Doping and defect engineering synergistically enhance sodium ion storage in surface-amorphized MnO2

In this study, we successfully fabricated cobalt-doped manganese dioxide nanorods with surface defects and an amorphous/crystalline interface. This was achieved through a straightforward hydrothermal process, followed by a treatment with sodium borohydride to further modify the material properties. These structural and compositional attributes significantly enhance ion adsorption and charge storage capabilities. Our material exhibits exceptional electrochemical performance, achieving a specific capacitance of 345 F g⁻¹, nearly double that of pristine MnO₂ (190 F g⁻¹). When integrated into an asymmetric supercapacitor, it delivers a high energy density of 45.5 Wh kg⁻¹ and maintains 89.4 % of its initial capacity after 10,000 cycles. This work provides valuable insights into defect engineering and doping strategies for advanced supercapacitor electrode materials, offering a promising avenue for high-performance energy storage devices.