The drive to a better lithium-ion battery has often hit a wall in the lab, with teasing innovations that can’t make the leap to scale and success.
NanoGraf believes it can make that leap, and in the process lighten the battery load for U.S. troops carrying or otherwise porting electronic equipment in the field. The Chicago-based startup has unveiled an 18650 lithium-ion cell it claims has the world’s highest energy density of its type: 800 watt-hours per liter.
NanoGraf’s chemical ambition is familiar, one that’s fueled the dreams of battery companies and researchers for years: Replacing a carbon graphite anode with a nanoengineered, oxidized silicon anode that can store vastly more lithium atoms. What’s different, according to company CEO Francis Wang, is that NanoGraf’s proprietary tech is stable and affordable enough to satisfy the global behemoths of battery production, and to be able to do this within the constraints of current manufacturing techniques.
Commercial battery advances have plateaued in recent years, Wang said. To substantiate this point, a company spokesperson pointed to a proprietary analysis of the recent history of battery industry performance (that Spectrum reviewed), which notes that the progress of state-of-the-art lithium ion batteries’ power capacity has slowed over the previous decade—which has also stalled out the previously steady price drop of commodity battery cells. But NanoGraf’s silicon-anode battery, Wang said, packs ten percent more energy density than even the industry’s top-performing 18650 cells.
“So this is a decade’s worth of improvement in a single technology,” Wang said.
The company, a spinout of Northwestern University and Argonne National Laboratory, has received most of its funding from the U.S. departments of Defense and Energy. And its proof-of-concept involves easing the burden for soldiers on patrol, who often lug 15 to 25 pounds of batteries to power GPS, night vision, radios and other gear. NanoGraf cells, already in the production-validation stage in North America, could reduce their pack weight by 15 percent.
“We hope to have our technology in the hands of soldiers in 2022. It all starts with them putting on a vest and seeing if they like it,” Wang said.
If NanoGraf can reach that beachhead market, its next goal is to scale the daunting walls of Detroit and other EV manufacturers, along with makers of consumer electronics.
Jung Hwi “Juny” Cho, a PhD candidate at Brown University who’s spent more than eight years researching lithium-ion batteries, outlined the challenges facing companies like NanoGraf.
Compared with graphite, silicon offers ten times the theoretical capacity to absorb lithium: 3572 mA h/g, versus graphite’s 372 mA h/g.
But silicon swells and expands by up to 300-400 percent during charging, reliably wreaking havoc on fine silicon particles and protective barriers between anode and electrolyte. To overcome it, Tesla is among battery makers adding tiny amounts of silicon to graphite powder. Manufacturing long-lasting Si-based anodes, affordably and at scale, are other major hurdles.
“That’s one of the most important points when looking at battery startups,” Cho said. “ It’s easy to create a working prototype with a high energy density, but a whole other level to mass manufacture them and create consistent batches over and over.”
Wang believes NanoGraf has fixed all those major “pain points.” He cites an impressive first-cycle Coulombic efficiency of 89 or 90 percent, within sight of graphite anodes, and high enough to intrigue any major battery maker. The battery dramatically reduces swelling versus carbon-coated silicon oxides, Wang adds, with a proprietary aqueous surface coating that protects the anode from damaging reactions.
“Ours expands less, with less wreaking of havoc and the degradation mechanism,” he said.
Finally, NanoGraf’s aqueous surface coating is more affordable and practical than conventional vapor-deposition coatings, Wang said, with the ability to “drop in” to existing battery-making facilities. An Oak Ridge Laboratory study said that, after battery materials, electrode manufacturing is the most expensive aspect of production, accounting for up to 40 percent of total battery pack cost.
Wang said that the battery giants, including LG Chem, Panasonic, Samsung and CATL, have reached roughly five percent silicon content in battery anodes, but are stuck there.
“Our tech will allow them to go far beyond that,” Wang said.
“Silicon will be slowly replacing graphite over time.”
The company currently manufacturers 10 tons each year of its oxidized silicon material in Japan—the company’s “secret sauce,” as Wang puts it. But NanoGraf is targeting 35 annual tons by next year from a planned facility in the West Loop of Chicago. That would be enough for modest military supply, with an ultimate goal of producing thousands of tons and expand into electric mobility.
“To reach Detroit and electric vehicles is the dream, but we have to get to fighting weight first,” Wang said.
NanoGraf would not cite its partnerships, but said it’s working with more than 50 companies, including some of the world’s leading consumer electronics, household appliance, and power tool brands, along with roughly a dozen strategic partners in electric mobility.
Cho noted that silicon faces stiff competition from lithium-metal or solid-state batteries, but that those technologies may face an even-longer path to commercial success. Until the technology takes the next big leap, silicon’s potential is clear.
“I think silicon will definitely help boost battery life and range; it’s a logical next step from the batteries we have.”