In situ doping of lithium iron phosphate with excellent water-soluble zinc salt was used to improve its magnification performance

Abstract

It has always been an important research direction for improving the intrinsic conductivity of Lithium iron phosphate materials. Doping can not only improve the intrinsic conductivity but also induce lattice distortion to increase the diffusion rate of lithium ions to improve the electrochemical performance. Zn-doped LiFe1-xZnxPO4 (x = 0, 0.025, 0.05, 0.075) is prepared from LiOH·H2O, FeSO4·7H2O, H3PO4, ZnSO4·7H2O. The composition, structure, morphology and electrochemical performance of the material are characterized in detail by XRD, SEM, EDS, cyclic voltammetry test, AC impedance test and other methods. The results show that the nano-spherical LiFe0.075Zn0.025PO4 exhibits excellent capacity performance and rate performance without intentionally coating C. The initial discharge specific capacity of the positive electrode material is 153.6 mAh·g−1 at 0.2C. The material also exhibits excellent cycle performance, with a discharge-specific capacity of 148.6mAh g−1 and a capacity retention rate of 96.7% after 100 cycles at a current density of 0.2C. Compared with the undoped samples, the doped ZnSO4 improves the actual capacitance of the samples. The high specific capacity retention rate at large rate charge-discharge indicates that zinc doping improves the structural stability of the samples. The crystal structure is not significantly damaged during the large current charge discharge process, and the magnification performance is improved.