CN116885383A - Core-shell material, preparation method thereof, diaphragm comprising core-shell material and lithium ion battery - Google Patents
Core-shell material, preparation method thereof, diaphragm comprising core-shell material and lithium ion battery Download PDFInfo
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- CN116885383A CN116885383A CN202310919513.1A CN202310919513A CN116885383A CN 116885383 A CN116885383 A CN 116885383A CN 202310919513 A CN202310919513 A CN 202310919513A CN 116885383 A CN116885383 A CN 116885383A
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- 239000011258 core-shell material Substances 0.000 title claims abstract description 61
- 238000002360 preparation method Methods 0.000 title claims abstract description 19
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 18
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 18
- 239000006185 dispersion Substances 0.000 claims abstract description 65
- 239000007788 liquid Substances 0.000 claims abstract description 64
- 239000002904 solvent Substances 0.000 claims abstract description 64
- 239000000843 powder Substances 0.000 claims abstract description 63
- 238000000576 coating method Methods 0.000 claims abstract description 51
- 239000011248 coating agent Substances 0.000 claims abstract description 32
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 29
- 238000000034 method Methods 0.000 claims abstract description 26
- 238000002156 mixing Methods 0.000 claims abstract description 25
- 239000003292 glue Substances 0.000 claims abstract description 19
- 229920005569 poly(vinylidene fluoride-co-hexafluoropropylene) Polymers 0.000 claims abstract description 19
- 239000000919 ceramic Substances 0.000 claims description 17
- 239000002002 slurry Substances 0.000 claims description 16
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 claims description 14
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 12
- 239000011230 binding agent Substances 0.000 claims description 12
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 12
- 238000001694 spray drying Methods 0.000 claims description 12
- 239000011247 coating layer Substances 0.000 claims description 10
- 239000000243 solution Substances 0.000 claims description 10
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims description 9
- 239000004698 Polyethylene Substances 0.000 claims description 9
- 239000003960 organic solvent Substances 0.000 claims description 8
- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Inorganic materials O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 7
- 238000004519 manufacturing process Methods 0.000 claims description 7
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 claims description 7
- 239000010410 layer Substances 0.000 claims description 6
- 239000011259 mixed solution Substances 0.000 claims description 6
- 229920000573 polyethylene Polymers 0.000 claims description 6
- -1 polypropylene Polymers 0.000 claims description 6
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 5
- 239000002245 particle Substances 0.000 claims description 5
- 239000004743 Polypropylene Substances 0.000 claims description 3
- 229920002125 Sokalan® Polymers 0.000 claims description 3
- 229910001593 boehmite Inorganic materials 0.000 claims description 3
- 239000002131 composite material Substances 0.000 claims description 3
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 claims description 3
- 239000004745 nonwoven fabric Substances 0.000 claims description 3
- 229920002401 polyacrylamide Polymers 0.000 claims description 3
- 229920000058 polyacrylate Polymers 0.000 claims description 3
- 239000004584 polyacrylic acid Substances 0.000 claims description 3
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 3
- 229920001721 polyimide Polymers 0.000 claims description 3
- 229920001155 polypropylene Polymers 0.000 claims description 3
- 239000002033 PVDF binder Substances 0.000 abstract description 12
- 229920002981 polyvinylidene fluoride Polymers 0.000 abstract description 12
- 239000000463 material Substances 0.000 abstract description 10
- 238000001035 drying Methods 0.000 abstract description 7
- 238000005191 phase separation Methods 0.000 abstract description 7
- 239000011257 shell material Substances 0.000 description 13
- 230000008569 process Effects 0.000 description 10
- 238000003756 stirring Methods 0.000 description 9
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 8
- 239000012046 mixed solvent Substances 0.000 description 8
- 239000012071 phase Substances 0.000 description 7
- 230000001070 adhesive effect Effects 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 238000005524 ceramic coating Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 102220043159 rs587780996 Human genes 0.000 description 5
- 239000002390 adhesive tape Substances 0.000 description 4
- 229910000831 Steel Inorganic materials 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 239000006255 coating slurry Substances 0.000 description 3
- 229920001577 copolymer Polymers 0.000 description 3
- 239000008367 deionised water Substances 0.000 description 3
- 229910021641 deionized water Inorganic materials 0.000 description 3
- 238000009776 industrial production Methods 0.000 description 3
- 238000005096 rolling process Methods 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- 239000010959 steel Substances 0.000 description 3
- 239000000853 adhesive Substances 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 238000004880 explosion Methods 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 230000002269 spontaneous effect Effects 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- 239000012790 adhesive layer Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000002346 layers by function Substances 0.000 description 1
- RAYLUPYCGGKXQO-UHFFFAOYSA-N n,n-dimethylacetamide;hydrate Chemical compound O.CN(C)C(C)=O RAYLUPYCGGKXQO-UHFFFAOYSA-N 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000003892 spreading Methods 0.000 description 1
- 230000007480 spreading Effects 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
-
- 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
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
Abstract
The application provides a core-shell material, a preparation method thereof, a diaphragm comprising the core-shell material and a lithium ion battery. The preparation method comprises the following steps: step S1, mixing inorganic powder with a first solvent to obtain a first dispersion liquid; mixing polyvinylidene fluoride-hexafluoropropylene copolymer with a second solvent to obtain a glue solution; step S2, mixing the first dispersion liquid and the glue liquid to obtain a second dispersion liquid; step S3, mixing the second dispersion liquid, water and a third solvent to obtain a third dispersion liquid; and S4, removing the solvent in the third dispersion liquid to obtain the core-shell material. Based on the method, the organic coating is realized on the surface of the inorganic powder by adopting a phase separation method in the drying process, so that the core-shell material is obtained, and PVDF in the material can be coated on the surface of the powder with higher binding force, so that the core-shell material has both the binding property and the heat resistance, thereby simplifying the diaphragm coating process and improving the heat deformation resistance of the diaphragm. The preparation method is simple and has low cost.
Description
Technical Field
The application relates to the technical field of lithium ion batteries, in particular to a core-shell material, a preparation method thereof, a diaphragm comprising the core-shell material and a lithium ion battery.
Background
With the rapid development of new energy automobiles in China, the demands of power type lithium ion battery products with high energy density and long cycle life are rapidly increasing. Based on the design characteristics of higher energy density, the volume of the winding core in the shell is close to the limit, and the winding core needs to be hot-pressed and shaped in the manufacturing process of the battery core so as to be convenient to be put into the shell. Therefore, the common scheme is to improve the interfacial adhesion performance between the pole pieces by coating a glue layer on the surface of the diaphragm. In recent years, spontaneous combustion or explosion accidents of power lithium ion batteries of automobiles are increasing, and the safety performance of the lithium ion batteries is required to be more focused. The diaphragm is one of four main materials of the lithium ion battery, and does not directly participate in electrochemical reaction, but has important influence on the electrical performance and safety performance of the lithium ion battery. The lithium ion battery can deform and shrink the diaphragm under the external influences of extrusion or puncture and the like in the high-power charge and discharge process, so that the positive electrode and the negative electrode in the battery are short-circuited, thermal runaway is formed, and spontaneous combustion or explosion occurs. Therefore, the heat-resistant deformation capacity of the diaphragm under the high-temperature condition is improved, and the diaphragm has positive significance for the application of lithium ion batteries.
Based on the requirements of cell design on the performance of a separator, a common solution is to coat a functional layer on the surface of a polyolefin-based film, including a ceramic coating for improving the heat deformation resistance and an adhesive coating for improving the interfacial adhesion. The traditional coating process adopts step-by-step coating, namely, ceramic layer coating is firstly carried out, then glue layer coating is carried out, the process is more complex, and the production cost is higher. Recently, ceramic and adhesive hybrid coating processes have also been proposed in the industry. The Chinese patent with application number 202110150874.5 discloses a preparation method of an aqueous binder for a lithium ion battery diaphragm, which is characterized in that two binder polymers with different particle diameters are added into ceramic slurry, and meanwhile, the bonding function between a ceramic coating and a base film and between the diaphragm and a pole piece is realized. However, the added binder polymer has poor heat distortion resistance, and thus the final coated separator has poor heat distortion resistance. The Chinese patent with application number 201710042601.2 discloses a preparation method of a PVDF or PVDF copolymer-containing coating diaphragm, which adopts a traditional step-by-step coating process and meets the requirements of the diaphragm on heat resistance and adhesive property, but has the defects of complex manufacturing process and high cost.
Disclosure of Invention
The application mainly aims to provide a core-shell material, a preparation method thereof, a diaphragm comprising the core-shell material and a lithium ion battery, and aims to solve the problems that in the prior art, a coating cannot meet the bonding performance and the heat-resistant deformation performance at the same time, so that the diaphragm coating process is complex and the heat-resistant deformation performance of the diaphragm is poor.
In order to achieve the above object, according to one aspect of the present application, there is provided a method for preparing a core-shell material, the method comprising: step S1, mixing inorganic powder with a first solvent to obtain a first dispersion liquid; mixing polyvinylidene fluoride-hexafluoropropylene copolymer with a second solvent to obtain a glue solution; step S2, mixing the first dispersion liquid and the glue liquid to obtain a second dispersion liquid; step S3, mixing the second dispersion liquid, water and a third solvent to obtain a third dispersion liquid; wherein the first solvent, the second solvent and the third solvent are respectively and independently nonpolar organic solvents; and S4, spray drying the third dispersion liquid to obtain the core-shell material.
Further, the inorganic powder is selected from one or more of aluminum oxide, zirconium dioxide and barium sulfate, and/or the inorganic powder is a combination of aluminum oxide and zirconium dioxide or a combination of aluminum oxide and barium sulfate; the particle diameter of the inorganic powder is preferably 0.1 to 5. Mu.m, and the shape of the inorganic powder is preferably a sphere-like shape.
Further, the first solvent, the second solvent and the third solvent are each independently selected from any one or more of N-methylpyrrolidone, N-dimethylacetamide and N, N-dimethylformamide; preferably, in the step S1, the amount of the inorganic powder is 10 to 30 parts by weight, and the amount of the first solvent is 70 to 90 parts by weight; preferably, in step S1, the amount of polyvinylidene fluoride-hexafluoropropylene is 1 to 10 parts by weight, and the amount of the second solvent is 90 to 99 parts by weight.
Further, in the step S2, the weight ratio of the inorganic powder to the polyvinylidene fluoride-hexafluoropropylene in the second dispersion liquid is 1:1-20:1; preferably, step S3 includes: mixing water and a third solvent to obtain a mixed solution; dripping the second dispersion liquid into the mixed solution to obtain a third dispersion liquid; preferably, the weight ratio of water to the third solvent is 1:1 to 4:1.
According to another aspect of the present application, there is provided a core-shell material prepared by the above-described preparation method.
According to still another aspect of the present application, there is provided a separator comprising a base film and a coating layer coated on both surfaces of the base film, the coating layer comprising the core-shell material as described above.
Further, the base film is selected from any one of a polypropylene porous film, a polyethylene-polypropylene-polyethylene three-layer composite porous film, a polyimide film and a non-woven fabric film; preferably, the thickness of the base film is 5 to 15 μm; preferably, the thickness of the coating is 1 to 3 μm.
According to still another aspect of the present application, there is provided a method for preparing the above-described separator, the method comprising: the slurry was coated on both surfaces of the base film using a gravure roll coating method.
Further, the slurry comprises, in parts by weight: 10-40 parts of ceramic powder, 1-10 parts of core-shell material, 0.1-5 parts of binder and 70-95 parts of water; preferably, the ceramic powder is aluminum oxide and/or boehmite; preferably, the binder is selected from one or more of polyacrylic acid, polyacrylate, polyacrylonitrile, polyacrylamide, polyvinylidene fluoride-hexafluoropropylene copolymer; preferably, the temperature of the gravure roll coating process is 30 to 70 ℃.
According to still another aspect of the present application, there is provided a lithium ion battery including a positive electrode, a negative electrode, and a separator, the separator being the separator described above.
By applying the technical scheme of the application, unlike the traditional preparation method of dispersing, coating and drying separation, the application comprises the steps of dispersing inorganic powder in a solvent, pre-coating, mixing second dispersion liquid, water and a third solvent to obtain third dispersion liquid, and then carrying out spray drying; wherein the first solvent, the second solvent and the third solvent are respectively and independently nonpolar organic solvents. Based on the method, a solvent phase in the third dispersion liquid forms a water-oil mixed phase, powder and PVDF can be distributed in a plurality of emulsion-like microdrops with smaller sizes in a spray drying process, so that organic coating is realized on the surface of inorganic powder by adopting a phase separation method in the drying process, a core-shell material is obtained, and PVDF in the material can be coated on the surface of the powder with higher binding force, so that the core-shell material has both binding performance and heat resistance, and the diaphragm coating process is simplified and the heat deformation resistance of the diaphragm is improved. The preparation method provided by the application is simple, low in cost and low in process difficulty, and is beneficial to industrial production.
Detailed Description
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The present application will be described in detail with reference to examples.
As analyzed by the background art, the prior art has the problems that the coating cannot meet the bonding performance and the heat-resistant deformation performance at the same time, so that the diaphragm coating process is complex and the heat-resistant deformation performance of the diaphragm is poor.
In an exemplary embodiment of the present application, there is provided a method for preparing the core-shell material, including: step S1, mixing inorganic powder with a first solvent to obtain a first dispersion liquid; mixing polyvinylidene fluoride-hexafluoropropylene copolymer with a second solvent to obtain a glue solution; step S2, mixing the first dispersion liquid and the glue liquid to obtain a second dispersion liquid; step S3, mixing the second dispersion liquid, water and a third solvent to obtain a third dispersion liquid; and S4, removing the solvent in the third dispersion liquid to obtain the core-shell material.
Different from the traditional preparation method of dispersing, coating and drying separation, the application comprises the steps of dispersing and pre-coating inorganic powder in a solvent, mixing second dispersion liquid, water and a third solvent to obtain third dispersion liquid, and then carrying out spray drying; wherein the first solvent, the second solvent and the third solvent are respectively and independently nonpolar organic solvents. Based on the method, a solvent phase in the third dispersion liquid forms a water-oil mixed phase, powder and PVDF can be distributed in a plurality of emulsion-like microdrops with smaller sizes in a spray drying process, so that organic coating is realized on the surface of inorganic powder by adopting a phase separation method in the drying process, a core-shell material is obtained, and PVDF in the material can be coated on the surface of the powder with higher binding force, so that the core-shell material has both binding performance and heat resistance, and the diaphragm coating process is simplified and the heat deformation resistance of the diaphragm is improved. The preparation method provided by the application is simple, low in cost and low in process difficulty, and is beneficial to industrial production.
The kind of the inorganic powder is not particularly limited in the present application. In order to improve the heat resistance of the core-shell material, in some embodiments, the inorganic powder is selected from one or more of aluminum oxide, zirconium dioxide, barium sulfate, and/or the inorganic powder is a combination of aluminum oxide and zirconium dioxide or a combination of aluminum oxide and barium sulfate; the particle size of the inorganic powder is preferably 0.1 to 5. Mu.m. The particle size of the inorganic powder is too large, which can affect the energy density of the battery cell. Preferably, the inorganic powder is in a sphere-like shape, and the polyvinylidene fluoride-hexafluoropropylene copolymer is easy to coat a polyvinylidene fluoride-hexafluoropropylene copolymer adhesive layer on the surface of the inorganic powder in the phase separation process, so that a core-shell structure is formed.
In some embodiments, the thickness of the shell in the core-shell material is 10-300 nm, and the weight of the shell is 1-10% of the core-shell material.
The present application is not particularly limited in the kind of solvent, and nonpolar organic solvents commonly used in the art can be applied to the present application. In some preferred embodiments, the first solvent, the second solvent, and the third solvent are each independently selected from any one or more of N-methylpyrrolidone, N-dimethylacetamide, N-dimethylformamide. The nonpolar organic solvent of the type is selected, and the nonpolar organic solvent can further form two phases with water in the third dispersion liquid, so that the phase separation effect is further exerted in the spray drying process, the PVDF coating layer is more complete and stable, and the PVDF coating layer has better promotion effect on the thermal stability of the material and the thermal stability of a battery in the later application.
In order to improve the heat resistance of the core-shell material, preferably, in the step S1, the amount of the inorganic powder is 10 to 30 parts by weight, and the amount of the first solvent is 70 to 90 parts by weight; the adhesion effect of the coating layer can be influenced due to excessive inorganic powder, the inorganic powder is too little, and the heat resistance of the core-shell material is reduced.
In order to improve the adhesive property of the core-shell material and to avoid the decrease of wettability due to the excessive thickness of the outer shell, it is preferable that the amount of polyvinylidene fluoride-hexafluoropropylene is 1 to 10 parts by weight and the amount of the second solvent is 90 to 99 parts by weight. Excessive polyvinylidene fluoride-hexafluoropropylene can increase the air permeability of the coated diaphragm, affect the internal resistance of the battery, and too little polyvinylidene fluoride-hexafluoropropylene can cause the reduction of the adhesive property of the core-shell material.
In order to further improve the heat resistance and the adhesive property of the core-shell material, in the step S2, the weight ratio of the inorganic powder in the second dispersion liquid to the polyvinylidene fluoride-hexafluoropropylene is 1:1-20:1. The inorganic powder and polyvinylidene fluoride-hexafluoropropylene are in the range, so that the adhesion effect of the material can be improved.
In order to phase-separate PVDF so as to coat the inorganic powder surface, preferably, step S3 includes mixing water and a third solvent to obtain a mixed solution; dripping the second dispersion liquid into the mixed solution to obtain a third dispersion liquid; the weight ratio of the water to the third solvent is 1:1-4:1. The rate of phase separation can be controlled to give a better pore size distribution by limiting the water and the second solvent to this range.
In another exemplary embodiment of the present application, a core-shell material is provided, which is prepared by the above preparation method. Preferably, the thickness of the shell in the core-shell material is 10-300 nm, and the weight of the shell accounts for 1-10% of the core-shell material.
In yet another exemplary embodiment of the present application, a separator is provided that includes a base film and a coating layer coated on a surface of the base film, the coating layer including the core-shell material described above. The coating containing the core-shell material can ensure that the diaphragm has good heat deformation resistance and good pole piece bonding performance.
The kind of the base film is not particularly limited in the present application, and any base film commonly used in the art may be applied to the present application. In some embodiments, the base film is selected from any one of a polypropylene porous film, a polyethylene-polypropylene-polyethylene three-layer composite porous film, a polyimide film, a nonwoven fabric film.
In order to improve the heat resistance and adhesion properties of the separator and to avoid the degradation of the electron transport ability due to the excessive thickness of the coating layer, it is preferable that the thickness of the base film is 5 to 15 μm; preferably, the thickness of the coating is 1 to 3 μm.
In still another exemplary embodiment of the present application, the present application provides a method for preparing the above-mentioned separator, comprising: the slurry was coated on both surfaces of the base film using a gravure roll coating method.
In order to improve the wettability of the slurry, the slurry comprises, in parts by weight: 10-40 parts of ceramic powder, 1-10 parts of core-shell material, 0.1-5 parts of binder and 70-95 parts of water;
the present application is not particularly limited in terms of the constituent components of the slurry, and constituent components commonly used in the art may be applied to the present application. Preferably, the ceramic powder is aluminum oxide and/or boehmite; preferably, the binder is selected from one or more of polyacrylic acid, polyacrylate, polyacrylonitrile, polyacrylamide, polyvinylidene fluoride-hexafluoropropylene copolymer.
The conditions of the gravure roll coating method are not particularly limited in the present application. In order to uniformly coat the slurry on the above base film, it is preferable that the temperature of the gravure roll coating method is 30 to 70 ℃.
In yet another exemplary embodiment of the present application, a lithium ion battery is provided, including a positive electrode, a negative electrode, and a separator, the separator being the separator described above.
The lithium ion battery with the diaphragm has good heat resistance.
The application is described in further detail below in connection with specific examples which are not to be construed as limiting the scope of the application as claimed.
Example 1
Preparing a core-shell material:
(1) Taking 2kg of alumina powder (similar to sphere, d50=2μm) and adding the alumina powder into 8kg of N-methyl pyrrolidone for uniformly dispersing to obtain a first dispersion liquid; then 0.5kg LBG powder (purchased from Accadema) is added into 9.5kg N-methyl pyrrolidone for dissolution to obtain glue solution; mixing the first dispersion liquid with the glue solution to obtain a second dispersion liquid;
(2) Adding the second dispersion liquid into a mixed solvent of water and N-methyl pyrrolidone, wherein the proportion of the water in the mixed solvent is 80%, and controlling the dropping rate and the stirring rate to obtain a third dispersion liquid;
(3) And removing the solvent from the third dispersion liquid through spray drying to obtain a core-shell material, wherein the thickness of a shell in the core-shell material is 10-300 nm, and the weight of the shell is 4.5% of that of the core-shell material.
Preparing ceramic coating slurry: taking 3kg of alumina powder (with the conventional morphology, D50=0.5 mu m), adding 0.5kg of core-shell structure material into 10kg of deionized water, stirring and dispersing uniformly, adding 0.8kg of acrylate copolymer binder, and stirring and dispersing uniformly to obtain the ceramic slurry for coating.
Preparing a ceramic coated diaphragm: the slurry is coated on two sides of a polyethylene-based film by adopting a gravure roll coating process, the coating speed is 100m/min, the temperature is 60 ℃, the rolling tension is 10N/m, the thickness of each coating is controlled to be 2 mu m, and the thickness of the base film is controlled to be 9 mu m.
Example 2
In step (1), 1kg of LBG powder (purchased from Accade) was added to 9kg of N-methylpyrrolidone and dissolved to obtain a dope, unlike example 1.
Example 3
Preparing a core-shell material:
(1) Adding 2kg of zirconium dioxide powder (similar to sphere, D50=5μm) into 7kg of N, N-dimethylacetamide to uniformly disperse to obtain a first dispersion liquid; then 0.1kg LBG powder (purchased from Accadema) is added into 9.9kg N, N-dimethylacetamide to be dissolved, thus obtaining glue solution; mixing the first dispersion liquid with the glue solution to obtain a second dispersion liquid;
(2) Adding the second dispersion liquid into a mixed solvent of water and N, N-dimethylacetamide, wherein the proportion of the water in the mixed solvent is 50%, and controlling the dropping rate and the stirring rate to obtain a third dispersion liquid;
(3) And removing the solvent from the third dispersion liquid through spray drying to obtain a core-shell material, wherein the thickness of a shell in the core-shell material is 10-300 nm, and the weight of the shell accounts for 1-10% of that of the core-shell material.
Preparing ceramic coating slurry: taking 3kg of alumina powder (with the conventional morphology, D50=0.5 mu m), adding 0.5kg of core-shell structure material into 10kg of deionized water, stirring and dispersing uniformly, adding 0.8kg of acrylate copolymer binder, and stirring and dispersing uniformly to obtain the ceramic slurry for coating.
Preparing a ceramic coated diaphragm: the slurry is coated on two sides of a polyethylene-based film by adopting a gravure roll coating process, the coating speed is 100m/min, the temperature is 60 ℃, the rolling tension is 10N/m, the thickness of each coating is controlled to be 2 mu m, and the thickness of the base film is controlled to be 9 mu m.
Example 4
Preparing a core-shell material:
(1) Adding 2kg of barium sulfate powder (similar to sphere, D50=0.1 μm) into 8kg of N-methylpyrrolidone, and uniformly dispersing to obtain a first dispersion liquid; then 0.5kg LBG powder (purchased from Accadema) is added into 9.5kg N-methyl pyrrolidone for dissolution to obtain glue solution; mixing the first dispersion liquid with the glue solution to obtain a second dispersion liquid;
(2) Adding the second dispersion liquid into a mixed solvent of water and N-methyl pyrrolidone, wherein the proportion of the water in the mixed solvent is 70%, and controlling the dropping rate and the stirring rate to obtain a third dispersion liquid;
(3) And removing the solvent from the third dispersion liquid through spray drying to obtain a core-shell material, wherein the thickness of a shell in the core-shell material is 10-300 nm, and the weight of the shell is 5.5% of that of the core-shell material.
Preparing ceramic coating slurry: taking 3kg of alumina powder (with the conventional morphology, D50=0.5 mu m), adding 0.5kg of core-shell structure material into 10kg of deionized water, stirring and dispersing uniformly, adding 0.8kg of acrylate copolymer binder, and stirring and dispersing uniformly to obtain the ceramic slurry for coating.
Preparing a ceramic coated diaphragm: the slurry is coated on two sides of a polyethylene-based film by adopting a gravure roll coating process, the coating speed is 100m/min, the temperature is 60 ℃, the rolling tension is 10N/m, the thickness of each coating is controlled to be 2 mu m, and the thickness of the base film is controlled to be 9 mu m.
Example 5
Unlike example 1, in step (1), 2kg of alumina and barium sulfate powder (spheroid, d50=0.1 μm) were added to 8kg of n, n-dimethylacetamide to uniformly disperse to obtain a first dispersion.
Example 6
Unlike example 1, in step (1), 3.5kg of alumina powder (spheroid, d50=2μm) was added to 6.5kg of N-methylpyrrolidone, and the mixture was uniformly dispersed to obtain a first dispersion.
Example 7
Unlike example 1, in step (1), 0.5kg of alumina powder (spheroid, d50=2μm) was added to 9.5kg of N-methylpyrrolidone, and the mixture was uniformly dispersed to obtain a first dispersion.
Example 8
In step (1), 1.5kg of LBG powder (commercially available from Accade) was added to 8.5kg of N, N-dimethylacetamide and dissolved to obtain a dope, unlike example 1.
Example 9
In step (1), unlike example 1, 0.05kg of LBG powder (purchased from Accade) was added to 9.95kg of N, N-dimethylacetamide to dissolve it, thereby obtaining a dope.
Example 10
Unlike example 1, the proportion of water in the mixed solvent was 85%.
Example 11
Unlike example 1, the proportion of water in the mixed solvent was 45%.
Comparative example 1
A commercially available 2 μm (ceramic+glue mix) +9. Mu.mPE+2 μm (ceramic+glue mix) diaphragm was taken, and glue mix refers to the roll coating of polyvinylidene fluoride-hexafluoropropylene dispersion.
Heat shrinkage test:
and (3) respectively and flatly placing the cut samples between two rapid glass plates, placing the glass plates into an oven, and setting the temperature. Taking out after a certain time, cooling, and measuring the length and the width of the square block respectively by using an imager, wherein the length and the width are respectively recorded as n1 and h1.
The calculation formula of heat shrinkage is:
longitudinal heat shrinkage= (n-n 1)/n×100%.
Transverse heat shrinkage= (h-h 1)/h×100%.
The test results are shown in table 1 below.
TABLE 1
And (3) testing adhesion performance with the pole piece:
and (3) spreading the diaphragm, the negative plate, the diaphragm and the positive plate on one side above the PE film in sequence, and then forming a cell sample on the other side of the PE film. After the temperature reaches the set temperature, the heating tool cover is opened, the prepared sample is tiled on the heating tool plate, one section of PE film fixed by the adhesive tape at one end of the prepared sample penetrates through one side of the electric roller press, and the on button of the roller press is clicked to open the roller press. The compounded unit pieces are cut into samples, the width of each test sample is 15mm, the length of each test sample is slightly larger than the length of the steel plate, the samples are prepared according to the sequence of the steel plate/3M double faced adhesive tape/pole piece/diaphragm, a common adhesive tape (the length of the common adhesive tape is required to be larger than that of the steel plate) with the length of about 15cm is reserved at the tail end of the diaphragm, and the test results are shown in the following table 2.
TABLE 2
From the above description, it can be seen that the above embodiments of the present application achieve the following technical effects:
different from the traditional preparation method of dispersing, coating and drying separation, the application comprises the steps of dispersing and pre-coating inorganic powder in a solvent, mixing second dispersion liquid, water and a third solvent to obtain third dispersion liquid, and then carrying out spray drying; wherein the first solvent, the second solvent and the third solvent are respectively and independently nonpolar organic solvents. Based on the method, a solvent phase in the third dispersion liquid forms a water-oil mixed phase, powder and PVDF can be distributed in a plurality of emulsion-like microdrops with smaller sizes in a spray drying process, so that organic coating is realized on the surface of inorganic powder by adopting a phase separation method in the drying process, a core-shell material is obtained, and PVDF in the material can be coated on the surface of the powder with higher binding force, so that the core-shell material has both binding performance and heat resistance, and the diaphragm coating process is simplified and the heat deformation resistance of the diaphragm is improved. The preparation method provided by the application is simple, low in cost and low in process difficulty, and is beneficial to industrial production.
The above is only a preferred embodiment of the present application, and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (10)
1. A method for preparing a core-shell material, the method comprising:
step S1, mixing inorganic powder with a first solvent to obtain a first dispersion liquid; mixing polyvinylidene fluoride-hexafluoropropylene copolymer with a second solvent to obtain a glue solution;
step S2, mixing the first dispersion liquid and the glue liquid to obtain a second dispersion liquid;
step S3, mixing the second dispersion liquid, water and a third solvent to obtain a third dispersion liquid; wherein the first solvent, the second solvent, and the third solvent are each independently a nonpolar organic solvent;
and S4, spray drying the third dispersion liquid to obtain the core-shell material.
2. The preparation method according to claim 1, wherein the inorganic powder is one or more selected from the group consisting of aluminum oxide, zirconium dioxide, and barium sulfate, and/or the inorganic powder is a combination of aluminum oxide and zirconium dioxide or a combination of aluminum oxide and barium sulfate; the particle diameter of the inorganic powder is preferably 0.1 to 5. Mu.m, and the shape of the inorganic powder is preferably a spheroid.
3. The production method according to claim 1 or 2, wherein the first solvent, the second solvent, and the third solvent are each independently selected from any one or more of N-methylpyrrolidone, N-dimethylacetamide, N-dimethylformamide;
preferably, in the step S1, the amount of the inorganic powder is 10 to 30 parts by weight, and the amount of the first solvent is 70 to 90 parts by weight;
preferably, in the step S1, the amount of the polyvinylidene fluoride-hexafluoropropylene is 1 to 10 parts by weight, and the amount of the second solvent is 90 to 99 parts by weight.
4. A production method according to any one of claims 1 to 3, wherein in the step S2, a weight ratio of the inorganic powder to the polyvinylidene fluoride-hexafluoropropylene in the second dispersion is 1:1 to 20:1;
preferably, the step S3 includes: mixing water and the third solvent to obtain a mixed solution; dropwise adding the second dispersion liquid into the mixed solution to obtain the third dispersion liquid; preferably, the weight ratio of the water to the third solvent is 1:1-4:1.
5. A core-shell material, characterized in that it is prepared by the preparation method according to any one of claims 1 to 4.
6. A separator comprising a base film and a coating layer applied to both surfaces of the base film, wherein the coating layer comprises the core-shell material of claim 5.
7. The separator according to claim 6, wherein the base film is any one selected from the group consisting of a polypropylene porous film, a polyethylene-polypropylene-polyethylene three-layer composite porous film, a polyimide film, and a nonwoven fabric film;
preferably, the thickness of the base film is 5-15 μm;
preferably, the thickness of the coating is 1 to 3 μm.
8. A method of making the separator of claim 6 or 7, comprising: the slurry was coated on both surfaces of the base film using a gravure roll coating method.
9. The method of manufacturing according to claim 8, wherein the slurry comprises, in parts by weight: 10-40 parts of ceramic powder, 1-10 parts of core-shell material, 0.1-5 parts of binder and 70-95 parts of water;
preferably, the ceramic powder is aluminum oxide and/or boehmite;
preferably, the binder is selected from one or more of polyacrylic acid, polyacrylate, polyacrylonitrile, polyacrylamide, polyvinylidene fluoride-hexafluoropropylene copolymer;
preferably, the temperature of the gravure roll coating method is 30-70 ℃.
10. A lithium ion battery comprising a positive electrode, a negative electrode and a separator, wherein the separator is the separator of claim 6 or 7.
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| CN202310919513.1A CN116885383A (en) | 2023-07-25 | 2023-07-25 | Core-shell material, preparation method thereof, diaphragm comprising core-shell material and lithium ion battery |
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| CN202310919513.1A CN116885383A (en) | 2023-07-25 | 2023-07-25 | Core-shell material, preparation method thereof, diaphragm comprising core-shell material and lithium ion battery |
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