Construction of core-shell structured CuS@CoS2 via ion exchange method for flexible all-solid-state asymmetric supercapacitors

Abstract

With the rapid advancement of energy storage technologies, there is growing demand for high-performance flexible supercapacitors. However, the practical application of metal sulfide electrodes remains hindered by structural instability, sluggish ion/electron transport, and complicated synthesis processes. In this study, an innovative core-shell structured CuS@CoS₂ material is fabricated through an optimized ion-exchange method. The unique architecture and large specific surface area provide abundant active sites and facilitate rapid electrolyte ion diffusion while effectively accommodating volume variations during charge-discharge cycles. Electrochemical characterization demonstrates exceptional performance, including a remarkable specific capacitance of 937.2 F g⁻¹ and 72.4 % capacitance retention after 10,000 cycles at 5 A g⁻¹. The assembled flexible all-solid-state asymmetric supercapacitor with activated carbon (AC//CuS@CoS₂) achieves outstanding energy/power densities (88.9 Wh kg⁻¹, 32,000 W kg⁻¹) and maintains 73.31 % capacitance after 10,000 cycles at 6 A g⁻¹. These superior properties underscore the great promise of core-shell CuS@CoS₂ composites for next-generation flexible energy storage devices.