A Mn-Rich LiMn0.7Fe0.3PO4 Nanoflower Cathode Solvothermally Synthesized with pH Control for Promoted Lithium-Ion Storage Performance

The escalating demand for lithium-ion batteries emphasizes the urgency of developing cobalt- and nickel-free cathodes ascribed to the high cost of these two metals. LiMnxFe1–xPO4 (LMFP) emerges as a promising candidate due to high operating voltage compared to LiFePO4 while suffering from inferior kinetics and cycling instability. This study demonstrates that precise pH control during the solvothermal process is pivotal for optimizing the LMFP/C microstructure and performance; furthermore, the mechanism of morphology evolution along with pH value and reaction duration is summarized. LiMn0.7Fe0.3PO4/C composites synthesized under varied pH conditions were thoroughly characterized and electrochemically evaluated. Results reveal that a moderately acidic environment (pH 4) facilitates the formation of a unique nanoflower architecture composed of (010)-oriented nanosheets with a highly graphitized carbon coating and minimal antisite defects after calcination. This optimal structure endows LiMn0.7Fe0.3PO4/C composite sample LMP/C-P4-24 with superior Li+ diffusion kinetics and charge-transfer efficiency, enabling a high discharge capacity (151.5 mAh g–1 at 1 C), outstanding cycling stability (96.1% retention after 500 cycles), and excellent rate capability (110.3 mAh g–1 at 10 C). In contrast, synthesis at higher pH induces structural disorder and inferior carbon quality with rapid performance degradation. This work establishes pH-mediated structural control as a powerful strategy for high-performance, resource-conscious, Mn-rich LiMn0.7Fe0.3PO4 cathode materials.