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

Despite the achievement in generating various hollow architectures, designing hollow composites with hierar-chical 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 ap-pearances 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 di-mensions 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.