Discovered Intermediate Phase and Improved Electrochemical Performance of Zn-Doped LiCoPO₄ for High-Energy Li-Ion Batteries

To improve the intrinsic electrochemical properties of LiCoPO4 (LCP), a promising high-energy cathode material, we explored the effects of Zn-doping on the material structure and electrochemical properties of LCP. During the delithiation/lithiation process, besides the reported intermediate phase Li2/3Co1–nZnnPO4, an unreported intermediate phase Li1/2Co1–nZnnPO4 was observed by electrochemical test and in situ X-ray diffraction. The reason for the appearance of the intermediate phase was revealed by Gibbs free energy diagram. Two conjectured configurations of Li1/2Co1–nZnnPO4 were proposed. The redox potential and the conductivity of Zn-doped LCP will increase with doping concentration, resulting in improved rate capability, cycle life, and energy efficiency.