CN113140870A - Water-based PVDF slurry for lithium ion battery and preparation method and application thereof - Google Patents
Water-based PVDF slurry for lithium ion battery and preparation method and application thereof Download PDFInfo
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- CN113140870A CN113140870A CN202110411885.4A CN202110411885A CN113140870A CN 113140870 A CN113140870 A CN 113140870A CN 202110411885 A CN202110411885 A CN 202110411885A CN 113140870 A CN113140870 A CN 113140870A
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- 239000002033 PVDF binder Substances 0.000 title claims abstract description 128
- 229920002981 polyvinylidene fluoride Polymers 0.000 title claims abstract description 128
- 239000002002 slurry Substances 0.000 title claims abstract description 89
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 67
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 67
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 36
- 238000002360 preparation method Methods 0.000 title claims abstract description 27
- 239000000839 emulsion Substances 0.000 claims abstract description 43
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 claims abstract description 41
- 239000002270 dispersing agent Substances 0.000 claims abstract description 32
- 238000009736 wetting Methods 0.000 claims abstract description 32
- 239000000843 powder Substances 0.000 claims abstract description 30
- 239000002562 thickening agent Substances 0.000 claims abstract description 23
- 239000002518 antifoaming agent Substances 0.000 claims abstract description 19
- 238000000576 coating method Methods 0.000 claims abstract description 19
- 239000011248 coating agent Substances 0.000 claims abstract description 18
- 239000002994 raw material Substances 0.000 claims abstract description 15
- 238000005507 spraying Methods 0.000 claims description 24
- 238000003756 stirring Methods 0.000 claims description 22
- 239000006185 dispersion Substances 0.000 claims description 17
- 239000004094 surface-active agent Substances 0.000 claims description 17
- 239000007788 liquid Substances 0.000 claims description 13
- 239000003960 organic solvent Substances 0.000 claims description 13
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical class O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 11
- 238000000034 method Methods 0.000 claims description 11
- 229920002125 Sokalan® Polymers 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- 238000000227 grinding Methods 0.000 claims description 5
- 229920002635 polyurethane Polymers 0.000 claims description 5
- 239000004814 polyurethane Substances 0.000 claims description 5
- 239000004908 Emulsion polymer Substances 0.000 claims description 4
- 230000015572 biosynthetic process Effects 0.000 claims description 4
- 229910017059 organic montmorillonite Inorganic materials 0.000 claims description 4
- 239000000377 silicon dioxide Substances 0.000 claims description 4
- 229920001296 polysiloxane Polymers 0.000 claims description 3
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 2
- 229910052744 lithium Inorganic materials 0.000 claims description 2
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 abstract description 8
- 238000003860 storage Methods 0.000 abstract description 8
- 239000000126 substance Substances 0.000 abstract description 5
- 239000002904 solvent Substances 0.000 abstract description 3
- 239000002131 composite material Substances 0.000 abstract description 2
- 239000008367 deionised water Substances 0.000 description 11
- 229910021641 deionized water Inorganic materials 0.000 description 11
- 238000001035 drying Methods 0.000 description 8
- 239000007787 solid Substances 0.000 description 6
- 239000003792 electrolyte Substances 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- BQCIDUSAKPWEOX-UHFFFAOYSA-N 1,1-Difluoroethene Chemical compound FC(F)=C BQCIDUSAKPWEOX-UHFFFAOYSA-N 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 229920001577 copolymer Polymers 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000000080 wetting agent Substances 0.000 description 3
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 229910052731 fluorine Inorganic materials 0.000 description 2
- 239000011737 fluorine Substances 0.000 description 2
- 229920001519 homopolymer Polymers 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000003921 oil Substances 0.000 description 2
- 239000004584 polyacrylic acid Substances 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 159000000000 sodium salts Chemical class 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- JSYPRLVDJYQMAI-ODZAUARKSA-N (z)-but-2-enedioic acid;prop-2-enoic acid Chemical compound OC(=O)C=C.OC(=O)\C=C/C(O)=O JSYPRLVDJYQMAI-ODZAUARKSA-N 0.000 description 1
- 229920002126 Acrylic acid copolymer Polymers 0.000 description 1
- 229920000178 Acrylic resin Polymers 0.000 description 1
- 239000004925 Acrylic resin Substances 0.000 description 1
- 229920006243 acrylic copolymer Polymers 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 239000011267 electrode slurry Substances 0.000 description 1
- 238000004945 emulsification Methods 0.000 description 1
- 239000003995 emulsifying agent Substances 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 239000011245 gel electrolyte Substances 0.000 description 1
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- -1 more specifically Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 230000001988 toxicity Effects 0.000 description 1
- 231100000419 toxicity Toxicity 0.000 description 1
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
Classifications
-
- 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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
-
- 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
Abstract
The invention belongs to the technical field of lithium ion batteries, and provides an aqueous PVDF slurry for a lithium ion battery, a preparation method and an application thereof, wherein the aqueous PVDF slurry preferably comprises the following raw materials in parts by mass: 20-50 parts of PVDF powder, 5-10 parts of acrylic emulsion, 0.1-1 part of wetting dispersant, 0.8-2 parts of thickening agent, 0.1-1 part of defoaming agent and the balance of water. Compared with the traditional PVDF slurry added with oily substances such as acetone and the like, the PVDF composite material uses water as a solvent, and is better in safety performance. In the slurry formula of the embodiment of the invention, the acrylic emulsion is used as an auxiliary film forming substance, and raw materials such as wetting dispersant and the like are matched, so that the slurry has good storage stability, and the binding force of the PVDF coating and the diaphragm is improved. The aqueous PVDF slurry is used in the lithium ion battery, so that the service life of the battery is ensured, and the safety is improved.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a stable-system aqueous PVDF slurry for a lithium ion battery, and a preparation method and application thereof.
Background
The lithium ion battery generally comprises a positive electrode, a negative electrode, a diaphragm and an electrolyte, wherein the positive electrode and the negative electrode can be used for embedding and removing lithium ions, the electrolyte has the functions of transporting ions and conducting current between the positive electrode and the negative electrode, and the electrolyte can be in a liquid state, a solid state and other types from a phase state. After the commercial application of the lithium ion battery, the lithium ion battery is widely applied to the field of battery energy due to the advantages of good cycle performance, service life, energy density and the like, and the usage amount per year is still greatly increased.
Polyvinylidene fluoride is a common binder which has been commercially applied in lithium ion battery positive electrode slurry; in the structural composition of the lithium ion battery, PVDF (polyvinylidene fluoride) slurry mainly plays a role in gel electrolyte and bonding a diaphragm and a pole piece, and can also increase the hardness of a battery core. Currently, the market is dominated by sprayable oil-based PVDF slurries and water-based PVDF slurries. Oil-based PVDF slurries are generally prepared by dissolving PVDF or the like in an NMP (N-methylpyrrolidone) organic solvent, and although they have good adhesion, they have some disadvantages: contains a large amount of organic solvent, needs to be recovered, on one hand, increases the input cost of recovery equipment in the preparation process, and on the other hand, the preparation method has complex process and low production efficiency. The water system PVDF slurry contains components such as water, PVDF and the like, is environment-friendly, high in safety and relatively low in price, and is one of the technical development trends.
In the prior art, for example, in chinese patent document No. 201510452494.1, the mass percentages of the components are 0.05-20% of PVDF powder, 0.1-10% of dispersant, 0.2-5% of wetting agent, and the balance water, calculated by 100% of the total mass. The aqueous PVDF slurry prepared by the method described in this patent document is safe because it does not contain organic solvents such as acetone, but has problems such as poor slurry stability and poor coating adhesion.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide the aqueous PVDF slurry for the lithium ion battery, and the preparation method and the application thereof.
In order to achieve the purpose, the invention provides an aqueous PVDF slurry for a lithium ion battery, which comprises the following raw materials: PVDF powder, acrylic emulsion, wetting dispersant, thickener and water; the acrylic emulsion is used for auxiliary system film formation; the aqueous PVDF slurry for the lithium ion battery does not contain an organic solvent.
The preferred embodiment of the invention provides an aqueous PVDF slurry for a lithium ion battery, which comprises the following raw materials in parts by mass: 20-50 parts of PVDF powder, 5-10 parts of acrylic emulsion, 0.1-1 part of wetting dispersant, 0.8-2 parts of thickening agent and the balance of water.
Preferably, the wetting and dispersing agent is selected from polyacrylic acid polymers.
Preferably, the acrylic emulsion is a silicon-modified high-temperature-resistant acrylic emulsion.
Preferably, the thickener is any one of modified organic montmorillonite and modified fumed silica.
Preferably, the aqueous PVDF slurry for lithium ion batteries further comprises a defoaming agent.
Further preferably, the defoaming agent is one or both of silica and silicone.
Preferably, the aqueous PVDF slurry for lithium ion batteries further comprises other surfactants, more preferably 0.5-2 parts.
Further preferably, the other surfactant is a polyurethane emulsion polymer.
In a preferred embodiment of the invention, the aqueous PVDF slurry for the lithium ion battery is prepared by mixing the following raw materials in parts by mass: 20-50 parts of PVDF powder, 5-10 parts of acrylic emulsion, 0.1-1 part of wetting dispersant, 0.8-2 parts of thickening agent, 0.1-1 part of defoaming agent, 0.5-2 parts of other surfactants and the balance of water.
The embodiment of the invention provides a preparation method of the aqueous PVDF slurry for the lithium ion battery, which comprises the following steps:
s1) mixing water and the wetting dispersant according to the mass ratio, adding PVDF powder, stirring and dispersing, and then grinding to obtain PVDF dispersion liquid;
s2) adding the PVDF dispersion liquid obtained in the step S1) and the rest raw materials into acrylic emulsion, and stirring and dispersing to obtain the aqueous PVDF slurry for the lithium ion battery.
Preferably, the stirring and dispersing time in the step S1) is 10-20 minutes, and the rotation speed is 800-1200 rpm;
the stirring and dispersing time in the step S2) is 20-60 minutes, and the stirring speed is 400-600 rpm.
The invention provides application of the aqueous PVDF slurry for the lithium ion battery in preparation of the lithium ion battery, and a coating is formed by adopting a spraying coating mode.
Preferably, the coating is formed by drying after the spraying, wherein the drying time is 10-20 minutes and the temperature is 240-260 ℃.
Preferably, the thickness of the coating is 15-20 μm, and the binding power is more than 15N/m.
Compared with the prior art, the invention forms a system which does not contain organic solvent and has simple preparation process mainly by adjusting the formula of the aqueous PVDF slurry. Compared with the traditional PVDF slurry added with oily substances such as acetone and the like, the PVDF composite material uses water as a solvent, and is better in safety performance. In the slurry formula, the acrylic emulsion is used as an auxiliary film forming substance, and raw materials such as a wetting dispersant and the like are matched, so that the slurry has good storage stability, and the binding force of the PVDF coating and the diaphragm is improved. The aqueous PVDF slurry is used in the lithium ion battery, so that the service life of the battery is ensured, and the safety is improved.
In addition, the preparation of the embodiment of the invention adopts a dispersing-grinding-dispersing process, thereby simplifying the preparation process flow.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides an aqueous PVDF slurry for a lithium ion battery, which comprises the following raw materials: PVDF powder, acrylic emulsion, wetting dispersant, thickener and water; the acrylic emulsion is used for auxiliary system film formation; the aqueous PVDF slurry for the lithium ion battery does not contain an organic solvent. In a preferred embodiment of the invention, the aqueous PVDF slurry for lithium ion batteries comprises the following raw materials in parts by mass: 20-50 parts of PVDF powder, 5-10 parts of acrylic emulsion, 0.1-1 part of wetting dispersant, 0.8-2 parts of thickening agent and the balance of water.
In order to solve the problems of poor storage stability and poor caking property of a slurry system in the existing aqueous PVDF spraying slurry for the lithium ion battery, the invention provides the aqueous PVDF slurry which does not contain an organic solvent and has excellent performance and is beneficial to being applied to the preparation of the lithium ion battery.
The aqueous PVDF slurry comprises 20-50 parts by mass of PVDF powder, wherein PVDF is the English abbreviation of Poly (vinylidene fluoride), and polyvinylidene fluoride mainly refers to vinylidene fluoride (VDF) homopolymer or a copolymer of vinylidene fluoride and other small amount of fluorine-containing vinyl monomers, and has the characteristics of both fluorine resin and general resin. In the embodiment of the invention, the PVDF powder sold in the market is adopted, and the dosage is specifically 20 parts, 30 parts, 50 parts and the like; the general molecular weight is more than 100 ten thousand, and the rotary viscosity is more than 8000mPa.S (normal temperature).
Considering that the dispersion effect of the PVDF powder in an aqueous system directly affects the service life of the battery, 5-10 parts of acrylic emulsion is preferably adopted in the embodiment of the invention, which can play a role in auxiliary film formation, is insoluble in electrolyte, and has no migration problem, so that the PVDF powder has good dispersion effect and storage stability in the acrylic emulsion. Meanwhile, the acrylic emulsion has excellent film-forming property, and can improve the binding force between the PVDF coating and the diaphragm.
The acrylic emulsion is a water-based emulsion system of pure acrylic resin, does not contain an organic solvent, and generally has the temperature resistance of 170-200 ℃. In the embodiment of the invention, PVDF powder slurry is baked and formed at high temperature (such as above 240 ℃), and the adopted acrylic emulsion is preferably silicon modified high-temperature-resistant acrylic emulsion which can resist the temperature of 300 ℃, has the solid mass content (solid content for short) of more than 40 percent and has the pH value of 7-9. The embodiment of the invention only needs to adopt the commercial acrylic emulsion products, and the dosage is 5 parts, 6 parts, 8 parts, 10 parts and the like.
Considering that there is a problem in safety in the conventional PVDF slurry in which an oily substance such as acetone is added as an organic solvent, the present invention uses water as a solvent, more specifically, deionized water. The balance of water in the embodiment of the invention means that the system is supplemented to 100 parts by mass. In addition, the slurry formula of the embodiment of the invention comprises 0.1-1 part of wetting dispersant, 0.8-2 parts of thickening agent, 0.1-1 part of defoaming agent and 0.5-2 parts of other surfactants, so that the aqueous PVDF spraying slurry for the lithium ion battery, which does not contain organic solvent, has good storage stability and strong cohesiveness, is obtained.
In an embodiment of the present invention, the wetting and dispersing agent of the aqueous PVDF spray coating paste for a lithium ion battery is further a polyacrylic acid polymer, and the polyacrylic acid polymer may be an acrylic copolymer or a homopolymer, and specifically is one or more of a maleic acid-acrylic acid copolymer, a polyacrylic acid sodium salt polymer, a methacrylic acid-methyl methacrylate copolymer, and a phosphorous acrylic acid-sodium acrylate copolymer, and mainly plays a role in wetting and dispersing.
In an embodiment of the present invention, the thickener of the aqueous PVDF spray slurry for a lithium ion battery is further any one of modified organic montmorillonite and modified fumed silica.
In an embodiment of the present invention, the defoaming agent of the above aqueous PVDF spray paste for a lithium ion battery is further one or both of silica and silicone.
In the embodiment of the invention, the other surfactant of the aqueous PVDF spraying slurry for the lithium ion battery is further polyurethane emulsion polymer, can be used as an emulsifier, has space stability, shortens the cycle time, is easy to prepare, can play a role in dispersing, provides shear stability, and can be compatible with fillers and the like.
In the embodiment of the present invention, the sources of the wetting dispersant, the thickener, the defoaming agent, and the like are not particularly limited, and commercially available products are generally used.
In a preferred embodiment of the invention, the aqueous PVDF slurry for the lithium ion battery is prepared by mixing the following raw materials in parts by mass: 20-50 parts of PVDF powder, 5-10 parts of acrylic emulsion, 0.1-1 part of wetting dispersant, 0.8-2 parts of thickening agent, 0.1-1 part of defoaming agent, 0.5-2 parts of other surfactants and the balance of water.
The embodiment of the invention provides a preparation method of the aqueous PVDF slurry for the lithium ion battery, which comprises the following steps:
s1) mixing water and the wetting dispersant according to the mass ratio, adding PVDF powder, stirring and dispersing, and then grinding to obtain PVDF dispersion liquid;
s2) adding the PVDF dispersion liquid obtained in the step S1) and the rest raw materials into acrylic emulsion, and stirring and dispersing to obtain the aqueous PVDF slurry for the lithium ion battery.
The invention preferably adopts a simple dispersing-grinding-dispersing process, and the aqueous PVDF slurry is prepared by adjusting the slurry formula and the process. Wherein the slurry formula and the like are as described above.
In the embodiment of the invention, deionized water can be used for dispersing the wetting dispersant, and then PVDF powder is added, stirred and dispersed for 10-20 minutes at the rotation speed of 800-1200rpm, such as 900-1100rpm, and is ground after being uniformly stirred and dispersed, preferably with the fineness of less than or equal to 10 mu m, so as to obtain the PVDF dispersion liquid.
In the embodiment of the invention, the obtained dispersion liquid and other components are added into the acrylic emulsion, and are dispersed for 20-60 minutes at the stirring speed of 400-600rpm, and after uniform stirring, the sprayable aqueous PVDF slurry is obtained.
The embodiment of the invention provides application of the aqueous PVDF slurry for the lithium ion battery in the preparation of the lithium battery, and the coating is formed by adopting a spraying coating mode in consideration of the uniformity of PVDF in film forming.
In the application method of the aqueous PVDF spraying slurry for the lithium ion battery in the embodiment of the invention, the coating method is spraying, the high-temperature baking forming is performed, the drying time can be 10 minutes to 20 minutes, for example, 15 minutes, and the drying temperature is preferably 240-260 ℃, and more preferably 250 ℃.
The water-based PVDF slurry provided by the embodiment of the invention is used for forming a coating, the film thickness can be 15-20 mu m, the binding power of the coating is more than 15N/m, and the VOC content is extremely low (less than or equal to 5%). According to the embodiment of the invention, by adjusting the slurry formula, the preparation process and the like, the problems of poor storage stability and poor cohesiveness of a slurry system existing in the conventional aqueous PVDF spraying slurry for the lithium ion battery are solved, a stable system which does not contain an organic solvent and has a simple preparation process is formed, toxicity to a human body is avoided, and the slurry is not inflammable and explosive and is beneficial to being used for the lithium ion battery.
For further understanding of the present application, the aqueous PVDF slurry for lithium ion batteries provided in the present application, and the preparation method and application thereof are specifically described below with reference to examples. It should be understood, however, that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention, which is defined by the following examples.
In the following examples, the PVDF powder has a molecular weight > 100 ten thousand and a rotational viscosity > 8000 mPa.S; the acrylic emulsion is silicon modified high temperature resistant acrylic emulsion, the solid content is more than or equal to 40 percent, the lowest film forming temperature is 20 ℃, and the pH value is 7-9; the wetting dispersant is a polyacrylic acid sodium salt polymer, and the solid content is more than or equal to 40 percent; the thickening agent is modified organic montmorillonite; the defoaming agent is silicon dioxide, and the purity is more than or equal to 98 percent; other surfactants are polyurethane emulsion polymers, the solid content is more than or equal to 30 percent, and the emulsification and dispersion effects are realized.
Example 1
An aqueous PVDF spraying slurry for a lithium ion battery is composed of the following components in parts by weight: 20 parts of PVDF powder, 0.1 part of wetting dispersant, 0.5 part of other surfactant, 0.8 part of thickening agent, 0.1 part of defoaming agent, 5 parts of acrylic emulsion and the balance of deionized water.
The preparation method comprises the following steps:
1) dispersing the wetting dispersant by using deionized water, then adding PVDF powder into the dispersion and stirring for 15 minutes at the rotating speed of 1000rpm, uniformly stirring and dispersing, and then grinding the mixture to obtain a PVDF dispersion liquid, wherein the fineness is less than or equal to 10 microns;
2) adding the dispersion liquid obtained in the step 1) and other components into an acrylic emulsion, dispersing for 50 minutes at a stirring speed of 500rpm, and uniformly stirring to obtain the aqueous PVDF spraying slurry.
And spraying the aqueous PVDF slurry to form a coating, wherein the drying time is 15 minutes, and the drying temperature is 250 ℃.
Example 2
An aqueous PVDF spraying slurry for a lithium ion battery is composed of the following components in parts by weight: 50 parts of PVDF powder, 1 part of wetting dispersant, 2 parts of other surfactants, 2 parts of thickening agent, 1 part of defoaming agent, 10 parts of acrylic emulsion and the balance of deionized water.
The preparation method comprises the following steps:
1) dispersing the wetting dispersant by using deionized water, then adding PVDF powder into the dispersion and stirring for 20 minutes at the rotating speed of 1200rpm, uniformly stirring and dispersing, and then grinding the mixture to obtain a PVDF dispersion liquid, wherein the fineness is less than or equal to 10 microns;
2) adding the dispersion liquid obtained in the step 1) and other components into an acrylic emulsion, dispersing for 30 minutes at a stirring speed of 600rpm, and uniformly stirring to obtain the aqueous PVDF spraying slurry.
And spraying the aqueous PVDF slurry to form a coating, wherein the drying time and the drying temperature are the same as those of the example 1.
Example 3
An aqueous PVDF spraying slurry for a lithium ion battery is composed of the following components in parts by weight: 30 parts of PVDF powder, 0.5 part of wetting dispersant, 1 part of other surfactant, 1.5 parts of thickening agent, 0.8 part of defoaming agent, 8 parts of acrylic emulsion and the balance of deionized water.
The preparation method is the same as that of example 1.
Example 4
An aqueous PVDF spraying slurry for a lithium ion battery is composed of the following components in parts by weight: 20 parts of PVDF powder, 0.3 part of wetting dispersant, 0.5 part of other surfactant, 1.2 parts of thickening agent, 0.3 part of defoaming agent, 10 parts of acrylic emulsion and the balance of deionized water.
The preparation method is the same as that of example 1.
Example 5
An aqueous PVDF spraying slurry for a lithium ion battery is composed of the following components in parts by weight: 50 parts of PVDF powder, 1 part of wetting dispersant, 1.8 parts of other surfactants, 1.8 parts of thickening agent, 0.8 part of defoaming agent, 5 parts of acrylic emulsion and the balance of deionized water.
The preparation method is the same as that of example 1.
Comparative example 1
An aqueous PVDF spraying slurry for a lithium ion battery is composed of the following components in parts by weight: 25 parts of PVDF powder, 0.1 part of wetting dispersant, 0.5 part of other surfactant, 0.8 part of thickening agent, 0.1 part of defoaming agent and the balance of deionized water.
The preparation method is basically the same as that of example 1.
Example 6
An aqueous PVDF spraying slurry for a lithium ion battery is composed of the following components in parts by weight: 20 parts of PVDF powder, 0.1 part of wetting dispersant, 0.8 part of thickening agent, 0.1 part of defoaming agent, 5 parts of acrylic emulsion and the balance of deionized water.
The preparation method is the same as that of example 1.
The storage stability and the coating adhesion of the aqueous PVDF slurry are determined by the GB/T6753.3-1986 method, the film thickness is determined by the GB13452.2-2008 method, and the adhesion is determined by the GB/T5210-2006 method.
TABLE 1 Properties of aqueous PVDF slurries of examples of the invention
In comparative example 1, the adhesion was poor without adding the acrylic emulsion. In example 6, the dispersibility and the adhesion were not affected to some extent by adding the polyurethane emulsion.
The above examples show that the aqueous PVDF spraying slurry system for the lithium ion battery has the characteristics of good storage stability and strong cohesiveness, has the advantages of no organic solvent, simple preparation process and the like, and is beneficial to application.
The above description is only a preferred embodiment of the present invention, and it should be noted that various modifications to these embodiments can be implemented by those skilled in the art without departing from the technical principle of the present invention, and these modifications should be construed as the scope of the present invention.
Claims (15)
1. The aqueous PVDF slurry for the lithium ion battery is characterized by comprising the following raw materials: PVDF powder, acrylic emulsion, wetting dispersant, thickener and water; the acrylic emulsion is used for auxiliary system film formation; the aqueous PVDF slurry for the lithium ion battery does not contain an organic solvent.
2. The aqueous PVDF slurry for the lithium ion battery as claimed in claim 1, which comprises the following raw materials in parts by mass: 20-50 parts of PVDF powder, 5-10 parts of acrylic emulsion, 0.1-1 part of wetting dispersant, 0.8-2 parts of thickening agent and the balance of water.
3. The aqueous PVDF slurry for lithium ion batteries according to claim 2, wherein the wetting dispersant is selected from polyacrylic acid polymers.
4. The aqueous PVDF slurry for lithium ion batteries according to claim 2, wherein the acrylic emulsion is a silicon-modified high temperature resistant acrylic emulsion.
5. The aqueous PVDF slurry for lithium ion batteries according to claim 2, wherein the thickener is any one of modified organic montmorillonite and modified fumed silica.
6. The aqueous PVDF slurry for lithium ion batteries according to any one of claims 1 to 5, further comprising a defoaming agent.
7. The aqueous PVDF slurry for lithium ion batteries according to claim 6, wherein the defoaming agent is one or both of silica and silicone.
8. The aqueous PVDF slurry for lithium ion batteries according to claim 6, wherein the aqueous PVDF slurry for lithium ion batteries further comprises other surfactants, and the other surfactants are polyurethane emulsion polymers.
9. The aqueous PVDF slurry for lithium ion batteries according to claim 8, wherein the other surfactant is 0.5-2 parts.
10. The aqueous PVDF slurry for the lithium ion battery as claimed in claim 9, wherein the aqueous PVDF slurry for the lithium ion battery is prepared by mixing the following raw materials in parts by mass: 20-50 parts of PVDF powder, 5-10 parts of acrylic emulsion, 0.1-1 part of wetting dispersant, 0.8-2 parts of thickening agent, 0.1-1 part of defoaming agent, 0.5-2 parts of other surfactants and the balance of water.
11. The method for preparing the aqueous PVDF slurry for lithium ion batteries according to any one of claims 1 to 10, comprising the following steps:
s1) mixing water and the wetting dispersant according to the mass ratio, adding PVDF powder, stirring and dispersing, and then grinding to obtain PVDF dispersion liquid;
s2) adding the PVDF dispersion liquid obtained in the step S1) and the rest raw materials into acrylic emulsion, and stirring and dispersing to obtain the aqueous PVDF slurry for the lithium ion battery.
12. The method as claimed in claim 11, wherein the stirring and dispersing time in step S1) is 10-20 minutes, and the rotation speed is 800-1200 rpm;
the stirring and dispersing time in the step S2) is 20-60 minutes, and the stirring speed is 400-600 rpm.
13. Use of an aqueous PVDF slurry for lithium ion batteries according to any of claims 1-10 in the preparation of lithium batteries, characterised in that the coating is formed by means of a spray coating.
14. The use according to claim 13, wherein the coating is formed by baking after spraying, the baking time being 10-20 minutes and the temperature being 240-260 ℃.
15. Use according to claim 13, wherein the coating has a thickness of 15-20 μm and a cohesion of above 15N/m.
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