When does a battery explode?

In addition to the numerous advantages, a lithium-ion battery can also be a real danger, especially if the battery starts to burn or, even worse, if a battery explodes. But when does a battery explode and how can this be prevented? The causes and corresponding preventive measures are explained below. In particular, the following points are covered:

What is the cause of an exploding battery?

A high-quality and intact battery does not simply explode, but several factors usually come together for this scenario, which in the worst case can (but do not necessarily have to) lead to an explosion. Typically, a battery that continues to be used and (incorrectly) charged after a defect or mechanical damage will explode.

Damage to the battery - or more precisely the separator layer - is the start of the problem

Serious problems with a battery usually occur when the separator layer inside the battery is damaged. A Li-ion battery is constructed in such a way that the cathode and anode layers are separated from each other by an extremely thin layer, the so-called separator layer. Damage to this inner layer can lead to short circuits and thus uncontrolled energy discharges. The causes can be manifold: Physical force caused by impacts, falls, etc., can damage this layer (which can lead to explosions, especially in e-bike batteries), but processing errors, inferior material quality, etc. are also possible causes of such damage.

Chain reaction of the cells (thermal runway) leads to explosion

Such damage to the separator layer and the subsequent short circuit can release a great deal of energy in a short space of time, which in turn results in extremely high heat development. The electrolytes contained in the lithium-ion battery are set on fire and a fire occurs. This can then set off an uncontrolled chain reaction, the so-called "thermal runway": the decomposition of the electrolyte releases further energy and oxygen is also released internally at the cathode, which intensifies the exothermic reaction within a very short time. This creates a self-reinforcing cycle that causes the battery to explode and normal discharging of batteries is then no longer possible.

The battery does not have to explode immediately after damage

The tricky thing about this effect is that there does not have to be a direct temporal connection between the damage to the separator layer and the explosion, i.e. the separator layer is often damaged, but the explosion only occurs (much) later. This means that a problem can gradually build up, which ultimately leads to the exploding battery.

Prevention is particularly important

An exploding battery is the greatest danger posed by this energy source. While a battery fire can still be extinguished and damage to the environment minimized, an explosion always poses an extremely high risk - to property, but in the worst case also to your own health. This makes it all the more important to take preventive measures to prevent a battery from exploding in the first place.

How do you prevent a battery from exploding?

The good news first: an exploding lithium-ion battery is fortunately extremely rare. If you pay attention to a few things during use and storage, you can further minimize the risk, which are explained below.

Charging a lithium-ion battery correctly

When charging a battery, the temperature in the individual battery cells always increases at the same time, so this period is always associated with a potential increase in risk. With intact batteries, however, this temperature increase is completely unproblematic and medium and large batteries in particular always have integrated charge management systems that regulate the temperature and interrupt or adjust charging if the deviation from the target values is too great.

Only use chargers approved by the manufacturer

However, improper charging, e.g. fast charging of batteries that are not suitable for this purpose or the use of chargers that are not approved for the respective batteries, can lead to the development of hazards during charging. This can result in the batteries heating up considerably and the consequences can be a fire or an exploding battery. It is therefore all the more important that even externally undamaged batteries are only ever charged in a protected environment, such as suitable battery bags.

The correct storage of rechargeable batteries

Battery safety cabinet Due to the potential dangers posed primarily by defective batteries, it is particularly important to store batteries safely and correctly throughout the year. There are a number of options for this, e.g. in suitable fireproof battery bags, but also in battery boxes and safety cabinets for batteries, which generally have fire protection classes and thus offer good protection for the environment in the event of a battery fire or even a battery explosion.

Never use or charge defective/damaged batteries

As explained above, mechanical defects are often the cause of a lithium-ion battery explosion. Therefore, one of the most important preventive measures is to never use or charge defective, deformed or otherwise impaired batteries, as the risk of explosion increases significantly.
In general, however, the following applies here: Intact lithium batteries that are charged properly and with the right equipment do not pose an increased risk. However, it is not always possible to tell from the outside whether a lithium battery is completely intact. It is therefore recommended that lithium-ion rechargeable batteries and lithium batteries are always charged in appropriately secured environments.