Preventing for the thermal runaway of lithium ion battery cell

Abstract

The present invention relates to a system for preventing the propagation of thermal runaway in a lithium-ion battery cell, and more specifically, to a system comprising an off-gas detection sensor, a heat detection sensor, an inert gas injection device, and a controller to determine in real time whether thermal runaway and venting have occurred, and to ensure safety by appropriately injecting an inert gas. A specific feature of the present invention is that it includes: a cell installation section in which lithium-ion battery cells are installed inside the housing; a detection section installed above the cell installation section inside the housing to detect the amount of oxygen and to detect abnormal conditions such as venting and thermal runaway; and a control section that receives a detection signal from the detection section, determines an abnormal condition, and injects an inert gas when an abnormal condition is determined.

Description

Technology Field

[0001] The present invention relates to a system for preventing the propagation of thermal runaway in a lithium-ion battery cell, and more specifically, to a system comprising an off-gas detection sensor, a heat detection sensor, an inert gas injection device, and a controller to monitor gas concentration and temperature inside a lithium-ion battery cell in real time, and to prevent the propagation of thermal runaway by appropriately injecting an inert gas according to the conditions of thermal runaway and venting. Background Technology

[0002] Lithium-ion batteries are widely used in various electronic devices, such as electric vehicles, smartphones, and laptops, and their performance and safety have established themselves as critical factors in technological advancement. However, lithium-ion batteries can face safety issues due to thermal runaway, which is triggered by the accumulation of gases and temperature increases within the battery cells. This thermal runaway can propagate to adjacent cells, posing a risk of large-scale fires or explosions. Consequently, there is a growing need for a thermal runaway prevention system to ensure the safety of lithium-ion batteries. Existing systems primarily rely on simple temperature detection and cutoff functions, often failing to monitor gas concentrations and temperatures in real-time to provide appropriate responses. Therefore, a more sophisticated and efficient thermal runaway prevention system is required, presenting the potential to significantly enhance the safety of lithium-ion batteries through an automated response mechanism utilizing inert gases.

[0003] The technical configuration disclosed in Patent Publication No. 10-2024-0049727 (Title of Invention: Fire Prevention Device and Method for Battery Case) (hereinafter referred to as "Prior Art") comprises a fire prevention device for a battery case comprising: a sealed case having a plurality of battery modules in an internal receiving space; an inert gas filled within the case; a first gas sensor for detecting the oxygen concentration in the internal receiving space of the case; a fire detection sensor for detecting a fire in the internal receiving space of the case during thermal runaway; a pressure sensor for detecting the pressure in the receiving space within the case; and a solenoid valve for regulating the pressure in the receiving space within the case.

[0004] Conventional technology involves filling the inside of a case with inert gas to prevent venting or thermal runaway phenomena; however, since the case must be precisely manufactured to prevent gas leakage in order to always keep the case fully filled with inert gas, the system becomes expensive to produce, and there is the inconvenience of having to refill the inert gas whenever the case is opened for internal inspection. The problem to be solved

[0005] The present invention provides a system for effectively preventing the propagation of thermal runaway in lithium-ion battery cells. Its purpose is to prevent thermal runaway and block propagation to adjacent cells by determining risk in real time through venting detection and heat detection, and by controlling oxygen concentration through the appropriate injection of an inert gas. means of solving the problem

[0006] According to the present invention having the above-mentioned problem and means of solution, a system for preventing the propagation of thermal runaway in lithium-ion battery cells, which detects the venting state and thermal runaway state of lithium-ion battery cells stored in a housing in which a lithium-ion battery is installed and sprays an inert gas to prevent thermal runaway, comprises: a cell installation part in which lithium-ion battery cells are installed inside the housing; a detection part installed above the cell installation part inside the housing to detect the amount of oxygen and detect abnormal states of the venting state and thermal runaway state; and a control part that receives the detection signal from the detection part, determines the abnormal state, and sprays an inert gas when an abnormal state is determined.

[0007] In addition, in the present invention, the detection unit preferably includes an oxygen detection sensor for detecting the amount of oxygen inside the housing, an off-gas detection sensor for detecting off-gas generated when venting occurs, a detection sensor for detecting thermal runaway, a temperature detector for detecting the temperature inside the housing and the temperature of the lithium-ion battery cell, and a fire detector equipped with a thermal imaging camera for capturing thermal images of the cells.

[0008] In addition, in the present invention, the housing is equipped with a control unit that injects nitrogen, an inert gas, during venting, a gas-based fire extinguishing agent injection unit that injects a gas-based fire extinguishing agent, an inert gas, during thermal runaway, and a PLC (Programmable Logic Controller) that controls the operation of the nitrogen injection unit and the gas-based fire extinguishing agent injection unit by comparing a signal input from the detection unit with a previously stored signal. It is preferable that the PLC operates the nitrogen injection unit when it determines that the venting state is determined by comparing the signal input from the detection unit with previously stored reference values, and operates the gas-based fire extinguishing agent injection unit when it determines that the thermal runaway state is determined by comparing the signal input from the detection unit with previously stored reference values.

[0009] In addition, in the present invention, it is preferable that the PLC controls the operation of the nitrogen injection unit to periodically repeat spraying for a first time and stopping for a second time, determines whether the venting state is terminated based on signals input from the detection unit, and terminates the spraying of the nitrogen injection unit when the venting state is terminated.

[0010] In addition, in the present invention, it is preferable to determine whether the venting state has ended when no thermal runaway occurs for 30 minutes after off-gas detection, and to stop the nitrogen injection unit.

[0011] It is preferable to determine whether the above venting state has ended by stopping the nitrogen injection unit when the off-gas detected by the above-mentioned off-gas detection sensor becomes zero, thereby determining that the state has ended.

[0012] In addition, in the present invention, it is preferable that the PLC controls the operation of the gas-based fire extinguishing agent injection unit to periodically repeat spraying for a third time and stopping for a fourth time, determines whether the thermal runaway state has ended based on signals input from the detection unit, and terminates the spraying operation of the fire extinguishing agent from the gas-based fire extinguishing agent injection unit when the thermal runaway state has ended.

[0013] In addition, in the present invention, it is preferable that the PLC determines that the thermal runaway phenomenon has ended when the measured temperature input from the temperature sensor becomes lower than a preset temperature. Effects of the invention

[0014] As described above, according to the present invention, a system for preventing thermal runaway propagation of a lithium-ion battery cell can significantly improve the safety of the lithium-ion battery cell by monitoring the condition in real time through a venting detection sensor and a heat detection sensor, and by appropriately responding to thermal runaway and venting situations through an inert gas injection device.

[0015] By spraying an appropriate amount of inert extinguishing agent in the event of venting or thermal runaway, normal battery cells unaffected by the fire can be recycled and reused, and the agent can also be used sparingly. Brief explanation of the drawing

[0016] FIG. 1 is a block diagram of an embodiment of the present invention. FIG. 2 is a flowchart for carrying out an embodiment of the present invention. Specific details for implementing the invention

[0017] [Mechanism of Thermal Runaway in Lithium-ion Batteries]

[0018] When a lithium-ion battery is subjected to thermal, electrical, or mechanical shock, its internal temperature rises, causing the electrolyte to boil. As the electrolyte vaporizes, the internal pressure of the battery increases; if this persists, a venting phenomenon occurs where the battery surface opens, releasing electrolyte vapor and decomposition gases to the outside. These are collectively defined as off-gases. Meanwhile, if stress on the lithium-ion battery persists, the rising internal temperature causes the separator to melt, eventually leading to an internal short circuit. When an internal short circuit occurs, a large amount of reaction gases (smoke) are released, which subsequently ignite due to the high heat, causing a fire; this phenomenon is known as thermal runaway. Furthermore, since thermal runaway in lithium-ion batteries continuously generates heat and oxygen until all internal energy is exhausted, it cannot be suppressed by conventional firefighting equipment, and the flammable gases concentrated near the battery can cause a massive explosion.

[0019] [Lithium-ion Battery Thermal Runaway Diffusion Characteristics]

[0020] Lithium-ion battery cells degrade due to stress or undergo thermal runaway due to quality defects, propagating this thermal stress to adjacent cells and spreading the runaway. Furthermore, since a lithium-ion battery cell within a module or pack does not trigger a fire all at once but rather spreads gradually from surrounding cells through thermal transfer, a fire can spread uncontrollably if the occurrence of runaway in just one or two cells is not addressed. For this reason, lithium-ion

[0021] When a battery fire occurs, the entire system tends to burn down completely. Meanwhile, lithium-ion battery fires are characterized by prolonged duration, and the concentration of flammable gases increases the risk of a fire explosion. Therefore, to prevent large-scale fires, technology is required to respond to lithium-ion battery fires early and prevent their spread.

[0022] [Inert Gas Extinguishing Characteristics]

[0023] Inert gas, also known as unreactive gas, refers to a gas that does not undergo a chemical reaction under a given set of conditions. Generally, inert gases include both Group 18 elements, which are called inert gases, and gases with low reactivity. Here, nitrogen is classified as a common gas that accounts for a large proportion of the natural atmosphere, and it is used as an inert gas due to its high natural abundance and relatively low cost. Therefore, nitrogen is selected as the inert gas to be utilized in the fire spread prevention technology for lithium-ion batteries because it is easily available and has low construction costs. Meanwhile, to prevent fire spread in lithium-ion batteries, experiments have shown that if the oxygen concentration is maintained at a specific level of 11.3% or lower, the size of the flame decreases and the fire does not spread to adjacent cells; therefore, an inert gas is injected to maintain the oxygen concentration below this specific level.

[0024] Furthermore, injecting water-based fire extinguishing agents into an ESS implies rendering other equipment and batteries, in addition to the battery where the fire occurred, unusable. However, by applying inert gas-based fire extinguishing technology, not only can the aforementioned oxygen concentration control and forced cooling effects be applied, but other equipment and lithium-ion batteries not involved in the fire can also be recycled. Therefore, to maximize the advantages of inert gas fire extinguishing characteristics, it is effective to use inert gas-based fire extinguishing agents for ESS fires. Here, the widely used NOVEC 1230 fire extinguishing agent was selected as the inert gas-based fire extinguishing agent and utilized as a measure to prevent thermal runaway in lithium-ion batteries.

[0025] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0026] FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a flowchart for carrying out an embodiment of the present invention.

[0027] The thermal runaway propagation prevention system (100) of the lithium-ion battery cell of the present invention comprises a housing (1) in which lithium-ion batteries are installed, a cell installation section (4) in which lithium-ion battery cells are electrically connected and stored adjacently inside the housing (1), a detection section (2) installed on the upper part of the cell installation section (4) inside the housing (1) to detect an abnormal state of the cell installation section (4), and a control section (3) that receives the detection state of the detection section (2), determines an abnormal state, and sprays an inert gas, such as nitrogen or a gaseous fire extinguishing agent (NOVEC 1230 fire extinguishing agent) when an abnormal state is determined.

[0028] Additionally, the detection unit (2) is preferably installed on the upper part of the cell installation unit (4) to detect gas generated from individual cells of the cell installation unit (4) within the housing (1) and to detect smoke, etc. The detection unit (2) is composed of an oxygen detection sensor (21) for detecting the amount of oxygen inside the housing (1), an off-gas detection sensor (22) for detecting off-gas generated when venting occurs, a detection sensor for detecting reaction gas (smoke) generated during thermal runaway, a temperature detector for detecting the temperature inside the housing and the lithium-ion battery cells, and a fire detector (23) in which a thermal imaging camera for taking thermal images of the cells is installed.

[0029] In addition, the control unit (3) consists of a nitrogen injection unit (32) that injects nitrogen, which is an inert gas, a gas-based fire extinguishing agent injection unit (33) that injects a gas-based fire extinguishing agent, and a PLC (Programmable Logic Controller) (31) that receives signals detected by sensors of the detection unit (2) and drives the nitrogen injection unit (32) and the gas-based fire extinguishing agent injection unit (33).

[0030] When venting occurs in the lithium-ion battery cells (S2), off-gas is generated, so the off-gas is detected by the off-gas detection sensor (22), and the detection signal of the off-gas detection sensor (22) is input to the PLC (31) (S3).

[0031] When an off-gas detection signal is input from the off-gas detection sensor (22), the PLC (31) compares the current oxygen concentration with a preset specific oxygen concentration value based on the signal input from the oxygen detection sensor (21). If the current oxygen concentration is higher than the preset specific oxygen concentration value, the nitrogen injection unit (32) is operated for a preset time. While stopping the injection operation for a preset time, the oxygen concentration value input from the oxygen detection sensor is compared to drop below the preset oxygen concentration value. If the oxygen concentration value is lower than the preset specific oxygen concentration value, the nitrogen injection unit (32) is stopped (S4).

[0032] Although the specific oxygen concentration value is typically set to 11.3% for lithium-ion batteries, it is not limited to this value and varies depending on the type and size of the battery. Therefore, it is desirable to experimentally determine and use an oxygen concentration value that prevents thermal runaway depending on the battery.

[0033] If off-gas is detected by the off-gas detection sensor (22) and the process of the nitrogen injection unit (32) periodically injecting nitrogen continues for 30 minutes, and then no fire is detected by the fire detector (23), the event is recognized as having ended in the venting stage and is determined not to have spread to the thermal runaway stage.

[0034] However, the fire detector (23) consists of a gas detector that detects the amount of smoke and gas generated during a fire, a temperature detector that detects the temperature of the battery cells during a thermal runaway, and an infrared camera that takes a thermal image. When the signal and image detected by the fire detector (23) are transmitted to the PLC (31), the PLC (31) compares the input signal and image with a stored reference value and determines that it is a thermal runaway. If it determines that it is a thermal runaway, it sprays NOVEC1230, a gas-based fire extinguishing agent, into the gas-based fire extinguishing agent spraying unit (33) for a preset time, and then periodically repeats the process of stopping and re-spraying for a preset time to determine whether the thermal runaway phenomenon has been suppressed and ended. At this time, the PLC (31) determines that the thermal runaway phenomenon has ended when the measured temperature input from the temperature sensor becomes lower than the preset temperature (S5), (S6), (S7).

[0035] Compared to liquid fire extinguishing agents, gaseous fire extinguishing agents allow parts that were not sprayed to remain intact and reusable when the thermal runaway phenomenon ends. However, since most of the battery cells inside the housing (1) cannot be reused when liquid fire extinguishing agents are sprayed, it is preferable to use gaseous fire extinguishing agents.

[0036] In addition, it is desirable to repeat the process of spraying the gaseous fire extinguishing agent for 30 seconds, stopping for 5 seconds, and then re-spraying. This cycle setting is not fixed but is determined experimentally based on the size of the housing and the amount of stored battery cells. Repeating the spraying stoppage periodically in this manner and detecting the thermal runaway stop state during this period to completely stop the spraying has the advantage of saving fire extinguishing agent and allowing the battery in a normal state to be recycled. Explanation of the symbols

[0037] 1: Housing 2: Detector 3: Control unit 4: Cell installation section 21: Oxygen detection sensor 22: Off-gas detection sensor 23: Fire detector 31: PLC 32: Nitrogen injection unit 33: Gaseous fire extinguishing agent injection unit 100: Thermal runaway prevention system for lithium-ion battery cells

Claims

Claim 1 In a system for preventing the propagation of thermal runaway in lithium-ion battery cells, which detects the venting and thermal runaway states of lithium-ion battery cells stored within a housing in which a lithium-ion battery is installed, and injects an inert gas to prevent thermal runaway: A cell installation section in which lithium-ion battery cells are installed inside the above housing; A sensing unit installed above the cell installation part inside the housing to detect oxygen levels and detect abnormal conditions such as venting and thermal runaway states; A system for preventing thermal runaway propagation of a lithium-ion battery cell, characterized by including a control unit that receives a detection signal from the above-mentioned detection unit, determines an abnormal state, and sprays an inert gas when an abnormal state is determined. Claim 2 A system for preventing the propagation of thermal runaway in a lithium-ion battery cell according to claim 1, wherein the sensing unit comprises an oxygen detection sensor for detecting the amount of oxygen inside the housing, an off-gas detection sensor for detecting off-gas generated when venting occurs, a detection sensor for detecting thermal runaway, a temperature detector for detecting the temperature inside the housing and the temperature of the lithium-ion battery cell, and a fire detector equipped with a thermal imaging camera for capturing thermal images of the cells. Claim 3 A system for preventing the propagation of thermal runaway in a lithium-ion battery cell according to claim 2, wherein the housing is equipped with a control unit comprising a nitrogen injection unit that injects nitrogen, an inert gas, during venting, a gas-based fire extinguishing agent injection unit that injects a gas-based fire extinguishing agent, an inert gas, during thermal runaway, and a PLC (Programmable Logic Controller) that controls the operation of the nitrogen injection unit and the gas-based fire extinguishing agent injection unit by comparing a signal input from the detection unit with a previously stored signal, and wherein the PLC operates the nitrogen injection unit if it determines that the state is venting by comparing a signal input from the detection unit with previously stored reference values, and operates the gas-based fire extinguishing agent injection unit if it determines that the state is thermal runaway by comparing a signal input from the detection unit with previously stored reference values. Claim 4 A system for preventing thermal runaway propagation of a lithium-ion battery cell according to claim 3, wherein the PLC controls the operation of the nitrogen injection unit to periodically repeat spraying for a first time and stopping for a second time, determines whether the venting state is terminated based on signals input from the detection unit, and terminates the spraying of the nitrogen injection unit when the venting state is terminated. Claim 5 A system for preventing thermal runaway propagation of a lithium-ion battery cell according to claim 4, characterized in that the determination of whether the venting state has ended is made when no thermal runaway occurs until 30 minutes have passed since off-gas detection, and the nitrogen injection unit is stopped. Claim 6 A system for preventing thermal runaway propagation of a lithium-ion battery cell according to claim 3, wherein the PLC controls the operation of the gas-based fire extinguishing agent spraying unit to periodically repeat spraying for a third time and stopping for a fourth time, determines whether the thermal runaway state is terminated by signals input from the detection unit, and terminates the spraying operation of spraying the fire extinguishing agent from the gas-based fire extinguishing agent spraying unit when the thermal runaway state is terminated. Claim 7 A system for preventing thermal runaway propagation of a lithium-ion battery cell according to claim 6, characterized in that the PLC determines that the thermal runaway phenomenon has ended when the measured temperature input from the temperature sensor becomes lower than a preset temperature.

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