Hydrothermal synthesis of LiMn0.79Fe0.2Mg0.01PO4/C composite cathode materials using different Li3PO4 precursors

Doping and particle size controlling are two important approaches to improve the electrochemical performance of LiMnxFe1−xPO4 cathode materials. By employing a straightforward hydrothermal method and utilizing cost-effective lithium phosphate (Li3PO4) as the precursor, we successfully synthesized high Mn-content LiMn0.79Fe0.2Mg0.01PO4/C composites. The results reveal that the minute amount of Mg substantially enhances the electrochemical performance. In the subsequent mechanism study using Li3PO4 precursors with different particle size, we found that the nucleation process, dependent on specific surface area and diffusion rate, is likely to play a critical role for the size and morphology of formed LiMn0.79Fe0.2Mg0.01PO4. LiMn0.79Fe0.2Mg0.01PO4/C (LMFP-1), synthesized from initially smaller-sized and less agglomerated Li3PO4 (LPO-1), exhibited the most diminutive average particle size coupled with the highest specific surface area, which further facilitated electrolyte interfacial interaction and promoted Li+ diffusion kinetics. At 1C, LMFP-1 displayed a specific capacity of 110.7 mAh g−1, with 97.07% capacity retention after 200 cycles. This study provides pivotal insights for the synthesis of high-performance LiMnxFe1−xPO4 materials.