Single Sided Bonding of Cylindrical Battery Cells

Abstract: Over the last ten years the Li-ion battery cells plays a significant role in the world’s decarbonization and reduction of CO2 emission. They are widely applied in many industries, such as consumer electronics, transportation and energy storage industries. The number of batteries cells varies from a few to thousands in a battery application, they are connected in series and/or parallel according to their designed voltage and capacity. It is a great advantage to be able to electrically connect the positive and negative sides of the battery from one side when designing and manufacturing battery modules and battery packs, because the whole built height of module could be a little lower and the rest of space below the cell body is free for cooling or thermal management. In this thesis project, different bonding technologies were compared, and ultrasonic wire bonding was selected to connect the negative electrode (shoulder) of battery and busbar. However, bonding on the shoulder of battery was still a challenge. The mechanism of ultrasonic wire bonding and the surface condition of the shoulder were studied in the project in order to develop the bonding process. Besides, the DoE experiment was used to further optimize the parameters of the wire bonding process. The 4 most influential factors were obtained from 7 factors from the screening factor experiment. Then a full factorial experiment was carried out for evaluation. Finally, a series of optimized parameters could be summarized.