Cation/Anion Doping\nStrategy for Na<sub>4</sub>MnV(PO<sub>4</sub>)<sub>3</sub> with High\nEnergy Density and Long Cycling Life\nthrough Construction by Aspergillus niger

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