Synthesis of Porous Yolk-Shelled NiSe₂–MnSe Heterojunctions for High-Cycling-Stability Asymmetric Supercapacitor Electrode Materials

Transition-metal selenide materials have the potential to be excellent power storage materials owing to their unique physical and structural features. The porous yolk-shelled NiMnSe3 nanospheres synthesized by a two-step hydrothermal and thermal treatment process were used as anode electrode materials for an asymmetric supercapacitor (ASC). The unique yolk-shelled structure and the bimetallic synergistic effect contributed to the improved charge transfer capability of the ASC. With density functional theory calculations, the NiSe2–MnSe heterojunctions illustrate the synergy between NiSe2 and MnSe components along with the charge transfer path at the heterogeneous interface. The NiMnSe3 electrode material has excellent electrochemical properties in the three-electrode system (1093 F g–1 at 0.5 A g–1). The ASC using the NiMnSe3 anode with an activated carbon cathode exhibited a maximum energy density of 74.5 Wh kg–1 and a maximum power density of 8259.3 W kg–1, retaining 99.5% of the initial capacitance after 12,000 cycles. This shows that metal selenide heterojunctions have promising potential for supercapacitor as ASCs.