Fabrication and multiphysics numerical investigations of carbon fiber structural batteries

The structural battery (SB) that uses carbon fibers as anodes is a lightweight composite material battery integrating load bearing and energy storage. However, during usage, diffusion-induced stress may result in structural failure and a reduction in the battery capacity. In this paper, a laminated structural battery (LSB) was fabricated using carbon fiber cloth as an anode and collector and successfully powered LEDs. Then, based on this laminated structure, a multiphysics field model based on electrochemical-mechanical coupling is established for the analysis of complicated diffusion-induced stresses in carbon fibers. Following this model, researchers investigate the electro-chemo-mechanical behaviors and influencing factors of the SB and compare them with those of the lithium-ion battery (LIB). The results show that diffusion polarization in carbon fibers is aggravated by their lower diffusion coefficient, larger radius, and higher discharge rate; in both types of batteries, there is a higher tensile diffusion stress and a higher probability of failure at the surface of the anode active material than in the interior; a more uniform distribution of diffusion-induced stress on the surface of fibers at different locations; when discharging at a high rate, the SB capacity hardly reduces, and the high strength and relatively low diffusion-induced stress in the carbon fiber make it much safer, showing excellent electrochemical performance and resistance to failure due to diffusion-induced stress. This study demonstrates the feasibility of the fabrication and safety of carbon fiber structural batteries, which may potentially offer recommendations for the fabrication and use of novel SBs.