A partial recap for late commers...
When they designed the 787 I think Lithuim Cobalt was the most proven of the Lithium cell technologies available.
Since then some/many other users have switched to Lithium Manganese for because of possible concerns over the safety of Lithium Cobalt.
It's possible Boeing were/are considered changing to Lithium Manganese but don't appear to have done so yet.
Last edited by cwatters; 29th January 2013 at 16:22.