A functional adhesive and its preparation method and application

Abstract

The present application relates to the technical field of lithium ion battery, and especially relates to a functional binder, a preparation method and application thereof.The functional binder comprises at least one imino group and one sulfide group; the structural formula of the functional binder is shown as the following formula I: the different groups on the binder can realize different functions: the imino group can improve the liquid absorption effect of the electrolyte on the electrode; through the physical and chemical adsorption effect of the sulfur-sulfur bond on the molecular chain of the functional binder on polysulfide, the utilization rate of sulfur can be improved, and the cycle performance of the lithium-sulfur battery is improved.The preparation method of the functional binder utilizes the electrode drying process, can further promote the cross-linking degree of the polymer in the binder, improve the mechanical stability of the electrode, and thus improve the cycle stability of the lithium-sulfur battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a functional binder and a preparation method and application thereof. BACKGROUND

[0002] Energy shortage and environmental pollution are two major problems in the world today. Considering the energy supply and tail gas pollution problems brought by traditional cars, developing new energy vehicles has become an important demand for countries around the world, and the full replacement of traditional fuel vehicles by new energy vehicles has been on the agenda. In order to continue to compete with traditional fuel vehicles in the market, new energy vehicles must be comparable to fuel vehicles in terms of endurance mileage and cost, which requires the energy density of battery monomer to reach 350Wh / kg or even higher. The theoretical specific capacity of elemental sulfur is 1675mAh·g -1 , and it is abundant in reserves and low in cost, and has no pollution to the environment. The theoretical energy density of lithium-sulfur battery with elemental sulfur as the positive electrode and lithium as the negative electrode is as high as 2600Wh / kg, several times that of the current lithium ion battery, so it has gradually attracted people's attention.

[0003] In view of the problems existing in lithium-sulfur batteries, researchers have taken various measures. The active material sulfur is coated and confined in the pores or cavities by using a suitable structure of carrier material for the sulfur positive electrode material, so as to inhibit the dissolution and diffusion of polysulfide into the electrolyte and play a certain role in relieving the volume expansion of the positive electrode; the use of metal oxides, metal sulfides and metal nitrides and other materials with polarity can produce strong chemical adsorption between the polar polysulfide; in addition to the above-mentioned metal compounds, some polar functional groups, such as -NH3, -SO3, -COOH, etc., can also produce strong adsorption to polysulfide, thereby inhibiting the shuttle of polysulfide ions. Although researchers have done a lot of work on the sulfur positive electrode, the problem cannot be completely solved, especially in the practical high-energy soft package battery, there are many problems and challenges, how to realize high specific energy, long cycle and large rate performance in the state of liquid deficiency is a key challenge. Researchers have studied lithium-sulfur soft package battery from four aspects of failure analysis, positive electrode construction, electrolyte design and negative electrode protection, but there is no report on the research of adhesive. SUMMARY

[0004] The present application provides a functional binder and its application in lithium-sulfur batteries to solve the above-mentioned problems existing in the prior art.

[0005] According to the first aspect of the present application, the present application provides a functional binder, which at least contains an imino group and a sulfide group; the structure of the functional binder is shown in the following formula I:

[0006]

[0007] The functional binder of the present application has different groups, which can realize different functions: the imino group can improve the liquid absorption effect of the electrode on the electrolyte; the sulfur-sulfur bond on the molecular chain of the functional binder can improve the physical and chemical adsorption of polysulfides, improve the utilization rate of sulfur, and improve the cycle performance of lithium-sulfur batteries.

[0008] According to the second aspect of the present application, a preparation method of a functional binder is provided, and a synthesis reaction equation of the functional binder is as follows:

[0009]

[0010] In a possible design, the preparation method comprises the following steps:

[0011] (1) Preparation of polymer precursor: polyethyleneimine is dissolved in a first solvent to obtain a polymer solution; isocyanatoethyl methacrylate is added to the polymer solution, or the polymer solution is added to isocyanatoethyl methacrylate, and the reaction is stirred sufficiently; the reaction liquid obtained by the reaction is precipitated in methanol and vacuum dried to obtain a polymer precursor with a vinyl functional group;

[0012] (2) Generation of cross-linked network: the polymer precursor, diallyl disulfide and an initiator are dissolved in a second solvent to obtain a binder solution; the binder solution is uniformly mixed with active material and conductive material in a certain proportion to obtain a mixed slurry; the mixed slurry is uniformly coated on a current collector, and a drying reaction is performed at a certain temperature to form the functional binder with a space network structure on the current collector.

[0013] In the above scheme, the functional binder is prepared by synthesizing a polymer precursor from polyethyleneimine and isocyanatoethyl methacrylate as raw materials, and then further reacting the polymer precursor and diallyl disulfide under the action of an initiator to form a functional binder with a space network structure. The reaction of the polymer precursor and diallyl disulfide under the action of the initiator is partly performed in the electrode drying process, which can further promote the cross-linking degree of the polymer and improve the mechanical stability of the electrode, thereby improving the cycle stability of the lithium-sulfur battery.

[0014] In a possible design, the first solvent is selected from an organic polar solvent or an organic non-polar solvent; preferably, the first solvent comprises at least one of alkane, aromatic hydrocarbon, ether, halogenated alkane and tetrahydrofuran.

[0015] Specifically, the alkane comprises C n H 2n+2(6≤n≤17); aromatic hydrocarbons include toluene, xylene, p-xylene, styrene, etc.; ethers include n-butyl ether, n-pentyl ether, iso-pentyl ether, triethylene glycol dimethyl ether, etc.; halogenated alkanes include chloroform, 1,2-dichloroethane, carbon tetrachloride, etc.

[0016] It can be understood that by selecting a suitable first solvent, the polyethyleneimine can be effectively dissolved, so that the polyethyleneimine can effectively react with the isocyanatoethyl methacrylate to form a stable polymer precursor.

[0017] In one possible design, the initiator is azobisisobutyronitrile.

[0018] It can be understood that by selecting a suitable initiator type, the reaction of the polymer precursor with the diallyl disulfide can be more effectively initiated, improving the reaction efficiency.

[0019] In one possible design, the second solvent can be selected from ethers or esters, wherein the ethers include n-butyl ether, n-pentyl ether, iso-pentyl ether, triethylene glycol dimethyl ether, ethylene glycol dimethyl ether, etc., and the esters include one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, etc.; in one possible design, the second solvent is selected from ethylene glycol dimethyl ether.

[0020] It can be understood that by reasonably selecting the type of the second solvent, the polymer precursor, the diallyl disulfide, and the initiator can be effectively dissolved, which is conducive to the reaction of the polymer precursor with the diallyl disulfide, improving the reaction efficiency.

[0021] In one possible design, in step (1), the molar ratio of the polyethyleneimine to the isocyanatoethyl methacrylate is (0.5-1.0):1.0.

[0022] Alternatively, in step (1), the molar ratio of the polyethyleneimine to the isocyanatoethyl methacrylate can be 0.5:1.0, 0.55:1.0, 0.6:1.0, 0.65:1.0, 0.7:1.0, 0.75:1.0, 0.8:1.0, 0.85:1.0, 0.9:1.0, 0.95:1.0, or 1.0:1.0, etc., and of course can also be other values within the above range, which are not limited herein.

[0023] It can be understood that by limiting the molar ratio of the polyethyleneimine to the isocyanatoethyl methacrylate within a reasonable range, the polymer precursor synthesis reaction can be facilitated, providing reaction efficiency.

[0024] In one possible design, the molar ratio of the isocyanatoethyl methacrylate to the diallyl disulfide is 1:(0.25-0.5).

[0025] Optionally, the molar ratio of the isocyanatoethyl methacrylate to the diallyl disulfide can be 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.45, or 1:0.5, and of course can be other values within the above range, which are not limited herein.

[0026] It can be understood that by limiting the molar ratio of the isocyanatoethyl methacrylate to the diallyl disulfide within a reasonable range, the functional binder synthesis reaction can be facilitated, and the reaction efficiency can be improved.

[0027] In one possible design, in step (2), the molar ratio of the diallyl disulfide to the initiator is (1.5-2.5):1.

[0028] Optionally, in step (2), the molar ratio of the diallyl disulfide to the initiator can be 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, or 2.5:1, and of course can be other values within the above range, which are not limited herein.

[0029] It can be understood that by limiting the molar ratio of the diallyl disulfide to the initiator within a reasonable range, the reaction can be more effectively initiated, the functional binder synthesis reaction can be facilitated, and the reaction efficiency can be improved.

[0030] In one possible design, in step (2), the binder solution accounts for 1%-20% of the total amount of the mixed slurry.

[0031] Optionally, in step (2), the percentage of the binder solution in the total amount of the mixed slurry can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%, and of course can be other values within the above range, which are not limited herein.

[0032] It can be understood that by limiting the percentage of the binder solution in the total amount of the mixed slurry within a reasonable range, the active material and the conductive material can be more stably bonded to the current collector, and the formation of the stable electrode can be facilitated.

[0033] In one possible design, in step (2), the drying reaction is performed at a temperature of 50°C-70°C for 8h-12h.

[0034] Optionally, in step (2), the temperature of the drying reaction can be 50℃, 52℃, 55℃, 58℃, 63℃, 65℃, 68℃ or 70℃, and of course can also be other values within the above range, which is not limited here, and the time can be 8h, 9h, 10h, 11h or 12h, and of course can also be other values within the above range, which is not limited here.

[0035] It can be understood that by limiting the temperature and time of the drying reaction to a reasonable range, the degree of cross-linking of the polymer can be further promoted, the mechanical stability of the electrode can be improved, and thus the cycle stability of the lithium-sulfur battery can be improved.

[0036] According to a third aspect of the present application, the present application also provides the use of the functional binder described above or prepared by the preparation method described above in a lithium-sulfur battery.

[0037] A general lithium-sulfur battery includes a positive electrode, a negative electrode, and an electrolyte.

[0038] In one possible design, the functional binder is applied to a sulfur positive electrode of the lithium-sulfur battery; and the sulfur positive electrode has a porosity of 40%-85%.

[0039] In one possible design, the negative electrode of the lithium-sulfur battery is at least one of metal lithium, lithium alloy, lithium-doped carbon, and lithium-doped silicon.

[0040] In one possible design, the electrolyte is at least one of a liquid electrolyte, a colloidal polymer electrolyte, and a solid-state electrolyte.

[0041] The functional binder provided by the present application has a structural formula shown in Formula I. The binder is formed by a functional polymer precursor generated by the reaction of polyethyleneimine and isocyanatoethyl methacrylate, a diallyl disulfide, and an initiator to form a binder system. The binder system is dissolved in a second solvent to obtain a binder solution. The active material, the conductive material, and the binder solution are mixed in a certain proportion to form a uniform mixture, which is coated on a current collector and subjected to a drying reaction to form a space network system through cross-linking polymerization during the electrode drying process. Different groups on the binder can achieve different functions: the imino group can improve the liquid absorption effect of the electrode on the electrolyte; and the physical and chemical adsorption of the polysulfide by the sulfur-sulfur bond on the molecular chain of the functional binder can improve the utilization rate of sulfur and improve the cycle performance of the lithium-sulfur battery. The preparation method of the functional binder of the present application utilizes the electrode drying process to further promote the cross-linking degree of the polymer in the binder, improve the mechanical stability of the electrode, and thus improve the cycle stability of the lithium-sulfur battery. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0043] Figure 1 is the charge-discharge curve of the lithium-sulfur soft pack battery in Example 1 and Comparative Example 1 provided by the present application;

[0044] Figure 2 is the cycle curve of the lithium-sulfur soft pack battery in Example 1 and Comparative Example 1 provided by the present application. DETAILED DESCRIPTION

[0045] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below in combination with the drawings in the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort belong to the protection scope of the present application.

[0046] Example 1

[0047] The present embodiment provides a functional binder, and the structural formula of the functional binder is a compound as shown in Formula I:

[0048]

[0049] The preparation method of the above functional binder comprises the following steps:

[0050] (1) Preparation of polymer precursor: 4.3 g of polyethyleneimine is weighed and placed in 100 mL of xylene solution, 15.5 g of isocyanatoethyl methacrylate is added to the xylene solvent containing polyethyleneimine, and the reaction is fully stirred; the reaction solution obtained by the reaction is dropped into a methanol solution for precipitation, and then vacuum dried at 50°C to obtain a polymer precursor.

[0051] (2) Generation of cross-linked network: the obtained polymer precursor, 14.6 g of diallyl disulfide, and 0.073 g of azobisisobutyronitrile are dissolved in 539.1 g of ethylene glycol dimethyl ether solvent to obtain a binder solution with a solid content of 6%; the sulfur positive electrode material, conductive carbon, and binder solution are uniformly mixed in a mass ratio of 70:20:10 using a homogenizer to obtain a mixed slurry; then the mixed slurry is coated on the surface of an aluminum foil, dried at 60°C for 10 h to form a functional binder with a space network structure on the surface of the aluminum foil, and a sulfur positive electrode is obtained.

[0052] The obtained sulfur cathode was assembled into a lithium-sulfur soft pack battery and its electrochemical performance was tested. The charge-discharge curve of the lithium-sulfur battery obtained in this example is shown in Figure 1 , the cycle curve is shown in Figure 2 , and the discharge capacity and cycle stability of the obtained lithium-sulfur battery are shown in Table 1 below.

[0053] Example 2

[0054] This example provides a functional binder, and the structural formula of the functional binder is a compound as shown in Formula I:

[0055]

[0056] The preparation method of the above-mentioned functional binder comprises the following steps:

[0057] (1) Preparation of polymer precursor: 4.3 g of polyethyleneimine was weighed and placed in 100 mL of xylene solution, 7.75 g of isocyanatoethyl methacrylate was added to the xylene solvent containing polyethyleneimine, and the reaction was stirred thoroughly; the reaction solution obtained by the reaction was dropped into a methanol solution for precipitation, and then vacuum dried at 50°C to obtain a polymer precursor.

[0058] (2) Generation of cross-linked network: the obtained polymer precursor, 3.65 g of diallyl disulfide, and 0.018 g of azobisisobutyronitrile were dissolved in 246.2 g of ethylene glycol dimethyl ether solvent to obtain a binder solution with a solid content of 6%; the sulfur cathode material, conductive carbon, and binder solution were uniformly mixed in a mass ratio of 70:20:10 using a homogenizer to obtain a mixed slurry; then the mixed slurry was coated on the surface of an aluminum foil and dried at 60°C for 10 h to form a functional binder with a space network structure on the surface of the aluminum foil, thereby obtaining a sulfur cathode.

[0059] The obtained sulfur cathode was assembled into a lithium-sulfur soft pack battery and its electrochemical performance was tested, and the discharge capacity and cycle stability of the obtained lithium-sulfur battery are shown in Table 1 below.

[0060] Example 3

[0061] This example provides a functional binder, and the structural formula of the functional binder is a compound as shown in Formula I:

[0062]

[0063] The preparation method of the above-mentioned functional binder comprises the following steps:

[0064] (1) Preparation of polymer precursor: 4.3 g of polyethyleneimine was weighed into 100 mL of xylene solution, 15.5 g of isocyanate ethyl methacrylate was added to the xylene solvent containing polyethyleneimine, and the mixture was stirred thoroughly; the reaction solution was dropped into a methanol solution for precipitation, and then vacuum dried at 50°C to obtain the polymer precursor.

[0065] (2) Cross-linked network generation: the obtained polymer precursor, 7.3 g of diallyl disulfide, and 0.036 g of azobisisobutyronitrile were dissolved in 425.1 g of ethylene glycol dimethyl ether solvent to obtain a binder solution with a solid content of 6%; a homogenizer was used to uniformly mix the sulfur positive electrode material, conductive carbon, and the binder solution in a mass ratio of 70:20:10 to obtain a mixed slurry; then the mixed slurry was coated on the surface of an aluminum foil, dried at 60°C for 10 h to form a functional binder with a space network structure on the surface of the aluminum foil, and a sulfur positive electrode was obtained.

[0066] The obtained sulfur positive electrode was assembled into a lithium-sulfur soft pack battery and its electrochemical performance was tested, and the discharge capacity and cycle stability of the obtained lithium-sulfur battery are shown in Table 1.

[0067] Example 4

[0068] The present embodiment provides a functional binder, and the structural formula of the functional binder is a compound as shown in Formula I:

[0069]

[0070] The preparation method of the above-mentioned functional binder comprises the following steps:

[0071] (1) Preparation of polymer precursor: 4.3 g of polyethyleneimine was weighed into 100 mL of xylene solution, 15.5 g of isocyanate ethyl methacrylate was added to the xylene solvent containing polyethyleneimine, and the mixture was stirred thoroughly; the reaction solution was dropped into a methanol solution for precipitation, and then vacuum dried at 50°C to obtain the polymer precursor.

[0072] (2) Cross-linked network generation: the obtained polymer precursor, 7.3 g of diallyl disulfide, and 0.036 g of azobisisobutyronitrile were dissolved in 425.1 g of ethylene glycol dimethyl ether solvent to obtain a binder solution with a solid content of 6%; a homogenizer was used to uniformly mix the sulfur positive electrode material, conductive carbon, and the binder solution in a mass ratio of 70:20:10 to obtain a mixed slurry; then the mixed slurry was coated on the surface of an aluminum foil, dried at 60°C for 10 h to form a functional binder with a space network structure on the surface of the aluminum foil, and a sulfur positive electrode was obtained.

[0073] Example 5

[0074] The embodiment provides a functional binder, and a structural formula of the functional binder is a compound as shown in formula I:

[0075]

[0076] The preparation method of the functional binder comprises the following steps:

[0077] (1) Preparation of a polymer precursor: 4.3 g of polyethyleneimine is weighed and placed in 100 mL of a dimethylbenzene solution, 12.4 g of isocyanatoethyl methacrylate is added to the dimethylbenzene solution containing the polyethyleneimine, and the reaction is stirred thoroughly; the reaction solution obtained by the reaction is dropped into a methanol solution, and then precipitated, and then vacuum dried at 50 DEG C to obtain the polymer precursor.

[0078] (2) Generation of a crosslinked network: the obtained polymer precursor, 7.3 g of diallyl disulfide and 0.036 g of azobisisobutyronitrile are dissolved in 376.6 g of ethylene glycol dimethyl ether solvent to obtain a binder solution with a solid content of 6%; a homogenizer is used to uniformly mix the sulfur positive electrode material, conductive carbon and the binder solution in a mass ratio of 70:20:10 to obtain a mixed slurry; then the mixed slurry is coated on the surface of an aluminum foil, dried at 60 DEG C for 10 h to form a functional binder with a space network structure on the surface of the aluminum foil, and a sulfur positive electrode is obtained.

[0079] The obtained sulfur positive electrode is assembled into a lithium-sulfur soft package battery, and the electrochemical performance is tested, and the discharge capacity and cycle stability of the lithium-sulfur battery are shown in Table 1.

[0080] Comparative Example 1

[0081] A homogenizer is used to uniformly mix the sulfur positive electrode material, conductive carbon and the binder (LA132) in a mass ratio of 70:20:10 to obtain a mixed slurry, and then the mixed slurry is coated on the surface of an aluminum foil, dried at 60 DEG C for 10 h to obtain a sulfur positive electrode.

[0082] The obtained sulfur positive electrode is assembled into a lithium-sulfur soft package battery, and the electrochemical performance is tested, and the charge-discharge curve of the lithium-sulfur battery obtained in Comparative Example 1 is as shown in Figure 1 , the cycle curve is as shown in Figure 2 , and the discharge capacity and cycle stability are shown in Table 1.

[0083] The test method of the electrochemical performance of the above embodiment and comparative example is as follows:

[0084] According to the size of the soft package battery pole piece, slicing is performed, and the pole piece is punched and formed, and then dried under vacuum conditions; the positive pole piece is assembled into a cell in a laminated manner; the tab is ultrasonically welded; then the aluminum plastic film of the appropriate size is cut; the formed aluminum plastic film is packaged into the cell, and top side sealing is performed on the top side sealing machine; a specific amount of electrolyte is injected into the cell using an injection device; the injected cell is placed under vacuum conditions; and finally, the battery is vacuum packaged to prepare a lithium-sulfur soft package battery.

[0085] The prepared lithium / sulfur soft package battery is subjected to constant current charge and discharge test using a charge and discharge instrument. The charge and discharge range of the lithium / sulfur battery is generally 1.7-2.6V. The charge and discharge mode is constant current mode. Since the positive electrode of the lithium / sulfur battery studied in this paper is sulfur and the negative electrode is lithium, the discharge is performed first and then the charge is performed. The discharge process uses a current of 0.1C.

[0086] Table 1 Discharge capacity and cycle stability comparison table of examples 1-5 and comparative example 1

[0087] Initial discharge capacity (mAh / g) 0.3 C cycle stability Example 1 1484.5 30 week capacity retention 90.6% Example 2 1328.6 30 week capacity retention 72% Example 3 1336.8 30 week capacity retention 75% Example 4 1351.5 30 week capacity retention 79% Example 5 1396.7 30 week capacity retention 86% Comparative Example 1 1291.3 30 week capacity retention 58%

[0088] From the results of Figure 1 and Figure 2 It can be seen that, compared with the existing conventional binder, the lithium-sulfur battery prepared by using the functional binder of the present application has excellent charge and discharge performance and cycle performance. As can be seen from the experimental results in Table 1, compared with the existing conventional binder, the lithium-sulfur battery prepared by using the functional binder of the present application has high initial discharge capacity and high capacity retention rate. In summary, the lithium-sulfur battery prepared by using the functional binder of the present application can improve the battery performance of the lithium-sulfur battery.

[0089] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement to part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a functional adhesive, characterized in that, Includes the following steps: (1) Preparation of polymer precursor: Polyethyleneimine is dissolved in a first solvent to obtain a polymer solution; Ethyl isocyanate methacrylate is added to the polymer solution, or the polymer solution is added to ethyl isocyanate methacrylate, and the reaction is stirred thoroughly; The reaction solution obtained is precipitated in methanol and dried under vacuum to obtain a polymer precursor with vinyl functional groups; (2) Crosslinking network generation: The polymer precursor, diallyl disulfide and initiator are dissolved in a second solvent to obtain an adhesive solution; the adhesive solution is mixed with active material and conductive material in a certain proportion to obtain a mixed slurry; the mixed slurry is uniformly coated on the current collector and dried at a certain temperature to form the functional adhesive with a spatial network structure on the current collector.

2. The preparation method according to claim 1, characterized in that, The first solvent is selected from organic polar solvents or organic nonpolar solvents; and / or, the initiator is azobisisobutyronitrile; And / or, the second solvent is selected from ethylene glycol dimethyl ether.

3. The preparation method according to claim 2, characterized in that, The first solvent includes at least one of alkanes, aromatic hydrocarbons, ethers, haloalkanes, and tetrahydrofuran.

4. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of polyethyleneimine to isocyanate methacrylate is (0.5-1.0):1.

0.

5. The preparation method according to claim 1, characterized in that, The molar ratio of isocyanate methacrylate to diallyl disulfide is 1:(0.25-0.5).

6. The preparation method according to claim 1, characterized in that, In step (2), the molar ratio of diallyl disulfide to the initiator is (1.5 to 2.5):

1.

7. The preparation method according to claim 1, characterized in that, In step (2), the binder solution accounts for 1% to 20% of the total amount of the mixed slurry.

8. The preparation method according to claim 1, characterized in that, In step (2), the drying reaction is carried out at a temperature of 50℃ to 70℃ for 8h to 12h.

9. The application of the functional binder prepared by the preparation method according to any one of claims 1-8 in lithium-sulfur batteries.

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