Flash Converted Graphene for Ultra‐High Power Supercapacitors

Abstract

Supercapacitors are known for their rapid energy charge–discharge properties, often ten to a hundred times faster than batteries. However, there is still a demand for supercapacitors with even faster charge–discharge characteristics to fulfill the requirements of emerging technologies. The power and rate capabilities of supercapacitors are highly dependent on the morphology of their electrode materials. An electrically conductive 3D porous structure possessing a high surface area for ions to access is ideal. Using a flash of light, a method to produce highly interconnected 3D graphene architectures with high surface area and good conductivity is developed. The flash converted graphene is synthesized by reducing freeze‐dried graphene oxide using an ordinary camera flash as a photothermal source. The flash converted graphene is used in coin cell supercapacitors to investigate its electrode materials properties. The electrodes are fabricated using either a precoating flash conversion or a postcoating flash conversion of graphene oxide. Both techniques produce supercapacitors possessing ultra‐high power (5–7 × 105 W kg−1). Furthermore, optimized supercapacitors retain >50% of their capacitance when operated at an ultrahigh current density up to 220 A g−1.

Flexible, Free‐Standing and Holey Graphene Paper for High‐Power Supercapacitors

“… Ragone plot comparing the areal energy and power densities obtained for the graphene paper GP‐3 (3 mg cm −2 , 35 μm) (A: 1 m Li 2 SO 4 and B: 1 m H 2 SO 4 ) with those obtained for other graphene‐based films: C (functionalized graphene film, 1 mg cm −2 ), D (graphene hydrogel film, 120 μm, 2 mg cm −2 ), E (holey graphene paper, 9 μm, 1 mg cm −2 ), F (chemically converted graphene hydrogel film, 0.76 g cm −3 ), G (chemically converted graphene hydrogel film, 1.33 g cm −3 ), H (solvated graphene film, 1 mg cm −2 ), I (flash converted graphene, 0.35 mg cm −2 ), J (solvated graphene film, 152 μm, 0.44 mg cm −2 ), K (solvated graphene film, 1 mg cm −2 ), L (graphene on cellulose, 0.44 mg cm −2 ) …”

“…However, although some of these GPs show high areal capacities (a high energy density) at low current densities, they fail when used as electrodes at fast charging/discharging rates, probably because, under such tough conditions, the transport of ions inside the porous network of the graphene paper is highly restricted. On the other hand, flexible/thin SCs able to achieve high areal power densities normally show a poor areal energy density (low areal capacity) . Therefore, the fabrication of GP‐based SCs that combine a high energy with a high power density still remains to be achieved.…”

Gold Nanoparticles Decorated Graphene as a High Performance Sensor for Determination of Trace Hydrazine Levels in Water

“…However, on one hand the reducing agents employed in these processes are carcinogenic and could contaminate the resulting materials and on the other hand, oxygenated species that cannot so far be fully removed by chemical treatment will heavily influence the electronic properties and thus limits graphene applications. Recently, green methods including laser scribing or using flash of light have been applied to produce highly interconnected and flexible graphene sheets. Alternative approach is the electrophoretic deposition (EPD), which is a well‐developed and economical method that has been successfully applied for the deposition of graphene films .…”

Performance of Microporous Carbon Electrodes for Supercapacitors: Comparing Graphene with Disordered Materials

“…Graphene was chosen because it has the largest ASA possible for a carbon material, and was therefore investigated as a promising electrode material for supercapacitors. [13][14][15][16] The electrolyte is a pure ionic liquid held at 400 K, the 1-butyl-3-methylimidazolium hexafluorophosphate, which is modelled using a coarse-grained description 17 validated in the context of electrochemical cells in our previous works. 18,19 Full supercapacitors are simulated by setting up symmetric cells in which the electrolyte is put in contact with two similar electrodes.…”