Rational construction of reduced NiCo2S4@CuCo2S4 composites with sulfur vacancies as high-performance supercapacitor electrode for enhancing electrochemical energy storage

Rational design of NiCo2S4-based nanostructures supercapacitor electrodes was considered as an important route for increasing specific capacitance in the field of electrochemical energy storage. Here we reported that a novel reduced NiCo2S4@CuCo2S4 (R–NiCo2S4@CuCo2S4) core-shell heterostructure with sulfur vacancies improved electrochemical performance of supercapacitor electrode material. These composites were designed and synthesized by a combination of solvothermal, electrochemical deposition and reduction of sodium borohydride (NaBH4). Among them, NiCo2S4 nanosheets were grown on nickel foam as a core and act scaffold for the reaction by a solvothermal method, while CuCo2S4 as a shell to aggrandizement specific surface area of reaction by electrochemical deposition method and to further raise active sites and conductivity of reaction, sulfur vacancies were further constructed in NiCo2S4@CuCo2S4. The construction of sulfur vacancies shortens the reaction distance and accelerated electrons and ions transmission. Therefore, R–NiCo2S4@CuCo2S4 exhibited an excellent capacity (2922.9 F g−1 at 0.5 A g−1), superior rate capability (68% retention from 0.5 A g−1 to 10 A g−1) and extraordinary cycling stability (99.92% capacitance after 10000 cycles at 30 A g−1). This strategy successfully fabricated the R–NiCo2S4@CuCo2S4 core-shell heterostructure with excellent electrochemical performance, making it a potential candidate as supercapacitor electrode materials for enhanced electrochemical energy storage.