An Experimental and Computational Study on the Orthotropic Failure of Separators for Lithium-Ion Batteries

Marian Bulla,Elham Sahraei,Stefan Kolling

doi:10.3390/en13174399

Abstract

In the present study, the mechanical properties of a dry-processed polyethylene (PE) separator are investigated in terms of deformation and failure limits. The focus is set on the anisotropic mechanical behavior of this material. A deeper understanding of the damage mechanism is important for further safety and crashworthiness investigations and predictions of damage before failure. It has been found that separator integrity is one of the crucial parts in preventing internal short circuit and thermal runaway in lithium-ion (Li-ion) batteries. Based on uniaxial tensile tests with local strain measurement, a novel failure criterion for finite element analysis (FEA), using the explicit FEA solver Altair Radioss, has been developed to predict the effect of high mechanical loads with respect to triaxiality, large plastic strain and orthotropy. Finally, a simulation model of a PE separator was developed combining the novel failure criterion with Hill’s yield surface and a Swift–Voce hardening rule. The model succeeded in predicting the anisotropic response of the PE separator due to deformation and failure. The proposed failure model can also be combined with other constitutive material laws.

Highlights

In recent years, the automotive market has been pushed to reduce CO2 emissions significantly and to ramp up their efforts to develop and produce electric-powered drivetrains
Finite element modeling (FEM) has been used extensively for many years to study the crashworthiness of vehicles, resulting in the development of many concepts for damage and failure criteria
The proposed new failure criterion predicted the failure strain for all three directions within a range of 3% and was in a very good agreement with the performed tests

Summary

Introduction

The automotive market has been pushed to reduce CO2 emissions significantly and to ramp up their efforts to develop and produce electric-powered drivetrains. The best industrial energy storage method is the lithium-ion (Li-ion) battery, which is already widely used in the consumer electronic industry (e.g., cellphones and computer laptops). The Li-ion cell is seen as the most promising energy storage source currently commercially available [2]. With the increasing use of batteries in those devices and vehicles, safety has become an issue due to inadvertent failures. Finite element modeling (FEM) has been used extensively for many years to study the crashworthiness of vehicles, resulting in the development of many concepts for damage and failure criteria

Methods

Results

Discussion

Conclusion