Probing Heterogeneity in Li-Ion Batteries with Coupled Multiscale Models of Electrochemistry and Thermal Transport using Tomographic Domains

T G Tranter,A Jnawali,S J Chapman,M D R Kok,V Sulzer,S G Marquis,R Timms,C P Please,D J L Brett,T M M Heenan,P R Shearing

doi:10.1149/1945-7111/aba44b

Abstract

This work presents a methodology for coupling two open-source modelling frameworks in a highly parallel fashion across multiple length scales to solve an electrical current and heat transport problem for commercial cylindrical lithium-ion batteries. The global current and heat transfer problems are formulated as resistor networks and solved using a finite difference method on a network extracted from an X-ray tomogram of an MJ1 18650 battery. The electrochemistry governing the heat generation is solved at the local level using a physically parameterized model. Electrochemical models are solved for different regions of a spirally wound cylindrical cell in parallel, coupled via charge conservation at the current collectors in a “battery of batteries” fashion, similar to the concept of modelling a pack. Thermal connections between layers in the spiral winding are established and heat transport is solved globally in a two-dimensional fashion, allowing for the subsequent extension to three dimensions. Great heterogeneity in local current density is predicted by the model which is also found to have some temperature dependence with ramifications for battery degradation.

Highlights

IntroductionUnder conditions of abuse, the Lithium-ion batteries (Li-ion) battery may experience temperature sufficient to trigger catastrophic uncontrolled reactions, termed thermal runaway
At the largest length scale, battery management system (BMS) models typically employ resistor-capacitor networks that can replicate the behavior of hundreds and even thousands of cells forming battery packs used in electric power trains and other systems.[28]
The number of tabs is varied with the base cases having an inner positive tab and outer negative tab (A—E), this is true to the real MJ1 structure

Summary

Introduction

Under conditions of abuse, the Li-ion battery may experience temperature sufficient to trigger catastrophic uncontrolled reactions, termed thermal runaway. These events can trigger levels of degradation in the cell that are so severe that shortcircuiting and exothermic electrolyte decomposition occur, potentially leading to cell ruptures and explosions. Under these conditions, the thermally insulating nature of the materials used as electrodes and separators, and geometrical configurations that place large portions of the cell away from any heat sinks may exacerbate the thermal runaway and reduce the temperature range over which batteries may safely operate.[13,14,15,16,17,18,19,20]. With definition of the appropriate boundary conditions at the particle level, it is possible to approximately model cell thermal transport over time with a lumped approach, but information is averaged and cell-level design features such as the placement of current collector tabs, that can transport both current and heat, are not resolved

Methods

Results

Conclusion