Failure mechanism, example.....
Quote......
"The use of copper as the current collector for the negative electrode has particular reliability and safety implications. At very low cell voltages (usually approximately 1 V for the cell), the potential at the copper current collector increases to the point where copper will begin to oxidize and dissolve as copper ions into the electrolyte. On subsequent recharge, the dissolved copper ions plate as copper metal onto negative electrode surfaces, reducing their permeability and making the cell susceptible to lithium plating and capacity loss. Usually, once a severe over- discharge event has occurred, cell degradation accelerates: once the negative electrode has become damaged by copper plating it will no longer be able to uptake lithium under “normal” charge rates. In such an instance, “normal” charge cycles cause lithium plating, which result in a greater loss of permeability of the surfaces. Ultimately, over-discharge of cells can lead to cell thermal runaway." ....Unquote
http://www.nfpa.org/assets/files/pdf...rieshazard.pdf
So it would seem that "internal protections" would be limited practically to a strict control of voltage within a frame of charge/discharge. protection from mechanical damage, and environental stressors are straightforward, nothing below -18 or above 60 (C).
Since the listed resrictions are "mitigating" rather than "prohibitive" (eliminating) as to failure, they can certainly be construed as "permissive of" smoke, runaway and even fire "events". A "mitigation" is by definition "may" not "may not"....