Two-step electrodeposition synthesis of nano-clustered Ni@NiCo-LDH heterostructure as cathodes for high-performance hybrid supercapacitors

In situ-grown porous structures enhance electrode material contact area with electrolyte, decrease ion propagation distance, as well as improve the electrochemical properties of electrode materials. The Ni@NiCo-LDH/CF heterostructure was effectively built by employing copper foam as the collector, the Ni layer as a connecting layer as a super channel for electron transport, and then secondary electrodeposition of NiCo-LDH. In comparison to primary Ni plating or primary NiCo-LDH plating, the nano-clustered Ni@NiCo-LDH/CF obtained by two-step electric deposition methods has exceptional electrochemical properties, including a high specific capacitance of 1620 F g−1 at 1 A g−1, excellent cycling stability, and rate performance (1143 F g−1 at 10 A g−1 and retaining 93.7 % after 5000 cycles). In addition, the hybrid supercapacitor assembled with activated carbon serving as the negative electrode has a capacity retention of 78.18 % after 12,000 cycles at 10 A g−1 and an extremely high energy density of 66.6 Wh kg−1 at 808 W kg−1. Furthermore, DFT studies suggest that Ni@NiCo-LDH/CF has a larger density of states (DOS) around the Fermi energy level. It offers suggestions for making high-energy-density electrodes.