Defect, Fire and Explosion of Lithium-Ion Batteries
The consequences of improper storage or incorrect transport, as explained in detail here, are damage to the battery. Depending on the size of the battery, the type of damage, and other factors, varying levels of danger can result — ranging from a simple defect to battery fires that are difficult to extinguish to intense explosions that pose an acute risk to the surroundings. One real advantage of Li-ion batteries, the high energy density, is the cause of the possible dangers and risks that can arise from them when stored or used incorrectly.
Limited functionality of defective lithium-ion batteries
The least dangerous consequence for the surroundings from improper storage or improper transport of lithium batteries and lithium-ion batteries is the limited functionality. Due to the defects, for example, a limited capacity can occur, so the battery can only store less energy — devices powered by the battery therefore run much shorter than with a healthy lithium battery. In extreme cases the battery can completely stop functioning, requiring proper disposal. This is annoying for the user and involves potentially high replacement costs. For e-bikes or electric cars, the lithium battery accounts for a large share of the total price, so replacing the battery often requires large investments.
Fires as a consequence of damaged lithium batteries
Much more dangerous than limited functionality are fires triggered by defective lithium batteries — a reason to store cells in special battery safety cabinets or storage containers / battery boxes and why a suitable fire extinguisher for lithium-ion batteries should always be within reach. For example, there are often images in the press of burning smartphones that have formed without external influence and could happen at any time. Nevertheless, battery fires usually occur in situations where the battery is stressed, such as during fast charging, mechanical stress, or improper storage. Micro-damages to the separator can then lead to overloading and fire. In addition to the known smartphone fires, there are currently increasing reports of fires in electric cars that can flare up for days after an accident.
Why do lithium batteries catch fire?
Typically it occurs as a result of improper use or a mechanical defect leading to a temperature rise. During warming of a battery cell, the electrolyte's boiling point is reached, causing it to vaporize. This puts the entire cell under high pressure and it swells (which can also lead to an explosion, see below). With sufficient heat, the electrolyte can also ignite, as these usually consist of hydrocarbons that are similarly flammable and combustible as gasoline. A key concept in this context is the so-called thermal runway of a lithium battery: with a defect, within a very short time up to 6–10 times the battery's capacity can be released as thermal energy. Individual defective cells then heat neighboring cells so strongly that they are destroyed and in turn ignite neighboring cells. This cannot be stopped from the outside; the result of the thermal runway with temperatures up to 600°C is not only the cell fire or the entire battery fire, but usually also the complete destruction of the lithium battery.
Deep discharge as a cause
What may sound paradoxical at first is also a possible cause of battery fires. If a Li-ion battery is discharged too deeply, the deep discharge can cause damage in the individual cells, which can then be the cause of a battery fire. This is usually prevented by the battery management system, but improper use or even manipulation of the battery management system can result in the batteries being discharged too far and thus becoming a potential fire cause.
What makes a lithium battery fire so special?
A battery fire is especially dangerous due to different properties. Not only the high temperatures, but also the possible reignition over long periods make battery fires a serious hazard.
High temperatures of burning lithium batteries
A battery can release many times its normal capacity in the form of thermal energy during a defect. As explained above, a cell can emit up to 10 times more thermal energy during a thermal runway than its normal charge capacity.
Burning batteries of electric cars are a special challenge
Images of burning lithium-ion batteries from the increasingly common electric cars circulate in the press, and laypeople often ask why these cannot simply be extinguished. The high capacity of batteries in electric cars and the large amount of stored energy mean that the fire department faces special challenges when combating these fires and must resort to special extinguishing agents for battery fires and to extraordinary measures. There are also images of entire vehicles being submerged in water-filled containers until the battery cools down enough to pose no danger.
Modern battery management systems are supposed to prevent fires
In the above-described problems of extinguishing burning batteries, there are also precautions to prevent a fire from starting in very powerful lithium batteries. The task of modern battery management systems is therefore to control the batteries and shut them down in an emergency so that uncontrolled energy discharge and a fire do not occur.
Fighting fires of lithium batteries
When there is a fire of lithium batteries, different measures must be taken to fight lithium-ion battery fires. Classic extinguishing media like water provide cooling of the system, but at the same time the electrical systems are often under high voltage. For example, there can be electric shocks if water is used. However, many designers have already recognized this risk and have incorporated safety devices into the systems that remove the voltage from the entire system when a problem is detected. How to best fight individual battery fires has been prepared in special articles:
If a battery or lithium battery catches fire, a suitable fire extinguisher is often the first means available for fire suppression. Thus, heated and burning batteries can be cooled; with the lithium extinguishers from Bavaria using Lithium-X as the extinguishing medium, the silicone discs create a robust barrier between the burning battery and the environment, minimizing damage. Generally, two types of battery extinguishers can be distinguished: those focusing on cooling the cells (water extinguishers and gel extinguishers) and those lithium extinguishers that can actually stop the battery fire.
Extinguishing granules like Pyrobubbles®, Extover, Vermiculite etc.
Besides water, so-called metal fire powders are also suitable for extinguishing burning lithium batteries. These are usually made from foaming glass or hollow glass granules and form a thin and impermeable layer when extinguishing the battery fire, so no further oxygen reaches the fire. This is achieved by melting the granules, which is caused by the heat from the battery fire. Known examples of these battery extinguishing agents are Pyrobubbles® from Genius, but other granules like Extover or Vermiculite are also used, based on a similar operating principle. In addition to active fire suppression of battery fires, the granules are also suitable for prevention by being used in battery storage containers and transport boxes for Li-ion batteries.
Fire blankets for combating battery fires
Similar to the use of extinguishing granules like Pyrobubbles® or the Bavaria lithium extinguishers, the goal when using fire blankets for Li-ion batteries is to isolate the fire. When deployed, the extinguishing blanket is laid over the fire source, covering it as completely as possible. Depending on the model, different battery fires can be contained, from burning e-bike batteries to burning electric cars. Fire blankets are particularly commonly used by fire brigades to extinguish increasingly common electric cars in case of fire.
Request sent successfully
Request wasn't send - a error occured. Please try again.
