Tin Particles on a Graphite Surface as an Anode

J. Phys. Chem. C 2007, 111, 16423-16427

16423

Nano-tin Oxide/Tin Particles on a Graphite Surface as an Anode Material for Lithium-Ion Batteries Chia-Chin Chang,*,† Shyh-Jiun Liu,‡ Jeng-Jang Wu,‡ and Chien-Hsin Yang§ Department of EnVironment and Energy and Department of Material Science, National UniVersity of Tainan, Tainan 70101, Taiwan, and Department of Chemical and Materials Engineering, National UniVersity of Kaohsiung, Kaohsiung 811, Taiwan ReceiVed: May 3, 2007; In Final Form: July 26, 2007

A tin oxide/tin-coated graphite composite was used as an alternate anode material in Li-ion batteries. Using an argon atmosphere pyrolysis technique, an inexpensive and easy way was developed to deposit nano-SnO and Sn onto the surface of graphite powders. The nanoparticle deposits were uniformly distributed on the surface of graphite powders through the examination of SEM. EDS, XRD, and XPS results show that these deposited particles possess the phases of SnO and Sn. The nano-SnO/Sn modified graphite anode materials were characterized by using CV, rate capability studies, cycle life testing, and thermal DSC. Results show that the nano-SnO/Sn deposits on graphite enhance capacity and cyclability in assembled Li-ion batteries.

1. Introduction Graphite- or coke-based carbon materials are widely used as anodes in commercial lithium-ion batteries owing to their low potential plateau, acceptable capacity, stable cycling performance, and low cost. However, some electrochemical properties (e.g., energy density, capacity, etc.) of the carbon anodes are insufficient for market needs. To increase the specific energy of lithium-ion batteries, new anode materials such as lithium alloys,1,2 tin oxides and tin alloys,3-7 silicon and its compounds,8,9 Mg2Ge,10 Li2.6Co0.4N,11,12 and CoSb313 have been studied. As compared to carbonaceous materials, Sn-, Si-, and Sb-based composite oxides and alloys show a higher specific capacity as anode active materials.14,15 However, most composite oxides and alloy anode materials exhibit a rather large capacity loss at the first charge/discharge cycle as well as a fading capacity during cycling. These phenomena originate from the following factors: decomposition of the surface oxide,7 formation of a solid electrolyte interphase on the surface of the material,16 irreversible trapping of Li ions by host atoms,7 serious aggregation of metal particles during electrochemical cycling,7 and a large volume change.17 Various works have shown that the problems of volume change and metal particle aggregation can be alleviated significantly by the use of superfine intermetallic compounds and active/inactive composite alloy materials, thereby providing large capacities with an acceptable irreversible capacity in the first cycle, although the cycle life remains problematic.2,5,18,19 Metalbased carbon composites such as metallic Sn,20-23 Sn oxides,17,24-27 Sn alloys,28-30 Sb alloys,31 and Si32-34 have shown promise in overcoming first-cycle capacity loss and multi-cycle capacity fade, although problems continue that are related to either capacity or cyclability. Chemical and electrochemical stability are also difficult to control in these systems. Electrochemical performance of the composites is influenced * Correspondingauthor.Tel.: +88662606123,ext.7208;fax: +88662602205; e-mail: [email protected]. † Department of Environment and Energy, National University of Tainan. ‡ Department of Material Science, National University of Tainan. § National University of Kaohsiung.

by the kinds of metals, particle size distribution of the metal compounds, and amount of metal on the material surface. Combining the good cycling behavior of carbon with the high capacity of Sn has yielded interesting results. In this approach, Santos-Peo`a et al.32 used the pyrolysis of tin chlorides with graphite in an argon atmosphere to synthesize Sn-C composites, showing that first-cycle irreversible capacity loss was reduced with suitable amounts of Sn on the graphite. In this work, we explore the improvement of graphite composite anodes for Liion batteries by using the pyrolysis of Sn onto graphite powder. The performance of the Sn-C composite anodes in the Li-ion batteries is presently studied by material and electrochemical characterization. 2. Experimental Procedures 2.1. Preparation of Sn Graphite Composite Anodes. The natural graphite powders (China Steel Chemical Co.) used in this work had an average particle size of 19.89 µm and a Brunauer-Emmett-Teller (BET) surface area of 5.0 m2 g-1. The preparation of the SnO/Sn-coated graphite material began with dissolving SnCl4 (SHOWA) into an isopropyl alcohol solution containing 30 vol % concentrated HCl in a 2.0 mol dm-3 concentration. Next, 60 g of graphite power was added into 285 mL of the previous SnCl4 solution sample and then mixed over 24 h. The mixture was heated to remove the solvent at 100 °C in an oven under continuous stirring. After about 6 h, the solvent was completely removed, and the mixed materials had aggregated into a granular solid state. The aggregated materials were heated to perform the pyrolysis in a furnace at 450 °C under Ar atmosphere for 2 h, and then the furnace was cooled to room temperature. The resulting tin oxide/tin-graphite composite samples were finally hand-milled in a mortar and sieved at a pore size of 200 µm. Electrodes were prepared by mixing Super S (1.53 wt %, MMM Carbon), poly(vinylidene difluoride) powder (3.57 wt %, PVDF W1300, Kureha Chemical Industry), and the tin oxide/ tin-graphite composite (94.9 wt %) in N-methylpyrolidinone (NMP, ISP) solvent. The mixed slurry was then coated onto copper foil (10 µm, Nippon Foil Co.) and dried at 90 °C. The

10.1021/jp073379l CCC: $37.00 © 2007 American Chemical Society Published on Web 10/09/2007

16424 J. Phys. Chem. C, Vol. 111, No. 44, 2007 dried electrode was compressed to make a smooth and compact film structure by a roller at room temperature. The composite anode was stored in a glove box with oxygen, and the humidity content was maintained below 5 ppm for more than 24 h before electrochemical characterization. 2.2. Electrochemical Characterization. Electrochemical performance of the tin-graphite composite anodes was examined by using two-electrode test cells (coin-type cells), which consisted of a composite electrode, a microporous separator (Celgard 2300), a metallic lithium electrode, and a electrolyte of 1 mol dm-3 LiPF6 in a 1:1 weight ratio mixture of ethylene carbonate (EC) and diethyl carbonate (DEC). Coin-type cells were assembled for testing in a glove box. A lithium sheet (FMC) of 0.02 mm thickness was cut into disk shapes for use as the negative electrode. The assembled cells were tested for charge/discharge behavior at a constant current mode, cycling galvanostatically at 0.1 C (0.325 mA cm-2) over the range of 0.01-2.0 V. CV measurements were carried out with an Autolab electrochemical analyzer (Autolab PGSTAT30, Eco Chemie) with a current sensitivity of 1 nA. A one-compartment threeelectrode glass cell was used, and the whole apparatus was set in a glove box. The tin oxide/tin-graphite composite electrode was used as the working electrode with an area of 1 cm × 1 cm. Lithium metal was employed as both counter and reference electrodes. The electrolyte was 1 mol dm-3 LiPF6 dissolved in the mixed solvents with a 1:1 weight ratio of EC and DEC. 2.3. Material Characterization. The tin content of the graphite composite was determined by inductively coupled plasma spectroscopy (ICP, Optima 2000 DV, PerkinElmer) using a composite sample digested in a HCl/HNO3 mixture with a volume ratio of 3:1. The surface morphology and surface semiquantitative composition of the composite electrodes were evaluated by scanning electron microscopy (SEM, JEOL JSM35 operating at 20 kV) and EDS. The X-ray diffraction (XRD, RIGAKU D/MAX2500) was conducted on the composite materials over the range of 2θ ) 20 to ∼80° by monochromatic Cu KR radiation at an angular speed of 4° (2θ) min-1. The oxidation state of tin on the graphite surface was determined by means of X-ray photoelectron spectroscopy (XPS, ESCA 210, V. G. Scientific Limited). DSC experiments were carried out after charging the electrodes to 0.0 V at 0.325 mA cm-2 using a DSC PerkinElmer calorimeter. In a glove box, approximately 4 mg of the anode composite containing the electrolyte was hermetically sealed in an aluminum DSC pan. The samples were analyzed in the DSC instrument at a temperature scan rate of 10 °C per min from 40 to 300 °C.

Chang et al.

Figure 1. SEM micrographs at 40 000× magnification of (a) pristine graphite and (b) tin-graphite composite.

3. Results and Discussion SEM observations were performed to characterize the morphologies of natural graphite and the tin-graphite composite. Figure 1 shows SEM images of the pristine graphite and tingraphite composite. The pristine graphite, Figure 1a, is found to have a flake-like shape. In Figure 1b, the deposits of Sn are present as bright spots on the surface of the flake-like graphite. This clearly indicates that the nanosized tin particles are loaded on the graphite surface through pyrolysis modification. EDS analysis on these bright spots proved the presence of tin and oxygen, which are not present on the pristine graphite. The Sn content on the graphite sample was analyzed by using ICP at about 0.54 wt %. The XRD patterns of pristine graphite and tin-graphite composite are shown in Figure 2. The peaks corresponding to graphite and SnO/Sn can be clearly observed in the diffraction. The relative amount of each oxidation state

Figure 2. X-ray diffraction patterns of (a) pristine graphite and (b) tin-graphite composite.

among the Sn0, SnII, and SnIV species allows them to be separated by using the deconvolution of XPS spectra. The XPS spectra of the tin-graphite composite are shown in Figure 3. The peak around 486.5 eV corresponding to the mixing state of SnII/IV is a major component (91 atom %). It may be difficult to distinguish the SnII state from the SnIV state in the XPS spectra, but we coupled the XPS data with the XRD results as

Nano-tin Oxide/Tin Particles on a Graphite Surface

J. Phys. Chem. C, Vol. 111, No. 44, 2007 16425

Figure 3. XPS of tin-graphite composite in the region of Sn 3d5/2.

Figure 5. Four-cycle cyclic voltammograms at a scan rate of 0.1 mV s-1 in 1 mol dm-3 LiPF6 EC-DEC (1:1 by wt) electrolyte on (a) pristine graphite and (b) tin-graphite composite anodes. Potential ranges from 2.0 to 0.0 V.

Figure 4. Cyclic voltammograms from (a) the first cycle and (b) the second cycle at a scan rate of 0.1 mV s-1 in 1 mol dm-3 LiPF6 ECDEC (1:1 by wt) electrolyte on pristine graphite and tin-graphite composite anodes. Potential ranges from 2.0 to 0.0 V.

a reference to clarify the presence of the SnII state in the tingraphite composite through pyrolysis modification. The influence of Sn on the electrochemical properties of the tin-graphite composite was studied by CV. The first and second cycles of the CV plots for the tin-graphite composite electrode in a 1 mol dm-3 LiPF6 EC-DEC solution are shown in Figure 4a,b, respectively. During the first reduction (Figure 4a, curve II), three peaks were observed at 1.05, 0.75, and 0 V (vs Li+/ Li), respectively. However, the peak of 1.05 V disappeared in further cycling (Figure 4b, curve II); this phenomenon is attributed to the irreversible reduction of tin oxide. The peaks between 1.2 and 0.9 V correspond to the formation of lithium oxide and metallic tin.17 The broad peak starting at 0.90 V and centered around 0.75 V presumably corresponds to the formation of a passivation film17 and, simultaneously, to the insertion of lithium into tin with the formation of lithium-tin alloys.17,25 Lithium insertion/deinsertion in graphite occurs in the potential range of 0-0.2 V. An examination of curve II in Figures 4a,b

Figure 6. Lithiation and delithiation of pristine graphite and tingraphite composite anodes. Current density is 0.325 mA cm-2 in the potential range of 0.01-2.0 V.

reveals that the lithium insertion/deinsertion currents between 0 and 0.2 V were obviously increased by the modification of tin on the graphite surface. This result implies that the lithiumgraphite intercalation/deintercalation behavior may be influenced by the incorporation of tin on the graphite surface. The fourcycle cyclic voltammograms of pristine graphite and the tingraphite composite are shown in Figure 5a,b, respectively. An examination of Figure 5a,b clearly reveals that the reversible properties of lithium-graphite intercalation/deintercalation are enhanced by the incorporation of tin on the graphite surface. Figure 6 shows the Li insertion and Li extraction curves of the graphite/Li and tin-graphite/Li cells at 0.325 mA cm-2 in the potential range of 0.01-2.0 V. The Li insertion curve (Figure 6, curve 2) can be divided into three parts: a shoulder at 0.9 V, a pseudo-plateau near 0.7 V, and consecutive plateaus for potentials lower than 0.2 V. The first shoulder of the Li insertion

16426 J. Phys. Chem. C, Vol. 111, No. 44, 2007

Figure 7. Discharge capacity vs cycle number of pristine graphite and tin-graphite composite anodes. Charge and discharge current density is 0.325 mA cm-2 in the potential range of 0.01-2.0 V.

curve at ca. 0.90 V shows the reduction of tin oxide by lithium with the subsequent formation of Li2O and metallic tin.35 The formation of Li2O and metallic tin appears as an irreversible reaction that partially contributes to the irreversibility of this system. During the insertion of Li, the Li-Sn alloys were successively formed in the potential range of 0.9-0.2 V,35 whereas the intercalation of Li ions into the interlayer of the graphite crystal lattice occurred mainly below 0.2 V. In contrast, the Li extraction process appeared to result from a two-phase reaction. Lithium deinsertion in graphite occurs in the potential range of 0.01-0.2 V. The decomposition reaction of lithiumtin alloys exists by a shoulder near 0.6 V (refer to Figure 6, Li extraction in curve 2). Significantly, the alloy reactions and the intercalation reactions are reversible. The Coulombic efficiency at the first cycle for the graphite and tin-graphite electrodes was 89 and 81%, respectively. The latter value is lower than that of the pristine graphite material, suggesting that the tin oxide reacts with Li+17,35 and/or that a solid electrolyte interphase (SEI) layer is present on the surface of the Sn particles during discharge/charge.35 This is consistent with the results of CV, the first cycle curve of Li insertion represented by a pseudoplateau near 0.8 V. This suggests a mechanism that is related to the concomitant formation of a passivation layer and the lithium-tin alloy, especially since it is known that SEI films form on both carbon materials and lithium storage metals.36 A comparison of Figures 4 and 5 shows that the SEI layer on the surface of the graphite electrode can be formed through the decomposition of ethylene carbonate in the presence of the nanoSnO/Sn particles. Prolonged cycling tests (Figure 7) verify the long-term stability of the SEI layer on graphite with the nanoSnO/Sn particles. Li et al.37 showed that Li2CO3 and C2H5OCO2Li were formed on the surface of a nanometer-scale SnO electrode in a 1 mol dm-3 LiPF6/EC-DEC solution. The formation of a SEI layer on a nanometer-scale tin powder electrode can be described by a mechanism corresponding to a graphite electrode.38 The thickness of the SEI layer on the surface of SnO38 (ca. 2 to ∼7 nm) is generally thicker than that on the surface of graphite39 (ca. 1.7 nm). Figure 7 shows the cycling characteristic of the pristine graphite and tin-graphite composite anodes over 50 cycles at 0.325 mA cm-2 between 0.01 and 2.0 V. An examination of Figure 7 reveals that the cycle performance of the tin-graphite composite (95.8% for 50 cycles vs a first cycle discharge capacity of 272.05 mA h g-1) is better than that of pristine graphite. After 20 cycles, the cycle performance of the tingraphite composite shows a higher specific capacity as compared to pristine graphite due to the presence of tin. This result is similar to that of Read et al.,3 indicating that SnO2-carbon

Chang et al.

Figure 8. DSC curves of lithiation anodes: (a) pristine graphite and (b) tin-graphite composite. Anode materials are charged to 0.0 V at 0.325 mA cm-2.

composite prepared by heat-treating a mixture of colloidal SnO2 demonstrates the reduced capacity fade. When the metallic salts are dissolved in organic solvents, a portion of the carbon may be deposited on the surface of graphite coupled with some metallic particles.29 This may enhance the connection strength between the metallic particles and the carbon matrix. The connection strength contributes to maintain the distance between the two metallic particles, leading to prevention of particle/ particle contact after volume expansion, as shown in Figure 1b (0.54 wt % Sn coated on graphite). Such a configuration seems to be able to reduce the mechanical stress caused by the volume effect and improve the morphological and conducting stability of the composites. To evaluate the effect of Sn loading on the thermal stability of the charged anodes, a DSC study was performed after charging the tin-graphite composite anodes to 0.0 V. The thermal stability of pristine graphite and the tin-graphite composite anodes are shown in Figure 8. The first exothermic reaction is the breakdown of SEI as judged from previous literature.40,41 SEI is comprised of stable compounds (LiF, Li2CO3, and other inorganic compounds) and metastable components (lithium-alkyl carbonates and lithium semi-carbonate).40 All these compounds may participate in the SEI decomposition reaction. However, the most possible reaction is40

(CH2OCO2Li)2 f Li2CO3 + C2H4v + CO2v + 0.5O2

(1)

From the examination of Figure 8, the onset temperatures corresponding to the thermal decomposition of pristine graphite and tin-graphite composites are 112 and 100 °C, respectively. This result indicates that the thermal decomposition of SEI as eq 1 on the surface of the nano-SnO/Sn particle is easier than that on graphite. After the breakdown of SEI, the salts and electrolyte can permeate through the bulk of Li2CO3 and LiF to reach the surface of lithiated graphite and the lithiated tin particles. The Li and LixSn on the intercalated graphite composites can react with an electrolyte, as is shown in eqs 2 and 3. Other reactions are also possible.

2Li + C3H4O3 f Li2CO3 + C2H4v

(2)

2LixSn + C3H4O3 f xLi2CO3 + C2H4v + 2SnOy + (1 - x)CO2v (3) Figure 8 shows the temperature of the exothermic peak present at 127 °C for pristine graphite. For the tin-graphite

Nano-tin Oxide/Tin Particles on a Graphite Surface composite anode, this peak shifts to 134 °C. The total exothermic peak area of the tin-graphite composite (48.53 J g-1) is higher than that of pristine graphite (23.56 J g-1), implying that the Sn metal reacts with the electrolyte to form the SEI film. The thickness of the SEI film on the surface of SnO38 (ca. 2 to ∼7 nm) is thicker than that on graphite39 (ca. 1.7 nm). The endothermic peak at ca. 205 °C may be due to the endothermic nature of LiPF6 decomposition to LiF and PF5.41,42 The onset temperature and peak area of the first exothermic peak show that the Sn deposits on the graphite surface may reduce the thermal stability of the anode using the lithium-ion battery. 4. Conclusion Sn particle-modified carbon materials can be prepared by a pyrolysis technique in an argon atmosphere. Using SEM, EDS, and ICP-OES results of tin-graphite composites, a small amount of nanoparticle tin material has been shown to intercalate onto the graphite. XRD and XPS results show that tin on the graphite surface is a mixture of Sn (9 atom %) and SnO (91 atom %). The electrochemical properties of the tin-graphite composite in the Li-ion cells can be enhanced by Sn incorporation. The cyclic capacity performance of the tin-graphite composite electrode is better than that of pristine graphite. DSC results show that the Sn deposits on the graphite surface would reduce the thermal stability of the anode. Our studies are being extended to other easy and quick modification methods for graphitemetal composite systems in the quest for the best electrochemical performance for Li-ion batteries. Acknowledgment. The authors are grateful for the financial support of this work by the China Steel Chemical Corporation, Taiwan and the National Science Council of Taiwan under Contracts NSC 95-2221-E024-017, NSC 94-2623-7-024-001ET, and NSC 95-ET-7-024-001-ET. References and Notes (1) Huggins, R. A. J. Power Sources 1999, 81-82, 13-19. (2) Besenhard, J. O.; Yang, J.; Winter, M. J. Power Sources 1997, 68, 87-90. (3) Read, J.; Foster, D.; Wolfenstine, J.; Behl, W. J. Power Sources 2001, 96, 277-281. (4) Li, H.; Shi, L.; Lu, W.; Huang, X.; Chen, L. J. Electrochem. Soc. 2001, 148, 915-922. (5) Idota, Y.; Kubota, T.; Matsufuji, A.; Maekawa, Y.; Miyasaka, T. Science 1997, 276, 1395-1397. (6) Lee, W. H.; Son, H. C.; Reucroft, P. J.; Lee, J. G.; Park, J. W. J. Mater. Sci. Lett. 2001, 20, 39-41. (7) Huang, H.; Kelder, E. M.; Chen, L.; Schoonman, J. J. Power Sources 1999, 81-82, 362-367. (8) Boukamp, B. A.; Lesh, G. C.; Huggins, R. A. J. Electrochem. Soc. 1981, 128, 725-729. (9) Sharma, R. A.; Seefurth, R. N. J. Electrochem. Soc. 1976, 123, 1763-1768. (10) Sakaguchi, H.; Honda, H.; Esaka, T. J. Power Sources 1999, 8182, 229-232.

J. Phys. Chem. C, Vol. 111, No. 44, 2007 16427 (11) Nishijima, M.; Kagohashi, T.; Takeda, Y.; Imanishi, M.; Yamamoto, O. J. Power Sources 1997, 68, 510-514. (12) Shodai, T.; Sakurai, Y.; Suzuki, T. Solid State Ionics 1999, 122, 85-93. (13) Alca´ntara, R.; Ferna´ndezmadrigal, F. J.; Lavela, P.; Tirado, J. L.; Jumas, J. C.; Oliverfourcade, J. J. Mater. Chem. 1999, 9, 2517-2521. (14) Xing, W.; Xue, J. S.; Dahn, J. R. J. Electrochem. Soc. 1996, 143, 3046-3052. (15) Zhao, X. B.; Cao, G. S. Electrochim. Acta 2001, 46, 891-896. (16) Courtney, I. A.; Dahn, J. R. J. Electrochem. Soc. 1997, 144, 20452052. (17) Lee, J. Y.; Zhang, R.; Liu, Z. Electrochem. Solid-State Lett. 2000, 3, 167-170. (18) Yang, J.; Wachtler, M.; Winter, M.; Besenhard, J. O. Electrochem. Solid-State Lett. 1999, 2, 161-163. (19) Mao, O.; Turner, R. L.; Courtney, I. A.; Fredericksen, B. D.; Buckett, M. I.; Krause, L. J.; Dahn, J. R. Electrochem. Solid-State Lett. 1999, 2, 3-5. (20) Veeraraghavan, B.; Durairajan, A.; Haran, B.; Popov, B.; Guidotti, R. J. Electrochem. Soc. 2002, 149, 675-681. (21) Wang, G. X.; Yao, J.; Liu, H. K.; Dou, S. X.; Ahn, J. H. Electrochim. Acta 2004, 50, 517-522. (22) Wang, T.; Lee, J. Y.; Deivaraj, T. C. J. Electrochem. Soc. 2004, 151, 1804-1809. (23) Wang, G. X.; Yao, J.; Ahn, J. H.; Liu, H. K.; Dou, S. X. J. Appl. Electrochem. 2004, 34, 187-190. (24) Wang, Y.; Lee, J. Y.; Chen, B. H. Electrochem. Solid-State Lett. 2003, 6, 19-22. (25) Lee, J. Y.; Zhang, R.; Liu, Z. J. Power Sources 2000, 90, 70-75. (26) Zhang, R.; Lee, J. Y.; Liu, Z. L. J. Power Sources 2002, 112, 596605. (27) Wang, Y.; Lee, J. Y. J. Power Sources 2005, 144, 220-225. (28) Liu, Y.; Xie, J. Y.; Yang, J. J. Power Sources 2003, 119-121, 572-575. (29) Guo, Z. P.; Zhao, Z. W.; Liu, H. K.; Dou, S. X. Carbon 2005, 43, 1392-1399. (30) Liao, X. Z.; Ma, Z. F.; Hu, J. H.; Sun, Y. Z.; Yuan, X. Electrochem. Commun. 2003, 5, 657-661. (31) Aldon, L.; Garcia, A.; Olivier-Fourcads, J.; Jumas, J. C.; Ferna´ndezMadrigal, F. J.; Lavela, P.; Vicente, C. P.; Tirado, J. L. J. Power Sources 2003, 119-121, 585-590. (32) Santos-Peo`a, J.; Brousse, T.; Schleich, D. M. Solid State Ionics 2000, 135, 87-93. (33) Dimov, N.; Kugino, S.; Yoshio, M. Electrochim. Acta 2003, 48, 1579-1587. (34) Yoshio, M.; Wang, H.; Fukuda, K.; Umeno, T.; Dimov, N.; Dgumi, Z. J. Electrochem. Soc. 2002, 149, 1598-1603. (35) Li, H.; Shi, L.; Wang, Q.; Chen, L.; Huang, X. Solid State Ionics 2002, 148, 247-258. (36) Shi, L.; Li, H.; Wang, Z.; Huang, X.; Chen, L. J. Mater. Chem. 2001, 11, 1502-1505. (37) Li, J.; Li, H.; Wang, Z.; Chen, L.; Huang, X. J. Power Sources 2002, 107, 1-4. (38) Choi, W.; Lee, J. Y.; Jung, B. H.; Lim, H. S. J. Power Sources 2004, 136, 154-159. (39) Dolle, M.; Grugeon, S.; Dupont, L.; Tarascon, J. M. J. Power Sources 2001, 97-98, 104-106. (40) Yang, H.; Bang, H.; Amine, K.; Prakash, J. J. Electrochem. Soc. 2005, 152, 73-79. (41) Ravdel, B.; Abraham, K. M.; Gitzendanner, R.; DiCarlo, J.; Lucht, B.; Campion, C. J. Power Sources 2001, 119-121, 805-810. (42) Botte, G. G.; White, R. E.; Zhang, Z. J. Power Sources 2001, 9798, 570-575.