Lithium-ion battery fire suppression composition and method of use

Abstract

A fire suppressant for suppressing thermal events in lithium-ion batteries and its use are provided. The fire suppressant comprises an aqueous solution of a potassium or sodium salt of a carboxylate, particularly lactic acid, acetic acid, citric acid, glycolic acid, butyric acid, or tartaric acid. The fire suppressant can be delivered to a battery cell or battery module containing a battery cell experiencing a thermal event such as thermal runaway to suppress the thermal event and prevent the cascading of the thermal event to adjacent cells.

Description

Technical Field

[0001] Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 63 / 518,011, filed Aug. 7, 2023, which is hereby incorporated by reference in its entirety.

[0002] Background of the Invention Field of the Invention Embodiments of the present invention relate to fire suppression compositions and the control of thermal events in batteries, particularly their use in suppressing fires and extinguishing fires in lithium-ion batteries.

[0003] Description of the Related Art Lithium-ion batteries can catch fire due to a phenomenon called thermal runaway. Thermal runaway is a chain reaction process that occurs when the temperature of the battery rises uncontrollably, leading to the release of energy and potentially causing a fire or explosion.

[0004] [[ID=2 (24]] Cascading thermal runaway in a lithium-ion battery (composed of multiple cells) refers to a scenario where thermal runaway propagates from one cell in a battery pack to adjacent cells, resulting in a widespread and uncontrollable release of energy. It occurs when thermal runaway in a single cell induces a chain reaction and adjacent cells also experience thermal runaway. When a single cell in a battery pack undergoes thermal runaway, it generates heat and gas that can ignite adjacent cells, potentially causing their thermal runaway as well. This process can continue to spread throughout the entire battery pack and may lead to a large-scale fire or explosion.

[0005] There are several reasons why thermal runaway occurs in lithium-ion batteries. Overheating: When a lithium-ion cell is exposed to high temperatures, internal components can be damaged, potentially causing thermal runaway. Heat can be generated by external factors such as exposure to direct sunlight, high-temperature environments, or operating the cell beyond its recommended temperature range.

[0006] Manufacturing defects: A poorly manufactured or damaged cell may have internal defects such as metal particles or impurities that can cause short circuits within the cell. These short circuits can lead to excessive heat generation and cause thermal runaway.

[0007] Overcharging or over-discharging: Charging lithium-ion cells beyond their recommended voltage or discharging them to extremely low voltage levels can stress the cells, potentially causing internal damage and thermal runaway.

[0008] Physical damage: Dropping, puncturing, or other physical damage to the lithium-ion cell can cause internal components to come into contact, leading to short circuits and overheating.

[0009] Contamination or electrolyte leakage: If the electrolyte in the cell, which is a flammable organic solvent, leaks or comes into contact with moisture or other reactive substances, it can cause a chemical reaction and generate heat.

[0010] Electrical Short Circuit: When external electrical contacts are directly short-circuited to each other, excessive current can be drawn, potentially leading to excessive heat generation, cell degradation, and / or thermal runaway. Note that external connections between multiple cells within a battery assembly can also be short-circuited by inhibitors deployed to control thermal events.

[0011] Thermal runaway process During a lithium-ion thermal runaway event, the battery temperature rises rapidly, leading to a self-persistent exothermic cycle. This cycle can cause the battery to release flammable gases, smoke, potentially explode, or cause a fire. The thermal runaway process typically involves several stages.

[0012] Initial heating: The battery's temperature increases due to external factors such as overcharging, short circuits, mechanical damage, or exposure to high temperatures.

[0013] Exothermic reaction: As the cell temperature rises, chemical reactions within the battery accelerate, leading to heat release. The generated heat further increases the battery temperature.

[0014] Gas generation: High temperatures cause the decomposition of electrolyte components, leading to the release of flammable gases such as hydrogen and carbon monoxide. Gas generation contributes to an increase in pressure within the cell.

[0015] Ventilation and Fire: At certain temperature and pressure thresholds, the cell may rupture or vent, releasing gas. If the released gas comes into contact with an ignition source such as a nearby flame or spark, it may ignite, causing a fire or explosion.

[0016] Cascading thermal runaway: The failure of one cell in a battery assembly can trigger a chain reaction that causes adjacent cells to fail, ultimately leading to all cells experiencing thermal runaway.

[0017] It is important to note that the specific behavior of lithium-ion cells during thermal runaway can vary depending on various factors such as the cell's chemical properties, design, and external conditions. Battery assemblies can contain thousands of lithium-ion battery cells, and cascaded thermal runaway within these assemblies can burn for several days.

[0018] Current solutions applied to lithium-ion batteries experiencing thermal events include water, cleaning agents, and aerosols. Alternatively, in some cases, the best solution may simply be to allow the battery to self-extinguish.

[0019] Regarding the application of water, both water mist and sprinklers are applied to lithium-ion battery systems, but this mitigating approach typically focuses on protecting the room or enclosure and is not typically applied at the battery assembly (or module) level. Water is a good heat absorber and does a good job of cooling fire and preventing its spread to flammable materials co-located within the same room or enclosure. However, water has not demonstrated the ability to stop cascading thermal runaway within battery modules. NFPA 855 specifies a minimum density of 0.3 GPM / ft in lithium-ion battery chambers.2 The use of a sprinkler system is recommended.

[0020] One challenge with water applications is that when used in batteries, spilled water can be contaminated and toxic to the environment, and therefore must be properly collected and purified. In addition, chemically impure water (typically tap water) is conductive and can cause electrical short circuits in batteries using battery assemblies, further exacerbating cascaded thermal runaway.

[0021] Cleaning agents such as FK-5-1-12 and inert gases are used in many energized applications and protect many special hazardous applications. These agents work by absorbing heat at the molecular level. Unfortunately, cleaning agent systems can do little to mitigate thermal runaway. These agents exist as gases at low temperatures and do little to interrupt thermal runaway events. Certain cleaning agents, such as FK-5-1-12, can also degrade at the extreme temperatures that occur in lithium battery fires, potentially releasing a combination of hydrofluoric acid gas and flammable hydrocarbons. This can create acute toxicity and / or explosive hazards if the gas is released or accumulated in the occupied area.

[0022] Regarding aerosol applications, certain aerosols contain chemicals that can disrupt the chemical chain reactions involved in combustion. These agents can impair the fuel's ability to ignite or sustain a flame, thereby extinguishing a fire. However, aerosols do not possess significant heat capacity and struggle to stop cascading thermal runaway.

[0023] Some battery system operators adopt a strategy of allowing the battery to self-extinguish and take little or no mitigation steps. The reason is that there is no proven solution for suppressing fires in lithium-ion batteries. Burning the fire will consume dangerous and explosive battery off-gases such as hydrogen, and many batteries are stored in remote locations such as near solar power plants or wind farms. Operators who choose this approach should note that they usually have a battery cabinet constructed from expensive high-insulation materials so that they can meet the performance requirements listed in the UL 9540a standard. However, there is still a strong sentiment that the do-nothing approach is not ideal because a burning battery still emits toxic gases that are harmful if ingested and can cause environmental damage.

[0024] Therefore, there is a need in the art for a method of suppressing and extinguishing fires in lithium-ion batteries.

Summary of the Invention

[0025] According to one embodiment of the present invention, a method of suppressing a battery fire is provided. The method includes applying an aqueous fire suppressant to a battery cell that has experienced a thermal event that has caused or is likely to cause a fire. The aqueous fire suppressant includes a carboxylate.

[0026] According to another embodiment, a method of suppressing a battery fire in one or more battery modules is provided, each battery module including a plurality of lithium-ion battery cells. The method includes detecting a condition within one or more battery modules associated with a battery thermal event. A flow of aqueous fire suppressant is initiated within the one or more battery modules. The aqueous fire suppressant includes a carboxylate. At least one of the plurality of battery cells disposed within the module is contacted by the aqueous fire suppressant.

[0027] According to a further embodiment, a fire suppression system is provided that includes a fire suppressant storage tank containing a certain amount of pressurized aqueous fire suppressant containing a carboxylate. The conduit network is connected to the fire suppressant storage tank and extends into one or more battery containers. The one or more battery containers include one or more battery modules. Each of the one or more battery modules includes a plurality of battery cells. The conduit network is configured to deliver a flow of aqueous fire suppressant to at least one of the one or more battery modules upon detection of a thermal event within at least one of the one or more battery modules.

[0028] According to yet another embodiment, an aqueous fire suppressant is provided that includes a carboxylate dispersed in water. The aqueous fire suppressant includes less than 0.01 wt% of a fluorosurfactant and / or a foaming agent.

[0029] According to yet another embodiment, an aqueous fire suppressant is provided that includes a carboxylate dispersed in water. The aqueous fire suppressant is formulated so as not to generate foam when delivered to an object during a fire.

[0030] According to still another embodiment, an aqueous fire suppressant is provided that consists essentially of, or consists of, water, a carboxylate, optionally a hydrofluoric acid resistant agent, and optionally a colorant.

Brief Description of the Drawings

[0031] [Figure 1] It is a cross-sectional view of a battery container provided with a plurality of battery modules arranged within the battery container and protected by a fire suppression system according to an embodiment of the present invention. [Figure 2] It is a side view of the battery container and the fire suppression system. [Figure 3] It is a schematic side view of a battery rack including a battery module and a fire suppressant delivery conduit having nozzles for delivering a chemical agent to each module. [Figure 4]This is a schematic diagram of a battery module having cells that are subjected to thermal events that result in the release of a fire suppressant from a storage tank into the module. [Figure 5] This chart demonstrates the control of thermal events occurring within a battery module and the prevention of thermal cascading from affected battery cells to adjacent cells within the module. [Modes for carrying out the invention]

[0032] Detailed description of preferred embodiments Specific embodiments of the present invention relate to fire suppressants that can be used to control or mitigate thermal events within batteries, particularly lithium-ion battery cells. As used herein, the term “fire suppressant” means a chemical composition that is formulated to suppress or can suppress the progression of a thermal event that, if left unchecked, is highly likely to result in a fire. The term “fire suppressant” should also be considered to include a chemical composition that is formulated to extinguish or can extinguish an existing fire. As used herein, the term “thermal event” refers to a situation relating to a battery or any part thereof that is subjected to high-temperature conditions. High-temperature conditions can be of internal or external origin and can result in a thermal runaway where further increases in battery temperature lead to self-sustaining (i.e., without requiring an external heating input) thermal runaway can result in the generation of flammable gases, as well as the combustion of such gases and other materials that make up the battery. Thermal runaway can also propagate from a single battery cell that is subjected to thermal runaway to adjacent battery cells. This phenomenon is called cascading thermal runaway and, if left unchecked, can spread to all cells in a battery module. In one or more embodiments, the fire suppressant can suppress or stop cascading thermal runaway, that is, it can suppress or stop the propagation of thermal runaway experienced by one or more battery cells to one or more additional battery cells located in very close proximity to the one or more battery cells experiencing thermal runaway. By suppressing cascading thermal runaway, actual or potential battery fires can be suppressed.

[0033] In one or more embodiments, a fire suppressant can control the temperature of one or more components constituting a battery, particularly a lithium-ion battery. These components include one or more battery cells, a battery case in which one or more battery cells are arranged, and any vapor space within the battery case. In certain embodiments, when a battery experiences a thermal event such as thermal runaway in one or more of the battery cells constituting the battery, one or more of the battery components experience a temperature rise. The application of a fire suppressant can lower the temperature of any of these components, thereby suppressing any actual or potential battery fire and preventing cascading thermal runaway within the battery.

[0034] According to one or more embodiments, the fire suppressant is an aqueous or water-containing material comprising, consisting of, or essentially comprising a carboxylate, particularly a C2-C6 carboxylate. In certain embodiments, the C2-C6 carboxylate comprises a lactate, acetate, citrate, glycolate, butyrate, or tartrate. In preferred embodiments, the C2-C6 carboxylate comprises potassium lactate or sodium lactate, acetate, citrate, glycolate, hydroxybutyrate, or tartrate, with potassium lactate being particularly preferred.

[0035] In one or more embodiments, the fire suppressant comprises, consists of, or is essentially composed of, 30% to 80% by weight, 35% to 75% by weight, 40% to 70% by weight, or 45% to 65% by weight, most preferably about 60% by weight, of a carboxylate dispersed in water. Thus, the water component can constitute 20% to 70% by weight, 25% to 65% by weight, 30% to 60% by weight, 35% to 55% by weight, or about 40% by weight of the fire suppressant.

[0036] Fire suppressants may further contain, consist of, or be essentially composed of one or more optional components that impart beneficial characteristics to the agent. These optional components include anti-hydrofluoric acid agents and colorants. In one or more embodiments, an anti-hydrofluoric acid agent is a compound or mixture of compounds that in some way counteracts the harmful effects of fluorine and / or fluorinated compounds that may be released during battery thermal events, particularly battery fires. Fluorine-containing materials are often associated with electrolytes used in batteries, especially lithium-ion batteries. In fact, the most commonly used electrolyte in lithium-ion batteries is LiPF6. As part of a thermal event, fluorine-containing electrolytes can react with other components to produce fluorine-containing gases (hydrofluoric acid gases), such as hydrogen fluoride (HF). Anti-hydrofluoric acid agents can act to prevent the reaction that forms HF, react with HF gas to form less toxic substances, and / or absorb or adsorb the generated HF gas so that it is not released into the environment surrounding the battery.

[0037] Exemplary antihydrofluoride agents that can be used in embodiments of the present invention include one or more selected from the group consisting of citronella oil (or its components including citronellal, citronellol, and geraniol), d-limonene, dipentene, p-cumene, β-pinene, oleic acid, and vitamin E. Citronella oil, its components, and d-limonene are particularly preferred antihydrofluoride agents. The fire suppressant may contain 0.01% to 2% by weight, 0.05% to 1.5% by weight, 0.1% to 1% by weight, 0.2% to 0.8% by weight, 0.3% to 0.6% by weight, or about 0.475% by weight of the antihydrofluoride agent.

[0038] The addition of a colorant can alter the spectral emissivity (and therefore absorptivity) of the fire suppressant, thereby improving the agent's ability to absorb thermal radiation emitted from a battery cell undergoing thermal runaway (and thermal radiation that would be absorbed by other cells in the battery assembly / module). In certain embodiments, the colorant is a pigment or dye, with dyes being particularly preferred due to their ability to solubility in water. In one or more embodiments, the fire suppressant may contain 0.01% to 1% by weight, 0.05% to 0.5% by weight, 0.1% to 0.25% by weight, or about 0.125% by weight of the colorant.

[0039] In one or more embodiments, the colorant absorbs light in the wavelength range of 500-750 nm, 550-700 nm, or 600-650 nm. In certain embodiments, the colorant makes the fire suppressant blue.

[0040] In one or more embodiments, the fire suppressant generates a small amount of foam or substantially no foam when delivered to an area of ​​an object subject to a thermal event (i.e., a burning object). In this regard, the fire suppressant generates little or no foam when placed inside a container such as a graduated cylinder or other tube, when air is introduced, or when the container is shaken. In one particular embodiment, 50 mL of the fire suppressant is placed in a graduated cylinder, air is introduced, and it is passed through a diffuser or sparger at a flow rate of 1 L / min, resulting in little or no foam being generated, or if foam is generated, the volume of foam generated completely collapses within 2 minutes, 1 minute, or 30 seconds. In further embodiments, the fire suppressant contains, consists of, or is essentially composed of less than 0.1% by weight, less than 0.01% by weight, or less than 0.001% by weight of a fluorosurfactant and / or foaming agent. Preferably, the fire suppressant is essentially free of all surfactants, including hydrocarbon surfactants, fluorinated surfactants, and foaming agents. In particular, the embodiment of the fire suppressant is a 27% activated solution RHF2CH2SO2NHCH2CH2CH2N+(CH3)2CH2COO- The fire suppressant does not contain fluorosurfactants such as amphoteric perfluoroalkyl surfactants, or contains only trace amounts of fluorosurfactants. Furthermore, in certain embodiments, the fire suppressant does not contain foam enhancers (or blowing agents) such as diethylene glycol monobutyl ether, or contains only trace amounts of foam enhancers (or blowing agents). Furthermore, in certain embodiments, the fire suppressant does not contain nonionic alkyl polyglycoside surfactants such as alkyl polyglycosides based on synthetic aliphatic (C9-C11) alcohols, or contains only trace amounts of nonionic alkyl polyglycoside surfactants.

[0041] In one or more embodiments, the fire suppressant has relatively good storage stability in that it does not precipitate or settle over long periods of time. In certain embodiments, the fire suppressant can be stored at 25°C for at least 3 months, at least 6 months, at least 12 months, at least 1 year, or at least 5 years without forming precipitates or deposits.

[0042] In one or more embodiments, the fire suppressant exhibits low conductivity. This characteristic prevents the fire suppressant from causing or contributing to an electrical short circuit in the battery module to which it is applied. In particular, the fire suppressant exhibits conductances of less than 1,500 microcymens / cm (μS / cm), less than 800 microcymens / cm (μS / cm), less than 500 microcymens / cm (μS / cm), less than 250 microcymens / cm (μS / cm), or less than 100 microcymens / cm (μS / cm). In alternative embodiments, the fire suppressant exhibits conductances of 0.5 to 1,000 μS / cm, 3 to 800 μS / cm, or 10 to 500 μS / cm.

[0043] The fire suppressants described herein can be used in fire suppression systems, particularly in conjunction with battery containers and assemblies. Referring to Figures 1 and 2, a fire suppression system 10 for protecting a battery container 12 is shown. In one or more embodiments, the battery container 12 may comprise a sealed structure 14 in which a plurality of battery modules 16 are arranged. The sealed structure 14 may be any suitable enclosure, such as a freestanding building, a room within a building, and a mobile container (e.g., a shipping container).

[0044] The battery container 12 is equipped with one or more fans 22. One function of the fans 22 is to provide ventilation within the battery container 12. In particular, the fans 22 are configured to draw vapor or gas from within the sealed structure 14 and direct them to a location outside the sealed structure. The arrangement of the fans 22 as shown in Figure 1 is merely illustrative, and other designs and configurations are possible without departing from the scope of the present invention. Furthermore, ductwork, not shown, can be provided to guide gas to a safe ventilation location.

[0045] The fire suppression system 10 comprises at least one fire suppressant storage tank 24 and optionally at least one propellant tank 26 connected to the storage tank 24 via a conduit 28. Note that the conduit 28 is shown schematically only, and various control devices and valves may be present as needed, especially when multiple tanks 24 and / or 28 are present. The fire suppressant storage tank 24 is configured to store a quantity of fire suppressant sufficient to provide a flow of water to one or more parts of the sealed structure 14 under pressure supplied by pressurized gas from the propellant tank 26. The pressurized gas in the propellant tank 26 is preferably an inert gas such as nitrogen or carbon dioxide, but any inert gas can be used that does not contain components that can act as an oxidizer for fires, especially battery fires. Note that in certain embodiments, the propellant tank 26 may not be required if the storage tank 24 is configured to hold a sufficient quantity of fire suppressant and propellant.

[0046] In one or more embodiments, the fire suppressant storage tank 24 and the propellant tank 26 are located in a first compartment 62 of a container 12, separate from the second compartment 64 in which the battery module 16 is located. Alternatively, the storage tank 24 and the propellant tank 26 may be completely separated from the battery container 12 and located in an external enclosure (not shown). The environmental control unit 32 is installed in the compartment 62 and can provide heating or cooling as needed to maintain a desired operating temperature within the compartment.

[0047] The fire suppression system 10 also includes a controller 52 coupled to the fire suppressant storage tank 24. The controller 52 is also located in a battery container 12 and is connected to one or more fans 22 configured to activate the fans 22 when it receives a signal representing the operating status associated with the storage tank 24. The controller 52 may include an addressable or conventional control device, such as a digital peer-to-peer bidirectional communication device available from Fike Corporation (Blue Springs, Missouri) under the name CHEETAH Xi.

[0048] In certain embodiments, the controller 52 has additional functions beyond detecting the operating status and fan control of the fire suppressant storage tank. For example, the controller 52 can use various techniques to detect smoke, flames, or off-gases generated by a battery experiencing a thermal event. Smoke detection can be achieved by using a photoelectric smoke detector or an air sampling smoke detector, such as a VESDA detector by Xtralis. Thermal detection can be achieved by monitoring sprinkler heads, using heating detectors, linear heating detection cables, fiber optic linear heating detection cables, and heating video analysis images. Gas detection can be achieved by using standalone gas detectors, such as a hydrogen detector (available from Honeywell Analytics), an in-rack gas detector (LI-ION TAMER by Xtralis), and a smoke detector with an in-line XCL gas sensor (available from Xtralis) for hydrogen or carbon monoxide detection. The controller 52 can also provide integration to a building management system or programmable logic controller (PLC) via a gateway to provide messages from the fire panel. The controller 52 can also be configured to shut down the battery charging circuit when a thermal event is detected. The controller 52 can be configured to provide communication with a central station or facility manager via a communicator and / or computer graphics workstation. The controller 52 can also activate local notification systems such as horns, bells, and strobes.

[0049] The fire suppressant storage tank 24 is connected to a conduit network 40 extending into the battery container 12. The conduit network 40 typically includes one or more supply pipes 42 connecting the fire suppressant storage tank 24 to a distribution header 44 located within the battery container 12. The distribution header 44 may have an outlet 45 for connecting the network to a header located within an additional battery container. Multiple fire suppressant delivery pipes 46 extend from the header 44 and connect the header 44 to a collection pipe 48. The collection pipe 48 may have an outlet 66 with a valve (not shown) that allows seepage of the conduit network 40 as needed. As shown in the figure, one fire suppressant delivery pipe 46 is provided for each rack assembly 18, but it is also within the scope of the invention for the conduit network 40 to be configured differently.

[0050] As shown in Figure 3, each delivery pipe 46 is provided with a plurality of nozzles or heads 50 distributed along its length. In one or more embodiments, at least one nozzle 50 is provided for each battery module located within the rack assembly 18, but this is not necessarily required depending on how the rack assembly 18 is configured. The nozzles 50 may include nozzles or heads of any type of fire suppression system known to those skilled in the art. However, in one or more embodiments, the nozzles 50 are passive and do not require input from other sensors or devices to actuate. An exemplary nozzle 50 includes a nozzle containing a heat-sensitive element, such as a glass valve or fusible link, which typically breaks or deforms sufficiently when exposed to high-temperature conditions between 70 and 95°C, thereby allowing water to flow through the nozzle. Thus, the nozzles 50 may be configured to release the flow of water when exposed to nearby high-temperature conditions related to a thermal event occurring within the battery module 16.

[0051] The operation of a fire suppression system in a method for suppressing battery fires, particularly within one or more battery modules each comprising multiple lithium-ion battery cells, is described below. Referring particularly to Figures 3 and 4, an exemplary battery rack assembly 18 is shown, in which multiple battery modules 16 are installed inside. The rack assembly 18 may be configured to include ducts or flow paths 20 to facilitate cooling or ventilation of the battery modules 16, as indicated by the arrows. Each battery module 16 comprises multiple individual battery cells 68 stacked together. The battery cells may be made of any chemical (preferably lithium-ion) or have configurations such as cylindrical or prismatic.

[0052] The fire suppressants and fire suppression systems described herein are capable of suppressing fires, in particular, battery fires located within one or more battery modules containing multiple battery cells. An exemplary battery module 16 is shown in the figure and described above. However, in its broadest sense as used herein, a battery module is simply a collection of individual battery cells. Most commonly, the cells within a module are electrically connected to one another via a common busbar or similar structure, but this is not necessarily required.

[0053] One or more embodiments of the present invention particularly focus on addressing the challenge of cascading thermal runaway, in which a thermal event occurring in one battery cell triggers thermal events in one or more adjacent battery cells. Therefore, in certain embodiments, the methods described herein aim not only to delay or stop the cascading effect of battery thermal events, but also to eliminate or suppress initial thermal events occurring within a battery module. For brevity, the term “suppress” or “suppressing” refers to both the action of controlling a thermal event from reaching a self-heating point where it is highly likely to ignite a fire, or to extinguish an active fire.

[0054] A method according to one or more embodiments includes a detection step in which a condition in one or more battery modules related to a battery thermal event is detected or identified. As described above, any type of sensor commonly used in fire detection and suppression systems, such as thermal sensors, optical sensors, video analysis images, and gas detectors, can be used. Such sensors may be active or passive. Conditions related to a thermal event include identifying a temperature rise in a battery module or battery cell that is greater than 30°C in less than 500 seconds, greater than 50°C in less than 500 seconds, greater than 75°C in less than 500 seconds, or greater than 100°C in less than 500 seconds. The rate of rise in battery temperature can also occur much more rapidly, in that the aforementioned temperature rise may be encountered in less than 250 seconds, less than 100 seconds, or less than 60 seconds. Other conditions to be detected may include reaching a specific predetermined temperature threshold, detecting battery cell off-gases such as hydrogen or carbon monoxide, detecting visible or infrared light, or smoke emitted by the thermal event.

[0055] Referring to Figure 4, when the presence of a thermal event that has resulted in an active fire, or has a high probability of resulting in an active fire, is detected, a flow of fire suppressant as described herein is initiated and directed towards the affected battery module(s). The initiation of the fire suppressant flow may be due to an active or passive event. In an active initiation of a flow condition, the controller may, based on the receipt of a signal from the detector, initiate the release of pressurized fire suppressant from the fire suppressant storage tank 24 into a piping network 40 that terminates inside the battery module(s) 16. Once introduced into the piping network 40, the fire suppressant may be released into the battery module(s) 16 via a nozzle(s) 50. The release of fire suppressant from the nozzle(s) 50 may occur automatically when the flow of fire suppressant from the tank(s) 24 is initiated, or the nozzle(s) 50 may include a heat-driven agent delivery device that includes a heat-sensitive element such as a glass valve or fusible link, which will rupture or deform sufficiently when exposed to high-temperature conditions, typically between 70 and 95°C resulting from a thermal event, allowing the fire suppressant to flow through it.

[0056] Alternatively, the piping network 40 can be pre-filled with aqueous fire suppressant supplied from the storage tank 24 before detection of conditions within one or more battery modules 16 related to a battery thermal event. The piping network 40 terminates within the battery modules 16 in one or more heat-driven agent delivery devices 50. The heat generated by the thermal event causes the devices 50 to open, releasing the flow of fire suppressant into the battery modules 16.

[0057] Once inside the battery module 16, the fire suppressant comes into contact with at least one of the multiple battery cells 68, in particular, the battery cell 70 experiencing a thermal event. During the contact process described above, the liquid fire suppressant comes into contact with the battery cell 70 experiencing the thermal event. It is also preferable that adjacent battery cells 68 come into contact with the fire suppressant. In one or more embodiments, the contact process described above includes immersing the battery module 16 in the fire suppressant. The operation of immersing the battery module 16 may include completely immersing one or more battery cells 68, 70 contained within the module 16 in the fire suppressant. In such embodiments, gases such as battery off-gas and ambient oxygen are displaced from the internal volume of the module 16, and thus serve to further control the progression of the thermal event or prevent an explosion within the module. Liquid fire suppressants generally contain a high heat capacity and a high boiling point, which helps to absorb the heat generated by the failed battery cell 70 and reduce the amount of heat delivered to adjacent cells.

[0058] Examples In this embodiment, the effectiveness of using a potassium lactate-containing fire suppressant to control thermal events in a lithium-ion battery module containing 36 lithium-ion pouch battery cells was investigated according to the present invention. A cylinder was filled with 375 pounds of fire suppressant composition containing 60 wt% potassium lactate and 40% water. The tank was connected to a suppressant delivery system having an outlet that terminates in the battery module. One cell in the battery module was heated using an external heating device. As shown in Figure 5, cell number 1 was heated using the external heater. Approximately 1500 seconds after the start of heating, at a temperature of approximately 150°C, the battery cell began to self-heat. After approximately 600 seconds, cell number 1 ruptured, and a thermal runaway reaction began immediately thereafter, at which point the fire suppressant was introduced into the battery module.

[0059] Approximately 200 seconds after the rupture of cell number 1, and approximately 100 seconds after the immersion of the battery module began, the adjacent cell number 2 experienced thermal runaway. However, as can be seen, the heat from the thermal runaway events in cells 1 and 2 subsided rapidly after the deployment of the fire suppressant. As the temperature decreased, an additional seven cells experienced thermal runaway. However, these only encountered mild temperature spikes as part of these runaway events, indicating that the heat from these events was readily absorbed by the fire suppressant. The temperature within the battery module continued to cool below the threshold for self-heating without any additional cells failing. Thus, the heat cascade was suppressed and its spread to the remaining cells in the module was effectively prevented.

Claims

1. A method for suppressing a battery fire, the method comprising the step of applying an aqueous fire suppressant to a battery cell that has caused a fire or is subject to a thermal event that could cause a fire, wherein the aqueous fire suppressant comprises a carboxylate.

2. The method according to claim 1, wherein the carboxylate salt comprises a potassium salt or sodium salt of lactic acid, acetic acid, citric acid, glycolic acid, butyric acid, or tartaric acid.

3. The method according to claim 1, wherein the aqueous fire suppressant comprises 30% to 80% by weight of the carboxylate.

4. The method according to claim 1, wherein the aqueous fire suppressant contains 20% to 70% by weight of water.

5. The method according to claim 1, wherein the aqueous fire suppressant comprises an antihydrofluoric acid agent and / or a coloring agent.

6. The method according to claim 5, wherein the hydrofluoric acid-resistant agent comprises one or more selected from the group consisting of citronella oil, d-limonene, dipentene, p-cumene, β-pinene, oleic acid, and vitamin E.

7. The method according to claim 5, wherein the aqueous fire suppressant comprises 0.01% to 2% by weight of the hydrofluoric acid anti-hydrofluoric acid agent and / or 0.01% to 1% by weight of the coloring agent.

8. The method according to claim 5, wherein the aqueous fire suppressant essentially consists of water, the carboxylate salt, optionally an antihydrofluoric acid agent, and optionally a colorant.

9. The method according to claim 1, wherein the battery cell includes a lithium-ion battery cell.

10. The method according to claim 1, wherein the thermal event is a fire.

11. The method according to claim 1, wherein the thermal event is a rise in battery temperature of more than 30°C in less than 500 seconds.

12. The method according to claim 1, wherein applying the aqueous fire suppressant to the battery cell includes immersing the battery cell with the aqueous fire suppressant.

13. A method for suppressing a battery fire in one or more battery modules, wherein each battery module comprises a plurality of lithium-ion battery cells, and the method is A step of detecting the state within one or more battery modules related to a battery thermal event, A step of initiating the flow of an aqueous fire suppressant into one or more battery modules, wherein the aqueous fire suppressant contains a carboxylate salt, A method comprising the step of bringing at least one of the plurality of battery cells located within the module into contact with the aqueous fire suppressant.

14. The method according to claim 13, wherein the detection step includes a step of detecting off-gas, smoke, light, or heat generated from the battery thermal event.

15. The method according to claim 14, wherein the aqueous fire suppressant is contained in a storage container, and when smoke, light, or heat generated from the thermal event is detected, the aqueous fire suppressant flows from the storage container into a piping network connected to one or more battery modules.

16. The method according to claim 15, wherein the piping network comprises one or more heat-driven agent delivery devices configured to deliver the aqueous fire suppressant from the piping network into one or more battery modules.

17. The method according to claim 16, wherein the heat from the thermal event activates one or more heat-driven agent delivery devices, thereby initiating the flow of the aqueous fire suppressant into one or more battery modules.

18. The method according to claim 13, wherein the aqueous fire suppressant is contained in a storage container operably connected to a piping network, and the piping network terminates inside one or more battery modules in one or more heat-driven agent delivery devices.

19. The method according to claim 18, wherein the piping network is pre-filled with the aqueous fire suppressant before the detection of the state in one or more battery modules related to the battery thermal event.

20. The method according to claim 19, wherein the heat from the battery thermal event activates one or more heat-driven agent delivery devices, thereby initiating the flow of the aqueous fire suppressant into one or more battery modules.

21. The method according to claim 13, wherein the contact step includes immersing one or more battery modules in the aqueous fire suppressant.

22. The method according to claim 13, wherein immersing one or more battery modules replaces substantially all of the gas contained within the battery modules.

23. The method according to claim 13, wherein the carboxylate salt comprises a potassium or sodium salt of lactic acid, acetic acid, citric acid, glycolic acid, butyric acid, or tartaric acid.

24. The method according to claim 13, wherein the aqueous fire suppressant comprises 30% to 80% by weight of the carboxylate.

25. The method according to claim 13, wherein the aqueous fire suppressant contains 20% to 70% by weight of water.

26. The method according to claim 13, wherein the aqueous fire suppressant comprises an antihydrofluoric acid agent and / or a coloring agent.

27. The method according to claim 26, wherein the anti-hydrofluoric acid agent comprises one or more selected from the group consisting of citronella oil or one or more components thereof, d-limonene, dipentene, p-cumene, β-pinene, oleic acid, and vitamin E.

28. The method according to claim 26, wherein the aqueous fire suppressant comprises 0.01% to 2% by weight of the hydrofluoric acid anti-hydrofluoride agent and / or 0.01% to 1% by weight of the coloring agent.

29. The method according to claim 26, wherein the aqueous fire suppressant essentially consists of water, the carboxylate salt, optionally an antihydrofluoric acid agent, and optionally a colorant.

30. A fire suppression system, A pressurized fire suppressant storage tank containing a certain amount of aqueous fire suppressant containing a carboxylate salt, The fire suppressant storage tank is connected to a conduit network that extends into one or more battery containers, and each of the one or more battery containers includes one or more battery modules, and each of the one or more battery modules includes a plurality of battery cells. A fire suppression system in which the conduit network is configured to deliver a flow of the aqueous fire suppressant to at least one of the one or more battery modules when a thermal event is detected in at least one of the one or more battery modules.

31. The fire suppression system according to claim 30, further comprising at least one sensor located in the one or more battery containers, which is capable of detecting conditions related to a battery thermal event.

32. The fire suppression system according to claim 30, wherein the conduit network is pre-filled with the aqueous fire suppressant.

33. The fire suppression system according to claim 30, wherein the fire suppression system includes a controller that can be operated to initiate the flow of the aqueous fire suppressant from the fire suppressant storage tank into the conduit network when the thermal event is detected in at least one of the one or more battery modules.

34. The fire suppression system according to claim 30, wherein the conduit network is configured to deliver a sufficient amount of the aqueous fire suppressant to one or more battery modules, thereby immersing the one or more battery modules in the aqueous fire suppressant.

35. The fire suppression system according to claim 30, wherein the conduit network is configured to deliver a sufficient amount of the aqueous fire suppressant to one or more battery modules to substantially replace all of the gas contained within the battery modules.

36. The fire suppression system according to claim 30, wherein the carboxylate salt comprises a potassium salt or sodium salt of lactic acid, acetic acid, citric acid, glycolic acid, butyric acid, or tartaric acid.

37. The fire suppression system according to claim 30, wherein the aqueous fire suppressant comprises 30% to 80% by weight of the carboxylate.

38. The fire suppression system according to claim 30, wherein the aqueous fire suppressant contains 20% to 70% by weight of water.

39. The fire suppression system according to claim 30, wherein the aqueous fire suppressant comprises an antihydrofluoric acid agent and / or a coloring agent.

40. The fire suppression system according to claim 39, wherein the antihydrofluoride agent comprises one or more selected from the group consisting of citronella oil or one or more components thereof, d-limonene, dipentene, p-cumene, β-pinene, oleic acid, and vitamin E.

41. The fire suppression system according to claim 39, wherein the aqueous fire suppressant comprises 0.01% to 2% by weight of the hydrofluoric acid-resistant agent and / or 0.01% to 1% by weight of the coloring agent.

42. The fire suppression system according to claim 30, wherein the aqueous fire suppressant essentially consists of water, the carboxylate salt, optionally an antihydrofluoric acid agent, and optionally a colorant.

43. An aqueous fire suppressant comprising a carboxylate dispersed in water, and comprising less than 0.01% by weight of a fluorosurfactant and / or a foaming agent.

44. This is an aqueous fire suppressant containing a carboxylate dispersed in water, formulated to prevent foaming upon delivery to an object during a fire.

45. The aqueous fire suppressant according to claim 43 or 44, wherein the carboxylate salt comprises a potassium salt or sodium salt of lactic acid, acetic acid, citric acid, glycolic acid, butyric acid, or tartaric acid.

46. The aqueous fire suppressant according to claim 43 or 44, wherein the aqueous fire suppressant comprises 30% to 80% by weight of the carboxylate.

47. The aqueous fire suppressant according to claim 43 or 44, wherein the aqueous fire suppressant contains 20% to 70% by weight of water.

48. The aqueous fire suppressant according to claim 43 or 44, wherein the aqueous fire suppressant comprises an antihydrofluoric acid agent and / or a coloring agent.

49. The aqueous fire suppressant according to claim 48, wherein the hydrofluoric acid-resistant agent comprises one or more components selected from the group consisting of citronella oil or one or more components thereof, d-limonene, dipentene, p-cumene, β-pinene, oleic acid, and vitamin E.

50. The aqueous fire suppressant according to claim 48, wherein the aqueous fire suppressant comprises 0.01% to 2% by weight of the hydrofluoric acid anti-hydrofluoride agent and / or 0.01% to 1% by weight of the coloring agent.

51. The aqueous fire suppressant according to claim 43 or 44, wherein the aqueous fire suppressant is essentially free of surfactants.

52. An aqueous fire suppressant essentially comprising water, a carboxylate, optionally an anti-hydrofluoric acid agent, and optionally a colorant.

53. The aqueous fire suppressant according to claim 52, wherein the carboxylate salt comprises a potassium salt or sodium salt of lactic acid, acetic acid, citric acid, glycolic acid, butyric acid, or tartaric acid.

54. The aqueous fire suppressant according to claim 52, wherein the hydrofluoric acid-resistant agent is selected from the group consisting of citronella oil or one or more components thereof, d-limonene, dipentene, p-cumene, β-pinene, oleic acid, vitamin E, and mixtures thereof.

55. The aqueous fire suppressor according to claim 52, wherein the carboxylate salt is present in the aqueous fire suppressor at a level of 30% to 80% by weight.

56. The aqueous fire suppressor according to claim 52, wherein the water is present in the aqueous fire suppressor at a level of 20% to 70% by weight.

57. The aqueous fire suppressor according to claim 52, wherein the hydrofluoric acid-resistant agent is present in the aqueous fire suppressor at a level of 0.01% to 2% by weight.

58. The aqueous fire suppressor according to claim 52, wherein the coloring agent is present in the aqueous fire suppressor at a level of 0.01% to 1% by weight.

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