ARPA-E Energy Innovation Summit 2024: Coolest Tech

_{Nearly 400 exhibitors representing the boldest energy innovations in the United States came together last week at the annual ARPA-E Energy Innovation Summit. The conference, hosted in Dallas by the U.S. Advanced Research Projects Agency–Energy (ARPA-E), showcased the agency’s bets on early-stage energy technologies that can disrupt the status quo. U.S. Secretary of Energy Jennifer Granholm spoke at the summit. “The people in this room are America’s best hope” in the race to unleash the power of clean energy, she said. “The technologies you create will decide whether we win that race. But no pressure,” she quipped. IEEE Spectrum spent three days meandering the aisles of the showcase. Here are five of our favorite demonstrations.}

Gas Li-ion batteries thwart extreme cold

South 8 Technologies demonstrates the cold tolerance of its Li-ion battery by burying it in ice at the 2024 ARPA-E Energy Innovation Summit.Emily Waltz

Made with a liquified gas electrolyte instead of the standard liquid solvent, a new kind of lithium-ion battery that stands up to extreme cold, made by
South 8 Technologies in San Diego, won’t freeze until temps drop below –80 °C. That’s a big improvement on conventional Li-ion batteries, which start to degrade when temps reach 0 °C and shut down at about –20 °C. “You lose about half of your range in an electric vehicle if you drive it in the middle of winter in Michigan,” says Cyrus Rustomji, cofounder of South 8. To prove the company’s point, Rustomji and his team set out a bucket of dry ice at nearly –80 °C at their booth at the ARPA-E summit and put flashlights in it—one powered by a South 8 battery and one powered by a conventional Li-ion cell. The latter flashlight went out after about 10 minutes, and South 8’s kept going for the next 15 hours. Rustomji says he expects EV batteries made with South 8’s technology to maintain nearly full range at –40 °C, and gradually degrade in temperatures lower than that.

South 8 Technologies

Conventional Li-ion batteries use liquid solvents, such as ethylene and dimethyl carbonate, as the electrolyte. The electrolyte serves as a medium through which lithium salt moves from one electrode to the other in the battery, shuttling electricity. When it’s cold, the carbonates thicken, which lowers the power of the battery. They can also freeze, which shuts down all conductivity. South 8 swapped out the carbonate for some industrial liquified gases with low freezing points (a recipe the company won’t disclose).

Using liquified gases also reduces fire risk because the gas very quickly evaporates from a damaged battery cell, removing fuel that could burn and cause the battery to catch fire. If a conventional Li-ion battery gets damaged, it can short-circuit and quickly become hot—like over 800 °C hot. This causes the liquid electrolyte to heat adjacent cells and potentially start a…