Co-precipitation synthesis of nickel cobalt hexacyanoferrate for binder-free high-performance supercapacitor electrodes

Prussian blue analogue with a typical metal-organic framework has been widely used as an electrode material in supercapacitor. In this work, nickel cobalt hexacyanoferrate (Ni2CoHCF) was grown on nickel foam directly using a simple co-precipitation method. The as-prepared Ni2CoHCF was tested by transmission electron microscope, scanning electron microscope, X-ray diffraction and X-ray electron energy spectrum. The results showed that Ni2CoHCF has a unique open face-centered cubic structure. The Ni2CoHCF was used to set an asymmetric supercapacitor directly. A series of electrochemical tests showed that Ni2CoHCF had an excellent electrochemical performance. The specific capacitance of the supercapacitor was 585 C g−1 (1300.0 F g−1, 162.5 mAh g−1) at the current density of 0.5 A g−1. After 2000 cycles, it still maintained 85.57% of its initial specific capacitance at the current density of 10 A g−1. The energy density was 30.59 Wh kg−1 at the power density of 378.7 W kg−1. The results show that the supercapacitor constructed by Ni2CoHCF as an electrode material has high-current charge-discharge capacity, high energy density and long cycle life.