The Application of Graphene-Based Supercapacitors in Conjunction with Today’s Technology By Jenna Cario

Today’s Electrical Storage Technology

Lithium ion (Li-ion) batteries and capacitors occupy very different niches in the realm of electrical storage. Supercapacitors combine elements of both, becoming a technology that is both capacitor and battery without truly completely being either.Li-ion Batteries• Store large amounts of

electrical energy through chemical reactions

• Release a gradual stream of energy at a given voltage

• Can be charged/discharged around 500 times before significant battery capacity drop

Capacitors• Store electrical energy in

electric fields generated between two conducting surfaces

• Release energy in quick bursts at a given voltage

• Can be charged/discharged thousands of times before a significant capacity drop

Supercapacitors

Supercapacitors are very similar in construction to capacitors. Where normal capacitor plates are be composed of metal, supercapacitors will have plates coated in a porous substance such as activated carbon. They also contain an electrolyte between the plates as opposed to the dielectric found between regular capacitor plates. With these changes, supercapacitors store substantially larger amounts of energy, closer in magnitude to Li-ion batteries. However, they still require only slightly longer than capacitors to discharge all of this energy, and they retain an effective longevity of tens of thousands of cycles.

Graphene

Graphene is a material one atom thick and composed solely of carbon bonded in a honeycomb formation. Some of graphene’s features include:• Superconductivity• A very high specific surface area of about

600 square meters per gram• High flexibility Since supercapacitors need to have conductive plates with very high surface areas, graphene is an excellent candidate for use on supercapacitor electrodes.

Synthesis

Graphene synthesis has progressed dramatically since its original synthesis in 2004. Many methods of graphene synthesis exist today. Some methods of graphene synthesis are as follows:• Mechanical exfoliation (original method)• Chemical exfoliation• Unzipping of Carbon Nanotubes• Reduction of graphene oxide

Arguably, one of the most pertinent methods of synthesis is laser scribing of graphene oxide. In this method, graphene oxide is spread on a compact disk and subjected to the laser of a standard disk drive. The resulting graphene film is already ready for supercapacitor application.

This table shows some carbon-based candidates for supercapacitor usage.

Application

Supercapacitors are currently used in situation where batteries are unfeasible. In these situations, batteries may not deliver or store enough energy quickly enough, or they may require too much maintenance/replacement.• Toys• Motor Starters• Security cameras/surveillance systems• Regenerative braking in vehicles (capturing

energy normally lost as heat during braking and using it to re-accelerate)

Graphene supercapacitors could, with more research, could open other technological pathways as well as building on the above:• Flexible electronics• Electronics, especially those with

medical/emergency applications, woven into clothing

• Supercapacitor-powered electric vehicles• Current-carrying “wires” for medical use As component costs drop lower, graphene supercapacitors will prove to be a green technology that opens pathways for future generations in true sustainable fashion.

This plot of specific energy versus specific power shows how supercapacitors compare to other forms of energy storage.

In particular, supercapacitors show promise as a method of energy storage in electric vehicles. Graphene supercapacitors, which are

highly flexible, could be fitted to the chassis of a car, reducing weight and improving efficiency.