Boosting lithium ion conductivity of antiperovskite solid electrolyte by potassium ions substitution for cation clusters.

Abstract

Solid-state electrolytes with high ionic conductivities are crucial for the development of all-solid-state lithium batteries, and there is a strong correlation between the ionic conductivities and underlying lattice structures of solid-state electrolytes. Here, we report a lattice manipulation method of replacing [Li₂OH]⁺ clusters with potassium ions in antiperovskite solid-state electrolyte (Li₂OH)_0.99K_0.01Cl, which leads to a remarkable increase in ionic conductivity (4.5 × 10^‒3 mS cm^‒1, 25 °C). Mechanistic analysis indicates that the lattice manipulation method leads to the stabilization of the cubic phase and lattice contraction for the antiperovskite, and causes significant changes in Li-ion transport trajectories and migration barriers. Also, the Li||LiFePO₄ all-solid-state battery (excess Li and loading of 1.78 mg cm^‒2 for LiFePO₄) employing (Li₂OH)_0.99K_0.01Cl electrolyte delivers a specific capacity of 116.4 mAh g^‒1 at the 150th cycle with a capacity retention of 96.1% at 80 mA g^‒1 and 120 °C, which indicates potential application prospects of antiperovskite electrolyte in all-solid-state lithium batteries.