Atomistic Insights into the Effects of Doping and Vacancy Clustering on Li-Ion Conduction in the Li₃OCl Antiperovskite Solid Electrolyte

Solid-state batteries are currently attracting increased attention because of their potential for significant improvements in energy density and safety as compared to liquid electrolyte-based batteries. Lithium-rich antiperovskites, such as Li3OCl, are of particular interest, but the effects of doping on lithium mobility are not fully understood at the atomic level. Here, we investigate the impact of divalent cation (Mg2+, Ca2+, Sr2+, and Ba2+) and F– doping on the ion conduction properties of Li3OCl, using both defect simulation and molecular dynamics techniques. Our results show that the F-doped system has a low conductivity and high activation barriers. This is attributable to high binding energies, which leads to the formation of stable dopant–vacancy pairs, preventing long-range lithium-ion mobility. In contrast to the F-doped system, Mg dopants (shown to be the most favorable dopant on the Li+ site) have lower binding energies to lithium vacancies, yielding higher lithium-ion conductivities and lower migration energies. Our results indicate a viable doping strategy to improve the electrochemical performance of antiperovskite solid electrolytes.