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article imageResearch lab blunder leads to 4x longer-lasting Li-ion battery

By James Walker     Aug 18, 2015 in Technology
Researchers who accidentally left a batch of anodes to soak in chemicals for hours longer than they were supposed to have stumbled across a method of getting Li-ion batteries to last for four times longer than they ordinarily would.
Hexus reports on the mistake by scientists working at Tsinghua University in Beijing and the Massachusetts Institute of Technology in Boston. The research team has been trying to find a way to prevent anodes in Li-ion batteries from decaying, causing the decreased battery life over time that will be familiar to any long-term smartphone user.
The decay occurs as lithium compounds build up on the anodes, causing them to expand and contract. The expansion and contraction can cause the compounds to come loose again, exposing the surface of the anode and gradually eroding it away.
Using aluminium anodes in place of the graphite ones of today would lead to greater battery life. Aluminium creates stronger batteries than graphite but unfortunately expands and contracts too much in each charge cycle to make its use viable, making it even less durable than graphite. What the aluminium ideally needs is a protective outer shell so that the surface of the anode isn't exposed and can't decay.
The research team thought nanoparticles could produce this effect. They left batches of anodes soaking in a chemical treatment. In a lab slip-up, one batch of anodes was inadvertently forgotten and left in the chemicals for several hours longer than had been intended.
In what could otherwise have been a great scientific loss, the scientists decided to test the anodes anyway once they had been found and recovered. When the results returned, they showed that an anode four times more durable than the units in today's devices had been created.
The anode had formed a solid outer shell made of titanium nanoparticles. Inside, lay a core made of aluminium material that could expand and contract without damaging the outer shell, like a yolk. After testing through 500 charge and discharge cycles, the team found that the structure retained four times more capacity than the graphite anodes in current batteries.
The scientists had been looking for a way to prevent the oxide coating forming on aluminium nanoparticles after they are exposed to air. They had been testing soaking the nanoparticles in sulphuric acid and titanium oxysulohate for various lengths of time. The chemicals converted the aluminium oxide to titanium oxide, a more conductive substance that does not degrade battery performance as much.
The accident resulted in the aluminium samples being left for much longer than they would have been otherwise. The time was enough for a protective nanoparticle shell to form around the aluminium, preventing it from oxidising while still allowing it to conduct electricity.
The procedure should be commercialised for use in future batteries after further testing. The method is simple and likely to be found inside the smart devices of the future.
More about Battery, Research, Discovery, Decay, Nanoparticles
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