Multi-scale modeling and performance study of carbon fiber heterogeneous electrode batteries based on electrochemical-mechanical coupling

Structural batteries with carbon fiber electrodes are designed to simultaneously withstand mechanical loads and store electrical energy. Conventional carbon fiber electrode battery models have adopted the P2D Newman model, which underestimates the impact of microscopic electrode structures on the electrochemical and mechanical behavior of the battery. This study proposes a multiscale electrochemical-mechanical coupled battery model based on the heterogeneous electrode geometry. This model better captures the microscopic structural details of the carbon fiber electrode. Based on this heterogeneous electrode model, the electrochemical performance of the structural battery can be visualized at the macroscale. At the microscale, the impact of diffusion-induced stresses resulting from electrochemical reactions on the microscopic electrode and battery porosity is investigated. The results show that the carbon fiber crenulations are more prone to high current density and high strain values compared to the carbon fibers themselves. Due to differences in diffusion and anisotropy, the axially stacked carbon fibers exhibit higher lithium concentration and induced stresses than the radially stacked ones. This multiscale coupled model can more comprehensively describe the complex electrochemical and mechanical behavior of carbon fiber batteries, providing a theoretical basis for optimizing the design of carbon fiber batteries.