In the quest to coax more capacity from electric vehicle batteries, automakers are increasingly turning to silicon, a widely available but fragile ingredient that promises to boost capacity by at least 20%.

Sila, Group14, Envoix, and Amprius are all trying to commercialize their silicon anode technology, hoping to cash in on consumers’ desire for ever more EV range.

Ionobell, a seed stage startup, is hoping to be at the top of that list, claiming its silicon material will be cheaper than the established competition.

The small startup uses an approach that’s most similar to Sila and Group14. Both established companies impregnate porous graphite structures with silicon; Sila also adds a coating to the particles. Ionobell appears to flip the script, according to the company’s patents. It starts with a porous silicon structure instead of a graphite one and then surrounds it with a coating.

“It doesn’t swell,” Ionobell co-founder and CEO Robert Neivert told TechCrunch. “Like dropping a nerf ball in water, it absorbs without the outer shell changing.”

Silicon can accept 10 times more lithium ions than graphite. But it swells a lot in the process, so much so that an ordinary silicon anode can crumble with repeated use. That fragility has kept manufacturers from incorporating too much of the element, typically less than 10%.

Still, silicon’s promise is too great to overlook.

Ionobell’s silicon supply comes from a waste material, Neivert said, which helps keep costs down. “Most of the cost savings is material,” he said, adding that Ionobell’s material is cheaper than graphite.

Neivert initially encountered Ionobell as an investor. At first, he said, “I rejected them as an investment,” telling them all the reasons why automotive suppliers wouldn’t adopt their technology. The team went back to work, solving the issues to Neivert’s satisfaction, including adapting their material to work on widely used manufacturing equipment. Neivert found some initial funding and joined them as CEO.

The last round closed in 2020, according to Pitchbook. Recently, though, Ionobell closed an unpriced $3.9 million seed extension, TechCrunch has exclusively learned. Dynamo Ventures and Trucks VC led the round.

Such extensions have become more commonplace as deep tech firms run short on capital but struggle to raise a new priced round as markets start to reset after a frothy start to the 2020s.

Like other battery materials companies, Ionobell faces a challenging road ahead. The validation process required by automotive companies can be long and arduous; not every material makes it through.

Plus, competitors like Group14 and Sila are close to commercialization, and their silicon-rich anodes will be hitting the market as early as this year and next.

Ionobell has a lot of ground to make up, though its promise of a lower price could give it a boost. Whatever the case, the next wave in lithium-ion innovation is almost here, and silicon is leading the pack.