Serpent-cactus-like Co-doped Ni(OH)2/Ni3S2 hierarchical structure composed of ultrathin nanosheets for use in efficient asymmetric supercapacitors

Herein, a rational Co-doped Ni(OH)2/Ni3S2 hybrid was designed and grown in situ on Ni foam (NiCo-10) via a one-pot hydrothermal reaction with two-step temperature control, avoiding the utilization of complicated production processes or high-end technology. Interestingly, the as-prepared NiCo-10 presents a distinct one-dimensional serpent-cactus-like structure consisting of ultrathin internal nanosheets. As a supercapacitor electrode, the hinder-free NiCo-10 exhibits an ultrahigh specific capacitance value of 3023.4 F g−1 at 1 A g−1 and excellent rate performance (capacitance retention of 82.9% up to 20 A g−1), owing to the distinct and available ultrathin serpent-cactus-like structure. Meanwhile, an asymmetric supercapacitor is developed, wherein NiCo-10 is utilized as a positive electrode and activated carbon as a negative electrode. The asymmetric device could exhibit a high specific capacitance value of 136.2 F g−1 (at 1 A g−1), high energy densities of 51.5 W h kg−1 (at 0.825 kW kg−1) and 23.0 W h kg−1 (even at 8.25 kW kg−1), and appropriate cycling stability. The efficient electrochemical performance of NiCo-10 makes it a promising electrode material for the energy storage field.