High-rate performance and long-cycle stability of Sn-doped Na0.44MnO2 cathode material

Abstract

Sodium-ion batteries, as one of the best alternatives to lithium-ion batteries, have a broad application prospect. Manganese-based oxide anode Na_0.44MnO₂ has attracted much attention due to its simple, environmentally friendly, and cost-effective synthesis method. However, continuous phase transition and kinetic retardation hinder its practical application. In this study, we synthesized trace Sn-doped Na_0.44MnO₂ using a solid-state method and obtained a cathode material Na_0.44Mn_0.99Sn_0.01O₂ (NMSO-1) with a more stable crystal lattice structure and faster sodium ion transport rate. The capacity retention of NMSO-1 cathode was 94.6 % after 200 cycles at 1C rate, and 91.6 % after 1000 cycles at 5C rate. The material analysis shows that the introduction of a small amount of Sn can increase the lattice spacing of the material and reduce its morphological particle size, which is conducive to the enhancement of the stability of the material structure and the shortening of the ion transport path, and the positive effect of Sn is quantitatively analyzed with the help of experiments and fitting calculations. This study provides a new scheme for the doping design of cathode materials with tunneling structure, which effectively improves the multiplication capacity and cycling performance of cathode material NMO.