ARTICLE pubs.acs.org/JPCC
Sulfur/Polythiophene with a Core/Shell Structure: Synthesis and Electrochemical Properties of the Cathode for Rechargeable Lithium Batteries Feng Wu,†,‡ Junzheng Chen,† Renjie Chen,*,†,‡ Shengxian Wu,† Li Li,†,‡ Shi Chen,†,‡ and Teng Zhao† †
Beijing Key Laboratory of Environmental Science and Engineering, School of Chemical Engineering and Environment, Beijing Institute of Technology, Beijing 100081, PR China ‡ National Development Center of High Technology Green Materials, Beijing 100081, PR China ABSTRACT: Novel sulfur/polythiophene composites with core/shell structure composites were synthesized via an in situ chemical oxidative polymerization method with chloroform as a solvent, thiophene as a reagent, and iron chloride as an oxidant at 0 °C. Different ratios of the sulfur/polythiophene composites were characterized by elemental analysis, FTIR, XRD, SEM, TEM, and electrochemical methods. A suitable ratio for the composites was found to be 71.9% sulfur and 18.1% polythiophene as determined by CV and EIS results. Conductive polythiophene acts as a conducting additive and a porous adsorbing agent. It was uniformly coated onto the surface of the sulfur powder to form a core/shell structure, which effectively enhances the electrochemical performance and cycle life of the sulfur cells. The initial discharge capacity of the active material was 1119.3 mA h g1, sulfur and the remaining capacity was 830.2 mA h g1 sulfur after 80 cycles. After a rate test from 100 to 1600 mA g1 sulfur, the cell remained at 811 mA h g1 sulfur after 60 cycles when the current density returned to 100 mA g1 sulfur. The sulfur utilization, the cycle life, and the rate performance of the SPTh core/shell electrode in a lithiumsulfur battery improved significantly compared to that of the pure sulfur electrode. The pore and thickness of the shell affected the battery performance of the lithium ion diffusion channels.
1. INTRODUCTION The development of portable electronic devices has led to a corresponding increase in the demand for secondary batteries having both a lighter weight and a higher capacity. Among the various types of rechargeable batteries, the lithiumsulfur battery system is a very attractive candidate because it has almost the highest possible theoretical capacity of 1672 mA h g1 and the highest possible theoretical specific energy of 2600 W h kg1, which is better than for any of the other known cathode materials.1 On the basis of the fact that sulfur is abundant, cheap, and environmentally friendly, the lithiumsulfur battery holds great potential for use in the next generation of high-energydensity lithium batteries. However, it has been reported that LiS batteries containing organic liquid electrolytes have some problems, including the low utilization of active materials and a poor cycle life.2,3 This occurs because sulfur is electrically and ionically insulating, leading to poor electrochemical accessibility and a low utilization of sulfur in the electrode. The discharge reaction of sulfur always involves stepwise reduction processes and leads to the generation of various forms of soluble intermediate lithium polysulfides, which can dissolve in the liquid electrolyte and cause a rapid irreversible loss of sulfur-active materials upon repeated cycling. Consequently, the cathode solution could cause a decrease in its r 2011 American Chemical Society
capacity. In addition, the solubility of the intermediate polysulfides can result in the shuttle mechanism, which will further reduce the cycle life of the lithium sulfur battery.47 These difficulties result in many researchers using sulfides or composite materials such as PDDTB (poly[1,4-di(1,3-dithiolan-2yl)benzene]), PDTDA (poly(2,20 -dithiodianiline)), FeS2, and CuS instead of elemental sulfur. However, their specific capacities are mostly less than 30% of the theoretical capacity of sulfur.811 To operate LiS batteries successfully, the sulfur cathode material must be mixed well with a conductive additive and a strong adsorbent such as porous active carbon1215 or carbon nanotubes.1618 Recently, conducting polymers have received plenty of attention because they can play different roles in improving the cathode1921 as a result of their good electrochemical stabilities and their favorable morphologies. In our previous work,22 we conducted novel research into the use of polythiophene powder as an additive in the cathode material of LiS rechargeable batteries, and we found that sulfurpolythiophene could potentially solve the associated problems. Polythiophene particles that serve as conductive additives and porous adsorbing Received: May 15, 2010 Revised: February 2, 2011 Published: March 16, 2011 6057
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Table 1. Elemental Analysis Results for PTh and SPTh element weight percentage composite
Figure 1. Synthesis of the SPTh composites.
agents were uniformly coated onto the surface of the sulfur powder. However, further work is required to determine the best ratio of the SPTh composites and a suitable thickness for the polythiophene shell by in situ chemical oxidative polymerization. Moreover, the detailed physicochemical properties of the composites and cells must be determined systematically to prove that the core/shell composites were synthesized and also to determine the mechanisms for the improvement of LiS batteries. In this work, we synthesized and measured different ratios of SPTh composites to improve the electrochemical performance and cycle life of LiS batteries further. Mechanisms for the improvement of the composites by investigating their porous surfaces and their detailed reactions such as between PTh and the lithium ion were also determined and are discussed. We believe that the detailed technique given in this article provides a facile and reliable method to enable the wide application of lithium/sulfur systems.
C
H
S
elemental sulfur polythiophene
PTh
57.21
4.42
38.37
0
100
SPTh A
21.75
1.68
76.57
62.0
38.0
SPTh B
16.16
1.21
82.63
71.9
28.1
SPTh C
6.25
0.47
93.28
82.5
17.5
2. EXPERIMENTAL SECTION 2.1. Preparation of SulfurPolythiophene Composites.
Sulfurpolythiophene (SPTh) composites and polythiophene were synthesized by an in situ chemical oxidative polymerization method (shown in Figure 1).23 Thiophene (1.34, 2.68, and 5.26 g; Sinopharm Chemical Reagent Corp.) was dissolved in 50 mL of chloroform. Three solutions of 10.00 g of sulfur (Merck, Aldrich), 100 mL of chloroform (Beijing Reagent Company), and different amounts of FeCl3 (4:1 m/m FeCl3/thiophene) were added to three different three-necked flasks marked SPTh A, SPTh B, and SPTh C and stirred for 30 min. The thiophene monomer mixture was added slowly to the above-mentioned flasks, and the mixture in each flask was stirred for 10 h at 0 °C. After polymerization, 100 mL of methanol was added to the mixture to dissolve the remaining iron chloride. The mixture was then filtered to remove the iron ions, and the remaining insoluble solid was collected. This washing was repeated three times. After this, the solid was transferred to a flask and 100 mL of 1 M hydrochloric acid was added. The mixture was stirred for 2 h at room temperature, and then the remaining solid was collected by filtration and washed using deionized water until a neutral pH was obtained. Finally, the brown mass was dried at 60 °C for 24 h under vacuum to give the pure SPTh powder. 2.2. Material Characterization. Elemental analysis was carried out on an Elementar Vario MICRO CUBE (Germany). Fourier transform infrared (FTIR) spectra were recorded using a Nicolet 7100 (Thermo, USA) from 4000 to 500 cm1. X-ray diffraction (XRD) measurements were made using a Rigaku X-ray diffractometer with a Cu KR radiation source at a scan rate of 10° min1. The surface morphology of the composites was obtained by scanning electron microscopy (SEM, S-3500N) and transmission electron microscopy (TEM, JEM-2100). 2.3. Electrochemical Measurements. The SPTh cathode slurry was made using a mixture of 70% composites, 20% carbon black, and 10% polyvinylidene fluoride (PVDF) binder in an N-methyl-2-pyrrolidinone (NMP) dispersant to form a homogeneous slurry. A sulfur cathode slurry containing 50%
Figure 2. FT-IR spectra of the composites: thiophene, PTh, and SPThs.
sulfur, 40% carbon black, and 10% PVDF binder was prepared in the same way as were the SPTh composites. The coated electrodes were dried in a vacuum oven at 60 °C for 24 h. Subsequently, the electrode was cut into disks of 11 mm diameter. Coin-type (CR2025) cells were assembled in an argon-filled glovebox to avoid contamination by moisture and oxygen. The electrolyte used was 1 M LiTFSI in a solvent mixture of DOL/ DME (1:1 v/v). The cells were discharged and charged on a LAND electrochemical station (Wuhan) from 1.0 to 3.0 V at a current density of 100 mA g1 sulfur to test the cycle life. Cyclic voltammograms (CV) were recorded on a CHI604c electrochemical workstation (Shanghai Chenhua) between 1.0 and 3.0 V to characterize the redox behavior and the kinetic reversibility of the cell. The ac impedance was measured with fresh cells at the open circuit potential (OCP). This was also carried out using a CHI 604c electrochemical workstation. The ac amplitude was (5 mV, and the frequency ranged from 100 kHz to 0.1 Hz.
3. RESULTS AND DISCUSSION Table 1 shows the element weight ratio of carbon, hydrogen, and sulfur in the PTh and SPTh composites. The result suggests that the empirical formula of the prepared PTh was C4H4S and the ratios of elemental sulfur in the SPTh A, SPTh B, and SPTh C composites were 62.0, 71.9, and 82.5%, respectively. Figure 2 shows the FTIR spectra of thiophene, the PTh powder, and the SPTh composites. We found that the spectral data of the products was fully consistent with those reported previously.2426 During the synthesis procedure, the ferric ions oxidized the thiophene monomer and were then reduced to ferrite ions, which were removed by washing as determined by AAS.23 The CdC double-bond stretching vibration in the 6058
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Scheme 1. Synthesis Mechanism of Polythiophene
Figure 3. XRD patterns of PTh, SPThs, and sulfur.
thiophene ring was observed at 1410 cm1. The absorption peaks at 1033 and 781 cm1 indicated a CssH out-of-phase bending vibration and an in-phase bending vibration. The polymer had a typical layered structure,24 and the thiophene monomer could be polymerized in three ways: RR conjunction, Rβ conjunction, and ββ conjunction (Scheme 1).25,27 The resonance absorption of the CRCR conjunction was observed at 1112 cm1 at 0 °C, and the RR conjunction became dominant because the thermal motion of the monomer is very slow so that the polymerized products gained a structured backbone. The appearance of peaks at 781, 1033, and 1112 cm1 confirmed that the PTh chain that was prepared via chemical polymerization was a CRCR dominant polymer because the absorption of CβH would weaken if the polymer gained a CβCβ conjunction. The CRCR conjunction polymer had good conductivity upon the maximum overlap of the CC interring carbon pz orbitals.28,29 The similarity of the PTh and SPTh spectra indicated that no chemical reaction occurred between sulfur and PTh, which confirmed that PTh serves as a conducting additive instead of being chemically bound to active sulfur. To confirm the structure of the SPTh composites further, the XRD patterns are given in Figure 3. The XRD pattern of PTh showed an atypical amorphous structure with a broad peak centered at 2θ = 20°. XRD analysis of elemental sulfur showed two prominent peaks at 2θ = 23 and 28° corresponding to an Fddd orthorhombic structure.3033 Compared with the pattern of elemental sulfur, the XRD spectra of the SPTh composites did not exhibit many changes except for the appearance of slight broad PTh peaks centered at 2θ = 20° demonstrating that the
Figure 4. (a) Cyclic voltammograms of the different ratios of SPTh composites. (b) Nyquest plots and the equivalent circuit for the sulfur and SPTh cathodes.
crystal structure of sulfur remained original and no new phase was formed during the in situ polymerization oxidation process.19 To determine the best ratio range between sulfur and polythiophene, cyclic voltammograms and electrochemical impedance spectra (EIS) at the OCP of the cells were obtained using PTh A, B, and C as the active cathode materials, as shown in Figure 4a,b, respectively. The CV results of the electrodes are similar, as shown in Figure 4a. Two reduction peaks are clear, and they result from the multiple reaction mechanisms between sulfur and lithium, as has been reported previously.34,35 The first step comprised the transformation of sulfur to higher-order lithium polysulfides (Li2Sn, 4 e n < 8) at around the 2.3 V reduction peak. These polysulfides were in a metastable phase and dissolved easily into the electrolyte, which led to LiS battery system degradation during the chargedischarge process. The 2.0 V reduction peak was caused by a reduction of the higher-order lithium polysulfides to lower-order lithium polysulfides (Li2Sn, n < 4), even to Li2S. The oxidation peak near 2.5 V was caused by the transformation to lithium polysulfides (Li2Sn, n > 2). However, the SPTh B electrode showed sharp, distinct peak shapes and the potential difference between the oxidation peaks and the reduction peak was much smaller than that of the other electrodes, which results in better reversible thermodynamics for the reaction of sulfur with lithium. Compared with SPTh B, the oxidation peak of SPTh A was more positive because of the formation of insoluble and insulating Li2S, which can block pores and cause polarization during lithium ion diffusion. Second, the impedance spectrum shows a semicircular loop at high frequencies. No new semicircle 6059
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Figure 5. (ac) SEM and (d) TEM images for (a) sulfur and (bd) core/shell SPTh B.
is present in Figure 4b after PTh coating, which means that the liquid electrolyte can easily access the electrochemically active sulfur core because of the porous shell surface of the composite electrodes. The conductive structure also provides electron and ion channels for electrochemical reactions and enhances the conduction properties of the sulfur cathode significantly. The charge-transfer resistance was fitted with a typical EIS equivalent circuit, as shown in Figure 4, which is a measure of the chargetransfer kinetics.3639 This revealed that the composite wherein the sulfur particles are coated with conductive polymer could improve the electrochemical kinetics of the sulfur present in the rechargeable lithium batteries. The charge-transfer resistance (Rct) values of the SPTh A and B composite electrodes were found to be 93.42 and 122.4 Ω, respectively, which are much lower than that of SPTh C (220 Ω) and the pure sulfur electrode (245.6 Ω). Therefore, SPTh A and B have better reversible electrochemical properties than do the other compounds.28 In addition, by increasing the percentage of elemental sulfur from 62 to 71.9%, the total capacity of the battery improved dramatically. Consequently, it is clear that SPTh B has all of the advantages of the SPTh composites as determined by the electrochemical tests. To prove that the core/shell structure and the porous surface of the SPTh B composite exists, the morphologies of the materials are shown in Figure 5ad. The sulfur particle has an S8 crown ring structure, and its size is aggregated to about 20 μm (Figure 5a). After the introduction of PTh, the SPTh B composite developed a porous spherical structure (Figure 5b). At high magnification (Figure 5c), the surface of the SPTh composite shows flakelike morphology with highly developed porous structures. The PTh matrix reduced the particle-to-particle contact resistance, which significantly enhanced the electrical conductivity of
Table 2. EDX Results from the TEM Images Shown in Figure 5d plot in Figure 5d
element
weight percentage
atom percentage
a
C
36.39
59.34
S
63.61
40.66
C S
61.05 38.95
78.68 21.32
b
the composite. Conversely, the porous structure allowed the electrolyte to distribute throughout the electrode, which could explain the improvement in the electrochemical reactions instead of a lithium ion blockage.13,22,40 TEM of the SPTh B was carried out to show that the coating of PTh was successful (Figure 5d) and the thickness of its shell was 2030 nm. The EDX results listed in Table 2 prove that the dark area was composed of sulfur and the lighter area was PTh, as shown in Figure 5d. Compared with the elemental analysis given in Table 1, the ratio of C to S was close to that obtained for polythiophene. Hence, this Figure and Table confirm that PTh uniformly coats the whole active sulfur surface, which can prevent the active sulfur from dissolving into the electrolyte. Figure 6 shows different CV cycles of the cell made with SPTh B as the active cathode material to determine its life performance. After three cycles, the reaction peaks barely shifted compared with the first cycle, indicating that the electrochemical kinetics of the SPTh B cathode was approximately reversible. Even after 80 cycles, the reaction peaks were similar to that of the first cycle. In addition, a weak oxidation peak was observed near 2.8 V, and it was still present after 80 cycles. To investigate the detailed reactions of this peak, the bare PTh electrode was cycled 6060
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Figure 7. Charge/discharge profiles of the cathodes: (a) sulfur and (b) the SPTh B composite. Figure 6. (a) Cyclic voltammograms of the SPTh B electrode. (Inset) Cyclic voltammograms of the SPTh B electrode at different scan rates. (b) Cyclic voltammograms of the bare polythiophene electrode.
between 1.0 and 3.0 V versus Li/Liþ to confirm that the peak near 2.8 V contributes to the doped-PTh oxidation (shown in Figure 6b). The overlapping curves of bare polythiophene are further evidence of the excellent electrochemical stability of PTh in the composites. PTh is a well-known electronic conducting polymer and high-capacity cathode material for lithium batteries because it gains two electrons during reactions.26 However, the cliff drop of the capacities must be resolved because the thioether groups in PTh may form thioether cations via oxidation and it may dissolve into the electrolyte and destroy the single and conjugated chain structure of the polymer. In this case, the CV results showed that the behavior of PTh between 1.0 and 3.0 V was like that of a supercapacitor because only one electron was carried per thiophene ring by the π-conjugated chain during the doping and dedoping process. The bond structure of the ring remained stable during the Li/S cycles. Therefore, the cell containing the SPTh composite cathode shows outstanding cycle performance. Moreover, typical CVs of SPTh B at various scan rates (Figure 6a, inset) showed a linear relationship between the peak current and the scan rate, which revealed that the SPTh active core/shell composite cathode was able to work at high current densities. The reduction in peak capacities was almost equal to those of the oxidation peaks from 0.1 to 1 mV s1, which indicated that PTh could prevent the overcharging problem at various scan rates in the lithium sulfur battery. Figure 7 shows typical chargedischarge curves for sulfur and SPTh electrodes in a rechargeable lithium battery at room
temperature. The discharge curves showed two typical plateaus for both the sulfur and SPTh electrodes, which should be assigned to the two-step reaction of sulfur with lithium during the discharge process, as shown by the CV measurements. It is clear that the PTh coating on the surface of the active sulfur can improve the performance of the low plateau in the Li/S cell. The shuttle phenomenon in the sulfur electrode caused a serious overcharge effect, which led the initial charge and discharge efficiency to drop to only 41.4%.41,42 However, the initial coulombic efficiency doubled to 97.9% for the SPTh electrode, which proves that the PTh coating inhibits overcharging effectively. Furthermore, the coulombic efficiency remained at 92.2% after 80 cycles, and thus the shuttle problem was successfully eliminated because of the polymer shell preventing the loss of sulfur cores. Figure 8a shows the discharge capacities versus cycle number for the cells made using the pure sulfur electrode and the SPTh electrodes. The initial discharge capacities of the sulfur and SPTh B composites were 1019 and 1119.3 mA h g1 sulfur, respectively. For the sulfur cathode without PTh, the discharge capacity decreased drastically with an increase in the cycle number. After 80 cycles, the specific capacity of the sulfur electrode was reduced to 282 mA h g1 sulfur, which was only about 28% of the initial capacity. This is typical cyclic behavior for LiS batteries with liquid-type electrolytes. On the contrary, the cyclic durability of the SPTh B electrode was significantly better than that of the sulfur electrode because after 80 cycles its specific capacity was around 830.2 mA h g1 sulfur, which was 74.2% of the initial capacity. To confirm the good electrochemical stability of polythiophene further, the same cycle test was 6061
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Figure 9. Rate capabilities of the sulfur and the SPTh composite cathodes.
Figure 8. Discharge capacities vs cycle number for (a) the sulfur and SPTh B composite and (b) pure polythiophene cathodes at a current density of 100 mA g1.
undertaken and the result is shown in Figure 8b. The PTh electrode had an initial capacity of 13 mA h g1. The capacity decreased upon cycling but remained stable after 5 cycles and was approximately 11 mA h g1. This capacity is lower than that reported previously because in that investigation into the use of polythiophene as a cathode material for rechargeable batteries, cycling took place between 1.5 and 4.0 V with resultant thioether reactions.26 As shown above, the improvement in the initial capacity and the cyclic durability of the cell with the SPTh composite electrode might occur because of the conductive PTh coating on the surface of the sulfur, which improves the conductivity of the SPTh electrode and also keeps the active particles dispersed rather than agglomerated during cycling. In addition, the porous structure of PTh results in easier electrolyte diffusion into the cathode, which assists the full discharge of sulfur. Furthermore, the porous surface morphology also absorbs polysulfides during the cycle process, and thus the dissolution of polysulfides into the liquid electrolyte is reduced. Additionally, sulfur utilization and cyclic durability are improved. However, 61.2% of the sulfur-containing composite (abbreviated as SPTh A in this article) electrode remains at 820 mA h g1 sulfur after 50 cycles according to our previous paper.22 Although the initial capacity of SPTh A was almost the same, its surface pores were smaller than that in SPTh B. This was due to insulating product Li2S being generated after a few cycles, which could easily fill the pore channels and inhibit the transport of lithium ions. Additionally, the difficulty of lithium ion diffusion from the surface to the core sulfur is increased by the double thickness of the redundant shell according to the TEM results of
SPTh A. Therefore, conducting PTh fulfills multiple purposes when coated onto the surface of the sulfur powder.43 To evaluate the rate performance of the SPTh A and B composite cathodes, tests were carried out at current densities from 100 to 1600 mA g1 sulfur and then back to 100 mA g1 sulfur, and the results are shown in Figure 9. In the rate-capability experiments, the initial discharge-specific capacity was measured as a function of current density. At a relatively low current density of 100 mA g1 sulfur, the specific capacities for the cells with sulfur and SPThs were comparable. However, as the current and the cycle number increased, the specific capacity of the SPTh B cathode was found to be overwhelmingly better than that of the other cathodes. In addition, after a rate test of 60 cycles, the cell remained at 811 mA h g1 sulfur when it returned to 100 mA g1 sulfur. This proves that it has better cycle performance than the other electrodes. This result demonstrates that the kinetics of the lithium sulfur redox reaction in the SPTh B electrode is faster than that of the other electrodes and that the reaction is therefore a candidate for use in electric vehicles.44 This confirms that at a sulfur ratio of nearly 72%, the pore diameters and the thickness of the shell are able to contain the insoluble products and allow the diffusion of lithium ions. This is also attributable to the porous structure of the SPTh composite that formed during the polymerization process, and it remained stable even under a high current.
4. CONCLUSIONS A novel composite consisting of sulfur powder coated with a conductive polythiophene was prepared via an in situ chemical oxidative polymerization method. The composite cathode underwent typical LiS cell electrochemical reactions, and polythiophene was electrochemically stable from 1.0 to 3.0 V. According to a controlled experiment, it was obvious that the optimized ratios of sulfur and polythiophene were about 71.9 and 18.1%, respectively, because the composite at these ratios showed the best electrochemical properties in the rechargeable lithium cell as determined by EIS and CV measurements. The conductive polythiophene in the cathode functioned as a conducting additive and as a porous adsorbing agent. The initial discharge capacity of the SPTh electrode was 1119.3 mA h g1 sulfur, and the remaining capacity was 830.2 mA h g1 sulfur after 80 cycles. After a rate test from 100 to 1600 mA g1 sulfur, the cell remained at 811 mA h g1 sulfur when the density returned to 100 mA g1 6062
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The Journal of Physical Chemistry C sulfur. Therefore, sulfur utilization, cyclic durability, and the rate capability of the SPTh composite electrode were significantly better than that of the pure sulfur electrode. Sulfur/PTh as a core/ shell structure material improves the conductivities of composites and also controls the morphology of the surface pore channels.
’ AUTHOR INFORMATION Corresponding Author
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’ ACKNOWLEDGMENT This work was supported by the National Key Program for Basic Research of China (no. 2009CB220100), the International S&T Cooperation Program of China (2010DFB63370), the National Science Foundation of China (NSFC, 20803003 and 20803042), the New Century Educational Talents Plan of the Chinese Education Ministry (NCET-10-0038), the Beijing Excellent Talent Support Program (2010D009011000005), and National Undergraduate Innovative Test Program (no. 101000734). ’ REFERENCES (1) Marmorstein, D.; Yu, T. H.; Striebel, K. A.; McLarnon, F. R.; Hou, J.; Cairns, E. J. J. Power Sources 2000, 89, 219. (2) Cheon, S. E.; Ko, K. S.; Cho, J. H.; Kim, S. W.; Chin, E. Y.; Kim, H. T. J. Electrochem. Soc. 2003, 150, A800. (3) Cheon, S. E.; Ko, K. S.; Cho, J. H.; Kim, S. W.; Chin, E. Y.; Kim, H. T. J. Electrochem. Soc. 2003, 150, A796. (4) Yamin, H.; Peled, E. J. Power Sources 1983, 9, 281. (5) Yamin, H.; Gorenshtein, A.; Penciner, J.; Sternberg, Y.; Peled, E. J. Electrochem. Soc. 1988, 135, 1045. (6) Evans, A.; Montenegro, M. I.; Pletcher, D. Electrochem. Commun. 2001, 3, 514. (7) Cheon, S. E.; Choi, S. S.; Han, J. S.; Choi, Y. S.; Jung, B. H.; Lim, H. S. J. Electrochem. Soc. 2004, 151, A2067. (8) Zhang, J. Y.; Kong, L. B.; Zhan, L. Z.; Tang, J.; Zhan, H.; Zhou, Y. H.; Zhan, C. M. J. Power Sources 2007, 168, 278. (9) Nuli, Y.; Guo, Z. P.; Liu, H. K.; Yang, J. Electrochem. Commun. 2007, 9, 1913. (10) Ardel, G.; Golodnitsky, D.; Freedman, K.; Peled, E.; Appetecchi, G. B.; Romagnoli, P.; Scrosati, B. J. Power Sources 2002, 110, 152. (11) Chung, J. S.; Sohn, H. J. J. Power Sources 2002, 108, 226. (12) Wang, J. L.; Liu, L.; Ling, Z. J.; Yang, J.; Wan, C. R.; Jiang, C. Y. Electrochim. Acta 2003, 48, 1861. (13) Wang, J.; Chew, S. Y.; Zhao, Z. W.; Ashraf, S.; Wexler, D.; Chen, J.; Ng, S. H.; Chou, S. L.; Liu, H. K. Carbon 2008, 46, 229. (14) Lai, C.; Gao, X. P.; Zhang, B.; Yan, T. Y.; Zhou, Z. J. Phys. Chem. C 2009, 113, 4712. (15) Wu, F.; Wu, S. X.; Chen, R. J.; Chen, S.; Wang, G. Q. Chin. Chem. Lett. 2009, 20, 1255. (16) Han, S. C.; Song, M. S.; Lee, H.; Kim, H. S.; Ahn, H. J.; Lee, J. Y. J. Electrochem. Soc. 2003, 150, A889. (17) Yuan, L. X.; Yuan, H. P.; Qiu, X. P.; Chen, L. Q.; Zhu, W. T. J. Power Sources 2009, 189, 1141. (18) Zheng, W.; Liu, Y. W.; Hu, X. G.; Zhang, C. F. Electrochim. Acta 2006, 51, 1330. (19) Wang, J.; Chen, J.; Konstantinov, K.; Zhao, L.; Ng, S. H.; Wang, G. X.; Guo, Z. P.; Liu, H. K. Electrochim. Acta 2006, 51, 4634. (20) Boyano, I.; Bengoechea, M.; de Meatza, I.; Miguel, O.; Cantero, I.; Ochoteco, E.; Rodriguez, J.; Lira-Cantu, M.; Gomez-Romero, P. J. Power Sources 2007, 166, 471. (21) Huang, Y. H.; Goodenough, J. B. Chem. Mater. 2008, 20, 7237.
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(22) Wu, F.; Wu, S. X.; Chen, R. J.; Chen, J. Z.; Chen, S. Electrochem. Solid State Lett. 2010, 13, A29. (23) Wang, H. M.; Tang, G. Q.; Jin, S. S.; Bian, C. X.; Han, F. F.; Liang, D.; Xu, X. C. Acta Chim. Sin. 2007, 65, 2454. (24) Kilic, G. B.; Toppare, L.; Yurtsever, E. Synth. Met. 1996, 78, 19. (25) Lei, Y.; Oohata, H.; Kuroda, S.; Sasaki, S.; Yamamoto, T. Synth. Met. 2005, 149, 211. (26) Tang, J.; Kong, L.; Zhang, J.; Zhan, L.; Zhan, H.; Zhou, Y. H.; Zhan, C. React. Funct. Polym. 2008, 68, 1408. (27) Wang, H. M.; Jin, S. S.; Tang, G. Q.; Han, F. F.; Liang, D.; Xu, X. C. Acta Chim. Sin. 2007, 65, 2923. (28) Roncali, J. Chem. Rev. 1992, 92, 711. (29) Bazzaoui, E. A.; Levi, G.; Aeiyach, S.; Aubard, J.; Marsault, J. P.; Lacaze, P. C. J. Phys. Chem. 1995, 99, 6628. (30) Ellis, B. L.; Lee, K. T.; Nazar, L. F. Chem. Mater. 2010, 22, 691. (31) Ji, X. L.; Nazar, L. F. J. Mater. Chem. 2010, 20, 9821. (32) Ji, X. L.; Lee, K. T.; Nazar, L. F. Nat. Mater. 2009, 8, 500. (33) Zhang, B.; Qin, X.; Li, G. R.; Gao, X. P. Energy Environ. Sci. 2010, 3, 1531. (34) Peled, E.; Gorenshtein, A.; Segal, M.; Sternberg, Y. J. Power Sources 1989, 26, 269. (35) Jeon, B. H.; Yeon, J. H.; Kim, K. M.; Chung, I. J. J. Power Sources 2002, 109, 89. (36) Li, Y. J.; Zhan, H.; Liu, S. Q.; Huang, K. L.; Zhou, Y. H. J. Power Sources 2010, 195, 2945. (37) Yuan, L. X.; Qiu, X. P.; Chen, L. Q.; Zhu, W. T. J. Power Sources 2009, 189, 127. (38) Sun, J.; Huang, Y. Q.; Wang, W. K.; Yu, Z. B.; Wang, A. B.; Yuan, K. G. Electrochem. Commun. 2008, 10, 930. (39) Zhang, W. Y.; Huang, Y. Q.; Wang, W. K.; Huang, C. J.; Wang, Y.; Yu, Z. B.; Zhang, H. J. Electrochem. Soc. 2010, 157, A443. (40) Wang, Y.; Huang, Y. Q.; Wang, W. K.; Huang, C. J.; Yu, Z. B.; Zhang, H.; Sun, J.; Wang, A. B.; Yuan, K. G. Electrochim. Acta 2009, 54, 4062. (41) Aurbach, D.; Pollak, E.; Elazari, R.; Salitra, G.; Kelley, C. S.; Affinito, J. J. Electrochem. Soc. 2009, 156, A694. (42) Mikhaylik, Y. V.; Akridge, J. R. J. Electrochem. Soc. 2004, 151, A1969. (43) Sun, M. M.; Zhang, S. C.; Jiang, T.; Zhang, L.; Yu, J. H. Electrochem. Commun. 2008, 10, 1819. (44) Zheng, W.; Hu, X. G.; Zhang, C. F. Electrochem. Solid State Lett. 2006, 9, A364.
’ NOTE ADDED AFTER ASAP PUBLICATION This article was published ASAP on March 16, 2011. A correction has been made to Table 1. The correct version was published on March 31, 2011.
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dx.doi.org/10.1021/jp1114724 |J. Phys. Chem. C 2011, 115, 6057–6063
