As rechargeable batteries are built ever larger and more dense, they become increasingly more explosive. Perhaps the most famous explosive batteries were found in Samsung's disastrous Note 7 phones, but explosive batteries have also cropped up in e-cigs, hoverboards, and even a NASA robot. It seems like nothing can escape the danger of exploding batteries.
So how are scientists and engineers combating the rise of explosive batteries? Mostly, they're not. Batteries are complicated and right now the best we're able to do is regulate how quickly they charge and discharge, in an attempt to reduce the odds of exploding. But one group of researchers has managed to , giving hope that we might soon be able to design a battery that doesn't explode at all.
The researchers, from Stanford University and the SLAC National Laboratory, used a new technique called cryo-electron microscopy (cryo-EM) to take these atomic-level images. Cryo-EM involves cooling a sample down to only a few degrees above absolute zero and studying it with powerful electron microscopes. Using this technique, researchers can study the intricate workings of batteries in extremely high resolution.
"With cryo-EM, you can look at a material that's fragile and chemically unstable and you can preserve its pristine state—what it looks like in a real battery—and look at it under high resolution," says researcher Yi Cui. "This is super exciting and opens up amazing opportunities."
Specifically, they were able to image dendrites—long filaments inside the battery—using this technique, which is the first time these have ever been directly imaged before. In the above video, using a traditional electron microscope simply causes the dendrite to collapse from the high-energy beam of electrons. Cryo-EM keeps the dendrite preserved long enough to capture details about its structure.
"Every time we tried to view lithium metal at high magnification with an electron microscope the electrons would drill holes in the dendrite or even melt it altogether. It's like focusing sunlight onto a leaf with a magnifying glass," says researcher Yuzhang Li. "But if you cool the leaf at the same time you focus the light on it, the heat will be dissipated and the leaf will be unharmed. That's what we do with cryo-EM."
Scientists believe that these dendrites are the reason that these types of batteries fail. Dendrites can grow all the way from one side of the battery to the other, shorting it and causing all the battery's energy to be released at once. Scientists have been trying to develop chemicals they can add to batteries to stop dendrites from forming, but until now no one was sure how those chemicals worked.
Using cryo-EM, the Stanford and SLAC researchers looked at the atomic structure of dendrites before and after chemical treatments and found substantial differences. In particular, dendrites treated with these chemicals have more orderly atomic structures, which the researchers believe is key to keeping those dendrites under control.
"This tool can help us understand what different electrolytes do and why certain ones work better than others," says researcher Yanbin Li.
With that information, the Stanford and SLAC researchers, along with other research groups across the country, can work to develop batteries that don't suffer from crippling dendrites, meaning we might finally be able to build large, powerful batteries that aren't in danger of exploding.
Hopefully someone can finish that tech in time to get it into Samsung's next Galaxy Note.