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).
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.
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.
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.
The latest graphene supercapacitor news:
New laser printing method rapidly and efficiently yields textiles embedded with graphene supercapacitors
Scientists from RMIT University in Melbourne, Australia, have developed a cost-efficient and scaleable method for rapidly fabricating textiles that are embedded with energy storage devices. The team reports that in just three minutes, the method can produce a 10x10cm smart textile patch that's waterproof, stretchable and readily integrated with energy technologies like graphene supercapacitors, laser printed directly onto the textiles.
As a proof-of-concept, the researchers connected the supercapacitor with a solar cell, delivering an efficient, washable and self-powering smart fabric that overcomes the key drawbacks of existing e-textile energy storage technologies.
Skeleton Technologies, European developer of graphene-based supercapacitors and energy storage systems for transportation and grid applications, will supply supercapacitor systems to Škoda Electric, a traction equipment manufacturer, for 114 trams to be delivered by Škoda Transportation to Mannheim, Heidelberg, and Ludwigshafen in Germany.
The system recuperates the braking energy of the trams and uses it for re-acceleration, saving energy and decreasing costs. Supercapacitors are ideal for this application due to their high efficiency, reliability, and ability to recharge in seconds.
Analysts from IDTechEx estimate that the global supercapacitor market is around $1.5 billion in annual sales, following several years of decline. IDTechEx, however, believes the market bottomed out in 2018-2019 and is set now for a sustained period of strong growth.
IDTechEx explains that the market is expected to grow quickly in the coming years, as companies are expected to increase the use of supercapacitors over batteries in electric and hybrid cars as the customers are seeking faster charging and safer transport. Allied Market Research estimates that the Supercapacitor market will grow at a CAGR of 28.7% from 2016 to 2022 and will reach $6.3 billion in 2022, while India-based also sees a fast growth rate of 22% from 2016 to 2022, and estimates a $4 billion market in 2022. Both market research companies did not see the down year in 2016-2019, but it is still interesting to note these market forecasts.
Graphene-Info's Batteries, Supercapacitors, Graphene Oxide, Lighting, Displays and Graphene Investments Market Reports updated to July 2019
Today we published new versions of all our graphene market reports. Graphene-Info provides comprehensive niche graphene market reports, and our reports cover everything you need to know about these niche markets. The reports are now updated to July 2019.
- The advantages using graphene batteries
- The different ways graphene can be used in batteries
- Various types of graphene materials
- What's on the market today
- Detailed specifications of some graphene-enhanced anode material
- Personal contact details into most graphene developers
The report package provides a good introduction to the graphene battery - present and future. It includes a list of all graphene companies involved with batteries and gives detailed specifications of some graphene-enhanced anode materials and contact details into most graphene developers. Read more here!
Researchers at Joseph Wang's Laboratory for Nanobioelectronics at UC San Diego demonstrated the synthesis of high-performance stretchable graphene ink using a facile, scalable, and low-cost laser induction method for the synthesis of the graphene component.
As a proof-of-concept, the researchers fabricated a stretchable micro-supercapacitor (S-MSC) demonstrating high capacitance. This is said to be the first example of using laser-induced graphene in the form of a powder preparation of graphene-based inks and subsequently for use in screen-printing of S-MSC.