Fabrication and multiphysics modeling of modified carbon fiber as structural anodes for lithium-ion batteries

The structural battery is a type of multifunctional battery that possesses energy storage and load-bearing capability simultaneously. Carbon fibers (CFs) serve as promising electrode materials used in structural batteries. However, most of the structural batteries and the corresponding component materials are fabricated unguided due to the lack of a full understanding of the multiphysics nature. Herein, we fabricated surface-modified CFs and investigated the electro-chemo-mechanical behaviors of the structural lithium-ion battery through a multiphysics modeling methodology. A two-dimensional multiphysics model is established by detail description of anode, cathode, separator, and electrolyte. The model is then validated comprehensively by the testing data from the fabricated cells with modified CFs as electrodes. We discover that with the higher volume fraction of modified CFs, the battery capacity increases without deteriorating the stress status; meanwhile, independently increasing the ratio of the modified layer on CFs leads to a higher specific capacity but lower stiffness. With the appropriate ratio of the modified layer controlled during fabrication, the modified CFs can achieve a specific capacity of 216 mA h/g and tensile stiffness of 138.8 GPa. Results provide theoretical insights for understanding the multiphysics nature and powerful modeling tool to the design of next-generation structural batteries.