A Promising Solid‐State Synthesis of LiMn1‐yFeyPO4 Cathode for Lithium‐ion Batteries

Abstract LiMn 1‐y Fe y PO 4 (LMFP) is a significant and cost‐effective cathode material for Li‐ion batteries, with a higher working voltage than LiFePO 4 (LFP) and improved safety features compared to layered oxide cathodes. However, its commercial application faces challenges due to a need for a synthesis process to overcome the low Li‐ion diffusion kinetics and complex phase transitions. Herein, a solid‐state synthesis process using LFP and nano LiMn 0.7 Fe 0.3 PO 4 (MF73) is proposed. The larger LFP acts as a structural framework fused with nano‐MF73, preserving the morphology and high performance of LFP. These results demonstrate that the solid‐state reaction occurs quickly, even at a low sintering temperature of 500 °C, and completes at 700 °C. However, contrary to the expectations, the larger LFP particles disappeared and fused into the nano‐MF73 particles, revealing that Fe ions diffuse more easily than Mn ions in the olivine framework. This discovery provides valuable insights into understanding ion diffusion in LMFP. Notably, the obtained LMFP can still deliver an initial capacity of 142.3 mAh g −1 , and the phase separation during the electrochemical process is significantly suppressed, resulting in good cycling stability (91.1% capacity retention after 300 cycles). These findings offer a promising approach for synthesizing LMFP with improved performance and stability.