Abstract:

Fe₂P is a common by-product during the generation of lithium iron phosphate（LiFePO₄，LFP），and its effect on the electrochemical performance of LFP has not been thoroughly studied so far.The effect of adding different proportions of Fe₂P into LFP by ball milling method on the electrochemical performance of LFP cathode materials was explored.The results showed that after doping Fe₂P，the crystal structure of LFP material remained unchanged，the particle morphology was highly organized，and the distribution of major elements was uniform.Additionally，the ion and electron conductivity of LFP material were improved to varying degrees.Especially，when the Fe₂P doping amount was 0.5%（mass fraction），the first discharge specific capacity reached 158.2 mA·h/g and 148.5 mA·h/g at 0.1C and 0.5C magnification，which were 8.90% and 7.2% higher than pure LFP，respectively.The difference in redox peak potential in CV curve（ΔE） was only 0.264 V，indicating that the introduction of Fe₂P was beneficial for improving the polarization of LFP materials，and the high overlap of the first three CV curves indicated that the material had a high degree of reversibility.The charge transfer resistance（R_ct） was only 41.56 Ω，which was 76.49% lower than pure LFP.The diffusion coefficient of lithium ions was 8.20×10^-9 cm²/s，which was 89.4% higher than pure LFP.At the same time，the improvement on rate capability and cycling performance was significant.

Key words: LiFePO₄, Fe₂P, EIS, Li diffusion coefficient, electrochemical performance