Quite aside from the detection issue and the auto-suppression systems not working with lithium fires, there's a very good reason that decent branded Li-Ion cells come with warnings not to charge below 0C (32F in old money). If you charge a cell below this temperature, it may precipitate lithium metal onto the anode and can short the cell, which is a Bad Thing. At even lower temperatures I suspect it doesn't even need to be charging for the cell to short.
Remind me again one of the reasons why stowaways don't survive in the wheel wells/cargo holds of planes?
Of course, bunging Li-Ion cells into the plane's own control systems outside the controlled environment of the cabin is also a Very Bad Idea, so all of you calling kettle|pot are quite correct.