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

Lithium cobalt phosphate (LiCoPO) 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: LiCoFeZnPO/C is utilized to enhance the battery performance of LiCoPO. The electrochemical properties of LiCoFeZnPO/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, which showed that 10 % Fe and 5 % Zn co-doping enhanced the electrochemical performance of LiCoPO as a cathode material in LIBs.