10018077 : Soni-Laser – Ultrasonic assisted laser welding for high volume assembly of automotive battery packs.

Laser welding has emerged as a very strong contending welding technique to respond to the increasing demand for EV battery manufacturing, being 4-5 times faster than the current welding processes, but challenges to its application remain.

Why laser welding?

Laser welding is a fusion process which means that both substrates being welded, melt during the laser welding process. Although the process is extremely fast, so the total heat input can be kept at low levels, there is the potential for the formation of brittle, high-resistance intermetallic compounds, especially when dissimilar materials are welded. Dissimilar joints, such as the aluminium-copper combination often found in batteries, are particularly prone to the formation of intermetallic compounds. These compounds have been shown to have a negative impact on the short-term electrical performance as well as the long-term mechanical performance of the joints in lithium batteries. Such adverse effects currently pose an industrial challenge for the automotive battery system manufacturing sector.

What is the Soni-Laser project aim?

Soni-Laser will introduce a non-contact Power-Ultrasonic Vibration Treatment (PUVT) subsystem that will assist the laser welding process of EV batteries and enhance the integrity and quality of welds. The PUVT subsystem will include both hardware -- power ultrasonic transducers -- and software -- computational models that will control process parameters such as ultrasonic frequencies. Using suitable power ultrasonic frequencies, not only can the intermetallic be redistributed, but also the weld geometry can be modified to suit the particular joint requirements.

The Soni-Laser solution will:

1. Reduce residual stresses, along with a 10% improvement in mechanical properties (e.g. strength) of the battery weld, due to grain refinement and phase distribution;
2. Prevent and minimise the formation of bulk intermetallics by 30%;
3. Increase the laser welding speed by at least 50%. Commercially, Soni-Laser will be a retrofittable bespoke solution, comprising the proposed PUVT subsystem and its optimisation models, customised to each client (EV battery manufacturers) and each battery module segment within their production line.