3D hierarchical NiCo2O4@WO3/Cu2S heterostructures and biomass-derived carbon electrodes for high-performance all-solid-state supercapacitors

The rationally designed three-dimensional (3D) hierarchical porous heterostructured nanomaterials possess enhanced electrical conductivity to improve the electrochemical performance of binary oxides with related hybrid materials by synergistic interactions between the components. This study is the first time reporting the synthesis of 3D NiCo2O4@WO3/Cu2S (NCO@W/CS) hierarchical microflower heterostructures by a simple hydrothermal method for energy storage applications. The hybrid electrode material exhibits a high specific capacitance of 1932 F/g with a high rate capability of 84 % and capacity retention of 96.7 % where hierarchical 3D microflowers embedded nanoparticles and nanoflakes heterojunction formation facilitates more active site, multiple redox reactions for fast transport of ions and electrons from its porous structure, resulting in enhanced energy storage capability. Further, the all-solid-state supercapacitor (ASSC) device demonstrates a high energy density of 79.9 Wh/kg under the power density of 8000 W/kg, where 3D NCO@W/CS (positive electrode) and Delonix regia flowers (DRF)-derived porous carbon (negative electrode) with Polyvinyl Alcohol/Polyvinylpyrrolidone/SiO2 (PVA/PVP/SiO2) polymer membrane (separator) are highly utilized to obtain high specific capacitance with remarkable capacitance retention of 94 %, indicating its high structural stability. The illumination of light-emitting diodes (LEDs) and the rotation of a small fan promote this ASSC device for next- generation energy storage devices in real-time use.