There are four main reasons why a lithium-ion battery explodes – and one of them reveals why the notorious Galaxy Note 7 mobile phone had to be withdrawn.

Everything from dropping your phone to using a badly made charger can cause the battery powering your mobile phone or other electronic device such as an iPad or laptop to catch fire and explode.

Although still rare, the number of incidents is growing and when it happens it can make big news … especially on aircraft.

That’s why many airlines now have specialist fire containment bags such as AvSax to deal with the hazard before they can cause a catastrophic problem and this video shows an AvSax containing an exploding electronic device at https://www.youtube.com/watch?v=iHW_HXSV4AU.

The very thing that makes lithium-ion batteries so useful is what also gives them the capacity to catch fire or explode. Lithium is really great at storing energy. When it’s released as a trickle, it powers your phone all day. When it’s released all in one go, the battery can explode.

The vast majority of incidents are caused by short-circuiting and to read about the technical side to how this happens then go to https://www.howtogeek.com/338762/why-do-lithium-ion-batteries-explode/

But the online magazine also reveals the 4 reasons a lithium-ion battery explodes.

1. Bad design or manufacturing defects. The battery is poorly designed, as with the Galaxy Note 7. In that case, there wasn’t enough space for the electrodes and separator in the battery. In some models, when the battery expanded a little as it charged, the electrodes bent and caused a short circuit. Even a well designed battery can fail if quality control isn’t kept tight enough or there’s some defect in manufacturing.
2. Extreme heat is nearly guaranteed to cause a failure. Batteries left too close to a heat source—or caught in a fire—have been known to explode. Other external factor can cause a lithium-ion battery to fail, too. If you drop your phone too hard (or too many times), there’s a chance you’ll damage the separator and cause the electrodes to touch. If you pierce the battery (either by accident or deliberately), then you’ll almost certainly cause a short circuit.
3. Charger problems. A badly made or poorly insulated charger can also damage a lithium-ion battery. If the charger shorts or generates heat near the battery, it can do enough damage to cause failure. Only use official chargers or at the very least, high quality third party ones from reputable brands. Lithium-ion batteries do have built in protections to stop them overcharging. While very rare, if these safety precautions fail, overcharging is a good way to overheat a battery.
4. Thermal Runaway.  While not relevant to single cell batteries like those found in most smartphones (the iPhone X actually has two cells), only one battery cell needs to fail for the whole battery to go. Once one cell overheats, you get a domino effect called “thermal runaway.” For batteries with hundreds of cells—like those in the Tesla Model S—thermal runaway has the potential to be a really big problem.

Several major airline companies now use AvSax fire containment bags in case electronic devices catch fire mid flight.

They are used to deal with burning electronic devices ranging from laptops and mobile phones to e-cigarettes. 

They were deployed on aircraft 20 times in 2017. 

If an electronic device starts to seriously overheat or emit smoke the cabin crew will pour at least two litres of water into an AvSax and then drop the burning device into the bag, adding additional water as required. The water activates the polymer gel inside the bag causing it to expand around the device. Should the device keep on venting then the AvSax is tough enough to absorb the force. 

The AvSax cools the batteries in the device, reducing the likelihood of the battery catching fire but if it does go into what is known as thermal runaway when all the battery cells catch fire at incredibly hot temperatures it is all contained within the bag.

Amazingly, the water is absorbed into the internal lining of the bag so the device is dry when it is removed.