Here's what I think I learned so far:
- Water-based electrolytes give you higher CV, lower ESR
- Water-based electrolytes are chemically aggressive (ie corrosive)
So essentially all 85 °C and 105 °C (boiling point of the water-based electrolyte has to be higher than 100 °C?) capacitors use water-based electrolytes. Old capacitors (pre-mid80s) use electrolytes based on organic solvents like GBL.
Organic electrolytes are chemically not nearly as aggressive, but result in lower CV, so poorer density.
Now, from a hobbyist's "I want stuff to last" perspective non-water electros seem to be the better choice. But they seem to be relatively rare. However, it seems like 125 °C and higher capacitors cannot be made using water-based electrolytes. For example, the Rifa/Kemet PEG124 series use GBL electrolyte. They don't advertise it, but
this paper confirms it. These capacitors would seem like a perfect fit to replace wet slug tantalums sometimes found in older test gear, among other things.
=> Are organic electrolytes truly superior in terms of reliability than water-based electrolytes?
=> Which are commonly available cap series using organic electrolytes?