Efficient synthesis of graphene-based powder via in situ spray pyrolysis and its application in lithium ion batteries

Abstract

Conventional solution-phase chemical reduction of exfoliated graphene oxide sheets followed by drying often results in serious reaggregation of the graphene sheets due to the high surface energy. Here we report a modification of the reduction process based on the Hummers method that involves an in situ spray pyrolysis. The process results in a series of graphene-based powders, the morphologies of which are mostly dependent on the spraying temperature. The effects of the spraying temperature were investigated in detail to gain insight into the spray pyrolysis process. The graphene-based powder obtained at a spraying temperature of 500 °C exhibits the lowest aggregation degree and manifests a spitball-like structure, consisting mainly of randomly curled thin graphene films. When evaluated for the electrochemical properties in lithium ion batteries as anode materials, the unique structure of these materials enables superior rate capability and cycling performance. A capacity of 180 mAh/g can be delivered even at an ultrahigh C rate of 40 C, and 95.4% of this capacity can be retained after 100 cycles. Production of such well-dispersed graphene powder is easily scaled up with relatively simple and continuous fabrication procedures, and can be incorporated with other active materials by simply adjusting the constitution of the spray precursor.