MOF-derived NiS2@carbon microspheres wrapped with carbon nanotubes for high cycle performance supercapacitors

Nickel sulfides are seemed as potential electrode materials of supercapacitors (SCs). Unfortunately, the unsatisfied structural stability of nickel sulfides lies in the way of their long-term working and applications. Herein, inspired by the biological structure of chestnuts, a ternary heterostructure composed of carbon nanotubes (CNTs) linked with NiS2@carbon microspheres (xNCC) was constructed by using Ni-MOF as precursor. Electrochemical evaluations showed that the as-obtained xNCC composites presented an optimal specific capacitance of 1572 F/g at 0.5 A/g. Additionally, the aqueous supercapacitor device exhibited a superior energy density of 21.6 Wh/kg, as well as a performance of 94.8% superior cycling stability after 10,000 cycles. It is supposed that the unique ternary heterostructure avoids/relieves the agglomeration of NiS2, weakens volume expansion and provides abundant as well as promote the stability of electrochemical active sites. More importantly, the 3D structural features of xNCC impart the electrodes with porous microstructures that are able to shorten the distance of iondiffusion, thus enhancing the cycling stability and electrochemical performance. The present strategy may enlighten the structural design of electrode materials that can be further applied in SCs and other energy storage devices.