Sulfide glasses are considered to be promising electrolytes for all-solid-state batteries because of their high ionic conductivities and favorable mechanical properties. In this paper, comprehensive studies of the mechanical properties of sulfide glasses were carried out based on the Li 2 SP 2 S 5 system, and we evaluated the effects of changing the glass former and modifier on the elastic moduli and formability of these glasses. Young's moduli of Li 2 SP 2 S 5 glasses increased when the glass former P was replaced with Ge or Si. Moreover, the Young's moduli of Li 2 SP 2 S 5 glasses also increased when substituting S with O. Irrespective of the glass modifier, the Young's moduli of R x S y P 2 S 5 glasses (R = Li, Na, Ag, Mg, or Sn) increased with the increase in content of each modifier. The measured Young's moduli are correlated with the mean atomic volumes of the glasses. We evaluated the formability of the sulfide glasses in powder-compaction tests at room temperature. Sulfide glasses with lower bonding energy, larger free volume, and more isolated structure exhibited higher densification ability. Pugh's ratio (B/G) (B is the bulk and G the shear modulus) was used to evaluate the ductile-brittle property of materials. The glasses with a larger B/G ratio, meaning higher ductility, tended to show a higher relative density. It is suggested that plastic deformation contributes to the densification. This study will provide valuable results for glass science, and will be useful for developing all-solid-state batteries.

Mechanical properties such as formability and elastic moduli of solid electrolytes are important for the fabrication of all-solid-state batteries and retention of their charge-discharge capacities. In this paper, xNa 2 S$(100 À x)P 2 S 5 (mol%) sulfide glass electrolytes (x ¼ 50, 67, and 75) were prepared and their formability and elastic moduli were evaluated by an ultrasonic pulse-echo technique and a compression test under uniaxial pressing. The glasses were better densified and showed lower Young's moduli (15-19 GPa) than the Li 2 S-P 2 S 5 glasses.

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Low-melting oxide glasses are promising as electrolytes for all-solid-state lithium rechargeable batteries. Glasses in the pseudobinary system Li 3 BO 3 Li 2 SO 4 were prepared by a mechanochemical technique. Raman spectra revealed that the glasses contained no macroanions which form networks but consisted only of Li + ions and two discrete ortho-oxoanions, BO 3 3¹ and SO 4 2¹. The density and molar volume increased and elastic moduli decreased with an increase in the Li 2 SO 4 content in the glasses. The heat treatment of the Li 3 BO 3 Li 2 SO 4 glasses at around 300°C brought about the crystallization to form ion conducting glassceramics. Electrical conductivities of the glasses and glass-ceramics in this system were maximized with the mixing of Li 3 BO 3 and Li 2 SO 4 . The conductivities were higher in the glass-ceramics of the compositions with small amounts of Li 2 SO 4 , ranging from 3 © 10 ¹6 to 1 © 10 ¹5 S cm ¹1 at room temperature, compared to the corresponding glasses. This conductivity enhancement by the heat treatment is probably due to the precipitation of solid solutions with a high temperature Li 3 BO 3 phase.