> They have a relatively high self-discharge (or leakage depending on how you measure it) compared to say Li-ion/NiMh cells which means basically they piss capacity away slowly.
Your claim is premature -- they haven't chosen an insulator yet. The graphene sheets are the conducting surfaces, not the insulating layer. Your claims are about the properties of the insulating layer between graphene sheets, which hasn't been selected yet. It looks like this:
Nanoscale is fun. A measly voltage of 1 Volt across a gap of 100 nm means there's an electric field of 10 MV/m. It's kind of hard to keep electrically charged particles, such as electrons, from moving under that kind of stimulus.
If memory serves, in air the disruptive voltage is 30kV/cm (or 3 MV/m) - above that one gets those sparkly electric arcs that melt metal, intentionally or not. (Other than that, air is an insulator.)
>> Your remark applies to any storage device, including batteries. So it's not an issue that sets supercapacitors apart.
> That is correct and is my point.
No, your point was that supercapacitors discharge faster than batteries because of leakage. But that's not true -- it depends on which insulating material is selected, and that hasn't been decided yet.
Here is what you said: "They aren't magic. They have a relatively high self-discharge (or leakage depending on how you measure it) compared to say Li-ion/NiMh cells which means basically they piss capacity away slowly."
Your claim is premature -- they haven't chosen an insulator yet. The graphene sheets are the conducting surfaces, not the insulating layer. Your claims are about the properties of the insulating layer between graphene sheets, which hasn't been selected yet. It looks like this: