Cyrus Rustomji, PhD ’15, has been called crazy on a couple occasions. He once drilled holes into his surfboard and installed electronics inside, creating a set of speakers he felt worthy of playing the Beach Boys. “People gave me a hard time because it was a perfectly good surfboard,” he says, “but in my defense it was waterlogged. It no longer floats, but it’s really loud because the acoustics work well with the fiberglass and foam core.”
Rustomji was also called crazy for the idea that ultimately led to his own business, South 8 Technologies, which is aiming to make lithium batteries work better in extreme cold. Low temperatures are known to wreak havoc on current battery performance, as they slow down the chemical reactions inside the battery that produce and store power. This can be a big problem if you want to drive an electric car in places like Minnesota, or wherever else winter temperatures regularly dip below freezing.
While he was a PhD student in professor Shirley Meng’s nanoengineering lab, Rustomji’s “crazy” idea for batteries was to create a new type of electrolyte—the chemical substance that moves charges back and forth inside batteries to create power. Conventional lithium batteries contain liquid electrolytes, which freeze at low temperatures. So Rustomji had the unconventional idea to replace the liquid electrolyte with something far more cold-hardy: liquefied gases.
Liquefied gases are a lot more common than they sound—your barbecue grill is likely fueled by liquid propane. But Rustomji realized that liquefied gases were key to making battery electrolytes that weather the cold, as they stay liquid at temperatures where conventional electrolytes freeze. “No one had ever done this in battery research,” Rustomji says. “Most battery scientists would say there are too many problems with using a gas. Even my PI thought I was crazy. But I thought there might be a way.”
There were plenty of problems to overcome, such as finding a gas that could dissolve salts (electrolytes are essentially salt solutions) and designing new hardware and experiments for testing liquefied gas electrolytes in batteries. Yet after years of trial and error, Rustomji formulated the ideal electrolyte using the gas fluoromethane. With it, lithium batteries tested in the lab not only worked better at record low temperatures, they could store more energy and were also safer—the electrolyte has a built-in safety mechanism that stops it from working at high temperatures, preventing the battery from overheating and potentially catching on fire.
So how cold is cold? Where today’s typical lithium batteries stop working at -4° F, a battery from South 8 Technologies can perform at a record low of -76° F. Such a radical difference can yield benefits well beyond electric cars in wintertime—it could be a game changer for any craft deployed to extremely cold environments, such as underwater vehicles, weather balloons and satellites.
With such potential, Rustomji wasted no time starting a business. South 8 Technologies was founded in 2015, the same year he earned his PhD. Yet Rustomji kept UC San Diego close after graduation: he continued working in Meng’s group as a postdoc to improve the new electrolyte chemistry, and later formed the company’s core team with fellow lab members, MBA students from the Rady School of Management and a business professional from UC San Diego’s Entrepreneurs–in-Residence program.
This team of Tritons hopes this low temperature breakthrough can make a big impact for the world in broadening the use and range of battery technology. The team is currently working on samples to send to automotive manufacturers, and even recently received funding from NASA to develop electrolytes that can run even colder, down to -148° F, to with the potential to power spacecraft or interplanetary rovers sent to explore planets like Jupiter and Saturn.
But whether their sights are set on space or deep under the ocean, Rustomji and his team will be working to take today’s batteries to crazy new levels.