Solid-state batteries have a credibility problem, and it is not a technical one. The field has produced a decade of announcements about cells that will arrive at the end of some decade or other, and very little you can drive.
Siyu Huang's answer to that is a number. 1,205 kilometres, Stuttgart to Malmö, in a Mercedes EQS running Factorial cells, arriving with 137 kilometres still in the pack.
Her assessment of where that puts Factorial relative to the field is blunt: she does not think anyone else has demonstrated ten.
The route there
Huang did a PhD in chemistry at Cornell and built her first company during business school, in battery material manufacturing. They sold it. What she took from that experience was a decision to stop.
Her reasoning was that chasing incremental improvement in lithium-ion was the wrong problem, because lithium-ion is approaching the ceiling of its performance. Building something that leapfrogged the existing technology was the better use of the next decade.
Factorial started as a Friday afternoon project inside that first business and was spun out in 2019. Hyundai and Kia invested in 2021. Mercedes and Stellantis later led a USD 200 million round.
The milestones since are specific enough to check. A 100 amp hour solid-state cell with lithium metal, launched with Stellantis at CES in 2023, at 390 Wh/kg. A B-sample shipped to Mercedes the following year at the same energy density. Thousands of cells shipped to global OEM customers. Then the vehicle: Factorial supplied the cells, Mercedes built the module and pack, and the car did the drive.
Huang's own framing of the progression is the useful one. From a first small cell, to a bigger cell that barely worked, to a working cell, to large volumes shipped with consistency.
Why the car is not the market
Here is where she departs from what you might expect from someone who has just put cells in a Mercedes.
Automotive is not the first market Factorial is entering commercially, and the reason is arithmetic. Automotive volumes are large enough that getting to gigafactory scale takes at least two to four years. Meanwhile, a facility sized as a pilot line for automotive is already mass production for several other industries. One of the largest drone makers in the United States needs tens of megawatt hours. That is more than enough for an automotive pilot facility and nowhere near enough for automotive mass production.
So Factorial is going at aerospace, defence and consumer robotics first. Huang describes this as prudent and stepwise. Revenue is part of the benefit; the larger part is that each step surfaces risks in quality, consistency and supply chain before the capital is committed.
Her line on the alternative: you would not want to be building a gigafactory with only one cell in your hand. That is a huge amount of risk to take before you scale.
The drone opening
The first market has acquired a policy dimension recently.
China has announced export controls covering batteries above 300 Wh/kg, which restricts high-end lithium-ion as well as solid state. Roughly 90% of United States drone batteries currently come from China.
Huang's word for the resulting situation is a vacuum. It is a rare case of a regulatory change creating demand for a technology at exactly the moment that technology becomes shippable.
What actually had to be solved
Asked about reliability, Huang draws a distinction that explains why solid state has taken so long to arrive in anything you can drive.
If you build one cell, you can always make a high-performance cell. A hero cell that runs five or ten thousand cycles. Building a vehicle is a different problem: every single cell has to perform consistently, and she is direct that this is not a trivial task.
Factorial's first cells were not consistent. Closing that gap was not a chemistry change. It meant working with suppliers and equipment makers over time to perfect the manufacturing.
The design decision underneath it is the one that shapes the company's whole strategy. Factorial's manufacturing process is highly consistent with lithium-ion, by design, which let it borrow existing know-how rather than invent a new process alongside a new chemistry.
Asset-light, and what that actually means
That design choice pays off in capital. Because the process is close to lithium-ion, existing lines can be converted rather than replaced, and there is a great deal of idle lithium-ion capacity available to convert. Factorial's plan is to use it with minimal investment rather than build its own gigafactories.
Which raises the obvious question of whether the company becomes a licensing business.
Huang's answer is more careful than a yes. Licensing is possible, but in batteries it cannot mean handing over the IP and wishing the licensee luck. This is not tech or pharma. The manufacturing process and know-how determine performance, quality, yield and cost alike. So the model is licensing combined with technology services, helping the manufacturer adopt the technology and reach efficiency.
Factorial keeps the part it is best at. Huang started as a cathode company, so the team has depth across cathode, anode, electrolyte and separator, and optimises all of them together rather than sequentially. She describes the company as a technology solution leader and is unusually clear-eyed about what that means for who funds the plants: other companies have a lower cost of capital and can put in two billion dollars against a ten-year payback. Why not work together, is how she puts it, and bring the technology to market as an industry standard.
It takes more than one company, she says, to make a technology into a standard.
The discipline, and where it came from
Factorial is around a hundred people, which for a company with this investor list is small on purpose.
Huang credits the founding team and early investors, and names one in particular. Joe Taylor, Factorial's chairman, is the former chairman and CEO of Panasonic Americas. He is the person who invested two billion dollars into Gigafactory Nevada for Tesla, back when building batteries was difficult rather than fashionable.
The advice he keeps giving is one line, and it is the opposite of how most deep-tech companies behave: if you overinvest in yourself, it is really hard to dial back.
She adds a second influence in Dieter Zetsche, an early investor, who has pushed the company to keep its attention on the product rather than on acquiring capacity. Her summary of the discipline that produces: it is not exciting to build capacity, it is about where your product is and where the opportunity to reach positive cash flow actually sits.
And on valuation, delivered without much ceremony: it is not about how big a valuation you have, it is about how much value you can deliver.
The word she uses about Europe
Huang was at the Future Battery Forum in Berlin in 2021 and again this year, and what she noticed between the two visits was the emphasis on partnership, and specifically on a coalition across Western automotive rather than each manufacturer working alone.
Her read on the position is candid. The Western hemisphere is a few years behind on lithium-ion. European cell companies have visibly struggled. So the opportunity, as she frames it, is not to catch up on lithium-ion any more.
It is to leapfrog.
This piece draws on the full conversation, which is available with a complete transcript on the episode page.