Review of Capacity Fade Models for Lithium-ion Batteries -- Effect of Mechanisms on Numerical Implementation

Abstract

Lithium-ion battery applications, such as EVs and PHEVs, require long battery life. However, capacity fade always occurs due to unwanted side reactions including electrolyte oxidation at the positive electrode, lithium deposition at the negative electrode, electrolyte decomposition processes, and the formation of the Solid-Electrolyte Interphase (SEI) layer[1]. To simulate the capacity fade, different models have been proposed in the literature[2-4]. In this work, we model the capacity fade by assuming the SEI layer formation to be the dominant mechanism. Even among SEI layer models, several different expressions have been used in many papers[5-8]. In most cases, the solid particles are assumed to be spherical, and the intercalation process is modeled using Fick’s law of diffusion in the radial direction. In this work, the SEI-forming side reaction based on the Single Particle Model (SPM) is studied. Three models are compared with different charging rates cycling study. For solving the solid-phase diffusion in the radial-dimension, many efficient mathematical algorithms of reformulation and simulation have been proposed in the past[9-12]. We address how those different SEI layer growth expressions affect the numerical implementation stability. The partial differential equations of the SPM are discretized using the finite difference method in the radial direction and solved in time using the numerical method of lines approaches.