Electric cars are increasingly popular with consumers because they are green and battery technology is maturing. Among them, lithium-ion battery technology is one of the key technologies of electric vehicles.

In lithium battery technology, there are three metal welding methods involved: copper/aluminum foil to TAB, TAB to TAB and TAB to bus. Among them, copper/aluminum foil welding to the pole plate, the most difficult. Because metal welding ends are made of metals of different thicknesses and materials, one end (TAB) is relatively thick (e.g. 0.2mm) and the other end consists of several layers of extremely thin metal sheets. The figure below shows a cross section of a lithium-ion battery unit.

Among them, the welding of pole foil to pole sheet is to connect all the Yin and Yang pole foil inside the battery to the corresponding pole sheet, so as to transfer the energy inside the battery to the outside. Hundreds of lithium-ion cells make up a typical lithium-ion battery pack. Each battery unit is combined in series or parallel. If the connection between a pole foil and a pole piece fails, the output of the whole battery pack will fail. Therefore, a steady and firm connection between polar foil and polar sheet is very important.

Ultrasonic metal welding, which will fasten the multilayer foil to the pole piece, is feasible.
The soldering process does not damage the foil.
Bonding occurs on the foil to pole (joint) surface and between each foil and foil, providing a stronger, more conductive metal connection.
Infrared photography showed that all joints remained below 60ºC during the welding cycle, indicating that the process did not cause damage to nearby thermal elements.