Investigating the Factors Affecting the In-Plane Tortuosity of Porous Graphite Electrode in Lithium-Ion Batteries

Due to the anisotropic nature of porous graphite electrodes composed of flake-like particles, it is crucial to determine both in-plane and through-plane tortuosity. These parameters are essential for the optimal design of three-dimensional structured electrodes, the validation of tomography-based image-driven numerical simulations, to understand the phenomenon of electrolyte motion-induced salt inhomogeneity (and associated capacity loss) in the case of cylindrical cells, and to accurately predict the edge-driven degradation in the overhang region. While through-plane tortuosity is explored in depth along with its dependence on various parameters like binder content, electrode porosity, particle shape, size distribution, etc, the literature is lean with the studies regarding the dependence of in-plane tortuosity on these parameters. This paper explores the dependence of the in-plane tortuosity of electrodes on the PVDF binder content, shape of particles (active material), and porosity. For PVDF binder content, the in-plane tortuosity follows the same trend as through-plane tortuosity (i.e., an increase in binder content increases tortuosity). Interestingly, for the chosen electrode with PVDF binder, the in-plane tortuosity decreases with calendering, unlike through-plane tortuosity (i.e., increase in through-plane tortuosity with calendering). Additionally, we extend the method to systems that are not strictly blocking (i.e., in the presence of side reactions).