Chain reaction in a lithium-ion cell producing its own heat and its own oxygen through decomposition of the internal materials, propagating from cell to cell for as long as stored energy remains to be released.
A conventional fire requires a fuel, an oxidiser and a heat source, and is extinguished by removing one of the three. Thermal runaway does not obey that logic: cooling slows it, starving it of air does not suffice. Propagation is the heart of the problem, the initial failure of one cell releasing heat that triggers failure in adjacent cells, which reaches the module, then the unit, then potentially the entire installation. A characteristic without equivalent among industrial risks follows: a storage loss is not over when it appears extinguished, the residual energy of cells not yet in runaway remaining available for days. The economic consequence reads directly, business interruption indemnity running throughout the cooling period, whose length depends on a chemical property rather than on a rebuilding schedule.
The peril is not an external event striking the asset, it is a property of the asset itself: the energy it contains is at once what gives it value and what destroys it.
thermal runaway, emballement de cellule, runaway thermique