Investigation of the structure-property relationship in binder free asymmetric supercapacitor device based on NiCo2O4.nH2O nanostructures

Hierarchical metal oxide nanostructures emerge as the promising candidate for energy storage application due to their huge surface area, porosity and interconnected electron transport pathways. In this article, we report for the first time the electrochemical properties of very uniform and efficient thorn apple fruit like nickel cobaltite nanostructures of different forms and investigated the structure-property relationship. NiCo2O4 is directly grown over the Ni-foam by a cheap, scalable and facile hydrothermal technique and characterized for structural, morphological and porous characteristics. Electrochemical properties are determined by conducting cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance analysis. The non-annealed NiCo2O4.nH2O possesses mesoporous nanostructure with pore size centering between 3 and 10 nm which being the optimum size enables the material to exhibit best electrochemical properties. Specific capacity reaches as high as 670C/g for NiCo2O4.nH2O at 0.5 A/g current density. Asymmetric supercapacitor device is fabricated by combining binder free cathode and activated carbon and investigated for device performance. Specific capacity, energy and power density as high as 129C/g, 55.9 Wh/kg and 751.4 W/kg are achieved at 0.5A/g current density with the fabricated device. The device exhibits 98% retention of specific capacity after 10,000 cycles demonstrating its potential for high energy durable supercapacitor application.