Temperature-dependent flexible hybrid capacitors based on Ni(OH)₂@NiS electrode materials

The morphology of the electrode materials seriously affect their structure and performances. The application of two-dimensional Ni(OH)₂ nanomaterials in supercapacitors is hindered by their low conductivity and limited active sites. Herein, we synthesized Ni(OH)₂@NiS composites via a two-step hydrothermal route. It increased the specific surface area and improved ion-transport rate of the composites. The Ni(OH)₂@NiS-2 sample delivered a specific capacitance of 1778 F g^-1 at 1 A g^-1 and good cycle stability (88% capacity retention at 2 A g^-1 after 10 000 cycles). Furthermore, an asymmetric supercapacitor (ASC) fabricated using the Ni(OH)₂@NiS-2 composite electrode achieved an energy density of 110.25 Wh kg^-1 at 2700 W kg^-1. Moreover, the device demonstrated stable cycling capability at extreme temperatures (-10 °C and -20 °C).