Multi-ion Conduction in Li₃OCl Glass Electrolytes

Antiperovskite glasses such as Li₃OCl and doped analogues have been proposed as excellent electrolytes for all-solid-state Li ion batteries (ASSB). Incorporating these electrolytes in ASSBs results in puzzling properties. This Letter describes a theoretical Li₃OCl glass created by conventional melt-quench procedures. The ion conductivities are calculated using molecular dynamics based on a polarizable force field that is fitted to an extensive set of density functional theory-based energies, forces, and stresses for a wide range of nonequilibrium structures encompassing crystal, glass, and melt. We find high Li⁺ ion conductivity in good agreement with experiments. However, we also find that the Cl^- ion is mobile as well so that the Li₃OCl glass is not a single-ion conductor, with a transference number t ⁺ ≈ 0.84. This has important implications for its use as an electrolyte for all-solid-state batteries because the Cl could react irreversibly with the electrodes and/or produce glass decomposition during discharge-charge.