New Silicon Anode Technology Promises 28 Percent Longer Run Times
With lithium-ion batteries, even small improvements can make a big difference, translating to range in an electric car or longer life in a computer or tablet. That’s why it’s potentially a big deal that the Chicago-based start-up NanoGraf says that its silicon anode will enable what CEO Francis Wang calls “the world’s most energy-dense cylindrical 18650 cell,” with 800 watt-hours per liter (Wh/L). That’s a 28 percent higher run time than what’s possible with traditional cell chemistry, the company said. Reduced weight is also promised, as is—long term—less cost.
NanoGraf’s technology was developed at Northwestern University in 2012, and the company was started to commercialize it. Wang isn’t a founder, but came on board in 2015 and has been CEO for the past three years. The company now has 32 employees and has raised $23 million since its inception—largely from the military.
The interest from the armed services is obvious, because NanoGraf says it can improve operating times for soldiers’ portable equipment, and cut the weight of a 20-pound battery pack (the second-heaviest thing they carry, after body armor) by more than 15 percent. “We are a small company and we have to start somewhere,” Wang said. “The military is a great beachhead market for us.”
Theoretically, silicon anodes could store 10 times the amount of lithium as traditional graphite, IEEE Spectrum reports. Wang translates that as graphite with 300 milliamp-hours per gram “compared to silicon with over 3000.” So why don’t all li-ion cells use silicon then?
It’s not easy. Battery makers have been adding small amounts of silicon powder to the graphite, but haven’t gone much further because silicon expands dramatically in charging scenarios.
According to Sam Abuelsamid, principal analyst for e-mobility at Guidehouse Insights, “Silicon anodes aren’t new. I haven’t looked at this specific company, but the big challenge with silicon anodes is swelling. Most battery companies have limited the anode to a mix of about 10 percent silicon and the rest graphite to get a boost in capacity while also limiting swelling. Because of the swelling, you have to leave more space in the pack to avoid squeezing the cells, and that offsets the increased density of individual cells. If NanoGraf has figured out a way to get the increased density without so much swelling, that would be a win.”
“It’s been a historical challenge, because silicon is not as stable as graphite,” admits Wang. “There is cycle-life degradation. We think we have by-and-large solved that, and we’re proving it in cells and real battery packs.”
NanoGraf President Dr. Kurt Breitenkamp said in a company release, “This is a breakthrough for the battery industry. Energy density has plateaued, only increasing eight percent or so over the last decade. We just achieved a 10 percent increase in a little under a year. That is over a decade’s worth of innovation in one technology.”
NanoGraf is currently producing 10 tons of its silicon anode material annually in Japan, but it plans to open a plant in 2022 on the west side of Chicago to produce 35 tons every year. The company has no plans to become a battery maker—the silicon powder is meant to be a drop-in solution for existing battery companies.
NanoGraf has an as-yet unnamed battery cell partner. “It’s not LG Chem or Panasonic, but it is one of the oldest lithium-ion producers, with a history going back to the 1980s,” Wang said. Don’t expect 2022 Teslas to sport “NanoGraf Inside” badges, but Wang said its technology will be in portable military electronic equipment as early as next year.
Wang, who drives a Tesla Model 3, said NanoGraf definitely has an eye on the huge automotive market. But he acknowledged that the current cost of silicon alternatives is higher than on-the-shelf graphite solutions. “We reach cost parity with graphite at 1000 tons per year,” Wang said.
That volume is still a ways off. “For transportation, we see possible early customers as producers of premium products, companies that care more about performance than cost,” Wang said. “Probably not Ford or GM, but more niche—John Deere or Lucid perhaps. Cost is definitely a factor, but our greater vision is to leapfrog into EVs.”
Wang said that range may not be the key factor in tomorrow’s EVs—quicker charge times, something his anodes can also support, may be a more critical factor.
