CN114267923A - Battery isolation membrane, preparation method thereof and secondary battery - Google Patents
Battery isolation membrane, preparation method thereof and secondary battery Download PDFInfo
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- CN114267923A CN114267923A CN202111591247.1A CN202111591247A CN114267923A CN 114267923 A CN114267923 A CN 114267923A CN 202111591247 A CN202111591247 A CN 202111591247A CN 114267923 A CN114267923 A CN 114267923A
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- 239000012528 membrane Substances 0.000 title abstract description 26
- 238000002360 preparation method Methods 0.000 title abstract description 9
- 238000002955 isolation Methods 0.000 title description 13
- 239000002245 particle Substances 0.000 claims abstract description 87
- 238000000576 coating method Methods 0.000 claims abstract description 78
- 239000011248 coating agent Substances 0.000 claims abstract description 69
- 229920000642 polymer Polymers 0.000 claims abstract description 23
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- -1 polytetrafluoroethylene Polymers 0.000 claims description 18
- 239000002002 slurry Substances 0.000 claims description 18
- 239000000758 substrate Substances 0.000 claims description 17
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 14
- 238000000034 method Methods 0.000 claims description 13
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- 238000005406 washing Methods 0.000 claims description 9
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 8
- 229910001593 boehmite Inorganic materials 0.000 claims description 8
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 claims description 8
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 7
- 239000004642 Polyimide Substances 0.000 claims description 6
- 229910001416 lithium ion Inorganic materials 0.000 claims description 6
- 229920001721 polyimide Polymers 0.000 claims description 6
- 229920000098 polyolefin Polymers 0.000 claims description 6
- 239000000377 silicon dioxide Substances 0.000 claims description 6
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 5
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 5
- 239000000395 magnesium oxide Substances 0.000 claims description 5
- 230000014759 maintenance of location Effects 0.000 claims description 5
- 239000004962 Polyamide-imide Substances 0.000 claims description 4
- 125000003118 aryl group Chemical group 0.000 claims description 4
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 claims description 4
- 238000007598 dipping method Methods 0.000 claims description 4
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- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims description 4
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- 238000002791 soaking Methods 0.000 claims description 4
- AVQQQNCBBIEMEU-UHFFFAOYSA-N 1,1,3,3-tetramethylurea Chemical compound CN(C)C(=O)N(C)C AVQQQNCBBIEMEU-UHFFFAOYSA-N 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
- 239000002033 PVDF binder Substances 0.000 claims description 3
- 108010081750 Reticulin Proteins 0.000 claims description 3
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 3
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 claims description 3
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- 229920001577 copolymer Polymers 0.000 claims description 3
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 3
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 claims description 2
- MKGYHFFYERNDHK-UHFFFAOYSA-K P(=O)([O-])([O-])[O-].[Ti+4].[Li+] Chemical compound P(=O)([O-])([O-])[O-].[Ti+4].[Li+] MKGYHFFYERNDHK-UHFFFAOYSA-K 0.000 claims description 2
- 239000004952 Polyamide Substances 0.000 claims description 2
- CVJYOKLQNGVTIS-UHFFFAOYSA-K aluminum;lithium;titanium(4+);phosphate Chemical compound [Li+].[Al+3].[Ti+4].[O-]P([O-])([O-])=O CVJYOKLQNGVTIS-UHFFFAOYSA-K 0.000 claims description 2
- OYLGJCQECKOTOL-UHFFFAOYSA-L barium fluoride Chemical compound [F-].[F-].[Ba+2] OYLGJCQECKOTOL-UHFFFAOYSA-L 0.000 claims description 2
- 229910001632 barium fluoride Inorganic materials 0.000 claims description 2
- 229910001634 calcium fluoride Inorganic materials 0.000 claims description 2
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims description 2
- 238000001125 extrusion Methods 0.000 claims description 2
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- 229920001002 functional polymer Polymers 0.000 claims description 2
- 229910000664 lithium aluminum titanium phosphates (LATP) Inorganic materials 0.000 claims description 2
- IDBFBDSKYCUNPW-UHFFFAOYSA-N lithium nitride Chemical compound [Li]N([Li])[Li] IDBFBDSKYCUNPW-UHFFFAOYSA-N 0.000 claims description 2
- 229910001386 lithium phosphate Inorganic materials 0.000 claims description 2
- GLNWILHOFOBOFD-UHFFFAOYSA-N lithium sulfide Chemical compound [Li+].[Li+].[S-2] GLNWILHOFOBOFD-UHFFFAOYSA-N 0.000 claims description 2
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 claims description 2
- 239000000347 magnesium hydroxide Substances 0.000 claims description 2
- 229910001862 magnesium hydroxide Inorganic materials 0.000 claims description 2
- 239000004745 nonwoven fabric Substances 0.000 claims description 2
- 229920001643 poly(ether ketone) Polymers 0.000 claims description 2
- 229920002492 poly(sulfone) Polymers 0.000 claims description 2
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- 239000004417 polycarbonate Substances 0.000 claims description 2
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- 229920001470 polyketone Polymers 0.000 claims description 2
- 229920006324 polyoxymethylene Polymers 0.000 claims description 2
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 2
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 2
- 238000001694 spray drying Methods 0.000 claims description 2
- TWQULNDIKKJZPH-UHFFFAOYSA-K trilithium;phosphate Chemical compound [Li+].[Li+].[Li+].[O-]P([O-])([O-])=O TWQULNDIKKJZPH-UHFFFAOYSA-K 0.000 claims description 2
- 238000001291 vacuum drying Methods 0.000 claims description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims 2
- 229910052582 BN Inorganic materials 0.000 claims 1
- 229930040373 Paraformaldehyde Natural products 0.000 claims 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 claims 1
- 239000000292 calcium oxide Substances 0.000 claims 1
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 claims 1
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims 1
- 229910052808 lithium carbonate Inorganic materials 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 claims 1
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- 239000004698 Polyethylene Substances 0.000 description 14
- 229920000573 polyethylene Polymers 0.000 description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 13
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- 230000008595 infiltration Effects 0.000 description 3
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
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- 229910000831 Steel Inorganic materials 0.000 description 2
- 230000036982 action potential Effects 0.000 description 2
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
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- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 2
- PIGFYZPCRLYGLF-UHFFFAOYSA-N Aluminum nitride Chemical compound [Al]#N PIGFYZPCRLYGLF-UHFFFAOYSA-N 0.000 description 1
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- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 1
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Images
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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
-
- 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 provides a battery isolating membrane, a preparation method thereof and a secondary battery, and relates to the technical field of batteries, wherein the isolating membrane comprises a base material with a porous structure and a heat-resistant polymer coating coated on at least one surface of the base material; the heat-resistant polymer coating layer includes a heat-resistant resin and non-conductive particles; the particle diameter D97 of the non-conductive particles is not more than the thickness of the heat-resistant polymer coating; the particle size distribution of the non-conductive particles satisfies: (D90-D10)/D50 is not more than 0.5 and not more than 3.0; the ratio of the specific surface area S of the nonconductive particles to the average particle diameter D50 satisfies: 0<S/D50≤5×107m/g. The diaphragm provided by the invention has a uniform porous coating, high temperature resistance and excellent electrochemical stability, and the assembly yield, the electrical property and the safety performance of the battery are greatly improved.
Description
Technical Field
The invention relates to the technical field of batteries, in particular to a battery isolating membrane, a preparation method thereof and a secondary battery.
Background
With the development of new energy technology, secondary batteries are applied to digital products, electric vehicles, and energy storage devices due to their high energy density, long life, and high safety. The secondary battery mainly comprises four major parts, namely a positive electrode, electrolyte, an isolating membrane and a negative electrode. The isolating membrane has the main functions of separating the positive electrode from the negative electrode and preventing the positive electrode from being in direct contact with the negative electrode to cause short circuit, in addition, the through hole structure in the isolating membrane can play a role of enabling positive and negative ions to pass through, and the quality of the performance of the isolating membrane directly influences important performances such as yield, capacity, internal resistance, circulation and the like of battery equipment.
At present, the substrate of the commercial battery isolation membrane is mostly made of polyolefin, and the isolation membrane can be seriously shrunk at the temperature of over 100 ℃ due to the lower melting point of the polyolefin, so that the contact of a positive electrode and a negative electrode is caused, and the battery is easy to cause fire explosion. In order to improve the problems, one or more layers of functional coatings are usually coated on the surface of a polyolefin substrate, and the common coatings mainly comprise an inorganic filler coating, a high-molecular polymer material coating and a mixed coating of an inorganic filler and a high-molecular polymer material; the high molecular polymer material has high melting point, but is coated on the surface of the base material as a coating, and is loosely adhered to the base material, so that the heat resistance is reduced, the battery is short-circuited, and safety accidents are caused.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
One of the purposes of the invention is to provide a battery isolating membrane, which selects non-conductive particles with specific requirements, so that the battery isolating membrane has a uniform porous coating, higher temperature resistance and excellent electrochemical stability, and the assembly yield, the electrical property and the safety performance of the battery are greatly improved.
The second purpose of the invention is to provide a preparation method of the battery isolating membrane.
It is a further object of the present invention to provide a secondary battery including the above battery separator.
In order to achieve the above purpose of the present invention, the following technical solutions are adopted:
in a first aspect, the present invention provides a battery separator comprising: a substrate having a porous structure and a heat-resistant polymer coating applied to at least one side of the substrate;
the heat-resistant polymer coating layer includes a heat-resistant resin and non-conductive particles;
wherein the particle diameter D97 of the non-conductive particles is not more than the thickness of the heat-resistant polymer coating;
the particle size distribution of the non-conductive particles satisfies: (D90-D10)/D50 is not more than 0.5 and not more than 3.0;
the ratio of the specific surface area S of the non-conductive particles to the average particle diameter D50 satisfies: 0<S/D50≤5×107m/g。
The peel strength of the battery isolation film is more than 10N/m, after the battery isolation film is placed in an environment at 130 ℃ for 1 hour, the shrinkage rates of the battery isolation film in the longitudinal direction and the transverse direction are both less than 15%, the ratio of the shrinkage rates of the battery isolation film in the longitudinal direction and the transverse direction is more than 1, after the battery isolation film is placed in the environment at 130 ℃ for 1 hour, the battery isolation film is soaked in electrolyte at 25 ℃, and the needle punching strength retention rate is more than 60% after 60 days.
In a second aspect, the invention provides a preparation method of the battery isolation film, which comprises the following steps:
(1) preparing a base material;
(2) putting the non-conductive particles into an organic solvent, uniformly dispersing, adding a heat-resistant resin, and continuously dispersing to obtain slurry;
(3) coating the slurry prepared in the step (2) on at least one side of a base material to obtain a coating film;
(4) the coating film is processed by coagulating bath or saturated steam, a heat-resistant resin porous coating forms a reticular fiber structure, and inorganic particles are uniformly distributed in the porous coating;
(5) and (4) washing and drying the coating film obtained in the step (4) to obtain the battery isolating film.
In a third aspect, the present invention provides a secondary battery comprising the above battery separator.
The invention has at least the following beneficial effects:
according to the invention, through screening the particle size and distribution of the non-conductive particles and the ratio of the specific surface area to the average particle size, the thickness and the pore size of the porous polymer coating are uniform, the assembly yield of the secondary battery and the cycle performance of the secondary battery are improved, the acting force and the stability among the particles are enhanced, a three-dimensional framework structure can be better built, the contraction of the diaphragm at high temperature is inhibited, and the liquid absorption and infiltration capacity of the diaphragm are obviously improved due to the excellent acting potential energy among the particles, so that the cycle performance of the battery is improved.
The peel strength of the isolating membrane obtained by the invention is more than 10N/m, after the isolating membrane is placed in an environment at 130 ℃ for 1 hour, the shrinkage rates of the isolating membrane in the longitudinal direction and the transverse direction are both less than 15%, the ratio of the shrinkage rates in the longitudinal direction and the transverse direction is more than 1, after the isolating membrane is placed in the environment at 130 ℃ for 1 hour, the isolating membrane is soaked in electrolyte at 25 ℃, and the needle punching strength retention rate is more than 60% after 60 days.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is an electron micrograph of a battery separator prepared in example 1 of the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are some, but not all, embodiments of the present invention. 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.
According to a first aspect of the present invention, there is provided a battery separator comprising a substrate having a porous structure and a heat-resistant polymer coating layer coated on at least one side of the porous substrate, the heat-resistant polymer coating layer comprising a heat-resistant resin and non-conductive particles;
wherein the particle diameter D97 of the non-conductive particles is not more than the thickness of the heat-resistant polymer coating;
the particle size distribution of the non-conductive particles satisfies: (D90-D10)/D50 is not more than 0.5 and not more than 3.0;
the ratio of the specific surface area S of the nonconductive particles to the average particle diameter D50 satisfies: 0<S/D50≤5×107m/g。
Base material
The porous substrate is not limited, and may be a material known in the art to be used as a separator, such as a polyolefin porous separator, a nonwoven fabric separator, an electrospun separator, and a separator prepared by coating inorganic particles or a functional polymer coating on the above-mentioned separator.
The polyolefin porous diaphragm material is Polyethylene (PE) or polypropylene (PP), and can be a single-layer PE layer or a PP layer, or a composite multilayer structure of Polyethylene (PE) and polypropylene (PP), and from the aspect of film forming performance, polyethylene and copolymer are preferred, and polyethylene can be obtained through one-step polymerization or multi-step polymerization.
Preferably, the polyethylene has a molecular weight of from 50 to 400 ten thousand, preferably from 60 to 300 ten thousand, particularly preferably from 80 to 300 ten thousand, and a particle size of not more than 100. mu.m.
The material of the polymer functional coating can be one or more of PMMA or PVDF.
In a preferred embodiment, the thickness of the substrate is between 1 and 30 μm, preferably between 5 and 20 μm, and the porosity of the substrate is between 10 and 70%, preferably between 20 and 60%.
Heat resistant polymer coating
The heat-resistant polymer porous coating layer includes a heat-resistant resin and non-conductive particles.
Wherein the heat-resistant resin material is selected from nitrogen-containing aromatic polymers, polyimide polyamide, polyamide-imide, polyimide, polyetherimide, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, polysulfone, polyketone, polyether ketone, polycarbonate and polyformaldehyde; among these, the nitrogen-containing aromatic polymer includes aromatic polyamide, aromatic polyimide, aromatic polyamideimide and the like, and is preferably a resin composed of aromatic polyamide, and particularly preferably para-aromatic polyamide having excellent physical properties, heat resistance and low heat shrinkage.
Preferably, the para-aromatic polyamide has an intrinsic viscosity of from 1.2 to 6.5g/l, preferably from 2 to 6g/l, more preferably from 3 to 5 g/l.
Preferably, the molecular weight of the para-aromatic polyamide is 10000-.
There is no particular limitation on the kind of the non-conductive particles as long as the electrochemical properties are stable. Preferably, the non-conductive particles are inorganic particles having a dielectric constant ε 5 or more. As a specific example, the inorganic particles may include, but are not limited to, silicon dioxide (SiO)2) Alumina (Al)2O3) Magnesium oxide (MgO), zirconium oxide (ZrO)2) Titanium oxide (TiO)2) Oxide particles such as calcium oxide (CaO), boehmite (AlOOH), and magnesium hydroxide (Mg (OH)2) Hydroxides such as aluminum nitride (AlN), Boron Nitride (BN), and barium sulfate (BaSO)4) Calcium fluoride (CaF)2) Barium fluoride (BaF)2) One or more of the insoluble ion crystal particles. The nonconductive particles may be selected from one of the above, or two or more of them may be selected in any ratio. Among these particles, oxide particles are preferable in view of stability in the electrolytic solution and potential. The non-conductive particles need to have a high thermal decomposition temperature (decomposition temperature higher than 200 ℃ C.), and low water absorption, and are preferably alumina, boehmite, magnesia, or silica, and particularly preferably alumina.
The shape of the nonconductive particles is not particularly limited, and examples thereof include a plate shape, a rod shape, a scale shape, a needle shape, a columnar shape, a spherical shape, a block shape, a polyhedral shape, and the like, and a plurality of kinds of inorganic fillers having the above shapes may be used in combination. From the viewpoint of improving permeability, a plate-like polyhedron shape including a plurality of faces, a columnar shape, and a rod shape is preferable.
The present invention has the following requirements for non-conductive particles:
1. the particle size of the non-conductive particles is D97 ≤ a, wherein D97 represents particles with particle size less than D97 in 97% and more than D97 in 3%; a represents the thickness of the porous coating layer of the battery separator.
When the particle diameter D97 of the non-conductive particles is not more than a, the thickness and the aperture of the porous polymer coating are uniform, thereby improving the assembly yield of the secondary battery and the cycle performance of the secondary battery.
2. The non-conductive particles have a particle size distribution of 0.5. ltoreq. D90-D10)/D50. ltoreq.3.0, for example 0.6, 0.8, 1.0, 1.2, 1.5, 1.6, 1.8, 2.0, 2.5, 3.0.
The particle size distribution of the non-conductive particles is in the range, the van der Waals force action among the particles is enhanced, the stability of the non-conductive particles after being prepared into slurry is enhanced, the consistency of the coated battery isolating membrane is improved, in addition, the non-conductive particles can be tightly attached to the surface of the base material in the baking process to form compact micro-pores and channels, and the channels are favorable for Li+Transportation and storage of electrolyte during charging and discharging. The three-dimensional framework mutually constructed among the particles can effectively inhibit the contraction of the diaphragm at high temperature.
3. Specific surface area of non-conductive particlesThe ratio to the average particle diameter D50 satisfies 0<S/D50≤5×107m/g, e.g. 0.1X 107、0.5×107、1×107、1.5×107、2×107、2.5×107、3×107、3.5×107、4×107、4.5×107、5×107m/g。
The specific surface area of the non-conductive particles is measured by a nitrogen adsorption method, the S/D50 of the non-conductive particles is located in the range, the non-conductive particles have excellent surface action potential, a three-dimensional framework structure can be better built, the contraction of the diaphragm at high temperature is inhibited, and the liquid absorption and infiltration capacity of the diaphragm are remarkably improved by the excellent action potential energy among the particles, so that the cycle performance of the battery is improved.
According to the invention, the non-conductive particles meeting the three requirements are selected, so that the thickness and the pore diameter of the porous polymer coating are uniform, the assembly yield of the secondary battery and the cycle performance of the secondary battery are improved, the acting force and the stability among the particles are enhanced, a three-dimensional framework structure can be better built, the contraction of the diaphragm at high temperature is inhibited, and the liquid absorption and infiltration capacity of the diaphragm are obviously improved due to the excellent acting potential energy among the particles, so that the cycle performance of the battery is improved.
The peeling strength of the isolating membrane obtained by the invention is more than 10N/m; after the separator is placed in an environment at 130 ℃ for 1 hour, the shrinkage rates of the separator in a Machine Direction (MD) and a Transverse Direction (TD) are both below 15%, the ratio of the shrinkage rates in the Machine Direction (MD) to the shrinkage rates in the Transverse Direction (TD) is more than 1, after the separator is placed in an environment at 130 ℃ for 1 hour, the separator is soaked in electrolyte at 25 ℃, and the needle punching strength retention rate is above 60% after 60 days.
Specifically, the peel strength test method:
cutting a sample by using a 2.5 cm-30 cm mould, flatly pasting the sample on a short steel ruler pasted with double-sided adhesive tape, rolling the sample back and forth three times by using a compression roller, manually peeling the sample by 1cm, clamping the sample on a tensile machine, and carrying out 180-degree test, wherein the tensile speed is 50mm/min, and taking the average value of the three measurement results.
Shrinkage test method:
taking a 15 cm-15 cm block isolation film, drawing two mutually perpendicular line segments (generally 10 cm-10 cm) according to the longitudinal direction and the transverse direction, and respectively measuring the longitudinal length and the transverse length of a sample by using a steel ruler (or a projector); the samples were placed flat in two sheets of a4 paper and subsequently placed in an oven at 130 ℃ for 1 h; after heating, taking out the samples, after the temperature is returned to room temperature, measuring the lengths of the longitudinal mark and the transverse mark again, respectively calculating the shrinkage rate according to the following formula, and finally taking the average value of the samples as the shrinkage rate.
MD direction heat shrinkage (%) (length in MD direction before heating-length in MD direction after heating)/length in MD direction before heating x 100.
TD direction heat shrinkage (%) (length in TD direction before heating-length in TD direction after heating)/length in MD direction before heating) × 100.
The method for testing the needling strength before and after soaking the electrolyte comprises the following steps:
puncture strength was tested as required by ASTM D4833-00e 1. Wherein the needle head is shaped into a hemisphere with the phi of 1.0mm, the needle head running speed is 1mm/s, a 15cm blocky isolation membrane is cut, the needling strength is measured once according to the method every 2cm, the average value of five measurement results is recorded as the needling strength c before the electrolyte is soaked0Preparing organic solvent from Ethylene Carbonate (EC), dimethyl carbonate (DMC) and Ethyl Methyl Carbonate (EMC) according to the mass ratio of 1:1:1, putting the block diaphragm to be measured into the prepared organic solvent, soaking the block diaphragm at 25 ℃ for 60day, taking out the block diaphragm, putting the block diaphragm into a fume hood for natural air drying, measuring the needling strength once according to the method every 2cm, taking the average value of five measurement results, and recording the needling strength as the needling strength c after soaking the electrolyte1The retention rate of the puncture strength is then: (c)0-c1)/c0。
In a preferred embodiment, the inorganic particles may further include particles having lithium ion transferring ability to improve the conductive property of lithium ions, and the particles having lithium ion transferring ability are selected from any one or a mixture of at least two of the following inorganic particles: lithium phosphate (Li)3PO4) Lithium titanium phosphate (Li)xTiy(PO4)3X is more than 0 and less than 2, y is more than 0 and less than 3), lithium aluminum titanium phosphate, lithium nitride and carbonic acidLithium, lithium chloride, lithium sulfide, lithium hexafluorophosphate.
According to a second aspect of the present invention, there is provided a method for preparing the above battery separator, comprising the steps of:
(1) preparing a base material;
(2) putting the non-conductive particles into an organic solvent, uniformly dispersing, adding a heat-resistant resin, and continuously dispersing to obtain slurry;
(3) coating the slurry prepared in the step (2) on at least one side of a base material to obtain a coating film;
(4) the coating film is processed by coagulating bath or saturated steam, a heat-resistant resin porous coating forms a reticular fiber structure, and inorganic particles are uniformly distributed in the porous coating;
(5) and (4) washing and drying the coating film obtained in the step (4) to obtain the battery isolating film.
In the step (1), the preparation method of the base material is not particularly limited, and dry uniaxial stretching, biaxial synchronous or asynchronous stretching and wet biaxial synchronous or asynchronous stretching can be adopted, and preferably, the preparation is carried out by a wet biaxial synchronous stretching method.
In the step (2), the organic solvent includes at least one of N-methylpyrrolidone (NMP), N-Dimethylformamide (DMF), N-Dimethylacetamide (DMAC), and Tetramethylurea (TMU).
In the step (3), the coating method of the slurry is not limited, and the coating method may be selected from a coating method, a dipping method, and the like. Examples of the coating method include doctor blade method, dipping method, reverse roll method, direct roll method, gravure roll method, extrusion method, spray method, and dispensing method. The coating is preferably performed by a gravure roll method and a doctor blade method in view of the uniformity of the thickness of the porous film.
In the step (5), the drying method of the coating film is not limited, and a drying method such as hot air, low-humidity air, vacuum drying, spray drying, or freeze drying may be selected.
According to a third aspect of the present invention, there is provided a secondary battery (including, but not limited to, a lithium ion battery) comprising the above-described separator.
The preparation method of the isolating membrane has the same advantages of the isolating membrane and the secondary battery, and the isolating membrane and the secondary battery are not described in detail.
The invention is further illustrated by the following examples. The materials in the examples are prepared according to known methods or are directly commercially available, unless otherwise specified.
Defining: α ═ (D90-D10)/D50; β is S/D50.
Example 1
(1) Adding 4 parts of alumina powder into 100 parts of NMP, stirring for 20min by using a high-speed dispersion emulsifying machine, then adding 2 parts of para-aramid, continuously stirring for 20min by using the high-speed dispersion emulsifying machine, and filtering by using a 1000-mesh filter screen to obtain uniform para-aramid slurry, wherein the alumina particle size D97 is 1.125, the particle size distribution alpha is 2.32, and beta is 3.852 x 107m/g；
(2) Selecting a polyethylene base film with the thickness of 9 mu m, wherein the porosity is 38 percent, and the air permeability is 150s/100cc, firstly coating one side of the base film with an organic solvent by adopting a gravure coating mode, and then coating the para-aramid slurry on the other side of the base film by adopting the gravure coating mode, wherein the thickness of the coating is 3.1 mu m;
(3) and the prepared coating film stays in the saturated steam atmosphere, then enters a pure water tank for water washing, and finally enters an oven for drying to obtain the battery isolating film.
Example 2
(1) Adding 4 parts of boehmite powder into 100 parts of NMP, stirring for 20min by a high-speed dispersion emulsifying machine, then adding 2 parts of para-aramid, continuously stirring for 20min by the high-speed dispersion emulsifying machine, and filtering by a 1000-mesh filter screen to obtain uniform para-aramid pulp, wherein the boehmite particle size D97 is 1.032, the particle size distribution alpha is 2.59, and beta is 3.53 multiplied by 107m/g；
(2) Selecting a polyethylene base film with the thickness of 9 mu m, wherein the porosity is 38 percent, and the air permeability is 150s/100cc, firstly coating one side of the base film with an organic solvent by adopting a gravure coating mode, and then coating the para-aramid slurry on the other side of the base film by adopting the gravure coating mode, wherein the thickness of the coating is 3.0 mu m;
(3) and the prepared coating film stays in the saturated steam atmosphere, then enters a pure water tank for water washing, and finally enters an oven for drying to obtain the battery isolating film.
Example 3
(1) Adding 4 parts of silicon dioxide powder into 100 parts of DMF, stirring for 20min by using a high-speed dispersion emulsifying machine, then adding 2 parts of para-aramid, continuously stirring for 20min by using the high-speed dispersion emulsifying machine, and filtering by using a 1000-mesh filter screen to obtain uniform para-aramid slurry, wherein the silicon dioxide particle size D97 is 0.785, the particle size distribution alpha is 0.816, and the beta is 3.244 multiplied by 107m/g；
(2) Selecting a polyethylene base film with the thickness of 9 microns, wherein the porosity is 38%, and the air permeability is 150s/100cc, firstly coating one side of the base film with an organic solvent by adopting a gravure coating mode, and then coating the para-aramid slurry on the other side of the base film by adopting a gravure coating mode, wherein the thickness of the coating is 3.2 microns;
(3) and the prepared coating film stays in the saturated steam atmosphere, then enters a pure water tank for water washing, and finally enters an oven for drying to obtain the battery isolating film.
Comparative example 1
(1) Adding 4 parts of silicon dioxide powder into 100 parts of NMP, stirring for 20min by using a high-speed dispersion emulsifying machine, then adding 2 parts of para-aramid, continuously stirring for 20min by using the high-speed dispersion emulsifying machine, and filtering by using a 1000-mesh filter screen to obtain uniform para-aramid slurry, wherein the silicon dioxide particle size D97 is 4.128, the particle size distribution alpha is 5.23, and beta is 5.167 multiplied by 107m/g；
(2) Selecting a polyethylene base film with the thickness of 9 mu m, wherein the porosity is 38 percent, and the air permeability is 150s/100cc, firstly coating one side of the base film with an organic solvent by adopting a gravure coating mode, and then coating the para-aramid slurry on the other side of the base film by adopting the gravure coating mode, wherein the thickness of the coating is 3.8 mu m;
(3) and the prepared coating film stays in the saturated steam atmosphere, then enters a pure water tank for water washing, and finally enters an oven for drying to obtain the battery isolating film.
Comparative example 2
(1) Adding 4 parts of alumina powder into 100 parts of NMP, stirring for 20min by a high-speed dispersion emulsifying machine, and then adding para-aramid fiber and high-aluminaStirring continuously for 20min by a fast dispersion emulsifying machine, and filtering by a 1000-mesh filter screen to obtain uniform para-aramid pulp, wherein the grain diameter of alumina D97 is 3.78, the grain diameter distribution alpha is 5.28, and beta is 2.17 multiplied by 107m/g；
(2) Selecting a polyethylene base film with the thickness of 9 mu m, wherein the porosity is 38 percent, and the air permeability is 150s/100cc, firstly coating one side of the base film with an organic solvent by adopting a gravure coating mode, and then coating the para-aramid slurry on the other side of the base film by adopting the gravure coating mode, wherein the thickness of the coating is 3.8 mu m;
(3) and the prepared coating film stays in the saturated steam atmosphere, then enters a pure water tank for water washing, and finally enters an oven for drying to obtain the battery isolating film.
Comparative example 3
(1) Stirring 4 parts of boehmite powder in 100 parts of DMF for 20min by a high-speed dispersion emulsifying machine, then adding para-aramid, continuously stirring for 20min by the high-speed dispersion emulsifying machine, and filtering by a 1000-mesh filter screen to obtain uniform para-aramid pulp, wherein the boehmite particle size D97 is 4.428, the particle size distribution alpha is 4.58, and beta is 0.96 multiplied by 107m/g；
(2) Selecting a polyethylene base film with the thickness of 9 mu m, wherein the porosity is 38 percent, and the air permeability is 150s/100cc, firstly coating one side of the base film with an organic solvent by adopting a gravure coating mode, and then coating the para-aramid slurry on the other side of the base film by adopting the gravure coating mode, wherein the thickness of the coating is 3.5 mu m;
(3) and the prepared coating film stays in the saturated steam atmosphere, then enters a pure water tank for water washing, and finally enters an oven for drying to obtain the battery isolating film.
Example and comparative example membrane parameters and properties were as follows:
the test methods were as described above.
As shown in examples 1-3, the inorganic particles with D97, alpha and beta meeting the required standards are selected to obtain the diaphragm with uniform coating thickness and aperture, better electrolyte resistance and higher safety performance, while the inorganic particles of comparative examples 1-3 are prepared into slurry and then coated with the diaphragm, the thickness uniformity is poor, the aramid fiber pores are not uniform, the electrolyte resistance of the diaphragm is lower than that of examples 1-3, and the shrinkage rate is obviously higher than that of examples 1-3.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A battery separator, comprising: a substrate having a porous structure and a heat-resistant polymer coating applied to at least one side of the substrate;
the heat-resistant polymer coating layer includes a heat-resistant resin and non-conductive particles;
wherein the particle diameter D97 of the non-conductive particles is not more than the thickness of the heat-resistant polymer coating;
the particle size distribution of the non-conductive particles satisfies: (D90-D10)/D50 is not more than 0.5 and not more than 3.0;
the ratio of the specific surface area S of the non-conductive particles to the average particle diameter D50 satisfies: 0<S/D50≤5×107m/g。
2. The battery separator according to claim 1, wherein the peel strength of the battery separator is 10N/m or more, the shrinkage of the battery separator in both the longitudinal and transverse directions after being left at 130 ℃ for 1 hour is 15% or less, the ratio of the shrinkage in the longitudinal and transverse directions is greater than 1, and the retention of the puncture strength after 60 days after soaking in an electrolyte at 25 ℃ after being left at 130 ℃ for 1 hour is 60% or more.
3. The battery separator according to claim 1 or 2, wherein the substrate comprises a polyolefin substrate, a non-woven fabric substrate, and a substrate prepared by coating inorganic particles or a functional polymer coating thereon.
4. The battery separator according to claim 1 or 2, wherein the substrate has a thickness of 1 to 30 μm, preferably 5 to 20 μm; the porosity of the substrate is 10-70%, preferably 20-60%; the thickness of the heat-resistant polymer coating is 1.5-10 μm.
5. The battery separator according to claim 1 or 2, wherein the heat-resistant resin is one or more selected from the group consisting of nitrogen-containing aromatic polymers, polyimide polyamides, polyamideimides, polyimides, polyetherimides, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymers, polytetrafluoroethylene, polysulfone, polyketone, polyetherketone, polycarbonate, and polyoxymethylene; wherein the nitrogen-containing aromatic polymer comprises aromatic polyamide, aromatic polyimide and aromatic polyamideimide, preferably aromatic polyamide, and particularly preferably para-aromatic polyamide;
preferably, the intrinsic viscosity of the para-aromatic polyamide is from 1.2 to 6.5g/l, preferably from 2 to 6g/l, more preferably from 3 to 5 g/l;
preferably, the viscosity average molecular weight of the para-aromatic polyamide is 10000-.
6. The battery separator according to claim 1 or 2, wherein the non-conductive particles comprise one or more of silica, alumina, magnesia, zirconia, titania, calcium oxide, boehmite, magnesium hydroxide, aluminum nitride, boron nitride, barium sulfate, calcium fluoride, barium fluoride; preferably alumina, boehmite, magnesia, silica, particularly preferably alumina;
the shape of the non-conductive particles includes plate-like, rod-like, scaly, needle-like, columnar, spherical, massive, polyhedral, preferably plate-like, polyhedral, columnar, rod-like;
the non-conductive particles may further contain particles having lithium ion transfer capability, including one or more of lithium phosphate, lithium titanium phosphate, lithium aluminum titanium phosphate, lithium nitride, lithium carbonate, lithium chloride, lithium sulfide, and lithium hexafluorophosphate.
7. A method for preparing the battery separator according to any one of claims 1 to 6, comprising the steps of:
(1) preparing a base material;
(2) putting the non-conductive particles into an organic solvent, uniformly dispersing, adding a heat-resistant resin, and continuously dispersing to obtain slurry;
(3) coating the slurry prepared in the step (2) on at least one side of a base material to obtain a coating film;
(4) the coating film is processed by coagulating bath or saturated steam, a heat-resistant resin porous coating forms a reticular fiber structure, and inorganic particles are uniformly distributed in the porous coating;
(5) and (4) washing and drying the coating film obtained in the step (4) to obtain the battery isolating film.
8. The method according to claim 7, wherein in the step (2), the organic solvent comprises one or more of N-methylpyrrolidone, N-dimethylformamide, N-dimethylacetamide and tetramethylurea.
9. The production method according to claim 7, wherein in the step (3), the coating comprises a coating method or a dipping method; the coating method comprises a doctor blade method, a dipping method, a reverse roll method, a direct roll method, a micro gravure roll method, an extrusion method, a spray coating method and a point coating method, and preferably the micro gravure roll method and the doctor blade method;
preferably, in the step (5), the drying manner includes hot air, low-humidity air, vacuum drying, spray drying, and freeze drying.
10. A secondary battery comprising the battery separator according to any one of claims 1 to 6.
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| CN114843708A (en) * | 2022-07-04 | 2022-08-02 | 中材锂膜(宁乡)有限公司 | Porous diaphragm, preparation method thereof and electrochemical device |
| CN115275519A (en) * | 2022-08-29 | 2022-11-01 | 中材锂膜有限公司 | Inorganic coating battery diaphragm and preparation method thereof and battery |
| WO2023115898A1 (en) * | 2021-12-23 | 2023-06-29 | 中材锂膜有限公司 | Battery separator film, preparation method therefor and secondary battery |
| WO2023236401A1 (en) * | 2022-06-07 | 2023-12-14 | 中材锂膜有限公司 | Battery separator and preparation method therefor, and secondary battery |
| WO2024077822A1 (en) * | 2022-10-14 | 2024-04-18 | 宁德时代新能源科技股份有限公司 | Separator and preparation method therefor, secondary battery and electric device |
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