Hierarchical hybrid electrodes with NiCo2S4 nanosheets and Co4S3 nanocages for high energy density supercapacitors

Abstract

Transition metal sulfides are gaining attention as a new highly capacitive active material for high-performance supercapacitors, however, it is still a challenge that synthesizes a distinctive structure to enhance the electrochemical characteristics and practical applications. In this work, hierarchical structural hybrid metal sulfides (NiCo2S4/Co4S3) based on nanosheets and nanocages are synthesized by sulfurating the NiCo-LDH/ZIF-67 precursors. The NiCo2S4/Co4S3 electrode with remarkable layered and porous structure effectively increase the electrochemical active surface area and accelerate the charge transfer, achieving a high specific capacitance of 8.43 F cm−2 at a current density of 2 mA cm−2 and good cyclic stability. An assembled asymmetric supercapacitor with activated carbon delivers a high energy density of 0.50 mWh cm−2 at a power density of 1.69 mW cm−2. These results demonstrate that NiCo2S4/Co4S3 is an ideal electrode material for high-performance electrochemical energy storage devices.