Design and synthesis of 3D hierarchical NiCo2S4@MnO2 core–shell nanosheet arrays for high-performance pseudocapacitors

Abstract

We report on the development of 3D hierarchical NiCo₂S₄@MnO₂ core–shell nanosheet arrays on Ni foam for supercapacitors. In our design, the highly conductive NiCo₂S₄ nanosheets can serve not only as a good pseudocapacitive material, which can be contributed to the capacitance of the whole electrode, but also as a 3D conductive scaffold for loading MnO₂ materials, which can overcome the limited conductivity of MnO₂ itself. Furthermore, the 3D NiCo₂S₄@MnO₂ hybrid electrode can provide efficient and rapid pathways for ion and electron transport. These merits together with the elegant synergy between NiCo₂S₄ and MnO₂ lead to a high areal capacitance of 2.6 F cm⁻² at 3 mA cm⁻² and good cyclic stability.