Magnetorheological fluid type battery thermal runaway flame retardant device and control method thereof

Abstract

The application provides a magnetorheological fluid type battery thermal runaway flame retardant device and a control method thereof, and belongs to the technical field of safety protection of new energy automobile power batteries, wherein the magnetorheological fluid type battery thermal runaway flame retardant device comprises a flame retardant space, a flame retardant storage module, an elastic energy storage module, a magnetorheological fluid medium and an electromagnetic coil; the flame retardant space comprises a flame retardant storage area and a magnetorheological fluid cavity; the flame retardant storage module has flame retardant substances inside; one end of the elastic energy storage module has a sharp part for piercing the flame retardant storage module; under the electrified state of the electromagnetic coil, the magnetorheological fluid medium locks the elastic energy storage module in the energy storage state; under the de-energized state of the electromagnetic coil, the sharp part on the elastic energy storage module pierces the flame retardant storage module to release the flame retardant substances. The application solves the technical problems that the existing battery thermal runaway protection device excessively depends on the continuous power supply of the BMS battery system and is prone to failure under extreme working conditions by using the core working mechanism of magnetorheological fluid medium solid-liquid phase change controlled by a magnetic field.

Description

Technical Field

[0001] This application belongs to the technical field of safety protection for power batteries of new energy vehicles, and more specifically, it relates to a flame-retardant device for thermal runaway of magnetorheological fluid batteries and its control method. Background Technology

[0002] With the rapid development of the new energy vehicle industry, the thermal safety issues of lithium-ion batteries, as a core power source, are becoming increasingly prominent. Battery thermal runaway refers to a serious accident caused by a rapid increase in battery temperature due to internal short circuits, overcharging, mechanical damage, etc., which can trigger a chain reaction and ultimately lead to fire and explosion.

[0003] Existing battery thermal runaway protection technologies mainly include: 1. Automatic Aerosol Fire Suppression System: This system detects a fire using temperature or smoke sensors and triggers an electric detonator or heater to release an aerosol extinguishing agent. The response time of this system is typically 300-1000 milliseconds, and it relies on an external power supply and complex control logic; it will fail if the control circuitry is damaged.

[0004] 2. Solenoid valve driven fire extinguishing system: The release of extinguishing agent is controlled by a solenoid valve, which has a fast response speed (100-500ms), but requires continuous power supply (5-20W). Once the battery system (BMS) fails or the power is interrupted, the entire protection system will fail.

[0005] Therefore, there is an urgent need for a battery thermal runaway flame retardant device that can quickly respond to flame retardant action in the event of BMS battery system failure or power outage. Summary of the Invention

[0006] The purpose of this application is to provide a magnetorheological fluid battery thermal runaway flame retardant device and its control method, so as to solve the technical problem that the battery thermal runaway protection function in the prior art relies too much on the BMS battery system and continuous power supply.

[0007] To achieve the above objectives, in a first aspect, the technical solution adopted in this application is: to provide a magnetorheological fluid-based battery thermal runaway flame-retardant device for installation in a battery compartment, wherein the battery compartment includes a shell and at least two battery cells; the magnetorheological fluid-based battery thermal runaway flame-retardant device includes: A flame-retardant space is disposed between two adjacent battery cells, and the flame-retardant space includes a flame-retardant storage area and a magnetorheological fluid cavity; A flame-retardant storage module is disposed within the flame-retardant storage area and contains flame-retardant materials. An elastic energy storage module is disposed within the magnetorheological fluid cavity. One end of the elastic energy storage module has a spike for piercing the flame-retardant storage module to release the flame-retardant material. A magnetorheological fluid medium is filled within the magnetorheological fluid cavity, encapsulating the elastic energy storage module therein; and An electromagnetic coil is arranged around the inner wall of the magnetorheological fluid cavity and is used to connect to the BMS battery system to generate a magnetic field on the magnetorheological fluid medium. When the electromagnetic coil is energized, the magnetorheological fluid medium is in a solidified state and locks the elastic energy storage module in an energy storage state. At this time, the elastic energy storage module has elastic potential energy toward the flame-retardant storage module. When the electromagnetic coil is de-energized, the magnetorheological fluid medium instantly transforms into a liquefied state and releases the locking restriction on the elastic energy storage module. The spikes on the elastic energy storage module pierce the flame-retardant storage module and release the flame-retardant substance.

[0008] In conjunction with the first aspect, in one possible implementation, the flame-retardant storage module includes: A sealing film sleeve is disposed within the flame-retardant storage area and has an enclosed space inside; both sides of the sealing film sleeve face the space above the adjacent battery cell. The flame-retardant material is filled inside the sealing membrane sleeve.

[0009] In conjunction with the first aspect, in one possible implementation, the sealing membrane sleeve comprises, from the outside to the inside: Polyamide film layer, with a thickness of 10-15 μm; Aluminum foil layer, with a thickness of 30-50μm; and A polyethylene or ethylene-tetrafluoroethylene copolymer film layer with a thickness of 20-30 μm; The outer side of the sealing film refers to the side facing away from the flame-retardant material, and the inner side refers to the side facing the flame-retardant material.

[0010] In conjunction with the first aspect, in one possible implementation, the flame-retardant material, from the flame-retardant storage area to the magnetorheological fluid cavity, sequentially includes: The vapor phase fire extinguishing layer is composed of multiple perfluorohexanone or heptafluoropropane microcapsules; The physically expanded layer is composed of expandable graphite particles; and The ceramicized layer is a composite of aluminum hydroxide and silicone rubber.

[0011] In conjunction with the first aspect, in one possible implementation, the resilient energy storage module includes: The base is located at the bottom of the flame-retardant space; An energy storage spring is disposed on the base and enclosed within the magnetorheological fluid medium; and A needle seat is disposed on the top of the energy storage spring, and the spike is disposed on the needle seat.

[0012] In conjunction with the first aspect, in one possible implementation, the magnetorheological fluid cavity has an opening at its bottom, the base is used to close the opening, and positioning grooves are provided on both sides of the opening; the elastic energy storage module further includes: A lifting handle is slidably mounted on the base. Two positioning rods are slidably disposed in the base, and the positioning rods correspond one-to-one with the positioning slots. The outer ends of the positioning rods are used to insert into the corresponding positioning slots. Two hinged rods, each corresponding one-to-one with one of the two positioning rods, each hinged rod having one end hinged to the lifting handle and the other end hinged to the positioning rod; and An elastic reset element is disposed within the base and connected to the lifting handle; when the elastic reset element is in a free state, the positioning rod is simultaneously located within the base and the positioning groove.

[0013] In conjunction with the first aspect, in one possible implementation, the magnetorheological fluid medium comprises: Carbonyl iron powder, volume fraction 35-45%, particle size 2-8μm; Sodium dodecylbenzenesulfonate surfactant, volume fraction 0.1-0.3%; and Fumed silica thixotropic agent, volume fraction 0.5-1.5%; The remainder is a carrier liquid, which is a mixture of deionized water and ethylene glycol, with a volume ratio of deionized water to ethylene glycol of 3:1 to 4:1.

[0014] In conjunction with the first aspect, in one possible implementation, the magnetorheological fluid battery thermal runaway flame-retardant device further includes: A metal thermally conductive layer, corresponding one-to-one with each of the battery cells, is disposed above each battery cell; and A temperature sensor is disposed below the metal thermally conductive layer and connected to the BMS battery system; Specifically, when the temperature sensor detects that the temperature value has reached the warning threshold, the BMS battery system cuts off the power supply to the electromagnetic coil.

[0015] Secondly, this application also provides a flame-retardant control method for thermal runaway of magnetorheological fluid batteries, applied to the aforementioned flame-retardant device for thermal runaway of magnetorheological fluid batteries, comprising: The electromagnetic coil is energized and generates a magnetic field, the magnetorheological fluid medium remains in a solidified state, the elastic energy storage module is locked in an energy storage state and has elastic potential energy toward the flame-retardant storage module, and a safe distance is maintained between the spike and the flame-retardant storage module. After the BMS battery system fails or the vehicle's main power is cut off, the electromagnetic coil is de-energized and the magnetic field disappears. The magnetorheological fluid medium recovers to a liquid state within 50-100ms and releases the locking restriction on the elastic energy storage module. The elastic energy storage module drives the spike to pierce the flame-retardant storage module and release the flame-retardant material.

[0016] In conjunction with the second aspect, in one possible implementation, a temperature sensor is disposed above the battery cell and is connected to the BMS battery system; when the temperature sensor detects that the temperature of the battery cell has reached a warning threshold, the BMS battery system cuts off the power supply to the electromagnetic coil.

[0017] The beneficial effects of the magnetorheological fluid-based battery thermal runaway flame retardant device provided in this application are as follows: Compared with the prior art, this application accurately solves the technical problems of existing battery thermal runaway protection devices that rely too much on the BMS battery system for continuous power supply, are prone to failure under extreme conditions, and have slow response by controlling the solid-liquid phase change of the magnetorheological fluid medium through the core working mechanism of magnetic field control.

[0018] The device uses the magnetic field generated by the energized electromagnetic coil as the sole condition for the solidification and locking of the magnetorheological fluid. The protection action is triggered immediately upon power failure, without the need for continuous power supply and complex electronic control logic. Even if the BMS battery system fails, the vehicle power is interrupted, or the circuit is physically damaged, the magnetorheological fluid will automatically liquefy after the magnetic field of the electromagnetic coil disappears, and the elastic energy storage module can act autonomously. This fundamentally eliminates the loss of protection function caused by power failure and meets the failure protection safety design requirements under extreme thermal runaway conditions.

[0019] Under the action of an external magnetic field, the magnetorheological fluid medium can complete the reversible transformation of liquefaction and solidification in a very short time. When energized, it solidifies instantly to form a rigid locking structure, which stably constrains the elastic energy storage module in a contracted state. After the power is cut off, the magnetic field disappears instantly, and the magnetorheological fluid quickly returns to a liquid state. The elastic energy storage module can instantly drive the spikes to pierce the flame-retardant storage module. The response speed is better than that of traditional electronically controlled and temperature-driven protection devices. It can intervene in the early stage of the battery thermal runaway chain reaction and effectively curb the spread of heat.

[0020] The beneficial effects of the magnetorheological fluid battery thermal runaway flame retardant control method provided in this application are as follows: Compared with the prior art, this application achieves the core control effects of extremely low energy consumption, millisecond-level response, pure passive triggering, and failure safety through a simplified control logic of power-on solidification lock-in and power-off liquefaction release, which subverts the control mode of traditional protection devices that rely on continuous power supply and complex electronic control.

[0021] Under normal operating conditions, the electromagnetic coil is energized, causing the magnetorheological fluid to solidify rapidly. The yield stress is sufficient to lock the elastic energy storage module. The device exists only as a solid spacer, with no additional operating losses or failure risks, and it operates stably for a long time. Under thermal runaway conditions, after the BMS battery system fails or the vehicle power is cut off, the magnetorheological fluid quickly returns to a liquid state within 50-100ms. The elastic energy storage module releases its action instantaneously, puncturing the flame-retardant storage module and releasing flame-retardant substances. The total response time is much shorter than that of traditional aerosol and solenoid valve driven systems, and it can effectively block the thermal runaway in its early stages. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A cross-sectional view of a magnetorheological fluid battery thermal runaway flame retardant device in normal working condition, provided in an embodiment of this application; Figure 2 A cross-sectional view of a magnetorheological fluid battery thermal runaway flame retardant device in a thermal runaway state, provided in an embodiment of this application. Figure 3 A cross-sectional view of the positioning groove provided in an embodiment of this application; Figure 4 A cross-sectional view of the flexible energy storage module provided in the embodiment of this application when it is in normal working condition; Figure 5 A cross-sectional view of the flexible energy storage module provided in the embodiments of this application when it is in a replacement state.

[0024] The labels for the attached figures are as follows: 1. Battery compartment; 11. Outer casing; 12. Battery cell; 13. Flame-retardant space; 131. Positioning slot; 2. Flame-retardant storage module; 21. Flame-retardant material; 22. Sealing membrane sleeve; 3. Elastic energy storage module; 31. Spike; 32. Base; 33. Energy storage spring; 34. Spike seat; 35. Lifting handle; 36. Positioning rod; 37. Hinge rod; 38. Elastic reset component; 4. Magnetorheological fluid medium; 5. Electromagnetic coil; 6. Metal thermally conductive layer; 7. Temperature sensor. Detailed Implementation

[0025] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the described embodiments are only a part of the embodiments of this application, not all of them. The specific embodiments described herein are only used to explain this application and are not intended to limit this application. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] It should be further noted that the accompanying drawings and embodiments of this application mainly describe the concept of this application. Based on this concept, some specific forms and arrangements of connection relationships, positional relationships, power mechanisms, power supply systems and control systems may not be fully described. However, under the premise that those skilled in the art understand the concept of this application, they can implement the above-mentioned specific forms and arrangements in a well-known manner.

[0027] The present application provides a flame-retardant device and control method for thermal runaway of magnetorheological fluid batteries.

[0028] like Figure 1 and Figure 2 As shown, the first embodiment of this application provides a flame-retardant device for thermal runaway of a magnetorheological fluid battery, which is installed in a battery compartment 1. The battery compartment 1 includes a shell 11 and at least two battery cells 12. The flame-retardant device for thermal runaway of a magnetorheological fluid battery includes a flame-retardant space 13, a flame-retardant storage module 2, an elastic energy storage module 3, a magnetorheological fluid medium 4, and an electromagnetic coil 5.

[0029] A flame-retardant space 13 is disposed between two adjacent cells 12. The flame-retardant space 13 includes a flame-retardant storage area and a magnetorheological fluid cavity. A flame-retardant storage module 2 is disposed within the flame-retardant storage area and contains a flame-retardant material 21. An elastic energy storage module 3 is disposed within the magnetorheological fluid cavity. One end of the elastic energy storage module 3 has a spike 31 for piercing the flame-retardant storage module 2 to release the flame-retardant material 21.

[0030] The magnetorheological fluid medium 4 fills the magnetorheological fluid cavity and encloses the elastic energy storage module 3 within it. Electromagnetic coils 5 are arranged around the inner wall of the magnetorheological fluid cavity and are used to connect to the BMS battery system to generate a magnetic field on the magnetorheological fluid medium 4.

[0031] When the electromagnetic coil 5 is energized, the magnetorheological fluid medium 4 is in a solidified state and locks the elastic energy storage module 3 in an energy storage state. At this time, the elastic energy storage module 3 has elastic potential energy toward the flame-retardant storage module 2.

[0032] When the electromagnetic coil 5 is de-energized, the magnetorheological fluid medium 4 instantly transforms into a liquefied state and releases the locking restriction on the elastic energy storage module 3. The spikes 31 on the elastic energy storage module 3 pierce the flame-retardant storage module 2 and release the flame-retardant substance 21.

[0033] Magnetorheological fluid (MRF) is a smart material formed by micron-sized magnetic particles suspended in a carrier fluid. Under the action of an external magnetic field, MRF can transform from a liquid state (viscosity of about 0.1-1 Pa·s) to a solid-like state (yield stress of up to 20-100 kPa) within milliseconds, and this process is completely reversible.

[0034] The magnetorheological fluid medium 4 can undergo a reversible transformation from liquefaction to solidification in a very short time under the action of an external magnetic field. Upon energization, it solidifies instantly to form a rigid locking structure, stably constraining the elastic energy storage module 3 into a contracted state. After power is cut off, the magnetic field disappears instantly, and the magnetorheological fluid medium 4 quickly returns to a liquid state. It should be noted that the above characteristics of the magnetorheological fluid medium 4 belong to existing technology.

[0035] After the magnetorheological fluid medium 4 returns to a liquid state, the elastic energy storage module 3 can instantly release elastic potential energy, driving the spike 31 to pierce the flame-retardant storage module 2 and release the flame-retardant substance 21 for flame retardancy. The response speed is better than that of traditional electronically controlled and temperature-driven protection devices, and it can intervene in the early stage of the battery thermal runaway chain reaction, effectively curbing the spread of heat.

[0036] This embodiment provides a magnetorheological fluid-based battery thermal runaway flame-retardant device. Compared with the prior art, it precisely solves the technical problems of existing battery thermal runaway protection devices that rely too much on the BMS battery system for continuous power supply, are prone to failure under extreme conditions, and have slow response by controlling the solid-liquid phase change of the magnetorheological fluid medium 4 through the core working mechanism of magnetic field control.

[0037] The device uses the magnetic field generated by the energized electromagnetic coil 5 as the sole condition for the solidification and locking of the magnetorheological fluid. The protection action is triggered immediately upon power failure, without the need for continuous power supply and complex electronic control logic. Even if the BMS battery system fails, the vehicle power supply is interrupted, or the circuit is physically damaged, the magnetorheological fluid will automatically liquefy after the magnetic field of the electromagnetic coil 5 disappears, and the elastic energy storage module 3 can act autonomously. This fundamentally eliminates the loss of protection function caused by power supply failure and meets the failure protection safety design requirements under extreme thermal runaway conditions.

[0038] The device is embedded in the flame-retardant space 13 of the adjacent battery cell 12. The flame-retardant storage module 2 is arranged at the top of the gap, the elastic energy storage module 3 is located below the flame-retardant storage module 2, and the magnetorheological fluid completely fills the gap and wraps the elastic energy storage module 3. The structure is compact and does not occupy additional space. It does not require major modifications to the original structure of the battery compartment 1 and the battery cell 12 module, and can be directly adapted to the battery compartment 1 structure of multi-cell 12 combination.

[0039] Under normal operating conditions, the solidified magnetorheological fluid forms a solid support, which can not only stably lock the elastic energy storage module 3 and prevent accidental triggering under daily operating conditions, but also serve as a structural support for the gap between the battery cells 12, improving the overall mechanical stability of the battery module. The core components of the device have no complex and easily damaged electronic parts, and have strong resistance to vehicle vibration, high and low temperature alternation, and electromagnetic interference. It has high long-term operational reliability and is suitable for the full life cycle usage needs of new energy vehicles.

[0040] like Figures 1 to 2 As shown, this application provides a further specific implementation method based on the first implementation method as follows: The flame-retardant storage module 2 includes a sealing film sleeve 22, which is disposed in the flame-retardant storage area and has a closed space inside; the two sides of the sealing film sleeve 22 face the space above the adjacent battery cell 12 respectively; wherein, the flame-retardant material 21 is filled inside the sealing film sleeve 22.

[0041] The sealing membrane sleeve 22 forms a fully enclosed storage cavity for the flame-retardant material 21 within the flame-retardant storage area. This effectively isolates the battery compartment 1 from external corrosive media such as electrolyte volatiles, air, moisture, and dust, significantly extending the effective storage period of the flame-retardant material 21 and the overall service life of the device, meeting the requirements for long-term stable use throughout the entire life cycle of new energy vehicles. Simultaneously, the sealing membrane sleeve 22 employs a flexible sealing structure, tightly conforming to the spatial shape of the flame-retardant storage area, preventing leakage or uneven distribution of the flame-retardant material 21, further ensuring the stability of long-term storage.

[0042] The sealing membrane sleeve 22 is precisely aligned with the core heating and ignition areas above the adjacent battery cells 12, creating a directional release and short-path diffusion channel for the flame-retardant material 21. When the spikes 31 of the elastic energy storage module 3 pierce the sealing membrane sleeve 22, the flame-retardant material 21 can quickly and evenly cover the core area of ​​the fire source along the side wall of the battery cell 12 and the flame-retardant space 13, greatly shortening the action response distance and diffusion time of the flame-retardant material 21, rapidly suppressing the combustion reaction and blocking the heat transfer path. In addition, the flexible membrane sleeve can be directly embedded in the gap between the battery cells 12 without occupying additional space in the battery compartment 1 or modifying the original structure of the battery module, greatly improving the versatility and cross-vehicle compatibility of the device.

[0043] like Figures 1 to 2 As shown, this application provides a further specific implementation method based on the first implementation method as follows: The sealing film sleeve 22 comprises, from the outside to the inside, a polyamide film layer, an aluminum foil layer, and a polyethylene or ethylene-tetrafluoroethylene copolymer film layer.

[0044] The polyamide film layer has a thickness of 10-15 μm; the aluminum foil layer has a thickness of 30-50 μm; and the polyethylene or ethylene-tetrafluoroethylene copolymer film layer has a thickness of 20-30 μm. The outer side of the sealing film sleeve 22 refers to the side facing away from the flame-retardant material 21, and the inner side refers to the side facing the flame-retardant material 21.

[0045] The outer polyamide film layer possesses excellent mechanical strength, wear resistance, and electrolyte corrosion resistance, protecting against vibration and friction during vehicle operation and internal chemical corrosion of the battery, thus safeguarding the integrity of the inner film layer structure. The middle aluminum foil layer provides superior gas and moisture barrier properties, completely preventing external environmental intrusion that could lead to the failure of the flame retardant 21, while also providing adequate structural support to maintain the formed state of the sealing film sleeve 22. The inner polyethylene / ethylene-tetrafluoroethylene copolymer film layer exhibits strong chemical stability and excellent flexibility, showing no chemical reaction upon direct contact with the flame retardant 21, and its puncture strength is controllable. It can withstand minor external impacts without damage in daily use, and can be quickly and effortlessly punctured by the spikes 31 in the event of thermal runaway.

[0046] The thickness of each membrane layer is strictly limited to the range of 10-50μm. The total thickness is thin and does not occupy space. This ensures the comprehensive protective performance of the sealing membrane sleeve 22, while avoiding puncture delay and slow response due to excessive membrane thickness. It ensures that the rhythm is perfectly matched with the millisecond-level phase change of the magnetorheological fluid and the instantaneous action of the elastic energy storage module 3.

[0047] like Figures 1 to 2 As shown, this application provides a further specific implementation method based on the first implementation method as follows: The flame-retardant material 21, from the flame-retardant storage area to the magnetorheological fluid cavity, sequentially comprises a vapor-phase extinguishing layer, a physical expansion layer, and a ceramicization layer. The vapor-phase extinguishing layer consists of multiple perfluorohexanone or heptafluoropropane microcapsules with a particle size of 50-100 μm and a filling rate of 60%, used for rapid vapor-phase extinguishing. The physical expansion layer consists of expandable graphite particles with a particle size of 0.5-1.5 mm and an expansion ratio of 200-400 times, used to form a heat-insulating worm-like carbon layer. The ceramicization layer is a composite of aluminum hydroxide and silicone rubber in a 1:1 mass ratio, used to decompose upon heating to generate an alumina ceramic layer with a temperature resistance >1500℃.

[0048] The upper layer consists of perfluorohexanone / heptafluoropropane microcapsules in a gaseous fire extinguishing layer. When heated, the microcapsules rupture instantly, releasing a clean gaseous fire extinguishing agent that quickly penetrates into the battery cell 12 and the electrode interface, interrupting the combustion chain reaction and achieving millisecond-level open flame suppression. Moreover, the fire extinguishing agent leaves no residue and is non-corrosive to circuits, avoiding damage to the internal components of the battery caused by traditional fire extinguishing agents.

[0049] The middle layer, composed of expandable graphite particles, expands rapidly upon heating, forming a fluffy and porous insulating carbon layer that instantly fills the gaps between the battery cells 12, creating a thermal barrier with low thermal conductivity. This effectively blocks the heat transfer from the thermally runaway battery cell 12 to adjacent battery cells 12, significantly slowing down the rate of heat spread and allowing sufficient time for firefighting.

[0050] The lower ceramicized layer, composed of aluminum hydroxide and silicone rubber composite, decomposes upon heating to generate a high-temperature resistant ceramic layer. This maintains structural integrity under extreme high-temperature conditions, preventing the device from melting through or collapsing, and continuously maintaining the isolation and protection effect to avoid further expansion of thermal runaway.

[0051] The three-layer flame-retardant material has 21 complementary functions, covering the entire cycle of battery thermal runaway warning, outbreak, and propagation. The protective effect is comprehensive and long-lasting, far superior to a single flame-retardant material, and fully meets the safety standards for power battery thermal runaway protection.

[0052] like Figures 1 to 2 As shown, this application provides a further specific implementation method based on the first implementation method as follows: The elastic energy storage module 3 includes a base 32, an energy storage spring 33, and a spike seat 34. The base 32 is located at the bottom of the flame-retardant space 13; the energy storage spring 33 is located on the base 32; the spike seat 34 is located on the top of the energy storage spring 33, and the spike 31 is located on the spike seat 34.

[0053] The solidified magnetorheological fluid can stably and persistently constrain the compressive potential energy of the energy storage spring 33. Even under long-term vehicle vibration and alternating high and low temperature conditions, there will be no problem of slow spring release or accidental contact of the flame-retardant storage module 2 by the spike 31. The daily operation safety is extremely high.

[0054] After the magnetorheological fluid liquefies, the locking force completely disappears, and the compressive potential energy of the energy storage spring 33 can be released instantaneously, driving the piercing needle seat 34 and the spike 31 to move at high speed, achieving high efficiency in piercing the flame-retardant storage module 2, further ensuring the response speed and reliability of thermal runaway protection. At the same time, this modular structure has no complex and vulnerable components, has strong vibration and interference resistance, is easy to produce and assemble, and is suitable for the mass integration needs of new energy vehicle battery modules.

[0055] like Figures 3 to 5 As shown, this application provides a further specific implementation method based on the first implementation method as follows: The magnetorheological fluid chamber has an opening at the bottom, and the base 32 is used to close the opening. Positioning grooves 131 are provided on both sides of the opening. The elastic energy storage module 3 also includes a lifting handle 35, a positioning rod 36, a hinge rod 37, and an elastic reset component 38.

[0056] The lifting handle 35 is vertically slidably mounted on the base 32. Two positioning rods 36 are horizontally slidably mounted inside the base 32, with each positioning rod 36 corresponding to a positioning groove 131. The outer end of the positioning rod 36 is used to insert into the positioning groove 131. In this embodiment, the top of the positioning rod 36 can be connected to the base 32 via a ball bearing slide rail.

[0057] Two hinge rods 37 correspond one-to-one with two positioning rods 36. One end of the hinge rod 37 is hinged to the lifting handle 35, and the other end is hinged to the positioning rod 36. An elastic reset member 38 is disposed in the base 32 and connected to the lifting handle 35. When the elastic reset member 38 is in a free state, the positioning rod 36 is simultaneously located in the base 32 and the positioning groove 131. In this embodiment, the elastic reset member 38 can be a rubber block or a silicone block.

[0058] The lifting handle 35, positioning rod 36, hinge rod 37 and elastic reset component 38 of the elastic energy storage module 3 form a quick-installation and quick-release positioning mechanism. During normal operation, the elastic reset component 38 pushes the positioning rod 36 to simultaneously engage with the positioning groove 131 of the base 32 and the magnetorheological fluid cavity, forming a double locking structure in the axial and radial directions. This ensures that the module does not loosen or shift under vehicle vibration and bumpy conditions, thus guaranteeing the structural stability of the device during long-term operation.

[0059] After thermal runaway is handled, the operator only needs to pull the lifting handle 35, which will cause the positioning rod 36 to retract and disengage from the positioning slot 131 via the hinge rod 37, so that the elastic energy storage module 3 can be quickly pulled out. After replacing the consumables, push the module in, release the handle, and the elastic reset component 38 will automatically drive the positioning rod 36 to spring back and lock, completing the quick positioning and fixing. No special tools or disassembly of the battery pack structure are required throughout the process, greatly improving maintenance efficiency.

[0060] The positioning mechanism is compactly integrated inside the base 32, without occupying the flame-retardant space 13, and without affecting the filling and phase change function of the magnetorheological fluid medium 4, thus achieving convenient maintenance and compatibility with core performance.

[0061] The top of the battery pack can be provided with an injection port for injecting magnetorheological fluid, and the bottom of the needle seat 34 can be provided with a pull rope that passes through the base 32 in a sealed manner, so that the replaced energy storage spring 33 remains in a contracted state before the magnetorheological fluid is injected.

[0062] Based on the first embodiment, this application provides another specific embodiment as follows: The magnetorheological fluid medium 4 includes carbonyl iron powder, sodium dodecylbenzene sulfonate surfactant, fumed silica thixotropic agent, and carrier liquid.

[0063] The carbonyl iron powder has a volume fraction of 35-45% and a particle size of 2-8 μm; sodium dodecylbenzene sulfonate surfactant has a volume fraction of 0.1-0.3%; fumed silica thixotropic agent has a volume fraction of 0.5-1.5%; the remaining volume is the carrier liquid, which is a mixture of deionized water and ethylene glycol, with a volume ratio of deionized water to ethylene glycol of 3:1 to 4:1.

[0064] The magnetorheological fluid medium 4 uses carbonyl iron powder with a volume fraction of 35-45% and a particle size of 2-8μm as the magnetic functional phase. It can solidify in milliseconds under the action of a magnetic field to form a high yield stress structure, which stabilizes and locks the elastic energy storage module 3. After power failure, it quickly returns to the liquid state. The low viscosity at zero field does not hinder the operation of the module, and the solid-liquid phase transition is reversible without hysteresis. Combined with 0.1-0.3% sodium dodecylbenzenesulfonate surfactant and 0.5-1.5% fumed silica thixotropic agent, it effectively prevents the sedimentation and agglomeration of magnetic particles, giving the magnetorheological fluid excellent dispersion stability and thixotropy, and ensuring uniform performance over long-term use.

[0065] The carrier liquid, which is a mixture of deionized water and ethylene glycol in a ratio of 3:1 to 4:1, does not freeze at low temperatures and does not volatilize at high temperatures. It also has good thermal conductivity. Furthermore, the thermal conductivity of water-based MRF (1.0-1.5 W / (m·K)) is significantly higher than that of silicone oil-based MRF (0.15 W / (m·K)), which is beneficial for the conduction of small amounts of heat under normal operating conditions. In addition, water-based carrier liquid is non-toxic, environmentally friendly, and has excellent compatibility with battery internal materials.

[0066] After optimization of the component ratio, the magnetorheological fluid exhibits excellent anti-aging and anti-fatigue properties, and has a long service life during cyclic phase change, matching the service life of the entire new energy vehicle, eliminating the need for frequent replacement.

[0067] like Figures 1 to 2 As shown, this application provides a further specific implementation method based on the first implementation method as follows: The flame-retardant device for thermal runaway of magnetorheological fluid batteries also includes a metal thermally conductive layer 6 and a temperature sensor 7.

[0068] The metal thermal conductive layer 6 corresponds one-to-one with the battery cell 12 and is positioned above the battery cell 12; the temperature sensor 7 is positioned below the metal thermal conductive layer 6 and is connected to the BMS battery system.

[0069] Specifically, when the temperature sensor 7 detects that the temperature value has reached the warning threshold, the BMS battery system cuts off the power supply to the electromagnetic coil 5.

[0070] The metal thermal conductive layer 6 is arranged one-to-one with the battery cell 12 on top of the battery cell 12. It can quickly and evenly conduct the heat of the battery cell 12 to help maintain the battery temperature balance, and also provide a stable and accurate detection carrier for the temperature sensor 7 to ensure real-time and accurate temperature data acquisition.

[0071] Temperature sensor 7 transmits the temperature of cell 12 to the BMS system in real time. When the temperature reaches the warning threshold, the BMS can actively cut off the power supply to electromagnetic coil 5, triggering the protection action in advance and intervening in the early stage of thermal runaway chain reaction to curb the expansion of the accident from the source.

[0072] The BMS active power-off trigger and the passive power-off trigger due to power failure provide dual protection. Even if the temperature sensor 7 fails or the BMS communication is interrupted, the device can still reliably operate through passive power-off, further enhancing its safety.

[0073] The metal thermal conductive layer 6 is only responsible for heat conduction under normal battery conditions and does not participate in thermal runaway protection. This achieves complete separation between daily heat dissipation and thermal runaway protection functions, avoids coupling interference between the two, ensures the specificity and reliability of the device's response to thermal runaway, and does not affect the normal thermal management performance of the battery module.

[0074] like Figure 1 and Figure 2 As shown, based on the same inventive concept, the second embodiment of this application provides a method for controlling the thermal runaway flame retardancy of a magnetorheological fluid battery, applied to the aforementioned magnetorheological fluid battery thermal runaway flame retardant device, comprising: When the electromagnetic coil 5 is energized, it generates a magnetic field. The magnetorheological fluid medium 4 remains in a solidified state. The elastic energy storage module 3 is locked in an energy storage state and has elastic potential energy toward the flame-retardant storage module 2. A safe distance is left between the spike 31 and the flame-retardant storage module 2. After the BMS battery system fails or the vehicle's main power is cut off, the electromagnetic coil 5 is de-energized and the magnetic field disappears. The magnetorheological fluid medium 4 returns to a liquid state within 50-100ms and releases the locking restriction on the elastic energy storage module 3. The elastic energy storage module 3 drives the spike 31 to pierce the flame-retardant storage module 2 and release the flame-retardant substance 21.

[0075] This embodiment provides a flame-retardant control method for thermal runaway of magnetorheological fluid batteries. Compared with the prior art, it achieves the core control effects of extremely low energy consumption, millisecond-level response, pure passive triggering, and failure safety through a simplified control logic of power-on solidification lock-in and power-off liquefaction release. It subverts the control mode of traditional protection devices that rely on continuous power supply and complex electronic control.

[0076] When the electromagnetic coil 5 is energized, the magnetorheological fluid medium 4 rapidly solidifies, and the yield stress is sufficient to lock the elastic energy storage module 3. The device exists only as a solid spacer, with no additional operating losses or failure risks, and operates stably for a long time. After the BMS battery system fails or the vehicle power is cut off, the magnetorheological fluid rapidly returns to a liquid state within 50-100ms, and the elastic energy storage module 3 releases its action instantaneously, piercing the flame-retardant storage module 2 and releasing the flame-retardant substance 21. The total response time is much shorter than that of traditional aerosol and solenoid valve driven systems, and effective blocking can be completed in the early stage of thermal runaway.

[0077] like Figures 1 to 2 As shown, this application provides a further specific implementation method based on the second implementation method as follows: In the event of thermal runaway, when the temperature sensor 7 detects that the temperature of cell 12 has reached the warning threshold, the BMS battery system cuts off the power to the electromagnetic coil 5. The warning threshold is 80-100℃, adjusted according to the battery chemistry system, with a safety margin of 10-20℃.

[0078] Temperature sensor 7 monitors the temperature of cell 12 in real time. When the temperature reaches the preset warning threshold, BMS directly and instantly cuts off the power supply to electromagnetic coil 5. There is no software judgment delay, no data transmission interference, zero distortion of the trigger signal, and extremely high control precision.

[0079] The warning threshold is set below the thermal runaway initiation temperature of cell 12, reserving a safety margin. It can release flame-retardant material 21 before thermal runaway actually occurs, curbing thermal runaway in its infancy, maximizing the protection of the battery module, and reducing accident losses. The temperature warning threshold can be flexibly adjusted according to different chemical systems of lithium-ion batteries, adapting to various cell types such as lithium iron phosphate and ternary lithium, thus broadening the application range of the device.

[0080] Example 1: Application of square lithium iron phosphate battery modules Application scenario: Battery pack for electric commercial vehicles, with a single pack capacity of 100kWh. Cell 12 is a lithium iron phosphate square battery with dimensions of 148mm×26mm×91mm. 20 cells 12 are connected in series to form a module.

[0081] Structural parameters: The outer shell 11 of the battery compartment 1 is made of aluminum alloy profile with a wall thickness of 2mm and a powder-coated surface.

[0082] The metal thermally conductive layer 6 is an aluminum foil-graphene composite film with a thickness of 2 mm and a thermal conductivity of 800 W / (m·K).

[0083] Temperature sensor 7 is an NTC thermistor, embedded in the bottom surface of metal thermally conductive layer 6, with a trigger threshold of 90℃.

[0084] The magnetorheological fluid is a water-based MRF with 40% carbonyl iron powder by volume, a particle size of 5 μm, a yield stress of 50 kPa under a 0.5 T magnetic field, and a zero-field viscosity of 0.25 Pa·s.

[0085] Electromagnetic coil 5 is made of copper enameled wire with a diameter of 0.6mm, a temperature resistance of 180℃, 120 turns, an operating current of 2.0A, and a magnetic field strength of 0.5T.

[0086] The sealing film sleeve 22 is a three-layer composite: an outer PI film of 12μm, a middle aluminum foil of 40μm, and an inner ETFE film of 30μm, with a total thickness of 82μm.

[0087] Flame retardant 21 consists of 1.2g of perfluorohexanone microcapsules in the upper layer, 2.0g of expandable graphite in the middle layer, and 2.0g of aluminum hydroxide / silicone rubber in the lower layer.

[0088] Performance testing: A K-type thermocouple was arranged on the surface of cell 12, and an external heating rod simulated thermal runaway. When the temperature reached 90℃, the current drop time of electromagnetic coil 5 was recorded by an oscilloscope (<20ms), and the movement of the piercing needle was recorded by a high-speed camera (1000fps). The results showed that the needle started moving in 85ms, the contact time with the film was 115ms, the time to complete puncture was 140ms, the time for the flame retardant material 21 to begin spraying was 160ms, and the time to completely fill the gap was 280ms.

[0089] A single-cell thermal runaway propagation test was conducted in a standard combustion chamber (ISO 5660). With this device, the surface temperature of adjacent cells 12 dropped from 150°C to 80°C within 5 minutes without thermal propagation; the control group without this device experienced cascading thermal runaway within 3 minutes, with the highest temperature exceeding 500°C.

[0090] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

[0091] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0092] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

Claims

1. A magnetorheological fluid-based battery thermal runaway flame retardant device, for installation in a battery compartment (1), the battery compartment (1) comprising a shell (11) and at least two battery cells (12); characterized in that, The magnetorheological fluid battery thermal runaway flame retardant device includes: A flame-retardant space (13) is provided between two adjacent cells (12), and the flame-retardant space includes a flame-retardant storage area and a magnetorheological fluid cavity; Flame-retardant storage module (2) is disposed in the flame-retardant storage area and contains flame-retardant material (21). An elastic energy storage module (3) is disposed in the magnetorheological fluid cavity. One end of the elastic energy storage module (3) has a spike (31) for piercing the flame-retardant storage module (2) so that the flame-retardant substance (21) can be released. A magnetorheological fluid medium (4) is filled within the magnetorheological fluid cavity and encloses the elastic energy storage module (3); and An electromagnetic coil (5) is arranged around the inner wall of the magnetorheological fluid cavity to connect to the BMS battery system and generate a magnetic field on the magnetorheological fluid medium (4). When the electromagnetic coil (5) is energized, the magnetorheological fluid medium (4) is in a solidified state and locks the elastic energy storage module (3) in an energy storage state. At this time, the elastic energy storage module (3) has elastic potential energy toward the flame-retardant storage module (2). When the electromagnetic coil (5) is de-energized, the magnetorheological fluid medium (4) instantly transforms into a liquefied state and releases the locking restriction on the elastic energy storage module (3). The spike (31) on the elastic energy storage module (3) pierces the flame-retardant storage module (2) and releases the flame-retardant substance (21).

2. The magnetorheological fluid-based battery thermal runaway flame-retardant device as described in claim 1, characterized in that, The flame-retardant storage module (2) includes: A sealing film sleeve (22) is disposed in the flame-retardant storage area and has a closed space inside; the two sides of the sealing film sleeve (22) face the space above the adjacent battery cell (12); The flame retardant material (21) is filled inside the sealing membrane sleeve (22).

3. The magnetorheological fluid-based battery thermal runaway flame-retardant device as described in claim 2, characterized in that, The sealing membrane sleeve (22) comprises, from the outside to the inside, the following components: Polyamide film layer, with a thickness of 10-15 μm; Aluminum foil layer, with a thickness of 30-50μm; and A polyethylene or ethylene-tetrafluoroethylene copolymer film layer with a thickness of 20-30 μm; Wherein, the outer side of the sealing film sleeve (22) refers to the side away from the flame retardant material (21), and the inner side refers to the side facing the flame retardant material (21).

4. The magnetorheological fluid-based battery thermal runaway flame-retardant device as described in claim 2, characterized in that, The flame retardant material (21) from the flame retardant storage area to the magnetorheological fluid cavity includes, in sequence: The vapor phase fire extinguishing layer is composed of multiple perfluorohexanone or heptafluoropropane microcapsules; The physically expanded layer is composed of expandable graphite particles; and The ceramicized layer is a composite of aluminum hydroxide and silicone rubber.

5. The magnetorheological fluid-based battery thermal runaway flame-retardant device as described in claim 1, characterized in that, The flexible energy storage module (3) includes: The base (32) is disposed at the bottom of the flame-retardant space (13); An energy storage spring (33) is disposed on the base (32) and enclosed within the magnetorheological fluid medium (4); and A needle seat (34) is disposed on the top of the energy storage spring (33), and the spike (31) is disposed on the needle seat (34).

6. The magnetorheological fluid-based battery thermal runaway flame-retardant device as described in claim 5, characterized in that, The magnetorheological fluid cavity has an opening at its bottom, and the base (32) is used to close the opening. Positioning grooves (131) are provided on both sides of the opening. The elastic energy storage module (3) also includes: A lifting handle (35) is slidably mounted on the base (32); Two positioning rods (36) are slidably disposed in the base (32). The positioning rods (36) correspond one-to-one with the positioning grooves (131). The outer ends of the positioning rods (36) are used to insert into the corresponding positioning grooves (131). Two hinge rods (37) correspond one-to-one with the two positioning rods (36). One end of each hinge rod (37) is hinged to the lifting handle (35), and the other end is hinged to the positioning rod (36). An elastic reset member (38) is disposed in the base (32) and connected to the lifting handle (35); when the elastic reset member (38) is in a free state, the positioning rod (36) is simultaneously located in the base (32) and the positioning groove (131).

7. The magnetorheological fluid-based battery thermal runaway flame-retardant device as described in claim 1, characterized in that, The magnetorheological fluid medium (4) includes: Carbonyl iron powder, volume fraction 35-45%, particle size 2-8μm; Sodium dodecylbenzenesulfonate surfactant, volume fraction 0.1-0.3%; and Fumed silica thixotropic agent, volume fraction 0.5-1.5%; The remainder is a carrier liquid, which is a mixture of deionized water and ethylene glycol, with a volume ratio of deionized water to ethylene glycol of 3:1 to 4:

1.

8. A flame-retardant device for thermal runaway of a magnetorheological fluid battery as described in any one of claims 1-7, characterized in that, The magnetorheological fluid battery thermal runaway flame retardant device also includes: A metal thermally conductive layer (6) corresponds one-to-one with each of the battery cells (12) and is disposed above each battery cell (12); and A temperature sensor (7) is disposed below the metal thermally conductive layer (6) and connected to the BMS battery system; When the temperature sensor (7) detects that the temperature value has reached the warning threshold, the BMS battery system cuts off the power supply to the electromagnetic coil (5).

9. A method for controlling thermal runaway and flame retardancy in a magnetorheological fluid battery, characterized in that, The flame-retardant device for thermal runaway of magnetorheological fluid batteries as described in any one of claims 1-7 comprises: The electromagnetic coil (5) is energized and generates a magnetic field. The magnetorheological fluid medium (4) remains in a solidified state. The elastic energy storage module (3) is locked in an energy storage state and has elastic potential energy toward the flame-retardant storage module (2). A safe distance is left between the spike (31) and the flame-retardant storage module (2). After the BMS battery system fails or the main power supply of the vehicle is cut off, the electromagnetic coil (5) is de-energized and the magnetic field disappears. The magnetorheological fluid medium (4) recovers to liquid state within 50-100ms and releases the locking restriction on the elastic energy storage module (3). The elastic energy storage module (3) drives the spike (31) to pierce the flame retardant storage module (2) and release the flame retardant substance (21).

10. The method for controlling thermal runaway and flame retardancy in a magnetorheological fluid battery as described in claim 9, characterized in that, A temperature sensor (7) is provided above the cell (12), and the temperature sensor (7) is connected to the BMS battery system. When the temperature sensor (7) detects that the temperature of the cell (12) reaches the warning threshold, the BMS battery system cuts off the power supply of the electromagnetic coil (5).

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