MOF-derived hierarchical nanosheet arrays constructed by interconnected NiCo-alloy@NiCo-sulfide core-shell nanoparticles for high-performance asymmetric supercapacitors

摘要

Bimetallic sulfides have been extensively used to supercapacitors due to their abundant active sites and synergistic redox behavior. However, the restricted conductivity hinders their further development in the application of supercapacitors. Herein, we exhibit a novel design of MOFs into granulated nanosheets on carbon fibers. Specially, a single nanosheet is composed of interconnected NiCo-alloy@NiCo-sulfide core-shell nanoparticles (CF@NiCo-A-S). The NiCo-alloy skeleton with ultrahigh-conductivity effectively provides a highway for electron transfer inside. In particular, the external NiCo-sulfide with average thickness of similar to 30 nm provides abundant active sites and availably suppresses the oxidation of alloy, which can realize charge storage with high utilization ratio of NiCo-A-S because that the impactful surface thickness of electrode materials is nearly 20 nm and other inaccessible volume is inactive for charge storage. Significantly, the CF@NiCo-A-S electrode exhibits an ultrahigh specific capacitance of 213 mAh g(-1) at 1 A g(-1). Moreover, we also designed the anode materials of carbon nanosheets embedded with Fe2O3/Fe3O4 (FexOy@CNS) based on MOFs. Above all, the supercapacitor device of CF@NiCo-A-S//FexOy@CNS delivers a maximum energy density of 48.2 Wh kg(-1) at 840 W kg(-1), with an excellent capacitance retention of 83.5% after 5000 charge-discharge cycles.