High energy density pouch-type supercapacitor achieved by MOFs derived 3D hollow N-doped carbon with Fe2O3 and hierarchical CuCo2S4@NiFe-LDH core-shell nanostructures

The multicomponent rational control and distinctive architectural design of electrode materials remain critical factors for enhancing the energy density of supercapacitors. Herein, metal-organic framework (MOF)-derived three-dimensional (3D) hollow nitrogen-doped carbon (NHCs) with Fe2O3 core-shell composite negative electrode materials (NHCs@Fe2O3) were developed. In this framework, 1) the high specific surface area caused by the distinctive core-shell structure facilitated the electrolyte infiltration in the hollow skeleton, which shortened the ion transport path and enabled fast electron transfer; and 2) the synergistic effect of the nitrogen-containing groups of the hollow carbon and the reversible Faraday reaction of metal oxides increased the ratio of the pseudocapacitance. These phenomena were the primary reasons for the enhanced capacity of the core-shell electrode. Additionally, hierarchical CuCo2S4@layered double hydroxide (NiFe-LDH) nanobelt core-shell heterostructure arrays integrated on the nickel foam were used for the positive electrode materials. The asymmetric pouch-type supercapacitor assembled with NHCs@Fe2O3 (negative electrode) and CuCo2S4@NiFe-LDH (positive electrode) exhibited a high energy density of 68.6 W h kg–1 at a power density of 828.9 W kg–1. This work offers an effective strategy for fabricating multicomponent core-shell materials and optimizing the interactions between the components to enhance the electrochemical performance in energy storage applications.