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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.

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).

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

Researchers demonstrate a simple approach to producing graphene nanosheets

Sep 28, 2016

Researchers from the University of Madras in India have managed to produce a monolayer or a few layers thick graphene nanosheets from graphite, using a simple, inexpensive and quick process without the use of strong oxidizing or reducing agents.

Liquid phase exfoliation methods are widely adopted for synthesizing graphene from graphite for their relative ease and cost-effectiveness. Still, the use of strong solvents and relatively low yield have turned out to be major drawbacks, limiting its utilization in the large-scale production of graphene. Now, the Madras team used ultrasound along with water, glacial acetic acid (CH3COOH - a mild solvent), and ethanol (C2H6O) to exfoliate graphite into graphene sheets.

Lomiko to present graphene supercapacitor prototype at Battery Materials Conference in Toronto

Sep 22, 2016

Lomiko Metals has announced that it will be presenting a summary of the Graphene Energy Storage Devices Corp. (GESD) Graphene Supercapacitor Project at the Battery Material Conference in Toronto September 2016.

Graphene ESD supercapacitor prototype image

GESD is currently working on scale-up of the technology and an in-field evaluation of the energy storage unit with Stony Brook University. The GESD-SBU team demonstrated design and implementation of a sealed high-voltage EDLCs energy storage unit. The unit is internally balanced, there is no need for an external circuit. The electrode is very cost-effective nano-carbon composite either of a commercial carbon or of graphene platelets with carbon nanotubes. The nano-carbon electrode materials were used for deposition and assembly of a working prototype of an internally balanced high-voltage energy storage unit. The bench-top prototype unit, tested up to 10 V, exhibited good discharge characteristics and charge retention. This development enables new compact energy storage solutions for grid and vehicular applications.

Graphene Investment Guide

Graphene-Info's supercapacitors market report and graphene investment guide updated to September 2016

Sep 08, 2016

Today we published a new version of our graphene supercapacitors market report and the graphene investment guide. Graphene-Info provides comprehensive niche graphene market reports, and our reports cover everything you need to know about these niche markets. These reports are now updated to September 2016.

The Graphene Supercapacitors Market Report:

  • Why graphene is exciting for supercapacitors
  • What is on the market today
  • Bridging the batteries - supercapacitors gap
  • Commercial activity and research achievements

The report package provides an introduction to the graphene supercapacitors market - present and future. It includes a list of all graphene companies involved with this market, discusses the latest research activities and includes market forecasts. Read more here!

Graphene-based stretchy supercapacitor is a step towards flexible electronics

Aug 30, 2016

A team of researchers at Nanyang Technological University, Singapore, has produced a stretchy micro-supercapacitor using ribbons of graphene. The team produces stretchable electrodes and integrated them into a supercapacitor, in what can be seen as a promising step towards bendy power sources for flexible electronics.

Stretchy supercapacitor made from graphene image

In this study, the team focused on the fact that graphene can be flexible and foldable, but it cannot usually be stretched; They attempted to fix that problem by looking at skin, which has a wave-like microstructure, and started to think of how to make graphene also more like a wave. They started by making graphene nano-ribbons, having more control over its structure and thickness that way (which can affect the conductivity of the electrodes and how much energy the supercapacitor overall can hold).

Skeleton Technologies secures €13 million investment

Aug 03, 2016

Skeleton Technologies logoSkeleton Technologies has received €13 million in an investment led by FirstFloor Capital, a Malaysian venture capital investment firm specializing in funding high-growth technology companies.

The Round C investment, which also includes existing Skeleton Technologies’ investors UP Invest and Harju Elekter, brings total financing to €26.7 million and will support Skeleton Technologies in its next phase of revenue ramp-up to bring graphene supercapacitors from high-end sectors to the mass market.