New Reduced-Order Lithium-Ion Battery Model to Account for the Local Fluctuations in the Porous Electrodes

Abstract

Numerical simulations of microscopic transport processes in porous electrodes of lithium‐ion batteries demonstrated presence of spatially localized fluctuations of physical quantities on the microstructure scale that can potentially influence the macroscopic battery characteristics (for example, the degradation rates). These fluctuations can not be captured in a straightforward manner by the widely used cell models based on the porous electrode theory by Newman and coworkers (DFN models). The latter treat the porous electrodes as macroscopically homogeneous composite materials and dramatically reduce the computational costs of battery numerical simulation. In this paper, we propose a modification of DFN model that incorporates the local fluctuations but preserves the computational efficiency. A numerical simulation example is presented that is specifically designed to test the accuracy of the reproduction of the local fluctuations. The main new feature lies in the mathematical representation of the slow transport processes in the active material and their influence on the macroscopic reaction rates. The assumptions used to justify the model originate in the rigorous mathematical analysis of the transition from a microscopic, microstructure‐resolving transport and reaction description to a macroscopic, volume averaging‐based one. The model construction methodology is open for further modifications for the applications in which some of the assumptions should be dropped or description of new processes, reactions, phases, etc. should be incorporated.