Lithium-Ion Battery Fires

Lithium-ion fires are a concerning and potentially hazardous phenomenon that can occur when the delicate balance within lithium-ion batteries is disrupted, leading to thermal runaway and combustion. These fires are characterized by their intense heat, rapid spread, and the release of toxic gases and smoke. The underlying cause of lithium-ion fires often lies in factors such as manufacturing defects, physical damage, overcharging, or overheating. When a battery’s internal components, including the anode, cathode, and electrolyte, interact in an unstable manner, it can trigger an exothermic chain reaction, causing the battery to heat up uncontrollably and ignite surrounding materials. Given the increasing and widespread use of lithium-ion batteries in various devices like smartphones, laptops, and electric vehicles, understanding the risks associated with lithium-ion fires and implementing stringent safety measures is of paramount importance to prevent accidents and protect both human safety and the environment.

What is thermal runaway?

As the temperature of the battery increases, more chemical reactions within the battery can occur, leading to more heat generation. Generally, heat generation is dictated by the materials inside the battery, while heat loss is determined by the battery can. The battery can is the outer packaging and protection of the battery, usually composed of a metal or alloy, such as aluminum or steel. The outer shell often features plastic materials for their lightweight and insulating properties. The battery can temperature changes with the ambient temperature and other surrounding conditions.

The anode is composed of graphite, which is separated by an electrolyte layer with lithium salts from the lithium oxide cathode. The lithium ions migrate to the anode when charging and to the cathode when discharging. A porous separator keeps the electrodes from touching. Anode and cathode decomposition reactions are exothermic and produce gas, and the released heat provides the necessary activation energy for subsequent reactions. The release of gas causes pressure inside the battery to rise. In extreme cases, this can result in the battery casing rupturing or the release of flammable electrolytes, potentially igniting a fire or explosion. At 152⁰F, the battery reaches the self-accelerating decomposition temperature (SADT), or the lowest temperature that the battery must be held for the heat of decomposition to exceed heat loss. The accelerating decomposition rate raises the battery to the temperature of no return. After the temperature of no return (typically 167⁰F), thermal runaway occurs, and fire or explosion are likely.

Preventative Measures

Due to the unpredictable nature of lithium-ion battery fires, it is critical to ensure utilize all available fire prevention methods. In addition to visual observation for signs of damage, temperature regulation and monitoring are useful to ensure there is no risk of overheating or fire. Such measures may include an infrared (IR) camera. Other preventative measures include:

• Quality assurance
• Avoid physical damage and extreme temperatures
• Use approved chargers
• Avoid overcharging and overdischarging
• Avoid mixing batteries
• Avoid unattended charging
• Transport safely
• Educate and train
• Store and handle properly

If a battery is hot or venting, it should be quarantined in a designated burn area, away from flammable or combustible materials. Hot batteries should not be packaged and should be observed for signs of fire.

Storage and Packaging

Proper storage and packaging are critical to avoiding lithium-ion battery fires. The following guidelines should be followed to prevent battery damage and fires:

Don’t:

• Store near combustible or flammable materials
• Store materials in racks or shelves above batteries
• Store batteries near exits or in exit pathways
• Store in direct sunlight
• Store in areas susceptible to physical abuse (shock, vibration, temperature)

Do:

• Isolate terminals prior to storing
• Inspect batteries prior to storing and following any physical abuse
• Segregate waste/DDR batteries from commodity batteries
• Maintain spacing between pallets of stored batteries
• Anchor storage racks

Fire Mitigation and Firefighting Measures

Lithium-ion batteries pose a significant fire hazard due to their highly flammable hydrocarbon-based electrolyte solution and high energy density. Consequently, conditions such as a short circuit, physical damage, or improper design/assembly can lead to overheating and ignition. Lithium-ion batteries are classified as Class B fire risks, due to the presence of a flammable liquid (the electrolyte solution). Traditional fire containment methods include standard dry chemical or ABC extinguishers. These methods control lithium-ion battery fires by smothering the fire or reducing a fuel source, but often do not have the heat capacity needed to stop overheating and thermal runaway.

Reducing the temperature of an overheating lithium-ion battery is critical to both preventing and eliminating fires. Water is the most viable option, given its high heat capacity and latent heat of vaporization. The battery should be isolated and drenched in copious amounts of water to cool the burning battery as much as possible. It should be noted that water can react with the battery components (specifically LiPF₆) to form hydrogen fluoride, a toxic gas. Furthermore, hydrogen fluoride can be reduced by lithium, producing combustible hydrogen. However, this gas release is only significant or hazardous in extremely confined spaces. Thus, avoid small, enclosed spaces when dousing a hot or venting battery.

ALL4 assists clients in the battery industry and beyond with training on the safe handling of lithium-ion batteries, evaluating local fire codes to ensure the safe storage of lithium-ion batteries, and also creating standard operating procedures around the safe management of lithium-ion batteries at a facility. If you are interesting in learning more about the lithium-ion battery safety and compliance services we off or have any questions on the content of this article, feel free to contact Maya Fors at mfors@all4inc.com or at (502) 276-6771.