While lithium-ion batteries are, on the whole, incredibly safe they do very very occasionally catch fire or explode. When it happens, like with Samsung's Galaxy Note 7 fiasco or HP's more recent laptop recall, information technology's always big news. So what's going on and why do batteries sometimes go out with a bang? Permit's find out.

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Rechargeable lithium-ion batteries—the kind of battery that'southward inside your laptop, phone, tablet, and pretty much every other mod gadget you own, as well as electrical cars and airplanes—are responsible for the portable device revolution. Without lithium-ion batteries, I wouldn't be able to write this article sitting in a coffee shop; instead, I'd need to exist plugged into a power source the whole time.

What'southward Inside a Lithium-Ion Battery?

To empathize why lithium-ion batteries sometimes fail, yous need to know what's going on under the hood. Within every lithium-ion bombardment, at that place are two electrodes—the positively charged cathode and the negatively charged anode—separated by a thin sheet of "microperferated" plastic that keeps the two electrodes from touching. When you accuse a lithium-ion battery, lithium ions are pushed past electricity from the cathode, through the microperferations in the separator and an electrically conductive fluid, and to the anode. When the battery discharges, the opposite happens with the lithium ions flowing from the anode toward the cathode. This is the reaction that powers your laptop.

Small batteries, like those establish in smartphones, ordinarily have merely a single lithium-ion prison cell. Larger batteries, like those in laptops, commonly have between 6 and 12 lithium-ion cells. The batteries in electrical cars and airplanes can have hundreds of cells.

What Makes a Lithium-Ion Battery Explode?

The very thing that makes lithium-ion batteries and then useful is what also gives them the capacity to take hold of fire or explode. Lithium is really not bad at storing energy. When it's released as a trickle, it powers your phone all day. When it's released all in i become, the bombardment tin can explode.

This lithium-ion bombardment from a Japan Airlines Boeing 787 caught burn in 2013.

Most lithium-ion bombardment fires and explosions come downwardly to a problem of brusque circuiting. This happens when the plastic separator fails and lets the anode and cathode touch. And once those 2 get together, the battery starts to overheat.

There are a number of reasons that the separator tin fail:

  • Bad Design or Manufacturing Defects: The battery is poorly designed, as with the Galaxy Annotation vii. 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 information technology charged, the electrodes bent and caused a curt excursion. Fifty-fifty a well designed battery tin fail if quality control isn't kept tight enough or there'southward some defect in manufacturing.
  • External Factors: Extreme heat is nigh guaranteed to cause a failure. Batteries left as well shut to a rut source—or caught in a burn down—take been known to explode. Other external gene can cause a lithium-ion bombardment to fail, too. If yous driblet your phone too hard (or too many times), there'southward a chance you'll impairment the separator and cause the electrodes to touch. If y'all pierce the battery (either past accident or deliberately), then yous'll well-nigh certainly cause a short circuit.

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  • Charger Problems: A badly made or poorly insulated charger can besides impairment a lithium-ion battery. If the charger shorts or generates heat almost the battery, it can exercise enough damage to cause failure. That's why we recommend using but official chargers (or at the very least, high quality 3rd party ones from reputable brands). Lithium-ion batteries do have built in protections to stop them overcharging. While very rare, if these condom precautions fail, overcharging is a proficient mode to overheat a battery.
  • Thermal Runaway and Multiple Cells: While not relevant to single prison 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 bombardment to go. In one case ane cell overheats, you get a domino outcome called "thermal runaway." For batteries with hundreds of cells—like those in the Tesla Model Due south—thermal runaway has the potential to exist a actually big trouble.

Even though examining why bombardment sometimes fail paints a frightening flick, lithium-ion batteries are a safe and mature applied science. The fact that it'due south e'er news when a battery explodes unexpectedly shows how rare an consequence those big failures are. Battery manufacturers put a lot of safeguards in place to preclude batteries failing, or at least mitigate the harm a failure tin cause.

Photo credit: wk1003mike/Shutterstock.com.

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