LeydenJar’s role in advancing scalable silicon anode production

LeydenJar, located in Leiden and Eindhoven, is a consortium partner in project 2, Next-gen Equipment for Batteries and Battery Materials, of NXTGEN Hightech Energy. The focus of this project is on the development of next-generation batteries and the related production processes and equipment. The role of LeydenJar is to focus scaling the production of 100% silicon anodes.

LeydenJar develops a foil-based silicon anode, using plasma-enhanced chemical vapour deposition (PECVD). Their goal within the NXTGEN Hightech project is to create a roll of copper foil with a layer of 100% pure silicon deposited on top. This makes them different from other partners in the consortium which develop silicon powder. LeydenJar does not produce powder, but a roll-to-roll anode foil that can be further processed in battery manufacturing.

The purity of the silicon is an important technical advantage. Because the silicon is deposited directly onto the copper foil, no additional binder is needed. In powder-based anode materials, the powder usually needs to be mixed with binders and then coated. The binders are inactive materials and do not contribute to energy storage. By avoiding them, LeydenJar can maximise the amount of active material in the anode. The less inactive material there is, the higher the potential energy density of the battery.

Within the NXTGEN Hightech project, LeydenJar is responsible for several activities. One of these activities focuses on developing a new, advanced plasma source. This source is the key technology behind their production process. LeydenJar used to work with microwave technology as the plasma source. But this technology did not offer the performance needed to scale towards the production volumes and productivity required by the market. The process had to become faster and more efficient.

The work resulted in a new plasma source that proved to be highly promising. This development turned out to be so relevant that LeydenJar decided to implement the new plasma source earlier than originally planned. As a result, the next part of the project was adjusted.

Another activity LeydenJar focuses on is to develop a functional model and design for a next-generation production machine. Until now, they worked with generation 1 and generation 2 machines, which originally came from other applications and were heavily modified for the production of silicon anodes. They are now working on a generation 3 machine, tailored to the requirements of LeydenJar’s own production process.

Because of the new plasma source, the design of the new generation 3 machine has been modified. The aim of this project is now to integrate the newly developed plasma source into this fully customised production tool. This is important for further scaling, but also for building intellectual property. LeydenJar is not only developing knowledge around the process itself, but also around the manufacturing tool and the related infrastructure.

Another part of LeydenJar’s activities within the NXTGEN Hightech project focuses on solid-state batteries. Solid-state batteries are seen as a next-generation battery technology. In these batteries, the liquid electrolyte is replaced by a solid material. This can offer advantages in terms of safety, because the liquid electrolyte in traditional batteries is flammable. Solid-state batteries can also enable higher energy density, allowing batteries to store more energy in the same space.

LeydenJar has already gained knowledge in this area, but these activities have recently been scaled back because solid-state batteries are further away from their direct commercial focus. However, LeydenJar remains involved in this topic through cooperation with Delft University of Technology, in particular with Professor Marnix Wagemaker. Together, they have set up an additional project in which two PhD candidates will work on solid-state batteries using LeydenJar’s silicon anodes. This keeps the knowledge development going and helps train new researchers in this field.

A difference compared to other anode developments is that LeydenJar deposits the silicon layer directly onto the copper foil in a single production step. Powder-based solutions require several steps: the powder needs to be mixed, binders need to be added, the material needs to be coated and then further processed. With the process LeydenJar is using, the final product is created in one step. This offers advantages in terms of energy consumption, process complexity and cost.

LeydenJar has also carried out a life cycle assessment comparing its own production technology with conventional graphite anode production. This shows that their production process could reduce emissions by up to 85% compared to the traditional graphite process. This makes the technology relevant not only from the perspective of battery performance, but also from the perspective of sustainability and production efficiency.

The Netherlands has a strong position in the field of innovative anode and electrode components. Several companies within the Dutch ecosystem are working on new battery materials and anode technologies, including E-magy, LionVolt and LeydenJar. The technologies differ, but they all focus on improving battery performance. While E-magy works with silicon powder and LionVolt focuses on other next-generation battery concepts, LeydenJar works on a foil-based 100% silicon anode.

In addition to the development of the plasma source and the production machine, LeydenJar is also working on post-processing techniques within the project. After the silicon layer has been deposited on the foil, the quality of the anodes needs to be checked before the material can be sent to customers. For this, LeydenJar is developing an inspection and rewinding tool. The roll of material is guided through the inspection system while inline sensors check the quality.

Different sensor technologies are being explored for this inspection step. These may range from visual inspection with cameras to techniques that provide more detailed information about the material itself. LeydenJar is also working on laser ablation. Because the copper foil is fully covered with silicon, parts of the silicon layer need to be removed in some areas to expose the copper current collector again. This is necessary to make electrical connections later in the battery manufacturing process. Laser ablation is a logical choice for this, as it is already widely used in cell manufacturing.

A deliverable focused on validating the anodes in real battery cells has also been added to this part of the project. LeydenJar develops anodes, but customers ultimately want to see how these anodes perform in actual battery cells. That’s why it’s important to show that the material performs as an anode foil and can also be successfully processed into cells by cell manufacturers.

LeydenJar is working on this with a cell manufacturer in China. They send their anodes to their partner, where they are processed into actual battery cells. These cells are sent back to be tested. This provides insight into how the anodes behave in a real cell production environment.

The choice of a partner in China is mainly practical and strategic. Currently, the Netherlands does not have full cell production capacity yet. There are developments, such as a future production line at the Automotive Campus, but China is leading in this field. In battery cell production, China is one of the most important players. By working with an experienced Chinese cell manufacturer, LeydenJar can learn from parties with expertise in large-scale cell production.

LeydenJar does not see China as a competitor. Especially in the battery industry, cooperation with China is important, because a lot of knowledge and production capacity is located there. The ultimate goal is to become more independent at Dutch and European level, but to get there, it is necessary to cooperate strategically and learn from the companies that are currently leading the field.

For LeydenJar, the NXTGEN Hightech project is closely aligned with its own development roadmap. The development and demonstration of the innovative plasma source in the first work package directly feeds into its implementation in the generation 3 production machine. This is seen as an important step in the company’s development.

For further scaling, LeydenJar sees several opportunities. The current process is not yet fully continuous but works in batches. This means that further optimisation is possible in terms of runtime and deposition speed. LeydenJar aims to scale by building more generation 3 machines once the first machine has been properly understood and validated. Around 2027, they expect to have a better view of how the machine performs and how it can be scaled even further.

The most important development within the NXTGEN Hightech project so far is the development of the innovative plasma source and its translation into the generation 3 production machine. The project has contributed to an important step in LeydenJar’s technological development. The combination of process development, machine development and scaling knowledge makes the project valuable for LeydenJar and for the broader development of battery technology in the Netherlands.

About NXTGEN Hightech

This project is made possible in part by a contribution from the National Growth Fund program NXTGEN Hightech. This program will invest as much as € 1 billion until 2030 with over 330 partners, in more than 60 projects and in six essential domains. In doing so, NXTGEN Hightech will make a significant contribution to the structural and sustainable economic growth in the Netherlands and offer solutions for the major societal challenges in the areas of energy transition, health, safety and food. For more information, please visit www.nxtgenhightech.nl