Session: 09-01-01: Electrochemical Energy Storage and Conversion Systems I

Paper Number: 165792

Electrochemical Model Based Degradation Analysis of a Lithium Ion Battery Using Computation Fluid Dynamics Tools 

Lithium-ion batteries have achieved ubiquitous acceptance within our lives for their usefulness in various everyday household and personal objects. From cell phones, laptops, and smart watches to the emerging markets for hybrid electric and all electric vehicles, a wide range of chemistries have been developed for Li-ion batteries that have different tradeoffs on their capacity and cycle life, among many other characteristics. One such chemistry that has gained widespread acceptance within industry is Lithium Iron Phosphate (LFP) used as an active cathode material. Having become a major player in such wide-ranging applications as Electric Vehicles (EVs) and consumer electronics, the need to understand how this battery chemistry performs over its entire life cycle is increasing.

With consumers often expecting the lifespan of a new vehicle to be in the range of 10-15 years, it becomes apparent that understanding how to model and predict the health of a battery is ever increasingly important. Furthermore, it is also necessary to consider the thermal aspects of a lithium-ion battery module as a major factor that impacts the safety of applications utilizing these systems. There are numerous ways to approach the challenge of modelling all these different characteristics, each with their own benefits and drawbacks. From empirical and numerical approaches to models that derive underlying physics and electrochemistry, the choice of model needs to be weighed in carefully.

 

Electrochemical models seek to describe the kinetic and transport phenomena that are going on “under the hood” of a lithium-ion battery in the hope that more accurate results are achieved than a model employing a numerical or empirical approach. Often incorporating and building off the Butler-Volmer equation, numerous different takes on this style of electrochemical model have been formulated. One such model is the pseudo-two-dimensional (P2D) model developed by Doyle, et al. [1]. This physics-based approach is commonly used and has been widely accepted and iterated on.

In this study, we have utilized electrochemical modeling capabilities of the computational fluid dynamics (CFD) program FLUENT for lithium-ion batteries. Among the many capabilities that Ansys FLUENT provides are battery pack and module thermal management simulations and battery cell and electrode simulations utilizing physics-based approaches. We developed an LFP battery electrochemical model within Ansys FLUENT that is compatible with the internal MSMD solution method. The model utilizes a 14.6 Ah LFP pouch cell designed to be compatible with FLUENT meshing. After meshing, various cases were simulated for the hypothetical cell, including various C-rates at single cycles and utilizing the cell aging mechanisms or degradation models that include solid-electrolyte interphase (SEI) layer growth and irreversible lithium plating [2].

This study demonstrated the development of an LFP cell that was modelled using Ansys FLUENT in order to solve the physics-based Newman P2D electrochemical model equations and incorporated degradation mechanics for SEI layer deposition and lithium plating. Simulation run on the developed CFD model simulated the thermal and electric characteristics of this cell at 0.5, 1, and 2 C rates. This model was then simulated with the addition of the degrading side reactions. Metrics for state of charge, cell voltage, cell temperature, and lithium concentrations were captured and shown to be consistent.

 

1.       M. Doyle, T. F. Fuller and J. Newman. “Modeling of Galvanostatic Charge and Discharge of the Lithium/Polymer/Insertion Cell”. J. of Electrochemical Soc.. Vol 140, No. 6. 1526-1533. 1993.

2.       Sohel Anwar and Ali Amini, “Development of Real-Time Algorithms for Diagnostics, Prognostics, and Fast Charging of Li-Ion Batteries for Electric Cars”, TUBITAK Sabbatical Report, Ankara, Turkey, 2023.

Presenting Author: Jonathan Bowyer Purdue University

Presenting Author Biography: Jonathan Bowyer received his MSME degree in Mechanical Engineering from Purdue University in 2024. His research focused on the degradation modeling of Lithium-Ion batteries. He is currently working with Rolls Royce Corporation in Indianapolis.

Authors:

Jonathan Bowyer Purdue University
Sohel Anwar Purdue University in Indianapolis