Computational insights into the ionic transport mechanism and interfacial stability of the Li2OHCl solid-state electrolyte

Lithium-rich antiperovskites are promising solid-state electrolytes for all-solid-state lithium-ion batteries because of their high structural tolerance and good formability. However, the experimentally reported proton-free Li3OCl is plagued by its inferior interfacial compatibility and harsh synthesis conditions. In contrast, Li2OHCl is a thermodynamically favored phases and is easier to achieve than Li3OCl. Due to the proton inside this material, it exhibits interesting lithium diffusion mechanisms. Herein, we present a systematic investigation of the ionic transport, phase stability, and electrochemical-chemical stability of Li2OHCl using first-principles calculations. Our results indicate that Li2OHCl is thermodynamically metastable and is an electronic insulator. The wide electrochemical stability window and high chemical stability of Li2OHCl against various electrodes are confirmed. The charged defects are the dominant conduction mechanism for Li-transport, with a low energy barrier of ∼0.50 eV. The Li-ion conductivity estimated by ab initio molecular dynamics simulations is about 1.3 × 10−4 S cm−1 at room temperature. This work identifies the origin of the high interfacial stability and ionic conductivity of Li2OHCl, which can further lead to the design of such as a cathode coating. Moreover, all computational methods for calculating the properties of Li2OHCl are general and can guide the design of high-performance solid-state electrolytes.