The speed of chemical reactions are usually proportional to surface area. If a fiber with a Li Ion core is exposed to air, the area will be limited to 2 tiny ci

The speed of chemical reactions are usually proportional to surface area. If a fiber with a Li Ion core is exposed to air, the area will be limited to 2 tiny circles from each side of the broken fiber. So, we're not talking about explosions here. What would be interesting to see, if the fibers work as a slow match or not: https://en.wikipedia.org/wiki/Slow_match https://en.wikipedia.org/wiki/Slow_match (basically, whether they keep burning at a slow rate, or self-extinguishing)