Packaging coating for fireproof and heat-insulating aerogel gasket of power battery cell and application thereof

Abstract

The application relates to the technical field of power battery fireproof and heat-insulating materials, and discloses a packaging coating for a power battery cell fireproof and heat-insulating aerogel gasket and application thereof. The packaging coating comprises the following components in parts by weight: 8-12 parts of a matrix resin, 6-20 parts of a curing agent, 30-40 parts of an intumescent flame retardant, 5-10 parts of nanofibers, 0-8 parts of expandable graphite and 0-0.4 parts of a dispersing agent. The packaging coating can solve the problem of aerogel gasket powder falling and can realize good fireproof performance at a lower thickness of the formed packaging coating.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fireproof and heat insulation materials for power batteries, and particularly relates to a packaging coating for a fireproof and heat insulation aerogel gasket of a power battery cell and application thereof. BACKGROUND

[0002] A battery pack of a power battery and an energy storage battery is composed of a plurality of single battery modules. In the use process, the battery cell may heat up due to charging, discharging, short circuit and other reasons, and heat runaway may occur. The heat runaway is transmitted and spread to other single battery cells, causing the temperature of the surrounding battery cells to rapidly rise, and the temperature may be as high as 500-1000 DEG C. Finally, the whole battery pack may catch fire and explode, which is one of the important problems that have plagued the new energy industry. A conventional and effective method is to use a heat insulation material to block the heat transfer path between the battery cells to avoid the spread of heat runaway, thereby preventing the spread of heat runaway.

[0003] Silica aerogel is a material with low thermal conductivity, and has attracted much attention in the field of cell heat insulation materials. The use of aerogel composite ceramic fiber felt to prepare a heat insulation gasket can solve the defect of insufficient mechanical properties of silica aerogel. However, in the process of automobile operation and battery assembly, the aerogel core material is easy to be affected by vibration and impact, and dust may fall off. The falling off of dust may affect the service life and safety of the battery cell. The silica dust accumulated in the cooling channel or heat dissipation surface of the battery module may hinder heat dissipation, affect the efficiency of the battery temperature control system, cause the battery to overheat, and increase the risk of heat runaway. If the aerogel heat insulation gasket is damaged or thinned in structure due to the falling off of dust, the heat insulation performance thereof will be reduced, and the temperature uniformity of the battery cell will be affected.

[0004] In view of the problem that the aerogel heat insulation gasket is easy to fall off dust, the current solution is to use a PET film or a PI film for packaging. Although this can effectively prevent the falling off of dust of the aerogel core material, these film materials do not have a fireproof effect. In addition, due to space limitations, the fireproof and heat insulation gasket used between power battery cells needs to be as light and thin as possible. However, when a conventional fireproof coating used in other fields is used in the fireproof and heat insulation gasket of a power battery cell, it is difficult to achieve an ideal fireproof effect at a low thickness. SUMMARY

[0005] In order to solve the above technical problems, that is, the conventional fireproof and heat insulation coating is difficult to achieve an ideal fireproof effect at a low thickness, the present application provides a packaging coating for a fireproof and heat insulation aerogel gasket of a power battery cell and application thereof. The use of the packaging coating can solve the problem of dust falling off of the aerogel gasket, and the formed packaging coating can achieve good fireproof performance at a relatively low thickness.

[0006] The specific technical scheme of the present application is as follows:

[0007] In a first aspect, the present application provides a packaging coating for a fireproof and heat-insulating aerogel gasket of a power battery cell, comprising the following components by weight: 8-12 parts of a base resin, 6-20 parts of a curing agent, 30-40 parts of an intumescent flame retardant, 5-10 parts of nanofibers, 0-8 parts of expandable graphite, and 0-0.4 parts of a dispersing agent.

[0008] The nanofibers, in cooperation with the intumescent flame retardant and the expandable graphite, can improve the fireproof performance of the packaging coating. Specifically, when the packaging coating is in a high temperature, the packaging coating will melt and foam under the action of the intumescent flame retardant and the expandable graphite, and form a flame-retardant carbon layer. The nanofibers interact with the expanded coating to form a stable three-dimensional crosslinked network structure, and the nanofibers are connected to each other and interpenetrate in the expanded coating and the flame-retardant carbon layer, which can provide additional physical support for the flame-retardant carbon layer, reduce the structural collapse of the flame-retardant carbon layer at high temperatures, so that the carbon layer can better play a role in blocking oxygen, and improve the expansion ratio of the flame-retardant system, so as to achieve better flame-retardant effect. Compared with the traditional micron-diameter fiber reinforcement, the number of uniformly dispersed short-cut nanofibers in a unit volume is more than 100 times that of micron-level fibers at the same addition amount (mass fraction), so that the nanofibers can significantly enhance and toughen the expanded carbon layer. In the above manner, the packaging coating can be thinned while ensuring the fireproof performance of the packaging coating, and the space occupied by the gasket with the packaging coating in the battery can be reduced.

[0009] Preferably, the base resin is a cycloaliphatic epoxy resin with an epoxy equivalent weight of 130-180.

[0010] The power battery will experience vibration and impact during use, which requires the packaging coating on the surface of the gasket to have high toughness and mechanical strength to maintain stability, not to crack or fall off in such an environment. In addition, since new energy vehicles often need to be used in cold regions, the packaging coating on the surface of the fireproof and heat-insulating gasket of the power battery cell needs to have good low-temperature flexibility to avoid brittle fracture, cracking and reduced adhesion at low temperatures, which may cause the overall packaging coating to fall off and be damaged, affecting the heat-insulating protection effect of the gasket on the power battery.

[0011] To meet the above special requirements, the present application selects a cycloaliphatic epoxy resin with an epoxy equivalent weight of 130-180 as the base resin in the packaging coating, which can endow the coating with good low-temperature flexibility, so that the coating can still maintain good integrity at low temperatures.

[0012] Preferably, the curing agent is a double-end amino polyether amine with a number average molecular weight of 1000-20000 Da.

[0013] The double-end amino polyether amine with a number average molecular weight of 1000-20000 Da has long chains and ether bonds in the molecular structure, has strong chain segment movement ability and small steric hindrance, and has strong molecular chain flexibility and movement ability after curing and cross-linking with the epoxy resin, small cross-linking density, and thus low glass transition temperature, which is beneficial to keeping good flexibility of the encapsulation coating in a low-temperature environment and keeping good adhesion between the encapsulation coating and the aerogel core material, thereby avoiding cracking and peeling of the encapsulation coating.

[0014] Preferably, the mass ratio of the base resin to the nanofiber is not less than 1:0.5.

[0015] Further, the mass ratio of the base resin to the nanofiber is 1:0.5-0.7.

[0016] In the encapsulation coating, when the content of the nanofiber is too low, the nanofiber has poor supporting effect on the flame-retardant carbon layer, and thus the encapsulation coating has poor fireproof performance; when the content of the nanofiber is too high, the bonding strength between the encapsulation coating and the aerogel core material is low, and the encapsulation coating is prone to cracking and peeling. Based on this, the mass ratio of the base resin to the nanofiber is controlled to be 1:0.5-0.7, which can improve the fireproof performance of the encapsulation coating and make the encapsulation coating have high bonding strength with the aerogel core material.

[0017] Preferably, the mass ratio of the base resin to the curing agent is 1:0.75-1.25.

[0018] Preferably, the nanofiber has a diameter of 100-300 nm and a length of 40-80 um.

[0019] Preferably, the nanofiber is porous silica nanofiber.

[0020] The silica nanofiber can form a stable slurry organization with other components in the encapsulation coating, and the porous structure on the surface of the silica nanofiber can improve the friction between the nanofibers and between the nanofiber and the base resin, so that the network structure formed by the mutual connection between the nanofibers and the interaction between the nanofiber and the base resin can provide better support for the flame-retardant carbon layer formed at high temperature, thereby improving the fireproof performance of the encapsulation coating.

[0021] Preferably, the intumescent flame retardant includes ammonium polyphosphate (APP), pentaerythritol (PER), and melamine (MEL).

[0022] The three components in the intumescent flame retardant cooperate with each other and can expand rapidly at high temperature to generate a flame-retardant carbon layer, which has excellent flame-retardant and heat-insulating effects.

[0023] Further, the mass ratio of the ammonium polyphosphate (APP), the pentaerythritol (PER) and the melamine (MEL) is 2-3:1:1-2.

[0024] As preferred, the expandable graphite is 3-8 parts by weight.

[0025] As preferred, the dispersant is 0.2-0.4 parts by weight.

[0026] As preferred, the dispersant comprises one or more of ethylamino acetic acid (MEA), diethanolamine (DEA) and sodium metaphosphate.

[0027] As preferred, the encapsulation coating further comprises a dispersion medium.

[0028] In a second aspect, the present application provides an application of the encapsulation coating in a fireproof and heat-insulating aerogel pad for power battery cells, the fireproof and heat-insulating aerogel pad comprising an aerogel core material and an encapsulation coating formed by the fireproof coating, the encapsulation coating being coated on the surface of the ceramic fiber aerogel core material.

[0029] As preferred, the thickness of the encapsulation coating is 150-200 μm.

[0030] As preferred, the preparation method of the fireproof and heat-insulating aerogel pad comprises the following steps:

[0031] S1: mixing all components of the encapsulation coating to prepare the encapsulation coating;

[0032] S2: coating the encapsulation coating on the outer surface of the aerogel core material, and after drying and solidifying, forming the encapsulation coating.

[0033] Further, in step S2, the specific process of drying and solidifying comprises the following steps: after natural surface drying, drying at 100-150 °C for 1-2 h.

[0034] Further, after step S2, hydrophobic modification is performed, and the specific process comprises the following steps: placing the pad prepared in step S2 in a sealed container, vacuumizing to -0.05 to -0.08 MPa, heating to 80-90 °C, then adding a mixed solution of hydrophobic silane modifier and acetic acid, and reacting for 2-3 h.

[0035] Further, the hydrophobic silane modifier is one or more of methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane and ethyltrichlorosilane.

[0036] As preferred, the surface porosity of the aerogel core material is not higher than 20%.

[0037] When the surface porosity of the core material is not higher than 20%, more anchor points can be provided for the encapsulation coating, so that the coating is easy to form a uniform and continuous coverage on the surface of the core material, thereby improving the bonding strength of the coating on the surface of the core material.

[0038] Preferably, the preparation method of the aerogel core material comprises the following steps:

[0039] (A) mixing polyethyl silicate, methyl triethoxysilane and 35-45 wt% basic silica sol in a mass ratio of 2-4:1-3:1 to obtain a silicon source precursor;

[0040] (B) mixing the silicon source precursor, ethanol and 0.5-2 mol / L hydrochloric acid in a mass ratio of 6:10-40:0.4-0.6, stirring and reacting for 8-24 h to obtain a hydrolysis solution;

[0041] (C) adding 0.5-2 mol / L ammonia water and 0.5-2 mol / L NH4F aqueous solution to the hydrolysis solution in a mass ratio of 41-42:1:0.1-0.3, stirring and reacting for 2-5 min to obtain a sol;

[0042] (D) under vacuum conditions, immersing the ceramic fiber felt in the sol, standing to form an alcogel on the surface of the ceramic fiber felt after gelation, obtaining an alcogel composite core material, and continuing to stand to age the gel.

[0043] The aerogel core material prepared by the above method can have a lower surface porosity while ensuring a lower thermal conductivity, so that the core material has a higher bonding strength with the encapsulation coating, and the gasket has better fireproof and heat insulation performance.

[0044] Further, after step (D), the aged alcogel composite core material is placed in a modification liquid for solvent replacement and silicon methylation modification, and then dried to obtain an aerogel core material.

[0045] Preferably, the preparation method of the nanofiber comprises the following steps:

[0046] (1) preparing a spinning solution by mixing a silicon source, a polymer pore former, an acid catalyst and water;

[0047] (2) spinning by using the spinning solution to obtain a precursor fiber;

[0048] (3) sintering the precursor fiber in an oxygen atmosphere, then mixing with water, dissociating and dispersing, removing the water, and then crushing and grinding to obtain a nanofiber.

[0049] By using the above method, porous silica nanofibers can be prepared.

[0050] Further, in step (1), the mass ratio between the silicon source and the polymer porogen is 1:0.3-0.4.

[0051] By controlling the ratio of the silicon source and the polymer porogen within the above range, the prepared nanofiber has higher porosity, thereby improving the friction between the nanofibers and between the nanofibers and the matrix resin, providing better support for the flame-retardant carbon layer formed at high temperature, thereby improving the fireproof performance of the encapsulation coating.

[0052] Further, in step (1), the silicon source is tetraethyl orthosilicate, the polymer porogen is polyvinyl alcohol, and the acid catalyst is HCl.

[0053] Further, the specific process of step (1) includes the following steps: adding 0.6-1 mol / L acid catalyst aqueous solution to 10-25 wt% silicon source aqueous solution, mixing, then adding 5-10 wt% polymer porogen aqueous solution, and mixing to obtain a spinning solution.

[0054] Further, the specific process of step (2) includes the following steps: using a needle tube to draw the spinning solution, spinning on a gas spinning machine, and obtaining a precursor fiber.

[0055] Further, in step (3), the sintering temperature is 500-800 DEG C, and the time is 10-30 min.

[0056] Further, in step (3), the specific process of removing water includes the following steps: filtering to collect the filter residue, and freeze-drying at -70 to -40 DEG C for 10-15 h.

[0057] Further, in step (3), the pulverizing and grinding method is ball milling, the rotation speed is 400-500 r / min, and the time is 1-3 h.

[0058] Compared with the prior art, the present application has the following advantages:

[0059] (1) The encapsulation coating in the present application can form an encapsulation coating on the surface of the aerogel core material, which has high strength and toughness, is not easy to crack and powder, and can effectively solve the problem of aerogel gasket powder.

[0060] (2) In the encapsulation coating of the present application, nanofibers are used in combination with intumescent flame retardants and expandable graphite, which can support the flame-retardant carbon layer formed at high temperature and improve the expansion ratio of the flame-retardant system, thereby making the encapsulation coating light and thin, and achieving good fireproof effect at a lower thickness.

[0061] (3) The packaging coating of the present application can impart good low-temperature flexibility to the coating layer by selecting specific matrix resin and curing agent, so that the coating layer can maintain good flexibility in low-temperature environment and maintain good adhesion with the aerogel core material, thereby avoiding cracking and peeling of the coating layer, and enabling the packaging coating to better adapt to the use requirements of the power battery in low-temperature environment. BRIEF DESCRIPTION OF DRAWINGS

[0062] Figure 1 Picture of the fireproof and thermal insulation aerogel gasket prepared in Example 1 after combustion. DETAILED DESCRIPTION

[0063] The present application will be further described in conjunction with examples. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application, and the changes and advantages that can be thought of by those skilled in the art without departing from the spirit and scope of the present application are included in the present application, and the appended claims and any equivalents thereof are the protection scope of the present application.

[0064] General examples

[0065] A packaging coating for a fireproof and thermal insulation aerogel gasket of a power battery cell, comprising the following components by weight: 8-12 parts of matrix resin, 6-20 parts of curing agent, 30-40 parts of intumescent flame retardant, 5-10 parts of nanofiber, 0-8 parts of expandable graphite, and 0-0.4 parts of dispersing agent.

[0066] As a specific embodiment, the packaging coating further comprises a dispersing medium.

[0067] As a specific embodiment, the weight of the expandable graphite is 3-8 parts, and the weight of the dispersing agent is 0.2-0.4 parts.

[0068] As a specific embodiment, the mass ratio of the matrix resin to the nanofiber is 1:0.5-0.7.

[0069] As a specific embodiment, the matrix resin is an alicyclic epoxy resin with an epoxy equivalent weight of 130-180; the curing agent is a double-end amino polyether amine with a number average molecular weight of 1000-20000 Da; and the mass ratio of the matrix resin to the curing agent is 1:0.75-1.25.

[0070] As a specific embodiment, the nanofiber is a porous silica nanofiber with a diameter of 100-300 nm and a length of 40-80 μm.

[0071] As a specific embodiment, the intumescent flame retardant comprises ammonium polyphosphate (APP), pentaerythritol (PER) and melamine (MEL) in a mass ratio of 2-3:1:1-2.

[0072] As a specific embodiment, the dispersant comprises one or more of ethylaminoacetic acid (MEA), diethanolamine (DEA) and sodium metaphosphate.

[0073] The application of the encapsulation coating in the fireproof and heat-insulating aerogel pad for power battery cells, the fireproof and heat-insulating aerogel pad comprising an aerogel core material and an encapsulation coating formed by the fireproof coating, the encapsulation coating being coated on the surface of the ceramic fiber aerogel core material.

[0074] As a specific embodiment, the thickness of the encapsulation coating is 150-200 μm.

[0075] As a specific embodiment, the preparation method of the fireproof and heat-insulating aerogel pad comprises the following steps:

[0076] S1: mixing all components of the encapsulation coating to prepare the encapsulation coating;

[0077] S2: applying the encapsulation coating to the outer surface of the aerogel core material, and after drying and solidification, forming the encapsulation coating.

[0078] As a specific embodiment, in step S2, the specific process of drying and solidification comprises the following steps: after natural surface drying, drying at 100-150 °C for 1-2 h.

[0079] As a specific embodiment, after step S2, hydrophobic modification is performed, and the specific process comprises the following steps: placing the pad prepared in step S2 in a sealed container, vacuumizing to -0.05 to -0.08 MPa, heating to 80-90 °C, then adding a mixed solution of hydrophobic silane modifier and acetic acid, and reacting for 2-3 h; the hydrophobic silane modifier is one or more of methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane and ethyltrichlorosilane.

[0080] As a specific embodiment, the surface porosity of the aerogel core material is not higher than 20%.

[0081] As a specific embodiment, the preparation method of the aerogel core material comprises the following steps:

[0082] (A) mixing polyethyl silicate, methyltriethoxysilane and 35-45 wt% basic silica sol in a mass ratio of 2-4:1-3:1 to obtain a silicon source precursor;

[0083] (B) mixing a silicon source precursor, ethanol and 0.5-2 mol / L hydrochloric acid with a mass ratio of 6:10-40:0.4-0.6, stirring and reacting for 8-24 h to obtain a hydrolysis solution;

[0084] (C) adding 0.5-2 mol / L aqueous ammonia and 0.5-2 mol / L aqueous NH4F to the hydrolysis solution with a mass ratio of 41-42:1:0.1-0.3, stirring and reacting for 2-5 min to obtain a sol;

[0085] (D) under vacuum, immersing the ceramic fiber felt in the sol, standing for 8-10 min to form an alcohol gel on the surface of the ceramic fiber felt, obtaining an alcohol gel composite core material, and continuing to stand for 24-48 h at 25-50℃ to age the gel.

[0086] As a specific embodiment, after step (D), the aged alcohol gel composite core material is placed in a modification liquid for solvent replacement and silicon methylation modification, and then dried to obtain an aerogel core material.

[0087] As a specific embodiment, the preparation method of the nanofiber comprises the following steps:

[0088] (1) preparing a spinning solution by mixing a silicon source, a polymer pore-forming agent, an acid catalyst and water;

[0089] (2) spinning using the spinning solution to obtain a precursor fiber;

[0090] (3) sintering the precursor fiber in an oxygen atmosphere, then mixing with water, dissociating and dispersing, removing the water, and then crushing and grinding to obtain a nanofiber.

[0091] As a specific embodiment, in step (1), the silicon source is tetraethyl orthosilicate, the polymer pore-forming agent is polyvinyl alcohol, and the acid catalyst is HCl; the mass ratio between the silicon source and the polymer pore-forming agent is 1:0.3-0.4; the specific process of step (1) comprises the following steps: adding 0.6-1 mol / L aqueous acid catalyst to a 10-25 wt% aqueous silicon source solution, mixing, then adding 5-10 wt% aqueous polymer pore-forming agent, and mixing to obtain a spinning solution.

[0092] As a specific embodiment, the specific process of step (2) comprises the following steps: using a needle tube to draw the spinning solution, and spinning on a gas spinning machine to obtain a precursor fiber.

[0093] As a specific embodiment, in step (3), the sintering temperature is 500-800℃, and the time is 10-30 min.

[0094] As a specific embodiment, in step (3), the specific process of removing water includes the following steps: collecting filter residue, and freeze-drying at -70 to -40℃ for 10 to 15 hours.

[0095] As a specific embodiment, in step (3), the pulverizing and grinding mode is ball milling, the rotation speed is 400 to 500 r / min, and the time is 1 to 3 hours.

[0096] Example 1

[0097] The fireproof and heat-insulating aerogel pad is prepared by the following method:

[0098] S1. Preparation of aerogel core material:

[0099] The aerogel core material is prepared according to Example 3 in patent CN202311633056.6 (the patent is a published patent, and the technical solution is developed by the inventor team), and the specific steps are as follows:

[0100] S1.1. Mixing three silicon sources, i.e., polyethyl silicate Si-40, methyl triethoxysilane, and 40wt% basic silica sol (Araldine), according to a mass ratio of 3:2:1 to obtain a silicon source precursor;

[0101] S1.2. Mixing the silicon source precursor, ethanol, and 1mol / L hydrochloric acid according to a mass ratio of 6:11.1:0.5, and stirring for 12 hours to obtain a hydrolysis solution;

[0102] S1.3. Adding 1mol / L ammonia water and 1mol / L NH4F aqueous solution to the hydrolysis solution, and stirring for 2 minutes to obtain a sol, wherein the mass ratio of the hydrolysis solution, the ammonia water, and the NH4F aqueous solution is 41.5:1:0.2;

[0103] S1.4. Preparing the ultra-fine mullite fiber felt according to the method in Example 1 of patent CN110846741B, wherein the volume density of the ultra-fine mullite fiber felt is 22mg / cm 3 , the room temperature thermal conductivity is 0.032W / (m·K), and the average diameter of the fibers is 0.6μm;

[0104] S1.5. Placing the ultra-fine mullite fiber felt into a vacuum tank, starting a vacuum pump, and pumping to a gauge pressure of -0.05MPa, then closing the vacuum pump and the vacuum pump inlet valve, and sucking the sol obtained in step S1.3 into the vacuum tank, so that the sol liquid surface completely immerses the upper surface of the ultra-fine mullite fiber felt, and the alcohol gel is formed on the surface of the ultra-fine mullite fiber felt after the gel is placed for 10 minutes, to obtain an alcohol gel composite core material; and heating the alcohol gel to 50℃ for 24 hours to age the gel;

[0105] S1.6 The alcohol gel composite core material is taken out of the vacuum tank, the floating glue on the surface of the core material is removed using a plastic scraper, and then the core material is placed in a container containing a modification liquid and heated to 50°C for solvent replacement and silylation modification. The above solvent replacement and silylation modification process is repeated 3 times, 24 h each time. The components of the modification liquid include heptane, ethanol, dimethyldiethoxysilane and trimethylchlorosilane in a mass ratio of 40:20:20:20.

[0106] S1.7 The modified alcohol gel composite core material is placed in a fume hood and spread out. The fume hood is opened and ventilated at room temperature for 8 h to obtain a substantially dried aerogel core material.

[0107] S1.8 The substantially dried aerogel core material is subjected to the following drying program in an oven: first, heating from room temperature to 120°C for 30 min, and then heating to 150°C for 10 min, and then heating at 150°C for 30 min. The aerogel core material is obtained after being taken out. It is found that the surface porosity of the aerogel core material prepared in this embodiment is 20%, and the apparent thermal conductivity at 25°C, 200°C, 500°C and 800°C is 0.019, 0.022, 0.048 and 0.122 W / (m·K), respectively.

[0108] S2 Preparation of nanofibers:

[0109] S2.1 A 20wt% tetraethyl orthosilicate aqueous solution is mixed with 1mol / L dilute hydrochloric acid, and then 10wt% polyvinyl alcohol aqueous solution is added and mixed uniformly to obtain a spinning solution. The mass ratio of the tetraethyl orthosilicate aqueous solution, dilute hydrochloric acid and polyvinyl alcohol aqueous solution is 59.95:0.05:40.

[0110] S2.2 The spinning solution is taken up using a needle tube, and spinning is performed on an air spinning machine at a flow rate of 10mL / h to obtain a precursor fiber; S2.3 The collected precursor fiber is sintered at 700°C for 10 min in an air atmosphere, dispersed into a 5% slurry concentration suspension in water, and then transferred to a standard fiber dissociator, dissociated at 3000r for 10 min, and then passed through a 250 mesh sieve. The filter residue is collected, freeze-dried at -60°C for 12 h, and then crushed and ground using a planetary ball mill at 500r / min for 3 h, and then passed through a 300 mesh sieve to obtain nanofibers with a diameter of 100-300nm and a length of 40-80μm.

[0111] S3 Preparation of encapsulation coating:

[0112] S3.1, 2 parts of sodium metaphosphate was dissolved in water, 200 parts of ammonium polyphosphate, 100 parts of pentaerythritol, 100 parts of melamine, 45 parts of expandable graphite, 250 parts of alicyclic epoxy resin emulsion (emulsion solid content is 40%, the epoxy equivalent weight of alicyclic epoxy resin is 150) and 50 parts of nanofiber were added, stirred at 500 rpm for 30 min, then transferred into a ball mill, ground for 10 times, ground to a fineness of ≤60 μM, after grinding, transferred to a batching cylinder, 75 parts of bis-amine polyether amine curing agent (number average molecular weight is 10 kDa) was added, stirred at 500 rpm for 3 h, to obtain the encapsulation coating;

[0113] S3.2, the fireproof coating was coated on the surface of the aerogel core material by using a doctor blade method, and was placed at room temperature for 30 min to be surface dried, and then was placed in an oven at 110 ℃ for 1.5 h to be dried, to form an encapsulation coating layer with a thickness of 150-180 μm, to obtain the encapsulation coating composite gasket.

[0114] S4 hydrophobic modification:

[0115] The encapsulation coating composite gasket was placed in a gas-phase hydrophobic tank, and after being sealed, was vacuumized to a gauge pressure of -0.05 MPa, and then the heating device was turned on, and the gas-phase hydrophobic tank was heated to 85 ℃, and a separatory funnel installed on the cover of the gas-phase hydrophobic tank was used to add a mixed solution containing 20 wt% methyltrimethoxysilane and 0.5 wt% acetic acid into the tank, and the tank was kept at 85 ℃ for 2 h for reaction, and after being cooled, was taken out, to obtain the fireproof and heat-insulating aerogel gasket.

[0116] The fireproof and heat-insulating aerogel gasket prepared by using the method of the present embodiment was subjected to combustion test, and the gasket after combustion was seen in Fig. 4. Figure 1 As can be seen from Fig. 4, the structure of the gasket was still compact after combustion, and there was a layer of compact structure of expanded carbon on the surface.

[0117] Example 2

[0118] The fireproof and heat-insulating aerogel gasket was prepared by the following method:

[0119] S1 preparation of aerogel core material:

[0120] The same as Example 1.

[0121] S2 preparation of nanofiber:

[0122] S2.1, 1 mol / L dilute hydrochloric acid was added into a 20 wt% tetraethyl orthosilicate aqueous solution, mixed and stirred, and then 10 wt% polyvinyl alcohol aqueous solution was added and mixed uniformly, to obtain a spinning solution; the mass ratio of the tetraethyl orthosilicate aqueous solution, the dilute hydrochloric acid and the polyvinyl alcohol aqueous solution was 62.45:0.05:37.5;

[0123] S2.2 The spinning solution was sucked by a needle tube and spun on an air spinning machine at a flow rate of 10 mL / h to obtain a precursor fiber; S2.3 After the collected precursor fiber was sintered at 700℃ for 10 min in an air atmosphere, it was dispersed into a 5% slurry concentration suspension in water, and then transferred to a standard fiber dissociator, dissociated at 3000 r for 10 min, and then passed through a 250 mesh sieve. The filter residue was collected, freeze-dried at -60℃ for 12 h, and then crushed and ground using a planetary ball mill at 500 r / min for 3 h, and then passed through a 300 mesh sieve to obtain nanofibers with a diameter of 100-300 nm and a length of 40-80 μm.

[0124] S3 Preparation of encapsulation coating:

[0125] S3.1 2 parts of sodium metaphosphate were dissolved in water, 200 parts of ammonium polyphosphate, 100 parts of pentaerythritol, 100 parts of melamine, 45 parts of expandable graphite, 250 parts of alicyclic epoxy resin emulsion (emulsion solid content is 40%, and the epoxy equivalent weight of alicyclic epoxy resin is 130), and 50 parts of nanofiber were added, stirred at 500 rpm for 30 min, and then transferred to a ball mill for grinding for 10 times. The grinding fineness was ≤60 μM. After grinding, it was transferred to a batching cylinder, 75 parts of a diamino polyether amine curing agent (number average molecular weight is 1 kDa) was added, and stirred at a speed of 500 rpm for 3 h to obtain an encapsulation coating;

[0126] S3.2 The fireproof coating was coated on the surface of the aerogel core material by a doctor blade method, allowed to dry at room temperature for 30 min, and then placed in an oven at 110℃ for 1.5 h to dry, to form an encapsulation coating with a thickness of 150-180 μm, thereby obtaining an encapsulation coating composite gasket.

[0127] S4 Hydrophobic modification:

[0128] The same as Example 1.

[0129] Example 3

[0130] The fireproof and heat-insulating aerogel gasket was prepared by the following method:

[0131] S1 Preparation of aerogel core material:

[0132] The same as Example 1.

[0133] S2 Preparation of nanofiber:

[0134] S2.1 1 mol / L dilute hydrochloric acid was added to a 20 wt% tetraethyl orthosilicate aqueous solution and stirred, and then 10 wt% polyvinyl alcohol aqueous solution was added and mixed uniformly to obtain a spinning solution; the mass ratio of the tetraethyl orthosilicate aqueous solution, the dilute hydrochloric acid and the polyvinyl alcohol aqueous solution was 54.95:0.05:45;

[0135] S2.2 The spinning solution is sucked by a needle tube and spun on an air spinning machine at a flow rate of 10 mL / h to obtain a precursor fiber; S2.3 After the collected precursor fiber is sintered at 700 DEG C for 10 min in an air atmosphere, it is dispersed into a 5% slurry concentration suspension in water, and then transferred to a standard fiber disintegrator, disintegrated at 3000 r for 10 min, and then sieved through a 250 mesh sieve, the residue is collected, frozen and dried at -60 DEG C for 12 h, then crushed and ground by a planetary ball mill at 500 r / min for 3 h, and then sieved through a 300 mesh sieve to obtain nanofibers with a diameter of 100-300 nm and a length of 40-80 μm.

[0136] S3 Preparation of encapsulation coating:

[0137] S3.1 2 parts of sodium metaphosphate are dissolved in water, 200 parts of ammonium polyphosphate, 100 parts of pentaerythritol, 100 parts of melamine, 45 parts of expandable graphite, 250 parts of an alicyclic epoxy resin emulsion (emulsion solid content is 40%, and the epoxy equivalent weight of the alicyclic epoxy resin is 180) and 50 parts of nanofibers are added, stirred at 500 rpm for 30 min, and then transferred to a ball mill for grinding for 10 times until the fineness is ≤60 μM. After grinding, it is transferred to a batching tank, 75 parts of a diamino polyether amine curing agent (number average molecular weight is 20 kDa) is added, and stirred at 500 rpm for 3 h to obtain an encapsulation coating;

[0138] S3.2 The fireproof coating is coated on the surface of the aerogel core material by a doctor blade method, allowed to dry at room temperature for 30 min, and then placed in an oven for drying at 110 DEG C for 1.5 h to form an encapsulation coating with a thickness of 150-180 μm, thereby obtaining an encapsulation coating composite gasket.

[0139] S4 Hydrophobic modification:

[0140] The same as Example 1.

[0141] Example 4

[0142] The difference between this example and Example 1 is that in step S3.1, the weight part of the diamino polyether amine curing agent is 100 parts. The rest is the same as in Example 1.

[0143] Example 5

[0144] The difference between this example and Example 1 is that in step S3.1, the weight part of the diamino polyether amine curing agent is 125 parts. The rest is the same as in Example 1.

[0145] Example 6

[0146] The difference between this embodiment and embodiment 1 is only that in step S3.1, the weight part of the double-end amino polyether amine curing agent is 150 parts. The rest is the same as in embodiment 1.

[0147] Embodiment 7

[0148] The difference between this embodiment and embodiment 1 is only that in step S3.1, the alicyclic epoxy resin is replaced by E-51 epoxy resin. The rest is the same as in embodiment 1.

[0149] Embodiment 8

[0150] The difference between this embodiment and embodiment 1 is only that in step S3.1, the double-end amino polyether amine curing agent is replaced by a double-end amino polyamide curing agent (number average molecular weight of 10 kDa). The rest is the same as in embodiment 1.

[0151] Embodiment 9

[0152] The difference between this embodiment and embodiment 4 is only that in step S3.1, the double-end amino polyether amine curing agent is replaced by a double-end amino polyamide curing agent (number average molecular weight of 3 kDa). The rest is the same as in embodiment 4.

[0153] Embodiment 10

[0154] The difference between this embodiment and embodiment 1 is only that in step S3.1, the weight part of the nanofiber is 70 parts. The rest is the same as in embodiment 1.

[0155] Embodiment 11

[0156] The difference between this embodiment and embodiment 1 is only that in step S3.1, the weight part of the nanofiber is 100 parts. The rest is the same as in embodiment 1.

[0157] Embodiment 12

[0158] The fireproof and heat-insulating aerogel pad is prepared by the following method:

[0159] S1 Aerogel core material:

[0160] The aerogel core material in this embodiment adopts Kao Ming ceramic aerogel heat-insulating pad core material. It is measured that the surface porosity of the aerogel core material used in this embodiment is 81%, and the apparent thermal conductivity at 25℃, 200℃, 500℃ and 800℃ is 0.016, 0.030, 0.068 and 0.12 W / (m·K) respectively.

[0161] S2 Preparation of nanofiber:

[0162] The same as embodiment 1.

[0163] S3 Preparation of encapsulating coating:

[0164] The same as Example 1.

[0165] S4 hydrophobic modification:

[0166] The same as Example 1.

[0167] Example 13

[0168] The difference between this example and Example 2 is that in step S2.1, the mass ratio of the tetraethyl orthosilicate aqueous solution, dilute hydrochloric acid and polyvinyl alcohol aqueous solution is 71.95:0.05:28. The rest is the same as in Example 2.

[0169] Comparative Example 1

[0170] The fireproof and thermal insulation aerogel gasket of this comparative example is prepared according to step S1 in Example 1, without subsequent steps S2-S4.

[0171] Comparative Example 2

[0172] The fireproof and thermal insulation aerogel gasket is prepared by the following method:

[0173] S1 preparation of aerogel core material:

[0174] The same as Example 1.

[0175] S2 PET film packaging:

[0176] The aerogel core material is hot-pressed and packaged using a PET film with a thickness of 0.1 mm to obtain a fireproof and thermal insulation aerogel gasket.

[0177] Comparative Example 3

[0178] The difference between this comparative example and Example 1 is that in step S3.1, no nanofiber is added. The rest is the same as in Example 1.

[0179] Comparative Example 4

[0180] The difference between this comparative example and Example 1 is that in step S3.1, the weight of the nanofiber is 25 parts. The rest is the same as in Example 1.

[0181] Comparative Example 5

[0182] The difference between this comparative example and Example 1 is that in step S3.1, the nanofiber is replaced by a short-cut aluminum silicate fiber with a diameter of 1-10 μm and a length of 300-800 μm. The rest is the same as in Example 1.

[0183] Test Example

[0184] The fireproof and thermal insulation aerogel pads prepared according to the methods in the examples and comparative examples were subjected to performance tests, and the test methods were as follows:

[0185] (1) Thermal insulation performance: The thermal conductivity of the fireproof and thermal insulation aerogel pad at room temperature was measured according to GB / T 10294-2008 “Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials by Guarded Hot Plate Method”.

[0186] (2) Mechanical properties: The strain of the fireproof and thermal insulation aerogel pad at 2mm / min compression rate and 2MPa pressure compared to the original thickness was tested according to GB / T 1448-2005 “Test Method for Compression Properties of Fiber Reinforced Plastics”.

[0187] (3) Dusting degree: The vibration mass loss rate test method in Appendix B of GB / T 34336-2017 “Nano Thermal Insulation Pore Aerogel Composite Thermal Insulation Products” was referred to.

[0188] (4) Flame impact resistance: After one side of the fireproof and thermal insulation aerogel pad was burned with a 1200℃ spray gun for 3min, the cold side temperature was detected.

[0189] (5) High and low temperature impact resistance: The fireproof and thermal insulation aerogel pad was subjected to temperature cycle test according to GB 38031-2020 “Safety Requirements for Power Accumulator for Electric Vehicles”, and the cycle number was 15 times, and the coating cracking and peeling were observed.

[0190] (6) Coating mechanical properties: The elongation at break of the cured fireproof coating sample was tested at a tensile rate of 5mm / min and a test environment of -20℃ according to ASTM D 638-08 test standard.

[0191] The test results are shown in Table 1.

[0192] Table 1 Performance test results of fireproof and thermal insulation aerogel pads

[0193]

[0194]

[0195] As can be seen from Table 1:

[0196] (1) The vibration mass loss rate of Examples 1-13 was significantly lower than that of Comparative Example 1, and the fire resistance was better than that of Comparative Example 2. It shows that the packaging coating of the present application can effectively solve the problem of easy dusting of aerogel pads, and can endow the pads with good fireproof performance.

[0197] (2) In Examples 1, 4-6, with the increase of the amount of polyetheramine curing agent, the high and low temperature impact resistance of the coating first increases and then decreases. It shows that within a certain range, increasing the amount of curing agent can improve the low temperature resistance of the encapsulation coating, but when the amount of curing agent is too large, it will cause poor low temperature resistance of the coating. The reason is that with the increase of the amount of curing agent, the crosslinking degree in the coating increases, which can improve the strength of the coating, but when the crosslinking degree is too large, it will cause poor low temperature flexibility of the coating.

[0198] (3) The high and low temperature impact resistance of the coating of Example 1 is better than that of Example 7. It shows that compared with E-51 epoxy resin, using alicyclic epoxy resin as the base resin can improve the low temperature resistance of the encapsulation coating. The reason is that alicyclic epoxy resin can give the coating good low temperature flexibility, so that the coating is not easy to become brittle, crack and reduce adhesion at low temperature, thereby keeping good integrity of the coating.

[0199] (4) The high and low temperature impact resistance of the coating of Examples 8, 9 is lower than that of Examples 1, 4. It shows that compared with polyamide curing agent, using polyetheramine curing agent can improve the low temperature resistance of the encapsulation coating. The reason is that the molecular structure of polyetheramine contains long chain and ether bond, the chain segment movement ability is strong, the steric hindrance is small, the molecular chain flexibility and movement ability after curing and crosslinking with epoxy resin are strong, the crosslinking density is small, and the glass transition temperature is low, which is beneficial to keeping good flexibility of the encapsulation coating in low temperature environment and keeping good adhesion between the coating and the aerogel core material, thereby avoiding cracking and peeling of the coating.

[0200] (5) The high and low temperature impact resistance of the coating of Examples 1, 10 is better than that of Example 11. The reason is that when the amount of nanofiber is too large, it will cause low bonding strength between the encapsulation coating and the aerogel core material, and thus lead to easy cracking and peeling of the coating.

[0201] (6) The high and low temperature impact resistance of the coating of Example 1 is better than that of Example 12. The reason is that the surface porosity of the aerogel core material in Example 12 is too high, which will cause the encapsulation coating to have less anchor points on its surface, and it is difficult to form a uniform and continuous coverage, thus affecting the bonding strength of the coating on the surface of the core material.

[0202] (7) The fire resistance of the gasket of Example 2 is better than that of Example 13. The reason is that in the process of preparing nanofiber in Example 13, the ratio between silicon source and polymer pore-forming agent is not properly controlled, which causes low porosity of the nanofiber. This will lead to small friction force between the nanofibers and between the nanofiber and the base resin, and the supporting effect on the flame-retardant carbon layer formed at high temperature is relatively weak, thus causing poor fire resistance.

[0203] (8) The gasket of Example 1 has a better fire resistance than Comparative Examples 3 and 4. It is shown that the nanofiber in the encapsulation coating can improve the fire resistance of the gasket, and when the amount of nanofiber is too low, the fire resistance of the gasket is poor. This is because: when the encapsulation coating is in high temperature, the encapsulation coating will melt and foam under the action of intumescent flame retardant and expandable graphite, and form a flame-retardant carbon layer. The nanofiber interacts with the expanded coating to form a stable three-dimensional cross-linked network structure, and the nanofiber is connected between each other and inserted into the expanded coating and the flame-retardant carbon layer, which can provide additional physical support for the flame-retardant carbon layer, reduce the structure collapse of the flame-retardant carbon layer at high temperature, so that the carbon layer can better play the role of blocking oxygen, and improve the expansion ratio of the flame-retardant system, so as to play a better flame-retardant effect.

[0204] (9) The gasket of Example 1 has a better fire resistance than Comparative Example 5. This is because: compared with the short-cut aluminum silicate fiber used in Comparative Example 5, the nanofiber used in Example 1 has a smaller diameter, and at the same addition amount, the number of nanofibers is larger, which is easy to connect with each other to form a network structure; and the surface of the nanofiber used in Example 1 has a porous structure, which can improve the friction between the nanofibers and between the nanofiber and the matrix resin, so as to utilize the network structure formed by the mutual connection of the nanofibers and the interaction between the nanofiber and the matrix resin. Under the combined action of the above two aspects, the nanofiber in Example 1 can play a better supporting role on the flame-retardant carbon layer formed at high temperature.

[0205] Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The raw materials and equipment used in the present application are conventional raw materials and equipment in the art, which can be obtained from conventional commercial channels, unless otherwise specified. The methods used in the present application are conventional methods in the art, unless otherwise specified.

[0206] The above description is only a preferred embodiment of the present application, and does not limit the present application in any way. Any simple modification, change and equivalent transformation of the above embodiment based on the technical essence of the present application still falls within the protection scope of the technical solution of the present application.

Claims

1. A fireproofing and thermally insulating aerogel mat for encapsulating a power battery cell, characterized in that, The composition comprises the following components by weight: 8-12 parts of a base resin, 6-20 parts of a curing agent, 30-40 parts of an intumescent flame retardant, 5-10 parts of nanofibers, 0-8 parts of expandable graphite, and 0-0.4 parts of a dispersing agent. The nanofibers are porous silica nanofibers.

2. The encapsulating coating of claim 1, wherein, The base resin is an alicyclic epoxy resin with an epoxy equivalent weight of 130-180.

3. The encapsulating coating according to claim 2, characterized in that The curing agent is a double-end amino polyether amine with a number average molecular weight of 1000-20000 Da.

4. The encapsulating coating of claim 1, wherein, The mass ratio of the base resin to the nanofibers is not less than 1:0.

5.

5. The encapsulating coating of claim 1, wherein The nanofibers have a diameter of 100-300 nm and a length of 40-80 µm.

6. Use of the encapsulating coating according to one of claims 1 to 5 in a fireproof and thermally insulating aerogel mat for the electrical cells of a power battery, characterized in that, The fireproof and heat-insulating aerogel gasket comprises an aerogel core material and an encapsulation coating layer formed by the encapsulation coating material, and the encapsulation coating layer is coated on the surface of the ceramic fiber aerogel core material.

7. Use according to claim 6, characterized in that, The thickness of the encapsulation coating layer is 150-200 µm.

8. Use according to claim 6, characterized in that, The surface porosity of the aerogel core material is not higher than 20%.

9. Use according to claim 6, characterized in that, The preparation method of the nanofibers comprises the following steps: (1) preparing a spinning solution by mixing a silicon source, a polymer pore-forming agent, an acid catalyst, and water; (2) spinning the spinning solution to obtain precursor fibers; (3) sintering the precursor fibers in an oxygen atmosphere, then mixing the sintered fibers with water, and performing dissociation and dispersion, and after removing the water, performing crushing and grinding to obtain the nanofibers.

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