High-Energy Asymmetric Supercapacitor Based on the Nickel Cobalt Oxide (NiCo2O4) Nanostructure Material and Activated Carbon Derived from Cocoa Pods

Nickel cobalt oxide (NiCo2O4) nanoagglomerates were effectively synthesized through a simplistic low-temperature co-precipitation technique. The obtained material was further calcined to enhance its morphological properties and reduce the size of its individual particle of agglomerates. The as-synthesized NiCo2O4 agglomerates were characterized through the employment of various techniques, which include scanning/transmission electron microscopies (SEM/TEM), X-ray diffraction, Raman spectroscopy and X-ray fluorescence spectroscopy (XRF), and thermogravimetric analysis (TGA). Electrochemical performances of the as-synthesized electrode materials evaluated in a three-electrode configuration could deliver an optimized specific capacity of 95.6 mA h g–1 at a 0.5 A g–1 specific current. A fabricated hybrid asymmetric supercapacitor (SC) composed of NiCo2O4 and the activated carbon obtained from cocoa pods (Cocoa AC-700) as the positive and negative electrodes (NiCo2O4//AC cocoa-700), respectively, delivered a specific capacity of around 168.7 mA h g–1 at 0.5 A g–1 and a corresponding specific energy and power of 47.7 W h kg–1 and 430.0 W kg–1, respectively. The SC exhibited a substantial cycling stability, resulting in a Coulombic efficiency of 97.2% with a related capacity retention of 96.6% recorded after a cycling test of over 11,000 cycles at 5 A g–1.