Forgetful scientists accidentally quadruple lithium-ion battery lifespan

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Forgetful scientists accidentally quadruple lithium-ion battery lifespan

Postby Peter » Sun Aug 23, 2015 4:26 pm

Until someone figures out a replacement for lithium-ion in rechargeable batteries, research will continue into how to cram more energy inside as well as extending their useful lifespan. Two scientists believe they have managed to extend the life of such batteries significantly, and all because of an accident in the lab.

Today’s lithium-ion batteries typically rely on graphite anodes to offer a long lifespan. Rechargeable battery performance declines and eventually falls off a cliff (becomes unusable) due to those anodes repeatedly expanding and contracting as lithium ions migrate during the cycle of charging and discharge. Lithium compounds build up on the electrodes during this process then break off during the expansion and contraction. This exposes the surface of the electrode and over time decomposes it to the point of failure.

A better alternative to using graphite for the anodes would be aluminum, but aluminum expands and contracts too much during each cycle. If scientists could stop that happening, we’d have much better performing batteries.

Dr Wang Changan of Tsinghua University and Dr Li Ju of MIT have been working together to stop the oxide coating that forms on the surface of aluminum nanoparticles when it is exposed to air. Their idea was to soak the nanoparticles in a sulfuric acid and titanium oxysuplphate mix, which would dissolve the aluminum oxide and replace it with titanium oxide.

Achieving the new outer coating required a set time of soaking. The accident occurred when Wang and Li forgot to remove one batch of the nanoparticles from the soaking process. That batch ended up soaking for several hours longer than intended with the result being the sulfuric acid and titanium oxysulfate mix leaked into the 50nm nanoparticles and dissolved some of the aluminum inside. What this left was a nanoparticle with a 4nm outer shell of titanium hydroxide and an inner 30nm “yolk” of aluminum.

Rather than discarding this forgotten batch, they decided to test it by building batteries using these particles. It turns out they have potentially solved the problem of using aluminum for the anodes in the battery. The extra long soak meant the anodes did not expand and contract, in fact they created a battery that over 500 charge/discharge cycles retained up to four-times the capacity of the equivalent graphite anode batteries. These batteries last considerably longer in terms of usable lifespan and, according to MIT, can hold up to three-times the energy.

Clearly, sometimes being a forgetful scientist can lead to a breakthrough. The discovery is expected to be an easy one to scale up to mass production, meaning the next-generation of rechargeable batteries could use aluminum anodes, bringing with it longer battery life per charge and batteries that have a much improved lifespan.

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