A disulfide-hydrogen bond synergistically modified PTFE binder, preparation method and application thereof

Abstract

The application discloses a kind of PTFE binder based on disulfide bond-hydrogen bond synergistic modification and preparation method and application, belong to all-solid battery technical field.The method for preparing PTFE binder based on disulfide bond-hydrogen bond synergistic modification first activates PTFE surface by plasma treatment, then grafts cystamine molecule containing disulfide bond and 1,3-dipropyl-6-amino urea uracil in turn, constructs dynamic covalent crosslinking network and multiple hydrogen bond crosslinking network.The PTFE binder obtained by the method is also disclosed, and its application in all-solid battery is disclosed.The modified PTFE binder and the solid electrolyte membrane prepared by compounding with sulfide electrolyte exhibit excellent interface stability and ionic conductivity.Solve the problem of poor interface compatibility and insufficient mechanical adaptability of traditional PTFE binder, provide a high-performance binder solution for all-solid lithium battery.The preparation process is simple, the cost is controllable, and has significant industrial application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of adhesives for all-solid-state batteries, and relates to a disulfide bond-hydrogen bond synergistically modified PTFE adhesive as well as a preparation method and application thereof, in particular to a method for preparing a PTFE adhesive based on dynamic disulfide bond-hydrogen bond synergistic modification, the PTFE adhesive, and application of the PTFE adhesive in dry film formation of all-solid-state sulfide electrolytes. BACKGROUND

[0002] Current all-solid-state lithium batteries have become a research hotspot due to their high safety and energy density, and sulfide solid electrolytes have attracted much attention due to their high ionic conductivity and good mechanical processability. However, the sulfide electrolyte particles have serious problems in the actual application due to poor solid-solid interface contact in the film formation process and interface failure caused by volume change in the cycle process. Traditional polytetrafluoroethylene (PTFE) adhesives are widely used in the field of lithium batteries due to their excellent chemical stability and thermal stability, but their inherent chemical inertness leads to poor interface compatibility with sulfide solid electrolytes, forming a high impedance layer at the electrode-electrolyte interface, which seriously affects the ion transmission efficiency of the battery. In addition, the PTFE adhesive lacks flexibility and dynamic repair ability, and is difficult to adapt to the volume change of sulfide particles during charging and discharging, which easily causes problems such as cracking of the electrolyte film and breaking of the ion transmission channel. More importantly, the hydrophobicity and low surface energy of PTFE make it prone to phase separation and pore defects during film formation, which significantly reduces the mechanical integrity and ionic conductivity of the electrolyte film, seriously restricting the performance improvement and practical application of all-solid-state sulfide batteries. Therefore, it is of great significance to develop a PTFE-based adhesive with room temperature self-repairing ability, high interface bonding strength and good process compatibility, which can promote the practical application of all-solid-state sulfide batteries. SUMMARY

[0003] To solve the above technical problems, the purpose of the present application is to provide a method for preparing a PTFE adhesive based on the synergistic modification of disulfide bonds and hydrogen bonds and its application in the dry film formation of all-solid-state sulfide electrolytes. First, the surface of PTFE is activated by plasma treatment, then cystamine molecules containing disulfide bonds are grafted on the surface of the activated PTFE to construct a dynamic covalent crosslinking network, and further introduce urea-based pyrimidone (UPy) derivatives to form a multiple hydrogen bond crosslinking network, thereby obtaining a PTFE adhesive with a double dynamic crosslinking structure. Then, the PTFE adhesive is used for fiberization dry film formation with sulfide solid electrolytes, effectively solving the problems of poor interface compatibility, insufficient mechanical adaptability and film formation defects of traditional PTFE adhesives in the application of sulfide all-solid-state batteries.

[0004] The purpose of the present application is achieved by the following technical solutions:

[0005] In a first aspect, the present application provides a method for preparing a PTFE (polytetrafluoroethylene) binder based on disulfide bond-hydrogen bond synergistic modification, comprising the following steps:

[0006] S1, performing plasma surface activation treatment on the PTFE;

[0007] S2, immersing the activated PTFE in a cystamine-containing ethanol solution to perform a grafting modification reaction, and then washing and drying to obtain a disulfide bond-modified PTFE intermediate;

[0008] S3, mixing the disulfide bond-modified PTFE intermediate with a urea-based pyrimidone derivative in an organic solvent to perform a reaction, and then washing and drying to obtain the product.

[0009] As some specific embodiments of the present application, step S1 is performed in a plasma treatment device, and the PTFE is subjected to plasma surface activation treatment in an inert atmosphere to generate active free radical sites on the surface of the PTFE.

[0010] The surface energy of PTFE is extremely low, which makes it difficult to graft. Compared with conventional chemical etching methods, the crystallinity of PTFE is damaged. In the present application, plasma surface activation treatment is used on PTFE to form a nanoscale roughness on the surface, which facilitates subsequent grafting reactions.

[0011] As some specific embodiments of the present application, the inert atmosphere includes at least one of argon, nitrogen, helium, and neon.

[0012] And / or, the power of the plasma surface activation treatment is 100-200 W, and the time is 10-30 min.

[0013] As some specific embodiments of the present application, in step S2, the concentration of the cystamine-containing ethanol solution is 3-6 wt%; the grafting modification reaction is performed under magnetic stirring, the rotation speed of the magnetic stirring is 600-1000 rpm, the temperature of the grafting modification reaction is 50-70℃, and the time is 6-12 h. The disulfide bond in the cystamine molecule is grafted onto the PTFE molecular chain through a free radical reaction.

[0014] As some specific embodiments of the present application, in step S2, the washing includes washing with ethanol for 2-6 times.

[0015] The modification of PTFE using cystamine molecules provides a disulfide bond. The cystamine molecule contains two amino groups (-NH2) and one disulfide bond (-S-S-), which can simultaneously realize covalent grafting with the free radicals on the surface of PTFE (through amino group reaction) and retain dynamic disulfide bonds for self-repairing. Compared with other disulfides, the fatty chain structure of cystamine has better compatibility with sulfide electrolytes and does not have side reactions with sulfide electrolytes.

[0016] As some specific embodiments of the present application, in step S3, the urea-based pyrimidine ketone derivative includes at least one of 1,3-dipropyl-6-amino urea pyrimidine, 1,3-diethyl-6-amino urea pyrimidine, 1,3-bis(2-methoxyethyl)-6-amino urea pyrimidine, 1,3-bis(3-trifluoromethyl benzyl)-6-amino urea pyrimidine. By mixing the disulfide-modified PTFE intermediate with the urea-based pyrimidine ketone derivative in an organic solvent, the UPy group is grafted onto the PTFE chain through a carbamate bond to form a multiple hydrogen bond crosslinking network. Since PTFE itself lacks polar groups, it is necessary to introduce urea pyrimidine derivatives to build a stable hydrogen bond network on the inert fluorocarbon chain. Moreover, conventional hydrogen bond networks are unstable on hydrophobic surfaces. The present application introduces a propyl chain as a "flexible spacer" to avoid direct contact between the hydrogen bond network and the hydrophobic surface.

[0017] Preferably, in step S3, the urea-based pyrimidine ketone derivative includes 1,3-dipropyl-6-amino urea pyrimidine, and the mass ratio of the disulfide-modified PTFE intermediate to 1,3-dipropyl-6-amino urea pyrimidine is 4-6:1.

[0018] Since the urea-based pyrimidine ketone has a quadruple hydrogen bond system, the bond energy of its UPy is much higher than that of conventional hydrogen bonds (such as carboxylic acid dimers), which can form a stable network on the inert surface of PTFE; and the propyl chain of 1,3-dipropyl-6-amino urea pyrimidine can also alleviate the conflict between the hydrophobicity of PTFE and the polarity of UPy.

[0019] As some specific embodiments of the present application, in step S3, the organic solvent is selected from any one of DMF, DMSO, acetone, acetonitrile. Preferably, DMF.

[0020] As some specific embodiments of the present application, the mixing reaction is carried out under the protection of an inert atmosphere, and the magnetic stirring reaction is carried out at a temperature of 70-90°C for 10-15 h; the stirring speed of the magnetic stirring is 600-1000 rpm.

[0021] As some specific embodiments of the present application, in step S3, the washing includes sequentially washing with DMF, ethanol and deionized water for 2-6 times, and the unreacted raw materials and by-products are removed by washing.

[0022] As some specific embodiments of the present application, in step S2 and / or step S3, the drying includes vacuum drying, and the vacuum drying is carried out at a temperature of 50-80°C for 10-25 hours under a vacuum degree of 0.05-0.08 MPa.

[0023] Specifically, in step S2, the vacuum drying is carried out for 10-16 h.

[0024] And / or, in step S3, the time of vacuum drying is 18-25h.

[0025] In a second aspect, the present application provides a PTFE binder prepared by the method of any one of the above.

[0026] Because the C-F bond of PTFE is extremely inert, its bond energy is as high as 485 kJ / mol, and the surface energy is extremely low (18.5 mN / m), it is generally believed in the art that it is difficult to achieve controllable chemical modification. However, in the present application, by first treating the surface of PTFE with plasma to generate radical sites on the surface, and then by two-step grafting method (first disulfide bond and then hydrogen bond), i.e. first treating with cystamine and then treating with ureido pyrimidone derivative, a stable hydrogen bond network is constructed on the inert fluorocarbon chain, realizing the synergistic chemical modification and modification of PTFE by disulfide bond / hydrogen bond.

[0027] In a third aspect, the present application provides the use of the PTFE binder as described above in the preparation of a full solid sulfide electrolyte membrane.

[0028] As some specific embodiments of the present application, the use comprises the following steps:

[0029] A1, uniformly mixing the PTFE binder with a sulfide solid electrolyte (in a mixer);

[0030] A2, hot pressing the mixture (using a roller press), and in the process of hot pressing, fiberizing into a membrane to obtain a sulfide electrolyte membrane (with certain toughness and thickness).

[0031] As some specific embodiments of the present application, in step A1, the sulfide solid electrolyte comprises at least one of Li6PS5Cl, Li3PS4, Li6PS5Cl, Li6PS5Br, Li6PS5I;

[0032] And / or, the mass fraction of PTFE binder in the mixing is 1-5%;

[0033] And / or, the rotation speed of the mixing is 4000-6000 rpm, and the mixing time is 5-20 min.

[0034] As some specific embodiments of the present application, in step A2, the temperature of the hot pressing is 40-60℃;

[0035] And / or, the thickness of the sulfide electrolyte membrane is 80-200 μm.

[0036] In the battery (especially solid-state battery) environment, avoiding the decomposition reaction of active substances and sulfide electrolyte contact is one of the key challenges to improve the performance and life of the battery. The traditional view believes that improving the chemical activity of PTFE will inevitably sacrifice its stability and compatibility with sulfide electrolyte. When electrochemically modifying PTFE to improve its chemical activity, the problem of interface compatibility and stability will be correspondingly brought. Based on this, the purpose of the modification of PTFE in the present application is to improve the interface stability of the solid-state battery and balance the dynamic repair and long-term conductivity. By plasma surface activation treatment of PTFE, combined with two-step method of cystamine and urea-based pyrimidone derivative treatment, the present application successfully utilizes disulfide bond and hydrogen bond to synergistically modify PTFE, and obtains PTFE binder with double dynamic crosslinking structure. Then it is applied to all-solid-state battery by fiberizing dry film with sulfide solid-state electrolyte. By controlling the action of disulfide bond and hydrogen bond, the side reaction with Li6PS5Cl is avoided, the interface impedance of Li6PS5Cl is reduced to 4.9 Ω (unmodified interface impedance > 8 Ω, PTFE will react with Li6PS5Cl to generate a layer of Li2S insulation layer, resulting in a decrease in ionic conductivity), and the high ionic conductivity, compatibility with sulfide electrolyte and interface strain buffer effect obtained by the present application far exceed the expectation in the field, bringing synergistic effect innovation to the application scenario of sulfide all-solid-state battery. While improving the chemical activity of PTFE, the interface compatibility with sulfide electrolyte is also improved, overcoming the challenge of electrochemical compatibility in the traditional view.

[0037] Compared with the prior art, the present application has the following beneficial effects:

[0038] (1) The present application synergistically modifies PTFE by plasma activation combined with disulfide bond and UPy hydrogen bond, so that the PTFE binder has excellent dynamic self-repairing performance and interface bonding strength. The cystamine molecules containing disulfide bond and 1,3-dipropyl-6-amino urea pyrimidine are grafted on PTFE to construct dynamic covalent crosslinking network and multiple hydrogen bond crosslinking network, so that the PTFE binder has excellent dynamic self-repairing performance and interface bonding strength. The synergistic effect of disulfide bond network and UPy four hydrogen bond network significantly improves the adaptability of the binder to the volume change of sulfide electrolyte; the solid-state electrolyte membrane prepared by compounding the modified PTFE binder with sulfide electrolyte exhibits lower interface impedance, more excellent interface stability and higher ionic conductivity, and has good mechanical strength. The problems of poor interface compatibility and insufficient mechanical adaptability of traditional PTFE binder are solved, providing a high-performance binder solution for all-solid-state lithium battery.

[0039] (2) The modified PTFE binder and the preparation method thereof have simple process and controllable cost, provide a new material solution for developing high-performance all-solid-state lithium batteries, and have significant industrial application value. BRIEF DESCRIPTION OF DRAWINGS

[0040] Other features, objects, and advantages of the application will become more apparent from the following detailed description of non-limiting embodiments, when read in conjunction with the accompanying drawings:

[0041] Figure 1 A flowchart for the preparation method of the PTFE binder based on disulfide bond-hydrogen bond synergistic modification and the dry film forming process for sulfide electrolyte;

[0042] Figure 2 An electrochemical EIS impedance diagram of a sulfide electrolyte film prepared in Example 1;

[0043] Figure 3 An electrochemical EIS impedance diagram of a sulfide electrolyte film prepared in Comparative Example 1;

[0044] Figure 4 An electrochemical EIS impedance diagram of a sulfide electrolyte film prepared in Comparative Example 3. DETAILED DESCRIPTION

[0045] The application will be described in detail below with specific embodiments. The following examples will help those skilled in the art to further understand the application, but do not limit the application in any form. It should be noted that for those skilled in the art, without departing from the concept of the application, a number of modifications and improvements can be made. These all belong to the protection scope of the application.

[0046] As shown in Figure 1 The application provides a preparation method of a PTFE binder based on disulfide bond-hydrogen bond synergistic modification, and the PTFE binder is used for dry film forming of sulfide electrolyte, specifically including the following steps:

[0047] I. The PTFE raw material is subjected to plasma surface activation treatment under an inert gas atmosphere to generate active free radical sites on the surface of the PTFE;

[0048] II. The activated PTFE is immersed in a cystamine-containing ethanol solution, and a disulfide bond is grafted to the PTFE molecular chain through a free radical reaction, and then washed and dried to obtain a disulfide bond modified PTFE intermediate;

[0049] III. The PTFE intermediate is reacted with a urea-based pyrimidone derivative in a DMF solvent to form a multiple hydrogen bond crosslinking network;

[0050] IV. The above product is sequentially washed with DMF, ethanol and deionized water to remove unreacted raw materials and byproducts, and vacuum dried to obtain a PTFE binder with synergistic modification of disulfide bond-hydrogen bond;

[0051] V. The modified PTFE binder is uniformly mixed with the sulfide solid electrolyte in a certain proportion in a mixer;

[0052] VI. The above mixture is hot-pressed using a roll press to obtain a sulfide electrolyte film with certain toughness and thickness by fiberization during hot pressing.

[0053] Example 1

[0054] The present embodiment provides a preparation method of a PTFE binder based on synergistic modification of disulfide bond-hydrogen bond, and a full-solid sulfide electrolyte film is prepared by dry film forming, and the specific steps are as follows:

[0055] (1) PTFE surface activation treatment: 5 g of PTFE powder is placed in a plasma treatment device and treated at a power of 150 W for 15 minutes in an argon atmosphere to generate active radical sites on the surface of PTFE;

[0056] (2) Disulfide bond grafting modification: 5 g of activated PTFE powder is immersed in a 100 mL ethanol solution containing 5 wt% cystamine, and stirred at 60°C for 8 hours at a magnetic stirring speed of 800 rpm. After the reaction is completed, the product is washed with ethanol for 3 times, and vacuum dried at 60°C for 12 hours at a vacuum degree of 0.07 MPa to obtain a disulfide bond modified PTFE intermediate;

[0057] (3) Hydrogen bond network construction: 3 g of the disulfide bond modified PTFE intermediate prepared in step (2) and 0.6 g of 1,3-dipropyl-6-amino uracil are dissolved in 50 mL of DMF, and the mixture is stirred at a magnetic stirring speed of 800 rpm at 80°C under nitrogen protection for 12 hours;

[0058] (4) Product purification: After the reaction solution is cooled to room temperature, it is sequentially washed with DMF, ethanol and deionized water for 3 times, and vacuum dried at 60°C for 24 hours at a vacuum degree of 0.08 MPa, to obtain a PTFE binder with synergistic modification of disulfide bond-hydrogen bond.

[0059] (5) Dry mixing: In an argon-filled glove box, 9.8 g of Li6PS5Cl sulfide solid electrolyte and 0.2 g of modified PTFE are added to a mixer and mixed at a mixer speed of 5000 rpm for 10 minutes;

[0060] (6) Hot roll dry method film forming: the above mixture is hot-pressed by a roller press, the temperature of the roller press is 50°C, the pressure is 10 MPa, the roller is pressed 6 times, the thickness of the formed film is 100 μm, and the electrolyte film is obtained by cutting into 10 mm diameter round pieces.

[0061] Example 2

[0062] The present embodiment provides a preparation method of a PTFE binder based on disulfide bond-hydrogen bond synergistic modification and its application in dry film forming of sulfide solid electrolyte, the steps are as follows:

[0063] (1) PTFE surface activation treatment: take 8 g of PTFE powder and place it in a plasma treatment device, treat it under an argon atmosphere at a power of 120 W for 20 minutes to generate active radical sites on the surface of the PTFE;

[0064] (2) Disulfide bond grafting modification: immerse 8 g of activated PTFE powder in a 120 mL ethanol solution containing 4 wt% cystamine, stir at 55°C for 10 hours, the magnetic stirring speed is 700 rpm, after the reaction is completed, wash with ethanol for 3 times, vacuum dry at 65°C for 14 hours, the vacuum degree is 0.06 MPa, and a disulfide bond modified PTFE intermediate is obtained;

[0065] (3) Hydrogen bond network construction: take 4 g of the above disulfide bond modified PTFE intermediate and 0.8 g of 1,3-dipropyl-6-amino uracil and dissolve them in 60 mL of DMF, the magnetic stirring speed is 700 rpm, and the reaction is carried out at 75°C under nitrogen protection for 14 hours;

[0066] (4) Product purification: after the reaction liquid is cooled to room temperature, wash it with DMF, ethanol and deionized water for 4 times respectively, vacuum dry at 65°C for 20 hours, the vacuum degree is 0.06 MPa, and finally a PTFE binder with disulfide bond-hydrogen bond synergistic modification is obtained;

[0067] (5) Dry mixing: operate in an argon-filled glove box, mix 9.8 g of Li6PS5Cl sulfide solid electrolyte and 0.2 g of modified PTFE in a mixer, the mixer speed is 5500 rpm, and the mixing time is 15 min;

[0068] (6) Hot roll dry method film forming: the above mixture is hot-pressed by a roller press, the temperature of the roller press is 50°C, the pressure is 10 MPa, the roller is pressed 6 times, the thickness of the formed film is 100 μm, and the electrolyte film is obtained by cutting into 10 mm diameter round pieces.

[0069] Comparative Example 1

[0070] Directly use the PTFE sample without any modification, follow the steps (5) and (6) in Example 1, and form a film with the sulfide electrolyte for testing.

[0071] Comparative Example 2

[0072] Cancel step (3) in Example 1, only use cystamine to modify PTFE by disulfide bond grafting, then form a film with the sulfide electrolyte, and the rest of the steps and parameters remain unchanged, all according to Example 1.

[0073] Comparative Example 3

[0074] Cancel step (2) in Example 1, only use 1,3-dipropyl-6-amino uracil to modify PTFE by hydrogen bond network construction, then form a film with the sulfide electrolyte, and the rest of the steps and parameters remain unchanged, all according to Example 1.

[0075] Comparative Example 4

[0076] Replace cystamine in step (2) of Example 1 with dithiodipropionic acid to modify PTFE by disulfide bond grafting, then form a film with the sulfide electrolyte, and the rest of the steps and parameters remain unchanged, all according to Example 1.

[0077] Comparative Example 5

[0078] Replace 1,3-dipropyl-6-amino uracil in step (3) of Example 1 with polyacrylic acid to modify PTFE by hydrogen bond network construction, form hydrogen bonds through carboxyl groups, then form a film with the sulfide electrolyte, and the rest of the steps and parameters remain unchanged, all according to Example 1. Compare the difference in hydrogen bond network stability between the small molecule crosslinking agent 1,3-dipropyl-6-amino uracil and the polymer crosslinking agent.

[0079] Comparative Example 6

[0080] Replace 1,3-dipropyl-6-amino uracil in step (3) of Example 1 with urea to modify PTFE by hydrogen bond network construction, then form a film with the sulfide electrolyte, and the rest of the steps and parameters remain unchanged, all according to Example 1.

[0081] Effect Example

[0082] 1. Electrochemical performance test of the electrolyte membranes prepared in each example and comparative example, method as follows:

[0083] Cut the electrolyte membranes prepared in each example and comparative example into small round pieces, load into a pressure battery mold, and punch under 1 ton of pressure for 1 min. Use an electrochemical workstation with specifications CHI660E to perform AC impedance test at room temperature. The test results are shown in Table 1.

[0084] Table 1 Electrochemical performance test results

[0085]

[0086] like Figures 2-4 The figures shown are the electrochemical EIS impedance spectra of the sulfide electrolyte membranes prepared in Example 1, Comparative Example 1, and Comparative Example 3, respectively. Figures 2-4 In the diagram, the horizontal axis represents the real impedance (Z'), which is the purely resistive component; the vertical axis represents the imaginary impedance (-Z''), which increases upwards to represent the capacitive component and downwards to represent the inductive component.

[0087] from Figures 2-4 From the results, the impedance of the electrolyte membrane in Example 1 was 4.91Ω, the impedance of the electrolyte membrane in Comparative Example 1 was 8.16Ω, and the impedance of the electrolyte membrane in Comparative Example 3 was 6.78Ω. The calculated ionic conductivity was 2.47 mS / cm, 1.46 mS / cm, and 1.76 mS / cm, respectively. It can be seen that the impedance values ​​of Comparative Example 1 and 3 samples are significantly higher than those of Example 1 sample, and the ionic conductivity of Comparative Example 1 and 3 samples is lower than that of Example 1 sample. This indicates that the unmodified PTFE has poor interfacial compatibility with the sulfide electrolyte after fiberization, resulting in increased impedance after film formation, hindered ion transport, and decreased ionic conductivity.

[0088] As shown in Table 1, the electrolyte membranes prepared in Examples 1 and 2 have significantly lower impedances than those in the comparative examples, while their ionic conductivity is higher. Lower impedance indicates better compatibility between the functional groups in the modified PTFE structure and the sulfide electrolyte, fewer side reactions, and greater facilitator for PTFE fiberization. In Comparative Example 4, a combination of dithiodipropionic acid (disulfide bond source) and 1,3-dipropyl-6-aminouracil (hydrogen bond source) was used to modify PTFE through hydrogen bond network construction. Due to the reaction of dithiodipropionic acid with the sulfide electrolyte, its ionic conductivity is low, and its electrochemical impedance is significantly higher than that of the other examples.

[0089] 2. The tensile properties of the electrolyte membranes prepared in the examples and comparative examples were tested, and the methods are as follows:

[0090] The operation was carried out in an argon-filled glove box. Tensile tests were performed on the electrolyte membranes of each embodiment and the comparative example at a stretching rate of 5 mm / min and a test temperature of room temperature. The test results are shown in Table 2.

[0091] Table 2 Tensile property test results

[0092]

[0093] As can be seen from Table 2, the film-forming properties of the electrolyte films prepared in Examples 1 and 2 are better than those of the comparative examples, and the surfaces of the films are smooth without cracks or wrinkles; at the same time, the tensile strength of the films is higher than that of the other samples of the comparative examples, indicating that they have more excellent mechanical properties. This is mainly because the PTFE binder is modified by plasma activation combined with disulfide bonds and UPy hydrogen bonds, so that the binder has excellent dynamic self-healing properties and interfacial bonding strength. The synergistic effect of the disulfide bond network and the UPy quadruple hydrogen bond network significantly improves the adaptability of the binder to the volume change of the sulfide electrolyte. The solid-state electrolyte film prepared by compounding the modified PTFE binder with the sulfide electrolyte exhibits lower interfacial impedance and higher ionic conductivity, and at the same time has good mechanical strength.

[0094] Compared with the examples, the cystamine (disulfide bond source) and polyacrylic acid (hydrogen bond source) are combined in Comparative Example 5 to modify the PTFE by constructing a hydrogen bond network. According to Table 2 above, the hydrogen bond network has insufficient strength, and the tensile strength after film formation is weak. Similarly, cystamine (disulfide bond source) and urea (hydrogen bond source) are combined in Comparative Example 6, and the hydrogen bond network strength is also significantly inferior to that of the examples, and the tensile strength after film formation is weak.

[0095] The modified PTFE binder and the preparation method thereof provided by the application have simple process and controllable cost, and provide a new material solution for developing high-performance all-solid-state lithium batteries.

[0096] The specific embodiments of the application are described above. It should be understood that the application is not limited to the above specific embodiments, and those skilled in the art can make various modifications or changes within the scope of the claims, which does not affect the essential content of the application.

Claims

1. A method for preparing a PTFE binder based on disulfide-hydrogen bond synergistic modification, characterized in that, The method comprises the following steps: S1, performing plasma surface activation treatment on PTFE; S2, immersing the activated PTFE in a cystamine-containing ethanol solution to perform graft modification reaction, and then washing and drying to obtain a disulfide bond modified PTFE intermediate; S3, mixing the disulfide bond modified PTFE intermediate with a urea-based pyrimidone derivative in an organic solvent to perform a reaction, and then washing and drying to obtain the product.

2. The method of claim 1, wherein, In step S1, the PTFE is subjected to plasma surface activation treatment under an inert atmosphere. The inert atmosphere comprises at least one of argon, nitrogen, helium and neon. The power of the plasma surface activation treatment is 100-200 W, and the time is 10-30 min.

3. The method of claim 1, wherein, In step S2, the concentration of the cystamine-containing ethanol solution is 3-6 wt%; the graft modification reaction is performed under magnetic stirring, the rotation speed of the magnetic stirring is 600-1000 rpm, the temperature of the graft modification reaction is 50-70℃, and the time is 6-12 h.

4. The method of claim 1, wherein, In step S3, the urea-based pyrimidone derivative comprises at least one of 1,3-dipropyl-6-amino urea pyrimidine, 1,3-diethyl-6-amino urea pyrimidine, 1,3-bis(2-methoxyethyl)-6-amino urea pyrimidine and 1,3-bis(3-trifluoromethyl benzyl)-6-amino urea pyrimidine.

5. The method of claim 1, wherein, In step S3, the organic solvent is selected from any one of DMF, DMSO, acetone and acetonitrile. The mixing reaction is performed under magnetic stirring under the protection of an inert atmosphere, the temperature of the reaction is 70-90℃, the time is 10-15 h, and the rotation speed of the magnetic stirring is 600-1000 rpm.

6. The method of claim 1, wherein, In step S2 and / or step S3, the drying comprises vacuum drying, the temperature of the vacuum drying is 50-80℃, the time is 10-25 h, and the vacuum degree is 0.05-0.08 MPa.

7. A PTFE binder characterized by, The product is prepared by the method according to any one of claims 1-6.

8. Use of the PTFE binder according to claim 7 for the production of an all-solid-state sulfide electrolyte membrane, characterized by, The application comprises the following steps: A1, uniformly mixing the PTFE binder and the sulfide solid electrolyte; A2, performing hot pressing on the mixture, and fiberizing into a film during the hot pressing to obtain a sulfide electrolyte film.

9. Use according to claim 8, characterized in that, In step A1, the sulfide solid electrolyte comprises at least one of Li6PS5Cl, Li3PS4, Li6PS5Cl, Li6PS5Br and Li6PS5I. The mass fraction of the PTFE binder in the mixture is 1-5%; The rotation speed of the mixing is 4000-6000 rpm, and the mixing time is 5-20 min.

10. Use according to claim 8, characterized in that, In step A2, the temperature of the hot pressing is 40-60℃, and / or the thickness of the sulfide electrolyte film is 80-200 μm.

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