![]() But some high-profile buyouts of solid-state technology startups have sputtered. Honda, Nissan, and Toyota have teamed up with Panasonic Corp. Recently, industry giants have also begun to invest in solid-state batteries. The new battery design has twice the energy density of conventional lithium-ion batteries and can be recharged 23,000 times. The plasticizer acts as a cushion to prevent cracking, Braga says. One problem with solid-state batteries is that as various materials expand and contract at different rates, the batteries’ interfaces crack. In their latest design, which they reported in April in the Journal of the American Chemical Society, they coat the flexible cathode with a special plasticizer solution. He and colleague Maria Helena Braga use a lithium-doped glassy material as the electrolyte. Last year, John Goodenough at the University of Texas at Austin unveiled a solid glass battery. Other labs remain focused on that vision of the ultimate solid-state battery. “But we think our semisolid approach is good enough.” “There are lots of people trying to find the 100 percent perfect solid-state approach,” Hu says. The downside is that it can be recharged only about 200 times, as opposed to more than 1,000 times for conventional batteries. The battery’s energy density is about 500 watt-hours per kilogram, twice that of a conventional lithium-ion battery’s 250 Wh/kg. The device is technically a semisolid battery but safer than conventional lithium-ion cells, Hu says. The electrolyte on the cathode contains just enough solvent to make the lithium salts conduct ions at room temperature. Weed Control: These ultrathin anodes, made of pure lithium foil, are covered in a polymer-ceramic coating to prevent harmful dendrites from sprouting. Another electrolyte, a paste of lithium salts, goes on the cathode. SolidEnergy’s workaround is to coat its ultrathin anode, made of a pure lithium foil, with a mixed polymer-ceramic electrolyte, which smothers dendrite growth. So battery researchers switched to carbon for the anode. But lithium metal anodes quickly grow mossy whiskers called dendrites, which can reach the cathode and short the battery. Lithium-ion battery pioneers originally chose lithium metal for the anode in the 1980s. In addition to being safer than their liquid counterparts, these alternatives could also support a pure lithium anode, which would boost energy density. Some ceramics, polymers, and glassy materials can also do that well. Its job is to shuttle ions between the carbon anode and the lithium transition metal oxide cathode. In today’s batteries, a dilute solution of lithium salts serves as the electrolyte. The company is currently testing its batteries for drones and expects to begin selling them later this year, followed by batteries for wearables in 2019 and for electric vehicles after 2021. With SolidEnergy’s new battery, those drones could fly for 40 minutes or more. ![]() For example, right now “advanced drones have sensors, cameras, and processors on board, so the battery lasts only 20 minutes, and it’s heavy,” says founder Qichao Hu. That means devices could work twice as long. The startup says it can pack twice as much energy into its battery as a conventional lithium-ion battery of the same weight can store. Now, SolidEnergy Systems, in Massachusetts, plans to become the first company to sell such batteries. But researchers have pursued solid-state battery technology for decades without coming up with any products. These devices swap out flammable liquid electrolytes for an inert solid such as plastic or ceramic. Researchers have touted solid-state lithium batteries as a safer alternative. But they have a dangerous tendency to burst into flames, leading to injuries, product recalls, and flight bans. ![]() Lithium-ion batteries boast a powerful blend of energy capacity and long cycle life.
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