Characterization of Li - ion Battery Segments Subjected to Lateral Compression and an In - Plane Tension

In the last two decades, Lithium-ion (Li-ion) batteries have become an inherent part of dayto-day life thanks to their widespread use in many consumer products and electric vehicles. While these batteries possess great advantages, they also carry an inherent safety liability: In case of a crash event, short-circuit failure of the battery may develop, leading to thermal runaway, fires and even explosions. Hence, a comprehensive study is required, aimed to modulate these batteries and optimize their testing standard. The objective of this research was to characterize the effect of lateral compression on the in-plane tensile failure load of Li-ion battery segments. A new experimental system was developed, which allows fine control of the compression load, and decouples the out-of-plain compression load and the in-plain tension load. Then, measurements were conducted with singlelayer, 4-layers and 11-layers specimens, producing characterizing graphs of the tensile load versus displacement. For all types of specimens, results show an observable decrease in the failure load for increasing pre-compression load, as expected. Furthermore, measurements confirmed that the relation between the tensile load and the displacement does not change for different compression loads. For the multi-layer specimens (4 layers), the failure sequence was studied. It was found that the sequence may alter for different pre-compression loads. Nevertheless, on all cases, the cathode failed first, and the anode failed second. Throughout all experiments, failures were located on the edge of the compression area of the specimen. Several methods were used to encourage emergence of failure at the center, but with no success. A hypothesis to explain the development of this mode of failure is suggested at the end of this work. 1 Acknowl edge ment The research presented in this document was carried out at the Impact and Crashworthiness Lab at the Department of mechanical engineering at MIT. It was completed with the support of several individuals, whom I would like to mention: First, I would like to thank Professor Tomasz Wierzbicki, founder and chief of the Impact and Crashworthiness Lab, for embracing me to the unique and prestige Li-ion battery research group. His profound knowledge and wide experience guided me towards a successful completion of this work. Also, I would like to express my deepest thanks to my brilliant advisor, Dr. Elham Sahraei, for her excellent guidance, high availability and endless patient and support. Thanks to her enlightening, knowledgeable, comments during our discussions, complicated issues were solved and new solutions were developed. Next, I would like to express my high appreciation and gratitude to the senior doctoral researcher in the Li-ion battery group, Mr. Xiaowei Zhang, for his thorough and comprehensive guidance at the lab and for his contribution along the design process. I would also like to thank Mr. Zhang for his encouragement and friendship. Finally, I would like to thank my precious family: My wife, Oshrit, for being so much more than a supportive spouse, best friend and a wonderful mother, and my beloved, beautiful children, Noam and Evyatar, who always keep my mind focused on what is truly important.