Lithium is the lightest metal, making it ideal for use in batteries for portable electronics, electric cars and airplanes. But there's a tiny problem. Lithium-ion batteries have been known to catch fire. Fortunately, researchers just discovered a way to make them safer, reports Mariella Moon for Engadget.
Battery-caused fires aren’t common, but they are problem. A reporter at The Economist explains:
In 2006 millions of lithium-ion battery packs made by Sony were replaced after several hundred overheated and a few caught fire. These batteries were used in laptop computers produced by a number of manufactures. Since then, production processes have improved and fires remain relatively rare. As Elon Musk, Tesla’s founder, has pointed out that with some 30,000 Tesla cars now on the road, fires have affected one in 10,000 vehicles—which sounds bad, but the equivalent statistic for petrol-powered cars is one in 1,300.
The fire-starting abilities come from small faults that can lead to short circuits within the battery as it ages. Like all batteries, lithium batteries contain an anode and a cathode separated by a barrier. Faults or damage to that barrier can allow outgrowths or dendrites of lithium to grow through the barrier and connect anode to cathode, which causes an out-of-control ion exchange and heat build up. Eventually, the battery catches fire.
To prevent this, Stanford University researchers figured out how to stop the growth of those lithium dendrites, Moon reports. Lithium nitrate, which is known to improve battery life, and lithium polysulfide, which can break down lithium, held the key. The team tested different mixes until they found the right proportions to add to the battery. With the successful mix, the growths that formed were shaped like pancakes, not dendrites, and didn’t push through the battery’s barrier. The team published their findings in Nature Communications.
Further, adding both chemicals made the batteries more resilient, as they continued to operate at 99 percent efficiency even after 300 charge-discharge cycles. Those that were only treated with lithium nitrate started becoming less efficient after 150 cycles.
The tests were in small batteries — the kind used to power calculators and remote controls, writes Andrew Gordon in a news release from Stanford’s National Accelerator Laboratory, SLAC. The next step will be to see if the same new chemistry helps in larger-scale batteries.
Given the problems with lithium, some research groups are working to find other metallic options and get even more energy out of each battery. But this improvement might keep lithium on the top of the list for a bit longer.