CN115286730A - Vinylidene fluoride copolymer and preparation method and application thereof - Google Patents
Vinylidene fluoride copolymer and preparation method and application thereof Download PDFInfo
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- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F214/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
- C08F214/18—Monomers containing fluorine
- C08F214/22—Vinylidene fluoride
- C08F214/225—Vinylidene fluoride with non-fluorinated comonomers
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- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J127/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Adhesives based on derivatives of such polymers
- C09J127/02—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Adhesives based on derivatives of such polymers not modified by chemical after-treatment
- C09J127/12—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Adhesives based on derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
- C09J127/16—Homopolymers or copolymers of vinylidene fluoride
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
- H01M4/622—Binders being polymers
- H01M4/623—Binders being polymers fluorinated polymers
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention belongs to the technical field of copolymers, and particularly relates to a vinylidene fluoride copolymer and a preparation method and application thereof. The vinylidene fluoride copolymer is prepared by polymerizing the 1, 1-difluoroethylene monomer and the N, N-dimethyl morpholine ester cyclic vinyl monomer, has good cohesiveness and alkali resistance, can reduce the gel phenomenon in the anode slurry of the ternary lithium battery and the lithium iron phosphate battery, and ensures the stability of the anode slurry. The preparation method is simple, the conditions are mild, the polymerization reaction can be carried out under the critical pressure of the 1, 1-difluoroethylene, and the method is suitable for large-scale production.
Description
Technical Field
The invention belongs to the technical field of copolymers. More particularly, relates to a vinylidene fluoride copolymer, a preparation method and an application thereof.
Background
Active materials (lithium iron phosphate, ternary positive electrode materials), conductive agents and current collectors can be bonded on a positive electrode of a PVDF (polyvinylidene fluoride copolymer) binder in the lithium battery, so that uniformity and stability of the active materials during pulping are maintained, electron conduction required in the electrode is provided, and the PVDF binder plays a vital role in capacity maintenance, service life and stability of the battery. However, the homopolymerized PVDF has poor caking property, and has poor alkali resistance in the positive electrode slurry of the high-nickel ternary material, so that the problem of gel is easily caused. In order to improve the problems of poor adhesion of PVDF and poor alkali resistance of positive electrode slurry in high nickel ternary materials, polar comonomers such as acrylic monomers are often introduced into PVDF. For example, the Chinese patent application discloses a novel vinylidene fluoride copolymer with high cohesiveness, which is prepared by copolymerizing a vinylidene fluoride monomer and at least one modified acrylate comonomer, wherein the cohesiveness is 6.2N/m at most, although the cohesiveness is improved to a certain extent, the improvement is not desirable, the further improvement is needed, and the alkali resistance is also needed to be further provided. Therefore, it is highly desirable to provide several vinylidene fluoride copolymers having high adhesion and excellent alkali resistance.
Disclosure of Invention
The invention aims to solve the technical problems of overcoming the defects and the defects of poor cohesiveness and poor alkali resistance of the existing vinylidene fluoride copolymer and providing the vinylidene fluoride copolymer with high cohesiveness and good alkali resistance.
The invention aims to provide a preparation method of a vinylidene fluoride copolymer.
Another object of the present invention is to provide a vinylidene fluoride copolymer for use as a binder.
The above object of the present invention is achieved by the following technical solutions:
the vinylidene fluoride copolymer is prepared by copolymerizing a 1, 1-difluoroethylene monomer (VDF) and an N, N-dimethylmorpholine ester cyclovinyl monomer, wherein the N, N-dimethylmorpholine ester cyclovinyl monomer has a structure shown in a formula (I):
wherein R is 1 、R 2 、R 3 Independently selected from hydrogen, C 1 -C 6 Alkyl or halo C 1 -C 6 An alkyl group; r is 4 Is C 0 -C 6 Alkyl or halo C 1 -C 6 Alkyl radical, when R 4 Is C 0 In the case of alkyl, the double bond is directly connected with the carbon-oxygen bond in the ester group;
the invention creatively adopts N, N-dimethylmorpholine ester cyclic vinyl monomers to prepare the vinylidene fluoride copolymer. On one hand, the monomer side chain ring structure has certain steric hindrance effect and positive charge repulsion effect, and can reduce block polymerization of the monomer in the PVDF chain segment and realize uniform distribution of the monomer on the PVDF chain segment; on the other hand, the monomer has a morpholine ester ring structure, and can be hydrolyzed under the alkalescent condition of the ternary lithium battery positive electrode material to generate carboxyl and hydroxyl, so that the alkali in a system can be neutralized, the pH value of the system can be reduced, the gelation phenomenon of positive electrode slurry can be reduced, and the polar group in the monomer structure can improve the adhesive force with a positive electrode plate. In the lithium iron phosphate battery, the tertiary amine group in the monomer structure has good repulsion to the surface group and positive charge of the lithium iron phosphate positive electrode material, the dispersibility of the monomer on the surface of the lithium iron phosphate battery positive electrode material can be improved, the gel phenomenon of the lithium iron phosphate battery positive electrode slurry is reduced, and the stability of the slurry is ensured.
Preferably, said R is 1 、R 2 、R 3 Independently selected from hydrogen, C 1 -C 4 Alkyl or halo C 1 -C 4 An alkyl group; r 4 Is C 0 -C 4 Alkyl or halogeno C of 1 -C 4 An alkyl group.
More preferably, said R 1 、R 2 、R 3 Independently selected from hydrogen or C 1 -C 4 An alkyl group; r is 4 Is C 1 -C 4 An alkyl group.
Preferably, the molar weight of the N, N-dimethyl morpholine ester cyclic vinyl monomer accounts for 0.05-10% of that of the 1, 1-difluoroethylene monomer.
More preferably, the molar amount of the N, N-dimethylmorpholinyl ester cyclovinyl monomer is 0.5 to 5 percent of that of the 1, 1-difluoroethylene monomer.
Preferably, the vinylidene fluoride copolymer also comprises other fluorine-containing monomers which are copolymerized together to prepare the vinylidene fluoride copolymer; the other fluorine-containing monomer is one or more of vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, pentafluoropropylene, hexafluoropropylene, perfluoromethyl vinyl ether or perfluoropropyl vinyl ether.
More preferably, the other fluorine-containing monomer structural unit accounts for 0.00 to 5.00% of the 1, 1-difluoroethylene monomer.
The invention further provides a preparation method of the vinylidene fluoride copolymer, which comprises the following steps:
adding an initiator, a chain transfer agent and a 1, 1-difluoroethylene monomer into a solution containing a dispersing agent, adding an N, N-dimethylmorpholinyl ester cyclovinyl monomer solution at 40-60 ℃ to react for 5-8 h under the condition that the oxygen content is less than 10ppm, and carrying out post-treatment to obtain the catalyst.
Preferably, the molar weight of the N, N-dimethyl morpholine ester cyclic vinyl monomer accounts for 0.1-10% of that of the 1, 1-difluoroethylene monomer.
Preferably, the 1, 1-difluoroethylene monomer is added to the dispersant-containing solution at the same time as the other fluorine-containing monomer is added.
More preferably, the molar amount of the other fluorine-containing monomer is 0 to 5% of the 1, 1-difluoroethylene monomer.
Preferably, the initiator is an organic peroxide initiator, a persulfate initiator, or a persulfate/sodium bisulfite initiator.
More preferably, the organic peroxide initiator is diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, diisobutyryl peroxide, tert-butyl peroxypivalate, or tert-amyl peroxypivalate.
More preferably, the persulfate initiator is ammonium sulfate.
Preferably, the initiator is added in an amount of 0.05 to 1% based on the 1, 1-difluoroethylene monomer.
Preferably, the dispersant is added in an amount of 0.05 to 1% based on the 1, 1-difluoroethylene monomer.
More preferably, the dispersant is methylcellulose, carboxymethylcellulose, polyvinyl alcohol, or hydroxypropylmethylcellulose.
Preferably, the reaction is maintained at an atmospheric pressure of 5 to 7.0 MPa.
Preferably, the N, N-dimethyl morpholine ester cyclovinyl monomer solution is added while stirring.
More preferably, the stirring rate of the stirring is 600 to 1000r/min.
Preferably, the chain transfer agent is ethyl acetate, diethyl malonate, diethyl carbonate, dimethyl carbonate, acetone, ethanol or n-propanol.
More preferably, the mass of the chain transfer agent accounts for 0.01-1% of the total mass of the 1, 1-difluoroethylene monomer and the N, N-dimethyl morpholine ester cyclic vinyl monomer.
Preferably, the post-treatment step comprises drying at 80-95 ℃ for 20-30 h after repeated washing until the conductivity of the filtrate is reduced to below 0.1.
The invention further protects the application of the vinylidene fluoride copolymer in preparing the binder.
Preferably, the binder is a lithium battery binder.
The invention has the following beneficial effects:
the vinylidene fluoride copolymer is prepared by polymerizing the 1, 1-difluoroethylene monomer and the N, N-dimethyl morpholine ester cyclic vinyl monomer, has good cohesiveness and alkali resistance, can reduce the gel phenomenon in the anode slurry of the ternary lithium battery and the lithium iron phosphate battery, and ensures the stability of the anode slurry. The preparation method is simple, the conditions are mild, the polymerization reaction can be carried out under the critical pressure of the 1, 1-difluoroethylene, and the method is suitable for large-scale production.
Drawings
FIG. 1 shows the polymer obtained in example 1 1 H-NMR chart.
Detailed Description
The invention is further described with reference to the drawings and the following detailed description, which are not intended to limit the invention in any way. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.
Unless otherwise indicated, reagents and materials used in the following examples are commercially available.
Example 1 preparation of polyvinylidene fluoride copolymer A
Adding 10kg of deionized water and 4g of methylcellulose into a 20L vertical polymerization kettle, closing the reaction kettle, vacuumizing, replacing with nitrogen for several times until the oxygen content in the reaction kettle is less than 10ppm, adding 5g of diisopropyl peroxydicarbonate, 5g of ethyl acetate and 4kg of VDF monomers until the pressure of the reaction kettle is 6.0MPa, heating the reaction kettle to 45 ℃, starting the reaction kettle for stirring at the rotation speed of 800r/min, dissolving 10g of 2- ((methacryloyloxy) methyl) -4, 4-dimethyl-6-oxomorpholine monomers in 500g of deionized water at 45 ℃, adding the mixture into the reaction kettle through an auxiliary agent pump, maintaining the pressure at 6.0MPa in the adding process, decompressing the reaction kettle after reacting for 6 hours, collecting a suspension liquid, repeatedly washing until the conductivity of a filtrate is reduced to be below 0.1, and finally drying in an oven at 95 ℃ for 24 hours to obtain a polyvinylidene fluoride copolymer A with the molecular weight of 100 ten thousand. The structure is as follows:
the content of 2- ((methacryloyloxy) methyl) -4, 4-dimethyl-6-oxomorpholine in polyvinylidene fluoride copolymer A is mainly determined by 1 H-NMR measurement of CH in 2- ((methacryloyloxy) methyl) -4, 4-dimethyl-6-oxomorpholine unit in the resulting polyvinylidene fluoride copolymer A 2 The strength of the H atom of the group (chemical shift at 4.4ppm, FIG. 1) relative to the CH in the VDF unit 2 The proportion of the strength of the H atoms of the group determines the proportion of polar monomer copolymerized.
The structural formula of the 2- ((methacryloyloxy) methyl) -4, 4-dimethyl-6-oxomorpholine unit is as follows:
example 2 preparation of polyvinylidene fluoride copolymer B
Adding 10kg of deionized water and 4g of methyl cellulose into a 20L vertical polymerization kettle, closing the reaction kettle, vacuumizing, replacing with nitrogen for several times until the oxygen content in the reaction kettle is less than 10ppm, adding 5g of diisopropyl peroxydicarbonate, 5g of ethyl acetate and 4kg of VDF monomers until the pressure in the reaction kettle is 6.0MPa, heating the reaction kettle to 45 ℃, starting the reaction kettle to stir at the rotation speed of 800r/min, dissolving 40g of 2- ((methacryloyloxy) methyl) -4, 4-dimethyl-6-oxomorpholine monomers into 500g of deionized water at 45 ℃, adding the mixture into the reaction kettle through an auxiliary agent pump, maintaining the pressure at 6.0MPa in the adding process, decompressing the reaction kettle after reacting for 6 hours, collecting suspended liquid, repeatedly washing until the conductivity of filtrate is reduced to below 0.1, and finally drying in an oven at 95 ℃ for 24 hours to obtain the polyvinylidene fluoride copolymer B. The molecular weight is 100 ten thousand.
Example 3 preparation of polyvinylidene fluoride copolymer C
Adding 10kg of deionized water and 4g of methyl cellulose into a 20L vertical polymerization kettle, closing the reaction kettle, vacuumizing, replacing with nitrogen for several times until the oxygen content in the reaction kettle is less than 10ppm, adding 5g of diisopropyl peroxydicarbonate, 5g of ethyl acetate and 4kg of VDF monomers until the pressure in the reaction kettle is 6.0MPa, heating the reaction kettle to 45 ℃, starting the reaction kettle to stir at the rotation speed of 800r/min, dissolving 80g of 2- ((methacryloyloxy) methyl) -4, 4-dimethyl-6-oxomorpholine monomers in 500g of deionized water at 45 ℃, adding the mixture into the reaction kettle through an auxiliary agent pump, maintaining the pressure at 6.0MPa in the adding process, reacting for 6 hours, decompressing the reaction kettle, collecting suspended liquid, repeatedly washing until the conductivity of filtrate is reduced to below 0.1, and finally drying in an oven at 95 ℃ for 24 hours to obtain the polyvinylidene fluoride copolymer C. The molecular weight is 100 ten thousand.
Example 4 preparation of polyvinylidene fluoride copolymer D
Adding 10kg of deionized water and 4g of methyl cellulose into a 20L vertical polymerization kettle, closing the reaction kettle, vacuumizing, replacing with nitrogen for several times until the oxygen content in the reaction kettle is less than 10ppm, adding 5g of diisopropyl peroxydicarbonate, 5g of ethyl acetate and 4kg of VDF monomer until the pressure of the reaction kettle is 6.0MPa, heating the reaction kettle to 45 ℃, starting the reaction kettle to stir at the rotating speed of 800r/min, dissolving 80g of 4, 4-dimethyl-2- (((3-methylbut-3-enoyl) oxy) methyl) -6-oxomorpholine monomer in 500g of deionized water at 45 ℃, adding the mixture into the reaction kettle through an auxiliary pump, maintaining the pressure at 6.0MPa in the adding process, reacting for 6 hours, decompressing the reaction kettle, collecting suspended liquid, repeatedly washing until the conductivity of filtrate is reduced to below 0.1, and finally drying in an oven at 95 ℃ for 24 hours to obtain the polyvinylidene fluoride copolymer D. The molecular weight is 100 ten thousand.
EXAMPLE 5 preparation of polyvinylidene fluoride copolymer E
Adding 10kg of deionized water and 4g of methylcellulose into a 20L vertical polymerization kettle, closing the reaction kettle, vacuumizing, replacing with nitrogen for several times until the oxygen content in the reaction kettle is less than 10ppm, adding 5g of diisopropyl peroxydicarbonate, 5g of ethyl acetate, 3.5kg of VDF monomer and 0.5kg of hexafluoropropylene monomer to the reaction kettle until the pressure of the reaction kettle is 6.0MPa, heating the reaction kettle to 45 ℃, starting the reaction kettle, stirring at the rotating speed of 800r/min, dissolving 80g of 2- ((methacryloyloxy) methyl) -4, 4-dimethyl-6-oxomorpholine monomer in 500g of deionized water at 45 ℃, adding the deionized water into the reaction kettle through an auxiliary pump, maintaining the pressure at 6.0MPa in the adding process, reacting for 6 hours, decompressing the reaction kettle, collecting a suspension liquid, repeatedly washing until the conductivity of a filtrate is reduced to be below 0.1, and finally drying in an oven at 95 ℃ for 24 hours to obtain the polyvinylidene fluoride copolymer E. The molecular weight is 100 ten thousand.
Comparative example 1 preparation of polyvinylidene fluoride copolymer D-A
Adding 10kg of deionized water and 4g of methyl cellulose into a 20L vertical polymerization kettle, closing the reaction kettle, vacuumizing, replacing with nitrogen for several times until the oxygen content in the reaction kettle is less than 10ppm, adding 5g of diisopropyl peroxydicarbonate, 5g of ethyl acetate and 4kg of VDF monomers until the pressure of the reaction kettle is 6.0MPa, heating the reaction kettle to 45 ℃, starting the reaction kettle to stir at the rotating speed of 800r/min, dissolving 10g of acrylic monomers in 500g of deionized water at 45 ℃, adding the acrylic monomers into the reaction kettle through an auxiliary agent pump, maintaining the pressure at 6.0MPa in the adding process, after reacting for 6 hours, decompressing the reaction kettle, collecting suspension liquid, repeatedly washing until the conductivity of filtrate is reduced to below 0.1, and finally drying in an oven at 95 ℃ for 24 hours to obtain the polyvinylidene fluoride copolymer D-A with the molecular weight of 100 ten thousand.
The only difference from example 1 is that 2- ((methacryloyloxy) methyl) -4, 4-dimethyl-6-oxomorpholine monomer is exchanged for acrylic acid monomer.
Comparative example 2 preparation of polyvinylidene fluoride copolymer D-B
Adding 10kg of deionized water and 4g of methyl cellulose into a 20L vertical polymerization kettle, closing the reaction kettle, vacuumizing, replacing with nitrogen for several times until the oxygen content in the reaction kettle is less than 10ppm, adding 5g of diisopropyl peroxydicarbonate, 5g of ethyl acetate and a certain amount of VDF monomer until the pressure of the reaction kettle is 6.0MPa, heating the reaction kettle to 45 ℃, starting the reaction kettle for stirring at the rotating speed of 800r/min, reacting for 6 hours, then decompressing the reaction kettle, collecting a suspension liquid, repeatedly washing until the conductivity of a filtrate is reduced to be below 0.1, and finally drying in a 95 ℃ oven for 24 hours to obtain a polyvinylidene fluoride copolymer D-B with the molecular weight of 100 ten thousand.
The only difference from example 1 is that no 2- ((methacryloyloxy) methyl) -4, 4-dimethyl-6-oxomorpholine monomer is added.
Experimental example: measurement of adhesion of polyvinylidene fluoride copolymer
Preparing a positive electrode of the lithium iron phosphate battery: 2g of PVDF prepared in examples 1 to 5 and comparative examples 1 to 2 was dissolved in 100g of N-methylpyrrolidone (NMP) solution, sufficiently stirred and dissolved, 2.8g of carbon black as a conductive agent and 56.2g of lithium iron phosphate were added under stirring, and further ultrasonic stirring was carried out for 2 hours to prepare a uniform slurry, and the obtained slurry was coated on a 12 μm rear electrode aluminum foil by a coater, and the aluminum foil was then dried in a vacuum oven at 60 ℃ for 12 hours to obtain a lithium iron phosphate battery positive electrode.
Preparation of a ternary lithium battery (NCM 811) positive electrode: 2g of PVDF prepared in examples 1 to 5 and comparative examples 1 to 2 was dissolved in 100g of NMP solution, sufficiently stirred and dissolved, 2.8g of carbon black as a conductive agent and 56.2g of NCM811 were added under stirring, further ultrasonic stirring was carried out for 2 hours to prepare a uniform slurry, the obtained slurry was coated on a 12 μm rear electrode aluminum foil by a coater, and the aluminum foil was then dried in a vacuum oven at 60 ℃ for 12 hours to obtain a ternary lithium battery positive electrode.
Adhesion Strength test Peel strength tests were performed according to the test method in the national Standard GB/T2790-1995 "test method for 180 ° Peel Strength of adhesive test method Flexible to rigid Material". Melting point the melting peak of the polymer was measured by DSC. The test results are shown in table 1:
TABLE 1 influence of PVDF obtained in examples 1 to 5 and comparative examples 1 to 2 on battery adhesion
As can be seen from Table 2, the viscosity increase rate of PVDF prepared in comparative example 1 in the lithium iron phosphate battery is as high as 700% after 24h, which proves that carboxyl on the surface of PVDF, lithium iron phosphate and carbon black are easy to form a network structure to form gel, and the stability of the slurry is poor. The PVDF prepared in the comparative example 2 has the viscosity growth rate of 500% in ternary NCM811 slurry after 24 hours, and proves that the PVDF is dissolved in NMP, and the alkaline groups on the surface of the positive electrode material can attack C-F and C-H bonds adjacent to the PVDF, so that the PVDF is easy to generate bimolecular elimination reaction, forms a part of carbon-carbon double bonds on a molecular chain, is easy to crosslink to form gel, and has poor alkali resistance. In the lithium iron phosphate battery, the viscosity increase rate of PVDF prepared in example 1 is only 40% after 24 hours, which is obviously lower than that of comparative example 1, and thus, the PVDF prepared in example 1 has good dispersibility in the lithium iron phosphate slurry. Example 1 in the NCM811 slurry, the viscosity increase rate is only 30% in 24 hours, the alkali resistance is good, and the basic groups on the surface of the positive electrode material can be effectively prevented from attacking the adjacent C-F and C-H bonds with PVDF, so that the bimolecular elimination reaction of PVDF is reduced. Therefore, compared with the comparative example, the PVDF prepared by the embodiment of the application has higher bonding strength in the ternary lithium battery and the ferric phosphate lithium battery; and the viscosity growth rate in 24 hours is obviously lower than that in a comparative example, and the alkali resistance is better and the stability is excellent.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (10)
1. The vinylidene fluoride copolymer is characterized by being prepared by copolymerizing a 1, 1-difluoroethylene monomer and an N, N-dimethyl morpholine ester cyclovinyl monomer, wherein the N, N-dimethyl morpholine ester cyclovinyl monomer has a structure shown in a formula (I):
wherein R is 1 、R 2 、R 3 Independently selected from hydrogen, C 1 -C 6 Alkyl or halo C 1 -C 6 An alkyl group; r is 4 Is C 0 -C 6 Alkyl or halo C 1 -C 6 Alkyl radical, when R 4 Is C 0 In the case of alkyl groups, the double bond is directly connected to the carbon-oxygen bond in the ester group.
2. The vinylidene fluoride copolymer of claim 1, wherein R is 1 、R 2 、R 3 Independently selected from hydrogen, C 1 -C 4 Alkyl or halo C 1 -C 4 An alkyl group; r is 4 Is C 0 -C 4 Alkyl or halogeno C of 0 -C 4 An alkyl group.
3. The vinylidene fluoride copolymer of claim 2, wherein R is 1 、R 2 、R 3 Independently selected from hydrogen or C 1 -C 4 An alkyl group; r is 4 Is C 0 -C 4 An alkyl group.
4. The vinylidene fluoride copolymer as claimed in claim 1, wherein the molar amount of the N, N-dimethylmorpholinyl ester cyclic vinyl monomer is 0.05-10% of that of the 1, 1-difluoroethylene monomer.
5. The vinylidene fluoride copolymer as claimed in claim 1, wherein the copolymer further comprises other fluorine-containing monomers copolymerized together; the other fluorine-containing monomer is one or more of vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, pentafluoropropylene, hexafluoropropylene, perfluoromethyl vinyl ether or perfluoropropyl vinyl ether.
6. A process for producing a vinylidene fluoride copolymer as defined in any one of claims 1 to 4, which comprises the steps of:
adding an initiator, a chain transfer agent and a 1, 1-difluoroethylene monomer into a solution containing a dispersing agent, adding an N, N-dimethylmorpholinyl ester cyclovinyl monomer solution at 40-60 ℃ to react for 5-8 h under the condition that the oxygen content is less than 10ppm, and carrying out post treatment to obtain the catalyst.
7. The method according to claim 6, wherein the dispersant is methylcellulose, carboxymethylcellulose, polyvinyl alcohol, or hydroxypropylmethylcellulose.
8. The method according to claim 6, wherein the initiator is an organic peroxide initiator, a persulfate initiator or a persulfate/sodium bisulfite initiator.
9. The method according to claim 6, wherein the chain transfer agent is ethyl acetate, diethyl malonate, diethyl carbonate, dimethyl carbonate, acetone, ethanol or n-propanol.
10. Use of the vinylidene fluoride copolymer according to any one of claims 1 to 5 as a binder.
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| CN117003920A (en) * | 2023-09-28 | 2023-11-07 | 山东华氟化工有限责任公司 | Fluorine-containing polymer, lithium battery positive electrode binder and preparation method |
| CN117003920B (en) * | 2023-09-28 | 2023-12-19 | 山东华氟化工有限责任公司 | Fluorine-containing polymer, lithium battery positive electrode binder and preparation method |
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| CN115286730B (en) | 2023-05-26 |
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