Electrical and mechanical properties of glass and glass-ceramic electrolytes in the system Li3BO3-Li2SO4

Abstract

Low-melting oxide glasses are promising as electrolytes for all-solid-state lithium rechargeable batteries. Glasses in the pseudobinary system Li3BO3Li2SO4 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, BO33- and SO42-. The density and molar volume increased and elastic moduli decreased with an increase in the Li2SO4 content in the glasses. The heat treatment of the Li3BO3-Li2SO4 glasses at around 300C 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 Li3BO3 and Li2SO4. The conductivities were higher in the glass-ceramics of the compositions with small amounts of Li2SO4, ranging from 3 × 10-6 to 1 × 10-5Scm-1 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 Li3BO3 phase.