Laser weld development for battery electrode stacks
Project challenges
Celltris are improving the range, cost and performance of battery cells by eliminating internal space. To do this, flexible manufacturing processes are required for joining electrode foils to tabs.
Business challenge
Product Innovation
Sector
Electrification
Technology or capability
Laser Processing
Working with Celltris, the MTC benchmarked infrared and green laser sources to weld copper foil stacks to a copper tab. Welds have been verified against key metrics including weld geometry, porosity and resistivity. Laser welding technology can enable greater design freedom for Celltris. The knowledge transfer provided by MTC has enabled Celltris to specify their future production equipment.
The Challenge
Celltris are improving the range, cost and performance of battery cells by eliminating internal space. To do this, flexible manufacturing processes are required for joining electrode foils to tabs.
Currently, foils are typically joined via ultrasonic welding, which requires a sonotrode to be in contact with the foils. This method limits the potential design of the battery due to access requirements for the sonotrode.
Laser welding is non-contact, with a long working distance, allowing greater design freedom. However, laser welding of copper is difficult due to the high reflectivity and high thermal conductivity properties of the material.
MTC's Solution
- The MTC conducted laser welding trials with a single mode IR laser using wobble beam manipulation.
- Fixtures, gas shielding and material preparation were developed to enable a repeatable welding process.
- Weld parameters were found that meet metallurgy, mechanical (tensile) and electrical resistance requirements.
Celltris are delighted with the outcomes achieved in this project with the MTC. The results have significantly accelerated our development programme alongside gaining us the language to engage equipment suppliers and customers.
Sam Alexander, Co-Founder, Celltris
The Outcome
- Robust and repeatable weld processes were developed for welding stacks of 50 copper foils either alone or to a 0.5mm copper busbar.
- The developed joining processes are capable of producing repeatable welds.
- Porosity and weld geometry targets were achieved.
- Tensile pull testing exceeded requirements (>100 N).
- Electrical resistance achieves target (<80 µOhms).
Benefits to the Client
- In depth understanding of the development process required for laser welding, including fixture design, gas shielding and parameter development was transferred to the customer.
- Celltris gained confidence that laser welded copper foils meet specification .
- Celltris are now able to specify their future production equipment, allowing them to get quotes and look for funding.
- Innovative cell and battery designs from Celltris have moved one step closer to reality, thanks to the laser welding process demonstrated at MTC.
MTC is proud to have supported process development and upskilling of the Celltris team, enabling Celltris to move closer to on-boarding laser technology into their business. Celltris designs are potentially game-changing in terms of battery performance and cost. The UK needs more innovative companies, like Celltris, in the battery space.
Mickey Crozier, Chief Engineer, MTC
