Double-silane coupling agent modified ethyl cellulose, composite binder, and preparation method and application of double-silane coupling agent modified ethyl cellulose and composite binder

Abstract

The invention discloses a preparation method and application of a disilane coupling agent modified composite binder, and particularly discloses a preparation method of disilane coupling agent modified ethyecellulose.The preparation method comprises the steps that a disilane coupling agent is hydrolyzed, specifically, a methacryloyloxy silane coupling agent and an amino silane coupling agent are mixed and then added into a solvent, and the mixture is stirred to be uniform; adjusting the pH value and carrying out hydrolysis reaction to obtain a hydrolyzed silane solution; grafting modification reaction: slowly dropwise adding the hydrolyzed silane solution into the ethyl cellulose solution, and carrying out grafting modification reaction to obtain a silane modified ethyl cellulose solution; and performing rotary evaporation, washing and drying to obtain the product. The invention also discloses the disilane coupling agent modified ethyl cellulose prepared by the preparation method, a disilane coupling modified composite binder, a preparation method of the disilane coupling modified composite binder, and application of the disilane coupling modified composite binder in wet film formation of sulfide electrolyte. The electrolyte membrane prepared by the method is controllable in thickness and high in ionic conductivity, and the electrolyte membrane has relatively high film-forming property and flexibility.

Description

Technical Field

[0001] The present invention relates to the technical field of all-solid-state batteries, and more specifically, to a double-silane coupling agent modified composite binder and its application in the wet film formation of sulfide electrolytes. Background Art

[0002] Sulfide solid electrolytes are considered ideal electrolyte materials for all-solid-state batteries due to their high ionic conductivity and good mechanical processability. However, their film formation process still faces many challenges: during the wet film formation process, sulfides are extremely sensitive to polar solvents (such as NMP, water), and are prone to decomposition reactions (such as generating H2S), resulting in the deterioration of electrolyte performance; at the same time, traditional binders (such as PVDF) rely on high-boiling solvents (such as NMP), which are not only difficult to completely remove, but also react with sulfides to produce side reactions, increasing the interfacial impedance. In addition, the electrolyte film after wet film formation often has structural defects (such as cracks), resulting in insufficient mechanical strength and poor interfacial contact, seriously affecting the cycle stability and rate performance of the all-battery.

[0003] Currently, for the wet film formation of sulfide electrolytes, the selection of solvents and binders is particularly crucial: ordinary organic solvents (such as toluene) can reduce the decomposition of sulfides, but have poor solubility in most binders and insufficient film formation uniformity; while single binders (such as PTFE or styrene-butadiene rubber) are difficult to simultaneously meet the requirements of high bonding strength and ion conduction. In addition, the electrolyte film after film formation is prone to shrinkage and cracking during the drying process, and has a high solid-solid interfacial impedance with the electrode material, restricting large-area preparation and industrial application. Therefore, developing a highly compatible solvent system and a multifunctional composite binder to achieve high-quality wet film formation of sulfide electrolytes has become a key technical problem in promoting the development of all-solid-state batteries. Summary of the Invention

[0004] To solve the above technical problems, the purpose of the present invention is to provide a double-silane coupling agent modified composite binder and a method for wet film formation of sulfide electrolytes based on the double-silane coupling agent modified composite binder. By synergistically modifying ethyl cellulose with two different silane coupling agents KH-570 (methacryloyloxy) and KH-550 (amino), and combining styrene-butadiene rubber to construct a three-dimensional network structure bonding system, a uniform film of sulfide electrolyte is achieved using a toluene / dibromomethane mixed solvent. The modified ethyl cellulose forms a chemical bond with the sulfide electrolyte through the silane coupling agent, reducing the interfacial impedance. Combining with the elastic properties of styrene-butadiene rubber, the sulfide electrolyte film has both excellent film formation performance and ion conduction performance.

[0005] The purpose of the present invention is achieved through the following technical solutions: In the first aspect, the present invention provides a preparation method for double-silane coupling agent modified ethyl cellulose, including the following steps: S1. Hydrolyze the bis-silane coupling agent: Mix the methacryloxy-type silane coupling agent and the amino-type silane coupling agent, then add them to a solvent, adjust the pH to carry out a hydrolysis reaction to obtain a hydrolyzed silane solution; S2. Graft modification reaction: Slowly drop the hydrolyzed silane solution prepared in step S1 into the ethyl cellulose solution to carry out a graft modification reaction to obtain a silane-modified ethyl cellulose solution; S3. Carry out rotary evaporation on the silane-modified ethyl cellulose solution, wash to remove the unreacted silane coupling agent, and dry it under vacuum to obtain the product.

[0006] As some specific embodiments of the present invention, step S1 includes at least one of the following technical features: 1. The methacryloxy-type silane coupling agent includes the silane coupling agent KH-570, namely 3-(methacryloxy)propyltrimethoxysilane; the amino-type silane coupling agent includes the silane coupling agent KH-550, namely γ-aminopropyltriethoxysilane; 2. The mass ratio of the methacryloxy-type silane coupling agent to the amino-type silane coupling agent is 1:1 - 1:3; in the hydrolyzed silane solution, the total mass fraction of the methacryloxy-type silane coupling agent and the amino-type silane coupling agent is 10 - 20%; specifically, the mass ratio of KH-570 to KH-550 is 1:1 - 1:3; in the hydrolyzed silane solution, the total mass fraction of the silane coupling agents KH-570 and KH550 is 10 - 20%; 3. The solvent is a mixed solvent of ethanol and water, and the volume ratio of ethanol to water is 9:1 - 8:2; 4. Adjust the pH to 4 - 5; the temperature for carrying out the hydrolysis reaction is 20 - 30 °C, preferably at room temperature, and the time is 30 - 60 min.

[0007] As some specific embodiments of the present invention, in step S2, the ethyl cellulose solution is obtained by adding ethyl cellulose to anhydrous ethanol and stirring to dissolve it. The temperature of the stirring and dissolving is 50 - 70 °C, the time is 5 - 10 h, stirring is carried out by a magnetic stirrer, and the stirring speed is 600 - 800 rpm to obtain a uniform ethyl cellulose solution, and the mass fraction of the ethyl cellulose solution is 5 - 10%.

[0008] As some specific embodiments of the present invention, in step S2, the mass ratio of the hydrolyzed silane solution to the ethyl cellulose solution is 1:3 - 1:5.

[0009] As some specific embodiments of the present invention, in step S2, the temperature of the graft modification reaction is 60 - 70 °C, and the reaction time is 5 - 8 h.

[0010] As some specific embodiments of the present invention, in step S3, the temperature of the rotary evaporation (rotary evaporation and concentration) is 40 - 80 °C, preferably 50 °C, and the time is 1 - 3 h; and / or, the detergent used for washing is anhydrous ethanol, and the number of washing times is 3 - 5 times; and / or, the temperature of the vacuum drying is 40 - 80 °C, the time is 10 - 15 h, and the vacuum degree is 0.03 - 0.08 MPa.

[0011] In a second aspect, the present invention provides an ethyl cellulose modified with a disilane coupling agent, which is obtained by using the preparation method described in any one of the above.

[0012] In a third aspect, the present invention provides a preparation method of a disilane coupling agent modified composite binder, including: adding the above-mentioned ethyl cellulose modified with a disilane coupling agent and styrene-butadiene rubber into a mixed solvent of toluene and dibromomethane, and stirring until completely dissolved to obtain it. Preferably at room temperature.

[0013] As some specific embodiments of the present invention, the mass ratio of the ethyl cellulose modified with a disilane coupling agent to styrene-butadiene rubber is 1:5 - 1:10; and / or, in the mixed solvent, the mass ratio of toluene to dibromomethane is 9:1 - 8:2.

[0014] As some specific embodiments of the present invention, the temperature of the stirring is 20 - 30 °C, preferably 23 - 28 °C, more preferably 25 °C, the time is 2 - 6 h, preferably 4 h, and the rotation speed is 300 - 700 rpm, preferably 500 rpm.

[0015] In a fourth aspect, the present invention provides a disilane coupling agent modified composite binder, which is obtained by using the preparation method described in any one of the above.

[0016] As some specific embodiments of the present invention, the solid content in the disilane coupling agent modified composite binder is 4 - 6%.

[0017] In a fifth aspect, the present invention provides an application of the above-mentioned disilane coupling agent modified composite binder in the wet film formation of sulfide electrolytes.

[0018] As some specific embodiments of the present invention, the wet film formation of sulfide electrolytes includes the following steps: A1. Preparation of sulfide electrolyte slurry: Forming a uniform sulfide electrolyte slurry by ball milling a sulfide solid electrolyte and a disilane coupling agent modified composite binder; A2. Sulfide electrolyte film formation: Forming a film of the sulfide electrolyte on a copper foil by wet coating, and drying to obtain a sulfide electrolyte film.

[0019] In some specific embodiments of the present invention, in step A1, the sulfide solid electrolyte includes at least one of Li3PS4 and thiogermanate electrolytes, and the thiogermanate electrolyte includes at least one of Li6PS5Cl, Li6PS5Br, and Li6PS5I; The mass ratio of the sulfide solid electrolyte to the bis-silane coupling agent modified composite binder is 9-99:1.

[0020] In some specific embodiments of the present invention, in step A1, the ball milling time is 1-2 h, the rotation speed is 200-300 rpm, and the ball milling is carried out in a sealed argon atmosphere; The ball milling is wet ball milling, the solvent includes toluene, and the mass ratio of toluene to the sulfide electrolyte is 0.5-1.5:1.

[0021] In some specific embodiments of the present invention, in step A1, in the prepared sulfide electrolyte slurry, the mass fraction of the bis-silane coupling agent modified composite binder is 1-5%.

[0022] In some specific embodiments of the present invention, in step A2, the thickness of the sulfide electrolyte membrane is 30-80 μm.

[0023] In some specific embodiments of the present invention, in step A2, the drying is carried out by vacuum drying, the temperature of the vacuum drying is 40-80 °C, the time is 10-15 h, and the vacuum degree is 0.03-0.08 MPa.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) In the present invention, the acyloxy group of the silane coupling agent KH-570 condenses with the hydroxyl group of ethyl cellulose to form a cross-linked network, and the amino group of the silane coupling agent KH-550 coordinates with the lithium ions on the surface of the sulfide, and the dual effects significantly improve the interfacial bonding force and reduce the interfacial impedance. (2) At the same time, the viscosity of styrene-butadiene rubber and the rigidity of ethyl cellulose cooperate to make the electrolyte membrane have both high film-forming property and flexibility, and the mixed solvent system effectively avoids the decomposition of the sulfide electrolyte.

[0025] (3) The electrolyte membrane prepared by the present invention has a controllable thickness and a high retention rate of ionic conductivity, solves the key problems of many interfacial side reactions and poor structural integrity in traditional wet film formation, and is suitable for large-scale production of high-performance sulfide all-solid-state batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, objects, and advantages of the present invention will become more apparent: Figure 1 Schematic flow chart for preparing the double-silane coupling agent modified composite binder in Example 1 and using it for wet film formation of sulfide electrolyte; Figure 2 Scanning electron microscope image (SEM image) of the sulfide electrolyte membrane prepared in Example 1. Detailed implementation manners

[0027] The present invention will be described in detail below with reference to specific examples. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made. These all belong to the protection scope of the present invention.

[0028] For the convenience of understanding, first, the abbreviations or nouns mentioned in the text are explained: Silane coupling agent KH-570: γ-methacryloxypropyltrimethoxysilane; Silane coupling agent KH-560: γ-(2,3-epoxypropoxy)propyltrimethoxysilane; Silane coupling agent KH-550: γ-aminopropyltriethoxysilane.

[0029] Example 1 This example provides a preparation method of a double-silane coupling agent modified composite binder and its use for wet film formation of sulfide electrolyte. The specific process is as Figure 1 shown.

[0030] 1. Preparation of the double-silane coupling agent modified composite binder: (1) Pretreatment of ethyl cellulose: Weigh 5 g of ethyl cellulose and add it to 95 g of absolute ethanol. Under the condition of a 60 °C water bath, stir at a magnetic stirring speed of 700 rpm for 6 h to obtain a uniform ethyl cellulose solution with a mass fraction of 5%.

[0031] (2) Hydrolysis of the silane coupling agent: Take 1.5 g of KH-570 silane coupling agent and 1.5 g of KH-550 silane coupling agent (mass ratio 1:1), mix them, add them to a mixed solvent composed of 27 mL of absolute ethanol and 3 mL of deionized water (volume ratio 9:1), adjust the pH to 4.5 with dilute hydrochloric acid, and magnetically stir and hydrolyze at room temperature of 25 °C for 45 min to obtain a hydrolyzed silane solution.

[0032] (3) Grafting modification reaction: Slowly drop the hydrolyzed silane solution (total mass 30 g) prepared in step (2) into the 100 g of ethyl cellulose solution prepared in step (1), control the dropping speed to be 1 mL / min, and react in an oil bath at 65 °C for 6 h to obtain a silane-modified ethyl cellulose solution.

[0033] (4) Post-treatment purification: The ethyl cellulose solution was concentrated by rotary evaporation at 50 °C and then washed 4 times with absolute ethanol. The washed product was placed in a vacuum drying oven and dried at 60 °C and 0.05 MPa for 12 h to finally obtain a solid sample of ethyl cellulose modified with a disilane coupling agent.

[0034] (5) Preparation of the composite binder: 1.0 g of the solid sample of ethyl cellulose modified with a disilane coupling agent and 5.0 g of styrene-butadiene rubber (mass ratio 1:5) were taken and added to a mixed solvent composed of 90 g of toluene and 10 g of dibromomethane (mass ratio 9:1). Magnetic stirring was carried out at 500 rpm at room temperature of 25 °C for 4 h to obtain a uniform modified composite binder solution with a solid content of 5.66%.

[0035] 2. Use the disilane coupling modified composite binder for wet film formation of sulfide electrolyte: (1) Preparation of the sulfide electrolyte slurry: The operation was carried out in a glove box filled with argon. 10 g of the sulfide electrolyte was taken and added to a ball milling tank, and then 5.3 g of the composite binder solution and 6 g of toluene solvent were added to uniformly disperse the electrolyte. After sealing, it was ball milled at room temperature for 2 h at a ball milling speed of 300 rpm to obtain a uniform electrolyte slurry. The mass fraction of the composite binder in the sulfide electrolyte was 3%.

[0036] (2) Wet film formation of the sulfide electrolyte: The operation was carried out in a glove box filled with argon. The electrolyte slurry was coated on a copper foil substrate with a thickness controlled at 60 μm and then directly dried by air blowing for 2 h. Then, drying treatment was carried out using a vacuum oven at a temperature of 50 °C, a vacuum degree of 0.05 MPa, and a constant temperature drying time of 12 h.

[0037] As Figure 2 shown, it is the scanning electron microscope image of the sulfide electrolyte membrane prepared in Example 1. It can be seen from Figure 2 that the surface of the sulfide electrolyte membrane is very flat and uniform, without unevenness or cracks, which is due to the enhanced film-forming property of the sulfide electrolyte by the modified composite binder.

[0038] Example 2 1. This example provides a preparation method of a composite binder modified with a disilane coupling agent, and the steps are as follows: (1) Pretreatment of ethyl cellulose: 8 g of ethyl cellulose was weighed and added to 92 g of absolute ethanol. Under the condition of a 65 °C water bath, magnetic stirring was carried out at a speed of 750 rpm for 8 h to obtain a uniform ethyl cellulose solution with a mass fraction of 8%.

[0039] (2)Hydrolysis of silane coupling agent: Take 1.2 g of KH-570 silane coupling agent and 2.4 g of KH-550 silane coupling agent (mass ratio 1:2), mix them, and add them to a mixed solvent composed of 24 mL of absolute ethanol and 6 mL of deionized water (volume ratio 8:2). Adjust the pH to 4.5 with dilute hydrochloric acid, and magnetically stir for hydrolysis at 25 °C room temperature for 50 min.

[0040] (3)Grafting modification reaction: Slowly add 30 g of the hydrolyzed silane solution prepared in step (2) dropwise to 100 g of the ethyl cellulose solution prepared in step (1), and control the dropping rate to 0.8 mL / min. React in an oil bath at 68 °C for 7 h to obtain an ethyl cellulose solution modified with a bis-silane coupling agent.

[0041] (4)Post-treatment purification: Rotate and evaporate the reaction solution for concentration at 55 °C, and then wash it 5 times with absolute ethanol. Place the washed product in a vacuum drying oven and dry it at 70 °C and 0.06 MPa for 14 h to finally obtain a solid sample of ethyl cellulose modified with a bis-silane coupling agent.

[0042] (5)Preparation of composite binder: Take 1.0 g of the ethyl cellulose sample modified with a bis-silane coupling agent and 5.0 g of styrene-butadiene rubber (mass ratio 1:5), and add a mixed solvent composed of 90 g of toluene and 10 g of dibromomethane (mass ratio 9:1). Magnetically stir at 500 rpm at 25 °C room temperature for 4 h to obtain a uniform composite binder solution with a solid content of 5.66%.

[0043] 2. Apply the bis-silane coupling modified composite binder to the wet film formation of sulfide electrolyte: (1)Preparation of sulfide electrolyte slurry: Operate in a glove box filled with argon. Take 10 g of sulfide electrolyte, add it to a ball milling tank, then add 5.3 g of the composite binder solution and 6 g of toluene solvent to uniformly disperse the electrolyte. After sealing, perform ball milling treatment at room temperature for 2 h with a ball milling speed of 300 rpm to obtain a uniform electrolyte slurry. The mass fraction of the composite binder in the sulfide electrolyte is 3%.

[0044] (2)Wet film formation of sulfide electrolyte: Operate in a glove box filled with argon. Coating the electrolyte slurry on a copper foil substrate with a thickness controlled at 60 μm, and then directly air-dry it for 2 h. Then use a vacuum oven for drying treatment at a temperature of 50 °C, a vacuum degree of 0.05 MPa, and a constant temperature drying time of 12 h.

[0045] Comparative Example 1 Cancel the steps of modifying ethyl cellulose with KH-570 and KH-550 silane coupling agents in Example 1, and directly prepare a composite binder solution with unmodified ethyl cellulose and styrene-butadiene rubber in a mixed solvent of toluene / dibromomethane. Then use the prepared composite binder solution for the wet film formation of sulfide electrolyte.

[0046] That is, compared with Example 1, when preparing the composite binder, steps (1) to (4) are not carried out. In step (5), take 1.0 g of solid sample of ethyl cellulose unmodified by bis-silane coupling agent and 5.0 g of styrene-butadiene rubber to prepare the composite binder, and the subsequent steps are carried out according to Example 1.

[0047] Comparative Example 2 In Example 1, only KH-570 silane coupling agent is used to modify ethyl cellulose, and then a composite binder solution is prepared with styrene-butadiene rubber in a mixed solvent of toluene / dibromomethane. Then use the prepared composite binder solution for the wet film formation of sulfide electrolyte.

[0048] That is, compared with Example 1, when preparing the composite binder, in step (2), only 1.5 g of KH-570 silane coupling agent is taken for hydrolysis, and KH-550 silane coupling agent is not taken, and the remaining steps are carried out according to Example 1.

[0049] Comparative Example 3 In Example 1, only KH-550 silane coupling agent is used to modify ethyl cellulose, and then a composite binder solution is prepared with styrene-butadiene rubber in a mixed solvent of toluene / dibromomethane. Then use the prepared composite binder solution for the wet film formation of sulfide electrolyte.

[0050] That is, compared with Example 1, when preparing the composite binder, in step (2), only 1.5 g of KH-550 silane coupling agent is taken for hydrolysis, and KH-570 silane coupling agent is not taken, and the remaining steps are carried out according to Example 1.

[0051] Comparative Example 4 Only use styrene-butadiene rubber as a single binder to prepare a binder solution in a mixed solvent of toluene / dibromomethane. Then use the prepared binder solution for the wet film formation of sulfide electrolyte.

[0052] That is, compared with Example 1, when preparing the composite binder, steps (1) to (4) are cancelled, and in step (5), only 5.0 g of styrene-butadiene rubber is taken and added to a mixed solvent composed of 90 g of toluene and 10 g of dibromomethane to prepare the binder solution, and the remaining steps are carried out according to Example 1.

[0053] Comparative Example 5 After the modification of ethyl cellulose with KH-570 and KH-550 silane coupling agents, it is directly used as a binder without adding styrene-butadiene rubber. A binder solution is prepared in a mixed solvent of toluene / dibromomethane, and a wet film-forming of sulfide electrolyte is carried out.

[0054] That is, compared with Example 1, when preparing the composite binder, in step (5), only 1.0 g of the solid sample of ethyl cellulose modified with bis-silane coupling agent is taken and added to a mixed solvent composed of 90 g of toluene and 10 g of dibromomethane to prepare the binder solution, without using styrene-butadiene rubber, and the remaining steps are carried out according to Example 1.

[0055] Comparative Example 6 Ethyl cellulose is modified with KH-570 and KH-550 silane coupling agents, and then compounded with styrene-butadiene rubber in a single solvent of toluene to prepare a binder solution. And a wet film-forming of sulfide electrolyte is carried out.

[0056] That is, compared with Example 1, when preparing the composite binder, in step (5), the mixed solvent composed of 90 g of toluene and 10 g of dibromomethane is replaced with 100 g of toluene solvent, and the remaining steps are carried out according to Example 1.

[0057] Comparative Example 7 Ethyl cellulose is modified with KH-570 and KH-550 silane coupling agents, and then compounded with styrene-butadiene rubber in a single solvent of dibromomethane to prepare a binder solution. And a wet film-forming of sulfide electrolyte is carried out.

[0058] That is, compared with Example 1, when preparing the composite binder, in step (5), the mixed solvent composed of 90 g of toluene and 10 g of dibromomethane is replaced with 100 g of dibromomethane solvent, and the remaining steps are carried out according to Example 1.

[0059] Comparative Example 8 Ethyl cellulose is modified with an epoxy-based silane coupling agent KH-560 (γ-(2,3-epoxypropoxy)propyltrimethoxysilane), and then compounded with styrene-butadiene rubber in a mixed solvent of toluene / dibromomethane to prepare a composite binder solution. And the prepared composite binder solution is used for the wet film-forming of sulfide electrolyte.

[0060] That is, compared with Example 1, when preparing the composite binder, in step (2), only 1.5 g of KH-560 epoxy-based silane coupling agent is taken for hydrolysis, and the remaining steps are carried out according to Example 1.

[0061] Comparative Example 9 Ethyl cellulose was modified with KH-550 and KH-560 silane coupling agents, and then a composite binder solution was prepared with styrene-butadiene rubber in a mixed solvent of toluene / dibromomethane. And the prepared composite binder solution was used for wet film formation of sulfide electrolyte.

[0062] That is, compared with Example 1, when preparing the composite binder, 1.5 g of KH-550 and 1.5 g of KH-560 silane coupling agents were used for hydrolysis in step (2), and the remaining steps were carried out according to Example 1.

[0063] Comparative Example 10 Ethyl cellulose was modified with KH-560 and KH-570 silane coupling agents, and then a composite binder solution was prepared with styrene-butadiene rubber in a mixed solvent of toluene / dibromomethane. And the prepared composite binder solution was used for wet film formation of sulfide electrolyte.

[0064] That is, compared with Example 1, when preparing the composite binder, 1.5 g of KH-560 and 1.5 g of KH-570 silane coupling agents were used for hydrolysis in step (2), and the remaining steps were carried out according to Example 1.

[0065] Effect Example The performance of the examples and comparative examples was tested as follows: The electrolyte membranes prepared in each example and comparative example were cut into small round pieces, loaded into a pressure battery mold, and stamped at a pressure of 1 ton for 1 min. An electrochemical workstation with the model CHI660E was used to conduct an AC impedance test at room temperature, and the test results are shown in Table 1.

[0066] Table 1 Electrochemical performance data of sulfide electrolyte membranes

[0067] It can be seen from Table 1 that the impedance of the sulfide electrolyte membranes in the examples is less than that in each comparative example, the ionic conductivity is higher than that in each comparative example, and the film-forming property and the surface uniformity and flatness of the film are better than those in each comparative example. This is mainly because after modifying ethyl cellulose with silane coupling agents KH-570 and KH-550, the acyloxy group of silane coupling agent KH-570 condenses with the hydroxyl group of ethyl cellulose to form a cross-linked network, and the amino group of silane coupling agent KH-550 coordinates with the lithium ions on the surface of the sulfide. The dual effects significantly improve the interfacial binding force and reduce the interfacial impedance; at the same time, the elasticity of styrene-butadiene rubber and the rigidity of ethyl cellulose cooperate to make the electrolyte membrane have both high film-forming property and flexibility, and the mixed solvent system effectively avoids the decomposition of the sulfide electrolyte, which can significantly improve the ionic conductivity of the electrolyte membrane.

[0068] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various modifications or alterations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A preparation method of a bis-silane coupling agent modified ethyl cellulose, characterized in that, It includes the following steps: S1. Hydrolyze the bis-silane coupling agent: Mix the methacryloxy-type silane coupling agent and the amino-type silane coupling agent, add them to a solvent, adjust the pH and carry out a hydrolysis reaction to obtain a hydrolyzed silane solution; S2. Graft modification reaction: Slowly drop the hydrolyzed silane solution prepared in step S1 into the ethyl cellulose solution to carry out a graft modification reaction to obtain a silane-modified ethyl cellulose solution; S3. Carry out rotary evaporation on the silane-modified ethyl cellulose solution, wash to remove the unreacted silane coupling agent, and carry out vacuum drying to obtain the product.

2. The preparation method according to claim 1, characterized in that, Step S1 includes at least one of the following technical features:

1. The methacryloxy-type silane coupling agent includes silane coupling agent KH-570; the amino-type silane coupling agent includes silane coupling agent KH-550; 2. The mass ratio of the methacryloxy-type silane coupling agent to the amino-type silane coupling agent is 1:1 - 1:3; in the hydrolyzed silane solution, the total mass fraction of the methacryloxy-type silane coupling agent and the amino-type silane coupling agent is 10 - 20%; 3. The solvent is a mixed solvent of ethanol and water, and the volume ratio of ethanol to water is 9:1 - 8:2; 4. Adjust the pH to 4 - 5, the temperature for the hydrolysis reaction is 20 - 30 °C, and the time is 30 - 60 min.

3. The preparation method according to claim 1, characterized in that, Step S2 includes at least one of the following technical features:

1. The ethyl cellulose solution is obtained by adding ethyl cellulose to anhydrous ethanol and stirring to dissolve it. The temperature for the stirring and dissolving is 50 - 70 °C, the time is 5 - 10 h, and the rotation speed is 600 - 800 rpm; the mass fraction of the ethyl cellulose solution is 5 - 10%; 2. The mass ratio of the hydrolyzed silane solution to the ethyl cellulose solution is 1:3 - 1:5; 3. The temperature for the graft modification reaction is 60 - 70 °C, and the reaction time is 5 - 8 h.

4. The preparation method according to claim 1, characterized in that, In step S3, the temperature for the rotary evaporation is 40 - 80 °C, and the time is 1 - 3 h; and / or, the detergent used for washing is anhydrous ethanol, and the number of washing times is 3 - 5 times; and / or, the temperature for the vacuum drying is 40 - 80 °C, the time is 10 - 15 h, and the vacuum degree is 0.03 - 0.08 MPa.

5. An ethyl cellulose modified with a disilane coupling agent, characterized in that, It is prepared by using the preparation method described in any one of claims 1 - 4.

6. A preparation method of a double-silane coupling agent modified composite binder, characterized in that, It includes: Adding the ethyl cellulose modified by the bis-silane coupling agent described in claim 5 and styrene-butadiene rubber to a mixed solvent of toluene and dibromomethane, and stirring until completely dissolved to obtain the product.

7. The preparation method according to claim 6, characterized in that, The mass ratio of the ethyl cellulose modified by the bis-silane coupling agent to styrene-butadiene rubber is 1:5 - 1:10; and / or, in the mixed solvent, the mass ratio of toluene to dibromomethane is 9:1 - 8:2; and / or, the temperature for the stirring is 20 - 30 °C, the time is 2 - 6 h, and the rotation speed is 300 - 700 rpm.

8. A double-silane coupling agent modified composite binder, characterized in that, It is prepared by using the preparation method described in claim 7, and the solid content of the bis-silane coupling agent modified composite binder is 4 - 6%.

9. Use of the double-silane coupling agent modified composite binder as described in claim 8 in the wet film formation of sulfide electrolytes, characterized in that, The wet film formation of the sulfide electrolyte includes the following steps: A1. Preparation of sulfide electrolyte slurry: A sulfide solid electrolyte and a double-silane coupling agent-modified composite binder are ball-milled to form a uniform sulfide electrolyte slurry; A2. Film formation of sulfide electrolyte: The sulfide electrolyte is formed into a film on a copper foil by wet coating and dried to obtain a sulfide electrolyte film.

10. The application according to claim 9, characterized in that, The application includes at least one of the following technical features: I. In step A1, the sulfide solid electrolyte includes at least one of Li3PS4 and thiogermanate-type electrolytes; the mass ratio of the sulfide solid electrolyte to the double-silane coupling agent-modified composite binder is 9-99:1; II. In step A1, the ball-milling time is 1-2 h, the rotation speed is 200-300 rpm, and the ball-milling is carried out in a sealed argon atmosphere; the ball-milling is wet ball-milling, and the solvent includes toluene, and the mass ratio of toluene to the sulfide solid electrolyte is 0.5-1.5:1; III. In step A1, in the prepared sulfide electrolyte slurry, the mass fraction of the double-silane coupling agent-modified composite binder is 1-5%; IV. In step A2, the thickness of the sulfide electrolyte film is 30-80 μm; V. In step A2, the drying is carried out by vacuum drying, the temperature of the vacuum drying is 40-80 °C, the time is 10-15 h, and the vacuum degree is 0.03-0.08 MPa.

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