In the far future, what would be the most efficient battery for an advanced civilization? Taking practicality, cost, efficiency, etc. into account?

Would it be like a huge black hole that hawking radiates almost no energy, then you drop things in to extract energy?

Or if you had a good superconductor could you just store energy in it with absolutely no bleed off from resistance? Or maybe storing antimatter as a battery? Then just annihilating it with matter for energy?

Or would you end up just using something more mundane?