High voltage supercapacitor is possible?

[Stanley514]

Energy density of supercap is equal to square of it`s voltage.
Is it possible to join together advantages of supercaps and high voltage
capacitors such as Ferroelectric caps?
What prevents to use high-k materials in supercaps?

 

[Curl]

dielectric brakedown. To have large capacitance, you need your plates to be very close to one another (micrometer or nanometer range). Now imagine having opposite charges so close to one another - the forces are enormous and the material will break, or in the best case, leak.

 

[Stanley514]

What do you think on following project:
http://www.technologyreview.com/energy/22297/"
Do you think it is going to fail?
Well,we could charge usual carbon supercap up to 4 volts only,
But carbon is far from best dielectric materials.Do you want to say
that if we will replace carbon with such material as barium titanate
it is not going to be charged even up to 30 volts?

 

[jimgram]

The present state-of-the-art (an example is Maxwell UltraCapacitor) is limited in voltage per cell of 2.8 volts because, as Curl reported, of the thin dielectric. The maximum capacitance however is 3000 farads (not micro, but farads). In order to use in most any application these are put into banks, both series and parallel, until the needed operating voltage (series) and capacitance (parallel). The only fly in this ointment is that the cells require a balancing circuit due to internal variations in leakage. This leakage, if unchecked, will allow some cells to exceed the 2.8 volt limit. Leakage current is microamps so any variation in internal resistance will cause a large voltage variation.

 

[Curl]

What do you think on following project:
http://www.technologyreview.com/energy/22297/"
Do you think it is going to fail?
Well,we could charge usual carbon supercap up to 4 volts only,
But carbon is far from best dielectric materials.Do you want to say
that if we will replace carbon with such material as barium titanate
it is not going to be charged even up to 30 volts?

30 volts with nano-scale spacing is a very large field. No matter what material you put in between (or even a vacuum) will allow charge to jump across if the field is strong enough.
Even if this doesn't occur, like I said, it will leak charge and the capacitor will discharge by just sitting there.

 

[DrZoidberg]

Well,we could charge usual carbon supercap up to 4 volts only,
But carbon is far from best dielectric materials.Do you want to say
that if we will replace carbon with such material as barium titanate
it is not going to be charged even up to 30 volts?

Carbon is not a dielectric at all. Supercapacitors don't have a dielectric. They use an electric double layer instead.
http://en.wikipedia.org/wiki/Electric_double-layer_capacitor

 

[Stanley514]

Carbon is not a dielectric at all. Supercapacitors don't have a dielectric. They use an electric double layer instead.

So what we would theoretically to do to increase voltage of supercup?
Find another electrolyte?

 

[Curl]

You increase space between plates... but if you do that, you lose capacitance. Its a trade.

 

[Stanley514]

How could we calculate theoretical capacitance of supercapacitor (in Farads/g) knowing
its surface area per gram?For example surface are is 2.000 m2/g.What would be capacitance if all this area is ideally utilized?