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

Abstract

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.