Stabilization of Superionic-Conducting High-Temperature Phase of Li(CB9H10) via Solid Solution Formation with Li-2(B12H12)

Abstract

We report the stabilization of the high-temperature (high-T) phase of lithium carba-closo-decaborate, Li(CB9H10), via the formation of solid solutions in a Li(CB9H10)-Li-2(B12H12) quasi-binary system. Li(CB9H10)-based solid solutions in which [CB9H10](-) is replaced by [B12H12](2-) were obtained at compositions with low x values in the (1-x)Li(CB9H10)-xLi(2)(B12H12) system. An increase in the extent of [B12H12](2-) substitution promoted stabilization of the high-T phase of Li(CB9H10), resulting in an increase in the lithium-ion conductivity. Superionic conductivities of over 10(-3) S cm(-1) were achieved for the compounds with 0.2 <= x <= 0.4. In addition, a comparison of the Li(CB9H10)-Li-2(B12H12) system and the Li(CB9H10)-Li(CB11H12) system suggests that the valence of the complex anions plays an important role in the ionic conduction. In battery tests, an all-solid-state Li-TiS2 cell employing 0.6Li(CB9H10)-0.4Li(2)(B12H12) (x = 0.4) as a solid electrolyte presented reversible battery reactions during repeated discharge-charge cycles. The current study offers an insight into strategies to develop complex hydride solid electrolytes.