Influence Mechanism of Precursor Crystallinity on ElectrochemicalPerformance of LiFePO4/C Cathode Material

Determining the impact of precursor properties is essential for the performance regulation of LiFePO4cathodematerial prepared by carbothermic reduction. In this study, FePO4with different crystallinities, as precursors, was obtained at variousprecalcinating temperatures and reduced to form LiFePO4/C to quantitatively investigate crystallinity'sinfluence. Thecharacterization and molecular dynamics (MD) simulation results showed that the crystallinity of FePO4increased markedlywith a higher dehydration temperature, while excessive sintering would occur at 700 degrees C, resulting in a severe particle aggregation.The electrochemical analysis manifested that FePO4crystallinity would not affect the cyclic stability of cathode materials, but amoderate dehydration temperature of the precursor could equip LiFePO4/C with the best performance via an excellent balancebetween crystallinity and charge transfer. The excessive sintering and low crystallinity both brought about obvious reduction to thedischarge capacity of LiFePO4/C such that the discharge capacity at a 0.1 C rate would decrease from the optimum of 151.8 mAhmiddotg-1to less than 121.0 mAhmiddotg-1and 141.0 mAhmiddotg-1for the precursors calcinated at 500 and 700 degrees C, respectively. Our work providesa clear understanding of the non-negligible role of FePO4crystallinity and a valid direction for the control of the electrochemicalperformances of LiFePO4.