> The flavour you want is polymer, single ion conducting solid state with an ion transport activation energy below 10kJ/mol at room temperature and no phase transitions from -40C to 80C.

what makes it so? I don't know anything about this subject, I'm really curious now about what the perfect battery would be.

No idea why polymer single ion conducting would stop dendrites (I know people are looking for it, I don't know why).

But 10kJ/mol of activation energy is another way of saying less than 100mV of internal loses, and avoiding phase transitions means that your battery won't stop working on that temperature range.