Interview with Thomas Devahif (CFL)

Can you tell us more about your organsiation’s role in greenSPEED?

The role of Circuit Foil Luxemburg (CFL) in greenSPEED is to design, develop and manufacture the best possible anodic copper current collectors for the different technologies of battery developed along the project. This ranges from fine-tuning the mechanical properties of the copper foil to adapt it to the manufacturing constraints, to developing a surface treatment that will help innovative technologies such as those developed by LeydenJar with pure Si anodes to achieve competitive cycling ability. CFL has decades of experience in the industrial surface treatment of copper foil for the Printed Circuit Board industry. These pure Si anodes, aside from being disruptively energy-rich, will also allow the use of a dry manufacturing process (from LeydenJar), thereby reducing the ecological footprint of producing such anodes. 

Finally, greenSPEED is all about sustainability and greener processes. Passivation of the copper foil is crucial to avoid the natural air oxidation of the copper foil. For decades, in the global market for copper current collectors for Li-Ion batteries has been based on the deposition of an extremely thin Cr(III) passivation layer on the surface of the copper foil using a Cr(VI)-containing process. Anyone who has seen the movie “Erin Brockovich” is probably aware of the risks associated with the use of hexavalent chromium on an industrial scale. Although the use of hexavalent chromium is now highly regulated and strict safety measures are in place for its industrial use, CFL is also working on a Cr(VI)-free passivation alternative to completely eliminate this substance from the production of copper current collectors. This new environmentally friendly passivation will therefore be introduced during the greenSPEED project.

When it comes to the collector foils, what challenges are you facing in the course of greenSPEED in comparison to State-of-the-Art technologies?

The challenges faced with current collector foils are quite numerous but also very exciting. 

First, current collectors do not store energy, their main role being to conduct electrons in and out of the battery cell. This means that the lighter they are and the less volume they occupy in the battery, the better the energy density. This has pushed current collector producers such as CFL to produce thinner and thinner foils. Even though this is a very good thing for energy density and the driving range of our future electric cars, this has a disadvantage: processability. Indeed, battery producers still need to be able to use these extremely thin copper foils in their manufacturing lines. This is why production of copper foil by electrodeposition process is so advantageous. Aside from being much cheaper to produce compared to rolled annealed copper when it comes to low thickness foils, the use of electrodeposition additives during the production process allows to finely control the mechanical properties of the copper foils in order to make those much stronger and resilient towards the battery manufacturing process. This is also a very appreciated feature when it comes to silicon anodes use. Whilst graphite particles (the traditional material used for Li-Ion batteries) tend to swell and contract ever so slightly during battery charge and discharge, silicon can, in turn, swells and contracts up to more than 300% of its original size. This can cause huge mechanical constraints on the copper current collector it is coated onto, which is why improving the mechanical properties of these foils is so important in order to avoid any mechanical damage of the copper current collector during cycling of a Si-rich battery. 

CFL develops special treatments to improve the adhesion between the silicon and the copper foil, as the swelling and contracting of the silicon can cause delamination from the current collector, translating into a progressive and detrimental reduction in the capacity of the battery. These treatments have to be applied on both sides of very thin copper foils, which is challenging. 

Why do you think that projects such as greenSPEED are important for the European Battery Production?

Reducing the environmental footprint and costs of battery cells production is not only an important and highly motivating goal from a socio-economic point of view, but it also becomes more and more of a necessity. Indeed, the objectives of the European Union in terms of CO2 neutrality are quite clear; and that means achieving carbon neutrality as fast as possible. More and more manufacturers are taking a keen interest in the environmental impact of the entire battery supply chain, which represents yet another motivation and strategic objective for companies like CFL to tackle this issue. 

At the end of the day, the trend towards sustainability is clearly visible in the industry in general and is likely to become a major competitive advantage sooner rather than later. This has become even more apparent to many companies in recent times as geopolitical turmoil has led to some very painful situations, particularly after the COVID pandemic, leading to surging energy prices eating into companies’ profits. 

A project like greenSPEED is very positive for the European Battery production, as it allows companies to bring together their respective knowledge in different key aspects of the value chain. They can then work together towards a motivating common objective, and by doing so, gaining important knowledge and building strong relationships, thereby accelerating the development of innovative technologies along the way, which is a very exciting prospect.