A liquid cooling tube, its preparation method, and its application in lithium battery safety control equipment.
By using a three-layer liquid cooling pipe, the temperature-sensitive and brittle substrate layer self-ruptures at high temperatures, the thermally conductive middle layer conducts heat, and the sealed and protective outer layer prevents leakage. This solves the problems of response lag and secondary damage during thermal runaway of lithium batteries, and achieves the integrated function of efficient heat dissipation and fire extinguishing, thus improving the safety of lithium battery energy storage systems.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUANGDONG HUADIAN ENERGY STORAGE CO LTD
- Filing Date
- 2026-05-14
- Publication Date
- 2026-07-31
AI Technical Summary
Existing lithium battery thermal management systems cannot accurately respond to temperature changes during thermal runaway. Traditional liquid cooling pipes cannot actively respond to high temperatures, leading to the spread of thermal runaway. Furthermore, gas extinguishing systems have a delayed response and poor targeting, resulting in secondary damage and difficulty in cleaning.
It adopts a three-layer synergistic structure consisting of a temperature-sensitive and brittle substrate layer, a thermally conductive and reinforced intermediate layer, and a sealing and protective outer layer. It utilizes the precise self-destruction of the temperature-sensitive and brittle substrate layer at high temperatures, the rapid heat conduction of the thermally conductive and reinforced intermediate layer, and the sealing and protective outer layer to prevent media leakage, thus achieving integrated functions of heat dissipation, fire extinguishing, and sealing.
It achieves precise response and efficient heat dissipation during lithium battery thermal runaway, and the fire extinguishing medium is released synchronously at high temperature, avoiding the response lag and secondary damage of traditional liquid cooling pipes, thus improving the safety and reliability of lithium battery energy storage systems.
Smart Images
Figure CN122494903A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium battery safety protection, and in particular to a liquid cooling pipe, its preparation method, and its application in lithium battery safety control equipment. Background Technology
[0002] Lithium-ion batteries, with their advantages of high energy density, long cycle life, and high charge / discharge efficiency, have been widely used in new energy vehicles, large-scale energy storage, and portable electronic devices. However, the thermal runaway problem of lithium-ion batteries remains a core bottleneck restricting the safe development of the industry. Under extreme conditions such as overcharging, over-discharging, short circuits, collisions, or aging, the internal temperature of lithium-ion batteries will rise sharply. When the temperature exceeds the critical threshold (usually 80-150 ℃), a chain exothermic reaction will be triggered, i.e., thermal runaway, which will eventually lead to safety accidents such as fires and explosions.
[0003] Currently, lithium battery thermal management and safety protection technologies are mainly divided into two categories: passive protection and active protection. Passive protection mainly relies on heat insulation materials, flame-retardant electrolytes, and explosion-proof valves, which can only delay the spread of thermal runaway and cannot effectively cool down and extinguish fires after thermal runaway occurs. Active protection mainly includes liquid cooling systems, gas extinguishing systems, and sprinkler cooling systems, among which liquid cooling systems are currently the mainstream high-efficiency thermal management solution. However, it can only achieve temperature control under normal operating conditions. When a lithium battery experiences thermal runaway and the temperature rises sharply to above 100°C, traditional liquid cooling pipes (mostly made of metal or ordinary polymer materials) cannot actively respond to temperature changes. The pipe structure remains intact and cannot release extinguishing media, making it difficult to stop the continued spread of thermal runaway. Gas extinguishing systems and sprinkler cooling systems have problems such as delayed response, poor fire suppression targeting, secondary damage to battery modules, and difficulty in subsequent cleaning.
[0004] Therefore, developing a liquid cooling pipe with a novel temperature-sensitive thermal conductive material system, simple structure, precise response, and high protection efficiency has become the key to solving the safety hazards of thermal runaway in lithium batteries. Summary of the Invention
[0005] This invention provides a liquid cooling pipe, its preparation method, and its application in lithium battery safety control equipment. It adopts a three-layer synergistic structure consisting of a temperature-sensitive and brittle substrate layer, a thermally conductive and enhanced intermediate layer, and a sealing and protective outer layer. This structure simultaneously achieves integrated functions of heat dissipation, high-temperature self-breakage cooling and fire extinguishing, and sealing and protection, effectively improving the safety and reliability of lithium battery energy storage systems.
[0006] To solve the above-mentioned technical problems, one of the objectives of this invention is to provide a liquid cooling pipe, which is prepared by blow molding of a temperature-sensitive thermally conductive composite film blank. The temperature-sensitive thermally conductive composite film blank includes a temperature-sensitive brittle substrate layer, a thermally conductive reinforced intermediate layer, and a sealing and protective outer layer, which are stacked sequentially from the inside to the outside of the liquid cooling pipe. The interior of the liquid cooling pipe is filled with a fire extinguishing medium. The temperature-sensitive brittle substrate layer includes a copolymer, which includes structural units 1 derived from N-vinylcaprolactam, structural units 2 derived from glycidyl methacrylate, and structural units 3 derived from polylactic acid in a molar ratio of (40-60):(20-30):(20-30). The thermally conductive reinforced intermediate layer comprises a thermally conductive filler and polyethylene glycol methyl ether in a mass ratio of (30-45):(55-70); The sealing and protective outer layer comprises a thermoplastic fluoropolymer and nano MOF material in a mass ratio of (85-95):(5-15).
[0007] The temperature-sensitive brittle substrate layer of this liquid cooling tube is responsible for responding to the high-temperature signal at the initial stage of lithium battery thermal runaway, achieving precise self-breakage, while also possessing flexibility and mechanical strength under normal operating conditions, capable of withstanding the working pressure of the liquid cooling system. The thermally conductive reinforced intermediate layer is responsible for rapidly transferring the heat generated by the lithium battery energy storage module to the fire extinguishing medium inside the tube, achieving efficient heat dissipation under normal operating conditions. The sealing and protective outer layer can prevent leakage of the fire extinguishing medium inside the tube, improving the tube's aging resistance, electrolyte corrosion resistance, and mechanical strength. Simultaneously, the thermoplastic fluoropolymer molecular chains contain fluorine atoms (-F), which have strong electronegativity and can form hydrogen bonds with the lone pairs of electrons on the surface of the nano-MOF. Furthermore, the porous structure of the nano-MOF material can adsorb the thermoplastic fluoropolymer molecular chains, enhancing the bonding force between the two and forming a uniform and stable composite. In addition, the hydroxyl groups on the surface of the nano-MOF can undergo a weak condensation reaction with the hydroxyl groups of mPEG in the thermally conductive reinforced intermediate layer, further enhancing the interlayer bonding force between the sealing and protective outer layer and the thermally conductive reinforced intermediate layer, thus adapting to the synergistic film-breaking performance of the three-layer structure. After blow molding, the thermally conductive composite film blank achieves a tighter and seamless bond between the layers, allowing the three layers to break down simultaneously at high temperatures without affecting the release of the extinguishing medium. It also integrates conventional heat dissipation, high-temperature self-rupture extinguishing, and sealing protection, which can meet the cooling and fire extinguishing safety control requirements of lithium battery energy storage systems.
[0008] In some embodiments, the copolymer comprises structural units 1 derived from N-vinylcaprolactam, structural units 2 derived from glycidyl methacrylate, and structural units 3 derived from polylactic acid in a molar ratio of 50:25:25.
[0009] The copolymer in the thermosensitive brittle substrate layer of this application is formed by free radical polymerization of N-vinylcaprolactam, glycidyl methacrylate, and polylactic acid in the above-mentioned preferred molar ratio, forming a three-dimensional network structure copolymer. This copolymer simultaneously possesses thermosensitive brittleness, chemical cross-linking network capability, and structural mechanical strength. It can maintain good flexibility and pressure resistance at room temperature, and can rapidly embrittle and break under high temperature conditions, achieving early and accurate response to thermal runaway of lithium batteries. The molar ratio of the three components is controlled within the above-mentioned preferred ratio range, which can achieve an optimal balance between thermosensitive response temperature, embrittlement rate, and mechanical strength, avoiding response lag, insufficient strength, or accidental breakage at room temperature due to monomer ratio imbalance. This ensures that the film breaks down synchronously with the thermally conductive reinforced intermediate layer and the sealing and protective outer layer, improving the stability and reliability of the liquid cooling pipe.
[0010] In some embodiments, the thickness ratio of the temperature-sensitive brittle substrate layer, the thermally conductive reinforced intermediate layer, and the sealing and protective outer layer in the temperature-sensitive thermally conductive composite film blank is (3-5):(2-4):(2-4).
[0011] In some embodiments, the thickness ratio of the temperature-sensitive brittle substrate layer, the thermally conductive reinforced intermediate layer, and the sealing and protective outer layer in the temperature-sensitive thermally conductive composite film blank is 4:3:3.
[0012] The thickness ratio of the temperature-sensitive brittle substrate layer, the thermally conductive reinforced intermediate layer, and the sealing and protective outer layer of the liquid cooling pipe in this application is within the above-mentioned preferred range. This ratio can balance the temperature-sensitive response speed, thermal conductivity, and structural strength, enabling the three layers to deform and break simultaneously at high temperatures. This thickness ratio can avoid the delay in film breaking caused by an excessively thick single layer or the mechanical failure caused by an excessively thin single layer, thus ensuring the stable performance of heat dissipation, fire extinguishing, and sealing and protective functions.
[0013] In some embodiments, the thickness of the temperature-sensitive brittle substrate layer is 0.08-0.2 mm.
[0014] In some embodiments, the thickness of the thermally enhanced interlayer is 0.06-0.15 mm.
[0015] In some embodiments, the thickness of the sealing and protective outer layer is 0.06-0.15 mm.
[0016] In some embodiments, the total thickness of the temperature-sensitive thermally conductive composite film blank is 0.2-0.5 mm.
[0017] In some embodiments, the thermally conductive filler includes at least one of graphene, aluminum nitride, aluminum oxide, silicon carbide, and zinc oxide.
[0018] In some embodiments, the nano-MOF material includes at least one of nano-ZIF-8, nano-ZIF-67, and nano-UiO-66.
[0019] In some embodiments, the particle size of the nano-MOF material is 50-200 nm.
[0020] In some embodiments, the thermoplastic fluoropolymer includes at least one of polyvinylidene fluoride, perfluoroalkoxyalkylene resin, perfluoroethylene propylene, and ethylene-tetrafluoroethylene copolymer.
[0021] In some embodiments, the thermally conductive filler comprises modified graphene and aluminum nitride in a mass ratio of (10-15):(85-90), wherein the modified graphene is graphene with a silane coupling agent grafted onto its surface.
[0022] The graphene surface of this application has a large number of hydroxyl groups (-OH). The ethoxy group of the silane coupling agent can undergo hydrolysis and condensation reaction with the hydroxyl groups on the graphene surface, and can also form hydrogen bonds with the hydroxyl groups (-OH) of mPEG, thereby improving the compatibility between graphene and mPEG, solving the problem of poor dispersibility and easy agglomeration of graphene in mPEG, and working together with aluminum nitride to improve the thermal conductivity and mechanical properties of the thermally enhanced intermediate layer.
[0023] In some embodiments, the preparation method of the modified graphene includes the following steps: adding graphene to a solvent, ultrasonically dispersing it, adding a silane coupling agent, adjusting the pH to 7.2-8, heating and stirring the reaction, centrifuging, washing, and drying to obtain the modified graphene.
[0024] In some embodiments, in the preparation method of the modified graphene, the silane coupling agent is 5%-10% of the graphene by mass.
[0025] In some embodiments, the ultrasonic dispersion time is 10-20 min and the ultrasonic power is 300-500 W in the preparation method of the modified graphene.
[0026] In some embodiments, the silane coupling agent in the preparation method of the modified graphene is KH-550.
[0027] In some embodiments, the heating temperature is 50-60 °C and the stirring reaction time is 2-3 h in the preparation method of the modified graphene.
[0028] In some embodiments, the molecular weight of the polylactic acid is 80,000-120,000.
[0029] In some embodiments, the number-average molecular weight of polyethylene glycol methyl ether in the thermally reinforced interlayer is 2000-4000.
[0030] In some embodiments, the number-average molecular weight of the thermoplastic fluoropolymer in the sealing and protective outer layer is 50,000-80,000.
[0031] In some embodiments, the extinguishing medium is an electronic fluorinated liquid.
[0032] In some embodiments, the electronic fluorinated liquid includes at least one of perfluoropolyether, hydrofluoroether, and perfluorocarbon.
[0033] In some embodiments, the volume fraction of the extinguishing medium in the liquid-cooled pipe is 85%-95%.
[0034] In some embodiments, the electronic fluorinated liquid is a perfluoropolyether.
[0035] The preferred extinguishing medium in this application is a perfluoropolyether-based electronic fluorinated liquid with a boiling point of 110-150 ℃. It exhibits good compatibility with the three-layer composite membrane material, does not react chemically, and possesses excellent insulation properties, preventing secondary short circuits during firefighting. Furthermore, it is non-flammable, non-toxic, leaves no residue after extinguishing, and is easy to clean up. The filling volume is 85%-95% of the tube's internal volume, with a 5%-15% expansion space reserved inside the tube to prevent accidental tube rupture due to thermal expansion of the electronic fluorinated liquid.
[0036] To address the aforementioned technical problems, a second objective of this invention is to provide a method for preparing a liquid-cooled tube, comprising the following steps: (1) The N-vinylcaprolactam, glycidyl methacrylate and polylactic acid are mixed to obtain a mixed monomer, a solvent is added and stirred to dissolve to obtain a mixed solution; an initiator is added and stirred to dissolve, and the reaction is carried out under an inert gas atmosphere to obtain a copolymer solution. The copolymer solution is coated and dried to form a temperature-sensitive and brittle substrate layer. (2) The thermally conductive filler and polyethylene glycol methyl ether are mixed and ultrasonically dispersed to obtain a composite material. The composite material is coated on the surface of a temperature-sensitive and brittle substrate layer and dried to form a thermally conductive and reinforced intermediate layer. (3) The thermoplastic fluoropolymer and nano MOF material are mixed to obtain a mixture, a solvent is added and mixed evenly to obtain a composite solution; the composite solution is coated on the surface of the thermally conductive reinforced intermediate layer, and after drying, a sealed protective outer layer is formed to prepare a temperature-sensitive thermally conductive composite film blank; (4) The temperature-sensitive thermally conductive composite film blank is blow-molded and molded to prepare the tube body; (5) Fire extinguishing medium is injected into the pipe body and hot-melt sealing is performed using a sealing joint to prepare a liquid-cooled pipe.
[0037] In some embodiments, in step (1), the mass fraction of the mixed monomers in the mixed solution is 20%-30%.
[0038] In some embodiments, in step (1), the initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, and dilauryl peroxide.
[0039] In some embodiments, in step (1), the initiator accounts for 0.5%-1.5% of the mass fraction of the mixed monomers.
[0040] In some embodiments, in step (1), the temperature of the heating and stirring reaction is 60-80 °C, the rate is 150-250 r / min, and the time is 4-6 h.
[0041] In some implementations, in step (2), the ultrasonic power is 400-600 W and the ultrasonic time is 30-60 min.
[0042] In some embodiments, in step (3), the mass fraction of the mixture in the composite solution is 15%-25%.
[0043] In some embodiments, in step (3), after the mixture is uniformly dispersed by ultrasonication at a power of 500-700 W for 40-60 min, it is placed in a water bath at 60-70 ℃ and stirred for 1-2 h.
[0044] In some embodiments, in step (4), the blow molding temperature is 160-180 ℃, the plasticizing time is 5-10 min, the blow ratio is 1.5-2.5, the traction speed is 0.5-1 m / min, and the die temperature is 170-180 ℃.
[0045] In some embodiments, in step (4), the inner diameter of the blow-molded tube is 3-8 mm and the outer diameter is 3.4-8.6 mm.
[0046] In some embodiments, in step (4), the molding temperature is 150-160 °C, the pressure is 0.5-1 MPa, and the time is 10-20 s.
[0047] In some embodiments, in step (5), the extinguishing medium injection rate is 1-2 mL / min.
[0048] To address the aforementioned technical problems, a third objective of this invention is to provide an application of a liquid cooling pipe in lithium battery safety control equipment.
[0049] In some embodiments, the lithium battery safety control device includes a liquid cooling pipe, a lithium battery energy storage system module, and a metal casing, wherein the liquid cooling pipe includes a liquid cooling tube.
[0050] In some embodiments, the liquid cooling pipes are arranged in a U-shape.
[0051] The liquid cooling pipes in this application can be repeatedly arranged in a U-shape to closely fit the surface of densely packed lithium battery cells, fully utilizing their flexibility to adapt to the module shape and achieve full-coverage heat conduction. This laying method ensures a large-area contact between the liquid cooling pipes and the battery module, while also allowing the fire extinguishing medium inside the pipes to circulate and quickly remove the heat generated by the battery under normal operating conditions. In the event of thermal runaway of the lithium battery, the U-shaped pipes can quickly respond to the high-temperature area by breaking the membrane and accurately releasing the fire extinguishing medium, achieving integrated protection of conventional heat dissipation and high-temperature membrane breaking fire extinguishing.
[0052] Compared with the prior art, the present invention has the following beneficial effects: 1. The liquid cooling tube of this application utilizes a temperature-sensitive and brittle substrate layer to respond to the high-temperature signal in the early stage of thermal runaway of lithium battery and achieve precise self-rupture. The thermally conductive and enhanced intermediate layer conducts the generated heat to the extinguishing medium, achieving efficient heat dissipation. The sealed and protective outer layer can prevent the leakage of the extinguishing medium inside the tube and improve the tube's aging resistance, electrolyte corrosion resistance and mechanical strength. The three layers of materials can rupture simultaneously at high temperature without affecting the release of the extinguishing medium. They work together to achieve the integrated functions of conventional heat dissipation, high-temperature self-rupture extinguishing and sealing protection, meeting the cooling and fire extinguishing safety control requirements of lithium battery energy storage systems.
[0053] 2. The fire extinguishing medium used in this application is a perfluoropolyether electronic fluorinated liquid, which has good compatibility with the liquid cooling pipe composite membrane material, does not react chemically, has excellent insulation performance, and can avoid secondary short circuits during fire extinguishing; it is also non-flammable, non-toxic, leaves no residue after fire extinguishing, and is easy to clean up afterwards. Attached Figure Description
[0054] Figure 1 This is a schematic diagram of the structure of a liquid cooling pipe prepared in an embodiment of the present invention; Figure 2 : SEM image of a liquid cooling pipe interface prepared in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the lithium battery safety control device used in the preparation of the liquid cooling tube in this embodiment of the invention. Detailed Implementation
[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0056] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.
[0057] 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. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.
[0058] As used in this article: In these embodiments, unless otherwise specified, the portions and percentages are all by weight.
[0059] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).
[0060] In the description of this invention, it should be understood that the terms "upper", "lower", "left", "right", "top", "bottom", etc., indicating orientation or positional relationship are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.
[0061] To further illustrate the present invention, the following detailed description is provided in conjunction with embodiments, but these should not be construed as limiting the scope of protection of the present invention. Unless otherwise specified, the raw materials used in the following embodiments and comparative examples are all commercially available, and the same raw materials were used in parallel experiments.
[0062] Preparation Example 1 A method for preparing modified graphene includes the following steps: Weigh 10 g of graphene powder, add 100 mL of deionized water, and ultrasonically disperse for 15 min at a power of 400 W. Then add KH-550 (7% by weight of graphene) to adjust the pH to 7.5. Stir and react at 55 ℃ for 2.5 h. Centrifuge at 9000 r / min for 12 min, wash, and dry to obtain modified graphene.
[0063] Example 1 A type of liquid cooling pipe, such as Figure 1 As shown, the liquid cooling pipe comprises, from the inside out, a temperature-sensitive and brittle substrate layer, a thermally conductive and enhanced intermediate layer, and a sealing and protective outer layer. The internal cavity of the liquid cooling pipe is filled with a fire extinguishing medium. This liquid cooling pipe can be used in lithium battery safety control equipment, such as... Figure 3 As shown, it includes a liquid cooling pipe, a lithium battery energy storage system module, and a metal casing. The liquid cooling pipe includes the aforementioned liquid cooling tube.
[0064] The above-mentioned method for preparing a liquid cooling tube includes the following steps: (1) Preparation of thermosensitive and brittle substrate layer: N-vinylcaprolactam (NVCL), glycidyl methacrylate (GMA), and polylactic acid (PLA, number average molecular weight 100,000) were added in a molar ratio of 50:25:25 to obtain mixed monomers. N,N-dimethylformamide (DMF) was added and stirred for 30 min until completely dissolved to obtain a mixed solution with a mixed monomer mass concentration of 25%. Azobisisobutyronitrile (AIBN) was added at a mass of 1% of the mixed monomers and stirred until dissolved. The solution was poured into a three-necked flask and high-purity nitrogen was introduced at a flow rate of 80 mL / min for 45 min to remove oxygen. Then, the copolymer was polymerized in a constant temperature water bath at 70 °C and a stirring speed of 200 r / min for 5 h to obtain a copolymer solution. The copolymer was coated onto the substrate with a doctor blade and dried in an oven at 90 °C for 3 h. After peeling, a thermosensitive and brittle substrate layer with a thickness of 0.12 mm was obtained. (2) Preparation of thermally conductive reinforced intermediate layer: Weigh the modified graphene and aluminum nitride (AlN) of Preparation Example 1 in a mass ratio of 12:88, mix them to obtain thermally conductive filler, add polyethylene glycol methyl ether (mPEG, number average molecular weight 3000), the mass ratio of thermally conductive filler to polyethylene glycol methyl ether is 31.7:68.3, stir for 12 min, then ultrasonically disperse for 45 min at a power of 500 W to obtain composite material; coat the composite material on the temperature-sensitive brittle substrate layer with a scraper, and dry it in an oven at 100 ℃ for 2 h to form a thermally conductive reinforced intermediate layer with a thickness of 0.09 mm; (3) Preparation of sealing and protective outer layer: Polyvinylidene fluoride (PVDF, number average molecular weight 60000, purity ≥99%) and nano ZIF-8 (particle size 120 nm) with a mass ratio of 92:8 were added to obtain a mixture. Then N-methylpyrrolidone (NMP) was added and stirred for 25 min. Then ultrasonic dispersion was performed for 50 min at a power of 600 W. Stirring was carried out at a temperature of 65 ℃ for 1.5 h to obtain a composite solution with a mass concentration of 20%. The mixture was coated on the surface of the thermally conductive reinforced intermediate layer by a scraper and dried at an oven temperature of 110 ℃ for 3 h. After cooling to room temperature, a sealing and protective outer layer with a thickness of 0.09 mm was formed, and a temperature-sensitive thermally conductive composite film blank with a total thickness of 0.3 mm was prepared. The thickness ratio of the temperature-sensitive brittle substrate layer, the thermally conductive reinforced intermediate layer and the sealing and protective outer layer was 4:3:3. (4) Preparation of tube body: The temperature-sensitive thermally conductive composite film blank is placed into the blow molding machine, and the barrel is temperature controlled in sections (feeding section 165 ℃, melting section 175 ℃, die head section 178 ℃), plasticizing time 8 min, blow-up ratio 2.0, traction speed 0.8 m / min, die temperature 175 ℃, and blow-molded into a flexible tube with an inner diameter of 5 mm and an outer diameter of 5.6 mm; molding treatment is carried out, molding temperature 155 ℃, pressure 0.8 MPa, time 15 s, to prepare thermally conductive protrusions with a height of 0.5 mm and a spacing of 8 mm on the surface of the tube. After cooling, it is cut into a tube body with a length of 3 m. (5) Fire extinguishing medium filling: Fire extinguishing medium is injected into the pipe body. The fire extinguishing medium is perfluoropolyether (PFPE, boiling point 130℃). The filling amount is 90%. The sealing joint prepared by the composite solution in step (3) is used. The sealing is completed in 15 s under the conditions of hot melting temperature 165 ℃ and pressure 0.4MPa. The liquid cooling pipe is then prepared.
[0065] Example 2 A method for preparing a liquid cooling tube, wherein each step and the raw materials, equipment and process parameters used in each step are the same as in Example 1, except that in step (1), the molar ratio of N-vinylcaprolactam (NVCL), glycidyl methacrylate (GMA) and polylactic acid (PLA, number average molecular weight 100,000) is 60:20:20. In step (2), the thermally conductive filler comprises modified graphene and aluminum nitride (AlN) of Preparation Example 1 in a mass ratio of 15:85, and the thermally conductive filler and polyethylene glycol methyl ether (mPEG, number average molecular weight 3000) in a mass ratio of 45:55. In step (3), the mass ratio of polyvinylidene fluoride (PVDF, number average molecular weight 60,000, purity ≥99%) to nano ZIF-8 (particle size 120 nm) is 95:5.
[0066] Example 3 A method for preparing a liquid cooling tube, wherein each step and the raw materials, equipment and process parameters used in each step are the same as in Example 1, except that in step (1), the thickness of the temperature-sensitive brittle substrate layer is 0.2 mm. In step (2), the thickness of the thermally enhanced intermediate layer is 0.15 mm; In step (3), the thickness of the sealing and protective outer layer is 0.15 mm, the total thickness of the temperature-sensitive thermally conductive composite film blank is 0.5 mm, and the thickness ratio of the temperature-sensitive brittle substrate layer, the thermally conductive reinforced intermediate layer and the sealing and protective outer layer is 4:3:3.
[0067] Example 4 A method for preparing a liquid cooling tube, wherein each step and the raw materials, equipment and process parameters used in each step are the same as in Example 1, except that in step (1), the thickness of the temperature-sensitive brittle substrate layer is 0.15 mm. In step (2), the thickness of the thermally enhanced intermediate layer is 0.07 mm; In step (3), the thickness of the sealing and protective outer layer is 0.08 mm, the total thickness of the temperature-sensitive thermally conductive composite film blank is 0.3 mm, and the thickness ratio of the temperature-sensitive brittle substrate layer, the thermally conductive reinforced intermediate layer and the sealing and protective outer layer is 5:2.3:2.7.
[0068] Example 5 A method for preparing a liquid cooling tube, wherein each step and the raw materials, equipment and process parameters used in each step are the same as in Example 1, except that in step (1), the thickness of the temperature-sensitive brittle substrate layer is 0.09 mm. In step (2), the thickness of the thermally enhanced intermediate layer is 0.11 mm; In step (3), the thickness of the sealing and protective outer layer is 0.1 mm, the total thickness of the temperature-sensitive thermally conductive composite film blank is 0.3 mm, and the thickness ratio of the temperature-sensitive brittle substrate layer, the thermally conductive reinforced intermediate layer and the sealing and protective outer layer is 3:3.7:3.3.
[0069] Example 6 A method for preparing a liquid cooling tube, wherein each step and the raw materials, equipment and process parameters used in each step are the same as in Example 1, except that in step (1), the molar ratio of N-vinylcaprolactam (NVCL), glycidyl methacrylate (GMA) and polylactic acid (PLA, number average molecular weight 100,000) is 40:30:30.
[0070] Example 7 A method for preparing a liquid cooling tube, wherein each step and the raw materials, equipment and process parameters used in each step are the same as in Example 1, except that in step (1), the molar ratio of N-vinylcaprolactam (NVCL), glycidyl methacrylate (GMA) and polylactic acid (PLA, number average molecular weight 100,000) is 60:20:20.
[0071] Example 8 A method for preparing a liquid cooling tube, wherein each step and the raw materials, equipment and process parameters used in each step are the same as those in Example 1, except that in step (2), the thermally conductive filler is the modified graphene of Example 1.
[0072] Example 9 A method for preparing a liquid cooling tube, wherein each step and the raw materials, equipment and process parameters used in each step are the same as in Example 1, except that in step (2), the thermally conductive filler is aluminum nitride (AlN).
[0073] Example 10 A method for preparing a liquid cooling tube, wherein each step and the raw materials, equipment and process parameters used in each step are the same as those in Example 1, except that in step (3), nano ZIF-8 is replaced by an equal amount of nano ZIF-67 (particle size of 120 nm).
[0074] Example 11 A method for preparing a liquid cooling tube, wherein each step and the raw materials, equipment and process parameters used in each step are the same as those in Example 1, except that in step (3), nano ZIF-8 is replaced by an equal amount of nano UiO-66 (particle size of 120 nm).
[0075] Example 12 A method for preparing a liquid cooling tube, wherein each step and the raw materials, equipment and process parameters used in each step are the same as those in Example 1, except that in step (2), the modified graphene in Example 1 is replaced by an equal amount of graphene.
[0076] Example 13 A method for preparing a liquid cooling pipe, wherein each step and the raw materials, equipment and process parameters used in each step are the same as in Example 1, except that in step (5), the filling amount of the fire extinguishing medium is 100%.
[0077] Comparative Example 1 A method for preparing a liquid cooling tube, wherein each step and the raw materials, equipment and process parameters used in each step are the same as those in Example 1, except that in step (1), the amount of glycidyl methacrylate (GMA) and polylactic acid (PLA, number average molecular weight 100,000) added is 0.
[0078] Comparative Example 2 A method for preparing a liquid cooling tube, wherein each step and the raw materials, equipment and process parameters used in each step are the same as those in Example 1, except that in step (1), the amount of N-vinylcaprolactam (NVCL) and polylactic acid (PLA, number average molecular weight 100,000) added is 0.
[0079] Comparative Example 3 A method for preparing a liquid cooling tube, wherein each step and the raw materials, equipment and process parameters used in each step are the same as in Example 1, except that in step (1), the amount of N-vinylcaprolactam (NVCL) and glycidyl methacrylate (GMA) added is 0, and polylactic acid (PLA, number average molecular weight 100,000) is added to N,N-dimethylformamide (DMF) and stirred for 30 min until completely dissolved to obtain a mixed solution with a monomer mass concentration of 25%; the solution is coated onto a substrate by a scraper and dried in an oven at 90 ℃ for 3 h, and after peeling, a temperature-sensitive brittle substrate layer with a thickness of 0.12 mm is obtained.
[0080] Comparative Example 4 A method for preparing a liquid cooling tube, wherein each step and the raw materials, equipment and process parameters used in each step are the same as those in Example 1, the difference being that in step (4), the temperature-sensitive thermally conductive composite film blank is replaced by an equal amount of PVDF film blank. The preparation method of the PVDF film blank includes the following steps: adding polyvinylidene fluoride (PVDF, number average molecular weight 60000, purity ≥99%) to N-methylpyrrolidone (NMP), stirring for 25 min, followed by ultrasonic dispersion for 50 min at a power of 600 W; stirring for 1.5 h at a temperature of 65 ℃ to obtain a composite solution with a PVDF mass concentration of 20%; coating the substrate surface with a scraper, drying at an oven temperature of 110 ℃ for 3 h, cooling to room temperature, and peeling to form a PVDF film blank with a thickness of 0.3 mm.
[0081] Comparative Example 5 A method for preparing a liquid cooling tube, wherein each step and the raw materials, equipment and process parameters used in each step are the same as in Example 1, except that in step (3), the amount of nano ZIF-8 (particle size 120 nm) added is 0.
[0082] Comparative Example 6 A method for preparing a liquid cooling tube, wherein each step and the raw materials, equipment and process parameters used in each step are the same as in Example 1, except that in step (2), polyethylene glycol methyl ether (mPEG, number average molecular weight 3000) is replaced by polyvinylidene fluoride (PVDF, number average molecular weight 60000, purity ≥99%) in an equal amount; In step (3), polyvinylidene fluoride (PVDF, number average molecular weight 60,000, purity ≥99%) is replaced by an equal amount of polyethylene glycol methyl ether (mPEG, number average molecular weight 3,000).
[0083] Comparative Example 7 A method for preparing a liquid cooling tube, wherein each step and the raw materials, equipment and process parameters used in each step are the same as in Example 1, except that in step (1), the thickness of the temperature-sensitive brittle substrate layer is 0 mm. In step (2), the thickness of the thermally enhanced intermediate layer is 0.15 mm; In step (3), the thickness of the sealing and protective outer layer is 0.15 mm, the total thickness of the temperature-sensitive thermally conductive composite film blank is 0.3 mm, and the thickness ratio of the temperature-sensitive brittle substrate layer, the thermally conductive reinforced intermediate layer and the sealing and protective outer layer is 0:1:1.
[0084] Comparative Example 8 A method for preparing a liquid cooling tube, wherein each step and the raw materials, equipment and process parameters used in each step are the same as in Example 1, except that in step (1), the thickness of the temperature-sensitive brittle substrate layer is 0.17 mm. In step (2), the thickness of the thermally enhanced intermediate layer is 0 mm; In step (3), the thickness of the sealing and protective outer layer is 0.13 mm, the total thickness of the temperature-sensitive thermally conductive composite film blank is 0.3 mm, and the thickness ratio of the temperature-sensitive brittle substrate layer, the thermally conductive reinforced intermediate layer and the sealing and protective outer layer is 4:0:3.
[0085] Performance testing 1. The cross-section of the liquid cooling tube prepared in Example 1 was monitored using a scanning electron microscope. The SEM image of the interface is shown below. Figure 2 As shown, the layer distribution and thickness ratio of the three-layer composite structure are clearly displayed. From the inside out, the layers are a temperature-sensitive and brittle substrate layer, a thermally conductive and enhanced intermediate layer, and a sealing and protective outer layer. The layers are tightly bonded by hydrogen bonding and weak condensation reaction, with no obvious interface gaps. This ensures the stability of the overall structure and allows it to break down synchronously in the event of thermal runaway without hindering the release of the extinguishing medium.
[0086] 2. Thermal conductivity: According to GB / T 10297-2015, the thermal conductivity was determined by the hot wire method. Under the condition of 25℃, the temperature difference and heat transfer rate at both ends of the liquid cooling tube obtained in the example and comparative examples were measured, and the thermal conductivity was calculated. The test results are shown in Table 1 below.
[0087] 3. Thermal response membrane rupture time: The liquid-cooled tubes prepared in the examples and comparative examples were placed in a constant temperature environment chamber at 130℃, and the time for the tubes to completely rupture was recorded in real time. The test was repeated 5 times and the average value was taken. The test results are shown in Table 1 below.
[0088] 4. Tensile strength: Using a universal testing machine, tensile tests were conducted on the liquid-cooled pipe samples prepared in the examples and comparative examples according to GB / T 1040.3-2006 standard. The tensile strength at fracture was recorded, and the test results are shown in Table 1 below.
[0089] 5. Extinguishing and cooling rate: By heating the lithium battery to induce a thermal runaway scenario (initial temperature 130℃), the time it took for the liquid cooling tube prepared in the example and comparative examples to break through the membrane and extinguish the fire under the action of the extinguishing medium was recorded. The average rate at which the temperature of the thermal runaway lithium battery dropped from 130℃ to 80℃ was recorded. The test results are shown in Table 1 below.
[0090] Table 1 - Performance test results of liquid cooling pipes prepared in the embodiments and comparative examples of this application The liquid cooling tubes of Embodiments 1-12 of this application utilize a temperature-sensitive brittle substrate layer to respond to the high-temperature signal at the initial stage of lithium battery thermal runaway, achieving precise self-rupture. A thermally enhanced intermediate layer is used to conduct the generated heat to the extinguishing medium, achieving efficient heat dissipation and improving the overall thermal conductivity. A sealed protective outer layer is used to prevent leakage of the extinguishing medium inside the tube, improving the tube's aging resistance, electrolyte corrosion resistance, and tensile strength. The three layers can rupture simultaneously at high temperatures, with a short thermal response film rupture time and a fast extinguishing and cooling rate, synergistically achieving the integrated functions of conventional heat dissipation, high-temperature self-rupture extinguishing, and sealed protection.
[0091] Compared to Example 1, the temperature-sensitive brittle substrate layer of Comparative Example 1 is formed only by the self-polymerization of NVCL. Due to the lack of epoxy chemical crosslinking sites of GMA, it cannot form a three-dimensional network structure, resulting in low molecular chain entanglement strength and insufficient toughness and compressive strength at room temperature. At the same time, it lacks the structural support of PLA, and only undergoes phase transformation softening at high temperatures without rapid brittle fracture, resulting in a severely delayed film rupture response. Furthermore, the interlayer bonding force is weak, and the heat conduction path is discontinuous, ultimately leading to a decrease in thermal conductivity, a decrease in tensile strength, and a significantly slower fire extinguishing and cooling rate.
[0092] Compared to Example 1, the temperature-sensitive brittle substrate layer of Comparative Example 2 is formed only by GMA self-polymerization. Since it does not contain NVCL temperature-sensitive structural units, the material does not have the low critical solution temperature (LCST) type temperature-sensitive brittleness characteristics. It has no active response capability to the high temperature in the early stage of lithium battery thermal runaway and can only rely on thermal degradation to slowly break down, which greatly prolongs the film breaking time. At the same time, the GMA self-polymerization crosslinking density is too high, resulting in high brittleness and poor toughness at room temperature. It lacks the flexibility of NVCL and the strength support of PLA, resulting in poor mechanical properties, low interfacial bonding and low thermal conductivity, which leads to a significant deterioration in the cooling and fire extinguishing effect.
[0093] Compared to Example 1, the temperature-sensitive brittle substrate layer of Comparative Example 3 is polylactic acid (PAL). PLA is a conventional biodegradable polymer and does not have the temperature-sensitive response function of NVCL. It has no ability to sense brittleness at high temperatures due to thermal runaway and can only slowly degrade and break down, resulting in the longest film rupture time. Due to the high brittleness and poor impact resistance of PLA at room temperature, and the lack of GMA cross-linking toughening and NVCL flexibility adjustment, the mechanical strength is reduced. In addition, the polarity matching degree between PLA and the thermally conductive reinforced intermediate layer and the sealing and protective outer layer is poor, resulting in weak interlayer interface bonding, hindering heat transfer of the liquid cooling pipe, reducing the thermal conductivity, and ultimately significantly reducing the fire extinguishing and cooling rate.
[0094] Compared to Example 1, Comparative Example 4 uses PVDF film preform blow molding and compression molding to prepare liquid cooling pipes. It does not have a temperature-sensitive embrittlement and thermally conductive composite layer structure. Because PVDF is resistant to high temperature and has high mechanical strength, the pipe body does not crack under the high temperature of lithium battery thermal runaway, resulting in the inability to release the fire extinguishing medium. At the same time, the lack of a thermally conductive reinforcement layer leads to poor heat dissipation, and ultimately the fire extinguishing and cooling function completely fails.
[0095] In Example 1 of this application, the strongly electronegative fluorine atoms (-F) in the PVDF molecular chain form hydrogen bonds with the nitrogen atoms (-N) on the imidazole rings of nano-ZIF-8. Simultaneously, the porous structure of ZIF-8 adsorbs the PVDF molecular chain, enhancing the bonding force between the two and forming a uniform and stable composite system. Furthermore, the hydroxyl groups on the surface of nano-ZIF-8 undergo a weak condensation reaction with the hydroxyl groups of mPEG in the thermally conductive reinforced intermediate layer, further enhancing the interlayer bonding force between the composite sealing and protective outer layer and the thermally conductive reinforced intermediate layer. Compared to Example 1, Comparative Example 5 did not include nano-ZIF-8 in its sealing and protective outer layer. The interlayer bonding force between the PVDF matrix and the thermally conductive reinforced intermediate layer decreased, resulting in weak interfacial bonding, asynchronous high-temperature film rupture, and a slower response. Insufficient material density and mechanical support led to a decrease in tensile strength, ultimately resulting in a significant reduction in the release delay and cooling rate of the extinguishing medium.
[0096] Compared to Example 1, in Comparative Example 6, mPEG in the thermally conductive reinforced intermediate layer is replaced by PVDF, and PVDF in the sealing and protective outer layer is replaced by mPEG. The use of PVDF in the thermally conductive reinforced intermediate layer will worsen the dispersibility of the thermally conductive filler, thus significantly reducing the thermal conductivity. The protective layer uses mPEG, and its mechanical strength, sealing performance, and corrosion resistance are all inferior to PVDF, resulting in a decrease in overall tensile strength. Furthermore, the poor interlayer compatibility leads to a slower thermal response film rupture, poor release of the extinguishing medium, and a significant decrease in the extinguishing and cooling rate.
[0097] Compared to Example 1, the liquid cooling pipe of Comparative Example 7 did not have a temperature-sensitive brittle substrate layer, and therefore lacked the ability to actively embrittle and break down the film at high temperatures, resulting in thermal response failure and the inability to release the extinguishing medium. Its extinguishing cooling rate was 0. The liquid cooling pipe of Comparative Example 8 did not have a thermally conductive enhanced intermediate layer, leading to impaired heat conduction, a significant reduction in the thermal coefficient, a marked decrease in the cooling rate, and poorer interlayer bonding, affecting simultaneous film rupture and mechanical strength.
[0098] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.
Claims
1. A liquid cooling pipe, characterized in that, The thermosensitive thermally conductive composite film blank is prepared by blow molding. The thermosensitive thermally conductive composite film blank includes a thermosensitive brittle substrate layer, a thermally conductive reinforced intermediate layer and a sealing and protective outer layer stacked sequentially from the inside to the outside of the liquid cooling pipe. The inside of the liquid cooling pipe is filled with fire extinguishing medium. The temperature-sensitive brittle substrate layer includes a copolymer, which includes structural units 1 derived from N-vinylcaprolactam, structural units 2 derived from glycidyl methacrylate, and structural units 3 derived from polylactic acid in a molar ratio of (40-60):(20-30):(20-30). The thermally conductive reinforced intermediate layer comprises a thermally conductive filler and polyethylene glycol methyl ether in a mass ratio of (30-45):(55-70); The sealing and protective outer layer comprises a thermoplastic fluoropolymer and nano MOF material in a mass ratio of (85-95):(5-15).
2. The liquid cooling pipe as described in claim 1, characterized in that, The thickness ratio of the temperature-sensitive brittle substrate layer, the thermally conductive reinforced intermediate layer, and the sealing and protective outer layer in the temperature-sensitive thermally conductive composite film blank is (3-5):(2-4):(2-4).
3. The liquid cooling pipe as described in claim 2, characterized in that, The thickness of the temperature-sensitive brittle substrate layer is 0.08-0.2 mm; And / or, the thickness of the thermally enhanced intermediate layer is 0.06-0.15 mm; And / or, the thickness of the sealing and protective outer layer is 0.06-0.15 mm; And / or, the total thickness of the temperature-sensitive thermally conductive composite film blank is 0.2-0.5 mm.
4. The liquid cooling pipe as described in claim 1, characterized in that, The thermally conductive filler includes at least one of graphene, aluminum nitride, aluminum oxide, silicon carbide, and zinc oxide; And / or, the nano MOF material includes at least one of nano ZIF-8, nano ZIF-67, and nano UiO-66; And / or, the particle size of the nano-MOF material is 50-200 nm; And / or, the thermoplastic fluoropolymer includes at least one of polyvinylidene fluoride, perfluoroalkoxyalkylene resin, perfluoroethylene propylene, and ethylene-tetrafluoroethylene copolymer.
5. The liquid cooling pipe as described in claim 1, characterized in that, The thermally conductive filler comprises modified graphene and aluminum nitride in a mass ratio of (10-15):(85-90), wherein the modified graphene is graphene with a silane coupling agent grafted onto its surface.
6. The liquid cooling pipe as described in claim 1, characterized in that, The molecular weight of the polylactic acid is 80,000-120,000.
7. The liquid cooling pipe as described in claim 1, characterized in that, The number-average molecular weight of the polyethylene glycol methyl ether in the thermally enhanced interlayer is 2000-4000; And / or, the number average molecular weight of the thermoplastic fluoropolymer in the sealing and protective outer layer is 50,000-80,000.
8. The liquid cooling pipe as described in claim 1, characterized in that, The extinguishing medium is an electronic fluorinated liquid; And / or, the volume fraction of the extinguishing medium in the liquid cooling pipe is 85%-95%.
9. A method for preparing a liquid-cooled tube as described in any one of claims 1-8, characterized in that, Includes the following steps: (1) The N-vinylcaprolactam, glycidyl methacrylate and polylactic acid are mixed to obtain a mixed monomer, a solvent is added and stirred to dissolve to obtain a mixed solution; an initiator is added and stirred to dissolve, and the reaction is carried out under an inert gas atmosphere to obtain a copolymer solution. The copolymer solution is coated and dried to form a temperature-sensitive and brittle substrate layer. (2) The thermally conductive filler and polyethylene glycol methyl ether are mixed and ultrasonically dispersed to obtain a composite material. The composite material is coated on the surface of a temperature-sensitive and brittle substrate layer and dried to form a thermally conductive and reinforced intermediate layer. (3) The thermoplastic fluoropolymer and nano MOF material are mixed to obtain a mixture, a solvent is added and mixed evenly to obtain a composite solution; the composite solution is coated on the surface of the thermally conductive reinforced intermediate layer, and after drying, a sealed protective outer layer is formed to prepare a temperature-sensitive thermally conductive composite film blank; (4) The temperature-sensitive thermally conductive composite film blank is blow-molded and molded to prepare the tube body; (5) Fire extinguishing medium is injected into the pipe body and hot-melt sealing is performed using a sealing joint to prepare a liquid-cooled pipe.
10. The application of a liquid cooling pipe as described in any one of claims 1-8 in a lithium battery safety control device.