Influence Mechanism of Precursor Crystallinity on Electrochemical Performance of LiFePO4/C Cathode Material

Determining the impact of precursor properties is essential for the performance regulation of LiFePO4 cathode material prepared by carbothermic reduction. In this study, FePO4 with different crystallinities, as precursors, was obtained at various precalcinating temperatures and reduced to form LiFePO4/C to quantitatively investigate crystallinity's influence. The characterization and molecular dynamics (MD) simulation results showed that the crystallinity of FePO4 increased markedly with a higher dehydration temperature, while excessive sintering would occur at 700 °C, resulting in a severe particle aggregation. The electrochemical analysis manifested that FePO4 crystallinity would not affect the cyclic stability of cathode materials, but a moderate dehydration temperature of the precursor could equip LiFePO4/C with the best performance via an excellent balance between crystallinity and charge transfer. The excessive sintering and low crystallinity both brought about obvious reduction to the discharge capacity of LiFePO4/C such that the discharge capacity at a 0.1 C rate would decrease from the optimum of 151.8 mAh·g–1 to less than 121.0 mAh·g–1 and 141.0 mAh·g–1 for the precursors calcinated at 500 and 700 °C, respectively. Our work provides a clear understanding of the non-negligible role of FePO4 crystallinity and a valid direction for the control of the electrochemical performances of LiFePO4.