291782 Graphene Oxide Composite Films As Na-Ion Battery Anodes

Monday, October 29, 2012
Hall B (Convention Center )
Ross J. Browne, School of Engineering, Brown University, Providence, RI

This research is concerned with the applications of graphene oxide, a novel form of carbon
with unique mechanical and electrical properties, in a new environmentally friendly battery
technology based on sodium-ions. Graphene oxide (GO) consists of a single-atom-thick sheet
of carbon with oxygen-containing functional groups decorating its basal plane and edge sites.
While the thickness of a single graphene oxide ‘molecule’ is on the scale of angstroms, the
lateral dimensions can be on the scale of microns. Due to its unique sheet-like nature, GO has
the capability to form films of significant mechanical stability due to the interactions (e.g. van
der Waals force and H-bonding) of stacked layers. These films are flexible and have very large
surface areas, and are therefore prime candidates for use as battery anodes. During the process
of charging and discharging the battery, the sodium ions must enter and withdraw from the
space between the layers of GO in the anode. This process introduces a great deal of stress
into the layered film structure, and tends to destroy the anode after repeated charging and
discharging cycles.

Most of this work has consisted of perfecting the assembly, stabilization, and characterization
of these films, mainly through the use of cross-linking agents and conductive dopants. Since
GO has functional groups covering its surface, many of which are reactive, it is possible to
chemically link adjacent sheets of GO in a film together using a chemical binder. We show that
the cross-linking treatment could significantly improve the mechanical stability of the films.
In addition to mechanical ruggedness, the films must also be highly conductive in order to be
effective battery anodes. Graphene oxide is a poor conductor on its own, but when a conductive
additive such as few-layer graphene is included in the film embedded between the layers, the
conductivity can be significantly increased. The synthesis, characterization, and electrochemical
properties will be discussed in this work.

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