Exploring the In-Situ Growth Process of Electroconductive and Pseudocapacitive Layers on Flexible Substrates: Synthesis Optimisation and Interfacial Connection Enhancement

Abstract

Abstract The growing desire for flexible, wearable, and portable electronics has prompted substantial studies into the creation of flexible electroconductive fibres and capacitive materials. These materials are necessary to realise the full potential of energy storage devices of the future generation, such as flexible supercapacitors. However, weak interfacial contacts between active materials and electroconductive substrates remain an important challenge, limiting the electrochemical performance and applications of these materials in various areas. The purpose of this work is to evaluate the in-situ creation of electroconductive and pseudocapacitive layers on three distinct substrates (cotton fabric, carbon fibre, and elastomer) utilising a binder-free approach to manufacture electrode materials. In substitute for a typical binder, a Polydopamine (PDA) coating is utilised to improve the adhesion between the substrate and the electrode material. The research involves both the synthesis of the substrates and the optimisation of the growth conditions of the layers on these substrates. The fourth and fifth chapters respectively focus on the development and integration of energy storage devices based on cotton fabric and carbon fibre. The sixth chapter discusses the creation of flexible strain sensors based on Ecoflex. The results demonstrate that the binderfree technique employing PDA coating is successful for fabricating low-resistance electroconductive and pseudocapacitive layers on cotton and carbon substrates. The developed energy storage devices and strain sensors exhibited promising electrochemical and sensing properties, making them potential candidates for various wearable electronics applications. To develop a high-performance, flexible capacitive material with improved interfacial connections, we investigated the in-situ growth of MnO2 on flexible carbon fibre substrates at different temperatures. Our results indicated that the highest specific capacitance values for deposition durations of 8h at 80C on Ni-coated cotton fabric and 24h at ambient temperature on carbon fibre were 247F/g and 174.5F/g, respectively. The XPS analysis confirmed the successful synthesis of MnO2 on the carbon substrate, providing valuable8 insights into the material's electronic structure, redox processes, and stability under various conditions. Research findings contribute to overcoming the difficulties posed by weak interfacial contacts in flexible electroconductive fibres and capacitive materials for energy storage applications. These findings pave the way for future optimisation efforts and broaden the applicability of MnO2-based materials in flexible supercapacitor devices, wearable electronics, and other emerging applications requiring transportable and adaptable energy storage systems with robust interfacial connections.

Date of Award	1 Aug 2024
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Xiaogang Chen (Supervisor), Ping Xiao (Supervisor) & Xuqing Liu (Supervisor)