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Capacitance is proportional area, and inversely proportional to gap distance. I've read all over the internet that you need to make capacitors have as small a gap distance as possible, but I wonder if anyone has considered area of supercapacitors?

I grabbed a couple of quotes from wikipedia: "apparent density will therefore be lower, typically 0.4 to 0.5 g/cm3" "just one gram of activated carbon has a surface area in excess of 3,000 m2" which were here:

https://en.wikipedia.org/wiki/Activated_carbon

So if I had about two cubic centimeters of carbon that'd be a gram and have a surface area of about 3k sqr meters, I could probably easily smear 2 cubic cm on a some test plates and if I ground it up nicely get the distance down bellow a mm but then what's to stop me from smearing on another gram, adding another mm but bringing my surface area up to 6 thou??

I just found this research paper and in the results and discussion part I found this:

"The capacitance trend depicted in fig 4.3 increases monotonically as we increase the thickness of the electrode"

which supports my idea. But they were only using a range of 50 to 250 microns.. Here is a link to the pdf:

http://www.ct-si.org/publications/proceedings/pdf/2011/1524.pdf

and if you're like me you'd rather have the google query used to find the paper which was:

"supercapacitor thicker activated carbon"

or the name of the paper:

"optimization study of supercapacitor electrode material"

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The surface area of activated carbon is the 3D area of the particles. A capacitor's charge migrates to the surface between the gap.

Think of the surface area of a brick wall as opposed the surface area of all the bricks that made the wall. So if a 10 foot square section of the brick wall is one brick deep or 10 bricks deep it still only has a surface area of 100 square feet.

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  • $\begingroup$ Not sure if you are worried that the second layer will prevent the electrolyte from reaching the first layer, or if you think the second layer will not be electrically connected to the metal current collector. I don't thin either is the case. $\endgroup$
    – user273872
    Commented Jan 26, 2017 at 6:18
  • $\begingroup$ How much paint does it take to cover a 10x10 foot brick wall that is one brick deep? How much paint does it take to cover a 10x10 foot brick wall that is 10 bricks deep? It is only the surface area between the gaps that is important. $\endgroup$
    – MaxW
    Commented Jan 26, 2017 at 6:29
  • $\begingroup$ Your reasoning isn't entirely wrong. Think of measuring the length of the coastline of Great Britain. As your measuring stick gets smaller the coast line gets longer. The math is "fractals". So we imagine the 10x10 foot area of brick wall to be 100 square feet. You don't count all the pores in the brick's surface, or the extra surface area caused the curve of the mortar. $\endgroup$
    – MaxW
    Commented Jan 26, 2017 at 6:30
  • $\begingroup$ That's the correct reasoning for why the smallest pores don't contribute on a given particle, however as long as the electrolyte ion size is smaller than most of a particular particles pores, then adding it to the electrode surface subtracts a small amount of area where it electrically connected and adds a large area for all it's surface. It shouldn't matter whether that particle is stuck directly on the metal or on a previous particle unless it was so packed the electrolyte couldn't get past the new material. $\endgroup$
    – user273872
    Commented Jan 26, 2017 at 7:49

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