A coating slurry, its preparation method and use

Abstract

The application provides a coating slurry, a preparation method and application thereof, and belongs to the technical field of lithium ion batteries.The preparation method is as follows: dispersing agent, ceramic particle modifier and nano inorganic ceramic particles are dissolved in deionized water, stirring and dispersing until uniform, and then grinding and secondary dispersing; subsequently, water-soluble acrylate-based polymer solution and polyurethane-based polymer emulsion are added, stirring and dispersing until uniform, and then adding a textural structure forming aid and stirring until uniform; finally, a wetting agent is added, stirring and slowly defoaming, and the coating slurry is obtained.The coating slurry provided by the application has heat shrinkage resistance of 150-200 DEG C when applied to a diaphragm, has water resistance, can be coated twice, and can be widely applied to the field of batteries.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and particularly relates to a coating slurry, its preparation method, and its application. Background Technology

[0002] With the rapid development of new energy vehicles, lithium-ion batteries, as their core components, have received increasing attention for their safety and performance. The battery separator is a key component of lithium-ion batteries, its main function being to isolate the positive and negative electrodes, prevent short circuits, and allow lithium ions to pass through. Currently, the mainstream battery separator materials on the market are polyethylene (PE) and polypropylene (PP). PE wet-process battery separators are produced through thermally induced phase separation and biaxial stretching. This process can produce separators with suitable pore size, uniform distribution, few defects, and thin thickness. Compared to dry processes, wet processes can produce separators with better uniform micropore distribution, higher porosity, and better hydrophilicity. These characteristics result in lower internal resistance, lower pore closing temperature, and higher biaxial tensile strength.

[0003] PE wet-process battery separators are widely used in high-end lithium-ion batteries due to their excellent performance. However, traditional PE wet-process battery separators are prone to thermal shrinkage at high temperatures, leading to decreased battery performance and even safety hazards. Aside from significant thermal shrinkage at high temperatures, wet-process PE lithium-ion battery separators have almost no other drawbacks. Therefore, developing a highly heat-resistant PE wet-process battery separator is of significant practical importance.

[0004] Currently, wet-process separators on the market mainly improve their heat shrinkage resistance through various coating modification technologies (such as water-based ceramic coating, oil-based aramid coating, and water-based PVDF coating). Water-based ceramic coated separators have become the main product in the current separator market due to their extremely high cost advantage. However, conventional ceramic separators lack sufficient thermal stability to rapidly conduct heat or provide flame retardancy to cope with the rapid temperature rise during battery short circuits. Conventional water-based ceramic heat-resistant products have a heat shrinkage resistance temperature of 130℃, while some water-based ceramic coated products use solution-based adhesives to ensure a coating heat resistance temperature of 150℃. However, solution-based adhesives have many drawbacks in use. First, solution-based adhesives are aqueous solutions of acrylate polymers, and their dissolution process is reversible. Therefore, when the diaphragm is coated a second time, the coating will disintegrate when it comes into contact with water. Second, during the drying process, the polymer molecules of solution-based adhesives will generate great shrinkage stress, causing the diaphragm to curl at the edges. Third, because solution-based adhesives are soluble in water, compared to emulsion-based adhesives, their polymer molecules are more likely to enter the pores of the base membrane with the slurry, resulting in a greater increase in the air permeability of the diaphragm. Summary of the Invention

[0005] The purpose of this invention is to provide a coating slurry, its preparation method, and its application, aiming to solve the problem of insufficient heat resistance in current ordinary water-based ceramic coatings, as well as the problems of poor water resistance, edge curling, and pore blockage in water-based high-temperature ceramic coating products using solution-type adhesives. This invention employs two polymers overlapping, inducing microphase separation to form an adhesive material with an interwoven skeleton structure. The two polymers undergo a combination of physical morphological changes at the molecular level, maintaining the chemical properties of the material itself while improving the shortcomings of the separator in terms of high-temperature resistance, water resistance, and coating stress shrinkage through a unique structure. The ceramic coating product of this invention has heat shrinkage resistance at 150-200℃, and also possesses water resistance, allowing for secondary coating. Furthermore, the coating can be made thinner while maintaining the same heat resistance. The coating's electrochemical stability and ionic conductivity are also superior to conventional products on the market. Using the separator prepared by this invention, batteries can have higher cycle performance and rate performance. Simultaneously, the coating is water-based, the preparation process is simple, and no additional modifications or large-scale equipment are required; conventional ceramic slurry preparation equipment can be used directly.

[0006] To achieve the above objectives, the present invention adopts the following specific technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a coating slurry, comprising the following steps:

[0008] S1: Dissolve the dispersant, ceramic particle modifier and nano-inorganic ceramic particles in deionized water, stir and disperse until uniform, and then grind and disperse again.

[0009] S2: Add water-soluble acrylate polymer solution and polyurethane polymer emulsion to the product of step S1, stir and disperse until uniform, then add textured structure molding aid and stir until uniform.

[0010] S3: Add a wetting agent to the product from step S2, stir and slowly defoam to obtain the final product.

[0011] By blending a water-soluble acrylate-based polymer solution and a polyurethane-based polymer emulsion, hydrogen bonding enables them to overlap, resulting in molecular-level nesting. Simultaneously, due to the branched structure and steric hindrance of the molecules, the two polymers nest without entanglement. Hydrogen bonding induces a certain degree of phase separation in the water-soluble polymer, ultimately forming an interwoven structure after the slurry is dried. This interwoven polymer acts as an adhesive, anchoring the ceramic particles and the base film to form a composite heat-resistant coating.

[0012] Secondly, the present invention also provides a coating slurry prepared by the preparation method described above.

[0013] Thirdly, the present invention also provides a diaphragm, wherein any coating of the diaphragm contains the coating slurry.

[0014] Fourthly, the present invention also provides a battery comprising the aforementioned separator.

[0015] Compared with existing technologies, this invention uses two polymers with different molecular forms: a water-soluble acrylate-based polymer solution and a polyurethane-based polymer emulsion. These two polymers are compounded and interlocked via hydrogen bonding, resulting in molecular-level nesting. Simultaneously, due to the branched structure and steric hindrance of the molecules, the two polymers nest without entanglement. Hydrogen bonding induces a certain degree of phase separation in the water-soluble polymer, ultimately forming an interwoven structure after the slurry is dried. This interwoven polymer acts as an adhesive, anchoring the ceramic particles and the base film to form a composite heat-resistant coating.

[0016] The two polymers are interlocked, and the cured cross-linked network structure, due to intermolecular anisotropy and the absence of dense entanglement, allows the internal stresses of the polymers to cancel each other out, reducing cohesive energy and minimizing internal stress shrinkage. The polymer chains form a textured structure, improving the overall water resistance of the material. The interlocked polymers cannot dissolve in water again, so the coating will not disintegrate when exposed to water. Furthermore, the interlocking and nesting of the two polymers forms a continuous structure, preventing adhesives from penetrating the pore structure of the base film, thus reducing pore blockage and resulting in a lower increase in the coating's air permeability.

[0017] In addition, the Tg temperature of acrylate-based polymers is 180-220℃, and that of polyurethane polymers is 120-160℃. The interwoven structure of the blended polymers formed by the compounding exhibits inert molecular motion at 150-200℃, which can maintain a certain hardness and preserve adhesion and structural stability at high temperatures. Compared with similar water-based ceramic coating products on the market, it has a higher heat resistance temperature, stronger overall coating support, and a higher heat shrinkage temperature for coatings of the same thickness. Similarly, under the same heat shrinkage conditions, a thinner coating can be achieved, improving the energy density and rate performance of the battery cell.

[0018] Both polymers exhibit excellent electrochemical stability, and their interwoven structure provides even greater electrochemical stability compared to adhesives used in conventional water-based coatings. Therefore, this coated separator product can offer better cycle stability to the battery cell. Furthermore, the interwoven structure has a degree of continuity, resulting in a more uniform distribution throughout the coating and improving the overall interface uniformity of ion conduction within the battery cell structure. This effectively reduces lithium dendrite formation, leading to higher safety performance for the battery cell. It can be seen that the ceramic-coated product of this invention offers superior safety and electrochemical performance compared to conventional ceramic-coated products.

[0019] The ceramic-coated product of this invention has a thickness of 1-4 μm and can be coated on one or both sides. When the overall coating thickness is 2 μm, it ensures the heat shrinkage resistance of the PE composite battery separator at 150-160℃; when the overall coating thickness is 3-4 μm, it ensures the heat shrinkage resistance of the PE composite battery separator at 150-200℃. Within the aforementioned temperature range, after 1 hour of storage, the bidirectional dimensional shrinkage rate of the separator is <5%. Furthermore, the coating is water-resistant, allows for secondary coating, and single-sided coating does not result in edge curling. Simultaneously, the increase in separator air permeability is 5-20 s / μm. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0021] Figure 1 This is a schematic diagram of the water resistance test in Embodiment 1 of the present invention.

[0022] Figure 2 This is a schematic diagram of the water resistance test in Embodiment 2 of the present invention.

[0023] Figure 3 This is a schematic diagram of the water resistance test of Comparative Example 1 of the present invention.

[0024] Figure 4 This is a schematic diagram of the water resistance test of Comparative Example 2 of the present invention. Detailed Implementation

[0025] As used in this article:

[0026] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0027] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0028] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0029] In these embodiments, unless otherwise specified, all parts and percentages are by weight, and all unstated proportions can be made in any proportion.

[0030] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0031] This invention provides a method for preparing a coating slurry, specifically including the following steps:

[0032] S1: Dissolve the dispersant, ceramic particle modifier and nano-inorganic ceramic particles in deionized water, stir and disperse until uniform, and then grind and disperse again.

[0033] Optionally, in some embodiments, the dispersant includes one or more of anionic dispersants, cationic dispersants, nonionic dispersants, or polymeric dispersants.

[0034] Optionally, in some embodiments, the ceramic particle modifier comprises CMC and / or CMC-Li solution.

[0035] Optionally, in some embodiments, the inorganic ceramic particles include one or more of aluminum oxide, silicon dioxide, magnesium hydroxide, zirconium dioxide, boehmite, lithium aluminum titanium phosphate (LATP), lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, or lithium lanthanum zirconium tantalum oxide.

[0036] In some embodiments, the inorganic ceramic particle size Dv50 is 100-800 μm; in some preferred embodiments, Dv50 is 300-600 μm.

[0037] In a preferred embodiment, the grinding process ensures that the mass ratio of free CMC and / or CMC-Li in the system is less than 0.1%. The applicant has found that excessive free CMC in water can affect the subsequent polymer intercalation. This invention effectively reduces the concentration of free CMC by controlling the amount and order of CMC addition. CMC is added before the inorganic ceramic particles, and a certain grinding time and intensity are ensured to guarantee that most of the CMC is grafted onto the surface of the ceramic particles. The concentration of free CMC in the test solution is indirectly fed back by measuring the apparent viscosity using a rotational viscometer. After grinding the slurry, an apparent viscosity ≤ 55 cp indicates that the mass concentration of free CMC is less than 0.1%.

[0038] S2: Add water-soluble acrylate polymer solution and polyurethane polymer emulsion to the product of step S1, stir and disperse until uniform, then add textured structure molding aid and stir evenly.

[0039] Optionally, in some embodiments, the water-soluble acrylate-based polymer includes one or more of carboxylated modified polyacrylate copolymers, polyacrylic acid-acrylonitrile-glycolic acid copolymers, carboxylated modified polyacrylamide, polyvinyl alcohol-grafted poly(N-isopropylacrylamide) copolymers, or citric acid-grafted modified polyvinyl alcohol.

[0040] Optionally, in some embodiments, the polyurethane-based polymer emulsion includes one or more of the following: oligomeric polyol type polyurethane emulsion, mixed polyurethane emulsion, vinyl polyurethane emulsion, polyisocyanate emulsion, blocked polyurethane emulsion, polyurethane-urea emulsion, or polyurethane emulsion made from oligomeric polyol, chain extender, and diisocyanate.

[0041] In some preferred embodiments, the oligomeric polyol type polyurethane emulsion includes polyether type, polyester type or polyolefin type, and the mixed polyurethane emulsion includes polyether-polyester or polyether-polybutadiene.

[0042] In some preferred embodiments, the Tg temperature of the water-soluble acrylate-based polymer is 180-220°C;

[0043] In some preferred embodiments, the polymer Tg temperature in the polyurethane-based polymer emulsion is 120-160°C.

[0044] Optionally, in some embodiments, the textured molding aid includes one or more of polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, hydroxyethyl cellulose, hydroxypropyl cellulose, polyethylene glycol diglycidyl ether, hyperbranched polyglycidyl ether, or ester polymers containing long-chain hydrophilic groups.

[0045] The textured structure forming aid can improve the compatibility of water-soluble acrylate-based polymer solutions and polyurethane-based polymer emulsions, making it easier to form a more perfect and continuous textured structure at the physical level. It can also effectively reduce the surface tension of the system, allowing the solid inorganic powder, polymer interwoven skeleton structure, and polyolefin substrate to be better combined. At the same time, it also plays a certain plasticizing role. Both polymers selected are products with high Tg. In order to prevent the polymer interwoven skeleton structure from being too hard, resulting in a hard and brittle coating, the textured structure forming aid, a small molecule substance, can be embedded in the polymer molecular chain, keeping the polymer intermolecular spacing relatively wide, which can improve the toughness of the polymer skeleton structure and make the structure more stable.

[0046] In a preferred embodiment, before adding the textural molding aid, the system is first heated to 40-50°C. After adding the textural molding aid and stirring evenly, the mixture is stirred at low speed and kept at this temperature for 1 hour, then cooled to room temperature. Heating in this process step can enhance the mobility of polymer molecules in the aqueous solution and the compatibilizing effect of the two polymer molecules. It also helps to assist and accelerate the formation of hydrogen bonds. Within the specified temperature and holding time range, a more perfect polymer blend textural structure can be formed, resulting in optimal membrane permeability, heat resistance, and water resistance.

[0047] Under external temperature conditions and with the help of textured molding agents, water-soluble acrylate-based polymer solutions and polyurethane-based polymer emulsions undergo induced microphase separation through intermolecular forces, forming molecular-level physical interactions and an interwoven structure.

[0048] S3: Add a wetting agent to the product from step S2, stir and slowly defoam to obtain the final product. Note that the remaining components in the slurry system should be replenished with deionized water.

[0049] Optionally, in some embodiments, the wetting agent includes one or more of the following: organosilicon-modified wetting agents, polyether wetting agents, alkynyl alcohol wetting agents, or alcohol wetting agents.

[0050] In some embodiments, the amount of dispersant added is 0.5-1.2 parts by weight; the amount of inorganic ceramic particles added is 20-50 parts; the amount of ceramic particle modifier added is 0.3-1 parts; the amount of water-soluble acrylate-based polymer solution is 1-5 parts by weight of solid matter; the amount of polyurethane-based polymer emulsion is 0.2-2 parts by weight of solid matter; the amount of textured molding aid is 0.01-0.1 parts; and the amount of wetting agent is 0.01-0.2 parts.

[0051] In a preferred embodiment, the amount of ceramic particle modifier added is 0.3-0.6 parts.

[0052] This invention also provides a coating slurry prepared by the aforementioned method. The two polymers are used to form an adhesive with an interwoven skeleton structure, which serves as the main functional component of the heat-resistant coating, enabling the coated composite substrate to possess both heat resistance and water resistance.

[0053] The present invention also provides a diaphragm, wherein any coating of the diaphragm contains the coating slurry.

[0054] In some embodiments, the coating slurry is coated onto a substrate separator, and then dried and wound to obtain a lithium battery separator. The substrate separator includes wet-process polyolefin porous membranes, dry-process polyolefin porous membranes, spun composite porous membranes, non-woven porous membranes, etc.

[0055] In some embodiments, the coating method can be any one of gravure coating, anilox roller coating, spraying, slot coating, screw extrusion coating, etc.

[0056] In some embodiments, the oven temperature range during the drying process is 40-90°C.

[0057] This invention also provides a battery comprising the aforementioned separator. The battery may be a lithium-ion battery, a semi-solid-state battery, a sodium-ion battery, or a lithium-sulfur battery.

[0058] In this embodiment of the invention, a series of tests were conducted on the prepared coated diaphragm, such as its high-temperature heat shrinkage resistance, water resistance, and anti-clogging performance.

[0059] The high-temperature heat shrinkage test method is as follows: Take a diaphragm of size 12*12cm, draw a 10*10cm coordinate axis on the diaphragm along the horizontal and vertical directions, place two A4 sheets of paper on the top and bottom of the sample, put it in a 150℃ oven, and measure the dimensional change rate of the diaphragm after 1 hour. The smaller the dimensional change, the better the temperature resistance of the diaphragm. The standard for high-temperature resistant products is that the dimensional change rate (150℃, 1h) is ≤5%.

[0060] The water resistance test method is as follows: Wipe the membrane coating with a black non-woven cloth dampened with water, and visually inspect the wiped area for any white coating peeling off. Apply a second water-based coating to one side of the membrane and observe for any coating defects such as missed coatings caused by coating breakdown.

[0061] The anti-clogging test method is as follows: The air permeability of the coated diaphragm is tested. The time it takes for specific air to pass through a diaphragm covering one square inch of area under a certain pressure is expressed as the Gurley value, typically measured in seconds per 100 ml. With a consistent base membrane, a lower air permeability value indicates better anti-clogging performance of the coating.

[0062] Example 1

[0063] (1) Add 0.8 kg of sodium polyacrylate dispersant to deionized water and stir until uniform.

[0064] (2) Add a solution with a mass concentration of 2.5% containing 0.5 kg of CMC to the product of step (1) and stir until homogeneous.

[0065] (3) Add 40 kg of aluminum oxide to the product of step (2). The aluminum oxide Dv50 particle size is about 500 nm. Stir at high speed until it is evenly dispersed. Use a sand mill to grind the product to graft CMC onto the aluminum oxide particles until the aluminum oxide Dv50 particle size in the whole slurry is 500-580 nm. At the same time, control the mass concentration of free CMC in the system to be less than 0.1%.

[0066] (4) Add an aqueous solution of 10% by mass containing 2.2 kg of carboxylated modified polyacrylate copolymer as the active ingredient to the product of step (3), and stir at low speed for 20 min until it is evenly dispersed.

[0067] (5) Add a modified polyurethane emulsion containing 1 kg of active ingredients to the product of step (4). The solid content of the emulsion is about 20%. Stir at low speed for 20 minutes until it is evenly dispersed.

[0068] (6) Heat the entire system of the product from step (5) to 45°C, add 2% by mass of a polyvinyl alcohol aqueous solution containing 0.1 kg of active ingredient, keep warm for 1 hour and then lower to room temperature, stirring continuously throughout the process.

[0069] (7) Add 0.05 kg of polyether organosilicon modified wetting agent to the product in step (6), stir evenly, and defoam the system under vacuum for 1 hour to obtain the coating slurry.

[0070] (8) The obtained coating slurry is coated on one side of a 9μm wet PE base film with a coating thickness of 2μm. Then, the film is dried, wound and packaged to obtain an aqueous ceramic coated separator with an interwoven skeleton polymer structure, which can then be applied to the preparation of lithium-ion batteries.

[0071] Example 2

[0072] (1) Add 0.5 kg of sodium polyacrylate dispersant to deionized water and stir until uniform.

[0073] (2) Add a solution with a mass concentration of 2.5% containing 0.3 kg CMC-Li to the product of step (1) and stir until homogeneous.

[0074] (3) Add 35 kg of aluminum oxide to the product of step (2). The aluminum oxide Dv50 particle size is about 600 nm. Stir at high speed until it is evenly dispersed. Use a sand mill to grind the product to graft CMC-Li onto the aluminum oxide particles until the aluminum oxide Dv50 particle size in the whole slurry is 600-700 nm. At the same time, control the mass concentration of free CMC-Li in the system to be less than 0.1%.

[0075] (4) Add an aqueous solution of 15% by mass containing 2.0 kg of carboxylated modified polyacrylamide as the active ingredient to the product of step (3), and stir at low speed for 20 min until it is evenly dispersed.

[0076] (5) Add 1 kg of hydroxyl chain-extended vinyl polyurethane emulsion containing 1 kg of active ingredient to the product of step (4). The solid content of the emulsion is about 15%. Stir at low speed for 20 min until it is evenly dispersed.

[0077] (6) Heat the entire system of the product from step (5) to 48°C, add 8% (w / w) of polyvinyl alcohol aqueous solution containing 0.01 kg of active ingredient, keep warm for 1 hour and then cool to room temperature, stirring continuously throughout the process.

[0078] (7) Add 0.01 kg of polyether organosilicon modified wetting agent to the product in step (6), stir evenly, and defoam the system under vacuum for 1 hour to obtain the coating slurry.

[0079] (8) The obtained coating slurry is coated on one side of a 12μm wet PE base film with a coating thickness of 3μm. Then, the film is dried, wound and packaged to obtain an aqueous ceramic coated separator with an interwoven skeleton polymer structure, which can then be applied to the preparation of lithium-ion batteries.

[0080] Example 3

[0081] (1) Add 1.2 kg of sodium polyacrylate dispersant to deionized water and stir until uniform.

[0082] (2) Add a solution with a mass concentration of 2.5% containing 0.8 kg of CMC to the product of step (1) and stir until homogeneous.

[0083] (3) Add 45 kg of LATP powder to the product in step (2). The LATPDv50 particle size is about 550 nm. Stir at high speed until it is evenly dispersed. Use a sand mill to grind the product to graft CMC onto LATP particles until the LATPDv50 particle size in the whole slurry is 550-600 nm. At the same time, control the mass concentration of free CMC in the system to be less than 0.1%.

[0084] (4) Add an aqueous solution of 15% by mass containing 3.0 kg of carboxylated modified polyacrylamide as the active ingredient to the product of step (3), and stir at low speed for 20 min until it is evenly dispersed.

[0085] (5) Add 1 kg of hydroxyl chain-extended vinyl polyurethane emulsion containing 1 kg of active ingredient to the product of step (4). The solid content of the emulsion is about 15%. Stir at low speed for 20 min until it is evenly dispersed.

[0086] (6) Heat the entire system of the product from step (5) to 50°C, add 5% (w / w) of polyvinyl alcohol aqueous solution containing 0.05 kg of active ingredient, keep warm for 1 hour and then cool to room temperature, stirring continuously throughout the process.

[0087] (7) Add 0.2 kg of polyether organosilicon modified wetting agent to the product in step (6), stir evenly, and defoam the system under vacuum for 1 hour to obtain the coating slurry.

[0088] (8) The obtained coating slurry is coated on one side of a 9μm wet PE base film with a coating thickness of 2μm. Then, the film is dried, wound and packaged to obtain an aqueous ceramic coated separator with an interwoven skeleton polymer structure, which can then be applied to the preparation of lithium-ion batteries.

[0089] Example 4

[0090] The difference from Example 1 is that the mass concentration of free CMC in the system is not controlled in step (3). After sand milling, the apparent viscosity of the slurry is tested with a rotational viscometer and is 74 cp. The CMC concentration of the filtered slurry solution is tested by the conductivity method. After conversion, the actual concentration of free CMC is 0.17%.

[0091] Example 5

[0092] The difference from Example 1 is that no heating is performed in step (6).

[0093] Comparative Example 1

[0094] The difference from Example 1 is that step (4) uses an acrylic polymer emulsion adhesive containing 3 kg of active ingredients, with an effective solid content of 45%, and steps (5) and (6) are omitted.

[0095] Comparative Example 2

[0096] The difference from Example 1 is that step (4) uses a high-temperature resistant acrylate polymer solution adhesive containing 3 kg of active ingredients, with an effective solid content of 15%, and steps (5) and (6) are omitted.

[0097] Table 1 Comparison of test data from Examples 1-5 and Comparative Examples 1-2

[0098]

[0099]

[0100] The test data are shown in Table 1. It can be seen that the increase in air permeability of the products in Examples 1-5 is significantly less than that in Comparative Example 2, indicating that the diaphragm product of the present invention has good anti-clogging performance, which can effectively reduce the internal resistance of the battery and improve the ion conductivity.

[0101] The products in Examples 1-5 showed significantly better heat shrinkage performance at 150℃ than those in Comparative Example 1, indicating that the products of the present invention have better high-temperature resistance and provide superior safety performance for the battery.

[0102] See Table 1 and Figure 1-4 After wet wiping, the products in Examples 1 and 2 showed no coating peeling, and their water resistance was better than that of Comparative Examples 1 and 2.

[0103] The products of Examples 1-3 are superior to those of Examples 4-5 in terms of breathability and heat resistance, indicating that the polymer interwoven structure of the products of Examples 1-3 is more perfect, resulting in better product performance.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0105] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of the invention and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing a coating slurry, characterized in that, Includes the following steps: S1: Dissolve the dispersant, ceramic particle modifier, and nano-inorganic ceramic particles in deionized water, stir and disperse until uniform, and then grind; the particle size Dv50 of the nano-inorganic ceramic particles is 100-800nm; S2: Add a water-soluble acrylate polymer solution or similar and a polyurethane polymer emulsion to the product of step S1, stir and disperse until uniform, then add a textured molding aid and stir until uniform; before adding the textured molding aid, heat the system to 40-50℃, and after adding the textured molding aid and stirring until uniform, cool to room temperature. S3: Add a wetting agent to the product of step S2, stir and slowly defoam to obtain the final product; The water-soluble acrylate-based polymer solution is a carboxylated modified polyacrylate copolymer; the analogue is a carboxylated modified polyacrylamide; The polyurethane-based polymer emulsion includes one or more of the following: oligomeric polyol type polyurethane emulsion, mixed type polyurethane emulsion, vinyl polyurethane emulsion, blocked type polyurethane emulsion, and polyurethane-urea emulsion. The ceramic particle modifier comprises CMC and / or CMC-Li solution; the mass concentration of free CMC and / or CMC-Li in the grinding process control system is less than 0.1%; The textured molding aid includes an aqueous solution of polyvinyl alcohol.

2. The preparation method according to claim 1, characterized in that, The dispersant includes one or more of anionic dispersants, cationic dispersants, nonionic dispersants, or polymeric dispersants; The nano-inorganic ceramic particles include one or more of aluminum oxide, silicon dioxide, zirconium dioxide, and boehmite.

3. The preparation method according to claim 1, characterized in that, The amount of the dispersant added is 0.5-1.2 parts by weight; The amount of the nano-inorganic ceramic particles added is 20-50 parts; The amount of ceramic particle modifier added is 0.3-1 part.

4. The preparation method according to claim 3, characterized in that, The amount of the ceramic particle modifier added is 0.3-0.6 parts by weight.

5. The preparation method according to claim 3, characterized in that, The water-soluble acrylate-based polymer solution comprises 1-5 parts by weight of solid matter. The polyurethane-based polymer emulsion comprises 0.2-2 parts of solid matter; The fabric structure forming aid is 0.01-0.1 parts; The wetting agent is 0.01-0.2 parts.

6. The preparation method according to claim 1, characterized in that, The wetting agent includes one or more of the following: organosilicon-modified wetting agents, polyether wetting agents, or alcohol wetting agents.

7. The preparation method according to claim 6, characterized in that, The oligomeric polyol type polyurethane emulsion includes polyether type, polyester type or polyolefin type, and the mixed polyurethane emulsion includes polyether-polyester or polyether-polybutadiene. The Tg temperature of the water-soluble acrylate-based polymer solution is 180-220℃; The polymer Tg temperature in the polyurethane-based polymer emulsion is 120-160℃.

8. A coating slurry prepared by the preparation method according to any one of claims 1-7.

9. A diaphragm, characterized in that, Any coating of the diaphragm contains the coating slurry as described in claim 8.

10. A battery, characterized in that, It includes the diaphragm as described in claim 9.

Images