Co(OH)2 nanoneedles grown on Cu/NF current collector with high areal capacitance for supercapacitors

Despite the demand for high energy-density supercapacitors has been realized when transition metal hydroxides are used as electrode materials, the ion diffusion dynamics are still limited by its high impedance. In this work, Cu is deposited on nickel foam (NF) by filtered cathodic vacuum arc (FCVA) technology to serve as an ion-diffusion-favored surface state. Co(OH)2 synthesized hydrothermally on this Cu/NF exhibits remarkably enhanced electrochemical properties compared with Co(OH)2 grown on pristine NF. The resultant electrode can deliver a large area capacity of 0.772 C cm−2 at 1 mA cm−2 and retain 80.92% of initial capacitance after 4000 cycles. Moreover, an assembled asymmetric supercapacitor shows a high energy density of 0.086 mW cm−2 at 0.4 mWh cm−2 with a long lifespan (80.67% retention after 3000 cycles). Our strategy may provide a new insight to prepare electrodes for assembling high areal capacitance supercapacitors.