A flame-retardant and heat-insulating aerogel blanket for power batteries and its encapsulation process

Abstract

This invention belongs to the field of aerogel technology, specifically to a flame-retardant and heat-insulating aerogel blanket for power batteries and its encapsulation process. The process of this invention includes the following steps: (1) preparing adhesive: mixing phosphate ester flame retardant, inorganic flame retardant, nitrile rubber, epoxy resin and dicyandiamide curing agent evenly and setting aside; (2) applying the adhesive to a PET film using a coating machine, and drying to obtain PET coated with adhesive; (3) compressing and encapsulating the intermediate body through an encapsulation mold at a set temperature, and curing to obtain a flame-retardant and heat-insulating aerogel blanket for power batteries. This invention compresses and encapsulates the aerogel heat-insulating blanket, thereby reducing the volume occupied by the aerogel heat-insulating blanket in the battery pack. Moreover, it uses V-0 flame-retardant PET, applies a special adhesive film, compresses and adheres it on both sides, and encapsulates it on all four sides, thereby achieving both volume reduction and lightweight and neatness, while solving the problem of powder shedding from the aerogel blanket filler.

Description

Technical Field

[0001] This invention belongs to the field of aerogel technology, specifically to a flame-retardant and heat-insulating aerogel blanket for power batteries and its encapsulation process. Background Technology

[0002] When a lithium-ion battery experiences an internal or external short circuit, it releases a large amount of heat in a short period, causing a rapid rise in temperature and leading to thermal runaway. The flammable liquid electrolyte ignites at high temperatures, causing the battery to catch fire. Through heat diffusion, a single thermally runaway battery pack can trigger thermal runaway in adjacent battery packs via heat conduction and flames, leading to thermal runaway of the entire battery module / pack and ultimately causing a fire or explosion. Traditional battery modules use flame-retardant plastic separators made of PP, ABS, or PVC to separate individual cells, but these do not provide adequate thermal insulation and can easily cause the separators to melt and ignite due to excessively high battery temperatures.

[0003] Silica aerogel is a porous solid material with a gaseous dispersion medium, characterized by low thermal conductivity, good insulation, Class A fire resistance, and lightweight. In recent years, aerogel materials have begun to be used in the field of fireproofing and insulation of power batteries. It is considered to be the most suitable thermal insulation material for fireproofing new energy vehicles and power batteries. In the event of thermal runaway in the battery cell, it can effectively suppress heat diffusion. Furthermore, it effectively reduces battery performance degradation in low-temperature environments, while saving more space in the limited battery pack. Many power battery companies, such as BYD and CATL, are gradually choosing pre-oxidized fiber insulation sheets and ceramic aerogel insulation blankets as flame-retardant insulation materials between battery cells to reduce the risk of battery combustion in new energy vehicles, extend escape time, and improve safety. However, aerogel insulation blankets are bulky and voluminous, and the filler is prone to powdering.

[0004] CN 108862286A discloses a flame-retardant and heat-insulating elastic silica aerogel sheet. The raw material components of the aerogel sheet include: methyltrimethoxysilane, a silicon source, a gelation promoter, a coagulant with structure-directing function, a solvent, and an environmentally friendly halogen-free flame retardant. 100-120 ml of the coagulant is added to 800-1000 ml of the solvent and stirred evenly. Then, 160-180 ml of methyltrimethoxysilane and 90-120 ml of the silicon source are added and stirred evenly. Next, 150-170 ml of the gelation promoter and the environmentally friendly halogen-free flame retardant are added and stirred evenly again. The resulting sheet-like wet gel is aged and then subjected to at least two solvent replacements to obtain a block-shaped wet gel, which is then dried. This technical solution modifies silica aerogel from a chemical composition perspective, solving the performance defects of silica aerogel such as brittleness, flame retardancy, and lack of vibration damping. However, it does not solve the problem of powder shedding.

[0005] CN 210136903U discloses a glass fiber cloth-coated silica aerogel felt product for electric vehicle batteries, specifically disclosing a high-silica glass fiber cloth layer and a silica aerogel felt layer. Each surface of the silica aerogel felt layer is covered and connected by a high-silica glass fiber cloth layer, and the openings of the covering are connected by high-silica thread stitching or bonding. This technical solution, by using glass fiber cloth to coat the silica aerogel felt product, maintains the extremely low thermal conductivity of the silica aerogel felt product and solves the problem of dust shedding and contamination. However, it does not fundamentally solve the problem of large volume and dust shedding, and there is still room for improvement.

[0006] CN 115411416A discloses a single-sided or double-sided thermally insulating foamed aerogel for new energy batteries and its preparation process. Specifically, it discloses raw materials comprising the following mass percentages: 10-30% methyltrimethoxysilane, 20-40% anhydrous ethanol, 1-10% water, 1-10% acidic catalyst, 1-10% alkaline catalyst, 2-10% modifier, 1-8% surfactant, 1-5% hydrophobic agent, 5-15% adhesive, 1-6% flame retardant, and 4-14% reinforcing film. This technical solution uses aerogel composite material formed by combining silica aerogel and a reinforcing film, where silica aerogel accounts for 90%-96% of the composite material. This improves the thermal insulation performance of the composite material and solves the problems of powder shedding and poor surface adhesion during use. However, this technical solution does not solve the problem of the large volume and bulkiness of silica aerogel, leaving room for improvement.

[0007] In summary, existing technologies still lack an aerogel insulation blanket that can solve problems such as large volume and easy powdering of the filling. Summary of the Invention

[0008] The purpose of this invention is to address the problems of bulky and large volume of existing aerogel insulation blankets, and the tendency for the filler to shed powder. This invention provides a flame-retardant and heat-insulating aerogel blanket for power batteries and its encapsulation process. The aerogel insulation blanket is compressed and encapsulated, thereby reducing its volume within the battery pack. Furthermore, it uses V-0 flame-retardant PET, coated with a special adhesive film, compressed and bonded on both sides, and encapsulated on all four sides, achieving both volume reduction and lightweight, neat design, while simultaneously solving the problem of powder shedding from the aerogel blanket filler. The detailed technical solution of this invention is described below.

[0009] An encapsulation process for a flame-retardant and heat-insulating aerogel blanket for power batteries includes the following steps:

[0010] (1) Prepare the adhesive: Mix the phosphate ester flame retardant, inorganic flame retardant, nitrile rubber, epoxy resin and curing agent evenly and set aside;

[0011] (2) Apply the adhesive to the PET film using a coating machine, and dry it to obtain the PET film coated with adhesive;

[0012] (3) Cut the silica aerogel into sheet-like blankets, sandwich the blankets with two PET sheets coated with adhesive to form a three-layer intermediate structure of the first PET layer - blanket layer - second PET layer. The intermediate is compressed and encapsulated at a set temperature by a packaging mold and cured to obtain the flame-retardant and heat-insulating aerogel blanket for power batteries.

[0013] Preferably, the encapsulation mold includes a first-stage mold and a second-stage mold. The first-stage mold is used to compress and degas the intermediate, thereby compressing the aerogel blanket. The second-stage mold is used to continue compression, sealing the blanket around its perimeter to prevent the aerogel blanket from rebounding.

[0014] Preferably, the compression and packaging operation time is 2-5 seconds.

[0015] Preferably, the set temperature is 50℃-90℃.

[0016] Preferably, the adhesive comprises, by weight, 10-25 parts of phosphate ester flame retardant, 10-15 parts of inorganic flame retardant, 25-35 parts of nitrile rubber, 35-55 parts of epoxy resin, and 2-3 parts of dicyandiamide curing agent.

[0017] Preferably, the phosphate ester flame retardant includes one or more of dimethyl methyl phosphate (DMMP), diethyl ethyl phosphate (DEEP), toluene diphenyl phosphate, tricresyl phosphate, triphenyl phosphate, tri(xyl) phosphate, and propylbenzene phosphates among butylbenzene phosphates.

[0018] Preferably, the inorganic flame retardant is a metal hydroxide.

[0019] Preferably, the nitrile rubber is a modified nitrile rubber, including one or more of TSRC, NANDA and RIWEN, and the curing agent is a dicyandiamide-based curing agent.

[0020] Preferably, the PET film in step (2) is a V-0 grade halogen-free flame-retardant PET substrate.

[0021] Preferably, the silica aerogel is FRA-G600 or FRA-P350.

[0022] The present invention also includes a flame-retardant and heat-insulating aerogel blanket for power batteries, which is prepared according to the encapsulation process described above.

[0023] The beneficial effects of this invention are:

[0024] (1) The present invention compresses and encapsulates the aerogel insulation blanket, thereby reducing the volume occupied by the aerogel insulation blanket in the battery pack. Moreover, it uses V-0 flame-retardant PET, coated with a special adhesive film, compressed and bonded on both sides, and encapsulated on all four sides, thereby achieving both volume reduction and lightweight and neatness, while solving the problem of powder shedding from the aerogel blanket filler.

[0025] (2) In addition to being halogen-free and flame-retardant, the adhesive of the present invention mainly adopts a formula that first has strong initial tack to improve the encapsulation speed and then has post-curing properties, so that the adhesive layer is thoroughly cured and matured to form an adhesive layer with high temperature resistance and excellent peel strength, which improves production efficiency and ensures product quality. Moreover, the adhesive formula of the present invention generally contains 10-25% phosphate ester flame retardant and 10-15% inorganic flame retardant to ensure that the overall flame retardancy level reaches V-0. In addition, the adhesive layer contains 25-35% nitrile rubber to ensure that the initial tack of the adhesive layer is very strong, and it can form good adhesion at a low temperature of 50-90℃, which is convenient for bonding and encapsulation. It contains 35-55% epoxy resin and 2-3% dicyandiamide curing agent to ensure that the adhesive layer is thoroughly cured and matured to form an adhesive with high temperature resistance and excellent peel strength.

[0026] (3) The packaging mold of the present invention adopts a two-stage mold. The first stage first presses the middle blanket together with the upper and lower PET packaging films to release air, so that the aerogel blanket is compressed and thinned. The second stage then presses down to seal the blanket around the perimeter to ensure that the aerogel blanket does not bounce back.

[0027] (4) The product prepared by the present invention can adapt to low temperature bonding and encapsulation, ensuring that the PET film will not shrink, deform or wrinkle during bonding, making the entire encapsulation film smooth and clean; moreover, it is resistant to friction and impact, high temperature, peeling, solvent erosion or various corrosions. It uses flame-retardant PET film material and epoxy system adhesive formula, which has considerable resistance to possible damage in the future.

[0028] (5) The epoxy resin adhesive of this invention has the advantages of good processability, high bonding strength, low shrinkage, excellent resistance to media, and good electrical insulation. Epoxy resin refers to a class of polymers containing two or more epoxy groups in their molecules. The epoxy group is a three-membered ring composed of one oxygen atom and two carbon atoms. It is a condensation product of epichlorohydrin and bisphenol A or polyol. Due to the chemical activity of epoxy groups, various compounds containing active hydrogen can be used to open the ring, cure and crosslink to form a network structure, so it is a thermosetting resin. When epoxy resin is cured with a curing agent containing primary amine groups, in the first stage, the primary amine and epoxy groups react to form a secondary amine; in the second stage, the generated secondary amine reacts with epoxy groups to form a tertiary amine, and the generated hydroxyl groups can also react with epoxy groups, tending to accelerate the reaction. The reaction between carboxyl-modified resin and epoxy resin, in the absence of an accelerator, firstly, the hydroxyl groups in the resin or the free carboxyl groups in the acid anhydride react to form a monoester or the hydroxyl groups continue to react with epoxy groups, finally forming a three-dimensional network structure. The cross-linking and curing reaction of this process involves two curing mechanisms occurring simultaneously. Moreover, the reaction can proceed slowly at room temperature, and the higher the temperature, the faster the reaction speed and the shorter the curing time required. If the temperature reaches above 100°C, it can be completely cured within two hours.

[0029] (6) The present invention compares and selects epoxy adhesive, polyurethane adhesive and polyester plus isocyanate formulations. It is found that the encapsulation temperature of polyurethane adhesive and polyester two-component adhesive reaches 110℃ and 130℃ respectively. The encapsulated film surface is more likely to wrinkle and wavy. Moreover, the heat-resistant peeling ability of polyurethane adhesive is lacking, and the peeling strength under heat is worrying. The encapsulation temperature of this epoxy adhesive is only 50-90℃. The encapsulated appearance is flat and stiff. After low temperature full curing, the peeling strength is high, the temperature resistance is strong, and it is not easy to delaminate when soaked in organic solvents. Attached Figure Description

[0030] Figure 1 Product image of the flame-retardant and heat-insulating aerogel blanket for power batteries of this invention. Detailed Implementation

[0031] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0032] Example 1

[0033] An encapsulation process for a flame-retardant and heat-insulating aerogel blanket for power batteries includes the following steps:

[0034] (1) Prepare adhesive: Mix 10g of phosphate ester flame retardant, 10g of inorganic flame retardant, 25g of nitrile rubber, 35g of epoxy resin and 2g of dicyandiamide curing agent evenly and set aside.

[0035] (2) Apply the adhesive to the PET film using a coating machine, and dry it to obtain the PET film coated with adhesive;

[0036] (3) Cut the silica aerogel into sheet-like blankets, and sandwich the blankets between two PET sheets coated with adhesive to form a three-layer intermediate structure: a first PET layer, a blanket layer, and a second PET layer. Compress and encapsulate the intermediate at 50°C using an encapsulation mold. The encapsulation mold includes a first-stage mold and a second-stage mold. The first-stage mold compresses for 1 second to compress and degas the intermediate, thus compressing the aerogel blanket. The second-stage mold compresses for 1 second to continue compression, sealing the blanket around its edges to prevent it from springing back. Curing and molding yields a flame-retardant and heat-insulating aerogel blanket encapsulation sheet for power batteries, such as... Figure 1 As shown.

[0037] In this embodiment, the nitrile rubber is modified nitrile rubber, the curing agent is a dicyandiamide curing agent, the PET film is a V-0 grade halogen-free flame-retardant PET substrate, and the silica aerogel is FRA-P350, all of which were purchased from the market.

[0038] The phosphate ester flame retardant is a 1:1 mass ratio mixture of dimethyl methyl phosphate (DMMP) and diethyl ethyl phosphate (DEEP); the inorganic flame retardant is magnesium hydroxide.

[0039] Example 2

[0040] The difference between this embodiment and Embodiment 1 is the ratio of adhesive.

[0041] (1) Prepare adhesive: Mix 25g of phosphate ester flame retardant, 15g of inorganic flame retardant, 35g of nitrile rubber, 55g of epoxy resin and 3g of dicyandiamide curing agent evenly and set aside.

[0042] (2) Apply the adhesive to the PET film using a coating machine, and dry it to obtain the PET film coated with adhesive;

[0043] (3) Cut the silica aerogel into sheet-like blankets, and sandwich the blankets between two pieces of PET coated with adhesive to form a three-layer intermediate structure of a first PET layer, a blanket layer, and a second PET layer. Compress and encapsulate the intermediate at 50°C using an encapsulation mold. The encapsulation mold includes a first-stage mold and a second-stage mold. The first-stage mold compresses for 1 second to compress and degas the intermediate, thus compressing the aerogel blanket. The second-stage mold compresses for 1 second to continue compression, sealing the blanket around its edges to prevent the aerogel blanket from rebounding. After curing, a flame-retardant and heat-insulating aerogel blanket encapsulation sheet for power batteries is obtained.

[0044] Comparative Example 1

[0045] The difference between this embodiment and Embodiment 1 is that it does not perform two-level encapsulation, as detailed below:

[0046] (1) Prepare adhesive: Mix 10g of phosphate ester flame retardant, 10g of inorganic flame retardant, 25g of nitrile rubber, 35g of epoxy resin and 2g of dicyandiamide curing agent evenly and set aside.

[0047] (2) Apply the adhesive to the PET film using a coating machine, and dry it to obtain the PET film coated with adhesive;

[0048] (3) Cut the silica aerogel into sheet-like blankets, and sandwich the blankets between two PET sheets coated with adhesive to form a three-layer intermediate structure: a first PET layer, a blanket layer, and a second PET layer. Compress and encapsulate the intermediate at 50°C using an encapsulation mold. The encapsulation mold includes a first-stage mold. The first-stage mold is compressed for 1 second to compress and degas the intermediate, thus compressing the aerogel blanket and curing it to obtain a flame-retardant and heat-insulating aerogel blanket encapsulation sheet for power batteries. Figure 1 As shown.

[0049] Comparative Example 2

[0050] The difference between this embodiment and embodiment 1 is that step (2) is different, as detailed below:

[0051] (1) Prepare adhesive: Mix 10g of phosphate ester flame retardant, 10g of inorganic flame retardant, 25g of nitrile rubber, 35g of epoxy resin and 2g of dicyandiamide curing agent evenly and set aside.

[0052] (2) Apply the adhesive to the silica aerogel using a coating machine, and dry it to obtain the silica aerogel coated with adhesive;

[0053] (3) Cut the silica aerogel into sheet-like blankets, and sandwich the blankets with two PET sheets coated with adhesive to form a three-layer intermediate structure of first PET layer-blanket layer-second PET layer. Compress and encapsulate the intermediate at 50°C using an encapsulation mold. The encapsulation mold includes a first-stage mold. The first-stage mold is compressed for 1 second to compress and degas the intermediate, thereby compressing the aerogel blanket and curing it to obtain a flame-retardant and heat-insulating aerogel blanket encapsulation sheet for power batteries.

[0054] The products prepared in the examples were tested. The powder shedding test involved observing whether powder shed from the packaged product after mechanical vibration. Flame retardancy and thermal conductivity tests were conducted according to ISO 22007-2-2008, Method for Measurement of Thermal Conductivity of Plastics.

[0055] After testing, the products obtained in Examples 1-2 were found to be completely sealed with no powder shedding, demonstrating excellent sealing. The overall flame retardant rating is UL94-V0, and the thermal conductivity at room temperature is less than 0.020 W / mK, while at 350℃ it is less than 0.040 W / mK, meeting the requirements for engineering applications.

[0056] Compared to Example 1, which lacked two-layer encapsulation, springback occurred, resulting in powder shedding.

[0057] In Comparative Example 2, the adhesive was applied to the silica aerogel, but it could not form a complete aerogel. Even after applying the special adhesive film to form a two-sided compression bond and sealing around the edges, powder still fell off.

[0058] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A packaging process for a flame-retardant and heat-insulating aerogel blanket for power batteries, characterized in that, Includes the following steps: (1) Prepare the adhesive: Mix the phosphate ester flame retardant, inorganic flame retardant, nitrile rubber, epoxy resin and curing agent evenly and set aside; (2) Apply the adhesive to the PET film using a coating machine, and dry it to obtain the PET film coated with adhesive; (3) Cut the silica aerogel into sheet-like blankets, sandwich the blankets with two PET sheets coated with adhesive to form a three-layer intermediate structure of the first PET layer - blanket layer - second PET layer. Compress and encapsulate the intermediates at a set temperature using an encapsulation mold, and solidify to obtain the flame-retardant and heat-insulating aerogel blanket for power batteries. The encapsulation mold includes a first-stage mold and a second-stage mold. The first-stage mold is used to compress and degas the intermediate, thereby compressing the aerogel blanket. The second-stage mold is used to continue compression, sealing the blanket around its perimeter to prevent the aerogel blanket from rebounding.

2. The packaging process according to claim 1, characterized in that, The compression and packaging process takes 2-5 seconds.

3. The packaging process according to claim 2, characterized in that, The set temperature is 50℃-90℃.

4. The packaging process according to claim 1, characterized in that, The adhesive, by weight, comprises 10-25 parts of phosphate ester flame retardant, 10-15 parts of inorganic flame retardant, 25-35 parts of nitrile rubber, 35-55 parts of epoxy resin, and 2-3 parts of dicyandiamide curing agent.

5. The packaging process according to claim 4, characterized in that, The phosphate ester flame retardants include one or more of dimethyl methyl phosphate, diethyl ethyl phosphonate, diphenyl methyl phosphate, tricresyl phosphate, triphenyl phosphate, tri(xyl) phosphate, butyl phosphate, and propyl phosphate.

6. The packaging process according to claim 5, characterized in that, The inorganic flame retardant is a metal hydroxide.

7. The packaging process according to claim 4, characterized in that, The nitrile rubber is a modified nitrile rubber.

8. The packaging process according to claim 1, characterized in that, The PET film mentioned in step (2) is a V-0 grade halogen-free flame-retardant PET substrate.

9. The packaging process according to claim 1, characterized in that, The silica aerogel is FRA-G600 or FRA-P350.

10. A flame-retardant and heat-insulating aerogel blanket encapsulation sheet for power batteries, characterized in that, It is prepared by the packaging process according to any one of claims 1-9.

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