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 LeydenJar

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. LeydenJar 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 PlantOne 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 LeydenJar, 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 LeydenJar'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 LeydenJar.

• 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 characterizing silicon-based anode materials (pure silicon, silicon-carbon composites, silicon-graphite blends, or related systems).

• PhD in Chemistry, Materials Science, Chemical Engineering, Electrical Engineering, or a related field; or a Master's degree with at least 2 additional years of relevant industry experience beyond the silicon experience above.

• Exceptional understanding of lithium-ion technology and electrochemistry, including a well-developed view of cell failure mechanisms as shaped by materials, design, and process choices.

• Strong practical experience using state-of-the-art electrochemical, chemical, and materials-characterization techniques to elucidate failure modes and mechanisms. Analyzing complex datasets and delivering clear takeaway messages.

• Hands-on experience with pouch cell manufacture, formation, and battery cell testing.

• Demonstrated experience leading technical projects end-to-end, coordinating multiple parties toward ambitious targets under tight deadlines.

• Demonstrated experience managing or mentoring individuals or small teams of Master's- or PhD-level scientists, supporting both technical delivery and personal development.

• Comfortable splitting time between desk work and lab. You believe getting your hands dirty is sometimes the fastest way to understand a process.

• Able to multi-task and work independently in a fast-paced environment with a great sense of urgency. You generate solutions rapidly and move quickly to validate them. Creative and 'out of the box' thinker to tackle problems head on.

• Clear communicator who can explain technical reasoning, assumptions, and uncertainty to experimental, customer, and leadership audiences.

• Strong customer focus and ownership mindset.

• Fluent in English.
  

Why LeydenJar?

• Unleash Your Potential: Step into a workplace where growth and ownership go hand in hand. We empower every individual regardless of background, gender, or identity to thrive and achieve their career aspirations.

• Pension & Insurance Security: We care about your future. LeydenJar contributes 10% on top of your monthly gross salary toward your pension and life insurance, ensuring long-term security for you and your loved ones.

• Recharge & Refresh: Enjoy 25 vacation days per year (based on full-time hours) because work-life balance is essential for everyone.

• Travel Made Easy: We cover your home-to-work travel costs with €0.23 per kilometer or provide an NS Business Card for hassle-free public transportation.

• Continuous Learning: Access our online learning platform (Udemy) to develop your skills and unlock new opportunities for personal and professional growth.

• Diverse, Inclusive & Equal: Be part of an international team of 20+ nationalities, where everyone’s voice matters, and where diversity, equity, and inclusion are more than values they’re actions.

• Community & Connection: From team-building events and monthly lunches to year-end celebrations and inclusive gatherings, we create spaces where everyone feels welcome and engaged.

Do you want to take on the challenge as Senior Battery Scientist - Engineer?

We are looking forward to your application!

If you'd like to learn more about LeydenJar amazing team, see below:

At LeydenJar we value diversity, and we provide equal opportunities to all applicants without regard to race, color, ethnicity, religion, gender, pregnancy/childbirth, age, national origin, sexual orientation, disability, etc. If there are two or more applicants of equal suitability for a certain position, LeydenJar can under circumstances decide to select applicants based on positive discrimination in full compliance with all relevant and applicable law.