12-Volt Battery Replacements

So, my 2004 Prius has a (so far only slightly) failing battery. It drops to 11.9 Volts after sitting overnight.
The battery does start the vehicle usually, but I've had to jump it once already.

So, I've been looking at replacements. It's already been modified so that another slightly more common size battery can be put in there, but I was wondering about taking that modification one step further: Why not substitute a more efficient battery chemistry like Lithium? (LiFePO4 specifically I'd assume?)

Does anyone know what the actual requirements are for the output current capabilities of the 12-volt battery in the Prius? I doubt the 'cold cranking amps' are very relevant on the currently installed one as the only thing (as far as I know) that the Prius does with that 12-volt battery is run lights, and engage the HV battery relays.
But I wanted to see if anyone had some information about the specifications required, so I could construct a lithium based replacement without having to just overkill it and make it capable of outputting 200 Amps continuous at ~12 volts.