Analysis of Li-Ion Battery Joining Technologies*

Wayne Cai, Ph.D.Manufacturing Systems Research Laboratory

General Motors Global R&D CenterWarren, MI, USA

wayne.cai@gm.com

International Battery Seminar and ExhibitMarch 21, 2017

* W. Cai, B. Kang, and S.J. Hu, (2017), Ultrasonic Welding of Lithium-Ion Batteries, ASME Press* W. Cai, (2016), Lithium-ion Battery Manufacturing for Electric Vehicles: A Contemporary Overview, in Advances in Battery Manufacturing, Service, and Management Systems (eds J. Li, S. Zhou and Y. Han), John Wiley & Sons, Inc., Hoboken, NJ, USA.

mailto:wayne.cai@gm.com

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Outline

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1. BATTERY ELECTRIC VEHICLES2. LI-ION BATTERY CELLS, MODULES AND PACKS

1) Formats of Li-ion Battery Cells2) Battery Modules and Pack

3. JOINING TECHNOLOGIES FOR BATTERIES 1) Ultrasonic Metal Welding2) Resistance Welding3) Laser Beam Welding4) Wire-bonding5) Mechanical Joining

4. BATTERY MANUFACTURING: THE INDUSTRIAL LANDSCAPE1) Cell Manufacturing2) Module Assembly (Cell-to-Cell)3) Pack Assembly (Module-to-Module)

5. CONCLUSIONS

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1. Battery Electrical Vehicle Landscape

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Updated 3/30/2015

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1. Battery Electrical Vehicles

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Chevy Volt

Source: Google images

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Hierarchy of Battery Pack Manufacturing

Electrodes-to-Tab

Joining Processes of Battery Pack

Cell Level

Module-to-Module

Module Level Pack Level

Case(Sealing) Cell-to-Cell

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2. LI-ION BATTERY CELLS, MODULES & PACKS

Cylindrical Cells(1) The cylindrical cells are known to be less volumetric efficient than prismatic cells, but were the first format of li-ion cells

(2) 18650 cylindrical cells are used in Tesla’s electric vehicles

(3) PTC, or Positive Temperature Coefficient, is a type of material that demonstrates significantly high electrical resistivity at high temperatures so as to melt the PTC itself to break the circuit at higher electrical current.

(4) CID, or Current Interrupt Device, is another passive device that breaks when the pressure inside a cell reaches high levels. Normally, when the cell is overheated, such as in a thermal-away, the pressure increases to a level to break the CID and thereof the circuit.

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2. LI-ION BATTERY CELLS, MODULES & PACKS

Prismatic Cells

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2. LI-ION BATTERY CELLS, MODULES & PACKS

Pouch Cells

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highly conductive materials

thin, multi-layer materials

dissimilarmaterials

100% reliability

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3. JOINING TECHNOLOGIES FOR BATTERIES

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3. JOINING TECHNOLOGIES FOR BATTERIES

Ultrasonic Welding

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3. JOINING TECHNOLOGIES FOR BATTERIES

Ultrasonic Welding

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3. JOINING TECHNOLOGIES FOR BATTERIES

Ultrasonic Welding

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3. JOINING TECHNOLOGIES FOR BATTERIES

The Ultrasonic Bonding Mechanisms

A combination of the following four mechanisms may attribute to the bonding: (a) micro-melting (e.g., a few microns of thin interface layer melting), (b) metal interlocking (due to plastic deformation, particularly the severe

deformation caused by sonotrode knurls), (c) atomic diffusion, and (d) metallic bonding

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Chevy Volt Ultrasonic Welding:between battery tabs and the interconnect bus bar

15http://insideevs.com/2013-chevy-volt-battery-

pack-and-drivetrain-disassembly-video/

B.S. Kang, W. Cai, and C.A. Tan, “Dynamic Stress Analysis of Battery Tabs under Ultrasonic

Welding,” ASME Journal of Manufacturing Science & Engineering, 136(4), 041011 (May 21, 2014).

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3. JOINING TECHNOLOGIES FOR BATTERIES

Ultrasonic Welding Quality Prediction #1: Temperatures and Bonding Quality

The finding: preheating enhances the bonding quality

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3. JOINING TECHNOLOGIES FOR BATTERIES

Ultrasonic Welding Quality Prediction #2: Fracture

Fractures of the top layers should be avoided

Simulated deformation as compared with the experimental results

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3. JOINING TECHNOLOGIES FOR BATTERIES

Ultrasonic Welding Quality Prediction #3: Vibration

Cautions should be exercised to void damage from vibrations

GM Confidential

Interconnect (Cu)

Tab 3 (Cu) Tab 2

Tab 1Tab 4

Tab 5Tab 6 (Al)

existing welds Anvil

Active welds

Sonotrode

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3. JOINING TECHNOLOGIES FOR BATTERIES

Resistance Spot Welding

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3. JOINING TECHNOLOGIES FOR BATTERIES

Laser Beam Welding

Laser Braze-Welding

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BMW i3: Laser Welding

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3. JOINING TECHNOLOGIES FOR BATTERIES

Wire-bonding

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3. JOINING TECHNOLOGIES FOR BATTERIES

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3. JOINING TECHNOLOGIES FOR BATTERIES

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4. BATTERY MANUFACTURING: THE INDUSTRIAL LANDSCAPE

Cell Manufacturing

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4. BATTERY MANUFACTURING: THE INDUSTRIAL LANDSCAPE

List of battery cell components requiring joining

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4. BATTERY MANUFACTURING: THE INDUSTRIAL LANDSCAPE

Welding occurs for the following four scenarios in a battery cell

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4. BATTERY MANUFACTURING: THE INDUSTRIAL LANDSCAPE

Module Assembly (Cell-to-Cell)

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Conclusions

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Thank You!

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