High-Performance Fiber-Shaped Flexible Asymmetric Microsupercapacitor Based on Ni(OH)₂ Nanoparticles-Decorated Porous Dendritic Ni–Cu Film/Cu Wire and Reduced Graphene Oxide/Carbon Fiber Electrodes

Miniaturization of electronic devices with portable, flexible and wearable characteristics created a great demand for high-performance microscale energy storage devices with lightweight and flexible properties. Among the energy storage devices, wire-shaped supercapacitors (WSSCs) have recently received tremendous attention due to their tiny volume, wearability, high flexibility and potential applications in the next-generation portable/wearable electronic devices. Herein, we successfully fabricated a porous dendritic Ni–Cu film on Cu wire substrate (CWE) for fabrication of high-performance wire-type supercapacitors. The porous structure with dendritic morphology provides a high surface area, short ion diffusion pathway and low contact resistance between electroactive materials and metal wire electrode. The Ni­(OH)2 electroactive material is then deposited on Ni–Cu/CWE. The fabricated Ni­(OH)2/Ni–Cu/CWE exhibits excellent electrochemical performances with high areal (volumetric and length) specific capacitance of 12.2 F cm–2 (1220.89 F cm–3, 1.53 F cm–1), respectively at a current density of 4 mA cm–2, and an excellent cycle stability (100% even after 3500 cycles). A novel fiber-shaped flexible asymmetric micro–supercapacitor (ASC) based on Ni­(OH)2/Ni–Cu/CW as positive electrode and reduced graphene oxide/carbon fiber (RGO/CF) as the binder free negative electrode was assembled. This device can be operated reversibly in the voltage range of 0–1.6 V and exhibited a maximum areal and volumetric energy (EA = 195 μWh cm–2, EV = 15.04 mWh cm–3) and power (PA = 7643 μW cm–2, PV = 588 mW cm–3) densities. In addition, the ASC device also exhibits an excellent cycling stability with 95.7% capacitance retention after 5000 cycles and good mechanical stability, which is checked by bending of the whole device at various angles. These promising results indicated the great potential of our fabricated device for portable, flexible and wearable applications