A NASICON‐typed Na4Mn0.5Fe0.5Al(PO4)3 cathode for low‐cost and high‐energy sodium‐ion batteries

Abstract Developing low‐cost and high‐voltage manganese (Mn)‐based Na superionic conductor (NASICON) cathode materials have attracted extensive interest. The low capacity and cycling instability of Na4MnAl(PO4)3 (NMAP), however, limits its performance in sodium‐ion batteries (SIBs). Herein, a binary Na4Mn0.5Fe0.5Al(PO4)3 (MNFAP) is fabricated to ease the structural instability and, in turn, deliver an improved reversible capacity of 102 mAh g−1 at 0.1 C and a high energy density of 287.7 Wh kg−1. The synergistic interaction of Fe and Mn in Na4Mn0.5Fe0.5Al(PO4)3/C composite leads to a one‐phase solid‐solution reaction mechanism with high structural reversibility. Theoretical calculations have also been performed to explain the upshifted voltage platform of both Fe2+/Fe3+ and Mn3+/Mn4+ redox potentials. The rational design of NASICON‐type cathodes by regulating their composition with dual metal ions provides new perspectives for developing high‐performance SIBs.