Poly(azure C)-coated CoFe Prussian blue analogue nanocubes for high-energy asymmetric supercapacitors.

[Display omitted] • Redox-active poly(azure C) (PAC) is grown on CoFe Prussian blue analogue (CoFePBA) nanocubes. • The electrochemical performance of the optimized composite is improved significantly. • The CoFePBA@PAC//activated carbon asymmetric supercapacitor is fabricated. • The supercapacitor device delivers high energy and power densities. Prussian blue analogues are considered as promising supercapacitor electrode materials due to their high theoretical capacitance and low cost. Yet, they suffer from poor electronic conductivity and cycling life. Here, a redox dye polymer, poly(azure C) (PAC), is in-situ grown uniformly on CoFe Prussian blue analogue (CoFePBA). As a polymer mediator, the PAC coating on each PBA not only enhances the electronic conductivity and surface area, but also improves the structural stability and specific capacitance of PBA. As a result, the optimized CoFePBA@PAC possesses ultrahigh specific capacitance (968.67 F g−1 at 1 A g−1), superior rate performance (665.78 F g−1 at 10 A g−1), and excellent long-cycling stability (92.45% capacity retention after 2000 cycles). As an application, a fabricated CoFePBA@PAC//AC asymmetric supercapacitor (AC = activated carbon) maintains 84.7% capacitance retention in 2000 cycles at 1 A g−1 and displays a superior specific energy of 29.16 W h kg−1 at the power density of 799.78 W kg−1. These results demonstrate that redox dye polymer-coated PBAs with outstanding performance have a promising prospect in the field of energy storage. [ABSTRACT FROM AUTHOR]