Lithium-ion batteries differ fundamentally from conventional fire loads. They are not passive materials, but rather high-energy electrochemical systems. In the event of a failure, a self-sustaining reaction can develop inside the battery.

Thermal Runaway (thermal runaway)

The primary risk associated with lithium-ion batteries is what is known as thermal runaway. This is a self-reinforcing reaction:

• A cell becomes damaged or overheats
• Chemical protective mechanisms fail
• The electrolyte decomposes into flammable gases
• Separators melt
• Oxygen can be released from the cell chemistry
• The temperature rises exponentially
  
  

What makes this unique is that the system can sustain itself with heat and oxygen. Therefore, simply cutting off the outside air is often insufficient.

Chain reaction between cells

In battery modules or packs, many cells are installed in close proximity to one another. If a cell enters thermal runaway, it can heat up neighboring cells. This propagation effect leads to:

• prolonged fire duration
• recurring flare-ups
• extremely high heat release
• difficult-to-predict dynamics
  
  

Especially in vehicle batteries or stationary storage systems, the event can last several hours.

Risk of re-ignition

A lithium-ion fire is often not over once the flames have been extinguished. Even if the surface appears calm, hotspots may still exist inside. Reignition can occur hours later. Therefore, the following tactics are required:

• sustained cooling
• temperature monitoring
• safe temporary storage
• containment, if necessary
  
  

Highly toxic smoke gases

Lithium-ion fires produce complex and highly toxic mixtures of smoke gases. In addition to typical fire gases, additional aggressive and corrosive compounds are formed. The consequences are:

• acute health hazard
• severe smoke contamination of buildings
• contaminated firefighting water
• significant cleanup costs

In enclosed spaces, the smoke gas problem is often more critical than the flames themselves.