Graphene nanocomposite a bridge to better batteries

July 29, 2011

Alternating layers of graphene and tin are used to create a nanoscale composite for renewable lithium ion batteries (credit: Lawrence Berkeley National Laboratory)

Researchers at the Lawrence Berkeley National Laboratory (Berkeley Lab) have created a graphene and tin nanoscale composite material for high-capacity energy storage in renewable lithium ion batteries. Electrochemical measurements showed very high reversible capacity and excellent cycling performance at a current density as high as 5 amperes per gram.

Graphene is a single-atom-thick, “chicken-wire” lattice of carbon atoms with stellar electronic and mechanical properties, far beyond silicon and other traditional semiconductor materials.

The researchers assembled alternating layers of graphene and tin to create a nanoscale composite. To create the composite material, a thin film of tin was deposited onto graphene. Next, another sheet of graphene was transferred on top of the tin film. This process was repeated to create a composite material, which was then heated to 300 degrees Celsius in a hydrogen and argon environment. During this heat treatment, the tin film transformed into a series of pillars, increasing the height of the tin layer.

The change in height between the graphene layers in these new nanocomposites helps during electrochemical cycling of the battery, because the volume change of tin improves the electrode’s performance. This accommodating behavior means the battery can be charged quickly and repeatedly without degrading — crucial for rechargeable batteries in electric vehicles, the researchers said.

Ref.: Liwen Ji, Zhongkui Tan, et al., Multilayer nanoassembly of Sn-nanopillar arrays sandwiched between graphene layers for high-capacity lithium storage, Energy & Environmental Science, 2011; [DOI: 10.1039/C1EE01592C]