Why do lithium batteries catch fire?

Lithium-ion batteries, while incredibly useful and common in our daily lives, do have a risk of catching fire or exploding under certain conditions. The main reason behind these instances is a phenomenon known as “thermal runaway.”

Here’s how it happens:

1. Internal Short Circuit: If for some reason a short circuit occurs inside the battery – this could be due to a manufacturing defect, damage to the battery, or improper handling – it can cause the battery to quickly discharge its energy. A rapid discharge of energy can generate a lot of heat.
2. Overcharging: Overcharging can lead to an excessive amount of lithium ions being sent to the anode, causing the formation of lithium “plates” or “plating” on the anode. These plates can cause an internal short circuit.
3. Overheating (Thermal Runaway): The heat generated from an internal short circuit or from external sources can cause the electrolyte (the medium that facilitates the ion flow) in the battery to heat up. If the temperature reaches a critical point, the electrolyte can break down and catch fire, leading to more heat being generated. This additional heat can cause other cells in the battery to break down and catch fire, leading to a chain reaction known as “thermal runaway.” In extreme cases, this can even result in an explosion.
4. Physical Damage: Physical damage to the battery can disrupt its internal structure and potentially lead to a short circuit. A damaged battery can be dangerous and should be handled with care.
5. Improper Storage: Storing a lithium-ion battery in conditions that are too hot or too cold can also cause it to malfunction and potentially catch fire.

Lithium-ion batteries contain safety mechanisms designed to prevent these scenarios. For example, they have built-in circuitry to prevent overcharging and overheating, and they often have safety vents and thermal interrupt devices. However, these safety features can fail in some circumstances, leading to the risks described above.

To minimize the risks, it’s important to handle and maintain these batteries properly. This includes not subjecting them to extreme temperatures, avoiding physical damage, and using the correct charger to avoid overcharging.