Thermal runaway is an uncontrolled chemical reaction that releases heat into the environment for as long as it lasts. This ‘exothermic’ process arrived in our world of batteries with the introduction of lithium-ion cells. We explore the chemistry causing thermal runaway in lithium batteries, as a step towards better battery safety.
Thermal Runaway in Lithium-Ion Battery Electrolyte
All electro-chemical batteries store chemical energy, including alkaline, nickel-metal, carbon-zinc, lithium-ion, and our own lead-acid types. But lithium-ion batteries are capable of thermal runaway, because of their unique chemical composition.
Several events can cause thermal runaway in this type of battery. Gasmet Technologies lists ‘mechanical damage, external heat, short circuit, or overcharging’ as potential root causes. Runaway occurs very rapidly, it explains, and can lead to a ‘battery fire or even explosion’.
It stands to reason that this chain reaction needs a trigger to start it. Heat is a natural by-product of electricity. This is why lithium batteries warm temporarily every time we use them in a device, and especially when we charge them. But normally this happens within limits, and they cool down again.
So How Does This Normal Process Spin Out of Control?
The answer to this could be your first learning point in this short series. We already know that if we overwork an electric motor in a garden tool, we can ‘burn it out’. We could damage a lithium-ion battery in several ways that might cause it to enter thermal runaway.
- Allow the battery to repeatedly overheat by over-stressing it.
- Overcharge the battery, or use the wrong battery charger.
- Physically damage the battery by applying mechanical stress.
Any of these unwise actions could trigger thermal runaway in lithium-ion batteries. Although good battery design should mostly be able to prevent this happening. A cheap lithium-ion battery may not be a wise purchase. This is your first learning point in this short series.
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Thermal Runaway Gas Production Factor
