Cation/Anion Doping Strategy for Na₄MnV(PO₄)₃ with High Energy Density and Long Cycling Life through Construction by Aspergillus niger

Na 4 MnV(PO 4 ) 3 (NMVP) has gained attention for its high redox potential, good cycling stability, and competitive price but suffers from poor intrinsic electronic conductivity and Jahn–Teller effect from Mn 3+ . In this work, cation/anion doping strategy was used for Aspergillus niger- bioderived carbon-coated NMVP (NMVP/AN) to improve the structural stability and electrochemical performance, where Al 3+ doping inhibited the dissolution of Mn and enhanced the Mn 3+ /Mn 2+ redox pair activity; besides, F – doping not only weakens the Na 2 –O bond but also endows the hierarchical and porous structure of NMVP/AN, which led to a more rapid and fluid transfer of Na + . The elaborately designed Na 3.9 Mn 0.9 Al 0.1 V(PO 4 ) 3 /AN (NMAVP/AN) exhibits 105.9 mA h g –1 at 0.5 C, and the as-prepared Na 3.1 MnV(PO 3.7 F 0.3 ) 3 /AN (NMVPF/AN) delivers 104.1 mA h g –1 at 5 C. Further demonstration of the hard carbon//NMAVP/AN full cell manifests the good potential of Al 3+ -doped NMVP/AN for practical applications (100.6 mA h g –1 at 1 C). These findings open up the possibility of unlocking the high-performance Na superionic conductor (NASICON).