A cooling system and method for blocking the propagation of thermal runaway of a battery cell

Abstract

This invention discloses a cooling system and method for blocking the propagation of thermal runaway in battery cells, belonging to the field of battery technology. It includes a cooling agent delivery component, a gas delivery component, and a control component. The cooling agent delivery component comprises a cooling agent storage tank, a first electric valve, a cooling agent delivery pump, a conversion interface, and a heat relief module connected in sequence. The heat relief module is made of a hot-melt material, encapsulated between the battery cells, and connected to the conversion interface via a delivery pipe. The gas delivery component comprises an inflation pump, a gas flow meter, a second electric valve, and a buffer tank connected in sequence. The inflation pump is connected to a gas source, and the buffer tank is connected to the conversion interface and equipped with a pressure gauge. The control component includes a controller. This invention enables precise positioning of thermally runaway battery cells and directional release of the cooling agent, thereby effectively blocking the propagation of thermal runaway while significantly reducing the amount of cooling agent used, reducing system weight, and improving battery safety and energy density.

Description

Technical Field

[0001] This invention relates to a cooling system and method for blocking the transmission of thermal runaway in battery cells, specifically a cooling system for blocking the transmission of thermal runaway in battery cells and a method for controlling the release of cooling agents, belonging to the field of battery technology. Background Technology

[0002] With the development of science and technology, a large number of rechargeable batteries, especially lithium-ion batteries, are used in automobiles, energy storage devices, and aircraft. Because thermal runaway within a battery cell can rapidly propagate to adjacent cells, reports of lithium battery fires are frequent. Although researchers have reduced the probability of thermal runaway by improving cell material selection and structural design, the risk cannot be completely eliminated. Cars and buses containing lithium batteries are often parked in relatively enclosed spaces such as underground garages and buildings. While the probability of thermal runaway and fire in these vehicles is not high, the consequences are extremely serious, causing significant insecurity for drivers and passengers. In aircraft powered by lithium batteries, thermal runaway during flight would also seriously jeopardize flight safety.

[0003] After a lithium-ion battery cell experiences thermal runaway, effectively preventing further thermal runaway between adjacent cells has become a key issue in preventing battery fires. Previous research has mainly focused on cell cooling and heat insulation. For example: Patent CN202323042757.0 discloses a flame-retardant lithium battery heat insulation plate, which has a flame-retardant plate with an aerosol film connected to one side of the battery cell to isolate the heat released by thermal runaway, thereby preventing the thermal runaway of one battery cell from being transmitted to other adjacent battery cells. Patent CN202311606588.0 discloses a barrier structure, battery module and battery pack for suppressing the spread of thermal runaway in lithium batteries, in which an aerogel heat insulation plate is set between two adjacent battery cells. When thermal runaway occurs inside the battery, it can prevent the heat generated by the single battery cell in a thermal runaway state from being transferred to the adjacent battery cells.

[0004] In addition, some studies have explored filling the spaces between or outside the battery cells with cooling or fire-extinguishing media. For example: Patent CN201610291427.0 discloses a fireproofing method for soft-pack lithium battery modules. A soft-pack plastic bag is wrapped around the outside of the soft-pack battery, and a fire-retardant liquid is filled between the plastic bag and the battery. When a cell experiences a serious malfunction leading to pack breakage, the fire-retardant liquid can directly dilute the electrolyte, achieving a fire-resistant effect. Patent CN201620091052.9 discloses a fireproofing structure for soft-pack lithium batteries, with a fire-retardant layer and a phase change layer placed between an aluminum-plastic film and the battery cell. When the battery cell overheats, the outer layer of the fire-retardant layer melts and cracks at high temperatures, releasing a fire extinguishing agent to cover the battery cell and electrode surfaces, preventing fire or explosion. Patent CN202421177796.3 discloses an immersion cooling system for power battery packs, with a foam assembly with a flow-guiding function placed between adjacent battery cells. Coolant directly contacts the battery cells through the foam assembly to achieve cooling. In the event of thermal runaway, the battery cells can rapidly cool down, thereby reducing the risk of heat spread.

[0005] Patent CN202322229494 discloses a lithium battery cooling and fire extinguishing system. The system's heat dissipation tank is in contact with the battery cell, and flame-retardant cooling oil circulates in the heat dissipation tank to remove the heat from the battery cell. When the battery cell is burning, flame-retardant cooling oil can be injected into the battery cell through the heat dissipation tank to block oxygen and cool it down quickly, thereby extinguishing the fire.

[0006] However, the aforementioned technologies still have their limitations: solutions based on thermal insulation materials (such as aerogel and flame-retardant plates) can slow down the heat transfer rate between adjacent cells, thereby delaying the spread of thermal runaway, but they cannot completely block its transmission. At the same time, the practical application of such solutions is greatly restricted by the stringent requirements of battery usage scenarios on the volume and weight of thermal insulation materials. Solutions that fill the cells with cooling or fire extinguishing media can block the transmission of thermal runaway between cells, but since the cells are always wrapped in cooling agent, the use of a large amount of cooling agent not only leads to a significant increase in battery weight, but also easily causes cooling agent leakage, thus also facing application limitations. In addition, traditional external cooling devices such as water-cooled plates are arranged on the outside of the stacked cells, with a small contact area with the cells. Heat inside the cells that is far from the heat dissipation surface is difficult to be removed in time, thus making it difficult to effectively block thermal runaway between adjacent cells.

[0007] In summary, existing technologies either fail to completely prevent the propagation of thermal runaway between adjacent cells or cannot simultaneously meet the practical requirements for increasing battery energy density. Therefore, there is an urgent need to develop a new technology that can effectively suppress the spread of thermal runaway while having a minimal impact on battery weight and volume. Summary of the Invention

[0008] The purpose of this invention is to provide a cooling system and method for blocking the transmission of thermal runaway in battery cells. It aims to solve the technical problems in the prior art, such as the difficulty in completely blocking the transmission of thermal runaway between adjacent cells, the large amount of cooling agent required and its easy leakage, and the difficulty in meeting the energy density requirements of the battery. By using a temperature-sensitive triggering mechanism of the thermal relief module combined with a dual-parameter judgment mechanism of pressure and time, it can achieve precise positioning of the thermal runaway cell and directional release of the cooling agent. This effectively blocks the spread of thermal runaway while significantly reducing the amount of cooling agent used, reducing the system weight, and improving the safety and energy density of the battery.

[0009] This invention is achieved through the following technical solution: a cooling system for blocking the transmission of thermal runaway in battery cells, comprising a cooling agent delivery assembly, a gas delivery assembly, and a control assembly. The cooling agent delivery assembly includes a cooling agent storage tank, a first electric valve, a cooling agent delivery pump, a conversion interface, and a heat relief module connected in sequence. The heat relief module is made of hot melt material, encapsulated between the battery cells, and connected to the conversion interface through a delivery pipe. The gas delivery assembly includes an air pump, a gas flow meter, a second electric valve, and a buffer tank connected in sequence. The air pump is connected to a gas source, the buffer tank is connected to the conversion interface, and a pressure gauge is provided on the buffer tank. The control component includes a controller, which is electrically connected to a first electric valve, a cooling agent delivery pump, an air pump, a gas flow meter, a second electric valve, and a pressure gauge.

[0010] The heat relief module includes a heat-melt seal and two layers of heat-melt plates. The heat-melt seal is located at the opening at the end of the delivery pipe to seal the opening and simultaneously bond the two layers of heat-melt plates.

[0011] The hot melt pressing sheet is made of a low melting point metal alloy or hot melt adhesive; the hot melt sealing element is made of hot melt adhesive or microcrystalline wax, and the melting point or softening point of the hot melt sealing element is 10-20°C lower than that of the hot melt pressing sheet.

[0012] A boundary gasket is also provided between adjacent cells, and the boundary gasket is made of silicone rubber, fluororubber or fluorosilicone rubber.

[0013] The delivery pipe includes a main pipe and several branch pipes connected to the main pipe. The branch pipes are inserted between adjacent battery cells, and the heat relief module is installed at their ends. The main pipe is located on one side of the battery cell assembly and is connected to the conversion interface.

[0014] Both ends of the battery cell assembly are provided with rubber sheets and battery covers. The rubber sheets and battery covers encapsulate both ends of the battery cell assembly and the delivery pipe (including the main pipe and the branch pipe), forming a lateral discharge channel connecting adjacent battery cells. At least one end of the main pipe extends through the lateral discharge channel to the outside of the battery for connecting the conversion interface.

[0015] The delivery tube located inside the battery includes inner and outer layer materials. The inner layer material is made of two layers of thin film material stacked and sealed at the edges. The wall thickness of each thin film material is 0.02 to 0.06 mm and the width is 5 to 36 mm. The outer layer material is attached to both sides of the inner layer material. The outer layer material is 6 to 20 mm wider than the inner layer material and has a wall thickness of 0.1 to 0.4 mm.

[0016] The delivery pipe located outside the battery is made of stainless steel, aluminum alloy, or silicone rubber. Silicone rubber is preferred when the cooling agent is not a fluorinated organic solvent.

[0017] Another technical solution of the present invention is to provide a cooling method for blocking the thermal runaway transmission of battery cells using the above-mentioned cooling system, comprising the following operations: Under normal operating conditions, when the pressure inside the buffer tank is lower than the set lower limit, the controller opens the second electric valve and starts the air pump to inflate the buffer tank until the pressure reaches the set upper limit. Then, the controller closes the second electric valve and stops the air pump. When a cell experiences thermal runaway, the hot melt material in the thermal relief module that is in contact with it melts or softens, causing the thermal relief module to leak and the pressure in the buffer tank to drop. After the controller detects that the pressure in the buffer tank has dropped to the set lower limit, it opens the second electric valve and starts the air pump to inflate the buffer tank. If the controller determines that the actual inflation time required to rise from the set lower limit to the set upper limit is greater than the preset time threshold, it determines that a continuous leak has occurred, and then closes the second electric valve and stops the inflation pump, while opening the first electric valve and starting the cooling agent delivery pump to deliver the cooling agent to the heat relief module where the leak occurred via the conversion interface and delivery pipe. Cooling agent flows out from the leak and comes into contact with the surface of the thermally runaway battery cell to cool it down.

[0018] When the controller determines that the actual time for filling the buffer tank with gas is greater than a preset time threshold, it further checks whether the flow rate of the gas flow meter is within the normal range. If the flow rate is normal, it confirms that a leak has occurred and executes the cooling agent delivery step.

[0019] The preset time threshold is set in advance based on the characteristics of thermal runaway of the battery cell, the requirements for battery safety control, and the time required for normal inflation when the thermal pressure relief module is not leaking.

[0020] When the thermal pressure relief module does not leak, the inflation time required for the gas pressure in the buffer tank to rise from the lower limit to the upper limit is the normal inflation time T0; the preset time threshold is 1.5 to 6 times T0.

[0021] The cooling agent is selected from pure water, antifreeze water containing freezing point inhibitors, or fluorinated organic solvents.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) In this invention, a thermal pressure relief module with a hot-melt material is encapsulated between adjacent cells. The corresponding thermal pressure relief module will only be activated when the cell experiences thermal runaway, causing the local temperature to reach the melting or softening point of the hot-melt material. The controller determines that leakage is ongoing by observing changes in the buffer tank pressure and the extension of the inflation time, and then starts the cooling agent delivery pump to deliver the cooling agent only to the cell where thermal runaway has occurred. Compared to the traditional approach where the cell is always wrapped in cooling agent or the cooling agent is released over a large area, this invention achieves precise and on-demand release of the cooling agent, significantly reducing the amount of cooling agent used and the system weight, which is beneficial for improving the energy density of the battery.

[0023] (2) This invention utilizes a buffer tank, an air pump, and a pressure gauge to form a closed-loop detection circuit. By monitoring the pressure drop in the buffer tank and whether the actual time it takes for the pressure to rise from the lower limit to the upper limit exceeds a preset threshold, it confirms whether the thermal runaway module is experiencing continuous leakage. A flow meter is used to detect whether the air flow rate is normal, avoiding misjudgments of thermal runaway module leakage due to abnormal air pump function. This method is not affected by single pressure fluctuations, effectively distinguishes between normal pressure maintenance operation and actual thermal runaway leakage events, and is highly responsive and reliable in its judgment, avoiding false triggering or missed triggering.

[0024] (3) The thermal pressure relief module of the present invention adopts a structure of a hot-melt seal and two layers of hot-melt plates, and the melting point or softening point of the hot-melt seal is 10-20°C lower than that of the hot-melt plates. When the battery cell experiences thermal runaway, the hot-melt seal and the hot-melt plates melt or soften, causing the seal to fail and releasing a pressure signal. This can guide the cooling agent to flow out in a predetermined direction and make full contact with the surface of the battery cell, ensuring both the timeliness of the signal triggering and the distribution effect of the cooling agent.

[0025] (4) Under normal operating conditions and without thermal runaway, the thermal relief module remains sealed, no cooling agent flows in the delivery pipe, and the cooling agent storage tank and the battery cell are isolated by the first electric valve. The buffer tank only needs to maintain a small amount of gas pressure for detection, and the entire system is in a "dry" standby mode when not triggered, which fundamentally avoids the risk of coolant leakage that has long existed in traditional liquid cooling or immersion solutions.

[0026] (5) In this invention, the inner layer of the battery's internal delivery pipe is made of double-layer thin film material (polyimide, polyetheretherketone, metal foil, etc.) with a thickness of 0.02-0.06 mm and a width of 5-36 mm, with overlapping and edge sealing. The structure is thin and flexible, and can be embedded in the narrow gaps between the battery cells without affecting the cell stacking density. The external delivery pipe of the battery is made of materials such as stainless steel, aluminum alloy, or silicone rubber to ensure the strength and sealing of the connection with the conversion interface. At the same time, the main pipe extends to the outside of the battery through the lateral discharge channel formed by the rubber sheet and the battery cover plate, with good overall encapsulation, which facilitates modular production.

[0027] (6) The cooling agent selected in this invention can be pure water, antifreeze water containing freezing point inhibitors, or fluorinated organic solvents, etc., to adapt to different working environments (such as low temperature, high temperature, and high voltage insulation requirements), and can flexibly match the safety and performance requirements of cooling media for different application scenarios such as passenger cars, energy storage stations, and aircraft. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the cooling system.

[0029] Figure 2 This is a schematic diagram of the discharge channel L1 between battery cells.

[0030] Figure 3 This is a schematic diagram of the main and branch pipes of the battery's internal delivery system.

[0031] Figure 4 This is a schematic diagram of the main pipeline, branch pipelines, and thermal pressure relief module inside the battery.

[0032] Figure 5 This is a schematic diagram of the delivery pipe branch and thermal relief module located in the stacked battery cells.

[0033] Figure 6 This is a schematic diagram of the side discharge channel L2 for stacked cells.

[0034] Figure 7 This is a schematic diagram of the inner delivery tube with unsealed edges.

[0035] Figure 8 A schematic diagram of the inner delivery tube with edge sealing.

[0036] Figure 9 This is a schematic diagram of the internal delivery tubes of the battery, which are bonded between the outer layers and between the inner and outer layers.

[0037] Figure 10 This is a schematic diagram of the thermal pressure relief module.

[0038] Among them, 1—gas source, 2—air pump, 3—second electric valve, 4—gas flow meter, 5—cooling agent, 6—cooling agent storage tank, 7—cooling agent delivery pump, 8—delivery pipe, 8-1—main pipeline, 8-2—branch pipe, 8-3—inner layer delivery pipe, 9—first electric valve, 10—enclosure gasket, 11—heat relief module, 11-1—heat melt pressing sheet, 11-2—heat melt sealing element, 12—buffer tank, 13—pressure gauge, 14—power supply, 15—controller, 16—rubber sheet, 17—conversion interface, 18—battery cell, 19—battery cover plate, 20—inner layer material, 21—outer layer material. Detailed Implementation

[0039] The invention's objective, technical solution, and beneficial effects will be further explained in detail below.

[0040] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the claimed invention. Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0041] This invention relates to a cooling system and method for blocking the transmission of thermal runaway in battery cells. The cooling system comprises a cooling agent delivery component, a gas delivery component, and a control component. The cooling agent delivery component directionally delivers cooling agent 5 to the leaking thermal relief module 11 when thermal runaway occurs, allowing the cooling agent 5 to contact the surface of the thermally runaway cell and remove heat. The gas delivery component maintains the gas pressure within the buffer tank 12 and monitors the sealing status of the thermal relief module 11 in real time by detecting pressure changes. The control component detects the pressure and inflation time of the buffer tank 12 to determine if a continuous leak has occurred, and automatically controls the start and stop of the cooling agent delivery component accordingly. This achieves precise positioning of the thermally runaway cell and on-demand release of the cooling agent 5, effectively blocking the transmission of thermal runaway between adjacent cells, while significantly reducing the amount of cooling agent 5 used and the system weight, thus improving battery safety and energy density.

[0042] like Figure 1 As shown, the technical solution of the present invention can be further summarized in detail as follows: Cooling agent delivery assembly: includes cooling agent storage tank 6, first electric valve 9, cooling agent delivery pump 7, conversion interface 17 and heat relief module 11, wherein the heat relief module 11 is made of hot melt material, encapsulated between battery cells 18, and connected to conversion interface 17 through delivery pipe 8.

[0043] Gas delivery assembly: includes an air pump 2, a gas flow meter 4, a second electric valve 3 and a buffer tank 12. The air pump 2 is connected to the gas source 1, the buffer tank 12 is connected to the conversion interface 17, and a pressure gauge 13 is provided on the buffer tank 12.

[0044] Control components: include controller 15, which is electrically connected to the first electric valve 9, the cooling agent delivery pump 7, the air pump 2, the gas flow meter 4, the second electric valve 3, and the pressure gauge 13.

[0045] Under normal operating conditions, the buffer tank 12 is pressurized by opening the air pump 2 and the second electric valve 3, with the working pressure range of the buffer tank 12 preset to the lower limit P1 to the upper limit P2. After pressurization is completed, the air pump 2 and the second electric valve 3 are closed. At this time, the outlet end of the delivery pipe 8 is sealed by the thermal pressure relief module 11, and the pressure inside the buffer tank 12 remains unchanged. When the pressure inside the buffer tank 12 is lower than the set lower limit P1, the controller 15 automatically opens the second electric valve 3 and starts the air pump 2 to pressurize the buffer tank 12 until the pressure reaches the set upper limit P2, then closes the second electric valve 3 and stops the air pump 2.

[0046] When a cell 18 experiences thermal runaway, the molten material in the thermal relief module 11, which is in contact with it, melts or softens due to heat, causing the thermal relief module 11 to leak, and the pressure in the buffer tank 12 drops accordingly. After the controller 15 detects that the pressure in the buffer tank 12 has dropped to the set lower limit value P1, it immediately opens the second electric valve 3 and starts the air pump 2 to inflate the buffer tank 12.

[0047] If the controller 15 determines that the actual time required for the value to rise from the lower limit P1 to the upper limit P2 is greater than the preset time threshold, it determines that a continuous leak has occurred. At this time, the controller 15 immediately closes the second electric valve 3 and stops the inflation pump 2, while simultaneously opening the first electric valve 9 and starting the cooling agent delivery pump 7, delivering the cooling agent 5 through the conversion interface 17 and the delivery pipe 8 to the thermal depressurization module 11 where the leak occurred. The cooling agent 5 flows out from the leak and comes into contact with the surface of the thermal runaway battery cell, cooling the thermal runaway battery cell.

[0048] Furthermore, a gas flow meter 4 is installed between the air pump 2 and the buffer tank 12, and the controller 15 is electrically connected to the gas flow meter 4. When the controller 15 determines that the actual inflation time is greater than the set time threshold, it further checks whether the flow rate of the gas flow meter 4 is within the normal range; if the flow rate is normal, it confirms that a leak has occurred and executes the cooling agent delivery step.

[0049] In this invention, the preset time threshold is pre-set based on the characteristics of cell thermal runaway, battery safety control requirements, and the time required for normal inflation when the thermal relief module 11 is not leaking. Specifically, when the thermal relief module 11 is not leaking, the inflation time required for the gas pressure in the buffer tank 12 to rise from the lower limit P1 to the upper limit P2 is defined as the normal inflation time T0. This preset time threshold is 1.5 to 6 times T0, preferably 2 to 3 times T0.

[0050] In a specific embodiment of the present invention, such as Figures 2 to 5 As shown, the delivery pipe 8 includes a main pipe 8-1 and several branch pipes 8-2 connecting the main pipe 8-1. The branch pipes 8-2 are inserted between adjacent battery cells 18, and a heat relief module 11 is provided at their ends. A perimeter gasket 10 is also provided between the battery cells 18. Under the action of adjacent battery cells 18, a narrow battery cell discharge channel L1 is formed between the battery cells 18 and the perimeter gasket 10. The heat relief module 11 and the branch pipes 8-2 of the delivery pipe 8 are located in this channel L1 and are sandwiched between two battery cells 18. By applying pressure to the adjacent battery cells 18, the surface of the battery cells 18 can be made to make close contact with the heat relief module 11 and the perimeter gasket 10. The main pipe 8-1 is located on one side of the battery cell assembly (comprising stacked battery cells 18) and is connected to the conversion interface 17.

[0051] like Figure 6 As shown, rubber sheets 16 (made of a similar material to the perimeter gasket 10) and battery covers are provided at both ends of the battery cell assembly. The rubber sheets 16 and battery covers enclose both ends of the battery cell assembly and the delivery pipes 8 (including the main pipe 8-1 and the branch pipes 8-2), forming a lateral discharge channel connecting adjacent battery cells 18 (inter-cell discharge channel L1). At least one end of the main pipe 8-1 extends through the lateral discharge channel to the outside of the battery for connecting the conversion interface 17. The sides of the battery cell assembly, the rubber sheets 16, and the battery covers 19 together constitute the lateral discharge channel L2 for the cooling agent 5 and its vapor.

[0052] In one specific embodiment of the present invention, the delivery pipe 8 is divided into a portion located inside the battery and a portion located outside the battery, and the two portions are made of different materials and have different structures. Specifically, the delivery pipe 8 located outside the battery can be made of stainless steel, aluminum alloy, or silicone rubber, with aluminum alloy being the preferred material in general. However, when the cooling agent 5 is not a fluorinated organic solvent (such as when the cooling agent 5 is water or an antifreeze aqueous solution), silicone rubber is preferred. When a fluorinated organic solvent is used as the cooling agent, fluorosilicone rubber is preferred. The delivery pipe 8 located inside the battery and in contact with the cooling agent 5 is made of polyimide, polyetheretherketone, polyetherimide, polyethersulfone, or metal foil, with aluminum foil being the most preferred metal foil.

[0053] Regarding the structure of the delivery pipe 8, the delivery pipe 8 located inside the battery can be a single-layer high-temperature resistant and aging-resistant thin-walled conduit, such as made of polyimide, polyether ether ketone, polyetherimide or polyether sulfone, with a wall thickness of 0.02 to 0.05 mm.

[0054] It can also be made of a composite of inner and outer materials, and its structure and preparation method are as follows: Figure 7 As shown, two inner thin film materials are stacked, each with a wall thickness of 0.02–0.06 mm and a width of 5–36 mm. (As shown...) Figure 8 As shown, the area 1-3 mm from the edge of the superimposed inner layer film material is sealed to form an edge-sealed inner layer delivery tube 8-3.

[0055] Furthermore, as the inner film material, if aluminum foil is used, the two edge areas can be sealed by welding; if polyimide, polyetheretherketone, polyetherimide, or polyethersulfone is used, the two edge areas can be sealed by adhesive bonding; if thermoplastic polyimide, polyetheretherketone, polyetherimide, or polyethersulfone film is used, ultrasonic welding sealing can also be used. The outer layer material 21 can be 6–20 mm wider than the inner film and has a wall thickness of 0.1–0.4 mm, and is made of silicone rubber or fluorosilicone rubber sheet.

[0056] like Figure 9 As shown, two outer layer materials 21 are placed on either side of the sealed inner layer delivery tube 8-3, with the inner layer delivery tube 8-3 sandwiched in the middle. Using an adhesive of the same type as the outer layer materials 21, the two outer layer materials 21 are bonded and sealed together, as well as between the outer layer materials 21 and the inner layer delivery tube 8-3, thereby forming a channel for the flow of gas or cooling agent 5.

[0057] In a specific embodiment of the present invention, such as Figure 10 As shown, the heat relief module 11 consists of two layers of heat-melt pressing sheets 11-1 and a heat-melt sealing element 11-2. The two layers of heat-melt pressing sheets 11-1 sandwich the end opening of the branch pipe 8-2 in the middle, and the end opening of the branch pipe 8-2 is sealed by the heat-melt sealing element 11-2. The heat-melt sealing element 11-2 also bonds the two heat-melt pressing sheets 11-1 together. The total thickness of the heat relief module 11 is 0.5 to 4.0 mm, preferably 0.8 to 2.5 mm.

[0058] The parameters for the hot-melt tablet 11-1 are as follows: Thickness: 0.1–1.5 mm, preferably 0.2–0.5 mm; The distance from the edge of the inner diameter of the branch pipe 8-2 to the end opening is 2-18 mm, preferably 6-12 mm. Material selection: Low melting point alloys with melting points of 80-180℃ can be used, preferably low melting point alloys with melting points of 90-160℃, and most preferably tin-bismuth low melting point alloys; or hot melt adhesives with softening points of 80-180℃ can be used by ring and ball method, preferably hot melt adhesives with softening points of 90-160℃, and most preferably polyvinyl acetate, polyamide or polyurethane.

[0059] The parameters for the heat-fused seal 11-2 are as follows: The filling thickness is 0.01 to 0.06 mm into the end opening of the branch pipe 8-2 within the extrusion area of ​​the two hot-melt pressing sheets 11-1. Material selection: hot melt adhesive with a softening point of 60-160℃ using the ring and ball method, or microcrystalline wax with a melting point of 60-120℃; The melting point or softening point of the hot melt seal 11-2 is 10-20°C lower than that of the hot melt pressing sheet 11-1.

[0060] During bonding, after the hot-melt pressure plate 11-1 is bonded and fixed to the end of the branch pipe 8-2, the length of the hot-melt seal 11-2 extending beyond the area covered by the hot-melt pressure plate 11-1 inside the branch pipe 8-2 shall not exceed 1mm. This design not only helps prevent leakage at the end of the branch pipe 8-2 of the delivery pipe 8 before the cell 18 thermally runs away, but also facilitates rapid connection between the end of the branch pipe 8-2 and the outside after thermal runaway, ensuring that the cooling agent 5 flows out in a timely manner.

[0061] The parameters of the boundary gasket 10 are as follows: The enclosure gasket 10 is made of thermosetting rubber with a temperature resistance greater than 200°C, preferably silicone rubber, fluororubber, or fluorosilicone rubber. The difference between the thickness of the enclosure gasket 10 and the total thickness of the heat relief module 11 is 0 to 0.4 mm, preferably 0.1 to 0.2 mm.

[0062] In another specific embodiment of the present invention, a single-layer hot-melt pressure plate 11-1 can also be used as an alternative structure to the pressure relief module. Specifically, it consists of a single hot-melt pressure plate 11-1 and a hot-melt seal 11-2. The hot-melt pressure plate 11-1 presses down the opening of the branch pipe 8-2; the opening at the end of the branch pipe 8-2 is sealed by the hot-melt seal 11-2, and the hot-melt seal 11-2 bonds the hot-melt pressure plate 11-1 to the end of the branch pipe 8-2. The length of the hot-melt seal 11-2 extending beyond the area covered by the hot-melt pressure plate 11-1 inside the branch pipe 8-2 also does not exceed 1 mm. In this structure, the total thickness of the heat relief module 11 is 0.5 to 3.0 mm.

[0063] To achieve the goal of accurately releasing cooling and extinguishing agent to the thermal runaway battery cell and reducing the amount of cooling agent 5 used and the risk of leakage, this invention also discloses a method for controlling the release of cooling agent 5 based on the above-mentioned cooling system.

[0064] In this invention, the cooling agent 5 can be a water-based cooling agent or a fluorinated organic solvent. As a water-based cooling agent, pure water or an antifreeze aqueous solution containing a freezing point inhibitor can be used. The freezing point inhibitor is composed of one or more of ethylene glycol, propylene glycol, and diethylene glycol, with a mass concentration of 5-40% in the aqueous solution. After the cooling agent 5 comes into contact with the surface of the heating element, it can remove heat from the element. As a fluorinated organic solvent, a low-toxicity, non-flammable fluorinated organic solvent with a boiling point between 50 and 150°C can be used, preferably with a boiling point between 60 and 100°C. Preferred examples include perfluorohexane, 11,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 3,3-dichloro-1,1,1,2,2-pentafluoropropane, or ethyl nonafluoroisobutyl ether.

[0065] The complete workflow of this invention is as follows: (1) When cell 18 is at normal operating temperature, the cooling system is in standby mode. The controller 15 and pressure gauge 13 are connected to the power supply 14.

[0066] The power supply to the first electric valve 9, the second electric valve 3, the air pump 2, and the cooling agent delivery pump 7 is disconnected, and all valves are in the closed state.

[0067] The heat-melting pressure plate 11-1 and heat-melting seal 11-2 in the heat relief module 11 are not melted or softened, and the end of the branch pipe 8-2 of the delivery pipe 8 remains sealed.

[0068] The pipelines connecting the first electric valve 9, the cooling agent delivery pump 7, the buffer tank 12, the second electric valve 3, and the heat relief module 11 are connected and leak-free.

[0069] The internal gas pressure of buffer tank 12 is within the upper and lower limits, and the time for the pressure to naturally decrease from the upper limit to the lower limit is greater than 24 hours.

[0070] (2) Normal pressure replenishment process Pressure gauge 13 monitors the pressure inside buffer tank 12 in real time. When controller 15 detects that the pressure has reached the lower limit P1, it connects the power supply to air pump 2 and the second electric valve 3 to inflate buffer tank 12; gas flow meter 4 detects the inflation flow rate. When the pressure inside buffer tank 12 reaches the upper limit P2, controller 15 disconnects the power supply to air pump 2 and the second electric valve 3, closes the second electric valve 3, and stops inflation.

[0071] (3) Thermal runaway triggering and leakage detection When a cell 18 inside the battery experiences thermal runaway, the surface temperature of the thermally runaway cell rises. The heat-fused pressure plate 11-1 and heat-fused seal 11-2 in the heat relief module 11, which are in contact with the thermally runaway cell, melt or soften, causing the end of the branch pipe 8-2 to lose its seal and connect to the outside. The gas in the buffer tank 12 is rapidly discharged through the leakage path, and the pressure drops rapidly until it falls below the lower limit value P1. By adjusting parameters such as the pipe diameter and the thickness of the heat-fused pressure plate 11-1, the pressure drop time M1 is set to be less than 10 seconds (preferably less than 5 seconds).

[0072] (4) Continuous leakage determination and injection of cooling agent 5 Controller 15 records the actual time T during this inflation process for the pressure to rise from the lower limit P1 to the upper limit P2. x And compared with the normal inflation time T0: If T x >1.5×T0 (preferred T) x If the gas flow rate detected by the gas flow meter 4 is within the normal range (>2×T0), then the controller 15 determines that the thermal pressure relief module 11 is in a continuous leakage state.

[0073] At this time, controller 15 performs the following operations: Disconnect the power supply to the air pump 2 and the second electric valve 3, close the second electric valve 3, and stop inflation; Connect the power supply to the cooling agent delivery pump 7 and the first electric valve 9, open the first electric valve 9, and pump the cooling agent 5 into the delivery pipe 8.

[0074] Since the end of the branch pipe 8-2 in the thermal relief module 11 that is in contact with the thermal runaway cell has lost its seal, the cooling agent 5 injected into the delivery pipe 8 flows out from this end and comes into contact with the surface of the thermal runaway cell, thereby cooling the heated cell. The cooling agent 5 and its vapor in contact with the thermal runaway cell are discharged from the battery through the cell-to-cell discharge channel L1, the lateral discharge channel L2, and the battery casing exhaust valve. After the heat of the thermal runaway cell is carried away by the cooling agent 5, the thermal runaway transfer between adjacent cells 18 is effectively blocked.

[0075] The specific implementation of the present invention will be described below with reference to the embodiments. Of course, the scope of protection of the present invention is not limited to the following embodiments.

[0076] Example 1: Fabrication of the internal delivery tube of the battery (inner layer of aluminum foil + outer layer of silicone rubber) The inner layer material 20 uses a short aluminum foil with a thickness of 0.05mm, a width of 20mm, and a length of 20cm. The bottom length of the U-shaped structure is determined according to the thickness of the battery cell 18. Another long aluminum foil of the same thickness and width is taken and overlapped with the bottom of the U-shaped and L-shaped short aluminum foil. After cleaning the area 1.5mm away from the edge of the overlap, ultrasonic welding is used to seal it, forming a U-shaped and L-shaped structure (branch pipe 8-2) with the main pipe 8-1 at the bottom and branch pipes on the sides.

[0077] The outer layer material 21 consists of short silicone rubber sheets with a thickness of 0.2 mm, a width of 28 mm, and a length of 20 cm. These sheets are arranged in a U-shape and L-shape, tightly adhering to the inner aluminum foil, sandwiching the aforementioned inner aluminum foil with sealed edges and a channel. Another long silicone rubber sheet of the same thickness and width is taken and overlapped at the bottom with the bottom of the U-shaped and L-shaped short silicone rubber sheets, sandwiching the inner aluminum foil in between. The edge of the silicone rubber sheet is 4 mm wider than the edge of the aluminum foil. A layer of thermosetting silicone rubber adhesive is evenly applied to the side of both silicone rubber sheets closest to the aluminum foil. The inner aluminum foil is then sandwiched in between, and pressure is applied until the two silicone rubber sheets are firmly bonded.

[0078] Example 2: Fabrication of the internal delivery tube of the battery (inner layer of polyimide film + outer layer of silicone rubber) The inner layer material 20 is a polyimide film with a thickness of 0.03 mm, a width of 20 mm, and a length of 20 cm. The bottom length of the U-shaped structure is determined according to the thickness of the battery cell 18. Another long polyimide film of the same thickness and width is taken and overlapped with the bottom of the U-shaped and L-shaped short films. After cleaning the area 2 mm away from the edge of the overlap, it is plasma treated and then bonded and sealed with polyimide adhesive to form a U-shaped and L-shaped structure (branch pipe 8-2) with the main pipe 8-1 at the bottom and branch pipes on the sides.

[0079] The material, size and bonding method of the outer layer material 21 are the same as in Example 1.

[0080] Example 3: Preparation of a heat relief module (low-melting-point alloy hot-melt sheet + polyamide hot-melt seal) A circular tin-bismuth low-melting-point alloy sheet with a thickness of 0.4 mm, a diameter of 30 mm, and a melting point of 115 °C was prepared as a two-layer hot-melt pressure plate 11-1. A delivery tube 8 prepared according to Example 1 or Example 2 was selected, and the two tin-bismuth low-melting-point alloy discs were clamped to the end of a branch tube 8-2 of the delivery tube 8, ensuring that the center of the opening at the end of the branch tube 8-2 coincided with the center of the discs. A small amount of molten polyamide hot-melt adhesive with a softening point of 100 °C (as a hot-melt seal 11-2) was added inside and outside the opening at the end of the branch tube 8-2. Under the push of the metal plate outside the alloy discs, the two alloy discs squeezed the end of the branch tube 8-2 and overlapped and pressed firmly together. After cooling, the total thickness of the heat relief module 11 was measured. The length of the hot-melt seal 11-2 extending beyond the coverage area of ​​the hot-melt pressure plate 11-1 inside the branch tube 8-2 did not exceed 1 mm. The total thickness of the resulting heat relief module 11 did not exceed 1.4 mm.

[0081] Example 4: Preparation of a heat relief module (polyamide hot melt adhesive sheet + polyamide hot melt sealant) Prepare polyamide hot melt adhesive discs with a thickness of 0.4 mm, a diameter of 30 mm, and a softening point of 140 °C as two-layer hot melt press sheets 11-1. Select the delivery pipe 8 prepared according to Example 1 or Example 2, heat the end of the branch pipe 8-2 to 130 °C, and add a small amount of molten polyamide hot melt adhesive with a softening point of 122 °C (as a hot melt sealant 11-2) into the opening at the end of the branch pipe 8-2. Use two baffles with non-stick surfaces to press and seal the opening end of the branch pipe 8-2. After the polyamide hot melt sealant solidifies, remove the sealant that overflows from the opening at the end of the branch pipe 8-2, and then apply a small amount of the same molten sealant to the opening at the end of the branch pipe 8-2. Clamp the two polyamide hot melt adhesive discs between the end of the delivery pipe 8 and the branch pipe 8-2, so that the center of the opening at the end of the branch pipe 8-2 coincides with the center of the discs. Under the push of the outer baffles, the two discs press the end of the branch pipe 8-2 and overlap and press firmly together. After cooling, measure the total thickness of the heat relief module 11. The length of the heat-melted seal 11-2 extending beyond the area covered by the heat-melted pressure plate 11-1 inside the branch pipe 8-2 shall not exceed 1 mm. The total thickness of the resulting heat relief module 11 shall not exceed 1.4 mm.

[0082] Example 5: Construction of Cooling Agent Discharge Channel The enclosure gasket 10 between the battery cells 18 is a thermosetting silicone rubber sheet with a specific heat relief module 11 that is 0.1 mm thick, 15 mm wide, and the same length as the battery cell 18. When assembled in the aforementioned manner, the enclosure gasket 10 and the heat relief module 11 are sandwiched between the battery cells 18, forming a cooling agent discharge channel between the battery cells 18 (cell discharge channel L1).

[0083] A thermosetting silicone rubber sheet, 4 mm thick and 15 mm wide, with the same length as the side of the stacked battery cell (cell assembly), is attached to both sides of the stacked battery cell as a lateral enclosure gasket. The side of the stacked battery cell, the two lateral enclosure gaskets, and the battery casing cover together form the lateral cooling agent discharge channel L2.

[0084] The main pipe 8-1 for delivering the cooling agent 5, located on the side of the battery cell 18, is bonded to the side of the battery cell 18 and to the side of the battery cell 18 using thermosetting silicone rubber adhesive. Pressure strips are used at both ends of the stacked battery cells to apply pressure to the battery cell 18, ensuring tight contact between the battery cell 18 and the perimeter gasket 10 and the thermal relief module 11. An outward-facing vent valve is provided at the junction of the outlet of the side discharge channel L2 and the battery casing. An aluminum alloy conversion interface 17 is provided at the junction of the battery casing and the delivery pipe 8 for connecting the inner and outer delivery pipes 8 of the battery.

[0085] Example 6: Controller Parameter Settings The controller 15 has one power input port, two control signal input ports, and four power output ports. Two of the power output ports are connected to the air pump 2 and the second electric valve 3 via wires, and the other two power output ports are connected to the cooling agent delivery pump 7 and the first electric valve 9 via wires. The controller 15 is connected to the transmitters of the power supply 14, the gas flow meter 4, and the pressure gauge 13 via wires.

[0086] When the pressure is below the lower limit, the controller 15 supplies power to the air pump 2 and the second electric valve 3; when the pressure is above the upper limit, the controller 15 stops supplying power to the air pump 2 and the second electric valve 3; when the actual time for the pressure to rise from the lower limit to the upper limit is greater than the set time, and the flow rate displayed by the gas flow meter 4 is normal, the controller 15 stops supplying power to the air pump 2 and the second electric valve 3, and simultaneously supplies power to the cooling agent delivery pump 7 and the first electric valve 9. Example 7: Cooling System Integration and Parameter Operation An aluminum alloy pipe with an inner diameter of 10 mm is used to connect the gas source 1, the air pump 2, the gas flow meter 4, the second electric valve 3, the buffer tank 12, the cooling agent delivery pump 7, the first electric valve 9, the cooling agent storage tank 6, the pressure gauge 13, and the conversion interface 17; a wire is used to connect the power supply 14, the controller 15, the air pump 2, the gas flow meter 4, the second electric valve 3, the cooling agent delivery pump 7, the first electric valve 9, and the pressure gauge 13; the conversion interface 17 is connected to the heat relief module 11 using a delivery pipe 8 prepared in Example 1 or Example 2.

[0087] The buffer tank 12 is a 1L aluminum alloy gas storage tank. The upper part of the tank has an opening for connection to the pressure gauge 13 and the second electric valve 3, while the bottom has an opening for connection to the pipeline between the cooling agent delivery pump 7 and the conversion interface 17. The gas flow rate of the inflation pump 2 is adjustable between 12 and 50 mL / s; the flow rate of the cooling agent delivery pump 7 is adjustable between 5 and 20 mL / s. The gas source 1 can be nitrogen or filtered air. The cooling agent 5 can be selected from pure water, a 40% propylene glycol aqueous solution, or ethyl nonafluoroisobutyl ether, depending on the battery ambient temperature.

[0088] The upper limit of the pressure inside the buffer tank 12 is set to 0.2 atm (gauge pressure), and the lower limit is 0.1 atm. When the controller 15 energizes the air pump 2 and the second electric valve 3 to inflate the buffer tank 12, if the time it takes for the pressure in the buffer tank 12 to rise from 0.1 atm to 0.2 atm exceeds 20 seconds, and the gas flow meter detects that the inflation flow is normal, the controller 15 connects the power supply to the cooling agent delivery pump 7 and the first electric valve 9, opens the first electric valve 9 to pump the cooling agent 5 into the delivery pipe 8, and simultaneously disconnects the power supply to the air pump 2 and the second electric valve 3, closes the second electric valve 3, and stops inflation. The cooling agent 5 flowing out from the thermal relief module 11 contacts the surface of the battery cell 18 and plays a cooling role, thereby preventing thermal runaway from being transmitted between adjacent battery cells 18.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A cooling system for blocking the transmission of thermal runaway in a battery cell, characterized in that: Includes cooling agent delivery components, gas delivery components, and control components. The cooling agent delivery assembly includes a cooling agent storage tank (6), a first electric valve (9), a cooling agent delivery pump (7), a conversion interface (17), and a heat relief module (11) connected in sequence. The heat relief module (11) is made of hot melt material, encapsulated between battery cells (18), and connected to the conversion interface (17) through a delivery pipe (8). The gas delivery assembly includes an air pump (2), a gas flow meter (4), a second electric valve (3) and a buffer tank (12) connected in sequence. The air pump (2) is connected to a gas source (1), the buffer tank (12) is connected to the conversion interface (17), and a pressure gauge (13) is provided on the buffer tank (12). The control component includes a controller (15), which is electrically connected to a first electric valve (9), a cooling agent delivery pump (7), an air pump (2), a gas flow meter (4), a second electric valve (3), and a pressure gauge (13).

2. The cooling system according to claim 1, characterized in that: The heat relief module (11) includes a heat-melt seal (11-2) and two heat-melt plates (11-1). The heat-melt seal (11-2) is located at the opening at the end of the delivery pipe (8) to seal the opening and simultaneously bond the two heat-melt plates (11-1).

3. The cooling system according to claim 2, characterized in that: The hot melt pressing sheet (11-1) is made of a low melting point metal alloy or hot melt adhesive; the hot melt sealing element (11-2) is made of hot melt adhesive or microcrystalline wax, and the melting point or softening point of the hot melt sealing element (11-2) is 10-20°C lower than that of the hot melt pressing sheet (11-1).

4. The cooling system according to claim 2, characterized in that: A boundary gasket (10) is also provided between adjacent cells (18), and the boundary gasket (10) is made of silicone rubber, fluororubber or fluorosilicone rubber.

5. The cooling system according to claim 1, characterized in that: The delivery pipe (8) includes a main pipe (8-1) and several branch pipes (8-2) that connect to the main pipe (8-1). The branch pipes (8-2) are inserted between adjacent cells (18), and the heat relief module (11) is provided at their ends. The main pipe (8-1) is located on one side of the cell assembly and is connected to the conversion interface (17).

6. The cooling system according to claim 5, characterized in that: The battery cell assembly has rubber sheets (16) and battery covers (19) on both sides. The rubber sheets (16) and battery covers (19) encapsulate the two sides of the battery cell assembly and the delivery pipe (8) together, forming a lateral discharge channel connecting adjacent battery cells (18). At least one end of the main pipe (8-1) extends through the lateral discharge channel to the outside of the battery for connecting the conversion interface (17).

7. The cooling system according to claim 6, characterized in that: The delivery tube (8) located inside the battery includes inner and outer layer materials. The inner layer material (20) is an inner delivery tube (8-3) made of two layers of thin film material stacked and sealed at the edges. The wall thickness of each thin film material is 0.02 to 0.06 mm and the width is 5 to 36 mm. The outer layer material (21) is attached to both sides of the inner delivery tube (8-3). The outer layer material (21) is 6 to 20 mm wider than the inner layer material (20) and has a wall thickness of 0.1 to 0.4 mm.

8. The cooling system according to claim 6, characterized in that: The delivery pipe (8) located outside the battery is made of stainless steel, aluminum alloy or silicone rubber.

9. A cooling method for blocking the thermal runaway propagation of a battery cell using the cooling system described in any one of claims 1 to 8, characterized in that: Includes the following operations: Under normal operating conditions, when the pressure in the buffer tank (12) is lower than the set lower limit, the controller (15) opens the second electric valve (3) and starts the air pump (2) to inflate the buffer tank (12) until the pressure reaches the set upper limit, then closes the second electric valve (3) and stops the air pump (2). When a certain cell (18) experiences thermal runaway, the hot melt material in the thermal relief module (11) in contact with it melts or softens, causing the thermal relief module (11) to leak, and the pressure in the buffer tank (12) drops; after the controller (15) detects that the pressure in the buffer tank (12) drops to the set lower limit value, it opens the second electric valve (3) and starts the air pump (2) to inflate the buffer tank (12); If the controller (15) determines that the actual time required to rise from the set lower limit to the set upper limit is greater than the preset time threshold, it determines that a continuous leak has occurred, and then closes the second electric valve (3) and stops the air pump (2), while opening the first electric valve (9) and starting the cooling agent delivery pump (7), and delivering the cooling agent (5) to the heat relief module (11) where the leak occurred through the conversion interface (17) and delivery pipe (8); Cooling agent (5) flows out from the leak and comes into contact with the surface of the thermal runaway battery cell to cool the thermal runaway battery cell.

10. The cooling method according to claim 9, characterized in that: When the controller (15) determines that the actual time for filling the buffer tank (12) with gas is greater than the preset time threshold, it further detects whether the flow rate of the gas flow meter (4) is within the normal range. If the flow rate is normal, it confirms that a leak has occurred and performs the cooling agent delivery step.

11. The cooling method according to claim 9, characterized in that: The preset time threshold is set in advance based on the thermal runaway characteristics of the cell (18), the battery safety control requirements, and the time required for normal inflation when the thermal pressure relief module (11) is not leaking.

12. The cooling method according to claim 9, characterized in that: When the heat relief module (11) does not leak, the inflation time required for the gas pressure in the buffer tank (12) to rise from the lower limit to the upper limit is the normal inflation time T0; the preset time threshold is 1.5 to 6 times T0.

13. The cooling method according to claim 9, characterized in that: The cooling agent (5) is selected from pure water, antifreeze water containing freezing point inhibitors, or fluorinated organic solvents.

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