Rational design of multiple Prussian-blue analogues/NF composites for high-performance surpercapacitors

In this study, a series of NiCoxFe1-x-PBA/NF (nickel foam) electrodes were successfully fabricated with different ratios of Co and Fe through anin situchemical etching process. Their structures and morphology were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Remarkably, this novel series of composites exhibit excellent supercapacitor performance. Among them, the NiCo-PBA/NF electrode exhibits the best electrochemical performance with an area specific capacitance of 2242 mF cm(-2)at 1 mA cm(-2)in 3 M KOH solution and good cycling stability. Furthermore, asymmetric supercapacitor cells with NiCo-PBA/NF as the positive electrode and active carbon coated on the nickel foam as the negative electrode deliver a very high energy density of 39.4 W h kg(-1)and a high power density of 4003 W kg(-1), which far exceed those of other devices reported previously. This work highlights the designing strategy of such composite materials with an optimized synergistic effect, which greatly promotes the supercapacitor development.