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

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 [Li 2 OH] + clusters with potassium ions in antiperovskite solid-state electrolyte (Li 2 OH) 0.99 K 0.01 Cl, 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||LiFePO 4 all-solid-state battery (excess Li and loading of 1.78 mg cm ‒2 for LiFePO 4 ) employing (Li 2 OH) 0.99 K 0.01 Cl 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. All-solid-state electrolytes for lithium batteries generally suffer from low ionic conductivity. Here, authors manipulate the lattice of antiperovskite-type Li 2 OHCl by potassium ion substitution, which alters the lattice structure and improves the lithium ion transport properties.