Designing graphene-wrapped nanoporous CuCo2O4 hollow spheres electrodes for high-performance asymmetric supercapacitors

Abstract

Increasing demand for green energy storage systems, arising from the rapid development of portable electronics, has triggered tremendous research efforts for designing new or high-performance electrodes. Herein, for the first time, we develop a graphene-wrapped CuCo₂O₄ hollow spheres electrodes with a 3D composite network, a high surface area of 106.2 m² g⁻¹ and nanopores mainly centred at 7.6 nm. This electrode exhibits excellent electrochemical performance with an ultrahigh specific capacitance of 1813 F g⁻¹ at 2 A g⁻¹ (3.63 F cm⁻² at 4 mA cm⁻²) and a significant rate capability of 63% capacitance retention even at an ultrafast rate of 120 mA cm⁻². Utilizing this nanocomposite as the positive electrode in a GW-CuCo₂O₄//rGO asymmetric configuration results in the development of devices with remarkable performance including excellent cycle life (4.8% loss after 6000 cycles), a maximum energy density of 45.2 W h kg⁻¹ and a power density up to 15 kW kg⁻¹, which is superior to state-of-the-art supercapacitors. The superior electrochemical performance of this electrode is attributed to the synergic effects between the components and its unique 3D nanoporous composite network that plays a key role in providing high conductivity, rich redox reactions, facile electron transfer, short ion diffusion distance, fast kinetics and great active sites for electrochemical reactions. This study presents a new platform for unique and efficient electrodes for the next generation of high-performance energy storage systems and portable electronics.