- Email: [email protected]
Effect of a rhombohedral phase on lithium intercalation capacity in graphite
Solid State Ionics 110 (1998) 173–178
Effect of a rhombohedral phase on lithium intercalation capacity in graphite Hong Huang a ,b , Weifeng Liu a , Xuejie Huang a , Liquan Chen a , Erik M. Kelder b , b, Joop Schoonman * b
a Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100080, China Laboratory for Inorganic Chemistry, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands
Received 20 February 1998; accepted 31 March 1998
Abstract Five natural graphites with different rhombohedral phase (3R phase) content have been investigated as anode materials for rechargeable lithium-ion batteries. The reversible capacity varies from 250 mA h / g to 350 mA h / g for the same intercalation conditions depending on the content of the 3R-phase. With increasing rhombohedral phase in the graphite, the intercalation capacity will be high. A peak at about 10 mV in the cyclic voltammograms (CV) of a sample with a large 3R-phase content is caused by lithium ions occupying boundaries between the rhombohedral (3R) phase and the hexagonal (2H) phase and is responsible for a capacity exceeding the theoretical value. 1998 Elsevier Science B.V. All rights reserved. Keywords: Rhombohedral phase; Graphite; Lithium intercalation
1. Introduction Carbonaceous materials have attracted widespread attention as anode material for rechargeable lithium-ion batteries due to their low cost, high capacity for lithium intercalation and deintercalation, as well as comparatively good electrochemical stability during the cycling process. Many carbonaceous materials such as natural and artificial graphites, pitches, cokes, and mesocarbon microsphere, as well as various heat-treated polymers have been found to be promising anodes [1–8]. They are usually classified into three basic groups, i.e. soft carbon, hard carbon, and graphite-like carbon. The *Corresponding author. E-mail: [email protected]
lithium intercalation characteristics and mechanism have been reported, and a relationship between structure, micro-structure of the carbon host, and the electrochemical performance of lithium insertion have also been discussed. To our knowledge, little attention has been paid to the influence of structure of graphite on the electrochemical properties, especially to the presence of the rhombohedral (3R) phase in graphite. Although the hexagonal (2H) phase is thermodynamically more stable than the 3R phase under normal conditions, the 3R phase exists in most natural and artificial graphites to some extent. In this study, preliminary results focusing on the role of the 3R phase in the natural graphites are presented. The relationship between the electrochemical capacity and the content
0167-2738 / 98 / $19.00 1998 Elsevier Science B.V. All rights reserved. PII: S0167-2738( 98 )00144-1
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H. Huang et al. / Solid State Ionics 110 (1998) 173 – 178
of the 3R-phase in these natural graphites will be discussed.
2. Experimental aspects Five natural graphites, i.e., JT, G1, G2, G3, and SJ are commercial products and have been used without further treatment. The grain sizes of the samples are all ranging from 10 to 50 mm. PAN-binded graphite electrodes were made using the doctor blade technique on copper foils. After the solvent had evaporated completely, the sheets were dried under vacuum at 1408C for 24 h. The thus prepared graphite sheet with 0.8 cm 2 area was used as the working electrode, while lithium foil was used both as reference and counter electrode. The electrolyte (Mitsubishi) is 1 M LiPF 6 in ethylene (EC) / diethyl carbonate (DEC). A Celgard 2400 polypropylene porous thin film was used as separator. All the (Li / / C) test cells were constructed in a dry box filled with argon (H 2 O content less than 0.1 ppm). The discharge profiles and the reversible capacities were obtained by discharging the above cells using a computer controlled galvanostat. The voltage range was controlled between 5 mV and 2.0 V. The cyclic voltammograms (CV) were performed at a very low rate of 50 mV/ s from 2 50 mV to 350 mV by using an EG&G 173 potentialstat / galvanostat in conjunction with a Wenking VSG83 Voltage Scanner and X–Y recorder. XRD experiments are carried out on a Rigaku DIMAX-YB diffractometer with Cu Ka radiation.
Table 1 Structural parameters and reversible capacities of the natural graphite samples Sample
JT
G3
G2
G1
SJ
d 002 (nm) 2H I 3R 101 /I 101 Q r (mA h / g)
0.335 0.303 250
0.335 0.334 280
0.335 0.347 300
0.335 0.352 310
0.335 0.549 350
Fig. 1. Discharge profiles of cells Li / / JT and Li / / SJ for a discharge current density of 0.0625 mA / cm 2 .
3. Results and discussion For the five natural graphite samples the reversible capacity was obtained under the same charge / discharge conditions (current density 0.0625 mA / cm 2 ). The results ranged from 250 to 350 mA h / g and are listed in Table 1. The second discharge profiles of the cells, i.e. Li / / JT and Li / / SJ are shown in Fig. 1. It is obvious that the polarization of sample JT is much larger compared with that of sample SJ. In particular, the lower-stage voltage plateau became shorter, which is very similar to the profile of sample
G3 discharged at a different current density (viz. Fig. 2). This result indicates that the different intercalation capacities for the five graphites are related to differences in intercalation kinetics. In Fig. 3 the CV curves at very low rate for JT and SJ, respectively are presented. The five reduction peaks can be distinguished clearly and appeared at approximately the same positions in the two samples. The peaks at about 210 mV, 175 mV, 150 mV, 100 mV, and 65 mV correspond to the 19 → 4, 4 → 3, 3 → 2L, 2L → 2, 2 → 1 phase transitions [9], respec-
H. Huang et al. / Solid State Ionics 110 (1998) 173 – 178
Fig. 2. Discharge profiles of cell Li / / G3 for different discharge current densities.
tively. Hence, if sample JT is discharged at a lower rate, the polarization becomes smaller and the more lithium can be intercalated. It is important to emphasize that a shoulder appeared at about 10 mV in the CV for sample SJ as marked with an arrow in Fig. 3(b). Besides the usual intercalation in sample SJ another process seems to occur, which may be another reason for the large capacity. The details will be discussed below. In order to understand the structural difference of lithium intercalation in the natural graphites, XRD has been carried out. At first glance, the XRD patterns are nearly the same for all the samples. All have a d 002 value of 0.335 nm, and La and Lc are not different. According to the relationship between the capacity and these parameters, all the graphite samples studied here should have similar intercalation capacity [10]. Yet the capacities are different. A careful comparison of the XRD patterns reveals an interesting difference. The relative intensities of
175
Fig. 3. The cyclic voltammogram at a rate of 50 mA / s for samples JT and SJ.
some peaks, especially those at 2u 5 43.348 and 44.58 are different (Fig. 4). According to the JCPDS data, the peak at 43.348 is the diffraction of the (101) plane in rhombohedral graphite(3R), while the peak at 44.58 originates from the (101) plane diffraction in hexagonal graphite (2H). Therefore, the relative content of the 3R-phase in the samples can be evaluated and the relationship between the intercalation capacity and the 3R-phase can be established (viz. Fig. 5) by comparing the intensity of these two peaks. It is clear that the larger capacity has been obtained for increased 3R-phase content in the graphites. The 2H- and 3R-phases are the two typical morphologies of graphite. For both phases the basic building block is similar in that the carbon layer consists of a series of honeycomb hexagons whose centers form the triangular planar lattice. The spac˚ ing between the carbon layers is the same (3.35 A).
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H. Huang et al. / Solid State Ionics 110 (1998) 173 – 178
Fig. 4. A part of the XRD patterns for three natural graphite samples.
Fig. 5. Reversible capacity (current density 0.0625 mA / cm 2 ) as a function of the XRD intensity ratio I2u 543.34 /I2u 544.50 .
The difference between the two phases arises from the stacking sequence of the graphite layers. The 2H-phase adopts ABABAB— stacking while the
3R-phase exhibits the sequence ABCABC—. Many graphites, either natural or artificial, have a certain amount of the 3R phase [11]. When lithium ions are intercalated into the graphite lattice to form LiC 6 , the carbon layers shift their stacking sequence from ABABAB— or ABCABC— into AAAAAA— [12–14]. Therefore, during the first stage of lithium intercalation into graphite, the coordination of a lithium ion is the same. At a later stage of intercalation, the coordination of a lithium ion will be slightly different in the two phases. Thus the formation energies of a samestage- lithium intercalation compound do not differ too much for the two graphite morphologies. Therefore, from this structural point of view, it is difficult to understand the difference in lithium intercalation behavior. The boundaries between the two phases seem to be the more important reason. As indicated by XRD results, the natural graphite samples contain a valuable amount of 3R-phase. Therefore, different amounts of grain boundaries between the two phases are present. Along the boundary regions, there are many dislocations and incomplete carbon atom hexagons or so-called zigzag and armchair sites [11,15]. They can be located either in the basal planes open to the atmosphere or within a small graphite crystallite, as shown in Fig. 6. It is well known that lithium ions cannot be inserted into the graphite lattice through the basal plane, but through zig-zag, armchair, and other sites [15]. The large existence of phase boundaries on the basal plane will certainly promote the lithium ions to intercalate into graphite lattices. From this point, the capacity could be enhanced with increasing the 3Rphase due to the kinetic process. Moreover, lithium ions can occupy the boundaries closed in the particle as long as the polarization is prevented as is true under very slow intercalation process conditions. The activation energies for lithium insertion or extraction in these sites may be higher than that for intercalation in the regular positions between the normal graphite layers. Thus the lithium ions are first preferably intercalated into the regular sites to form the staging compound. Once LiC 6 has been formed, the lithium ions may occupy these traps and their removal requires more energy. The reduction peak at about 10 mV in the CV of the
H. Huang et al. / Solid State Ionics 110 (1998) 173 – 178
Fig. 6. A model of the boundaries between 2H- and 3R-phases.
SJ sample may be related to lithium ions occupying these boundary sites. If the above analysis is correct, the graphite samples containing enough 3R-phase should have higher capacity than the theoretical value of 372 mA h / g calculated according to the formula LiC 6 . The higher capacity will appear at a lower voltage than that for the stage 1 compound during intercialating at a higher voltage than usual when de-intercialating. Fig. 7 is the discharge / charge profile of a Li / / SJ cell at a current density of about 0.02 mA / cm 2 . The same profile amplifying the range below 400mV is given in the inset. It is interesting to notice that the reversible capacity has reached a value of about 400 mAh / g. Furthermore, according to the literature [16] the reversible capacity for graphite has also reached about 410 mAh / g (x 5 1.1, x in Li x C 6 ) after the sample was ball milled for about 10 h in Fritsch P7 ball mixer, viz. Fig. 3(b). The XRD and electrochemical results are very similar to the results for the SJ sample. Our samples, i.e. JT, G3, have
177
Fig. 7. Discharge / charge profile of cell Li / / SJ for a current density of 0.02 mA / cm 2 . The magnification reveals significant structure in the profile in the range 0–400 mV.
been ball milled and the intensity ratio of the peaks at 43.348 over 45.508 increases with the ball milling time, which showed that the 3R-phase content in the graphite increased upon ball milling for 20 h without broadening of the (002) diffraction peak. These results strongly support the presented analysis. The electrochemical intercalation will be further studied.
4. Conclusion The rhombohedral phase exists in natural graphite samples to some extent. The lithium intercalation capacity increases with 3R-phase content. The defects on the basal plane along the boundaries between the 3R and 3H phases will reduce the incorporation impedance of lithium ions into the graphite lattice leading to an enhancement of the capacity. Furthermore, the boundary position within the crystallites can be occupied by lithium ions to form Li x C 6 with x . 1.
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H. Huang et al. / Solid State Ionics 110 (1998) 173 – 178
References [1] R. Yazami, K. Zaghib, M. Deschamps, J. Power Sources 143 (1996) 3466. [2] K. Sato, M. Noguchi, A. Memachi, N. Oki, M. Endo, Science 264 (1994) 556. [3] K. Sawai, Y. Imakoshi, T. Ohzuku, Solid State Ionics 69 (1994) 273. [4] T.D. Tran, J.H. Feikert, X. Song, K. Kinosjita, J. Electrochem. Soc. 142 (1995) 3297. [5] T. Zheng, Y. Liu, E.N. Fuller, S. Tseng, U. von Sacken, J.R. Dahn, J. Electrochem. Soc. 142 (1995) 2581. [6] H. Shi, J. Baker, M.Y. Saidi, R. Koksband, J. Electrochem. Soc. 143 (1996) 3466. [7] J.R. Dahn, T. Zheng, Y. Liu, J.S. Xue, Science 270 (1995) 590.
[8] Y. Matrumuro, S. Wang, J. Mondori, Carbon 33 (1995) 1457. [9] J.R. Dahn, Phys. Rev. B 44 (1991) 9170. [10] G. Li, Z. Lu, B. Huang, H. Huang, R. Xue, L. Chen, Solid State Ionics 81 (1995) 15. [11] B.T. Kelly, Physics of Graphite, Applied Science Publications, London, 1981. [12] A. Herold, Physics and chemistry of materials with layered structures, in: F. Levy (Ed.), D. Reidel Publishing Company, Dordrecht, Holland, 1979. [13] J.R. Dahn, A.K. Sleigh, H. Shi, J.R. Reimers, Q. Zhong, B.M. Way, Electrochim. Acta 38 (1993) 1179. [14] R.C. Boehm, A. Banerjee, J. Chem. Phys. 96 (1992) 1150. [15] E. Peled, C. Menachem, D. Bar-Tow, A. Melman, J. Electrochem. Soc. 143 (1996) L4. [16] F. Disma, L. Aymard, L. Dupont, J.M. Tarascon, J. Electrochem. Soc. 143 (1996) 3959.
Effect of a rhombohedral phase on lithium intercalation capacity in graphite Hong Huang a ,b , Weifeng Liu a , Xuejie Huang a , Liquan Chen a , Erik M. Kelder b , b, Joop Schoonman * b
a Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100080, China Laboratory for Inorganic Chemistry, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands
Received 20 February 1998; accepted 31 March 1998
Abstract Five natural graphites with different rhombohedral phase (3R phase) content have been investigated as anode materials for rechargeable lithium-ion batteries. The reversible capacity varies from 250 mA h / g to 350 mA h / g for the same intercalation conditions depending on the content of the 3R-phase. With increasing rhombohedral phase in the graphite, the intercalation capacity will be high. A peak at about 10 mV in the cyclic voltammograms (CV) of a sample with a large 3R-phase content is caused by lithium ions occupying boundaries between the rhombohedral (3R) phase and the hexagonal (2H) phase and is responsible for a capacity exceeding the theoretical value. 1998 Elsevier Science B.V. All rights reserved. Keywords: Rhombohedral phase; Graphite; Lithium intercalation
1. Introduction Carbonaceous materials have attracted widespread attention as anode material for rechargeable lithium-ion batteries due to their low cost, high capacity for lithium intercalation and deintercalation, as well as comparatively good electrochemical stability during the cycling process. Many carbonaceous materials such as natural and artificial graphites, pitches, cokes, and mesocarbon microsphere, as well as various heat-treated polymers have been found to be promising anodes [1–8]. They are usually classified into three basic groups, i.e. soft carbon, hard carbon, and graphite-like carbon. The *Corresponding author. E-mail: [email protected]
lithium intercalation characteristics and mechanism have been reported, and a relationship between structure, micro-structure of the carbon host, and the electrochemical performance of lithium insertion have also been discussed. To our knowledge, little attention has been paid to the influence of structure of graphite on the electrochemical properties, especially to the presence of the rhombohedral (3R) phase in graphite. Although the hexagonal (2H) phase is thermodynamically more stable than the 3R phase under normal conditions, the 3R phase exists in most natural and artificial graphites to some extent. In this study, preliminary results focusing on the role of the 3R phase in the natural graphites are presented. The relationship between the electrochemical capacity and the content
0167-2738 / 98 / $19.00 1998 Elsevier Science B.V. All rights reserved. PII: S0167-2738( 98 )00144-1
174
H. Huang et al. / Solid State Ionics 110 (1998) 173 – 178
of the 3R-phase in these natural graphites will be discussed.
2. Experimental aspects Five natural graphites, i.e., JT, G1, G2, G3, and SJ are commercial products and have been used without further treatment. The grain sizes of the samples are all ranging from 10 to 50 mm. PAN-binded graphite electrodes were made using the doctor blade technique on copper foils. After the solvent had evaporated completely, the sheets were dried under vacuum at 1408C for 24 h. The thus prepared graphite sheet with 0.8 cm 2 area was used as the working electrode, while lithium foil was used both as reference and counter electrode. The electrolyte (Mitsubishi) is 1 M LiPF 6 in ethylene (EC) / diethyl carbonate (DEC). A Celgard 2400 polypropylene porous thin film was used as separator. All the (Li / / C) test cells were constructed in a dry box filled with argon (H 2 O content less than 0.1 ppm). The discharge profiles and the reversible capacities were obtained by discharging the above cells using a computer controlled galvanostat. The voltage range was controlled between 5 mV and 2.0 V. The cyclic voltammograms (CV) were performed at a very low rate of 50 mV/ s from 2 50 mV to 350 mV by using an EG&G 173 potentialstat / galvanostat in conjunction with a Wenking VSG83 Voltage Scanner and X–Y recorder. XRD experiments are carried out on a Rigaku DIMAX-YB diffractometer with Cu Ka radiation.
Table 1 Structural parameters and reversible capacities of the natural graphite samples Sample
JT
G3
G2
G1
SJ
d 002 (nm) 2H I 3R 101 /I 101 Q r (mA h / g)
0.335 0.303 250
0.335 0.334 280
0.335 0.347 300
0.335 0.352 310
0.335 0.549 350
Fig. 1. Discharge profiles of cells Li / / JT and Li / / SJ for a discharge current density of 0.0625 mA / cm 2 .
3. Results and discussion For the five natural graphite samples the reversible capacity was obtained under the same charge / discharge conditions (current density 0.0625 mA / cm 2 ). The results ranged from 250 to 350 mA h / g and are listed in Table 1. The second discharge profiles of the cells, i.e. Li / / JT and Li / / SJ are shown in Fig. 1. It is obvious that the polarization of sample JT is much larger compared with that of sample SJ. In particular, the lower-stage voltage plateau became shorter, which is very similar to the profile of sample
G3 discharged at a different current density (viz. Fig. 2). This result indicates that the different intercalation capacities for the five graphites are related to differences in intercalation kinetics. In Fig. 3 the CV curves at very low rate for JT and SJ, respectively are presented. The five reduction peaks can be distinguished clearly and appeared at approximately the same positions in the two samples. The peaks at about 210 mV, 175 mV, 150 mV, 100 mV, and 65 mV correspond to the 19 → 4, 4 → 3, 3 → 2L, 2L → 2, 2 → 1 phase transitions [9], respec-
H. Huang et al. / Solid State Ionics 110 (1998) 173 – 178
Fig. 2. Discharge profiles of cell Li / / G3 for different discharge current densities.
tively. Hence, if sample JT is discharged at a lower rate, the polarization becomes smaller and the more lithium can be intercalated. It is important to emphasize that a shoulder appeared at about 10 mV in the CV for sample SJ as marked with an arrow in Fig. 3(b). Besides the usual intercalation in sample SJ another process seems to occur, which may be another reason for the large capacity. The details will be discussed below. In order to understand the structural difference of lithium intercalation in the natural graphites, XRD has been carried out. At first glance, the XRD patterns are nearly the same for all the samples. All have a d 002 value of 0.335 nm, and La and Lc are not different. According to the relationship between the capacity and these parameters, all the graphite samples studied here should have similar intercalation capacity [10]. Yet the capacities are different. A careful comparison of the XRD patterns reveals an interesting difference. The relative intensities of
175
Fig. 3. The cyclic voltammogram at a rate of 50 mA / s for samples JT and SJ.
some peaks, especially those at 2u 5 43.348 and 44.58 are different (Fig. 4). According to the JCPDS data, the peak at 43.348 is the diffraction of the (101) plane in rhombohedral graphite(3R), while the peak at 44.58 originates from the (101) plane diffraction in hexagonal graphite (2H). Therefore, the relative content of the 3R-phase in the samples can be evaluated and the relationship between the intercalation capacity and the 3R-phase can be established (viz. Fig. 5) by comparing the intensity of these two peaks. It is clear that the larger capacity has been obtained for increased 3R-phase content in the graphites. The 2H- and 3R-phases are the two typical morphologies of graphite. For both phases the basic building block is similar in that the carbon layer consists of a series of honeycomb hexagons whose centers form the triangular planar lattice. The spac˚ ing between the carbon layers is the same (3.35 A).
176
H. Huang et al. / Solid State Ionics 110 (1998) 173 – 178
Fig. 4. A part of the XRD patterns for three natural graphite samples.
Fig. 5. Reversible capacity (current density 0.0625 mA / cm 2 ) as a function of the XRD intensity ratio I2u 543.34 /I2u 544.50 .
The difference between the two phases arises from the stacking sequence of the graphite layers. The 2H-phase adopts ABABAB— stacking while the
3R-phase exhibits the sequence ABCABC—. Many graphites, either natural or artificial, have a certain amount of the 3R phase [11]. When lithium ions are intercalated into the graphite lattice to form LiC 6 , the carbon layers shift their stacking sequence from ABABAB— or ABCABC— into AAAAAA— [12–14]. Therefore, during the first stage of lithium intercalation into graphite, the coordination of a lithium ion is the same. At a later stage of intercalation, the coordination of a lithium ion will be slightly different in the two phases. Thus the formation energies of a samestage- lithium intercalation compound do not differ too much for the two graphite morphologies. Therefore, from this structural point of view, it is difficult to understand the difference in lithium intercalation behavior. The boundaries between the two phases seem to be the more important reason. As indicated by XRD results, the natural graphite samples contain a valuable amount of 3R-phase. Therefore, different amounts of grain boundaries between the two phases are present. Along the boundary regions, there are many dislocations and incomplete carbon atom hexagons or so-called zigzag and armchair sites [11,15]. They can be located either in the basal planes open to the atmosphere or within a small graphite crystallite, as shown in Fig. 6. It is well known that lithium ions cannot be inserted into the graphite lattice through the basal plane, but through zig-zag, armchair, and other sites [15]. The large existence of phase boundaries on the basal plane will certainly promote the lithium ions to intercalate into graphite lattices. From this point, the capacity could be enhanced with increasing the 3Rphase due to the kinetic process. Moreover, lithium ions can occupy the boundaries closed in the particle as long as the polarization is prevented as is true under very slow intercalation process conditions. The activation energies for lithium insertion or extraction in these sites may be higher than that for intercalation in the regular positions between the normal graphite layers. Thus the lithium ions are first preferably intercalated into the regular sites to form the staging compound. Once LiC 6 has been formed, the lithium ions may occupy these traps and their removal requires more energy. The reduction peak at about 10 mV in the CV of the
H. Huang et al. / Solid State Ionics 110 (1998) 173 – 178
Fig. 6. A model of the boundaries between 2H- and 3R-phases.
SJ sample may be related to lithium ions occupying these boundary sites. If the above analysis is correct, the graphite samples containing enough 3R-phase should have higher capacity than the theoretical value of 372 mA h / g calculated according to the formula LiC 6 . The higher capacity will appear at a lower voltage than that for the stage 1 compound during intercialating at a higher voltage than usual when de-intercialating. Fig. 7 is the discharge / charge profile of a Li / / SJ cell at a current density of about 0.02 mA / cm 2 . The same profile amplifying the range below 400mV is given in the inset. It is interesting to notice that the reversible capacity has reached a value of about 400 mAh / g. Furthermore, according to the literature [16] the reversible capacity for graphite has also reached about 410 mAh / g (x 5 1.1, x in Li x C 6 ) after the sample was ball milled for about 10 h in Fritsch P7 ball mixer, viz. Fig. 3(b). The XRD and electrochemical results are very similar to the results for the SJ sample. Our samples, i.e. JT, G3, have
177
Fig. 7. Discharge / charge profile of cell Li / / SJ for a current density of 0.02 mA / cm 2 . The magnification reveals significant structure in the profile in the range 0–400 mV.
been ball milled and the intensity ratio of the peaks at 43.348 over 45.508 increases with the ball milling time, which showed that the 3R-phase content in the graphite increased upon ball milling for 20 h without broadening of the (002) diffraction peak. These results strongly support the presented analysis. The electrochemical intercalation will be further studied.
4. Conclusion The rhombohedral phase exists in natural graphite samples to some extent. The lithium intercalation capacity increases with 3R-phase content. The defects on the basal plane along the boundaries between the 3R and 3H phases will reduce the incorporation impedance of lithium ions into the graphite lattice leading to an enhancement of the capacity. Furthermore, the boundary position within the crystallites can be occupied by lithium ions to form Li x C 6 with x . 1.
178
H. Huang et al. / Solid State Ionics 110 (1998) 173 – 178
References [1] R. Yazami, K. Zaghib, M. Deschamps, J. Power Sources 143 (1996) 3466. [2] K. Sato, M. Noguchi, A. Memachi, N. Oki, M. Endo, Science 264 (1994) 556. [3] K. Sawai, Y. Imakoshi, T. Ohzuku, Solid State Ionics 69 (1994) 273. [4] T.D. Tran, J.H. Feikert, X. Song, K. Kinosjita, J. Electrochem. Soc. 142 (1995) 3297. [5] T. Zheng, Y. Liu, E.N. Fuller, S. Tseng, U. von Sacken, J.R. Dahn, J. Electrochem. Soc. 142 (1995) 2581. [6] H. Shi, J. Baker, M.Y. Saidi, R. Koksband, J. Electrochem. Soc. 143 (1996) 3466. [7] J.R. Dahn, T. Zheng, Y. Liu, J.S. Xue, Science 270 (1995) 590.
[8] Y. Matrumuro, S. Wang, J. Mondori, Carbon 33 (1995) 1457. [9] J.R. Dahn, Phys. Rev. B 44 (1991) 9170. [10] G. Li, Z. Lu, B. Huang, H. Huang, R. Xue, L. Chen, Solid State Ionics 81 (1995) 15. [11] B.T. Kelly, Physics of Graphite, Applied Science Publications, London, 1981. [12] A. Herold, Physics and chemistry of materials with layered structures, in: F. Levy (Ed.), D. Reidel Publishing Company, Dordrecht, Holland, 1979. [13] J.R. Dahn, A.K. Sleigh, H. Shi, J.R. Reimers, Q. Zhong, B.M. Way, Electrochim. Acta 38 (1993) 1179. [14] R.C. Boehm, A. Banerjee, J. Chem. Phys. 96 (1992) 1150. [15] E. Peled, C. Menachem, D. Bar-Tow, A. Melman, J. Electrochem. Soc. 143 (1996) L4. [16] F. Disma, L. Aymard, L. Dupont, J.M. Tarascon, J. Electrochem. Soc. 143 (1996) 3959.