Synthesis, characterization and lithium-ion migration dynamics simulation of LiFe_(1-x)T_xPO_4 (T = Mn, Co, La and Ce) doping cathode material for lithium-ion batteries

摘要

LiFePO_4 was doped by metallic cation in Fe sites via ball milling by a solid-state reaction method synthesis, and with very low-level doping of these samples, such as Li_(0.95)T_(0.05)FePO_4 (where T = Mn~(2+), Co~(2+), La~(3+), Ce~(4+)). The effects of doping were studied by X-ray diffraction pattern, Raman shift, scanning electronic microscopy and energy-dispersive X-ray spectroscopy as sample characterizations. The results indicate that these dopants have no significant effect on the structure of the material, but considerably improve its electrochemical behavior. First-principles calculations were used to obtain the migration pathway of Li ions along the one-dimensional (010) direction in LiFePO_4, and molecular dynamics simulation was used to investigate the lithium-ion diffusion coefficients (D_(Li)) inside LiFePO_4, which were derived from the slope of the mean square displacement versus time plots. The evolution of the structure during the simulation was analyzed by the radial distribution function to obtain the data, and radial distribution functions and mean square displacements were used to confirm the formation of crystalline units and the evolution of structure.