: Why do lithium ion batteries explode/catch fire when they are punchered?
In: Chemistry
It’s a battery’s job to hold on to energy and release it when you need it. If you traumatize the battery, it may release surprising amounts of energy in unpredictable ways like catching its internal components on fire, changing shape, getting extremely hot, or spitting sparks.
You discharge a battery by connecting a load between its negative and positive terminals. If there is no load, like if you just connect a wire with low resistance, you get a lot of current flowing and that turns into heat.
If you puncture the battery, you can have the same effect: touch the positively-charged part of the battery to the negatively-charged part and turn the energy into heat.
They don’t. The problem with lithium ion batteries is a phenomenon called Thermal Runaway. A lithium ion battery needs to be heated up to catch fire but it doesn’t take as much heat as a person would assume and unlike a conventionally flammable material like paper or even oily rags, a lithium battery undergoes chemical changes when heated that make it hotter in and of themselves and also release a lot of oxygen, which is one of the vital components of combustion.
A common issue is called “thermal runaway”. When the battery gets hot past a certain point, chemical reactions start to happen, which creates more heat, which increases the reaction, which creates more heat, and so on. This leads to fires and explosions.
Common root causes are:
internal shorts
overcharging
temperatures outside the rated operation of the battery (too hot, or….too cold)
Batteries contain energy. The normal way of using that energy is connecting an electrical load and slowly draining the battery. When you puncture a battery, you can create a short circuit, connecting the positive and negative terminals of the battery inside the battery. This releases energy very quickly by causing a lot of current to flow, and that heats up the battery. Then the battery can become hot enough to enter thermal runaway, starting other chemical reactions which release even more heat.
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