Microstructural design of interconnected Cu@Ni core-shell nanowire-based networks as high-performance electrodes for supercapacitors

Abstract

Copper nanowires (CuNWs) are highly attractive for electrochemical energy storage devices due to their high electrical conductivity and commercial accessibility; however, their susceptibility to oxidation remains a significant challenge. In this study, ultralong copper and Cu@Ni core-shell nanowires were synthesized via a solution-phase method to develop a unique network-like architecture for high-performance composite supercapacitor electrodes. The nickel shell effectively protects the copper core from degradation in alkaline electrolytes, maintaining microstructural stability, flexibility, and high conductivity. In contrast, bare CuNWs undergo complete degradation into CuO nanoparticles, collapsing the network structure. The study also identifies the significant impact of conductive carbon content and electrolyte concentration on the performance of the materials. Reducing the carbon component to 20 wt% in 3 M KOH facilitates a rate-dependent redistribution of charge storage contributions: from a battery-type behavior at low scan rates (78% at 2 mV s −1 ), to a pseudocapacitive-dominated contribution (66% at 100 mV s −1 ). Under this optimal combination (20 wt% C, 3 M KOH), the electrode achieved high areal capacitance (460 mF cm −2 at j = 2 mA cm −2 ), maintaining a balance between capacitance retention (92%) and coulombic efficiency (89%) over 2000 cycles. An assembled asymmetric supercapacitor delivered a competitive areal capacitance (115 mF cm −2 at 0.5 mA cm −2 ) and an energy density of 35.9 μWh cm −2 at a power density of 0.38 mW cm −2 , alongside high cycling stability (84.1% retention after 10,000 cycles). These results demonstrate the high potential of Cu@Ni nanowire-based network-like electrodes for efficient energy storage devices.