22. A. Konarov, D. Gosselink, T. N. L. Doan, Y. Zhang, Y. Zhao, and P. Chen,

J. Power Sources, 259, 183 (2014).23. L. Xiao, Y. Cao, J. Xiao, B. Schwenzer, M. H. Engelhard, L. V. Saraf, Z. Nie, G. J.

Exarhos, and J. Liu, Adv. Mater., 24, 1176 (2012).24. X. Liang, Z. Wen, Y. Liu, X. Wang, H. Zhang, M. Wu, and L. Huang, Solid State

Ionics, 192, 347 (2011).25. J. Wang, J. Chen, K. Konstantinov, L. Zhaoa, S. H. Ng, G. X. Wang, Z. P. Guo,

and H. K. Liu, Electrochim. Acta, 51, 4634 (2006).26. Y. Zhang, Z. Bakenov, Y. Zhao, A. Konarov, T. N. L. Doan, M. Malik, T. Paron,

and P. Chen, J. Power Sources, 208, 1 (2012).27. X. Liang, Y. Liu, Z. Wen, L. Huang, X. Wang, and H. Zhang, J. Power Sources,

196, 6951 (2011).28. P. Wei, M. Q. Fan, X. R. Yang, H. M. Wu, J. Chen, T. Li, L. W. Zeng, C. M. Li,

Q. J. Ju, D. Chen, G. L. Tian, and C. J. Lv, Renew. Energy, 86, 148 (2016).29. Y. Sun, S. Wang, H. Cheng, Y. Dai, J. Yu, and J. Wu, Electrochim. Acta, 158, 143

(2015).30. H. Nagata and Y. Chikusa, J. Power Sources, 264, 206 (2014).31. S. Urbonaite and P. Novák, J. Power Sources, 249, 497 (2014).32. S. S. Zhang, J. Power Sources, 231, 153 (2013).33. Y. Aihara, T. Bando, H. Nakagawa, H. Yoshida, K. Hayamizu, E. Akiba, and W. S.

Pricec, J. Electrochem. Soc., 151, A119 (2004).34. J. Brückner, S. Thieme, H. T. Grossmann, S. Dorfler, H. Althues, and S. Kaskel,

J. Power Sources, 268, 82 (2014).35. J. Zheng, M. Gu, C. Wang, P. Zuo, P. K. Koech, J. Zhang, J. Liu, and J. Xiao,

J. Electrochem. Soc., 160, A1992 (2013).36. X. Cheng, J. Huang, H. Peng, J. Nie, X. Liu, Q. Zhang, and F. Wei, J. Power

Sources, 253, 263 (2014).37. C. M. Fang, H. C. Gao, Y. Ho, Z. G. Cai, and Y. Zhang, Solid State Ionics, 48, 289

(1991).

Figure 8. Cyclic voltammetry analysis of (a) PANi-coated sulfur composite with 31wt%S and (b) PANi raw material.

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