Modeling the Effects of Electrode Microstructural Heterogeneities on Li-Ion Battery Performance and Lifetime

Abstract

Local variations of mechanical, structural, transport, and kinetic properties, referred to as heterogeneity can detrimentally affect battery life and performance. Local heterogeneity results in non-uniform current, temperature, state of charge (SOC), and aging. In this work, we introduce a model that combines Newman-type and equivalent circuit submodels to further understand and quantify the effects of electrode inhomogeneities. For modeling purposes, three regions of different microstructural properties are connected in parallel, to represent measured electrode heterogeneity. Multiple cases of heterogeneities, such as non-uniform ionic resistance and active material loading, are studied at different rates of discharge and charge. The results show that higher rates increase non-uniformities of dependent properties such as temperature, current density, positive and negative electrode states of charge, and charge and discharge capacities, especially in the case of charging. In addition, by calculating the overpotential on the negative electrode, it is shown that lithium could plate non-uniformly on the negative electrode during high rates of charge. Finally, a sensitivity analysis is performed to understand the significance of heterogeneity on different properties.