Lithium-ion batteries are relatively safe but can still pose risks of fire or explosion. Researchers may now have solved that problem using a material commonly found in bullet proof vests.
The researchers are using a material derived from Kevlar to insulate parts of the battery responsible for the storage and discharge of energy. Leaks in that wall can cause short circuits, so preventing those them greatly reduces the risk of fire.
The batteries will be used first in robots and for military applications, but after that they'll come to laptops, tablets, smartphones, electric cars and other electronics, said Dan VanderLey, CIO and co-founder of Elegus Technologies, a startup that's commercializing the technology for scientists at the University of Michigan, Ann Arbor.
Over the years, millions of laptops and other gadgets from Dell, Lenovo, Sony and others have had to be recalled because of fire risk. In a handful of cases, smartphones and other devices have caught fire and exploded. And lithium-ion batteries caused problems in the new Boeing 787 Dreamliner.
Lithium-ion batteries have two electrodes and an electrolyte fluid that allows the lithium ions to flow between them. They're separated currently by a film of polyethylene or polypropylene, but it's porous and if material passes through it a short circuit can result.
The scientists are using a nanofiber material made from Kevlar to separate the cathode and the anode. It's more dense than current separators and will prevent the leaks that can lead to short circuits. The researchers make the nanofiber by dissolving it in a proprietary chemical formula.
Aside from reducing fire risk, the new separator material could increase the energy density and lifetime of batteries, according to VanderLey. It can be used in any lithium battery type, including lithium-ion, lithium-air, lithium-polymer or other chemistries. It also works with a wide variety of liquid and solid electrolytes.
The researchers are developing only the separator, and it will be up to battery makers to use the technology. Elegus has shipped samples to manufacturers and hopes they'll be able to start production late next year.
One snag is that Kevlar is that it's expensive, and the consumer electronics industry doesn't like high costs. Silver-zinc batteries, for instance, never broke through in laptops because of the cost of silver.
But VanderLey dismissed such concerns. A smartphone maker may have to spend 10 or 15 cents more per handset, but it would also be able to make thinner, lighter handsets and get 10 to 20 percent better energy density.
"Because we can produce thinner materials, it lowers material costs," VanderLey said.
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