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Structure and properties of lithium ion conducting oxysulfide glasses prepared by rapid quenching
SOLID STATE Solid State Ionics 86-88
ELSEVIER
loNlcs
(1996) 487-490
Structure and properties of lithium ion conducting oxysulfide glasses prepared by rapid quenching Masahiro Tatsumisagoa’*,
Koichi Hirai”, Toshiyuki Tsutomu Minami”
Hirataa, Masanari Takahashib,
*Department of Applied Materials Science, Osaka Prefecture University, Sakai, Osaka 59.3, Japan “Osaka Municipal Technical Research institute, Joto, Osaka 536, Japan
Abstract Lithium ion conducting oxysuhide glasses were prepared in the systems (0.6Li,S. OASIS,)-Li,MO, (Li,MO, = Li,BO,, Li,SiO,, Li,PO,, Li,GeO,) by twin-roller rapid quenching. In any case of Li,MO, the addition of 5 mol% Li,MO, improved the ionic conductivity and the stability against crystallization. At the same composition a large number of silicon atoms in the glasses were coordinated with both sulfur and oxygen atoms. Such unique structural units contributed to improve the conductivity and the stability against crystallization. Keywords:’ Ion conducting
glasses; Crystallization;
Ion conductivity
1. Introduction Glassy materials are one of the most promising candidates for solid electrolytes utilized for lithium secondary batteries [l]. Much attention has been focused on the glassy systems based on lithium thiosilicate L&S-SiS, [2-51 because of their high conductivities of 10-4-10-3 S cm-’ at room temperature, easy preparation without vacuum sealing, and high stability against chemical reactions with lithium metal. We have prepared a variety of oxysulfide glasses in the systems LizS-SiS*-Li,MO, (Li,MO,: lithium ortho-oxosalt) by twin-roller rapid quenching [6-g]. The doping of small amounts of Li,MOy to Li,S-SiS, improved the glass stability against crystallization and the lithium ion conductivities. The glass structure of these oxysulfide *Corresponding
author.
glasses has also been investigated by NMR spectroscopy [8,9] and it was found that some unique structural units were present in the glasses with small amounts of Li,MO,. The present paper reports the relation between the structure and thermal and electrical properties of the oxysulfide glasses in the systems L&S-SiS,-LiXMO, (Li,MOy = Li,BO,, Li,SiO,, and Li,PO,, Li,GeO,).
2. Experimental Reagent-grade chemicals of Li,S, SiS,, L&CO,, B,O,, SiO,, Li,PO,, and GeO, were used as starting materials. Details of the glass preparation were described previously [6,7]. Thermal analyses of the glasses were performed for the powdered samples sealed in an Al pan using Mac-Science DTA.
0167.2738/96/$15.00 Copyright 01996 Elsevier Science B.V. All rights reserved PII SOl67-2738(96)00179-8
488
M. Tatsumimgo
et al. I Solid State lonics 86-88
(1996) 487-490
The conductivity measurements were carried out in dry Ar atmosphere using an HP impedance analyzer 4192A in the temperature range 25-200°C. 29Si MAS-NMR spectra were obtained using a JEOL GX-270 NMR spectrometer. Detailed conditions for NMR measurements were described in our previous paper [9].
a:LirBOa q:LImoI 0:LirPO4 n:LhGeO4
20 -
3. Results and discussion As a base glass composition of the thiosilicate system the composition 0.6Li,S * 0.4SiS2 (mole fraction) was chosen, and several amounts of a lithium ortho-oxosalt Li,MO, were doped to the base glass. The glass-forming regions of each system were 0 < mol% Li,BO, ~25, O
Fig. 2. Composition dependence of the TL-Tg values for the (0.6LizS. 0.4SiS2)-Li,MO, (LirMOb = Li,BO,, Li,SiO,, Li,PO,, Li,GeO,) glasses.
maximum at the composition with 5 mol% Li,,MO,. It is thus concluded that the doping of 5 mol% Li,MO, is most effective to stabilize the glassy state against crystallization. Fig. 3 shows the composition dependence of conductivity at 25°C uZ5, and the activation energy, E,, for conduction for all the systems. The crzs values maximize at the composition with 5 mol% L&MO, in all the systems, indicating that the doping of a small amount of Li,MO, enhances conductivities. A minimum of E, is observed in most systems at the same composition where the maximum of a,, is observed. It is noteworthy that the flZ25values were
-60
a:LiaBOs q:LlrSiOl 0:LirPO4 n:LlrGeOa
I
/ - 50 r E” 2 -40 w
200
250
300
350
Temperature
400
450
500
lo.“0
30 10
20 30 40 Mot% LixhlOy
50
/ “C
Fig. I. Differential thermal analysis curves for the (100 -z) (0.6Li,S. 0.4SiS,). zLi,SiO, (z = 0, 5, 20) glasses.
Fig. 3. Composition dependence the (0.6Li,S .0.4SiS,)-LixMO, Li,PO,, Li,GeO,) glasses.
of the values of uz5 and E, for (Li,MO” = Li,BO,, LQiO,,
M. Tatsumisago
et al. I Solid State Ionics 86-88
489
(1996) 487-490
es--Si-0-Si-Se
I
I
:
z Scheme
10
spectra of the (100 - z) (0.6Li,S. Fig. 4. “Si MAS-NMR 0.4SiS,). zLi,SiO, (z = 0, 5, 10, 20) glasses.
maximized at the composition where the T,-T, values were also maximized in all the systems. spectra of Fig. 4 shows the 29Si MAS-NMR (100 - z)(0.6Li2S. 0.4SiS2). zLi,SiO, (mol%) glasses as an example. The spectrum of the base glass 6OLi,S * 4OSiS, (Z = 0) is similar to that reported by Eckert [lo]. The peaks at around - 25 and - 105 ppm observed in the base glass are the blank due to a sealant used in a sample tube (these peaks are denoted by cross marks). The peaks at 5 and - 3 ppm observed in the base glass are due to silicon atoms coordinated with four sulfur atoms [lo]. The glasses with Li,SiO, (z = 5, 10, 20) exhibit several - 80, -90 and - 108 peaks at around - 25, -55, ppm in addition to the peaks at 5 and - 3 ppm. The - 55 ppm are steeply -25 and peaks at strengthened with the addition of 5 mol% Li,SiO,. The intensity of the peaks at - 80, - 90 and - 108 ppm is, however, gradually increased with an increase in the content of Li,SiO,. The peaks from - 80 to - 108 ppm are due to silicon atoms coordinated with four oxygen atoms [ll]. We have concluded that the peaks at - 25 and - 55 ppm, which are located between the peaks due to SiS, and SiO, units, must be due to silicon atoms coordinated with both sulfur and oxygen atoms like SiO,S,_, (n = 1, 2, 3) [9]. The NMR spectra of the glasses with 5 and 10 mol% Li,SiO, suggest that the dominant structural units are those with silicon atoms surrounded by both oxygen and sulfur atoms.
1
Scheme 1 shows one of the structural units expected to be mainly present in the oxysulfide glasses with 5 mol% Li,MO,: this unit contains six non-bridging sulfur atoms and one bridging oxygen atom. The presence of such a structural unit has not been known in any crystalline compound. If this type of structural unit is characteristic of the glassy state, it is understandable that the stability against crystallization was improved in the glasses with small amounts of Li,MO, because the crystallization should accompany large rearrangement of chemical bonds in these glasses. Such a unique glass structure also probably brought about the enhancement of lithium ion conductivity.
Acknowledgments This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science, Sports and Culture of Japan. Also by the Proposal-Based Advanced Industrial Technology R&D Program from the New Energy and Industrial Technology Department Organization (NEDO).
References [I] C. Julien and G-A. Nazri, Solid State Batteries: Materials Design and Optimization (Kluwer, Netherlands, 1994). [2] J.H. Kennedy, Mater. Chem. Phys. 23 (1989) 29. [3] J.H. Kennedy, Z. Zhang and H. Eckert, J. Non-Cryst. Solids 123 (1990) 328. [4] J.H. Kennedy and Z. Zhang, J. Electrochem. Sot. 135 (1988) 859. [5] S. Kondo, K Takada and Y. Yamamura, Solid State Ionics 53-56 (1992) 1183. [6] M. Tatsumisago, K. Hirai, T. Minami, K. Takada and S. Kondo, J. Ceram. Sot. Jpn. 101 (1993) 1315.
490
M. Tatsumisago
et al. ! Solid State Ionics 86-88
[7] K. Hirai, M. Tatsumisago and T. Minami, Solid State Ionics 78 (1995) 264. [8] M. Tatsumisago, K. Hirai and T. Minami, Phys. Chem. Glasses, in press. [9] K. Hirai, M. Tatsumisago and T. Minami, I. Amer. Ceram. Sot. 79 (1996) 349.
[lo]
(1996) 487-490
H. Eckert, J.H. Kennedy, A. Pradel and M. Ribes, J. NonCryst. Solids 113 (1989) 287. [ 111 A-R Grimmer, M. Magi, M. Hahnert, H. Stade, A. Samoson, W. Wieker and E. Lippmaa, Phys. Chem. Glasses 25 (1984) 105.
ELSEVIER
loNlcs
(1996) 487-490
Structure and properties of lithium ion conducting oxysulfide glasses prepared by rapid quenching Masahiro Tatsumisagoa’*,
Koichi Hirai”, Toshiyuki Tsutomu Minami”
Hirataa, Masanari Takahashib,
*Department of Applied Materials Science, Osaka Prefecture University, Sakai, Osaka 59.3, Japan “Osaka Municipal Technical Research institute, Joto, Osaka 536, Japan
Abstract Lithium ion conducting oxysuhide glasses were prepared in the systems (0.6Li,S. OASIS,)-Li,MO, (Li,MO, = Li,BO,, Li,SiO,, Li,PO,, Li,GeO,) by twin-roller rapid quenching. In any case of Li,MO, the addition of 5 mol% Li,MO, improved the ionic conductivity and the stability against crystallization. At the same composition a large number of silicon atoms in the glasses were coordinated with both sulfur and oxygen atoms. Such unique structural units contributed to improve the conductivity and the stability against crystallization. Keywords:’ Ion conducting
glasses; Crystallization;
Ion conductivity
1. Introduction Glassy materials are one of the most promising candidates for solid electrolytes utilized for lithium secondary batteries [l]. Much attention has been focused on the glassy systems based on lithium thiosilicate L&S-SiS, [2-51 because of their high conductivities of 10-4-10-3 S cm-’ at room temperature, easy preparation without vacuum sealing, and high stability against chemical reactions with lithium metal. We have prepared a variety of oxysulfide glasses in the systems LizS-SiS*-Li,MO, (Li,MO,: lithium ortho-oxosalt) by twin-roller rapid quenching [6-g]. The doping of small amounts of Li,MOy to Li,S-SiS, improved the glass stability against crystallization and the lithium ion conductivities. The glass structure of these oxysulfide *Corresponding
author.
glasses has also been investigated by NMR spectroscopy [8,9] and it was found that some unique structural units were present in the glasses with small amounts of Li,MO,. The present paper reports the relation between the structure and thermal and electrical properties of the oxysulfide glasses in the systems L&S-SiS,-LiXMO, (Li,MOy = Li,BO,, Li,SiO,, and Li,PO,, Li,GeO,).
2. Experimental Reagent-grade chemicals of Li,S, SiS,, L&CO,, B,O,, SiO,, Li,PO,, and GeO, were used as starting materials. Details of the glass preparation were described previously [6,7]. Thermal analyses of the glasses were performed for the powdered samples sealed in an Al pan using Mac-Science DTA.
0167.2738/96/$15.00 Copyright 01996 Elsevier Science B.V. All rights reserved PII SOl67-2738(96)00179-8
488
M. Tatsumimgo
et al. I Solid State lonics 86-88
(1996) 487-490
The conductivity measurements were carried out in dry Ar atmosphere using an HP impedance analyzer 4192A in the temperature range 25-200°C. 29Si MAS-NMR spectra were obtained using a JEOL GX-270 NMR spectrometer. Detailed conditions for NMR measurements were described in our previous paper [9].
a:LirBOa q:LImoI 0:LirPO4 n:LhGeO4
20 -
3. Results and discussion As a base glass composition of the thiosilicate system the composition 0.6Li,S * 0.4SiS2 (mole fraction) was chosen, and several amounts of a lithium ortho-oxosalt Li,MO, were doped to the base glass. The glass-forming regions of each system were 0 < mol% Li,BO, ~25, O
Fig. 2. Composition dependence of the TL-Tg values for the (0.6LizS. 0.4SiS2)-Li,MO, (LirMOb = Li,BO,, Li,SiO,, Li,PO,, Li,GeO,) glasses.
maximum at the composition with 5 mol% Li,,MO,. It is thus concluded that the doping of 5 mol% Li,MO, is most effective to stabilize the glassy state against crystallization. Fig. 3 shows the composition dependence of conductivity at 25°C uZ5, and the activation energy, E,, for conduction for all the systems. The crzs values maximize at the composition with 5 mol% L&MO, in all the systems, indicating that the doping of a small amount of Li,MO, enhances conductivities. A minimum of E, is observed in most systems at the same composition where the maximum of a,, is observed. It is noteworthy that the flZ25values were
-60
a:LiaBOs q:LlrSiOl 0:LirPO4 n:LlrGeOa
I
/ - 50 r E” 2 -40 w
200
250
300
350
Temperature
400
450
500
lo.“0
30 10
20 30 40 Mot% LixhlOy
50
/ “C
Fig. I. Differential thermal analysis curves for the (100 -z) (0.6Li,S. 0.4SiS,). zLi,SiO, (z = 0, 5, 20) glasses.
Fig. 3. Composition dependence the (0.6Li,S .0.4SiS,)-LixMO, Li,PO,, Li,GeO,) glasses.
of the values of uz5 and E, for (Li,MO” = Li,BO,, LQiO,,
M. Tatsumisago
et al. I Solid State Ionics 86-88
489
(1996) 487-490
es--Si-0-Si-Se
I
I
:
z Scheme
10
spectra of the (100 - z) (0.6Li,S. Fig. 4. “Si MAS-NMR 0.4SiS,). zLi,SiO, (z = 0, 5, 10, 20) glasses.
maximized at the composition where the T,-T, values were also maximized in all the systems. spectra of Fig. 4 shows the 29Si MAS-NMR (100 - z)(0.6Li2S. 0.4SiS2). zLi,SiO, (mol%) glasses as an example. The spectrum of the base glass 6OLi,S * 4OSiS, (Z = 0) is similar to that reported by Eckert [lo]. The peaks at around - 25 and - 105 ppm observed in the base glass are the blank due to a sealant used in a sample tube (these peaks are denoted by cross marks). The peaks at 5 and - 3 ppm observed in the base glass are due to silicon atoms coordinated with four sulfur atoms [lo]. The glasses with Li,SiO, (z = 5, 10, 20) exhibit several - 80, -90 and - 108 peaks at around - 25, -55, ppm in addition to the peaks at 5 and - 3 ppm. The - 55 ppm are steeply -25 and peaks at strengthened with the addition of 5 mol% Li,SiO,. The intensity of the peaks at - 80, - 90 and - 108 ppm is, however, gradually increased with an increase in the content of Li,SiO,. The peaks from - 80 to - 108 ppm are due to silicon atoms coordinated with four oxygen atoms [ll]. We have concluded that the peaks at - 25 and - 55 ppm, which are located between the peaks due to SiS, and SiO, units, must be due to silicon atoms coordinated with both sulfur and oxygen atoms like SiO,S,_, (n = 1, 2, 3) [9]. The NMR spectra of the glasses with 5 and 10 mol% Li,SiO, suggest that the dominant structural units are those with silicon atoms surrounded by both oxygen and sulfur atoms.
1
Scheme 1 shows one of the structural units expected to be mainly present in the oxysulfide glasses with 5 mol% Li,MO,: this unit contains six non-bridging sulfur atoms and one bridging oxygen atom. The presence of such a structural unit has not been known in any crystalline compound. If this type of structural unit is characteristic of the glassy state, it is understandable that the stability against crystallization was improved in the glasses with small amounts of Li,MO, because the crystallization should accompany large rearrangement of chemical bonds in these glasses. Such a unique glass structure also probably brought about the enhancement of lithium ion conductivity.
Acknowledgments This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science, Sports and Culture of Japan. Also by the Proposal-Based Advanced Industrial Technology R&D Program from the New Energy and Industrial Technology Department Organization (NEDO).
References [I] C. Julien and G-A. Nazri, Solid State Batteries: Materials Design and Optimization (Kluwer, Netherlands, 1994). [2] J.H. Kennedy, Mater. Chem. Phys. 23 (1989) 29. [3] J.H. Kennedy, Z. Zhang and H. Eckert, J. Non-Cryst. Solids 123 (1990) 328. [4] J.H. Kennedy and Z. Zhang, J. Electrochem. Sot. 135 (1988) 859. [5] S. Kondo, K Takada and Y. Yamamura, Solid State Ionics 53-56 (1992) 1183. [6] M. Tatsumisago, K. Hirai, T. Minami, K. Takada and S. Kondo, J. Ceram. Sot. Jpn. 101 (1993) 1315.
490
M. Tatsumisago
et al. ! Solid State Ionics 86-88
[7] K. Hirai, M. Tatsumisago and T. Minami, Solid State Ionics 78 (1995) 264. [8] M. Tatsumisago, K. Hirai and T. Minami, Phys. Chem. Glasses, in press. [9] K. Hirai, M. Tatsumisago and T. Minami, I. Amer. Ceram. Sot. 79 (1996) 349.
[lo]
(1996) 487-490
H. Eckert, J.H. Kennedy, A. Pradel and M. Ribes, J. NonCryst. Solids 113 (1989) 287. [ 111 A-R Grimmer, M. Magi, M. Hahnert, H. Stade, A. Samoson, W. Wieker and E. Lippmaa, Phys. Chem. Glasses 25 (1984) 105.