Disulfide bond-hydrogen bond synergistically modified PTFE (Polytetrafluoroethylene) binder as well as preparation method and application thereof

Abstract

The invention discloses a PTFE binder based on disulfide bond-hydrogen bond synergistic modification and a preparation method and application thereof, and belongs to the technical field of all-solid-state batteries. The method for preparing the PTFE binder based on disulfide bond-hydrogen bond synergistic modification comprises the following steps: firstly, activating the surface of PTFE through plasma treatment, and then sequentially grafting cystamine molecules containing disulfide bonds and 1, 3-dipropyl-6-aminouracil to construct a dynamic covalent cross-linked network and a multi-hydrogen bond cross-linked network. The invention further discloses the PTFE binder obtained through modification by the method and application of the PTFE binder in an all-solid-state battery. The solid electrolyte membrane prepared by compounding the modified PTFE binder and sulfide electrolyte shows excellent interface stability and ionic conductivity. The problems of poor interfacial compatibility, insufficient mechanical adaptability and the like of a traditional PTFE binder are solved, and a high-performance binder solution is provided for all-solid-state lithium batteries. The preparation process is simple, the cost is controllable, and the method has remarkable industrial application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of binders for all-solid-state batteries, and relates to a PTFE binder modified by disulfide bonds and hydrogen bonds, a preparation method and an application thereof, and specifically relates to a method for preparing a PTFE binder based on dynamic disulfide bond and hydrogen bond synergistic modification, a PTFE binder and an application thereof in dry film formation of all-solid-state sulfide electrolytes. Background Art

[0002] All-solid-state lithium batteries (ALLS) are currently a hot topic of research due to their high safety and energy density. Sulfide solid electrolytes, in particular, have attracted considerable attention due to their high ionic conductivity and excellent machinability. However, their practical application is severely hampered by problems such as poor solid-solid interface contact during sulfide electrolyte particle formation and interfacial failure caused by volume changes during cycling. Traditional polytetrafluoroethylene (PTFE) binders are widely used in lithium batteries due to their excellent chemical and thermal stability. However, their inherent chemical inertness leads to poor interfacial compatibility with sulfide solid electrolytes, forming a high-impedance layer at the electrode-electrolyte interface, which severely impacts the battery's ion transport efficiency. Furthermore, PTFE binders lack flexibility and dynamic repair capabilities, making it difficult to adapt to the volume changes of sulfide particles during charge and discharge, which can lead to electrolyte membrane cracking and ion transport channel disruption. Furthermore, PTFE's hydrophobicity and low surface energy make it prone to phase separation and pore defects during film formation, significantly reducing the mechanical integrity and ionic conductivity of the electrolyte membrane, severely hindering the performance improvement and practical application of ALLS SUBSTANCE BATTERIES. Therefore, developing a PTFE-based binder that has room temperature self-healing ability, high interfacial bonding strength and good process compatibility is of great significance to promoting the practical application of all-solid-state sulfide batteries. Summary of the Invention

[0003] To solve the above technical problems, the purpose of the present invention is to provide a method for preparing a PTFE binder 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. The present invention first uses plasma treatment to activate the surface of PTFE, and then grafts disulfide bond-containing cystamine molecules on the surface of the activated PTFE to construct a dynamic covalent cross-linked network; further introduces ureidopyrimidone (UPy) derivatives to form a multiple hydrogen bond cross-linked network, thereby obtaining a PTFE binder with a dual dynamic cross-linked structure, and then forms a film with the sulfide solid electrolyte through a fiberization dry film formation, effectively solving the problems of poor interface compatibility, insufficient mechanical adaptability and film-forming defects of traditional PTFE binders in sulfide all-solid-state battery applications.

[0004] The object of the present invention is achieved through the following technical solutions: In a first aspect, the present invention provides a method for preparing a PTFE (polytetrafluoroethylene) binder based on disulfide bond-hydrogen bond synergistic modification, comprising the following steps: S1. Plasma surface activation treatment of PTFE; S2, immersing the activated PTFE in an ethanol solution containing cystamine to carry out a graft modification reaction, washing and drying to obtain a disulfide bond-modified PTFE intermediate; S3, mixing the disulfide bond-modified PTFE intermediate and the ureidopyrimidone derivative in an organic solvent for reaction, washing, and drying to obtain the product.

[0005] As some specific embodiments of the present invention, step S1 is performed in a plasma treatment device, wherein the PTFE is subjected to a plasma surface activation treatment under an inert atmosphere to generate active free radical sites on the surface of the PTFE.

[0006] PTFE has an extremely low surface energy, which makes it difficult to graft. Compared with conventional chemical etching methods that destroy the crystallinity of PTFE, the present invention uses plasma surface activation treatment on PTFE to form nano-scale roughness on its surface, which facilitates subsequent grafting reactions.

[0007] As some specific embodiments of the present invention, the inert atmosphere includes at least one of argon, nitrogen, helium, and neon; And / or, the power of the plasma surface activation treatment is 100-200 W, and the time is 10-30 min.

[0008] In some specific embodiments of the present invention, in step S2, the concentration of the cystamine-containing ethanol solution is 3-6 wt %. The grafting modification reaction is carried out under magnetic stirring at a speed of 600-1000 rpm, at a temperature of 50-70° C., and for 6-12 hours. The disulfide bonds in the cystamine molecules are grafted onto the PTFE molecular chains through a free radical reaction.

[0009] As some specific embodiments of the present invention, in step S2, the washing comprises washing with ethanol 2-6 times.

[0010] The present invention uses cystamine molecules to modify PTFE to provide disulfide bonds. The cystamine molecule contains two amino groups (-NH2) and one disulfide bond (-SS-), which can simultaneously achieve covalent grafting with free radicals on the PTFE surface (through amino group reaction) and retain dynamic disulfide bonds for self-repair. Compared with other disulfides, the fatty chain structure of cystamine is more compatible with sulfide electrolytes and will not produce side reactions with sulfide electrolytes.

[0011] As some specific embodiments of the present invention, in step S3, the ureidopyrimidone derivative includes at least one of 1,3-dipropyl-6-aminouracil, 1,3-diethyl-6-aminouracil, 1,3-bis(2-methoxyethyl)-6-aminouracil, and 1,3-bis(3-trifluoromethylbenzyl)-6-aminouracil. By mixing the disulfide bond-modified PTFE intermediate with the ureidopyrimidone derivative in an organic solvent, the UPy group is grafted onto the PTFE chain through a carbamate bond to form a multiple hydrogen bond cross-linked network. Since PTFE itself lacks polar groups, it is necessary to additionally introduce uracil derivatives to construct a stable hydrogen bond network on the inert fluorocarbon chain. In addition, conventional hydrogen bond networks are unstable on hydrophobic surfaces. The present invention introduces a propyl chain as a "flexible spacer arm" and directly grafts UPy, resulting in interface stratification, which avoids direct contact between the hydrogen bond network and the hydrophobic surface.

[0012] Preferably, in step S3, the ureidopyrimidone derivative includes 1,3-dipropyl-6-aminouracil, and the mass ratio of the disulfide bond-modified PTFE intermediate to 1,3-dipropyl-6-aminouracil is 4-6:1.

[0013] Because ureidopyrimidone has a quadruple hydrogen bond system, the bond energy of its UPy far exceeds that of conventional hydrogen bonds (such as carboxylic acid dimers), and can form a stable network on the inert surface of PTFE; and the propyl chain of 1,3-dipropyl-6-aminouracil can also alleviate the conflict between the hydrophobicity of PTFE and the polarity of UPy.

[0014] In some specific embodiments of the present invention, in step S3, the organic solvent is selected from any one of DMF, DMSO, acetone, and acetonitrile, preferably DMF.

[0015] In some specific embodiments of the present invention, the mixing reaction is carried out under inert atmosphere with magnetic stirring, the reaction temperature is 70-90° C., the reaction time is 10-15 h, and the magnetic stirring speed is 600-1000 rpm.

[0016] As some specific embodiments of the present invention, in step S3, the washing comprises washing with DMF, ethanol and deionized water 2-6 times each in sequence, and removing unreacted raw materials and by-products by washing.

[0017] As some specific embodiments of the present invention, in step S2 and / or step S3, the drying includes vacuum drying, the vacuum drying temperature is 50-80° C., the time is 10-25 hours, and the vacuum degree is 0.05-0.08 MPa.

[0018] Specifically, in step S2, the vacuum drying time is 10-16 hours; And / or, in step S3, the vacuum drying time is 18-25 hours.

[0019] In a second aspect, the present invention provides a PTFE binder prepared by any of the methods described above.

[0020] Because PTFE's C-F bonds are extremely inert, with bond energies as high as 485 kJ / mol and extremely low surface energy (18.5 mN / m), controlled chemical modification is generally considered difficult in the field. However, the present invention first plasma-treats the PTFE surface to generate free radical sites. Then, through a two-step grafting process (disulfide bonds followed by hydrogen bonds), treatment with cystamine followed by a ureidopyrimidone derivative creates a stable hydrogen-bonded network on the inert fluorocarbon chains, achieving synergistic chemical modification of PTFE with disulfide and hydrogen bonds.

[0021] In a third aspect, the present invention provides a use of the PTFE binder as described above in the preparation of an all-solid-state sulfide electrolyte membrane.

[0022] As some specific embodiments of the present invention, the application includes the following steps: A1. Evenly mixing the PTFE binder and the sulfide solid electrolyte (in a mixer); A2. The mixed material is hot-pressed (using a roller press), and fiberized into a membrane during the hot-pressing process to obtain a sulfide electrolyte membrane (with a certain toughness and thickness).

[0023] As some specific embodiments of the present invention, in step A1, the sulfide solid electrolyte includes at least one of Li6PS5Cl, Li3PS4, Li6PS5Cl, Li6PS5Br, and Li6PS5I; And / or, the mass fraction of the PTFE binder in the mixture is 1-5%; And / or, the mixing speed is 4000-6000 rpm, and the mixing time is 5-20 min.

[0024] As some specific embodiments of the present invention, in step A2, the temperature of the hot pressing is 40-60°C; And / or, the thickness of the sulfide electrolyte membrane is 80-200 μm.

[0025] In the battery (especially solid-state battery) environment, avoiding the decomposition reaction of active substances in contact with sulfide electrolytes is one of the key challenges to improving battery performance and life. The traditional view is that improving the chemical activity of PTFE will inevitably sacrifice its stability and compatibility with sulfide electrolytes. When PTFE is electrochemically modified to improve its chemical activity, it will correspondingly bring about problems of interface compatibility and decreased stability. Based on this, the purpose of modifying PTFE in the present invention is to improve the interface stability of solid-state batteries and balance dynamic repair with long-term conductivity. By performing plasma surface activation treatment on PTFE and combining it with a two-step treatment of cystamine and ureidopyrimidone derivatives, the present invention successfully utilizes disulfide bonds and hydrogen bonds to synergistically modify PTFE to obtain a PTFE binder with a dual dynamic cross-linking structure. It is then combined with a sulfide solid electrolyte through a fiberized dry film formation method for application in all-solid-state batteries. By controlling the interaction between disulfide bonds and hydrogen bonds, and avoiding side reactions with Li6PS5Cl, the interfacial impedance of Li6PS5Cl is reduced to 4.9 Ω (the unmodified interfacial impedance is >8 Ω; PTFE reacts with Li6PS5Cl to form a Li2S insulating layer, resulting in a decrease in ionic conductivity). Furthermore, the high ionic conductivity, compatibility with sulfide electrolytes, and interfacial strain buffering achieved by this invention far exceed expectations in the field, bringing synergistic innovations to sulfide all-solid-state battery applications. While enhancing the chemical activity of PTFE, it also improves its interfacial compatibility with sulfide electrolytes, overcoming the challenges of electrochemical compatibility traditionally considered.

[0026] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention combines plasma activation with dual modification of disulfide bonds and UPy hydrogen bonds, making the PTFE binder have both excellent dynamic self-healing properties and interfacial bonding strength. Disulfide-containing cystamine molecules and 1,3-dipropyl-6-aminouracil are grafted onto PTFE to construct a dynamic covalent cross-linking network and a multiple hydrogen bond cross-linking network, making the PTFE binder have both 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 binder's adaptability to the volume change of the sulfide electrolyte; the solid electrolyte membrane prepared by combining the modified PTFE binder with the sulfide electrolyte exhibits lower interfacial impedance, better interfacial stability and higher ionic conductivity, while also having good mechanical strength. This solves the problems of poor interfacial compatibility and insufficient mechanical adaptability of traditional PTFE binders, providing a high-performance binder solution for all-solid-state lithium batteries.

[0027] (2) The modified PTFE binder and its preparation method provided by the present invention have simple process and controllable cost, providing a new material solution for the development of high-performance all-solid-state lithium batteries and having significant industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings: Figure 1 Schematic diagram of the process for preparing a PTFE binder based on disulfide bond-hydrogen bond synergistic modification and its use in dry film formation of sulfide electrolytes; Figure 2 This is the electrochemical EIS impedance diagram of the sulfide electrolyte membrane prepared in Example 1; Figure 3 The electrochemical EIS impedance diagram of the sulfide electrolyte membrane prepared in Comparative Example 1; Figure 4 This is the electrochemical EIS impedance diagram of the sulfide electrolyte membrane prepared in Comparative Example 3. DETAILED DESCRIPTION

[0029] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0030] like Figure 1 As shown, the present invention provides a method for preparing a PTFE binder based on disulfide bond-hydrogen bond synergistic modification, and using the PTFE binder for dry film formation of sulfide electrolyte, which specifically includes the following steps: 1. Plasma surface activation treatment of PTFE raw materials in an inert gas atmosphere to generate active free radical sites on the PTFE surface; 2. Immersing the activated PTFE in an ethanol solution containing cystamine to graft disulfide bonds onto the PTFE molecular chain through a free radical reaction, followed by washing and drying to obtain a disulfide-modified PTFE intermediate; 3. Reacting the PTFE intermediate with a ureidopyrimidone derivative in DMF solvent to form a multi-hydrogen bond cross-linked network; Fourth, the product was washed with DMF, ethanol and deionized water in sequence to remove unreacted raw materials and by-products, and vacuum dried to obtain a PTFE binder with disulfide bond-hydrogen bond synergistic modification; 5. Evenly mix the modified PTFE binder and the sulfide solid electrolyte in a mixer according to a certain ratio; 6. The above mixture is hot-pressed by a roller press, and fiberized into a film during the hot-pressing process to obtain a sulfide electrolyte membrane with a certain toughness and thickness.

[0031] Example 1 This embodiment provides a method for preparing a PTFE binder based on disulfide bond-hydrogen bond synergistic modification, and using the binder to form an all-solid-state sulfide electrolyte membrane through dry film formation. The specific steps are as follows: (1) PTFE surface activation treatment: 5 g of PTFE powder was placed in a plasma treatment device and treated at 150 W power for 15 minutes under an argon atmosphere to generate active free radical sites on the PTFE surface; (2) Disulfide bond grafting modification: 5 g of activated PTFE powder was immersed in 100 mL of ethanol solution containing 5 wt% cystamine, and the mixture was stirred at 60 °C for 8 hours with a magnetic stirring speed of 800 rpm. After the reaction was completed, it was washed with ethanol three times and vacuum dried at 60 °C for 12 hours with a vacuum degree of 0.07 MPa to obtain a disulfide bond-modified PTFE intermediate. (3) Construction of hydrogen bond network: 3 g of the disulfide bond-modified PTFE intermediate prepared in step (2) and 0.6 g of 1,3-dipropyl-6-aminouracil were dissolved in 50 mL of DMF, stirred at 800 rpm, and reacted at 80 °C under nitrogen protection for 12 h; (4) Product purification: After the reaction solution was cooled to room temperature, it was washed with DMF, ethanol and deionized water three times each, and vacuum dried at 60 °C for 24 hours with a vacuum degree of 0.08 MPa to finally obtain a PTFE binder with disulfide bond-hydrogen bond synergistic modification.

[0032] (5) Dry mixing: In an argon-filled glove box, 9.8 g of Li6PS5Cl sulfide solid electrolyte and 0.2 g of modified PTFE were added to a mixer and mixed at a mixer speed of 5000 rpm for 10 min. (6) Hot roller pressing dry film formation: The above mixture is hot pressed using a roller press. The temperature of the roller press is 50°C, the pressure is 10 MPa, and the roller press is performed 6 times. The thickness of the film is 100 μm, and it is cut into 10 mm diameter discs to obtain an electrolyte membrane.

[0033] Example 2 This embodiment provides a preparation method of a PTFE binder based on disulfide bond-hydrogen bond synergistic modification and its application in dry film formation of sulfide solid electrolytes, and the steps are as follows: (1) PTFE surface activation treatment: 8 g of PTFE powder was placed in a plasma treatment device and treated at 120 W power for 20 minutes under an argon atmosphere to generate active free radical sites on the PTFE surface; (2) Disulfide bond grafting modification: 8 g of activated PTFE powder was immersed in 120 mL of ethanol solution containing 4 wt% cystamine, and stirred at 55 °C for 10 hours with a magnetic stirring speed of 700 rpm. After the reaction was completed, it was washed with ethanol three times and vacuum dried at 65 °C for 14 hours with a vacuum degree of 0.06 MPa to obtain a disulfide bond-modified PTFE intermediate; (3) Construction of hydrogen bond network: 4 g of the above-mentioned disulfide bond-modified PTFE intermediate and 0.8 g of 1,3-dipropyl-6-aminouracil were dissolved in 60 mL of DMF, stirred at 700 rpm, and reacted at 75 °C under nitrogen protection for 14 h; (4) Product purification: After the reaction solution was cooled to room temperature, it was washed with DMF, ethanol and deionized water four times each, and dried under vacuum at 65 °C for 20 hours with a vacuum degree of 0.06 MPa to obtain a PTFE binder with disulfide bond-hydrogen bond synergistic modification. (5) Dry mixing: In an argon-filled glove box, 9.8 g of Li6PS5Cl sulfide solid electrolyte and 0.2 g of modified PTFE were added to a mixer and mixed at a mixer speed of 5500 rpm for 15 min. (6) Hot roller pressing dry film formation: The above mixture is hot pressed using a roller press. The temperature of the roller press is 55°C, the pressure is 10 MPa, and the roller press is performed 6 times. The thickness of the film is 100 μm, and it is cut into 10 mm diameter discs to obtain an electrolyte membrane.

[0034] Comparative Example 1 A PTFE sample without any modification was directly used to form a film with a sulfide electrolyte according to steps (5) and (6) in Example 1, and then prepared for testing.

[0035] Comparative Example 2 Step (3) in Example 1 was eliminated, and only cystamine was used to perform disulfide bond grafting modification on PTFE, followed by film formation with sulfide electrolyte. The remaining steps and parameters remained unchanged and were carried out according to Example 1.

[0036] Comparative Example 3 Step (2) in Example 1 was eliminated, and only 1,3-dipropyl-6-aminouracil was used to modify the PTFE by hydrogen bond network construction, and then the film was formed with the sulfide electrolyte. The remaining steps and parameters remained unchanged and were carried out according to Example 1.

[0037] Comparative Example 4 The cystamine in step (2) of Example 1 was replaced with dithiodipropionic acid, and the PTFE was subjected to disulfide bond grafting modification, and then film-formed with a sulfide electrolyte. The remaining steps and parameters remained unchanged and were carried out according to Example 1.

[0038] Comparative Example 5 The 1,3-dipropyl-6-aminouracil in step (3) of Example 1 was replaced with polyacrylic acid, and the PTFE was modified by hydrogen bond network construction, hydrogen bonds were formed through the carboxyl groups, and then a film was formed with the sulfide electrolyte. The remaining steps and parameters remained unchanged and were all carried out according to Example 1. The difference in hydrogen bond network stability between the small molecule crosslinker 1,3-dipropyl-6-aminouracil and the polymer crosslinker was compared.

[0039] Comparative Example 6 The 1,3-dipropyl-6-aminouracil in step (3) of Example 1 was replaced with urea, the PTFE was modified by hydrogen bond network construction, and then formed into a film with a sulfide electrolyte. The remaining steps and parameters remained unchanged and were carried out according to Example 1.

[0040] Effect embodiment 1. The electrochemical performance of the electrolyte membranes prepared in each embodiment and comparative example was tested as follows: The electrolyte membranes prepared in each embodiment and comparative example were cut into small discs, loaded into a pressure battery mold, and punched for 1 minute under a pressure of 1 ton. An electrochemical workstation with specification model CHI660E was used to perform an AC impedance test at room temperature. The test results are shown in Table 1.

[0041] Table 1 Electrochemical performance test results

[0042] like Figure 2-Figure 4 Shown are the electrochemical EIS impedance spectra of the sulfide electrolyte membranes prepared in Example 1, Comparative Example 1 and Comparative Example 3, respectively. Figure 2-Figure 4 In the figure, the horizontal axis is the real impedance (Z'), which represents the pure resistive component; the vertical axis is the imaginary impedance (-Z''), which increases upwards, representing the capacitive component, and increases downwards, representing the inductive component.

[0043] from Figure 2-4 It can be concluded that the impedance of the electrolyte membrane in Example 1 is 4.91Ω, the impedance of the electrolyte membrane in Comparative Example 1 is 8.16Ω, and the impedance of the electrolyte membrane in Comparative Example 3 is 6.78Ω. The calculated ionic conductivities are 2.47mS / cm, 1.46mS / cm, and 1.76mS / cm, respectively. It can be seen that the impedance values ​​of the samples in Comparative Examples 1 and 3 are significantly higher than the impedance of the sample in Example 1, and the ionic conductivities of the samples in Comparative Examples 1 and 3 are lower than the ionic conductivity of the sample in Example 1, indicating that the unmodified PTFE has poor interfacial compatibility with the sulfide electrolyte after fiberization, resulting in increased impedance after film formation, obstructed ion transport, and reduced ionic conductivity.

[0044] As can be seen from Table 1, the impedance of the electrolyte membranes obtained in Examples 1 and 2 is significantly smaller than that of the comparative examples, while their ionic conductivities are higher than those of the comparative examples. The smaller the impedance, the better the compatibility of the functional groups in the modified PTFE structure with the sulfide electrolyte, the fewer side reactions, and the more conducive to the fibrosis and film formation of PTFE. Among them, in Comparative Example 4, dithiodipropionic acid (disulfide bond source) and 1,3-dipropyl-6-aminouracil (hydrogen bond source) are combined to modify the PTFE by hydrogen bond network construction. Due to the reaction of dithiodipropionic acid with the sulfide electrolyte, its ionic conductivity is low, and the electrochemical impedance is also significantly higher than that of each embodiment.

[0045] 2. The tensile properties of the electrolyte membranes prepared in the examples and comparative examples were tested as follows: The operation was carried out in a glove box filled with argon. The electrolyte membranes of the embodiments and comparative examples were subjected to a tensile test at a tensile rate of 5 mm / min and a test temperature of room temperature. The test results are shown in Table 2.

[0046] Table 2 Tensile properties test results

[0047] As can be seen from Table 2, the film-forming properties of the electrolyte membranes prepared in Examples 1 and 2 are better than those of the comparative examples, and the surface of the membranes is flat and smooth, without cracks or wrinkles; at the same time, the tensile strength measured is higher than that of other samples in the comparative example, indicating that they have better mechanical properties. This is mainly because the PTFE binder has excellent dynamic self-healing properties and interfacial bonding strength through plasma activation combined with dual modification of disulfide bonds and UPy hydrogen bonds. The synergistic effect of the disulfide bond network and the UPy quadruple hydrogen bond network significantly improves the binder's adaptability to volume changes in the sulfide electrolyte; the solid electrolyte membrane prepared by composite preparation of the modified PTFE binder and the sulfide electrolyte exhibits lower interfacial impedance and higher ionic conductivity, while having good mechanical strength.

[0048] Compared to the Examples, Comparative Example 5 uses a combination of cystamine (a source of disulfide bonds) and polyacrylic acid (a source of hydrogen bonds) to modify the PTFE by building a hydrogen bond network. Table 2 shows that the hydrogen bond network strength is insufficient, resulting in weak tensile strength after film formation. Similarly, Comparative Example 6 uses a combination of cystamine (a source of disulfide bonds) and urea (a source of hydrogen bonds). The hydrogen bond network strength is also significantly lower than that of the Examples, resulting in weak tensile strength after film formation.

[0049] The modified PTFE binder and preparation method thereof provided by the present invention have simple process and controllable cost, and provide a new material solution for the development of high-performance all-solid-state lithium batteries.

[0050] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a PTFE binder based on disulfide bond-hydrogen bond synergistic modification, characterized in that: The steps include: S1. Plasma surface activation treatment of PTFE; S2, immersing the activated PTFE in an ethanol solution containing cystamine to carry out a graft modification reaction, washing and drying to obtain a disulfide bond-modified PTFE intermediate; S3, mixing the disulfide bond-modified PTFE intermediate and the ureidopyrimidone derivative in an organic solvent for reaction, washing, and drying to obtain the product.

2. The method according to claim 1, characterized in that In step S1, PTFE is subjected to plasma surface activation treatment under an inert atmosphere; The inert atmosphere includes at least one of argon, nitrogen, helium, and neon; And / or, the power of the plasma surface activation treatment is 100-200 W, and the time is 10-30 min.

3. The method according to claim 1, characterized in that In step S2, the concentration of the cystamine-containing ethanol solution is 3-6 wt %; the graft modification reaction is carried out under magnetic stirring at a speed of 600-1000 rpm, a temperature of 50-70° C., and a time of 6-12 h.

4. The method according to claim 1, wherein In step S3, the ureido-pyrimidinone derivative includes at least one of 1,3-dipropyl-6-aminouracil, 1,3-diethyl-6-aminouracil, 1,3-bis(2-methoxyethyl)-6-aminouracil, and 1,3-bis(3-trifluoromethylbenzyl)-6-aminouracil.

5. The method according to claim 1, characterized in that In step S3, the organic solvent is selected from any one of DMF, DMSO, acetone, and acetonitrile; And / or, the mixing reaction is carried out under inert atmosphere protection with magnetic stirring, the reaction temperature is 70-90° C., the reaction time is 10-15 h; and the rotation speed of the magnetic stirring is 600-1000 rpm.

6. The method according to claim 1, characterized in that In step S2 and / or step S3, the drying includes vacuum drying, the vacuum drying temperature is 50-80° C., the time is 10-25 hours, and the vacuum degree is 0.05-0.08 MPa.

7. A PTFE adhesive, characterized in that The method is prepared according to any one of claims 1 to 6.

8. Use of the PTFE binder according to claim 7 in preparing an all-solid-state sulfide electrolyte membrane, characterized in that: The application comprises the following steps: A1, uniformly mixing the PTFE binder and the sulfide solid electrolyte; A2. The mixed material is hot-pressed, and fiberized into a membrane during the hot-pressing process to obtain a sulfide electrolyte membrane.

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

10. The use according to claim 8, characterized in that In step A2, the hot pressing temperature is 40-60° C., and / or the thickness of the sulfide electrolyte membrane is 80-200 μm.

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