The Science behind Thermal Runaway in Lithium-Ion Batteries
The Science of Thermal Runaway in Lithium-Ion Batteries
Lithium-ion batteries power much of our modern world, from smartphones and laptops to e-bikes, electric vehicles (EVs), and even large-scale energy storage systems. While these batteries are efficient and powerful, they also pose unique fire risks—most notably through a dangerous process called thermal runaway.
This article explores the science behind lithium-ion batteries, their chemical makeup, how thermal runaway occurs, and the best fire suppression methods for different situations.
A Brief History of Lithium-Ion Batteries
The development of lithium-ion batteries began in the 1970s when M. Stanley Whittingham created the first rechargeable lithium intercalation battery at Exxon. In the 1980s, John Goodenough advanced the technology by using lithium cobalt oxide as a cathode material.
In 1985, Akira Yoshino developed a prototype using a petroleum coke anode and lithium cobalt oxide cathode, leading to the first commercially safe, rechargeable battery. Sony released this technology to the public in 1991, sparking the widespread use of lithium-ion batteries in consumer electronics.
What’s Inside a Lithium-Ion Battery?
Lithium-ion batteries are primarily built from various metal oxide compounds, including:
Lithium cobalt oxide (LiCoO₂)
Lithium manganese oxide (LiMn₂O₄)
Lithium iron phosphate (LiFePO₄)
Lithium nickel manganese cobalt oxide (NMC)
During operation, lithium ions move between the anode (often graphite) and cathode, storing or releasing energy through oxidation and reduction reactions. Key raw materials—lithium, cobalt, and graphite—are classified as critical minerals by the U.S. government due to their strategic importance and vulnerable supply chains.
When discarded in the trash, these valuable materials are lost forever. Recycling is essential to recover critical minerals and reduce environmental impact. For recycling options, visit:
Learn more about critical minerals at the U.S. Geological Survey.
Why Firefighters Need to Know the Chemistry
Just as firefighters study building materials or know the difference between grease fires and electrical fires, understanding lithium-ion battery chemistry is critical to responding safely. The structure and behavior of these batteries directly influence how fires ignite, spread, and should be extinguished.
What Causes Thermal Runaway?
Thermal runaway occurs when a battery’s internal temperature increases uncontrollably, triggering a self-sustaining chain reaction. Common causes include:
Manufacturing defects – impurities or flaws may create internal short circuits.
Overcharging – using the wrong charger or excessive charging generates heat.
Physical damage – punctures, crushing, or impacts destabilize the battery.
Extreme temperatures – prolonged heat exposure or direct sunlight accelerates breakdown.
Internal short circuits – often caused by defects or “lithium plating,” which misdirects current flow and generates heat.
The Fire Cycle of Lithium-Ion Batteries
Initiation – A short circuit, physical damage, or heat spike raises internal temperature.
Chain Reaction – Heat accelerates chemical reactions, which generate even more heat.
Electrolyte Ignition – Flammable liquid electrolytes break down and ignite in the presence of oxygen.
Fire and Explosion – Rapid gas release and extreme heat can cause violent fires or explosions.
Because of these risks, lithium-ion batteries should be stored and charged away from flammable materials.
Common Applications
The NFPA categorizes lithium-ion batteries into three main groups:
Small electronics – laptops, power tools, smartwatches.
E-bikes and e-scooters – typically powered by 24–72V batteries, depending on performance.
Electric vehicles (EVs) – battery sizes vary by manufacturer and model. For example, some Honda, Toyota, Subaru, and Nissan models use Group 35 batteries, while Tesla vehicles often rely on multiple battery groupings outside the standard BCI classifications.
Extinguishing Lithium-Ion Battery Fires
Not all fires are the same—and lithium-ion fires require specific suppression methods.
Small electronics and e-bike batteries
Best option: ABC Dry Chemical extinguisher (Class B fires).
Alternative: If unavailable, submerge in water or douse with large amounts from a safe distance—but note the explosion risk.
Electric vehicles and larger batteries
Primary option: ABC Dry Chemical extinguisher.
Supplemental: Fire blankets specifically designed for EVs.
Water should only be used when absolutely necessary, and in large, sustained volumes.
Buildings with large-scale batteries (e.g., data centers, BESS sites)
Best option: Clean agent suppression systems such as:
HFC-227ea – removes heat and disrupts free radicals without harming electronics.
FK-5-1-12 – a fluorinated ketone agent, effective with minimal environmental impact.
BESS Systems and Firefighter Preparedness
Battery Energy Storage Systems (BESS) are increasingly used by power companies, tech firms, and solar energy providers. These systems store massive amounts of energy in containerized lithium-ion banks.
Because of the fire risks, Indiana passed House Enrolled Act 1173 (2023), mandating that systems over 1 MW comply with NFPA 855, meet elevation standards, maintain emergency response plans, and provide annual training for local fire departments. Other states may have different requirements, so check your state’s fire safety codes.
Firefighters should be familiar with:
Which facilities in their jurisdiction house large lithium-ion installations.
The suppression systems in place.
Mutual aid planning for incidents involving large-scale lithium fires.
Final Thoughts
Lithium-ion batteries are here to stay, powering everything from our phones to our cars to our energy grids. But with their benefits come risks. Firefighters and safety professionals must understand battery chemistry, thermal runaway, and suppression methods to respond effectively.
When in doubt, ABC Dry Chemical extinguishers should be the first line of defense. Water can be used in emergencies but must be applied carefully, in large quantities, and from a safe distance.
Stay informed, train regularly, and know the facilities in your jurisdiction that rely on large-scale lithium storage. Preparation is the key to safe response.
For training opportunities or questions about lithium-ion battery fire response, visit Summit Response Group.
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