A diaphragm coating slurry for solid-state batteries and preparation method thereof

Abstract

The present invention provides a diaphragm coating slurry for solid-state batteries and a preparation method thereof, belonging to the technical field of diaphragm coating slurries. The diaphragm coating slurry for solid-state batteries comprises the following raw material components, measured by mass percentage: 25-30% modified alumina, 4-4.5% carboxymethyl cellulose, 0.6-1% dispersant, 1.3-1.5% inorganic sol, 1.5-2% nanosilicate, 0.5-0.8% interfacial compatibilizer, and the balance water; the modified alumina is prepared by acid-washing alumina and then surface-treating it with a silane coupling agent. The present invention can effectively improve the adhesion between the coating and the diaphragm substrate to prevent it from falling off; at the same time, it can also improve the tensile strength to prevent the coating itself from being easily damaged, thereby enhancing the long-term stability of the battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of diaphragm coating slurry, and in particular relates to a diaphragm coating slurry for solid-state batteries and a preparation method thereof. Background Art

[0002] A solid-state battery is a battery whose electrolyte is a solid substance. Compared with traditional liquid electrolyte lithium batteries, it has potential advantages in safety, energy density, etc. Due to the difference in the physical state of the electrolyte, there are significant differences in the internal structure and functional implementation of the two, which also affects the use of the diaphragm. The diaphragm is located between the positive and negative poles of the battery. Its main function is to physically isolate the two poles and prevent short circuits caused by direct contact. This is crucial in any type of lithium battery. In traditional liquid lithium batteries, the diaphragm also needs to ensure that the electrolyte can fully infiltrate to form an efficient ion transmission channel. In solid-state batteries, although the electrolyte is replaced by a solid electrolyte, the role of the diaphragm is still to maintain the efficiency and stability of ion transmission.

[0003] As battery technology evolves from liquid to solid and quasi-solid state, separators are also evolving. In all-solid-state batteries, the electrolyte becomes completely solid, potentially eliminating the need for a traditional separator. However, most current solid-state battery designs still utilize some form of separator or composite separator to provide critical physical isolation and electrochemical protection, ensuring safe and efficient battery operation.

[0004] In terms of diaphragm coating slurry, diaphragm coating ceramics can improve its mechanical strength and extend its service life. However, in some application scenarios, such as high-energy-density solid-state batteries, although the mechanical strength of the ceramic coating is improved, it may break due to external stress during battery assembly or use. Especially when the battery is impacted or pressurized, the insufficient adhesion between the ceramic coating and the diaphragm substrate will cause the coating to gradually fall off during use. In addition, hard ceramic particles in the coating can easily become stress concentration points, which will also cause the binder skeleton to be more easily destroyed when subjected to stress, affecting the long-term stability of the battery. Summary of the Invention

[0005] In order to solve the problems existing in the background technology, the present invention provides a diaphragm coating slurry for solid-state batteries and a preparation method thereof, which can effectively improve the adhesion between the coating and the diaphragm substrate to prevent it from falling off; at the same time, it improves the tensile strength to prevent the coating itself from being easily damaged, thereby enhancing the long-term stability of the battery.

[0006] In order to achieve the above-mentioned objectives, in a first aspect, the present invention provides a diaphragm coating slurry for solid-state batteries, which comprises the following raw material components, calculated by mass percentage: 25-30% modified alumina, 4-4.5% carboxymethyl cellulose, 0.6-1% dispersant, 1.3-1.5% inorganic sol, 1.5-2% nanofiller, 0.5-0.8% interfacial compatibilizer and the remainder water; the modified alumina is prepared by acid-washing alumina and then surface-treating the surface with a silane coupling agent.

[0007] Furthermore, the preparation method of the modified alumina is as follows:

[0008] A1. Immerse the aluminum oxide in a 5-6% hydrofluoric acid aqueous solution, stir at a constant speed of 70-80 r / min for 3-4 minutes at room temperature, then filter and wash with water until neutral to obtain roughened aluminum oxide;

[0009] A2. Immerse the roughened alumina obtained in A1 in a 10-11% silane coupling agent n-butanol solution, heat to 80-85°C, stir at a constant speed of 55-65 r / min for 4-4.5 hours, then filter and dry to obtain modified alumina.

[0010] Furthermore, the silane coupling agent is γ-aminopropyltriethoxysilane.

[0011] Furthermore, the inorganic sol includes silica sol and / or aluminum sol.

[0012] Furthermore, the nanofiller includes any one of nanosilicate, carbon nanotube, and graphene.

[0013] Furthermore, the nano-silicate includes any one of kaolin, anorthite, quartz, and tourmaline powder, or a mixture of at least two of them.

[0014] Furthermore, the dispersant is polyethylene glycol dioleate.

[0015] Furthermore, the interfacial compatibilizer is maleic anhydride grafted polyethylene.

[0016] In a second aspect, the present invention provides a method for preparing the above-mentioned solid-state battery separator coating slurry, comprising the following steps:

[0017] S1. dissolving carboxymethyl cellulose in water to obtain a colloidal solution;

[0018] S2, mixing the modified alumina and the nanofiller to obtain mixed particles;

[0019] S3. Put the colloidal solution obtained in S1 and the mixed particles obtained in S2 into a blender, and then add a dispersant, an inorganic sol and an interfacial compatibilizer, stir and mix them evenly to obtain a diaphragm coating slurry for a solid-state battery.

[0020] Furthermore, in S3, the stirring speed is 1500-1700 r / min, and the stirring time is 50-60 min.

[0021] This application has the following beneficial effects:

[0022] The addition of carboxymethyl cellulose in the present invention can form a protective film on the surface of the material. When the dosage is appropriate, the film can maintain a certain porosity and prevent the loss of pores caused by excessive sealing. Carboxymethyl cellulose has good water retention capacity. An increase in dosage will form more hydrogels in the coating. These hydrogels gradually lose water during the drying process, leaving tiny pores, increasing the number of pores and the porosity. If the carboxymethyl cellulose content is too high, the pores will be dense, and more dense connections will occur, the pore size will increase, the porosity will increase, but the number of pores will decrease, thereby affecting the peeling strength of the coating and the tensile strength of the prepared diaphragm.

[0023] The modified alumina coating has a more optimized pore structure, which allows silica sol and nanosilicate to more easily enter and fill the pores. Experimental results show that when the carboxymethyl cellulose content is 4-4.5%, the modified alumina treatment according to the present invention and the addition of silica sol and calcined kaolin (4000 mesh) have a synergistic effect, achieving the best results in improving the adhesion of the coating and the tensile strength of the diaphragm.

[0024] The present invention can effectively improve the adhesion between the coating and the diaphragm substrate, with the measured peel strength reaching over 2.81 N / cm, effectively preventing it from falling off. At the same time, it can also improve the tensile strength, with the measured tensile strength reaching over 50.2 MPa, effectively preventing the coating itself from being damaged by stress. The battery also has excellent long-term stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 , a comparative trend chart of peel strength test data of ceramic diaphragm coatings prepared in Examples 1-6 of the present invention and Comparative Examples 1-11;

[0026] Figure 2 , a comparison trend chart of the tensile strength test data of the ceramic diaphragms prepared in Examples 1-6 of the present invention and Comparative Examples 1-11. DETAILED DESCRIPTION

[0027] The present application is further described in detail below with reference to the embodiments.

[0028] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0029] Example 1: (1) Preparation of modified alumina, the preparation method is as follows:

[0030] A1. Immerse the aluminum oxide in a 5.5% hydrofluoric acid aqueous solution, stir at 75 rpm for 3.5 minutes at room temperature, then filter and wash with water until neutral to obtain roughened aluminum oxide.

[0031] Alumina was calcined α-alumina, 260 mesh, purchased from Zibo Yishengjia Aluminum Co., Ltd. Hydrofluoric acid (first-grade product) was purchased from Shaanxi Lanxin Chemical Co., Ltd.

[0032] A2. Immerse the roughened alumina obtained in A1 in a 10.5% n-butanol solution of γ-aminopropyltriethoxysilane, heat to 82°C, and stir at a constant speed of 60 r / min for 4.2 hours. Then filter and dry to obtain modified alumina.

[0033] γ-Aminopropyltriethoxysilane (KH550) was purchased from Shandong Hengyu New Materials Co., Ltd. n-Butanol was purchased from Jinan Century Tongda Chemical Co., Ltd.

[0034] (2) Preparation of solid-state battery separator coating slurry, the preparation method is as follows:

[0035] S1. Calculate the raw material components by mass percentage: 28% modified alumina, 4.2% carboxymethyl cellulose, 0.8% dispersant, 1.4% inorganic sol, 1.8% nanofiller, 0.6% interfacial compatibilizer and 63.2% water.

[0036] Among them, the modified alumina is prepared by (1). Carboxymethyl cellulose was purchased from Hebei Shenghai Environmental Protection Technology Co., Ltd. The inorganic sol is silica sol, specifically chemical nano-grade acidic silica sol (30%), purchased from Guangzhou Changhao Chemical Co., Ltd. The nanofiller is nanosilicate, specifically calcined kaolin (4000 mesh), purchased from Changxing Innovation Ultrafine Powder Co., Ltd. The dispersant is polyethylene glycol dioleate (content 98%, density 10g / cm 3 ), purchased from Wuhan Kamik Technology Co., Ltd. The interfacial compatibilizer was maleic anhydride grafted polyethylene (grafting rate 0.8-1.0%), purchased from Shandong Shoucheng Chemical Co., Ltd.

[0037] S2. Dissolve the carboxymethyl cellulose weighed in S1 in the water weighed in S1 to obtain a colloidal solution. Specifically, after mixing the two, stir at 150 rpm for 10 minutes.

[0038] S3. Mix the modified alumina and the nanofiller weighed in S1 to obtain mixed particles. Specifically, after mixing the two, stir at 100 rpm for 10 minutes.

[0039] S4. Put the colloidal solution obtained in S2 and the mixed particles obtained in S3 into a blender, and then add the dispersant, inorganic sol and interfacial compatibilizer weighed in S1. Stir at a constant speed of 1600 r / min for 55 minutes to obtain a solid-state battery separator coating slurry.

[0040] (3) A ceramic diaphragm is prepared as follows: First, a PE film with a thickness of 12±2 μm is selected, the brand of which is SK of South Korea and is purchased from Shenzhen Yuanchenghui Electronics Co., Ltd. Then, the solid-state battery diaphragm coating slurry prepared in (2) is coated on the PE film, and the water is dried in an oven at a temperature of 55-65°C to form a coating with a thickness of about 4 μm, thereby obtaining a ceramic diaphragm.

[0041] Example 2: The difference between this example and Example 1 is that: (1) modified alumina is prepared, and the preparation method is as follows:

[0042] A1. Immerse the aluminum oxide in a 5% hydrofluoric acid aqueous solution, stir at 70r / min at room temperature for 3 minutes, then filter and wash with water until neutral to obtain roughened aluminum oxide.

[0043] A2. Immerse the roughened alumina obtained in A1 in a 10% n-butanol solution of γ-aminopropyltriethoxysilane, heat to 80°C, and stir at a constant speed of 55 rpm for 4 hours. Then filter and dry to obtain modified alumina.

[0044] Example 3: The difference between this example and Example 1 is that: (1) modified alumina is prepared by the following method:

[0045] A1. Immerse the aluminum oxide in a 6% hydrofluoric acid aqueous solution, stir at 80 r / min for 4 minutes at room temperature, then filter and wash with water until neutral to obtain roughened aluminum oxide.

[0046] A2. Immerse the roughened alumina obtained in A1 in an 11% n-butanol solution of γ-aminopropyltriethoxysilane, heat to 85°C, and stir at a constant speed of 65 r / min for 4.5 hours. Then filter and dry to obtain modified alumina.

[0047] Example 4: The difference between this example and Example 1 is that: (2) a diaphragm coating slurry for a solid-state battery is prepared, and the preparation method is as follows:

[0048] S1. Calculate the raw material components by mass percentage: 25% modified alumina, 4% carboxymethyl cellulose, 0.6% dispersant, 1.3% inorganic sol, 1.5% nanofiller, 0.5% interfacial compatibilizer and 67.1% water.

[0049] S2. Dissolve the carboxymethyl cellulose weighed in S1 in the water weighed in S1 to obtain a colloidal solution.

[0050] S3. Evenly mix the modified alumina weighed in S1 and the nanofiller weighed in S1 to obtain mixed particles.

[0051] S4. Put the colloidal solution obtained in S2 and the mixed particles obtained in S3 into a blender, and then add the dispersant, inorganic sol and interfacial compatibilizer weighed in S1. Stir at a constant speed of 1500 r / min for 50 minutes and mix thoroughly to obtain a solid-state battery separator coating slurry.

[0052] Example 5: The difference between this example and Example 1 is that: (2) a diaphragm coating slurry for a solid-state battery is prepared, and the preparation method is as follows:

[0053] S1. Calculate the raw material components by mass percentage: 30% modified alumina, 4.5% carboxymethyl cellulose, 1% dispersant, 1.5% inorganic sol, 2% nanofiller, 0.8% interfacial compatibilizer and 60.2% water.

[0054] S2. Dissolve the carboxymethyl cellulose weighed in S1 in the water weighed in S1 to obtain a colloidal solution.

[0055] S3. Evenly mix the modified alumina weighed in S1 and the nanofiller weighed in S1 to obtain mixed particles.

[0056] S4. Put the colloidal solution obtained in S2 and the mixed particles obtained in S3 into a blender, and then add the dispersant, inorganic sol and interfacial compatibilizer weighed in S1. Stir at a constant speed of 1700 r / min for 60 min and mix thoroughly to obtain a diaphragm coating slurry for solid-state batteries.

[0057] Example 6: The difference between this example and Example 1 is that: (2) a diaphragm coating slurry for a solid-state battery is prepared by the following method:

[0058] S1. Calculate the raw material components by mass percentage: 30% modified alumina, 4% carboxymethyl cellulose, 1% dispersant, 1.5% inorganic sol, 2% nanofiller, 0.8% interfacial compatibilizer and 60.7% water.

[0059] S2. Dissolve the carboxymethyl cellulose weighed in S1 in the water weighed in S1 to obtain a colloidal solution.

[0060] S3. Evenly mix the modified alumina weighed in S1 and the nanofiller weighed in S1 to obtain mixed particles.

[0061] S4. Put the colloidal solution obtained in S2 and the mixed particles obtained in S3 into a blender, and then add the dispersant, inorganic sol and interfacial compatibilizer weighed in S1. Stir at a constant speed of 1600 r / min for 55 minutes to obtain a solid-state battery separator coating slurry.

[0062] Comparative Example 1: The difference between this comparative example and Example 1 is that the modified alumina is replaced by alumina; the silica sol and calcined kaolin (4000 mesh) are deleted; and the mass percentage of carboxymethyl cellulose is 2.5%.

[0063] Specifically, in the preparation of the diaphragm coating slurry for solid-state batteries: S1, weigh the raw material components 28% of aluminum oxide, 2.5% of carboxymethyl cellulose, 0.8% of dispersant, 0.6% of interfacial compatibilizer and 68.1% of water in percentage by mass.

[0064] Comparative Example 2: This comparative example differs from Example 1 in that the modified alumina is replaced by alumina; and the silica sol and calcined kaolin (4000 mesh) are deleted.

[0065] Specifically, in the preparation of the diaphragm coating slurry for solid-state batteries: S1, weigh the raw material components 28% of aluminum oxide, 4.2% of carboxymethyl cellulose, 0.8% of dispersant, 0.6% of interfacial compatibilizer and 66.4% of water in percentage by mass.

[0066] Comparative Example 3: This comparative example differs from Example 1 in that: modified alumina is replaced by alumina; silica sol and calcined kaolin (4000 mesh) are deleted; and the mass percentage of carboxymethyl cellulose is 6%.

[0067] Specifically, in the preparation of the diaphragm coating slurry for solid-state batteries: S1, weigh the raw material components of modified alumina 28%, carboxymethyl cellulose 6%, dispersant 0.8%, interfacial compatibilizer 0.6% and water 64.6% by mass percentage.

[0068] Comparative Example 4: This comparative example differs from Example 1 in that silica sol and calcined kaolin (4000 mesh) are deleted, and the mass percentage of carboxymethyl cellulose is 2.5%.

[0069] Specifically, in the preparation of the diaphragm coating slurry for solid-state batteries: S1, weigh the raw material components of modified alumina 28%, carboxymethyl cellulose 2.5%, dispersant 0.8%, interfacial compatibilizer 0.6% and water 68.1% by mass percentage.

[0070] Comparative Example 5: This comparative example differs from Example 1 in that silica sol and calcined kaolin (4000 mesh) are deleted.

[0071] Specifically, in the preparation of the diaphragm coating slurry for solid-state batteries: S1, weigh the raw material components of modified alumina 28%, carboxymethyl cellulose 4.2%, dispersant 0.8%, interfacial compatibilizer 0.6% and water 66.4% by mass percentage.

[0072] Comparative Example 6: This comparative example differs from Example 1 in that the silica sol and calcined kaolin (4000 mesh) are deleted; and the mass percentage of carboxymethyl cellulose is 6%.

[0073] Specifically, in the preparation of the diaphragm coating slurry for solid-state batteries: S1, weigh the raw material components of modified alumina 28%, carboxymethyl cellulose 6%, dispersant 0.8%, interfacial compatibilizer 0.6% and water 64.6% by mass percentage.

[0074] Comparative Example 7: This comparative example differs from Example 1 in that the modified alumina is replaced by alumina; and the mass percentage of carboxymethyl cellulose used is 2.5%.

[0075] Specifically, in the preparation of the diaphragm coating slurry for solid-state batteries: S1, weigh the raw material components 28% alumina, 2.5% carboxymethyl cellulose, 0.8% dispersant, 1.4% silica sol, 1.8% calcined kaolin (4000 mesh), 0.6% interfacial compatibilizer and 64.9% water in percentage by mass.

[0076] Comparative Example 8: The difference between this comparative example and Example 1 is that the modified alumina is replaced by alumina.

[0077] Specifically, in the preparation of the diaphragm coating slurry for solid-state batteries: S1, weigh the raw material components 28% alumina, 4.2% carboxymethyl cellulose, 0.8% dispersant, 1.4% silica sol, 1.8% calcined kaolin (4000 mesh), 0.6% interfacial compatibilizer and 63.2% water in percentage by mass.

[0078] Comparative Example 9: This comparative example differs from Example 1 in that the modified alumina is replaced by alumina; and the mass percentage of carboxymethyl cellulose used is 6%.

[0079] Specifically, in the preparation of the diaphragm coating slurry for solid-state batteries: S1, weigh the raw material components of 28% alumina, 6% carboxymethyl cellulose, 0.8% dispersant, 1.4% silica sol, 1.8% calcined kaolin (4000 mesh), 0.6% interfacial compatibilizer and 61.4% water in percentage by mass.

[0080] Comparative Example 10: The difference between this comparative example and Example 1 is that the mass percentage of carboxymethyl cellulose used is 2.5%.

[0081] Specifically, in the preparation of the diaphragm coating slurry for solid-state batteries: S1, weigh the raw material components 28% modified alumina, 2.5% carboxymethyl cellulose, 0.8% dispersant, 1.4% silica sol, 1.8% calcined kaolin (4000 mesh), 0.6% interfacial compatibilizer and 64.9% water in percentage by mass.

[0082] Comparative Example 11: The difference between this comparative example and Example 1 is that the mass percentage of carboxymethyl cellulose is 6%.

[0083] Specifically, in the preparation of the diaphragm coating slurry for solid-state batteries: S1, weigh the raw material components of modified alumina 28%, carboxymethyl cellulose 6%, dispersant 0.8%, silica sol 1.4%, calcined kaolin (4000 mesh) 1.8%, interfacial compatibilizer 0.6% and water 61.4% by mass percentage.

[0084] Test example: Test object: Ceramic diaphragms were prepared according to Examples 1-6 and Comparative Examples 1-11.

[0085] Test items: ① Adhesion-peel strength of coating; ② Tensile strength of ceramic diaphragm.

[0086] Test basis: ① Peel strength was tested according to Method 2 of the national standard GB / T 2792-2014 "Test method for peel strength of adhesive tapes"; ② Tensile strength was tested according to GB / T1040.3-2006, using a Type 2 specimen with a width of 15 mm, an initial distance between the clamps of 100 mm, and a test speed of 250 mm / min.

[0087] Test results: See Table 1.

[0088] Table 1. Test data of experimental example

[0089]

[0090] Result analysis: Analyze Examples 1-6 and Comparative Examples 1-11 and combine the data in Table 1 and Figure 1-2 It can be seen that the present invention can effectively improve the adhesion between the coating and the diaphragm substrate, with the measured peel strength reaching over 2.81 N / cm, effectively preventing it from falling off. At the same time, it can also improve the tensile strength, with the measured tensile strength reaching over 50.2 MPa, effectively preventing the coating itself from being damaged by stress. The battery also has excellent long-term stability.

[0091] Analyze comparative examples 1-3 and combine the data in Table 1 and Figure 1-2 It can be seen that when the alumina is not modified and the slurry raw materials do not contain silica sol and calcined kaolin (4000 mesh), the peel strength and tensile strength test data are all compared in the order of Comparative Example 1 (2.5% carboxymethyl cellulose) > Comparative Example 2 (4.2% carboxymethyl cellulose) > Comparative Example 3 (6% carboxymethyl cellulose). This shows that when the carboxymethyl cellulose content is low, the adhesion of the coating and the tensile strength of the separator are greater. This is because when the carboxymethyl cellulose content is low, the porosity of the coating is lower, and the bonding area between the coating and the substrate is larger.

[0092] Analyze Comparative Examples 1-3 and Comparative Examples 4-6 and combine the data in Table 1 and Figure 1-2 As can be seen, compared to Comparative Examples 1-3, after the aluminum oxide was modified according to the present invention, the peel strength and tensile strength test data were all in the order of Comparative Example 4 (2.5% carboxymethyl cellulose) > Comparative Example 5 (4.2% carboxymethyl cellulose) > Comparative Example 6 (6% carboxymethyl cellulose). This indicates that the present invention achieves better results when the aluminum oxide is modified with a lower carboxymethyl cellulose content (2.5%).

[0093] In addition, in terms of peel strength, Comparative Example 4>Comparative Example 1, an increase of 0.43N / cm; Comparative Example 5>Comparative Example 2, an increase of 0.34N / cm; Comparative Example 6>Comparative Example 3, an increase of 0.26N / cm; in terms of tensile strength, Comparative Example 4>Comparative Example 1, an increase of 6MPa; Comparative Example 5>Comparative Example 2, an increase of 4.7MPa; Comparative Example 6>Comparative Example 3, an increase of 3.7MPa. It can be seen that after the aluminum oxide is modified by the present invention, the increase in the effect of 2.5% carboxymethyl cellulose is greater than the increase in the effect of 4.2% carboxymethyl cellulose, and the increase in the effect of 6% carboxymethyl cellulose. This shows that when the content of carboxymethyl cellulose is low (2.5%), the modification of the aluminum oxide by the present invention is more conducive to improving the adhesion of the coating and the tensile strength of the diaphragm.

[0094] Analyze Comparative Examples 1-3 and Comparative Examples 7-9 and combine the data in Table 1 and Figure 1-2 It can be seen that compared to Comparative Examples 1-3, after adding silica sol and calcined kaolin (4000 mesh), the peel strength and tensile strength test data are as follows: Comparative Example 7 (2.5% carboxymethyl cellulose) > Comparative Example 8 (4.2% carboxymethyl cellulose) > Comparative Example 9 (6% carboxymethyl cellulose). This indicates that the addition of silica sol and calcined kaolin (4000 mesh) and a lower carboxymethyl cellulose content (2.5%) achieve the best results.

[0095] Analyze Comparative Examples 1-3 and Example 1, Comparative Examples 10-11 and combine the data in Table 1 and Figure 1-2 It can be seen that compared to Comparative Examples 1-3, the modification of alumina according to the present invention and the addition of silica sol and calcined kaolin (4000 mesh) show a synergistic effect. The peel strength and tensile strength test data are as follows: Example 1 (4.2% carboxymethyl cellulose) > Comparative Example 10 (2.5% carboxymethyl cellulose) > Comparative Example 11 (6% carboxymethyl cellulose). This indicates that the modification of alumina according to the present invention and the addition of silica sol and calcined kaolin (4000 mesh) achieve the best results when the carboxymethyl cellulose content is 4.2%.

[0096] In addition, in terms of peel strength, Example 1 is greater than Comparative Example 2, with an increase of 0.79 N / cm; Comparative Example 10 is greater than Comparative Example 1, with an increase of 0.50 N / cm; Comparative Example 11 is greater than Comparative Example 3, with an increase of 0.66 N / cm. In terms of tensile strength, Example 1 is greater than Comparative Example 2, with an increase of 10.9 MPa; Comparative Example 10 is greater than Comparative Example 1, with an increase of 7.1 MPa; Comparative Example 11 is greater than Comparative Example 3, with an increase of 6.8 MPa. Thus, it can be seen that the modification of alumina by the present invention and the addition of silica sol and calcined kaolin (4000 mesh) have a greater increase in peel strength than the 4.2% increase in carboxymethyl cellulose by 6% and the 2.5% increase in carboxymethyl cellulose by 2.5%. In terms of tensile strength, the 4.2% increase in carboxymethyl cellulose by 2.5% and the 6% increase in carboxymethyl cellulose by 6% are greater. It shows that when the content of carboxymethyl cellulose is 4.2%, the aluminum oxide is modified according to the present invention and silica sol and calcined kaolin (4000 mesh) are added, and the two work synergistically to achieve the best effect on improving the adhesion of the coating and the tensile strength of the diaphragm.

[0097] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0098] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A solid-state battery separator coating slurry, characterized in that: The raw material components are as follows: 25-30% modified alumina, 4-4.5% carboxymethyl cellulose, 0.6-1% dispersant, 1.3-1.5% inorganic sol, 1.5-2% nanofiller, 0.5-0.8% interfacial compatibilizer and the balance water. The modified alumina is prepared by acid-washing alumina and then surface-treating it with a silane coupling agent. The inorganic sol is silica sol; the nano filler is 4000 mesh calcined kaolin; The preparation method of the modified alumina is as follows: A1. Immerse the alumina in a 5-6% hydrofluoric acid aqueous solution, stir at 70-80 rpm for 3-4 minutes at room temperature, then filter and wash with water until neutral to obtain roughened alumina. A2. Immerse the roughened alumina obtained in A1 in a 10-11% silane coupling agent n-butanol solution, heat to 80-85°C, and stir at a constant speed of 55-65 rpm for 4-4.5 hours. Then filter and dry to obtain modified alumina. The silane coupling agent is γ-aminopropyltriethoxysilane.

2. The solid-state battery separator coating slurry according to claim 1, characterized in that: The dispersant is polyethylene glycol dioleate.

3. The solid-state battery separator coating slurry according to claim 1, characterized in that: The interfacial compatibilizer is maleic anhydride grafted polyethylene.

4. A method for preparing a solid-state battery separator coating slurry according to any one of claims 1 to 3, characterized in that: The steps include: S1. dissolving carboxymethyl cellulose in water to obtain a colloidal solution; S2, mixing the modified alumina and the nanofiller to obtain mixed particles; S3. Put the colloidal solution obtained in S1 and the mixed particles obtained in S2 into a blender, and then add a dispersant, an inorganic sol and an interfacial compatibilizer, stir and mix them evenly to obtain a diaphragm coating slurry for a solid-state battery.

5. The method for preparing a solid-state battery separator coating slurry according to claim 4, wherein: In S3, the stirring speed is 1500-1700 r / min, and the stirring time is 50-60 min.

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