Meaning
Self-sustaining exothermic reaction within an electrochemical cell initiated by localized heating, mechanical damage, or electrical abuse. In energy storage systems, cell thermal runaway represents the point where internal heat generation exceeds the rate of heat dissipation, leading to a rapid temperature rise. This process governs the release of toxic, flammable gases and can cause physical destruction of the cell casing.
It stops applying once the active chemical constituents are fully consumed and the cell has cooled back to ambient levels. In large-scale installations, the onset of this phenomenon requires immediate activation of fire suppression and ventilation systems to minimize the risk of cascading failures.
Initiation Vector
Internal short circuits often occur due to manufacturing defects or dendrite growth through the separator. These localized failures trigger cell thermal runaway by creating low-resistance pathways that discharge stored electrical energy as heat. Mechanical intrusion or external heating can similarly breach the separator to initiate this uncontrolled reaction.
Gas Discharge
Vaporization of the liquid electrolyte generates immense pressure within the sealed cell housing before the safety vent breaches. During cell thermal runaway, the released off-gas contains a mixture of carbon monoxide, hydrogen, and volatile organic compounds that can form explosive mixtures. Capturing these emissions requires active extraction systems designed to handle rapid volumetric flows.
Thermal Propagation
Conduction through touching cell walls and radiant heat transfer can warm neighboring cells past their own critical temperature limits. Preventing this domino effect depends on deploying specialized insulating materials between individual cells. If these barriers fail, the thermal event spreads across the entire module and compromises the larger energy storage system.
