Fluorine-containing copolymer as well as preparation method and application thereof

Abstract

The invention provides a fluorine-containing copolymer as well as a preparation method and application thereof. The fluorine-containing copolymer comprises a structural unit A, a structural unit B and a structural unit C, wherein the structural unit A, the structural unit B and the structural unit C are shown in the specification. According to the invention, tetrafluoroethylene, vinylidene fluoride and carbon monoxide are copolymerized to obtain the fluorine-containing copolymer, so that the processing and bonding properties of the fluorine-containing copolymer are improved, and the problems of slow reaction and low molecular weight can be avoided.

Description

Technical Field

[0001] This invention relates to the field of polymer technology, and more specifically to a fluorinated copolymer, its preparation method, and its application. Background Technology

[0002] Fluoropolymers exhibit excellent high-temperature resistance, media resistance, aging resistance, weather resistance, oxidation resistance, dielectric properties, and low surface energy due to the low fluorine atom susceptibility, strong electronegativity, small van der Waals radius, and high carbon-fluorine bond energy (485 kJ / mol). They are widely used in petrochemical, construction, automotive, aerospace, and aviation industries.

[0003] Lithium-ion batteries are widely used in electric vehicles, portable electronic devices, and other fields due to their high voltage, high energy density, and lightweight properties. Polyvinylidene fluoride (PVDF), widely used as a binder for the positive electrode of lithium batteries, has also gained attention in recent years due to the rapid development of new energy vehicles, and its production capacity is expanding rapidly. However, during the preparation of a slurry by dissolving PVDF binder in N-methylpyrrolidone (NMP) and mixing it with high-nickel content electrode materials, increased viscosity and gelation occur, making stable application difficult. The fundamental reason is the low fluorine content (mol%) in PVDF, which fails to provide adequate shielding to prevent chemical corrosion. A conventional solution is to increase the fluorine content in the polymer, such as by copolymerizing tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and trifluoroethylene (TrFE) with PVDF to obtain polymers with higher fluorine content. However, with the increase in fluorine content, its processing and bonding properties deteriorate, failing to meet the requirements for manufacturing high-energy-density lithium-ion batteries. To address the aforementioned issues, patent WO2018066430 describes a method for adding a third monomer. Although this method improves the processing and bonding properties of the binder by introducing carboxyl groups through the addition of a modified monomer, in actual semi-continuous synthesis processes, the addition of the modified monomer can lead to slower reaction times and lower molecular weights. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a fluorinated copolymer, its preparation method and application.

[0005] In a first aspect, the present invention provides a fluorinated copolymer comprising structural unit A, structural unit B, and structural unit C.

[0006]

[0007] The inventors of this application have discovered that by introducing structural unit C into fluorinated copolymers, while ensuring that the fluorinated copolymers have a high fluorine content, the processing performance and bonding performance of the fluorinated copolymers can also be improved, thereby meeting the requirements for preparing high energy density batteries.

[0008] In some embodiments, the structural unit C accounts for x mol% of the fluorinated copolymer, where 0 < x ≤ 2.

[0009] In some implementations, x can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.4, 0.5, 0.8, 1.1, 1.4, 1.7, 2 or any value between them.

[0010] In some embodiments, the structural unit C accounts for x mol% of the fluorinated copolymer, 0 < x ≤ 1.

[0011] In some embodiments, the structural unit C accounts for x mol% of the fluorinated copolymer, 0 < x ≤ 0.5.

[0012] In some embodiments, the molar ratio between structural unit A and structural unit B is (75-90):(15-20); for example, 75:(15-20), 80:(15-20), 85:(15-20), 90:(15-20), (75-90):15, (75-90):17, (75-90):19 or any value between them.

[0013] In some embodiments, the molar ratio between structural unit A and structural unit C is (99-100):(0.05-1), for example (99-100):0.05, (99-100):0.1, (99-100):0.3, (99-100):0.5, (99-100):0.7, (99-100):0.9, 99:(0.05-1), 99.5:(0.05-1), 100:(0.05-1) or any value between them.

[0014] In some embodiments, the weight-average molecular weight of the fluorinated copolymer is 100 × 10⁻⁶. 4 g / mol - 150 × 10 4 g / mol, for example, 100 × 10 4 g / mol, 105×10 4 g / mol, 110×10 4 g / mol, 115×10 4 g / mol, 120×10 4 g / mol, 125×10 4g / mol, 130×10 4 g / mol, 135×10 4 g / mol, 140×10 4 g / mol, 145×10 4 g / mol, 150×10 4 g / mol or any value between them.

[0015] In some embodiments, the pre-compression peel strength of the fluorinated copolymer is 15-40 N / m, for example, 15 N / m, 20 N / m, 25 N / m, 30 N / m, 35 N / m, 40 N / m or any value between them.

[0016] In a second aspect, the present invention provides a method for preparing a fluorinated copolymer, comprising: copolymerizing a mixture of monomers comprising tetrafluoroethylene, vinylidene fluoride and carbon monoxide.

[0017] In some embodiments, the temperature of the copolymerization reaction is 50-160°C, for example 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C or any value between them.

[0018] In some embodiments, the copolymerization reaction is carried out at a temperature of 60-120°C.

[0019] In some embodiments, the copolymerization reaction pressure is 1.0-12.0 MPa, for example, 1.2 MPa, 1.5 MPa, 2 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, 11 MPa, 12 MPa, or any value between them.

[0020] In some embodiments, the copolymerization reaction is carried out at a pressure of 2.0-6.0 MPa.

[0021] In some embodiments, the copolymerization reaction is a batch polymerization reaction, a semi-continuous polymerization reaction, or a continuous polymerization reaction.

[0022] In some embodiments, the molar ratio of vinylidene fluoride to tetrafluoroethylene in the mixed monomers is (2-10):1; for example, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1 or any value between them.

[0023] In some embodiments, the molar ratio of tetrafluoroethylene to carbon monoxide in the mixed monomers is 1:(0.01-0.1); for example, 1:0.02, 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, 1:0.1 or any value between them.

[0024] In some embodiments, the molar ratio of tetrafluoroethylene, vinylidene fluoride, and carbon monoxide in the mixed monomers is (75-90):(12-20):(0.1-1), for example, 80:(12-20):(0.1-1), 85:(12-20):(0.1-1), 90:(12-20):(0.1-1), (75-90):15:(0.1-1), (75-90):17:(0.1-1), (75-90):20:(0.1-1), (75-90):(12-20):0.3, (75-90):(12-20):0.5, (75-90):(12-20):0.8, or any value between them.

[0025] In some embodiments, the initiator of the copolymerization reaction is one or more of an organic peroxide initiator, an inorganic peroxide initiator, or a redox initiator.

[0026] In some embodiments, the organic peroxide initiator is tert-butyl peroxide and / or peroxide dicarbonate.

[0027] In some embodiments, the peroxide dicarbonate is selected from diisopropyl peroxide dicarbonate.

[0028] In some embodiments, the inorganic peroxide initiator is one or more of potassium persulfate, ammonium persulfate, or sodium thiosulfate.

[0029] In some embodiments, the redox initiator is a system of benzoyl peroxide and N,N-dimethylaniline, potassium persulfate and sodium sulfite, etc.

[0030] In some embodiments, the initiator is ammonium persulfate and sodium thiosulfate.

[0031] In some embodiments, the copolymerization reaction is a free radical polymerization reaction.

[0032] In some embodiments, the copolymerization reaction is one of emulsion polymerization or suspension polymerization.

[0033] In some embodiments, the emulsifier for the copolymerization reaction is a fluorinated emulsifier or a non-fluorinated emulsifier.

[0034] In some embodiments, the fluorinated emulsifier is selected from C6-C14 fluorinated or perfluoroalkyl carboxylic acids, sulfuric acid, phosphoric acid, sulfonic acid and their salts, C6-C14 ether-modified fluorinated or perfluoroalkyl carboxylic acids, sulfuric acid, phosphoric acid, sulfonic acid and their salts, or polymeric emulsifiers.

[0035] In some embodiments, the fluorinated emulsifier has the following general formula:

[0036] C n F m O z H 2n-m+1 -R1R2

[0037] Where n = 6 - 14, z = 0 - 6, 1 ≤ m ≤ 2n + 1, and R1 is selected from COO. - SO4 - SO3 - HPO3 - Or ArSO3 - R2 is selected from H + NH4 + Or a monovalent metal cation.

[0038] In some embodiments, the monovalent metal cation is selected from K + and / or Na + .

[0039] In some embodiments, the fluorinated emulsifier is selected from ammonium perfluorooctanoate, perfluorooctanoic acid, perfluorooctyl sulfonic acid, perfluorohexanoic acid, and their salts.

[0040] In some embodiments, the polymeric emulsifier is selected from perfluorosulfonic acid resins, perfluorocarboxylic acid resins, perfluorosulfuric acid resins, and their salts.

[0041] In some embodiments, the non-fluorinated emulsifier is selected from ionic surfactants or nonionic surfactants.

[0042] In some embodiments, the ionic surfactant is selected from polyacrylic acid, polyacrylic acid copolymers, polyoxyethylene ethers and their salts.

[0043] In some embodiments, the nonionic surfactant is selected from polyvinyl alcohol-polyacryl alcohol block copolymers and / or Triton X100.

[0044] In some embodiments, the emulsifier is ammonium perfluorooctanoate.

[0045] In some embodiments, when the copolymerization reaction is an emulsion polymerization reaction, the molecular weight regulator of the copolymerization reaction is one or more of alkanes, esters, or halogenated hydrocarbons.

[0046] In some embodiments, when the copolymerization reaction is an emulsion polymerization reaction, the molecular weight regulator of the copolymerization reaction is one or more of ethane, ethyl acetate, diiodomethane, or diiodooctafluorobutane.

[0047] In some embodiments, when the copolymerization reaction is a suspension polymerization reaction, the dispersant for the copolymerization reaction is a cellulose dispersant and / or an inorganic dispersant.

[0048] In some embodiments, the dispersant is selected from one or more of hydroxypropyl methylcellulose, methylcellulose, or calcium hydroxyphosphate.

[0049] In some embodiments, the dispersant is hydroxypropyl methylcellulose.

[0050] In some embodiments, the mass concentration of the dispersant aqueous solution is 5-15%, for example, 5%, 7%, 9%, 11%, 13%, 15% or any value between them.

[0051] In some embodiments, the copolymerization reaction is carried out in a reaction vessel.

[0052] In some embodiments, the reactor is evacuated before the copolymerization reaction is carried out until the oxygen content is ≤30ppm.

[0053] In some embodiments, the preparation method further includes post-treatment: washing and drying the copolymer emulsion obtained from the copolymerization reaction.

[0054] In some embodiments, during the copolymerization process, mixed monomers need to be added until the solid content of the copolymer emulsion is 10-35%, for example, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34% or any value between them.

[0055] In some embodiments, the molar ratio of tetrafluoroethylene, vinylidene fluoride and carbon monoxide in the added mixed monomers is (75-90):(12-20):(0.1-1).

[0056] In some embodiments, the molar ratio of tetrafluoroethylene, vinylidene fluoride, and carbon monoxide in the added mixed monomers is the same as that in the initially added mixed monomers.

[0057] In some implementations, the amount of monomer used in the copolymerization reaction is related to the size of the reactor, and the amount of added mixed monomers is calculated using pressure drop.

[0058] In some implementations, a 50L reactor typically requires 10–15 kg of monomer.

[0059] In some embodiments, the preparation method includes the following steps:

[0060] 1) Add deionized water to the reactor and evacuate the reactor until the oxygen content is ≤30ppm;

[0061] 2) Add emulsifier to the reactor, heat to 50-160℃, add mixed monomers of vinylidene fluoride, tetrafluoroethylene and carbon monoxide, raise the pressure in the reactor to 1.0-12.0MPa, add initiator and start polymerization reaction, continuously add mixed monomers, maintain the pressure in the reactor at 1.0-12.0MPa, and obtain copolymer emulsion with a solid content of 20-35%;

[0062] 3) Remove unreacted monomers from the copolymer emulsion, then wash and dry.

[0063] In a third aspect, the present invention provides an adhesive comprising the fluorinated copolymer described in the first aspect of the present invention or the fluorinated copolymer obtained by the preparation method described in the second aspect of the present invention.

[0064] In a fourth aspect, the present invention provides the application of the binder described in the third aspect of the present invention in a secondary battery.

[0065] In some embodiments, the secondary battery is a lithium battery.

[0066] Compared with the prior art, the present invention has the following beneficial effects:

[0067] This invention obtains a new fluorinated copolymer by copolymerizing tetrafluoroethylene, vinylidene fluoride and carbon monoxide. Compared with traditional PVDF products, the fluorinated copolymer of this invention has good bonding properties and excellent processing properties. Attached Figure Description

[0068] Figure 1 The ATR-IR spectra of the fluoropolymer and PVDF in Example 1 of this invention are shown below.

[0069] Figure 2 The image shows the Tr-IR spectra of the fluoropolymer and PVDF in Example 1 of this invention. Detailed Implementation

[0070] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way.

[0071] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0072] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the reagents used in the following embodiments are conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained commercially or by existing methods; unless otherwise specified, the reagent dosages are those used in routine experimental operations; unless otherwise specified, the experimental methods are conventional methods.

[0073] The weight-average molecular weight in this invention can be determined by volume exclusion chromatography according to GB / T 36214 standard.

[0074] Example 1

[0075] The preparation of fluoropolymers using emulsion polymerization includes the following steps:

[0076] 1) Add 3L of deionized water to a 5L reactor and evacuate the reactor until the oxygen content is ≤30ppm;

[0077] 2) Add 3.5g of ammonium perfluorooctanoate as an emulsifier to the reactor, heat to 60℃, and add a mixed monomer containing vinylidene fluoride (VDF), tetrafluoroethylene (TFE), and carbon monoxide (CO). The monomer molar ratio is VDF:TFE:CO = 84.5:15:0.5. Increase the pressure in the reactor to 3.3MPa, add 0.2g of ammonium persulfate and 0.1g of sodium thiosulfate, and start the polymerization reaction. Continuously add the mixed monomer to maintain the pressure in the reactor at 3.3MPa. When the amount of mixed monomer added is 0.6kg, stop the reaction. At this time, the solid content of the VDF, TFE, and CO copolymer emulsion is 20%.

[0078] 3) Unreacted monomers were recovered, then washed, dried, and pulverized to obtain approximately 500g of white resin. Its ATR-IR spectrum is shown below. Figure 1 As shown, the Tr-IR spectrum is as follows Figure 2 As shown. According to Figure 1 and Figure 2 It can be seen that the obtained polymer is at 1680cm -1 The presence of a carbonyl absorption peak indicates the presence of CO in the polymer.

[0079] 4) The molecular weight of the obtained polymer was determined by volume exclusion chromatography, and the result was analyzed by carbon NMR spectroscopy. 13 The molar ratio of carbon monoxide in the polymer was determined by C-NMR. The results are shown in Table 1.

[0080] Example 2

[0081] Fluorinated copolymers are prepared by suspension polymerization, comprising the following steps:

[0082] 1) Add 3L of deionized water to a 5L reactor and evacuate the reactor until the oxygen content is ≤30ppm;

[0083] 2) Add 10g of hydroxypropyl methylcellulose (10wt% aqueous solution) as a dispersant to the reactor, heat to 60℃, and add a mixture of monomers including vinylidene fluoride (VDF), tetrafluoroethylene (TFE), and carbon monoxide (CO). The monomer molar ratio is VDF:TFE:CO = 84.5:15:0.5. Increase the pressure inside the reactor to 4.5MPa, add 3g of diisopropyl peroxide (50wt% hydrofluoroether solution) to start the polymerization reaction, and continue to add the mixed monomers to maintain the pressure inside the reactor at 4.8MPa. When the amount of mixed monomers added is 0.6kg, stop the reaction.

[0084] 3) Unreacted monomers were recovered, and after washing, drying and pulverizing, approximately 500g of white resin was obtained.

[0085] 4) The molecular weight of the obtained polymer was determined by volume exclusion chromatography.

[0086] Example 3

[0087] Unlike Example 1, in step (2), the monomer molar ratio VDF:TFE:CO = 84.5:15:1.

[0088] Example 4

[0089] Unlike Example 1, in step (2), the monomer molar ratio VDF:TFE:CO = 84.5:15:0.1.

[0090] Comparative Example 1

[0091] 1) Add 3L of deionized water to a 5L reactor and evacuate the reactor until the oxygen content is ≤30ppm;

[0092] 2) Add 3.5g of ammonium perfluorooctanoate as an emulsifier to the reactor, heat to 60℃, add mixed monomers of vinylidene fluoride (VDF) and tetrafluoroethylene (TFE) with a monomer molar ratio of VDF:TFE = 85:15, raise the pressure in the reactor to 3.3MPa, add 0.2g of ammonium persulfate and 0.1g of sodium thiosulfate and start the polymerization reaction. Continuously add mixed monomers to maintain the pressure in the reactor at 3.3MPa. When the amount of mixed monomers added is 0.6kg, the solid content of the emulsion is 20%, and the reaction is stopped.

[0093] 3) Unreacted monomers were recovered to obtain a VDF / TFE copolymer emulsion. Magnesium chloride was added to the reacted emulsion, followed by washing and oven drying to obtain approximately 500g of white resin.

[0094] 4) The molecular weight of the obtained polymer was determined by volume exclusion chromatography.

[0095] Comparative Example 2

[0096] Unlike Example 1, in step (2), VDF is not added and the monomer molar ratio TFE:CO = 15:0.5.

[0097] Comparative Example 3

[0098] Unlike Example 1, in step (2), TFE is not added and the monomer molar ratio VDF:CO = 84.5:0.5.

[0099] The polymers obtained in the above examples and comparative examples were formulated with NMP to form a 7 w / v% solution, and the NMP solubility of the polymers obtained in the above examples and comparative examples was tested.

[0100] Table 1

[0101]

[0102] As shown in Table 1, when the CO content is too high (Example 3), the solubility of the fluorinated copolymer in NMP decreases and the processing performance is reduced; when the CO content is too low (Example 4) or there is no CO (Comparative Example 1), the pre-press peel strength of the fluorinated copolymer decreases.

[0103] In summary, the fluorinated copolymer of this application has good bonding properties and excellent processing properties.

[0104] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A fluorinated copolymer, comprising the following structural unit A, structural unit B, and structural unit C, Structural unit A, Structural Unit B, Structural unit C.

2. The fluorinated copolymer according to claim 1, characterized in that, The structural unit C accounts for x mol% of the fluorinated copolymer, 0 < x ≤ 2, preferably 0 < x ≤ 1, more preferably 0 < x ≤ 0.5; and / or The molar ratio between structural unit A and structural unit B is (75–90):(15–20); and / or The molar ratio between structural unit A and structural unit C is (99–100):(0.05–1); and / or The weight-average molecular weight of the fluorinated copolymer is 100 × 10⁻⁶. 4 g / mol - 150 × 10 4 g / mol; and / or The pre-press peel strength of the fluorinated copolymer is 15-40 N / m.

3. A method for preparing a fluorinated copolymer, comprising: The mixture of monomers containing tetrafluoroethylene, vinylidene fluoride and carbon monoxide is copolymerized. Preferably, the copolymerization reaction is carried out at a temperature of 50-160°C, more preferably 60-120°C; and / or The copolymerization reaction is carried out at a pressure of 1.0-12.0 MPa, preferably 2.0-6.0 MPa; and / or The copolymerization reaction is a batch polymerization reaction, a semi-continuous polymerization reaction, or a continuous polymerization reaction; and / or In the mixed monomers, the molar ratio of vinylidene fluoride to tetrafluoroethylene is (2-10):1; and / or In the mixed monomers, the molar ratio of tetrafluoroethylene to carbon monoxide is 1:(0.01-0.1); Preferably, in the mixed monomers, the molar ratio of tetrafluoroethylene, vinylidene fluoride and carbon monoxide is (75-90):(12-20):(0.1-1).

4. The preparation method according to claim 3, characterized in that, The initiator for the copolymerization reaction is one or more of organic peroxide initiators, inorganic peroxide initiators, or redox initiators. Preferably, the organic peroxide initiator is tert-butyl peroxide and / or peroxide dicarbonate; preferably, the peroxide dicarbonate is selected from diisopropyl peroxide dicarbonate; and / or The inorganic peroxide initiator is one or more of potassium persulfate, ammonium persulfate, or sodium thiosulfate; and / or The redox initiator is selected from benzoyl peroxide and N,N-dimethylaniline, potassium persulfate and sodium sulfite.

5. The preparation method according to claim 3 or 4, characterized in that, The copolymerization reaction is a free radical polymerization reaction; Preferably, the copolymerization reaction is one of emulsion polymerization or suspension polymerization; Preferably, the emulsifier in the copolymerization reaction is a fluorinated emulsifier or a non-fluorinated emulsifier; Preferably, the fluorinated emulsifier is selected from C6-C14 fluorinated or perfluoroalkyl carboxylic acids, sulfuric acid, phosphoric acid, sulfonic acid and their salts, C6-C14 ether-modified fluorinated or perfluoroalkyl carboxylic acids, sulfuric acid, phosphoric acid, sulfonic acid and their salts, or polymer emulsifiers. Preferably, the fluorinated emulsifier has the following general formula: W n F m THE z H 2n-m+1 -R1R2 Where n = 6 - 14, z = 0 - 6, 1 ≤ m ≤ 2n + 1, and R1 is selected from COO. - SO4 - SO3 - HPO3 - Or ArSO3 - R2 is selected from H + NH4 + Or a monovalent metal cation; Preferably, the monovalent metal cation is selected from K. + and / or Na + ; Preferably, the fluorinated emulsifier is selected from ammonium perfluorooctanoate, perfluorooctanoic acid, perfluorooctyl sulfonic acid, perfluorohexanoic acid and their salts; and / or The polymeric emulsifier is selected from perfluorosulfonic acid resins, perfluorocarboxylic acid resins, perfluorosulfuric acid resins, and their salts; and / or The non-fluorinated emulsifier is selected from ionic surfactants or nonionic surfactants; Preferably, the ionic surfactant is selected from polyacrylic acid, polyacrylic acid copolymers, polyoxyethylene ethers and their salts; and / or The nonionic surfactant is selected from polyvinyl alcohol-polyacryl alcohol block copolymer and / or triton X100.

6. The preparation method according to claim 5, characterized in that, When the copolymerization reaction is an emulsion polymerization reaction, the molecular weight regulator of the copolymerization reaction is one or more of alkanes, esters or halogenated hydrocarbons, preferably one or more of ethane, ethyl acetate, diiodomethane or diiodooctafluorobutane.

7. The preparation method according to claim 5, characterized in that, When the copolymerization reaction is a suspension polymerization reaction, the dispersant for the copolymerization reaction is a cellulose dispersant and / or an inorganic dispersant; Preferably, the dispersant is selected from one or more of hydroxypropyl methylcellulose, methylcellulose, or calcium hydroxyphosphate.

8. The preparation method according to any one of claims 3-7, characterized in that, The preparation method further includes post-treatment: washing and drying the copolymer emulsion obtained by the copolymerization reaction; Preferably, during the copolymerization process, mixed monomers need to be added until the solid content of the copolymer emulsion is 10-35%.

9. An adhesive comprising the fluorinated copolymer of claim 1 or 2 or the fluorinated copolymer obtained by any one of claims 3-8.

10. The application of the binder of claim 9 in a secondary battery, preferably, the secondary battery is a lithium battery.

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