Mechanochemically Prepared Li2S–P2S5–LiBH4 Solid Electrolytes withan Argyrodite Structure

摘要

Solid electrolytes with compositions of (100 – x)(0.75Li2S·0.25P2S5)·xLiBH4 (mol %, 0 ≤ x ≤ 100) were mechanochemically prepared from the 75Li2S·25P2S5 (mol %) glass and LiBH4 crystal. The samples with x ≥ 43 have crystalline phases and those with x ≤ 33 formed a glassy phase. The crystalline phase was identified as argyrodite Li6PS5(BH4). The x = 50 sample formed a crystalline phase and demonstrated a high lithium-ion conductivity of 1.8 × 10^–3 S cm^–1 at 25 °C with an activation energy of 16 kJ·mol^–1. The argyrodite-type crystal with a BH4^– anion that occupies the halide site is a novel and promising solid electrolyte.