Ultra high-rate performance LiFePO4 cathode material for next generation fast charging Li-ion batteries

Abstract

High-power cathode materials are essential for designing high-rate Li-ion batteries (LIBs), as the demand for fast charging and accelerated operation drive their growing use in applications such as electric vehicles, drones, and industrial power tools. This work investigates a high rate performing LiFePO₄ (LFP) cathode material developed through a synergistic approach combining magnesium (Mg²⁺) ion doping, carbon coating, and the formation of micron-sized particles. Structural and morphological analyses confirm the formation of phase-pure Mg²⁺ doped LFP with particle size of 0.2 μm. Rietveld analysis reveals shortened P-O, Fe-O bonds, along with widened Li-O bonds upon Mg²⁺ doping in LiFePO₄. The extended Li-O bonds are expected to significantly enhance the Li-ion kinetics even at higher current rates. These findings are further supported by density functional theory (DFT) calculations, which confirm the reduced diffusion barrier with Mg²⁺ doping. Electrochemical studies show that Mg²⁺ doped LiFePO₄ delivers high-rate capability of 105 mAh/g at 20C, compared to 75 mAh/g for pristine LiFePO₄, along with more than 85 % capacity retention after 800 cycles at the same rate. The enhanced high-rate performance is attributed to smaller particle size, uniform carbon coating, and widened Li-ion diffusion channels induced by Mg²⁺ doping in the LiFePO₄ crystal structure.