Energy

Researchers achieve a 10x supercapacitor energy density breakthrough

Researchers achieve a 10x supe...
This flexible graphene supercapacitor design can store 10 times more energy than comparable existing technology
This flexible graphene supercapacitor design can store 10 times more energy than comparable existing technology
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In testing, the supercapacitor was able to function almost exactly the same whether it was lying flat or bent 180 degrees
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In testing, the supercapacitor was able to function almost exactly the same whether it was lying flat or bent 180 degrees
This flexible graphene supercapacitor design can store 10 times more energy than comparable existing technology
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This flexible graphene supercapacitor design can store 10 times more energy than comparable existing technology

Supercapacitors can charge almost instantly, and discharge enormous amounts of power if needed. They could completely erase the Achilles heel of electric vehicles – their slow charging times – if they could hold more energy. And now Chinese and British scientists say they've figured out a way to store 10 times more energy per volume than previous supercapacitors.

A team split between University College London and the Chinese Academy of Sciences has released a study and proof of concept of a new supercapacitor design using graphene laminate films and concentrating on the spacing between the layers, the researchers discovering that they could radically boost energy density when they tailored the sizes of pores in the membranes precisely to the size of electrolyte ions.

Using this design, the team says it's achieved a massive increase in volumetric energy density. Where "similar fast-charging commercial technology" tends to offer around 5-8 watt-hours per liter, this new design has been tested at a record 88.1 Wh/l. The team claims it's "the highest ever reported energy density for carbon-based supercapacitors."

That figure is toward the high end of what a typical lead-acid battery stores, but while lead-acid batteries charge very slowly and offer fairly low power density, the supercapacitors can charge very, very quickly and offer massive power densities around 10 kilowatts per liter.

In addition, the supercapacitors appear to have a long service life, retaining 97.8 percent of their energy capacity after 5,000 cycles, and they're very flexible, performing almost exactly the same when bent 180 degrees as when they were lying flat.

In testing, the supercapacitor was able to function almost exactly the same whether it was lying flat or bent 180 degrees
In testing, the supercapacitor was able to function almost exactly the same whether it was lying flat or bent 180 degrees

There is a but. There is always a but. Indeed, there's three big buts here, beyond the fact that this is still at the research proof of concept stage.

The first is that these supercaps are still far less dense than a top-shelf lithium EV battery. Closest estimate I can find on what Tesla is running is a 2018 estimate of 877.5 Wh/l, which would mean a supercap would have to be 10 times the size of a Tesla battery pack to offer the same range. Not gonna happen. Mind you, EVs won't have to offer 430-mile (700 km) range figures once they're even quicker to top up than a petrol car. The vast majority of car use would easily be less than 100 miles (160 km) in a day, and a short stop every hour and a half on a long trip might be no big deal for many drivers.

What's more, we've written before about the extraordinary things you can do when you pair lithium batteries with supercapacitors in a hybrid arrangement. This kind of density development could increase the amount of supercapacitor you might be able to run in such a setup, further maximizing the benefits.

The second issue: supercapacitors tend to leak energy rather than storing it very well. You might find your EV out of power if you leave it off the charger for a week or two. Although to be fair, when they charge so fast, you might not mind.

And the third issue: this thing is made of graphene, everyone's favorite wonder-material which is set to revolutionize everything from electronics to mosquito protection to aviation to hair dye to concrete to running shoes to bulletproofing to loudspeakers and every other field it's been researched in... But to date, nobody's producing it in mass commercial quantities at a price that makes huge graphene supercapacitor cells feasible.

Still, the researchers are optimistic. “Successfully storing a huge amount of energy safely in a compact system is a significant step towards improved energy storage technology," said senior author and Dean of UCL Mathematical & Physical Sciences, Professor Ivan Parkin (UCL Chemistry). "We have shown it charges quickly, we can control its output and it has excellent durability and flexibility, making it ideal for development for use in miniaturized electronics and electric vehicles. Imagine needing only 10 minutes to fully-charge your electric car or a couple of minutes for your phone and it lasting all day.”

Oh, we're imagining, Professor Parkin, we're imagining alright. And there are numerous other uses for supercapacitors where this kind of technology could instantly shine if it makes it through to production.

The study was published in the Nature Energy journal.

Source: University College, London

14 comments
Simon Redford
This is very encouraging but not necessarily for bulk energy storage. As the supercapacitor can be charged and discharged very quickly, this makes it unsafe for holding large quantities of energy for automotive applications – lots of energy + very fast discharge => explosive potential! However, for regenerative braking this is good news – supercapacitor absorbs the braking energy which can either be returned for acceleration shortly after or transferred relatively slowly and efficiently to the main storage batteries. As for fast charging – yet again the infrastructure and safety aspects of rapid charging are being ignored – charging 100kWh in even five minutes is equivalent to 1.2MW and is still slow compared to liquid fuelling. Emphasise the ‘hybrid’ element of the supercapacitor.

By way of an example, to stop a (small) 1 tonne car in 15 seconds from 60mph (96.6kM/h) generates ~100Wh (360kJ) of energy at a rate of ~24kW, so 3 litres of the new supercapacitor could comfortably take all the braking power and release it to support acceleration shortly afterwards. Reducing the current draw from the main batteries during acceleration may also be advantageous for efficiency and battery life.
clay
An interesting side benefit of this cap density is that it will enable the capability to conveniently build very high voltage motors... e.g. smaller wire...less current.. more watts.

It will be interesting to see 4800v pmdc axial flux motors the size of a dinner plate that can lay down 100KW of output:-)
guzmanchinky
Those are some big buts, but I see new breakthroughs every week here so I know the 500 mile car that charges in 5 minutes is just around the corner...
Grunchy
Once barriers of cost begin to fall this could spell the end of lead acid batteries. I've watched with interest some youtube videos of people who removed their car's lead acid batteries and ran around using strictly a large capacitor. The battery is just to get the engine started, once it's running the car electric system is powered completely by the alternator.
(Capacitors, especially large capacitors, are tremendously dangerous so make absolutely sure you know what you're doing before you ever try something like this yourself).
paul314
For most purposes, this could massively simplify the design of EV battery packs and make them safer. A lot of the cooling and long-term stability issues for lithium batteries are about fast charge and discharge. If you could set things up so that batteries only provide enough power for cruising, while capacitors handle acceleration and braking, that would be way easier.
usugo
there is an article like this popping up every other year
like this one
https://iopscience.iop.org/article/10.1088/1361-6528/aa8948
claiming a whopping 148.75 Wh kg−1
Jay Dresser
I imagine the military would be interested in this for rail guns.
CAVUMark
With more research I remain optimistic, understanding the Hybrid design is up an running on a currently available motorcycle. Now just bring the cost down.
-dphiBbydt
For the average driver and vehicle the recharging time for BEVs or capacitor storage will be irrelevant as soon as ranges get to about 400 miles. So few drivers will drive 300 miles (approx 5 hours) and then be in such a hurry to 'fill up' only to drive another 5 hours. The average driver with an average car drives about 10,000 miles and if the average speed is 30mph then that's 330 odd hours of driving meaning that 96% of the time through the year the vehicle is completely stationary and in a good situation to be recharged. Obviously there will be exceptions for professional drivers but for the vast majority of people fast charge times will become irrelevant.
Incra Mant
You can include this into the solar panel itself and have instant power from the sun without batteries.