Zr4+-doped sodium manganese oxide: enhanced electrochemical performance as a cathode in sodium ion batteries.

Abstract

Sodium manganese oxides are regarded as a valuable class of cathode materials for sodium-ion batteries. By varying the stoichiometry of Na, Mn and O, it is possible to obtain layered, tunnel and spinel type structures, which can withstand the electrochemically-triggered sodiation-desodiation process. In this work, we report the electrochemical performance of Na4Mn2O5, a sodium-rich manganese oxide, which has been previously reported to suffer from structural instability due to the Jahn-Teller distortion of the Mn3+ ion. It was observed that the Na4Mn2-xZrxO5 (x = 0.1) cathode delivered a discharge capacity of ∼203 mA h g-1 post 250 cycles with a capacity retention rate of ∼82.8% on doping with Zr4+ ions. The improvement in cycling ability and rate capability is attributed to the enhanced structural stability and improved electronic conduction brought about by the substitution of Mn3+ by Zr4+ in Na4Mn2O5. Density functional theory-based studies were conducted, which adequately support the obtained results.