Fast Lithium Ionic Conductivity in Complex Hydride-Sulfide Electrolytes by Double Anions Substitution.

Hydride-based solid-state electrolytes (SSEs) can maintain their stability against Li metal and exhibit high compatibility with a Li metal anode owing to their reducing property and flexible character. However, poor ionic conductivity at room temperature is a major challenge for hydride materials used as SSEs in a lithium ion battery. In this work, a room-temperature fast lithium-ion conductor is explored in response to double anion substitution, (100-x)(3LiBH 4 -LiI)-xP 2 S 5 (LLPx, 0 ≤ x ≤ 50). Among these samples, LLP20 respectively delivers an ionic conductivity up to 3.77 × 10 -4 S cm -1 at 30 °C and 1.0 × 10 -2 S cm -1 at 100 °C, with a stable electrochemical window of 0-5 V. A Li plating/stripping test has been conducted under a current density of 1.0 mA cm -2 , which exhibits an excellent stability even after 1000 h. Moreover, the all solid-state cell exhibits a remarkable electrochemical performance in a wide temperature range including high reversible capacity, good rate capability, and long cycling durability. These outstanding performances present a practical strategy for developing ambient-temperature, fast ionic conductors for all solid-state batteries in near future.