K + -stabilized nanostructured amorphous manganese dioxide: excellent electrochemical properties as cathode material for sodium-ion batteries

Various transition metal oxide materials like MnO2 have been reported as cathode for sodium-ion batteries. However, the large sodium-ion radius and migration barrier cause its poor structural stability and low electrochemical performance. Herein, we present a simple pre-potassiation way to stabilize the nanostructure of amorphous manganese dioxide (a-MnO2). The pre-potassiation amorphous manganese dioxide (K-a-MnO2) heating treatment at 400 °C manifests outstanding electrochemical properties in the aspect of specific capacity and cyclic stabilization, the reversible specific capacity maintains at 180.8 mAh g−1 after 200th cycles under a current density of 0.1 C, and it shows a rate capability of 178.2 mAh g−1, 157.5 mAh g−1, 120.8 mAh g−1, 95.5 mAh g−1, 71.4 mAh g−1, and 47.1 mAh g−1 at 0.1 C, 0.2 C, 0.5 C, 1 C, 2 C and 5 C, respectively. The findings exhibit that the pre-potassiation way can stabilize the structural of a-MnO2 and effectively improve its electrochemical performance.