Mechanical performance and electrical resistance of ultrasonic welded multiple Cu-Al layers

The mechanical performance and electrical resistance of dissimilar and multi-layered Cu-Al sheets, which represent the battery electrodes and tabs, were evaluated by ultrasonic welding (UW). Different possibilities of lap-joining configurations using sheets of Cu and Al were considered. The weld strength at each weld interface of the multi-layered joint was evaluated by 90° peel test and by heat input measured by an infrared imager (IR). The strength of each weld interface of UW joined multiple Cu-Al layers were found to be strong enough to produce a through-thickness tearing. A typical weld criterion for producing a developed nugget was achieved. Weld quality at interfaces was assessed by cross-sectioning the UW joint parts. Depending on the lap-joint configuration, weld interfaces were characterized by bonded and unbonded interfaces. Measuring the electrical resistance passing through the joints demonstrated that the unbonded weld interface produced an increase in the joint electrical resistance. The joint electrical resistance measurement is shown to be used as a criterion to validate the quality of Cu-Al battery cell joints.