Flower-shaped NiMnO3@NiCo2S4 heterojunction nanosheets for a high-performance asymmetric supercapacitor

Abstract

The rational design of heterostructured electrode materials provides a promising strategy for enhancing the electrochemical performance of supercapacitors. In this study, flower-shaped NiMnO₃@NiCo₂S₄ heterojunction nanosheets with superior electrochemical properties were synthesized on nickel foam (NF) via a combined hydrothermal and thermal treatment approach. This structure enhances ion diffusion and increases the active area, thereby boosting electrochemical performance. The NiMnO₃@NiCo₂S₄ composite electrode shows a remarkable specific capacitance of 2296.55 F g⁻¹ (1263.1 C g⁻¹) at a current density of 1 A g⁻¹ under standard three-electrode conditions, with a capacitance retention of 90.12% and a coulombic efficiency of 95.04% after 15 000 cycles. When assembled as a supercapacitor with NiMnO₃@NiCo₂S₄ as the positive electrode and activated carbon as the negative electrode, the device achieves a specific capacitance of 172.47 F g⁻¹ at 1 A g⁻¹. It retains 92.86% capacity and 97.67% coulombic efficiency after 20 000 cycles at 20 A g⁻¹, with an energy density of 69.24 W h kg⁻¹ at 850.10 W kg⁻¹ power density. These results highlight the great potential of the NiMnO₃@NiCo₂S₄ composite electrode as an energy storage material.