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

LiFePO 4 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, LiFePO 4 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 Li 3 PO 4, 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 cm 2 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 LiFePO 4, providing theoretical insights and practical guidance for the scalable production of high-performance LiFePO 4 -based cathode materials