In this work, we introduce a computationally efficient Newman-type model to further understand and quantify the effects of local inhomogeneities, particularly non-uniform ionic and electronic impedance. As shown in Fig. 1, we imitate the real heterogeneity of the cell by a system consisting of three localized Li-ion domains, each with specific properties ion-transport associated with “cold” (high tortuosity and low porosity [2]), “middle” (moderate tortuosity and porosity), and “hot” (low tortuosity and high porosity) spots. The properties for each of the domains are obtained experimentally through a combination of SEM/FIB and localized conductivity measurements. The three simulated domains are treated as separate cells electrically connected in parallel. This approach can simplify mathematical treatment and significantly reduces intensive computation requirements needed for true 3D modeling.
[1] M.M. Forouzan, C.-W. Chao, D. Bustamante, B.A. Mazzeo, D.R. Wheeler, Journal of Power Sources, 312 (2016) 172-183.
[2] M.M. Forouzan, M. Wray, L. Robertson, D.R. Wheeler, J. Electrochem. Soc., 164 (2017) A3117-A3130.
Figure 1: Heterogeneity of the NMC electrode using SEM/FIB images and equivalent circuit used in the Newman-type model.