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

Abstract

Lithium cobalt phosphate (LiCoPO₄) 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 LiCoPO₄: LiCo_0.9-xFe_0.1Zn_xPO₄/C is utilized to enhance the battery performance of LiCoPO₄. The electrochemical properties of LiCo_0.85Fe_0.1Zn_0.05PO₄/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 LiCoPO₄, which showed that 10 % Fe and 5 % Zn co-doping enhanced the electrochemical performance of LiCoPO₄ as a cathode material in LIBs.

Keywords: Co-doping; High voltage; LiCoPO(4); Structural transformation; operando X-ray diffraction.