Nickel Foam-Supported NiCo₂O₄ Urchin-Shaped Microparticles Sheathed with NiCoO₂ Nanosheets as Electrolyte-Wettable Electrodes for Supercapacitors

Self-supported NiCo2O4–NiCoO2 sheathed architectures on nickel foam (NCO-nco/NF), obtained by a two-step hydrothermal, postcalcination treatment, are demonstrated to be an efficient battery-type electrode for supercapacitors. NiCoO2 nanosheets uniformly extend over the NiCo2O4 urchin resulting in a synergistic association wherein the intrinsic redox ability of the scaffold and the sheath’s superior hydroxyl adsorption capacity enabled enhanced electrochemical performance compared to a reverse architecture (nco-NCO/NF). Moreover, the NCO-nco/NF composite electrode with a favorable meso–macro porosity gave a high specific charge of 1373 C g–1 (1961 F g–1) with appreciable endurance in KOH electrolyte (5000 cycles). Additionally, an NCO-nco/NF and activated carbon hybrid supercapacitor assembly demonstrated a high energy density of 66.6 W h kg–1 at a power density of 400 W kg–1. The unique electrode design combining the individual attributes of the constituent units offers the possibility of developing high-performing electrode materials for supercapacitor applications.