Electric field-induced ball-cactus-like CuCo2Sx(OH)y nano-heterostructure towards high-performance supercapacitors

Abstract

Developing advanced negative electrode materials with high capacity for supercapacitors currently remains a challenge. To address this issue, an effective strategy through a simple electric field-induced anion exchange process was raised to prepare a novel nanostructured CuCo₂S_x(OH)_y heterostructure based on CuCo₂S₄ nanosheets as the substrate. Notably, the unique nano-heterostructure featured an extremely high area specific capacitance of 2.94 F cm⁻² at 5 mA cm⁻² and exhibited excellent cycle life and rate capacity. Moreover, the corresponding assembled supercapacitors using the obtained CuCo₂S_x(OH)_y heterostructure as the negative electrode exhibited superior capacitive performance. More specifically, the assembled hybrid supercapacitor possessed a high energy density of 0.54 mW h cm⁻² at a power density of 4.01 mW cm⁻² and the capacitance retention rate was 94.7% even after 10 000 cycles, which confirmed the practicality of the synthesized negative electrode material. Density functional theory calculations further showed that an enhanced conductivity and increased OH⁻ adsorption capability could be achieved in the CuCo₂S_x(OH)_y nano-heterostructure. This work presents a feasible and effective in situ anion exchange strategy to construct the CuCo₂S_x(OH)_y nano-heterostructure as a negative electrode material toward high-performance supercapacitors, improving the current deficiency of negative electrode materials.