Graphene-tin composite could improve lithium-ion batteries

Researchers at the United States Department of Energy’s Lawrence Berkeley National Laboratory have created a graphene and tin nanoscale composite material for rechargable lithium-ion batteries that allows quick and repeated charging without degradation, a feature which the researchers say makes it well suited for electric vehicles.

"For electric cars, you need a lightweight battery that can be charged quickly and holds its charge capacity after repeated cycling. Here, we’ve shown the rational design of a nanoscale architecture, which doesn’t need an additive or binder to operate, to improve battery performance," said Yuegang Zhang, a member of Berkeley Lab’s Molecular Foundry.

To create this battery, the researchers worked with tin and graphene, a virtually transparent and highly conductive carbon material that resembles chicken-wire in its formation. What they did with tin and graphene was to assemble them in alternating thin layers to create a nanoscale composite.

After layers have been formed, it is heated to 300 degrees Celsius in a hydrogen and argon environment. The heat transforms the tin films into pillars which increases the height of the tin layer.

The researchers pointed out that the height between the graphene layers in the nanocomposites help during electrochemical cycling of the battery, as the volume change of tin improves the electrode’s performance.

"The formation of these tin nanopillars from a thin film is very particular to this system, and we find the distance between the top and bottom graphene layers also changes to accommodate the height change of the tin layer," said Liwen Ji, a post-doctoral researcher at the Molecular Foundry.

They concluded that with this accommodating behavior of the material, the battery can be charged quickly and repeatedly without degrading. Mr. Zhang has had previous experience with graphene, having endeavored to study its conductance fluctuation, or "noise" of its electrons, to better understand its nature.

Just this May, another of the department’s labs, Brookhaven National Laboratory, also explored the capabilities of graphene in improving the performance of supercapacitors which are similar to batteries in terms of storing electric charge.