N-doped bimetallic sulfides hollow spheres derived from MOF as battery-type electrode for asymmetric supercapacitors

Despite the significant progress in bimetallic MOFs electrodes, strategies to seamlessly interconnect of hollow spherical structure MOFs and electrically conductive substrate materials without adhesives are still deficient. In this study, we designed an original method for in situ synthesis of hollow spherical bimetallic MOF-derived sulfides (HN2CMS) on nickel foam by using self-grown ZIF-67 on nickel foam as precursor and template followed by two simple hydrothermal reactions. The prepared electrodes exhibit a high specific capacitance of 938.1C g−1 at the current density of 1 A g−1, low electrochemical resistance and excellent cycling stability (85.0 % after 5000 cycles) in a 3 M KOH aqueous electrolyte. More importantly, an assembled asymmetric supercapacitor based on HN2CMS provides an ultra-high energy density of 51.2 Wh kg−1 with a power density of 800 W kg−1. And it exhibits an outstanding lifetime of 81.1 % capacity remained after 5000 cycles, demonstrating that hollow spherical bimetallic MOF-derived sulfides are a prospective candidate for SC electrode materials. This synthesis method breaks a new path to developing binder-free electrodes with hollow structures based on bimetallic MOFs, thus improving the electrochemical performance of asymmetric SC.