CoNi Layered Double Hydroxide Nanosheets Vertically Grown on Electrodeposited Dendritic Copper Substrates for Supercapacitor Applications

Layered double hydroxides (LDHs) have attracted numerous interests in developing high-performance electrochemical supercapacitors (SCs). However, the anchored conductive substrates are critical in the high-dense growth of LDH with favorable crystal orientations for maximizing performances, in which the conventional amorphous carbon-based materials and microporous nickel foams cannot be fitted. Herein, we utilize the electrodeposited 3D dendritic copper as the conductive substrate for the vertical growth of CoNi-LDH nanosheets. The composite possesses excellent electrical conductivity, a high degree of crystallinity with (003) orientation, and a large surface area, resulting in an impressive specific capacitance of 5743 mF cm–2 at 1 mA cm–2 with 56.6% rate capability at 20 mA cm–2 and excellent cycling lifespan. In comparison, pure CoNi-LDH shows a smaller specific capacitance of 1798.18 mF cm–2 at 1 mA cm–2 with 46.1% rate capability at 20 mA cm–2. Such improved electrochemical performances of the composite electrode are possibly due to the sufficient exposure of the active centers, the shortened diffusion distance of electrolyte ions, and the synergistic interaction of the copper core and the LDH shell. The assembled asymmetric supercapacitor device based on the as-prepared composite anode and the activated carbon cathode exhibits an energy density of 0.33 mW h cm–2 at a large power density of 1.5 mW cm–2. This work reveals a facile and feasible strategy for improving the performances of LDH-based SC devices through the engineering of conductive substrates.