Electrical and mechanical properties of glass and glass-ceramic electrolytes in the system Li<sub>3</sub>BO<sub>3</sub>–Li<sub>2</sub>SO<sub>4</sub>

Abstract

Low-melting oxide glasses are promising as electrolytes for all-solid-state lithium rechargeable batteries. Glasses in the pseudobinary system Li3BO3–Li2SO4 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 300°C brought about the crystallization to form ion conducting glass-ceramics. 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 × 10−5 S cm−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.