Sila Nanotechnologies raises $70 million for silicon anodes

Sila Nanotechnologies, a start-up based in Alameda, Calif., has raised $70 million in its fourth round of venture funding from Sutter Hill Ventures; Next 47, a venture firm backed by Siemens; and Amperex Technology, a Chinese battery maker. Sila is working to commercialize lithium-ion battery anodes made primarily of silicon.

Researchers have long known that replacing traditional graphite anodes with ones made with silicon can greatly increase the energy density of lithium-ion batteries. But the trick is formulating the material to prevent its bad habit of swelling.

Lithium-ion battery anodes store lithium that settles there when batteries are charged. Graphite is a cheap, durable anode material; the catch is that it has limited storage capacity. Silicon can store much more lithium, but the resulting swelling ends up degrading the battery.

Sila says it gets around this problem with nanostructured materials. It’s not the only one on the hunt: Germany’s Wacker Chemie is also working on nonswelling silicon particle formulations. And in the U.K., Synthomer and the battery materials company Nexeon are developing polymers to bind silicon anode materials.

Sila says its anodes can replace graphite in current battery manufacturing lines. CEO Gene Berdichevsky says the company has spent seven years on materials development. “With the chemistry proven, we are now moving into a new phase of market application and manufacturing at industry scale,” he says.