Senior Battery Scientist-Engineer

Do you want to contribute to a more sustainable world? Are you excited to help shape the future of battery technology and consequently the future of consumer electronics and mobility? Can you not wait to dive into a VC-backed deep tech scale-up with the ambition to change the world?
We are looking for an  Senior Battery Scientist - Engineer  to join our innovative and ambitious organization and drive deep understanding and performance improvement of 100% silicon-anode lithium-ion cells, lead technical projects, and help shape the next generation of high-energy batteries.
About Leyden Jar  High energy density is an urgent, unmet need across consumer electronics, mobility, and the wider electrification of industry. Yet the battery industry typically improves by only 3% per year. Leyden Jar addresses this by tackling the energy density bottleneck: the anode. Our 100% silicon anode, regarded as the holy grail of the battery industry, enables up to 50% increase in energy density.
We have demonstrated 500+ cycles without external pressure on multilayer pouch cells using our 100% silicon anode. We are now progressing into scaled-up production, with increasing customer traction, and our first anode factory Plant One opening in 2026.
Continued advancement under increasingly demanding conditions requires ever-deepening fundamental understanding of cell behavior and failure mechanisms. This role of  Senior Battery Scientist - Engineer  is central to that effort.
Your mission  As  Senior Battery Scientist - Engineer  at Leyden Jar, your mission is to drive the continued performance improvement of our 100% silicon anode cells across the full performance envelope: energy density, cycle life, fast charging, voltage range, temperature range, and abuse tolerance.
You will operate as a senior generalist with deep technical credibility across the cell - silicon anode, cathode, electrolyte, separator, cell design, and formation - and translate that breadth into concrete improvements in cell performance. As an immediate first focus, you will lead failure mode and failure mechanism analysis and the characterization work that underpins it, with particular attention to high-temperature and high-voltage operation.

From that base, you will broaden into cell chemistry development, cell design, and process optimization, and take technical lead on multi-disciplinary projects toward customer-relevant performance targets.
You will help shape technical direction within the Battery R&D function, develop more junior scientists, and represent the team in cross-functional and leadership forums.
Your primary location will be Leiden. You may be required to work occasionally in Eindhoven.
You will report to the VP of Battery and work closely with Battery R&D, Product Development, Data Science, and other internal partners, as well as external cell maker partners, material suppliers, and university collaborators.
You will join a small yet highly effective team. You are expected to deliver rigorous science with startup-level speed and pragmatism.
Your responsibilities   Drive the continuous improvement of Leyden Jar's silicon anode cells across energy density, cycle life, fast charging, voltage range, temperature range, and abuse tolerance, combining characterization insight with cell chemistry, design, and process development.
Take technical lead on selected projects, coordinating across Battery R&D, Product Development, Data Science, and Production toward customer-relevant performance targets and tight deadlines.
Characterize and optimize cell chemistries - anode, cathode, electrolyte, separator - and contribute to cell design and pouch-cell production process development.
As an immediate first focus, lead failure mode and failure mechanism analysis on full cells and components, with particular attention to high-temperature and high-voltage operation, and translate findings into concrete materials, design, and process improvements.
Design and execute characterization and fundamental studies, internally and via partnerships, using a broad toolkit including electrochemical methods, chemical and surface analysis, mechanical and physical methods, in-situ and operando.
Develop and introduce new electrochemical, chemical, and mechanical characterization methods where existing techniques fall short.
Develop and optimize formation and cycling protocols with demonstrable impact on cell performance metrics.
Mentor and line-manage junior colleagues, supporting their technical work and personal development.
Contribute to the technical strategy of Battery R&D, and represent the team in cross-functional and leadership forums as required. Liaise with suppliers, customers, and external partners as a technical representative of Leyden Jar.
Contribute to IP identification and patent novel findings.
Communicate clearly and concisely to technical, customer, and leadership audiences, both in writing and orally.
About you   At least 3 years of hands-on industry experience developing or…