Thermal Management of Lithium-Ion Batteries · Comparison of Thermal Management Methods 15 Thermal...

Compact | Lightweight | Long Lasting

Thermal Management of

Lithium-ion Batteries

APEC 2018

Greg Albright

1


What Are We Talking About?

▪ Maximize Vehicle Range (battery kWh; regen; charge time)

▪ Maximize Performance (power)

▪ Minimize Cost ($/mile)

▪ For as many years as possible

2

Compact | Lightweight | Long Lasting 3

How a Battery Stores Energy

▪Two electrodes separated by an electrolyte

▪During discharge, lithium moves from the negative to positive electrode

▪During charge, it reverses

Positive

electrodeNegative

electrode

ElectrolyteSe

parato

r

Li+

e-


Main Battery Components

▪Negative electrode (anode): graphite, silicon, titanate

▪ Positive electrode: metal oxide (NMC, NCA, LCO, LFP)

▪ Electrolyte: liquid salt solution (flammable!)

▪ Separator – porous plastic

4

Handbook of Batteries, 3rd Ed. , Linden, Reddy

Positive

Electrode

(cathode)

Negative

Electrode

(anode)

ElectrolyteSe

parato

r


Why Does My Battery Die?

▪ Every battery has a lifetime

▪ Calendar life: storage

▪ Cycle life: number of cycles

▪ Unwanted chemical reactions

consume lithium and block its

movement

▪ Try to avoid:

▪ Storing at high temperature and

fully charged

▪ Always cycling the full range (0-

100%)

▪ Power and Energy both fade

5

18650 Storage

23°C, 50% SOC

23°C, 100% SOC

32°C, 100% SOC

32°C, 50% SOC

Compact | Lightweight | Long Lasting 6

5000

vs.


The Most Important Slide

7

▪𝐶 = 𝐶0 − 𝛼𝑡𝑛 − 𝛽𝑄𝑚

▪𝛼 = 𝑘1 ∗ 𝑒𝑥𝑝 −𝐸𝑎

𝑅

1

𝑇−

1

𝑇𝑟𝑒𝑓𝑒𝑥𝑝

𝑎1𝐹

𝑅

1+𝑎2𝑆𝑂𝐶+𝑎3𝑆𝑂𝐶2

𝑇−

1+𝑎2𝑆𝑂𝐶𝑟𝑒𝑓+𝑎3𝑆𝑂𝐶𝑟𝑒𝑓2

𝑇𝑟𝑒𝑓

▪𝛽 = 𝑘2𝐷𝑂𝐷

𝐷𝑂𝐷𝑟𝑒𝑓

𝑏1

▪C – Capacity today

▪C0 – Initial capacity

▪t – time

▪k1, k2, a1, a2, a3, b1, n, m – experimentally fit exponent unique to each cell model

▪Q – Ah throughput for the cell

▪Ea – Activation Energy

▪R, F – Gas constant and Faraday Constant

▪T, Tref – Cell temperature and reference temperature

▪SOC – State of Charge

Calendar fade Cycle fade


Calendar Capacity Loss vs. Temperature

8

90% SOC; NMC 18650


Calendar Capacity Loss vs. SOC

9

45°C; NMC 18650


The Other Most Important Slide (Manage a)

▪ Cell Heat Gen: Q = I2R+I*T*dOCV/dT

▪ R = f(SOC, T, SOH)

▪ dOCV/dT = f(OCV)

▪ I = Current from vehicle drive profile

▪ Other pack components have I2R heating

▪ Current collectors/bus bars

▪ Electronics

10

https://www.nrel.gov/docs/fy13osti/57747.pdf


Example Resistance Graph

11

Q = I2R+I*T*dOCV/dT

Temperature Increase

dOCV/dT is the change

of open circuit voltage as

a function of

temperature


Example dOCV/dT (Absorb or Release Heat)

12

Q = I2R+I*T*dOCV/dT


Thermal Runaway Heat Generation

13

0

100

200

300

400

500

600

700

800

0 200 400 600 800 1000 1200 1400

Tem

pera

ture

(°C

)

Total Test Time (min)

Temperature vs Time ( 2.9 Ah cell)

Cell goes into

thermal runaway


Goals of Thermal Management

▪ Keep Target Temperature Everywhere

▪ Prevent Spread of Thermal Runaway

▪ Keep neighboring cells below ~120°C

▪ Don’t Ruin

▪ Cost

▪ Efficiency

▪ Robustness

▪ Scale

▪ Weight/Volume

▪ Complexity

▪ Supply chain

▪ Safety

14


Comparison of Thermal Management Methods

15

Thermal

Runaway

Thermal

Management

Ambient

Heat

Weight Efficiency Cost Ease of Use Continuous

Liquid

Cooling2 1 1 2 8 4 8 1

Air Cooling 2 8 10 1 7 6 8 3

Potting

compounds or

no cooling2 8 1 5 2 1-8 2 9

PCM –

Phase

change

materials

2 3 2 2 2 5 9 5

1 = Good; 10 = Bad

Air + PCM No Cooling Liquid

*Source: AllCell analysis


Basic Battery Module

16

Cells

Cell Holders

Current Collectors

Space for thermal management


How to Execute Design

▪ Modeling

▪ 0D tells you what you need here

▪ 2D, 3D tells you how to achieve it for all cells

▪ Testing tells you how wrong your models are

▪ Component

▪ System

17


2D/3D Model

18

Input Geometry and Mesh Define Material Properties Define Boundary and Initial

Conditions

Input Heat GenerationOutput Temperature


Test Module/Pack

19


Tesla Model S Battery

20

Source: Elektrek


Tesla Serpentine Liquid Cooling

21

Cooling Channel

- Water or coolant

mixture


Liquid Cold Plate Becoming More Popular

22

https://insideevs.com/new-tesla-p100d-battery-pack-conceptualized/


Chevy Volt Cooling System

23

Cold liquid in

Hot liquid out

Liquid cooling plate goes

between alternating cells

https://insideevs.com/tesla-or-gm-who-has-the-best-battery-thermal-management-bower/


Chevy Volt Coolant Loop

24

Source: http://gm-volt.com/2010/12/09/the-chevrolet-

volt-coolingheating-systems-explained/

Flow Valve Positions

A. Max Heat Loop

B. Max Cold Loop

C. Temp Regulating

C. Temp Regulating

B. Max Cold Loop

A. Max Heat Loop


Thank You

▪ Questions?

▪ Further Reference

▪ https://www.nrel.gov/docs/fy13osti/57747.pdf

25

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