Binder-free Co–Ni hexacyanoferrate as a battery-type electrode material for hybrid supercapacitors

In this study, Co–Ni hexacyanoferrate (CoxNi3-xHCF) electrodes with different Co and Ni ratios were directly synthesized on Ni foam (NF) via a simple and cost-effective hydrothermal approach, and their physical and electrochemical properties were studied. The binder-free CoxNi3-x[email protected] composites exhibited battery-like electrochemical storage mechanisms. Among them, the CoNi2[email protected] composite exhibited the better charge storage properties with a specific capacity of 817 C g−1 at 1 A g−1. Furthermore, a hybrid supercapacitor (HSC) device with a CoNi2[email protected] composite as the battery type and activated carbon as supercapacitor electrodes delivered a high energy density of 36 Wh Kg−1 at a power density of 1056 W kg−1 along with good cycling performance. This study introduces a feasible method to design such binder-free materials with optimized synergetic effects that are beneficial for designing next-generation HSC devices.