Meaning
Thermal safety parameters define the critical temperature at which self-sustaining exothermic decomposition reactions inside a cell generate heat faster than it can be dissipated to the surroundings. Exceeding the thermal runaway threshold leads to uncontrolled temperature escalation, gas venting and eventual cell fire or explosion. The parameter marks the boundary where passive thermal dissipation fails to arrest internal degradation chemistry.
Initial solid electrolyte interphase breakdown initiates exothermic reactions that trigger separator melting and cathode breakdown. Mechanics stop being controllable once self-heating rates exceed one degree Celsius per minute.
Trigger Mechanism
Initial solid electrolyte interphase breakdown occurs around eighty to one hundred twenty degrees Celsius, releasing heat and gas. Anode active materials then react directly with liquid electrolyte solvents, pushing cell temperatures toward cathode decomposition thresholds. Oxygen release from cathode structures accelerates violent organic solvent combustion.
Measurement Protocol
Accelerating rate calorimetry measures self-heating rates under adiabatic conditions to establish exact onset temperatures. Test protocols isolate target cells from heat loss to identify the precise threshold where reaction kinetics turn self-sustaining.
Safety Mitigation
Cell chemistry modifications incorporate flame retardant additives and ceramic-coated separators to raise the onset temperature. Module design incorporates phase-change thermal barriers to prevent heat propagation to adjacent cells when single-cell failure occurs.
