Synergistic V/F Co-doping and Mn2+-Trapping separator for long-life LiMn0.8Fe0.2PO4 cathodes

High-manganese-to-iron-ratio lithium manganese iron phosphate (LMFP) is a promising candidate for next-generation electric vehicle cathodes due to its high energy density, low cost, and safety. However, its poor cycling reversibility, especially at elevated temperatures, has limited its practical application, which is mainly due to the Jahn-Teller effect and Mn-ion dissolution. Ion doping is a commonly used modification method. Herein, in this work, a novel V/F co-doping and Mn 2+ capture membrane coated with CNT-doped hydroxyapatite (HAP-C) were employed to modify LMFP. The V/F co-doped LMFP showed enhanced structure stability during cycling tests compared to LMFP, and the capacity retention rate increased to 89.5 % after 300 cycles at 1C/1C. Meanwhile, the Mn 2+ -capturing separator further protected the anode stability by preventing the deposition of dissolved manganese ions. Due to these combined properties, the doped cathode battery using the HAP-C modified separator exhibited less manganese deposition on the anode. After 300 cycles at 1C/1C, 25 °C, the capacity retention rate further improved to 96.7 %, and after 300 cycles at 0.5C/0.5C, 45 °C, the capacity retention rate increased to 84.0 %, demonstrating outstanding cycling stability. This comprehensive strategy provides a basis for developing high-energy-density and long-cycle-life lithium-ion battery.