CN114243218B - Diaphragm with smooth diaphragm surface and preparation method and application thereof - Google Patents
Diaphragm with smooth diaphragm surface and preparation method and application thereof Download PDFInfo
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- CN114243218B CN114243218B CN202210174045.5A CN202210174045A CN114243218B CN 114243218 B CN114243218 B CN 114243218B CN 202210174045 A CN202210174045 A CN 202210174045A CN 114243218 B CN114243218 B CN 114243218B
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- 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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/52—Separators
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
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- 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
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- 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
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- 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
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- 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
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- 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
- Y02E60/13—Energy storage using capacitors
Abstract
The invention provides a diaphragm with a flat diaphragm surface and a preparation method and application thereof, and relates to the technical field of diaphragms, wherein the curling degree of the diaphragm cut in the TD direction meets the following requirements: (L1-L2)/L1 x 100% is less than or equal to 7%; the thermal shrinkage TD of the diaphragm in the TD direction after cutting meets the following requirements: (L1-L3)/L1 x 100 percent is less than or equal to 1.5 percent; the preparation method controls the distance from the edge of the coating sizing agent to the edge of the base film on any side of the TD direction of the diaphragm to be more than or equal to 5% and less than or equal to 15% of the width of the base film when the sizing agent is coated. The diaphragm surface of the invention is flat, the problems of edge folding, folding and the like of the battery core diaphragm caused by diaphragm curling in the assembly process are reduced, the heat shrinkage rate in the TD direction is small, and the safety of the lithium ion battery is improved.
Description
Technical Field
The invention relates to the technical field of diaphragms, in particular to a diaphragm with a flat diaphragm surface and a preparation method and application thereof.
Background
The diaphragm is one of four key materials in the lithium ion battery, directly influences the performance and safety of the battery, and the diaphragm with good appearance and excellent performance has important influence on improving the comprehensive performance of the lithium ion battery.
The conventional polyolefin diaphragm has the problems of poor thermal stability, easy deformation and the like, and the surface of the polyolefin diaphragm is coated with a single-layer or double-layer inorganic filler, so that the problems of high thermal shrinkage rate and easy deformation of the polyolefin diaphragm can be improved to a certain extent. However, the surface density of the ceramic coating diaphragm is high, and after the temperature exceeds the melting point of polyolefin, the integrity of the diaphragm is difficult to ensure by the non-continuous inorganic coating, so more and more diaphragm products adopt heat-resistant high polymer materials as the coating to solve the problem of diaphragm heat shrinkage.
However, the heat-resistant polymer-coated separator produced at present still has some problems in the production process, for example, the problem that the separator curls due to the residual stress generated in the film-forming process of the polymer coating and the difference of the thermal expansion coefficients of the heat-resistant polymer material and the polyolefin material, and the like, and the dimensional stability and the lithium ion battery assembly performance of the separator are greatly influenced. The curling problem cannot be solved by simple adjustment of process parameters such as vehicle speed, drying, heat setting temperature and the like; the method for reducing the water content of the film surface by matching with equipment improvement such as increasing a compression roller and improving the height of a guide roller is greatly limited by the vehicle speed and the coating thickness, and has higher cost; and other materials are coated on the other side of the polyolefin base film to inhibit the diaphragm from curling, so that the materials are remained in the pores of the diaphragm, other side reactions are possibly generated in the charge and discharge processes of the lithium ion battery, and the electrical property and the safety of the lithium ion battery are reduced.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
The invention aims to provide a diaphragm with a flat diaphragm surface, which has low curling degree and low heat shrinkage rate.
The second objective of the present invention is to provide a method for preparing a flat membrane, which is to control the distance from the edge of the membrane coating slurry to the edge of the base membrane to obtain a flat membrane.
The invention also aims to provide a lithium ion battery which comprises a diaphragm with a flat film surface.
The fourth object of the present invention is to provide a super capacitor, which includes a membrane with a flat membrane surface.
In order to achieve the above purpose of the present invention, the following technical solutions are adopted:
the invention provides a diaphragm with a flat diaphragm surface, which comprises: a base film and a coating layer disposed on the base film;
the curling degree of the diaphragm in the TD direction after being cut meets the following conditions: (L1-L2)/L1 x 100 percent is less than or equal to 7 percent;
the thermal shrinkage TD of the diaphragm in the TD direction after cutting meets the following requirements: (L1-L3)/L1 x 100 percent is less than or equal to 1.5 percent;
wherein, L1 is the length of the diaphragm in the TD direction when the diaphragm is flattened in the TD direction under the action of an external force;
l2 is the projection length of the separator in the TD direction when the separator is naturally curled in the TD direction without applying an external force;
l3 is the length of the separator in the TD direction when the separator is held at 130 ℃ for 1 hour in two sheets of paper and then stretched by an external force.
The base film is one of a polyethylene base film, a polypropylene base film, a mixed base film of polyethylene and polypropylene or a multi-layer base film, and is preferably a polyethylene base film.
The source of the base film is not limited, and the base film can be prepared by the existing method, and can also be obtained by commercial purchase, for example, the polyolefin base film can be prepared by adopting a wet method or a dry method for unidirectional or bidirectional stretching.
The thickness of the base film is not particularly limited as long as it is suitable for use as a separator for a lithium battery. The thickness is generally 20 μm or less, and may be, for example, 4 to 20 μm, for example, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 μm.
The coating layer may include a heat-resistant polymer material and a heat-resistant inorganic filler;
the heat-resistant polymer material is not particularly limited, and may be a polymer material having a melting point higher than that of polyolefin known in the art, and examples thereof include polyamide, polyimide, polyetherimide, polyamideimide, polysulfone, polyethersulfone, polyarylsulfone, and the like, preferably aromatic polyamide, and particularly preferably para-aromatic polyamide.
The heat-resistant inorganic filler is not particularly limited, and may be at least one of alumina, boehmite, magnesia, calcium oxide, barium oxide, zinc oxide, silica, titania, zirconia, magnesium hydroxide, and aluminum hydroxide, and alumina is preferable.
In one embodiment, the alumina has a particle size D50 ≦ 600 nm.
The thickness of the coating layer is not particularly limited as long as it is suitable for use as a separator for a lithium battery. For example, it may be 1 to 6 μm, for example 1, 2, 3, 4, 5, 6 μm.
Preferably, the coating thickness accounts for more than 20% of the total thickness of the separator.
The method for testing the TD-direction curling degree of the diaphragm is shown in figure 1:
A. cutting a section (for example, 100-150mm length) of the diaphragm sample fully covered by the coating, flattening the sample under the action of an external force, and measuring the length of the diaphragm sample in the TD direction at the moment, wherein the length is marked as L1 (mm);
B. horizontally placing the diaphragm sample on a table top, and naturally curling the diaphragm in the TD direction under the action of no external force; measuring the length of the rolled diaphragm sample projected on a horizontal table in the TD direction, and recording as L2 (mm);
formula of degree of membrane curl: (L1-L2)/L1X 100%.
The TD test method for the thermal shrinkage rate of the diaphragm at 130 ℃ for 1h comprises the following steps:
A. cutting a section (for example, 100-150mm length) of the diaphragm sample fully covered by the coating, flattening the sample under the action of an external force, and measuring the length of the diaphragm sample in the TD direction at the moment, wherein the length is marked as L1 (mm);
B. the membrane samples were placed flat in two sheets of a4 paper and then placed in an oven at 130 ℃ for 1 hour; after the heating was completed, the sample was taken out, and after the temperature was returned to room temperature, the sample was flattened by applying an external force, and the length of the separator sample in the TD direction at this time was measured and recorded as L3 (mm).
The thermal shrinkage TD of the diaphragm is: (L1-L3)/L1X 100%.
The degree of TD direction curl of the separator of the present invention is 7% or less, preferably 3 to 7%, for example, 6.5%, 6%, 5.5%, 5%, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.5%, 1%.
The heat shrinkage TD of the separator of the present invention is 1.5% or less, preferably 0.6 to 0.9%, for example, 1.2%, 1%, 0.8%, 0.6%, 0.5%, 0.3%, 0.2%, 0.1% at 130 ℃ for 1 hour.
The invention provides a preparation method of a diaphragm with a flat diaphragm surface, which comprises the following steps:
(1) adding an inorganic filler into the heat-resistant polymer material stock solution for dispersion to obtain coating slurry;
(2) coating the coating slurry on the surface of the base film to obtain a coating diaphragm;
(3) separating out a three-dimensional network structure coating with uniform pore diameter by using inorganic filler as a crosslinking point through saturated steam or a coagulating bath;
(4) washing, drying and heat setting to obtain a diaphragm with a flat film surface;
wherein, the distance from the edge of the coating slurry on any side of the coating control diaphragm TD direction of the step (2) to the edge of the base film is more than or equal to 5% of the width of the base film and less than or equal to 15%, preferably more than or equal to 5% of the width of the base film and less than or equal to 10%.
Step (1)
In the step, inorganic filler with a certain proportion is added into the stock solution of the heat-resistant polymer material, and the coating slurry is obtained by dispersion and filtration.
The heat-resistant polymer material may be, for example, polyamide, polyimide, polyetherimide, polyamideimide, polysulfone, polyethersulfone, polyarylsulfone, or the like, and preferably an aromatic polyamide, and particularly preferably a para-aromatic polyamide.
Preferably, the weight percentage of the para-aromatic polyamide in the para-aromatic polyamide stock solution is 2 +/-1%; preferably, the inherent viscosity of the para-aramid stock solution is 2. + -. 1 dL/g, preferably 2. + -. 0.5 dL/g. Can be prepared by itself or purchased commercially, such as Mitsuokai chemical company, Shandong Polyarylhydrocarbon New materials, Shanghai Conbo New materials, Nicotai and New materials, Hebei Si-Gu chemical company, Guangdong Cai Yan company, etc.
The inorganic filler may be at least one of alumina, boehmite, magnesia, calcium oxide, barium oxide, zinc oxide, silica, titania, zirconia, magnesium hydroxide, aluminum hydroxide, and preferably alumina.
In one embodiment, the alumina has a particle size D50 ≦ 600 nm.
The ratio of the stock solution of the heat-resistant polymer material to the inorganic filler is not particularly limited, and may be, for example, 1.5 to 2.5 in terms of the mass ratio of the inorganic filler to the heat-resistant polymer material.
Step (2)
In this step, the slurry is coated on the surface of the base film, the distance from the edge of the slurry coated on any side of the diaphragm in the TD direction to the edge of the base film is controlled to be greater than or equal to 5% of the width of the base film and less than or equal to 15% of the width of the base film, and a coating control schematic diagram is shown in fig. 2.
In the figure, the base film width is W1; the distance from the edge of the coating slurry to the edge of the base film is W2 or W3;
the distance from the edge of the dressing to the edge of the base film on either side in the TD direction of the separator is controlled to be 5% or more, 15% (preferably 10%) or less of the width of the base film, and the deviation of both sides is 0.5% or less, i.e., 5% or less and W2/W1 x 100% or less and 15% (e.g., 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%), 5% or less and W3/W1 x 100% or less and 15% (e.g., 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%), and | W2-W3|/W1 is 0.5% or less.
The coating method is not particularly limited as long as it is suitable for preparing a separator, for example, blade coating, wire bar coating, slit coating, gravure coating, and the like.
Step (3)
In this step, the coating membrane is passed through saturated steam or coagulation bath to precipitate the three-dimensional network structure coating.
The manner of pre-coagulation by saturated steam or coagulation bath is not particularly limited and may be carried out in any manner known in the art.
Step (4)
The washing method is not particularly limited as long as it is suitable for elution of the residual solvent of the coating film, and for example, a method of placing the pre-solidified coating film in a water tank provided with pure water and overflowing from the rear to the front may be employed.
The temperature for drying is not particularly limited as long as it is suitable for membrane drying. For example, it may be oven dried at 75-90 deg.C.
The temperature for heat-setting is not particularly limited as long as it is suitable for heat treatment of the separator. For example, the heat treatment may be performed at 110-135 ℃.
The diaphragm with flat film surface is obtained by the method, particularly the control coated in the step (2).
The separator prepared by the method has the following characteristics:
the curling degree of the diaphragm in the TD direction after cutting satisfies the following conditions: (L1-L2)/L1 x 100 percent is less than or equal to 7 percent;
the thermal shrinkage ratio TD in the TD direction after the membrane is cut meets the following requirements: (L1-L3)/L1 x 100 percent is less than or equal to 1.5 percent;
according to a third aspect of the present invention, there is provided a lithium ion battery, including the above separator with a flat membrane surface or the separator with a flat membrane surface prepared by the above preparation method.
According to a fourth aspect of the invention, a supercapacitor is provided, which comprises the diaphragm with a flat film surface or the diaphragm with a flat film surface prepared by the preparation method.
The lithium ion battery or the super capacitor has the same advantages as the separator described above, and the description thereof is omitted.
The technical scheme of the invention has the following beneficial effects:
1. the invention can realize the flattening of the diaphragm without coating other substances on the other side of the polyolefin base film, has simple components of the diaphragm and is beneficial to reducing the side reaction in the charging and discharging process of the lithium ion battery.
2. The invention does not need special modification of equipment, is less limited by vehicle speed and coating thickness, and has simple process.
3. The diaphragm obtained by the invention has flat and stable diaphragm surface and size, can improve the winding or lamination rate of the lithium ion battery, reduces the problems of edge folding, folding and the like of the diaphragm of the battery cell caused by diaphragm curling in the assembly process, and improves the safety of the lithium ion battery.
4. The diaphragm obtained by the invention has small heat shrinkage rate in the TD direction, and is beneficial to improving the safety of a lithium ion battery.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a schematic diagram of a TD direction curl degree test method of a diaphragm according to the present invention;
FIG. 2 is a schematic view illustrating a control of coating slurry on the surface of a base film in the method for manufacturing a separator according to the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
The present invention is further illustrated by the following examples, which are provided for illustrative purposes only and are not to be construed as limiting the scope of the invention.
The starting materials, reagents, methods and the like used in the examples are those conventional in the art unless otherwise specified.
Example 1
(1) Adding 7 kg of Al into 200kg of para-aramid stock solution (the solid content is 2 percent, and the inherent viscosity is 2 dL/g)2O3(500nm), stirring for 30min by a high-speed dispersion emulsifying machine, and filtering by a 500-mesh filter screen to obtain uniformly dispersed para-aramid slurry;
(2) selecting a wet-process synchronous double-drawing polyethylene diaphragm with the thickness of 12 mu m and the width of 650mm, coating the para-aramid slurry obtained in the step (1) on one side of the base film in a scraper coating mode, and controlling the distance between the edges of the auxiliary materials on two sides of the diaphragm in the TD direction and the edge of the base film to be equal to 12% of the width of the base film by adjusting the distance between partition plates on two sides of a trough, namely the distance is 78 mm; the coating thickness was adjusted to 4 μm by controlling the blade gap.
(3) And (3) solidifying and forming the prepared coating film by a 20% NMP (N-methyl pyrrolidone) coagulating bath with the concentration of 40%, then washing the coating film in a pure water tank, then drying the coating film in an oven at 85 ℃, and carrying out heat setting at 130 ℃ to obtain the p-aramid coated lithium ion battery diaphragm.
Example 2
(1) Adding 7 kg of Al into 200kg of para-aramid stock solution (the solid content is 2 percent, and the inherent viscosity is 2 dL/g)2O3(500nm), stirring for 30min by a high-speed dispersion emulsifying machine, and filtering by a 500-mesh filter screen to obtain uniformly dispersed para-aramid slurry;
(2) selecting a wet-process synchronous double-drawing polyethylene diaphragm with the thickness of 7 mu m and the width of 800mm, coating the para-aramid slurry obtained in the step (1) on one side of the base film in a scraper coating mode, and controlling the distance between the edges of the auxiliary materials on two sides of the diaphragm in the TD direction and the edge of the base film to be equal to 10% of the width of the base film by adjusting the distance between the partition boards on two sides of a trough, namely the distance is 80 mm; the coating thickness was adjusted to 2 μm by controlling the blade gap.
(3) And (3) solidifying and forming the prepared coating film by a 20% NMP (N-methyl pyrrolidone) coagulating bath with the concentration of 40%, then washing the coating film in a pure water tank, then drying the coating film in a 75 ℃ drying oven, and carrying out heat setting at 110 ℃ to obtain the p-aramid coated lithium ion battery diaphragm.
Example 3
(1) To 200kg of7 kg of Al is added into the aramid fiber stock solution (the solid content is 2 percent, and the inherent viscosity is 2 dL/g)2O3(500nm), stirring for 30min by a high-speed dispersion emulsifying machine, and filtering by a 500-mesh filter screen to obtain uniformly dispersed para-aramid slurry;
(2) selecting a wet-process synchronous double-drawing polyethylene diaphragm with the thickness of 9 mu m and the width of 750mm, coating the para-aramid slurry obtained in the step (1) on one side of the base film in a scraper coating mode, and controlling the distance between the edges of the auxiliary materials on two sides of the diaphragm TD direction and the edge of the base film to be equal to 8% of the width of the base film, namely the distance is 60 mm, by adjusting the distance between the partition plates on two sides of a trough; the coating thickness was adjusted to 3 μm by controlling the blade gap.
(3) And (3) solidifying and forming the prepared coating film by a 20% NMP (N-methyl pyrrolidone) coagulating bath with the concentration of 40%, then washing the coating film in a pure water tank, then drying the coating film in an oven at 80 ℃, and carrying out heat setting at 120 ℃ to obtain the p-aramid coated lithium ion battery diaphragm.
Example 4
(1) Adding 7 kg of Al into 200kg of para-aramid stock solution (the solid content is 2 percent, and the inherent viscosity is 2 dL/g)2O3(500nm), stirring for 30min by a high-speed dispersion emulsifying machine, and filtering by a 500-mesh filter screen to obtain uniformly dispersed para-aramid slurry;
(2) selecting a wet-process synchronous double-drawing polyethylene diaphragm with the thickness of 12 microns and the width of 650mm, coating the para-aramid slurry obtained in the step (1) on one side of the base film in a scraper coating mode, and controlling the distance between the edges of the auxiliary materials on two sides of the diaphragm TD direction and the edge of the base film to be equal to 5% of the width of the base film, namely the distance to be 32.5mm, by adjusting the distance between the partition plates on two sides of a trough; the coating thickness was adjusted to 4 μm by controlling the blade gap.
(3) And (3) solidifying and forming the prepared coating film by a 20% NMP solidifying bath with the concentration of 40%, then washing the coating film in a pure water tank, then drying the coating film in an oven at the temperature of 85 ℃, and carrying out heat setting at the temperature of 130 ℃ to obtain the p-aramid fiber coating lithium ion battery diaphragm.
Comparative example 1
(1) Adding 7 kg of Al into 200kg of para-aramid stock solution (the solid content is 2 percent, and the inherent viscosity is 2 dL/g)2O3(500nm) by high speed dispersionStirring for 30min by an emulsifying machine, and filtering by a 500-mesh filter screen to obtain uniformly dispersed para-aramid slurry;
(2) selecting a wet-process synchronous double-drawing polyethylene diaphragm with the thickness of 9 mu m and the width of 750mm, coating the para-aramid slurry on one side of the base film in a scraper coating mode, and controlling the distance between the edge of the auxiliary material on any side of the diaphragm TD direction and the edge of the base film to be equal to 3% of the width of the base film, namely the distance to be 22.5 mm, by adjusting the distance between the partition plates on the two sides of the trough; the coating thickness was adjusted to 3 μm by controlling the blade gap.
(3) And (3) solidifying and forming the prepared coating film by a 20% NMP (N-methyl pyrrolidone) coagulating bath with the concentration of 40%, then washing the coating film in a pure water tank, then drying the coating film in an oven at 80 ℃, and carrying out heat setting at 120 ℃ to obtain the p-aramid coated lithium ion battery diaphragm.
Comparative example 2
(1) Adding 7 kg of Al into 200kg of para-aramid stock solution (the solid content is 2 percent, and the inherent viscosity is 2 dL/g)2O3(500nm), stirring for 30min by a high-speed dispersion emulsifying machine, and filtering by a 500-mesh filter screen to obtain uniformly dispersed para-aramid slurry;
(2) selecting a wet-process synchronous double-drawing polyethylene diaphragm with the thickness of 12 microns and the width of 650mm, coating the para-aramid slurry on one side of the base film in a scraper coating mode, and controlling the distance between the edge of the auxiliary material on any side of the diaphragm TD direction and the edge of the base film to be equal to 0% of the width of the base film by adjusting the distance between partition plates on two sides of a trough, namely, the coating completely covers the surface of the base film; the coating thickness was adjusted to 4 μm by controlling the blade gap.
(3) And (3) solidifying and forming the prepared coating film by a 20% NMP (N-methyl pyrrolidone) coagulating bath with the concentration of 40%, then washing the coating film in a pure water tank, then drying the coating film in an oven at 85 ℃, and carrying out heat setting at 130 ℃ to obtain the p-aramid coated lithium ion battery diaphragm.
Test example
The separators obtained in examples and comparative examples were subjected to performance test:
the degree of curling of the separator and the heat shrinkage in the TD direction at 130 ℃ for 1 hour were measured according to the above test methods. The results are shown in Table 1.
TABLE 1
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (9)
1. The diaphragm with the flat diaphragm surface is characterized by comprising a base film and a coating layer arranged on the base film;
the curling degree of the diaphragm in the TD direction after being cut meets the following conditions: (L1-L2)/L1 x 100 percent is less than or equal to 7 percent;
the thermal shrinkage TD of the diaphragm in the TD direction after cutting meets the following requirements: (L1-L3)/L1 x 100% is less than or equal to 1.5%;
wherein, L1 is the length of the diaphragm in the TD direction when the diaphragm is flattened under the action of an external force;
l2 is the length of the diaphragm projected to the horizontal plane in the TD direction when the diaphragm is naturally curled without external force;
l3 is the length of the diaphragm in TD direction when the diaphragm is flat under the action of external force after being clamped between two pieces of paper and kept at 130 ℃ for 1 h;
the membrane is prepared by a preparation method comprising the following steps:
(1) adding an inorganic filler into the heat-resistant polymer material stock solution for dispersion to obtain coating slurry;
(2) coating the coating slurry on the surface of the base film to obtain a coating diaphragm;
(3) separating out a three-dimensional network structure coating from the coating diaphragm through saturated steam or a coagulating bath;
(4) washing, drying and heat setting to obtain a diaphragm with a flat film surface;
wherein the distance from the edge of the coating slurry on any side of the coating control diaphragm TD direction in the step (2) to the edge of the base film is more than or equal to 5% of the width of the base film and less than or equal to 15% of the width of the base film; and the deviation of the two sides is less than or equal to 0.5 percent.
2. The separator according to claim 1, wherein the base film is one of a polyethylene base film, a polypropylene base film, a mixed base film of polyethylene and polypropylene, or a multi-layered base film.
3. The separator according to claim 1, wherein the coating layer comprises a heat-resistant polymer material and a heat-resistant inorganic filler;
the heat-resistant high polymer material is at least one of polyamide, polyimide, polyetherimide, polyamideimide, polysulfone, polyethersulfone and polyarylsulfone;
the heat-resistant inorganic filler is at least one of aluminum oxide, boehmite, magnesium oxide, calcium oxide, barium oxide, zinc oxide, silicon dioxide, titanium dioxide, zirconium dioxide, magnesium hydroxide and aluminum hydroxide.
4. The separator according to claim 3, wherein the heat-resistant polymer material is an aromatic polyamide;
the heat-resistant inorganic filler is alumina;
the grain diameter D50 of the alumina is less than or equal to 600 nm.
5. The preparation method of the diaphragm with the flat diaphragm surface is characterized by comprising the following steps:
(1) adding an inorganic filler into the heat-resistant polymer material stock solution for dispersion to obtain coating slurry;
(2) coating the coating slurry on the surface of the base film to obtain a coating diaphragm;
(3) separating out a three-dimensional network structure coating from the coating diaphragm through saturated steam or a coagulating bath;
(4) washing, drying and heat setting to obtain a diaphragm with a flat film surface;
wherein the distance from the edge of the coating slurry on any side of the coating control diaphragm TD direction in the step (2) to the edge of the base film is more than or equal to 5% of the width of the base film and less than or equal to 15% of the width of the base film; and the deviation of the two sides is less than or equal to 0.5 percent;
the curling degree of the obtained diaphragm in the TD direction after cutting meets the following conditions: (L1-L2)/L1 x 100 percent is less than or equal to 7 percent;
the thermal shrinkage TD of the obtained diaphragm in the TD direction after cutting meets the following requirements: (L1-L3)/L1 x 100 percent is less than or equal to 1.5 percent;
wherein, L1 is the length of the diaphragm in the TD direction when the diaphragm is flattened under the action of an external force;
l2 is the length of the diaphragm projected to the horizontal plane in the TD direction when the diaphragm is naturally curled without external force;
l3 is the length of the separator in the TD direction when the separator is held between two sheets of paper at 130 deg.C for 1h and then flattened by the application of external force.
6. The preparation method according to claim 5, wherein the weight percentage of the heat-resistant polymer material in the stock solution of the heat-resistant polymer material in the step (1) is 2 ± 1%; and/or
The inherent viscosity of the stock solution of the heat-resistant high polymer material obtained in the step (1) is 2 +/-1 dL/g.
7. The method according to claim 5, wherein the coating manner of the step (2) comprises any one of blade coating, wire bar coating, slit coating and gravure coating.
8. A lithium ion battery, characterized in that the lithium ion battery comprises the separator with flat membrane surface according to any one of claims 1 to 4 or the separator with flat membrane surface prepared by the preparation method according to any one of claims 5 to 7.
9. A supercapacitor, which comprises the membrane with a flat membrane surface according to any one of claims 1 to 4 or the membrane with a flat membrane surface prepared by the preparation method according to any one of claims 5 to 7.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210174045.5A CN114243218B (en) | 2022-02-25 | 2022-02-25 | Diaphragm with smooth diaphragm surface and preparation method and application thereof |
| PCT/CN2022/101964 WO2023159835A1 (en) | 2022-02-25 | 2022-06-28 | Separator having flat surface as well as preparation method therefor and use thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210174045.5A CN114243218B (en) | 2022-02-25 | 2022-02-25 | Diaphragm with smooth diaphragm surface and preparation method and application thereof |
Publications (2)
| Publication Number | Publication Date |
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| CN114243218A CN114243218A (en) | 2022-03-25 |
| CN114243218B true CN114243218B (en) | 2022-05-06 |
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| CN202210174045.5A Active CN114243218B (en) | 2022-02-25 | 2022-02-25 | Diaphragm with smooth diaphragm surface and preparation method and application thereof |
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| Country | Link |
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| CN (1) | CN114243218B (en) |
| WO (1) | WO2023159835A1 (en) |
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| CN114243218B (en) * | 2022-02-25 | 2022-05-06 | 湖南中锂新材料科技有限公司 | Diaphragm with smooth diaphragm surface and preparation method and application thereof |
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| WO2023159835A1 (en) | 2023-08-31 |
| CN114243218A (en) | 2022-03-25 |
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Address after: 410600 No.188 Jinshui East Road, Ningxiang high tech Industrial Park, Changsha City, Hunan Province Patentee after: Sinoma lithium film (Ningxiang) Co.,Ltd. Address before: 410600 No.188 Jinshui East Road, Ningxiang high tech Industrial Park, Changsha City, Hunan Province Patentee before: HUNAN CHINALY NEW MATERIAL TECHNOLOGY Co.,Ltd. |
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