NiCo₂S₄ nanosheet-decorated 3D, porous Ni film@Ni wire electrode materials for all solid-state asymmetric supercapacitor applications

Wire type supercapacitors with high energy and power densities have generated considerable interest in wearable applications. Herein, we report a novel NiCo₂S₄-decorated 3D, porous Ni film@Ni wire electrode for high performance supercapacitor application. In this work, a facile method is introduced to fabricate a 3D, porous Ni film deposited on a Ni wire as a flexible electrode, followed by decoration with NiCo₂S₄ as an electroactive material. The fabricated NiCo₂S₄-decorated 3D, porous Ni film@Ni wire electrode displays a superior performance with an areal and volumetric capacitance of 1.228 F cm^-2 and 199.74 F cm^-3, respectively, at a current density of 0.2 mA cm^-1 with a maximum volumetric energy and power density (E_V: 6.935 mW h cm^-3; P_V: 1.019 W cm^-3). Finally, the solid state asymmetric wire type supercapacitor is fabricated using the fabricated NiCo₂S₄-decorated 3D, porous Ni film@Ni wire as a positive electrode and N-doped reduced graphene oxide (N-rGO) as a negative electrode and this exhibits good areal and volumetric capacitances of C_A: 0.12 F cm^-2 and C_V: 19.57 F cm^-2 with a higher rate capability (92%). This asymmetric wire type supercapacitor demonstrates a low leakage current and self-discharge with a maximum volumetric energy (E_V: 5.33 mW h cm^-3) and power (P_V: 855.69 mW cm^-3) density.