Insights into Diffusion Mechanisms in P2 Layered Oxide Materials by First-Principles Calculations

Significant progress has been made in Na-intercalation compounds for rechargeable Na batteries. P2 NaxMO2 layered oxides have been shown to have high capacity, good cyclability, and improved rate capability. In this study, we investigate the diffusion mechanisms in P-2 NaxCoO2 using ab initio molecular dynamics simulations and nudged elastic band calculations. We identify the Na diffusion mechanisms in P-2 NaxCoO2 at nondilute Na concentrations and illustrate the strong effect of Na-Na interactions on Na diffusion. Our computational results demonstrate that P-2 sodium layered oxides are fast Na ionic conductors over a wide range of Na concentrations and are promising cathode materials with high rate capabilities.