(138c) Graphene-Silicon Composite for Li-Ion Battery Anodes

Because of its high volumetric and gravimetric charge density, Si is a very attractive candidate as the active component for the anode in a Li-ion battery. The high surface to volume ratio of Si nanoparticles offers the potential of fast charge-discharge kinetics. However, experimental results show that anodes, made from simply admixing Si nanoparticles with carbon powder (carbon black), degrade rapidly; they lose most of their charge capacity after only a few charge/discharge cycles. Previously, we have shown that significant improvement in stability could be obtained by encapsulating the Si nanoparticles in a carbon layer derived from carbonizing a resorcinol-formaldehyde (RF) gel. The results also suggested the possibility that a more flexible matrix than the carbonized RF gel may offer superior behavior. Graphene sheets are thin and conducting, and are derived from exfoliating graphite. They can impart electrical conductivity to an otherwise insulating material when dispersed in it, and have been used to convert polystyrene into a highly conducting material. Thus, they can serve as highly efficient electrical conducting material in place of carbon powder in an anode of Si nanoparticles due to their high surface area to volume ratios. The results of using composites of graphene and Si nanoparticles as the anode for a Li-ion battery, the charge/discharge behavior, the effect of addition of polymer and pretreatment conditions will be presented.