Coating slurry, diaphragm and lithium ion battery

Abstract

The invention discloses coating slurry, a diaphragm and a lithium ion battery, and belongs to the technical field of lithium batteries. The coating slurry comprises the following raw materials in parts by weight: 1-3 parts of bio-based particles, 20-40 parts of inorganic ceramic particles, 1-5 parts of a modified metal organic framework, 0.1-0.4 part of a dispersing agent, 5-10 parts of an adhesive and 50-70 parts of water; the modified metal organic framework is a zinc-based metal organic framework modified by epoxy group polyethylene glycol silane, and the zinc-based metal organic framework contains a furan group. The diaphragm prepared by the preparation method disclosed by the invention has relatively high liquid absorption rate, thermal shrinkage rate and tensile property and relatively high safety, and the application scene of the diaphragm in a lithium battery is expanded.

Description

Technical Field

[0001] The present invention relates to the field of lithium batteries, and in particular to a coating slurry, a diaphragm and a lithium ion battery. Background Art

[0002] The automotive industry has experienced rapid growth in recent years, but this has also brought negative impacts such as environmental pollution and rapid depletion of oil resources. Consequently, countries around the world are actively developing electric vehicles. Lithium-ion batteries are the primary power source for electric vehicles. Lithium-ion batteries generally consist of three main components: a positive electrode, a negative electrode, and a separator that carries an electrolyte. As a crucial component of lithium-ion batteries, the separator primarily prevents internal short circuits and acts as an electrolyte carrier, providing a pathway for lithium ions to migrate. The separator significantly impacts the operating environment, specific capacity, safety, and service life of lithium-ion batteries. Therefore, research and development of polymer separators with superior performance, simple preparation processes, and suitability for industrial production are crucial for improving the application of lithium-ion batteries.

[0003] As new energy vehicles place increasing demands on battery safety, higher performance requirements are also being placed on separators. Currently, commonly used separators, such as polyethylene separators, suffer from low melting points and high shrinkage at high temperatures. Existing technologies, coating the polyethylene separator with heat-resistant ceramic particles, are considered an effective strategy with controllable costs and ease of scalable production. However, when ceramic materials are dense, the gaps between the particles are small, making it difficult for liquids to penetrate the material, resulting in reduced liquid absorption. Furthermore, the ceramic coating's limited temperature resistance cannot meet today's safety requirements for lithium batteries. Summary of the Invention

[0004] The present invention provides a coating slurry, a diaphragm and a lithium ion battery, which can solve the problems in the prior art of poor liquid absorption and limited temperature resistance of ceramic coating slurry.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a coating slurry comprising the following raw materials in parts by weight:

[0007] 1-3 parts of bio-based particles, 20-40 parts of inorganic ceramic particles, 1-5 parts of modified metal organic framework, 0.1-0.4 parts of dispersant, 5-10 parts of adhesive, and 50-70 parts of water; the modified metal organic framework is a zinc-based metal organic framework modified with epoxy polyethylene glycol silane.

[0008] Bio-based granular materials have been proven to improve the high temperature resistance of diaphragm products. Metal organic framework (MOFs) materials have extremely low density and a highly porous skeleton structure, and their specific surface area can reach hundreds to thousands of square meters per gram. This structure provides a large number of pores and channels, allowing the electrolyte to quickly penetrate and fill the interior of the diaphragm, thereby significantly improving the liquid absorption rate of the diaphragm. In addition, the appropriate pore size of MOFs can effectively control the shuttling of electrolyte ions, inhibit the occurrence of adverse side reactions, reduce the heat and gas generated by side reactions, and reduce the possibility of thermal runaway of the battery at high temperatures, thereby improving the safety performance of the battery at high temperatures and indirectly enhancing the temperature resistance of the diaphragm.

[0009] Furthermore, the bio-based particles are one or more of furan-based polyamide, furan-based polyimide and furan polyester.

[0010] Furthermore, the inorganic ceramic particles are one or more of alumina, silica, and titanium dioxide. Alumina, silica, and titanium dioxide are all ceramic particles containing hydroxyl groups, which are strong hydrophilic groups and can improve the poor liquid absorption performance of inorganic ceramic particles.

[0011] Furthermore, the dispersant is one or more of polyester ammonium salts, quaternary ammonium salts, polyurethanes, polyesters and silanols.

[0012] Furthermore, the adhesive is one or more of polyimides, polyamides, polyacrylates and polyacrylic acids.

[0013] Furthermore, the preparation method of the modified metal organic framework is:

[0014] S1. Preparation of a zinc-based metal organic framework: adding zinc nitrate hexahydrate, 2,5-furandicarboxylic acid, and 2-aminobenzimidazole to N,N-dimethylacetamide, reacting at 80-100° C. for 48-72 hours, then cooling to room temperature, filtering, washing, and drying to obtain a zinc-based metal organic framework;

[0015] The dosage ratio of zinc nitrate hexahydrate, 2,5-furandicarboxylic acid, 2-aminobenzimidazole and N,N-dimethylacetamide is 2.97 g: 1.56 g: 1.33 g: 90-100 mL.

[0016] In the above steps, a zinc-based metal-organic framework (MOF) containing furan groups was prepared using 2,5-furandicarboxylic acid and 2-aminobenzimidazole as organic ligands. This MOF has a similar chemical structure to bio-based particles, improving their compatibility.

[0017] S2. Preparation of modified metal organic framework: Add zinc-based metal organic framework to DMF, then add epoxy polyethylene glycol silane, stir and react at 50-60°C for 20-24h, then centrifuge, discard the supernatant, wash the precipitate and vacuum dry to obtain the modified metal organic framework.

[0018] The usage ratio of the zinc-based metal organic framework, DMF, and epoxy polyethylene glycol silane is 3 g: 30-40 mL: 0.1-0.4 g.

[0019] In the above steps, epoxy polyethylene glycol silane is grafted onto the zinc-based metal organic framework by utilizing the property that epoxy groups easily react with amino groups to obtain a modified metal organic framework. The zinc-based metal organic framework itself has poor dispersibility in water. By grafting epoxy polyethylene glycol silane, the epoxy polyethylene glycol silane chain segments grafted on the surface of the zinc-based metal organic framework can form a protective layer, increasing the steric hindrance between the zinc-based metal organic framework particles. This steric hindrance effect can prevent direct contact and aggregation between the zinc-based metal organic framework particles, thereby improving its dispersibility and allowing the modified metal organic framework to better function. In addition, the silane groups on the surface of the modified metal organic framework will undergo hydrolysis in water to generate silanol groups (Si-OH). The hydrolyzed silanol groups (Si-OH) can undergo a condensation reaction with the hydroxyl groups (-OH) on the surface of the inorganic ceramic particles to form silicon-oxygen-silicon bonds (Si-O-Si), thereby allowing the modified metal organic framework to be evenly dispersed in the raw materials, which is beneficial for it to function.

[0020] Furthermore, the molecular weight of the epoxy polyethylene glycol silane in step S2 is 0.4-1K.

[0021] In a second aspect, the present invention provides a diaphragm comprising a base film and a coating, wherein the coating is coated on the outer surface of the base film, and the coating is formed by coating the above-mentioned coating slurry on at least one side of the base film.

[0022] Furthermore, the coating layer has a thickness of 1-10 μm, and the base film has a thickness of 4-6 μm.

[0023] In a third aspect, the present invention provides a lithium-ion battery comprising a positive electrode, a negative electrode and a battery separator, wherein the battery separator adopts the above-mentioned separator, and the separator is arranged between the positive electrode and the negative electrode.

[0024] Beneficial effects of the present invention:

[0025] 1. The present invention incorporates a modified metal-organic framework (MOF) into the raw materials of the coating slurry. The modified MOF is a zinc-based MOF modified with epoxy polyethylene glycol silane. This MOF contains furan groups and silane, exhibiting good compatibility with both bio-based particles and inorganic ceramic particles. The MOF can be evenly dispersed throughout the raw materials, facilitating its growth-promoting effect and significantly improving the membrane's liquid absorption rate. Furthermore, polyethylene glycol, a flexible chain segment, can enhance the membrane's mechanical properties.

[0026] 2. The present invention achieves optimal overall performance by precisely controlling the amount of modified metal-organic framework added. Adding too much or too little modified metal-organic framework can negatively impact the overall performance of the membrane. Excessive addition of the modified metal-organic framework can lead to poor dispersibility, resulting in an uneven slurry, which can affect coating and reduce membrane performance. Excessive addition can lead to insignificant strengthening effects from the modified metal-organic framework, resulting in reduced membrane performance. DETAILED DESCRIPTION

[0027] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0028] Example 1

[0029] This embodiment provides a diaphragm, and the specific steps are:

[0030] 1 part furan-based polyamide, 20 parts silica particles, 1 part modified metal-organic framework, 0.1 part polyurethane dispersant, and 5 parts polyamide binder were uniformly dispersed in 50 parts water and stirred to obtain a separator coating slurry. The separator coating slurry was then coated on one side of a 5μm PE base film using a gravure roller coating process to a coating thickness of 5μm, ultimately producing a lithium battery separator.

[0031] The preparation method of the modified metal organic framework is:

[0032] S1: Add 2.97 g of zinc nitrate hexahydrate, 1.56 g of 2,5-furandicarboxylic acid, and 1.33 g of 2-aminobenzimidazole to 100 mL of N,N-dimethylacetamide, and react at 80°C for 48 h. Then cool to room temperature, filter, wash, and dry to obtain a zinc-based metal organic framework.

[0033] S2: Add 3 g of zinc-based metal organic framework to 30 mL of DMF, then add 0.1 g of epoxy polyethylene glycol silane (0.4K), stir and react at 50°C for 20 h, then centrifuge, discard the supernatant, wash the precipitate and vacuum dry to obtain a modified metal organic framework.

[0034] Example 2

[0035] This embodiment provides a diaphragm, and the specific steps are:

[0036] 2 parts furan-based polyamide, 30 parts silica particles, 2 parts modified metal-organic framework, 0.25 parts polyurethane dispersant, and 7.5 parts polyamide binder were uniformly dispersed in 60 parts water and stirred to obtain a separator coating slurry. The separator coating slurry was then coated onto one side of a 5μm PE-based film using a gravure roller coating process. The coating thickness reached 5μm, ultimately producing a lithium battery separator.

[0037] The preparation method of the modified metal organic framework is:

[0038] S1: Add 2.97 g of zinc nitrate hexahydrate, 1.56 g of 2,5-furandicarboxylic acid, and 1.33 g of 2-aminobenzimidazole to 100 mL of N,N-dimethylacetamide, and react at 90°C for 72 h. Then cool to room temperature, filter, wash, and dry to obtain a zinc-based metal organic framework.

[0039] S2: Add 3 g of zinc-based metal organic framework to 40 mL of DMF, then add 0.25 g of epoxy polyethylene glycol silane (0.4K), stir and react at 55°C for 22 h, then centrifuge, discard the supernatant, wash the precipitate and vacuum dry to obtain a modified metal organic framework.

[0040] Example 3

[0041] This embodiment provides a diaphragm, and the specific steps are:

[0042] 3 parts furan-based polyamide, 40 parts silica particles, 3 parts modified metal-organic framework, 0.4 parts polyurethane dispersant, and 10 parts polyamide binder were uniformly dispersed in 70 parts water and stirred to obtain a separator coating slurry. The separator coating slurry was then coated onto one side of a 5μm PE-based film using a gravure roller coating process. The coating thickness reached 5μm, ultimately producing a lithium battery separator.

[0043] The preparation method of the modified metal organic framework is:

[0044] S1: Add 2.97 g of zinc nitrate hexahydrate, 1.56 g of 2,5-furandicarboxylic acid, and 1.33 g of 2-aminobenzimidazole to 100 mL of N,N-dimethylacetamide, and react at 100°C for 72 h. Then cool to room temperature, filter, wash, and dry to obtain a zinc-based metal organic framework.

[0045] S2: Add 3 g of zinc-based metal organic framework to 40 mL of DMF, then add 0.4 g of epoxy polyethylene glycol silane (0.4K), stir and react at 60°C for 24 h, then centrifuge, discard the supernatant, wash the precipitate and vacuum dry to obtain a modified metal organic framework.

[0046] Example 4

[0047] Compared with Example 3, this example is different in that the modified metal organic framework is 4 parts, and the other raw materials and steps are the same as Example 3.

[0048] Example 5

[0049] Compared with Example 3, this example is different in that the modified metal organic framework is 5 parts, and the other raw materials and steps are the same as Example 3.

[0050] Comparative Example 1

[0051] Compared with Example 1, this comparative example is different in that the amount of the modified metal organic framework is replaced from "1 part" to "0.5 parts", and the remaining raw materials and steps are the same as Example 1.

[0052] Comparative Example 2

[0053] This comparative example is different from Example 5 in that the amount of the modified metal organic framework is replaced from "5 parts" to "5.5 parts", and the remaining raw materials and steps are the same as Example 5.

[0054] Comparative Example 3

[0055] This comparative example is different from Example 1 in that epoxy polyethylene glycol silane is replaced with KH-560 during the preparation of the modified metal organic framework. The specific steps are as follows:

[0056] S1: Add 2.97 g of zinc nitrate hexahydrate, 1.56 g of 2,5-furandicarboxylic acid, and 1.33 g of 2-aminobenzimidazole to 100 mL of N,N-dimethylacetamide, and react at 80°C for 48 h. Then cool to room temperature, filter, wash, and dry to obtain a zinc-based metal organic framework.

[0057] S2: 3 g of zinc-based metal organic framework was added to 30 mL of DMF, followed by 0.5 g of KH-560. The mixture was stirred at 50°C for 20 h, and then centrifuged. The supernatant was discarded, the precipitate was washed, and vacuum dried to obtain a modified metal organic framework.

[0058] The remaining materials and steps are the same as in Example 1.

[0059] Comparative Example 4

[0060] This comparative example is different from Example 1 in that epoxy polyethylene glycol silane is omitted in the process of preparing the modified metal organic framework. The specific steps are as follows:

[0061] 2.97 g of zinc nitrate hexahydrate, 1.56 g of 2,5-furandicarboxylic acid, and 1.33 g of 2-aminobenzimidazole were added to 100 mL of N,N-dimethylacetamide, and reacted at 80° C. for 48 h. The reaction was then cooled to room temperature, filtered, washed, and dried to obtain a modified metal organic framework.

[0062] The remaining materials and steps are the same as in Example 1.

[0063] Comparative Example 5

[0064] Compared with Example 1, this comparative example is different in that the modified metal organic framework is replaced by MOF-5 (Zn), and the remaining raw materials and steps are the same as Example 1.

[0065] The performance tests of the diaphragms prepared in Examples 1 to 5 and Comparative Examples 1 to 5 were conducted. The test items are as follows, and the results are shown in Table 1:

[0066] 1. Thermal shrinkage: The test condition is to bake the diaphragm samples at 160℃ for 1 hour, and calculate the thermal shrinkage of each group of diaphragm samples.

[0067] 2. Liquid absorption: Cut the diaphragm into 40mm×40mm samples, dry the samples at 90℃ for 2h, weigh them after cooling and record them as m0, then immerse the diaphragm in electrolyte and take it out after soaking for 2h, where the electrolyte is prepared by adding 1g of ethylene carbonate and 1g of dimethyl carbonate to 1mol of lithium hexafluorophosphate, then use filter paper to absorb the excess electrolyte on the surface of the diaphragm and weigh it, record it as m1, where the liquid absorption rate P = (m1-m0) / m0×100%.

[0068] 3. Tensile strength: Cut the diaphragm samples into 45×5mm size and stretch them at a rate of 5mm / min. Each sample is grouped into 5 pieces and the average value is taken as the final result.

[0069] Table 1

[0070]

[0071] It can be seen from Table 1 that the comprehensive performance of the diaphragms prepared in Examples 1 to 5 is better than the comprehensive performance of the diaphragms prepared in Comparative Examples 1 to 5.

[0072] The amount of modified metal-organic framework added in Comparative Examples 1 and 2 was lower than that in Example 1 and higher than that in Example 5, respectively. As can be seen in Table 1, the performance of Comparative Examples 1 and 2 was lower than that in Example 1 and 5, respectively. This indicates that the present invention achieves optimal overall performance by precisely controlling the amount of modified metal-organic framework added. Adding too much or too little modified metal-organic framework will affect the overall performance of the membrane. When the amount of modified metal-organic framework added is too high, its dispersibility deteriorates, resulting in an uneven slurry, affecting the coating effect and causing a decrease in membrane performance. When the amount added is too low, the enhanced effect of the modified metal-organic framework is not significant, and membrane performance is reduced.

[0073] In Comparative Example 3, epoxy polyethylene glycol silane is replaced with KH-560. From Table 1, it can be found that the tensile strength of Comparative Example 3 is lower than that of Example 1, indicating that polyethylene glycol is a flexible segment that can improve the mechanical properties of the diaphragm.

[0074] In Comparative Example 4, epoxy polyethylene glycol silane is omitted, and its comprehensive performance is lower than that of Example 1, indicating that the epoxy polyethylene glycol silane chain segment grafted on the surface of the zinc-based metal organic framework can form a protective layer, increasing the steric hindrance between the zinc-based metal organic framework particles. This steric hindrance effect can prevent direct contact and aggregation between the zinc-based metal organic framework particles, thereby improving its dispersibility and allowing the modified metal organic framework to play a better role. The silane groups on the surface of the modified metal organic framework can be hydrolyzed in water to generate silanol groups (Si-OH), and the silanol groups (Si-OH) generated by hydrolysis can condense with the hydroxyl groups (-OH) on the surface of the inorganic ceramic particles to form silicon-oxygen silicon bonds (Si-O-Si), thereby allowing the modified metal organic framework to be evenly dispersed in the raw materials, which is beneficial for it to play a role.

[0075] Comparative Example 5, using MOF-5(Zn), had the worst dispersibility and, consequently, the worst overall performance. This suggests that the furan-containing zinc-based metal-organic framework (MOF) has a similar chemical structure to the bio-based particles, improving their compatibility and facilitating their reinforcing effect.

[0076] The above disclosures are only a few specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the scope of protection of the present invention.

Claims

1. A coating slurry, characterized in that: It includes the following raw materials in parts by weight: 1-3 parts of bio-based particles, 20-40 parts of inorganic ceramic particles, 1-5 parts of modified metal organic framework, 0.1-0.4 parts of dispersant, 5-10 parts of adhesive, and 50-70 parts of water; the modified metal organic framework is a zinc-based metal organic framework modified with epoxy polyethylene glycol silane.

2. A coating slurry according to claim 1, characterized in that, The bio-based particles are one or more of furan-based polyamide, furan-based polyimide and furan polyester.

3. A coating slurry according to claim 1, characterized in that: The inorganic ceramic particles are one or more of alumina, silicon dioxide, and titanium dioxide.

4. A coating slurry according to claim 1, characterized in that, The dispersant is one or more of polyester ammonium salts, quaternary ammonium salts, polyurethanes, polyesters and silanols; the adhesive is one or more of polyimides, polyamides, polyacrylates and polyacrylic acids.

5. A coating slurry according to claim 1, characterized in that, The preparation method of the modified metal organic framework is: S1. Preparation of a zinc-based metal organic framework: adding zinc nitrate hexahydrate, 2,5-furandicarboxylic acid, and 2-aminobenzimidazole to N,N-dimethylacetamide, reacting at 80-100° C. for 48-72 hours, then cooling to room temperature, filtering, washing, and drying to obtain a zinc-based metal organic framework; S2. Preparation of modified metal organic framework: Add zinc-based metal organic framework to DMF, then add epoxy polyethylene glycol silane, stir and react at 50-60°C for 20-24h, then centrifuge, discard the supernatant, wash the precipitate and vacuum dry to obtain the modified metal organic framework.

6. A coating slurry according to claim 5, characterized in that: In step S1, the usage ratio of zinc nitrate hexahydrate, 2,5-furandicarboxylic acid, 2-aminobenzimidazole, and N,N-dimethylacetamide is 2.97 g: 1.56 g: 1.33 g: 90-100 mL.

7. The coating slurry according to claim 5, characterized in that: In step S2, the usage ratio of the zinc-based metal organic framework, DMF, and epoxy polyethylene glycol silane is 3 g: 30-40 mL: 0.1-0.4 g; the molecular weight of the epoxy polyethylene glycol silane is 0.4-1K.

8. A diaphragm, characterized in that: The invention comprises a base film and a coating layer, wherein the coating layer is coated on the outer surface of the base film, and the coating layer is formed by coating the coating slurry according to any one of claims 1 to 7 on at least one side of the base film.

9. A diaphragm according to claim 8, characterized in that: The coating layer has a thickness of 1-10 μm, and the base film has a thickness of 4-6 μm.

10. A lithium ion battery, characterized in that: The battery separator comprises a positive electrode, a negative electrode and a battery separator, wherein the battery separator is the separator according to claim 8 or 9, and the separator is arranged between the positive electrode and the negative electrode.

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