Correlation Between Heat Production and Strain in Lithium-Ion Battery Separator Layers Daniel Bautista, Alex Francis, Mason Pingel, Michael Powley and Dr. Ilya Avdeev

Motivation 2013 Tesla Model S 2011 Chevy Volt

Motivation 2013 Tesla Model S 2011 Chevy Volt

Design of a battery pack with predictable response to crash Motivation Design of a battery pack with predictable response to crash

Previous Research Cross section Surface view Before compression After compression

100 6P Li-Ion Battery Separators Sample

Compression Test Setup

Compression Test Methods Four different samples of 100 layers of Li-Ion separator layers. Loaded at four different load levels Yield 45,000N 30,000N 15,000N

Load vs Extension Results Sample 1 -- Yield Sample 2 – 45,000N Sample 3 – 30,000N Sample 4 – 15,000N

Combined Stress-Strain Results

Determining Change in Resistance 𝑅= 𝑅 𝑒 𝜏𝑙 Φ𝐴 ∆𝑅= 𝑅 0 1−𝜀 𝛼+1 1−𝜀/ Φ 0 𝛼 −1 𝜏= Φ 1−𝛼 Cathode R R R R R Anode

Resistance Scenerios Three main cases that can take place at different parts of the impacted cell.

Objectives Pack Level Cell Level Laminate Level Explicit dynamic FEA Parametric design Multiphysics Enclosure design Cooling Cell design Jelly-roll vs. pouch Connectors Stresses/strains Energy balance Electric shorts

Impact Test Setup Drop cart weight Custom designed drop-test apparatus Height: 2.8 m Impact velocity: 7.4 m/s Impact tests: Lateral test Lateral using rigid bar Axial test Drop cart weight 11.34 and 22.68 Kg

Layered Model

Cell/Unit model progress Thermal Solution Mechanical Loads Electric Load History Electro-Chemical Model Thermo-Mechanical Model Strain Stress Temp. Current Output Solution File Sequential Incremental Coupling

Thermal Model Review: Heat generation models Thermal properties Deformed cell model development Thermal simulation: transient charge

Irregular Temperature Distribution Time 30 s 145 s

References Gilaki, M., & Avdeev, I. (2016). Impact modeling of cylindrical lithium-ion battery cells: a heterogeneous approach. Journal of Power Sources, 328, 443-451. Gilaki, Mehdi, Alex Francis, Daniel Bautista, and Ilya Avdeev. "Progress Toward Understanding Catastrophic Failure of Electric Vehicle Li-Ion Batteries: Multi-Physics Modeling."Volume 14: Emerging Technologies; Materials: Genetics to Structures; Safety Engineering and Risk Analysis (2016): n. pag. Web. J. Cannarella, C. B. Arnold, Ion transport restriction in mechanically strained separator membranes, Journal of Power Sources 226 (2013) 149-155