CN114709562A - Separator, method for producing separator, and electrochemical device - Google Patents
Separator, method for producing separator, and electrochemical device Download PDFInfo
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- CN114709562A CN114709562A CN202210631790.8A CN202210631790A CN114709562A CN 114709562 A CN114709562 A CN 114709562A CN 202210631790 A CN202210631790 A CN 202210631790A CN 114709562 A CN114709562 A CN 114709562A
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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
- H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
- H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
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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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
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- 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
- H01M50/491—Porosity
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Abstract
The invention discloses an isolation membrane, a preparation method of the isolation membrane and an electrochemical device. The invention provides a separation film, comprising: a base film; the first coating layer is coated on at least one side of the base film in the thickness direction and adopts inorganic oxide with a first particle size and a temperature-resistant high polymer resin material; the second coating layer is coated on one side, far away from the base film, of the first coating layer and is made of inorganic oxide with a second particle size and a temperature-resistant high polymer resin material; the melting point of the temperature-resistant polymer resin material in the first coating layer is higher than that of the temperature-resistant polymer resin material in the second coating layer, and the first particle size is larger than the second particle size. Through the coating of two-layer different materials, according to the melting point difference of different coatings, make different coatings melt in proper order, can provide the ability of self-closing aperture for the barrier film to give battery work buffering space, reduce the high temperature in the battery and block in the twinkling of an eye to the barrier film hole sealing in the twinkling of an eye unusually.
Description
Technical Field
The invention relates to the technical field of batteries, in particular 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 safety performance of the battery.
Disclosure of Invention
The invention aims to provide a separation membrane, a separation membrane preparation method and an electrochemical device, which can improve the mechanical strength of the obtained separation membrane, thereby improving the safety performance of a secondary battery.
In a first aspect of the embodiments of the present invention, there is provided an isolation film, including:
a base film;
the first coating layer is coated on at least one side of the base film in the thickness direction and is made of inorganic oxide and a temperature-resistant high polymer resin material;
the second coating layer is coated on one side, far away from the base film, of the first coating layer and is made of inorganic oxide and a temperature-resistant high polymer resin material;
the first coating layer and the second coating layer are made of temperature-resistant high polymer resin materials with different melting points; the average particle size D50 of the inorganic oxide in the first coating layer and the second coating layer is a first particle size and a second particle size respectively, and the first particle size is larger than the second particle size.
Adopt above-mentioned structure, through the coating of two-layer different materials, according to the melting point difference of different coatings, make different coatings melt in proper order, can provide the ability in self-closing aperture for the barrier film to give battery work buffering space, reduce in the battery and seal the hole in the twinkling of an eye at high temperature anomaly in the twinkling of an eye and block, make the barrier film deformation lead to the battery short circuit to take place the detonation. Secondly, the inorganic oxide and the polymer resin material with the gradient particle size are arranged, so that the polymer resin material serving as the adhesive on the coating layer on the surface of the isolating membrane is firstly melted under the high-temperature condition, the inorganic oxide with the small particle size in the second coating layer is released, gaps among the inorganic oxides with the large particle size in the first coating layer are effectively filled, the positive electrode and the negative electrode of the battery are finally and thoroughly separated, the condition of electrochemical reaction of the battery is lost, the blocking process has an obvious gradient process, a buffer space can be provided for high-temperature blocking, the instantaneous loss is reduced, and the high-temperature safety performance of the battery is effectively guaranteed.
In some alternative embodiments of the invention, the first particle size is 25nm to 65nm and the second particle size is 20nm to 60 nm.
In some alternative embodiments of the present invention, the difference between the first particle size and the second particle size is 3nn to 10nm, and more preferably 5 nm.
By adopting the structure, the space for blocking and buffering can be controlled through the difference value of the first particle size and the second particle size, if the difference value is smaller, the space for blocking and buffering is smaller, the difference value is larger, the space for blocking and buffering in a certain interval is larger, but when the difference value exceeds a certain threshold value, the inorganic oxide particles with the second particle size are difficult to fill the gaps among the first particle sizes, and the blocking effect is lost.
In some alternative embodiments of the present invention, the inorganic oxide in the first coating layer is 55 to 70wt% by mass, and the inorganic oxide in the second coating layer is 30 to 45wt% by mass.
In some alternative embodiments of the present invention, the first coating layer has a thickness of 0.5 μm to 1.5 μm, and the second coating layer has a thickness of 1 μm to 2 μm.
In some alternative embodiments of the present invention, the inorganic oxide in the first and second coating layers is spherical or spheroidal.
In some alternative embodiments of the present invention, the inorganic oxide is at least one of alumina and titania.
In some alternative embodiments of the present invention, the base film is at least one of polyethylene, polypropylene and polyimide.
In some optional embodiments of the present invention, the temperature-resistant polymer resin is at least one of polyethylene, polypropylene and polyvinyl chloride, and the material of the temperature-resistant polymer resin in the second coating layer is different from that of the temperature-resistant polymer resin in the first coating layer.
Adopt above-mentioned scheme, because first coating and second coating need realize the melting process of gradient, so choose different materials for use, can further differentiate the hot melt temperature of first coating and second coating, provide gradient hot melt space, realize blocking the setting in buffering space, reduce instantaneous loss.
In some optional embodiments of the present invention, a melting point of the temperature-resistant polymer resin material in the first coating layer is higher than a melting point of the temperature-resistant polymer resin material in the second coating layer.
In some optional embodiments of the present invention, the temperature-resistant polymer resin in the first coating layer accounts for 30wt% to 45wt% by mass, and the temperature-resistant polymer resin in the second coating layer accounts for 55wt% to 70wt% by mass.
In a second aspect of the embodiments of the present invention, there is provided a method for preparing the above-mentioned isolation film, including the following steps:
providing a base film;
coating a first coating layer on at least one side of the base film;
coating a second coating layer on the side of the first coating layer away from the base film;
and (5) drying and shaping.
In a third aspect of the embodiments of the present invention, there is provided an electrochemical device including the above separator.
The invention has the following beneficial effects:
(1) compared with the prior art, in the preparation method of the isolating membrane and the isolating membrane, two coating layers made of different materials are arranged, different coating layers are sequentially melted according to different melting points of different coating layers, the capability of automatically closing the aperture can be provided for the isolating membrane, a working buffer space is provided for a battery, instantaneous loss of the sealing holes of the isolating membrane at the moment of high-temperature abnormity of the battery is effectively prevented, and deflagration caused by the deformation of the isolating membrane at the moment of high-temperature abnormity can be prevented.
(2) According to the preparation method of the isolating membrane and the isolating membrane provided by the embodiment of the invention, the inorganic oxide and the polymer resin material with gradient particle sizes are arranged, so that the polymer resin material serving as an adhesive on the coating layer on the surface of the isolating membrane is firstly melted under a high-temperature condition, the inorganic oxide with small particle size in the second coating layer is released, gaps among the inorganic oxides with large particle size in the first coating layer are effectively filled, the positive electrode and the negative electrode of the battery are finally and thoroughly separated, the battery loses the condition of electrochemical reaction, the blocking process has an obvious gradient process, a buffer space can be provided for high-temperature blocking, the instantaneous loss is reduced, and the high-temperature safety performance of the battery is effectively guaranteed.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a sectional view of a separator in the thickness direction in the present invention;
fig. 2 is an enlarged schematic view of a portion a in fig. 1.
Reference numerals:
1. a base film; 2. a first coating layer; 3. a second coating layer.
Detailed Description
In order to make the objects, technical solutions and advantageous technical effects of the present invention more clear, 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 invention and are not intended to limit the present invention.
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 inventive composition also consists essentially of or consists of that component, and that the inventive process also consists essentially of or consists of that 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 invention is not intended to describe each disclosed embodiment or every implementation of the present invention. 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 key 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 related technology, the coating material on the conventional isolating membrane has high temperature resistance, and can effectively prevent the battery spontaneous combustion accident caused by overheating inside the battery. However, in practical use, the inventor of the present invention finds that when a high temperature condition occurs inside a battery, a coating layer formed by compounding an adhesive and ceramic particles adopted in a conventional isolating membrane is prone to occur, and the ceramic is resistant to high temperature, so that the aperture on the isolating membrane is closed, the positive electrode and the negative electrode in the battery are completely separated, the electrochemical reaction path is completely lost, an instant power failure phenomenon is caused, and thus, an instant power failure loss is caused to a power terminal device, and even the battery is subjected to deflagration.
The inventor of the invention finds that by arranging different types of polymer resins as adhesives and utilizing different hot melting temperature characteristics of different polymer resins, a gradient temperature difference is formed, buffer intervals are provided in different temperature intervals, and loss caused by instant power failure is reduced.
As shown in fig. 1 and 2, fig. 1 is a cross-sectional view of a separator in the present invention along a thickness direction, and fig. 2 is an enlarged schematic view of a portion a in fig. 1. The embodiment of the invention provides a separation film, which comprises a base film 1, a first coating layer 2 and a second coating layer 3. The first coating layer 2 is coated on at least one side of the base film 1 in the thickness direction (x-axis direction in fig. 1), and is made of inorganic oxide with a first particle size and a temperature-resistant polymer resin material. The second coating layer 3 is coated on one side of the first coating layer 2 far away from the base 1 film, and inorganic oxide and temperature-resistant high polymer resin materials with second particle sizes are adopted, wherein the first particle size and the second particle size are respectively the average particle size D50 of the inorganic oxide in the first coating layer 2 and the second coating layer 3. And the first particle size is larger than the second particle size.
Through the coating of two-layer different materials, according to the melting process difference of different coatings, make different coatings melt in proper order, can provide the ability in self-closing aperture for the barrier film, give battery work buffering space, prevent effectively that the battery from in the twinkling of an eye that the high temperature is unusual, cause instantaneous loss to the barrier film hole sealing, can also prevent simultaneously that the high temperature is unusual in the twinkling of an eye, make the barrier film deformation lead to the battery short circuit to take place the detonation. Secondly, the inorganic oxide and the polymer resin material with the gradient particle size are arranged, so that the polymer resin material serving as the adhesive on the coating layer on the surface of the isolating membrane is firstly melted under the high-temperature condition, the inorganic oxide with the small particle size in the second coating layer is released, gaps among the inorganic oxides with the large particle size in the first coating layer are effectively filled, the positive electrode and the negative electrode of the battery are finally and thoroughly separated, the condition of electrochemical reaction of the battery is lost, and the high-temperature safety performance of the battery is effectively guaranteed.
In some alternative embodiments of the invention, the first particle size is from 25nm to 65nm and the second particle size is from 20nm to 60 nm.
The size of the difference between the first particle size and the second particle size can control the space of the blocking buffer, and if the difference between the first particle size and the second particle size is smaller, the space of the blocking buffer is smaller, the difference between the first particle size and the second particle size is larger, the space of the blocking buffer in a certain interval is larger, but when the difference exceeds a certain threshold value, the inorganic oxide particles with the second particle size are difficult to fill the gaps between the first particle size, and the blocking effect is lost.
In some alternative embodiments of the present invention, the inorganic oxide in the first coating layer accounts for 55wt% to 70wt% by mass, and the inorganic oxide in the second coating layer accounts for 30wt% to 45wt% by mass.
In some alternative embodiments of the present invention, the thickness of the first coating layer is 0.5 μm to 1.5 μm, and the thickness of the second coating layer is 1 μm to 2 μm.
In some alternative embodiments of the present invention, the inorganic oxide in the first coating layer and the second coating layer is spherical or spheroidal.
By arranging the inorganic oxide in the first coating layer and the second coating layer to be spherical or spheroidal, for example, the spheroidal can be olive-shaped, ellipsoid-shaped or the like, a network can be formed under the support of the adhesive, and the obtained gaps on the network are uniform, so that when the adhesive is melted, the inorganic oxide with small particle size can be more easily filled into the gaps among the inorganic oxides with large particle size.
In some alternative embodiments of the present invention, the inorganic oxide is at least one of alumina and titania.
In some alternative embodiments of the present invention, the base film is at least one of polyethylene, polypropylene, and polyimide.
In some optional embodiments of the present invention, the temperature-resistant polymer resin is at least one of polyethylene, polypropylene and polyvinyl chloride.
The adhesive is made of polyethylene, polypropylene and polyvinyl chloride, so that the physical properties of the base film and the adhesive are similar or identical, the problems of different physical properties and low compatibility caused by the fact that polyvinylidene fluoride is generally adopted as the adhesive in the related technology can be effectively solved, and the defects of poor dispersion property and easy uneven coating of polyvinylidene fluoride are overcome.
In some alternative embodiments of the present invention, the temperature-resistant polymer resin in the second coating layer and the first coating layer are made of different materials.
Because the melting process of gradient need be realized with the second coating to first coating, select for use different materials, can further differentiate the hot melt temperature of first coating and second coating, provide gradient hot melt space, realize blocking the setting in buffering space, reduce instantaneous loss.
In some optional embodiments of the present invention, the temperature-resistant polymer resin in the first coating layer is 30wt% to 45wt% by mass, and the temperature-resistant polymer resin in the second coating layer is 55wt% to 70wt% by mass.
In some alternative embodiments of the present invention, there is also provided a method of preparing a separator film, comprising the steps of:
s01, providing a base film;
s02, coating a first coating layer on at least one side of the base film;
s03, coating a second coating layer on the side, far away from the base film, of the first coating layer;
and S04, drying and shaping.
In some alternative embodiments of the present invention, there is also provided an electrochemical device including the above-described separator.
Specifically, the electrochemical device can be a single battery, and at least includes a housing, and a pole piece assembly disposed in the housing, where the pole piece assembly includes a positive pole piece, a negative pole piece, and an isolation film disposed therebetween. The battery cell may be a secondary battery cell or a primary battery cell, or may be a lithium ion battery cell, a sodium ion battery cell, a magnesium ion battery cell, or the like, which is not limited in the embodiment of the present invention. 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 illustrations only, since various modifications and changes 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:
taking a polyethylene base film with the thickness of 7 mu m, the porosity of 40% and the pore diameter of 10nm, mixing titanium oxide with the average particle size D50 of 25nm and polypropylene, by mass, 70wt% of titanium oxide and 30wt% of polypropylene to obtain a first coating layer coating, coating the first coating layer coating on the surface of the base film to form a first coating layer, wherein the thickness of the first coating layer is 0.5 mu m, mixing titanium oxide with the average particle size D50 of 20nm and polyvinyl chloride with the mass of 45wt% of titanium oxide and 65wt% of polyvinyl chloride to obtain a second coating layer coating, coating the second coating layer coating on the surface, far away from the base film, of the first coating layer to form a second coating layer, wherein the thickness of the second coating layer is 1 mu m, and drying and shaping to obtain the isolating film.
Example 2
Preparing an isolating membrane:
taking a polyethylene base film with the thickness of 7 mu m, the porosity of 40 percent and the pore diameter of 10nm, mixing titanium oxide with the average particle size D50 of 35nm and polypropylene with 65wt percent of titanium oxide and 35wt percent of polypropylene by mass to obtain a first coating layer coating, coating the first coating layer coating on the surface of the base film to form a first coating layer, wherein the thickness of the first coating layer is 0.8 mu m, mixing titanium oxide with the average particle size D50 of 30nm and polyvinyl chloride with 40wt percent of titanium oxide and 60wt percent of polyvinyl chloride by mass to obtain a second coating layer coating, coating the second coating layer coating on the surface, far away from the base film, of the first coating layer to form a second coating layer, wherein the thickness of the second coating layer is 1.2 mu m, and drying and shaping to obtain the isolating film.
Example 3
Preparing an isolating membrane:
taking a polyethylene base film with the thickness of 7 mu m, the porosity of 40 percent and the pore diameter of 10nm, mixing titanium oxide with the average particle size of 45nm with polypropylene, mixing 65wt percent of titanium oxide and 35wt percent of polypropylene by mass to obtain a first coating layer coating, coating the first coating layer coating on the surface of the base film to form a first coating layer, wherein the thickness of the first coating layer is 1.0 mu m, mixing titanium oxide with the average particle size D50 of 40nm with polyvinyl chloride, mixing 40wt percent of titanium oxide and 60wt percent of polyvinyl chloride by mass to obtain a second coating layer coating, coating the second coating layer coating on the surface, far away from the base film, of the first coating layer to form a second coating layer, wherein the thickness of the second coating layer is 1.5 mu m, and drying and shaping to obtain the isolating film.
Example 4
Preparing an isolating membrane:
taking a polyethylene base film with the thickness of 7 mu m, the porosity of 40 percent and the pore diameter of 10nm, mixing titanium oxide with the average particle size D50 of 55nm and polypropylene with 60wt percent of titanium oxide and 40wt percent of polypropylene by mass to obtain a first coating layer coating, coating the first coating layer coating on the surface of the base film to form a first coating layer, wherein the thickness of the first coating layer is 1.2 mu m, mixing titanium oxide with the average particle size D50 of 50nm and polyvinyl chloride with 40wt percent of titanium oxide and 60wt percent of polyvinyl chloride by mass to obtain a second coating layer coating, coating the second coating layer coating on the surface, far away from the base film, of the first coating layer to form a second coating layer, wherein the thickness of the second coating layer is 1.8 mu m, and drying and shaping to obtain the isolating film.
Example 5
Preparing an isolating membrane:
taking a polyethylene base film with the thickness of 7 mu m, the porosity of 40% and the pore diameter of 10nm, mixing 55wt% of titanium oxide and 45wt% of polypropylene with titanium oxide with the average particle size D50 of 65nm by mass to obtain a first coating layer coating, coating the first coating layer coating on the surface of the base film to form a first coating layer, wherein the thickness of the first coating layer is 1.5 mu m, mixing 30wt% of titanium oxide and 70wt% of polyvinyl chloride with titanium oxide with the average particle size D50 of 60nm by mass to obtain a second coating layer coating, coating the second coating layer coating on the surface, far away from the base film, of the first coating layer to form a second coating layer, wherein the thickness of the second coating layer is 2 mu m, and drying and shaping to obtain the isolating film.
Example 6
Preparing an isolating membrane:
taking a polyethylene base film with the thickness of 7 mu m, the porosity of 40% and the pore diameter of 10nm, mixing 55wt% of titanium oxide and 45wt% of polyethylene with the average particle size D50 of 65nm by mass to obtain a first coating layer coating, coating the first coating layer coating on the surface of the base film to form a first coating layer, mixing 30wt% of titanium oxide and 70wt% of polypropylene with the average particle size D50 of 60nm by mass to obtain a second coating layer coating, coating the second coating layer coating on the surface, far away from the base film, of the first coating layer to form a second coating layer, wherein the thickness of the second coating layer is 2 mu m, and drying and shaping to obtain the isolating film.
Example 7
Preparing an isolating membrane:
taking a polyethylene base film with the thickness of 7 mu m, the porosity of 40% and the pore diameter of 10nm, mixing 55wt% of titanium oxide and 45wt% of polyvinyl chloride by mass with titanium oxide with the average particle size D50 of 65nm to obtain a first coating layer coating, coating the first coating layer coating on the surface of the base film to form a first coating layer, coating the first coating layer coating with the thickness of 1.5 mu m, mixing 30wt% of titanium oxide and 70wt% of polyethylene by mass with titanium oxide with the average particle size D50 of 60nm to obtain a second coating layer coating, coating the second coating layer coating on the surface of the first coating layer far away from the base film to form a second coating layer, and drying and shaping to obtain the isolating film, wherein the second coating layer is 2 mu m in thickness.
Example 8
Preparing an isolating membrane:
taking a polyethylene base film with the thickness of 7 mu m, the porosity of 40% and the pore diameter of 10nm, mixing 55wt% of alumina and 45wt% of polypropylene by mass with alumina with the average particle size D50 of 65nm to obtain a first coating layer coating, coating the first coating layer coating on the surface of the base film to form a first coating layer, wherein the thickness of the first coating layer is 1.5 mu m, mixing 30wt% of alumina and 70wt% of polyvinyl chloride by mass with alumina with the average particle size D50 of 60nm to obtain a second coating layer coating, coating the second coating layer coating on the surface, far away from the base film, of the first coating layer to form a second coating layer, wherein the thickness of the second coating layer is 2 mu m, and drying and shaping to obtain the isolating film.
Example 9
Preparing an isolating membrane:
taking a polypropylene base film with the thickness of 7 mu m, the porosity of 40 percent and the pore diameter of 10nm, mixing 55wt percent of alumina and 45wt percent of polypropylene by using alumina with the average particle size D50 of 65nm and polypropylene by mass to obtain a first coating layer coating, coating the first coating layer coating on the surface of the base film to form a first coating layer, wherein the thickness of the first coating layer is 1.5 mu m, mixing 30wt percent of alumina and 70wt percent of polyvinyl chloride by using alumina with the average particle size D50 of 60nm to obtain a second coating layer coating, coating the second coating layer coating on the surface, far away from the base film, of the first coating layer to form a second coating layer, wherein the thickness of the second coating layer is 2 mu m, and drying and shaping to obtain the isolating film.
Example 10
Preparing an isolating membrane:
taking a polyimide base film with the thickness of 7 mu m, the porosity of 40% and the pore diameter of 10nm, mixing 55wt% of alumina and 45wt% of polypropylene by mass with alumina with the average particle size D50 of 65nm to obtain a first coating layer coating, coating the first coating layer coating on the surface of the base film to form a first coating layer, wherein the thickness of the first coating layer is 1.5 mu m, mixing 30wt% of alumina and 70wt% of polyvinyl chloride by mass with alumina with the average particle size D50 of 60nm to obtain a second coating layer coating, coating the second coating layer coating on the surface, far away from the base film, of the first coating layer to form a second coating layer, wherein the thickness of the second coating layer is 2 mu m, and drying and shaping to obtain the isolating film.
Comparative example 1
Preparing an isolating membrane:
mixing and uniformly stirring alumina ceramic particles and a polyvinylidene fluoride solvent on the surface of a polyethylene base film with the thickness of 7 mu m, the porosity of 40% and the pore diameter of 10nm, and uniformly coating the surface of the polyethylene base film, wherein the average particle size D50 of the alumina ceramic particles is 300nm, and the coating thickness is 1 mu m.
Test method
Temperature resistance test
And (3) placing a plurality of groups of same isolating membranes in a drying box, taking out the isolating membranes at different temperatures respectively, measuring the air permeability of the isolating membranes, and when the air permeability of the isolating membranes is reduced to 0, indicating that the isolating membranes are completely closed at the temperature value and have a complete blocking function, wherein the highest temperature resistance value is the temperature value.
Porosity test
1) Cutting 5 100mm × 100mm isolation films (width less than 100mm, length direction 100 mm);
2) measuring the length, width and thickness of the sample by reference to national standards;
3) weighing the mass of the sample by using an analytical balance with the measurement precision of 0.0001g, and converting the mass into gram weight;
4) the porosity was calculated according to the following formulas 1 and 2.
Wherein:
ρ 1-grammage of the sample in grams per square meter (g/m 2);
m-mass of the sample in grams (g);
l-the length of the sample in meters (m);
b-width of the sample in meters (m);
p-porosity of the sample, expressed in%;
d-thickness of the sample in micrometers (um);
ρ 0-the density of the feedstock in grams per cubic centimeter (g/cm 3).
Shrinkage test
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 diaphragm sample in an oven, and placing for 10min at 105 ℃;
4) taking out the isolation film after high-temperature baking, and measuring the width of the isolation film as L2;
5) the shrinkage was calculated according to the following formula
（L1-L2）/L1*100%。
Specific capacity test
Mixing a positive electrode active substance LiFePO4, a conductive agent and a binder into slurry according to the mass ratio of 8: 1, coating the slurry on an aluminum foil, airing, and drying in vacuum (133 Pa) at 105 ℃ for 10 hours to prepare an electrode wafer (the content of the active substance is 3 mg) with the diameter of 12 mm. LiPF6 was dissolved in a mixed solvent of ethylene carbonate, diethyl carbonate, and dimethyl carbonate at a volume ratio of 1: 1 to prepare an electrolyte solution having a concentration of 1 mol/L. And assembling the CR2032 button cell by taking a metal lithium sheet as a negative electrode in a dry glove box filled with argon. Electrochemical performance tests were performed using the CT2001A battery test system. The specific capacity value is measured by adopting a constant-current charging and discharging method and testing at 25 ℃, wherein the voltage is 2.0V to 4.2V.
The specific test results are shown in table 1.
Table 1: preparation parameters and test results of examples 1 to 5 and comparative example 1
As can be seen from table 1, compared with comparative example 1, the insulation films obtained in examples 1 to 10 of the present invention have higher temperature resistance, porosity and specific capacity, and the shrinkage rate of the insulation films obtained in examples 1 to 10 of the present invention is significantly lower than that of comparative example 1, which indicates that the insulation film provided by the present invention can maintain the form for a longer time in a high temperature environment, has a low deformation amount, and effectively reduces the instantaneous loss.
Compared with the prior art, in the preparation method of the isolating membrane and the isolating membrane, the two coating layers made of different materials are used, different coating layers are sequentially melted according to different melting processes of different coating layers, the capability of automatically closing the aperture can be provided for the isolating membrane, a working buffer space is provided for a battery, instantaneous loss of the sealing holes of the isolating membrane at the moment of high-temperature abnormity of the battery is effectively prevented, and deflagration caused by the deformation of the isolating membrane at the moment of high-temperature abnormity can be prevented. Secondly, the inorganic oxide and the polymer resin material with the gradient particle size are arranged, so that the polymer resin material serving as the adhesive on the coating layer on the surface of the isolating membrane is firstly melted under the high-temperature condition, the inorganic oxide with the small particle size in the second coating layer is released, gaps among the inorganic oxides with the large particle size in the first coating layer are effectively filled, the positive electrode and the negative electrode of the battery are finally and thoroughly separated, the condition of electrochemical reaction of the battery is lost, and the high-temperature safety performance of the battery is effectively guaranteed.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (12)
1. A separator, comprising:
a base film;
the first coating layer is coated on at least one side of the base film in the thickness direction and is made of inorganic oxide and a temperature-resistant high polymer resin material;
the second coating layer is coated on one side, far away from the base film, of the first coating layer and is made of inorganic oxide and a temperature-resistant high polymer resin material;
wherein the temperature-resistant polymer resin in the first coating layer accounts for 30-45 wt% by mass; the temperature-resistant polymer resin in the second coating layer accounts for 55-70 wt% by mass;
the melting point of the temperature-resistant polymer resin material in the first coating layer is higher than that of the temperature-resistant polymer resin material in the second coating layer;
the average particle size D50 of the inorganic oxide in the first coating layer and the second coating layer is a first particle size and a second particle size respectively, and the first particle size is larger than the second particle size.
2. The separator of claim 1, wherein the first particle size is 25nm to 65nm and the second particle size is 20nm to 60 nm.
3. The separator according to claim 1, wherein the difference between the first particle size and the second particle size is 3nn to 10 nm.
4. The separator according to claim 1, wherein the inorganic oxide in the first coating layer accounts for 55wt% to 70wt% by mass, and the inorganic oxide in the second coating layer accounts for 30wt% to 45wt% by mass.
5. The separator according to claim 1, wherein the thickness of the first coating layer is 0.5 μm to 1.5 μm, and the thickness of the second coating layer is 1 μm to 2 μm.
6. The separator of claim 1, wherein the inorganic oxide in the first and second coating layers is spherical or spheroidal.
7. The separator according to any one of claims 1 to 6, wherein said inorganic oxide is at least one of alumina and titania.
8. The separator of claim 1, wherein the base film is at least one of polyethylene, polypropylene, and polyimide.
9. The separator according to claim 1, wherein the temperature-resistant polymer resin is at least one of polyethylene, polypropylene, and polyvinyl chloride.
10. The separator according to claim 1, wherein the temperature-resistant polymer resin in the second coating layer and the first coating layer are made of different materials.
11. A method for producing the separator according to claim 1, comprising the steps of:
providing a base film;
coating a first coating layer on at least one side of the base film;
coating a second coating layer on the side of the first coating layer away from the base film;
and (5) drying and shaping.
12. An electrochemical device comprising the separator according to any one of claims 1 to 10.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105609688A (en) * | 2014-11-19 | 2016-05-25 | 三星Sdi株式会社 | Separator for rechargeable lithium battery and rechargeable lithium battery including same |
| CN113224465A (en) * | 2020-01-17 | 2021-08-06 | 厦门大学 | Ceramic diaphragm with multilayer composite structure and battery thereof |
| 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 |
| CN114583396A (en) * | 2022-03-22 | 2022-06-03 | 湖南文理学院 | High-safety lithium ion battery diaphragm and preparation method thereof |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105609688A (en) * | 2014-11-19 | 2016-05-25 | 三星Sdi株式会社 | Separator for rechargeable lithium battery and rechargeable lithium battery including same |
| CN113224465A (en) * | 2020-01-17 | 2021-08-06 | 厦门大学 | Ceramic diaphragm with multilayer composite structure and battery thereof |
| 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 |
| CN114583396A (en) * | 2022-03-22 | 2022-06-03 | 湖南文理学院 | High-safety lithium ion battery diaphragm and preparation method thereof |
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