Investigation of environmentally friendly materials for high performing flexible energy storage devices

This research study contributes to the advancement in utilisation of environmentally friendly materials, such as water hyacinth-based cellulose, for the fabrication of three innovative flexible energy storage devices. By applying these environmentally friendly materials, this research not only contributes to the advancement in future energy storage devices but also promotes a more environmentally sustainable approach to energy storage solutions. First, a commercially available, electrically non-conductive cellulose cloth was treated with conductive, environmentally friendly, excellent thermal stability and biocompatible poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) with various widely used and low-cost secondary dopants such as Dimethylsulfoxide, Methanol, Glycerol, Polyethylene glycol, and Ethylene glycol to further enhance its conductivity for supercapacitor (SC) application. The resulting best combination of poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) with secondary dopants was utilised with an environmentally friendly active electrode material consisting of Tungsten Oxide and ethyl cellulose binder to enhance the electrochemical performance of the symmetrical SC. This combination ensures the resulting E-textile SC is not only functional but also suitable for flexible/wearable applications. Secondly, water hyacinth cellulose stems were collected from a freshwater lake in Taman Tasik Seri Aman, Puchong, Malaysia and surface modified by carboxymethylation reaction, which is then used to fabricate a conductive hydrogel. It features an environmentally friendly sweat-activated conductive hydrogel made from an anionic polyelectrolyte water hyacinth carboxymethyl cellulose nanofibers and a cationic polyelectrolyte chitin. Also, it contains environmentally friendly materials such as PEG 400, citric acid, and NaCl. This hydrogel is employed to fabricate a new sweat-activated ultra-low voltage and high capacitance E-textile hybrid SC with piezoelectric effect through the generation of an electric charge in response to mechanical stress. Lastly, water hyacinth cellulose nanofibers (WHCNF) were utilised to fabricate a novel environmentally friendly bilayer separator. The bilayer WHCNF separator was prepared by fabricating the base layer by freeze-thawing process, comprising of WHCNF and polyethylene glycol 4000. Polyethylene glycol is a non-toxic, inexpensive, stable, easy-to-use, and biodegradable plasticiser, that imparts crosslinking, flexibility, increased wettability, and electrolyte uptake to the separator. Layer two via doctor blade and non-solvent induced phase separation is made of non-toxic, low environmental impact, and low-cost polyvinyl alcohol, which includes its high chemical resistance, aqueous solubility, and biodegradability. Furthermore, utilising a WHCNF bilayer separator to fabricate an environmentally friendly paper-based energy storage device with active electrodes comprises of a MnO2/carbon composite, while carbon black combined with Zn metal serves as the anode, resulting in a high-performance, environmentally friendly paper-based SC.