CN114725622A - Separator, method for producing separator, and electrochemical device - Google Patents
Separator, method for producing separator, and electrochemical device Download PDFInfo
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- CN114725622A CN114725622A CN202210391737.5A CN202210391737A CN114725622A CN 114725622 A CN114725622 A CN 114725622A CN 202210391737 A CN202210391737 A CN 202210391737A CN 114725622 A CN114725622 A CN 114725622A
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- 239000011247 coating layer Substances 0.000 claims abstract description 150
- 238000000576 coating method Methods 0.000 claims abstract description 78
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- NLYAJNPCOHFWQQ-UHFFFAOYSA-N kaolin Chemical compound O.O.O=[Al]O[Si](=O)O[Si](=O)O[Al]=O NLYAJNPCOHFWQQ-UHFFFAOYSA-N 0.000 claims abstract description 30
- 239000011230 binding agent Substances 0.000 claims abstract description 27
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- 229910001593 boehmite Inorganic materials 0.000 claims abstract description 19
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- 239000002174 Styrene-butadiene Substances 0.000 claims description 4
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- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 11
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Classifications
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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
- H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
-
- 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
- H01M50/431—Inorganic material
-
- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Inorganic Chemistry (AREA)
- Cell Separators (AREA)
Abstract
The embodiment of the application provides an isolating membrane, an isolating membrane preparation method and an electrochemical device, wherein the isolating membrane comprises the following components: a base film; the first coating layer is arranged on at least one side of the thickness direction of the base film and comprises a binder and nano kaolin; the second coating layer is arranged on one side, far away from the base film, of the first coating layer and comprises a binder and a second base material; wherein the second substrate in the second coating layer adopts nano boehmite powder coated with nano kaolin. Through setting up the setting of two-layer coating on the base film, not only can effectively improve the high temperature resistant ability of barrier film, reduce the battery under high temperature environment, because of the incident that barrier film shrink warp and lead to, still have outstanding infiltration ability, can be convenient for conductive ion and pierce through, improved the electrochemical properties of battery.
Description
Technical Field
The application belongs to the technical field of isolating membranes, and particularly relates to an isolating membrane, a preparation method of the isolating membrane and an electrochemical device.
Background
In recent years, electric devices powered by secondary batteries are widely used and popularized in industries such as various electronic products and new energy automobiles. Higher demands are made on the cycle performance of the battery.
The separator is one of the key inner layer components of the secondary battery. The isolating membrane is arranged between the positive pole piece and the negative pole piece, mainly plays a role in preventing the short circuit of the positive pole and the negative pole, and can enable ions to pass through. Improving the performance of the separator is critical to improving the electrochemical performance of the battery.
Disclosure of Invention
The embodiment of the application provides an isolating membrane, an isolating membrane preparation method and an electrochemical device, which can improve the wettability of the isolating membrane on electrolyte.
In a first aspect of embodiments of the present application, there is provided an isolation film, including:
a base film;
the first coating layer is arranged on at least one side of the thickness direction of the base film and comprises a binder and nano kaolin;
the second coating layer is arranged on one side, far away from the base film, of the first coating layer and comprises a binder and a second base material;
wherein the second substrate in the second coating layer adopts nano boehmite powder coated with nano kaolin.
Adopt above-mentioned structure, through the setting that sets up two-layer coating on the base film, not only can effectively improve the high temperature resistance ability of barrier film, reduce the battery under high temperature environment, because of the incident that barrier film shrink deformation leads to, still have outstanding infiltration ability, the conducting ion that can be convenient for pierces through, the electrochemical performance of battery has been improved, secondly, through the nanometer kaolin in first coating and the second coating, also can strengthen the stability of first coating and second coating inter-lamination connection, reduce the problem that the coating drops.
In some optional embodiments of the present application, the ratio of the binder to the nano kaolin in the first coating layer is (1.0 to 3.0): (7.0 to 9.0) by mass.
In some alternative embodiments of the present application, the ratio by mass of the binder to the second substrate in the second coating layer is (0.3 to 1.0): (9.0 to 9.7), and the ratio by mass of the nano kaolin to the nano boehmite in the second substrate is (2.0 to 3.0): (7.0 to 8.0).
In some alternative embodiments of the present application, the first coating layer has a thickness of 0.5 μm to 5.0 μm, and the second coating layer has a thickness of 0.1 μm to 5.0 μm.
In some alternative embodiments of the present application, the nano kaolin in the first coating layer has a particle size of 300nm to 800 nm.
With the structure, the particle size of the first coating layer is selected to be 300nm to 800nm, so that the bonding force between the first coating layer and the base film is enhanced, and filling gaps can be reserved for particles in the second coating layer to form a whole.
In some alternative embodiments of the present application, the second coating layer has a second substrate particle size of 100nm to 500 nm.
In some alternative embodiments of the present application, the nano-boehmite in the second substrate has a particle size of 80nm to 400nm and the nano-kaolin has a particle size of 20nm to 100 nm.
Adopt above-mentioned structure, through setting up the second substrate into 100nm to 500nm, can make the granule in the second coating be less than the granule in the first coating, be convenient for form stable mosaic structure after melting, secondly, because the cladding of second substrate surface has nanometer kaolin, is the same with first coating material, can play homogeneous effect, is favorable to combining together between first coating and the second coating layer.
In some optional embodiments of the present application, the binder in the first and second coating layers is at least one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), styrene-butadiene latex, polyvinyl alcohol, and polyurethane.
In some optional embodiments of the present application, the binder in the first coating layer and the second coating layer is polyvinylidene fluoride.
By adopting the structure, polyvinylidene fluoride is selected as the binder, so that better temperature resistance can be obtained, the viscosity is higher, and better bonding compatibility with nano kaolin is facilitated.
In some optional embodiments of the present application, the base film is at least one of a polyolefin film, a polypropylene film, a polyethylene film, and a propylene-ethylene copolymer film.
In some alternative embodiments of the present application, the base film has a thickness of 7 to 20 μm and a porosity of 45 to 65%.
In a second aspect of the embodiments of the present application, there is provided a method for preparing an isolation film, including the steps of:
providing a base film;
coating a first coating layer on at least one side of the base film, and pressing after drying;
and coating a second coating layer on one side of the first coating layer far away from the base film, and pressing after drying.
In a third aspect of the embodiments of the present application, there is provided an electrochemical device including the above-described separator.
Compared with the prior art, in the isolating membrane, the isolating membrane preparation method and the electrochemical device of the embodiment of the application, through the arrangement of two coating layers arranged on the base membrane, the high temperature resistance of the isolating membrane can be effectively improved, the safety accident of the battery caused by shrinkage deformation of the isolating membrane under a high-temperature environment is reduced, the isolating membrane also has excellent infiltration capacity, conductive ions can penetrate conveniently, the electrochemical performance of the battery is improved, and secondly, the stability of connection between the first coating layer and the second coating layer can be enhanced through the nano kaolin in the first coating layer and the second coating layer, and the problem of coating falling is reduced.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and it is obvious for a person skilled in the art to obtain other drawings based on the drawings without any creative effort.
Fig. 1 is a cross-sectional view of a separator in the thickness direction in the present application.
Reference numerals:
1. a base film; 2. a first coating layer; 3. a second coating layer.
Detailed Description
In order to make the purpose, technical solution and advantageous technical effects of the present invention clearer, the present invention is further described in detail with reference to the following embodiments. It should be understood that the embodiments described in this specification are only for the purpose of explaining the present application and are not intended to limit the present application.
For the sake of brevity, only some numerical ranges are explicitly disclosed herein. However, any lower limit may be combined with any upper limit to form ranges not explicitly recited; and any lower limit may be combined with any other lower limit to form a range not explicitly recited, and similarly any upper limit may be combined with any other upper limit to form a range not explicitly recited. Also, although not explicitly recited, each point or individual value between endpoints of a range is encompassed within the range. Thus, each point or individual value can form a range not explicitly recited as its own lower or upper limit in combination with any other point or individual value or in combination with other lower or upper limits.
In the description herein, when a composition is described as containing, comprising, or including a particular component, or when a process is described as containing, comprising, or including a particular process step, it is contemplated that the composition of the present application also consists essentially of, or consists of, the component, and that the process of the present application also consists essentially of, or consists of, the process step.
The use of the terms "comprising," "including," "containing," and "having" are generally to be construed as open-ended and non-limiting unless otherwise expressly specified.
In the description herein, it is to be noted that, unless otherwise specified, "above" and "below" are inclusive, and "a plurality" of "one or more" means two or more.
The above summary of the present application is not intended to describe each disclosed embodiment or every implementation of the present application. The following description more particularly exemplifies illustrative embodiments. At various points throughout this application, guidance is provided through a list of embodiments that can be used in various combinations. In each instance, the list is merely a representative group and should not be construed as exhaustive.
The performance of the separator, which is one of the most critical inner layer components in the structure of the secondary battery, directly affects the capacity, rate, service life, safety and other properties of the battery. The interface compatibility between the isolating membrane material and the electrode and the retention of the isolating membrane to the electrolyte have important influences on the charge and discharge performance, the cycle performance and the service life of the secondary battery.
In the correlation technique, for solving the temperature resistance and the security performance of barrier film, generally adopt the mode of coating pottery on the base film, make the base film surface form composite coating, improve the temperature resistance of base film, if when the high temperature in barrier film operational environment, reduce the shrinkage deformation degree of barrier film, and then reduce the short circuit condition of battery under high temperature environment. However, the foregoing manner of coating ceramic mostly adopts alumina ceramic material, and the wettability of the obtained isolation film is poor, so that the penetration resistance of conductive ions is increased, and the electrochemical performance of the battery is reduced.
The inventor of the application discovers through research that the tolerance capability of the isolating membrane under the high-temperature environment can be effectively improved by arranging two layers of high-temperature-resistant coating layers on the base membrane, and the nano kaolin and the nano boehmite are selected as the coating layer materials, so that the high-temperature-resistant capability can be obtained, the thermal stability is good, the wettability of the isolating membrane on electrolyte can be ensured, the high ionic conductivity is realized, the electrochemical performance of the battery can be ensured, the high-rate performance and the long-term circulation performance are realized, and the safety is high. In view of this, embodiments of the present application provide a separation film, a method of manufacturing the separation film, and an electrochemical device.
As shown in fig. 1, fig. 1 is a cross-sectional view of a separator in the thickness direction in the present application. The embodiment of the application provides a barrier film, including base film, first coating and second coating. The first coating layer is disposed on at least one side of the thickness direction (x-axis direction in fig. 1) of the base film, and includes a binder and nano kaolin. The second coating layer is arranged on one side, far away from the base film, of the first coating layer and comprises a binder and a second base material. The second substrate in the second coating layer adopts nano boehmite powder coated with nano kaolin.
Through setting up the setting of two-layer coating on the base film, not only can effectively improve the high temperature resistance ability of barrier film, reduce the battery under high temperature environment, because of the incident that barrier film shrink deformation leads to, still have outstanding infiltration ability, the conducting ion that can be convenient for pierces through, the electrochemical performance of battery has been improved, secondly, through the nanometer kaolin in first coating and the second coating, also can strengthen the stability of first coating and second coating inter-lamination connection, reduce the problem that the coating drops.
In some alternative embodiments of the present application, the ratio of the binder to the nano kaolin in the first coating layer is (1.0 to 3.0): (7.0 to 9.0) by mass.
In some alternative embodiments of the present application, the ratio of the binder to the second substrate in the second coating layer is (0.3 to 1.0) to (9.0 to 9.7) by mass, and the ratio of the nano-kaolin to the nano-boehmite in the second substrate is (2.0 to 3.0) to (7.0 to 8.0) by mass.
In some alternative embodiments of the present application, the first coating layer has a thickness of 0.5 μm to 5.0 μm, and the second coating layer has a thickness of 0.1 μm to 5.0 μm.
In some alternative embodiments of the present application, the nano kaolin in the first coating layer has a particle size of 300nm to 800 nm.
In some alternative embodiments of the present application, the second coating layer has a second substrate particle size of 100nm to 500 nm.
In some optional embodiments of the present application, the binder in the first coating layer and the second coating layer is at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, styrene-butadiene latex, polyvinyl alcohol, polyurethane, and polyionic liquid.
In some alternative embodiments of the present application, the binder in the first coating layer and the second coating layer is polyvinylidene fluoride.
In some alternative embodiments of the present application, the base film is at least one of a polyolefin film, a polypropylene film, a polyethylene film, and a propylene-ethylene copolymer film.
In some alternative embodiments of the present application, the base film has a thickness of 7 to 20 μm and a porosity of 45 to 65%.
In some alternative embodiments of the present application, there is also provided a method of preparing a separator film, including the steps of:
s01, providing a base film;
s02, coating a first coating layer on at least one side of the base film, drying and pressing;
and S03, coating a second coating layer on the side, far away from the base film, of the first coating layer, drying and pressing.
Specifically, the step S02 further includes: and preparing a first coating layer, namely providing a binder and nano kaolin, fully dissolving the binder and the nano kaolin, and uniformly mixing to obtain the first coating layer paint.
Specifically, the step S03 further includes: and preparing a second coating layer, namely providing a binder and a second base material, fully dissolving the binder and the second base material, and uniformly mixing to obtain a second coating layer paint.
In some alternative embodiments of the present application, there is also provided an electrochemical device including the above-described separator.
Specifically, the electrochemical device can be a battery cell, and at least comprises a shell and a pole piece assembly arranged in the shell, wherein the pole piece assembly comprises a positive pole piece, a negative pole piece and an isolating membrane arranged between the positive pole piece and the negative pole piece. The battery cell may be a secondary battery cell or a primary battery cell, or may also be a lithium ion battery cell, a sodium ion battery cell, or a magnesium ion battery cell, and the like, which is not limited in this embodiment of the present application. The battery unit can be in a cylinder, a flat body, a cuboid or other shapes.
Examples
The present disclosure is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported in the following examples are on a weight basis, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the equipment used in the examples is commercially available.
Example 1
Preparing an isolating membrane:
(1) preparing a first coating layer paint: 0.4g of polyvinylidene fluoride was weighed and dissolved in 8.6g of anhydrous N-methylpyrrolidone (NMP), and stirred at room temperature for 4 hours to obtain a polyvinylidene fluoride solution having a mass fraction of 4%. Mixing nano kaolin (HNT) with the particle size of 300nm and the obtained polyvinylidene fluoride solution according to the mass ratio of 9:1, stirring for 10 hours at room temperature, and carrying out ultrasonic treatment for 1.0 hour to obtain a first coating layer coating.
(2) Preparing a second coating layer paint: weighing 0.4g of polyvinylidene fluoride, dissolving the polyvinylidene fluoride in 9.6g of anhydrous N-methyl pyrrolidone, and stirring the mixture at room temperature for 4 hours to obtain a polyvinylidene fluoride solution with the mass fraction of 4%. 2.0g of nano-kaolin and 8.0g of boehmite were mixed and milled using a high energy ball mill for 5 hours at room temperature to provide a second substrate of nano-kaolin coated boehmite having a particle size of 100 nm. And mixing the second base material and the obtained polyvinylidene fluoride solution according to the mass ratio of 9.7:0.3, stirring for 10 hours at room temperature, and carrying out ultrasonic treatment for 1.0 hour to obtain a second coating layer coating.
(3) Coating: uniformly coating the first coating layer coating on two sides of a 9-micron polyethylene base film by a scraper, wherein the thickness of the first coating layer coating is 3 microns, after a large amount of solvent is volatilized, placing the first coating layer coating in a vacuum oven for vacuum drying for 12 hours at 50 ℃, and pressing the first coating layer coating for 30 seconds under the pressure of a hot press under 4MPa after drying. And uniformly coating the second coating layer on one side of the first coating layer, which is far away from the base film, by using a scraper, wherein the thickness of the second coating layer is 1 mu m, after a large amount of solvent is volatilized, placing the second coating layer in a vacuum oven for vacuum drying for 12 hours at 50 ℃, and pressing the second coating layer for 50 seconds under the pressure of 4MPa of a hot press after drying to obtain the isolating film.
Example 2
Preparing an isolating membrane:
(1) preparing a first coating layer paint: weighing 0.4g of polyvinylidene fluoride, dissolving the polyvinylidene fluoride in 9.6g of anhydrous N-methyl pyrrolidone, and stirring the mixture at room temperature for 4 hours to obtain a polyvinylidene fluoride solution with the mass fraction of 4%. Mixing nano kaolin with the particle size of 400nm and the obtained polyvinylidene fluoride solution according to the mass ratio of 8:1, stirring at room temperature for 10 hours, and carrying out ultrasonic treatment for 1.0 hour to obtain a first coating layer coating.
(2) Preparing a second coating layer paint: 0.4g of polyvinylidene fluoride is weighed and dissolved in 9.6g of anhydrous N-methylpyrrolidone, and stirred for 4 hours at room temperature to obtain a polyvinylidene fluoride solution with the mass fraction of 4%. 2.0g of nano-kaolin and 8.0g of boehmite were mixed and milled using a high energy ball mill for 5 hours at room temperature to provide a second substrate of nano-kaolin coated boehmite having a particle size of 200 nm. And mixing the second base material and the obtained polyvinylidene fluoride solution according to the mass ratio of 9.5:0.5, stirring for 10 hours at room temperature, and carrying out ultrasonic treatment for 1.0 hour to obtain a second coating layer coating.
(3) Coating: uniformly coating the first coating layer coating on two sides of a 9-micron polyethylene base film by a scraper, wherein the thickness of the first coating layer coating is 3 microns, after a large amount of solvent is volatilized, placing the first coating layer coating in a vacuum oven for vacuum drying for 12 hours at 50 ℃, and pressing the first coating layer coating for 30 seconds under the pressure of a hot press under 4MPa after drying. And uniformly coating the second coating layer on one side of the first coating layer, which is far away from the base film, by using a scraper, wherein the thickness of the second coating layer is 1 mu m, after a large amount of solvent is volatilized, placing the second coating layer in a vacuum oven for vacuum drying for 12 hours at 50 ℃, and pressing the second coating layer for 50 seconds under the pressure of 4MPa of a hot press after drying to obtain the isolating film.
Example 3
Preparing an isolating membrane:
(1) preparing a first coating layer paint: weighing 0.4g of polyvinylidene fluoride, dissolving the polyvinylidene fluoride in 9.6g of anhydrous N-methyl pyrrolidone, and stirring the mixture at room temperature for 4 hours to obtain a polyvinylidene fluoride solution with the mass fraction of 4%. Mixing nano kaolin with the particle size of 500nm and the obtained polyvinylidene fluoride solution according to the mass ratio of 7:1, stirring for 10 hours at room temperature, and carrying out ultrasonic treatment for 1.0 hour to obtain a first coating layer coating.
(2) Preparing a second coating layer paint: weighing 0.4g of polyvinylidene fluoride, dissolving the polyvinylidene fluoride in 9.6g of anhydrous N-methyl pyrrolidone, and stirring the mixture at room temperature for 4 hours to obtain a polyvinylidene fluoride solution with the mass fraction of 4%. 2.0g of nano-kaolin and 8.0g of boehmite were mixed and milled using a high energy ball mill for 5 hours at room temperature to provide a second substrate of nano-kaolin coated boehmite having a particle size of 300 nm. And mixing the second base material with the obtained polyvinylidene fluoride solution according to the mass ratio of 9.5:0.5, stirring for 10 hours at room temperature, and carrying out ultrasonic treatment for 1.0 hour to obtain a second coating layer coating.
(3) Coating: uniformly coating the first coating layer coating on two sides of a 9-micron polyethylene base film by a scraper, wherein the thickness of the first coating layer coating is 3 microns, after a large amount of solvent is volatilized, placing the first coating layer coating in a vacuum oven for vacuum drying for 12 hours at 50 ℃, and pressing the first coating layer coating for 30 seconds under the pressure of a hot press under 4MPa after drying. And uniformly coating the second coating layer on one side of the first coating layer, which is far away from the base film, by using a scraper, wherein the thickness of the second coating layer is 1 mu m, after a large amount of solvent is volatilized, placing the second coating layer in a vacuum oven for vacuum drying for 12 hours at 50 ℃, and pressing the second coating layer for 50 seconds under the pressure of 4MPa of a hot press after drying to obtain the isolating film.
Example 4
Preparing an isolating membrane:
(1) preparing a first coating layer paint: 0.4g of polyvinylidene fluoride is weighed and dissolved in 9.6g of anhydrous N-methylpyrrolidone, and stirred for 4 hours at room temperature to obtain a polyvinylidene fluoride solution with the mass fraction of 4%. Mixing nano kaolin with the particle size of 700nm and the obtained polyvinylidene fluoride solution according to the mass ratio of 8:2, stirring for 10 hours at room temperature, and carrying out ultrasonic treatment for 1.0 hour to obtain a first coating layer coating.
(2) Preparing a second coating layer paint: weighing 0.4g of polyvinylidene fluoride, dissolving the polyvinylidene fluoride in 9.6g of anhydrous N-methyl pyrrolidone, and stirring the mixture at room temperature for 4 hours to obtain a polyvinylidene fluoride solution with the mass fraction of 4%. 2.5g of nano-kaolin and 7.5g of boehmite were mixed and milled using a high energy ball mill for 5 hours at room temperature to provide a second substrate of nano-kaolin coated boehmite having a particle size of 400 nm. And mixing the second base material and the obtained polyvinylidene fluoride solution according to the mass ratio of 9:1, stirring for 10 hours at room temperature, and carrying out ultrasonic treatment for 1.0 hour to obtain a second coating layer coating.
(3) Coating: uniformly coating the first coating layer coating on two sides of a 9-micron polyethylene base film by a scraper, wherein the thickness of the first coating layer coating is 3 microns, after a large amount of solvent is volatilized, placing the first coating layer coating in a vacuum oven for vacuum drying for 12 hours at 50 ℃, and pressing the first coating layer coating for 30 seconds under the pressure of a hot press under 4MPa after drying. And uniformly coating the second coating layer on one side of the first coating layer, which is far away from the base film, by using a scraper, wherein the thickness of the second coating layer is 1 mu m, after a large amount of solvent is volatilized, placing the second coating layer in a vacuum oven for vacuum drying for 12 hours at 50 ℃, and pressing the second coating layer for 50 seconds under the pressure of 4MPa of a hot press after drying to obtain the isolating film.
Example 5
Preparing an isolating membrane:
(1) preparing a first coating layer paint: weighing 0.4g of polyvinylidene fluoride, dissolving the polyvinylidene fluoride in 9.6g of anhydrous N-methyl pyrrolidone, and stirring the mixture at room temperature for 4 hours to obtain a polyvinylidene fluoride solution with the mass fraction of 4%. Mixing nano kaolin with the particle size of 800nm and the obtained polyvinylidene fluoride solution according to the mass ratio of 7:3, stirring for 10 hours at room temperature, and carrying out ultrasonic treatment for 1.0 hour to obtain a first coating layer coating.
(2) Preparing a second coating layer paint: 0.4g of polyvinylidene fluoride is weighed and dissolved in 9.6g of anhydrous N-methylpyrrolidone, and stirred for 4 hours at room temperature to obtain a polyvinylidene fluoride solution with the mass fraction of 4%. 3.0g of nano-kaolin and 7.0g of boehmite were mixed and milled using a high energy ball mill for 5 hours at room temperature to provide a second substrate of nano-kaolin coated boehmite having a particle size of 500 nm. And mixing the second base material and the obtained polyvinylidene fluoride solution according to the mass ratio of 9:1, stirring for 10 hours at room temperature, and carrying out ultrasonic treatment for 1.0 hour to obtain a second coating layer coating.
(3) Coating: uniformly coating the first coating layer coating on two sides of a 9-micron polyethylene base film by a scraper, wherein the thickness of the first coating layer coating is 3 microns, after a large amount of solvent is volatilized, placing the first coating layer coating in a vacuum oven for vacuum drying for 12 hours at 50 ℃, and pressing the first coating layer coating for 30 seconds under the pressure of a hot press under 4MPa after drying. And uniformly coating the second coating layer on one side of the first coating layer, which is far away from the base film, by using a scraper, wherein the thickness of the second coating layer is 1 mu m, after a large amount of solvent is volatilized, placing the second coating layer in a vacuum oven for vacuum drying for 12 hours at 50 ℃, and pressing the second coating layer for 50 seconds under the pressure of 4MPa of a hot press after drying to obtain the isolating film.
Example 6
This embodiment is substantially the same as embodiment 1 except that: the adhesive in the first coating layer and the second coating layer adopts polyvinylidene fluoride-hexafluoropropylene, and the base film adopts a polyolefin film.
Example 7
This embodiment is substantially the same as embodiment 1 except that: the binder in the first coating layer and the second coating layer is polyvinylidene fluoride-hexafluoropropylene, and the base film is a polypropylene film.
Example 8
This embodiment is substantially the same as embodiment 1 except that: the adhesive in the first coating layer and the second coating layer adopts styrene-butadiene latex and a basal membrane propylene-ethylene copolymer membrane.
Example 9
This embodiment is substantially the same as embodiment 1 except that: the adhesive in the first coating layer and the second coating layer is polyvinyl alcohol.
Example 10
This embodiment is substantially the same as embodiment 1 except that: and the adhesive in the first coating layer and the second coating layer is polyurethane.
Comparative example 1
Preparing an isolating membrane:
dispersing alumina ceramic with the particle size of 500nm by using polyvinylidene fluoride to form uniform slurry, and performing double-sided coating on the surface of a polyethylene base film with the thickness of 20 mu m according to a conventional coating process to obtain the isolating film.
Test method
And (3) measuring wettability:
the wetting property is characterized by the liquid absorption amount, which is measured by the electrolyte. The release film samples were cut into 2cm by 2cm squares and M1 was weighed, whereuponThe electrolyte used is LiPF of lmol/L6. The electrolyte system is Ethylene Carbonate (EC): dimethyl carbonate (DMC): diethyl carbonate (EMC) ═ 1: 1: 1(V/V), soaking the sample membrane in the electrolyte for 30min, taking out, sucking the electrolyte on the surface of the sample membrane by using filter paper, weighing M2, and calculating the wettability according to the following formula.
The calculation formula is as follows: p ═ M2-M1)/M1 × 100%
In the formula: ml-base film mass (g); m2-mass after soaking (g).
Specific capacity determination:
the positive electrode part of the battery is made of active material LiCoO2Uniformly mixing a conductive agent (Super-P carbon) and a binding agent polyvinylidene fluoride into slurry according to the mass ratio of 8:1:1, uniformly coating the slurry on an aluminum foil by using a scraper, naturally airing the slurry, then beating the dried slurry into a wafer, and drying the wafer in vacuum at 105 ℃ to obtain an electrode plate, wherein a metal lithium plate is used as a negative electrode, and an electrolyte is 1mol/L LiPF6The volume ratio of Ethylene Carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) is 1:1, and the isolating membrane obtained in the above embodiment is adopted to assemble a CR2032 button cell under the argon environment, a CT2001A cell testing system is used for carrying out electrochemical performance test, a constant current charging and discharging method is adopted to carry out the test at 25 ℃, the voltage is 2.0V to 4.2V, and the specific capacity is measured.
And (3) shrinkage rate measurement:
(1) cutting 5 100mm × 100mm isolation films (width less than 100mm, length direction 100 mm);
(2) the width of the reference national standard measurement sample is marked as L1;
(3) placing the isolation film sample in an electric heating constant temperature air drying oven (DHG-9076A) for drying, and placing for 2h at 105 ℃;
(4) taking out the isolation film after high-temperature baking, and measuring the width of the isolation film as L2;
(5) shrinkage (L1-L2)/L1 by 100% was calculated.
The specific test results are shown in table 1.
Table 1: production parameters and test results of examples 1 to 10 and comparative example 1
As can be seen from table 1, the separators obtained in examples 1 to 10 of the present application have better shrinkage and specific capacity than comparative example 1, and the wetting solutions of the separators obtained in examples 1 to 10 of the present application are significantly better than that of comparative example 1.
Compared with the prior art, in the isolating membrane, the isolating membrane preparation method and the electrochemical device of the embodiment of the application, through the arrangement of two coating layers arranged on the base membrane, the high temperature resistance of the isolating membrane can be effectively improved, the safety accident of the battery caused by shrinkage deformation of the isolating membrane under a high-temperature environment is reduced, the isolating membrane also has excellent infiltration capacity, conductive ions can penetrate conveniently, the electrochemical performance of the battery is improved, and secondly, the stability of connection between the first coating layer and the second coating layer can be enhanced through the nano kaolin in the first coating layer and the second coating layer, and the problem of coating falling is reduced.
While the invention has been described with reference to specific embodiments, the scope of the invention is not limited thereto, and those skilled in the art can easily conceive various equivalent modifications or substitutions within the technical scope of the invention. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (11)
1. A separator, comprising:
a base film;
the first coating layer is arranged on at least one side of the thickness direction of the base film and comprises a binder and nano kaolin;
the second coating layer is arranged on one side, far away from the base film, of the first coating layer and comprises a binder and a second base material;
wherein the second substrate in the second coating layer adopts nano boehmite powder coated with nano kaolin.
2. The separator of claim 1, wherein the binder and the nano kaolin in the first coating layer are in a ratio of (1.0 to 3.0) to (7.0 to 9.0) by mass.
3. The separator according to claim 2, wherein the ratio by mass of the binder to the second substrate in the second coating layer is (0.3 to 1.0): (9.0 to 9.7), and the ratio by mass of the nano kaolin to the nano boehmite in the second substrate is (2.0 to 3.0): (7.0 to 8.0).
4. The separator of any of claims 1-3, wherein the first coating layer has a thickness of 0.5 μm to 5.0 μm and the second coating layer has a thickness of 0.1 μm to 5.0 μm.
5. The separator of any of claims 1-3, wherein the nano kaolin in the first coating layer has a particle size of 300nm to 800 nm.
6. The separator of any of claim 5, wherein the second substrate particle size in the second coating layer is from 100nm to 500 nm.
7. The separator of claim 1, wherein the binder in the first coating layer and the second coating layer is at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, styrene-butadiene latex, polyvinyl alcohol, and polyurethane.
8. The separator of claim 7, wherein the binder in the first and second coating layers is polyvinylidene fluoride.
9. The separator according to claim 7 or 8, wherein the base film is at least one of a polyolefin film, a polypropylene film, a polyethylene film, and a propylene-ethylene copolymer film.
10. A preparation method of a separation film is characterized by comprising the following steps:
providing a base film;
coating a first coating layer on at least one side of the base film, and pressing after drying;
and coating a second coating layer on one side of the first coating layer far away from the base film, and pressing after drying.
11. An electrochemical device comprising the separator according to any one of claims 1 to 9.
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| US20170356135A1 (en) * | 2014-12-03 | 2017-12-14 | Imerys Minerales Limited | Coated substrate |
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| CN112563670A (en) * | 2020-12-17 | 2021-03-26 | 合肥国轩高科动力能源有限公司 | Lithium ion battery composite diaphragm, preparation method thereof and lithium ion battery |
| CN113675534A (en) * | 2021-08-23 | 2021-11-19 | 长园泽晖新能源材料研究院(珠海)有限公司 | Environment-friendly high-rate coating diaphragm |
| CN113745754A (en) * | 2021-07-29 | 2021-12-03 | 东风汽车集团股份有限公司 | High-heat-resistance diaphragm and preparation method and application thereof |
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| US20170356135A1 (en) * | 2014-12-03 | 2017-12-14 | Imerys Minerales Limited | Coated substrate |
| CN108269956A (en) * | 2016-12-30 | 2018-07-10 | 比亚迪股份有限公司 | A kind of composite membrane of polymer and preparation method thereof and lithium ion battery |
| CN110783516A (en) * | 2019-11-15 | 2020-02-11 | 吉林大学 | Lithium ion battery diaphragm, lithium ion battery and preparation method thereof |
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