Fabrication of an Advanced Asymmetric Supercapacitor Based on Three-Dimensional Copper–Nickel–Cerium–Cobalt Quaternary Oxide and GNP for Energy Storage Application

We demonstrate a cost-effective synthesis of 3D quaternary copper–nickel–cerium–cobalt oxide (Cu–Ni–Ce–Co oxide) through a one-step hydrothermal protocol followed by a heat treatment process. The mesoporous Cu–Ni–Ce–Co oxide (with pore diameter 4.34 nm) shows a higher specific surface area (86.9 m2 g–1). The as-synthesized quaternary oxide provides an ultrahigh specific capacitance of 2696 F g–1 at 1 A g–1 along with a moderate cycle stability of 86.5% after 3000 charge–discharge cycles. Furthermore, an asymmetric supercapacitor (ASC) was established by assembling Cu–Ni–Ce–Co oxide and graphene nanoplatelets (GNP) as positive and negative electrode materials, respectively, and the supercapacitor performances were executed thoroughly. The ASC delivers a remarkable energy density of ≈51 Wh kg–1 at a power density of 581.9 W kg–1 together with long-term cyclic stability (92% specific capacitance retention after 3000 cycles). The compositional and morphological features together with superior electrochemical properties can make it advantageous for practical use in energy and power applications.