Ultrasonic Welding of lithiUm-ion Batteries
Wayne W. cai
Bongsu Kang
s. Jack hu
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library of Congress Cataloging-in-Publication data Names: Cai, wayne w., author.
Title: Ultrasonic welding of lithium-ion batteries / [edited] by wayne w. Cai.
description: New York : ASME Press, [2017] | Includes bibliographical references.
Identifiers: lCCN 2016043603 | ISbN 9780791861257
Subjects: lCSh: lithium ion batteries–design and construction. | Ultrasonic welding.
Classification: lCC Tk2945.l58 U58 2017 | ddC 621.31/2423--dc23 lC record available at https://lccn.loc.gov/2016043603
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table of Contents
Preface and about the authors ix
chapter 1: introduction 1
Wayne Cai, Shawn Lee, and S. Jack Hu
Abstract 1
1.1 The Era of vehicular Electrification 1
1.2 li-Ion battery Cells, Modules and Packs 2
1.3 battery Joining 4
1.3.1 Inside a Cell 4
1.3.2 Module Assembly (Cell-to-Cell) 4
1.3.3 Pack Assembly (Module-to-Module) 4
1.4 battery Joining Technologies 6
1.4.1 Ultrasonic Metal welding 7
1.4.2 resistance welding 9
1.4.3 laser beam welding 10
1.4.4 wire-bonding 10
1.4.5 Mechanical Joining 11
1.4.6 Summary of battery Joining Technologies 11
1.5 Chapter Summary 11
1.6 organization of the book 12
references 13
chapter 2: defining Joint Quality Using Weld attributes 15 S. Shawn Lee, Tae Hyung Kim, S. Jack Hu, Wayne Cai, Jeffrey A. Abell, and Jingjing Li
Abstract 15
2.1 Introduction 15
2.2 Materials and Experiments 17
2.2.1 Experiments 17
2.2.2 weld Performance Testing 18
2.2.3 Sample Preparation/Microscopy/hardness Testing 18 2.3 definition of Attributes and weld Characterization 19
2.3.1 definition of weld Attributes 19
2.3.2 Characterization of Ultrasonic welds Using weld Attributes 20 2.4 Correlation between weld Attributes and quality 26
2.4.1 bond density 27
2.4.2 Post-weld Thickness 28
2.4.3 Thermo-Mechanically Affected Zone (TMAZ) and weld Nugget 29
2.4.4 Surface Cracks 32
2.4.5 Summary of Correlation between weld Attributes and quality 34
2.5 Conclusions 34
references 35
chapter 3: Welding mechanism and failure of Ultrasonic Welds 37 Xin Wu, Teng Liu, and Wayne Cai
Abstract 37
3.1 Introduction 37
3.2 Ultrasonic welding and weld Testing 40
3.3 Microstructural Analysis of cccC welds 41
3.4 Microstructural Analysis of aaaC welds 45
3.5 Conclusions 49
references 51
chapter 4: transient temperature and heat flux measurement Using thin-film microsensors 55
Jingzhou Zhao, Hang Li, Hongseok Choi, Chao Ma, Wayne Cai, Jeffrey A. Abell, and Xiaochun Li
Abstract 55
4.1 Introduction 56
4.1.1 background 56
4.1.2 Ultrasonic welder and workpieces 57
4.2 design, fabrication, and Calibration of Thin-film Sensors 58
4.2.1 design of Thin film Microsensors 58
4.2.2 Sensor fabrication 60
4.2.3 Sensor Calibration 62
4.3 welding Experiments and results 65
4.3.1 Temperature Measurement results on Cu bus bars 65 4.3.2 heat flux Measurement results on Cu bus bars 66 4.3.3 Temperature Sensing results with Inserted Sensor Unit 68
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Table of Contents v 4.4 validation of the Three-Stage bonding Theory 70
4.5 Conclusions 72
references 73
chapter 5: motion analysis for multilayer sheets 75 S. Shawn Lee, Tae Hyung Kim, S. Jack Hu, Wayne Cai,
and Jeffrey A. Abell
Abstract 75
5.1 Introduction 75
5.2 Experiment 76
5.2.1 Ultrasonic welding Process 76
5.2.2 high-Speeding Imaging 77
5.2.3 Multilayer welding Experiment 78
5.2.4 Post-weld Performance Testing/Microscopy/
bond density Measurement 79
5.3 results and discussion 79
5.3.1 observation of vibration development in Multiple layers 79 5.3.2 weld formation Mechanism in Multilayer welding 81 5.3.3 Effect of weld Tool geometry on bond density and Joint Strength 83
5.4 Conclusions 84
references 85
chapter 6: coupled thermo-mechanical simulation 87 Dongkyun Lee, Elijah Kannatey-Asibu Jr, and Wayne Cai
Abstract 87
6.1 Introduction 87
6.2 Theory 88
6.2.1 Mechanical Model 89
6.2.2 Thermal Model 90
6.3 finite Element Analysis Procedure 93
6.3.1 basic Units Selected for This Study 94 6.3.2 finite Element Procedures Using Abaqus 94 6.4 fEA Procedure verification and Case Studies 96 6.4.1 verification Test for Abaqus/Explicit 96 6.4.2 verification Test for Abaqus/Standard 99
6.4.3 Case Study (1): Abaqus/Explicit 102
6.4.4 Case Study (2): Abaqus/Standard 104
6.5 Conclusions 107
references 107
chapter 7: microstructure evolution and Physics-Based modeling 109 Hongtao Ding, Ninggang Shen, Avik Samanta, and Wayne Cai
Abstract 109
7.1 Introduction 109
7.2 Microstructure Evolution in Ultrasonic welding 111
7.3 Modeling 115
7.3.1 flow Stress Model under Ultrasonic vibration 115 7.3.2 Modeling for Microstructural Evolution 116
7.3.3 Process Modeling 118
7.4 Simulation results and discussions 120
7.5 Summary and Conclusions 124
references 125
chapter 8: Process monitoring Using online sensor signals 129 S. Shawn Lee, Chenhui Shao, Tae Hyung Kim, S. Jack Hu,
Elijah Kannatey-Asibu, Wayne Cai, J. Patrick Spicer, and Jeffrey A. Abell
Abstract 129
8.1 Introduction 129
8.2 weld formation Mechanism in Ultrasonic Metal welding 131 8.3 Sensor Signals from Ultrasonic welding Process 132
8.3.1 Experiment 133
8.3.2 Sensor Signals 133
8.3.3 Signal variation under Process disturbance 135 8.4 relationship between weld Attributes and Signal features 137
8.4.1 features from online Signals 137
8.4.2 Effect of welding Parameters on Signal features 138 8.4.3 relationship between weld Attributes and Signal features 139
8.5 Conclusions 141
references 142
chapter 9: tool Wear monitoring for Ultrasonic metal Welding
of lithium-ion Batteries 145
Chenhui Shao, Tae Hyung Kim, S. Jack Hu, Jionghua (Judy) Jin, Jeffrey A. Abell, and J. Patrick Spicer
Abstract 145
9.1 Introduction 145
9.2 Tool wear Characterization 147
9.2.1 Monitoring feature generation 148
9.2.2 Tool wear Progression in the horizontal direction 148 9.2.3 Tool wear Progression in the vertical direction 149
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Table of Contents vii
9.3 Impression Method 151
9.4 Tool Condition Classification 152
9.4.1 Monitoring feature generation 152
9.4.2 feature Selection 155
9.4.3 Classification 158
9.5 Conclusions 160
references 160
chapter 10: fundamental dynamics of Ultrasonic Welding 163 Bongsu Kang, Wayne Cai, and Chin-An Tan
Abstract 163
10.1 Introduction 163
10.2 Energy dissipation at frictional Interface 166
10.2.1 Single degree of freedom System 166
10.2.2 Multiple degrees of freedom System 174
10.2.3 Summary and Conclusions 180
10.3 dynamics of a Sonotrode 180
10.3.1 Natural frequencies and Modeshapes 181
10.3.2 frequency response Analysis 183
10.3.3 frequency response of a bar with variable Cross-Section 183 references 188
chapter 11: dynamics and Vibrations of Battery tabs under Ultrasonic
Welding 191
Bongsu Kang, Wayne Cai, and Chin-An Tan
Abstract 191
11.1 Introduction 192
11.2 dynamics of battery Tabs under Ultrasonic welding 192
11.2.1 Theory and Modeling 193
11.2.2 dynamics of the battery Tabs 196
11.2.3 Experimental results and discussion 207
11.2.4 Summary and Conclusions 213
11.3 dynamic Stress Analysis of battery Tabs 214 11.3.1 longitudinal and flexural vibrations of a beam 215
11.3.2 dynamic Stress in battery Tab 219
11.3.3 Summary and Conclusions 224
11.4 vibrational Energy loss Analysis in battery Tab Ultrasonic welding 225 11.4.1 Energy dissipation by Material damping in longitudinal vibration 226 11.4.2 Energy dissipation by Material damping in flexural vibration 229 11.4.3 vibrational Energy loss of the overhang 232
11.4.4 Summary and Conclusions 239
references 242
chapter 12: concluding remarks and future Work 243 Wayne Cai, and S. Jack Hu
12.1 Understanding the Physics of weld formation and System dynamics 244
12.2 weld quality Prediction 244
12.3 weld quality Evaluation, Monitoring, and Control 245 12.4 Innovative Ultrasonic welding Technologies 245 references 245
index 247
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PrefaCe
Since its commercialization in the early 1990s, the lithium-ion (li-ion) battery has seen rapid growth due to its advantages of high voltage and high power/energy density. The growth has become particularly strong during the past decade with the development of li-ion bat- tery powered electric vehicles. In 2016, the global li-ion battery industry generates about 90 gwh output with $20b revenue for a combined consumer electronics (60%), electric vehicles (35%), and grid (5%) usage. It is estimated that the global li-ion battery output for electric vehicles alone will grow to 195 gwh or about $35b in 2020, translating to 3 mil- lion pure electric vehicles out of a market of 100 million units per year. with the prevailing consensus that battery electric vehicles will become mainstream by 2050, the economical impact of li-ion battery industry will be at trillion dollar levels. hence, the li-ion battery technologies including the associated manufacturing technologies are deemed very critical.
Ultrasonic metal welding (USMw), a process in which high-power ultrasonic vibra- tion is used to produce relative tangential motion and then frictional heat to create bonds between two or multiple metal sheets, has rapidly become one of the key manufactur- ing technologies for joining li-ion battery cells, modules, and packs. being a solid state joining process, USMw is firstly ideal in dissimilar materials joining largely due to its ability to avoid or significantly reduce the amount of brittle and non-conductive intermetal- lic compounds commonly formed in fusion welding. when applied to li-ion battery cell, module, and pack joining in battery electric vehicles, the advantages of USMw become even more evident due to its excellent characteristics for joining thin, multiple, and highly conductive materials such as copper, aluminum, and nickel. while it is well known that successful USMw depends on such design and manufacturing process parameters as the materials, stack-up configurations, tool knurl geometry, vibration amplitude, welding force, and welding time/energy, the underlying physics of the USMw process has not been fully understood and trial-and-error is still the dominant engineering practice. In particular, is- sues such as the interfacial bond failure, excessive thinning and fracture, and system vibra- tory responses are both perplexing and elusive to predict and prevent. Therefore, scientific understanding of the USMw mechanism, process, and thereafter sound engineering design and manufacturing guidance are much needed.
This book hence seeks to make an original contribution to the knowledge base under- pinning USMw, particularly for the manufacturing of li-ion battery cells, modules, and packs as used in electric vehicles. More specifically:
1. from a physics point of view, the book (Chapters 2–7) strives to significantly advance the fundamental understanding of the USMw mechanism and subsequently the weld qual- ity predictability by using a combined mechanics-materials approach including cyclic
plasticity and microstructural simulations. Throughout the chapters, a number of state- of-the-art metrology techniques are employed to measure key product/process charac- teristics in order to better understand the process and to validate the theoretical results.
To detect transient temperature and heat flow of the workpieces and the tool, a novel in-situ thin-film thermocouple and thermopile sensing method is developed. Super-high- speed field imaging establishes real-time phenomenological observation on the multi- layer USMw process by analyzing the vibration behavior of metal layers through direct measurement of the lateral displacement of each metal layer. Advanced SEM/EdX methods provide the essential microscopic information to exam the bonding mechanism and fracture behaviors. The classification of the ultrasonic weld quality and the analyses of two limiting factors affecting ultrasonic weld quality (i.e., the interfacial bonding strength between metal layers and the metal perforation/fracture on top layer(s)) from these chapters shed great light on ultrasonic weld formation and quality.
2. The book (Chapters 10–11) attempts to establish the relationship between the weld tool vibration (input) and the system vibration (output) by studying the fundamental aspects of dynamics involved in USMw. Nonlinear dynamics analyses clearly indicate that both the product design (e.g., the materials, geometries, boundary conditions, and damping) and the process design (e.g., the tool stiffness and placement) significantly impact the system stresses which can exert strains on the system components and, in certain conditions, cause system failure. laser scanning vibrometry provides much first-hand validation data.
3. As a critical element of the ultrasonic weld quality evaluation, data-drive approaches were adopted (Chapters 8–9) to establish a correlation between USMw signal features and the USMw process conditions and eventually joint quality. The book also develops the algorithms for monitoring welding process and its impact on weld quality, based on the tool wear conditions.
The book focuses mainly on two-layer and multi-layer aluminum (with and without anodizing) and copper (with and without nickel coating) welding configurations. Thus, its value to the practitioners in li-ion batteries and battery electric vehicles is self-evident.
Nevertheless, the theories and methods presented in the book are highly transferable and extendable to all other li-ion battery applications, and can be of significant values to bat- tery manufacturers and the automotive industry in general for judicious implementations.
furthermore, the new knowledge generated can drive the development of such innovative technologies as single-sided USMw, and thermally enhanced USMw for multiple layers of thick-sheets and hard-to-weld materials. It is expected that the book may have even broader implications in understanding and developing more effective solid state joining processes such as cladding, impact welding, friction stir welding, and ultrasonic consolidations for additive manufacturing, which are all strongly governed by the similar solid-state physics.
The key contributors to the book represent a team of leading experts in the field.
Dr. Wayne Cai, is a Staff researcher at general Motors global r&d Center, and guest professor at Shanghai Jiaotong Uni- versity (China). he is well-recognized for his innovation in automotive technologies, particularly li-ion battery design and manufacturing technologies with over thirty US and interna- tional patents (or patent pending) and over sixty peer-reviewed research papers. he is currently Chair of SAE hybrid Electric vehicle Committee, and vice Chair of ASME Manufacturing Process Technical Committee. he also serves as an Associate Editor for ASME Journal of Manufacturing Science and Engi- neering and SME Journal of Manufacturing Processes.
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Preface xi Dr. Bongsu Kang is a Professor of Mechanical Engineering at Indiana University - Purdue University fort wayne. his research interests include dynamics and vibrations of distributed parameter systems. he has conducted various academic and applied research projects on friction-induced vibration problems including the work on modeling and vibration analysis of elastic bodies under ultra- sonic excitation with application to ultrasonic metal welding of battery tabs in manufacturing of battery pack modules for electric vehicles.
Dr. S. Jack Hu is the J. reid and Polly Anderson Professor of Manu- facturing at the University of Michigan, Ann Arbor, USA. he is also professor of Mechanical Engineering and professor of Industrial &
operations Engineering. dr. hu has made significant contributions to advanced manufacturing research and education. he is a member of US National Academy of Engineering, an elected fellow of the American Society of Mechanical Engineers (ASME) and of the Inter- national Academy for Production Engineering (CIrP).
we wish to express our gratitude to all the co-authors of the book, whose enthusiasms and contributions have really made this book possible. Special thanks also go to Mary grace Stefanchik of ASME Press and other editorial staff who have made this strenuous process a pleasant experience.
wayne Cai, gM global r&d, warren, MI, USA
bongsu kang, Purdue University fort wayne, fort wayne, IN, USA S. Jack hu, The University of Michigan, Ann Arbor, MI, USA
