Investigation of Lithium-Ion Diffusion in LiCoPO4 Cathode Material by Molecular Dynamics Simulation

Abstract

One of the common cathode materials in the lithium ion battery is the olivine structure LiMPO4, where M is one of Co, Mn, Ni, Fe elements or their combination. Due to its high energy density LiCoPO4 is considered as a cathode material in the lithium ion battery. Lithium ion diffusion at the atomic scale is very important for determining the electrode charge/discharge rate-capability. A molecular dynamics simulation method can be used to investigate the lithium ion diffusion in a material from the atomic point of view. In this study, the diffusevity and structural properties of the LiCoPO4 cathode material are investigated by evaluating the mean square displacement curves, radial distribution function plots, and z-density profiles obtained using the molecular dynamics simulation implemented in the DL-POLY software. The results 10−12 m2/s to 10−13 m2/s at different show that the diffusion coefficient of crystalline LiCoPO4 ranges from 10−2 m2/s to 10−2 m/s at different temperatures. By comparing the diffusion coefficient in different directions, it is found that the motion of lithium ions along the [010] channel is significantly more convenient than that along [100] and [001] channels. By substituting other metals, such as iron, nickel and manganese, for cobalt, the transport and structural properties of the resulting material are investigated. The results indicate that the cobalt-containing structure has a more capability for fast charging and discharging.