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Ultrasonic assisted laser welding for automotive battery packs

SoniLaser: Ultrasonic assisted laser welding for high volume assembly of automotive battery packs

Background

Electric vehicle (EV) sales will reach 44 million vehicles per year by 2030 with many European countries, including the UK, aiming at zero emissions within the next 30 years. Therefore, there is an increasing need for the manufacturing of battery packs to meet demand. Whilst Asia remains the stronghold (projected to reach 800GWh by 2025), Europe is expanding rapidly with a projected production capacity of 450GWh/year by 2030.

Laser welding has emerged as the optimal welding technique to respond to the increasing demand for EV battery manufacturing; being 4-5 times faster than the current welding processes. While laser welding is well suited to the increasing manufacturing demand and the joining needs of the battery pack assembly, challenges to its application in this industry remain. Typically, a standard battery pack consists of hundreds, even thousands, of individual cells which are connected to deliver the required power and capacity.

Making the required joints represent several metallurgical challenges, including, joining of multiple dissimilar materials of varying thicknesses.

SoniLaser will introduce a Power-Ultrasonic Vibration Treatment that will assist the laser welding process of EV batteries in order to enhance the integrity and quality of welds.

Objective

The aim of the SoniLaser project is to ‘non-invasively’ control and modify the microstructure during solidification between dissimilar battery joints while using power-ultrasonic vibration treatment, via the use of transducers. This ultrasonic excitation is expected to interact with the molten pool flow, solidification mode, mixing of alloying elements and diffusion that occurs during the solidification. Through breaking the continuous flows such as the Marangoni convection within the weld pool, SoniLaser will minimise the formation of undesired intermetallics and precipitates.

SoniLaser will focus on developing a hybrid ultrasonic-assisted welding process in the battery manufacturing sector, through understanding the mechanisms by which application of the excitation influences the solidification of the molten pool. Understanding its interaction with different chemistries of the materials of interest and the solidification process parameters is critical to optimise the technique, which can be accomplished through a large amount of data that will be acquired using a methodical design of experiments. The effect of ultrasonic excitation (vibration) during the laser welding between dissimilar metals (i.e. aluminium, nickel, copper) will control the thickness of the intermetallic compound layers during solidification and reduce or avoid the generation of defects which can severely limit the mechanical properties of welded joints.

Benefits

SoniLaser will introduce PUVT (Power-Ultrasonic Vibration Treatment) during the laser welding process as an effective strategy to enhance the mechanical properties of several dissimilar welds, by limiting the formation of IMCs and other defects.

Benefits in the advancements in the battery manufacture are expected to be:

  1. A reduction in porosity and residual stresses by 25% along with improved mechanical properties of the battery weld, due to grain refinement and phase distribution, by 10%.
  2. Decrease of bulk intermetallics by 30%. Due to lower viscosity, higher diffusion of materials within the molten pool is obtained.
  3. At least a 50% increase in the laser welding speed, enabling a 10-15% improvement in total battery productivity

Brunel Innovation Centre's Role

Brunel Innovation Centre (BIC) is a leader in PUT (Power Ultrasound) research and innovation. Our PUT team is focused on the use of low frequency ultrasonic vibration (frequency range 20--100kHz) as a platform technology for solving many industrial problems. In this project BIC will build on the extensive work already achieved to date and will further develop the PUT technology approach. BIC shall also be  advising on overall system design and test sample design, leading the hardware development and the deployment of computational models for process control.

Project Partners

Carrs Welding Technologies Limited

Brunel University London


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Related Research Group(s)

Design and Manufacturing

Design and Manufacturing - Developing products, services and manufacturing processes that will deliver economically and environmentally sustainable solutions, based on design principles derived from an understanding of human capabilities and limitations.

Brunel Innovation Centre

Brunel Innovation Centre - A world-class research and technology centre that sits between the knowledge base and industry.


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Project last modified 07/02/2022