Modeling study of Li ion diffusion and microstructure of LiFePO4

Molecular dynamics technique has been employed to investigate the relationship between the intrinsic structure and transport properties of lithium ions in LiFePO4 cathode materials. The results show that it is more favorable for Li ion diffusion when crystalline LiFePO4 grows along specific [100] directions, which may cause higher lithium diffusivity through a one dimensional [010] migration path. The change of Li ion diffusivity with temperature reveals that higher temperatures result in higher disorder of the atoms (or ions) and makes Li-O bonding relatively weaker, suggesting that Li diffusion is influenced by the microstructure of LiFePO4, particularly the bonding strength between Li and O atoms. (C) 2011 Elsevier Masson SAS. All rights reserved.