Conductive Graphene Fibers for Wire-Shaped Supercapacitors Strengthened by Unfunctionalized Few-Walled Carbon Nanotubes

Abstract

Graphene fibers are a promising electrode material for wire-shaped supercapacitors (WSSs) that can be woven into textiles for future wearable electronics. However, the main concern is their high linear resistance, which could be effectively decreased by the addition of highly conductive carbon nanotubes (CNTs). During the incorporation process, CNTs are typically preoxidized by acids or dispersed by surfactants, which deteriorates their electrical and mechanical properties. Herein, unfunctionalized few-walled carbon nanotubes (FWNTs) were directly dispersed in graphene oxide (GO) without preoxidation or surfactants, allowing them to maintain their high conductivity and perfect structure, and then used to prepare CNT-reduced GO (RGO) composite fibers by wet-spinning followed by reduction. The pristine FWNTs increased the stress strength of the parent RGO fibers from 193.3 to 385.7 MPa and conductivity from 53.3 to 210.7 S cm(-1). The wire-shaped supercapacitors (WSSs) assembled based on these CNT-RGO fibers presented a high volumetric capacitance of 38.8 F cm(-3) and energy density of 3.4 mWh cm(-3). More importantly, the performance of WSSs was revealed to decrease with increasing length due to increased resistance, revealing a key issue for graphene-based electrodes in WSSs.

Recent advances in flexible supercapacitors based on carbon nanotubes and graphene

“…When woven into textile electrodes, the composite fibers maintained their flexibility and showed an areal capacitance of 0.98 mF cm −2 and a gravimetric specific capacitance of 200.4 F g −1 . GO/ MWCNT fibers can also be prepared using a wet-spinning method [91]. After reduction in an acid bath, the composite fiber exhibited enhanced stress strength (385.7 MPa) and better conductivity (210.7 S cm .…”

Elastomeric and Dynamic MnO2/CNT Core–Shell Structure Coiled Yarn Supercapacitor

“…Nevertheless, most fiber-based supercapacitors (FBSs) simply possess the flexibility with limited tensile strain and stretchability [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] because they are mostly based on nonstretchable electrodes such as carbon nanotube (CNT) spun yarn, 2-7 graphene fiber, [8][9][10][11][12] carbon fiber, 13,14 and metal wire. 15 This lack of stretchability of these FBSs leads to limitation for more advanced utilization, e.g., as a power source for artificial muscles 17 or wearable devices that are exposed to high strain, especially in the joint part.…”

“…For example, the volumetric capacitance of our coiled supercapacitor (34. 11 . Such high specific capacitances of our coiled supercapacitor compared with other FBSs can be attributed to the following two aspects.…”

Toward High Performance Nanocarbon Fibers

“…47 A more recent study used wetspinning of GO LCs with dispersed few-walled CNTs (FWNTs). 48 When the CNT/GO ratio was lower than 1:3, the CNTs were shown to align in the axial direction. 48 Following reduction, the hybrid fibers were shown to have an increase in tensile strength of about 200 MPa.…”

“…48 When the CNT/GO ratio was lower than 1:3, the CNTs were shown to align in the axial direction. 48 Following reduction, the hybrid fibers were shown to have an increase in tensile strength of about 200 MPa. 48 All three of the studies also investigated electrical conductivity and determined that the combination of rGO and CNTs leads to more optimal electrical properties.…”