Morphology design of carbon fiber cathodes for high electrochemical and mechanical performance in structural battery composites

Functionalized carbon fibers have the potential to serve as effective conductive electrodes while maintaining their role as reinforcements in structural battery composites. In this study, we developed LiFePO 4 (LFP)-based carbon fiber cathodes for structural Li-ion battery composites using an electrostatic assembly of active materials combined with an electrophoretic deposition (EPD) process. This work investigates how carbon fiber cathode morphology influences electrochemical and mechanical performance. The optimized cathode, composed of sub-micron LFP particles, 3 wt% carboxyl-functionalized carbon nanotubes (CNT), and polyvinylpyrrolidone (PVP) as the binder deposited on carbon fibers, achieved a specific capacity of 134 mAh/g at 0.1 C and retained 96 % after 200 cycles. The morphological features of the coated cathode including particle size, coating thickness, interfacial surface area, and conductive network design were found to significantly contribute to the interfacial mechanisms by altering charge transfer resistance, Li-ion diffusion pathways, and active material utilization, as well as load transfer across the interface. The CNT network demonstrated a robust conductive framework that mitigated electrochemical stress and prevented particle isolation during cycling. The insights gained from this research advance materials development and scalable processing methods for carbon-fiber cathodes, enabling high energy density and superior mechanical performance in structural battery applications. • Electrophoretic deposition creates uniform LFP-PVP-CNT coatings on carbon fibers. • Small-particle-thin cathodes deliver 134 mAh/g and 96 % cycling stability. • Optimized morphology balances electrochemical and mechanical performance.