Electro-chemo-mechanical coupling in structural lithium-ion batteries: Experimental findings and numerical modelling

Structural batteries offer a promising route to reduce weight and volume in electrified systems by combining energy storage and mechanical functionality within a single composite material. However, understanding and quantifying the coupled electro-chemo-mechanical behaviour of such multifunctional materials remains a critical challenge, particularly at the level of full cell composites under mechanical load. Here, we present an integrated experimental–computational framework to capture voltage–strain coupling in laminated structural battery full cells composed of commercial lithium iron phosphate based positive electrodes, carbon fibre negative electrodes, and a phase separated structural battery electrolyte. To interpret the experimental findings, we extend a continuum multiphysics model that captures the coupled chemo-mechanical behaviour of both electrodes, including a homogenised formulation for the lithium iron phosphate cathode. The model accurately reproduces the experimental potential shifts and identifies the carbon fibre electrode as the dominant contributor to the voltage–strain response. Notably, the weak coupling observed in the particle-based positive electrode provides critical insight into the electro-mechanical behaviour that can be expected in solid-state batteries employing similar cathode architectures. These findings offer a mechanistic understanding of stress–voltage interactions in structural battery systems and contribute to the broader knowledge base needed to advance structurally integrated energy storage technologies.