CN115020915A - Electrochemical diaphragm, preparation method and electrochemical device - Google Patents
Electrochemical diaphragm, preparation method and electrochemical device Download PDFInfo
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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
-
- 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
- H01M50/431—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
- 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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- 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)
- Materials Engineering (AREA)
- Cell Separators (AREA)
Abstract
The application provides an electrochemical diaphragm, a preparation method and an electrochemical device, wherein the electrochemical diaphragm comprises: a base film; the coating is arranged on at least one side of the thickness direction of the base film and comprises a first coating layer and a second coating layer which are arranged in a stacked mode, and the first coating layer comprises spherical alpha-Al 2 O 3 And spherical gamma-Al 2 O 3 The second coating layer comprises spherical alpha-Al 2 O 3 Linear gamma-Al 2 O 3 And gamma-AlOOH. The electrochemical diaphragm provided by the application adopts the composite coating, and the application of the electrochemical diaphragm to electrolyte is improvedThe chemical diaphragm has the advantages of wettability and high imbibition rate, can facilitate the penetration of conductive ions, improves the electrochemical performance of the battery, has good thermal stability and stable electrochemical window, has high safety of the secondary battery adopting the chemical diaphragm, has simple preparation process, and has great application potential in the aspect of high-safety batteries such as lithium ion batteries.
Description
Technical Field
The application relates to the technical field of electrochemistry, in particular to an electrochemical diaphragm, a preparation method 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 diaphragm 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 electrochemical diaphragm, a preparation method and an electrochemical device, which can improve the wettability of an isolating film on electrolyte.
In a first aspect of embodiments of the present application, there is provided an electrochemical separator including: a base film; a coating layer disposed on at least one side of the base film in a thickness direction thereof, the coating layer including a first coating layer and a second coating layer disposed in a stacked manner, the first coating layer including spherical alpha-Al 2 O 3 And spherical gamma-Al 2 O 3 The second coating layer comprises spherical alpha-Al 2 O 3 Linear gamma-Al 2 O 3 And gamma-AlOOH.
Optionally, the number of the first coating layer and the second coating layer in the coating layer is one, and the second coating layer is arranged on one side, far away from the base film, of the first coating layer; or the number of the first coating layer and the second coating layer in the coating is multiple, and the layers are alternately distributed in the thickness direction.
Optionally, the spherical alpha-Al in the first coating layer 2 O 3 And spherical gamma-Al 2 O 3 The ratio is (3.0-5.0) by mass: (5.0-7.0); the spherical alpha-Al in the second coating layer 2 O 3 Linear gamma-Al 2 O 3 And gamma-AlOOH, wherein the mass ratio is (3.0-5.0): (1.0-3.0):(1.0～4.0)。
optionally, the thickness of the first coating layer is 0.5 μm to 5.0 μm; and/or the thickness of the second coating layer is 0.1-5.0 μm.
Optionally, the spherical alpha-Al in the first coating layer 2 O 3 The particle size is 300nm to 800 nm; and/or the spherical gamma-Al 2 O 3 The particle size is 100-500 nm; and/or said linear gamma-Al 2 O 3 The length of the glass is 80-300 nm, and the diameter of the glass is 50-100 nm; and/or the particle size of the gamma-AlOOH is 100-200 nm.
Optionally, the first coating layer and the second coating layer further include a dispersant, and the dispersant includes at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, styrene-butadiene latex, polyvinyl alcohol, and polyurethane.
Optionally, polyvinylidene fluoride is used as the dispersant in the first coating layer and the second coating layer.
Optionally, the base film comprises at least one of a polypropylene film, a polyethylene film, and a propylene-ethylene copolymer film.
Optionally, the wettability of the electrochemical separator satisfies: 90% -120%; the specific capacity meets the following requirements: 190 mAh/g-220 mAh/g; the shrinkage rate satisfies: 0.6-1%; the coating hardness satisfies: 48-58 Hv.
Optionally, the wettability of the electrochemical separator satisfies: 100% -110%; the specific capacity meets the following requirements: 200 mAh/g-210 mAh/g; the shrinkage rate satisfies: 0.6 to 0.9 percent; the coating hardness satisfies: 50 Hv-58 Hv.
In a second aspect of the embodiments of the present application, there is provided a method for preparing a barrier film, including the steps of:
mixing spherical alpha-Al 2 O 3 And spherical gamma-Al 2 O 3 Mixing to obtain a first composite base material, and mixing the first composite base material with a dispersant solution to obtain a first coating layer slurry; mixing spherical alpha-Al 2 O 3 Linear gamma-Al 2 O 3 Mixing the slurry with gamma-AlOOH, grinding to obtain a second composite base material, and mixing the second composite base material with a dispersant solution to obtain a second coating layer slurry; laminating and coating a first coating on at least one side of the base filmAnd drying the coating layer slurry and the second coating layer slurry, and pressing to obtain the electrochemical diaphragm, wherein the number of the first coating layer and the second coating layer is a single layer or multiple layers.
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, the application has at least the following beneficial effects:
the electrochemical diaphragm provided by the application adopts a composite coating, and spherical alpha-Al is arranged in a first coating layer 2 O 3 And spherical gamma-Al 2 O 3 Spherical alpha-Al is provided in the second coating layer 2 O 3 Linear gamma-Al 2 O 3 And gamma-AlOOH containing a hydroxyl functional group, using spherical alpha-Al 2 O 3 The stability and the large lattice energy can improve the strength of the electrochemical diaphragm, and the spherical gamma-Al is utilized 2 O 3 The spherical particles have good fluidity, are easy to disperse, have good particle uniformity, and can increase the coating uniformity of the diaphragm coating layer. Linear gamma-Al 2 O 3 The specific surface area of the coating layer can be increased, the gamma-AlOOH contains hydroxyl functional groups with good hydrophilicity, the wettability of the electrochemical diaphragm on electrolyte is improved, the liquid absorption rate is high, conductive ions can penetrate conveniently, the electrochemical performance of the battery is improved, meanwhile, the thermal stability is good, the electrochemical window is stable, the safety of a secondary battery adopting the chemical diaphragm is high, the preparation process is simple, and the chemical diaphragm has great application potential in the aspect of high-safety batteries such as lithium ion batteries.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required 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 those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic diagram of a diaphragm structure in the present application.
FIG. 2 is a linear form of gamma-Al 2 O 3 Scanning electron microscope image of
FIG. 3 is a scanning electron micrograph of a first composite substrate
FIG. 4 is a scanning electron micrograph of a second composite substrate
In the drawings, the drawings are not necessarily drawn to scale. Wherein, each reference mark in the figure is:
1. a base film; 2. a first coating layer; 3. a second coating layer; 4. is linear gamma-Al 2 O 3 。
Detailed Description
In order to make the application purpose, technical solution and beneficial technical effects of the present application clearer, the present application 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 a few 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 of the present application, it is to be noted that, unless otherwise specified, "above" and "below" are inclusive of the present number, and "plural" 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 diaphragm, 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 diaphragm material and the electrode and the retentivity of the diaphragm 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, conventional alpha-Al 2 O 3 The ceramic has the defects of poor wettability, poor dispersibility and the like, increases the penetration resistance of conductive ions in the internal reaction of the battery, and reduces the electrochemical performance of the battery. While conventional Al is present 2 O 3 The hardness is high, and the coating equipment is easily abraded greatly and pierces through the diaphragm.
Based on this, the inventors have conducted a great deal of research and have aimed at providing an electrochemical separator having good wettability, high liquid absorption rate, good thermal stability, and stable electrochemical window.
Electrochemical separator
An embodiment of the first aspect of the present application provides an electrochemical separator, including: a base film; the coating is arranged on at least one side of the thickness direction of the base film and comprises a first coating layer and a second coating layer which are arranged in a stacked mode, and the first coating layer comprises spherical alpha-Al 2 O 3 And spherical gamma-Al 2 O 3 The second coating layer comprises spherical alpha-Al 2 O 3 Linear gamma-Al 2 O 3 And gamma-AlOOH.
Coating material Al 2 O 3 The crystal structure of (a) is divided into two categories, Face Centered Cubic (FCC) and Hexagonal Close Packed (HCP). According to Al 3+ The difference of crystal lattices can also be changed into Al 2 O 3 Is divided intoThe same crystal form. Al (Al) 2 O 3 The crystal form of (A) is more than ten, and the common crystal form is alpha-Al 2 O 3 、θ-Al 2 O 3 、κ-Al 2 O 3 、γ-Al 2 O 3 、δ-Al 2 O 3 And eta-Al 2 O 3 And the like.
Providing spherical alpha-Al in a first coating layer 2 O 3 And spherical gamma-Al 2 O 3 Wherein, spherical alpha-Al 2 O 3 Is the most stable phase, has larger lattice energy, can improve the strength of the electrochemical diaphragm, and is spherical alpha-Al 2 O 3 The preparation cost is low, and the cost can be reduced; gamma-Al 2 O 3 The preparation method has the characteristics of good dispersion performance and low hardness, and in addition, the spherical particles have good fluidity and are easy to disperse, the particle uniformity is good, and the coating uniformity of a diaphragm coating layer can be improved. Providing spherical alpha-Al in the second coating layer 2 O 3 Linear gamma-Al 2 O 3 And gamma-AlOOH containing hydroxyl functional groups, wherein all components in the coating layer are mutually wrapped to form a three-dimensional interwoven coating layer structure, and the spherical alpha-Al 2 O 3 Linear gamma-Al for enhancing strength of coating 2 O 3 The method is used for increasing the specific surface area of the coating layer, and the gamma-AlOOH contains hydroxyl functional groups with good hydrophilicity, so that the wettability and the liquid absorption rate of the electrochemical diaphragm to electrolyte can be enhanced.
In the embodiment of the application, spherical alpha-Al in the first coating layer 2 O 3 And spherical gamma-Al 2 O 3 Scanning Electron microscopy after mixing referring to FIG. 3, spherical α -Al in the second coating layer 2 O 3 Linear gamma-Al 2 O 3 FIG. 4 shows a scanning electron microscope image of the mixture of gamma-AlOOH with hydroxyl functional groups, and FIG. 2 shows linear gamma-Al 2 O 3 Scanning electron microscope image (c).
The electrochemical diaphragm provided by the application adopts the composite coating, and solves the problem of conventional alpha-Al 2 O 3 The problem of high hardness is solved, the wettability of the electrochemical diaphragm to the electrolyte is improved, the liquid absorption rate is high, the penetration of conductive ions can be facilitated, and the improvement is convenientThe electrochemical performance of the battery is improved, the thermal stability is good, the electrochemical window is stable, the safety of the secondary battery adopting the chemical diaphragm is high, the preparation process is simple, and the chemical diaphragm has great application potential in the aspect of high-safety batteries such as lithium ion batteries.
In some embodiments, the number of layers of the first coating layer and the second coating layer in the coating layer is one, and the second coating layer is arranged on one side of the first coating layer far away from the base film; or the number of the first coating layer and the second coating layer in the coating is multiple, and the first coating layer and the second coating layer are alternately distributed in the thickness direction.
In the embodiment of the present application, the number of layers of the first coating layer and the second coating layer is not limited, and both the first coating layer and the second coating layer may be one layer, and the second coating layer is disposed on one side of the first coating layer, which is far away from the base film, as shown in fig. 1, or may be multiple layers, and the multiple layers of the first coating layer and the multiple layers of the second coating layer are alternately distributed in the thickness direction of the electrochemical diaphragm.
In some embodiments, the spherical alpha-Al in the first coating layer 2 O 3 And spherical gamma-Al 2 O 3 The ratio is (3.0-5.0) by mass: (5.0-7.0); spherical alpha-Al in the second coating layer 2 O 3 Linear gamma-Al 2 O 3 And gamma-AlOOH, the mass ratio is (3.0-5.0): (1.0-3.0): (1.0-4.0).
In the embodiment of the application, the mass ratio of the components in the coating is controlled within a proper range, so that the wettability and the strength are improved, and the coating with high strength, good dispersibility and good wettability is formed.
In some embodiments, the thickness of the first coating layer is 0.5 μm to 5.0 μm; and/or the thickness of the second coating layer is 0.1-5.0 μm.
In the embodiment of the application, the thickness of each coating layer is controlled within a proper range, so that the wettability and the strength are improved, the permeability of ions in electrolyte in the coating layers is improved, and the excellent cycle performance of the secondary battery is ensured.
In some embodiments, spherical alpha-Al in the first coating layer 2 O 3 The particle size is 300nm to 800 nm; and/or spherical gamma-Al 2 O 3 The particle size is 100-500 nm; and/or linear gamma-Al 2 O 3 The length of the glass is 80-300 nm, and the diameter of the glass is 50-100 nm; and/or the particle size of the gamma-AlOOH is 100-200 nm.
In the embodiment of the application, the volume average particle size of the non-conductive particles is in a proper range, so that the prepared coating layer slurry can obtain a stable dispersion state, the coating layer slurry has high shearing resistance in the coating process, the particles are uniformly stacked in the coating process, and the improvement of the permeability of ions in electrolyte is facilitated.
In some embodiments, the first coating layer and the second coating layer further include a dispersant, and the dispersant includes at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, styrene-butadiene latex, polyvinyl alcohol, and polyurethane.
In the embodiment of the application, the dispersing agent can improve the dispersibility of each component in the coating layer, and can improve the bonding strength of the coating layer on the surface of the base film, so that the coating particles can be prevented from falling off in the winding process of the battery, and the swelling and dissolution of the coating layer in the electrolyte can be inhibited, thereby preventing the influence of the falling of the coating layer on the circulation and high-temperature storage of the battery.
In some embodiments, polyvinylidene fluoride is used as the dispersing agent in the first coating layer and the second coating layer, and the polyvinylidene fluoride has the advantages of low density, good fluidity and the like.
In some embodiments, the base film comprises at least one of a polypropylene film, a polyethylene film, and a propylene-ethylene copolymer film.
In some embodiments, the wettability of the electrochemical separator satisfies: 90% -120%; the specific capacity meets the following requirements: 190 mAh/g-220 mAh/g; the shrinkage rate satisfies: 0.6-1%; the coating hardness satisfies: 48-58 Hv.
Optionally, the wettability of the electrochemical separator satisfies: 100% -110%; the specific capacity meets the following requirements: 200 mAh/g-210 mAh/g; the shrinkage rate satisfies: 0.6 to 0.9 percent; the coating hardness satisfies: 50 Hv-58 Hv.
The wetting property is characterized by the liquid absorption amount, which is measured by the electrolyte. The release film sample was cut into a square of 2cm x 2cm,m1 was weighed using lmol/L LiPF as electrolyte 6 . The electrolyte system is Ethylene Carbonate (EC): dimethyl carbonate (DMC): diethyl carbonate (EMC) ═ 1: 1: 1(V/V), the sample film was immersed in the electrolyte for 30min and then taken out, the electrolyte on the surface of the sample film was sucked off by a filter paper, M2 was weighed, and the wettability was calculated according to the following equation.
The calculation formula is as follows: p ═ M2-M1)/M1 × 100%
In the formula: ml-base film mass (g); m2-mass after soaking (g).
The wettability of the electrochemical diaphragm provided by the embodiment of the application meets the following requirements: the wettability may be, for example, 100%, 101%, 102%, 103%, 104%, 105%, 106%, 107%, 108%, 109%, or 110% or may be in any combination of the above values, 100% to 110%.
The specific capacity determination method in the application comprises the following steps: the positive electrode part of the battery is made of active material LiCoO 2 Uniformly 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 LiPF 6 The 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.
The specific capacitance of the electrochemical diaphragm provided by the embodiment of the application meets the following requirements: 200 mAh/g-210 mAh/g, for example, the specific capacitance can be 200mAh/g, 201mAh/g, 202mAh/g, 303mAh/g, 204mAh/g, 205mAh/g, 206mAh/g, 207mAh/g, 208mAh/g, 209mAh/g or 210mAh/g, and can also be any combination range of the above values.
The shrinkage rate measuring method of the present application:
(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 calculation was 100%.
The shrinkage rate of the electrochemical diaphragm provided by the embodiment of the application meets the following requirements: 0.6% to 0.9%, for example, the shrinkage may be 0.6%, 0.7%, 0.8%, or 0.9%, or may be in any combination of the above values.
This application adopts the vickers hardness tester to measure coating hardness, and the coating hardness of the electrochemistry diaphragm that this application embodiment provided satisfies: the coating hardness may be, for example, 50Hv to 58Hv, 50Hv, 51Hv, 52Hv, 53Hv, 54Hv, 55Hv, 56Hv, 57Hv or 58Hv, or may be any combination of these values.
Compared with the traditional diaphragm, the electrochemical diaphragm in the embodiment of the application has excellent wettability, smaller shrinkage and better specific capacity, and meanwhile, the hardness of the coating is reduced, so that the electrochemical performance of the battery is improved.
In some embodiments, the kind of the base film is not particularly limited, and may be selected according to actual requirements, and any known porous structure film having good chemical stability and mechanical stability may be selected. For example, the fiber may be one or more selected from polyethylene, polypropylene, polyvinylidene fluoride-hexafluoropropylene, polyimide, polyethylene terephthalate, polysulfone, and aromatic polyamide fiber. From the viewpoint of film-forming properties, it is preferable that the base film is selected from polyethylene and copolymers thereof.
Embodiments of the second aspect of the present application provide a method of preparing an electrochemical separator, including mixing spherical alpha-Al 2 O 3 And spherical gamma-Al 2 O 3 Mixing to obtain a first composite base material, and mixing the first composite base material with a dispersant solution to obtain a first coating layer slurry; mixing spherical alpha-Al 2 O 3 Linear gamma-Al 2 O 3 And gamma-AMixing and grinding lOOH to obtain a second composite base material, and mixing the second composite base material with a dispersant solution to obtain a second coating layer slurry; and coating a first coating layer slurry and a second coating layer slurry on at least one side of the base film in a laminating manner, drying and pressing to obtain the electrochemical diaphragm, wherein the number of the first coating layer and the second coating layer is single layer or multiple layers.
The preparation method provided by the embodiment of the application has the characteristics of simple process, low cost and environmental friendliness.
Embodiments of the third aspect of the present application provide an electrochemical device comprising an electrochemical separator as described above.
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, a magnesium ion battery cell, or the like, which is not limited in this application. The battery cell 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 electrochemical diaphragm:
preparing first coating layer slurry: 0.4g of polyvinylidene fluoride (PVDF) was weighed and dissolved in 9.6g of anhydrous N-methylpyrrolidone (NMP), and stirred at room temperature for 4 hours to obtain a PVDF solution with a mass fraction of 5%. The particle diameter of 3.0gSpherical alpha-Al of 300nm 2 O 3 And 7.0g of spherical gamma-Al having a particle diameter of 200nm 2 O 3 And respectively adding the PVDF solution into the mixture to mix, stirring the mixture for 10 hours at room temperature, and carrying out ultrasonic treatment for 1.5 hours to obtain first coating layer slurry.
Preparing a second coating layer slurry: 0.1g of polyvinylidene fluoride (PVDF) was weighed and dissolved in 5.6g of anhydrous N-methylpyrrolidone (NMP), and stirred at room temperature for 4 hours to obtain a PVDF solution with a mass fraction of 3%. 3.0g of spherical alpha-Al with a particle size of 300nm 2 O 3 3.0g of linear gamma-Al having a length of 80nm and a diameter of 50nm 2 O 3 And 4.0g of gamma-AlOOH with the particle size of 100nm is added into the PVDF solution for mixing, the PVDF solution is used as a dispersing agent, the mixture is ground for 8 hours at room temperature by using a high-energy ball mill, the composite is mixed with the PVDF solution, the mixture is stirred for 10 hours at room temperature, and ultrasonic treatment is carried out for 1.0 hour to obtain second coating layer slurry.
Coating: uniformly coating the first coating layer slurry on two sides of a 7-micron-thick polyethylene diaphragm by using a scraper, controlling the thickness of the first coating layer to be 1 micron, after a large amount of solvent is volatilized, placing the first coating layer slurry in a vacuum oven for vacuum drying at 70 ℃ for 10 hours, and pressing the first coating layer slurry for 30 seconds by using a hot press under the pressure of 4MPa after drying. And uniformly coating the second coating layer on one side, far away from the base film, of the first coating layer by using a scraper, controlling the thickness of the second coating layer to be 0.6 mu m, after a large amount of solvent is volatilized, placing the second coating layer in a vacuum oven for vacuum drying at 70 ℃ for 10 hours, pressing the second coating layer for 50 seconds by using a hot press under the pressure of 4MPa after drying, and placing the second coating layer in a glove box for storage to obtain the electrochemical diaphragm.
Example 2
Preparing an electrochemical diaphragm:
preparing first coating layer slurry: 0.4g of polyvinylidene fluoride (PVDF) was weighed and dissolved in 9.6g of anhydrous N-methylpyrrolidone (NMP), and stirred at room temperature for 4 hours to obtain a PVDF solution with a mass fraction of 5%. 4.0g of spherical alpha-Al with a particle size of 400nm 2 O 3 And 6.0g of spherical gamma-Al having a particle size of 400nm 2 O 3 And respectively adding the PVDF solution into the mixture to mix, stirring the mixture for 10 hours at room temperature, and carrying out ultrasonic treatment for 1.5 hours to obtain first coating layer slurry.
Preparation of the secondCoating layer slurry: 0.1g of polyvinylidene fluoride (PVDF) was weighed and dissolved in 5.6g of anhydrous N-methylpyrrolidone (NMP), and stirred at room temperature for 4 hours to obtain a PVDF solution with a mass fraction of 3%. 4.0g of spherical alpha-Al with a particle size of 400nm 2 O 3 2.0g of linear gamma-Al having a length of 100nm and a diameter of 60nm 2 O 3 And 4.0g of gamma-AlOOH with the particle size of 150nm is added into the PVDF solution for mixing, the PVDF solution is used as a dispersing agent, the PVDF solution is ground for 8 hours at room temperature by using a high-energy ball mill, then the composite and the PVDF solution are mixed, stirred for 10 hours at room temperature, and subjected to ultrasonic treatment for 1.0 hour to obtain second coating layer slurry.
Coating: uniformly coating the first coating layer slurry on two sides of a 7-micron-thick polyethylene diaphragm by using a scraper, controlling the thickness of the first coating layer to be 2 microns, after a large amount of solvent is volatilized, placing the first coating layer slurry in a vacuum oven for vacuum drying at 70 ℃ for 10 hours, and pressing the first coating layer slurry for 30 seconds by using a hot press under the pressure of 4MPa after drying. And uniformly coating the second coating layer on one side, far away from the base film, of the first coating layer by using a scraper, controlling the thickness of the second coating layer to be 1 mu m, after a large amount of solvent is volatilized, placing the second coating layer in a vacuum oven for vacuum drying at 70 ℃ for 10 hours, pressing the second coating layer for 50 seconds by using a hot press under the pressure of 4MPa after drying, and placing the second coating layer in a glove box for storage to obtain the electrochemical diaphragm.
Example 3
Preparing an electrochemical diaphragm:
preparing first coating layer slurry: 0.4g of polyvinylidene fluoride (PVDF) was weighed and dissolved in 9.6g of anhydrous N-methylpyrrolidone (NMP), and stirred at room temperature for 4 hours to obtain a PVDF solution with a mass fraction of 5%. 5.0g of spherical alpha-Al with a particle size of 500nm 2 O 3 And 5.0g of spherical gamma-Al having a particle size of 500nm 2 O 3 And respectively adding the PVDF solution into the mixture to mix, stirring the mixture for 10 hours at room temperature, and carrying out ultrasonic treatment for 1.5 hours to obtain first coating layer slurry.
Preparing a second coating layer slurry: 0.1g of polyvinylidene fluoride (PVDF) was weighed and dissolved in 5.6g of anhydrous N-methylpyrrolidone (NMP), and stirred at room temperature for 4 hours to obtain a PVDF solution with a mass fraction of 3%. 5.0g of spherical alpha-Al with a particle size of 500nm 2 O 3 2.0g of linear gamma-Al having a length of 200nm and a diameter of 60nm 2 O 3 And 3.0g of gamma-AlOOH with the particle size of 200nm is added into the PVDF solution for mixing, the PVDF solution is used as a dispersing agent, the mixture is ground for 8 hours at room temperature by using a high-energy ball mill, the composite is mixed with the PVDF solution, the mixture is stirred for 10 hours at room temperature, and the mixture is subjected to ultrasonic treatment for 1.0 hour to obtain second coating layer slurry.
Coating: uniformly coating the first coating layer slurry on two sides of a 7-micron-thick polyethylene diaphragm by using a scraper, controlling the thickness of the first coating layer to be 3 microns, after a large amount of solvent is volatilized, placing the first coating layer slurry in a vacuum oven for vacuum drying at 70 ℃ for 10 hours, and pressing the first coating layer slurry for 30 seconds by using a hot press under the pressure of 4MPa after drying. And uniformly coating the second coating layer on one side, far away from the base film, of the first coating layer by using a scraper, controlling the thickness of the second coating layer to be 2 micrometers, after a large amount of solvent is volatilized, placing the second coating layer in a vacuum oven for vacuum drying at 70 ℃ for 10 hours, pressing the second coating layer for 50 seconds under the pressure of 4MPa of a hot press after the second coating layer is dried, and placing the second coating layer in a glove box for storage to obtain the electrochemical diaphragm.
Example 4
Preparing an electrochemical diaphragm:
preparing first coating layer slurry: 0.4g of polyvinylidene fluoride (PVDF) was weighed and dissolved in 9.6g of anhydrous N-methylpyrrolidone (NMP), and stirred at room temperature for 4 hours to obtain a PVDF solution with a mass fraction of 5%. 3.0g of spherical alpha-Al with the particle size of 600nm 2 O 3 And 7.0g of spherical gamma-Al having a particle size of 500nm 2 O 3 And respectively adding the PVDF solution into the mixture to mix, stirring the mixture for 10 hours at room temperature, and carrying out ultrasonic treatment for 1.5 hours to obtain first coating layer slurry.
Preparing second coating layer slurry: 0.1g of polyvinylidene fluoride (PVDF) was weighed and dissolved in 5.6g of anhydrous N-methylpyrrolidone (NMP), and stirred at room temperature for 4 hours to obtain a PVDF solution with a mass fraction of 3%. 5.0g of spherical alpha-Al with a particle size of 600nm 2 O 3 3.0g of linear gamma-Al having a length of 300nm and a diameter of 80nm 2 O 3 And 2.0g of gamma-AlOOH with the particle size of 200nm is added into the PVDF solution for mixing, the PVDF solution is used as a dispersing agent, the mixture is ground for 8 hours at room temperature by using a high-energy ball mill, the composite is mixed with the PVDF solution, the mixture is stirred for 10 hours at room temperature, and ultrasonic treatment is carried out for 1.0 hourAnd obtaining second coating layer slurry.
Coating: uniformly coating the first coating layer slurry on two sides of a 7-micron-thick polyethylene diaphragm by using a scraper, controlling the thickness of the first coating layer to be 3 microns, after a large amount of solvent is volatilized, placing the first coating layer slurry in a vacuum oven for vacuum drying at 70 ℃ for 10 hours, and pressing the first coating layer slurry for 30 seconds by using a hot press under the pressure of 4MPa after drying. And uniformly coating the second coating layer on one side, far away from the base film, of the first coating layer by using a scraper, controlling the thickness of the second coating layer to be 2 microns, after a large amount of solvent is volatilized, placing the second coating layer in a vacuum oven for vacuum drying at 70 ℃ for 10 hours, pressing the second coating layer for 50 seconds under the pressure of 4MPa of a hot press after drying, and placing the second coating layer in a glove box for storage to obtain the electrochemical diaphragm.
Example 5
Preparing an electrochemical diaphragm:
preparing first coating layer slurry: 0.4g of polyvinylidene fluoride (PVDF) was weighed and dissolved in 9.6g of anhydrous N-methylpyrrolidone (NMP), and stirred at room temperature for 4 hours to obtain a PVDF solution with a mass fraction of 5%. 3.0g of spherical alpha-Al with a particle size of 400nm 2 O 3 And 7.0g of spherical gamma-Al having a particle size of 400nm 2 O 3 And respectively adding the PVDF solution into the mixture to mix, stirring the mixture for 10 hours at room temperature, and carrying out ultrasonic treatment for 1.5 hours to obtain first coating layer slurry.
Preparing a second coating layer slurry: 0.1g of polyvinylidene fluoride (PVDF) was weighed and dissolved in 5.6g of anhydrous N-methylpyrrolidone (NMP), and stirred at room temperature for 4 hours to obtain a PVDF solution with a mass fraction of 3%. 5.0g of spherical alpha-Al 2 O 3 Adding 3.0g of linear gamma-Al 2O3 and 4.0g of gamma-AlOOH with the particle size of 400nm into the PVDF solution, mixing, grinding for 5-10 hours at room temperature by using the PVDF solution as a dispersing agent and using a high-energy ball mill, mixing the composite with the PVDF solution, stirring for 10 hours at room temperature, and performing ultrasonic treatment for 1.0 hour to obtain second coating layer slurry.
Coating: uniformly coating the first coating layer slurry on two sides of a 7-micron-thick polyethylene diaphragm by using a scraper, controlling the thickness of the first coating layer to be 4 microns, after a large amount of solvent is volatilized, placing the first coating layer slurry in a vacuum oven for vacuum drying for 8-12 hours at 50-80 ℃, and pressing the first coating layer slurry for 30 seconds under the pressure of a hot press at 2-4 MPa after drying. And uniformly coating the second coating layer on one side, far away from the base film, of the first coating layer by using a scraper, controlling the thickness of the second coating layer to be 3 microns, after a large amount of solvent is volatilized, placing the second coating layer in a vacuum oven for vacuum drying for 8-12 hours at 50-80 ℃, pressing the second coating layer for 50 seconds by using a hot press under the pressure of 2-4 MPa, and placing the second coating layer in a glove box for storage to obtain the electrochemical diaphragm.
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 is polyvinylidene fluoride-hexafluoropropylene, the first coating layer and the second coating layer are both two layers and are stacked in the thickness direction of the electrochemical diaphragm.
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 polyvinyl alcohol and a base film propylene-ethylene copolymer film.
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 separator specimen was cut into a 2cm X2 cm square and weighed M1 using an electrolyte of lmol/L LiPF 6 . 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 LiCoO 2 Uniformly 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 drying the slurry, then making the slurry into a circular sheet, and drying the circular sheet in vacuum at 105 ℃ to obtain an electrode sheet, wherein a metal lithium sheet is a negative electrode, and an electrolyte is 1mol/L LiPF 6 The 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 calculation was 100%.
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 shown in table 1, compared with comparative example 1, the separators obtained in examples 1 to 8 of the present application have better shrinkage and specific capacity, and the wetting fluid of the separators obtained in examples 1 to 8 of the present application is significantly better than that of comparative example 1.
Compared with the prior art, in the electrochemical diaphragm, the preparation method of the isolating membrane and the electrochemical device, the composite coating is adopted, so that the problem of conventional alpha-Al is solved 2 O 3 The chemical diaphragm has the advantages of improving the wettability of the electrochemical diaphragm to electrolyte, being high in liquid absorption rate, being convenient for conductive ions to penetrate through, improving the electrochemical performance of the battery, being good in thermal stability and stable in electrochemical window, being high in safety of the secondary battery adopting the chemical diaphragm, being simple in preparation process and having great application potential in the aspect of high-safety batteries such as lithium ion batteries.
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 (12)
1. An electrochemical separator, comprising:
a base film;
a coating layer disposed on at least one side of the base film in a thickness direction thereof, the coating layer including a first coating layer and a second coating layer disposed in a stacked manner, the first coating layer including spherical alpha-Al 2 O 3 And spherical gamma-Al 2 O 3 The second coating layer comprises spherical alpha-Al 2 O 3 Linear gamma-Al 2 O 3 And gamma-AlOOH.
2. The electrochemical separator according to claim 1, wherein the number of layers of the first coating layer and the second coating layer in the coating layer is one, and the second coating layer is disposed on a side of the first coating layer away from the base film; or,
the number of the first coating layer and the second coating layer in the coating is multiple, and the first coating layer and the second coating layer are alternately distributed in the thickness direction.
3. The electrochemical separator of claim 2, wherein the spherical alpha-Al in the first coating layer 2 O 3 And spherical gamma-Al 2 O 3 The ratio is (3.0-5.0) by mass: (5.0-7.0);
the spherical alpha-Al in the second coating layer 2 O 3 Linear gamma-Al 2 O 3 And gamma-AlOOH, the mass ratio is (3.0-5.0): (1.0-3.0): (1.0-4.0).
4. The electrochemical separator according to any one of claims 1 to 3, wherein the thickness of the first coating layer is 0.5 μm to 5.0 μm; and/or
The thickness of the second coating layer is 0.1-5.0 μm.
5. The electrochemical separator according to any one of claims 1 to 3, wherein the spherical alpha-Al in the first coating layer 2 O 3 The particle size is 300nm to 800 nm; and/or
The spherical gamma-Al 2 O 3 The particle size is 100-500 nm; and/or
The linear gamma-Al 2 O 3 The length of the glass is 80-300 nm, and the diameter of the glass is 50-100 nm; and/or
The particle size of the gamma-AlOOH is 100-200 nm.
6. The electrochemical separator according to claim 1, wherein the first and second coating layers further comprise a dispersant, the dispersant comprising at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, styrene butadiene latex, polyvinyl alcohol, and polyurethane.
7. The electrochemical separator according to claim 6, wherein the dispersant in the first coating layer and the second coating layer is polyvinylidene fluoride.
8. The electrochemical separator according to claim 1, wherein the base film comprises at least one of a polypropylene film, a polyethylene film, and a propylene-ethylene copolymer film.
9. An electrochemical separator according to any one of claims 1 to 3, wherein the wettability of the electrochemical separator satisfies: 90% -120%; the specific capacity meets the following requirements: 190 mAh/g-220 mAh/g; the shrinkage rate satisfies: 0.6-1%; the coating hardness satisfies: 48-58 Hv.
10. An electrochemical separator according to any one of claims 1 to 3, wherein the wettability of the electrochemical separator satisfies: 100 to 110 percent; the specific capacity meets the following requirements: 200 mAh/g-210 mAh/g; the shrinkage rate satisfies: 0.6 to 0.9 percent; the coating hardness satisfies: 50 Hv-58 Hv.
11. A method for preparing an electrochemical separator, comprising the steps of:
mixing spherical alpha-Al 2 O 3 And spherical gamma-Al 2 O 3 After mixing, obtaining a first composite base material, and mixing the first composite base material with the dispersant solution to obtain a first coating layer slurry;
mixing spherical alpha-Al 2 O 3 Linear gamma-Al 2 O 3 Mixing the slurry with gamma-AlOOH, grinding to obtain a second composite base material, and mixing the second composite base material with the dispersant solution to obtain a second coating layer slurry;
and coating the first coating layer slurry and the second coating layer slurry on at least one side of the base film in a laminating manner, drying and pressing to obtain the electrochemical diaphragm, wherein the number of the first coating layer and the second coating layer is single layer or multiple layers.
12. An electrochemical device comprising an electrochemical separator according to any one of claims 1 to 10.
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| CN116111281B (en) * | 2023-04-10 | 2023-06-27 | 宁德新能源科技有限公司 | Separator, electrochemical device and electronic device |
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