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

XFNano graphene materials used in advanced energy application research

The following is a sponsored post by XFNano

XFNano's graphene materials were recently used in two fascinating research work focused on advanced energy applications.

NiCo-HS@G fabrication (XFNano)

The first is a work by teams from Anhui Normal University, Chinese Academy of Sciences (CAS) and the University of the Chinese Academy of Sciences which developed a fast, one-step strategy to prepare sandwiched metal hydroxide/graphene composites through a kinetically controlled coprecipitation under room temperature. Such NiCo-HS@G nano-composite exhibits good electrocatalytic activity for OER, superior to most of the reported OER catalysts. Such performance and the facile preparation of NiCo-HS@G opens up a new avenue for the cost-effective and low-energy-consumption production of various sandwiched metal hydroxides/graphene composites as efficient OER electrocatalysts with desired morphology and competing performance for the applications in diverse energy devices.

Graphene-Info's Batteries, Graphene Oxide, Supercapacitors, Lighting, Displays and Graphene Investments Market Reports updated to April 2018

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 April 2018.

Graphene batteries market report 3D cover

The Graphene Batteries Market Report:

  • 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!

The Graphene Handbook

Discarded lithium ion batteries transformed into rGO-based supercapacitors

Scientists from CSIR–Central Electrochemical Research Institute (CSIR-CECRI) and CSIR–Central Salt and Marine Chemicals Research Institute (CSIR-CSMCRI) in India have collected discarded lithium-ion batteries and created reduced graphene oxide from them. The material reportedly showed high specific capacity at low current, making it an ideal material for next generation high-performance supercapacitors.

“The specific capacity was found to be 112 farad per gram from fundamental evaluation, which is almost equal to the commercially available ones. Also the ones available in market today are created using activated carbon which is expensive and environmentally hazardous while our method is cheaper and fully environmental friendly” explains the team.

Ionic Industries provides updates on supercapacitor and water treatment work

Ionic Industries logoIonic Industries has provided updates on its research, commercial products and industry outreach. Among the mentioned highlights is the fact that Ionic is engaging with a number of companies to develop collaborations focused on its printed micro planar supercapacitors, named MICRENs. Also, on Ionic's other printed supercapacitor technology, the ORIGAMI Caps, the Company is working toward developing a prototype device for use in Internet of Things applications and is aiming to have a product to test in the next month.

On the Company's water treatment work, it was said that work with Clean TeQ and Monash under the CRC-P program continues apace. Much focus at this point is on upscaled manufacturing, ensuring the feasibility of manufacturing the membranes and graphene oxide (GO) sand products at industrial scales. The next major milestone that Ionic is aiming for is triggering the formation of a joint venture with Clean TeQ when the path to market (and revenues) for this technology will become much clearer.

New tree-inspired electrodes could boost supercapacitors’ performance

Researchers from the UCLA, Mississippi State University, University of Nevada and China's Central South have designed an efficient and long-lasting graphene-based electrode for supercapacitors. The device’s design was inspired by the structure and function of leaves on tree branches, and it is said to be more than 10 times more efficient than other designs.

An efficient and long-lasting graphene-based electrode for supercapacitors image

The electrode design reportedly provides the same amount of energy storage, and delivers as much power as similar electrodes, despite being much smaller and lighter. In experiments it produced 30% better capacitance — a device’s ability to store an electric charge — for its mass compared to the best available electrode made from similar carbon materials, and 30 times better capacitance per area. It also produced 10 times more power than other designs and retained 95% of its initial capacitance after more than 10,000 charging cycles.

Versarien - Think you know graphene? Think again!Versarien - Think you know graphene? Think again!