Update.
http://www.valence.com/assets/pdf/ex...nal_report.pdf shows the relative safety of the different battery types. We have put the Valence cells into the DL designed products using larger batteries. Drawbacks are larger size (almost double), for a given output, and unusual charging circuitry.
Looks like Lithium Phosphate (e.g. the Valence Saphion), are still the most appropriate for rebreather use or suit heating.
Li-Mn can explode, from a test we did with high PPO2: the case ruptures and the chemicals insides burn. The Li-Co cells are even more exciting: little bombs in a high O2 environment.
The lithium ion cell risks are real enough for airlines to limit the size of cell you can take on. A large cell in a torch battery could blow a hole through the airframe.
The only safe cells right now seem to the Valence cells.
Alex