Direct growth of highly organized, 2D ultra-thin nano-accordion Ni-MOF@NiS₂@C core-shell for high performance energy storage device

Metal-organic framework (MOF) as an active material is a state-of-the-art challenge to improve performance of energy storage devices due to its high porosity, ion diffusion channel and provision of redox sites. Nevertheless, the development of next-generation devices requires overcoming shortcomings such as low electrical conductivity and low MOF stability. Herein, the in situ growth of a nickel-based MOF on a Ni foam and the formation of a Ni-MOF@NiS₂@C (NMSC) core-shell hetero-nanostructure is reported to overcome the challenge of using MOFs as active materials. Additionally, a surfactant-assisted approach is demonstrated to construct an ultra-thin 2D nano-accordion structure with interstitial gaps between the nanosheets. The unique nano-accordion structure facilitates faster ion diffusion and decreases the total resistance owing to the excellent charge transfer ability. In particular, the solid-state flexible supercapacitor exhibited a high performance with a specific capacitance of 283.5 F g⁻¹ with an excellent energy density of 77.2 W h kg⁻¹ at a power density of 7000 W kg⁻¹.