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Gas-Assisted Electrospraying Slurries of Silicon Fibers with Graphene Oxide for Binder-Free Electrode Fabrication

Tuesday, 30 May 2017: 10:50
Grand Salon D - Section 21 (Hilton New Orleans Riverside)
J. M. Carlin Jr., L. Fei, and Y. L. Joo (Cornell University)
The development of lithium-ion anode materials with both high capacity and high cyclic retention has been a large research challenge in recent years. With increasing power demands, new materials need to maintain performance at high charge and discharge rates. To meet these needs, a multilayered silicon fiber/ reduced graphene oxide (RGO) slurry was directly fabricated onto current collectors with a gas-assisted electrospraying method. The sprayed solution is a slurry of silicon fibers and graphene oxide (GO) sheets in water. The silicon fibers used were made via a magnesium reduction of silica fibers formed from electrospinning. Electrospinning was used due to its advantage in forming micron to sub-micron materials, both uniformly and scalable. The GO sheets used are commercially available, single layer, exfoliated sheets 25 microns in length. The gas-assisted spraying method has several advantages over the conventional slurry-cast approach in that it uses no binder, no toxic solvents, sprays dry onto the current collector, and is also industrially scalable. Once sprayed, the electrodes were thermally annealed in a nitrogen atmosphere to form the Si/RGO composite. The fabricated electrodes feature layers of silicon fibers wrapped by RGO sheet forming a conductive network while also accommodating the mechanical stress from silicon volume expansion. The electrochemical performance of the Si/RGO electrodes shows high capacity retention and can maintain performance at rates up to 1 A/g. Reversible capacities in half cells can reach more than 1600 mAh/g at 0.1 A/g and 800 mAh/g at the high rate of 1 A/g (based on combined Si/RGO mass). The gas-assisted electrospraying method is a simple, scalable approach to wrap silicon in RGO for high performance lithium-ion anodes.