Technological advancements in the chemistry, configuration, materials and management systems of Li-ion batteries, have contributed towards increased efficiency and safety. Despite these advancements, Li-ion batteries still pose a significant fire hazard. A single defective cell, or one that has been subjected to mechanical, electrical or thermal abuse, may lead to an increase in its internal temperature, triggering a thermal runaway. The resulting fire will develop within minutes and can propagate to neighbouring cells if not suppressed and controlled on time.
FirePro has been working closely with accredited laboratories and prominent Li-ion battery manufacturers, performing nearly 100 tests over the past seven years, aimed at analysing the complex and diverse fire, explosion and off-gassing behaviour of Li-ion batteries.
Thermal runaway
Our test campaigns have shown that during thermal runaway, the Li-ion battery’s electrolyte will start to decompose(~120°C), releasing a large volume of gases, which due to pressure build-up will rupture the metal or plastic pouch casing containing the electrolyte. These gasses will burn (flash fire) at temperatures in excess of 800°C when in contact with the atmosphere (O2) producing a toxic, flammable or explosive mixture depending on the type of electrolyte used in the cell. Some examples of these gasses are hydrogen (H₂), carbon monoxide (CO), hydrogen fluoride (HF), hydrochloric acid (HCI), hydrogen cyanide (HCN), sulphur dioxide (SO2) and hydrogen sulphide (H2S). Furthermore, the excessive loss of lithium ions from the cathode material leads to a structural collapse of the cathode electrode, causing the release of oxygen (O2).
Main challenges of Li-ion battery fires
Heat output – In the scenario where the Li-ion batteries have entered an advanced thermal propagation stage, the battery will generate its own heat, making it difficult to cool down fast enough.
Oxygen supply – The production of oxygen during electrolyte decomposition supports the chemical processes that occur during a fire.
Battery pack – Li-ion battery cells are densely stored in their packs, making it hard for a fire suppression agent to reach the fire.
How FirePro suppresses Li-ion battery fires
FirePro Condensed Aerosol suppresses fire by interrupting the chemical chain reactions that occur in the flame, rather than by cooling and/or depleting oxygen in the enclosure. Upon activation, the condensed aerosol-forming compound transforms from a solid state into a rapidly expanding two-phased fire-suppression agent consisting of potassium carbonate solid particles K2CO3 (the active agent) suspended in a carrier gas. When the condensed aerosol reaches and reacts with the flame, the potassium radicals (K*) are formed mainly from the dissociation of K2CO3. The K*s bind to other flame-free radicals (hydroxyls OH-) forming stable products such as KOH. KOH then further reacts in the presence of CO2 and forms stable K2CO3.
In the event of a Li-ion battery fire, both the active agent K2CO3 and the intermediate product KOH react with the electrolyte’s decomposition products, such as hydrogen fluoride (HF), forming stable products such as potassium fluoride (KF) and potassium bifluoride (KHF2). Thus, preventing the formation of highly flammable gases such as hydrogen (H2). The resulting neutralizing action ultimately controls the fire and allows the temperature in the enclosure to drop below the threshold necessary (~120°C) for thermal runaway to sustain itself. Test results have shown that FirePro can protect the enclosure against reignition for as long as the minimum required fire-suppression density is maintained, allowing time for post-fire management of the battery.
Solutions
The main components of a FirePro system are its pre-engineered generators which when activated release the fire-suppression agent. Each generator is an all-in-one container and is the equivalent of the agent storage tank, piping and nozzles of a pressurized gas system.
A complete suppression system can be configured to include single or multiple generators, depending on the physical and technical parameters of the protected area, such as the class of fire, volume and height. In the case of a Li-ion battery special hazard, the agent density used is the one proven to be effective in tests replicating real-life scenarios.
Protection of Li-ion battery small enclosures
FirePro cylindrical models are compact and provide a practical solution for applications with space limitations such as home battery-storage systems, electric-vehicle charging stations and electric-vehicle battery compartments. These generator models are placed within the enclosure which houses the batteries and are activated automatically either through electrical or mechanical means.
A wide range of control and monitoring equipment is available. One of the simplest, most compact and innovative solutions developed by FirePro is the stand-alone Bulb Thermal Actuator (BTA). The BTA combines both detection and activation for a single FirePro condensed aerosol generator.
In case of a fire, once the temperature in the enclosure reaches the pre-selected detection rating (57°C, 68°C, 79°C, 93°C, 141°C, 182°C), the bulb will burst and mechanically activate the FirePro generator.
The BTA operates without electricity. It can be easily installed, and its maintenance requirements are limited to visual inspection. These features make it ideal for remote installations. Activation feedback can also be provided to the battery’s BMS.
Protection of Li-ion battery large enclosures
Larger volumes, such as battery rooms or battery energy storage systems (ESS) generally require more than one generator. In these cases, multiple generator configuration systems are designed using our pre-engineered box-type models, which are either wall or ceiling mounted. The main components of such systems include a combination of detection technologies and control panel, which in the event of a fire will electrically activate the FirePro generators. The detection methods employed in the case of Li-ion battery fires are a combination of smoke, heat, carbon monoxide, gas, aspiration, flame, linear heat cables or any other suitable technology, depending on the expectations and the fire strategy.
Some key benefits of the FirePro systems:
- Suitable for Li-ion battery fires
- Do not contribute to pressure increase
- 15-year product life
- Non-pressurized
- Minimal maintenance required
- No piping or nozzles required
- Easy and quick to install
- Can tolerate small openings in the enclosure
- Operating temperature from -54°C to +54°C
- Space and weight saving
Fire-suppression systems may be the last resort when it comes to lithium-ion battery fire-risk management, but they are an integral part of the strategy. While proper design, operations and maintenance are key to preventing fires, fire-suppression systems provide an additional layer of protection. FirePro systems can detect and suppress the fires quickly, preventing costly damage and potential loss of life. In addition, they can allow time for emergency responders to arrive and carry out post-fire procedures, such as assessing the damage and safely removing the batteries.
About the Author
Dr Gian Guido Gianfilippi De Parenti
Dr. Gianfilippi de Parenti is the Technical and Executive Director at FirePro. He has worked in the fire suppression industry for more than 30 years and has made significant contributions to the creation of international standards related to condensed aerosol technology.
Dr. Gianfilippi de Parenti has been at the forefront of FirePro's R&D efforts, leading the team in conducting over 100 Li-ion tests over the past 7 years.
He is an active member of:
- ISO/TC21/SC 8 - Committee on Gaseous media and firefighting systems using gas
- ISO/TC 21/SC 8/WG 10 - Working Group on Condensed aerosol fire extinguishing systems
- CEN/TC 191 - Committee on Fixed Firefighting Systems
- CEN/TC 191/WG 6 - Committee on Gas Extinguishing Systems
- National Fire Protection Association (NFPA) – Technical Committee on Aerosol Extinguishing Technology
- International Maritime Organization (IMO) - Sub-committee on Fire Extinguishing
- UL Technical Committee 0300 - Extinguishing Systems
| SFPE Cyprus Chapter | (Founding member) |
