Energy storage battery immersed cooling liquid based on fluorinated nanofluid and preparation method of energy storage battery immersed cooling liquid

Abstract

The invention provides energy storage battery immersed cooling liquid based on fluorinated nanofluid and a preparation method, and belongs to the technical field of heat management of energy storage equipment, the energy storage battery immersed cooling liquid comprises 74-84% of perfluoropolyether base liquid, 10-15% of surface modified boron nitride nanosheets, 5-8% of microencapsulated perfluorohexanone and 1-3% of polydimethylsiloxane modified silicon dioxide. Microencapsulated perfluorohexanone is integrated into the cooling liquid to achieve the dual functions of heat dissipation and fire extinguishment, and synergistic effects are generated in the aspects of heat conduction, insulation, fire extinguishment and the like through combined use of the perfluoropolyether base liquid, the surface modified boron nitride nanosheets, the microencapsulated perfluorohexanone and polydimethylsiloxane modified silicon dioxide and specific modification performance of the perfluoropolyether base liquid, the surface modified boron nitride nanosheets, the microencapsulated perfluorohexanone and the polydimethylsiloxane modified silicon dioxide. And experimental data can prove that the comprehensive performance of the material has substantive features and remarkable progress in the aspects of heat conductivity coefficient improvement, fire extinguishing time and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage device thermal management, in particular to a fluorinated nanofluid-based immersion cooling liquid for energy storage batteries and a preparation method thereof. BACKGROUND

[0002] Although the existing cooling liquid adds Al2O3, graphene and other thermal conductive fillers, the thermal conductivity can be improved, but there are problems such as sedimentation (delamination rate > 15% after standing for 24h) and viscosity surge (> 100 mPa·s). Fluorine-containing ether fluids (such as HFE-7100) have non-flammability, but their low boiling point (≈60℃) is prone to gas-liquid phase change, resulting in pressure fluctuations in the cooling system.

[0003] The existing cooling liquid has the following problems:

[0004] Insufficient thermal conductivity: the thermal conductivity of traditional mineral oil and silicone oil cooling liquid is less than 0.1 W / m·K, which cannot meet the heat dissipation requirements of high-energy-density batteries, resulting in a large temperature difference (> 5℃) between the cells, accelerating capacity decay.

[0005] Flammability risk: the flash point of conventional cooling liquid is generally lower than 200℃, and the oxygen index (OI) is less than 30%, which can easily become a combustible agent during battery thermal runaway, increasing the risk of fire.

[0006] Single function: the existing immersion liquid only focuses on heat dissipation, lacks active fire extinguishing mechanism, and needs to be equipped with a fire extinguishing system, increasing the complexity and cost of the system. SUMMARY

[0007] To solve the above technical problems, the present application provides a high-efficiency fire extinguishing type cooling medium suitable for immersion liquid cooling battery system, especially for the thermal runaway inhibition and rapid heat dissipation requirements of lithium ion battery pack under high-rate charging and discharging conditions.

[0008] To solve the above technical problems, the technical solution provided by the present application is:

[0009] A fluorinated nanofluid-based immersion cooling liquid for energy storage batteries, comprising perfluoropolyether base fluid 74-84%, surface-modified boron nitride nanosheet 10-15%, microencapsulated perfluorohexanone 5-8%, and polydimethylsiloxane modified silicon dioxide 1-3%.

[0010] Preferably, the surface-modified boron nitride nanosheet has a lateral size of 1-3 μm, a thickness of 5-20 nm, and a surface grafted fluorosilane coupling agent.

[0011] Preferably, the perfluoropolyether base fluid is a linear PFPE with a molecular weight range of 8000-12000, and has a high flash point > 300℃.

[0012] Preferably, the polydimethylsiloxane-modified silica is hydrophobic fumed silica that is grafted with polydimethylsiloxane to form a three-dimensional network structure and maintain a viscosity of less than 80 mPa·s.

[0013] Preferably, the microencapsulated perfluorohexanone capsules are broken when the temperature is greater than 180°C.

[0014] A method for preparing an energy storage battery immersion coolant based on fluorinated nanofluids comprises the following steps:

[0015] S1, mixing the surface-modified boron nitride nanosheets with a perfluoropolyether base liquid, and ultrasonically dispersing them at 38-42 kHz and 580-620 W power for 1.5-2.5 h;

[0016] S2, adding microencapsulated perfluorohexanone and polydimethylsiloxane-modified silica, and degassing under vacuum at -0.1 MPa for 28-35 min;

[0017] S3, purify through 0.18-0.25 μm microfiltration membrane to obtain the finished product.

[0018] Preferably, the wall material of the microencapsulated perfluorohexanone is a polyurea-silica hybrid material, and the capsule core accounts for ≥85%.

[0019] After adopting the above formula and method, the present invention has the following advantages:

[0020] The microencapsulated perfluorohexanone of the present invention is integrated into the coolant to achieve the dual functions of heat dissipation and fire extinguishing. Through the combined use of perfluoropolyether base liquid, surface-modified boron nitride nanosheets, microencapsulated perfluorohexanone and polydimethylsiloxane-modified silica and the specific modification, a synergistic effect is produced in terms of thermal conductivity, insulation, fire extinguishing, etc., and experimental data can confirm that its comprehensive performance has substantial characteristics and significant improvements in terms of improved thermal conductivity coefficient and fire extinguishing time.

[0021] The above summary is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features of the present invention will be readily apparent from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] none DETAILED DESCRIPTION

[0023] Reference will now be made in detail to the specific embodiments of the application. While the application will be described in conjunction with these specific embodiments, it will be understood that it is not intended to limit the application to these specific embodiments. On the contrary, it is intended to cover alternatives, modifications, and equivalents, which can be included within the spirit and scope of the application as defined by the claims. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. The present application can be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the present application.

[0024] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0025] The application will be further described in conjunction with the entire text.

[0026] In conjunction with the entire text, a fluorinated nanofluid-based energy storage battery immersion coolant includes a perfluoropolyether base fluid 74-84%, surface-modified boron nitride nanosheets 10-15%, microencapsulated perfluorohexanone 5-8%, and polydimethylsiloxane-modified silica 1-3%.

[0027] The surface-modified boron nitride nanosheets have a lateral size of 1-3 μm, a thickness of 5-20 nm, and a surface grafted fluorosilane coupling agent.

[0028] The perfluoropolyether base fluid is a linear PFPE with a molecular weight range of 8000-12000, and a high flash point >300°C.

[0029] The polydimethylsiloxane-modified silica is a hydrophobic fumed silica that is grafted and modified with polydimethylsiloxane to form a three-dimensional network structure, and maintains a viscosity <80 mPa·s.

[0030] The microencapsulated perfluorohexanone ruptures at a temperature >180°C. Specifically, the microencapsulated perfluorohexanone is introduced into the coolant, which simultaneously enhances the heat dissipation and fire extinguishing functions, and has a synergistic effect,

[0031] A preparation method of a fluorinated nanofluid-based energy storage battery immersion coolant includes the following steps:

[0032] S1, surface-modified boron nitride nanosheets are mixed with a perfluoropolyether base fluid, ultrasonic dispersion is performed at 38-42 kHz and 580-620 W power for 1.5-2.5 h, the liquid temperature is controlled to be <50°C, and uniform dispersion of the nanosheets is ensured without structural damage.

[0033] S2, add microencapsulated perfluorohexanone and polydimethylsiloxane modified silica, vacuum degassing at -0.1 MPa for 28-35 min to eliminate air bubbles entrained during dispersion and avoid air blockage in the microfiltration stage.

[0034] S3, purified through a 0.18-0.25 μm microfiltration membrane to obtain the finished product.

[0035] Specifically, the un-dispersed BNNS agglomerates and impurities are removed through a 0.18-0.25 μm nylon filter membrane to obtain a clear and transparent nanofluid.

[0036] The wall material of the microencapsulated perfluorohexanone is a polyurea-silica hybrid material, and the core proportion is ≥85%.

[0037] The perfluoropolyether (PFPE) base fluid can select a linear PFPE with a molecular weight range of 8000-12000. The high flash point (>300℃) and low viscosity (40℃ kinematic viscosity <50 cSt) characteristics of PFPE take into account the flowability and thermal stability.

[0038] The surface-modified boron nitride nanosheet (BNNS, 10-15 wt%) has a lateral size of 1-3 μm and a thickness of 5-20 nm. The BNNS is surface-modified with a fluorosilane coupling agent to improve the interfacial compatibility with PFPE. The directional arrangement mechanism: the microflow field generated by 40 kHz ultrasonic cavitation effect promotes the ordered arrangement of BNNS along the heat flow direction, forming an efficient heat conduction path, and the thermal conductivity is >0.5 W / m·K.

[0039] The microencapsulated perfluorohexanone (5-8 wt%) is used as a liquid extinguishing agent and is dispersed in the base fluid in the form of microcapsules. When the temperature is >180℃, the capsules rupture, releasing perfluorohexanone to absorb heat (latent heat of vaporization ≈110 kJ / kg) and isolate oxygen (oxygen index >95%), achieving "cooling-asphyxia" dual extinguishing.

[0040] The modified silica (1-3 wt%) is a hydrophobic fumed silica modified by polydimethylsiloxane grafting to form a three-dimensional network structure, which inhibits the sedimentation of BNNS (30-day sedimentation rate <3%) while maintaining a viscosity <80 mPa·s. The polydimethylsiloxane-modified silica not only improves the stability of the coolant but also enhances its low surface energy characteristics. The use of hydrophobic fumed silica helps to improve the dispersibility and stability of the coolant due to its high solid content and small particle size. The polydimethylsiloxane-modified silica in the coolant has the effects of improving hydrophobicity, improving rheological properties, enhancing oxidation resistance and thermal stability, reducing foaming, and optimizing interfacial phenomena.

[0041] The surface of the surface-modified boron nitride nanosheet is grafted with a fluorosilane coupling agent to improve dispersibility and interfacial thermal conductivity.

[0042] The existing coolant only uses perfluorohexanone as a diluent and does not achieve functional encapsulation. The polydimethylsiloxane modified silica is not used as a stabilizer or leveling agent in the existing technology. This component can improve the flowability and thermal stability of the liquid. The microencapsulated perfluorohexanone of the present application is integrated into the coolant to achieve the dual functions of heat dissipation and fire extinguishing. Through the combined use of perfluoropolyether base fluid, surface-modified boron nitride nanosheet, microencapsulated perfluorohexanone, and polydimethylsiloxane modified silica, and specific modifications such as surface treatment of boron nitride and introduction of microencapsulated perfluorohexanone, synergistic effects can be achieved in terms of thermal conductivity, insulation, fire extinguishing, and the like.

[0043] The technical effects of the present application are as follows:

[0044] Synergistic improvement of thermal conductivity and insulation: The combination of surface-modified boron nitride nanosheet (high thermal conductivity) and perfluoropolyether (high insulation) can simultaneously meet the stringent requirements of immersion coolant for thermal conductivity and insulation.

[0045] Integration of active fire extinguishing function: Microencapsulated perfluorohexanone can rupture and release fire extinguishing agent at high temperature, solving the pain point of traditional coolant lacking active safety protection.

[0046] Synergism of BNNS directional arrangement and perfluorohexanone temperature-controlled release, making the coolant efficiently dissipate heat (thermal conductivity improved by 5 times) in normal state and start fire extinguishing in seconds (fire extinguishing time <10s) in thermal runaway.

[0047] Process adaptability: Microencapsulation of perfluorohexanone reduces volatility (low GWP), and polydimethylsiloxane modified silica enhances system stability, conforming to environmental trends. The modified silica network cooperates with the surface modification of BNNS, solving the contradiction between high solid content nanofluid and viscosity, and ensuring long-term circulation performance.

[0048] Environmental compatibility: The perfluoro component has zero ODP and low GWP, conforming to the requirements of EU F-gas regulations.

[0049] Example 1:

[0050] An energy storage battery immersion coolant based on fluorinated nanofluid, comprising perfluoropolyether base fluid 84%, surface-modified boron nitride nanosheet 10%, microencapsulated perfluorohexanone 5%, and polydimethylsiloxane modified silica 1%.

[0051] The surface-modified boron nitride nanosheet has a lateral size of 2 μm and a thickness of 8 nm, and is grafted with a fluorosilane coupling agent.

[0052] The perfluoropolyether base liquid is a linear PFPE with a molecular weight range of 10000, and has a high flash point of 350 DEG C.

[0053] A preparation method of a fluorinated nanofluid-based energy storage battery immersion coolant, comprising the following steps:

[0054] S1, mix the surface-modified boron nitride nanosheet with the perfluoropolyether base liquid, and ultrasonically disperse for 1.5 h under 40 kHz and 600 W power;

[0055] S2, add microencapsulated perfluorohexanone and polydimethylsiloxane-modified silicon dioxide, and vacuum degas at -0.1 MPa for 30 min;

[0056] S3, purify through a 0.2 μm microfiltration membrane to obtain a finished product.

[0057] Example Two:

[0058] A fluorinated nanofluid-based energy storage battery immersion coolant, comprising a perfluoropolyether base liquid 79%, a surface-modified boron nitride nanosheet 15%, microencapsulated perfluorohexanone 5%, and polydimethylsiloxane-modified silicon dioxide 1%.

[0059] The surface-modified boron nitride nanosheet has a lateral size of 2 μm, a thickness of 8 nm, and a fluorosilane coupling agent grafted on the surface.

[0060] The perfluoropolyether base liquid is a linear PFPE with a molecular weight range of 10000, and has a high flash point of 350 DEG C.

[0061] A preparation method of a fluorinated nanofluid-based energy storage battery immersion coolant, comprising the following steps:

[0062] S1, mix the surface-modified boron nitride nanosheet with the perfluoropolyether base liquid, and ultrasonically disperse for 1.5 h under 40 kHz and 600 W power;

[0063] S2, add microencapsulated perfluorohexanone and polydimethylsiloxane-modified silicon dioxide, and vacuum degas at -0.1 MPa for 30 min;

[0064] S3, purify through a 0.2 μm microfiltration membrane to obtain a finished product.

[0065] Example Three:

[0066] A fluorinated nanofluid-based energy storage battery immersion coolant, comprising a perfluoropolyether base liquid 76%, a surface-modified boron nitride nanosheet 15%, microencapsulated perfluorohexanone 8%, and polydimethylsiloxane-modified silicon dioxide 1%.

[0067] The surface-modified boron nitride nanosheet has a lateral size of 2 μm, a thickness of 8 nm, and a fluorosilane coupling agent grafted on the surface.

[0068] The perfluoropolyether base liquid has a linear PFPE with a molecular weight range of 10000, and a high flash point of 350℃.

[0069] A preparation method of a fluorinated nanofluid-based energy storage battery immersion coolant, comprising the following steps:

[0070] S1, mix the surface-modified boron nitride nanosheet with the perfluoropolyether base liquid, and ultrasonically disperse for 2h under 40kHz and 600W power;

[0071] S2, add microencapsulated perfluorohexanone and polydimethylsiloxane-modified silicon dioxide, and vacuum degas at -0.1MPa for 30min;

[0072] S3, purify through a 0.22μm microfiltration membrane to obtain the finished product.

[0073] Example Four:

[0074] A fluorinated nanofluid-based energy storage battery immersion coolant, comprising perfluoropolyether base liquid 74%, surface-modified boron nitride nanosheet 15%, microencapsulated perfluorohexanone 8%, and polydimethylsiloxane-modified silicon dioxide 3%.

[0075] The surface-modified boron nitride nanosheet has a lateral size of 2μm, a thickness of 8nm, and a surface grafted fluorosilane coupling agent.

[0076] The perfluoropolyether base liquid has a linear PFPE with a molecular weight range of 10000, and a high flash point of 350℃.

[0077] A preparation method of a fluorinated nanofluid-based energy storage battery immersion coolant, comprising the following steps:

[0078] S1, mix the surface-modified boron nitride nanosheet with the perfluoropolyether base liquid, and ultrasonically disperse for 2h under 40kHz and 600W power;

[0079] S2, add microencapsulated perfluorohexanone and polydimethylsiloxane-modified silicon dioxide, and vacuum degas at -0.1MPa for 30min;

[0080] S3, purify through a 0.22μm microfiltration membrane to obtain the finished product.

[0081] Example Five:

[0082] A fluorinated nanofluid-based energy storage battery immersion coolant, comprising perfluoropolyether base liquid 84%, surface-modified boron nitride nanosheet 10%, microencapsulated perfluorohexanone 5%, and polydimethylsiloxane-modified silicon dioxide 1%.

[0083] The surface-modified boron nitride nanosheet has a lateral size of 3μm, a thickness of 20nm, and a surface grafted fluorosilane coupling agent.

[0084] The molecular weight of the perfluoropolyether base liquid is 10000, the linear type PFPE has a high flash point of 400 DEG C.

[0085] A preparation method of a fluorinated nanofluid-based energy storage battery immersion coolant, comprising the following steps:

[0086] S1, the surface modified boron nitride nanosheet is mixed with the perfluoropolyether base liquid, and ultrasonic dispersion is carried out at 40 kHz and 600 W power for 2 h;

[0087] S2, adding microencapsulated perfluorohexanone and polydimethylsiloxane modified silicon dioxide, vacuum degassing at-0.1 MPa for 30 min;

[0088] S3, purified through a 0.2 mu m microfiltration membrane to obtain a finished product.

[0089] Comparative experiment:

[0090] The comparative example uses commercial silicone oil, and then tests and experiments of example one, example two, example three, example four and example five are carried out to detect the heat conductivity coefficient improvement, fire extinguishing response time shortening and the like, and test data are shown in table 1.

[0091] Table 1

[0092]

[0093] The application realizes the synergistic optimization of heat conduction, insulation, fire extinguishing, environmental protection and the like through component innovation combination and modification technology, and experimental data can prove that the comprehensive performance is significantly better than that of the prior art (such as heat conductivity coefficient improvement, fire extinguishing time and the like), so that it has outstanding substantial features and significant progress.

[0094] The above describes the application and its embodiments, which are not limited, and the shown in the full text is only one of the embodiments of the application, and the actual structure is not limited thereto. In general, if a person skilled in the art is inspired thereby, without departing from the purpose of the application, without creative design, similar structure and embodiments of the technical scheme can be obtained, which should belong to the protection scope of the application.

Claims

1. An immersion coolant for energy storage batteries based on fluorinated nanofluids, characterized in that: The invention comprises 74-84% of perfluoropolyether base liquid, 10-15% of surface-modified boron nitride nanosheets, 5-8% of microencapsulated perfluorohexanone and 1-3% of polydimethylsiloxane-modified silicon dioxide.

2. The fluorinated nanofluid-based energy storage battery immersion coolant according to claim 1, characterized in that: The surface-modified boron nitride nanosheet has a lateral size of 1-3 μm and a thickness of 5-20 nm, and a fluorosilane coupling agent is grafted onto the surface.

3. The fluorinated nanofluid-based energy storage battery immersion coolant according to claim 1, characterized in that: The perfluoropolyether base liquid is a linear PFPE with a molecular weight ranging from 8000 to 12000 and a high flash point greater than 300°C.

4. The fluorinated nanofluid-based energy storage battery immersion coolant according to claim 1, characterized in that: The polydimethylsiloxane-modified silica is hydrophobic fumed silica that is grafted with polydimethylsiloxane to form a three-dimensional network structure and maintain a viscosity of less than 80 mPa·s.

5. The fluorinated nanofluid-based energy storage battery immersion coolant according to claim 1, characterized in that: The microencapsulated perfluorohexanone capsules are broken when the temperature is greater than 180°C.

6. A method for preparing an immersion coolant for energy storage batteries based on fluorinated nanofluids, characterized in that: The following steps are involved: S1, mixing the surface-modified boron nitride nanosheets with a perfluoropolyether base liquid, and ultrasonically dispersing them at 38-42 kHz and 580-620 W power for 1.5-2.5 h; S2, adding microencapsulated perfluorohexanone and polydimethylsiloxane-modified silica, and degassing under vacuum at -0.1 MPa for 28-35 min; S3, purify through 0.18-0.25 μm microfiltration membrane to obtain the finished product.

7. The method for preparing the immersion coolant for energy storage batteries based on fluorinated nanofluids according to claim 6, characterized in that: The wall material of the microencapsulated perfluorohexanone is a polyurea-silica hybrid material, and the capsule core accounts for ≥85%.

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