[maxvortex]

Hi.
Before i start my original question i have one sub question :-).

1.)
In supercapacitor one can use graphite or activated carbon as electrodes.
Ok. Carbon is not conductive or it has very low conductivity. Graphite has great conductivity but it has not so big "surface". Activated carbon should have both.
But, is activated carbon so good conductive and how could this be when we know that carbon is not conductive. Why is activated carbon conductive ?

2.)
As far as i know electrolyte in non graphene supercapacitor is salt.
Can this be any kind of salt ? Btw. why salt in the first place?

Regards, Max

[Arkcon]

I'm guessing you know, (or at least know to look up,) what a capacitor is.  But there are many topics on this page:  http://en.wikipedia.org/wiki/Types_of_capacitor  that begin to address the various types of real capacitors, how they're made, and why they're made that way.  Sorry to go all "bog standard" on you, but:

2.)
As far as i know electrolyte in non graphene supercapacitor is salt.
Can this be any kind of salt ? Btw. why salt in the first place?

Regards, Max

But that question is way too broad and simple a topic to answer in less than a dozen posts.

[maxvortex]

I'm working with capacitors for cca 15 years, so you can say i know what capacitor is :-). The reason why I'm interesting in supercapacitor is because i have build few but i can not get over 5 Farad's. Or course the main problem is electrode construction and electrolyte but what i want to know is how is activated carbon charged in some commercial versions and if amount of electrolyte solution (that went into electrodes ) has much to do with this charging. In my lab I have 2,4V 300F capacitor which is really strong one. I checked all datasheets and all kind of infos but non of them can help me out with this process.

Btw. can you please point me to this kind of topic. I have searched but didn't find much regarding this particular subject.

[Arkcon]

I know one thing about capacitor electrolyte.  Some shifty Hong Kong firm copied the formulation from a published patent.  The capacitors ended up in many US desktop computers.  Then they began to fail catastrophically.  Turns out the patent deliberately contained a bogus information just to cause this result.  So briefly, the formulation of a good electrolyte for an electrolytic capacitor is kept very secret by everyone involved.  However, here's a resource for quick and dirty information on the current research in ionic liquids for super-capacitors: http://www.sigmaaldrich.com/technical-documents/articles/material-matters/ionic-liquids-for.html  You can get these sorts of mini-app notes/adverts from Sigma-Aldrich delivered to your home or office.  I get them all the time.  I can barely understand most of the concepts.  But they're short and easy to read.  And of course, once you have the author, you could also look up their publications in peer-reviewed journals.

[maxvortex]

OK. thank you for link i will take a look. So what are we have so far...
Ionic liquid can be any salt that can be dissolved in some room temperature ?
So, i can use epsom, regular, or some third salt to make the "ionic liquid" ?

Max

[Arkcon]

Nope.  That's not the definition of ionic liquid.  Ionic liquids are quite a hot topic lately.  Although, briefly, they are any are organic salts that are liquid at, or close to, room temperature.  They can be really simple, like acetate or dicyanamide, or very complex organic salts.  Do read the link carefully.  You can even go and buy some of the reagents from Sigma-Aldrich ... that's why they published this mini- technical review for everyone to have for free.

[curiouscat]

I know one thing about capacitor electrolyte.  Some shifty Hong Kong firm copied the formulation from a published patent.  The capacitors ended up in many US desktop computers.  Then they began to fail catastrophically.  Turns out the patent deliberately contained a bogus information just to cause this result. 

I remember circa 2005 when I was a sys admin at a computer cluster and we had to literally scrap one motherboard a week (all Dell Optiplex Destops). All because of leaky capacitors. And you could literally see the failed capacitor.

Wonder if that's the same catastrophe. Anyways, we were lucky and got free replacements on all of them!

[Arkcon]

Wonder if that's the same catastrophe. Anyways, we were lucky and got free replacements on all of them!

That was the one (there have been many such incidents it seems) I was talking about:  http://en.wikipedia.org/wiki/Capacitor_plague#Industrial_espionage_implicated

[maxvortex]

I read the article and it's quite interesting.
As amateur i can conclude that there are bunch of ways to make ionic salt as long as you have some good base and access to materials like barium, calcium, or some oxides like KOH etc.
------------------------------------
Tell me if i want to make some thing like ionic liquid at home, what can i do ?
What would you suggest ? Btw. I have some KOH an Ammonium pellets left so we can try to use them for some test application.
--------------------
Some other ideas for constructing basic ultracapacitor:
copper sheet / some acid / activated carbon or graphite
aluminium / nacl / activated carbon or graphite

Suggestions ?

[billnotgatez]

@maxvortex

or some oxides like KOH

Although probably a typo
I think you would want to use another example of an oxide

http://en.wikipedia.org/wiki/Potassium_hydroxide

I think I remember, as a child using aluminum foil and wax paper to make a capacitor

I am curious as to what you used already in your attempts to make a super capacitor (if it is not secret)

[maxvortex]

Yea it was typo.

And of course its not a secret. I’m not some freaking scientist whose main goal is to get rich and famous :-). I'm thinking open source because this is the only way society can evolve. Maybe some scientist will read this article and use some informations but then again if he will do so, i hope he will share his knowledge with others.
 
I'm making stack capacitor because rolled version is complicated for this kind of design.
Both electrodes are from activated powder pressed onto glued surface. When the electrode is done you got really wide surface with good conductivity. Metal sheet is inserted into electrodes before i press them and the corners of electrode are superglued. As separator im using paper towel that was inserted into nacl solution.
So, electrode A / wet separator / electrode B . When the stack is done i put it in box and seal it with silicon. 

Max

[Arkcon]

Or you can seal them with silicone, instead.    No, seriously, you're able to get 5 farad, that's halfway to the advanced stuff I read about in the reference I gave you.  What were you using until this point?  Can you purchase some of the ionic liquids?  Are they compatible with what you've been building?

[maxvortex]

I can purchase some ionic liquid and i think that they should be compatible with this kind of setup but im not sure. Now, giving 30 Euros for few drops of ionic liquid is for me to expensive. I dont want to make capacitors with commercial liquid because i have plans to make one big capacitor bank and for that i would have to spend cca 500 euros, so i will try to make something similar.

Max

[maxvortex]

I forgot to ask...
What kind of separator is used in commercial version of supercapacitor and what would be the best substitute ?
Max