Article last updated on: Oct 24, 2018

Graphene supercapacitors

Graphene is a thin layer of pure carbon, tightly packed and bonded together in a hexagonal honeycomb lattice. It is widely regarded as a “wonder material” because it is endowed with an abundance of astonishing traits: it is the thinnest compound known to man at one atom thick, as well as the best known conductor. It also has amazing strength and light absorption traits and is even considered ecologically friendly and sustainable as carbon is widespread in nature and part of the human body.

Graphene is often suggested as a replacement for activated carbon in supercapacitors, in part due to its high relative surface area (which is even more substantial than that of activated carbon). The surface area is one of the limitations of capacitance and a higher surface area means a better electrostatic charge storage. In addition, graphene based supercapacitors will utilize its lightweight nature, elastic properties and mechanical strength.

Graphene-based supercapacitors are said to store almost as much energy as lithium-ion batteries, charge and discharge in seconds and maintain all this over tens of thousands of charging cycles. One of the ways to achieve this is by using a a highly porous form of graphene with a large internal surface area (made by packing graphene powder into a coin-shaped cell and then dry and press it).

What are supercapacitors?

Supercapacitors, also known as EDLC (electric double-layer capacitor) or Ultracapacitors, differ from regular capacitors in that they can store tremendous amounts of energy.

A basic capacitor usually consists of two metal plates, separated by an insulator (like air or a plastic film). During charging, electrons accumulate on one conductor and depart from the other. One side gains a negative charge while the other side builds a positive one. The insulator disturbs the natural pull of the negative charge towards the positive one, and that tension creates an electric field. Once electrons are given a path to the other side, discharge occurs.

Supercapacitors also contain two metal plates, only coated with a porous material known as activated carbon. They are immersed in an electrolyte made of positive and negative ions dissolved in a solvent. One plate is positive and the other is negative. During charging, ions from the electrolyte accumulate on the surface of each carbon-coated plate. Supercapacitors also store energy in an electric field that is formed between two oppositely charged particles, only they have the electrolyte in which an equal number of positive and negative ions is uniformly dispersed. Thus, during charging, each electrode ends up having two layers of charge coating (electric double-layer).



Supercapacitor design

Batteries and Supercapacitors

Unlike capacitors and supercapacitors, batteries store energy in a chemical reaction. This way, ions are inserted into the atomic structure of an electrode, instead of just clinging to it like in supercapacitors. This makes supercapacitors (and storing energy without chemical reactions in general) able to charge and discharge much faster than batteries. Due to the fact that a supercapacitor does not suffer the same wear and tear as a chemical reaction based battery, it can survive hundreds of thousands more charge and discharge cycles.

Supercapacitors boast a high energy storage capacity compared to regular capacitors, but they still lag behind batteries in that area. Supercapacitors are also usually more expensive per unit than batteries. Technically, it is possible to replace the battery of a cell phone with a supercapacitor, and it will charge much faster. Alas, it will not stay charged for long. Supercapacitors are very effective, however, at accepting or delivering a sudden surge of energy, which makes them a fitting partner for batteries. Primary energy sources such as internal combustion engines, fuel cells and batteries work well as a continuous source of low power, but cannot efficiently handle peak power demands or recapture energy because they discharge and recharge slowly. Supercapacitors deliver quick bursts of energy during peak power demands and then quickly store energy and capture excess power that's otherwise lost. In the example of an electric car, a supercapacitor can provide needed power for acceleration, while a battery provides range and recharges the supercapacitor between surges.

Supercapacitor vs Battery charge times

Common supercapacitor applications

Supercapacitors are currently used to harvest power from regenerative braking systems and release power to help hybrid buses accelerate, provide cranking power and voltage stabilization in start/stop systems, backup and peak power for automotive applications, assist in train acceleration, open aircraft doors in the event of power failures, help increase reliability and stability of the energy grid of blade pitch systems, capture energy and provide burst power to assist in lifting operations, provide energy to data centers between power failures and initiation of backup power systems, such as diesel generators or fuel cells and provide energy storage for firming the output of renewable installations and increasing grid stability.

Rivaling materials

Several materials exist that are researched and suggested to augment supercapacitors as much (or even more than) graphene. Among these materials are: hemp, that was used by Canadian researchers to develop hemp fibers that are at least as efficient as graphene ones in supercapacitor electrodes, Cigarette filters, which were used by Korean researchers to prepare a material for supercapacitor electrodes that exhibits a better rate capability and higher specific capacitance than conventional activated carbon and even higher than N-doped graphene or N-doped CNT electrodes.

Graphene supercapacitors commercialization

Graphene supercapacitors are already on the market, and several companies, including Skeleton Technology, the CRRC, ZapGoCharger, Angstron Materials and Sunvault Energy are developing such solutions. Read our Graphene Supercapacitors market report to learn more about this exciting market and how graphene will effect it.

Graphene supercapacitors market report

Further reading

Latest Graphene Supercapacitors news

Team at Australia's RMIT finds silicon contamination of graphene as a hindrance to commercial adoption

Researchers at Royal Melbourne Institute of Technology (RMIT) have found that graphene could better fulfill its potential when purified to remove silicon, doubling its electrical performance.

Despite researchers demonstrating countless possible applications of graphene, many people feel that graphene is thus far showing rather sluggish industrial adoption. Now, researchers based at RMIT have proposed a possible reason for this and suggested how graphene's full potential could be unlocked.

Thales and M-SOLV develop large-scale spray coating tool for graphene supercapacitors

Graphene Flagship partners Thales and M-SOLV have developed a large-scale spray coating tool, reportedly capable of meeting the high volume manufacturing requirements for high power graphene supercapacitors to be used in aerospace applications.

Thales has been working on incorporating graphene into supercapacitors since the start of the Graphene Flagship and has been able to significantly increase the storage potential of supercapacitor devices. "Using graphene, we have been able to increase the power of supercapacitors by five times. We deposited our supercapacitors using spray coating, enabling us to use a variety of substrates, thus allowing us to develop flexible, high power supercapacitors," said Dr. Paolo Bondavalli, Thales Research and Technology.

Graphene Batteries Market Report

Ionic Industries enters agreement with Nanothings to develop graphene-based supercapacitors for IoT applications

Ionic Industries logoIonic Industries has signed an LOI with US-based Nanothings for development of graphene supercapacitors for IoT applications. The two companies will work together to develop an energy storage solution that will enable a new generation of IoT tracking technologies based on Nanothings’ proprietary NanoTag devices.

The terms of the LOI cover a range of details about how the technology will be developed and how it might be commercialized jointly.

KAIST team develops a fast and powerful graphene-based aqueous hybrid capacitor that may lead to a new type of energy storage system

A KAIST research team has developed a graphene-based hybrid storage device with power density 100 times faster than conventional batteries, allowing it to be charged within a few seconds. The team states that it could be suitable for small portable electronic devices.

KAIST team develops a fast and powerful graphene-based aqueous hybrid capacitor that may lead to a new type of energy storage system imagePorous metal oxide nanoparticles formed on graphene in the aqueous hybrid capacitor. (Image: KAIST)

The researchers developed an aqueous hybrid capacitor (AHC) that boasts high energy density, high power, and excellent cycle stability by synthesizing two types of porous metal oxide nanoclusters on graphene to create positive and negative electrodes for AHCs.

Bedimensional receives €18 million private investment

Be Dimensional logoBedimensional has received €18 million to promote their main goal – discover new applications of graphene and related materials in consumer products. The investment was made by Italian 'Pellan Group,' specialized in groundbreaking technical materials.

Bedimensional is an Associated Member of the Graphene Flagship, and is part of a network of companies associated to the Graphene Flagship developing new solutions in the field of composites for energy harvest and storage, such as batteries, super capacitors and solar cells, as well as foster the development of new composite materials, some of which are already available on the market.

XFNANO: Graphene and graphene-like materials since 2009 XFNANO: Graphene and graphene-like materials since 2009