Compact | Lightweight | Long Lasting
Thermal Management of
Lithium-ion Batteries
APEC 2018
Greg Albright
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Compact | Lightweight | Long Lasting
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
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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-
Compact | Lightweight | Long Lasting
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
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Handbook of Batteries, 3rd Ed. , Linden, Reddy
Positive
Electrode
(cathode)
Negative
Electrode
(anode)
ElectrolyteSe
parato
r
Compact | Lightweight | Long Lasting
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
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18650 Storage
23°C, 50% SOC
23°C, 100% SOC
32°C, 100% SOC
32°C, 50% SOC
Compact | Lightweight | Long Lasting
The Most Important Slide
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▪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
Compact | Lightweight | Long Lasting
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
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https://www.nrel.gov/docs/fy13osti/57747.pdf
Compact | Lightweight | Long Lasting
Example Resistance Graph
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Q = I2R+I*T*dOCV/dT
Temperature Increase
dOCV/dT is the change
of open circuit voltage as
a function of
temperature
Compact | Lightweight | Long Lasting
Example dOCV/dT (Absorb or Release Heat)
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Q = I2R+I*T*dOCV/dT
Compact | Lightweight | Long Lasting
Thermal Runaway Heat Generation
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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
Compact | Lightweight | Long Lasting
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
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Compact | Lightweight | Long Lasting
Comparison of Thermal Management Methods
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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
Compact | Lightweight | Long Lasting
Basic Battery Module
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Cells
Cell Holders
Current Collectors
Space for thermal management
Compact | Lightweight | Long Lasting
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
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Compact | Lightweight | Long Lasting
2D/3D Model
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Input Geometry and Mesh Define Material Properties Define Boundary and Initial
Conditions
Input Heat GenerationOutput Temperature
Compact | Lightweight | Long Lasting
Tesla Serpentine Liquid Cooling
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Cooling Channel
- Water or coolant
mixture
Compact | Lightweight | Long Lasting
Liquid Cold Plate Becoming More Popular
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https://insideevs.com/new-tesla-p100d-battery-pack-conceptualized/
Compact | Lightweight | Long Lasting
Chevy Volt Cooling System
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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/
Compact | Lightweight | Long Lasting
Chevy Volt Coolant Loop
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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