Dangers when handling lithium-ion batteries

Lithium-ion batteries are a comparatively recent technology. But since their market launch in the early 1990s, they have left a lasting mark on the energy storage market and gradually displaced old technologies. Today, it is impossible to imagine our everyday life without lithium batteries - and for good reason: they can be particularly small and at the same time very efficient and are therefore of interest for a wide range of applications. Not only smartphones and tablets draw their energy from lithium batteries, they also play an important role in the field of electromobility. Lithium energy storage devices are an ideal choice here due to their high energy density with low weight and fast charging.

The other side of the coin: dangerous incidents involving lithium energy storage devices are repeatedly reported. In 2017, a fire in a parking garage made the headlines, caused by the battery of an e-bike. In 2018 a man from Hamburg died when a battery charger exploded. There is no question: explosions and fires involving lithium-ion batteries can have devastating consequences, causing expensive consequential damage or, in the worst case, costing human lives. It's not just members of the public, but also companies who are faced with the urgent problem of ensuring the safest possible handling and storage. The fact remains that §5 ArbSchG obliges employers to identify and assess hazards and to implement suitable protective measures.

By today's manufacturing standards, lithium batteries are considered comparatively safe. As a rule, various safety tests are carried out by the manufacturer before (series) products are put on the market. For example, the transport of lithium energy storage devices is only permitted if a test certificate in accordance with UN 38.3 is available. To obtain this certificate, a number of series of tests must be successfully completed in which the batteries are tested under various transport conditions. This includes:

Nevertheless, special care should be taken when handling lithium-ion batteries - because dangerous fires occur time and again. If anything happens, the consequences are often disastrous. The risk lies in the construction of the battery itself. Where materials with a high energy density come into contact with highly flammable electrolyte, these create an extremely dangerous mix. The situation becomes especially dangerous when a lithium battery releases its stored energy in an uncontrolled manner. As soon as the heat created exceeds the melting point of the separator, an uncontrollable chain reaction is started, the dreaded "thermal runaway".

The high levels of heat energy then vaporise the electrolyte fluid, creating additional heat and combustible gases. If the pressure rises above a certain point, the flammable gases are released and form an ignitable mixture with the air - flames develop on the outside of the battery. Thermal runaway in just one cell is enough to heat up the neighbouring cells in a battery block so that a devastating chain reaction is created. Once set in motion, it only takes a few minutes until the battery will burn and explode. These lithium-ion battery fires are difficult to control and the fire spreads quickly. The fire brigade can often only protect neighbouring areas.

In normal operation, the use of lithium batteries is considered safe. But according to VDE, this only applies as long as everyone handles them properly. For example, if lithium-ion batteries are handled or stored incorrectly, they can pose a significant safety risk. In addition, factory defects cannot always be ruled out.

Electrical overload

A typical risk in handling lithium batteries is actually quite common: namely charging and discharging. An electrical overload can occur here for a number of reasons, e.g. due to the use of an incorrect charger. But a fire can also occur as a result of a deep discharge. If lithium-ion batteries are not used for a long time, they can become completely discharged. Incorrect storage conditions - for example, storage outside the manufacturer's recommended storage temperature - can promote this effect. This leads to the decomposition of the electrolyte liquid and consequently to the formation of highly flammable gases. If an attempt is then made to recharge the deeply discharged lithium-ion cells, the energy supplied can no longer be converted correctly due to the lack of electrolyte fluid. A short circuit or fire may occur.

Mechanical damage

When handling lithium-ion batteries, there is always a certain risk of damaging them. Collisions with company vehicles, a fall onto hard ground or crushing due to incorrect storage conditions are just a few examples of mechanical damage. If cells are deformed as a result, this can lead to internal short circuits and a fire in the battery. Also, contamination during the production of the cells themselves cannot be 100% ruled out. In rare cases, particles that enter the cell during production can damage it from the inside over time. Internal short circuits can then also occur.

Thermal overload

External heat or energy sources can heat up lithium batteries and thus lead to a fire due to thermal overload. Typical sources of danger are, for example, open fire, hot machine parts or storage in direct sunlight.