Hierarchical Co-Ni layered double hydroxide nanosheets enwrapped CuO nanorods by electrodeposition for excellent energy storage devices

A hierarchical structure consisting of Co-Ni - Ni layered double hydroxide nanosheets (LDH-NSs) enwrapped copper oxide nanorods (CuO-NRs) was synthesized in situ on the surface of copper foam (CF) through direct oxidation and electrodeposition methods. The CF skeleton provided the desired electrical conductivity, while in-situ oxidation of CuO-NRs eliminated the need for binders. Moreover, the uniform growth of LDH-NSs on CuONRs via electrodeposition facilitated the formation of a stratified structure, effectively inhibiting the aggregation of LDH-NSs and providing ample active sites for the adsorption/desorption and transportation of electrolyte ions. Adjusting the molar ratio of Co2+ 2+ to Ni2+ 2+ in the electrolyte influenced the electrochemical properties, resulting in efficient in-situ growth, a porous structure, and uniform morphological control. The CF@CuO@Co-Ni LDH-2 (Co: Ni =1:2) sample demonstrated the most favorable electrochemical performance, primarily attributed to its superior Ni: Co synergistic effect. As a wonderful electrode material, it exhibited a high specific capacitance of 2628.4 F g- 1 at a current density of 2 A g- 1 . Even after 5000 cycles at 20 A g- 1 , it maintained an outstanding retention rate of 95.00 %. As expected, the assembled asymmetric supercapacitor displayed a remarkable energy density of 101.54 Wh kg-1 . The supercapacitor exhibited an impressive retention rate of 87.57 % after 10,000 cycles at 20 A g- 1 . This study highlighted the potential of hierarchical electrode materials prepared via direct oxidation and electrodeposition for supercapacitor applications. The electrodeposition method preserved all active components on the carrier surface and improved the utilization rate of active sites, while avoiding the use of adhesives, templates, or surfactants, simplifying the procedure.