Theses

Structural batteries are a class of structural power composites capable of storing electrochemical energy while simultaneously bearing mechanical load. This novel technology offers the potential for “massless” energy storage, in which the structural components of a vehicle or aircraft also function as the battery itself. These multifunctional systems may have the potential for significant benefits in energy efficiency, range, and weight reductions. However, to realise these advantages, an improved understanding of the coupled electro-chemo-mechanical behaviour of constituent materials and scalable methods for manufacturing integrated battery structures are required.

This thesis has addressed these challenges through three interconnected research strands. The first part of the thesis investigated the multifunctionality of carbon fibre anodesusing in situ and in operando synchrotron X-ray diffraction. These studies establisheda direct link between lithium intercalation and atomic-scale expansion within the carbon fibre lattice. Interlayer spacing in the [002] direction expanded during lithiation and contracted upon delithiation, while in-plane expansion along [100] was smaller but followed a similar trend. When mechanical tension was applied during charging, the [002] spacing contracted and only partially recovered upon unloading, revealing a strong coupling between electrochemical and mechanical responses. The second part focused on developing scalable electrode and separator coatings compatible with continuous fibre manufacturing. Electrophoretic deposition was shown to produce broadly uniform LFP coatings on carbon fibres, and a reel-to-reel coating system was developed to demonstrate process scalability. Dynamically coated electrodes exhibited greater long-term stability and lower overpotentials than static coatings, despite slightly reduced capacity. Electropolymerisation was explored as a method for producing thin, conformal separator coatings directly onto electrode surfaces. These coatings maintained electrochemical functionality with minimal performance loss relative to uncoated fibres. Dual-layer electrodes were produced, that successfully demonstrated integrated functionality, though with increased resistance due to the separator layer. Additionally, the incorporation of a solid biphasic electrolyte achieved comparable electrochemical performance to liquid systems, suggesting promise for lightweight, solid-state structural battery configurations.

Together, these results provide a clear pathway toward scalable, multifunctional manufacturing processes for structural battery components.iv The final part of the thesis demonstrated a proof-of-concept full-cell, combining dynamically coated LFP cathodes with EP-coated carbon fibre anode–separator systems. The assembled cells exhibited measurable electrochemical performance and revealed key insights into interfacial and separator behaviour. Notably, the presence of an effectively double separator layer increased internal resistance and overpotential, underscoring the crucial role of separator design in overall cell performance. Attempts to remove the glass fibre separator led to immediate short-circuiting, confirming that the EP coating alone was not yet sufficient as a standalone separator. Nonetheless, achieving such functionality would represent an exciting step toward fully intermingled, separator-free structural battery architectures.