Lithiation induced interfacial debonding in carbon fiber structural battery composites

This paper investigates the interfacial debonding along the fiber-electrolyte interface induced by fiber lithiation in carbon fiber structure batteries using a shear-lag model, with the model validated through finite element simulations. The results demonstrate that as lithiation progresses, the interface transitions from a purely elastic state to a cohesive damage phase, ultimately leading to interfacial debonding. Once debonding initiates, cracks propagate rapidly along the fiber-electrolyte interface, impeding ion and electron transport and significantly degrading the electrochemical performance and load-bearing capacity of the battery. To mitigate interfacial debonding, this study systematically examines the impacts of electrode length, modulus of carbon fiber and solid-state electrolyte, and cross-sectional size ratio. The findings indicate that electrode length and carbon fiber modulus have limited impacts on interfacial debonding, while reducing the modulus of solid-state electrolyte effectively decreases shear stress at the interface, thereby inhibiting debonding. Furthermore, a smaller cross-sectional size ratio alleviates interfacial stress, reducing the possibility of debonding. This research offers theoretical insights for the design of carbon fiber-based batteries, particularly in enhancing their structural stability and performance under electromechanical coupling environment.