Effect of Na-Mn Co-Doping on the Structure and Performance of LiFePO4 Cathode Materials
Li0.97Na0.03Fe7/8Mn1/8PO4 cathode materials were successfully prepared by carbothermal reduction method.The crystal structure,morphology,elemental distribution,and electrochemical performance of the material were studied by XRD,SEM,EDS,and electrochemical tests,with first-principle calculation being used to analyze the mechanism of the material's improved performance.The results show that on the one hand,Na-Mn doping leads to the lattice distortion in LiFePO4 and the expansion of lattice volume,expan-ding the lithium ion migration channels and providing more space for lithium ion insertion and extraction.On the other hand,the material exhibits excellent high-rate performance and cycle stability in electrochemi-cal performance.Na-Mn doping is advantageous in improving the lithium-ion diffusion coefficient and con-ductivity of the material,thereby improving its electrochemical performance.The first-principle calculation results show that Na-Mn co-doping induces lattice expansion of LiFePO4,increases lattice volume,narrows energy band gap,enhances electronic density of states near Fermi level,and improves the electronic conduc-tivity and lithium ion mobility of the material.
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