Why do lithium-ion batteries catch fire?

Lithium-ion batteries are a vital part of modern society, with the batteries forming the backbone of most modern technologies that require battery support, from everyday household electronics such as laptops, mobile phones, and tablets, to large-scale energy storage systems and electric vehicles (EVs).

With their growing prominence, lithium-ion batteries also carry a fire safety risk that needs to be considered. It is worth noting that the frequency of fire from lithium-ion batteries is actually very low, but the consequences can be significant. This advice and guidance article details how lithium batteries work, their fire safety risks, why they can catch fire, and methods to minimising risk.

How do lithium-ion batteries work?

The US Department of Energy states that a lithium-ion battery is made up of an anode, cathode, separator, electrolyte, and two current collectors (positive and negative). The electrolyte carries positively charged lithium ions from the anode to the cathode and vice versa through the separator. The movement of the lithium ions creates free electrons in the anode which creates a charge at the positive current collector. The electrical current then flows from the current collector through a device being powered (cell phone, computer, etc.) to the negative current collector. The separator blocks the flow of electrons inside the battery.”

Do lithium batteries catch fire?

Like any technology that is exposed to the conditions of energy creation, storage, and use, the potential malfunction, physical damage, or heat exposure of lithium-ion batteries can lead to fire under adverse conditions. Whilst fires and accidents triggered by these batteries are rare, they can be very dangerous so every precaution should be taken to avoid lithium ion battery fires.

Why do lithium-ion batteries catch fire?

Lithium-ion battery cells combine a flammable electrolyte with significant stored energy, and if a lithium-ion battery cell creates more heat than it can effectively disperse, it can lead to a rapid uncontrolled release of heat energy, known as ‘thermal runaway’, that can result in a fire or explosion.

Thermal runaway can be caused by a number reasons, including an internal short circuit due to manufacturing defects, ’lithium plating’ (formation of metallic lithium on an anode surface within a battery cell), or mechanical damage (e.g. piercing, dropping). Other possible causes of thermal runaway are exposure to heat from an external source or overcharging/over-discharging.

Thermal runaway can result in the ejection of a range of flammable and toxic gases from battery casings. The flammable gases generated often ignite immediately, but may also spread out unignited, until an external ignition source is encountered, resulting in an explosion.

Lithium-ion battery fires generate their own oxygen and can be very difficult to extinguish. Specialist Aqueous Vermiculite Dispersion (AVD) fire extinguishers may be an option for small incipient fires, where extinguishing media can be applied directly to the cells of a battery, providing a combination of cooling and oxygen depletion, but these fires are very often only controlled and extinguished when the Fire & Rescue Service deliver copious amounts of water to the burning materials.

How to minimise risk

It can be very hard to identify how and when a lithium-ion battery may catch fire, but there are some preventative measures to minimise the risk of lithium-ion battery fires:

  • Only use batteries purchased from a reputable manufacturer or supplier.
  • Protect batteries against being damaged and do not attempt to recharge lithium-ion batteries with any signs of damage. These should be safely disposed of.
  • Only charge batteries with the original charger supplied.
  • Do not leave batteries charging in unoccupied locations and disconnect/remove batteries from chargers after charging is complete.
  • Avoid storing, using, or charging batteries at very high or very low temperatures and never cover chargers or charging devices. Don't leave any equipment that may contain lithium-ion batteries such as mobile phones in high temperature environments, such as in direct sunlight, or a hot vehicle.
  • Don’t overcharge your batteries as this is a potential case of thermal runaway.
  • Avoid keeping lithium-ion battery products in close proximity. While keeping these products close together does not increase the risk of a fire occurring, keeping these products away from each other can reduce the risk of fire spread from one battery/battery-powered-device to another.
  • Remember to store batteries or products using lithium-ion batteries in a cool dry place away from flammable and combustible materials.

Further information

Please be aware that considerable efforts have been made to ensure the accuracy of the information contained within this article at the time of publication, however any legislative (or other) changes that come into effect after this may render the information out of date until it is reviewed and updated as part of the FPA’s content review cycle.