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.