Interface Modification and Halide Substitution To Achieve High Ionic Conductivity in LiBH-Based Electrolytes for all-Solid-State Batteries.

A fast solid-state Li-ion conductor Li(BH)I@g-CN was synthesized using a simple ball-milling process. Because of the combined effect of halide substitution and the formation of an interface between Li(BH)I and g-CN, Li(BH)I@g-CN delivers a high ionic conductivity of 3.15 × 10 S/cm at 30 °C, which is about 1-2 orders of magnitude higher than that of Li(BH)I. Additionally, Li(BH)I@g-CN exhibits good electrochemical stability at a wide potential window of 0-5.0 V (vs Li/Li) and excellent thermal stability. The Li/Li symmetrical cell based on the Li(BH)I@g-CN electrolyte achieves long-term cycling with a small increase in overpotential, confirming superior electrochemical stability against Li foil. More importantly, Li(BH)I@g-CN-based Li batteries are compatible with S-C and FeF cathodes and MgH anodes and can achieve long-term cycling with LiTiO anodes at a temperature range from 30 to 60 °C. The developed strategy of coupling halide substitution together with interface modifications may open a new avenue toward the development of LiBH-based high ionic conductivity electrolytes for room-temperature all-solid-state Li batteries.