EIC Accelerator Report Card: LeydenJar's Pure Silicon Anodes

Silicon can hold about ten times as much lithium as the graphite in today's battery anodes, but it swells by up to 300% when it charges and cracks. LeydenJar Technologies, a spin-off of the Dutch research organisation TNO, grows silicon in porous columns on copper foil, using plasma deposition equipment adapted from solar cell factories, so that the material can swell into its own gaps. In January 2019 the European Commission selected the company in the EIC SME Instrument Phase 2, the Horizon 2020 forerunner of the EIC Accelerator, and gave it €2,152,106.25 towards a €3,074,437.50 project to prove the anode and build a roll-to-roll demonstration line, according to CORDIS.

Seven years later the company is active and better financed than most 2019 winners. It closed a capital raise of €43 million in January 2026, according to a joint release with the pension investor APG, and in August 2026 it said anode roll production was under way at its first factory in Eindhoven. What it has not yet shown is a named consumer device on sale with its anode inside, and full-rate production has moved from 2026 to 2027.

Where LeydenJar Stands in 2026

LeydenJar is registered at Emmy Noetherweg in Leiden, with a corporate purpose that still describes its origin: developing silicon anodes "based on exclusive license from ECN", the energy research centre later folded into TNO, according to North Data, which draws on the Dutch Chamber of Commerce (KvK). No insolvency, liquidation or name change appears there. Accounts for 2025 were filed on 3 September 2026.

The product is now called Silyte, a roll of copper foil coated with 100% silicon that cell makers wind into lithium-ion batteries. On 4 August 2026 the company launched a sampling programme around a 27 by 27 millimetre reference cell for smartwatches, made at partner cell manufacturers, and said that core infrastructure at PlantOne was complete and that "anode roll production is currently underway, with expanded commercial capacity coming online in 2027", according to its release. In May 2026 it won the Peter Wennink Tech Award of the Dutch technology industry association FME, as reported by IO+ and the company's own announcement.

The Technology: Silicon Grown in Columns

Commercial anodes are made by coating copper foil with a slurry of graphite particles. Graphite has reached its theoretical capacity, so cell makers blend in silicon particles, but only a few per cent: the CORDIS report puts the state of the art at "a maximum of 5% silicon in the graphite anode". LeydenJar instead deposits pure silicon in a single plasma-enhanced chemical vapour deposition (PECVD) step. The silicon grows as columns, and the space between and inside them absorbs the swelling, the final project report says. The company claims the anode is up to ten times thinner than a graphite one and that its dry process cuts CO2 emissions by 85% compared with graphite production, figures repeated in its March 2026 product launch and in its 2024 factory announcement.

The weak point of pure silicon has always been cycle life. At the end of the EIC project LeydenJar reported about 200 cycles. In February 2025 it announced 500 cycles without external pressure on the cell, with 80% of capacity left after 500 cycles and 70% after 700, as reported by Bits&Chips, and the March 2026 specification gives "500+ cycles at 80% capacity retention", with 80% charge in 7 minutes. Those are company figures. The only independent check named in the record is DNV GL's confirmation of the 2020 energy density and cycle result, as stated by the company in July 2020 and in the CORDIS report.

The numbers do not quite line up. The July 2020 release reported 1,350 Wh/L "for more than 100 cycles"; the final CORDIS report, covering the period to March 2021, claims more than 1,400 Wh/L; the commercial product launched in 2026 is specified at 1,350 Wh/L. Each figure beats the project target of 1,200 Wh/L.

What the EIC Project Promised, and What CORDIS Shows

The Commission's list of SME Instrument Phase 2 winners names LeydenJar Technologies BV, Leiden, under the 9 January 2019 cut-off, as the only company on the project. It was LeydenJar's second step: a €50,000 Phase 1 feasibility study had run from April to August 2017, according to CORDIS. The Phase 2 grant was signed on 12 April 2019 with a start date of 1 April, and the project closed on schedule on 31 March 2021.

The project had three objectives: anodes enabling 1,200 Wh/L at stack level, a demonstration roll-to-roll production machine, and validation of the rolls "in a battery production plant". Instead of building its own machine, LeydenJar bought an existing roll-to-roll PECVD tool and adapted its gas supply and software, which the report says saved time and risk. It reports depositing "hundreds of meters" of double-sided anode and working "with external parties for quality evaluation purposes", without naming a battery plant. It also reports "substantial commercial collaborations with three automotive majors and with two globally leading consumer electronics companies", none of them named.

1. 1,200 Wh/L at stack levelDeliveredOver 1,400 Wh/L claimed in the final report; 1,350 Wh/L in the 2026 product.
2. Demo roll-to-roll PECVD machineDeliveredA bought and adapted tool "in full operation" by 2021.
3. Validation in a battery production plantPartialOnly unnamed external evaluations by 2021; a named cell maker, Highpower, followed in October 2025.
4. Cycle life fit for productsLateAbout 200 cycles at project end; 500 announced in 2025.
5. Series A of €15M in 2021Delivered€22M closed in August 2021.

On the narrow terms of the grant, the record is good: the final report says the target number was beaten, the demonstration line ran, and the follow-on round was larger than planned. The gap is the step the project called validation in a battery plant. No cell maker was named until 2025, four years after the project ended.

What LeydenJar Has Achieved Since the Award

The private money came quickly. In August 2021 LeydenJar raised €22 million from Catalus Capital, Yard Energy, Invest-NL, ING Sustainable Investments and Somerset Capital Partners, with existing investors BOM and DOEN Participaties, plus a subsidy of over €5 million from the Netherlands Enterprise Agency, according to the company and Silicon Canals, which reported plans to grow from 25 to 70 staff within 18 months. In December 2022 the European Investment Bank agreed a €30 million loan facility, backed by the Commission's InnovFin Energy Demonstration Projects, towards a €60 million first factory, according to the company. The EIB's own release of 9 December 2022 confirms the terms and calls the €30 million "quasi equity financing", backed by a European Commission guarantee.

In September 2025 Extantia and Invest-NL led €13 million of new equity, and a "leading US-based consumer electronics company", not named, committed €10 million of customer funding for production equipment, as reported by Tech.eu and the company. In January 2026 APG, for the pension fund ABP, led a further €7.8 million with TNO; the APG release counts €21 million of equity, €10 million of customer funding and €12 million of grants and loans in the year, €43 million in all, a total also reported by Zag Daily. EU state aid records list two Dutch NXTGEN HIGHTECH awards totalling €8,772,609 in 2023, according to North Data. The EIC Fund is not named among the investors in any of these announcements; the 2019 award was grant only.

The commercial partner it can name is Highpower Technology, a Chinese cell maker. In October 2025 the two companies said they had "already shipped thousands of prototype cells built on a pre-production assembly line to major consumer electronics customers" and planned tens of thousands of cells for qualification in 2026, according to the joint release, also reported by IO+. In January 2026 LeydenJar opened a sales office in Richmond, Virginia, and showed Silyte at CES, according to Bits&Chips and the company. No product on sale that uses its anode has been announced.

The company also took part in greenSPEED, a Horizon Europe project on greener electrode production coordinated by Virtual Vehicle Research GmbH in Austria, with an EU contribution of €301,250 to LeydenJar between July 2022 and December 2025, according to CORDIS. North Data lists ten European patent filings from 2022 to 2025, including one for the PECVD apparatus itself.

The Money and the Moving Factory

LeydenJar is still a loss-making development company. Its consolidated net loss was €12,639,272 in 2024 and €9,908,015 in 2025, according to the accounts filed with the KvK as published by North Data. Revenue, equity and staff figures from those accounts could not be checked without a paid subscription.

The factory has changed shape and date with each announcement. In December 2022 it was a 100 MWh plant "fully operational by 2026". In March 2024 the company chose a former Philips building at Strijp-T in Eindhoven for a 70 MWh plant to "open in 2026", as also reported by IO+. From September 2025 the target became 125,000 m² of anode a year, enough for 5 million smartphone batteries, with operations starting in 2027, and APG's January 2026 release says "early 2027".

1. Dec 2022
   100 MWh plantFully operational by 2026
2. Mar 2024
   70 MWh at Strijp-TTo open in 2026
3. Sep 2025
   125,000 m² a yearOperations start in 2027delayed
4. Aug 2026
   Rolls in productionExpanded commercial capacity in 2027

Why Europe Should Care

The Commission calls batteries "a strategic part of Europe's clean and digital transition" and has run the European Battery Alliance since 2017 to build a European supply chain. The Net-Zero Industry Act aims for EU manufacturing of strategic clean technologies to approach at least 40% of annual deployment needs by 2030. Anode material is one of the links Europe barely makes, and the CORDIS report argued in 2021 that Europe should not "become too dependent on Asian suppliers".

The record shows the limits of that ambition. LeydenJar's anode is made in the Netherlands, but the cells it goes into are built by a Chinese partner, its application engineers sit in Taipei, and its first customers are consumer electronics brands, one of them a US company that is co-funding the plant. That is a European materials supplier in a global chain, not a European battery industry.

The Verdict

LeydenJar has not been asked for comment for this article. It is based on public records, EU project data and published statements, linked throughout.