Modeling and Simulation of Fiber-Based Electrodes for Li-Ion Batteries

Abstract

Fiber-based electrodes represent viable solutions for high-performance and multifunctional batteries. Thanks to the establishment of production techniques such as electrospinning, batteries can nowadays be devised using a fiber-reinforced composite material in which active and conductive material fibers are dispersed in a solid polymer electrolyte matrix.In order to maximize the active material utilization in fiber-based electrodes, the most suitable fiber arrangement can be identified so that internal pathways for electrons and ions are ensured. In particular, the optimal mixture of fibers (active and conductive) and electrolyte in structural batteries is a compromise between several requirements. First, conductive fibers have to form a conductive network for electrons. Second, the space left for the active material must be sufficient to guarantee a reasonable energy storage capacity. Third, mechanics requires enough fibers to attain a specific load bearing capacity without additional electrochemically-inactive reinforcement. Fourth, the solid polymer electrolyte must provide mechanical connection between fibers and, at the same time, the path for ionic conduction. The electrode design-battery performance relationship is investigated by means of numerical simulations. Three-dimensional composite structures are generated by randomly distributing fibers in the electrolyte hosting matrix. Effective electrode properties and charge/discharge performance are evaluated by means of Monte Carlo and finite element simulations. To ease the generation of the finite element mesh, fibers are reduced to mathematically equivalent one-dimensional objects using a mesh-independent embedded fiber method. In the numerical simulations, results of the dimensionally-reduced model are validated against reference finite element solutions.