Batteries

Published on August 3rd, 2013 | by James Ayre

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Graphene Supercapacitors — Next-Generation Energy Storage Now One Step Closer

August 3rd, 2013 by  

This article has been reposted from Green Building Elements.
An entirely new strategy for engineering graphene-based supercapacitors has been developed by researchers at Monash University — potentially leading the way to powerful next-generation renewable energy storage systems. The new strategy also opens up the possibility of using graphene-based supercapacitors in electric vehicles and consumer electronics.

Supercapacitors — which are typically composed of highly porous carbon that is impregnated with a liquid electrolyte — are known for possessing an almost indefinite lifespan and the impressive ability to recharge extremely rapidly, in seconds even. But existing versions also possess a very low energy-storage-to-volume ratio — in other words, a low energy density. Because of this low energy density — 5-8 Watt-hours per liter in most supercapacitors — they’re not practical for most purposes. They would either need to be extremely large or be recharged very, very often for most uses.

Graphene supercapacitors

Image Credit: 3D model of graphene sheet via Shutterstock.


But, now, new research has resulted in the creation of a supercapacitor free from the above-mentioned limitations. Through the use of graphene, the researchers created a supercapacitor that possesses an energy density of 60 Watt-hours per liter, which is comparable to lead-acid batteries and about twelve times higher than commercially available supercapacitors. “It has long been a challenge to make supercapacitors smaller, lighter and compact to meet the increasingly demanding needs of many commercial uses,” stated lead researcher Professor Dan Li of the Department of Materials Engineering.

Monash University continues:

Graphene, which is formed when graphite is broken down into layers one atom thick, is very strong, chemically stable and an excellent conductor of electricity. To make their uniquely compact electrode, Professor Li’s team exploited an adaptive graphene gel film they had developed previously. They used liquid electrolytes — generally the conductor in traditional supercapacitors (SCs) — to control the spacing between graphene sheets on the sub-nanometer scale. In this way the liquid electrolyte played a dual role: maintaining the minute space between the graphene sheets and conducting electricity.

Unlike in conventional, “hard” porous carbon, where space is wasted with unnecessarily large “pores,” density is maximized without compromising porosity in Professor Li’s electrode. To create its material, the research team used a method similar to that used in traditional paper-making, meaning the process could be easily and cost-effectively scaled up for industrial use.

“We have created a macroscopic graphene material that is a step beyond what has been achieved previously. It is almost at the stage of moving from the lab to commercial development,” explained Professor Li.

The new research was just published in the journal Science.


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About the Author

's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy. You can follow his work on Google+.



  • Trevor Davies

    They seem to be a possible solution for energy storage, but something that worries me a little is what will happen if a short circuit occurs inside a capacitor cell? Below someone is talking about 60KWhrs in a cubic metre, that would be great, about a weeks electricity for my house, but a pin prick short circuit, and the whole 60KWhrs could be dissipated in a small part of the cell. Quite a bang! I guess if my cubic metre cell is actually made up of 1000 one Litre cells, connected by fuses to a common bus……. problem solved!

  • Pat Ravasio

    Holy Buckyworld! I always thought that the discovery of the Carbon 60 molecule (known as the BuckminsterFullerene, in honor of Buckminster Fuller) would have something to do with solving the energy problem, since Bucky called the synergetic geometry upon which the design of the Fullerene is based “the coordinate building system of the universe”. Now, within a 24-hour period, I have read about an entirely new economic paradigm based on Bucky’s syntropic theories, and now, a possible solution to renewable energy storage. Buckminster Fuller’s ideas are clearly thriving in 2013, thirty years after his death. Life is looking better and better for the crew aboard United Spaceship Planet Earth. Read more about Bucky’s ideas for today at http://www.buckyworld.me.

  • NotRappaport

    How does this compare to lithium ion batteries in energy density per kilogram?

    • Bob_Wallace

      You can work it out from here. (I’m too tired to do math at the moment. The result might not look pretty….)

      • Guest

        Thanks.

      • Matt

        Thanks Bob, should have know to use salt when ready a press release. “60 Watt-hours per liter, which is comparable to lead-acid batteries” same order of magnitude but still in last. And 1/5 of NiMh 🙁
        Since they didn’t include a Wh/kg I guess I should assume it isn’t that amazing either. Oh well it is still good new for SC application, just not as good as it looked without coffee.

        • UKGary

          Watt hours per kg will be much better than Lead Acid as carbon is only a fraction of the density of Lead.

          • geedavey

            plus with its flat and flexible form factor you can basically fill all the holes in the car structure with battery.

          • UKGary

            I understand that Volvo are prototyping structural batteries which serve dual function as body panels such as doors – so potentially lowering the weight of their electric cars. I would however have some concerns that an impact which causes a puncture might in some situations cause the battery to short to ground through the other vehicle.

      • Wayne Williamson

        Bob, thanks again.
        Another thought, I wish they would have kept pursing the NiMH tech.

        • Bob_Wallace

          I assume NiMH research is continuing. I don’t know why it’s not getting more love with EVs. I spent a few minutes looking on the web to see what’s happened with NiMH but it’s pretty clogged up with Chevron hate and conspiracy stuff.

          I did find this one comment which I’ll offer because it sounds good. Don’t know how accurate it is…

          “NiMH batteries are well known for their fast degradation as cycle count increase. They don’t last as long as the NiCd batteries they replaced, although development have reduced that difference.

          NiMH batteries used for hybrid vehicles are a sort of
          “heavy duty” NiMH battery, designed to be durable and provide good power. This does however come at a cost, the energy density is not as good as other NiMH batteries. To reduce degradation hybrid cars also keep the batteries state of charge in a narrow range; typically less than half the actual capacity. The result is a poor energy density, only about 30 Wh/kg.

          There isn’t one type of lithium ion battery,
          there are several different types. The most common are the cobalt oxide, manganese and iron phosphate types. The lithium ion cobalt oxide type provide good energy density, today in excess of 200 Wh/kg (just the cell alone), but they are unstable (safety issue), and they offer a poor power density. When they degrade over time, which is both cycle and age ralated, they lose capacity and the internal resistance increase (the latter will limit power output over time). These batteries are mostly suitable to low power portable devices where maximum battery time is of great importance. But such a battery is not suitable for a production car.

          Lithium ion manganese and iron phosphate batteries offer a
          higher power, and they are are much more stable (safe). But this comes at the cost of a lower energy density – about 110-140 Wh/kg on a cell level. Power densities can be in excess of 3 kW/kg. To improve battery life, the battery is oversized just as with NiMH. Using half the
          capacity we’re down to about 55-70 Wh/kg and for a complete pack about 50 Wh/kg is reasonable; some 60% better than a NiMH pack. Chevrolet Voltfor instance uses a lithium ion manganese spinel battery. These batterytypes are also common in power tools which require durable high power batteries.

          Lithium ion have other advantages too. They don’t
          require large amounts of nickel which would be problematic for large scale production of batteries, they don’t have a high self discharge andtheir charge/discharge efficiency is very high. The latter means less battery heat during charge/discharge and greater fuel efficiency. NiMH batteries suffer froma particulary high internal resistance when they approach a high state of charge.

          Today NiMH batteries are used for two reasons; they are safe and cheap. But NiMH is also a mature technology. This means they batteries are proven, but it also means there isn’t much room for improvement. NiMH are about as good and cheap they can be.

          Cobasys did also offer NiMH batteries to the large
          car manufacturers, but there wasn’t much interrest after California dropped the demand of zero emissions cars. Electric cars where neither practical or cost effective and it took a great deal of development until Toyota actually made a profit from their hybrids, and these have abattery that can store just slightly more energy than a regular lead acid car battery (at several times the cost). Small electric car
          manufacturers never could offer the volumes required to start series production.”

          http://www.supercars.net/PitLane?viewThread=y&gID=1&fID=2&tID=183739

          • Wayne Williamson

            The reason I brought it up, it was in the movie “who killed the electric car” (I think thats the name;-). I believe it was GM that bought the manufacturer of their batteries and then shut them down. Also, my old wireless phone system(for the house) used them, and they lasted over eight years of constant use.
            Just looking for another tool in the toolbox….

        • mds

          It’s about DEEP cycle-life guys!

          DEEP cycle-life is of paramount importance of EVs/PHEVs and gird energy storage applications. The highest cycle-life requirements are for Wind turbine blade control, frequency adjustment/control on the gird, and regenerative braking for EVs/PHEVs. Supercapacitors can or already are used for the later applications. I’m sure there are other, maybe industrial electric motor power, but I’m not an expert in this area. Supercapacitors are typically higher cost and lower energy density than chemical energy storage batteries (lead-acid, NiMH, Lithium). You still need a chemical energy storage battery to go the distance in an EV or PHEV. Lithium is the best of the three and many lithium ion batteries can provide a lot of power for a short time, so why even add expensive supercapacitors for regenerative braking?

          lead-acid something like 20 to 60 deep cycles, maybe more nowadays. I’ve read 700 or 1,500 deep cycles for carbon-lead-acid. I don’t know how much of that is bs/hype.

          I have several year old information that says NiMH batteries are about twice the energy density of lead-acid and are good for 500 to 700 DEEP cycles. An order of magnitude better than most lead-acid for cycle-life.

          Lithium ion batteries are typically good for several thousand DEEP cycles. (My old table, not updated in a few years, lists 9 lithium ion batteries claiming 3,0000 DEEP cycles or more. Altairnano claimed 85% good after 15,000 DEEP cycles for their Lithium Titanium Oxide batteries. Toshiba has claimed 80% after 6,000 DEEP cycles for their Lithium Titanium Oxide SCiB batteries.) Another order of magnitude better than NiMH batteries. This is why Lithium batteries are predominantly used in EVs and PHEVs.
          Bob is correct about Lithium MnO2/Mn2O4 and Lithium FePO4 chemistries being available in addition to Lithium TiO2. There are some others and an awful lot of research in this area right now.
          There are even more diverse chemistries being used for lower cost grid storage. For those applications weight and energy density are lower order issues and low cost, determined by including number of DEEP cycles they can be used, is of greatest importance.

          Toyota uses NiMH batteries in the Prius because the design is over ten years old and they don’t want to change it. You can get away with this in an HEV because you are just using it for load leveling on the Internal Combustion engine. (ICEs have an efficiency curve with the greatest efficiency at a narrow speed range… Hence the need for complex gears/transmissions. The electric motor/generator in parallel is used to keep the ICE operating at a more optimal speed.) The Prius battery charge controls rarely allow it to come close to full discharge level. My own Prius rarely goes below 1/3 discharged and 2/3 charged. This allows the inferior NiMH chemistry to work for the HEV application, but means you are carrying around a lot of dead weight most of the time.

          Toyota bad mouths Lithium battery technology, but they lie. They are trying to make as much profit as possible from the Prius design without changing much. The plug-in Prius uses a lithium ion battery. NiMH would not do the job. The lithium ion in the plug-in Prius does more and is apparently about half the size.

          The original EV1 design used lead-acid batteries, but was later improved using NiMH. Now we have EVs that run circles around the EV1 at a fraction of the production cost (order of magnitude lower cost) using Lithium ion batteries. The Nissan Leaf, Ford’s EV, GM’s Spark and Volt, and Tesla Roadster and Tesla Model-S all use Lithium batteries. The Tesla battery is interesting. I believe they use, or maybe originally used, lithium-cobalt which is the “unsafe” lithium chemistry invented in the 1970s. They solved this problem with electronic controls and mechanical isolation. If the individual cell starts to misbehave then it is isolated electronically. If it gets hot and fails by burning up, then it is still isolated mechanically from effecting the other cells. They have not had problems with this design and it allowed them to use low cost cylindrical Lithium batteries made by large companies in the millions for electronics use. Don’t remember if they are moving or have moved to a safer chemistry. Doesn’t matter. It’s already safe. Waaaayyyy safer than gasoline.

          I think there was a conspiracy surrounding the NiMH technology originally invented and brought to the market by Energy Conversion Devices. I think there was a semi-successful effort to purchase patents and keep this tech off the market. Ancient history. Multiple lithium chemistries are out there now. They are way better and the future profit potential is greater than what the oil companies can pay to keep it off the market.

          Don’t forget DEEP cycle-life is important!

          • Bob_Wallace

            “lead-acid something like 20 to 60 deep cycles, maybe more nowadays”

            I’m looking at some Trojan T-105 RE lead acid batteries for my off-grid use. They are rated at 1,000 100% DoD cycles. 4,000 20% cycles.

            I believe there are lead-acids rated for more cycles, but don’t know the numbers offhand.

            If lead-acids weren’t so bulky/heavy a set of REs in a 200 mile range EV would be 160k to 200k mile batteries.

          • mds

            Wow, “1,000 100% DoD cycles”. Impressive! Thanks for the info! I’ll update own info on that. I was wondering how they could still be talking about lead-acid batteries for that type of application. Now I know.

          • UKGary

            The other concerns with deep cycle Lead Acid are cycle efficiency which deteriorates substantially with fast charge and discharge, and a partially related factor of reduced cycle life when such batteries get hot.

            If you have a high power intermittent application in a hot desert – where you will be charging and discharging the battery fast, then Lead Acid will have a greatly shortened life – battery life halves for every 11 centigrade above 25C, which gets worse for a battery with poor cycle efficiency as the losses turn into unwanted heat in the battery!

  • Wayne Williamson

    I’m not sure this the solution. 60 watt hours per liter is not a lot…a cubic meter contains 1000 liters. This gives a cubic meter of this stuff the ability to store 68 kilowatt hours…I think just regular lion batteries have at least twice that capacity…

    • Wayne Williamson

      Don’t know how I got to 68 from 60, my typo I guess.

    • Altair IV

      You can’t talk about whether it’s a good “solution” unless you specify what it’s supposed to be a solution for. Certainly this won’t make them a replacement for things that need a very high energy density, but there are places where high-speed charging/discharging and longevity are more important than absolute capacity. Supercapacitors already have many uses, and the additional energy density would simply make them more flexible and usable in more situations.

      • UKGary

        The other things of importance are cycle efficiency which should be phenomenally high for Graphene supercapacitor, and long life – the best batteries tend to be good for a few thousand cycles at best, whilst supercapacitors can be good for 500 thousand to 1 million full cycles.

        If the price can come down into an affordable range, then they will be fantastic for frequency control of the power grids (regulating power on the grid up and down in the range milliseconds to a few minutes.) and also for un-interruptible power supplies where the need is often to deliver power instantly when the grid goes down and maintain it for a few minutes until standby generators can be started.

        • Bob_Wallace

          Lots of good information in your post, Gary, thanks.

    • geedavey

      Li-ion batteries take 20 minutes to “fast” charge to 80% capacity; graphene supercapacitors (GSCs) can fully charge and discharge in 2 seconds. Lithium burns fiercely in oxygen; graphene is very hard to burn. Li-ion batteries last thousands of charge cycles; GSCs last millions of cycles. Graphene is durable and flexible and more plentiful than silicon; lithium is a difficult to handle scarce mineral.

      • Bob_Wallace

        Now give us the list of reasons why we don’t see supercapactors in our EVs….

        • geedavey

          Current gen SCs are very heavy–just check them out on YouTube. This new tech will change that

  • Matt

    If this does work then I can see using your EV SC “battery” to balance the grid, since:
    (A) it doesn’t impact how long you can use it
    (B) charges so far,recharge time isn’t an issue
    Plus can take a much bigger brake regen charge.

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