The porous spherical Mn and Ti co-doped Li2FeSiO4/C cathodes material for lithium-ion batteries

Abstract

Li2Fe1-x-yMnxTiySiO4/C (x = 0.05~0.20, y = 0.02~0.08), a porous spherical cathode material for lithium-ion batteries, has been prepared by combining the sol-gel, spray drying, and microwave synthesis method, and co-doped Li2FeSiO4 with the Mn2+ and Ti4+on the iron site. The effects of Mn2+ and Ti4+ co-doping on the crystal structure, microstructure, and electrochemical performance Li2FeSiO4 were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical tests. The results showed that the modified sample (Li2Fe0.81Mn0.15Ti0.04SiO4/C), when x and y are 0.15 and 0.04, respectively, has the higher specific capacity and better cycle stability as well as lower impedance and better reversibility. Its electronic conductivity reached 6.85 × 10−4 S/cm, lithium-ion diffusion coefficient reached 1.65 × 10−13 cm2/s, and initial charge/discharge–specific capacity reaches 197.7/187.8 mAh/g and high capacity retention of 78% after 20 charge/discharge cycles at 2 C. According to the study, the Li2FeSiO4/C cathodes material of Mn and Ti co-substitution at the Fe site could partly make up the disadvantage of single Mn doping, and might provide an effective guide for the dopant incorporation to Li2FeSiO4 systems.