Page 252 - Carbon Nanotube Fibres and Yarns

CHAPTER 10

CNT yarn-based supercapacitors

a
b
Qiufan Wang , Sufang Chen , Daohong Zhang a
a Key Laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education & Hubei Key Laboratory
of Catalysis and Materials Science, South-Central University for Nationalities, Wuhan, China
b Key Laboratory for Green Chemical Process of Ministry of Education, Wuhan Institute of Technology,
Wuhan, China

10.1 Introduction
10.1.1 Background of electrochemical capacitors

Energy has been one of the most important and active research topics in re-
cent decades. The increasing depletion of fossil fuels and the environmental
pollution associated with their consumption have inspired the development
of clean and sustainable energy sources. The rapid developments of electric
vehicles powered by batteries and portable consumer electronics create a
demand for high power density, energy density, and flexible energy storage
systems. Electrochemical energy storage devices with the characteristics of
high efficiency, flexibility, and versatility are playing an increasingly import-
ant role. Among different electrochemical energy storage systems, superca-
pacitors (SCs) and batteries are the most successful players on the Ragone
chessboard and are widely investigated in both academia and industries
[1–6]. The basic differences between SCs and batteries lie in their charge
storage mechanisms and their materials and structures [7–11]. SCs, also
called ultracapacitors and electrochemical capacitors, present the attractive
advantage of bridging the energy density gap between traditional capacitors
and batteries (Fig. 10.1) [12–15]. They can provide a higher power density
than batteries and a higher energy density than conventional capacitors
while offering long cycle lifetimes [16].
In general, an SC consists of two electrodes and a separator sandwiched
between them. The sandwich-like electrode/separator/electrode device
structure is immersed in an aqueous or organic electrolyte. The separator
prevents direct contact of the two electrodes while allowing electrolyte ions
freely passing through. To maintain sufficient functional liquid electrolyte in
the device from leakage, which is also harmful to our living environment,

Carbon Nanotube Fibers and Yarns Copyright © 2020 Elsevier Ltd.
https://doi.org/10.1016/B978-0-08-102722-6.00010-9 All rights reserved. 243