Science

High-performance supercapacitor doubles performance of commercial alternatives

High-performance supercapacito...
From left, supercapacitor developers Mihrimah Ozkan, Cengiz Ozkan and Zachary Favors (Photo: UCR)
From left, supercapacitor developers Mihrimah Ozkan, Cengiz Ozkan and Zachary Favors (Photo: UCR)
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From left, supercapacitor developers Mihrimah Ozkan, Cengiz Ozkan and Zachary Favors (Photo: UCR)
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From left, supercapacitor developers Mihrimah Ozkan, Cengiz Ozkan and Zachary Favors (Photo: UCR)
The foam is built by depositing graphene, carbon nanotubes and RuO2 nanoparticles over a nickel substrate (Image: UCR)
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The foam is built by depositing graphene, carbon nanotubes and RuO2 nanoparticles over a nickel substrate (Image: UCR)
The RuO2 nanoparticles used in the foam are only a few nanometers in size (Image: UCR)
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The RuO2 nanoparticles used in the foam are only a few nanometers in size (Image: UCR)

Researchers at the University of California, Riverside have developed a new graphene-based supercapacitor that uses a nanoscale architecture to double its energy and power performance compared to commercially-available alternatives. This breakthrough is another important step toward making supercapacitors viable for use in fast-charging, high-performance electric cars and personal electronics.

Supercapacitors are energy storage devices that are very stable and long-lived, with high power density (power per unit of volume) but very low specific energy (energy stored per unit of mass). This means supercapacitors are able to deliver large amounts of power, but only for a few seconds at a time.

A team of researchers led by Prof. Cengiz S. Ozkan at UCR has now developed a new design for a supercapacitor with a specific energy of 39.3 Wh/kg and power density of 128 kW/kg, which is roughly double the performance of commercial supercapacitors in both these respects.

The researchers achieved this result by developing a new 3D carbon nanotube porous foam. The nanoscale pores provide a very large surface area that facilitates the infiltration of electrolyte and allows it to store energy much more densely than in conventional designs.

The foam is built by depositing graphene, carbon nanotubes and RuO2 nanoparticles over a nickel substrate (Image: UCR)
The foam is built by depositing graphene, carbon nanotubes and RuO2 nanoparticles over a nickel substrate (Image: UCR)

The foam was prepared by chemical vapor deposition of graphene and carbon nanotubes over a nickel substrate (see illustration above), and successive deposition of nanoparticles of hydrous ruthenium oxide (RuO2), where each particle was under five nanometers in size. Inside the foam, graphene acts as both a current collector and a buffer layer to facilitate the conduction of electrons and insulate the foam from the electrolyte.

One of the main strengths of supercapacitors over batteries is their superior cycling performance, and this device is no exception. Curiously, its capacitance (the capacity of the device to hold an electric charge) not only stabilized, but actually improved by 6 percent after 8,100 charge-discharge cycles. The researchers believe that this is due to the electrochemical activation of the active material.

The excellent performance, stability and ease of preparation of this system make it an attractive solution for future mass-production. And although its specific energy has ways to go to catch up with lithium-ion battery technology, it is certainly an important step in the right direction.

An open-access paper describing the advance was published on the journal Nature Scientific Reports.

Source: UC Riverside

6 comments
Anne Ominous
Minor corrections: "Supercapacitors are energy storage devices that are very stable and long-lived, with high power density (power per unit of volume) but very low specific energy (energy stored per unit of mass). " ... is not a definition of supercapacitors, but merely a description of their typical modern properties. I would appreciate it very much if you kept "typical properties" separate from attempts to define. They are not the same. Example: "annoying" is a common human trait, but it is not part of the definition of human. In the same vein, "low specific energy" is a common trait of capacitors, but does not define them. Indeed, one of the goals is to increase the specific energy... which if achieved would negate the latter part of your description, but would not at the same time make them something other than capacitors.
Slowburn
Just wait until a high energy capacitor gets damaged. It might as well be dynamite.
asdf
Great as long as we're aware of the health hazards of graphene. The miracle materials have not always been as fantastic as initially thought.
VirtualGathis
My only question is "When can Maxwell have this tech in its EV supercapacitors?" It might not replace a battery but it will make an excellent buffer to extend the working life of the battery pack. Pulling large currents, using high speed charging, or deep discharging batteries severely reduces their life. Adding a large enough capacitor will buffer the most of that.
warren52nz
For those who are interested, I have a G6 chemistry Lithium Polymer battery that has a capacity of 152 Watt-Hours/Kg and this capacitor is 39. But they're getting there. I think super capacitors have a great future.
Boota Mughal
I am surprised by this post simply because the method used (CVD) is challenging to make it commercial, second, I am astonished to see people still use RuO2 by knowing the toxicity and cost. We all know, by using Ru or related metals one can show higher numbers.. Nothing is surprising for me.