Which statement best describes thermal runaway in lithium batteries?

Which statement best describes thermal runaway in lithium batteries?

• A. A rapid cooling process that prevents ignition.
• B. Self-sustaining, exothermic reaction that rapidly increases temperature, potentially causing fire or explosion.
• C. A controlled battery discharge event.
• D. A mechanical failure without heat generation.

Answer: (B)

Thermal runaway is a self-sustaining exothermic reaction inside a lithium battery that rapidly raises temperature, potentially causing fire or explosion. Once initiated, the heat produced by the ongoing chemical reactions cannot be removed quickly enough, creating a positive feedback loop that drives temperatures higher and can lead to venting, ignition, or an explosion. Triggers include overcharge, internal shorts, physical damage, or exposure to high temperatures, and the effect can propagate to neighboring cells in a pack. The other statements don’t fit because cooling rapidly to prevent ignition misses the fundamental issue—the runaway is driven by heat generation, not cooling. A controlled battery discharge is not the same as an uncontrolled runaway event. Mechanical failure without heat generation ignores the reality that many failures produce rapid heat that can trigger runaway.

Thermal runaway is a self-sustaining exothermic reaction inside a lithium battery that rapidly raises temperature, potentially causing fire or explosion. Once initiated, the heat produced by the ongoing chemical reactions cannot be removed quickly enough, creating a positive feedback loop that drives temperatures higher and can lead to venting, ignition, or an explosion. Triggers include overcharge, internal shorts, physical damage, or exposure to high temperatures, and the effect can propagate to neighboring cells in a pack.

The other statements don’t fit because cooling rapidly to prevent ignition misses the fundamental issue—the runaway is driven by heat generation, not cooling. A controlled battery discharge is not the same as an uncontrolled runaway event. Mechanical failure without heat generation ignores the reality that many failures produce rapid heat that can trigger runaway.