A Mn-Rich LiMn_0.7Fe_0.3PO₄ Nanoflower Cathode Solvothermally Synthesized with pH Control for Promoted Lithium-Ion...

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. LiMn_xFe_1-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. LiMn_0.7Fe_0.3PO₄/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 LiMn_0.7Fe_0.3PO₄/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 LiMn_0.7Fe_0.3PO₄ cathode materials.