Sulfonyl-containing high-voltage-resistant positive electrode adhesive, preparation method thereof, battery positive electrode and lithium ion battery

Abstract

The invention discloses a sulfonyl-containing high-voltage-resistant positive electrode adhesive, a preparation method thereof, a battery positive electrode and a lithium ion battery, and belongs to the technical field of lithium batteries. The adhesive is a random copolymer of an acrylonitrile monomer, a sulfonyl-containing monomer and poly (ethylene glycol) methyl ether methacrylate, the sulfonyl-containing monomer has excellent oxidation resistance, can assist in forming CEI rich in inorganic components, and is beneficial to maintaining the structural stability and electrochemical stability of the CEI in the cyclic process; acrylonitrile can improve the adhesion and stabilize the surface structure of the positive electrode active material; by adding poly (ethylene glycol) methyl ether methacrylate, the flexibility of the polymer can be improved, and stress generated by volume change in the long-term charging and discharging process can be buffered. The sulfonyl-containing high-voltage-resistant positive electrode functional adhesive can effectively regulate and control CEI components, inhibits interface side reactions, and effectively improves the cycling stability of a high-voltage positive electrode battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium batteries, and particularly relates to a high-voltage resistant cathode binder containing sulfonyl groups, a preparation method thereof, a battery cathode, and a lithium-ion battery. Background Art

[0002] With the progress of technology and the demand for sustainable development, lithium-ion batteries are widely used in fields such as mobile phones, laptops, and electric vehicles. People's demand for long battery life of lithium-ion batteries is increasing continuously, and improving the energy density of lithium-ion batteries has become the only way. Improving the theoretical specific capacity of active materials or increasing the working voltage of cathode materials can effectively improve the energy density. Currently, researchers are working hard to develop high-voltage cathode materials to promote the improvement of the energy density of lithium-ion batteries. However, in a high working voltage environment, lithium-ion batteries face serious capacity attenuation and poor capacity retention.

[0003] The serious capacity attenuation of lithium-ion batteries at high voltages is mainly caused by the serious side reactions between the cathode active material and the electrolyte interface. When a lithium-ion battery is cycled at a high voltage (≥4.3V), organic solvents and lithium salts represented by carbonate electrolytes will undergo side reactions such as oxidative ring-opening and decomposition, and produce polycarbonate oligomers, species with lower fluorine content, and free radicals, etc. These by-products will deposit on the surface of the cathode active material to form an uneven and discontinuous solid electrolyte interface layer (CEI). In subsequent cycling processes, on the one hand, the electrolyte will continuously contact the highly oxidized active material through the uneven and discontinuous CEI, accelerating the oxidative decomposition of the electrolyte. On the other hand, the formed CEI is rich in organic components and is not resistant to high voltage, and will undergo oxidative decomposition. Over time, the dynamic formation and reconstruction process of CEI will lead to continuous attenuation of the battery capacity.

[0004] To solve the problem of interface side reactions at high voltages, a common strategy is electrolyte modification. For example, in CN118800965A, the antioxidant ability and high-voltage stability of the electrolyte are improved by designing high-voltage resistant electrolyte components, thereby reducing the occurrence of interface side reactions. CN117497855A discloses a high-voltage resistant electrolyte, in which additives can form a dense and uniform CEI film on the cathode surface, effectively preventing and inhibiting the oxidative decomposition of the electrolyte, and improving the interface stability at high voltages.

[0005] However, there is less research on traditional binders in regulating the CEI components and inhibiting interface side reactions. As an important component of the electrode, the binder can adhere the active material and the conductive agent to the current collector, and ensure the processability of the electrode sheet and the structural stability during the cycling process. The traditional commercial binder polyvinylidene fluoride (PVDF) adheres to the components of the electrode through weak van der Waals forces, cannot form a uniform and continuous CEI, and cannot effectively maintain the integrity of the electrode structure during long cycling.

[0006] Therefore, there is an urgent need for a high-voltage-resistant adhesive that can regulate the composition and modulus of the CEI, induce a stable and uniform CEI interface through the adhesive, inhibit interfacial side reactions under high voltage, and improve the cycle stability of lithium-ion batteries. SUMMARY OF THE INVENTION

[0007] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a sulfonyl group-containing high-voltage-resistant cathode adhesive, a preparation method thereof, a battery cathode, and a lithium-ion battery, so as to solve the technical problems such as the inability of the cathode adhesive in the prior art to effectively improve the CEI composition and inhibit interfacial side reactions.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions: A sulfonyl group-containing high-voltage-resistant cathode adhesive, wherein the cathode adhesive is a poly(acrylonitrile-sulfonyl group-containing monomer-poly(ethylene glycol) methyl ether methacrylate) copolymer, and the structural formula is:

[0009] Among them, n is 8, m is 90-95, p is 1-5, q is 1-5, and m, p, and q are all natural numbers; R is a sulfonyl group-containing repeating unit.

[0010] A further improvement of the present invention lies in: Preferably, the sulfonyl group-containing repeating unit is one or more of the following structural formulas: .

[0011] Preferably, when p is 2 or more, each R is the same or different.

[0012] The preparation method of the above-mentioned sulfonyl group-containing high-voltage-resistant cathode adhesive includes the following steps: Step 1, dissolve acrylonitrile monomer, a sulfonyl group-containing reaction raw material monomer, and poly(ethylene glycol) methyl ether methacrylate in N,N-dimethylformamide according to a molar ratio of (90-95):(1-5):(1-5), and stir evenly to form a reaction system A; Step 2, add an initiator to the reaction system A to form a reaction system B; Step 3, heat up the reaction system B to carry out a polymerization reaction to generate a reaction system C; Step 4, obtain a precipitate from the reaction system C, wash and dry the precipitate to obtain a poly(acrylonitrile-sulfonyl group-containing monomer-poly(ethylene glycol) methyl ether methacrylate) copolymer, which is the cathode adhesive.

[0013] Preferably, in step 1, the reaction raw material monomer containing a sulfonyl group is any one or more of vinylsulfonyl fluoride, 1-methylvinylsulfonyl fluoride, 1-propene-1-sulfonyl fluoride, 2-propene-1-sulfonyl fluoride, 2-butene-1-sulfonyl fluoride, 3-butene-1-sulfonyl fluoride, 2-methyl-2-propene-1-sulfonyl fluoride, 4-pentene-1-sulfonyl fluoride, 3-vinylbenzene-1-sulfonyl fluoride, 4-vinylbenzene-1-sulfonyl fluoride, and 4-butenylbenzene-1-sulfonyl fluoride.

[0014] Preferably, in step 1, the total solid mass content of acrylonitrile monomer, sulfonyl group-containing monomer, and poly(ethylene glycol) methyl ether methacrylate in N, N-dimethylformamide is 20-80%.

[0015] Preferably, in step 2, the addition amount of the initiator is 0.5-1.2% of the sum of the masses of acrylonitrile monomer, sulfonyl group-containing monomer, and poly(ethylene glycol) methyl ether methacrylate.

[0016] Preferably, in step 3, the polymerization reaction temperature is 60-70 °C, and the polymerization reaction time is 8-12 hours.

[0017] In step 4, a mixture of methanol and water is added to reaction system C to obtain a precipitate.

[0018] A battery positive electrode includes a current collector and a positive electrode paste attached to the current collector. The positive electrode paste includes a positive electrode active material, a conductive additive, and a binder, and the binder is the positive electrode binder described in claim 1.

[0019] A lithium-ion battery includes the above-mentioned battery positive electrode, a negative electrode, and a separator.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a high-voltage-resistant cathode binder containing sulfonyl groups. The binder is a random copolymer of acrylonitrile monomer, sulfonyl group-containing monomer, and poly(ethylene glycol) methyl ether methacrylate. The sulfonyl group-containing monomer has excellent antioxidant properties and can assist in forming a CEI rich in inorganic components on the cathode surface. The inorganic components are lithium fluoride and lithium nitride, and the inorganic components have good antioxidant properties and modulus, which helps to maintain the electrochemical stability and structural stability of the CEI during cycling. A large number of cyano groups in acrylonitrile can form coordination interactions with transition metal ions in the cathode material. On the one hand, it can improve the adhesion, help the binder to uniformly coat the surface of the active material, reduce the contact between the active material and the electrolyte, thereby inhibiting interfacial side reactions. On the other hand, it can inhibit the dissolution of transition metal ions and stabilize the surface structure of the cathode active material. The addition of poly(ethylene glycol) methyl ether methacrylate can improve the flexibility of the polymer. The high mechanical property binder is beneficial to buffering the stress generated by the volume change of the cathode active material during long-term charge and discharge processes, thereby maintaining the structural integrity of the electrode sheet and the integrity of the internal conductive network. The present invention combines the high-voltage-resistant advantages of acrylonitrile and sulfonyl group-containing monomers, making the finally synthesized random copolymer have excellent high-voltage-resistant performance, suitable for working voltages of 4.3 V and above. Moreover, the binder of the present invention can effectively regulate the CEI components and modulus, inhibit interfacial side reactions under high voltages, and improve the cycle stability of the battery under high voltages.

[0021] The present invention discloses a preparation method of a cathode binder. In the first step of this preparation method, acrylonitrile monomer, sulfonyl group-containing monomer, and poly(ethylene glycol) methyl ether methacrylate are dissolved in N, N-dimethylformamide, and free radicals are generated by an initiator under the condition of 60-70 °C, and a random copolymer is generated through free radical polymerization. The synthesis method is simple and has strong adhesion.

[0022] The present invention discloses a battery cathode. The cathode includes the prepared high-voltage-resistant cathode binder containing sulfonyl groups. After assembling a button battery with the cathode prepared by this binder, it exhibits good discharge specific capacity and cycle stability.

[0023] The present invention also discloses a lithium-ion battery. After the lithium-ion battery using the high-voltage-resistant cathode binder containing sulfonyl groups of the present invention is cycled 100 weeks at 0.5 C, the capacity retention rate is above 99%; after being cycled 200 weeks at 1 C, the capacity retention rate is about 82%. Description of the Drawings

[0024] Figure 1 It is the NMR spectrum of the binder in Example A5 ( 1 H NMR) Figure 2 It is a comparison chart of the peel strength of the lithium-ion battery cathode sheets of the binder A5 in Application Example 5 and the binder B1 in Comparative Example 1.

[0025] Figure 3 XPS spectrum of the positive electrode sheet prepared with binder A5 in Application Example 5 before cycling.

[0026] Figure 4 LSV curves of binder A5 in Example 5 and the blank sample.

[0027] Figure 5 0.5C long cycle curve of the lithium-ion battery half-cell prepared with binder A5 in Application Example 5 and binder B1 in the comparative example.

[0028] Figure 6 1C long cycle curve of the lithium-ion battery half-cell prepared with binder A5 in Application Example 5 and binder B1 in the comparative example.

[0029] Figure 7 Statistical chart of the CEI modulus on the surface of the electrode sheet after the electrode sheet prepared with binder A5 in Application Example 5 and binder B1 in the comparative example is activated at 0.1C for one week.

[0030] Figure 8 XPS spectrum of the surface of the electrode sheet after the electrode sheet prepared with binder A5 in Application Example 5 and binder B1 in the comparative example is activated at 0.1C for one week. Detailed implementation manners

[0031] The present invention will be further described in detail below with reference to the accompanying drawings: To enable those skilled in the art to understand the features and effects of the present invention, the following terms and expressions mentioned in the specification and claims will be generally described and defined. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art for the present invention. In case of conflict, the definition in this specification shall prevail.

[0032] In this article, unless otherwise specified, terms such as "comprising", "including", "containing", "having" or similar expressions cover the meanings of "consisting of" and "mainly consisting of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A only comprises a".

[0033] The present invention will be further illustrated with specific examples below. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0034] Conventional instruments and equipment in the art are used in the following examples. For the experimental methods without specific conditions noted in the following examples, they are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer. Various raw materials are used in the following examples. Unless otherwise stated, commercially available products are used, and their specifications are the conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0035] The first aspect of the present invention discloses a high-pressure resistant cathode binder containing a sulfonyl group. The binder is a random copolymer of acrylonitrile, a sulfonyl group-containing monomer, and poly(ethylene glycol) methyl ether methacrylate, poly(acrylonitrile - sulfonyl group-containing monomer - poly(ethylene glycol) methyl ether methacrylate), and its molecular structural formula is:

[0036] Among them, n is 8, m is 90 - 95, p is 1 - 5, q is 1 - 5, and m, p, and q are all natural numbers. R is a sulfonyl group-containing repeating unit.

[0037] R is one or more sulfonyl group-containing repeating units, and its structural formula is shown in Table 1.

[0038] Furthermore, when p is 2 or more, each R is the same or different.

[0039] The sulfonyl group-containing reaction raw material monomers corresponding to the sulfonyl group-containing repeating units are vinylsulfonyl fluoride, 1-methylvinylsulfonyl fluoride, 1-propene-1-sulfonyl fluoride, 2-propene-1-sulfonyl fluoride, 2-butene-1-sulfonyl fluoride, 3-butene-1-sulfonyl fluoride, 2-methyl-2-propene-1-sulfonyl fluoride, 4-pentene-1-sulfonyl fluoride, 3-vinylbenzene-1-sulfonyl fluoride, 4-vinylbenzene-1-sulfonyl fluoride, 4-buteneylbenzene-1-sulfonyl fluoride. The structural formulas and names of the sulfonyl group-containing repeating units and the corresponding reaction raw material monomers are shown in Table 1 below.

[0040] Table 1 Structural formulas of the sulfonyl group-containing repeating unit R and structural formulas and names of the corresponding reaction raw material monomers

[0041] The second aspect of the present invention discloses a preparation method of a high-pressure resistant cathode binder containing a sulfonyl group. The preparation method includes the following steps: Step 1: Dissolve acrylonitrile monomer, reaction raw material monomer containing sulfonyl group, and poly(ethylene glycol) methyl ether methacrylate oligomer in N,N-dimethylformamide. The molar ratio of acrylonitrile monomer, monomer containing sulfonyl group, and poly(ethylene glycol) methyl ether methacrylate oligomer is (90 - 95):(1 - 5):(1 - 5). Stir evenly to form reaction system A. In this step, to ensure that the binder can effectively adhere each component of the electrode to the current collector without the occurrence of active material shedding and powdering, the molar proportion of acrylonitrile in the reactants is increased to 90% or more, and adhesion is provided through the coordination between the cyano group and transition metal elements. While the adhesion performance of the monomer containing sulfonyl group and poly(ethylene glycol) methyl ether methacrylate is poor, the sum of their molar ratios does not exceed 10%.

[0042] Step 2: Add an initiator to reaction system A, deoxygenate reaction system A, and introduce a protective gas to form reaction system B. Step 3: Heat reaction system B to 60 - 70 °C and maintain for 8 - 12 hours to carry out a polymerization reaction to form reaction system C. The principle of this polymerization reaction is free radical polymerization. Under heating conditions, the initiator decomposes to generate free radicals, the free radicals open the double bonds in the monomer molecules and quickly add, and form a macromolecular active center to initiate the next reaction. Eventually, the polymer chain continuously grows to form a random copolymer, and the monomers are randomly arranged in the polymer macromolecular chain.

[0043] Step 4: Drop reaction system C into a mixed solution of methanol and water for sedimentation to obtain an insoluble precipitate. Wash the precipitate multiple times and then dry it under vacuum to constant weight to obtain a poly(acrylonitrile - monomer containing sulfonyl group - poly(ethylene glycol) methyl ether methacrylate) random copolymer binder.

[0044] In some embodiments of the present invention, in Step 1, the reaction raw material monomer containing sulfonyl fluoride is one or more of vinylsulfonyl fluoride, 1-methylvinylsulfonyl fluoride, 1-propene-1-sulfonyl fluoride, 2-propene-1-sulfonyl fluoride, 2-butene-1-sulfonyl fluoride, 3-butene-1-sulfonyl fluoride, 2-methyl-2-propene-1-sulfonyl fluoride, 4-pentene-1-sulfonyl fluoride, 3-vinylbenzene-1-sulfonyl fluoride, 4-vinylbenzene-1-sulfonyl fluoride, 4-buteneylbenzene-1-sulfonyl fluoride.

[0045] In some embodiments of the present invention, in Step 1, the total solid mass content of the three raw materials in the N,N-dimethylformamide solution is 20 - 80%.

[0046] In some embodiments of the present invention, in Step 1, the average molecular weight of the poly(ethylene glycol) methyl ether methacrylate oligomer is about 475.

[0047] In some embodiments of the present invention, in step 2, the initiator is an azo initiator: azobisisobutyronitrile, azobisisoheptonitrile or dimethyl azobisisobutyrate.

[0048] In some embodiments of the present invention, in step 2, the addition amount of the initiator is 0.5 - 1.2% of the sum of the masses of acrylonitrile monomer, sulfonyl group-containing monomer and poly(ethylene glycol) methyl ether methacrylate oligomer; In some embodiments of the present invention, in step 2, the protective gas is nitrogen or argon.

[0049] In some embodiments of the present invention, in step 2, the process of removing oxygen by the protective gas is to repeat the method of liquid nitrogen freezing - vacuum pumping (3 min) - thawing - inert gas filling (3 min) three times to remove oxygen in the reaction system and prevent the failure of free radical polymerization. After deoxygenation, reaction system B is formed.

[0050] In some embodiments of the present invention, in step 4, in the mixed solution of methanol and water, the volume ratio of methanol to water can be adjusted according to the actual situation, as long as it can ensure the formation of a precipitate. Exemplarily, the volume ratio can be 1:1, 1:2, 2:1 or other values.

[0051] In some embodiments of the present invention, in step 4, the drying temperature only needs to ensure that the precipitate can be completely dried.

[0052] The present invention also discloses a battery positive electrode, including a current collector and a lithium - ion battery positive electrode paste attached to the current collector. The lithium - ion battery positive electrode paste includes a positive active material, a conductive additive and a binder with a mass ratio of (75 - 95):(2.5 - 15):(2.5 - 15), and the binder is the above - mentioned positive electrode binder.

[0053] Preferably, the positive active material is a nickel - cobalt - manganese ternary material, lithium manganate, lithium cobaltate or lithium nickelate; the conductive additive is a carbon black - based conductive agent Super P, acetylene black or Ketjen black; among them, the nickel - cobalt - manganese ternary material is LiNi 0.8 Co 0.1 Mn 0.1 O2‌ (NCM811), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.5 Co 0.3 Mn 0.2 O2 (NCM532) or LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM111).

[0054] The present invention also discloses a lithium-ion battery, which includes the battery positive electrode prepared by the above operations. The lithium-ion battery includes a positive electrode, a negative electrode, an electrolyte, a separator, and positive and negative electrode cases. The positive electrode includes a positive electrode active material, a binder, a conductive agent, and a current collector.

[0055] In a specific embodiment of the present invention, a specific preparation process of a lithium-ion battery including the above binder is also disclosed. Using a nickel-cobalt-manganese ternary positive electrode (NCM811) as the positive electrode of the lithium-ion battery, the specific preparation process includes the following steps: (1) After mixing the positive electrode active material, the conductive additive, and the binder according to a mass ratio of (75-95):(2.5-15):(2.5-15), uniformly disperse them into N, N-dimethylformamide by a planetary ball mill to obtain a uniformly dispersed positive electrode slurry.

[0056] (2) Uniformly coat the slurry obtained in (1) onto a 5-micron-thick aluminum foil by an automatic coater, with the coating thickness of the slurry being 150 microns. Then place the electrode in a vacuum oven overnight to obtain a dried positive electrode sheet with the solvent removed.

[0057] (3) Cut the area where the slurry is uniformly covered on the positive electrode sheet obtained in (2) into positive electrode sheets with a diameter of 12 mm by a cutting machine, and weigh the mass of the electrode sheets with a diameter of 12 mm.

[0058] (4) Assemble the electrode sheets obtained in (3) into 2032 coin-type half-cells in a glove box filled with argon. The negative electrode is matched with lithium metal, the separator is a Celgard2325 polypropylene-polyethylene-polypropylene membrane (PP-PE-PP), and the electrolyte is a mixed solution of fluorinated ethylene carbonate (FEC) and diethyl carbonate (DEC) (volume ratio of 1:2) containing 0.6 M lithium difluorooxalate borate (LiDFOB) and 0.6 M lithium tetrafluoroborate (LiBF4).

[0059] (5) Perform electrochemical performance tests on the coin-type half-cells obtained in (4) within a voltage range of 3-4.3 V. The test environment is room temperature. The 0.5C long cycle test procedure is to stand for 8 h - cycle activation at 0.1C rate for 3 weeks - charge and discharge cycles at 0.5C rate, and the 1C long cycle test procedure is to stand for 8 h - cycle activation at 0.1C rate for 3 weeks - charge and discharge cycles at 1C rate. Here, 1C is 180 mAh / g.

[0060] The following is further illustrated with specific embodiments.

[0061] Comparative Example Take the commercial binder polyvinylidene fluoride (PVDF) as the control sample B1, apply it to the positive electrode and assemble a lithium-ion battery according to the above method. The preparation process is as follows: (1) NCM811, Super P, and PVDF were mixed in a mass ratio of 80:10:10 and then uniformly dispersed in N-methylpyrrolidone by a planetary ball mill to obtain a uniformly dispersed positive electrode slurry.

[0062] (2) The slurry obtained in (1) was uniformly coated onto a 5-μm-thick aluminum foil by an automatic coater with a coating thickness of 150 μm. Then, the electrode was placed in a vacuum oven overnight to obtain a dried positive electrode sheet with the solvent removed.

[0063] (3) The area on the positive electrode sheet obtained in (2) where the slurry was uniformly covered was cut into positive electrode sheets with a diameter of 12 mm by a cutting machine, and the mass of the 12-mm-diameter electrode sheets was weighed.

[0064] (4) The electrode sheets obtained in (3) were assembled into 2032 coin-type half-cells in a glove box filled with argon. The negative electrode was matched with lithium metal, the separator was a Celgard 2325 polypropylene-polyethylene-polypropylene membrane (PP-PE-PP), and the electrolyte was a mixed solution of fluoroethylene carbonate (FEC) and diethyl carbonate (DEC) (volume ratio of 1:2) containing 0.6 M lithium difluorooxalate borate (LiDFOB) and 0.6 M lithium tetrafluoroborate (LiBF4).

[0065] (5) The coin-type half-cells obtained in (4) were subjected to electrochemical performance tests in a voltage range of 3 - 4.3 V at room temperature. The 0.5C long-cycle test procedure was to rest for 8 h - activate at a rate of 0.1C for 3 weeks - charge and discharge at a rate of 0.5C. The 1C long-cycle test procedure was to rest for 8 h - activate at a rate of 0.1C for 3 weeks - charge and discharge at a rate of 1C, where 1C is 180 mAh / g.

[0066] Example 1 (1) According to a molar ratio of 90:5:5, 4.77 g (90 mmol) of acrylonitrile, 0.93 g (5 mmol) of 4-vinylbenzene-1-sulfonyl fluoride, and 2.376 g (5 mmol, average molecular weight of 475) of poly(ethylene glycol) methyl ether methacrylate were dissolved in 8.076 g of N, N-dimethylformamide and stirred well. The solid content of the mixed system was 50%.

[0067] (2) 81 mg of azobisisobutyronitrile initiator was added to (1), and the system was subjected to three cycles of liquid nitrogen freezing - vacuum pumping - thawing - inert gas filling for deoxygenation. The amount of the initiator was 1% of the total mass of the above three raw materials.

[0068] (3) The system obtained in (2) was heated to 60 °C and stirred for 12 h.

[0069] (4) The random copolymer obtained in (3) was precipitated with a mixed solution of methanol and water with a volume ratio of 1:1, washed three times with methanol solution, and transferred to a blast drying oven at 70 °C for drying to constant weight to obtain an acrylonitrile-(4-vinylbenzene-1-sulfonyl fluoride)-poly(ethylene glycol) methyl ether methacrylate random copolymer, and this adhesive is designated as A1.

[0070] The prepared A1 adhesive was prepared and applied to the positive electrode sheet according to the above method to assemble a lithium-ion battery, and its preparation method was as follows: After mixing NCM811, Super P and A1 in a mass ratio of 80:10:10, it was uniformly dispersed into N, N-dimethylformamide by a planetary ball mill to obtain a uniformly dispersed positive electrode paste. The paste obtained in (1) was uniformly coated on a 5-μm-thick aluminum foil by an automatic coater, and the coating thickness of the paste was 150 μm. Then the electrode was placed in a vacuum oven overnight to obtain a dried positive electrode sheet with the solvent removed.

[0071] The place where the paste was uniformly covered on the positive electrode sheet obtained in (2) was cut into a positive electrode sheet with a diameter of 12 mm by a cutting machine, and the mass of the electrode sheet with a diameter of 12 mm was weighed.

[0072] The electrode sheet obtained in (3) was assembled into a 2032 coin-type half-cell in a glove box filled with argon. Its negative electrode was matched with lithium metal, the separator was a Celgard 2325 polypropylene-polyethylene-polypropylene membrane (PP-PE-PP), and the electrolyte was a mixed solution of fluoroethylene carbonate (FEC) and diethyl carbonate (DEC) (volume ratio of 1:2) containing 0.6 M lithium difluorooxalate borate (LiDFOB) and 0.6 M lithium tetrafluoroborate (LiBF4).

[0073] The coin-type half-cell obtained in (4) was subjected to electrochemical performance tests in a voltage range of 3-4.3 V. The test environment was room temperature. The 0.5C long cycle test procedure was to rest for 8 h - activate at a 0.1C rate for 3 weeks - charge and discharge at a 0.5C rate. The 1C long cycle test procedure was to rest for 8 h - activate at a 0.1C rate for 3 weeks - charge and discharge at a 1C rate. Among them, 1C is 180 mAh / g.

[0074] Example 2 The preparation method and purification method of the acrylonitrile-(4-vinylbenzene-1-sulfonyl fluoride)-poly(ethylene glycol) methyl ether methacrylate random copolymer were the same as those in Example 1, but the molar ratio of acrylonitrile, 4-vinylbenzene-1-sulfonyl fluoride and poly(ethylene glycol) methyl ether methacrylate was 92.5:2.5:5. The prepared adhesive was labeled as A2.

[0075] Apply the prepared A2 to the positive electrode according to the above method and assemble a lithium-ion battery to test the cycle performance.

[0076] Example 3 The preparation method and purification method of acrylonitrile-(4-vinylbenzene-1-sulfonyl fluoride)-poly(ethylene glycol) methyl ether methacrylate random copolymer are the same as those in Example 1, but the molar ratio of acrylonitrile, 4-vinylbenzene-1-sulfonyl fluoride and poly(ethylene glycol) methyl ether methacrylate is 92.5:5:2.5. The prepared binder is labeled as A3.

[0077] Apply the prepared A3 to the positive electrode according to the above method and assemble a lithium-ion battery to test the cycle performance.

[0078] Example 4 The preparation method and purification method of acrylonitrile-(4-vinylbenzene-1-sulfonyl fluoride)-poly(ethylene glycol) methyl ether methacrylate random copolymer are the same as those in Example 1, but the molar ratio of acrylonitrile, 4-vinylbenzene-1-sulfonyl fluoride and poly(ethylene glycol) methyl ether methacrylate is 95:1:4. The prepared binder is labeled as A4.

[0079] Apply the prepared A4 to the positive electrode according to the above method and assemble a lithium-ion battery to test the cycle performance.

[0080] Example 5 (1) The preparation method and purification method of acrylonitrile-(4-vinylbenzene-1-sulfonyl fluoride)-poly(ethylene glycol) methyl ether methacrylate random copolymer are the same as those in Example 1, but the molar ratio of acrylonitrile, 4-vinylbenzene-1-sulfonyl fluoride to poly(ethylene glycol) methyl ether methacrylate is 95:2.5:2.5. Take 5.035 g (95 mmol) of acrylonitrile, 0.465 g (2.5 mmol) of 4-vinylbenzene-1-sulfonyl fluoride, 1.188 g (2.5 mmol, average molecular weight of 475) of poly(ethylene glycol) methyl ether methacrylate, and the amount of initiator is 67 mg, which is 1% of the total mass of the three raw materials. This binder is designated as A5. The measured NMR spectrum of A5 is as Figure 1 shown, where the peak at 7.94 ppm represents the hydrogen on the benzene ring, the peak at 3.50 ppm represents the hydrogen on the repeating segment of the poly(ethylene glycol) methyl ether methacrylate oligomer, the peak at 3.00 - 3.10 corresponds to the hydrogen on the polymer backbone, and the -C=CH2 at 5.50 and 6.00 ppm disappears, proving the successful synthesis of Example A5.

[0081] Prepare and apply the prepared A5 binder to the positive electrode sheet according to the above method, and assemble a lithium-ion battery for electrochemical performance testing.

[0082] Figure 2The 180° peel strength test of the positive electrode sheet prepared in Example 5 and the positive electrode sheet prepared in the comparative example is shown. From the perspective of peel strength, the average peel strength of the positive electrode sheet in Example 5 is 0.66 N / mm, which is higher than that of the positive electrode sheet in Example 1. Compared with the peel strength of the positive electrode sheet prepared from B1 in the comparative example (0.45 N / mm), it is increased by 1.5 times, indicating that the adhesive has excellent adhesion performance. From X-ray photoelectron spectroscopy (XPS) Figure 3 it can be seen that the cyano group forms a coordination interaction with transition metal ions, which is the source of excellent adhesion.

[0083] Figure 4 Figure 6 shows the LSV test curve of Example A5. The homopolymer adhesive prepared by polymerizing the sulfonyl group-containing monomer (poly(4-vinylbenzene-1-sulfonyl fluoride)) alone was subjected to LSV test, and it was found that it could maintain electrochemical inertness in the voltage range of 0-5V and did not undergo electrochemical decomposition, which was beneficial to improving the antioxidant performance of CEI and inhibiting interfacial side reactions. Adhesive A5 maintains electrochemical inertness in the voltage range of 5V and has excellent antioxidant performance.

[0084] Figure 5 Figure 7 shows the 0.5C cycle performance test of the positive electrode and lithium-ion battery prepared in the example and the positive electrode and lithium-ion battery prepared in the comparative example at room temperature. As Figure 5 shown, after 100 cycles of the half-cell in Example 5 and the half-cell in the comparative example, the half-cell in Example 5 still had a discharge specific capacity of 176.41 mAh·g -1 , and the capacity retention rate was 99.21%; while the half-cell in the comparative example only had a discharge specific capacity of 165.20 mAh·g -1 after 100 cycles, and the capacity retention rate was 92.30%.

[0085] Figure 6 Figure 8 shows the 1C cycle performance test of the positive electrode and lithium-ion battery prepared in Example 5 and the comparative example at room temperature. As Figure 6 shown, after 200 cycles of the half-cell in Example 5 and the half-cell in the comparative example, the half-cell in Example 5 still had a discharge specific capacity of 143.55 mAh·g -1 , and the capacity retention rate was 81.96%; while the comparative example only had a discharge specific capacity of 124.26 mAh·g -1 after 100 cycles, and the capacity retention rate was 69.93%.

[0086] Figure 7After the positive electrode sheets prepared in Example 5 and Comparative Example B1 were activated at 0.1C for one week, the CEI multi-point modulus was tested by atomic force microscopy (AFM) and the statistical data were obtained. The average Young's modulus of the electrode sheet prepared in Example 5 was 1.45 GPa, which was improved to a certain extent compared with the modulus of 1.21 GPa of the electrode sheet in the comparative example. Inorganic components have a relatively large Young's modulus, indicating that there are relatively more inorganic components in the electrode sheet of Example 5 after cycling. The CEI rich in inorganic components has good mechanical properties, which can effectively maintain the structural integrity of the CEI layer and inhibit interfacial side reactions. After a button half-cell was cycled for one week with the binder of poly(4-vinylbenzene-1-sulfonyl fluoride) containing sulfonyl groups, the average modulus of its CEI was high. A higher modulus indicates an increase in the proportion of inorganic components in the CEI formed with the assistance of sulfonyl groups. The CEI rich in inorganic components generally has good mechanical properties and antioxidant properties, which is beneficial to maintaining the structural stability of the CEI during cycling and reducing the rupture of the CEI.

[0087] Figure 8 X-ray photoelectron spectroscopy diagrams of the positive electrode sheets prepared with the binder of Example 5 and the binder of the comparative example after being activated at 0.1C for one week. After cycling, TM-O was not detected in the O 1s of the positive electrode sheet of Example 5, indicating that the CEI coating on the electrode surface is uniform; the LiF peak of the CEI component in the F 1s spectrum of the positive electrode sheet of Example 5 after cycling is stronger than that of the F 1s spectrum of the positive electrode sheet of the comparative example, and the Li3N component appears, indicating that there are more inorganic components in the CEI component, which is consistent with the modulus test results. It can be seen that the binder of the present invention effectively regulates the CEI components and modulus, thereby inhibiting interfacial side reactions and improving the capacity retention rate of lithium-ion batteries during long cycling at high voltage.

[0088] Example 6 The preparation method and purification method of acrylonitrile-(4-vinylbenzene-1-sulfonyl fluoride)-poly(ethylene glycol) methyl ether methacrylate random copolymer are the same as those in Example 1, but the molar ratio of acrylonitrile, 4-vinylbenzene-1-sulfonyl fluoride and poly(ethylene glycol) methyl ether methacrylate is 95:4:1. The prepared binder is labeled as A6.

[0089] The prepared A6 was applied to the positive electrode according to the above method and a lithium-ion battery was assembled to test the cycling performance.

[0090] Example 7 (1) Acrylonitrile, 2-propene-1-sulfonyl fluoride, and poly(ethylene glycol) methyl ether methacrylate were dissolved in N, N-dimethylformamide according to a molar ratio of 90:5:1 and stirred well. The solid content of the mixed system was 20%.

[0091] (2) 1.2% of azodiisobutyronitrile initiator was added to (1), and the nitrogen freezing-vacuum pumping-thawing-inert gas filling cycle was carried out three times for deoxygenation.

[0092] (3) Heat the system obtained in (2) to 65 °C and stir for reaction for 12 h.

[0093] (4) Precipitate the random copolymer obtained in (3) with a mixed solution of methanol and water with a volume ratio of 1:1, wash it three times with a methanol solution, transfer it to a blast drying oven at 70 °C and dry it to constant weight to obtain a pure acrylonitrile-(2-propene-1-sulfonyl fluoride)-poly(ethylene glycol) methyl ether methacrylate random copolymer. This binder is designated as A7.

[0094] Prepare the positive electrode with the prepared binder A7. The preparation method is to mix NCM811, acetylene black, and A7 obtained in step (4) according to a mass ratio of 70:15:15, uniformly disperse them into N,N-dimethylformamide by a planetary ball mill to obtain a uniform slurry, and the remaining steps are to prepare a half-cell according to Example 1 and conduct an electrochemical performance test.

[0095] Example 8 (1) Dissolve acrylonitrile, 1-methylvinylsulfonyl fluoride, and poly(ethylene glycol) methyl ether methacrylate in N,N-dimethylformamide according to a molar ratio of 90:5:1 and stir well. The solid content of the mixed system is 30%.

[0096] (2) Add 1.1% of azodiisooctanenitrile initiator to (1), and conduct three cycles of liquid nitrogen freezing - vacuum pumping - thawing - inert gas filling for deoxygenation.

[0097] (3) Heat the system obtained in (2) to 65 °C and stir for reaction for 11 h.

[0098] (4) Precipitate the random copolymer obtained in (3) with a mixed solution of methanol and water with a volume ratio of 1:1, wash it three times with a methanol solution, transfer it to a blast drying oven at 70 °C and dry it to constant weight to obtain a pure acrylonitrile-(1-methylvinylsulfonyl fluoride)-poly(ethylene glycol) methyl ether methacrylate random copolymer. This binder is designated as A8.

[0099] Prepare the positive electrode with the prepared binder A8. The preparation method is to mix NCM811, acetylene black, and A8 obtained in step (4) according to a mass ratio of 75:10:15, uniformly disperse them into N,N-dimethylformamide by a planetary ball mill to obtain a uniform slurry, and the remaining steps are to prepare a half-cell according to Example 1 and conduct an electrochemical performance test.

[0100] Example 9 (1)Dissolve acrylonitrile, 4-pentene-1-sulfonyl fluoride, and poly(ethylene glycol) methyl ether methacrylate in N, N-dimethylformamide in a molar ratio of 90:5:3 and stir well to make the solid content of the mixed system 30%.

[0101] (2)Add 1.0% of azodiisooctanenitrile initiator to (1), and perform the liquid nitrogen freezing-vacuum pumping-thawing-inert gas filling cycle three times for deoxygenation.

[0102] (3)Heat the system obtained in (2) to 65 °C and stir and react for 10 h.

[0103] (4)Precipitate the random copolymer obtained in (3) with a mixed solution of methanol and water with a volume ratio of 1:1, wash it three times with methanol solution, transfer it to a 70 °C blast drying oven and dry it to constant weight to obtain a pure acrylonitrile-(4-pentene-1-sulfonyl fluoride)-poly(ethylene glycol) methyl ether methacrylate random copolymer, and this adhesive is designated as A9.

[0104] Prepare the positive electrode with the prepared adhesive A9. The preparation method is to mix NCM622, acetylene black, and A9 obtained in step (4) in a mass ratio of 75:10:15, and uniformly disperse them into N, N-dimethylformamide through a planetary ball mill to obtain a uniform slurry. The remaining steps are to prepare a half-cell according to Example 1 and conduct electrochemical performance tests.

[0105] Example 10 (1)Dissolve acrylonitrile, 3-butene-1-sulfonyl fluoride, and poly(ethylene glycol) methyl ether methacrylate in N, N-dimethylformamide in a molar ratio of 90:1:5 and stir well to make the solid content of the mixed system 40%.

[0106] (2)Add 0.9% of azodiisooctanenitrile initiator to (1), and perform the liquid nitrogen freezing-vacuum pumping-thawing-inert gas filling cycle three times for deoxygenation.

[0107] (3)Heat the system obtained in (2) to 65 °C and stir and react for 10 h.

[0108] (4)Precipitate the random copolymer obtained in (3) with a mixed solution of methanol and water with a volume ratio of 1:1, wash it three times with methanol solution, transfer it to a 70 °C blast drying oven and dry it to constant weight to obtain a pure acrylonitrile-(3-butene-1-sulfonyl fluoride)-poly(ethylene glycol) methyl ether methacrylate random copolymer, and this adhesive is designated as A10.

[0109] Prepare the positive electrode with the prepared binder A10. The preparation method is to mix NCM532, acetylene black, and A10 obtained in step (4) in a mass ratio of 75:12.5:12.5, and uniformly disperse them into N, N-dimethylformamide through a planetary ball mill to obtain a uniform slurry. The remaining steps are to prepare a half-cell according to Example 1 and conduct an electrochemical performance test.

[0110] Example 11 (1) Dissolve acrylonitrile, 3-vinylbenzenesulfonyl fluoride, and poly(ethylene glycol) methyl ether methacrylate in N, N-dimethylformamide according to a molar ratio of 90:3:5 and stir well. The solid content of the mixed system is 50%.

[0111] (2) Add 0.8% of azodiisobutyronitrile initiator to (1), and conduct three cycles of liquid nitrogen freezing - vacuum pumping - thawing - inert gas filling for deoxygenation.

[0112] (3) Heat the system obtained in (2) to 65 °C and stir for 9 h.

[0113] (4) Use a mixed solution of methanol and water with a volume ratio of 1:1 to precipitate the random copolymer obtained in (3), wash it three times with methanol solution, transfer it to a 70 °C blast drying oven and dry it to constant weight to obtain a pure acrylonitrile-(3-vinylbenzenesulfonyl fluoride)-poly(ethylene glycol) methyl ether methacrylate random copolymer. This binder is designated as A11.

[0114] Prepare the positive electrode with the prepared binder A11. The preparation method is to mix lithium cobaltate, acetylene black, and A11 obtained in step (4) in a mass ratio of 75:12.5:12.5, and uniformly disperse them into N, N-dimethylformamide through a planetary ball mill to obtain a uniform slurry. The remaining steps are to prepare a half-cell according to Example 1 and conduct an electrochemical performance test.

[0115] Example 12 (1) Dissolve acrylonitrile, 4-butylenebenzenesulfonyl fluoride, and poly(ethylene glycol) methyl ether methacrylate in N, N-dimethylformamide according to a molar ratio of 90:3:5 and stir well. The solid content of the mixed system is 60%.

[0116] (2) Add 0.8% of azobisisobutyronitrile initiator to (1), and conduct three cycles of liquid nitrogen freezing - vacuum pumping - thawing - inert gas filling for deoxygenation.

[0117] (3) Heat the system obtained in (2) to 65 °C and stir for 9 h.

[0118] (4) The random copolymer obtained in (3) was precipitated with a mixed solution of methanol and water with a volume ratio of 1:1, washed three times with a methanol solution, and transferred to a blast drying oven at 70 °C for drying to constant weight to obtain a pure acrylonitrile-(4-butene-1-sulfonyl fluoride)-poly(ethylene glycol) methyl ether methacrylate random copolymer, and this adhesive is designated as A12.

[0119] The prepared adhesive A12 was used to prepare the positive electrode. The preparation method was that lithium manganate, Ketjenblack, and A12 obtained in step (4) were mixed in a mass ratio of 80:10:10, and uniformly dispersed in N,N-dimethylformamide by a planetary ball mill to obtain a uniform slurry. The remaining steps were the same as those in Example 1 to prepare a half-cell and conduct electrochemical performance tests.

[0120] Example 13 (1) Acrylonitrile, (vinylsulfonyl fluoride and 4-pentene-1-sulfonyl fluoride), and poly(ethylene glycol) methyl ether methacrylate were dissolved in N,N-dimethylformamide in a molar ratio of 92:3:5 and stirred thoroughly. The solid content of the mixed system was 60%.

[0121] (2) 0.7% of azobisisobutyronitrile initiator was added to (1), and the system was subjected to three cycles of liquid nitrogen freezing-vacuum pumping-thawing-inert gas filling for deoxygenation.

[0122] (3) The system obtained in (2) was heated to 70 °C and stirred for reaction for 9 h.

[0123] (4) The random copolymer obtained in (3) was precipitated with a mixed solution of methanol and water with a volume ratio of 1:1, washed three times with a methanol solution, and transferred to a blast drying oven at 70 °C for drying to constant weight to obtain a pure acrylonitrile-vinylsulfonyl fluoride-(4-pentene-1-sulfonyl fluoride)-poly(ethylene glycol) methyl ether methacrylate random copolymer, and this adhesive is designated as A13.

[0124] The prepared adhesive A13 was used to prepare the positive electrode. The preparation method was that lithium manganate, acetylene black, and A13 obtained in step (4) were mixed in a mass ratio of 80:10:10, and uniformly dispersed in N,N-dimethylformamide by a planetary ball mill to obtain a uniform slurry. The remaining steps were the same as those in Example 1 to prepare a half-cell and conduct electrochemical performance tests.

[0125] Example 14 (1) Acrylonitrile, (3-butene-1-sulfonyl fluoride, 4-pentene-1-sulfonyl fluoride, and 4-butene-1-sulfonyl fluoride), and poly(ethylene glycol) methyl ether methacrylate were dissolved in N,N-dimethylformamide in a molar ratio of 92:3:5 and stirred thoroughly. The solid content of the mixed system was 70%.

[0126] (2) Add 0.6% of isobutyl azobisisobutyrate initiator to (1), and conduct three cycles of liquid nitrogen freezing - vacuum pumping - thawing - inert gas filling for deoxygenation.

[0127] (3) Heat the system obtained in (2) to 70 °C and stir - react for 9 h.

[0128] (4) Use a mixed solution of methanol and water with a volume ratio of 1:1 to precipitate the random copolymer obtained in (3), wash it three times with methanol solution, transfer it to a 70 °C forced - air drying oven and dry it to a constant weight to obtain a pure acrylonitrile - (3 - butene - 1 - sulfonyl fluoride)-(4 - pentene - 1 - sulfonyl fluoride)-(4 - butenylbenzene - 1 - sulfonyl fluoride)-poly(ethylene glycol) methyl ether methacrylate random copolymer. This adhesive is designated as A14.

[0129] Prepare the positive electrode with the prepared adhesive A14. The preparation method is to mix lithium nickelate, Super P, and A14 obtained in step (4) in a mass ratio of 85:5:10, uniformly disperse them into N, N - dimethylformamide by a planetary ball mill to obtain a uniform slurry, and the remaining steps are to prepare a half - cell according to Example 1 and conduct electrochemical performance tests.

[0130] Example 15 (1) Dissolve acrylonitrile, (4 - vinylbenzene - 1 - sulfonyl fluoride, 4 - pentene - 1 - sulfonyl fluoride, 3 - butene - 1 - sulfonyl fluoride, and 2 - acryloyl - 1 - sulfonyl fluoride), and poly(ethylene glycol) methyl ether methacrylate in N, N - dimethylformamide according to a molar ratio of 92:5:3 and stir well. The solid content of the mixed system is 80%.

[0131] (2) Add 0.5% of isobutyl azobisisobutyrate initiator to (1), and conduct three cycles of liquid nitrogen freezing - vacuum pumping - thawing - inert gas filling for deoxygenation.

[0132] (3) Heat the system obtained in (2) to 70 °C and stir - react for 9 h.

[0133] (4) Use a mixed solution of methanol and water with a volume ratio of 1:1 to precipitate the random copolymer obtained in (3), wash it three times with methanol solution, transfer it to a 70 °C forced - air drying oven and dry it to a constant weight to obtain a pure acrylonitrile - (4 - vinylbenzene - 1 - sulfonyl fluoride)-(4 - pentene - 1 - sulfonyl fluoride)-(3 - butene - 1 - sulfonyl fluoride)-(2 - acryloyl - 1 - sulfonyl fluoride)-poly(ethylene glycol) methyl ether methacrylate random copolymer. This adhesive is designated as A15.

[0134] The prepared binder A15 was used to prepare the positive electrode. The preparation method was to mix lithium nickelate, Ketjen black, and A15 obtained in step (4) in a mass ratio of 85:5:10, and uniformly disperse them into N,N-dimethylformamide through a planetary ball mill to obtain a uniform slurry. The remaining steps were to prepare a half-cell according to Example 1 and conduct electrochemical performance tests.

[0135] Example 16 (1) Acrylonitrile, (4-butenylbenzene-1-sulfonyl fluoride, 4-penten-1-sulfonyl fluoride, 3-buten-1-sulfonyl fluoride, 2-propen-1-sulfonyl fluoride, and vinylsulfonyl fluoride), and poly(ethylene glycol) methyl ether methacrylate were dissolved in N,N-dimethylformamide according to a molar ratio of 92:5:3 and stirred thoroughly to be uniform. The solid content of the mixed system was 50%.

[0136] (2) 0.5% of azobisisobutyronitrile initiator was added to (1), and the system was subjected to three cycles of liquid nitrogen freezing - vacuum pumping - thawing - inert gas filling for deoxygenation.

[0137] (3) The system obtained in (2) was heated to 70 °C and stirred and reacted for 8 h.

[0138] (4) The random copolymer obtained in (3) was precipitated with a mixed solution of methanol and water with a volume ratio of 1:1, washed three times with a methanol solution, and transferred to a 70 °C blast drying oven for drying to constant weight to obtain an acrylonitrile-(4-butenylbenzene-1-sulfonyl fluoride)-(4-penten-1-sulfonyl fluoride)-(3-buten-1-sulfonyl fluoride)-(2-propen-1-sulfonyl fluoride)-(vinylbenzene sulfonyl fluoride)-poly(ethylene glycol) methyl ether methacrylate random copolymer, and this binder was designated as A16.

[0139] The prepared binder A16 was used to prepare the positive electrode. The preparation method was to mix MCN811, Super P, and A16 obtained in step (4) in a mass ratio of 90:5:5, and uniformly disperse them into N,N-dimethylformamide through a planetary ball mill to obtain a uniform slurry. The remaining steps were to prepare a half-cell according to Example 1 and conduct electrochemical performance tests.

[0140] Example 17 (1) Acrylonitrile, (4-butenylbenzene-1-sulfonyl fluoride, 4-vinylbenzene-1-sulfonyl fluoride, 4-penten-1-sulfonyl fluoride, 3-buten-1-sulfonyl fluoride, 2-propen-1-sulfonyl fluoride, and vinylsulfonyl fluoride), and poly(ethylene glycol) methyl ether methacrylate were dissolved in N,N-dimethylformamide according to a molar ratio of 92:5:3 and stirred thoroughly to be uniform. The solid content of the mixed system was 50%.

[0141] (2) Add 0.5% azobisisobutyronitrile initiator to (1), and conduct three cycles of liquid nitrogen freezing - vacuum pumping - thawing - inert gas filling for deoxygenation.

[0142] (3) Heat the system obtained in (2) to 70 °C and stir - react for 8 h.

[0143] (4) Use a mixed solution of methanol and water with a volume ratio of 1:1 to precipitate the random copolymer obtained in (3), wash it three times with methanol solution, transfer it to a 70 °C blast drying oven and dry it to constant weight to obtain pure acrylonitrile - (4 - butenylbenzene - 1 - sulfonyl fluoride) - (4 - vinylbenzene - 1 - sulfonyl fluoride) - (4 - pentene - 1 - sulfonyl fluoride) - (3 - butene - 1 - sulfonyl fluoride) - (2 - propene - 1 - sulfonyl fluoride) - (vinylbenzenesulfonyl fluoride) - poly(ethylene glycol) methyl ether methacrylate random copolymer, and this adhesive is denoted as A17.

[0144] Prepare the positive electrode with the prepared adhesive A17. The preparation method is to mix MCN811, Super P, and A17 obtained in step (4) in a mass ratio of 95:2.5:2.5, uniformly disperse them into N, N - dimethylformamide through a planetary ball mill to obtain a uniform slurry, and the remaining steps are to prepare a half - cell according to Example 1 and conduct electrochemical performance tests.

[0145] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A sulfonyl-containing high-voltage positive electrode binder, characterized in that: The positive electrode binder is a poly(acrylonitrile-sulfonyl-containing monomer-poly(ethylene glycol) methyl ether methacrylate) copolymer, and the structural formula is: Wherein, n is 8, m is 90-95, p is 1-5, q is 1-5, m, p and q are all natural numbers; and R is a sulfonyl-containing repeating unit.

2. The sulfonyl-containing high-voltage positive electrode binder according to claim 1, characterized in that: The sulfonyl-containing repeating unit is one or more of the following structural formulas: 。 3. The sulfonyl-containing high-voltage positive electrode binder according to claim 1, characterized in that: When p is 2 or more, each R is the same or different.

4. The method for preparing the sulfonyl-containing high-voltage positive electrode binder according to claim 1, characterized in that: The following steps are involved: Step 1, dissolving acrylonitrile monomer, a sulfonyl-containing reaction raw material monomer and poly(ethylene glycol) methyl ether methacrylate in N, N-dimethylformamide at a molar ratio of (90-95):(1-5):(1-5), and stirring to form a reaction system A; Step 2, adding an initiator to the reaction system A to form a reaction system B; Step 3, heating the reaction system B to cause a polymerization reaction to generate a reaction system C; Step 4: obtaining a precipitate from the reaction system C, washing and drying the precipitate to obtain a poly(acrylonitrile-sulfonyl-containing monomer-poly(ethylene glycol) methyl ether methacrylate) copolymer, which is a positive electrode binder.

5. The method for preparing a sulfonyl-containing high-voltage positive electrode binder according to claim 4, characterized in that: In step 1, the sulfonyl-containing reaction raw material monomer is any one or more of vinyl sulfonyl fluoride, 1-methylvinyl sulfonyl fluoride, 1-propylene-1-sulfonyl fluoride, 2-propylene-1-sulfonyl fluoride, 2-butene-1-sulfonyl fluoride, 3-butene-1-sulfonyl fluoride, 2-methyl-2-propylene-1-sulfonyl fluoride, 4-pentene-1-sulfonyl fluoride, 3-vinylbenzene-1-sulfonyl fluoride, 4-vinylbenzene-1-sulfonyl fluoride and 4-butenylbenzene-1-sulfonyl fluoride.

6. The method for preparing a sulfonyl-containing high-voltage positive electrode binder according to claim 4, characterized in that: In step 1, the total solid mass content of acrylonitrile monomer, sulfonyl group-containing monomer and poly(ethylene glycol) methyl ether methacrylate in N, N-dimethylformamide is 20-80%.

7. The method for preparing a sulfonyl-containing high-voltage positive electrode binder according to claim 4, characterized in that: In step 2, the amount of the initiator added is 0.5-1.2% of the sum of the mass of the acrylonitrile monomer, the sulfonyl group-containing monomer and the poly(ethylene glycol) methyl ether methacrylate.

8. The method for preparing a sulfonyl-containing high-voltage positive electrode binder according to claim 4, characterized in that: In step 3, the polymerization reaction temperature is 60-70° C., and the polymerization reaction time is 8-12 hours; In step 4, a mixture of methanol and water is added to the reaction system C to obtain a precipitate.

9. A positive electrode of a battery, characterized in that: The invention comprises a current collector and a positive electrode slurry attached to the current collector, wherein the positive electrode slurry comprises a positive electrode active material, a conductive additive and a binder, and the binder is the positive electrode binder according to claim 1.

10. A lithium ion battery, characterized in that: The battery comprises the positive electrode, negative electrode and separator as described in claim 9.

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