Theoretical insights into interfacial stability and ionic transport of Li2OHBr solid electrolyte for all-solid-state batteries

Abstract

Li-rich antiperovskite materials are promising candidates as inorganic solid electrolytes (ISEs) for all-solid-state Li-ion batteries (ASSLIBs). However, the material faces several pressing issues for its application, concerning the phase stability and electrochemical stability of the synthesized material and the Li-ion transport mechanism in it. Herein, we performed first-principles computational studies on the phase stability, interfacial stability, defect chemistry, and electronic/ionic transport properties of Li₂OHBr material. The calculation results show that the Li₂OHBr is thermodynamically metastable at 0 K and can be synthesized experimentally. This material exhibits a wider intrinsic electrochemical stability window (0.80-3.15 V) compared with sulfide solid electrolytes. Moreover, the Li₂OHBr displays significant chemical stability when in contact with typical cathode materials (LiCoO₂, LiMn₂O₄, LiFePO₄) and moisture. The dominant defects of Li₂OHBr are predicted to be V_Li^- and Li_i ⁺, corresponding to lower Li-ion migration barriers of 0.38 and 0.49 eV, respectively, while the replacement of some of the OH^- by F^- is shown to be effective in decreasing migration barriers in Li₂OHBr. These findings provide a theoretical framework for further designing high performance ISEs.