(229b) 3-D Graphenic Network Composites for High-Performance Li-Ion Battery Electrodes

Three-dimensional, highly conducting, networks constructed from graphene sheets have been found to be very useful scaffolds to form composite materials with high charge-storage capacities for Li ion batteries.  Additional treatment of the graphene sheets to introduce in-plane defects greatly enhances the cross-plane ionic conductivity, which results in much enhanced rate capability of such materials.  Such materials have exhibited power density as high as that of supercapacitors.  We have constructed electrode materials suitable for use as anode or cathode for Li ion batteries.  For anode materials, a three-dimensional graphenic network with in-plane defects exhibits a stable, repeatable power capability of 180 mAh/g at a rate of 2 A/g, corresponding to a recharge rate of less than 5 min.  Imbedding Si nanoparticles into the network greatly improves the charge storage capacity, achieving >3100 mAh/g at low rates, and >1000 mAh/g at a high rate of 8 A/g, with a coulomb efficiency as high as 99.9%, and typically >99.6%.  Cathode materials can be formed by imbedding metal fluorides or sulfides/sulfur into these scaffolds.  These materials also exhibit a much higher charge storage capacity than the conventional Li metal oxides (M= Co, Ni, Mn).  However, capacity fade remains an issue that needs to be overcome.  The characterization results of these materials will be presented.