From IEEE Spectrum, May 31:
Five Cool Tech Demos From the ARPA-E Summit
New batteries and mining techniques shine at the annual energy showcase
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....
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.
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 fire.
There’s another benefit to this battery, and this one will make EV drivers very happy: It will take only 10 minutes to reach an 80 percent charge in EVs powered by these batteries, Rustomji estimates. That’s because liquified gas has a lower viscosity than carbonate-based electrolytes, which allows the lithium salt to move from one electrode to the other at a faster rate, shortening the time it takes to recharge the battery.
South 8’s latest improvement is a high-voltage cathode that reduces material costs and could enable fast charging down to 5 minutes for a full charge. “We have the world record for a high-voltage, low-temperature cathode,” says Rustomji.
