Process and Quality Characterization for Ultrasonic Welding of Lithium-Ion Batteries.

[摘要] Lithium-ion batteries have received a great deal of attention in the electric or hybrid-electric vehicle industry due to the advantage of providing the highest energy density compared with other available battery systems. Manufacturing of lithium-ion battery packs demands a significant amount of joining, such as welding, to fulfill the desired power and capacity requirements. However, conventional fusion welding processes, such as resistance spot welding and laser welding, face difficulties in joining multiple thin sheets of highly conductive, dissimilar materials. Ultrasonic metal welding overcomes such difficulties by using its inherent solid-state process characteristics. Despite a considerable amount of past research on ultrasonic metal welding, the fundamental mechanisms behind this process are still uncertain. Moreover, there is a lack of scientific quality guidelines for implementing ultrasonic welding in volume production. This dissertation develops methods for comprehensive characterization of the process and quality in ultrasonic welding of multiple thin layers of battery materials for high power lithium-ion battery packs. Three research topics are addressed in this dissertation: 1. Several physical weld attributes are identified by experimentally characterizing the weld formation over time using copper-to-nickel plated copper welding as an example. The weld attributes are then correlated to weld performance by examining the cross-sectioned samples of different weld quality using optical microscopy, scanning electronic microscopy, and hardness measurements. 2. Online process monitoring using sensors is a key enabler of securing product quality and process stability in manufacturing. To develop a robust and reliable monitoring system for ultrasonic welding, this research establishes an in-depth characterization of the sensor signals and their relationship to the welding process and quality. Selected online features are correlated to weld attributes in order to understand the physics behind the weld formation under abnormal process conditions. 3. This research establishes real-time phenomenological observation on multilayer ultrasonic welding by analyzing the vibration behaviors of metal layers. Such behaviors are characterized by a direct measurement of the lateral displacement of each metal layer using high-speed images.This dissertation provides new knowledge and insights for enhancing the process stability and quality in ultrasonic metal welding in lithium-ion battery pack manufacturing.

[发布机构] University of Michigan

[效力级别] Lithium-ion Battery Joining

[关键词] Ultrasonic Welding;Lithium-ion Battery Joining;Mechanical Engineering;Engineering;Mechanical Engineering