Composite adhesive and preparation method and application of high-temperature-resistant ceramic diaphragm thereof

Abstract

The present application relates to the technical field of ceramic diaphragm, and particularly relates to a composite adhesive, a preparation method and application of high-temperature-resistant ceramic diaphragm, wherein the composite adhesive is prepared by establishing a ternary composite system, and the ternary system of the composite adhesive is accurately compounded in proportion, so that a multi-point anchoring and three-dimensional chemical energy network structure can effectively disperse stress, avoid diaphragm rupture caused by local overheating, and the coating prepared by the adhesive can effectively improve the temperature resistance of the diaphragm, reduce the moisture of the diaphragm, especially keep the integrity and dimensional stability under the environment of 200 DEG C, prevent large-scale short circuit caused by diaphragm shrinkage or rupture, and greatly improve the safety performance of lithium batteries.

Description

Technical Field

[0001] This invention relates to the field of ceramic diaphragm technology, and in particular to a composite adhesive and its high-temperature resistant ceramic diaphragm preparation method and application. Background Technology

[0002] The rapid growth of the new energy storage and new energy vehicle industries has brought a new wave of opportunities for the development of new rechargeable batteries such as lithium-ion and sodium-ion batteries. The separator is one of the four main materials used in these batteries. When the battery temperature rises abnormally, the separator can separate the positive and negative electrodes to prevent short circuits. Therefore, the safety of the battery largely depends on the performance of the separator, and innovation in separator technology has great potential to improve the overall performance of these batteries. Currently, the separators used commercially in the market are mainly polyolefin separators, composite separators, and ceramic separators. Ceramic separators, due to their high thermal and chemical stability, are receiving increasing attention in terms of the safety of new energy vehicle batteries.

[0003] Ceramic separators are a secondary modification of polyolefin separators. The main process involves incorporating inorganic ceramic particles into the surface or body of the polymer separator, which improves its thermal stability and electrolyte wettability, while also exhibiting superior mechanical strength and thermal shutdown properties. For example, application number 2024102098402 discloses coating a ceramic composite slurry onto a polymer substrate to prepare a ceramic separator with high-temperature resistance, especially after electrolyte immersion.

[0004] However, the applicant's research found that ceramic separators commonly used in the market generally begin to shrink violently or even rupture when the temperature reaches above 180°C, causing extremely large positive and negative contact areas, resulting in irreversible and violent temperature rise, fire, and explosion of the battery, which seriously affects the safety of use. Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose a composite adhesive and its preparation method and application for a high-temperature resistant ceramic diaphragm, so as to solve the problem of poor thermal stability of existing ceramic diaphragms above 180°C.

[0006] To achieve the above objectives, the present invention provides a composite adhesive comprising:

[0007] Adhesive A, wherein the water-soluble groups in the molecular structure of adhesive A are modified polyimide, and the branched functional groups are at least one of amide groups and imide groups;

[0008] Adhesive B, wherein the molecular structure of adhesive B is based on a carbon chain and the branched functional groups include at least one of carboxyl, cyano, and amide groups;

[0009] Adhesive C, wherein the molecular structure of adhesive C is based on a carbon chain and the branched functional groups include hydroxyl groups;

[0010] The mass ratio of adhesive A, adhesive B and adhesive C is 16:(2~12):1.

[0011] Beneficial effects: The multiple sets of strong hydrogen bonds formed by the amide and imide groups in adhesive A and the carboxyl groups in adhesive B, as well as the multiple sets of hydrogen bonds formed by the cross-interaction of the carbonyl groups with amino and hydroxyl groups of both, constitute a three-dimensional hydrogen bond network. This multi-point anchoring and network structure makes the adhesive interface very strong, effectively dispersing stress throughout the entire interface region, thereby improving high-temperature adhesive strength and forming enhanced cross-linking density and thermal stability.

[0012] The present invention also provides a high-temperature resistant ceramic diaphragm, comprising a substrate and a ceramic coating applied to the substrate, wherein the solid component of the ceramic coating comprises the following components in the following mass percentages: 65-95% ceramic particles, 1-10% of the composite adhesive, 0.5-5% wetting agent, and the remainder being thickener and dispersant.

[0013] A method for preparing the aforementioned high-temperature resistant ceramic diaphragm is also provided, comprising the following steps:

[0014] Mix the dispersant, thickener and deionized water and stir for 10-30 minutes to obtain mixture A;

[0015] Add ceramic particles to mixture A and stir for 20-90 minutes to obtain mixture B;

[0016] Grind and disperse mixture B for 10-50 minutes to obtain dispersion C;

[0017] Add the composite binder to dispersion C and stir for 30-60 minutes to obtain mixture D;

[0018] Add a wetting agent to mixture D and stir for 10-30 minutes to obtain mixture E;

[0019] The mixture E is passed through a magnetic filter device, slowly stirred for 5-20 minutes, and then filtered through a 250-mesh filter to obtain a ceramic coating slurry.

[0020] The obtained ceramic coating slurry is applied to the substrate at 58~65℃ and dried to obtain a high-temperature resistant ceramic diaphragm.

[0021] Beneficial effects: Due to the dipole-dipole interactions and hydrogen bond network formed between the components of the composite adhesive, as well as the optimized compounding ratio to balance hydrogen bond density and thermal properties, the heat resistance and membrane rupture temperature are significantly improved. The ceramic coating prepared using this composite adhesive can effectively improve the temperature resistance of the separator and reduce its moisture content. In particular, it maintains integrity and dimensional stability at 200℃, preventing large-scale short circuits caused by separator shrinkage or rupture, thus significantly improving the safety performance of lithium batteries.

[0022] Finally, the present invention also provides an application of the high-temperature resistant ceramic separator described above, which is used in a membrane battery.

[0023] Beneficial effects: The high-temperature resistant ceramic separator prepared by this invention has a very strong bonding interface due to the multi-point anchoring and mesh structure formed by the compound adhesive components in the ceramic coating. This effectively disperses stress throughout the interface area, thereby enabling the coated separator to maintain its integrity and dimensional stability at 200°C. This solves the problem that ordinary ceramic separators are difficult to maintain their integrity and dimensional stability at 200°C, thus significantly improving the safety performance of the separator battery, especially in high-temperature and harsh environments. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram illustrating the action mechanism of each component of the composite adhesive in an embodiment of the present invention;

[0026] Figure 2 The image shows the results of a membrane rupture test at 200°C for the ceramic diaphragm prepared in Example 4 of this invention.

[0027] Figure 3 The image shows the rupture test results of the ceramic diaphragm prepared in Example 5 of this invention at 200°C.

[0029] Figure 4 The image shows the results of the ceramic diaphragm prepared in Comparative Example 3 of this invention under a membrane rupture test at 180°C.

[0030] Figure 5 The image shows the rupture test results of the ceramic diaphragm prepared in Comparative Example 3 of this invention at 200°C. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0032] Because the ceramic separators commonly used in the market generally begin to shrink violently or even rupture when they reach temperatures above 180°C, resulting in extremely large positive and negative contact areas, the battery experiences irreversible and violent temperature rise, fire, and explosion, seriously affecting safety.

[0033] In order to solve the above-mentioned problems of the prior art, the present invention proposes a composite adhesive and its preparation method and application of a high-temperature resistant ceramic diaphragm.

[0034] Embodiment 1 of the present invention provides a composite adhesive, comprising:

[0035] Adhesive A, wherein the water-soluble groups in the molecular structure of adhesive A are modified polyimide, and the branched functional groups are at least one of amide groups and imide groups.

[0036] Specifically, adhesive A comprises polyamide-imide, with polyamide-imide as the main component. The water-soluble groups are modified polyimide, and the branched functional groups include amide groups and imide groups. The glass transition temperature (Tg) is greater than 300℃. The modified polyimide can be prepared by the polyamic acid salt method (PAAS method): using pyromellitic dianhydride (PMDA) or biphenyl dianhydride (BPDA) and diamine monomers such as 4,4'-diaminodiphenyl ether (ODA) as raw materials, polycondensation is carried out in a polar solvent to generate polyamic acid (PAA). Subsequently, triethylamine or diethanolamine and other organic amines are added for neutralization and salt formation reaction to obtain water-soluble polyamic acid salt. This salt polymer is soluble in deionized water or water / alcohol mixed solvent. After coating, it is thermally imidized at 280~300℃ to restore the polyimide structure, and the glass transition temperature can reach above 300℃.

[0037] Specifically, 0.1 mol of pyromellitic dianhydride and 0.1 mol of 4,4'-diaminodiphenyl ether were dissolved in 500 mL of N-methylpyrrolidone and reacted at room temperature for 24 hours under nitrogen protection to obtain a polyamic acid solution. Then, 0.2 mol of triethylamine was slowly added dropwise to this solution, and the reaction was continued with stirring for 2 hours to obtain a water-soluble polyamic acid salt. The reaction solution was poured into excess deionized water to precipitate, filtered, washed, and dried to obtain solid adhesive A. Testing showed that its heat of imidization at 300℃ was greater than 300℃.

[0038] Adhesive B, wherein the molecular structure of adhesive B is based on a carbon chain, and the branched functional groups include at least one of carboxyl, cyano, and amide groups.

[0039] Specifically, adhesive B comprises at least one of polyacrylamide polymers, sodium polyacrylate polymers, and polyacrylonitrile polymers, with a carbon chain as the main chain and branched functional groups including at least one of carboxyl, cyano, and amide groups, and a glass transition temperature (Tg) > 200℃. Adhesive B can be prepared by free radical copolymerization: using acrylonitrile and acrylamide as monomers, or further introducing high-Tg monomers such as N-cyclohexylmaleimide (CHMI) for ternary copolymerization, initiated by ammonium persulfate in an aqueous phase at 60-80℃, and by adjusting the monomer ratio (e.g., acrylonitrile:acrylamide:CHMI = 40:30:30), the copolymer Tg can reach above 200℃;

[0040] Specifically, 40g of acrylonitrile, 30g of acrylamide, and 30g of N-cyclohexylmaleimide were dissolved in 400g of deionized water, and the mixture was purged with nitrogen for 30 minutes to remove oxygen. The temperature was raised to 70℃, and 0.5g of ammonium persulfate was added as an initiator. The polymerization reaction was carried out at a constant temperature under nitrogen protection for 6 hours. After the reaction was completed, the product was precipitated with ethanol, filtered, washed, and dried to obtain solid binder B. DSC analysis showed that its Tg was 212℃.

[0041] Adhesive C, wherein the molecular structure of adhesive C is based on a carbon chain and the branched functional groups include hydroxyl groups.

[0042] Specifically, adhesive C is polyvinyl alcohol, with a carbon chain as the main chain and branched functional groups including hydroxyl groups, and a glass transition temperature (Tg) of approximately 85°C. Adhesive C is commercially available polyvinyl alcohol, model PVA-1788, with a Tg of 85°C.

[0043] The mass ratio of adhesive A, adhesive B and adhesive C is 16:(2~12):1.

[0044] Specifically, the mass ratio of adhesive A, adhesive B and adhesive C is from 16:2:1 to 16:12:1, preferably from 8:2:1 to 6:1:1.

[0045] The mechanism of action of each component of the composite adhesive is as follows: Figure 1 As shown. Specifically:

[0046] (1) Dipole-dipole interaction improves high-temperature bonding strength.

[0047] High temperatures weaken the adhesion between materials. If the interface has only weak van der Waals forces, heat can easily break this bond, leading to adhesive failure. Adhesive A contains a strongly polar carbonyl group (C=O, derived from imide and amide structures) and an imide ring (a conjugated polar system). Adhesive B contains a strongly polar cyano group (-C≡N). When the two are in close contact, a dipole-dipole interaction occurs between the C=O on the adhesive A chain and the -C≡N on the adhesive B chain, resulting in high adhesive strength. The high-strength physical cross-linking interface formed by this dipole-dipole interaction has a binding energy much higher than that of ordinary physical adsorption. To break this robust interface, a large amount of thermal energy is required to overcome these intermolecular forces. This means that the adhesive interface can maintain its structural integrity at higher temperatures and will not fail prematurely due to interface debonding, setting a higher thermal damage threshold for the adhesive interface and improving high-temperature adhesive strength.

[0048] (2) The formation of hydrogen bond network enhances crosslinking density and thermal stability.

[0049] The main functional groups of the three adhesives have complementary hydrogen bond donor and acceptor properties, which promotes the formation of intermolecular hydrogen bonds, thereby enhancing crosslinking density and thermal stability.

[0050] Adhesive A: Amide group (-NH-CO-R), imide group (-C(O)-N(R)-C(O)-R), with strong polarity, which is conducive to the formation of hydrogen bonds and is a good hydrogen bond donor;

[0051] Adhesive B: Ester group (-COO-R), cyano group (-C≡N), which facilitates the formation of hydrogen bonds and serves as a good hydrogen bond acceptor.

[0052] Adhesive C: Hydroxyl group (-OH), a good hydrogen bond donor.

[0053] Between A and B: The amide and imide groups of A form hydrogen bonds with the ester and cyano groups of B, increasing the intermolecular forces.

[0054] Between A and C: The amide / imide group of A forms a hydrogen bond with the hydroxyl group of C. However, since both A and C are hydrogen bond donors, the direct hydrogen bond between them is relatively weak. But through the bridging effect of B, the network can be indirectly strengthened.

[0055] Between B and C: The acceptor of B (ester group, cyano group) and the donor of C (hydroxyl group) form strong hydrogen bonds, which enhance structural stability.

[0056] The three adhesives form a three-dimensional hydrogen bond network, which restricts the movement of molecular chains, improves the glass transition temperature (Tg) and thermal stability, and enables the coating film to maintain structural integrity and delay cracking at high temperatures.

[0057] (3) By optimizing the compounding ratio to balance the hydrogen bond density and thermal properties, the heat resistance and film breaking temperature were significantly improved.

[0058] Adhesive A provides the skeletal support and a high Tg base, ensuring heat resistance. Adhesive B acts as a hydrogen bond acceptor bridge, connecting A and C and increasing the crosslinking density. Adhesive C acts as a hydrogen bond donor reinforcing agent, effectively interacting with adhesive B to strengthen the network. This synergistic effect enables the composite adhesive to remain stable at high temperatures.

[0059] The entire system forms a three-dimensional hydrogen bond network, which greatly restricts the movement of molecular chains, resulting in enhanced thermal stability and increased membrane rupture temperature on a macroscopic scale.

[0060] ① Enhanced thermal stability: Hydrogen bonds do not break immediately at high temperatures but reversibly recombine, absorbing some heat energy and thus delaying thermal degradation. The imide group of adhesive A has an aromatic ring structure, which endows it with inherent high thermal stability (Tg>300℃), while the cyano and ester groups of B also contribute some thermal resistance. The hydrogen bond network improves the cohesive force of the adhesive and its adhesion to the substrate, preventing shrinkage or cracking at high temperatures.

[0061] ② Increased membrane rupture temperature: The hydrogen bond network maintains the integrity of the adhesive at high temperatures, preventing the separator from rupturing due to thermal shrinkage or softening. As the temperature rises, the hydrogen bond network maintains the strength of the adhesive layer, thereby increasing the membrane rupture temperature from 150℃ to over 200℃, enhancing battery safety.

[0062] Embodiment 2 of the present invention provides a high-temperature resistant ceramic diaphragm and its preparation method. The high-temperature resistant ceramic diaphragm includes a substrate and a ceramic coating applied to the substrate. The solid components of the ceramic coating include the following components in the following mass percentages: 65-95% ceramic particles, 1-10% of the composite adhesive, 0.5-5% wetting agent, and the remainder being thickener and dispersant.

[0063] The substrate is a polyolefin porous membrane selected from polyethylene, polypropylene, polymethylpentene, and nonwoven fabric, with a porosity of 30-70%, preferably 30-45%.

[0064] Preferably, the solid components of the ceramic coating include the following components in the indicated mass percentages: 80-90% ceramic particles, 2-4% of the composite binder, 1-3% wetting agent, and the remainder being thickener and dispersant.

[0065] The ceramic particles are at least one of nano-alumina, aluminum hydroxide, magnesium hydroxide, boehmite, and silicon dioxide, with a particle size of 0.15~3μm, preferably 0.2~0.5μm.

[0066] The wetting agent is at least one of succinic acid, fluoroalkyl methoxy ether alcohol, sodium polyacrylate, ethynyl glycol vinyl ether, fatty acid polyoxyethylene ether, and polyether-modified siloxane.

[0067] This embodiment provides a method for preparing a high-temperature resistant ceramic diaphragm, comprising the following steps:

[0068] Mix the dispersant, thickener and deionized water and stir for 10-30 minutes to obtain mixture A;

[0069] Add ceramic particles to mixture A and stir at 800~1500 rpm for 20~90 min to obtain mixture B;

[0070] Transfer mixture B to a sand mill, add zirconia grinding beads and grind and disperse for 10~50 min, control the slurry particle size D90 ≤ 1μm to obtain dispersion C;

[0071] Add the composite binder to dispersion C and stir for 30-60 minutes to obtain mixture D;

[0072] Add a wetting agent to mixture D and stir for 10-30 minutes to obtain mixture E;

[0073] The mixture E is passed through a magnetic filter device, slowly stirred for 5-20 minutes, and then filtered through a 250-mesh filter to obtain a ceramic coating slurry.

[0074] The obtained ceramic coating slurry is applied to the substrate at 58~65℃ and dried to obtain a high-temperature resistant ceramic diaphragm.

[0075] Preferably, the coating is at least one of microgravure coating, bar coating, and slit coating.

[0076] Ceramic coating slurry can be applied to the substrate on one side or both sides.

[0077] Specifically, in Embodiment 3 of the present invention, a composite adhesive is provided, comprising adhesive A (prepared by the above method), adhesive B (prepared by the above method), and adhesive C (commercially available PVA-1788) in a mass ratio of 6:1:1.

[0078] A high-temperature resistant ceramic membrane includes a polyethylene microporous membrane substrate with a thickness of 7 μm and a porosity of 40%, and a ceramic coating with a thickness of 1.5 μm coated on one side of the substrate. The ceramic coating comprises the following components in the indicated mass percentages: 85% silica with a particle size of 0.3 μm, 3% of the composite adhesive (composed of adhesive A, adhesive B and adhesive C in a mass ratio of 6:1:1), 2% sodium polyacrylate, and 10% deionized water.

[0079] A method for preparing a high-temperature resistant ceramic diaphragm includes: weighing the above-mentioned formula for the high-temperature resistant ceramic diaphragm; mixing and stirring the dispersant, thickener, and deionized water for 25 minutes to obtain mixture A; adding silica particles to mixture A and stirring at 1200 rpm for 80 minutes to obtain mixture B; transferring mixture B to a sand mill, adding 0.3 mm zirconia beads, and grinding and dispersing for 40 minutes, controlling the slurry particle size D90 = 0.8 μm to obtain dispersion C; adding a composite binder to dispersion C and stirring for 50 minutes to obtain mixture D; adding a wetting agent to mixture D and stirring for 20 minutes to obtain mixture E; passing mixture E through a magnetic filter device, stirring slowly for 15 minutes, and then filtering with a 250-mesh filter to obtain a ceramic coating slurry; coating the ceramic coating slurry onto a polyethylene microporous membrane at 60°C using a microgravure method, and drying to obtain the high-temperature resistant ceramic diaphragm.

[0080] Specifically, in Embodiment 4 of the present invention, a high-temperature resistant ceramic diaphragm is provided, which is the same as in Embodiment 3, except that it adopts double-sided coating with a ceramic coating thickness of 1.5μm.

[0081] Specifically, in Embodiment 5 of the present invention, a high-temperature resistant ceramic diaphragm is provided, which is the same as in Embodiment 3, except that it is coated on both sides with a ceramic coating thickness of 2μm.

[0082] Specifically, the high-temperature resistant ceramic diaphragm provided in Comparative Example 1 of the present invention contains only a polyethylene microporous membrane substrate with a thickness of 7μm and a porosity of 40%.

[0083] Specifically, the high-temperature resistant ceramic diaphragm provided in Comparative Example 2 of the present invention is the same as that in Example 3, except that it adopts a single-sided coating with a thickness of 1.5 μm and no composite adhesive.

[0084] Specifically, the high-temperature resistant ceramic diaphragm provided in Comparative Example 3 of the present invention is the same as that in Example 3, except that it adopts a double-sided coated ceramic coating with a thickness of 1.5 μm without composite adhesive.

[0085] Specifically, the high-temperature resistant ceramic diaphragm provided in Comparative Example 4 of the present invention was prepared using the method of Example 1 of Patent Application No. 2024102098402.

[0086] Finally, the present invention also provides an application of the high-temperature resistant ceramic separator described above, which is used in a membrane battery.

[0087] Performance testing

[0088] The high-temperature resistant ceramic diaphragms and electrodes from Examples 3-5 and Comparative Examples 1-4 were cold-pressed and their performance was tested.

[0089] Referring to GB / T 36363-2018 standard, the membrane rupture temperature (°C) of each group of samples was tested, and the temperature at which the diaphragm began to melt was recorded. Each group of samples was tested three times, and the average value was calculated.

[0090] Referring to the GB / T 13519-2016 standard, the area of ​​each group of samples before and after being placed at different temperatures for 1 hour was measured, and their thermal shrinkage rates were compared.

[0091] Specific test results are as follows Figures 2-5 As shown in Table 1.

[0092] Table 1. Performance test results of high-temperature resistant ceramic diaphragms in Examples 3-5 and Comparative Examples 1-4

[0093]

[0094] Specifically, Embodiment 6 of the present invention is the same as Embodiment 4, except that the composite adhesive is adhesive A.

[0095] Specifically, Embodiment 7 of the present invention is the same as Embodiment 4, except that the composite adhesive is adhesive B.

[0096] Specifically, Embodiment 8 of the present invention is the same as Embodiment 4, except that the composite adhesive is adhesive C.

[0097] Specifically, Embodiment 9 of the present invention is the same as Embodiment 4, except that the composite adhesive is adhesive A and adhesive B.

[0098] Specifically, Embodiment 10 of the present invention is the same as Embodiment 4, except that the composite adhesive is adhesive A and adhesive C.

[0099] Specifically, Embodiment 11 of the present invention is the same as Embodiment 4, except that the composite adhesive is adhesive B and adhesive C.

[0100] The specific test results are shown in Table 2.

[0101] Table 2 shows the test results of the high-temperature resistant ceramic diaphragms in Examples 6-11.

[0102]

[0103] This invention patent breaks through the technical scope of traditional single or binary adhesives by establishing a ternary composite adhesive system. It also achieves precise compounding ratio of the ternary composite adhesive system, constructs a multi-point anchoring and three-dimensional chemical energy network structure that can effectively disperse stress and avoid diaphragm rupture caused by local overheating.

[0104] As can be seen from the data in Table 1, compared with ordinary diaphragms (Comparative Examples 1-3) and diaphragms prepared under binary adhesive systems (Comparative Example 4), this invention, through the synergistic mechanism of dipole-dipole interactions and hydrogen bond networks, raises the membrane breakage temperature to above 200℃ and controls the thermal shrinkage rate at 200℃ to within 2%, thus solving the industry pain point of "diaphragm breakage and shrinkage at high temperatures".

[0105] Meanwhile, the technical solution employs conventional coating processes such as microgravure and wire-bar coating, requiring no special production equipment. Those skilled in the art should understand that the above formula represents the mass percentage of solid components in the ceramic coating. In actual preparation of the ceramic slurry, solvents such as deionized water need to be added. The overall solid content of the slurry can be controlled between 20% and 40%, exhibiting good fluidity. At a coating temperature of approximately 60°C, with the addition of appropriate wetting agents (such as sodium polyacrylate, ethylene glycol ether, etc.), the slurry viscosity can be significantly reduced, meeting the requirements of microgravure and wire-bar coating processes. Examples 4-5 of this application have successfully prepared ceramic separators with uniform thickness and excellent performance, proving the feasibility of this process. The thickness and permeability of the prepared separators are within the practical range for battery separators, presenting no obstacles to technological implementation. The production process is compatible with existing production lines, and after production, it is expected to achieve a performance premium at a reasonable cost, demonstrating promising market prospects.

[0106] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in the details for the sake of brevity.

[0107] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A composite adhesive, characterized in that, include: Adhesive A, wherein the water-soluble groups in the molecular structure of adhesive A are modified polyimide, and the branched functional groups are at least one of amide groups and imide groups; Adhesive B, wherein the molecular structure of adhesive B is based on a carbon chain and the branched functional groups include at least one of carboxyl, cyano, and amide groups; Adhesive C, wherein the molecular structure of adhesive C is based on a carbon chain and the branched functional groups include hydroxyl groups; The mass ratio of adhesive A, adhesive B and adhesive C is 16:(2~12):

1.

2. The composite adhesive according to claim 1, characterized in that, The glass transition temperatures (Tg) of adhesives A, B, and C are >300℃, >200℃, and 85℃, respectively.

3. The composite adhesive according to claim 1 or 2, characterized in that, The adhesive B is at least one of polyacrylamide polymers, sodium polyacrylate polymers, and polyacrylonitrile polymers.

4. A high-temperature resistant ceramic diaphragm, characterized in that, The material includes a substrate and a ceramic coating applied to the substrate. The solid component of the ceramic coating comprises the following components in the indicated mass percentages: 65-95% ceramic particles, 1-10% of the composite adhesive, 0.5-5% wetting agent, and the remainder being thickener and dispersant.

5. The high-temperature resistant ceramic diaphragm according to claim 4, characterized in that, The substrate is a polyolefin porous membrane selected from polyethylene, polypropylene, polymethylpentene, and nonwoven fabric, with a porosity of 30-70%.

6. The high-temperature resistant ceramic diaphragm according to claim 4, characterized in that, The ceramic particles are at least one of nano-alumina, aluminum hydroxide, magnesium hydroxide, boehmite, and silicon dioxide, with a particle size of 0.15~3μm.

7. The high-temperature resistant ceramic diaphragm according to claim 4, characterized in that, The wetting agent is at least one of succinic acid, fluoroalkyl methoxy ether alcohol, sodium polyacrylate, ethynyl glycol vinyl ether, fatty acid polyoxyethylene ether, and polyether-modified siloxane.

8. A method for preparing a high-temperature resistant ceramic diaphragm according to any one of claims 4 to 7, characterized in that, The steps include the following: Mix the dispersant, thickener and deionized water and stir for 10-30 minutes to obtain mixture A; Add ceramic particles to mixture A and stir for 20-90 minutes to obtain mixture B; Grind and disperse mixture B for 10-50 minutes to obtain dispersion C; Add the composite binder to dispersion C and stir for 30-60 minutes to obtain mixture D; Add a wetting agent to mixture D and stir for 10-30 minutes to obtain mixture E; The mixture E is passed through a magnetic filter device, slowly stirred for 5-20 minutes, and then filtered through a 250-mesh filter to obtain a ceramic coating slurry. The obtained ceramic coating slurry is applied to the substrate at 58~65℃ and dried to obtain a high-temperature resistant ceramic diaphragm.

9. The preparation method according to claim 8, characterized in that, The coating is at least one of microgravure coating, bar coating, and slit coating.

10. The application of the high-temperature resistant ceramic diaphragm according to any one of claims 4 to 7, characterized in that, The high-temperature resistant ceramic separator is used in membrane batteries.

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