One would hope that these are not lithium cobalt oxide cells.......
(edit: It seems Boeing may have changed to lithium manganese in 2008. The following original post is probably outdated information) They are. The battery cells in question have Lithium cobalt oxide (LiCoO2) cathodes. Around 10 years ago - when the 787 design process started - that was the only material available. The Supplier, GS Yuasa, was awarded the contract in 2005 (by Thales, who did the system integration).
Here's the spec sheet:
http://www.s399157097.onlinehome.us/...s/LVP10-65.pdf
And yes, newer lithium-based chemistries have more desirable thermal properties in a runaway condition (click to enlarge):
