Why do lithium batteries explode? -Thermal runaway

by:CTECHi     2021-08-19

The back of the lithium battery will warn 'Do not throw into fire, beware of explosion'. This article explores why lithium batteries explode.

   There is a danger of explosion of lithium-ion batteries due to a process called 'thermal runaway' in the reaction inside the battery. 'Thermal runaway' is a positive energy feedback cycle: increased temperature will cause the system to heat up, and the system will heat up and increase the temperature, which in turn makes the system hotter. Thermal runaway is a very common phenomenon. Thermal runaway may occur in a large number of physical and chemical processes ranging from concrete curing (which releases heat) to star explosions (supernovae are the product of cosmic thermal runaway).

(The picture is for reference only, has nothing to do with the content of the article!)

   There are many reasons for the thermal runaway of lithium-ion batteries, such as a 9V battery When the two ends are bridged by a coin, the tearing of the membrane that separates the negative and positive electrodes of the lithium-ion battery will cause a short circuit, and the short circuit will often cause thermal breakdown. The reasons for the fire of the lithium-ion battery include: the ambient temperature exceeds 60°C, frequent overcharging, and unauthorized modification of the casing.

   The size, configuration, and number of cells all affect the intensity of thermal runaway. Small battery packs (such as those on digital SLR cameras) have only a few battery power sources, so the chance of thermal runaway spreading from the problematic battery unit to other units is relatively low. The recent Boeing 787 battery problem is another matter: they are contained in a sealed metal box and cannot emit waste heat. As a result, when one battery cell is hot enough to ignite the electrolyte, the remaining battery cells will quickly follow up.

   But don’t worry too much, your laptop is not a ticking time bomb. As long as some maintenance is done regularly, the lithium-ion battery will work safely and reliably. Lithium ion has a short lifespan and can generally last for two to three years (regardless of whether you use it or not). Because of this, all lithium-ion battery packs should be replaced every 36 months or so. Moreover, whenever the power drops to 50%, you should be able to charge it. Lithium ions have no memory effect, but too low a voltage can seriously damage them.

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