Molecular dynamics simulation unveiling anion charge and lattice volume dependent Li ion diffusion in lithium compounds

Abstract

To fill knowledge gaps between anion sublattice models and real lithium compounds in terms of the influence of Li-anion interaction on Li ion diffusion, herein, molecular dynamics calculations were applied to systematically study impacts of anion charge and lattice volume on Li ion diffusion in lithium battery materials. Regardless of different Li occupation patterns, Li sublattice type, anion sublattice types and Li ion diffusion channels, there is a universal physical picture of anion charge dependent activation energy (Ea) for Li ion diffusion in lithium compounds, and that is the more negative anion charges increase Ea for Li ion diffusion and then decrease them. While large lattice volumes not always reduce Ea for Li ion migration, and even increase Ea, distinguished from the traditional understandings. These physical pictures of anion charge and lattice volume dependent Ea guide us to apply strains and choose appropriate elements for doping or substituting lithium compounds to reduce Ea for fast Li ion diffusion.