NiCo Prussian-Blue-Derived Cobalt–Nickel-Layered Double Hydroxide with High Electrochemical Performance for Supercapacitor Electrodes

High-performance electrode materials are crucial to the improvement of the supercapacitor performance index. Ni2Co1HCF@CoNi-LDH composites with a core–shell structure were prepared by a combination of coprecipitation and constant potential electrodeposition, and the microscopic morphology and phase composition of the composites were characterized by XRD, SEM, FTIR and XPS. The results showed that the NiCo Prussian blue (Ni2Co1HCF) was grown on the nickel foam (NF) substrate by in situ etching, while the nickel–cobalt double hydroxide (CoNi-LDH) was covered on the NiCo Prussian blue surface by electrodeposition, and the composite still retained the cubic skeleton morphology of the NiCo Prussian blue. The electrochemical properties of the composites were investigated using a three-electrode system in 2 M KOH. The results showed that their discharge specific capacity was as high as 1937 F·g−1 at a current density of 1 A·g−1 and still had 81.3% capacity retention at 10 A·g−1, and they exhibited an excellent rate capability. The capacity retention rate was 87.1% after 1000 cycles at 5 A·g−1 and, thus, the composite material has good application prospects as a supercapacitor electrode material.