My little (25 ton) airplane uses Ni-Cads, two of them right in the nose. They're outside the pressure vessel and get to go from soaking on a 120 degree ramp in DFW to -50 or -60 Centigrade in about half an hour and do that several times a day in the summer.
They seldom give trouble and are supposed to give me 40 to 45 minutes of power to the essential things while I'm in the air, though I've never had to test that out for myself. A battery overtemp condition is a big deal and on our "short list" of baddest of the bad emergencies.
The Lithiom Ion batteries are a big deal in aviation in that they (FAA) are looking to severely restrict their transport, banning them on cargo shipments. They're lighter for the same energy capacity, hence Boeing using them on the 787. If the membranes in the battery get damaged they can make their own thermal runaway. These are teething problems and not surprising considering the technology leap in the 787.