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Solid electrolyte may end the catastrophic failures of lithium batteries

Lithium batteries have become a very popular technology, powering everything from cell phones to cars. But that doesn’t mean the technology is without its problems; lithium batteries have been implicated in some critical technological snafus, from exploding laptops to grounded airplanes. Most of these problems can be traced back to the electrolyte, a liquid that helps ions carry charges within the battery. Liquid electrolytes can leak, burn, and distort the internal structure of the battery, swelling it in ways that can lead to a catastrophic failure.

The solution, of course, to get rid of the liquids. But ions don’t tend to move as easily through solids, which creates another set of problems. Now, researchers have formulated a solid in which lithium ions can move about five times faster than any previously described substance. Better yet, the solid—a close chemical relative of styrofoam—helps provide structural stability to the battery. Don’t expect to see a styrofoam battery in your next cellphone though, as the material needs to be heated to 60°C in order to work.

The problem with liquid electrolytes has to do with the fact that, during recharging, lithium ions end up forming deposits of metal inside the battery. These create risks of short circuits (the problem that grounded Boeing’s Dreamliner 787) and can damage the battery’s structure, causing leaks and a fire risk. Solid electrodes get around this because the lithium ions will only come out of the electrolyte at specific locations within the solid, and can’t form the large metal deposits that cause all of the problems.

However, as noted above, solids don’t allow lithium to move through them very easily. This creates a bit of a practical problem, in that the batteries typically need to be heated to around 80°C before charges start moving at all. But long term performance problems are even worse. Because the ions move so slowly, a gradient of lithium gets built up across the battery during discharging, with ions piling up near the negative electrode. This slows the rate at which they can charge and discharge.


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