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

Abstract

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 (E A = 195 μWh cm–2, E V = 15.04 mWh cm–3) and power (P A = 7643 μW cm–2, P V = 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.

Recent Advances in Fiber‐Shaped Supercapacitors and Lithium‐Ion Batteries

“…With electrodeposition, the surface morphology and properties of capacitive materials can be precisely manipulated by varying deposition conditions, such as current, voltage, time, and precursor concentration. As shown in Figure e–m, Shahrokhian and co‐workers electrodeposited dendritic Ni–Cu and Ni(OH) 2 nanoparticles on a Cu wire electrode for pseudocapacitors . Highly porous dendritic Ni–Cu film with a maximized electrode specific surface area for the formation of Ni(OH) 2 nanoparticles and fast electrolyte ion diffusions was achieved.…”

“…m) The cross‐sectional image of Ni(OH) 2 /Ni−Cu/CW electrode. e–m) Reproduced with permission . Copyright 2018, ACS Publications.…”

A Route Toward Smart System Integration: From Fiber Design to Device Construction

“…For instance, NiCo 2 S 4 nanosheets were coated on Ni wire as an electrode for fiber‐shaped supercapacitor . Ni(OH) 2 nanoparticles were coated on Cu wire also as an electrode for fiber‐shaped supercapacitor . And TiO 2 nanotubes were grown on Ti wire (Figure b) as the working electrode for fiber‐shaped solar cell …”

NiCo2O4/RGO Hybrid Nanostructures on Surface-Modified Ni Core for Flexible Wire-Shaped Supercapacitor

“…Furthermore, as a current collector, metal wires have been seen perform a crucial role in obtaining the flexible SCs, predominantly owing to their superior mechanical strength and high electrical and thermal conductivity [ 21 , 22 , 23 , 24 , 25 , 26 ]. The application of a highly conductive core such as metal wire is considered to enhance the flexible SC performance by the reduction in loss of charge, and simultaneous improved transmission of electrical power and charge storage [ 27 , 28 ].…”

“…However, metal wires also possess major downsides such as the weak adhesion between the electrode and electroactive materials, low surface area, and low porosity. One of the most effective ways to get rid of such drawbacks is the direct growth of electrode materials with high porous structures on conductive substrates [ 24 , 25 , 26 ]. Additionally, the substrate roughening treatment has been recognized to improve the film adhesion to the substrate [ 29 ] and it has also been seen to increase the surface area, thus providing more reactive sites for surface modification [ 30 , 31 ].…”