Iiirc, there are many hundreds of pages on the web (going back a few decades) claiming that one can revive all sorts of batteries by freezing them - with many contradictory claims (e.g. some say it works for NiCad but not Li-ion, but others claim success with Li-ion too). But I've never seen any scientific data to back up these claims, nor have I seen any tests that are designed with careful enough controls to prove that the improvements were due to freezing. As such, I've always considered this to be an old wives tale. If anyone is aware of anything that rigorously proves otherwise I'd be grateful for links.