Influence Mechanism of Mg²⁺Doping on Electrochemical Properties of LiFePO₄Cathode Materials

For this work, a Mg²⁺-doped LiFePO₄(LFP) cathode material was prepared using a solid-state method with Mg(CH₃COO)₂as the Mg²⁺dopant. X-ray diffraction and refinement data suggested that an appropriate doping amount of Mg²⁺can reduce the cell volume of LFP, shorten the Fe-O and P-O bonds, and elongate the Li-O bond, thereby facilitating the diffusion of Li⁺. X-ray photoelectron spectroscopy test results revealed that Mg²⁺doping prevents the formation of Li-Fe antisite defects while also promoting the formation of Fe₂P, thereby improving the electronic conductivity of the LFP. The electronic conductivity was measured using a four-probe teste, and the Li⁺diffusion rate was fitted and calculated according to the electrochemical impedance spectroscopy test results. The results found that electron conductivity expanded by 275 times and the Li⁺diffusion coefficient increased by 3.6 times following LFP being doped with Mg²⁺. Charge/discharge curves and cyclic voltammetry test reveal that LFP with Mg²⁺doping has superior reversibility, rate performance, and cycle stability, and the capacity can be maintained at 162 mA h g^-1following 300 cycles at 0.1 C.