Hierarchical CuCo2O4@CoS-Cu/Co-MOF core-shell nanoflower derived from copper/cobalt bimetallic metal-organic frameworks for supercapacitors

Rational design of composite materials with unique core-shell nanoflower structures is an important strategy for improving the electrochemical properties of supercapacitors such as capacitance and cycle stability. Herein, a two-step electrodeposition technique is used to orderly synthesize CuCo₂O₄ and CoS on Ni foam coated with Cu/Co bimetal metal organic framework (Cu/Co-MOF) to fabricate a hierarchical core-shell nanoflower material (CuCo₂O₄@CoS-Cu/Co-MOF). This unique structure can increase the electrochemically active site of the composite, promoting the Faradaic redox reaction and enhancing its electrochemical properties. CuCo₂O₄@CoS-Cu/Co-MOF shows a prominent specific capacitance of 3150 F g^-1 at 1 A g^-1, marvelous rate performance of 81.82% (2577.3 F g^-1 at 30 A g^-1) and long cycle life (maintaining 96.74% after 10,000 cycles). What is more, the assembled CuCo₂O₄@CoS-Cu/Co-MOF//CNTs device has an energy density of 73.19 Wh kg^-1 when the power density is 849.94 W kg^-1. It has unexpected application prospects.

Three-dimensional hierarchical core-shell CuCo2O4@Co(OH)2 nanoflakes as high-performance electrode materials for flexible supercapacitors

Rational design of composite electrode materials with novel nanostructures plays an important role in improving both high energy density and structure stability of flexible and wearable supercapacitors. Herein, numerous peculiar three-dimensional hierarchical core-shell CuCo₂O₄@Co(OH)₂ nanoflakes directly grown on Ni foam are synthesized via a facile hydrothermal method and subsequent electrodeposition technique. Ultrathin Co(OH)₂ nanosheets arrays vertically anchored on CuCo₂O₄ nanoflakes can not only improve the electrical conductivity, but also provide interconnected channels for ion diffusion and enrich electrochemical active sites to boost faradaic redox reaction, leading to the enhanced electrochemical behavior. Excellent electrochemical performance of CuCo₂O₄@Co(OH)₂ electrode can be reflected on a higher specific capacitance of 1558 F/g and lower resistance compared with that of the pristine CuCo₂O₄ electrode. The asymmetric flexible supercapacitor assembled by the optimized CuCo₂O₄@Co(OH)₂ electrode and activated carbon exhibits high energy density of 62.5 Wh/kg at 893 W/kg, outstanding cycle stability of 88.6% capacitance retention after 10,000 cycles and remarkable mechanical flexibility, performing the best electrochemical behavior among various metal oxides based asymmetric supercapacitors. All above results indicate that the resulted hierarchical core-shell CuCo₂O₄@Co(OH)₂ electrode can be a promising candidate for flexible energy storage devices.