Aug 27, 2014

Why do laptop and cell batteries occasionally explode?

It seems that every month or so I see a news story along the lines of “Brand X smartphone explodes in man’s pocket,” or “Brand Y laptop battery explodes, burning cute fluffy kitten.”  In fact, I just saw an article today about a OnePlus One catching fire, and that is a well reviews, relatively high end bit of kit. What causes a battery to explode? Is it user abuse or just one of those things that sometimes happens? Batteries have been around for a long time, it seems to me that we would be past the point of them being miniature IEDs that we are all carrying around in our pockets.

Why do batteries explode?

"While lithium is great for making high-capacity batteries, these same properties make it highly reactive and more prone to thermal runaway. Lithium is an Alkali Metal along with sodium, potassium, and the rest of the first group of the periodic table. Not only are these elements highly flammable, but they are so reactive that tossing a few grams into water will cause an explosion. So when a Li-ion battery does heat up, the lithium in it can accelerate the breakdown of other cells.

There is always the possibility that the occasional battery is going to have a manufacturing defect, or that it will be damaged, leading to a failure. "

These aren’t your grandpa’s alkaline batteries that are catching on fire, they are usually lithium-ion. Lithium is great for batteries, but it is also very reactive. If there is a fault in the material that sperates the components of the battery that allows the lithium to come into direct contact with the other elements of the battery, it can cause a thermal runaway due to the internal short circuit. Heat builds up, and the battery can swell, burst or cause a fire. 

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