A new laser welding technology that creates safe contacts between temperature-sensitive battery cells has been developed by the Fraunhofer Institute for Laser Technology (ILT). The technique is now ready for series production, and currently in the validation phase of the project, which sees the team improving the process and making it safe to use. Improved battery joining – the process of connecting individual cells into packs – will benefit applications including portable computers, power tools, and non-standard electric cars, such as the Tesla Roadster.
Using a method called oscillation laser welding the team was able to apply a precise amount of energy into the batteries. Up to 1kW fibre lasers can be used, with the laser beam superimposing circular oscillation onto the feed movement, allowing a high level of control. The process briefly heats a very small area that cools quickly after welding.
‘Take [computer] notebook cells, for instance. Here, we weld very thin steel plates to copper alloys directly over temperature-sensitive plastic,’ explained Benjamin Mehlmann, expert for the metallic materials micro-joining at the Fraunhofer ILT. ‘What makes this possible is that the method is incredibly fast and has a low energy input.’ Currently, oscillation laser welding is being used to join 4,800 standard cells, each with a diameter of 18mm and a height of 65mm into a battery pack suitable for use in an electric vehicle. Mehlmann added: ‘It’s an interesting option for SMEs wanting to use the method to develop their own solutions for portable and stationary applications.’
These developments are the result of Fraunhofer ILT collaborating with F & K Delvotec – based in Ottobrunn, Germany – in a publicly funded project. Fraunhofer ILT will be presenting this joint project on 27-29 April at its booth at the Battery Power conference at the Eurogress in Aachen, Germany. The ILT is now working with other Fraunhofer institutes to create a complete battery pack.
Think laser! - Jessica Rowbury looks at the design considerations that need to be made when turning to laser processing