Layered double hydroxides/prussian blue analogs toward improved capacitive performances

Nickel-based bimetallic hydroxides are widely used as supercapacitor electrodes owing to their high theoretical capacitance and cost-effectiveness. Nevertheless, challenges of low conductivity and substantial volume expansion exist during cycling processes. Herein, NiCo-layered double hydroxides (NiCo-LDH) nanosheets are electrodeposited on nickel foam (NF), followed by the generation of prussian blue analogs (PBA) on the surface of NiCo-LDH via the ion exchange, obtaining the NiCo-LDH/PBA. The introduction of PBA can enhance the structural stability and reduce the agglomeration of the NiCo-LDH during cycling. By optimizing the ion exchange duration, the spherical flower-like NiCo-LDH/PBA exposing substantial redox active sites can be obtained. The optimal NiCo-LDH/PBA yields specific capacitances of 1973.0 and 1604.4 F g^-1 at 2 and 10 A g^-1, respectively. Asymmetric supercapacitors assembled with NiCo-LDH/PBA and activated carbon delivers an energy density of 66.3 Wh kg^-1 at a power density of 725.0 W kg^-1 and acceptable cycling stability. These remarkable performances of the NiCo-LDH/PBA electrode render it one promising candidate as advanced supercapacitor electrodes.