CN113416270B - Polymer and preparation method and application thereof - Google Patents

Polymer and preparation method and application thereof Download PDF

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Publication number
CN113416270B
CN113416270B CN202110603096.0A CN202110603096A CN113416270B CN 113416270 B CN113416270 B CN 113416270B CN 202110603096 A CN202110603096 A CN 202110603096A CN 113416270 B CN113416270 B CN 113416270B
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polymer
monomer
diaphragm
battery
solvent
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CN113416270A (en
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王燕
马六甲
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Zhuhai Chenyu New Material Technology Co ltd
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Zhuhai Chenyu New Material Technology Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F212/00—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 an aromatic carbocyclic ring
    • C08F212/02—Monomers containing only one unsaturated aliphatic radical
    • C08F212/04—Monomers containing only one unsaturated aliphatic radical containing one ring
    • C08F212/06—Hydrocarbons
    • C08F212/08—Styrene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/10—Esters
    • C08F220/12—Esters of monohydric alcohols or phenols
    • C08F220/14—Methyl esters, e.g. methyl (meth)acrylate
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/10—Esters
    • C08F220/12—Esters of monohydric alcohols or phenols
    • C08F220/16—Esters of monohydric alcohols or phenols of phenols or of alcohols containing two or more carbon atoms
    • C08F220/18—Esters of monohydric alcohols or phenols of phenols or of alcohols containing two or more carbon atoms with acrylic or methacrylic acids
    • C08F220/1808—C8-(meth)acrylate, e.g. isooctyl (meth)acrylate or 2-ethylhexyl (meth)acrylate
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/417—Polyolefins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • 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

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Polymers & Plastics (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Cell Separators (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

Abstract

The invention belongs to the technical field of battery materials, and discloses a polymer and a preparation method and application thereof. The raw material components for preparing the polymer comprise: monomer A, monomer B and monomer C; monomer A is an alkenoate; monomer B contains carbon-carbon double bond; the monomer C is a substance containing carboxyl and/or maleic anhydride. The polymer is prepared from the monomer A, the monomer B and the monomer C, and the polymer is coated on the surface of the battery diaphragm, so that the thermal stability of the battery diaphragm can be obviously improved, the volume thermal shrinkage rate of the battery diaphragm is not more than 3.3% at a high temperature, for example 130 ℃, and the volume thermal shrinkage rate of the polyolefin battery diaphragm in the prior art is 20%. The monomer C structure contained in the polymer prepared by the invention has active functional groups, can effectively improve the bonding strength applied to the surface of the diaphragm, improve the connection firmness between the diaphragm and the electrode plate, reduce the pores in the interface, improve the mass transfer rate of lithium ions and simplify the production process of the battery.

Description

Polymer and preparation method and application thereof
Technical Field
The invention belongs to the technical field of battery materials, and particularly relates to a polymer and a preparation method and application thereof.
Background
The application of the lithium ion battery technology is very wide, and the lithium ion battery technology is widely applied to various fields such as new energy vehicles, large-sized energy storage equipment, small-sized electronic mobile equipment and the like.
In lithium ion batteries, the battery separator physically blocks the contact of the positive and negative electrodes of the battery, thereby reducing the possibility of explosion caused by internal short circuits. Currently, polyolefin separators are widely used in lithium ion batteries by virtue of their excellent mechanical properties, stable electrochemical properties, and low cost advantages. However, as the application requirements of lithium ion batteries are increased, and due to the inherent properties of polyolefin molecular chains, electrolyte affinity and thermal stability of polyolefin separators have yet to be improved. To solve this problem, a surface treatment method has been attempted in addition to the modification of the separator substrate. At present, in order to improve the affinity and the thermal stability of polyolefin diaphragm electrolyte, a main method is to coat an inorganic particle coating on the surface of a diaphragm by the action of a binder to prepare an organic/inorganic composite diaphragm. In the prior art, even if an adhesive is adopted, the problem of unstable connection between the diaphragm and the electrode plate cannot be solved.
Therefore, it is necessary to provide a polymer which can improve the thermal stability of a separator and the connection between the separator and an electrode sheet when applied to a separator of a battery.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems in the prior art described above. Therefore, the invention provides a polymer, a preparation method and application thereof, and the polymer is coated on the surface of the diaphragm in the form of emulsion, so that the problem of poor thermal stability of the traditional polyolefin diaphragm can be solved, and the connection firmness between the diaphragm and an electrode plate is improved.
A first aspect of the invention provides a polymer.
Specifically, a polymer, the raw material components for preparing the polymer comprise: monomer A, monomer B and monomer C;
the monomer A is olefine acid ester;
the monomer B contains carbon-carbon double bonds;
the monomer C is a substance containing carboxyl and/or maleic anhydride.
Preferably, the monomer A is acrylate.
Further preferably, the monomer a is at least one selected from ethyl acrylate, isooctyl acrylate, butyl acrylate, and n-octyl acrylate.
Preferably, the monomer B is at least one selected from styrene, methyl acrylate, methyl methacrylate, methacrylonitrile, acrylonitrile or acrylamide.
Preferably, the carboxyl group-containing substance is at least one selected from the group consisting of vinyl acetic acid, methacrylic acid, acrylic acid, itaconic acid and fumaric acid.
Preferably, the raw material component for preparing the polymer further comprises at least one of a dispersant, an initiator or a solvent.
Preferably, the dispersant is a nonionic dispersant.
Further preferably, the dispersing agent is at least one selected from polyvinylpyrrolidone, hydroxypropyl cellulose, carboxymethyl cellulose, and polyacrylic acid.
Preferably, the initiator includes an oil-soluble initiator and a water-soluble initiator. The oil-soluble initiator and the water-soluble initiator are used simultaneously, so that the reaction is uniformly and stably carried out.
Preferably, the oil-soluble initiator is selected from at least one of azobisisobutyronitrile or benzoyl peroxide.
Preferably, the water-soluble initiator is a persulfate; further preferably, the persulfate includes at least one of potassium persulfate, sodium persulfate, or ammonium persulfate.
Preferably, the solvent is water and/or alcohol.
Preferably, the alcohol is methanol and/or ethanol.
Preferably, the solvent consists of alcohol and water according to the mass ratio of (0-4): (6-10); further preferably, the solvent is composed of alcohol and water according to the mass ratio of (0-3): (7-10). The solvent is composed of alcohol and water in a specific proportion, so that the monomer A, the monomer B, the monomer C, the initiator and the dispersing agent form a uniform system, and the uniform reaction is facilitated.
Preferably, the glass transition temperature of the polymer is from-6 to 68 ℃; further preferably, the glass transition temperature of the polymer is from-5 to 65 ℃.
Preferably, the dosage ratio of the monomer A to the monomer B to the monomer C is 30-65: (10-50): (3-28); further preferably, the ratio of the amount of the monomer A to the amount of the monomer B to the amount of the monomer C is 40-60: (15-40): (5-25).
Preferably, the initiator is used in an amount of 0.3 to 4.0% of the total weight of the monomers A, B and C; further preferably, the initiator is used in an amount of 0.3 to 3.0% by weight based on the total weight of the monomers A, B and C.
Preferably, the dispersant is used in an amount of 0.5 to 6.0% of the total weight of the monomers A, B and C; further preferably, the dispersant is used in an amount of 1.0 to 5.0% by weight based on the total weight of the monomers A, B and C.
Preferably, the solvent is used in an amount of 90.0 to 300.0% of the total weight of the monomers A, B and C; further preferably, the solvent is used in an amount of 100.0 to 250.0% by weight based on the total weight of the monomers A, B and C.
The monomer A, the monomer B and the monomer C form the polymer through polymerization reaction, the polymer contains the structures of the monomer A, the monomer B and the monomer C, and the connection relation of the monomer A, the monomer B and the monomer C in the polymer can be monomer B-monomer C-monomer A.
In a second aspect, the invention provides a method of preparing a polymer.
Specifically, the preparation method of the polymer comprises the following steps:
and (3) reacting the monomer A, the monomer B and the monomer C to obtain the polymer.
Preferably, a method for preparing a polymer comprises the steps of:
and mixing the dispersing agent with a solvent, adding the monomer A, the monomer B, the monomer C and an initiator in an inert gas atmosphere, stirring, and reacting to obtain the polymer.
Preferably, the inert gas is selected from nitrogen or a noble gas.
Preferably, the stirring speed is 700-1000 rpm; further preferably, the stirring speed is 750-850 rpm.
Preferably, the stirring time is 4-30 minutes; further preferably, the stirring time is 5 to 30 minutes. The stirring aim is to uniformly mix the components in the system or uniformly disperse the components, which is beneficial to uniformly carrying out the reaction.
Preferably, the temperature of the reaction is 45-90 ℃; further preferably, the temperature of the reaction is 50-90 ℃.
Preferably, the reaction time is 5 to 24 hours; further preferably, the reaction time is 6 to 24 hours.
Preferably, the polymer is in an emulsion state.
Preferably, the average particle size of the polymer in emulsion state is 2-10 μm; further preferably, the average particle diameter of the polymer in emulsion state is 3 to 8. Mu.m. The polymer in the emulsion state is rich in a plurality of active groups such as-OH, -COOH, -NH-and the like, and can effectively improve the bonding strength of the polymer applied to the surface of the diaphragm.
Preferably, the pH of the polymer in emulsion state is alkaline, and more preferably, the pH of the polymer in emulsion state is 7.2 to 11.0.
The preparation method of the polymer adopts a dispersion polymerization process, and the large-particle-diameter microsphere aqueous emulsion is obtained by polymerization under the action of a dispersing agent, wherein the monomer C structure contained in the polymer is provided with an active functional group, so that the bonding strength of the polymer applied to the surface of a diaphragm can be effectively improved.
The dispersing agent used in the reaction process can enable each component (monomer A, monomer B, monomer C and initiator) to form a homogeneous system, polymer chains generated after polymerization are precipitated from the homogeneous system, the polymer chains are coalesced into small particles along with the progress of the reaction, and then the small particles are stably suspended in the system under the action of steric hindrance of the dispersing agent, so that a stable emulsion state is finally formed. The above monomer a may be referred to as a hard monomer, the monomer B may be referred to as a soft monomer, and the monomer C may be referred to as a functional monomer.
A third aspect of the invention provides the use of the above polymer.
In particular, the use of the above polymers in the field of batteries.
A composite separator comprising a substrate and a film layer on the surface of the substrate; the film layer contains the polymer of the invention.
Preferably, the substrate is a plastic substrate; further preferably, the substrate is a polyolefin.
The preparation method of the composite diaphragm comprises the following steps:
the polymer and the auxiliary agent are stirred and mixed to prepare ceramic slurry, the ceramic slurry is coated on the surface of a substrate, the thickness of the coating is 2.5-3.5 mu m, and the composite diaphragm is prepared by drying.
Preferably, the auxiliary agent comprises at least one of alumina powder, sodium carboxymethyl cellulose or wetting agent.
Preferably, the preparation method of the composite membrane comprises the following steps:
adding 35-39 parts by weight of alumina powder, 40-48 parts by weight of deionized water and 0.2-1 part by weight of sodium carboxymethyl cellulose into a high-speed refiner, stirring at a high speed for 40-60 minutes, adding 10-12 parts by weight of polymer and 0.2-1 part by weight of wetting agent, stirring uniformly to obtain ceramic slurry, uniformly coating the ceramic slurry on one side of a polyolefin substrate by using a scraping plate, controlling the coating thickness to be 2.5-3.5 mu m, and drying for 5-6 hours in a vacuum environment at 75-80 ℃ to remove the solvent, thereby obtaining the composite diaphragm.
A battery comprising the composite separator of the present invention.
Compared with the prior art, the invention has the following beneficial effects:
(1) The polymer is prepared from the monomer A, the monomer B and the monomer C, and is coated on the surface of the battery diaphragm, so that the thermal stability of the battery diaphragm can be remarkably improved, the volume thermal shrinkage rate of the battery diaphragm is not more than 3.3% at high temperature (more than 120 ℃ for example 130 ℃), and the volume thermal shrinkage rate of the polyolefin battery diaphragm in the prior art at 130 ℃ is 20%.
(2) The monomer C (also called as functional monomer) structure contained in the polymer has active functional groups, so that the bonding strength applied to the surface of the diaphragm can be effectively improved, the connection firmness between the diaphragm and the electrode plate is improved, the pores in the interface are reduced, the mass transfer rate of lithium ions is improved, and the production process of the battery is simplified.
(3) The polymer provided by the invention is applied to a battery, can increase the liquid retention amount of electrolyte, and improves the stability and safety of the electrochemical performance of the battery.
Drawings
FIG. 1 is an SEM (scanning electron microscope) image of a polymer emulsion prepared in example 1 of the present invention;
FIG. 2 is a SEM image of the surface and cross section of a composite separator according to application example 1 of the present invention;
FIG. 3 is a plot of the bond strength of the polymer emulsions prepared in examples 1-2 of the present invention.
Detailed Description
In order to make the technical solutions of the present invention more apparent to those skilled in the art, the following examples will be presented. It should be noted that the following examples do not limit the scope of the invention.
The starting materials, reagents or apparatus used in the following examples are all available from conventional commercial sources or may be obtained by methods known in the art unless otherwise specified.
Example 1: preparation of polymers in emulsion state
A polymer, the raw material components for preparing the polymer comprising: 40g of isooctyl acrylate, 50g of styrene, 10g of itaconic acid, 3g of polyvinylpyrrolidone, 0.3g of azobisisobutyronitrile and 200g of solvent (the mass ratio of ethanol to water in the solvent is 3:7).
A method of preparing a polymer comprising the steps of:
in a four-neck flask with a condenser, a thermometer, a nitrogen pipe and a stirring device, 3g of polyvinylpyrrolidone is dissolved in 200g of solvent with the mass ratio of ethanol to water of 3:7; then 50g of styrene, 40g of isooctyl acrylate, 10g of itaconic acid and 0.3g of azodiisobutyronitrile are added, the mixture is stirred and pre-emulsified for 30 minutes at a stirring speed of 800 revolutions per minute, the mixture is heated to 70 ℃ under the protection of nitrogen, and the mixture is stirred and reacted for 12 hours at the temperature, so that the polymer (or called polymer emulsion) in a white emulsion state is obtained.
FIG. 1 is an SEM (scanning electron microscope) image of a polymer emulsion prepared in example 1 of the present invention; the average particle diameter of the polymer emulsion obtained in example 1 was 5.0. Mu.m.
Example 2: preparation of polymers in emulsion state
A polymer, the raw material components for preparing the polymer comprising: 25g of ethyl acrylate, 25g of butyl acrylate, 50g of methyl methacrylate, 50g of itaconic acid, 6g of polyvinylpyrrolidone, 0.3g of azobisisobutyronitrile and 200g of solvent (the mass ratio of ethanol to water in the solvent is 3:7).
A method of preparing a polymer comprising the steps of:
6g of polyvinylpyrrolidone is dissolved in 200g of solvent with the mass ratio of ethanol to water of 3:7 in a four-neck flask with a condenser, a thermometer, a nitrogen pipe and a stirring device; then 50g of methyl methacrylate, 25g of ethyl acrylate, 25g of butyl acrylate, 50g of itaconic acid and 0.3g of azodiisobutyronitrile are added, the mixture is stirred and pre-emulsified for 30 minutes at a stirring speed of 800 revolutions per minute, under the protection of nitrogen, the temperature is raised to 70 ℃, and the mixture is stirred and reacted for 16 hours at the temperature, so that the polymer (or called polymer emulsion) in a white emulsion state is obtained.
The average particle diameter of the polymer emulsion obtained in this example 2 was 0.8. Mu.m.
Example 3: preparation of polymers in emulsion state
A polymer, the raw material components for preparing the polymer comprising: 25g of styrene, 45g of isooctyl acrylate, 25g of methyl methacrylate, 5g of acrylic acid, 3g of polyvinylpyrrolidone, 0.15g of benzoyl peroxide and 150g of water.
A method of preparing a polymer comprising the steps of:
in a four-necked flask with condenser, thermometer, nitrogen tube and stirring apparatus, 3g of polyvinylpyrrolidone was dissolved in 150g of water; then adding 25g of methyl methacrylate, 25g of styrene, 45g of isooctyl acrylate, 5g of acrylic acid and 0.15g of benzoyl peroxide, stirring and pre-emulsifying for 30 minutes at a stirring speed of 800 revolutions per minute, introducing nitrogen for protection, heating to 80 ℃, and stirring and reacting for 8 hours at the temperature to obtain the polymer in a white emulsion state.
Example 4: preparation of polymers in emulsion state
A polymer, the raw material components for preparing the polymer comprising: 30g of styrene, 60g of isooctyl acrylate, 10g of itaconic acid, 3g of polyacrylic acid, 0.2g of sodium persulfate and 180g of water.
A method of preparing a polymer comprising the steps of:
in a four-necked flask with a condenser, thermometer, nitrogen tube and stirring apparatus, 3g of polyacrylic acid was dissolved in 180g of water; then adding 30g of styrene, 60g of isooctyl acrylate, 10g of itaconic acid and 0.2g of sodium persulfate, stirring and pre-emulsifying for 30 minutes at a stirring speed of 800 revolutions per minute, heating to 65 ℃ under the protection of nitrogen, and stirring and reacting for 24 hours at the temperature to obtain the polymer in a white emulsion state.
Example 5: preparation of polymers in emulsion state
In comparison with example 4, 0.1g of benzoyl peroxide and 0.1g of sodium persulfate were used in example 5 instead of 0.2g of sodium persulfate in example 4, and the other components and preparation method were the same.
Application example 1
A composite separator comprising a polyolefin substrate and a film layer on the surface of the polyolefin substrate; the film layer contained the polymer prepared in example 1.
The preparation method of the composite diaphragm comprises the following steps:
39 parts by weight of alumina powder, 48 parts by weight of deionized water, 0.5 part by weight of sodium carboxymethylcellulose were added to a high-speed homogenizer, and after 60 minutes of high-speed stirring (stirring speed of 800 rpm), 12 parts by weight of the polymer in a white emulsion state obtained in example 1 and 0.5 part by weight of a wetting agent (propylene glycol) were added and uniformly stirred to prepare a ceramic slurry, the ceramic slurry was uniformly coated on one side of a polyolefin substrate with a blade, the coating thickness was controlled at 3 μm, and then dried in a vacuum atmosphere at 80 ℃ for 6 hours to remove the solvent, thereby preparing a composite separator.
FIG. 2 is a SEM image of the surface and cross section of a composite separator according to application example 1 of the present invention; fig. 2 (a) shows an SEM image of the surface (the surface means the side of the polyolefin base material, i.e., the surface on which the film layer is formed) of the composite separator according to application example 1 of the present invention, and fig. 2 (b) shows an SEM image of the cross section (the cross section means the direction perpendicular to the surface) of the composite separator according to application example 1 of the present invention.
Application example 2
A composite separator comprising a polyolefin substrate and a film layer on the surface of the polyolefin substrate; the film layer contained the polymer prepared in example 2.
The preparation method of the composite diaphragm comprises the following steps:
36 parts by weight of alumina powder, 42 parts by weight of deionized water and 0.5 part by weight of sodium carboxymethylcellulose were added to a high-speed homogenizer, and after 50 minutes of high-speed stirring (stirring speed of 800 rpm), 12 parts by weight of the polymer in a white emulsion state obtained in example 2 and 0.5 part by weight of a wetting agent (propylene glycol) were added and uniformly stirred to prepare a ceramic slurry, the ceramic slurry was uniformly coated on one side of a polyolefin substrate with a blade, the coating thickness was controlled at 3 μm, and then dried for 6 hours in a vacuum environment at 80℃to remove the solvent, thereby preparing a composite separator.
Application example 3
A composite separator comprising a polyolefin substrate and a film layer on the surface of the polyolefin substrate; the film layer contained the polymer prepared in example 3.
The preparation method of the composite diaphragm comprises the following steps:
after adding 35 parts by weight of alumina powder, 43 parts by weight of deionized water, and 0.3 parts by weight of sodium carboxymethylcellulose in a high-speed refiner and stirring at a high speed (stirring speed of 800 rpm) for 60 minutes, 12 parts by weight of the polymer in a white emulsion state obtained in example 3 and 0.5 parts by weight of a wetting agent (propylene glycol) were added and stirred uniformly to prepare a ceramic slurry, the ceramic slurry was uniformly coated on one side of a polyolefin substrate with a blade, the coating thickness was controlled at 3 μm, and then dried in a vacuum environment at 80 ℃ for 6 hours to remove the solvent, thereby preparing a composite separator.
Application example 4
A composite separator comprising a polyolefin substrate and a film layer on the surface of the polyolefin substrate; the film layer contained the polymer prepared in example 4.
The preparation method of the composite diaphragm comprises the following steps:
after adding 37 parts by weight of alumina powder, 40 parts by weight of deionized water and 0.8 part by weight of sodium carboxymethylcellulose in a high-speed refiner and stirring at a high speed (stirring speed of 800 rpm) for 55 minutes, 12 parts by weight of the polymer in a white emulsion state obtained in example 4 and 0.5 parts by weight of a wetting agent (glycerin) were added and stirred uniformly to obtain a ceramic slurry, the ceramic slurry was uniformly coated on one side of a polyolefin substrate with a blade, the coating thickness was controlled at 3 μm, and then dried in a vacuum environment at 80 ℃ for 6 hours to remove the solvent, thereby obtaining a composite separator.
Application example 5
A composite separator comprising a polyolefin substrate and a film layer on the surface of the polyolefin substrate; the film layer contained the polymer prepared in example 5.
The preparation method of the composite diaphragm comprises the following steps:
38 parts by weight of alumina powder, 47 parts by weight of deionized water and 0.5 part by weight of sodium carboxymethylcellulose were added to a high-speed homogenizer, and after 60 minutes of high-speed stirring (stirring speed of 800 rpm), 12 parts by weight of the polymer in a white emulsion state obtained in example 5 and 0.5 part by weight of a wetting agent (glycerin) were added and uniformly stirred to prepare a ceramic slurry, the ceramic slurry was uniformly coated on one side of a polyolefin substrate with a blade, the coating thickness was controlled at 3 μm, and then dried under a vacuum environment at 75 ℃ for 6 hours to remove the solvent, thereby preparing a composite separator.
Application example 6
A battery comprising the composite separator produced in application example 1.
Comparative example 1
In comparison with example 1, itaconic acid was not used in the preparation of the polymer of comparative example 1, other components and preparation methods were the same as those of example 1, and the polymer of comparative example 1 was prepared to prepare a comparative example composite separator according to the method of application example 1.
Product effect test
1. Thermal stability test
The composite separator and polyolefin (polyolefin was directly used as a battery separator in the prior art) prepared in application examples 1 to 5 were measured for volume heat shrinkage after being kept at 130℃for 30 minutes, and the results are shown in Table 1.
Table 1: volume heat shrinkage test results
Volume heat shrinkage (%)
Application example 1 3.0
Application example 2 3.3
Application example 3 3.1
Application example 4 3.2
Application example 5 2.9
Comparative example 1 15.1
Polyolefin 20.0
As can be seen from Table 1, the volume heat shrinkage of the composite membrane prepared in application examples 1 to 5 of the present invention is significantly lower than that of polyolefin after the composite membrane is maintained at 130℃for 30 minutes, and it can be seen that the use of the polymer emulsions prepared in examples 1 to 5 of the present invention to prepare the composite membrane contributes to the improvement of the heat stability of the composite membrane.
2. Bond strength test
The polyolefin substrate cannot be adhered to the electrode plate by coating the polyolefin substrate with a commercially available adhesive (the main component is polyvinylidene fluoride) and then attaching the electrode plate.
The polymer emulsions prepared in examples 1-2 of the present invention were each tested for adhesion strength between the electrode sheet and the polyolefin substrate after being coated on the surface of the polyolefin substrate, and the results are shown in fig. 3.
FIG. 3 is a plot of the bond strength of the polymer emulsions prepared in examples 1-2 of the present invention; wherein, the curve "(1)" in FIG. 3 represents the bond strength curve of the polymer emulsion produced in example 1 of the present invention, and the curve "(2)" in FIG. 3 represents the bond strength curve of the polymer emulsion produced in example 2 of the present invention (the ordinate "Load" in FIG. 3 represents "Load", and the abscissa "Displacement"). The average particle diameter of the polymer emulsion prepared in example 1 was 5.0. Mu.m, the average particle diameter of the polymer emulsion prepared in example 2 was 0.8. Mu.m, and as can be seen from FIG. 3, the adhesive strength of the polymer emulsion prepared in example 1 was greater than that of the polymer emulsion prepared in example 2, and thus it was seen that the average particle diameter of the polymer emulsion had an effect on the strength of the adhesive strength.

Claims (5)

1. A polymer characterized in that the raw materials of the polymer consist of the following components: isooctyl acrylate, styrene, itaconic acid, polyvinylpyrrolidone, azobisisobutyronitrile and solvent;
the solvent is water and ethanol;
the weight ratio of the isooctyl acrylate to the styrene to the itaconic acid is 40:50:10;
the preparation method of the polymer comprises the following steps:
mixing the polyvinylpyrrolidone with the solvent, adding the isooctyl acrylate, the styrene, the itaconic acid and the azodiisobutyronitrile in an inert gas atmosphere, stirring and reacting to obtain the polymer;
wherein the inert gas is selected from nitrogen or a rare gas;
the temperature of the reaction is 45-90 ℃, and the time of the reaction is 5-24 hours;
the polymer is in emulsion state, and the average particle size of the polymer is 3-8 mu m.
2. The polymer of claim 1, wherein the polymer is composed of the following components: 40g of isooctyl acrylate, 50g of styrene, 10g of itaconic acid, 3g of polyvinylpyrrolidone, 0.3g of azobisisobutyronitrile and 200g of solvent;
the mass ratio of the ethanol to the water in the solvent is 3:7.
3. Use of the polymer according to claim 1 or 2 in the field of batteries.
4. A composite diaphragm, which is characterized by comprising a substrate and a film layer on the surface of the substrate; the film layer comprising the polymer of claim 1 or 2; the thickness of the film layer is 2.5-3.5 mu m.
5. A battery comprising the composite separator of claim 4.
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