ZIF-derived hollow cattail-shaped composites with hierarchical channels towards enhanced electrochemical properties for supercapacitors

Abstract

Despite the achievement in generating various hollow architectures, designing hollow composites with hierarchical channels remains challenging to achieve excellent electrochemical energy storage performance. To address this issue, we developed an in situ self-assembly strategy to prepare hollow composites using zeolitic-imidazolate frameworks and carbon nanotubes (ZIF@CNT). These ZIF@CNT architectures with different appearances are prepared by adjusting the stirring rate during the reaction. Subsequently, the sulfurization strategy is applied to convert ZIF-67 to cobalt sulfide (CoS), resulting in the hollow CoS@CNT hybrids. These hierarchical channels include the hollow CoS cavities and CNT channels. The unique hollow composites with different dimensions played a synergistic effect between subunits, thus giving excellent electrochemical properties. The impact of particle cavity channel size on electrochemical properties was evaluated systematically. As expected, CoS@CNT with hollow cattail-shape structures (HCCoS@CNT) resulted in the optimal specific capacitance (1250 F/g) and cyclic stability (90.4 % for over 10,000 times of cycling at 10 A/g). The designed hybrid supercapacitor, HCCoS@CNT//active carbon (AC), delivered an exceptional energy density of 40 Wh kg−1 at 800 W kg−1 of the power density. Together, these findings provide a reference for preparing complex hollow structures as high-performance electrodes, clarifying the optimization of composites for improved electrochemical properties.