http://www.s399157097.onlinehome.us/...06_12_2005.pdf
Note from this 2005 document that Thales says they selected the battery - of course they might have had guidance from their customer.
In 2005 LiCo may well have been the best "proven" technology, and having made that choice, the aerospace industry does not lightly change its path. There is so much "process" involved - drawings, procedures, manuals, ICDs (Interface Control Documents) - that even after two fires and an OAG fleet the best way forward is still to leave everything as unchanged as possible, and put a steel box around it.
In the 80's and 90's we joked about paperwork, saying we couldn't launch until the weight of the paperwork equaled the weight of the vehicle. Those were the good old days. (We also joked that a camel was a horse developed by a committee. Today meeting-rooms full of brain-deadened team players are busily turning out camel after camel.)