Contacting battery cells using a nanosecond-pulsed laser welding process

Summary:

High performance energy storage systems are in strong demand due to the increasing electrification in the automotive industry. The production is based on battery cells as feedstock, preferably with Lithium Ion technology, which need to be electrically connected to an electrical system. For the connection of the cells different joining technologies are feasible, for example screw connection or welding. Laser beam welding offers numerous advantages, but poses also challenges.
High-current connectors made of copper or aluminum with large cross-sections are required for the low-loss transmission of the resulting currents. The preferred contacting method for these power electronic components is based on a material-locking connection with minimal heat-affected zone. In this way a mechanically and thermally resilient connection can be generated.
However, electrical connection technology often has to be carried out on thermally and mechanically sensitive substrates such as printed circuit boards, DCBs (ceramics) and battery cells. Due to the high thermal conductivity of the contact materials, standard welded joints are usually associated with a high heat input. Contacting with a laser beam welding process, however, allows precise control of the energy input and the welding depth with minimal stress to the material. Currently, welding joints in high-performance electronics and battery technology are realized with a continuously emitting single-mode fiber laser. A novel approach for better control of heat input and for contacting unidentical materials is the use of nanosecond-pulsed laser sources. These are usually used for ablation applications like surface structuring and laser drilling.
The aim of this work is the evaluation of a nanosecond laser welding process for contacting a copper connector on 18650 or 21700 round cells without damaging the active materials.