Optimizing Electrochemical Performance of LiFePO ₄ through Synergistic Modulation of Sintering Temperature and Li/Fe Ratio under Constant Grain Size

LiFePO4 has been extensively employed as a cathode material for lithium-ion batteries due to its excellent thermal stability, safety, and long cycle life. However, its practical applications are still hindered by intrinsically low electronic conductivity and sluggish lithium-ion diffusion kinetics. Additionally, the precursor stoichiometry and thermal treatment conditions significantly influence the crystal structure and electrochemical performance. In this study, LiFePO4 was systematically investigated by varying the Li/Fe molar ratios (1.03, 1.05, and 1.07) and sintering temperatures (730 °C, 750 °C, and 770 °C) to evaluate their effects on structural evolution, impurity phase formation, electrochemical properties, and Li+ transport behavior. The results demonstrate that a moderate lithium excess (Li/Fe = 1.03) combined with a lower sintering temperature (730 °C) effectively suppresses the formation of inert impurities such as Li3PO4, maintains high crystallinity, and optimizes the unit cell structure, thereby facilitating smoother Li+ migration pathways. Under these optimized conditions, the material exhibits the highest discharge capacity (162.62 mAh g–1), minimal polarization, and superior rate performance. Electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration techniques (GITT) further confirm that the sample achieves the highest lithium-ion diffusion coefficient, reaching 1.27 × 10–12 cm2 s–1. This study clearly demonstrates that tailoring the precursor stoichiometry and sintering parameters can synergistically enhance the structural stability, electrical conductivity, and Li+ transport kinetics of LiFePO4, providing theoretical insights and practical guidance for the scalable production of high-performance LiFePO4-based cathode materials