Paul van Gerven
7 September 2021

Aiming to revolutionize the battery industry, Leydenjar raised 22 million euros to perfect its silicon anode recipe as well as the equipment to manufacture these components in high volumes. The first tool shipments are expected in two years’ time.

Christian Rood is a happy man. And why wouldn’t he be, having recently closed a 22-million-euro investment round. “Investors will only put money into companies like Leydenjar, which don’t generate much revenue yet, if their prospects are bright. Clearly, our investors are impressed by the technological progress we’re making, by our efforts to industrialize our manufacturing equipment and by the companies that have started working with us,” says the CEO of Leydenjar Technologies.

The startup founded in 2016 has developed a lithium-ion battery anode made entirely from silicon. This metalloid is an excellent host for lithium ions but in bulk form has a propensity to crack under the constant stress of taking in and letting go of its guest. Leydenjar adopted a plasma-enhanced chemical vapor deposition (PECVD) process originally developed for thin-film solar cells to manufacture nanotextured silicon that can accommodate the volume changes associated with lithium loading and unloading.

Leydenjar silicon
Close-up of Leydenjar’s nanotextured silicon. Credit: Leydenjar

A year ago, the Leiden-headquartered company showed that its silicon anodes are capable of storing up to 70 percent more energy by weight than conventional lithium-ion battery anodes made from graphite. Additionally, they’re also considerably more friendly for the environment: on top of an altogether cleaner manufacturing process, Leydenjar claims a reduced CO2 footprint of 85 percent.


The silicon anode’s lifespan, however, still compares unfavorably to that of its graphite counterpart. The best batteries fitted with conventional anodes can reach up to a thousand charge and discharge cycles before losing too much performance, while Leydenjar has recently passed only 200 cycles. Still, says Rood, “that’s good progress. It’s twice the cycle life we had a year ago.”


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Rood isn’t worried that silicon will eventually prove less durable than graphite. “When lithium-ion batteries were commercially introduced in 1991, they also lasted only 200 cycles or so. Cycle life has been greatly increased over time, thanks to R&D efforts by academia and industry. The same will happen for silicon. Just about the entire battery industry is working on it right now.”

Not just battery makers, but also manufacturers of electric vehicles, eager to extend driving range, are pursuing the technology hands-on. Tesla and Porsche, for example, have made public statements about their work on silicon anodes. Leydenjar is currently talking to “every major European car manufacturer,” Rood reveals.

Tough potentially extremely lucrative, the automotive market isn’t Leydenjar’s first target, however. The company’s battle plan is to first satisfy the specifications of consumer electronics markets, ranging from laptops to power tools. “These applications require a cycle life of about 500. Once we’ve reached that, we’re ready to address a mass market and start making sales.” From there, the company intends to keep improving its technology to serve even more demanding markets. This isn’t just about increasing cycle life, by the way – different markets require a range of different battery characteristics, such as power density and temperature dependence.

Public listing

As hard as Leydenjar is working right now to gear up its silicon anode technology, it won’t be selling the anodes itself but the equipment to produce them. Depending on the tool specs that his company will deliver, future gigafactories might need as much as a hundred tools per factory, Rood estimates.

“Currently, we have an R&D tool in our pilot production facility in Eindhoven. That’s being used in demonstration projects, ranging from small samples to semi-industrial production. For commercially relevant manufacturing, however, throughput needs to increase. Next to anode technology optimization, this is another top priority right now.”

Leydenjar pilot facility
Credit: Leydenjar

For assembly as well as equipment manufacturing, Leydenjar will be partnering with companies in the Brainport ecosystem. “We’re aiming for our products to be future-proof Industry 4.0 tools. To achieve that goal, we’d be foolish not to take advantage of the knowledge and expertise in the region. The deposition process is our core competence and we’ll gladly work with partners to take care of other aspects.”

Rood projects Leydenjar will need another two years before it’s ready to ship the first machines. With the raised capital, the company plans to expand its workforce from 25 to about 70 FTEs in the next 1.5 years, move to a bigger laboratory in Leiden, scale up the plant in Eindhoven to demonstrate high-volume roll-to-roll production (Leydenjar’s silicon is deposited on copper foils) while simultaneously expanding qualification projects with customers. “If all goes to plan, we’ll be considering exit options together with our investors. A public listing is definitely an option, but let’s see how things pan out.”