Lithium batteries catch fire primarily due to a phenomenon called thermal runaway, a chain reaction that occurs when the battery generates more heat than it can dissipate. This leads to rapid temperature rise, causing chemical reactions inside the battery that release flammable gases and heat, potentially resulting in fire or explosion.
Causes of Lithium Battery Fires
- Thermal Runaway: Triggered by overheating, physical damage (such as puncturing or crushing), or internal short circuits, leading to uncontrollable self-heating of the battery cells.
- Physical Damage: Crushing, puncturing, or other mechanical stresses can cause internal short circuits, rapidly releasing energy and heat.
- Overcharging or Faulty Charging: Using incompatible or damaged chargers, or charging beyond recommended limits, can cause formation of metallic lithium and internal shorts.
- Exposure to High Temperature: Operating or storing the battery outside its safe temperature range causes instability and increased reaction rates inside the battery.
- Manufacturing Defects: Impurities or contamination during production can cause internal shorts and thermal runaway.
Why Thermal Runaway Is Dangerous
Thermal runaway causes the battery’s electrolyte—often a flammable liquid or gel—to vaporize and produce flammable and toxic gases. When the battery casing fails due to pressure, these gases can ignite in the presence of oxygen, sustaining and spreading battery fires. Once thermal runaway begins, it cannot be stopped by unplugging or isolating the battery. In summary, lithium batteries catch fire mainly because their internal chemical reactions can spiral out of control upon damage, overheating, or improper charging, creating heat, flammable gases, and oxygen that fuel fires.
