Lignocellulosic Biomass-Derived Carbon Electrodes for Flexible Supercapacitors: An Overview

Abstract

With the increasing demand for high-performance electronic devices in smart textiles, various types of flexible/wearable electronic device (i.e., supercapacitors, batteries, fuel cells, etc.) have emerged regularly. As one of the most promising wearable devices, flexible supercapacitors from a variety of electrode materials have been developed. In particular, carbon materials from lignocellulosic biomass precursor have the characteristics of low cost, natural abundance, high specific surface area, excellent electrochemical stability, etc. Moreover, their chemical structures usually contain a large number of heteroatomic groups, which greatly contribute to the capacitive performance of the corresponding flexible supercapacitors. This review summarizes the working mechanism, configuration of flexible electrodes, conversion of lignocellulosic biomass-derived carbon electrodes, and their corresponding electrochemical properties in flexible/wearable supercapacitors. Technology challenges and future research trends will also be provided.

Keywords: electrochemical performance; electrode; flexible/wearable supercapacitor; lignocellulose-derived carbon.

Figure 1

Overview diagram of lignocellulosic biomass-derived carbon electrodes for flexible supercapacitors (reproduced with permission from ref. [31] Copyright 2014 John Wiley and Sons) in this review.

Figure 2

Energy storage principles of (a) electrical double-layer capacitors (EDLCs), (b) pseudocapacitors, and (c) asymmetric supercapacitors. Reprinted from ref. [32], an open-access article.

Figure 3

Assembly of fiber-shaped supercapacitors (FSSCs) with (a) parallel, (b) twisted and (c) coaxial structure. Reproduced with permission from ref. [45] Copyright 2019 John Wiley and Sons.

Figure 4

(a) Picture of the knitting process. (b) Cotton yarn (white) with integrated fiber-shaped supercapacitors (black). (c) Schematics of yarn fabrication. (d) Scanning electron microscopy (SEM) image of an as-drawn yarn. (e) A long yarn rolled on a rod and knotted. (f) A cloth knitted by the as-drawn yarn and cotton yarn. (a,b) Reproduced with permission from ref. [46] Copyright 2015 John Wiley and Sons. (c–f) Reproduced with permission from ref. [47] Copyright 2015 American Chemical Society.

Figure 5

(a–d) The assembled wearable supercapacitor provides high energy/power capacity as worn in the real cloth. Reproduced with permission from ref. [56] Copyright 2014 Elsevier.

Figure 6

(a) Illustration of fabricating wood-derived C-AL/CNF-5; (b) Transmission electron microscope (TEM) image of CNF; Scanning Electronic Microscope (SEM) images of (c) A-AL/CNF-5 and (d) C-AL/CNF-5. C, A, AL, CNF represent carbon aerogel, aerogel, alkali lignin, cellulose nanofiber, respectively, and 5 indicates that the concentration of AL and CNF is 5%. (a–d) Reproduced with permission from ref. [62] Copyright 2020 John Wiley and Sons.

Figure 7

The diagram illustrating typical electrode materials for different types of supercapacitor. Carbon aerogels, activated carbons, carbon fibers, carbon nanotubes and graphene are mainly for EDLCs; metal oxide and conducting polymers are used for pseudocapacitors; carbon materials/conducting polymers or carbon materials/metal oxides are for asymmetric capacitors.

Figure 8

Cellulose strands are surrounded by hemicellulose and lignin in wood cell wall, and the corresponding chemical structures of carbohydrates (reproduced with permission from ref. [69] Copyright 2016 Elsevier) and lignin (reproduced with permission from ref. [70] Copyright 2002 John Wiley and Sons).

Figure 9

(a) Schematic illustration showing the transformation of a Modal textile into a graphite-like carbon textile through a thermal treatment process. (b) Fabrication of a stretchable supercapacitor using weft-knitted Modal fabric as the electrodes. (c) Cyclic voltammetry (CV) curves of the supercapacitor at different scan rates. (d) CV curves of the supercapacitor at a scan rate of 100 mV/s and under strains of 0%, 10%, 30%, and 50%. (a–d) Reproduced with permission from ref. [58] Copyright 2017 American Chemical Society.

Figure 10

Preparation mechanism of modification reaction with lignin and cellulose acetate. Reproduced with permission from ref. [151] Copyright 2019 American Chemical Society.

Figure 11

The EC performance of cellulose acetate-based flexible SC at different bending angles. (a) Schematic illustration of the flexible supercapacitor. (b) The small fan powered by the flexible supercapacitor at different bending angles. (c) CV curves under 10 mV/s. The inset depicts a bending angle. (d) Capacitance retentions and the corresponding bulb brightness. The inset shows the galvanostatic charge/discharge (GCD) curves at 1 A/g. (e) CV cycle test at 10 mV/s. The inset shows a supercapacitor wristband. (a–e) Reproduced with permission from ref. [199] Copyright 2019 John Wiley and Sons.