Multifunctional carbon fibres for battery electrodes

Research Project, 2022 – 2025

Multifunctional composites with ability to simultaneously store and deliver electrical energy while carry mechanical loads have been coined as “structural batteries”. The concept is to employ carbon fibres for mechanical performance and as electrodes, and to use a lithium ion conductive structural battery electrolyte matrix.  The dual functionality obviously distinguishes structural batteries from conventional Li-ion batteries. For an electric vehicle (car, ship, aircraft) the real engineering innovation is the possibility to entirely avoid the parasitic (heavy and spacious) batteries pertinent to traditional battery technology, such that the energy storage function is performed rather by the car body, the boat hull or the aircraft fuselage. Therefore, the structural battery design is often referred to as massless energy storage. Clearly, energy efficient designs meeting the demands on larger payloads and/or higher performance of electric vehicles can be met only if the lightweight solution is combined with a matching energy storage capability.

Current structural battery composites utilize commercially available carbon fibres. To date, no attempt to design and make multifunctional CF for structural battery electrodes, or fibre electrodes for that matter, has been made. We seek to close this gap. In collaboration with Deakin University, at their pilot plants for precursors and CF manufacture at Carbon Nexus, we aim to demonstrate carbon fibres with unprecedented multifunctional properties.

We propose development of a new type of multifunctional carbon fibre for use as negative electrode in structural battery composites. Modifying the process conditions in the different stages of the carbon fibre production line at Carbon Nexus at Deakin University, tailor-made carbon fibres with desired crystal size and orientation as well as chemical composition will result. Altering dwell times, temperature and tension in the different stages of the process carbon fibres with small crystals and high amounts of nitrogen atoms in their preferred state for high electrochemical capacity, and crystal orientation and size for the desired elastic modulus and strength will be made. The fibre’s microstructure and chemical composition will be characterized using state-of-the-art methods, like atomic probe tomography for analysis of the nitrogen content in different regions of the fibre and XPS or Hard X-ray photoelectron spectroscopy (HAXPES) to measure the chemical states of the nitrogen. High-resolution TEM will be used to determine orientation and size of the crystals. The multifunctional properties of the carbon fibres will then be measured in a set-up allowing for combined galvanostatic cycling and tensile loading of the fibre tow. Finally, interfacial treatments for improved interfacial strength and SEI control will be pursued and ranked for their performance.