Safe Storage of Lithium-ion Batteries

Lithium-ion batteries are a relatively new technology. However since their market launch in the early 1990s, they have left a lasting mark on the market for energy storage and gradually supplanted old technologies.

Today lithium batteries are no longer indispensable in our daily lives - and with good reason: They are particularly small and efficient and therefore interesting for a variety of applications. Not only do smartphones and tablets draw their energy from lithium cells, they also play an important role in the area of electromobility.

Among other things, lithium energy storage systems score highly with their high energy density, low dead weight and fast charging technology. The downside would be again and again you hear about dangerous incidents in connection with lithium-ion batteries.

In 2017, a parking garage fire in Hannover made headlines - caused by the battery of an e-bike. In 2018, a man from Hamburg died in the explosion of a battery charger. Explosions and fires of lithium-ion batteries can have disastrous consequences, causing expensive consequential damage; in the worst case, costing lives.

The urgent question? What is the most secure handling and storage options? In our practice guide, we take a close look at the potential dangers of lithium energy storage and give you some valuable tips



How a lithium-ion battery works

In order to be able to assess the risks posed by lithium energy storage, the knowledge of how it works is extremely important.

It is important to know that there are multiple types of lithium batteries. There are a variety of different energy storage systems in which lithium is used in pure or bound form.

A distinction is made between primary (non-rechargeable) and secondary (rechargeable) lithium-ion cells. The general usage refers to the latter when we speak of lithium-ion batteries.

A battery pack is composed of several cells depending on the power. Each lithium-ion cell consists of a positive and a negative electrode, the anode and the cathode. Between them is an ion-conducting electrolyte. This guarantees the transport of lithium ions between the electrodes during the charging or discharging process. The best known form of lithium energy storage devices are the lithium-ion batteries, in which a liquid electrolyte is used.

Another important component is the separator. It prevents the direct contact between anode and cathode and thus prevents a short circuit. When discharging, lithium ions and electrons are released on the anode side. The electrons flow through the external circuit and do the electrical work. At the same time, the lithium ions migrate through the electrolyte fluid and through the separator to the cathode.

When charging, this process is reversed. Depending on the system, the structure and materials used may vary depending on the lithium-ion battery. In the lithium-polymer accumulator, the electrolyte is incorporated into the molecular framework of a polymer film. This makes it possible to dispense with the separate separator. Lithium-polymer energy storage can deliver only low discharge currents.

However, the polymer film allows a flat design, which is why such energy storage find especially in mobile phones and laptops use. The thin-film lithium cell is an energy storage in which the electrolyte is replaced by an ion-conductive gas. This allows the use of lithium metal and thus an extremely high energy density. This technique is currently an important part of lithium energy storage research.


How dangerous are lithium-ion batteries?

With today's manufacturing standards, lithium batteries are considered to be relatively safe. As a rule, various safety tests are already carried out by the manufacturer before products are placed on the market.

For example, transport of lithium energy storage devices is only permitted if a test certificate according to UN 38.3 is available. In order to obtain this certificate, a series of tests must be successfully completed in which the batteries are tested under various transport conditions.

  • Altitude simulation

  • Thermal test

  • Vibration

  • Blow

  • Outer short

  • Impact / crush test

  • Overload

  • Forced discharge

Risk of fire due to overcharging or high temperatures

Since the batteries in such tests can be claimed beyond their load limits, they take place under special safety precautions. Many of our customers also conduct their own test series, e.g. to verify the safety of the accumulators in connection with their products. For this you use DENIOS technical room systems as a safe test environment. Are you interested in testing lithium energy storage? Find out more by clicking here.

 

In order to increase the safety of lithium-ion batteries, manufacturers can already equip them with various safety features at the cell level. If a flammable electrolyte is used inside the cell, flame-retardant additives, for example, can be added to ensure better protection.

A crash-proof housing of the accumulator in a corrosion-resistant housing with fire-retardant foam can also be an effective measure. Nevertheless, one should take special care in dealing with lithium-ion batteries - because it always comes back to dangerous fires. For example, if lithium-ion batteries are handled or stored incorrectly, they can pose a significant security risk. Also, factory-made technical defects can not always be excluded from the outset.

The problem: when something happens, the consequences are often devastating. The danger arises from the design of the battery itself. Where materials with high energy densities and highly flammable electrolytes come together, these literally form a fire-dangerous mixture. Here are some common causes of lithium ion battery problems:

Risk of fire due to overcharging or high temperatures

If lithium energy storage is overloaded or exposed to high temperatures, cells may overheat. The so-called thermal runaway is a highly exothermic reaction that can cause the stored lithium to ignite and cause a metal fire. The high heat energy initially leads to evaporation of the electrolyte, resulting in additional heat and combustible gases. If the ignition temperature of a gas is exceeded, it ignites and in turn sets the reactive lithium on fire. Already the thermal run through of only one cell is sufficient to heat up the neighboring cells of the battery pack so far that a momentous chain reaction is created. Once set in motion, it only takes a few minutes for the battery to explode.

Fire hazard due to deep discharge

A deep discharge of lithium-ion batteries is a fire hazard. If lithium-ion batteries are not used for a long time, they can completely discharge. Cold outside temperatures - for example, during the winter months - may favour this effect. Again, it comes to the decomposition of the electrolyte liquid and consequently to the formation of easily combustible gases. If an attempt is subsequently made to recharge the deeply discharged lithium-ion cells, the supplied energy can no longer be correctly converted due to the lack of electrolyte fluid. It can cause a short circuit or a fire.

Fire hazard due to mechanical damage

When handling lithium-ion batteries, there is always a certain risk of damaging them. Collisions with operating vehicles, a fall on hard ground or squeezing under incorrect storage conditions are just a few examples. If cells are deformed as a result, this can lead to internal short-circuiting and fire of the battery. Also impurities in the production of the cells themselves can not be excluded 100%. In rare cases, it is possible that particles that are falsely released into the cell during production damage them from the inside over time. Here, too, internal short circuits can occur.

Extinguishing of lithium-ion battery fires

When a lithium-ion battery burns, it is a hard-to-extinguish fire. Extinguishing attempts with inert means are usually unsuccessful, since lithium-ion cells generate the oxygen needed for the fire itself. Only special extinguishing powders and granules are suitable for combating fires of class D. However, they can no longer be a suitable means for advanced propagation (here, among other things, there is the problem of a nationwide distribution).

Nevertheless, it may well be recommendable to stock extinguishing powder or granules in sufficient quantities to prevent fires of compact energy storage as a preventative measure or to be able to tackle them directly during formation and to "nip them in the bud": By covering the fire load with granules Oxygen is displaced and separated from the fuel.

Like glass, Extover granules melts at a certain temperature. The granules absorb a lot of heat in the form of melting energy, thereby cooling the fire and at the same time forming an impermeable envelope over the fire load. A reaction with oxygen is effectively prevented.

Regarding the use of water as an extinguishing agent, there are different views. Since lithium is very reactive, some advise against bringing it into contact with water. Recent studies, however, suggest that larger amounts of water are able to stem and effectively combat lithium fires.

As an explanation here u.a. called the cooling effect, which slows down the reaction of the cells. Also, the fire spread can be reduced in that the fire does not skip over to other media. However, firefighting requires a significantly higher amount of water than conventional fires. In order to accelerate the success and if necessary to reduce the amount of water required, various additives can also be added to the extinguishing water.

In general, it is important to assess the individual risks and dangers present in the company and to develop a suitable extinguishing and fire protection concept in cooperation with experts and property insurers. Unfortunately, breaking a fire is not the only risk posed by lithium-ion batteries. In a reaction, there is also the danger that harmful substances such as hydrochloric or hydrofluoric acid from the interior of the cell are secreted.

These can occur, for example, in the form of vapors and damage people through skin contact or inhalation. During the extinguishing process, they can be diluted with extinguishing water, seep into the ground (if there is no suitable catching device) and cause environmental damage.

In general, the potential hazard of lithium-ion batteries increases the more energy the used / stored batteries can store and the larger the amount stored. This, as well as your individual operational and structural conditions, processes and organisational boundary conditions should always be assessed on a case-by-case basis as part of a risk assessment.


Measures for loss prevention

The storage of lithium-ion batteries poses a dilemma for many companies. According to The HSE, they are generally required to assess hazards during operation and to counteract these with suitable protective measures. So far, however, there are no legal regulations for the storage of lithium energy storage devices that could be used to orientate oneself.

Therefore, it is up to the companies themselves to determine and implement appropriate measures. Among other things, due to the large number of different battery types, it is currently not possible to make generally valid statements on suitable protective measures and concepts. An individual case analysis is therefore necessary in every case.

It is advisable to cooperate with fire brigades, property insurers and licensing offices to develop a holistic protection concept for your individual storage situation. Of course, as experts in the field of hazardous materials storage, we are also happy to assist you. Just contact us! Below are a number of sources of information from which you can also obtain instructions for the safe storage of lithium-ion batteries:

Manufacturer information

The manufacturer gives you general advice on the safe handling and storage of your products - for example, on the optimum operating and storage temperatures. These specifications, which you will usually find in the operating instructions and / or safety data sheets, should be strictly adhered to. Manufacturers are also obliged to inform about the substances contained in their products and their effects on the environment and human health. From this you can also draw conclusions for your risk assessment.

Trade media and publications

Not only the daily press deals with the safety aspects around the topic of lithium energy storage. Due to the ongoing relevance publish again and again trade media corresponding articles. We have researched for you and summarized the most common tips and tips for handling lithium batteries for you.

In general, it is recommended to treat lithium energy storage as a hazardous substance and to design the handling accordingly, ie. carry out a risk assessment, derive appropriate measures from it, create specific safety instructions and train the employees in the proper handling of the dangerous media.

General safety instructions for the daily handling of lithium-ion batteries can be summarized in five simple terms:

Avoid thermal stress
Avoid thermal stress
 No contact with moisture
No contact with moisture
 Use only suitable chargers
Use only suitable chargers
Caution on loading
Caution on loading
Avoid damage
Avoid damage

Thermal loads not only can affect the life, but also the safety of lithium-ion batteries. Do not expose the energy storage devices directly and permanently to high temperatures or heat sources. This includes direct sunlight. Even longer-term cold should be avoided, as it favors a deep discharge in use. If deeply discharged lithium energy storage devices are subsequently reconnected to a charger, it can also lead to a fire. Therefore, follow the manufacturer's recommended operating and storage temperatures.

The contact with moisture (for example, by precipitation, condensation or splash water) can lead to a short circuit of the accumulator. Therefore, you should always store lithium energy storage dry and protect it from moisture during transport as well as during use.

One of the most common causes of battery fires, especially in the private sector, is the use of incompatible or unofficial chargers. These may e.g. have a higher voltage than needed for the battery and thereby destroy it. Use only chargers designed for use with your battery model.

In addition to the use of wrong chargers exist more risks during the charging process. Do not charge lithium batteries for long periods when they are not needed. Also, flammable items nearby are not a good idea. If possible, place the battery on concrete or tile floors while charging. If you want to store (re) store batteries, a charge level (SoC) of approx. 30% is recommended. This reduces the amount of energy that can cause damage in an emergency. Attention: A certain minimum charge level should always be present to prevent a deep discharge. Set up here according to the manufacturer's specifications.

Mechanical damage can cause cell deformation inside the battery and lead to internal short circuits. Therefore, ensure that the lithium energy storage devices are not subjected to shocks, impacts or collisions. If something happens, damaged batteries should never be used, but should be removed immediately, stored separately for disposal and disposed of properly. As a precaution, you should also secure the poles of damaged batteries, e.g. by means of polar ice caps. Of course, lithium batteries should not be disassembled, opened or crushed.


Specialised Solutiuons by DENIOS

Depending on the storage situation, it is important to assess which dangers can occur with what probability and with what consequences. There is no standard solution here - rather, your individual requirements should be precisely evaluated and the security concept should be adapted accordingly.

It is important to involve property insurers in the structural safety measures concepts at an early stage - and to select a manufacturer with decades of expertise in storing hazardous substances. We are happy to assist you with a wide range of experience.

Technical room systems: tailor-made to your needs

The potential danger of lithium energy storage presents special challenges for storage systems. Here we offer you security rooms that are specially designed for this purpose.

In addition to 90-minute fire protection both inside and outside, the systems can be equipped with numerous safety features such as pressure relief surfaces in the roof area, technical ventilation, room monitoring systems (eg gas detection, temperature monitoring or early fire detection), integrated drip pans for optimum safety in the event of an accident or integrated extinguishing systems.

If you want to test lithium-ion batteries, we will design the right, safe environment for you. Test rooms can be realized for example as a climate chamber, which allows the testing of energy storage within different temperature ranges.

Precisely because there are no standardized regulations for the storage of lithium energy storage devices and risks can vary greatly depending on the operation, a room system should always be precisely adapted to your individual operational requirements. That is why our engineers develop together with you an optimal and tailor-made concept for your storage or test system.

Many companies rely on DENIOS for the safe storage of lithium energy storage devices. We have also already realized test rooms for many well-known customers. Read our exciting practical reports: Among other things, we developed a showroom for energy storage for the well-known manufacturer HOPPECKE, a test bench for stationary energy storage for Voltavision GmbH and a hazardous materials warehouse for lithium-ion batteries of KTM-Sportmotorcycle AG.


We are happy to advise you

At DENIOS, we started to build expertise in 1986 in all matters relating to safe, legally compliant storage and handling of hazardous substances. We understand the many commitments you must make to companies to meet your daily responsibilities. Building on this knowledge, we can also assist our customers around the topic of storing and testing lithium energy storage systems. Contact us!

Need more information or advice? Call 01952 700 567 to speak to a DENIOS expert.