A First-Principles Study of Anion Doping in LiFePO₄ Cathode Materials for Li-Ion Batteries

Doping anions into LiFePO₄ can improve the electrochemical performance of lithium-ion batteries. In this study, structures, electronic properties and Li-ion migration of anion (F⁻, Cl⁻, and S²⁻) doping into LiFePO₄ were systematically investigated by means of density functional theory calculations. Anion substitution for oxygen atoms leads to an expansion of the LiFePO₄ lattice, significantly facilitating Li-ion diffusion. For Cl⁻ and F⁻ anion doped into LiFePO₄, the energy barrier of Li-ion migration gets lowered to 0.209 eV and 0.283 eV from 0.572 eV. The introduction of anions narrows the forbidden band of LiFePO₄, enhancing its electronic conductivity. This work pays a way towards the rational design of high-performance lithium-ion batteries.