Before the 787, I have never heard of any lithum-tech batteries being used for anything mission-critical in aerospace (please enlighten me if I am wrong).
Apparently the International Space Station, the F22 and F35 and the A380 all have LiIon batteries.
The same ones fitted to the 787 have "1.3 million hours of flight time" according the Boeing - so they are used in other places. I would suggest anything on the ISS is "mission critical" as its not easy to land if something goes wrong!
