Nanoflower-like NiCo₂O₄ grown on biomass carbon coated nickel foam for asymmetric supercapacitor

Nanoflower-like NiCo₂O₄ is grown directly on a three-dimensional gelatin-based carbon–nickel foam (GCNF), which is prepared by a facile hydrothermal strategy with annealing treatment. The as-synthesized binder-free NiCo₂O₄/GCNF composites are used for high-performance supercapacitors. The binder-free design can avoid the “dead surface” caused by binders and additives in traditional electrodes, thus achieving more efficient charge and mass exchange, leading to improved conductivity of electrodes. Furthermore, the proposed design provides a wider interface area and abundant active sites, which significantly improve the electrochemical capacitance performance. The electrode has a high specific capacitance of 1416 F g⁻¹ at a current density of 1 A g⁻¹, and excellent cycling performance. An asymmetric supercapacitor (ASC) was assembled with the structure NiCo₂O₄/GCNF//activated carbon and a maximum voltage of 1.5 V delivers a high energy density of 48.6 W h kg⁻¹ at a power density of 749.3 W kg⁻¹. Moreover, the ASC shows good cycling performance with 88.5% capacitance retention after 10,000 cycles at a high rate of 5 A g⁻¹.