Theoretical Insights into Li-Ion Transport in LiTa2PO8

Recently, a solid electrolyte material LiTa2PO8 (LTPO) with a high room-temperature ionic conductivity (1.6 mS/cm) has been reported in experiment. To understand its Li transport mechanism and find its theoretical performance limit, we systematically investigate the properties of LTPO using density functional theory and ab initio molecular dynamic (AIMD) simulations. Our results show that LTPO is electrochemically stable with a wide electrochemical window. AIMD simulations indicate that Ta, P, and O are immobile during Li diffusion, indicating a high stability of the material. The Li-ion diffusion channels form a quasi-two-dimensional honeycomb framework. The intrinsic ionic conductivity of LTPO is predicted to be as high as 35.3 mS/cm at room temperature. The diffusion activation energy is only 0.16 eV, consisting of a low-energy barrier obtained from the minimum-energy path calculations. These results encourage further experimental studies on this promising solid-state electrolyte material.