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Lithium insertion into ceramic SrVO3−δ
Solid State Ionics 70/71 North-Holland
SOLID SKATE Iowus
( 1994) 429-433
Lithium insertion into ceramic SrV03 _ 6 Yue Jin Shan, Liquan Chen ‘, Yoshiyuki Mitsuru Itoh and Tetsurb Nakamura Research Laboratory ofEngineering
Inaguma,
Masahiro
Shikano,
Materials, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 227, Japan
Lithium was electrochemically inserted into SrV0,_6 by using a galvanic cell: Li 11M LiClO, in PC 1SrVOg_+ After the insertion of the amount x= 0.1 in Li$jrV03_b, metallic conductivity was maintained being accompanied by an increase of the absolute value of one order of magnitude and a very small volume increase was observed. The results indicate the possibility to use SrVOa_d as a cathode without any conductive additives in rechargeable lithium batteries.
1. Introduction In recent years much attention has been paid to the development of rechargeable lithium batteries with high energy densities. Although large number of cathode materials have already been developed, they have not met all the requirements yet. For instance the cathode material should have not only high ionic conductivity but also has good electronic conductivity in order to avoid polarization at the interface between electrolyte and cathode. Most of the cathode materials, however, are rather poor electronic conductors. For example, the electronic conductivity of most promising cathode LiMn,04 at room temperature is 1.4x 10m4 S cm-’ [ 11. In practice 10 to 50 wt% electronic conductive materials such as graphite or carbon black has to be mixed with the active oxides [ 2 1. As a result the energy density of the batteries are reduced. Therefore, a cathode material with both good ionic and electronic conductivities are required for large energy density of rechargeable batteries. SrV0J_6 is one of the perovskite related compounds in the system of Srfi+lVn03n+l. Due to an electron in the de band, it possesses a metallic electronic conductivity at room temperature as low as 10e3 R cm [ 3,4]. The present work is to study the effect of lithium ions insertion into the lattice on the ’ On leave from Institute of Physics, Academia 603, Beijing 100080, China. 0167-2738/94/$
Sinica, P.O. Box
07.00 0 1994 Elsevier Science B.V. All rights reserved.
physical properties of the compound and to show the possibility of using this material as a cathode in rechargeable lithium batteries.
2. Experimental 2. I. Preparation of samples Stochiometric mixture of SrC03 (3N) and V,05 (3N) powders was mixed, ground and calcined in air at 1273 K for 12 h. The calcined powder was pressed into 10 mm diameter pellet under 80 MPa and fired at 1573 K for 24 h in the stream of pure hydrogen gas with the intermediate grinding. 2.2. Electrochemical insertion The lithium ions were inserted electrochemically into SrV03_6 by a galvanic cell using Hokuto Denko, HA-30 1 Potentiogalvanostat. Galvanic cell: Li 11M LiC104 in PC 1SrV03_6, which consists of a pure lithium foil anode, a piece of non-woven polypropylene cloth soaked with 1M LiC104-PC (Mitsubishi Petrochemical Co.), and SrV03_G, as the cathode. The SrV03_6 pellets were used as cathode. Sheettype cathode made of SrV03_6 and 3 wt% teflon powder was used for the determination of the chemical diffusion coefficient and the coulometric titration curve. The whole assembly was placed in a Teflon container covered with a brass screw cap on both
430
Y.J. Shan et al. /Lithium insertion into ceramic SrVOJ_&
ends and sealed under an argon atmosphere. The lithium contents in the samples were controlled by coulometric titration using a Hokuto Denko HF-20 1 coulometer and checked by using Seiko SPS 1500 inductively coupled plasma spectroscopy (ICP). The lattice parameters of lithiated samples were determined by powder X-ray diffraction (Mac Science MXP18 system ). 2.3. Measurements of physical properties Samples with various lithium content were obtained by galvanostatic titration with a current density of 1.3 mA cm-2. After lithiation the samples were washed with ethylalcohol and dried under vacuum prior to the measurement. The electrical resistivities were measured in the temperature range lo-300 K using a standard dc four-probe technique. The magnetization was measured under magnetic fields of 10000 Oe using a Quantum Design MPMS-2 Squid magnetometer in the temperature range from 5 to 300 K.
3.0 2.5 t_ -i ’._ _) r > _ 4
2.0 1.51.0 -
0.00
0.10
0.05
0.15
0.20
x in Li,SrV03.~ Fig. 1. Open circuit voltage versus lithium content of cell: Li 1I M LiClO, in PC 1Li,SrVO,_,.
2.4. Determination of electrochemical properties When the voltage variation was less than 6 mV day-‘, the value was defined as an equilibrium one at that composition. The chemical diffusion coeflicient of lithium was measured with the galvanostatic intermittent titration technique [ 5 1. The reversibility of insertion and deinsertion was investigated by a cyclic voltammogram of a cell Li 11M LiC104 in PC 1SrV03_6 scanned at a rate 1 mV s-i and by the rechargeability of a prototype battery.
3. Results and discussion 3.1. Lithium insertion Open circuit voltage of Li 11M LiClO, in PC]SrV03_d as a function of lithium content is shown in fig. 1. The initial voltage was about 3.0 V. After lithium insertion, the open circuit voltage (OCV) decreased gradually from 3.0 to 1.5 V as x increased from 0 to 0.1, then a plateau of 1.5 V from 0.1 to 0.13 was maintained. This voltage plateau represents two phases in equilibrium. According to the
0
3c site
8
Sr+’ (lb)
.
O-‘(3d)
0
V+4 (la)
Fig. 2. The model of pathway for Li+ migration one-eighth of the unit cell are presented.
in SrVO,_+
only
results of powder X-ray diffraction, a second phase was not discovered for all the samples. Since the lithium insertion can be considered as a formation process of a solid solution Li,SrVOJ_m inserted lithium ions are considered to occupy two different positions in the lattice of SrV03_6. The two positions of lithium ions in SrV0x_6 can be considered as follows. The space group of SrV03_6 with perovskite structure is Pm3m and the unit cell parameter, a, is equal to 0.3840 nm. One-eighth of the unit cell of SrV03_,structure is shown in fig. 2. The empty 3c site in fig. 2 has a spacing of 0.096 nm using the ionic radius of Sr2+ 0.144 nm [ 61. Since the radius of Li+ in 4-
431
Y.J. Shan et al. /Lithium insertion into ceramicSrVOJ-6
coordinated sides, 6-coordinated sides and S-coordinated sides are 0.059 nm, 0.076 nm and Cl.092 nm, respectively, 3c sites may be one of candidate positions accommodating inserted lithium ions. On the other hand, inserted lithium ions may be caught easily by the tetrahedral sites which are surrounded by three oxygen ions and one strontium ion. It is possible for lithium ions to occupy 3c sites, and to migrate via the tetrahedral sites from one 3c site to the another. The further work is under way to give more evidence. A cyclic voltammogram of a Li ( SrV03_8 cell is presented in fig. 3. The cycling was performed between 1.0 and 3.4 V at a rate of 1 mV s-‘. Both insertion and deinsertion reactions could be observed clearly. It can also be seen that the reversibility of lithium ions insertion and extraction is very good. The lattice parameter versus lithium content in the samples of SrV03_6 (0 5x5 0.1) is plotted in fig. 4. All the samples were found to have the perovskite structure. The lattice parameters are seen to increase somewhat, and the expansion of lattice volume is as small as 0.3% with the increase of x up to 0.1.
i
. . . . . . . . . . .._..
..;
. ..j
._...,....
;
.
.
:
/
i
i_
;
;
_ .^.....
0.3850 ,
0.3842 t 0.00
Fig. 4. Lattice parameter
0.00
2.0
1.0 EIV
3.0
.,.
0.10
0.12
in Li,SrVO,.s
0.02
0.04
0.06
0.08
0. 0
in Li ,SrVO,.,
resistivity
versus lithium content.
3.2. Physical properties of lithiated SrV03-6
4.0
vs.Li/Li’
Fig. 3. Cyclic voltammogram of the cell Lil IM LiC104 --PCIL~$TVO~_~ between 1 .O to 3.4 V at a scanning rate of 1 mV s-l.
0.08
change with lithium insertion.
x
.
.i
0.06
~
Fig. 5. Room temperature
0.0
0.04
0.02
x
0-
.
I
0.3840 '
All the samples inserted with lithium showed a metallic conduction down to 15 K as well as SrV03_8. Fig. 5 shows the relation of the room-temperature electrical resistivities and lithium content x. As the amount of lithium inserted to the SrV03_, increases, the mean valence of vanadium decreases to keep electroneutrality. The decrease in vanadium valence causes the increase of electron carrier; however, local distortion of the lattice around the inserted Li+ may influence the V3dr-02pn-V3dC bonding, being the origin of the metallic conductivity of SrV03_6. The temperature dependence of the mag-
Y.J. Shun et al. /Lithium
432
insertion mto cerarmc SrC’03_,+
netic susceptibility for Li,SrV03_a samples are shown in fig. 6. After lithium insertion, the samples still maintained Pauli-paramagnetic behavior above 50 K. Below 50 K, the magnetic susceptibilities for Li,SrVOj_B (O
.
coefficients of lithium in TiS2 (1.1x10-*8.1 x lo-l2 cm2 s-l), NbSe,(3.2x 10-‘“-6.3~ lo-” cm2 s-l) [6] and LiMn,O, (4.9x 1O-9-6.O~ lO_“’ cm2 s-l) [ I]. SrV03_6 is predominantly an electronic conductor and therefore the partial lithium ion conductivity is given by the following [ 51:
(1)
cJ’L,+= -
where D is the chemical diffusion coefficient, V,,, is the molar volume, F is Faraday’s constant, and (dE/ dx) is the local slope of the coulometric titration curve. The partial lithium ion conductivity of Li,SrV03_d (O
x=0
X=o.nis x=0.055
0
X
* 3.0 to
ml
n
’ 50
100
’
150
’
(
200
250
’ 300
’ 350
TIK
Fig. 6. Temperature dependence of magnetic susceptibilities of lithiated SrVOl_a.
Fig, 7. Discharge curves of prototype battery using SrVk6 cathode.
Table 1 Magnetic parameters of lithiated SrVOS-d. Composition
Temperature range (K)
X0=’ (emu~mol-I)
c (emu,mol-‘,K)
8 (K)
SrV0,_6 Li0.01$rV03--d
5-300 S-300 S-300
2.54x 1O-4 2.62x lo-” 2.52x 1o-4
4.69x lo-’ 4.39x 1o-2 3,32x lo-*
_ 126 - 105 -63
Lio.ossSrvO~-d “‘x=Ko+C/(T-8).
as
Y.J. Shari et al. /Lithium insertion into ceramicSrVOj_6
5
3 ,x
.
1.6
‘.*
-
‘G 1.2 x J
80
g
f - 60
3 5 ._ c" - 40 k
0
1.0
-
2 0.8 ._ f 0.6 z L 0.4
- 20 0.2
433
of the cell Li I SrV03_6 decreased from 3.0 V for pure SrV0s_6 to about 1.5 V for lithium content x=0.1 and followed by a plateau of 1.5 V. The chemical diffusion coefficient is in the order of 1O-8 cm2 s-r. The unit cell is only about 0.3% enlarged and the resistivity becomes 7 times higher by inserting 0.1 lithium ions. A prototype lithium battery using SrV03_8 as cathode can be discharged at 130 and 13 uA cm-’ and showed a good rechargeability. Thus SrVOJ_B may be a potential cathode for rechargeable lithium batteries.
0.0 t-----JO 0
2
4
6
8
10
12
Acknowledgement
cycle number
Fig. 8. Cyclic behavior PC 1SrV03_a.
of prototype
battery
Li] IM LiC104 in
for discharging the cell to 1.0 V at a current density of 130 and 13 uA cmv2 respectively. At the conditions cut-off voltage 0.5 V and discharged current density 13 l.tA cm-2, 0.58 molecule Li can be inserted in SrV03_+ The evolution of relative capacity and coulomb efficiency with cycling number is presented in fig. 8. Both values are close to 100% and have little change during 10 times cycling. It means that the reversibility of lithium insertion into and extraction from SrV0s_6 is rather good.
4. Conclusion The lithium ions can be reversibly inserted into and deinserted from the lattice of SrV03_+ The OCV
Liquan Chen is grateful to Prof. Akira B. Sawaoka, the director of the Center for Ceramics Research, Prof. S. Tanabe and Dr. H. Tamura for their encouragement and enthusiasm. The authors would like to thank Prof. M. Wakihara, Prof. T. Uchida and Dr. H. Ikuta for their useful discussion and technical help. References [ I] L. Chen and J. Schoonman, Solid State Ionics 67 ( 1993) 17. [2] N. Kumagai, S. Tanifuji and K. Tanno, J. Power Sources 35 (1991) 313. [3] A. Nozaki, H. Yoshikawa, T. Wada, H. Yamauchi and S. Tanaka, Phys. Rev. B 43 ( 199 1) 18 1. [ 41 M. Itoh, M. Shikano, H. Kawaji and T. Nakamura, Solid State Commun. 80 (1991) 545. [ 51 W. Weppner and R.A. Huggins, J. Electrochem. Sot. 124 (1977) 1569. [ 61 R.D. Shannon, Acta Cryst. A 32 ( 1976) 5 1. [7] B.V. Ratnakumar, G. Nagasubramanian, S. Di Stefano and C.P. Bankston, J. Electrochem. Sot. 139 ( I992 ) 15 13.
SOLID SKATE Iowus
( 1994) 429-433
Lithium insertion into ceramic SrV03 _ 6 Yue Jin Shan, Liquan Chen ‘, Yoshiyuki Mitsuru Itoh and Tetsurb Nakamura Research Laboratory ofEngineering
Inaguma,
Masahiro
Shikano,
Materials, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 227, Japan
Lithium was electrochemically inserted into SrV0,_6 by using a galvanic cell: Li 11M LiClO, in PC 1SrVOg_+ After the insertion of the amount x= 0.1 in Li$jrV03_b, metallic conductivity was maintained being accompanied by an increase of the absolute value of one order of magnitude and a very small volume increase was observed. The results indicate the possibility to use SrVOa_d as a cathode without any conductive additives in rechargeable lithium batteries.
1. Introduction In recent years much attention has been paid to the development of rechargeable lithium batteries with high energy densities. Although large number of cathode materials have already been developed, they have not met all the requirements yet. For instance the cathode material should have not only high ionic conductivity but also has good electronic conductivity in order to avoid polarization at the interface between electrolyte and cathode. Most of the cathode materials, however, are rather poor electronic conductors. For example, the electronic conductivity of most promising cathode LiMn,04 at room temperature is 1.4x 10m4 S cm-’ [ 11. In practice 10 to 50 wt% electronic conductive materials such as graphite or carbon black has to be mixed with the active oxides [ 2 1. As a result the energy density of the batteries are reduced. Therefore, a cathode material with both good ionic and electronic conductivities are required for large energy density of rechargeable batteries. SrV0J_6 is one of the perovskite related compounds in the system of Srfi+lVn03n+l. Due to an electron in the de band, it possesses a metallic electronic conductivity at room temperature as low as 10e3 R cm [ 3,4]. The present work is to study the effect of lithium ions insertion into the lattice on the ’ On leave from Institute of Physics, Academia 603, Beijing 100080, China. 0167-2738/94/$
Sinica, P.O. Box
07.00 0 1994 Elsevier Science B.V. All rights reserved.
physical properties of the compound and to show the possibility of using this material as a cathode in rechargeable lithium batteries.
2. Experimental 2. I. Preparation of samples Stochiometric mixture of SrC03 (3N) and V,05 (3N) powders was mixed, ground and calcined in air at 1273 K for 12 h. The calcined powder was pressed into 10 mm diameter pellet under 80 MPa and fired at 1573 K for 24 h in the stream of pure hydrogen gas with the intermediate grinding. 2.2. Electrochemical insertion The lithium ions were inserted electrochemically into SrV03_6 by a galvanic cell using Hokuto Denko, HA-30 1 Potentiogalvanostat. Galvanic cell: Li 11M LiC104 in PC 1SrV03_6, which consists of a pure lithium foil anode, a piece of non-woven polypropylene cloth soaked with 1M LiC104-PC (Mitsubishi Petrochemical Co.), and SrV03_G, as the cathode. The SrV03_6 pellets were used as cathode. Sheettype cathode made of SrV03_6 and 3 wt% teflon powder was used for the determination of the chemical diffusion coefficient and the coulometric titration curve. The whole assembly was placed in a Teflon container covered with a brass screw cap on both
430
Y.J. Shan et al. /Lithium insertion into ceramic SrVOJ_&
ends and sealed under an argon atmosphere. The lithium contents in the samples were controlled by coulometric titration using a Hokuto Denko HF-20 1 coulometer and checked by using Seiko SPS 1500 inductively coupled plasma spectroscopy (ICP). The lattice parameters of lithiated samples were determined by powder X-ray diffraction (Mac Science MXP18 system ). 2.3. Measurements of physical properties Samples with various lithium content were obtained by galvanostatic titration with a current density of 1.3 mA cm-2. After lithiation the samples were washed with ethylalcohol and dried under vacuum prior to the measurement. The electrical resistivities were measured in the temperature range lo-300 K using a standard dc four-probe technique. The magnetization was measured under magnetic fields of 10000 Oe using a Quantum Design MPMS-2 Squid magnetometer in the temperature range from 5 to 300 K.
3.0 2.5 t_ -i ’._ _) r > _ 4
2.0 1.51.0 -
0.00
0.10
0.05
0.15
0.20
x in Li,SrV03.~ Fig. 1. Open circuit voltage versus lithium content of cell: Li 1I M LiClO, in PC 1Li,SrVO,_,.
2.4. Determination of electrochemical properties When the voltage variation was less than 6 mV day-‘, the value was defined as an equilibrium one at that composition. The chemical diffusion coeflicient of lithium was measured with the galvanostatic intermittent titration technique [ 5 1. The reversibility of insertion and deinsertion was investigated by a cyclic voltammogram of a cell Li 11M LiC104 in PC 1SrV03_6 scanned at a rate 1 mV s-i and by the rechargeability of a prototype battery.
3. Results and discussion 3.1. Lithium insertion Open circuit voltage of Li 11M LiClO, in PC]SrV03_d as a function of lithium content is shown in fig. 1. The initial voltage was about 3.0 V. After lithium insertion, the open circuit voltage (OCV) decreased gradually from 3.0 to 1.5 V as x increased from 0 to 0.1, then a plateau of 1.5 V from 0.1 to 0.13 was maintained. This voltage plateau represents two phases in equilibrium. According to the
0
3c site
8
Sr+’ (lb)
.
O-‘(3d)
0
V+4 (la)
Fig. 2. The model of pathway for Li+ migration one-eighth of the unit cell are presented.
in SrVO,_+
only
results of powder X-ray diffraction, a second phase was not discovered for all the samples. Since the lithium insertion can be considered as a formation process of a solid solution Li,SrVOJ_m inserted lithium ions are considered to occupy two different positions in the lattice of SrV03_6. The two positions of lithium ions in SrV0x_6 can be considered as follows. The space group of SrV03_6 with perovskite structure is Pm3m and the unit cell parameter, a, is equal to 0.3840 nm. One-eighth of the unit cell of SrV03_,structure is shown in fig. 2. The empty 3c site in fig. 2 has a spacing of 0.096 nm using the ionic radius of Sr2+ 0.144 nm [ 61. Since the radius of Li+ in 4-
431
Y.J. Shan et al. /Lithium insertion into ceramicSrVOJ-6
coordinated sides, 6-coordinated sides and S-coordinated sides are 0.059 nm, 0.076 nm and Cl.092 nm, respectively, 3c sites may be one of candidate positions accommodating inserted lithium ions. On the other hand, inserted lithium ions may be caught easily by the tetrahedral sites which are surrounded by three oxygen ions and one strontium ion. It is possible for lithium ions to occupy 3c sites, and to migrate via the tetrahedral sites from one 3c site to the another. The further work is under way to give more evidence. A cyclic voltammogram of a Li ( SrV03_8 cell is presented in fig. 3. The cycling was performed between 1.0 and 3.4 V at a rate of 1 mV s-‘. Both insertion and deinsertion reactions could be observed clearly. It can also be seen that the reversibility of lithium ions insertion and extraction is very good. The lattice parameter versus lithium content in the samples of SrV03_6 (0 5x5 0.1) is plotted in fig. 4. All the samples were found to have the perovskite structure. The lattice parameters are seen to increase somewhat, and the expansion of lattice volume is as small as 0.3% with the increase of x up to 0.1.
i
. . . . . . . . . . .._..
..;
. ..j
._...,....
;
.
.
:
/
i
i_
;
;
_ .^.....
0.3850 ,
0.3842 t 0.00
Fig. 4. Lattice parameter
0.00
2.0
1.0 EIV
3.0
.,.
0.10
0.12
in Li,SrVO,.s
0.02
0.04
0.06
0.08
0. 0
in Li ,SrVO,.,
resistivity
versus lithium content.
3.2. Physical properties of lithiated SrV03-6
4.0
vs.Li/Li’
Fig. 3. Cyclic voltammogram of the cell Lil IM LiC104 --PCIL~$TVO~_~ between 1 .O to 3.4 V at a scanning rate of 1 mV s-l.
0.08
change with lithium insertion.
x
.
.i
0.06
~
Fig. 5. Room temperature
0.0
0.04
0.02
x
0-
.
I
0.3840 '
All the samples inserted with lithium showed a metallic conduction down to 15 K as well as SrV03_8. Fig. 5 shows the relation of the room-temperature electrical resistivities and lithium content x. As the amount of lithium inserted to the SrV03_, increases, the mean valence of vanadium decreases to keep electroneutrality. The decrease in vanadium valence causes the increase of electron carrier; however, local distortion of the lattice around the inserted Li+ may influence the V3dr-02pn-V3dC bonding, being the origin of the metallic conductivity of SrV03_6. The temperature dependence of the mag-
Y.J. Shun et al. /Lithium
432
insertion mto cerarmc SrC’03_,+
netic susceptibility for Li,SrV03_a samples are shown in fig. 6. After lithium insertion, the samples still maintained Pauli-paramagnetic behavior above 50 K. Below 50 K, the magnetic susceptibilities for Li,SrVOj_B (O
.
coefficients of lithium in TiS2 (1.1x10-*8.1 x lo-l2 cm2 s-l), NbSe,(3.2x 10-‘“-6.3~ lo-” cm2 s-l) [6] and LiMn,O, (4.9x 1O-9-6.O~ lO_“’ cm2 s-l) [ I]. SrV03_6 is predominantly an electronic conductor and therefore the partial lithium ion conductivity is given by the following [ 51:
(1)
cJ’L,+= -
where D is the chemical diffusion coefficient, V,,, is the molar volume, F is Faraday’s constant, and (dE/ dx) is the local slope of the coulometric titration curve. The partial lithium ion conductivity of Li,SrV03_d (O
x=0
X=o.nis x=0.055
0
X
* 3.0 to
ml
n
’ 50
100
’
150
’
(
200
250
’ 300
’ 350
TIK
Fig. 6. Temperature dependence of magnetic susceptibilities of lithiated SrVOl_a.
Fig, 7. Discharge curves of prototype battery using SrVk6 cathode.
Table 1 Magnetic parameters of lithiated SrVOS-d. Composition
Temperature range (K)
X0=’ (emu~mol-I)
c (emu,mol-‘,K)
8 (K)
SrV0,_6 Li0.01$rV03--d
5-300 S-300 S-300
2.54x 1O-4 2.62x lo-” 2.52x 1o-4
4.69x lo-’ 4.39x 1o-2 3,32x lo-*
_ 126 - 105 -63
Lio.ossSrvO~-d “‘x=Ko+C/(T-8).
as
Y.J. Shari et al. /Lithium insertion into ceramicSrVOj_6
5
3 ,x
.
1.6
‘.*
-
‘G 1.2 x J
80
g
f - 60
3 5 ._ c" - 40 k
0
1.0
-
2 0.8 ._ f 0.6 z L 0.4
- 20 0.2
433
of the cell Li I SrV03_6 decreased from 3.0 V for pure SrV0s_6 to about 1.5 V for lithium content x=0.1 and followed by a plateau of 1.5 V. The chemical diffusion coefficient is in the order of 1O-8 cm2 s-r. The unit cell is only about 0.3% enlarged and the resistivity becomes 7 times higher by inserting 0.1 lithium ions. A prototype lithium battery using SrV03_8 as cathode can be discharged at 130 and 13 uA cm-’ and showed a good rechargeability. Thus SrVOJ_B may be a potential cathode for rechargeable lithium batteries.
0.0 t-----JO 0
2
4
6
8
10
12
Acknowledgement
cycle number
Fig. 8. Cyclic behavior PC 1SrV03_a.
of prototype
battery
Li] IM LiC104 in
for discharging the cell to 1.0 V at a current density of 130 and 13 uA cmv2 respectively. At the conditions cut-off voltage 0.5 V and discharged current density 13 l.tA cm-2, 0.58 molecule Li can be inserted in SrV03_+ The evolution of relative capacity and coulomb efficiency with cycling number is presented in fig. 8. Both values are close to 100% and have little change during 10 times cycling. It means that the reversibility of lithium insertion into and extraction from SrV0s_6 is rather good.
4. Conclusion The lithium ions can be reversibly inserted into and deinserted from the lattice of SrV03_+ The OCV
Liquan Chen is grateful to Prof. Akira B. Sawaoka, the director of the Center for Ceramics Research, Prof. S. Tanabe and Dr. H. Tamura for their encouragement and enthusiasm. The authors would like to thank Prof. M. Wakihara, Prof. T. Uchida and Dr. H. Ikuta for their useful discussion and technical help. References [ I] L. Chen and J. Schoonman, Solid State Ionics 67 ( 1993) 17. [2] N. Kumagai, S. Tanifuji and K. Tanno, J. Power Sources 35 (1991) 313. [3] A. Nozaki, H. Yoshikawa, T. Wada, H. Yamauchi and S. Tanaka, Phys. Rev. B 43 ( 199 1) 18 1. [ 41 M. Itoh, M. Shikano, H. Kawaji and T. Nakamura, Solid State Commun. 80 (1991) 545. [ 51 W. Weppner and R.A. Huggins, J. Electrochem. Sot. 124 (1977) 1569. [ 61 R.D. Shannon, Acta Cryst. A 32 ( 1976) 5 1. [7] B.V. Ratnakumar, G. Nagasubramanian, S. Di Stefano and C.P. Bankston, J. Electrochem. Sot. 139 ( I992 ) 15 13.