Scientists working out of Oak Ridge National Laboratory and the University of Rochester have come up with a way to help make the use of lithium-ion batteries even safer, products that are known for bursting into flames when packaged badly or damaged.
Principal investigator on the project Gabriel Veith explained that these batteries contain a small piece of plastic that keeps the two electrodes separate. But if the battery itself is damaged and this plastic fails, the electrodes can touch each other and cause the liquid electrolyte in the battery to catch alight.
But he was inspired to come up with way of solving this problem while playing with his children and mixing together water and corn starch to make a substance known as oobleck. This particular mixture flows like a liquid when on a surface, but solidifies once it’s touched or pressure is applied in some way. Once this pressure is removed, the mixture becomes liquid again.
After this, the team mixed an additive into the electrolyte in order to create an impact-resistant electrolyte that solidifies when hit so that the electrodes can’t touch each other if the battery is damaged in some way.
It depends on a colloid (a suspension of tiny solid particles in a liquid) in order to work in this way, in this particular case silica suspended in common liquid electrolytes to work in lithium-ion batteries.
One of the biggest advances is for the production process for these batteries, where electrolytes are added into the battery case at the end before the battery can be sealed. Mr Veith said: “You can’t do that with a shear-thickening electrolyte because the minute you try to inject it, it solidifies.” As a result, the silica is put in place before the electrolyte.
Similarly, a team of scientists at the US Army Research Laboratory and the University of Maryland recently developed a lithium-ion battery that used a water-salt solution as the electrolyte, reaching the 4.0 volt mark required for use in electronics such as laptop computers.
A gel polymer electrolyte coating was produced that could be applied to either anode, expelling water molecules from around the electrode surface. When charging, this then decomposes and you’re left with a stable interphase that protects the anode from side reactions.
Dr Kang Xu, co-author of this particular project, said at the time that before this a non-aqueous lithium-ion battery had be chosen if high energy was required, but this would mean compromising on safety. If safety was key, then an aqueous battery could be used but this would mean having to settle for lower energy. But this latest development means that high energy and high safety can be achieved simultaneously.
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