CN116565457B - Separator for lithium ion battery, preparation method and electrochemical device - Google Patents
Separator for lithium ion battery, preparation method and electrochemical device Download PDFInfo
- Publication number
- CN116565457B CN116565457B CN202310771210.XA CN202310771210A CN116565457B CN 116565457 B CN116565457 B CN 116565457B CN 202310771210 A CN202310771210 A CN 202310771210A CN 116565457 B CN116565457 B CN 116565457B
- Authority
- CN
- China
- Prior art keywords
- containing polymer
- separator
- lithium ion
- coating
- nitrogen
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 55
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 55
- 238000002360 preparation method Methods 0.000 title claims abstract description 43
- 229920000642 polymer Polymers 0.000 claims abstract description 178
- 239000011248 coating agent Substances 0.000 claims abstract description 107
- 238000000576 coating method Methods 0.000 claims abstract description 107
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims abstract description 84
- 229910052731 fluorine Inorganic materials 0.000 claims abstract description 71
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims abstract description 70
- 239000011737 fluorine Substances 0.000 claims abstract description 70
- 239000011148 porous material Substances 0.000 claims abstract description 25
- 125000001153 fluoro group Chemical group F* 0.000 claims abstract description 15
- 125000004433 nitrogen atom Chemical group N* 0.000 claims abstract description 14
- 239000000463 material Substances 0.000 claims abstract description 12
- 239000011247 coating layer Substances 0.000 claims abstract description 7
- 239000000203 mixture Substances 0.000 claims description 103
- 239000002002 slurry Substances 0.000 claims description 101
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims description 98
- 239000002033 PVDF binder Substances 0.000 claims description 40
- 239000002245 particle Substances 0.000 claims description 40
- 238000003756 stirring Methods 0.000 claims description 40
- 239000012528 membrane Substances 0.000 claims description 38
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 38
- 239000000919 ceramic Substances 0.000 claims description 36
- 238000010438 heat treatment Methods 0.000 claims description 29
- 230000001112 coagulating effect Effects 0.000 claims description 27
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims description 23
- 239000002798 polar solvent Substances 0.000 claims description 23
- -1 polytetrafluoroethylene Polymers 0.000 claims description 18
- 229920006231 aramid fiber Polymers 0.000 claims description 16
- 239000007788 liquid Substances 0.000 claims description 16
- 238000005406 washing Methods 0.000 claims description 16
- 238000002156 mixing Methods 0.000 claims description 15
- 229920000098 polyolefin Polymers 0.000 claims description 15
- 230000015271 coagulation Effects 0.000 claims description 14
- 238000005345 coagulation Methods 0.000 claims description 14
- 239000002904 solvent Substances 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 13
- 238000001035 drying Methods 0.000 claims description 13
- 238000004519 manufacturing process Methods 0.000 claims description 13
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 11
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 10
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 10
- 239000004962 Polyamide-imide Substances 0.000 claims description 10
- 239000004642 Polyimide Substances 0.000 claims description 10
- 229920002312 polyamide-imide Polymers 0.000 claims description 10
- 229920001721 polyimide Polymers 0.000 claims description 10
- 238000002844 melting Methods 0.000 claims description 9
- 230000008018 melting Effects 0.000 claims description 9
- 230000035699 permeability Effects 0.000 claims description 9
- 239000004697 Polyetherimide Substances 0.000 claims description 7
- 229920001601 polyetherimide Polymers 0.000 claims description 7
- 238000001228 spectrum Methods 0.000 claims description 7
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims description 6
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 claims description 6
- 229920001577 copolymer Polymers 0.000 claims description 6
- OQMIRQSWHKCKNJ-UHFFFAOYSA-N 1,1-difluoroethene;1,1,2,3,3,3-hexafluoroprop-1-ene Chemical group FC(F)=C.FC(F)=C(F)C(F)(F)F OQMIRQSWHKCKNJ-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
- 230000001070 adhesive effect Effects 0.000 claims description 5
- 238000009826 distribution Methods 0.000 claims description 5
- DQWPFSLDHJDLRL-UHFFFAOYSA-N triethyl phosphate Chemical compound CCOP(=O)(OCC)OCC DQWPFSLDHJDLRL-UHFFFAOYSA-N 0.000 claims description 5
- 229910001593 boehmite Inorganic materials 0.000 claims description 4
- 238000012512 characterization method Methods 0.000 claims description 4
- 230000003247 decreasing effect Effects 0.000 claims description 4
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 claims description 4
- 239000000126 substance Substances 0.000 claims description 4
- 239000000853 adhesive Substances 0.000 claims description 3
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 claims description 3
- 229910000019 calcium carbonate Inorganic materials 0.000 claims description 3
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 claims description 3
- 239000000347 magnesium hydroxide Substances 0.000 claims description 3
- 229910001862 magnesium hydroxide Inorganic materials 0.000 claims description 3
- 150000004767 nitrides Chemical class 0.000 claims description 3
- 239000011255 nonaqueous electrolyte Substances 0.000 claims description 3
- 239000011224 oxide ceramic Substances 0.000 claims description 3
- 229910052574 oxide ceramic Inorganic materials 0.000 claims description 3
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 3
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 3
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims description 3
- 229910010271 silicon carbide Inorganic materials 0.000 claims description 3
- 238000010183 spectrum analysis Methods 0.000 claims description 3
- 238000009423 ventilation Methods 0.000 claims description 3
- 229910052882 wollastonite Inorganic materials 0.000 claims description 3
- 239000010456 wollastonite Substances 0.000 claims description 3
- 238000004062 sedimentation Methods 0.000 claims 1
- 239000006185 dispersion Substances 0.000 abstract description 10
- 230000007547 defect Effects 0.000 abstract description 6
- 239000000843 powder Substances 0.000 description 50
- 238000000034 method Methods 0.000 description 25
- 229920005989 resin Polymers 0.000 description 21
- 239000011347 resin Substances 0.000 description 21
- 230000000052 comparative effect Effects 0.000 description 19
- 229920002313 fluoropolymer Polymers 0.000 description 19
- 239000004811 fluoropolymer Substances 0.000 description 19
- 238000000227 grinding Methods 0.000 description 13
- 230000008569 process Effects 0.000 description 13
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 11
- 239000004698 Polyethylene Substances 0.000 description 10
- 238000004090 dissolution Methods 0.000 description 10
- 229920000573 polyethylene Polymers 0.000 description 10
- 239000000758 substrate Substances 0.000 description 10
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 7
- 229910052744 lithium Inorganic materials 0.000 description 7
- 238000012360 testing method Methods 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- 239000005416 organic matter Substances 0.000 description 6
- 239000004760 aramid Substances 0.000 description 5
- 239000007789 gas Substances 0.000 description 5
- BQCIDUSAKPWEOX-UHFFFAOYSA-N 1,1-Difluoroethene Chemical compound FC(F)=C BQCIDUSAKPWEOX-UHFFFAOYSA-N 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- LCGLNKUTAGEVQW-UHFFFAOYSA-N Dimethyl ether Chemical compound COC LCGLNKUTAGEVQW-UHFFFAOYSA-N 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 4
- 229920003235 aromatic polyamide Polymers 0.000 description 4
- 239000011521 glass Substances 0.000 description 4
- HCDGVLDPFQMKDK-UHFFFAOYSA-N hexafluoropropylene Chemical group FC(F)=C(F)C(F)(F)F HCDGVLDPFQMKDK-UHFFFAOYSA-N 0.000 description 4
- 238000007581 slurry coating method Methods 0.000 description 4
- OLBVUFHMDRJKTK-UHFFFAOYSA-N [N].[O] Chemical compound [N].[O] OLBVUFHMDRJKTK-UHFFFAOYSA-N 0.000 description 3
- 239000003292 glue Substances 0.000 description 3
- 239000010410 layer Substances 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 230000003321 amplification Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 229920006026 co-polymeric resin Polymers 0.000 description 2
- 238000010668 complexation reaction Methods 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000011010 flushing procedure Methods 0.000 description 2
- 238000004255 ion exchange chromatography Methods 0.000 description 2
- 239000000178 monomer Substances 0.000 description 2
- 238000003199 nucleic acid amplification method Methods 0.000 description 2
- 229910052573 porcelain Inorganic materials 0.000 description 2
- 229910021642 ultra pure water Inorganic materials 0.000 description 2
- 239000012498 ultrapure water Substances 0.000 description 2
- 239000006087 Silane Coupling Agent Substances 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical group [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 239000011203 carbon fibre reinforced carbon Substances 0.000 description 1
- 238000005524 ceramic coating Methods 0.000 description 1
- 125000003636 chemical group Chemical group 0.000 description 1
- 239000006255 coating slurry Substances 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000002381 microspectrum Methods 0.000 description 1
- 238000012946 outsourcing Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 238000011895 specific detection Methods 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
- DENFJSAFJTVPJR-UHFFFAOYSA-N triethoxy(ethyl)silane Chemical compound CCO[Si](CC)(OCC)OCC DENFJSAFJTVPJR-UHFFFAOYSA-N 0.000 description 1
- CPUDPFPXCZDNGI-UHFFFAOYSA-N triethoxy(methyl)silane Chemical compound CCO[Si](C)(OCC)OCC CPUDPFPXCZDNGI-UHFFFAOYSA-N 0.000 description 1
- 238000005303 weighing Methods 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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/403—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
-
- 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
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
-
- 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 diaphragm for a lithium ion battery, a preparation method and an electrochemical device. The separator includes a base film and a coating layer formed on at least one surface of the base film; the material of the coating comprises a nitrogen-containing polymer and a fluorine-containing polymer; and R is N‑F < 3R; wherein R is N‑F R is the maximum pore diameter in the surface and internal pores of the coating, which is the maximum distance between adjacent N atoms and F atoms in the coating. The application also provides the separator, a preparation method thereof and an electrochemical device using the separator. The diaphragm for the lithium ion battery and the preparation method thereof provided by the application improve the defect of uneven dispersion of the polymer in the coating on the diaphragm in the prior art.
Description
Technical Field
The application relates to the technical field of electrochemical elements, in particular to a diaphragm for a lithium ion battery, a preparation method and an electrochemical device.
Background
The lithium battery diaphragm is an electric insulation film with a porous structure, and is used as an important component of a lithium battery, and the lithium battery diaphragm is mainly used for blocking a positive plate and a negative plate and preventing internal short circuit of the battery. The polyolefin material has good mechanical strength and chemical stability because of low price, and is widely applied to lithium battery separators. However, the common polyolefin separator has lyophobic surface and low surface energy, has poor wettability to electrolyte and affects the cycle life of the battery. Meanwhile, the polyolefin has a low melting point, severe heat shrinkage can occur when the temperature is too high, and the internal heat accumulation condition in the use process of the battery is easy to cause the deformation of the diaphragm so as to lead the anode and the cathode to be in direct contact, thereby causing the short circuit of the battery and causing fire or explosion.
In order to improve the temperature resistance of polyolefin membranes, the current market is mainly realized by coating ceramic on the surface of a polyolefin-based membrane, so that the membrane is endowed with a high heat-resistant function, and the heat shrinkage rate of the membrane is reduced, thereby more effectively reducing the internal short circuit of a lithium ion battery and preventing the thermal runaway of the battery caused by the internal short circuit of the battery. However, the effect of using a ceramic coating to improve the thermal stability of a polyolefin separator is very limited, and in order to further improve the thermal stability of the separator and reduce the thermal shrinkage of the separator and improve the adhesion between the separator and a pole piece, a scheme of co-applying ceramic and a polymer such as polyvinylidene fluoride (PVDF) to the polyolefin separator has been proposed in the industry. In order to further optimize the properties of the separator, such as heat resistance, various polymers are often used in the coating of polyolefin separators in combination with ceramics.
Disclosure of Invention
It is an object of the present application to provide a separator for lithium ion batteries, which overcomes the defect of uneven dispersion of polymer in a coating layer on a separator in the prior art.
Still another object of the present application is to provide a method for preparing a separator for a lithium ion battery.
It is still another object of the present application to provide an electrochemical device.
The fluoropolymers employed in the coating of the separator, such as PVDF, are readily soluble in polar solvents, which therefore become common solvents for the slurries used to form the separator coating; however, at normal temperature or higher, the fluorine-containing polymer is often easily agglomerated, and the dispersibility thereof is poor, and the dissolution time is long, which affects the production efficiency and the performance of the separator. When a plurality of polymers are used in the coating layer of the separator, the solubility of different polymers in the same solvent is different, which further results in poor stability and uniformity of the slurry used for coating. Taking PVDF and polyamide imide as examples, the membrane obtained by compounding the two polymers can endow the membrane with better bonding performance with a battery pole piece, and the polyamide imide can endow the membrane with better heat resistance; however, when PVDF and polyamideimide are blended in a polar solvent, the polyamideimide having a poorer solubility is directly crystallized and precipitated, both the slurry stability and uniformity are poor, and a quality-superior product cannot be obtained after coating.
Aiming at the technical problems, the inventor provides a diaphragm for a lithium ion battery and a preparation method thereof, and the specific scheme is as follows:
In a first aspect, the application discloses a separator for a lithium ion battery, comprising a base film and a coating layer formed on at least one surface of the base film; the material of the coating comprises a nitrogen-containing polymer and a fluorine-containing polymer; and R is N-F ＜3R；
Wherein R is N-F R is the maximum pore diameter in the surface and internal pores of the coating, which is the maximum distance between adjacent N atoms and F atoms in the coating.
Further, in some embodiments of the application, the R N-F The method is characterized by electron microscope energy spectrum;
the characterization method of the electron microscope energy spectrum comprises the following steps: and acquiring a distribution spectrum of N atoms and F atoms in the diaphragm by utilizing a scanning electron microscope and energy spectrum analysis, and acquiring the distance between adjacent N atoms and F atoms.
Further, in some embodiments of the application, the mass ratio of the fluoropolymer to the nitrogen-containing polymer is (1:4) - (4:1); and/or
The content of the nitrogen-containing polymer in the coating is 10% -40% by mass.
Further, in some embodiments of the present application, the bulk viscosity of the fluoropolymer is 0.1 to 0.5l/g and the melting point is 120 to 170 ℃; and/or
The bulk viscosity of the nitrogen-containing polymer is 0.05-0.6L/g, and the melting point is higher than 150 ℃.
Further, in some embodiments of the present application, the weight average molecular weight of the fluoropolymer is 50000-1000000; and/or
The weight average molecular weight of the nitrogen-containing polymer is 100000-1500000.
Further, in some embodiments of the application, the fluoropolymer comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, copolymers of vinylidene fluoride-hexafluoropropylene; and/or
The nitrogen-containing polymer is one or more of polyimide, polyamide imide, polyether imide, aramid fiber and polysulfonamide.
Further, in some embodiments of the application, the separator has a chloride ion content of no more than 500ppm.
Further, in some embodiments of the application, the coating further comprises inorganic ceramic particles having a Dv50 of 0.1 μm to 2.0 μm; wherein the content of the inorganic ceramic particles in the coating is 20% -85% by mass.
Further, in some embodiments of the present application, the inorganic ceramic particles include oxide ceramic particles, nitride ceramic particles, and at least one of boehmite, aluminum hydroxide, magnesium hydroxide, barium sulfate, calcium carbonate, wollastonite, and silicon carbide.
Further, in some embodiments of the present application, the base film is a polyolefin-based film having a thickness of 3 to 15 μm and a ventilation value of < 250s/100cc.
Further, in some embodiments of the present application, the membrane has a gas permeability value of 100-400s/100cc, the coating on one side has a thickness of 0.3-4 μm, and a surface density of 0.3-2.0g/m per coating 2 /mm, 130℃shrinkage of the membraneLess than 7.5%; the adhesive strength of the coating and the base film is higher than 3N/m.
In a second aspect, the present application also provides a method for preparing a separator for a lithium ion battery, including:
s1, mixing a solvent, a nitrogen-containing polymer and a fluorine-containing polymer at a temperature of not higher than 10 ℃ to obtain a mixture; wherein the solvent is a polar solvent;
s2: adding anhydrous lithium chloride accounting for 0.1-6% of the mass fraction of the mixture into the mixture, mixing for 0.5-2 hours, completely dissolving the anhydrous lithium chloride, the nitrogen-containing polymer and the fluorine-containing polymer, and defoaming to obtain slurry;
s3: forming a coating liquid film on the surface of the base film at 15-35 ℃ by using slurry; and forming a coating by using a coagulating bath at a temperature of 15-35 ℃, wherein the temperature difference between the slurry temperature and the coagulating bath is controlled within 5 ℃; washing and drying to obtain the diaphragm.
Further, in some embodiments of the application, the bath liquid of the coagulation bath contains polar organic matters, and the concentration of the polar organic matters is 20-60%.
Further, in some embodiments of the application, the polar solvent is at least one of N-methylpyrrolidone, N-dimethylacetamide, N-dimethylformamide, acetone, dimethylsulfoxide, and triethylphosphate.
Further, in some embodiments of the present application, the mass concentration of the nitrogen-containing polymer in the mixture is 0.5-7.5%; the mass concentration of the fluorine-containing polymer in the mixture is 0.5-7.5%.
Further, in some embodiments of the present application, the nitrogen-containing polymer and the fluorine-containing polymer are added to the polar solvent in multiple portions, and the addition amounts of the nitrogen-containing polymer and the fluorine-containing polymer are sequentially decreased; the temperature in S1 is controlled within the range of-10 ℃ to 10 ℃.
Further, in some embodiments of the present application, the polar solvent is at least one of N-methylpyrrolidone, N-dimethylacetamide, N-dimethylformamide, acetone, dimethylsulfoxide, triethylphosphate, and the water content in the polar solvent is not higher than 1%.
Further, in some embodiments of the application, the slurry obtained in S2 has a viscosity of 20-1000 mpa.s at a temperature of 25 ℃.
Further, in some embodiments of the present application, the S2 includes:
Heating the mixture to 35-60 ℃, adding anhydrous lithium chloride with the mass fraction of 0.1-6% into the mixture, stirring for 0.5-2 h until the anhydrous lithium chloride, the nitrogen-containing polymer and the fluorine-containing polymer are completely dissolved, and defoaming to obtain the slurry.
Further, in some embodiments of the present application, in the coagulation bath, the time for immersing the coating liquid film in the coagulation bath is 1 to 10 seconds.
Further, in some embodiments of the present application, before the deaeration in S2, after the anhydrous lithium chloride, nitrogen-containing polymer, and fluorine-containing polymer are completely dissolved, inorganic ceramic particles are added and mixed to obtain a slurry containing inorganic ceramic particles, the Dv50 of the inorganic ceramic particles is 0.1 μm to 2.0 μm, and the concentration of the inorganic ceramic particles in the formed mixture is 2 to 15%.
In a third aspect, the present application also provides an electrochemical device comprising a positive electrode, a negative electrode, a nonaqueous electrolyte, and the separator for a lithium ion battery according to the first aspect or the separator for a lithium ion battery obtained by the production method according to the second aspect.
The application has the beneficial effects that:
the application provides a diaphragm for a lithium ion battery, which adopts two different polymers: the fluorine-containing polymer and the nitrogen-containing polymer are used as one of the components of the coating, the dispersibility of the two polymers in the coating is good, the dispersion uniformity of the fluorine-containing polymer and the nitrogen-containing polymer is improved, the density of the fluorine-containing polymer and the nitrogen-containing polymer is improved, and the adhesive property and the heat resistance of the diaphragm are improved.
The application also provides a preparation method of the diaphragm for the lithium ion battery, which is characterized in that the temperature of the slurry and the temperature in the coagulating bath process are strictly controlled in the process of forming the coating by using the slurry, so that the nitrogen-containing polymer and the fluorine-containing polymer are distributed more uniformly in the coating; meanwhile, the mixing temperature of the nitrogenous polymer and the fluorine-containing polymer is controlled to be not higher than 10 ℃ in the preparation process of the adopted slurry, and then the mixture is heated and dissolved, so that the dissolving efficiency of the polymer can be improved, the defect that the nitrogenous polymer and the fluorine-containing polymer are easy to agglomerate when dispersed in a polar solvent, and further the dispersion and dissolution are difficult can be overcome; in addition, anhydrous lithium chloride is introduced in the process of dissolving the polymer, and interaction is formed among chloride ions and lithium ions, the polymer and the polar solvent, so that the co-dissolution capacity of the fluorine-containing polymer and the nitrogen-containing polymer in the solvent is improved, the dissolving process is accelerated, and meanwhile, the stability of the formed slurry and the dispersion uniformity of the fluorine-containing polymer and the nitrogen-containing polymer in the slurry are improved.
Drawings
Fig. 1 is an SEM image of a coating in a separator for a lithium ion battery according to embodiment 3 of the present application;
fig. 2 is a graph showing the distribution of nitrogen atoms and fluorine atoms in the coating layer in the separator for lithium ion batteries according to example 3 of the present application.
Detailed Description
For a better explanation of the present application, the main content of the present application is further elucidated with reference to the embodiments of the present application, and is further elucidated with reference to the specific examples, but the content of the present application is not limited to the following examples.
The inventor aims at the defect that the performance of a diaphragm is affected by the uneven dispersion of various polymers when the various polymers are adopted in the coating in the prior art, and provides a diaphragm for a lithium ion battery, which comprises a base film and a coating formed on at least one surface of the base film; the material of the coating comprises a nitrogen-containing polymer and a fluorine-containing polymer; and R is N-F ＜3R；
Wherein R is N-F R is the maximum pore diameter in the surface and internal pores of the coating, which is the maximum distance between adjacent N atoms and F atoms in the coating.
The nitrogen-containing polymer of the present application does not contain fluorine elementSince the fluoropolymer does not contain nitrogen, R in the present application N-F It is also understood that the maximum distance between adjacent fluoropolymer molecules and nitrogen-containing polymer molecules is not more than three times the diameter of the largest internal pores.
Wherein the R is N-F Can be obtained by electron microscope energy spectrum (SEM-EDS) characterization, and the characterization method comprises the following steps: and acquiring a distribution spectrum of N atoms and F atoms in the diaphragm by utilizing a scanning electron microscope and energy spectrum analysis, and acquiring the distance between adjacent N atoms and F atoms. The pore diameters of the surface and the inner pores of the coating are usually 0.1 to 2.0 μm, and the pore diameters of the largest pores of the surface and the inner pores are usually 0.1 to 2.0 μm.
In some embodiments, the mass ratio of the fluoropolymer to the nitrogen-containing polymer is (1:4) - (4:1); preferably (1:3) - (3:1), and more preferably (1:2) - (2:1), so that the adhesive property and the heat resistance of the obtained diaphragm can be both achieved.
In some embodiments, the fluoropolymer content in the coating is 10% -40% by mass; the content of the nitrogen-containing polymer in the coating is 10% -40% by mass. The content of the fluorine-containing polymer in the coating is not easy to be too high or too low, and is preferably 15% -35%; more preferably 18% -32%; the content of the nitrogen-containing polymer in the coating is not easy to be too high or too low, and is preferably 15% -35%; more preferably, the content is 18% to 32%.
The fluorine-containing polymer in the application refers to a polymer in which all or part of hydrogen atoms connected with carbon-carbon bonds in a high molecular polymer are replaced by fluorine atoms, the bulk viscosity is 0.05-0.6L/g, and the melting point is 110-180 ℃ of fluorine-containing resin, such as one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene and copolymer of vinylidene fluoride-hexafluoropropylene. Preferably, the fluoropolymer is selected from a copolymer of vinylidene fluoride and hexafluoropropylene or at least comprises vinylidene fluoride and hexafluoropropylene, because hexafluoropropylene in the copolymer breaks molecular chains of the vinylidene fluoride polymer which are too neat to crystallize, so that the absorption rate of the diaphragm to electrolyte can be increased, and the ion conductivity of the diaphragm can be improved.
Wherein the weight average molecular weight of the fluorine-containing polymer is not easy to be too large or too small, and preferably, the weight average molecular weight is 30-90 ten thousand; more preferably 40 to 80 ten thousand. Meanwhile, the bulk viscosity of the fluorine-containing polymer is not too large or too small, and preferably, the bulk viscosity of the fluorine-containing polymer is 0.1-0.5L/g; more preferably 0.2 to 0.4L/g. The melting point of the fluorine-containing polymer is preferably 120-170 ℃; more preferably 130 to 160 ℃.
The nitrogen-containing polymer in the application refers to a polymer containing nitrogen element in a high molecular polymer, the bulk viscosity is 0.05-0.6L/g, and the melting point is higher than 150 ℃ and is one or more of polyimide, polyetherimide, aramid and polysulfonamide. The nitrogen-containing compound is selected from nitrogen-containing compounds containing amide bonds or imide bonds, so that chloride ions and lithium ions in lithium chloride can have certain complexation with the nitrogen-containing compound, and meanwhile, when the liquid is washed under the action of a large amount of hydroxyl groups, the complexation of the nitrogen-containing polymer and the lithium chloride is extremely easy to decompose, so that the nitrogen-containing polymer is separated out, the elution of the lithium chloride is facilitated, the solubility and the dispersibility of the nitrogen-containing polymer in slurry are improved, the dispersibility of the nitrogen-containing polymer in the slurry is better, the stability of the formed slurry is also better, and the dispersibility of the nitrogen-containing polymer and the fluorine-containing polymer in the obtained diaphragm is better and the consistency is also more uniform.
Wherein the weight average molecular weight of the nitrogen-containing polymer is not easy to be too large or too small, and preferably, the weight average molecular weight is 5-50 ten thousand; more preferably 8 to 30 ten thousand. Meanwhile, the temperature is higher than 200 ℃; more preferably above 250 ℃.
In some embodiments, the coating further comprises inorganic ceramic particles having a Dv50 of 0.1 μm to 2.0 μm, preferably, the inorganic ceramic particles have a volume particle size in the range of 0.5 μm to 2.0 μm and a volume average particle size of 0.5 μm to 1.0 μm; the content of the inorganic ceramic particles in the coating is 20% -85% by mass, preferably 40% -75% by mass, and more preferably 50% -70% by mass. The content of inorganic ceramic particles, nitrogen-containing polymer and fluorine-containing polymer in the coating is controlled within a certain range, so that the viscosity and stability of the obtained slurry for the coating can be controlled within a required range, and the coating with strong cohesiveness, uniform polymer molecule dispersion, high polymer molecule density and better performance is obtained.
In some embodiments, the inorganic ceramic particles comprise oxide ceramic particles, nitride ceramic particles, and at least one of boehmite, aluminum hydroxide, magnesium hydroxide, barium sulfate, calcium carbonate, wollastonite, silicon carbide, preferably at least one of alumina or boehmite.
In some embodiments, the inorganic ceramic particles may be non-modified inorganic ceramic particles, or may be modified inorganic ceramic particles, preferably modified inorganic ceramic particles, which are commercially available with silane coupling agents, such as methyltriethoxysilane and ethyltriethoxysilane, so as to further improve the dispersibility and adhesion of the inorganic ceramic particles in the fluorine-containing resin.
In some embodiments, the separator has a chloride ion content of no greater than 500ppm. Chloride ions can have negative effects on batteries, such as reducing the voltage of the battery, causing battery planning, reducing battery capacity, and can migrate out of the coating very easily and be very corrosive, so control over the content of chloride ions is often required in lithium batteries.
In some embodiments, the base film is a polyolefin-based film having a thickness of 3 to 15 μm and a gas permeation value of < 250 s/100cc. Wherein the porosity of the polyolefin-based film may be 30 to 50%, preferably 35 to 45%.
In some embodiments, the membrane has a gas permeability value of 100-400s/100cc, the coating on one side has a thickness of 0.3-4 μm, and a areal density per coating of 0.3-2.0 g/m 2 The 130 ℃ shrinkage of the membrane is lower than 7.5 percent; the adhesive strength of the coating and the base film is higher than 3N/m. Wherein, the 130 ℃ shrinkage of the separator is lower than 7.5%, which means that the shrinkage in both the transverse and longitudinal directions thereof is lower than 7.5%.
In a second aspect, the present application also provides a method for preparing a separator for a lithium ion battery, including:
s1, mixing a solvent, a nitrogen-containing polymer and a fluorine-containing polymer at a temperature of not higher than 10 ℃ to obtain a mixture; wherein the solvent is a polar solvent;
s2: adding anhydrous lithium chloride accounting for 0.1-6% of the mass fraction of the mixture into the mixture, mixing for 0.5-2 hours, completely dissolving the anhydrous lithium chloride, the nitrogen-containing polymer and the fluorine-containing polymer, and defoaming to obtain slurry;
s3: forming a coating liquid film on the surface of the base film at 15-35 ℃ by using slurry; and forming a coating by using a coagulating bath at a temperature of 15-35 ℃, wherein the temperature difference between the slurry temperature and the coagulating bath is controlled within 5 ℃; washing and drying to obtain the diaphragm.
Wherein the addition amount of the anhydrous lithium chloride is preferably 0.5-3% of the mixture, and more preferably 0.8-2%. The addition amount of the anhydrous lithium chloride is not too high or too low, and when the addition amount is too low, the improvement effect of the additive on the co-dissolution of the nitrogen-containing polymer and the fluorine-containing polymer is not obvious, and the addition amount is too high, so that the additive is not beneficial to removal in a later coagulation bath and washing, and the chloride ion content in the obtained diaphragm is high, and the performance of the diaphragm is influenced.
In some embodiments, the polar solvent is brought to a low temperature prior to adding the nitrogen-containing polymer and the fluorine-containing polymer, so that the polar solvent is in a low temperature state, and poor dispersion of the nitrogen-containing polymer and the fluorine-containing oxide due to high temperature in the process of mixing the nitrogen-containing polymer and the fluorine-containing polymer is avoided. The polar solvent is illustratively maintained at a low temperature of-30 to 10 c, preferably-30 to 0 c.
In step S1, the solvent, the nitrogen-containing polymer and the fluorine-containing polymer are mixed at a temperature of not higher than 10 ℃, which means that the raw materials used therein and the resulting mixture are not higher than 10 ℃ in the whole process.
In some embodiments, the mass concentration of nitrogen-containing polymer in the mixture is 0.5-7.5%; the mass concentration of the fluoropolymer in the mixture is 0.5-7.5%. The concentration of the nitrogen-containing polymer and the fluorine-containing polymer is not too high, so that poor dispersing effect is avoided, the concentration is not too low, and the heat resistance or bonding effect of the prepared diaphragm is avoided, so that the lithium battery cannot be used. Preferably, the mass concentration of nitrogen-containing polymer in the mixture is from 2 to 5%; the mass concentration of the fluorine-containing polymer in the mixture is 2-5%; more preferably, the mass concentration of nitrogen-containing polymer in the mixture is 3-4%; the mass concentration of the fluoropolymer in the mixture is 3-4%.
In some embodiments, the nitrogen-containing polymer and the fluoropolymer are added to the polar solvent in multiple portions, and the addition of the nitrogen-containing polymer and the fluoropolymer is sequentially decreased; the temperature in S1 is controlled within the range of-10 ℃ to 10 ℃. Illustratively, the nitrogen-containing polymer and the fluorine-containing polymer are added in decreasing amounts of 1/2 of the last addition in order of the next addition, while the addition of the nitrogen-containing polymer and the fluorine-containing polymer for the first addition does not exceed 1/2 of the total amount of the nitrogen-containing polymer and the fluorine-containing polymer to be added; meanwhile, when the amount of the remaining nitrogen-containing polymer and fluorine-containing polymer is less than 1/16 of the total amount of the nitrogen-containing polymer and fluorine-containing polymer to be added, the remaining nitrogen-containing polymer and fluorine-containing polymer may be added at one time; or whether to add at one time is judged by the mass of the remaining nitrogen-containing polymer and fluorine-containing polymer, if the amount of the remaining nitrogen-containing polymer and fluorine-containing polymer is less than 1kg, then at one time.
In S1, the mixing manner of the solvent, the fluoropolymer and the nitrogen-containing polymer may be a common mixing manner, such as stirring; when the stirring is carried out mechanically or magnetically, the stirring rotation speed is controlled to be 500-2000 r/min; the stirring time can be controlled to be 0.1-0.5-h, and uniform mixing is realized. In addition, the fluoropolymer and the nitrogen-containing polymer are gradually added to the solvent during the stirring.
In some embodiments, the S2 comprises:
heating the mixture to 35-60 ℃, adding anhydrous lithium chloride with the mass fraction of 0.1-6% into the mixture, stirring for 0.5-2 h until the anhydrous lithium chloride, the nitrogen-containing polymer and the fluorine-containing polymer are completely dissolved, and defoaming to obtain the slurry.
In step S2, when the anhydrous lithium chloride and the mixture are mixed, the mixing method may be a mixing process such as stirring and grinding, and a grinding process is preferable.
Wherein the defoaming may be a conventional defoaming process such as standing or vacuum defoaming, preferably vacuum defoaming.
In some embodiments, the temperature of the mixture is controlled to be above 5 ℃ per minute during the step of heating the mixture to 35-60 ℃ to achieve rapid temperature rise and avoid prolonged dissolution of the nitrogen-containing polymer or fluoropolymer.
In some embodiments, before the deaeration in S2, after the anhydrous lithium chloride, nitrogen-containing polymer, and fluoropolymer are completely dissolved, inorganic ceramic particles are added and mixed; a slurry containing inorganic ceramic particles having a Dv50 of 0.1 μm to 2.0 μm and a concentration of 1.5% to 20% of the inorganic ceramic particles in the resulting mixture is obtained.
After the anhydrous lithium chloride, the nitrogen-containing polymer and the fluorine-containing polymer are completely dissolved, the inorganic ceramic particles are added before defoaming, and the inorganic ceramic particles are uniformly dispersed in the slurry by a mixing process such as stirring and grinding. Avoiding the influence on the dispersion and dissolution of anhydrous lithium chloride, nitrogen-containing polymer and fluorine-containing polymer due to the addition of inorganic ceramic particles, thereby influencing the performance of the diaphragm.
In some embodiments, the slurry obtained in S2 has a viscosity of 20-1000 mpa·s at a temperature of 25 ℃, preferably the viscosity of the slurry is controlled to 150-600 mpa·s.
In some embodiments, the coagulation bath has a bath liquid containing polar organic matter, and the concentration of the polar organic matter is 20-60%. It should be noted that the polar organic matter and the polar solvent are preferably the same or organic matter with a polarity closer to that of the polar organic matter, so as to achieve better washing out of the lithium chloride in the process, and be favorable for better reducing the content of chloride ions in the obtained diaphragm. Thus, the polar solvent and the polar organic matter may each be selected from at least one of N-methylpyrrolidone, N-dimethylacetamide, N-dimethylformamide, acetone, dimethylsulfoxide, and triethylphosphate.
In some embodiments, the water content in the polar solvent is no greater than 1% to control the water content in the slurry.
In some embodiments, in the coagulation bath, the time for immersing the coating liquid film in the coagulation bath is 1-10 s.
In a third aspect, the present application also provides an electrochemical device comprising a positive electrode, a negative electrode, a nonaqueous electrolyte, and the separator for a lithium ion battery according to the first aspect or the separator for a lithium ion battery obtained by the production method according to the second aspect;
the electrochemical device can be any electronic product containing the electrochemical device, such as a tablet computer, a computer, an unmanned aerial vehicle, an electric automobile and other devices driven by electric power.
The present application will be described in more detail with reference to the following examples, which are not intended to limit the scope of the application.
Wherein the polyvinylidene fluoride (PVDF) resin used in the following examples has a weight average molecular weight of 30-80 ten thousand, a bulk viscosity of 0.05-0.5L/g, and a melting point of 120-160 ℃, and is commercially available, such as available from Shandong Dongyue group China Shenzhou New Material, arkema (Suzhou) high molecular materials, suweite polymers (well-known), wu Yu (well-known) fluorine materials, and well-known blue sky group;
Al used in the following examples 2 O 3 The particles have a Dv50 of 0.64 μm and are commercially available, for example from the wide aluminium group, the new materials technology, the Shandong national porcelain materials, the Shandong West-officials, the alumina technology, the Bobo Yi Deye, the Shandong national porcelain materials;
the anhydrous lithium chloride used in the following examples was purchased from Yu Yunmei chemical group at a purity of 99.5%;
the aramid fibers and polysulfonamides used in the examples below were purchased from Shandong Tai and technology Co., ltd, and the monomers used were rigid para-diamine and rigid para-acyl chloride;
the polyimide, polyamide imide and polyether imide adopted in the following examples are purchased from new materials of China Shenzhou, a group of east and east of Shandong, and the monomers used are rigid para-diamine and rigid para-dianhydride;
the polyolefin-based film used in the following examples is a commercially available product made by middle lithium film Co., ltd, and has a model of SNC07 and a thickness of 7 μm to 13 μm; commercially available base films having a thickness of 7 μm to 13 μm, a porosity of 30% and an average pore diameter of 50 to 100nm may be used.
Solvents used in the following examples were purchased from national pharmaceutical chemicals, inc., and were analytically pure;
Example 1:
the embodiment of the application provides a preparation method of a diaphragm for a lithium ion battery, which specifically comprises the following steps:
s1: preparation of the mixture: taking 85 parts by weight of Dimethylacetamide (DMAC) with the temperature of 5 ℃, 1.5 parts by weight of PVDF resin and 4.5 parts by weight of aramid; adding PVDF resin and aramid fiber into DMAC in batches at a stirring speed of 1000 r/min and a mixture temperature of 5 ℃, wherein the adding amount of each powder is 1/2 of the total mass of the residual powder; when the powder mass is lower than 1 kg, the rest powder is added; stirring 0.5. 0.5 h to obtain a mixture;
s2: preparation of the slurry: heating the mixture to 35 ℃ at a heating rate of 10 ℃/min, adding anhydrous lithium chloride powder accounting for 1% of the mass of the mixture, stirring until PVDF, aramid fiber and lithium chloride are completely dissolved, adding alumina accounting for 8% of the mass of the mixture, grinding and dispersing until slurry is uniformly dispersed, decompressing and defoaming for 120min at 25Pa to obtain slurry, wherein the viscosity of the slurry at 25 ℃ is 230 mpa.s;
s3: coating the slurry on the two sides of a polyethylene porous substrate (with the thickness of 7 mu m, the porosity of 35% and the average pore diameter of 70 nm), and controlling the temperature of the slurry at 20 ℃; immersing the coated coating film into a coagulating bath for 5s, wherein the temperature of the coagulating bath is controlled at 18 ℃; washing with water and drying to obtain the membrane with the coating thickness of 4.0 μm.
Example 2
The embodiment of the application provides a preparation method of a diaphragm for a lithium ion battery, which specifically comprises the following steps:
s1: preparation of the mixture: taking 85 parts by weight of DMAC (dimethyl ether) with the temperature of 5 ℃, 4.5 parts by weight of PVDF (polyvinylidene fluoride) resin and 1.5 parts by weight of aramid; adding PVDF resin and aramid fiber into DMAC in batches at a stirring speed of 1000 r/min and a mixture temperature of 5 ℃, wherein the adding amount of each powder is 1/2 of the total mass of the residual powder; when the powder mass is lower than 1 kg, the rest powder is added; stirring 0.5. 0.5 h to obtain a mixture;
s2: preparation of the slurry: heating the mixture to 50 ℃ at a heating rate of 10 ℃/min, adding anhydrous lithium chloride powder accounting for 1% of the mass of the mixture, stirring until PVDF, aramid fiber and lithium chloride are completely dissolved, adding alumina accounting for 8% of the mass of the mixture, grinding and dispersing until slurry is uniformly dispersed, decompressing and defoaming for 120min at 25Pa to obtain slurry, wherein the viscosity of the slurry at 25 ℃ is 180 mpa.s;
s3: coating the slurry on the two sides of a polyethylene porous substrate (with the thickness of 7 mu m, the porosity of 35% and the average pore diameter of 70 nm), and controlling the temperature of the slurry at 20 ℃; immersing the coated coating film into a coagulating bath for 5s, wherein the temperature of the coagulating bath is controlled at 18 ℃; washing with water and drying to obtain the membrane, wherein the coating thickness of the membrane is 5 mu m.
Example 3
The embodiment of the application provides a preparation method of a diaphragm for a lithium ion battery, which specifically comprises the following steps:
s1: preparation of the mixture: taking 85 parts by weight of DMAC (dimethyl ether) with the temperature of 5 ℃, 3 parts by weight of PVDF (polyvinylidene fluoride) resin and 3 parts by weight of aramid fiber; adding PVDF resin and aramid fiber into DMAC in batches at a stirring speed of 1000 r/min and a mixture temperature of 5 ℃, wherein the adding amount of each powder is 1/2 of the total mass of the residual powder; when the powder mass is lower than 1 kg, the rest powder is added; stirring 0.5. 0.5 h to obtain a mixture;
s2: preparation of the slurry: heating the mixture to 45 ℃ at a heating rate of 10 ℃/min, adding anhydrous lithium chloride powder accounting for 0.1% of the mass of the mixture, stirring until PVDF, aramid fiber and lithium chloride are completely dissolved, adding alumina accounting for 8% of the mass of the mixture, grinding and dispersing until slurry is uniformly dispersed, decompressing and removing bubbles for 120min at 25Pa to obtain slurry, wherein the viscosity of the slurry at 25 ℃ is 150 mpa.s;
s3: coating the slurry on the two sides of a polyethylene porous substrate (the thickness is 9 mu m, the porosity is 35%, the average pore diameter is 70 nm), and controlling the temperature of the slurry at 25 ℃; immersing the coated coating film into a coagulating bath for 5s, wherein the temperature of the coagulating bath is controlled at 25 ℃; washing with water and drying to obtain the membrane, wherein the coating thickness of the membrane is 3.5 mu m.
Example 4
The embodiment of the application provides a preparation method of a diaphragm for a lithium ion battery, which specifically comprises the following steps:
s1: preparation of the mixture: taking 85 parts by weight of DMAC, 3 parts by weight of PVDF resin and 3 parts by weight of polysulfonamide at a temperature of 5 ℃ based on 100 parts by weight of the mixture; adding PVDF resin and aramid fiber into DMAC in batches at a stirring speed of 1000 r/min and a mixture temperature of 5 ℃, wherein the adding amount of each powder is 1/2 of the total mass of the residual powder; when the powder mass is lower than 1 kg, the rest powder is added; stirring 0.5. 0.5 h to obtain a mixture;
s2: preparation of the slurry: heating the mixture to 45 ℃ at a heating rate of 10 ℃/min, adding anhydrous lithium chloride powder accounting for 0.5% of the mass of the mixture, stirring until PVDF, aramid fiber and lithium chloride are completely dissolved, adding alumina accounting for 8% of the mass of the mixture, grinding and dispersing until slurry is uniformly dispersed, decompressing and removing bubbles for 120min at 25Pa to obtain slurry, wherein the viscosity of the slurry at 25 ℃ is 265 mpa.s;
s3: coating the slurry on the two sides of a polyethylene porous substrate (with the thickness of 12 mu m, the porosity of 35 percent and the average pore diameter of 70 nm), and controlling the temperature of the slurry at 25 ℃; immersing the coated coating film into a coagulating bath for 5s, wherein the temperature of the coagulating bath is controlled at 25 ℃; washing with water and drying to obtain the membrane with the coating thickness of 2.0 μm.
Example 5
The embodiment of the application provides a preparation method of a diaphragm for a lithium ion battery, which specifically comprises the following steps:
s1: preparation of the mixture: taking 85 parts by weight of DMAC, 3 parts by weight of PVDF resin and 3 parts by weight of polysulfonamide at a temperature of 5 ℃ based on 100 parts by weight of the mixture; adding PVDF resin and polysulfonamide into DMAC in batches at a stirring speed of 1000 r/min and a mixture temperature of 5 ℃, wherein the adding amount of each powder is 1/2 of the total mass of the residual powder; when the powder mass is lower than 1 kg, the rest powder is added; stirring 0.5. 0.5 h to obtain a mixture;
s2: preparation of the slurry: heating the mixture to 45 ℃ at a heating rate of 10 ℃/min, adding anhydrous lithium chloride powder accounting for 1% of the mass of the mixture, stirring until PVDF, polysulfonamide and lithium chloride are completely dissolved, adding alumina accounting for 8% of the mass of the mixture, grinding and dispersing until slurry is uniformly dispersed, decompressing and removing bubbles for 120min at 25Pa to obtain slurry, wherein the viscosity of the slurry at 25 ℃ is 670 mpa.s;
s3: coating the slurry on the two sides of a polyethylene porous substrate (with the thickness of 7 mu m, the porosity of 35% and the average pore diameter of 70 nm), and controlling the temperature of the slurry at 20 ℃; immersing the coated coating film into a coagulating bath for 5s, wherein the temperature of the coagulating bath is controlled at 18 ℃; washing with water and drying to obtain the membrane, wherein the coating thickness of the membrane is 3.5 mu m.
Example 6
The embodiment of the application provides a preparation method of a diaphragm for a lithium ion battery, which specifically comprises the following steps:
s1: preparation of the mixture: taking 85 parts by weight of DMAC, 3 parts by weight of PVDF resin and 3 parts by weight of polyimide at a temperature of 5 ℃ based on 100 parts by weight of the mixture; adding PVDF resin and polyimide into DMAC in batches at a stirring speed of 1000 r/min and a mixture temperature of 5 ℃, wherein the adding amount of each powder is 1/2 of the total mass of the residual powder; when the powder mass is lower than 1 kg, the rest powder is added; stirring 0.5. 0.5 h to obtain a mixture;
s2: preparation of the slurry: heating the mixture to 45 ℃ at a heating rate of 10 ℃/min, adding anhydrous lithium chloride powder with the mass of 1.5% of the mixture, stirring until PVDF, polyimide and lithium chloride are completely dissolved, adding alumina with the mass ratio of 8% of the mixture, grinding and dispersing until slurry is uniformly dispersed, decompressing and removing bubbles for 120min at 25Pa to obtain slurry with the viscosity of 273 mpa.s at 25 ℃;
s3: coating the slurry on the two sides of a polyethylene porous substrate (with the thickness of 7 mu m, the porosity of 35% and the average pore diameter of 70 nm), and controlling the temperature of the slurry at 25 ℃; immersing the coated coating film into a coagulating bath for 5s, wherein the temperature of the coagulating bath is controlled at 25 ℃; washing with water and drying to obtain the membrane, wherein the coating thickness of the membrane is 3.5 mu m.
Example 7
The embodiment of the application provides a preparation method of a diaphragm for a lithium ion battery, which specifically comprises the following steps:
s1: preparation of the mixture: taking 85 parts by weight of DMAC, 3 parts by weight of PVDF resin and 3 parts by weight of polyamide imide at a temperature of 5 ℃ based on 100 parts by weight of the mixture; adding PVDF resin and polyamide imide into DMAC in batches at a stirring speed of 1000 r/min and a mixture temperature of 5 ℃, wherein the adding amount of each powder is 1/2 of the total mass of the residual powder; when the powder mass is lower than 1 kg, the rest powder is added; stirring 0.5. 0.5 h to obtain a mixture;
s2: preparation of the slurry: heating the mixture to 45 ℃ at a heating rate of 10 ℃/min, adding anhydrous lithium chloride powder accounting for 2% of the mass of the mixture, stirring until PVDF, polyamide imide and lithium chloride are completely dissolved, adding alumina accounting for 8% of the mass of the mixture, grinding and dispersing until slurry is uniformly dispersed, decompressing and defoaming for 120min at 25Pa to obtain slurry, wherein the viscosity of the slurry at 25 ℃ is 475 mpa.s;
s3: coating the slurry on the two sides of a polyethylene porous substrate (with the thickness of 7 mu m, the porosity of 35% and the average pore diameter of 70 nm), and controlling the temperature of the slurry at 25 ℃; immersing the coated coating film into a coagulating bath for 5s, wherein the temperature of the coagulating bath is controlled at 25 ℃; washing with water and drying to obtain the membrane, wherein the coating thickness of the membrane is 1.5 mu m.
Example 8
The embodiment of the application provides a preparation method of a diaphragm for a lithium ion battery, which specifically comprises the following steps:
s1: preparation of the mixture: taking 85 parts by weight of DMAC, 3 parts by weight of PVDF resin and 3 parts by weight of aramid fiber with a temperature of 0 ℃ based on 100 parts by weight of the mixture; adding PVDF resin and aramid fiber into DMAC in batches at a stirring speed of 1000 r/min and a mixture temperature of 5 ℃, wherein the adding amount of each powder is 1/2 of the total mass of the residual powder; when the powder mass is lower than 1 kg, the rest powder is added; stirring 0.5. 0.5 h to obtain a mixture;
s2: preparation of the slurry: heating the mixture to 45 ℃ at a heating rate of 10 ℃/min, adding anhydrous lithium chloride powder accounting for 1% of the mass of the mixture, stirring until PVDF, aramid fiber and lithium chloride are completely dissolved, adding alumina accounting for 8% of the mass of the mixture, grinding and dispersing until slurry is uniformly dispersed, decompressing and defoaming for 120min at 25Pa to obtain slurry, wherein the viscosity of the slurry at 25 ℃ is 268 mpa.s;
s3: coating the slurry on the two sides of a polyethylene porous substrate (with the thickness of 7 mu m, the porosity of 35% and the average pore diameter of 70 nm), and controlling the temperature of the slurry at 35 ℃; immersing the coated coating film into a coagulating bath for 5s, wherein the temperature of the coagulating bath is controlled at 35 ℃; washing with water and drying to obtain the membrane, wherein the coating thickness of the membrane is 3.5 mu m.
Example 9
The embodiment of the application provides a preparation method of a diaphragm for a lithium ion battery, which specifically comprises the following steps:
s1: preparation of the mixture: taking 87 parts by weight of methyl pyrrolidone (NMP) at a temperature of 5 ℃, 3 parts by weight of copolymer resin of vinylidene fluoride-hexafluoropropylene and 3 parts by weight of polyimide based on 100 parts by weight of the mixture; adding copolymer resin of vinylidene fluoride-hexafluoropropylene and polyimide into NMP in batches at a stirring speed of 800r/min and a mixture temperature of 10 ℃, wherein the adding amount of each powder is 1/2 of the total mass of the residual powder; when the powder mass is lower than 1 kg, the rest powder is added; stirring for 0.3h to obtain a mixture;
s2: preparation of the slurry: heating the mixture to 45 ℃ at a heating rate of 10 ℃/min, adding anhydrous lithium chloride powder accounting for 1% of the mass of the mixture, stirring until polyimide, a copolymer of vinylidene fluoride and hexafluoropropylene and lithium chloride are completely dissolved, adding SiO2 accounting for 6% of the mass of the mixture, grinding and dispersing until slurry is uniformly dispersed, decompressing and defoaming for 120min at 25Pa to obtain slurry, wherein the viscosity of the slurry at 25 ℃ is 248 mpa.s;
s3: coating the slurry on the two sides of a polyethylene porous substrate (with the thickness of 7 mu m, the porosity of 35% and the average pore diameter of 70 nm), and controlling the temperature of the slurry at 25 ℃; immersing the coated coating film into a coagulating bath for 5s, wherein the temperature of the coagulating bath is controlled at 25 ℃; washing with water and drying to obtain the membrane, wherein the coating thickness of the membrane is 3.0 μm.
Example 10
The embodiment of the application provides a preparation method of a diaphragm for a lithium ion battery, which specifically comprises the following steps:
s1: preparation of the mixture: taking 85 parts by weight of DMAC, 3 parts by weight of PVDF resin and 3 parts by weight of polyetherimide at a temperature of 5 ℃ based on 100 parts by weight of the mixture; adding PVDF resin and polyetherimide into DMSO in batches at a stirring speed of 1000 r/min and a mixture temperature of 5 ℃, wherein the adding amount of each powder is 1/2 of the total mass of the rest powder; when the powder mass is lower than 1 kg, the rest powder is added; stirring 0.5. 0.5 h to obtain a mixture;
s2: preparation of the slurry: heating the mixture to 45 ℃ at a heating rate of 10 ℃/min, adding anhydrous lithium chloride powder accounting for 1% of the mass of the mixture, stirring until PVDF, polyetherimide and lithium chloride are completely dissolved, adding alumina accounting for 10% of the mass of the mixture, grinding and dispersing until slurry is uniformly dispersed, decompressing and defoaming for 120min at 25Pa to obtain slurry, wherein the viscosity of the slurry at 25 ℃ is 390 mpa.s;
s3: coating the slurry on the two sides of a polyethylene porous substrate (with the thickness of 7 mu m, the porosity of 35% and the average pore diameter of 70 nm), and controlling the temperature of the slurry at 25 ℃; immersing the coated coating film into a coagulating bath for 5s, wherein the temperature of the coagulating bath is controlled at 25 ℃; washing with water and drying to obtain the membrane, wherein the coating thickness of the membrane is 2.8 mu m.
Comparative example 1
In this comparative example, the temperature of the polar solvent in step S1 was 25℃and the temperature of the mixture during the mixing was controlled at 25℃as compared with example 3, and the remaining steps were the same as in example 10, to obtain a separator having a coating thickness of 3.5. Mu.m.
Comparative example 2
In this comparative example, compared with example 3, the temperature was maintained at 5℃during the preparation of the slurry in step S2, and the rest of the procedure was the same as in example 3, to obtain a separator having a coating thickness of 3.5. Mu.m.
Comparative example 3
In this comparative example, as compared with example 3, lithium chloride was not added in step S2, and the rest of the procedure was the same as in example 3, so that a separator having a coating thickness of 3.5 μm was obtained.
Comparative example 4
In this comparative example, the temperature at the time of slurry coating was controlled at 10℃in step S3, the temperature of the coagulation bath was also controlled at 10℃as compared with example 3, and the rest of the procedure was the same as that of example 3, so that a separator having a coating thickness of 3.5 μm was obtained.
Comparative example 5
In this comparative example, the temperature at the time of slurry coating was controlled at 20℃and the temperature of coagulation bath was also controlled at 35℃in step S3, as compared with example 3, and the rest of the procedure was the same as in example 3, so that a separator having a coating thickness of 3.5 μm was obtained.
Comparative example 6
In this comparative example, the temperature at the time of slurry coating was controlled at 35℃and the temperature of coagulation bath was also controlled at 20℃in step S3, as compared with example 13, and the rest of the procedure was the same as in example 3, so that a separator having a coating thickness of 3.5 μm was obtained.
Comparative example 7
In this comparative example, the temperature at the time of slurry coating was controlled at 45℃and the temperature of coagulation bath was also controlled at 50℃in step S3, as compared with example 3, and the rest of the procedure was the same as in example 3, so that a separator having a coating thickness of 3.5 μm was obtained.
Comparative example 8
In this comparative example, the amount of aramid fiber added in step S1 was 6 parts by weight, PVDF was not added, and the other steps were the same as in example 3, so that a separator having a coating thickness of 3.5 μm was obtained.
Comparative example 9
In this comparative example, the PVDF was added in an amount of 6 parts by weight in step S1, and no aramid was added, and the other steps were the same as in example 3, so that a separator having a coating thickness of 3.5 μm was obtained.
Experiment
The physical parameters and performance parameters of the diaphragms obtained in examples 1 to 9 and comparative examples 1 to 9 were respectively tested by the following test methods, which are as follows:
the testing method comprises the following steps:
dissolution time t1 of 1-Nitrogen-containing Polymer and fluoropolymer
And (3) taking the glue solution in the step S2 by using a 250ml transparent glass bottle, taking the glue solution once every 10min, irradiating the glue solution in the glass bottle by using a strong light flashlight, visually observing the liquid in the bottle, and when floccules and solid particles are not formed, considering that the fluorine-containing polymer, the nitrogen-containing polymer and the LiCl are completely dissolved, and recording the time at the moment as the dissolution time t1 of the nitrogen-containing polymer and the fluorine-containing polymer.
2-areal density per unit thickness ρ
The areal density per unit thickness of the separator was tested according to standard FZ/T60003.
Shrinkage at 3-130 DEG C
The test was performed with reference to the requirements of GB/T12027-2004.
Cutting a composite diaphragm with the size of 15 multiplied by 15cm, and measuring the longitudinal and transverse lengths of a sample respectively by using a ruler on the longitudinal and transverse directions marked on the surface of the composite diaphragm;
measuring the longitudinal and transverse lengths of the sample by a ruler;
the sample was spread in a jig and then placed in an oven and held at 130 ℃ for 60min;
after the heating is finished, taking out the samples, measuring the length of the longitudinal and transverse marks again after the room temperature is restored, calculating the shrinkage rate according to the following formula respectively, and finally taking the average value of a plurality of samples as the shrinkage rate.
Δl—heat shrinkage in the longitudinal direction of the sample, expressed in%;
L 0 -the length of the sample in the longitudinal direction before heating in millimeters (mm);
l, the length of the sample in the longitudinal direction after heating is measured in millimeters (mm);
Δt—thermal shrinkage in the transverse direction of the specimen, expressed in%;
T 0 -the length of the sample in the transverse direction before heating in millimeters (mm);
t-the length in the transverse direction after heating of the sample in millimeters (mm).
4-maximum pore diameter R
Observing the surface of the film by using a Scanning Electron Microscope (SEM), randomly taking 5 photos with 10000 times of different bit amplification multiplying power, drawing out the outline of the hole by using a pen, measuring the distances between the two ends of the hole by using image processing software, and taking the maximum value as the maximum aperture R.
5-R F-N
Randomly taking 5 photos with 10000 times of different bit amplification rates by using a scanning electron microscope element, scanning F element and N element in an image by using an element analyzer, measuring the distance between adjacent F atom and N atom by using image processing software, and taking the maximum value as R F-N 。
6-chloride ion content
The sample outsourcing detection is carried out, the detection mechanism is an Shanghai micro-spectrum analysis test center, and the specific detection method comprises the following steps: weighing 0.1g (with the accuracy of 0.1 mg) of diaphragm sample, burning in an oxygen-nitrogen environment, taking 15mL of ultrapure water as an absorption liquid to fully absorb combustion products, filtering the absorption liquid and oxygen-nitrogen flushing liquid through a 0.45 micrometer filter membrane, transferring the absorption liquid and the oxygen-nitrogen flushing liquid into a 100mL volumetric flask, using the ultrapure water to fix the volume to a scale mark, performing blank experiments before each sample burning, and testing by using Ion Chromatography (IC).
7-Polymer settling time t2
Taking the slurry prepared in the step S2 by using a 250ml transparent glass bottle, standing, taking the slurry of the uppermost layer 1cm and the slurry of the lowermost layer 1cm of the glass bottle every 10min, putting into a vacuum oven at 200 ℃ for 2h, and measuring the solid content of the slurry of the upper layer Lower slurry solids content +.>When->When the content of the polymer is more than 5%, recording the standing time of the slurry at the moment as the polymer settling time t2.
8-coating air permeability value F
A membrane sample with a porous membrane of 100mm multiplied by 100mm is cut, a 100cc test gas mode is used for testing by using a Gurley 4110N air permeability tester in the United states, and the time for the test gas to pass through the isolating membrane sample with the porous membrane is recorded, namely the air permeability value R of the membrane 2 . The air permeability value of the coating is the air permeability value R of the membrane provided with the porous coating 2 The air permeability value of the separator (i.e., polyolefin porous base film) without the porous coating layer was subtracted.
9-bonding Strength
The test is carried out with reference to the requirements of GB/T2792.
TABLE 1
/>
TABLE 2
As can be seen from tables 1 and 2, the preparation method of the diaphragm provided by the application has the advantages that the raw materials are mixed at a low temperature, the dissolution time of the raw materials can be shortened, meanwhile, the stability of slurry formed after the dissolution is ensured to be good, the dispersibility of the nitrogen-containing polymer and the fluorine-containing polymer in the obtained diaphragm is very good, the shrinkage rate is low, the bonding strength is high, meanwhile, the diaphragm has excellent performance on parameters such as a ventilation value, a density of unit thickness and the like, the defect that the polymers in the coating slurry are easy to agglomerate in the prior art is overcome, and the problems of difficult dispersion and poor slurry stability caused by different solubilities of the two polymers in solvents are especially solved. In addition, although lithium chloride is added in the preparation process, the inventor controls the technological parameters in the coagulation bath process to ensure that the obtained diaphragm has good effect of washing out chloride ions, the content of the chloride ions can be controlled in an extremely low range, and the use of the diaphragm is ensured. In addition, the membrane provided by the application adopts two polymers in the coating, and overcomes the defects of higher membrane shrinkage and poor thermal stability of a single polymer (such as a single PVDF).
Fig. 1 and 2 show Scanning Electron Microscope (SEM) images of the coating of the diaphragm obtained in example 3, and the distribution of nitrogen atoms and fluorine atoms in this part of the coating was obtained according to an elemental analyzer, respectively. From the figure, the distance between the nitrogen-containing polymer (molecule with nitrogen atom) and the fluorine-containing polymer (molecule with fluorine atom) in the coating of the diaphragm provided by the application is small, so that the dispersibility of the nitrogen-containing polymer and the fluorine-containing polymer is good, and the uniformity of single consistency is good. The present application can be implemented in other forms than the above-described forms within a range not exceeding the gist of the present application. The disclosed embodiments of the present application are examples and are not limited to these.
Claims (21)
1. A separator for a lithium ion battery, comprising a base film and a coating layer formed on at least one surface of the base film; the material of the coating comprises a nitrogen-containing polymer and a fluorine-containing polymer; and R is N-F ＜3R；
Wherein R is N-F Is in the coatingThe maximum distance between adjacent N atoms and F atoms, R is the maximum aperture in the surface and internal pores of the coating;
the R is N-F Is obtained through the characteristic of electron microscope energy spectrum,
the characterization method comprises the following steps: and acquiring a distribution spectrum of N atoms and F atoms in the diaphragm by utilizing a scanning electron microscope and energy spectrum analysis, and acquiring the distance between adjacent N atoms and F atoms.
2. The separator for lithium ion batteries according to claim 1, wherein: the mass ratio of the fluorine-containing polymer to the nitrogen-containing polymer is (1:4) - (4:1); and/or
The content of the fluorine-containing polymer in the coating is 10-40% by mass fraction; the content of the nitrogen-containing polymer in the coating is 10-40% by mass.
3. The separator for lithium ion batteries according to claim 1, wherein: the bulk viscosity of the fluorine-containing polymer is 0.1-0.5L/g, and the melting point is 120-170 ℃; and/or
The bulk viscosity of the nitrogen-containing polymer is 0.05-0.6L/g, and the melting point is higher than 150 ℃.
4. The separator for lithium ion batteries according to any one of claims 1 to 3, wherein: the weight average molecular weight of the fluorine-containing polymer is 50000-1000000; and/or
The weight average molecular weight of the nitrogen-containing polymer is 100000-1500000.
5. The separator for lithium ion batteries according to claim 4, wherein: the fluorine-containing polymer comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene and copolymer of vinylidene fluoride-hexafluoropropylene; and/or
The nitrogen-containing polymer is one or more of polyimide, polyamide imide, polyether imide, aramid fiber and polysulfonamide.
6. The separator for lithium ion batteries according to claim 1, wherein: the content of chloride ions in the diaphragm is not higher than 500ppm.
7. The separator for lithium ion batteries according to claim 1, wherein: the coating also comprises inorganic ceramic particles with Dv50 of 0.1-2.0 mu m; wherein the content of the inorganic ceramic particles in the coating is 20% -85% by mass.
8. The separator for lithium ion batteries according to claim 7, wherein: the inorganic ceramic particles include at least one of oxide ceramic particles, nitride ceramic particles, boehmite, aluminum hydroxide, magnesium hydroxide, barium sulfate, calcium carbonate, wollastonite, and silicon carbide.
9. The separator for lithium ion batteries according to claim 1, wherein: the base film is a polyolefin-based film, the thickness of the polyolefin-based film is 3-15 mu m, and the ventilation value is less than 250s/100cc.
10. The separator for lithium ion batteries according to claim 9, wherein: the air permeability value of the diaphragm is 100-400 s/100cc, the thickness of the coating on one side is 0.3-4 mu m, and the surface density of the unit coating is 0.3-2.0 g/m 2 The 130 ℃ shrinkage of the membrane is lower than 7.5 percent; the adhesive strength of the coating and the base film is higher than 3N/m.
11. The preparation method of the separator for the lithium ion battery is characterized by comprising the following steps of:
s1, mixing a solvent, a nitrogen-containing polymer and a fluorine-containing polymer at a temperature of not higher than 10 ℃ to obtain a mixture; wherein the solvent is a polar solvent;
s2: adding anhydrous lithium chloride accounting for 0.1-6% of the mass fraction of the mixture into the mixture, mixing for 0.5-2 hours, completely dissolving the anhydrous lithium chloride, the nitrogen-containing polymer and the fluorine-containing polymer, and defoaming to obtain slurry;
s3: forming a coating liquid film on the surface of the base film at 15-35 ℃ by using slurry; and forming a coating by using a coagulating bath at a temperature of 15-35 ℃, wherein the temperature difference between the slurry and the coagulating bath is controlled within 5 ℃; washing and drying to obtain the diaphragm.
12. The method for producing a separator for a lithium ion battery according to claim 11, wherein the bath liquid of the coagulation bath contains a polar organic substance, and the concentration of the polar organic substance is 20 to 60%.
13. The method for producing a separator for a lithium ion battery according to claim 12, wherein the polar solvent is at least one of N-methylpyrrolidone, N-dimethylacetamide, N-dimethylformamide, acetone, dimethylsulfoxide, and triethylphosphate.
14. The method for producing a separator for a lithium ion battery according to claim 11, wherein the mass concentration of the nitrogen-containing polymer in the mixture is 0.5 to 7.5%; the mass concentration of the fluorine-containing polymer in the mixture is 0.5-7.5%.
15. The method for producing a separator for a lithium ion battery according to claim 11, wherein the nitrogen-containing polymer and the fluorine-containing polymer are added to the polar solvent in multiple times, and the addition amounts of the nitrogen-containing polymer and the fluorine-containing polymer are sequentially decreased; the temperature in S1 is controlled within the range of-10 ℃ to 10 ℃.
16. The method for producing a separator for a lithium ion battery according to claim 11, wherein the polar solvent is at least one of N-methylpyrrolidone, N-dimethylacetamide, N-dimethylformamide, acetone, dimethylsulfoxide, and triethylphosphate, and the water content in the polar solvent is not higher than 1%.
17. The method for producing a separator for a lithium ion battery according to claim 11, wherein the slurry obtained in S2 has a viscosity of 20 to 1000 mpa·s at 25 ℃; and/or
The sedimentation time of the nitrogen-containing polymer and/or the fluorine-containing polymer in the mixture obtained in S1 is not less than 60 minutes.
18. The method for producing a separator for a lithium ion battery according to claim 17, wherein S2 comprises:
and heating the mixture to 35-60 ℃, adding anhydrous lithium chloride with the mass fraction of 0.1-6% into the mixture, stirring for 0.5-2 h until the anhydrous lithium chloride, the nitrogen-containing polymer and the fluorine-containing polymer are completely dissolved, and defoaming to obtain the slurry.
19. The method for producing a separator for a lithium ion battery according to claim 11, wherein the time for immersing the coating liquid film in the coagulation bath is 1 to 10 seconds.
20. The method for producing a separator for lithium ion batteries according to claim 11, wherein before the deaeration in S2, after the anhydrous lithium chloride, the nitrogen-containing polymer and the fluorine-containing polymer are completely dissolved, inorganic ceramic particles are added and mixed, to obtain a slurry containing inorganic ceramic particles, the Dv50 of the inorganic ceramic particles is 0.1 μm to 2.0 μm, and the concentration of the inorganic ceramic particles in the formed mixture is 1.5% to 20%.
21. An electrochemical device comprising a positive electrode, a negative electrode, a nonaqueous electrolyte, and the separator for a lithium ion battery according to any one of claims 1 to 10 or the separator for a lithium ion battery obtained by the production method according to claims 11 to 20.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310771210.XA CN116565457B (en) | 2023-06-28 | 2023-06-28 | Separator for lithium ion battery, preparation method and electrochemical device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310771210.XA CN116565457B (en) | 2023-06-28 | 2023-06-28 | Separator for lithium ion battery, preparation method and electrochemical device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN116565457A CN116565457A (en) | 2023-08-08 |
| CN116565457B true CN116565457B (en) | 2023-09-05 |
Family
ID=87502081
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202310771210.XA Active CN116565457B (en) | 2023-06-28 | 2023-06-28 | Separator for lithium ion battery, preparation method and electrochemical device |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116565457B (en) |
Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4810384A (en) * | 1986-06-20 | 1989-03-07 | Rhone-Poulenc Recherches | Hydrophilic PVDF semipermeable membrane |
| JP2004253343A (en) * | 2002-12-27 | 2004-09-09 | Matsushita Electric Ind Co Ltd | Electrochemical element |
| CN105659426A (en) * | 2013-10-31 | 2016-06-08 | 日本瑞翁株式会社 | Particulate polymer for use in binder for lithium-ion secondary battery,adhesive layer,and porous-membrane composition |
| JP2016216550A (en) * | 2015-05-15 | 2016-12-22 | ダイセルファインケム株式会社 | Vinyl composition, coating agent and separator for non-aqueous secondary battery |
| CN108963154A (en) * | 2018-07-10 | 2018-12-07 | 福建师范大学 | The preparation method of the coating film of low-inensity radiation |
| CN111370625A (en) * | 2020-03-22 | 2020-07-03 | 华南理工大学 | Aramid fiber phase-transition coating lithium ion battery diaphragm and preparation method thereof |
| CN111477816A (en) * | 2020-04-13 | 2020-07-31 | 华鼎国联四川动力电池有限公司 | Lithium ion battery diaphragm and preparation method thereof |
| CN111509168A (en) * | 2019-01-31 | 2020-08-07 | 青岛蓝科途膜材料有限公司 | Lithium ion battery diaphragm with high-temperature-resistant coating and preparation method thereof |
| CN116093542A (en) * | 2023-03-07 | 2023-05-09 | 中材锂膜有限公司 | Separator for nonaqueous electrolyte lithium secondary battery, method for producing same, and electrochemical device |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10196273T1 (en) * | 2000-05-29 | 2003-05-08 | Mitsubishi Paper Mills Ltd | Separator for electrochemical device and method for its production and electrochemical device |
-
2023
- 2023-06-28 CN CN202310771210.XA patent/CN116565457B/en active Active
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4810384A (en) * | 1986-06-20 | 1989-03-07 | Rhone-Poulenc Recherches | Hydrophilic PVDF semipermeable membrane |
| JP2004253343A (en) * | 2002-12-27 | 2004-09-09 | Matsushita Electric Ind Co Ltd | Electrochemical element |
| CN105659426A (en) * | 2013-10-31 | 2016-06-08 | 日本瑞翁株式会社 | Particulate polymer for use in binder for lithium-ion secondary battery,adhesive layer,and porous-membrane composition |
| JP2016216550A (en) * | 2015-05-15 | 2016-12-22 | ダイセルファインケム株式会社 | Vinyl composition, coating agent and separator for non-aqueous secondary battery |
| CN108963154A (en) * | 2018-07-10 | 2018-12-07 | 福建师范大学 | The preparation method of the coating film of low-inensity radiation |
| CN111509168A (en) * | 2019-01-31 | 2020-08-07 | 青岛蓝科途膜材料有限公司 | Lithium ion battery diaphragm with high-temperature-resistant coating and preparation method thereof |
| CN111370625A (en) * | 2020-03-22 | 2020-07-03 | 华南理工大学 | Aramid fiber phase-transition coating lithium ion battery diaphragm and preparation method thereof |
| CN111477816A (en) * | 2020-04-13 | 2020-07-31 | 华鼎国联四川动力电池有限公司 | Lithium ion battery diaphragm and preparation method thereof |
| CN116093542A (en) * | 2023-03-07 | 2023-05-09 | 中材锂膜有限公司 | Separator for nonaqueous electrolyte lithium secondary battery, method for producing same, and electrochemical device |
Also Published As
| Publication number | Publication date |
|---|---|
| CN116565457A (en) | 2023-08-08 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN108346765B (en) | Composite lithium ion battery diaphragm and preparation method thereof | |
| JP2021141078A (en) | Improved coated separator and related method for lithium battery | |
| TWI714744B (en) | Separator for secondary battery and secondary battery | |
| US20110236762A1 (en) | Porous membranes and methods of making the same | |
| KR101636857B1 (en) | Separator containing coating layer, manufacturing thereof and battery using the separator | |
| CN109096757B (en) | Porous polyimide film, method for producing polyimide precursor solution, and polyimide precursor solution | |
| EP2580270A1 (en) | Microporous composite film with high thermostable organic/inorganic coating layer | |
| CN108807818B (en) | Aromatic polyamide composite diaphragm and preparation method thereof | |
| JP5439772B2 (en) | Porous film and power storage device | |
| JP6969143B2 (en) | Porous Membrane and Laminated Porous Membrane | |
| CN112538162A (en) | Modified aramid polymer, aramid film casting liquid, lithium battery diaphragm, preparation method and lithium battery | |
| CN113136121B (en) | Bio-based diaphragm coating liquid, preparation method thereof and application thereof in lithium battery | |
| CN113594632A (en) | Low-moisture solvent type PVDF coating diaphragm | |
| JP5130700B2 (en) | Battery electrode manufacturing method and secondary battery | |
| CN110429231B (en) | Crosslinked graphene oxide/polypropylene composite diaphragm, preparation method and application | |
| US20220025087A1 (en) | Vinylidene fluoride polymer dispersion | |
| CN114843708A (en) | Porous diaphragm, preparation method thereof and electrochemical device | |
| KR20160142696A (en) | Preparation method of hollow fiber membrane and hollow fiber membrane | |
| CN116565457B (en) | Separator for lithium ion battery, preparation method and electrochemical device | |
| CN111592717B (en) | Polypropylene microporous membrane containing polytetrafluoroethylene modifier and preparation method thereof | |
| KR100982905B1 (en) | A porous polymeric membrane comprising vinylidene fluoride, a process for producing the same, and a laminate comprising the same | |
| CN114957891A (en) | Perfluorosulfonyl fluoride resin composition | |
| KR101296109B1 (en) | Menufacturing Method of Meta-Aramid Based Porous Membrane for Secondary Battery and Porous Membrane thereby | |
| CN114079124B (en) | Organic-inorganic composite lithium ion battery diaphragm and preparation method thereof | |
| CN114709558A (en) | High-heat-resistance polyamide-imide composite diaphragm and preparation method thereof |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |