Processing of 2D Layered Materials for Supercapacitors Applications

Graphene has generated huge interest in recent years due to its unique physics properties [1, 2]. We have shown that high-quality monolayer graphene can be produced at significant yields by non-chemical, solution-phase exfoliation of graphite in certain organic solvents. Until a few years ago the standard procedure used to make graphene was micromechanical cleavage [1], which is a very low yield production method. In order to fully exploit graphene’s outstanding properties, a mass production method was necessary and the development of a method to exfoliate cheap, commercial graphite in organic solvents down to large area single graphene flakes with high yield was one major achievement [3]. Recently this work had been extended to a wide range of two-dimensional inorganic nanomaterials [4, 5]. These are potentially important because they occur in hundreds of different types with a wide range of electronic properties, varying from metallic to semiconducting.

In this work we present a cost-effective spray deposition technology for the fabrication of both semi-industrial scale and laboratory size film supercapacitor electrodes. Based on graphene and other two-dimensional nanomaterials. Cylic voltammetry, and charge discharge studies revealed a combination of a double layer capacitance and pseudocapacitance charge storage mechanisms that, unlike the many graphene-oxide derived electrodes reported to date, was maintained at unusually high scan rates of 20,000 mV/s. The performance of these graphene electrodes contrasts with that of functionalised single walled carbon nanotubes (SWNTs) electrodes similarly fabricated, which show a sharp decrease in capacitance above a voltage scan rate of 200 mV/s and a nearly complete resistive behaviour at 4,000 mV/s. Electrochemical impedance spectroscopy analysis showed a capacitor response of 17.3 ms and cyclability for 5,000 cycles with 100 % capacitance retention at 10,000 mV/s [6]. We have also exploited the concept of hybridization to combine the properties of two 2D materials in a "hybrid" synthesized by a single step liquid-phase exfoliation method. First synthesized metal oxide-graphene hybrids showed an improved charge storage capacity. This work constitutes the proof-of-concept work for future investigation on rational design of functional 2D hybrid nanomaterials.

 

1. A. K. Geim, Science 324, 1530 (Jun, 2009).
2. S. Stankovich et al., Nature 442, 282 (Jul, 2006).
3. Y. Hernandez et al., Nature Nanotechnology, 3, 9, 563 (2008).
4. J. N. Coleman et al., Science, 331, 6017, 568-571 (2011).
5. 5.     V. Nicolosi et al., Science, 340, 6139, 1420 (2013)
6. B. Sanchez et al, Carbon, 52, 337-346 (2013).