Defect, fire and explosion of lithium-ion batteries

The consequences of improper storage or incorrect transportation are damage to the battery, as explained in detail here. Depending on the size of the battery, the type of damage and other factors, this can result in varying degrees of danger - from a simple defect to battery fires that are difficult to extinguish to violent explosions that pose an acute danger to the environment. One of the actual advantages of lithium-ion batteries, their high energy density, is the cause of the potential dangers and risks that they can pose if stored or used incorrectly.

Limited functionality of defective lithium-ion batteries

The least dangerous consequence for the environment of incorrect storage or improper transportation of lithium batteries and lithium-ion batteries is their limited functionality. Defects can, for example, result in reduced capacity, meaning that the battery can only store less energy - the devices operated with the battery will therefore only run for a much shorter time than with an intact lithium battery. In extreme cases, the rechargeable battery may even stop working completely, making it necessary to dispose of it. This is correspondingly annoying for the user of the battery and is sometimes associated with high replacement costs. In the case of e-bikes or electric cars, the lithium battery accounts for a large proportion of the total price, meaning that replacing the battery often requires a large investment.

Fires as a result of damaged lithium batteries

Much more dangerous than limited functionality are fires caused by defective lithium batteries - one reason why the cells are best stored in special battery safety cabinets or storage containers / battery boxes and why an appropriate fire extinguisher for lithium-ion batteries should always be to hand. For example, pictures of burning smartphones can often be seen in the press, some of which have formed without any external influence and can therefore occur at any time. Nevertheless, battery fires usually occur in situations where the battery is put under stress, such as during (fast) charging, mechanical stress or improper storage. Micro-damage to the separator can then lead to overstressing and a fire. In addition to the well-known smartphone fires, there are currently more and more reports of fires in electric cars, some of which can flare up repeatedly for days after an accident.

Why do lithium batteries catch fire?

As a rule, an increase in temperature occurs as a result of improper use or a mechanical defect. When a battery cell heats up, the boiling point of the electrolyte is reached and it evaporates. This puts the entire cell under high pressure and causes it to inflate (which can also lead to an explosion, see below). The electrolyte can also catch fire when heated, as these normally consist of hydrocarbons, which are as flammable and combustible as gasoline. The so-called thermal runway of a lithium battery is important in this context: in the event of a defect, 6 to 10 times the battery capacity can be released in the form of thermal energy within a very short time. Individual defective battery cells then heat neighboring cells to such an extent that they are also destroyed and in turn "infect" the neighboring cells. This cannot be interrupted from the outside; the result of the thermal runway with temperatures of up to 600°C is not only cell fire or the fire of the entire battery, but usually also the complete destruction of the lithium battery.

Deep discharge as the cause

This may sound paradoxical at first, but it is also a possible cause of battery fires. If a lithium-ion battery is discharged too deeply, the deep discharge can lead to damage in the individual cells, which in turn can cause a battery fire. Although this is usually prevented by the battery management system, improper use or even manipulation of the battery management system can result in the batteries being discharged too far and thus becoming a potential cause of fire.

What makes a lithium battery fire so special?

A battery fire is particularly dangerous due to various characteristics. Not only the high temperatures, but also the possible reignition over long periods of time make battery fires a serious danger.

High temperatures burning lithium batteries

A battery can release many times its normal capacity in the form of thermal energy in the event of a defect. As explained above, a cell releases up to 10 times more thermal energy during a thermal runway than its normal charging capacity.

Burning electric car batteries are a particular challenge

Images of burning lithium-ion batteries from the increasingly widespread use of electric cars are constantly appearing in the press and laypeople often ask themselves why they cannot simply be extinguished. The high capacity of batteries in electric cars and the correspondingly large amount of stored energy mean that firefighters are faced with special challenges when fighting these fires and, in addition to special extinguishing agents for battery fires, must also resort to extraordinary measures. There are also repeated images of entire vehicles being submerged in water-filled containers until the battery has cooled down to such an extent that it no longer poses a danger.

Modern battery management systems should prevent fires

With the problems described above of extinguishing batteries that have caught fire, there are of course also precautions to prevent a fire in lithium batteries, especially very powerful ones. The task of modern battery management systems is therefore to control the batteries and switch them off in an emergency so that an uncontrolled discharge of energy and a fire do not occur.

Fighting lithium battery fires

If lithium batteries catch fire, various measures must be taken to extinguish the fire. Although conventional extinguishing agents such as water ensure that the system cools down, the electrical systems are often under high voltage. This can lead to electric shocks, for example, if water is used. However, many designers have already recognized this danger and have built appropriate safety devices into the systems that remove the voltage from the entire system if a problem is detected. We have prepared special articles on how best to fight individual battery fires:

Extinguishing agents for lithium battery fires

Due to the very special characteristics of battery fires, normal extinguishing agents and conventional fire extinguishers are generally only recommended to a limited extent for fighting battery fires. Accordingly, there is a range of extinguishing agents that have been developed by different manufacturers to fight battery fires, from fire extinguishers for lithium-ion batteries to extinguishing granules such as pyrobubbles and extinguishing blankets for lithium batteries.

Fire extinguishers for lithium-ion batteries

If a rechargeable battery or a lithium battery catches fire, a suitable fire extinguisher is often the first tool to hand for fighting the fire. In this way, heated and burning batteries can be cooled down; in the case of Bavaria's lithium fire extinguishers with Lithium-X as the extinguishing agent, the silicon platelets create a robust barrier between the burning battery and the environment, so that damage is minimized. A general distinction must therefore be made between the two battery fire extinguishers, on the one hand the models that primarily focus on cooling the cells (water fire extinguishers and gel fire extinguishers) and on the other hand the lithium fire extinguishers that can really stop the battery fire.

Extinguishing granulates such as Pyrobubbles®, Extover, Vermiculite etc.

In addition to water, so-called metal fire powders are therefore suitable for extinguishing burning lithium batteries. These are usually made of expanded glass or hollow glass granules and form a tough and impermeable layer when extinguishing the battery fire, so that no further oxygen can reach the site of the fire. This is achieved by melting the granules, which in turn is caused by the heat of the battery fire. Well-known examples of these battery extinguishing agents are Pyrobubbles® from Genius, but other granulates such as Extover or Vermiculite are also used here, which are based on a similar functional principle. In addition to actively fighting battery fires, the granules are also suitable for fire prevention, for example by being used in battery storage containers and transport boxes for Li-ion batteries.

Extinguishing blankets for fighting battery fires

Similar to the use of extinguishing granules such as Pyrobubbles® or the lithium fire extinguishers from Bavaria, the aim of using extinguishing blankets for Li-ion batteries is to isolate the fire. During use, the extinguishing blanket is placed/thrown over the source of the fire so that it is covered as completely as possible. Depending on the model, different battery fires can be contained in this way, from e-bike batteries that have caught fire to burning electric cars. The fire blankets for electric cars are used particularly frequently by fire departments, for example, to extinguish the ever-increasing number of electric cars in the event of a fire.