Full synergistic effect of hydrothermal NiCo₂O₄ nanosheets/CuCo₂O₄ nanocones supported on Ni foam for high-performance asymmetric supercapacitors

Highlights: • The CuCo₂O₄ can improve the electrical conductivity of the NiCo₂O₄ nanosheets. • The structure increase the specific surface area and active sites to boost the electrochemical activity of the material. • An asymmetric supercapacitor was assembled, and the energy density can reach up to 15 W h kg^-1. - Abstract: In this work, a series of NiCo₂O₄/CuCo₂O₄ composites were prepared by a two-step hydrothermal method. The optimized NiCo₂O₄/CuCo₂O₄ electrode shows more than 5 times area capacitance (4.97 F cm⁻²) than pure NiCo₂O₄ at the current density of 1 mA cm⁻². The best performance of sample assembled an asymmetric supercapacitor could reach up to 42 F g⁻¹ at the current density of 1 A g⁻¹. In addition, the maximum energy density of 15 W h kg⁻¹ was achieved with the power density of 814 W kg⁻¹. The as-prepared active electrode material also reveals excellent cycling stability with 90.6% capacitance retention after 5000 cycles. These results indicate potential application in developing energy storage devices with high energy density power density.