What is the difference in the internal structures of electrolytic capacitors with the same capacitance value but different voltages?

[bunalmis]

What is the difference in the internal structures of electrolytic capacitors with the same capacitance value but different voltages?

 

[dick_freebird]

The dielectric on aluminum electrolytic capacitors is
formed by anodizing. Growing the aluminum oxide is
a direct trade of C vs V, dielectric thickness. The difference
may be unobservable without construction analysis and
the oxide thickness is likely to be in a range where you
need a SEM to see it.