Aerosol fire suppression systems for lithium batteries: how they work and why they improve safety

Thermal runaway and fire: what really happens

When discussing lithium battery safety, one of the most common misconceptions is treating thermal runaway and fire as synonymous. In reality, they are two distinct phenomena, although they are closely related.

Thermal runaway is an internal cell phenomenon in which electrochemical reactions become self-sustaining, causing a rapid rise in temperature. The energy generated by the internal reactions accelerates the process further, triggering a sequence of events that may eventually lead to the decomposition of cell materials. During this phase, internal pressure increases progressively until the safety vent opens, when present. The cell then releases heat, electrolyte, and a mixture of gases. This stage is particularly critical because the released gases are generally flammable and may include hydrogen, carbon monoxide, and light hydrocarbons. If an ignition source such as a spark or a hot surface is present, these gases can ignite, turning an internal cell event into a combustion incident.

It is important to clarify that thermal runaway does not necessarily mean a fire. It is a process that can develop initially without visible flames. At this stage, it remains primarily an electrochemical and thermal phenomenon rather than a fire event.

Fire, on the other hand, is a separate and subsequent event. If the gases released by the battery encounter an ignition source such as a spark, high-temperature surface, or electrical arc, they may ignite, causing combustion and flame propagation. At the same time, the opposite scenario must also be considered: a fire originating from other system components, such as wiring or electronic equipment, may spread to the battery and contribute to the onset of thermal runaway.

Understanding this distinction is essential because it highlights that risk management cannot focus solely on preventing thermal runaway. It must also include the ability to respond quickly in the presence of a developing fire. On the one hand, it is necessary to reduce the likelihood of a thermal runaway occurring through careful battery design and continuous monitoring of operating parameters. On the other hand, it is important to have systems in place that can respond quickly should a fire start, limiting its spread and its effects on the system.

An effective safety strategy must therefore operate on multiple levels:

• Proper battery design (chemistry, assembly, and electronics)
• Prevention of fault conditions through the Battery Management System (BMS)
• Continuous monitoring of operating parameters
• Rapid intervention in potentially critical situations

Nail Penetration Test

The Nail Penetration Test is a safety test used to simulate an internal short circuit. During the test, a cell is pierced with a nail to evaluate battery behavior under one of the most severe failure conditions.

The objective is not to preserve battery functionality, but to verify that the system reacts in a controlled manner without causing uncontrolled fires or explosions.

Aerosol fire suppression systems: a fast, targeted response

Among the solutions adopted, aerosol fire suppression systems are an important active containment measure.  In the field of active safety solutions for lithium batteries, aerosol suppression systems represent a highly effective technology, designed to act quickly in the event of an incipient fire.

In fact, condensed aerosol fire suppression systems are an advanced solution for protecting batteries and energy storage systems (BESS), especially where traditional methods such as water or gas are ineffective or harmful.

These devices are activated automatically when they detect an abnormal rise in temperature, releasing a suppressing agent in the form of aerosol that can quickly put out the start of a fire without collateral damage to the electronics.

 Unlike systems based on water, gas or powder, the aerosol agent acts at the core of the combustion process, interrupting the chemical chain reactions that feed the fire, rather than simply smothering the flames or cooling the environment.

The extinguishing agent, released in the form of ultra-fine particles (less than 10 microns), binds to the free radicals generated by the fire, neutralising the propagation process.  This mechanism is particularly effective against lithium-ion battery fires, which can escalate rapidly and are difficult to contain with conventional systems. Moreover, aerosol doesn’t damage sensitive electronic components, enabling targeted and safe action within battery compartments or confined spaces.

Advantages over traditional solutions

Aerosol suppression systems offer a range of tangible benefits that make them particularly suitable for industrial applications and energy storage systems (BESS).

One of their main strengths is the speed of response: activation takes place within seconds of detecting a thermal anomaly, a crucial factor when dealing with events such as thermal runaway, which can evolve very quickly.

Furthermore, the ability to operate in enclosed, complex spaces makes aerosol an ideal solution where pressurised or water-based systems cannot be used or would be harmful. The absence of pressurisation and the compact size of the devices simplify integration into modular architectures.

There is also an additional advantage: the suppressing agent leaves no harmful residue, protecting the integrity of power electronics and reducing restoration times after an event.

Finally, it’s a safe solution from an environmental perspective as well: the suppressing agent is halon-free, non-toxic and compliant with the Montreal Protocol. In terms of integrated and sustainable safety, aerosol is therefore a technologically advanced and highly effective choice.

How we integrate aerosol fire suppression systems into flash battery packs

From a design standpoint, the integration of aerosol fire suppression systems is sized according to the specific characteristics of the battery pack, particularly its internal volume and the geometry of the areas to be protected.

Within Flash Battery solutions, devices are installed in a distributed configuration, with multiple units used within the same battery pack when necessary.

This approach ensures uniform coverage even in large battery systems or complex internal layouts, where compartmentalization or longer distances might reduce the effectiveness of a single intervention point.

Activation occurs automatically when a predefined temperature threshold is exceeded. The device then releases the extinguishing agent directly into the protected volume, enabling rapid and localized intervention.

Typically, each device is designed to protect volumes ranging from approximately 0.2 to 0.6 m³, with the standard Flash Battery configuration averaging around 0.4 m³ per unit.

The number and positioning of the devices therefore become an integral part of the overall safety design of the system.

Lithium battery safety: an integrated approach combining prevention and intervention

Safety in lithium batteries cannot be achieved through a single solution. Rather, it is the result of an integrated approach that combines prevention, monitoring, and intervention capabilities.

This is complemented by active safety tools such as advanced monitoring and early detection of abnormal signals, enabling action to be taken before critical conditions develop.

Within this framework, aerosol fire suppression systems provide an effective risk mitigation solution by enabling rapid and efficient intervention during the initial stages of combustion, limiting fire propagation and preserving system integrity.

Integrating all these solutions in a coherent way is what transforms a high-energy-density technology into a safe, reliable system suitable for the most demanding industrial applications.

If you would like to learn more about designing a battery system with a safety-focused approach, the Flash Battery technical team can help evaluate the solution best suited to your application, considering operational requirements, design constraints, and required protection levels.