CN116606616A

CN116606616A - Heat-resistant diaphragm binder and preparation method and application thereof

Info

Publication number: CN116606616A
Application number: CN202310578893.7A
Authority: CN
Inventors: 佟锐; 曾锐明; 贾宝泉
Original assignee: Shenzhen Perfect Power Technology Co ltd
Current assignee: Shenzhen Perfect Power Technology Co ltd
Priority date: 2023-05-22
Filing date: 2023-05-22
Publication date: 2023-08-18

Abstract

The invention provides a heat-resistant diaphragm binder, a preparation method and application thereof, wherein the heat-resistant diaphragm binder is polymer particles with a core-shell structure, the polymer particles comprise core polymers and shell polymers, and the glass transition temperature of the core polymers is more than or equal to 80 ℃; the glass transition temperature of the shell polymer is less than or equal to 0 ℃. Improving heat resistance of the heat resistant separator binder by using a core polymer having a specific glass transition temperature; and the shell polymer with specific glass transition temperature is matched to improve the room temperature cold pressing binding force of the heat-resistant diaphragm binder, so that the application of the heat-resistant diaphragm binder in lithium ion batteries can be fully satisfied.

Description

Heat-resistant diaphragm binder and preparation method and application thereof

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a heat-resistant diaphragm binder and a preparation method and application thereof.

Background

The lithium ion battery is a chargeable battery with wide application prospect, has high energy density, long service life, small volume, no maintenance and environmental friendliness, is favored by various industries, has moved from the fields of mobile phones, notebook computers and the like to the fields of electric bicycles, electric automobiles, energy storage and various portable equipment, and is an ideal mobile power supply.

Lithium ion batteries generally consist of a positive electrode, a negative electrode, a separator, an electrolyte, and a battery housing, wherein the separator is one of the key internal components that functions to separate the positive and negative electrodes of the battery and prevent the positive and negative electrodes from contacting to short-circuit. The separator used in the lithium ion battery at present is generally a polyolefin porous film, and because the polyolefin porous film has a low melting point, when the temperature of the battery is increased due to internal or external factors, the polyolefin porous film can shrink or melt, so that the positive electrode and the negative electrode are directly contacted, the battery is short-circuited, and accidents such as combustion explosion and the like of the battery are caused. In order to solve these problems, it is common to apply inorganic particles to the surface of a separator substrate with a polymer binder to produce a composite separator, for example, to apply ceramic particles to the surface of a separator substrate to produce a ceramic/polymer composite separator, and it is desirable to use the heat resistance of the ceramic particles to reduce the thermal shrinkage of the separator. Meanwhile, a layer of polymer binder is coated on the surface of the ceramic coating and used for binding the diaphragm and the positive and negative plates, so that the effect of fixing the battery structure is achieved. However, the current process of coating ceramic and polymer binder layers is relatively complex, e.g., for a double coated separator, a total of 4 applications are required, i.e., two ceramic layers and two polymer binder layers. In addition, the polymer binder coated on the surface of the ceramic layer is usually a polymer with smaller granularity, and is easy to form a film in the subsequent forming process of the battery, so that the air permeability of the separator is reduced, and the performance of the battery is affected.

CN112940650a discloses a diaphragm binder which can be mixed with ceramic particles for coating, the preparation process of the diaphragm is greatly simplified, the cost is reduced, the air permeability of the diaphragm is not affected, and the diaphragm binder has better binding force with a pole piece. However, the separator adhesive prepared by the method has only one glass transition temperature although the glass transition temperature is distributed between 35 and 90 ℃, which causes a series of problems during application. If the vitrification temperature of the binder is lower, the heat resistance of the diaphragm after the binder is used for the diaphragm is poorer, so that the diaphragm has large heat shrinkage. If the glass transition temperature of the binder is high, the adhesion tends to be lowered.

CN112635914a discloses a lithium ion battery separator with heat resistance and high mechanical strength, comprising a polyolefin porous base material and a porous heat-resistant layer coated on one side surface or two side surfaces of the base material, wherein the porosity of the polyolefin porous base material is 20% -60%, the needling strength is not less than 200gf, and the peeling strength of the porous heat-resistant layer is not less than 10N/m; the porous heat-resistant layer comprises an inorganic filler, a binder, a thickener, a dispersing agent and a wetting agent, and the porous heat-resistant layer is coated on at least one side surface of the polyolefin porous substrate, so that the heat resistance of the diaphragm is improved, the safety of the lithium ion battery is effectively improved, the phenomena of fire explosion and the like caused by thermal shock are prevented, the problems of large heat shrinkage rate and great reduction of strength after heating are solved, and the problem of poor binding force still exists.

CN106953058A discloses a lithium ion battery separator, which comprises a non-woven fabric layer and a polyolefin porous membrane, wherein the upper part and the lower part of the non-woven fabric layer are respectively provided with grooves, the polyolefin porous membrane is pressed on the upper side and the lower side of the non-woven fabric layer, micropores are uniformly distributed on the surface of the non-woven fabric layer, the porosity is 80%, the thickness of the non-woven fabric layer is 3-6 mu m, the safety performance of the lithium ion battery is improved, and meanwhile, the thickness of the non-woven fabric layer of 3 mu m can obviously improve the thermal stability and the mechanical performance of the separator, but the bonding performance is poor.

The heat-resistant diaphragm in the prior art has the problems of high heat shrinkage, small adhesive force and the like, and the performances of the heat-resistant diaphragm cannot be balanced. Therefore, developing a heat-resistant separator with low heat shrinkage and strong adhesion to meet the application requirements in lithium ion batteries is a problem to be solved in the art.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a heat-resistant diaphragm adhesive, a preparation method and application thereof, wherein the heat-resistant diaphragm adhesive is polymer particles with a core-shell structure, the polymer particles comprise a core polymer and a shell polymer, and the glass transition temperature of the core polymer is more than or equal to 80 ℃; the glass transition temperature of the shell polymer is less than or equal to 0 ℃, so that the heat-resistant diaphragm has excellent adhesive property and low heat shrinkage rate, and can fully meet the application of the heat-resistant diaphragm in lithium ion batteries.

To achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a heat-resistant separator binder, which is a polymer particle having a core-shell structure, the polymer particle comprising a core polymer and a shell polymer, the glass transition temperature of the core polymer being equal to or greater than 80 ℃, such as 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃, 200 ℃, and specific point values between the above point values, the present invention is not exhaustive of the specific point values included in the range, for reasons of space and brevity.

The glass transition temperature of the core polymer is more than or equal to 80 ℃, and the heat-resistant diaphragm adhesive can be endowed with excellent heat resistance.

The glass transition temperature of the shell polymer is less than or equal to 0 ℃, and can be, for example, -50 ℃, -45 ℃, -40 ℃, -35 ℃, -30 ℃, -25 ℃, -20 ℃, -15 ℃, -10 ℃, -5 ℃, 0 ℃, and specific point values between the above point values, limited in space and for simplicity, the invention is not exhaustive of the specific point values included in the range.

The glass transition temperature of the shell polymer is less than or equal to 0 ℃, and the heat-resistant diaphragm adhesive can be endowed with excellent adhesive force.

As a preferred embodiment of the present invention, "heat-resistant" in the heat-resistant separator binder means having a low heat shrinkage rate under high temperature conditions, and illustratively, the heat shrinkage rate of the separator comprising the heat-resistant separator binder after being left for 1 hour at 130 ℃ is <5%, more preferably <4%, and still more preferably not more than 3.5%, indicating that the heat-resistant separator binder and the separator comprising the same have excellent heat resistance.

The particle size of the polymer particles is 2-7 μm, and may be, for example, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, and specific point values between the above point values, and the present invention is not intended to be exhaustive of the specific point values included in the range for reasons of space and for reasons of brevity.

Preferably, the particle size of the core in the core-shell structure is 1-5 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, and specific point values between the above point values, and the present invention is not exhaustive of the specific point values included in the range for the sake of brevity and conciseness.

Preferably, the polymeric monomers of the core polymer comprise a combination of reactive monomers a1 and cross-linkers a 2.

Preferably, the reaction monomer a1 includes any one or a combination of at least two of styrene, methyl styrene, ethyl styrene, acrylonitrile, methacrylonitrile, methyl methacrylate, cyclohexyl methacrylate, isobornyl acrylate, dicyclopentenyl acrylate, maleic acid monoester, maleic acid diester, maleic amide, and maleimide.

Preferably, the cross-linking agent a2 comprises any one or a combination of at least two of divinylbenzene, diallyl phthalate, diethanol diacrylate, ethylene glycol dimethacrylate, allyl methacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol diacrylate or pentaerythritol triacrylate.

Preferably, the mass of the crosslinking agent a2 is from 1 to 20% by mass, calculated as 100% of the mass of the polymerized monomer of the core polymer, and may be, for example, 1%, 3%, 5%, 7%, 9%, 11%, 13%, 15%, 17%, 19%, 20%, and specific point values between the above point values, limited in space and for the sake of brevity, the present invention is not exhaustive of the specific point values included in the range.

Preferably, the polymeric monomers of the shell polymer include a combination of reactive monomers b1, cross-linking agents b2, acidic monomers b3 and long chain alkyl monomers b 4.

Preferably, the reaction monomer b1 includes any one or a combination of at least two of ethyl acrylate, n-butyl acrylate, isobutyl acrylate, isooctyl acrylate, hexyl methacrylate, or tetrahydrofurfuryl acrylate.

Preferably, the cross-linking agent b2 comprises any one or a combination of at least two of divinylbenzene, diallyl phthalate, diethanol diacrylate, ethylene glycol dimethacrylate, allyl methacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol diacrylate or pentaerythritol triacrylate.

Preferably, the acidic monomer b3 includes any one or a combination of at least two of acrylic acid, methacrylic acid, itaconic acid, beta-carboxyethyl acrylate, fumaric acid, crotonic acid, or maleic acid.

Preferably, the long-chain alkyl monomer b4 is an alkyl acrylate and/or alkyl methacrylate having 12 carbons or more (for example, 13 carbons, 14 carbons, 15 carbons, 16 carbons, 17 carbons, 18 carbons, 19 carbons, 20 carbons, 21 carbons, 22 carbons, 23 carbons, 24 carbons, 25 carbons), and more preferably an alkyl acrylate and/or alkyl methacrylate having 12 to 26 carbons.

Preferably, the long chain alkyl monomer b4 includes any one or a combination of at least two of dodecyl acrylate, tetradecyl acrylate, hexadecyl acrylate, octadecyl acrylate, eicosyl acrylate, docosyl acrylate, dodecyl methacrylate, tetradecyl methacrylate, hexadecyl methacrylate, octadecyl methacrylate, eicosyl methacrylate, or docosyl methacrylate.

Preferably, the mass of the crosslinking agent b2 is 0.05 to 2% based on 100% of the mass of the polymerized monomer of the shell polymer, and may be, for example, 0.05%, 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, and specific point values between the above point values, which are limited in length and for brevity, the present invention is not exhaustive.

Preferably, the mass of the polymerized monomer of the shell polymer is from 1 to 5% and the mass of the acidic monomer b3 is, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, and specific point values between the above point values, limited in length and for brevity, the present invention is not exhaustive of the specific point values included in the range.

Preferably, the mass of the polymerized monomer of the shell polymer is from 5 to 10% and the mass of the long chain alkyl monomer b4 may be, for example, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10% based on 100% of the mass of the polymerized monomer, and specific point values among the above point values are limited in space and for brevity, and the present invention is not exhaustive to list the specific point values included in the range.

Preferably, the mass percentage of core polymer in the polymer particles is 15-80%, for example 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, and specific point values between the above point values, are limited in space and for the sake of brevity, the invention is not intended to be exhaustive of the specific point values comprised in the range.

Preferably, the mass percentage of shell polymer in the polymer particles is 20-85%, for example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, and specific point values between the above point values, are limited in space and for the sake of brevity, the invention is not intended to be exhaustive of the specific point values included in the ranges.

In a second aspect, the present invention provides a method for preparing the heat-resistant separator binder according to the first aspect, the method comprising the steps of:

(1) Reacting the reaction monomer a1 with a cross-linking agent a2 to obtain a nuclear polymer;

(2) And (3) carrying out seed polymerization reaction on the core polymer obtained in the step (1) serving as a seed, the reactive monomer b1, the cross-linking agent b2, the acid monomer b3 and the long-chain alkyl monomer b4 to obtain the durable diaphragm binder.

Preferably, the reaction of step (1) is a suspension polymerization reaction, which is carried out in the presence of a dispersant a3 and an initiator a 4.

Preferably, the dispersant a3 comprises polyvinyl alcohol.

Preferably, the polyvinyl alcohol has an alcoholysis level of 70-90%, for example, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, and specific point values between the above point values, and the present invention is not intended to be exhaustive of the specific point values included in the range for reasons of brevity and conciseness.

Preferably, the dispersant a3 is an aqueous solution of polyvinyl alcohol.

Preferably, the aqueous solution of polyvinyl alcohol has a mass fraction of 0.1 to 3wt%, for example, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, and specific point values between the above point values, which are limited in space and for simplicity, the present invention is not exhaustive of the specific point values included in the range.

Preferably, the initiator a4 is an oil-soluble initiator.

Preferably, the initiator a4 comprises any one or a combination of at least two of azobisisobutyronitrile, azobisisoheptonitrile, azobisisovaleronitrile, dibenzoyl peroxide or dilauroyl peroxide.

Preferably, the initiator a4 is used in an amount of 0.1 to 3wt% of the total mass of the reactive monomer a1 and the crosslinking agent a2, for example, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, and specific point values between the above point values, are limited in space and for the sake of brevity, the present invention is not exhaustive of the specific point values included in the range.

Preferably, the reaction monomer a1, the cross-linking agent a2 and the initiator a4 are stirred and mixed before the reaction in the step (1), then added into the aqueous solution of the dispersing agent a3, homogenized into aqueous dispersion by a high-speed homogenizer, and then reacted.

Preferably, the particle size of the aqueous dispersion is from 1 to 5. Mu.m, for example, 1. Mu.m, 2. Mu.m, 3. Mu.m, 4. Mu.m, 5. Mu.m, and specific values between the above values are limited in space and for the sake of brevity the invention is not intended to be exhaustive of the specific values comprised in the range.

Preferably, the core polymer obtained by the reaction in step (1) is an aqueous dispersion of the core polymer.

Preferably, the mass ratio of the total mass of the reactive monomer a1 and the crosslinking agent a2 to water is 1 (2.5-10), for example, may be 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, 1:10, and specific point values between the above point values, which are limited in space and for brevity, the present invention is not exhaustive.

Preferably, the reaction of step (1) is carried out under an atmosphere of nitrogen.

Preferably, the temperature of the reaction in step (1) is 50-90 ℃, for example, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, and specific values between the above values are limited in space and for the sake of brevity, the invention is not exhaustive of the specific values comprised in the range.

Preferably, the reaction time in step (1) is 3-12h, for example, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, and the specific point values between the above point values, are limited in space and for the sake of brevity, the present invention is not exhaustive of the specific point values included in the range.

Preferably, the seed polymerization of step (2) is carried out in the presence of an initiator b5 and an emulsifier b 6.

Preferably, the initiator b5 is a water-soluble initiator.

Preferably, the initiator b5 comprises any one or a combination of at least two of potassium sulfate, sodium persulfate or ammonium persulfate.

Preferably, the emulsifier b6 is any one or a combination of at least two of sodium dodecyl benzene sulfonate, sodium dodecyl sulfate or sodium fatty alcohol polyoxyethylene ether sulfate.

Preferably, the emulsifier b6 in step (2) is an aqueous solution of the emulsifier b 6.

Preferably, the mass of the emulsifier b6 is 0.1 to 2wt% of the total mass of the reactive monomer b1, the crosslinking agent b2, the acidic monomer b3 and the long-chain alkyl monomer b4, and may be, for example, 0.1wt%, 0.3wt%, 0.5wt%, 0.7wt%, 0.9wt%, 1wt%, 1.2wt%, 1.4wt%, 1.6wt%, 1.8wt%, 2wt%, and specific point values between the above point values, and the present invention is not exhaustive of the specific point values included in the range for reasons of brevity and conciseness.

Preferably, deionized water is added into the aqueous dispersion of the core polymer in the step (1) to prepare a reaction primer before the seed polymerization in the step (2).

Preferably, before the reaction in the step (2), the reaction monomer b1, the cross-linking agent b2, the acid monomer b3, the long-chain alkyl monomer b4 and the aqueous solution of the emulsifier b6 are mixed for emulsification, so as to obtain the pre-emulsion.

Preferably, the emulsifying time is 5-20min, for example, 5min, 10min, 15min, 20min, and specific point values among the above point values, which are not exhaustive in the present invention for the sake of brevity and conciseness.

Preferably, the seed polymerization reaction of step (2) adds the initiator b5 to the reaction base material while dropping the pre-emulsion.

Preferably, the time of the dropping is 2-6h, for example, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, and the specific point values among the above point values, which are limited in space and for the sake of brevity, the present invention is not exhaustive of the specific point values included in the range.

Preferably, the seed polymerization of step (2) is carried out under an atmosphere of nitrogen.

Preferably, the temperature of the seed polymerization reaction in step (2) is 65-90 ℃, for example, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, and specific point values between the above point values, and the present invention is not exhaustive of the specific point values included in the range for reasons of space and for reasons of simplicity.

Preferably, the time of the seed polymerization reaction in step (2) is 3-6h, for example, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, and the specific point values between the above point values, are limited in space and for the sake of brevity, the present invention is not exhaustive of the specific point values included in the range.

In a third aspect, the present invention provides a heat resistant separator comprising a porous polyolefin substrate and a coating disposed on the porous polyolefin substrate, the material of the coating comprising the heat resistant separator binder of the first aspect.

Preferably, the material of the coating comprises the following components in parts by mass: 5-10 parts of heat-resistant diaphragm binder, 80-100 parts of ceramic particles, 3-5 parts of ceramic binder and 1-3 parts of rheology regulator.

Preferably, the heat-resistant separator binder is 5 to 10 parts, for example, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, and specific point values between the above point values, are limited in space and for the sake of brevity, and the present invention is not exhaustive of the specific point values included in the range.

As a preferable technical scheme of the invention, the heat-resistant diaphragm adhesive mainly aims at ensuring the adhesion between the diaphragm and the pole piece.

Preferably, the ceramic particles comprise any one or a combination of at least two of boehmite, zirconia, alumina or silica.

Preferably, the ceramic particles are 80-100 parts, for example 80 parts, 81 parts, 82 parts, 83 parts, 84 parts, 85 parts, 86 parts, 87 parts, 88 parts, 89 parts, 90 parts, 91 parts, 92 parts, 93 parts, 94 parts, 95 parts, 96 parts, 97 parts, 98 parts, 99 parts, 100 parts, and specific point values between the above point values, are not exhaustive list of the specific point values included in the range for reasons of brevity and conciseness.

Preferably, the ceramic binder comprises any one or a combination of at least two of polyacrylate, styrene-butadiene latex or polyvinylidene fluoride.

Preferably, the glass transition temperature of the ceramic binder is-70 to 10 ℃, for example, -70 ℃, -65 ℃, -60 ℃, -55 ℃, -50 ℃, -45 ℃, -40 ℃, -35 ℃, -30 ℃, -25 ℃, -20 ℃, -15 ℃, -10 ℃, -5 ℃, 0 ℃, 5 ℃, 10 ℃, and specific point values between the above point values, are limited in length and for simplicity, the invention is not exhaustive list of specific point values included in the range.

Preferably, the particle size of the ceramic binder is 50-1000nm, for example, 1000nm, 900nm, 800nm, 700nm, 600nm, 500nm, 400nm, 300nm, 200nm, 100nm, 50nm, and specific point values between the above point values, which are not exhaustive in the present invention for reasons of brevity and conciseness, are preferably 100-700nm.

Preferably, the ceramic binder is 3-5 parts, for example, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, and specific point values between the above point values, and the present invention is not intended to be exhaustive of the specific point values included in the range for reasons of space and brevity.

As a preferred embodiment of the present invention, the ceramic binder mainly serves to secure adhesion between ceramic particles and adhesion between a ceramic layer and a membrane substrate.

Preferably, the rheology modifier comprises any one or a combination of at least two of carboxymethyl cellulose, sodium polyacrylate or lithium polyacrylate.

Preferably, the rheology modifier is 1-3 parts, for example, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, and specific point values between the above point values, are limited in space and for brevity, and the invention is not intended to be exhaustive of the specific point values included in the range.

As a preferred embodiment of the present invention, the rheology modifier functions to adjust the viscosity of the ceramic slurry to facilitate coating.

Preferably, the porous polyolefin separator substrate is a porous polypropylene film and/or a porous polyethylene film.

Preferably, the porous polyolefin separator substrate has a thickness of 7-11 μm, for example, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, and specific point values between the above point values, which are not exhaustive of the list of specific point values included in the range for the sake of brevity and conciseness.

Preferably, the preparation method of the heat-resistant separator comprises the following steps: and mixing the heat-resistant diaphragm binder, the ceramic particles, the ceramic binder and the rheology modifier to obtain water-dispersible ceramic slurry, coating the water-dispersible ceramic slurry on the surface of the porous polyolefin substrate, and drying to obtain the heat-resistant diaphragm.

Preferably, the water-dispersible ceramic slurry has a solids content of 30-50wt%, such as 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, and specific point values between the above point values, are limited in space and for simplicity, the present invention is not exhaustive of the specific point values included in the range.

Preferably, the temperature of the drying is 40-80 ℃, for example, 40 ℃,45 ℃,50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, and specific point values between the above point values, which are limited in space and for the sake of brevity, the present invention is not exhaustive of the specific point values included in the range.

Preferably, the drying time is 10-300s, for example, 10s, 20s, 30s, 60s, 120s, 180s, 240s, 300s, and specific point values among the above point values, which are limited in space and for the sake of brevity, the present invention is not exhaustive.

Preferably, the heat-resistant separator after drying has a single-sided coating thickness of 1 to 5 μm, for example, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, and specific point values between the above point values, which are limited in length and for brevity, the present invention is not exhaustive of the specific point values included in the range, preferably 1 to 3 μm.

In a fourth aspect, the present invention provides a lithium ion battery, which includes at least one of the heat-resistant separator binder according to the first aspect and the heat-resistant separator according to the third aspect.

Compared with the prior art, the invention has the following beneficial effects:

the invention provides a heat-resistant diaphragm binder, which is polymer particles with a core-shell structure, wherein the polymer particles comprise a core polymer and a shell polymer, and the glass transition temperature of the core polymer is more than or equal to 80 ℃; the glass transition temperature of the shell polymer is less than or equal to 0 ℃. The membrane adhesive core layer has higher glass transition temperature, and can effectively reduce the thermal shrinkage of the membrane; the shell layer has lower glass transition temperature, the cold pressing bonding performance at room temperature is obviously improved, the heat-resistant diaphragm for the lithium ion battery prepared by the diaphragm adhesive has lower heat shrinkage rate, the heat shrinkage rate of the heat-resistant diaphragm is less than or equal to 5% at 130 ℃, and the diaphragm and the negative electrode plate have stronger bonding force, and the bonding strength is more than or equal to 1.4N/m.

Detailed Description

The technical scheme of the invention is further described by the following specific embodiments. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.

The experimental materials used in the examples, comparative examples, application examples and comparative application examples of the present invention are as follows:

(1) Dispersant a3: polyvinyl alcohol with alcoholysis degree of 70-90% and polyvinyl alcohol 1788.

(2) Porous polyolefin separator substrate: from middling lithium film limited;

(3) Ceramic binder: brand SWA610, from Shenzhen electric technologies Co., ltd;

(4) Rheology modifier: carboxymethyl cellulose.

Example 1

The embodiment provides a heat-resistant diaphragm binder and a preparation method thereof, wherein the heat-resistant diaphragm binder is polymer particles with a core-shell structure, the polymer particles comprise a core polymer and a shell polymer, the glass transition temperature of the core polymer is 90 ℃, the polymerization monomer comprises 40 parts of styrene and 10 parts of divinylbenzene, the glass transition temperature of the shell polymer is-50 ℃, and the polymerization monomer comprises a combination of 29.88 parts of butyl acrylate, 0.72 part of diallyl phthalate, 1.8 parts of acrylic acid and 3.6 parts of lauryl acrylate.

The preparation method specifically comprises the following steps:

(1) Adding 40 parts of styrene, 10 parts of divinylbenzene and 1.5 parts of azobisisobutyronitrile into a beaker, mixing, stirring and dissolving uniformly to obtain a mixed monomer; 15 parts of polyvinyl alcohol 1788 are dissolved in deionized water to prepare an aqueous solution of dispersant, wherein the concentration of the dispersant is 3wt%; pouring the mixed monomer into a dispersing agent aqueous solution, homogenizing for 10 minutes by adopting a high-speed homogenizer at 8000 revolutions per minute to obtain a mixed monomer aqueous dispersion with the particle size of 5 mu m; the mixed monomer aqueous dispersion is transferred into a reaction kettle with a stirrer, a thermometer and a nitrogen inlet, the temperature is raised to 70 ℃ after nitrogen is introduced for 30 minutes, the polymerization is carried out for 12 hours at constant temperature, and the core polymer aqueous dispersion with the solid content of 11.5wt% and the particle size of about 4.9 mu m is obtained after the polymerization is completed.

(2) Adding all the core polymer dispersion liquid into a reaction kettle with a stirrer, a thermometer and a nitrogen inlet to form a reaction bed charge; 29.88 parts of butyl acrylate, 0.72 part of diallyl phthalate, 1.8 parts of acrylic acid and 3.6 parts of lauryl acrylate are added to an 84g deionized water solution containing 0.72 part of sodium dodecyl benzene sulfonate, and the mixture is stirred and emulsified for 10 minutes to form a pre-emulsion; after the reaction bed charge was purged with nitrogen for 30 minutes, the temperature was raised to 80℃and 0.72 parts of ammonium persulfate was added, and at the same time, the pre-emulsion was started to be added dropwise for 4 hours. And after the dripping is finished, continuing to perform heat preservation reaction for 3 hours, and cooling to obtain the heat-resistant diaphragm adhesive with the core-shell structure, wherein the solid content is 15.1%, and the particle size is 6.2 mu m.

Example 2

The embodiment provides a heat-resistant separator binder and a preparation method thereof, wherein the heat-resistant separator binder is polymer particles with a core-shell structure, the polymer particles comprise a core polymer and a shell polymer, the glass transition temperature of the core polymer is about 105 ℃, the polymerization monomer comprises 198 parts of cyclohexyl methacrylate and 2 parts of allyl methacrylate, the glass transition temperature of the shell polymer is about-5 ℃, and the polymerization monomer comprises a combination of 164.4 parts of hexyl methacrylate, 164.4 parts of isobutyl acrylate, 0.175 part of trimethylolpropane triacrylate, 3.5 parts of itaconic acid and 17.5 parts of behenyl acrylate.

The preparation method specifically comprises the following steps:

(1) 198 parts of cyclohexyl methacrylate, 2 parts of allyl methacrylate and 0.2 part of dilauryl peroxide are added into a beaker, and the mixture is mixed, stirred and dissolved uniformly to obtain a mixed monomer; in another beaker, 0.5 part of polyvinyl alcohol 1788 was dissolved in 499.5 parts of deionized water to prepare an aqueous dispersion, at which the concentration of the dispersion was 0.1wt%; pouring the mixed monomer into a dispersing agent aqueous solution, and homogenizing for 10 minutes by adopting a high-speed homogenizer at 7000 r/min to obtain a mixed monomer aqueous dispersion with the particle size of about 5.5 mu m; the mixed monomer aqueous dispersion is transferred into a reaction kettle with a stirrer, a thermometer and a nitrogen inlet, the temperature is raised to 90 ℃ after nitrogen is introduced for 30 minutes, the polymerization is carried out for 3 hours at constant temperature, and the core polymer aqueous dispersion with the solid content of 28.5wt% and the particle size of about 5.5 mu m is obtained after the polymerization is completed.

(2) Adding all the core polymer dispersion liquid into a reaction kettle with a stirrer, a thermometer and a nitrogen inlet to form a reaction bed charge; 164.4 parts of hexyl methacrylate, 164.4 parts of isobutyl acrylate, 0.175 parts of trimethylolpropane triacrylate, 3.5 parts of itaconic acid and 17.5 parts of docosyl acrylate are added to a solution of 400g of deionized water containing 0.35 parts of sodium dodecyl sulfate, and stirred and emulsified for 10 minutes to form a pre-emulsion; and (3) introducing nitrogen into the reaction bed charge for 30 minutes, heating to 70 ℃, adding 0.35 part of potassium persulfate, simultaneously starting to dropwise add the pre-emulsion for 6 hours, continuing to perform heat preservation reaction for 6 hours after the dropwise adding is finished, and cooling to obtain the heat-resistant diaphragm binder with the core-shell structure, wherein the solid content is 38.0%, and the particle size is 7.0 mu m.

Example 3

The embodiment provides a heat-resistant diaphragm binder and a preparation method thereof, wherein the heat-resistant diaphragm binder is polymer particles with a core-shell structure, the polymer particles comprise a core polymer and a shell polymer, the glass transition temperature of the core polymer is 170 ℃, the polymerization monomer comprises 45 parts of isobornyl methacrylate and 5 parts of trimethylolpropane triacrylate, the glass transition temperature of the shell polymer is-70 ℃, and the polymerization monomer comprises a combination of 311.5 parts of isooctyl acrylate, 3.5 parts of ethylene glycol diacrylate, 10.5 parts of methacrylic acid and 24.5 parts of octadecyl acrylate.

The preparation method specifically comprises the following steps:

(1) 45 parts of cyclohexyl methacrylate, 5 parts of trimethylolpropane triacrylate and 0.5 part of azodiisoheptanenitrile are added into a beaker, and the mixture is mixed, stirred and dissolved uniformly to obtain a mixed monomer; in another beaker, 2.5 parts of polyvinyl alcohol 1788 was dissolved in 497.5 parts of deionized water to prepare an aqueous dispersion, at which the concentration of the dispersion was 0.5wt%; pouring the mixed monomer into a dispersing agent aqueous solution, and homogenizing for 10 minutes by adopting a high-speed homogenizer at 25000 r/min to obtain a mixed monomer aqueous dispersion with the particle size of about 1 mu m; the mixed monomer aqueous dispersion is transferred into a reaction kettle with a stirrer, a thermometer and a nitrogen inlet, the temperature is raised to 50 ℃ after nitrogen is introduced for 30 minutes, the polymerization is carried out for 5 hours at constant temperature, and the core polymer aqueous dispersion with the solid content of 9.5wt% and the particle size of about 5.5 mu m is obtained after the polymerization is completed.

(2) Adding all the core polymer dispersion liquid into a reaction kettle with a stirrer, a thermometer and a nitrogen inlet to form a reaction bed charge; 311.5 parts of isooctyl acrylate, 3.5 parts of ethylene glycol diacrylate, 10.5 parts of methacrylic acid and 24.5 parts of octadecyl acrylate are added into a solution of 3.5 parts of sodium dodecyl sulfate in 150g of deionized water, and the mixture is stirred and emulsified for 10 minutes to form a pre-emulsion; and (3) introducing nitrogen into the reaction bed charge for 30 minutes, heating to 90 ℃, adding 3.5 parts of potassium persulfate, simultaneously starting to dropwise add the pre-emulsion for 2 hours, continuing to perform heat preservation reaction for 4 hours after the dropwise adding is finished, and cooling to obtain the heat-resistant diaphragm binder with the core-shell structure, wherein the solid content is 39.0%, and the particle size is 2.2 mu m.

Example 4

The embodiment provides a heat-resistant diaphragm binder and a preparation method thereof, wherein the heat-resistant diaphragm binder is polymer particles with a core-shell structure, the polymer particles comprise a core polymer and a shell polymer, the glass transition temperature of the core polymer is 90 ℃, the polymerized monomers comprise 45 parts of styrene and 5 parts of divinylbenzene, the glass transition temperature of the shell polymer is-50 ℃, and the polymerized monomers comprise a combination of 84 parts of butyl acrylate, 1 part of diallyl phthalate, 5 parts of acrylic acid and 10 parts of lauryl acrylate.

The preparation method specifically comprises the following steps:

(1) Adding 45 parts of styrene, 5 parts of divinylbenzene and 1 part of azobisisobutyronitrile into a beaker, mixing, stirring and dissolving uniformly to obtain a mixed monomer; in another beaker, 2.5 parts of polyvinyl alcohol 1788 was dissolved in 497.5 parts of deionized water to prepare an aqueous dispersion, at which the concentration of the dispersion was 0.5wt%; pouring the mixed monomer into a dispersing agent aqueous solution, and homogenizing for 10 minutes by adopting a high-speed homogenizer at 9500 r/min to obtain a mixed monomer aqueous dispersion with the particle size of 4 mu m; the mixed monomer aqueous dispersion is transferred into a reaction kettle with a stirrer, a thermometer and a nitrogen inlet, the temperature is raised to 70 ℃ after nitrogen is introduced for 30 minutes, the polymerization is carried out for 12 hours at constant temperature, and the core polymer aqueous dispersion with 17.0wt% of solid content and the particle diameter of about 4.1 mu m is obtained after the polymerization is completed.

(2) Adding all the core polymer dispersion liquid into a reaction kettle with a stirrer, a thermometer and a nitrogen inlet to form a reaction bed charge; 84 parts of butyl acrylate, 1 part of diallyl phthalate, 5 parts of acrylic acid and 10 parts of lauryl acrylate are added to 66.7g of deionized water solution containing 0.5 part of sodium dodecyl benzene sulfonate, and the mixture is stirred and emulsified for 10 minutes to form a pre-emulsion; and (3) introducing nitrogen into the reaction bed charge for 30 minutes, heating to 80 ℃, adding 0.5 part of ammonium persulfate, simultaneously starting to dropwise add the pre-emulsion for 4 hours, continuing to perform heat preservation reaction for 3 hours after the dropwise adding is finished, and cooling to obtain the heat-resistant diaphragm binder with the core-shell structure, wherein the solid content is 26.5%, and the particle size is 5.3 mu m.

Comparative example 1

A heat-resistant separator binder, which is different from example 1 in that the heat-resistant separator binder is a polymer particle of a non-core-shell structure, which is obtained by blending a polymer having a glass transition temperature of 90 ℃ with a polymer having a glass transition temperature of-50 ℃ (the amount of core-shell polymer is consistent with that of example 1), is prepared as follows:

(1) Adding 40 parts of styrene, 10 parts of divinylbenzene and 1.5 parts of azobisisobutyronitrile into a beaker, mixing, stirring and dissolving uniformly to obtain a mixed monomer; 15 parts of polyvinyl alcohol 1788 are dissolved in 485 parts of deionized water in another beaker to prepare an aqueous solution of dispersant, wherein the concentration of the dispersant is 3wt%; pouring the mixed monomer into a dispersing agent aqueous solution, homogenizing for 10 minutes by adopting a high-speed homogenizer at 8000 revolutions per minute to obtain a mixed monomer aqueous dispersion with the particle size of 5 mu m; the mixed monomer aqueous dispersion is transferred into a reaction kettle with a stirrer, a thermometer and a nitrogen inlet, the temperature is raised to 70 ℃ after nitrogen is introduced for 30 minutes, the polymerization is carried out for 12 hours at constant temperature, and the high glass transition temperature aqueous polymer dispersion with the solid content of 11.5wt% and the grain diameter of about 4.9 mu m is obtained after the polymerization is completed.

(2) 29.88 parts of butyl acrylate, 0.72 part of diallyl phthalate, 1.8 parts of acrylic acid and 3.6 parts of lauryl acrylate are added to a reaction kettle with a stirrer, a thermometer and a nitrogen inlet, and the mixture is stirred and emulsified for 10 minutes to form a pre-emulsion, wherein the pre-emulsion contains 0.72 part of sodium dodecyl benzene sulfonate and 84g of deionized water; and introducing nitrogen into the reaction bed charge for 30 minutes, heating to 80 ℃, adding 0.72 part of ammonium persulfate, carrying out heat preservation reaction for 3 hours, and cooling to obtain the polymer with low glass transition temperature.

And (3) mixing all the polymers obtained in the step (1) and the step (2) to obtain the polymer blend with a non-core-shell structure.

Comparative example 2

A heat resistant separator binder differing from example 1 only in that the core polymer has a glass transition temperature of 53 ℃; the kinds, amounts and preparation methods of the other components were the same as in example 1.

The preparation method specifically comprises the following steps:

(1) Adding 40 parts of isobutyl methacrylate, 10 parts of divinylbenzene and 1.5 parts of azobisisobutyronitrile into a beaker, mixing, stirring and dissolving uniformly to obtain a mixed monomer; 15 parts of polyvinyl alcohol 1788 are dissolved in 485 parts of deionized water in another beaker to prepare an aqueous solution of dispersant, wherein the concentration of the dispersant is 3wt%; pouring the mixed monomer into a dispersing agent aqueous solution, homogenizing for 10 minutes by adopting a high-speed homogenizer at 8000 revolutions per minute to obtain a mixed monomer aqueous dispersion with the particle size of 5 mu m; the mixed monomer aqueous dispersion is transferred into a reaction kettle with a stirrer, a thermometer and a nitrogen inlet, the temperature is raised to 70 ℃ after nitrogen is introduced for 30 minutes, the polymerization is carried out for 12 hours at constant temperature, and the core polymer aqueous dispersion with the solid content of 11.0wt% and the particle size of about 4.7 mu m is obtained after the polymerization is completed.

(2) Adding all the core polymer dispersion liquid into a reaction kettle with a stirrer, a thermometer and a nitrogen inlet to form a reaction bed charge; 29.88 parts of butyl acrylate, 0.72 part of diallyl phthalate, 1.8 parts of acrylic acid and 3.6 parts of lauryl acrylate are added to an 84g deionized water solution containing 0.72 part of sodium dodecyl benzene sulfonate, and the mixture is stirred and emulsified for 10 minutes to form a pre-emulsion; and (3) introducing nitrogen into the reaction bed charge for 30 minutes, heating to 80 ℃, adding 0.72 part of ammonium persulfate, simultaneously starting to dropwise add the pre-emulsion for 4 hours, continuing to perform heat preservation reaction for 3 hours after the dropwise adding is finished, and cooling to obtain the heat-resistant diaphragm binder with the core-shell structure, wherein the solid content is 15.3%, and the particle size is 6.0 mu m.

Comparative example 3

A heat resistant separator binder differing from example 1 only in that the shell polymer has a glass transition temperature of 7 ℃; the kinds, amounts and preparation methods of the other components were the same as in example 1.

The preparation method specifically comprises the following steps:

(1) Adding 40 parts of styrene, 10 parts of divinylbenzene and 1.5 parts of azobisisobutyronitrile into a beaker, mixing, stirring and dissolving uniformly to obtain a mixed monomer; 15 parts of polyvinyl alcohol 1788 are dissolved in 485 parts of deionized water in another beaker to prepare an aqueous solution of dispersant, wherein the concentration of the dispersant is 3wt%; pouring the mixed monomer into a dispersing agent aqueous solution, homogenizing for 10 minutes by adopting a high-speed homogenizer at 8000 revolutions per minute to obtain a mixed monomer aqueous dispersion with the particle size of 5 mu m; the mixed monomer aqueous dispersion is transferred into a reaction kettle with a stirrer, a thermometer and a nitrogen inlet, the temperature is raised to 70 ℃ after nitrogen is introduced for 30 minutes, the polymerization is carried out for 12 hours at constant temperature, and the core polymer aqueous dispersion with the solid content of 11.5wt% and the particle size of about 4.9 mu m is obtained after the polymerization is completed.

(2) Adding all the core polymer dispersion liquid into a reaction kettle with a stirrer, a thermometer and a nitrogen inlet to form a reaction bed charge; 29.88 parts of methyl acrylate, 0.72 part of diallyl phthalate, 1.8 parts of acrylic acid and 3.6 parts of lauryl acrylate are added to an 84g deionized water solution containing 0.72 part of sodium dodecyl benzene sulfonate, and the mixture is stirred and emulsified for 10 minutes to form a pre-emulsion; and (3) introducing nitrogen into the reaction bed charge for 30 minutes, heating to 80 ℃, adding 0.72 part of ammonium persulfate, simultaneously starting to dropwise add the pre-emulsion for 4 hours, continuing to perform heat preservation reaction for 3 hours after the dropwise adding is finished, and cooling to obtain the heat-resistant diaphragm binder with the core-shell structure, wherein the solid content is 15.1%, and the particle size is 6.2 mu m.

Comparative example 4

A heat resistant separator binder differing from example 1 only in that the polymerized monomer of the shell polymer does not contain lauryl acrylate, the amount of butyl acrylate is 33.48 parts (parts of butyl orthoacrylate and lauryl acrylate and sum), the glass transition temperature of the core polymer is 90 ℃, and the glass transition temperature of the shell polymer is-43 ℃; the kinds, amounts and preparation methods of the other components were the same as in example 1.

Comparative example 5

A heat-resistant separator binder differing from example 1 only in that in the heat-resistant separator binder, acrylic acid is not contained in the polymerized monomer of the shell polymer, the amount of butyl acrylate is 31.68 parts (parts of butyl acrylate and acrylic acid and sum), the glass transition temperature of the core polymer is 90 ℃, and the glass transition temperature of the shell polymer is-51 ℃; the kinds, amounts and preparation methods of the other components were the same as in example 1.

Comparative example 6

A heat-resistant separator binder differing from example 1 only in that in the heat-resistant separator binder, acrylic acid and lauryl acrylate are not contained in the polymerized monomer of the shell polymer, the amount of butyl acrylate is 35.28 parts (parts of butyl acrylate, acrylic acid and lauryl acrylate and the like), the glass transition temperature of the core polymer is 90 ℃, and the glass transition temperature of the shell polymer is-47 ℃; the kinds, amounts and preparation methods of the other components were the same as in example 1.

The heat resistant separator adhesives provided in examples 1-4, comparative examples 1-6 were subjected to glass transition temperature testing as follows:

the glass transition temperatures of the core polymer and the shell polymer were measured using a differential scanning calorimeter (Shanghai group-HongAN_SNer Co., ltd., model: DSC-100).

Application example 1

The application example provides a heat-resistant diaphragm and a preparation method thereof, wherein the heat-resistant diaphragm comprises a polyethylene porous film and a coating arranged on the polyethylene porous film, and the coating comprises the following materials in parts by mass: 10 parts of heat-resistant diaphragm binder (example 1), 82 parts of hydrated alumina, 5 parts of SWA610 ceramic binder and 1 part of carboxymethyl cellulose;

the preparation method specifically comprises the following steps:

(1) Preparing ceramic slurry: 82 parts of hydrated alumina (average particle diameter: 0.825 μm), 10 parts of the heat-resistant separator binder of example 1, 5 parts of SWA610 ceramic binder, 1 part of carboxymethyl cellulose, an appropriate amount of deionized water, and a stirring speed of 1000rpm and stirring at room temperature for 4 hours were added to a stirring vessel to obtain a ceramic slurry having a solid content of 30%, wherein the heat-resistant separator binder and the ceramic binder were dry weight.

(2) The ceramic slurry obtained in the step (1) is coated on two sides of a polyethylene porous film with the diameter of 7 mu m by a roller coating mode, and is dried at the temperature of 60 ℃. The thickness of the dried single-sided ceramic layer is 3 mu m.

Application example 2

A heat-resistant separator was different from application example 1 only in that a heat-resistant separator binder was obtained in example 2, and the kinds, amounts and preparation methods of other components were the same as those of application example 1.

Application example 3

A heat-resistant separator was different from application example 1 only in that the heat-resistant separator binder was obtained in example 3, the thickness of the dried single-sided ceramic layer was 1 μm, and the kinds, amounts and preparation methods of other components were the same as those of application example 1.

Application example 4

A heat-resistant separator was different from application example 1 only in that a heat-resistant separator binder was obtained in example 4, and the kinds, amounts and preparation methods of other components were the same as those of application example 1.

Application example 5

A heat-resistant separator was different from application example 1 only in that the heat-resistant separator binder was obtained in example 1, the ceramic particles used were boehmite (average particle diameter: 1.5 μm), and the heat-resistant separator was coated on both sides of a porous polypropylene separator of 11 μm, and the thickness of the single-sided coating after drying was 1. Mu.m.

Application example 6

A heat-resistant separator was different from application example 1 only in that the heat-resistant separator binder was obtained in example 1, the ceramic particles used were boehmite (average particle diameter: 1.5 μm), and the separator was coated on one surface of a 7 μm porous polyethylene separator, and the thickness of the one surface coating after baking was 5. Mu.m.

Comparative application example 1

A heat-resistant separator which differs from application example 1 only in that the heat-resistant separator binder was obtained in comparative example 1; the kinds, amounts and preparation methods of the other components were the same as in application example 1.

Comparative application example 2

A heat-resistant separator differing from application example 1 only in that the heat-resistant separator binder was obtained in comparative example 2; the kinds, amounts and preparation methods of the other components were the same as in application example 1.

Comparative application example 3

A heat-resistant separator differing from application example 1 only in that the heat-resistant separator binder was obtained in comparative example 3; the kinds, amounts and preparation methods of the other components were the same as in application example 1.

Comparative application example 4

A heat-resistant separator differing from application example 1 only in that the heat-resistant separator binder was obtained in comparative example 4; the kinds, amounts and preparation methods of the other components were the same as in application example 1.

Comparative application example 5

A heat-resistant separator differing from application example 1 only in that the heat-resistant separator binder was obtained in comparative example 5; the kinds, amounts and preparation methods of the other components were the same as in application example 1.

Comparative application example 6

A heat-resistant separator differing from application example 1 only in that the heat-resistant separator binder was obtained in comparative example 6; the kinds, amounts and preparation methods of the other components were the same as in application example 1.

The heat resistant separators provided in application examples 1 to 6 and comparative application examples 1 to 6 were subjected to performance test as follows:

And (3) testing the bonding strength between the diaphragm and the negative electrode plate: the diaphragm and the graphite negative plate manufactured by the scheme of the invention are respectively cut into 20 mm long strips, cold-pressed for 20s at the room temperature of 25 ℃ and the pressure of 1MPa, and the bonding strength is tested by an electronic tensile machine.

And (3) testing heat resistance of the diaphragm: the diaphragms prepared by the scheme of the invention are stacked into 3 stacks, air between the diaphragms is discharged, a sample which is cut into 300mm and 100mm is taken out, and the length A1 of the cut sample is measured. The temperature of the oven is set to 130 ℃, and the temperature is kept for 1h after the temperature is reached. The sample was placed in an oven and incubated for 1h. After the heat preservation is completed, taking out the diaphragm, cooling for 10min, measuring the length A2 of the sample, and thermally shrinking the diaphragm

＝(A1-A2)/A1*100％。

The test results are shown in Table 1.

TABLE 1

	Heat shrinkage (%)	Bonding Strength (N/m)
			Application example 1	3.4	1.5
Application example 2	2.8	1.6
			Application example 3	2.9	2.1
Application example 4	3.0	1.9
			Application example 5	3.0	1.6
Application example 6	3.5	1.8
			Comparative application example 1	4.7	0.9
Comparative application example 2	7.5	1.6
			Comparative application example 3	2.4	1.3
Comparative application example 4	3.3	1.2
			Comparative application example 5	3.9	1.3
Comparative application example 6	4.2	1.0

As can be seen from the data in Table 1, the heat-resistant diaphragms of application examples 1 to 6 prepared by using the heat-resistant diaphragm adhesives with core-shell structures obtained in examples 1 to 4 have lower heat shrinkage rate, the heat shrinkage rate of the heat-resistant diaphragm is less than or equal to 5% at 130 ℃, and the diaphragm and the negative electrode plate have stronger adhesive force, and the adhesive strength is more than or equal to 1.4N/m. And the adhesive prepared by simply blending polymers with different glass transition temperatures has extremely low adhesive force. When the glass transition temperature of the core polymer is lower than that of the core polymer of the embodiment, the heat resistance of the separator may be lowered. The glass transition temperature of the shell polymer is not within a preferred range, or when an acid-based monomer or a long-chain alkyl monomer is not used, the adhesive prepared has insufficient adhesive power.

The applicant states that the present invention is illustrated by the above examples as a heat resistant separator adhesive, and a method of preparing the same and application thereof, but the present invention is not limited to the above examples, i.e., it does not mean that the present invention must be practiced depending on the above examples. It should be apparent to those skilled in the art that any modification of the present invention, equivalent substitution of raw materials for the product of the present invention, addition of auxiliary components, selection of specific modes, etc., falls within the scope of the present invention and the scope of disclosure.

Claims

1. The heat-resistant diaphragm binder is characterized in that the heat-resistant diaphragm binder is polymer particles with a core-shell structure, the polymer particles comprise a core polymer and a shell polymer, and the glass transition temperature of the core polymer is more than or equal to 80 ℃;

the glass transition temperature of the shell polymer is less than or equal to 0 ℃.

2. The heat resistant separator binder of claim 1 wherein the polymer particles have a particle size of 2-7 μm;

preferably, the core in the core-shell structure has a particle size of 1-5 μm.

3. The heat resistant separator binder according to claim 1 or 2, wherein the polymerized monomers of the core polymer comprise a combination of reactive monomer a1 and crosslinking agent a 2;

Preferably, the reaction monomer a1 comprises any one or a combination of at least two of styrene, methyl styrene, ethyl styrene, acrylonitrile, methacrylonitrile, methyl methacrylate, cyclohexyl methacrylate, isobornyl acrylate, dicyclopentenyl acrylate, maleic acid monoester, maleic acid diester, maleic amide and maleimide;

preferably, the cross-linking agent a2 comprises any one or a combination of at least two of divinylbenzene, diallyl phthalate, diethanol diacrylate, ethylene glycol dimethacrylate, allyl methacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol diacrylate or pentaerythritol triacrylate;

preferably, the mass of the crosslinking agent a2 is 1 to 20% based on 100% of the mass of the polymerized monomer of the core polymer.

4. A heat resistant separator binder according to any one of claims 1-3 wherein the polymeric monomers of the shell polymer comprise a combination of reactive monomer b1, cross-linker b2, acidic monomer b3 and long chain alkyl monomer b 4;

preferably, the reaction monomer b1 includes any one or a combination of at least two of ethyl acrylate, n-butyl acrylate, isobutyl acrylate, isooctyl acrylate, hexyl methacrylate, or tetrahydrofurfuryl acrylate;

Preferably, the cross-linking agent b2 comprises any one or a combination of at least two of divinylbenzene, diallyl phthalate, diethanol diacrylate, ethylene glycol dimethacrylate, allyl methacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol diacrylate or pentaerythritol triacrylate;

preferably, the acidic monomer b3 comprises any one or a combination of at least two of acrylic acid, methacrylic acid, itaconic acid, beta-carboxyethyl acrylate, fumaric acid, crotonic acid or maleic acid;

preferably, the long-chain alkyl monomer b4 is an alkyl acrylate and/or alkyl methacrylate having 12 carbons or more;

preferably, the long-chain alkyl monomer b4 comprises any one or a combination of at least two of dodecyl acrylate, tetradecyl acrylate, hexadecyl acrylate, octadecyl acrylate, eicosyl acrylate, docosyl acrylate, dodecyl methacrylate, tetradecyl methacrylate, hexadecyl methacrylate, octadecyl methacrylate, eicosyl methacrylate or docosyl methacrylate;

Preferably, the mass of the crosslinking agent b2 is 0.05 to 2% based on 100% of the mass of the polymerized monomer of the shell polymer;

preferably, the mass of the acid monomer b3 is 1 to 5% based on 100% of the mass of the polymerized monomer of the shell polymer;

preferably, the mass of the polymerized monomer of the shell polymer is 100% and the mass of the long chain alkyl monomer b4 is 5 to 10%.

5. The heat resistant separator binder of any of claims 1-4 wherein the mass percent of core polymer in the polymer particles is 15-80%;

preferably, the mass percentage of shell polymer in the polymer particles is 20-85%.

6. A method of preparing the heat resistant separator binder of any one of claims 1-5, comprising the steps of:

7. The process according to claim 6, wherein the reaction in step (1) is a suspension polymerization reaction carried out in the presence of a dispersant a3 and an initiator a 4;

Preferably, the dispersant a3 comprises polyvinyl alcohol;

preferably, the alcoholysis degree of the polyvinyl alcohol is 70-90%;

preferably, the initiator a4 is an oil-soluble initiator;

preferably, the initiator a4 comprises any one or a combination of at least two of azobisisobutyronitrile, azobisisoheptonitrile, azobisisovaleronitrile, dibenzoyl peroxide or dilauroyl peroxide;

preferably, the temperature of the reaction in step (1) is 50-90 ℃;

preferably, the reaction time of step (1) is 3-12 hours;

preferably, the seed polymerization of step (2) is carried out in the presence of an initiator b5 and an emulsifier b 6;

preferably, the initiator b5 is a water-soluble initiator;

preferably, the initiator b5 comprises any one or a combination of at least two of potassium sulfate, sodium persulfate or ammonium persulfate;

preferably, the emulsifier b6 comprises any one or a combination of at least two of sodium dodecyl benzene sulfonate, sodium dodecyl sulfate or sodium fatty alcohol polyoxyethylene ether sulfate;

preferably, the temperature of the seed polymerization reaction in the step (2) is 65-90 ℃;

preferably, the time of the seed polymerization reaction in the step (2) is 3-6h.

8. A heat resistant separator comprising a porous polyolefin substrate and a coating disposed on the porous polyolefin substrate, the material of the coating comprising the heat resistant separator binder of any of claims 1-5.

9. The heat-resistant separator according to claim 8, wherein the material of the coating layer comprises, in parts by mass: 5-10 parts of heat-resistant diaphragm binder, 80-100 parts of ceramic particles, 3-5 parts of ceramic binder and 1-3 parts of rheology regulator;

preferably, the ceramic particles comprise any one or a combination of at least two of boehmite, zirconia, alumina or silica;

preferably, the ceramic binder comprises any one or a combination of at least two of polyacrylate, styrene-butadiene latex or polyvinylidene fluoride;

preferably, the ceramic binder has a glass transition temperature of-70 to 10 ℃;

preferably, the particle size of the ceramic binder is 50-1000nm, preferably 100-700nm;

preferably, the rheology modifier comprises any one or a combination of at least two of carboxymethyl cellulose, sodium polyacrylate or lithium polyacrylate;

preferably, the porous polyolefin membrane substrate is a porous polypropylene film and/or a porous polyethylene film;

Preferably, the porous polyolefin separator substrate has a thickness of 7 to 11 μm.

10. A lithium ion battery comprising at least one of the heat resistant separator binder of any one of claims 1-5, the heat resistant separator of claim 8 or 9.