Investigating Performance Change in Lithium-ion Batteries from Non-Destructive External Mechanical Abuse

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Candidate Name: John Sherman Program: Mechanical Engineering and Engineering Sciences Committee Chair: Dr. Anthony Bombik Committee Members: Dr. Lin Ma, Dr. Ronald Smelser, Dr. Christopher Bejger

Abstract: Lithium-ion batteries (LIBs) have become commonly used as energy storage for battery electric vehicles and hybrid electric vehicles. These vehicles are often subject to crash events which may lead the batteries to diminished performance or lead them to be completely inoperable. Plenty of previous research has looked into the understanding the reaction of LIBs to destructive testing, however there still is limited understanding in the performance of batteries under incidental mechanical damage. This dissertation seeks to expand this knowledge by exploring the ways in which recoverable damage can be measured. A framework of establishing mechanical damage which allows for further cyclability of cells is defined, with the evolution of cell specific parameters over future cycle life being discussed. Using the known changes to performance, modes of damage relating to electrode structural changes are individually explored. First the effects of compression are defined on performance of both electrode substrate and whole cell stack. Second investigations into the effects of impact loading of the jellyroll material are performed, measuring the response of shearing on electrode structure and electrochemical performance. By using results from these investigations, impact detection signals informed from electrochemical techniques are proposed and coupled with regrowth models to predict the capacity retention of cells based on electrochemical measurements.