National Geographic News

Supercapacitors like the ones shown here in 2009 can boost or replace batteries in vehicles, storing energy as an electrical charge.

Photograph courtesy Argonne National Laboratory

David LaGesse

For National Geographic

Published August 20, 2013

Imagine charging your cell phone in just a few seconds. Or consider how transportation would be transformed if it took only a few minutes to fuel up an electric car.

The technology for rapid-fire power-ups has been around for decades—in supercapacitors. Supercapacitors not only charge faster than batteries, they last longer because they don't suffer the physical toll in charging and discharging that wears down batteries. They also have a number of safety advantages. However, supercapacitors' super size—they have to be much larger to hold the same energy as batteries—and their super-high cost have held them back.

But a number of scientists believe that recent breakthroughs put the fast, reliable, and potentially safer power storage in supercapacitors, sometimes known as ultracapacitors, well within reach of competing better with batteries.

"Ultracapacitors are kind of like lightning in a bottle, if you will," said Michael Sund, vice president of Maxwell Technologies, a leading manufacturer of the new technology, which is selling thousands of the units to charge buses in China.

Safety Woes for Batteries

Anyone who has run low on charge during an important phone call, or has tried to calm a child whose toy truck has suddenly stopped dead knows the limits of batteries. Batteries take a long time to charge, are relatively heavy—a big problem for the electric car market—and their safety often arises as an issue.

Just this summer, a major retailer had to recall thousands of replacement batteries for laptops made by Apple, only one of many makers of laptops and cell phones that have seen their own batteries recalled because of safety concerns. (See related quiz: "What You Don't Know About Batteries.")

Fires involving batteries earlier this year also helped temporarily ground Boeing's new Dreamliner. In one of the worst tragedies traced to battery failure, two crew members died in the 2010 crash of a UPS airplane in Dubai that investigators tied to flames rising from a cargo of batteries. (See related story: "Reshaping Flight For Fuel Efficiency: Five Technologies on the Runway.")

The dangerous pitfalls of battery use are part of what's helping boost renewed interest in supercapacitors.

Safety is much more of an issue than it has been in the past, said Peter Harrop, chairman of IDTechEx, a market research firm based in Cambridge, U.K. He and other fans of the emerging technology contend supercapacitors will thrive as companies seek new and more robust power sources that are also safer than today's batteries.

Instead of the chemicals that make batteries difficult to manage, supercapacitors use a sort of static electricity for storing power. That means their performance is more predictable, their materials are more reliable and less vulnerable to temperature changes, and they can be fully discharged for safer shipping, Harrop said. (See related photos: "Seven Ingredients for Better Electric Car Batteries.")

An Opening for Supercapacitors?

Scientists long have known that energy can be stored as electrical charge, instead of in chemical reactants as in batteries. Benjamin Franklin's famous experiment with rows of Leyden jars, which he called a "battery" after the military term for weapons functioning together, actually was an early version of a capacitor.

But recent breakthroughs in supercapacitor materials could make them competitors to batteries in more applications. "Supercapacitors are improving much faster than are batteries," Harrop said.

Then again, supercapacitors have been on the verge of commercial success for years. A 1995 headline, for example, suggested that ultracapacitors were "surging ahead." But they have remained a small business compared to rechargeable batteries—primarily because they store relatively little energy compared to conventional cells.

In batteries, storing an electrical charge is called "energy density," a distinction from "power density," or how quickly energy is delivered.

The energy density of supercapacitors pales against lithium ion batteries, the technology typically used today in phones and laptops. Lithium ion batteries store perhaps 20 times the energy of supercapacitors for a given weight and size. That means the iPhone 5 might have to be two or three inches thicker to hold a supercapacitor, making for a device that is hardly svelte.

Supercapacitors, on the other hand, excel when it comes to power density. They pack tremendous power—they can be charged quickly and release that power in fast bursts of current. Think of those sharp electrical jolts that can occur after one rubs the wrong way on shag carpeting. Or, perhaps better, think of the streaks of electricity that light up a summer storm.

Supercapacitor manufacturer Maxwell Technologies' largest sales have gone to bus manufacturers, Sund said. Operators use the supercapacitors to capture energy generated when a bus brakes for one of its many stops, and then discharge the power to help the bus get started from its dead stop. For that purpose, supercapacitors can replace batteries entirely on hybrid buses, while all-electric buses require fewer batteries.

That's likely the best way to continue selling supercapacitors, as supplements to batteries or engines that run on fuels, Sund said. "Supercapacitors will often be complementary to batteries," he said. "So we try to stay away from what we call 'battery bashing.'"

Still, there are other places where supercapacitors are replacing batteries entirely. One example is in wind turbines, particularly those that are offshore and difficult to reach. Supercapacitors can provide, for example, the bursts of power needed to adjust turbine blades in changing wind conditions.

Batteries traditionally have met that need. But batteries wear out because their chemicals lose potency over time. Because they don't rely on chemicals for storing electricity, capacitors last much longer, an important factor for turbines, whose height and remote positioning make them expensive to maintain.

Some European cars also use supercapacitors in a fashion similar to buses. The European "micro-hybrid" cars turn themselves off when they would normally be idling. That "start-stop" technology normally runs off batteries alone, but French carmaker PSA uses Maxwell supercapacitors in some of its Citroen and Peugeot cars.

Batteries, though, continue to grab most of the micro-hybrid market because the supercapacitors and accompanying electronics can add a couple hundred dollars to a car's cost. The technology's backers argue that the supercaps cost less in the long run because they last longer than batteries and save more fuel because they work more reliably.

Still, when it comes to micro-hybrid cars, initial purchase price so far trumps efficiency and long-term cost of ownership, Sund said.

Hurdles to Overcome

New materials might help supercapacitors compete better on energy density. Many scientists are focusing on graphene, carbon that is only one atom thick and that has generated much excitement since it was refined about ten years ago. Graphene has proven expensive to manufacture. But a lab recently showed that a cheap, common household device could make graphene in inexpensive, high-quality sheets. A graduate student used a DVD burner to make graphene in a chemistry lab run by Ric Kaner, a professor at the University of California, Los Angeles.

The DVD drive had a feature called LightScribe that etches images onto the surface of the DVDs. It turns out that the laser also converts a common material, graphite oxide, into sheets of graphene. The discovery was described last year in the journal Science.

The laser produces graphene with a characteristic that makes it especially promising for supercapacitors: It emerges with holes, or pores. This highly porous graphene can be stacked many layers deep while both sides of each layer remain accessible. In experiments, that has doubled or tripled the energy density of supercapacitors made with graphene.


A DVD-size disc of micro-supercapacitors.
A DVD-size disc from Ric Kaner's lab holds micro-supercapacitors.

Photograph courtesy UCLA


A single layer of carbon atoms doesn't store much energy, Kaner said. "It's when you can stack hundreds or even thousands of layers—and that's what we're doing."

He won't predict when the new material might appear in commercial supercapacitors, other than saying he hopes it won't be ten or even five years. Even then, the supercapacitors will likely work in tandem with batteries. "They are not a replacement for batteries, as of yet," Kaner said.

But if they eventually can store enough energy to compete with batteries, supercapacitors have key advantages, including that they can provide high power and be used for millions of cycles, Kaner said. "Also, unlike batteries, they don't overcharge and they don't overheat."

The safety advantages of supercapacitors will grow as the demand for portable energy grows, said Harrop of IDTechEX. Capacitors themselves present their own concerns with safety, because any technology that stores energy is potentially dangerous. But makers are phasing out toxic and flammable chemicals that have been used in supercapacitors, and even those supercapacitors have better safety records than lithium ion batteries, he said.

Meanwhile, battery safety will become more of an issue as the cells get larger, such as those now being used in electric vehicles. The larger a battery, the more likely it is that something can go wrong, Harrop added. "It's easier to make a battery safe for something like a phone than it is for a car."

This story is part of a special series that explores energy issues. For more, visit The Great Energy Challenge.

Eng Kiat Chen
Eng Kiat Chen

First of all, a "battery" that is made of ultracapacitor should not be called a battery, this is because "battery" by definition "a device that store power in electrochemical form". Thus hereafter we will named our product as ultracap cell.

Merely short 7 months from this article, we are already going to roll out our first ultracap cell for car. The date for commercial release will be around end of July.

Our ultracap cell will replace entirely the lead-acid battery used in cars.

With ever demanding electrical power to meet today modern cars, ultracapacitor can give sudden burst of electrical energy required by the car - fast discharging; and get charged instantly by the alternator - fast charging.

I have a 2010 Mercedes E250, a 1.8L with turbo, and it is now running on our ultracap since 3 months. The car performance has improved, coming for fast discharge to the engine, especially the spark plugs. If spark plugs are fired up well with high current they draw from ultracap, the fuel combustion is more complete, the performance and efficiency is improved and thus giving a fuel saving of 5-10%.

Not to mention, the ultracapcitor is 100% electronic vs battery electrochemical, the life span of a ultracapacitor can last up to 10 years or beyond.

The ultracapacitors are CE certified for safety and indeed it is safer than Lithium batteries.

Khalil Haddad
Khalil Haddad

It seems that we are about to enter a revolutionary era in battery use.

Rodney Howard
Rodney Howard

Has any one heard from the ESSTOR crowd. It was probably a fraud, but the tecnology described for it was very similar to this, but the purported results were much more amazing.

Rodney Howard
Rodney Howard

Has anyone heard of anything from the ESSTOR crowd? It was probably a fraud, but the tecnology decribed was very similar to this. The stated results were far more amazing if true.

m s
m s

This would be a major win for home and EV car enhancement. I'd suggest tho that they use a combination. There's no 1 single power source that will solve the whole thing. Even in Scyfy shoes where they have devices and system of the future, we see them use multiple types of power sources. 

ST for example uses fusion fission antimatter-matter explosions plasma and electrical conduction and phase conduction to power their ships.

Why would it be difficult once these problems are solved to combine in a car for example supercapacitors, LI batteries and combine those with the systems for charging like the break charge system, solar panels, hydrogen fuel cells, and even using fuels like the vegetable oil system that some car owners have converted their cars to use as an alternative when battery and capacitor systems run low. I dont' see the problem with all of these technologies, why can't we completely replace oil and gasoline in our vehicles?!

Roger Bird
Roger Bird

And now for the Champion of the World in all categories, energy density, power density, environmental cleanliness, safety . . . .the Greatest Energy Source in the History of the World:  (drum roll, please)  Andrea Rossi's E-Cat.

You may not have heard about it yet because hot-fusionists are financially motivated to try to keep it a secret.  Hot Fusion energy producing devices have not created so much as a single watt of excess energy in almost 60 years of trying, but Rossi's E-Cat has produced untold excess hours of kilowatts, in tests supervised by independent and credentialed and honorable scientists from Sweden and Italy.

You can find all about it here:   [NOTHING that I have written here has been so much as an exaggeration.  It has all been exactly the truth.]

Gemma Seymour-Amper
Gemma Seymour-Amper

Mr. Meyering, perhaps throwing eggs at people isn't exactly productive. 

It isn't about what kind of car you drive, or how many miles to the gallon your car gets, it's *that* you drive at all.

It's about the fact that everything in our society, from the the design of our homes, to our food distribution system, to our working environmentsm to our markets...literally everything is based around a concept of motorised personal transportation that is extremely wasteful no matter what fuel powers it.

I currently own and operate a 2001 Ford F-150 4x4 off-road pickup that gets on a good day about 15 mpg on the highway. But, I use my truck maybe once a week to drive a few miles, at most, because I live in the downtown area of a city in a high-rise apartment building. And when I go out in my truck, it's usually not during rush hours, so I don't get stuck in traffic a whole lot.

I also don't go on a whole lot of long road trips, because at $4.00+ USD a gallon for gas, a 300-mile round trip is going to cost me somewhere around $100 in gas, which I just don't have. So, if I need to go away for the weekend, I take public transportation, or I don't go, at all.

If you compare my usage patterns to a person who drives a 2012 Toyota Prius 30 miles each way back and forth to work 5 days a week, replaces it every three years when the lease is up, parks it in the driveway of a suburban detached house, and also drives many miles a day on average fulfilling the needs of operating that suburban home, plus feels that because their car is so efficient, they have no qualms about taking long road trips, who do you think has more impact on the environment?

I'm willing to bet it's not me, but I'm also willing to bet that if you passed me on the street or the highway in my beat-up, gas-guzzling 12 year old pickup truck, with the windows down blasting some country music, with that attitude, you're probably going to feel pretty superior to me, aren't you?

Chris Meyering
Chris Meyering

I really hope it comes to market, I would love to throw egg in the face of the anti-electric car crowd.

Joe Average
Joe Average

Seems like banks of ultra-capacitors and stationary batteries would be a great match for the "green tech grid". Space and weight is not a big concern that way. Maybe pair up the ultra-capacitors with a long lasting nickel-iron battery?

J Matta
J Matta

Well I cant disagree with your premise or the eloquence with which Science Fiction Writers both create and borrow from real science in their tales.  

The Capacitor was invented in 1745 and was in wide use as an electrical device and battery well before Mr. Farmers birth.  The difference today is that we are able  to manipulate materials with such precision, creating order of magnitude efficiency gains.

Bob Jarvis
Bob Jarvis

This sounds a lot like a batacitor, as described by Philip Jose Farmer in "The Fabulous Riverboat" (part of the Riverworld series).  If a scientist thnks he's inventing something new, he'll probably find it's been described about 40 years earlier by a science fiction writer.  :-)

David Dyar
David Dyar

@Eng Kiat Chen That is very exciting and encouraging.   Thank you for sharing the progress and we look forward to see what you will do with it.

David Dyar
David Dyar

@Rodney Howard No, eestor was nothing like this.  They were hyping some silly barium titanate powder like it was a breakthrough.  It's simply a material with some interesting qualities that doesn't actually work to make a supercapicotor.  But they were telling everyone they could do magic with it and they seemed to actually believe that if they said it enough that it would somehow be true.  

There was nothing new about barium titanate and there was nothing they could do that was magic.  

David Dyar
David Dyar

@Roger Bird Why is there some nut job on every tech forum talking about rossi and his con-job like it's some kind of religion they're clinging to?

Robert Kabbes
Robert Kabbes

@Roger Bird 

Another name for devices such as E-Cat is LENR (Low Energy Nuclear Reactor).To confirm its reality just note the government entities involved with LENR. All one has to do is enter into Google LENR & NASA or LENR & Navy LENR & Air Force or just LENR and a repository of facts and data will be at your disposal.Many companies are now in the planning process of setting up manufacturing plants to release new domestic and larger commercial LENR devices like that of the E-Cat within a few months to a couple of years.I know this is too incredible to believe but a major energy game changer is about to enter the stage.The realities are beginning.Hang on.

Joe Murray
Joe Murray

@Gemma Seymour-Amper Not going to get humans to stop moving around, so making our transportation emission free crade to grave and recycled materials and so on. That is our best option. I hate it when people complain without a real solution. That is why I appreciate people who work on practical solutions.

Chris Meyering
Chris Meyering

@Gemma Seymour-Amper 

lol...its a harmless expression. 

Regardless, deciding not to drive might work out just fine for you , but where I live, Public transportation is non-existent (the Auto Companies bought it all up and ripped it out ), Absolutely everyone has to commute to find work and to hold a job. And everyone is going to sit in traffic for hours (electric cars turn off when not moving) 

You are also confusing a Prius with an electric car, its not.

But in the end, your rant pretty much proves my point. 

Roger Bird
Roger Bird

Joe, keep looking.  This story isn't finished.  In fact, it has barely gotten started.  By 1908, there were still scientists who said that heavier-than-air flight was impossible.  Even Scientific American gave the Wright Bros. bad marks as late as January 13, 1905.

There has been a third party independent verification of Rossi's E-cat, and not only was the report glowing, so also was the E-cat.  (:->)  There were 3 tests.  The 1st test the E-cat melted.  The 2nd test lasted for 96 hours with splendid results.  The 3rd test lasted for 116 hours also with splendid results.  The last two tests were ended voluntarily.  The tests were conducted by heavy hitters who had reputations at risk.

Alain Samoun
Alain Samoun

@Joe Cowan@Roger Bird


Do not trust "Pop Science"

There is a 3rd party report this last May, that was written by serious scientists that proves that the Rossi's E-cat works:

The testers were:
Giuseppe Levi,  Assistant Professor in the Department of Physics and Astronomy, Bologna University
Evelyn Foschi, Product Development Department for medical devices, University of Bologna, Italy.
Torbjörn Hartman, Senior Research Engineer, The Svedberg Laboratory, Uppsala, Sweden.
Bo Höistad, Professor,  Department of Physics and Astronomy, Nuclear Physics, Uppsala University, Sweden.
Roland Pettersson,  Senior Lecturer, Department of Chemistry, Uppsala University, Sweden.
Lars Tegnér,  Professor Emeritus, Department of Engineering Sciences, Division of Electricity, Uppsala University, Sweden.
Hanno Essen, Docent and Lecturer,  Department of Mechanics of the KTH Royal Institute of Technology, Stockholm, Sweden. 

Gemma Seymour-Amper
Gemma Seymour-Amper

@Chris Meyering No, actually, I didn't prove your point. But you sure did prove mine.

Maybe y'all ought to consider moving to a place where you don't need to drive so much, and I'll consider selling the truck and replacing it with nothing. Heck, I wouldn't even have the thing, if it weren't for that I inherited it from my daddy. If it'd been my choice, and if I could have afforded to buy a car at the time, instead of using my daddy's hand-me-down, I'd have bought something a whole lot smaller, anyway.

Oh, and just so you know, I'm a professional technology consultant. I'm pretty sure I know what goes in a Prius, and the last time I checked, it had a whole bunch of batteries in it that need to be replaced every few years or so.

The point is, electric cars ain't gonna save the planet. You see, there's this little thing called the Jevons Paradox. The more "efficient" the product, the more people use energy. Y'all might want to look into that.

Rodney Howard
Rodney Howard

@Roger BirdRoger Bird From what I’ve read, the controls on these verifications were questionable. The scientist used Rossi's equipment at his site. The generator was already running. And several of these independent experts had been involved in this project before, and were deceived before by faulty sensors attached the equipment. Hopefully its true, and we have a breakthrough, but I am a skeptic. Also there have been some interesting developments in hot fusion with the production of an economical hot fusion reactor by 2017

Rodney Howard
Rodney Howard

@Alain Samoun @Joe Cowan @Roger BirdRoger Bird From what I’ve read, the controls on these verifications were questionable. The scientist used Rossi's equipment at his site. The generator was already running. And several of these independent experts had been involved in this project before, and were deceived before by faulty sensors attached the equipment. Hopefully its true, and we have a breakthrough, but I am a skeptic. Also there have been some interesting developments in hot fusion with the production of an economical hot fusion reactor by 2017

Richard Nygaard
Richard Nygaard

@Gemma Seymour-Amper @Chris Meyering  YOu are assuming the planet needs saving, there are many who would say it does not.  

Also the Prius battery does not need to be replaced every "few" years unless you define few as 10.

So your solution to the problem is we all move to places that are congested enough to make public transportation viable.  With the size of the US and the number of people here thats just nuts.  I guess we could all move to Texas and just pick one other normal sized state and we can leave the rest of the country empty.  

Rodney Howard
Rodney Howard

@Gemma Seymour-Amper @Chris Meyering Picups are expensive to drive and should only be used to perform chores. For everyday driving you should get a nice economy car. Public transpotation outside of major cities isnt practical at this time. Many gas power economy cars perform as well or better than so called hybreds when you consider all the costs and end of use polution from current day batteries..

Casper McGrady
Casper McGrady

@Gemma Seymour-Amper

I'm not a Prius fan, but the batteries do not need replacement every "few years or so".  The batteries last upwards of 10 years.  That shows me you really know nothing about this technology or at least didn't even bother to do your homework before trolling.  Tisk tisk...

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