Graphene breakthrough hints at smartphone batteries that could last 25 percent longer

Italian researchers have come up with a new way of squeezing extra life out of standard lithium ion batteries, thanks to the miracle material.
Written by Raffaele Mastrolonardo, Contributor

Next time you're worried your smartphone's going to let you down in the middle of the day or you'll have to bring with you an array of chargers for a two-day business trip, don't despair — Italian researchers have got your back.

At the Italian Institute of Technology (IIT), a group of local scientists has just produced a new kind of lithium-ion battery that exceeds current batteries' efficiency by 25 percent. The extra battery life is achieved by exploiting the high electrical conductivity of graphene — used for the battery's anode — at an unprecedented scale.

Graphene, which is derived from graphite, was isolated in 2004 by physicists Andre Geim and Konstantin Novoselov, who were awarded with the Physics Nobel Prize in 2010 for their discovery. Since then, researchers have examined its potential applications in various fields, from renewable energy to semiconductors

IIT's experiment is not the first of its kind. Graphene, which is basically a single layer of graphite, has been exploited in lithium-ion batteries before but, according to the Italian scientists, such levels of performance from a full battery haven't been reached before.

The achievement — which was described in a paper published in the journal Nano Letters — was made possible because the researchers used a purer form of the material than had featured in earlier experiments.

"Almost all past experiments used chemically modified graphene, such as graphene oxide — a material derived from graphite oxide that, as such, cannot be used immediately. It needs further treatment to partially restore the electrical conductivity, thus affecting the performance of the battery," Vittorio Pellegrini, IIT's graphene labs' director, told ZDNet.

Pellegrini's group instead obtained graphene through the exfoliation of pristine graphite. The process entails breaking up a piece of graphite that's been mixed in an organic solution using ultrasound waves.

The mixture is then centrifuged to separate out the graphene flakes according to their thickness. What the researchers eventually get is a small bottle of graphene ink, drops of which can be spread onto a copper surface. The graphene-coated copper can then be integrated in to the battery without needing any further chemical or physical processes, and no loss of electrical conductivity.

The procedure has other advantages too: "We can also control the flakes' dimension which, as we found out, it is an important feature when it comes to batteries," said Francesco Bonaccorso, an IIT researcher who worked on the project. Apparently lithium's ions have a weakness for small flakes with a lot of edges. "The edges are the place where ions better attach and detach, so having flakes with such characteristics increases the lithium uptake performance," he said.

Using the process, IIT's scientists managed to create a battery that outperformed its current lithium-ion equivalents by 25 percent, offering up the prospect that gadget users will get more life out of their device in future.

"Let's imagine that you have a smartphone with a traditional battery optimised to work for 24 hours. If you power it with our graphene-based battery, you can achieve, say, a 30-hour lifespan. Or, you can have the same life but with a significant decrease in the battery's width," Pellegrini said.

These figures, though, should be taken with a grain of salt: it's impossible to calculate how much the improved efficiency will add to real-world battery life without having optimised the battery for a certain device and having extensively tested it, the scientist added. 

Looking for new markets

Even though smartphones and other portable devices are the first application that comes to mind for the technology, the Italian researchers have ambitions for their discovery that go beyond consumer electronics.

They've also set their sights on electric cars, a market which, unlike smartphones, has been hampered by battery life so far. "We could enable those cars to drive for more kilometres or to cover the same distance but with a significant reduction in weight," Bonaccorso said.

If that’s not enough, IIT's people think graphene-based batteries could pave the way for superfast charging. "Right now, these vehicles cannot drive for too many kilometres and take hours to re-charge. Imagine if this time were reduced to a few minutes", Pellegrini said.

How so? Thanks to graphene you could, at least in theory, create hybrid systems which combines the virtues of lithium-ion batteries and the so called supercapacitors, which can charge and release energy quickly but, unlike batteries, are less efficient when it comes to storing it. "At least on paper, these hybrid systems are made more feasible by the use of graphene. That's a possible future development of our discovery," Pellegrini said.

In the meantime, his group will work on getting their battery ready for commercialisation, a plan that's likely to take some time to come to fruition. According to the Italian scientists, a version of their creation that's refined and tested enough to be handed onto a company for mass production will come within 24 months. Some electric vehicles manufacturers, they added, have already shown interest in the research.

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