Interface construction of CuCoSe@NiS based on an ultrathin nanosheet for high-performance supercapacitors

Abstract

Transition metal selenides and sulfides have attracted much attention as supercapacitor electrode materials, and reasonable construction and modification strategies can effectively improve their actual energy storage capacity. Herein, a CuCoSe@NiS/NF electrode material was optimized from the two dimensions of the material structure and microstructure using a self-supported bimetallic CuCo-MOF template and surface modification. The in situ growth not only secures the structural integrity of the electrode material but also eliminates the unwanted internal resistance, thereby enhancing the material's conductivity. The distribution of different spaces of the nanosheets greatly increased the specific surface area of the material, which endowed it with sufficient electrochemical active sites, thus obtaining the desired electrochemical performance. The strong electronic interactions between the CuCoSe nanosheets and NiS sheet layers significantly increased the charge transport rate. Consequently, the specific capacitance of the prepared CuCoSe@NiS/NF material reached a satisfactory specific capacitance of 2937.6 F g⁻¹ at 1 A g⁻¹. The assembled asymmetric supercapacitor (ASC) delivers a high energy density of 41.8 W h kg⁻¹ at 800 W kg⁻¹. This work provides insights for the rational construction of sulfur and selenium coexisting composite electrode materials and the optimisation of the electrode structures.