Low density (100-x)Li3BS3-xLiI solid-state electrolyte with ultra-long cycling stability for solid-state battery

Abstract

Thioborate solid-state electrolytes are considered to be ideal solid-state electrolytes (SSEs) due to their high theoretical ionic conductivity, wide electrochemical stability window, abundant raw materials, and low density. However, due to the demanding synthesis conditions, thioborate SSEs have yet to be investigated systematically and their electrochemical properties remain largely underdeveloped. In this work, a series of (100-x)Li₃BS₃-xLiI SSEs was prepared from Li₂S, B, S, and LiI by melt quenching, and the effects of I doping on the electrochemical properties of Li₃BS₃ SSEs were investigated systematically. The as-prepared 40Li₃BS₃-60LiI SSEs exhibits an excellent ionic conductivity of 0.42 mS cm⁻¹ and a low apparent density of 1.334 g cm⁻³ at 25 °C. The ultra-high dissolution capacity up to 60% mol ratio of LiI in Li₃BS₃ enhances interfacial stability, which contributes to a long cycling life of 330 h at 0.1 mA cm⁻² without significant interfacial degradation. These results suggest that Li₃BS₃-LiI SSEs with high ionic conductivity and excellent interfacial stability could facilitate the development of all-solid-state batteries with high energy density, long-term cycling stability, and low cost.