Page 265 - Carbon Nanotube Fibres and Yarns

CNT yarn-based supercapacitors 255

Fig. 10.4 (A) Schematic showing the formation of the core/sheath yarn structure.
(B) Cross-section of Pt/CNT/PANI core/sheath yarn resulted from coarse FIB milling.
(C) Knitted tubular fabric containing the Pt/CNT/PANI supercapacitor and a nylon
monofilament. (Reproduced with permission from D.H. Zhang, M. Miao, H.T. Niu, Z.X.
Wei, ACS Nano 8 (2014) 4571–4579.)

MWNT fibers. They enhanced the electrical conductivity of CNT elec-
trodes by winding the MWNT fiber around a metal wire, resulting in a
low internal resistance, faster charge transportation, and higher capacitance.
Zhang et al. [74] produced a core-sheath structured carbon nanotube yarn
architecture using a one-step continuous spinning method (Fig. 10.4). In
the core/sheath structured yarn, the carbon nanotubes form a thin surface
layer around a highly conductive metal filament core, which serves as a
current collector so that charges produced on the active materials along
the length of the supercapacitor are transported efficiently, resulting in sig-
nificant improvement in electrochemical performance and scale-up of the
supercapacitor length. The supercapacitor was strong and flexible enough to
be knitted into a fine-gauge tube (Fig. 10.4C).
Another method for incorporating a metal current collector is twisting a
metal filament with a CNT yarn to form a two-ply electrode (Fig. 10.5A)
[83]. Different metal filaments, such as platinum, gold, silver, copper, and alloys,
were used. As a reflection of the charge (electrons and ions) transfer rate, ESR
of the SCs reduced from 1300 Ω to 36–91 Ω after introducing metal filament
(Fig. 10.5B). However, the improvement of capacitance for metal/CNT plied