Here's why smartphone batteries explode

It's due to a series of chemical reactions.

Every now and then you’ll hear stories about smartphone batteries spontaneously exploding, but have you ever wondered what causes it?

As part of their Reactions video series, researchers from the American Chemical Society (ACS) explain the chemical reactions behind lithium-ion battery explosions.

A battery is made up of an anode (-), a cathode (+) and an electrolyte fluid.

It works when the electrons flow from the negative anode along the circuit to the positively charged cathode when hooked up to an electrical circuit.

Lithium is a current standard for cathodes, mainly because it allows for the easy transfer of electrons and is light in weight, which is handy for making portable battery packs.

However, lithium does have its downsides. It is an alkali metal, which means it is highly reactive. Also, batteries tend to contain organic electrolytes like dimethyl carbonate, which are also extremely combustible. Together, the two create what is called a thermal runaway.

“The lithium and the electrolyte are two pieces of the flaming hot chemical puzzle that’s known as thermal runaway,” the ACS explains.

“Thermal runaway is what happens when a battery cell spontaneously explodes.

Lithium batteries.
(Janaka Maharage Dharmasena/Getty Images)

“There are a few different reasons why this happens – overcharging of the battery, overheating, physical damage and faulty manufacturing resulting in electrical shortages.”

The ACS says basically anything that can lead to a rapid increase in heat can increase the risk of explosion.

“When multiple chemical reactions cause the super heating, lithium cobalt oxide (the cathode in lithium batteries) tends to release oxygen which can react with alkyl carbonate (in the electrolyte) and cobalt oxide,” it explains.

“Also during charging, the alkyl carbonate can break down, creating carbon dioxide gas that can expand upward and burst the electrolyte open, exposing its flammable contents.”

The ACS said scientists are developing alternatives to lithium batteries.

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