Nonequilibrium Electron-Coupled Lithium Ion Diffusion in LiFePO4: Nonadiabatic Dynamics with Multistate Trajectory Approach

Abstract

The recently developed multistate trajectory approach is implemented for nonadiabatic molecular dynamics simulations on electron-coupled Li ion diffusion in LiFePO4, a promising cathode material for lithium ion batteries. The approach is demonstrated to be highly efficient and numerically stable in treating realistic complex molecular systems including tens of electronic states and hundreds of particles and to be capable of providing inspiring molecular pictures via a multistate representation on nonadiabatic quantum dynamics, such as Li ion diffusion and its correlation with electron transport in LiFePO4. The results from our real time nonequilibrium simulations indicate that the electron-coupled Li ion diffusion is significantly enhanced upon the formation of a small polaron, and nonadiabatic couplings further facilitate Li ion diffusion. Therefore, we suggest that nonequilibrium diffusion and nonadiabatic couplings could also be responsible for the wide range of Li ion diffusion coefficients obtained f...