Effect of Fe and Zn co-doping on LiCoPO4 cathode materials for High-Voltage Lithium-Ion batteries

Lithium cobalt phosphate (LiCoPO ₄ ) has great potential to be developed as a cathode material for lithium-ion batteries (LIBs) due to its structural stability and higher voltage platform with a high theoretical energy density. However, the relatively low diffusion of lithium ions still needs to be improved. In this work, Fe and Zn co-doped LiCoPO ₄ : LiCo _0.9-x Fe _0.1 Zn _x PO ₄ /C is utilized to enhance the battery performance of LiCoPO ₄ . The electrochemical properties of LiCo _0.85 Fe _0.1 Zn _0.05 PO ₄ /C demonstrated an initial capacity of 118 mAh/g, with 93.4 % capacity retention at 1C after 100 cycles, and a good capacity of 87 mAh/g remained under a high current density of 10C. In addition, the diffusion rate of Li ions was investigated, proving the improvement of the materials with doping. The impedance results also showed a smaller resistance of the doped materials. Furthermore, operando X-ray diffraction displayed a good reversibility of the structural transformation, corresponding to cycling stability. This work provided studies of both the electrochemical properties and structural transformation of Fe and Zn co-doped LiCoPO ₄ , which showed that 10 % Fe and 5 % Zn co-doping enhanced the electrochemical performance of LiCoPO ₄ as a cathode material in LIBs.