Review—Recent Developments in the Doped LiFePO4Cathode Materials for Power Lithium Ion Batteries

Lithium ion batteries have been investigated extensively to optimize their power and energy densities to meet the growing demands of electronics and electric vehicles. The olivine structured LiFePO4 material is considered as a competitive candidate of cathode material for lithium ion batteries, but its poor electronic conductivity and low lithium ion diffusion coefficient limited its further application. Many efforts have been devoted to improve electrochemical performance of the LiFePO4 cathode, and this review focus on the doping effects on the electrochemical properties of LiFePO4 cathodes. It can be concluded that proper ions substitute on Li-site can increase the width of the one-dimensional diffusion channels of lithium ion and in turn decrease the charge transfer resistance, while ion doping on Fe-site can enhance the intrinsic electronic conductivity and lithium ion diffusion coefficient, and ion doping on O-site can facilitate the easy migration of lithium ion in the diffusion channels. Moreover, the multi-elements doping method exhibits a combined modification of Li-site doping, Fe-site doping and O-site doping, which would be an effective method to improve the electrochemical properties of the olivine structured cathode materials.