Paper-Based Supercapacitor Will Get Boost in Energy Density

Using a simple layer-by-layer coating technique, researchers from the U.S. and Korea have developed a paper-based flexible supercapacitor that could be used to help power wearable devices. The device uses metallic nanoparticles to coat cellulose fibers in the paper, creating supercapacitor electrodes with high energy and power densities – and the best performance so far in a textile-based supercapacitor.

Above – Image shows that the flexible metallized paper developed in this research retains its conducting properties even when crumpled and folded. (Credit: Ko et al., published in Nature Communications)

By implanting conductive and charge storage materials in the paper, the technique creates large surface areas that function as current collectors and nanoparticle reservoirs for the electrodes. Testing shows that devices fabricated with the technique can be folded thousands of times without affecting conductivity.

“This type of flexible energy storage device could provide unique opportunities for connectivity among wearable and internet of things devices,” said Seung Woo Lee, an assistant professor in the Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. “We could support an evolution of the most advanced portable electronics. We also have an opportunity to combine this supercapacitor with energy-harvesting devices that could power biomedical sensors, consumer and military electronics, and similar applications.”

The research, done with collaborators at Korea University, was supported by the National Research Foundation of Korea and reported September 14 in the journal Nature Communications.

Energy storage devices are generally judged on three properties: their energy density, power density and cycling stability. Supercapacitors often have high power density, but low energy density – the amount of energy that can be stored – compared to batteries, which often have the opposite attributes. In developing their new technique, Lee and collaborator Jinhan Cho from the Department of Chemical and Biological Engineering at Korea University set out to boost energy density of the supercapacitors while maintaining their high power output.

They began by dipping paper samples into a beaker of solution containing an amine surfactant material designed to bind the gold nanoparticles to the paper. Next they dipped the paper into a solution containing gold nanoparticles. Because the fibers are porous, the surfactants and nanoparticles enter the fibers and become strongly attached, creating a conformal coating on each fiber.

By repeating the dipping steps, the researchers created a conductive paper on which they added alternating layers of metal oxide energy storage materials such as manganese oxide. The ligand-mediated layer-by-layer approach helped minimize the contact resistance between neighboring metal and/or metal oxide nanoparticles. Using the simple process done at room temperatures, the layers can be built up to provide the desired electrical properties.

“It’s basically a very simple process,” Lee said. “The layer-by-layer process, which we did in alternating beakers, provides a good conformal coating on the cellulose fibers. We can fold the resulting metallized paper and otherwise flex it without damage to the conductivity.”

Though the research involved small samples of paper, the solution-based technique could likely be scaled up using larger tanks or even a spray-on technique. “There should be no limitation on the size of the samples that we could produce,” Lee said. “We just need to establish the optimal layer thickness that provides good conductivity while minimizing the use of the nanoparticles to optimize the tradeoff between cost and performance.”

The researchers demonstrated that their self-assembly technique improves several aspects of the paper supercapacitor, including its areal performance, an important factor for measuring flexible energy-storage electrodes. The maximum power and energy density of the metallic paper-based supercapacitors are estimated to be 15.1 mW/cm2 and 267.3 uW/cm2, respectively, substantially outperforming conventional paper or textile supercapacitors.

The next steps will include testing the technique on flexible fabrics, and developing flexible batteries that could work with the supercapacitors. The researchers used gold nanoparticles because they are easy to work with, but plan to test less expensive metals such as silver and copper to reduce the cost.

CITATION: Yongmin Ko, Minseong Kwon, Wan Ki Bae, Byeongyong Lee, Seung Woo Lee & Jinhan Cho, “Flexible supercapacitor electrodes based on real metal-like cellulose papers,” (Nature Communications, 2017) http://dx.doi.org/10.1038/s41467-017-00550-3

Nature Communications – Flexible supercapacitor electrodes based on real metal-like cellulose papers

Abstract

The effective implantation of conductive and charge storage materials into flexible frames has been strongly demanded for the development of flexible supercapacitors. Here, we introduce metallic cellulose paper-based supercapacitor electrodes with excellent energy storage performance by minimizing the contact resistance between neighboring metal and/or metal oxide nanoparticles using an assembly approach, called ligand-mediated layer-by-layer assembly. This approach can convert the insulating paper to the highly porous metallic paper with large surface areas that can function as current collectors and nanoparticle reservoirs for supercapacitor electrodes. Moreover, we demonstrate that the alternating structure design of the metal and pseudocapacitive nanoparticles on the metallic papers can remarkably increase the areal capacitance and rate capability with a notable decrease in the internal resistance. The maximum power and energy density of the metallic paper-based supercapacitors are estimated to be 15.1 mW cm−2 and 267.3 μWh cm−2, respectively, substantially outperforming the performance of conventional paper or textile-type supercapacitors.

6 thoughts on “Paper-Based Supercapacitor Will Get Boost in Energy Density”

  1. This reminds me of a report of alien human interaction at a secret underground base at Dulce.
    According to the witness who survived the gun fight between the aliens and the military the
    following occurred. The alien moved his hand in a circular pattern over the front of his body
    and energy discharge occurred that knocked this man to the ground and burnt off several of his fingers. The military lost several soldiers in the battle and then backed off.
    This device, a supercapacitor based on paper which can be crumbled without detriment, brings some thoughts to mind.
    Please bear with me on this analysis of the harmful grays.
    1) their suits act like super capacitors and the alien mentioned above directed a discharge
    at the ghuman victim
    2) alien autopsies show no stomach consider the possiblity that the suits provide the energy
    needed for their body cells activities rather than needing food supplying biochemicals to be broken down creating the energy the body needs to funtion.

    3) being supercapacitors theri suits would be subject to uncontrolled discharges with resultant bodily damage to the alien should short circuits be induced such as via
    conductive water, metallic filings, carbon based mettalic filaments(such as used to attack
    power stations and transmission lines).

    4) they are hostile to life other than theirown – evidenced, possibly by their failure to help
    the Martians in their time of need, perhaps drying out their atmosphere during their war against teh Martains who refused to cave to their dedmands,
    Vensus, where hhigh resolution radar scans have sshown areas which seem to have structures indicating destryoed cities, also a world without a water atmosphere, now.
    5) consider the U.S> government has made treaties with them allowing them do pretty much whatever they want in exchange for technology – BUT in the meantime they, the aliens are
    destroying the world’s ecology thereby dooming humankind. Note recent report from Europe indicating about 70% of the flying insects have disappeared, note also dying great barrier reefs posing unrecoverable damage to the oceans. the disappearnce of the insects destroys land based food production while the destruction of the seas destroyes sea based food.

    There is a war going on and now we know how to fight them individually on the battelfields or where ever they try to abduct people.

    Remember twow things :
    1) at night while you are sleeping you normally drift between conscious levels going deeper into sleep normally and naturally. BUT if you find yourself suddenly dropping off into a deeper sleep FORCE yourself awake because they are coming or are there already !!!
    2) considering now that their suits act like ssupercapacitors have conductors like water, perhaps an oil solution containing iron filings, etc to disrupt the operation of their suits.

    Please share this post.

    Bill C.

    Reply
    • Excellent start, but you’ll need some hero in the story as well as a bad guy. Please do not come up with some sort of school kid who has to save the world while still pretending to be a normal student to their teachers and parents. Something original would be a refreshing change. How about the reverse? A housewife who has to pretend to be normal to her children and husband? That might offer some possibilities.

      I do like the way you try to induce insomnia in the reader, that can lead them to associate your story with sleeplessness, and hence with strong emotions. Sneaky.

      Reply
  2. Cool. If the paper has a specific capacitance of 1 kF/m² then it would take a charge of 4.6 volts to attain the specific charge of 9612 J/m² (2.67 Wh/m²) that is being quoted. Other fun calculations…

    1 standard sheet of 20 lb bond is ¹/₅₀₀ of 20 lbs and is 17″ by 22″ in size. So, 9.09 kg (20 lb) divided by 500, divided by 0.43 m by 0.56 m is 0.0754 kg/m² of this stuff. Its specific unit mass in the MKS system.

    The power density therefore becomes 2.67 Wh/m² or 9600 J/m². Good … now divide those by 0.0754 kg/sheet and we get 128,000 J/kg. Which is 0.0354 kWh/kg. The inspirational power delivery is 150 W/m² by the same computational path, and likewise 2,000 W/kg.

    If your car needs, say 100 kWh and 300,000 W of energy and power respectively, then you need 100 ÷ 0.0354 = 2,800 kg of paper (less enclosure and all that) for the energy but only 150 kg for the power-delivery rate. CLEARLY the energy density is very poor and insufficient. 6,200 lb of paper for a car-with-practical 360 mile range … is too much. One also must wonder how much gold is involved. It can be expensive.

    596 liters for the 100 kWh of paper.
    31 liters for the 300,000 W power output.

    AS FINAL FUNNY NUMBERS let’s consider it in kg of TNT. If we really do assemble the 6,000 lbs ÷ 600 liters of the stuff into our car, it has a energy capacity of 86 kg of TNT in that big ol’ battery. A potential power delivery rate of 5.8 megawatts of stored-energy to heat-energy delivery. Per second. Kind of like BOOM. Big bada boom.

    LOL
    GoatGuy

    Reply
    • 1 standard sheet of 20 lb bond is ¹/₅₀₀ of 20 lbs and is 17″ by 22″ in size. So, 9.09 kg (20 lb) divided by 500, divided by 0.43 m by 0.56 m is 0.0754 kg/m² of this stuff. Its specific unit mass in the MKS system.

      Which is why in the metric world it’s called 75 gsm paper. 75 grams/square meter.
      Just a convenient check on your numbers.

      Reply
      • Thanks, Doc. Being steeped in Imperial Wonderfulness, I’d actually not heard of “gsm”. Its good to see that pencil-and-paper calculations correlate to the easy-peasy metric ones. Dunno. I still like cups, teaspoons and base-2 fractions of inches for carpentry. Old school. And I make myself feel worse about my weight by working in pounds instead of kilograms, or the almost ridiculous British stone.

        Reply
        • Cups and teaspoons are fine for cooking, because you are doing stuff that is dealt with by cups, and spoons.

          Likewise the one thing I really think feet and inches work best with is measuring humans, because clearly the measurement units were developed by measuring humans.

          I did my wood and metalwork classes with mm from the start, so I can’t relate there.

          And I feel best if I measure my weight in hogsheads. Of lead.

          Reply

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