New Multifunctional Thermoplastic Polymer Nanocomposites for Structural Power Materials, Towards Green Aviation

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The transport sector is a significant contributor to greenhouse gases, and electrification of these systems would undoubtedly help to decarbonize the atmosphere. This is where we enter the exciting field of 'Structural Power Composites' which act as both structural materials and energy storage devices. The Imperial College London Structural Power Composites group has already made significant progress in the development of structural supercapacitors. These typically utilize an electrolyte that is made by mixing an epoxy with an Ionic Liquid (IL), however, issues at the microstructural level persist whereby carbon fibers are being sheathed by the structural phase of the electrolyte. Improving the structural electrolyte is still one of the biggest challenges associated with the field. This is because materials with high ionic conductivity typically have poor mechanical performance and vice-versa, so it is difficult to obtain a good balance between the two.The primary aim of this research is to extend the work done on structural supercapacitors by incorporating thermoplastics (TPs) into the electrolyte with the ultimate goal being to improve both the mechanical and electrochemical performance of these devices. Other benefits of using TPs include: higher toughness, improved recyclability and higher chemical stability. Some of the questions that the project intends to answer are: What TPs are suitable to be used in structural electrolytes? Can the use of TPs offer benefits such as lighter-weight energy storage devices? Can structural supercapacitors be manufactured at a lower cost and at a larger scale using TPs in the electrolyte? Can we recycle TP-based structural electrolytes? The main strategies that will be employed are: i) blending TPs with ionic liquids or ii) backfilling porous TPs with liquid electrolytes like aqueous electrolytes, ionic liquids, lithium salts solutions. The first stage of the project will be to select suitable high-performance thermoplastics (HPTPs) based on a few criteria such as the 'glass transition temperature', 'melting temperature', and 'price per unit mass'. The objective will be to conduct solubility tests of these TPs in the ionic liquids, initially qualitatively by observing the behavior when mixing the two together and then quantitatively. The KAT polarity scale is essentially a system that depicts solvent properties using polarity, acidity, and basicity and can be used to quantify the solubility of a TP in an ionic liquid. These KAT parameters for HPTPs are not widely available in the literature and so this research project aims to find and publish them for the wider scientific community. After obtaining the KAT parameters for some common HPTPs, systematic work will be done to build, for the first time, bi-phasic phase diagrams for different HPTP/IL systems. These essentially show how different combinations of HPTPs and IL interact with each other. HPTPs are typically processed at high temperatures which could cause complications when blending the HPTP with the IL, due to possible degradation of the latter. It will therefore be important to study the processing window of the shortlisted HPTPs experimentally, to narrow down the search for the optimal structural electrolyte. After finalizing the possible candidates of HPTPs and ILs, the next objective will be to optimize the structure of the HPTP and IL blends such that they are thoroughly mixed and interconnected. The morphologies obtained will be studied by 'Scanning Electron Microscopy' and the full mechanical and electrochemical properties of the structural electrolyte will be investigated. In conclusion, opening the research on structural electrolytes to TPs could potentially revolutionize the field, bringing us one step closer to greener, more sustainable aviation.