Na_3.8MnV_0.8Zr_0.2(PO₄)₃/C/rGO composite cathode for sodium-ion battery with enhanced cycling stability and rate capability

Na₄MnV(PO₄)₃ (NMVP) cathode materials have attracted significant attention as potential candidates for grid applications due to their distinctive structure and high theoretical capacity. However, their inadequate electronic conductivity compromises both cycling stability and rate capability, presenting a challenge for practical implementation. To address this issue, we employed a strategy involving Zr⁴⁺ doping and dual-carbon coating to enhance the electrochemical performance of NMVP. The resulting Na_3.8MnV_0.8Zr_0.2(PO₄)₃/C/rGO composite demonstrated markedly improved rate capability (71.9 mAh g⁻¹ at 60 °C) and sustained cyclic stability (84.8% retention at 2 C after 1000 cycles), as validated through comprehensive kinetics assessments. The enhanced performance can be attributed to the expanded Na-ion pathways facilitated by large size ion doping and the improved electronic conductivity enabled by the dual-layer coating.