Fabrication of high capacitance electrospun fibrous net for flexible supercapacitor

As technology becomes increasingly more mobile, the next step is to integrate devices and advanced functionalities into wearable textiles that can have a wide field of actions, e.g., device-to device communications, cyber-physical systems, virtual/ augmented reality, when coupled with solutions such as the Internet of Things (IoT), data analysis (big data) or artificial intelligence (AI), among others. The tremendous research interest has been focused recently on flexible high-capacitance supercapacitors (SCs), as the energy storage device to power up the wearable and portable electronics, due to their good flexibility, high power density, rapid charge/discharge rate and long lifecycle times. Moreover, with the deterioration of environment and the depletion of traditional fossil fuels, as well as the global energy crisis, renewable and sustainable energy has been attracted much attention. Despite numerous research on this field, it is still a technological challenge to develop mechanically flexible electrode with superior electrochemical performance. The main aim of the presented project is the fabrication of high-conductive and high-capacitance electrospun fibrous net as flexible electrodes for SC applications, based on the incorporation of 2D MXene/carbon nanotubes doped with nitrogen (N-CNT) into cellulose acetate (CA) during electrospinning. The usage of a new family of two-dimensional (2D) materials, the transition metal carbide and nitride called MXenes have shown great promise as potential materials for electrochemical energy storage, due to their high conductivity (up to 20,000 S/cm). Moreover, MXenes possess higher strength and stiffness compared to other solution-processed 2D materials, good hydrophilicity, high thermal conductivity and efficient photothermal conversion behaviour, excellent ion intercalation behaviour, scalable solution syntheses (kg batches), sufficient environmental stability for a large variety of applications, biocompatibility, and aqueous solution processing without surfactants addition. Efficacious fabrication of flexible textile-based SC electrodes will depend above all on the preparation of Ti3C2Tx MXenes nanosheets with suitable structure, flake size and properties, using ˝green˝ synthesis approach. In addition, stable dispersion of carbon nanotubes doped with nitrogen (N-CNT) will be prepared for incorporation between MXene nanosheets, enhancing the stability and capacitance of Mxene. As prepared MXenes will be incorporated into optimised electrospinning cellulose acetate (CA) solution using lab-scale single/double-needle electrospinning system. The process will be additionally up-scaled on semi-industrial needle-less system electrospinning device, increasing the production rate. Diversely prepared MXene/N-CNT/CA nanofibers will be characterised, i.e., surface morphology, chemical composition, physical-mechanical and optical properties, electrical conductivity, etc. will be determined. A thin layer of selected hydrophobic final finish will be applied on the surface of electrospun MXene/N-CNT/CA net, increasing its lifetime, i.e., protection of Mxene from oxidation/degradation due to water, sweat, temperature and mechanical forces. Finally, the all-solid-state fibrous-based symmetrical supercapacitors will be assembled and validated. In the presented project, two different research groups, each of them already having proved their extensive expertise within their own respective fields, will work together, and, thus, contribute to the successful knowledge transfer, trans-disciplinary cooperation between laboratories and researchers, enabling the development of high-conductive and high-capacitance electrospun fibres for flexible SC, considering ecologically friendly approach. Moreover, some additional functionalities will be evaluated, e.g., water-repellency and flame-retardancy, widening the application scope of newly developed electrospun fibrous net.