CN117239353A - Coating slurry, battery separator and preparation method - Google Patents
Coating slurry, battery separator and preparation method Download PDFInfo
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- CN117239353A CN117239353A CN202311499463.2A CN202311499463A CN117239353A CN 117239353 A CN117239353 A CN 117239353A CN 202311499463 A CN202311499463 A CN 202311499463A CN 117239353 A CN117239353 A CN 117239353A
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- 239000006255 coating slurry Substances 0.000 title claims abstract description 60
- 238000002360 preparation method Methods 0.000 title abstract description 6
- 239000002245 particle Substances 0.000 claims abstract description 175
- 239000000919 ceramic Substances 0.000 claims abstract description 65
- 229920000642 polymer Polymers 0.000 claims abstract description 63
- 239000007787 solid Substances 0.000 claims abstract description 19
- 239000011248 coating agent Substances 0.000 claims description 35
- 238000000576 coating method Methods 0.000 claims description 35
- 239000000758 substrate Substances 0.000 claims description 22
- 239000011230 binding agent Substances 0.000 claims description 17
- 239000002270 dispersing agent Substances 0.000 claims description 17
- 239000004014 plasticizer Substances 0.000 claims description 17
- 239000011247 coating layer Substances 0.000 claims description 16
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 claims description 9
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 9
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 9
- 239000002904 solvent Substances 0.000 claims description 9
- 239000002033 PVDF binder Substances 0.000 claims description 7
- 239000008367 deionised water Substances 0.000 claims description 7
- 229910021641 deionized water Inorganic materials 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 claims description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 claims description 6
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 6
- 229920000058 polyacrylate Polymers 0.000 claims description 6
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 6
- 238000001035 drying Methods 0.000 claims description 5
- 229920003229 poly(methyl methacrylate) Polymers 0.000 claims description 5
- 239000004926 polymethyl methacrylate Substances 0.000 claims description 5
- PQUXFUBNSYCQAL-UHFFFAOYSA-N 1-(2,3-difluorophenyl)ethanone Chemical compound CC(=O)C1=CC=CC(F)=C1F PQUXFUBNSYCQAL-UHFFFAOYSA-N 0.000 claims description 3
- 239000004354 Hydroxyethyl cellulose Substances 0.000 claims description 3
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims description 3
- 229920003171 Poly (ethylene oxide) Polymers 0.000 claims description 3
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 claims description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 3
- 229910001593 boehmite Inorganic materials 0.000 claims description 3
- 239000001768 carboxy methyl cellulose Substances 0.000 claims description 3
- 229920003090 carboxymethyl hydroxyethyl cellulose Polymers 0.000 claims description 3
- HPXRVTGHNJAIIH-UHFFFAOYSA-N cyclohexanol Chemical compound OC1CCCCC1 HPXRVTGHNJAIIH-UHFFFAOYSA-N 0.000 claims description 3
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 claims description 3
- 235000019447 hydroxyethyl cellulose Nutrition 0.000 claims description 3
- 239000001866 hydroxypropyl methyl cellulose Substances 0.000 claims description 3
- 229920003088 hydroxypropyl methyl cellulose Polymers 0.000 claims description 3
- 235000010979 hydroxypropyl methyl cellulose Nutrition 0.000 claims description 3
- UFVKGYZPFZQRLF-UHFFFAOYSA-N hydroxypropyl methyl cellulose Chemical compound OC1C(O)C(OC)OC(CO)C1OC1C(O)C(O)C(OC2C(C(O)C(OC3C(C(O)C(O)C(CO)O3)O)C(CO)O2)O)C(CO)O1 UFVKGYZPFZQRLF-UHFFFAOYSA-N 0.000 claims description 3
- 229920005569 poly(vinylidene fluoride-co-hexafluoropropylene) Polymers 0.000 claims description 3
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 3
- 239000000377 silicon dioxide Substances 0.000 claims description 3
- 229940047670 sodium acrylate Drugs 0.000 claims description 3
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 claims description 3
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 claims description 3
- 229920003048 styrene butadiene rubber Polymers 0.000 claims description 3
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 claims description 3
- 239000011787 zinc oxide Substances 0.000 claims description 3
- 230000000052 comparative effect Effects 0.000 description 16
- 238000012360 testing method Methods 0.000 description 10
- 238000006243 chemical reaction Methods 0.000 description 5
- 239000004743 Polypropylene Substances 0.000 description 3
- 230000001070 adhesive effect Effects 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 230000035699 permeability Effects 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000012982 microporous membrane Substances 0.000 description 2
- 238000009423 ventilation Methods 0.000 description 2
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000003213 activating effect Effects 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- OJIJEKBXJYRIBZ-UHFFFAOYSA-N cadmium nickel Chemical compound [Ni].[Cd] OJIJEKBXJYRIBZ-UHFFFAOYSA-N 0.000 description 1
- 230000001186 cumulative effect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- -1 polypropylene Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000007761 roller coating Methods 0.000 description 1
- 238000007650 screen-printing Methods 0.000 description 1
- 230000011218 segmentation Effects 0.000 description 1
- 229910001415 sodium ion Inorganic materials 0.000 description 1
- 238000004528 spin coating Methods 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
-
- 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 application provides a coating slurry, a battery diaphragm and a preparation method thereof; wherein the coating slurry comprises solid content, and the weight of the solid content accounts for 20-40% of the total weight of the coating slurry; the solid content comprises polymer particles and ceramic particles, and the ratio of the average particle diameter D50 of the polymer particles to the average particle diameter D50 of the ceramic particles is 0.1:1 to 0.83:1. The coating slurry of the present application contains ceramic particles and polymer particles, wherein the ceramic particles can impart excellent heat resistance to the battery separator; meanwhile, the application controls the ratio of the average particle diameter D50 of the ceramic particles and the polymer particles in the coating slurry, so that the polymer particles with smaller particle diameters are easy to float on the outermost surface of the battery separator, and on the other hand, the polymer particles can be better dispersed among the ceramic particles, thereby ensuring that the battery separator coated with the coating slurry has better pole piece adhesion. The battery separator provided by the application has good heat resistance and adhesion.
Description
Technical Field
The application relates to the field of secondary batteries, in particular to a coating slurry, a battery diaphragm and a preparation method.
Background
The battery diaphragm is an important component for forming the battery core of the secondary battery, and is a film for separating the positive electrode from the negative electrode and preventing direct reaction from losing energy when in electrolytic reaction. The performance of the battery diaphragm determines the interface structure, internal resistance and the like of the battery, directly influences the capacity, circulation, safety performance and other characteristics of the battery, and the battery diaphragm with excellent performance plays an important role in improving the comprehensive performance of the battery.
In the prior art, the battery separator cannot simultaneously achieve heat resistance and adhesion. The above problems are technical problems to be solved in the art.
Disclosure of Invention
The application mainly solves the technical problem of providing a coating slurry with heat resistance and adhesion, a battery diaphragm and a preparation method thereof.
According to a first aspect, the present application provides a coating slurry comprising solids, the weight of the solids comprising 20% to 40% of the total weight of the coating slurry;
the solid content comprises polymer particles and ceramic particles, and the ratio of the average particle diameter D50 of the polymer particles and the ceramic particles is 0.1:1 to 0.83:1.
In an alternative embodiment, the ratio of the average particle size D50 of the polymer particles and the ceramic particles is from 0.3:1 to 0.6:1.
In an alternative embodiment, the coating paste satisfies at least one of the conditions (1) to (4):
(1) The average particle diameter D50 of the ceramic particles is 300nm-1000nm; optionally, the average particle diameter D50 of the ceramic particles is 300nm to 500nm;
(2) The ceramic particles comprise one or more of alumina, silica, zinc oxide, and boehmite;
(3) The average particle diameter D50 of the polymer particles is 100nm-250nm;
(4) The polymer particles include one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyethylene oxide, and polymethyl methacrylate.
In an alternative embodiment, the weight ratio of the polymer particles to the ceramic particles is from 0.25:1 to 0.55:1.
In an alternative embodiment, the solid content further comprises one or more of a binder, a dispersant, and a plasticizer.
In an alternative embodiment, the coating paste satisfies at least one of the conditions (1) to (7):
(1) The binder comprises one or more of polyacrylate and styrene-butadiene rubber;
(2) The weight of the binder accounts for 0.1% -5% of the total weight of the coating slurry;
(3) The dispersing agent comprises one or more of sodium acrylate, ammonium polyacrylate, n-butanol and cyclohexanol;
(4) The weight of the dispersing agent accounts for 0.1% -5% of the total weight of the coating slurry;
(5) The plasticizer comprises one or more of sodium carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl methyl cellulose;
(6) The weight of the plasticizer accounts for 0.01% -2% of the total weight of the coating slurry;
(7) The coating slurry includes a solvent; optionally, the solvent is one or more of deionized water, acetone, tetrahydrofuran, methyl ethyl ketone, dimethylformamide and dimethylacetamide.
According to a second aspect, the present application provides a battery separator comprising a porous substrate; and
a porous coating layer disposed on at least one side surface of the porous substrate, the porous coating layer comprising polymer particles and ceramic particles, the ratio of the average particle diameter D50 of the polymer particles and the ceramic particles being 0.1:1 to 0.83:1;
the porous coating comprises a first region and a second region with the same thickness, the second region is positioned on one side of the first region away from the porous substrate, and the volume ratio of the polymer particles in the first region is smaller than that of the polymer particles in the second region.
In an alternative embodiment, the volume ratio of the ceramic particles in the first region is greater than the volume ratio of the ceramic particles in the second region.
In an alternative embodiment, the thickness of the porous coating is 0.5 μm to 4 μm, alternatively the thickness of the porous coating is 0.5 μm to 2 μm.
The third aspect of the application provides a preparation method of the battery separator, comprising the following steps:
coating the coating slurry on at least one side surface of the porous substrate;
and drying and curing the coating slurry to prepare the battery separator.
The application has the beneficial effects that: the coating slurry of the present application contains ceramic particles and polymer particles, wherein the ceramic particles can impart excellent heat resistance to the battery separator; meanwhile, the application controls the ratio of the average particle diameter D50 of the ceramic particles and the polymer particles in the coating slurry, so that the polymer particles with smaller particle diameters are easy to float on the outermost surface of the battery separator, and on the other hand, the polymer particles can be better dispersed among the ceramic particles, thereby ensuring that the battery separator coated with the coating slurry has better pole piece adhesion. The battery separator provided by the application has good heat resistance and adhesion.
Drawings
Fig. 1 is a schematic view showing a layered structure of a battery separator according to an embodiment of the present application.
Fig. 2 is a schematic view showing a layered structure of a battery separator according to another embodiment of the present application.
Reference numerals: a porous substrate 1 and a porous coating 2.
Detailed Description
The application will be described in further detail below with reference to the drawings by means of specific embodiments. Wherein like elements in different embodiments are numbered alike in association. In the following embodiments, numerous specific details are set forth in order to provide a better understanding of the present application. However, one skilled in the art will readily recognize that some of the features may be omitted, or replaced by other elements, materials, or methods in different situations. In some instances, related operations of the present application have not been shown or described in the specification in order to avoid obscuring the core portions of the present application, and may be unnecessary to persons skilled in the art from a detailed description of the related operations, which may be presented in the description and general knowledge of one skilled in the art.
Furthermore, the described features, operations, or characteristics of the description may be combined in any suitable manner in various embodiments. Also, various steps or acts in the method descriptions may be interchanged or modified in a manner apparent to those of ordinary skill in the art. Thus, the various orders in the description and drawings are for clarity of description of only certain embodiments, and are not meant to be required orders unless otherwise indicated.
The numbering of the components itself, e.g. "first", "second", etc., is used herein merely to distinguish between the described objects and does not have any sequential or technical meaning. The term "coupled" as used herein includes both direct and indirect coupling (coupling), unless otherwise indicated.
In the present application, the term "secondary battery" refers to a battery that can be continuously used by activating an active material by charging after discharging the battery. Such cells typically utilize the reversibility of chemical reactions, i.e., after one chemical reaction is converted to electrical energy, the chemical system can also be repaired with electrical energy and then converted to electrical energy by the chemical reaction. Among them, more common secondary batteries include, but are not limited to, nickel-hydrogen batteries, nickel-cadmium batteries, lead-acid (or lead-storage) batteries, lithium ion batteries, polymer lithium ion batteries, sodium ion batteries, and the like.
In the present application, the following terms are known and clearly understood in the art, and such abbreviations do not pose any obstacle to the understanding of the application by those skilled in the art, wherein:
solid content refers to solid matters insoluble in a solvent in the slurry; particle diameter D50, also called median or median, is the particle diameter corresponding to the cumulative particle size distribution percentage of the sample reaching 50%.
The application discloses a coating slurry, which comprises a solvent and solid matters, wherein the weight of the solid matters accounts for 20-40% of the total weight of the coating slurry; specifically, the solid content at least comprises polymer particles and ceramic particles, wherein the ratio of the average particle diameter D50 of the polymer particles to the average particle diameter D50 of the ceramic particles is 0.1:1 to 0.83:1. Illustratively, the ratio of the average particle size D50 of the polymer particles and the ceramic particles may be 0.1:1, 0.3:1, 0.5:1, 0.6:1, or 0.83:1.
The solvent used for coating the slurry is not particularly limited, and the solvent can be adaptively adjusted based on the specific components of the ceramic particles and the polymer particles; illustratively, the solvent is one or more of deionized water, acetone, tetrahydrofuran, methyl ethyl ketone, dimethylformamide, dimethylacetamide.
The main bodies of the coating slurry are ceramic particles and polymer particles; wherein the ceramic particles are capable of imparting excellent heat resistance to the battery separator; meanwhile, by controlling the ratio of the average particle diameter D50 of the ceramic particles and the polymer particles in the coating slurry, on one hand, the polymer particles with smaller particle diameters are easy to float on the outermost surface of the battery separator, and on the other hand, the polymer particles can be well dispersed among the ceramic particles, so that the battery separator coated with the coating slurry has better pole piece adhesion.
In some alternative designs, the ratio of the average particle size D50 of the polymer particles to the ceramic particles is from 0.3:1 to 0.6:1. In this particle size ratio range, the coating formed by coating the slurry has better heat resistance and adhesion.
In some alternative designs, the ceramic particles have an average particle size D50 of 300nm to 1000nm; alternatively, the ceramic particles have an average particle diameter D50 of 300nm to 500nm. For example, the average particle diameter D50 of the ceramic particles may be 300nm, 400nm, 500nm, 600nm, 700nm, 800nm or 1000nm. For example, the ceramic particles include one or more of alumina, silica, zinc oxide, and boehmite.
In some alternative designs, the average particle size D50 of the polymer particles is 100nm to 250nm; for example, the average particle diameter D50 of the above polymer particles may be 100nm, 150nm, 200nm or 250nm.
Exemplary, for example, the polymer particles include one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyethylene oxide, and polymethyl methacrylate. The polymer particles have certain adhesive property and can endow the battery separator with certain adhesive property.
In the application, the average particle diameter D50 of the ceramic particles and the polymer particles is controlled within the range, so that the polymer particles and the ceramic particles can be better dispersed, the formed coating has better heat resistance and cohesiveness, and the ceramic particles and the polymer particles can be prevented from blocking the gaps on the substrate.
In some alternative designs, the weight ratio of polymer particles to ceramic particles is from 0.25:1 to 0.55:1. For example, the weight ratio of polymer particles to ceramic particles may be 0.25:1, 0.3:1, 0.4:1, 0.5:1, or 0.55.
In the coating paste disclosed in the present application, the above solid content may further include one or more of a binder, a dispersant and a plasticizer, and various properties of the coating paste can be improved by adding the binder, the dispersant or the plasticizer to the coating paste.
In some examples, the adhesion of a coating formed from the coating paste can be effectively improved by adding a binder to the coating paste. The binder may be exemplified by one or more selected from the group consisting of polyacrylate and styrene-butadiene rubber.
When a binder is added to the coating slurry, the binder may be added in an amount of 0.1wt% to 5wt% based on the total weight of the coating slurry; for example, the binder may be added in an amount of 0.1wt%, 1wt%, 2wt%, 3wt%, 4wt% or 5wt%.
In some examples, the individual solids in the coating slurry can be better dispersed in the coating slurry by adding a dispersant to the coating slurry; illustratively, the above-mentioned dispersing agent may be selected from one or more of sodium acrylate, ammonium polyacrylate, n-butanol and cyclohexanol.
When the dispersing agent is added into the coating slurry, the adding amount of the dispersing agent can be 0.1-5 wt% of the total weight of the coating slurry; for example, the dispersant may be added in an amount of 0.1wt%, 1wt%, 2wt%, 3wt%, 4wt% or 5wt%.
In some examples, a plasticizer may be added to the coating slurry to improve the plasticization of the formed coating; illustratively, the plasticizer may be selected from one or more of sodium carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl methyl cellulose.
When the plasticizer is added into the coating slurry, the addition amount of the plasticizer is 0.01-2 wt% of the total weight of the coating slurry; for example, the plasticizer may be added in an amount of 0.01wt%, 0.05wt%, 0.1wt%, 0.15wt% or 2wt%.
In addition, the present application also provides a battery separator, as shown in fig. 1 and 2, which includes a porous substrate 1 and a porous coating layer 2.
Wherein the porous coating layer 2 is arranged on at least one side surface of the porous substrate 1, and the porous coating layer 2 comprises polymer particles and ceramic particles; for example, the porous coating 2 may be formed by spin coating, spray coating, roll coating, screen printing, or the like on one side (for example, as shown in fig. 1) or on two opposite sides (for example, as shown in fig. 2) of the porous substrate 1 by using the coating slurry provided by the present application, and the porous coating 2 attached to the porous substrate 1 may be obtained by curing and drying the coating slurry. The specific curing and drying temperature can be adaptively adjusted based on the different components of the coating slurry, and can be cured for 1-30min under normal temperature or heating conditions by way of example, and the application is not particularly limited.
In the porous coating layer 2 described above, the ratio of the average particle diameter D50 of the polymer particles and the ceramic particles is 0.1:1 to 0.83:1.
The application divides the porous coating 2 into a first area and a second area with the same thickness, wherein the second area is positioned at one side of the first area far away from the porous substrate 1; for example, taking the example of providing the porous coating layer 2 only on the upper surface of the porous substrate 1, the layered structure of the battery separator is the porous substrate 1, the first region and the second region in this order from bottom to top; it should be understood that the first and second regions referred to herein are merely for convenience of describing the present application, and in fact, the first and second regions are the complete porous coating 2, and have no obvious segmentation.
In the present application, since the ratio of the average particle diameter D50 of the polymer particles and the ceramic particles is controlled to be 0.1:1 to 0.83:1, the polymer particles having a smaller particle diameter float up at the time of coating (at the time of coating, the substrate is usually located at the bottom, i.e., the polymer particles easily float up into the second region away from the porous substrate 1), so that the volume ratio of the polymer particles from the first region can be made smaller than that in the second region; meanwhile, by controlling the ratio of the average particle diameter D50 of the polymer particles and the ceramic particles, the polymer particles in the coating can be well dispersed among the ceramic particles, and when the battery diaphragm is assembled into a battery core, the adhesive property of the battery diaphragm and the pole piece can be ensured because the content of the polymer particles in the area of the porous coating 2 close to the pole piece is higher.
Meanwhile, since the volume ratio of the polymer particles in the second region is larger, more ceramic particles are located in the first region, and at this time, the volume ratio of the ceramic particles in the first region is larger than that of the ceramic particles in the second region.
On the other hand, the average particle diameter D50 of the ceramic particles is larger than the average particle diameter D50 of the polymer particles, and based on this effect, the polymer particles are less likely to block the pores of the porous substrate 1 in the region close to the porous substrate 1, so that higher air permeability can be maintained.
In an alternative embodiment, the thickness of the porous coating layer 2 is 0.5 μm to 4 μm, and optionally, the thickness of the porous coating layer 2 is 0.5 μm to 2 μm. For example, the thickness of the porous coating layer 2 may be 0.5 μm, 1 μm, 1.5 μm, 2 μm3 μm or 4 μm.
In order to facilitate the explanation of the technical effects of the present application, the present application also provides the following specific embodiments:
comparative example 1:
a microporous membrane having a thickness of 14 μm and not provided with a coating PP (polypropylene) was prepared as comparative example 1.
Example 1:
preparing coating slurry, specifically, the coating slurry comprises the following components in parts by mass:
60 parts of deionized water, 8 parts of PVDF (polyvinylidene fluoride) particles, 30 parts of ceramic particles, 0.8 part of binder, 1 part of dispersing agent and 0.2 part of plasticizer.
And mixing the components according to the parts by weight to obtain the coating slurry.
Preparing a battery separator, specifically coating the coating slurry on a PP microporous membrane with the thickness of 14 mu m in a roller coating mode, and then drying for 1min to obtain the battery separator.
Samples 1 to 3 and comparative examples 2 and 3 were prepared respectively with reference to the above-described methods, except that the particle diameter parameters of PVDF particles and ceramic particles were different in each sample; wherein the particle diameter parameters of the porous coating layers 2 in samples 1 to 3 and comparative example 1 and comparative example 2 are shown in table 1.
Example 2:
a battery separator was prepared by the method of example one, and samples 4 to 6 were obtained, in which the coating slurries of sample 4 and sample 6, which formed the porous coating layer 2, were as follows:
the coating slurry in sample 4 comprises the following components in parts by mass: 60 parts of deionized water, 7.6 parts of PMMA (polymethyl methacrylate) particles, 30.4 parts of ceramic particles, 0.8 part of a binder, 1 part of a dispersing agent and 0.2 part of a plasticizer.
The coating slurry in sample 5 comprises the following components in parts by mass: 70 parts of deionized water, 10 parts of PVDF particles, 18 parts of ceramic particles, 0.8 part of binder, 1 part of dispersing agent and 0.2 part of plasticizer.
The coating slurry in sample 6 comprises the following components in parts by mass: 70 parts of deionized water, 6 parts of PVDF particles, 14 parts of ceramic particles, 0.4 part of binder, 0.5 part of dispersing agent and 00.1 parts of plasticizer.
The particle diameter parameters in the porous coating layers 2 formed in the above samples 4 to 6 are shown in table 1.
TABLE 1
| Sequence number | Solid content (%) | Polymer particles D50 (. Mu.m) | Mass percent of polymer particles (%) | Ceramic particles D50 (μm) | Ceramic particle mass percent (%) | Particle size ratio | Mass ratio |
| Sample 1 | 40 | 100 | 8 | 1000 | 30 | 0.1:1 | 0.27:1 |
| Sample 2 | 40 | 250 | 8 | 500 | 30 | 0.5:1 | 0.27:1 |
| Sample 3 | 40 | 100 | 8 | 300 | 30 | 0.3:1 | 0.27:1 |
| Sample 4 | 40 | 300 | 7.6 | 500 | 30.4 | 0.6:1 | 0.25:1 |
| Sample 5 | 30 | 200 | 10 | 400 | 18 | 0.5:1 | 0.55:1 |
| Sample 6 | 20 | 250 | 5 | 300 | 14 | 0.83:1 | 0.35:1 |
| Comparative example 1 | / | / | / | / | / | / | / |
| Comparative example 2 | 40 | 1000 | 8 | 500 | 30 | 2:1 | 0.27:1 |
| Comparative example 3 | 40 | 250 | 8 | 200 | 30 | 1.25:1 | 0.27:1 |
Example 3:
the respective properties of the above samples 1 to 6 and comparative examples 1 to 3 were tested, and specific test results are shown in table 2.
Wherein, thickness test: reference to GB/T6672-2001, a handheld thickness gauge is used for measurement, 5 points are taken every 5cm along the TD (Transverse Direction, i.e. longitudinal) direction of the membrane, and the average value of the measurement is the total thickness of the battery diaphragm, and the thickness unit is mu m. The thickness of the porous substrate 1 is subtracted from the total thickness of the battery separator to obtain the thickness of the porous coating 2.
Adhesion to pole piece (peel strength): the battery diaphragm sample is cut into a spline of 20mm multiplied by 200mm, the positive plate is cut into a plate of 20mm multiplied by 80mm, and the plate is hot-pressed for 1min at 80 ℃ under the pressure of 1MPa to prepare a test sample. And then, testing at a speed of 100mm/min on an electronic tension machine by adopting a 180-degree direction peeling strength testing method to separate the sample strip from the positive plate, and obtaining the bonding force of the sample strip and the pole piece according to peeling strength data (in the test, an average value of 5 parallel test samples is taken as the bonding force of the sample strip and the pole piece for each sample strip).
Thermal shrinkage test (thermal shrinkage value): the testing method is carried out by referring to GB/T12027-2004, 3 pieces of sample pieces larger than or equal to 100mm multiplied by 100mm are taken for each sample, the size of the sample piece in the MD direction (Machine Direction, namely the mechanical direction) before heating is measured, the sample piece is clamped in the middle of the A4 paper and is put into a baking oven at 130 ℃, after baking for 30min, the size of the sample piece after heating is taken out, and the thermal shrinkage value is obtained by calculating according to a thermal shrinkage formula.
Ventilation value: the test was performed according to the method disclosed in GB/T458-2008.
TABLE 2
| Sequence number | Thickness of porous coating 2 (μm) | Ventilation value (s/100 mL) | Peel strength (N/m) | Heat shrinkage value (MD,%) |
| Sample 1 | 3.1 | 283 | 17.5 | 2.0 |
| Sample 2 | 2.8 | 278 | 20.8 | 1.9 |
| Sample 3 | 1.8 | 256 | 16.8 | 2.4 |
| Sample 4 | 2.4 | 259 | 17.8 | 2.1 |
| Sample 5 | 1.2 | 243 | 30.3 | 2.6 |
| Sample 6 | 0.76 | 236 | 22.7 | 3.5 |
| Comparative example 1 | / | 210 | / | 10 |
| Comparative example 2 | 4.5 | 249 | 12.5 | 3.1 |
| Comparative example 3 | 1.5 | 261 | 5.1 | 2.0 |
As can be seen from table 2, the present application provides samples 1 to 6 with better peel strength in the case of the porous coating layer 2 having a close thickness, compared to comparative examples 2 and 3; meanwhile, the present application showed no significant difference from comparative examples 2 and 3 in heat shrinkage property and was far superior to comparative example 1; samples 1 to 6 provided by the present application also showed no significant difference from comparative examples 1 to 3 in terms of air permeability value.
The battery separator provided by the application has good heat resistance, adhesion and air permeability.
The foregoing description of the application has been presented for purposes of illustration and description, and is not intended to be limiting. Several simple deductions, modifications or substitutions may also be made by a person skilled in the art to which the application pertains, based on the idea of the application.
Claims (10)
1. The coating slurry is characterized by comprising solid matters, wherein the weight of the solid matters accounts for 20% -40% of the total weight of the coating slurry;
the solid content comprises polymer particles and ceramic particles, and the ratio of the average particle diameter D50 of the polymer particles and the ceramic particles is 0.1:1 to 0.83:1.
2. The coating slurry of claim 1, wherein the ratio of the average particle size D50 of the polymer particles and the ceramic particles is from 0.3:1 to 0.6:1.
3. The coating slurry of claim 1, wherein the coating slurry satisfies at least one of conditions (1) to (4):
(1) The average particle diameter D50 of the ceramic particles is 300nm-1000nm;
(2) The ceramic particles comprise one or more of alumina, silica, zinc oxide, and boehmite;
(3) The average particle diameter D50 of the polymer particles is 100nm-250nm;
(4) The polymer particles include one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyethylene oxide, and polymethyl methacrylate.
4. A coating slurry according to any one of claims 1 to 3, wherein the weight ratio of the polymer particles and the ceramic particles is from 0.25:1 to 0.55:1.
5. A coating slurry according to any one of claims 1 to 3, wherein the solids content further comprises one or more of a binder, a dispersant and a plasticizer.
6. The coating slip of claim 5, wherein the coating slip meets at least one of conditions (1) to (7):
(1) The binder comprises one or more of polyacrylate and styrene-butadiene rubber;
(2) The weight of the binder accounts for 0.1% -5% of the total weight of the coating slurry;
(3) The dispersing agent comprises one or more of sodium acrylate, ammonium polyacrylate, n-butanol and cyclohexanol;
(4) The weight of the dispersing agent accounts for 0.1% -5% of the total weight of the coating slurry;
(5) The plasticizer comprises one or more of sodium carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl methyl cellulose;
(6) The weight of the plasticizer accounts for 0.01% -2% of the total weight of the coating slurry;
(7) The coating slurry includes a solvent; the solvent is one or more of deionized water, acetone, tetrahydrofuran, methyl ethyl ketone, dimethylformamide and dimethylacetamide.
7. A battery separator comprising a porous substrate; and
a porous coating layer disposed on at least one side surface of the porous substrate, the porous coating layer comprising polymer particles and ceramic particles, the ratio of the average particle diameter D50 of the polymer particles and the ceramic particles being 0.1:1 to 0.83:1;
the porous coating comprises a first region and a second region with the same thickness, the second region is positioned on one side of the first region away from the porous substrate, and the volume ratio of the polymer particles in the first region is smaller than that of the polymer particles in the second region.
8. The battery separator of claim 7 wherein the volume ratio of the ceramic particles in the first region is greater than the volume ratio of the ceramic particles in the second region.
9. The battery separator of claim 7 or 8, wherein the porous coating has a thickness of 0.5 μm to 4 μm.
10. A method of producing the battery separator according to any one of claims 7 to 9, comprising the steps of:
applying the coating slurry according to any one of claims 1 to 6 to at least one side surface of a porous substrate;
and drying and curing the coating slurry to prepare the battery separator.
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