The increased application for lithium batteries in electric cars and many electronic devices means fiber laser welding is used in the product design. Components carrying electric current produced from copper or aluminum alloys join terminals using fiber laser welding to connect a series of cells in the battery.
Aluminum alloys, typically 3000 series, and pure copper are laser welded to create electrical contact to positive and negative battery terminals. The full range of materials and material combinations used in batteries that are candidates for the new fiber laser welding processes.
Overlap, butt and fillet-welded joints make the various connections within the battery. Laser welding of tab material to negative and positive terminals creates the pack’s electrical contact. The final cell-assembly welding step, seam sealing of the aluminum cans, creates a barrier for the internal electrolyte.
Because the battery is expected to operate reliably for 10 or more years, these laser welds are consistently high quality. The bottom line: With the correct fiber laser welding equipment and process, laser welding is proven to consistently produce high-quality welds in 3000 series aluminum alloys that have connections within dissimilar metal joints.
With the current strong interest in energy storage, QCW lasers look set to play their role beside CW lasers. Welding of battery tabs at high speed using single laser pulses from a QCW laser is now well established. Dissimilar metal joints between aluminum and steel and even copper and aluminum have now been developed.
There are two approaches to achieving sufficient electrical contact in battery connections from laser welding:
- A spinning beam technique (WOBBLE) to produce spiral or small-diameter concentric ring welds
- A number of high-pulse-energy, single-pulse laser welds, one beside the other, on each tab
Using combinations of dissimilar metals produces welds that might not be recognized as such by welding metallurgists, but clever design of the modules to limit mechanical loads on these joints appears to have solved some of these issues. But Continuious Wave Welding with a wobble function stay far superior over the pulsed QCW if we consider the mechanical loads capacity: a circle has alway more contact than differnt points.