First-Principles Study on a Layered Antiperovskite LiOBr Solid Electrolyte.

Lithium-rich antiperovskites (LiRAPs) have garnered recent attention as solid electrolytes for solid-state lithium-ion batteries (SSLIBs) with high safety and high energy density. Among them, the layered antiperovskite LiOBr exhibits superior Li conductivity compared to cubic antiperovskite LiOBr. However, the pure phase of LiOBr has not been synthesized to date, impeding an in-depth investigation of its migration mechanism and electrochemical properties. Herein, we employ density functional theory (DFT) calculations to examine the physical and electrochemical properties of LiOBr. Our results reveal that LiOBr is dynamically stable in its ground state, featuring electrical insulation with a wide bandgap of approximately 5.83 eV. Moreover, LiOBr exhibits improved malleability compared to LiOBr, making it favorable for material processing. Notably, the calculated energy barrier for Li migration in LiOBr is 0.26 eV, lower than that in LiOBr (0.4 eV), primarily attributed to the softened phonons of Li at the edge layers within the LiOBr lattice. We also investigated the impact of various defect types on Li diffusion in LiOBr, with the results indicating that LiBr defects effectively facilitate Li mobility. Additionally, we constructed a pressure-temperature-Gibbs (PTG) free energy phase diagram for LiOBr to explore appropriate experimental synthesis conditions. These findings hold substantial promise for promoting the research and development of innovative solid electrolyte materials for advanced SSLIBs.