What is Thermal Leakage and How to Reduce Its Risks

What is Thermal Leakage?

Thermal runaway is an uncontrolled reaction that can occur in lithium ion batteries. Damage to the battery or a short circuit may cause heat and pressure to build up in the battery. If this reaches to a certain level, it triggers chemical reactions that generate more heat and pressure, causing a positive feedback loop. Thermal leakage can spread rapidly from one battery to another, causing catastrophic explosions and fires. Thermal leakage by-products may contain large amounts of flammable hydrogen and other toxic fluoroorganic gases.

Potential triggers of thermal leakage include damage such as overcharging of the battery, overheating of the battery or exposure to high temperatures, excessively high discharge rate, short circuit or puncture. Any of these factors can destabilize the high-energy materials and organic components of the battery, causing them to generate their own heat. If this heat does not dissipate quickly enough, the battery temperature will continue to increase, which will speed up the heat release process.

How to Reduce Thermal Leakage?

Some of the preventive safety measures include a robust battery case, an efficient cooling system, and protective design and control features. Flame retardant additives can be used in the electrolyte or separator to improve the thermal stability of the battery and prevent it from igniting in the first place.

Prevention Zone

Stage 1: Battery Abuse

At this initial stage, thermal, electrical or mechanical abuse causes cell damage, causing battery cell temperatures and pressures to increase.

Stage 2: Non-Gas Production

As cell temperatures and pressures rise, flammable gases escape from the cells. This is the critical point at which action should be taken to prevent thermal leakage and fire incident.

Stage 3: Thermal Leakage

Thermal leakage indicates the end of the prevention zone and the beginning of the containment zone. Temperatures rise rapidly and smoke forms. At this point, a catastrophic failure is imminent.

Enclosure Zone

Stage 4: Fire Formation

After thermal escape, fever occurs. Lithium-ion battery racks are configured to maximize energy storage density, while this also allows for rapid fire spread. When a fire occurs, the flame can easily pass into adjacent cells and building materials and become uncontrollable.