Explained in plain English

Why do laptop batteries catch fire?

The lithium-ion batteries in laptops, phones, and other devices can overheat and ignite, a process known as 'thermal runaway'. This happens when a battery cell enters an uncontrolled, self-heating state. Damage, defects, or overcharging can trigger it. On a plane, the contained environment makes such an incident particularly serious, as seen with the American Airlines flight.