CN108091806B - Lithium ion battery diaphragm and preparation method thereof - Google Patents
Lithium ion battery diaphragm and preparation method thereof Download PDFInfo
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- CN108091806B CN108091806B CN201711273257.4A CN201711273257A CN108091806B CN 108091806 B CN108091806 B CN 108091806B CN 201711273257 A CN201711273257 A CN 201711273257A CN 108091806 B CN108091806 B CN 108091806B
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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
- 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
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention provides a lithium ion battery diaphragm and a preparation method thereof, wherein the lithium ion battery diaphragm at least comprises a polyolefin substrate layer with micropores and a hole sealing object formed on at least one side surface of the polyolefin substrate layer, and the melting point of the hole sealing object is lower than that of the polyolefin substrate layer. In the lithium ion battery diaphragm, when the battery temperature is higher, the hole sealing material on the polyolefin substrate layer can be automatically melted before the polyolefin substrate layer is possibly melted, and the melted hole sealing material just blocks the micropores on the polyolefin substrate layer, so that the electrification of the battery can be stopped, the danger can be prevented, and the safety performance of the diaphragm is greatly improved.
Description
Technical Field
The invention relates to the field of new energy lithium ion battery diaphragms, in particular to a lithium ion battery diaphragm and a preparation method thereof.
Background
At present, with the wide application of power automobiles in life, the safety performance of lithium ion batteries is concerned by the appearance of a large number of series-parallel battery packs. The requirements of the lithium ion battery on the safety of the battery, particularly the short circuit prevention performance and the contact performance between the diaphragm and the interface of the positive and negative electrodes, are higher and higher as the diaphragm for separating the positive and negative electrode materials. The separator used in the lithium ion battery is generally a polyolefin-based microporous membrane, because the melting point of the polyolefin-based microporous membrane is lower than 150 ℃, and a large number of micropores exist on the membrane. When the temperature in the lithium ion battery reaches a higher value, the diaphragm starts to melt, but the conduction is continued, so that the danger is high, and short circuit and even explosion can occur.
Therefore, it is an object to be solved by those skilled in the art to provide a lithium ion battery separator having high safety and a method for preparing the same.
Disclosure of Invention
In view of the above disadvantages of the prior art, an object of the present invention is to provide a lithium ion battery separator and a preparation method thereof, which are used to solve the problems in the prior art that the lithium ion battery separator is easily melted at a higher temperature, and short circuits and even explosions occur.
To achieve the above and other related objects, the present invention provides a lithium ion battery separator, comprising at least: the sealing device comprises a polyolefin base material layer with micropores and a sealing object formed on at least one side surface of the polyolefin base material layer, wherein the melting point of the sealing object is lower than that of the polyolefin base material layer, so that when the temperature of the lithium ion battery rises, the sealing object is melted before the polyolefin base material layer and sealed into the micropores of the polyolefin base material layer, and the electrified path of the lithium ion battery is blocked.
As an optimized scheme of the lithium ion battery diaphragm, the polyolefin substrate layer is selected from one or more of ultrahigh molecular weight polyethylene with the weight average molecular weight of 200 ten thousand or more, linear polyethylene, branched polyethylene, high density polyethylene with the density of 0.941-0.960, low density polyethylene with the density of 0.915-0.940 g/cubic centimeter, cross-linked polyethylene and polypropylene;
or a mixture of at least two selected from the group consisting of the ultra high molecular weight polyethylene having a weight average molecular weight of 200 ten thousand or more, the linear polyethylene, the branched polyethylene, the high density polyethylene having a density of between 0.941 and 0.960, the low density polyethylene having a density of between 0.915 and 0.940 g/cc, the crosslinked polyethylene, the polypropylene, and the copolymer.
As an optimized scheme of the lithium ion battery separator, the polyolefin substrate layer comprises a mixture of ultrahigh molecular weight polyethylene with the weight-average molecular weight of 200 ten thousand or more and high density polyethylene with the density of 0.950-0.960, the mass ratio of the ultrahigh molecular weight polyethylene to the high density polyethylene is 20/60-60/30, and the density of the mixture is 0.92-0.97g/cm3。
As an optimized scheme of the lithium ion battery separator, the thickness of the polyolefin substrate layer is between 1 and 50 mu m, the porosity is between 30 and 46 percent, the longitudinal tensile strength is between 180 and 260MPa, the transverse tensile strength is between 110 and 160MPa, and the air permeability is between 150 and 260sec/100 ml.
As an optimized scheme of the lithium ion battery diaphragm, the hole sealing material comprises a mixture of polyethylene oxide and polyethylene, and the weight ratio of the polyethylene oxide to the polyethylene is 3: 7-7: 3.
As an optimized scheme of the lithium ion battery diaphragm, the hole sealing material is formed at the upper right corner of each micropore on the polyolefin substrate layer, and the distance between the hole sealing material and the micropore is 80-120 nm.
As an optimized scheme of the lithium ion battery diaphragm, the hole sealing object is hemispherical, and the diameter of the hole sealing object is between 300 and 800 nm.
As an optimized scheme of the lithium ion battery diaphragm, the melting point of the hole sealing material is between 80 and 125 ℃, the solid content is between 31 and 48 percent, the viscosity is between 15 and 190m Pa.S, and the melting point of the polyolefin substrate layer is between 135 and 150 ℃.
In addition, the invention also provides a preparation method of the lithium ion battery diaphragm, which at least comprises the following steps:
preparing a polyolefin substrate layer with micropores;
and forming a hole sealing object on the surface of at least one side of the polyolefin base material layer, wherein the melting point of the hole sealing object is lower than that of the polyolefin base material layer, so that when the temperature of the lithium ion battery rises, the hole sealing object is melted before the polyolefin base material layer and sealed into micropores of the polyolefin base material layer, and the electrified path of the lithium ion battery is blocked.
As an optimized scheme of the preparation method of the lithium ion battery diaphragm, the polyolefin substrate layer with the micropores is prepared by adopting a thermally induced phase separation process.
As an optimized scheme of the preparation method of the lithium ion battery separator, the step of forming a hole sealing object on at least one side surface of the polyolefin substrate layer comprises the following steps:
1) weighing polyoxyethylene and polyethylene according to the weight ratio;
2) dissolving the polyethylene oxide and polyethylene in a solvent, and stirring to form uniform slurry;
3) dispersing the slurry to obtain a finished product slurry;
4) and dripping the finished slurry on the polyolefin substrate layer, and drying to remove water to form a hole sealing object.
As an optimized scheme of the preparation method of the lithium ion battery separator, in the step 1), the weight ratio of the polyethylene oxide to the polyethylene is 3: 7-7: 3.
As an optimized scheme of the preparation method of the lithium ion battery diaphragm, the step 2) is stirred for more than 1 hour to form uniform slurry, and the step 3) is dispersed for more than half an hour to obtain finished slurry.
As an optimized scheme of the preparation method of the lithium ion battery diaphragm, the hole sealing object is formed at the upper right corner of each micropore on the polyolefin substrate layer, and the distance between the hole sealing object and the micropore is 80-120 nm.
As an optimized scheme of the preparation method of the lithium ion battery diaphragm, the hole sealing object is hemispherical, and the diameter of the hole sealing object is 300-800 nm.
As an optimized scheme of the preparation method of the lithium ion battery diaphragm, the melting point of the hole sealing material is between 80 and 125 ℃, and the solid content is between 31 and 48 percent; the viscosity is between 15 and 190m Pa.S, and the melting point of the polyolefin substrate layer is between 135 and 150 ℃.
As described above, according to the lithium ion battery separator and the preparation method thereof of the present invention, the lithium ion battery separator at least includes a polyolefin substrate layer having micropores and a sealer formed on at least one side surface of the polyolefin substrate layer, and a melting point of the sealer is lower than a melting point of the polyolefin substrate layer. In the lithium ion battery diaphragm, when the battery temperature is higher, the hole sealing material on the polyolefin substrate layer can be automatically melted before the polyolefin substrate layer is possibly melted, and the melted hole sealing material just blocks the micropores on the polyolefin substrate layer, so that the electrification of the battery can be stopped, the danger can be prevented, and the safety performance of the diaphragm is greatly improved.
Drawings
Fig. 1 is a schematic structural diagram of a lithium ion battery separator according to the present invention.
Description of the element reference numerals
1 polyolefin substrate layer
2 micro-pores
3 hole sealing material
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Please refer to the attached drawings. It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
The invention provides a lithium ion battery diaphragm, as shown in figure 1, the lithium ion battery diaphragm at least comprises: the sealing structure comprises a polyolefin base material layer 1 with micropores 2 and a sealing object 3 formed on at least one side surface of the polyolefin base material layer 1, wherein the melting point of the sealing object 3 is lower than that of the polyolefin base material layer 1, so that when the temperature of a lithium ion battery rises, the sealing object 3 is melted in the polyolefin base material layer 1 and sealed in the micropores 2 of the polyolefin base material layer 1 in advance, and the electrified path of the lithium ion battery is blocked.
Illustratively, the polyolefin substrate layer 1 is a polymer microporous membrane, and the polyolefin substrate layer 1 is selected from copolymers formed by one or more of ultrahigh molecular weight polyethylene with the weight average molecular weight of 200 ten thousand or more, linear polyethylene, branched polyethylene, high density polyethylene with the density of 0.941-0.960, low density polyethylene with the density of 0.915-0.940 g/cubic centimeter, cross-linked polyethylene and polypropylene;
or a mixture of at least two selected from the group consisting of the ultra high molecular weight polyethylene having a weight average molecular weight of 200 ten thousand or more, the linear polyethylene, the branched polyethylene, the high density polyethylene having a density of between 0.941 and 0.960, the low density polyethylene having a density of between 0.915 and 0.940 g/cc, the crosslinked polyethylene, the polypropylene, and the copolymer.
Further, the polyolefin substrate layer 1 is a mixture of two polymers. Preferably, the polyolefin substrate layer 1 comprises a mixture of ultra-high molecular weight polyethylene with a weight average molecular weight of 200 ten thousand or more and high density polyethylene with a density of 0.950-0.960 (the weight average molecular weight is about 100 ten thousand, and the melt index is 0.5-2 g/10 min), the mass ratio of the ultra-high molecular weight polyethylene to the high density polyethylene is 20/60-60/30, and the density of the mixture is 0.92-0.97g/cm3。
More preferably, the mass ratio of the ultra-high molecular weight polyethylene to the high density polyethylene is between 30/50 and 70/50, and the density of the mixture is between 0.94 and 0.96g/cm3。
By way of example, the thickness of the polyolefin substrate layer 1 is between 1 to 50 μm, preferably 5 to 30 μm, and more preferably 9 to 25 μm, within this range, the volume of the battery is greatly reduced, the internal resistance of the battery is also reduced, and the energy density of the battery is remarkably improved.
By way of example, the porosity of the polyolefin substrate layer 1 is between 30% and 46%, preferably 35% to 45%, more preferably 38% to 42%, and most preferably 39% to 40%; the longitudinal tensile strength is between 180 and 260MPa, preferably 190 to 250MPa, more preferably 200 to 240MPa, and preferably 210 to 230 MPa; the transverse tensile strength is between 110 and 160MPa, preferably between 120 and 150MPa, and more preferably between 130 and 140 MPa.
The air permeability of the polyolefin substrate layer 1 is between 150-260sec/100ml, preferably 180-250sec/100ml, and more preferably 190-230sec/100 ml.
By way of example, the plugs 3 comprise a mixture of polyethylene oxide and polyethylene, and the weight ratio of the polyethylene oxide to the polyethylene is 3: 7-7: 3.
By way of example, the hole sealing material 3 is formed on the upper right corner of each micropore 2 on the polyolefin substrate layer 1, and the distance between the hole sealing material 3 and the micropore 2 is between 80 and 120 nm. Of course, the sealer 3 may also be formed on the upper left corner or the top of each of the micropores 2 on the polyolefin substrate layer 1 as long as the sealer 3 can smoothly seal the micropores 2 after being melted. The upper right corner of each micropore 2 preferably corresponds to only one hole sealing object 3, and the hole sealing objects 3 are distributed on one side or two side surfaces of the polyolefin base material layer 1 in an isotactic manner integrally. In this embodiment, the distance between the hole sealing material 3 and the micropores is 100 nm.
The shape of the hole sealing material 3 is not limited, and preferably, the hole sealing material 3 is hemispherical, and the diameter is between 300 and 800 nm. The diameter of the plugs 3 is preferably matched to the diameter of the pores 2.
The melting point of the hole sealing object 3 is required to be lower than the melting point of the polyolefin substrate layer 1, so that when the battery reaches the temperature which can enable the polyolefin substrate layer 1 to melt, the hole sealing object 3 can melt and seal the micropores 2 on the polyolefin substrate layer 1, the current is blocked, and the danger is reduced. Preferably, the melting point of the hole sealing matter 3 is between 80 and 125 ℃, and the melting point of the polyolefin substrate layer is between 135 and 150 ℃.
The sealer 3 is required to have a certain viscosity so that the sealer 3 can be firmly adhered to the surface of the polyolefin base material layer 1 without falling off. By way of example, the solid content of the sealing material 3 is between 31 and 48 percent, and the viscosity is between 15 and 190mPa & S.
The invention also provides a preparation method of the lithium ion battery diaphragm, which can prepare the diaphragm and at least comprises the following steps:
firstly, preparing a polyolefin substrate layer with micropores;
and then, forming a hole sealing object on at least one side surface of the polyolefin substrate layer, wherein the melting point of the hole sealing object is lower than that of the polyolefin substrate layer, so that when the temperature of the lithium ion battery rises, the hole sealing object is melted before the polyolefin substrate layer and is sealed into micropores of the polyolefin substrate layer, and an electrified path of the lithium ion battery is blocked.
The polyolefin substrate layer having micropores may be prepared using a method conventional in the art.
As an example, the polyolefin substrate layer may be prepared using a thermally induced phase separation process. The method comprises the following steps:
(a) dissolving the polymer component in a solvent with high boiling point and low volatility at high temperature to form homogeneous liquid;
(b) cooling to make the solution produce liquid-solid phase separation or liquid-liquid phase separation;
(c) extracting the high-boiling-point solvent by using a volatile reagent, and drying to obtain the microporous polyolefin substrate layer.
And performing synchronous or asynchronous biaxial stretching on the formed polyolefin substrate layer before solvent extraction, performing qualitative rolling after extraction, and performing steps of edge cutting, rolling, slitting and the like.
The method of preparing the plugs of the present invention is not particularly limited, and may be any conventional method known in the art as long as the plugs can be formed on the polymer microporous membrane. The mixing device suitable for the method of the present invention is not particularly limited, and may be any conventional mixing device known in the art as long as the components in the plugs can be mixed.
As an example, the step of coating the sealer on at least one surface of the polyolefin substrate layer includes:
1) weighing polyoxyethylene and polyethylene according to the weight ratio;
2) dissolving the polyethylene oxide and the polyethylene in a solvent, and stirring to form uniform slurry;
3) dispersing the slurry to obtain a finished product slurry;
4) and dripping the finished slurry on the polyolefin substrate layer, and drying to remove water to form a hole sealing object.
Further, in the step 1), the weight ratio of the polyethylene oxide to the polyethylene is between 3:7 and 7: 3.
Stirring for more than 1 hour in the step 2) to form the uniform slurry, and dispersing for more than half an hour in the step 3) to obtain the finished slurry.
By way of example, the hole sealing material is formed on the right upper corner of each micropore on the polyolefin substrate layer, and the hole sealing material is 80-120 nm away from the micropore.
As an example, the hole sealing object is hemispherical, and the diameter of the hole sealing object is 300-800 nm.
For example, the melting point of the sealing compound is between 80 and 125 ℃, and the solid content is between 31 and 48 percent; the viscosity is between 15 and 190m Pa.S, and the melting point of the polyolefin substrate layer is between 135 and 150 ℃.
In the step 4), the drying and water removal method may be infrared electronic drying or hot warm air blast drying, which is not limited herein.
Specific examples are listed below to illustrate the advantages of the lithium ion battery separator of the present invention.
Example 1
1. Selecting ND12 series PE microporous base films prepared by a thermotropic phase separation (TIPS) method and an asynchronous double-pulling process of Shanghai Enjie company, wherein the mass ratio of the two polyolefins is 30/50, the density is 0.954, the thickness is 12 mu m, the porosity is 40%, and the air permeability is 200sec/100 ml;
2. the PE microporous base membrane was coated by MCD type coater (from fuji mechanical industries) with the sealer polyethylene oxide to polyethylene ratio of 3:7, melting point 85 ℃, diameter 350nm, and distance 95nm from micropores. The slurry of the composition is coated on a PE microporous membrane, the coating rate of hole sealing substances is 80%, and finally, the high-safety lithium ion battery isolating membrane can be prepared after baking in an oven.
Example 2
1. Selecting ND12 series PE microporous base films prepared by a thermotropic phase separation (TIPS) method and an asynchronous double-pull process of Shanghai Enjie company, wherein the mass ratio of the two polyolefins is 40/50, the density is 0.958, the thickness is 12 mu m, the porosity is 40%, and the air permeability is 200sec/100 ml;
2. the PE microporous base membrane was coated by MCD type coater (available from fuji mechanical industries) with the sealer having a polyethylene oxide to polyethylene ratio of 4:6, melting point 90 ℃, diameter 400nm, and distance of 98nm from micropores. The slurry of the composition is coated on a PE microporous membrane, the coating rate of hole sealing materials is 90%, and finally, the high-safety lithium ion battery isolating membrane can be prepared after baking in an oven.
Example 3
1. Selecting ND12 series PE microporous base films prepared by a thermotropic phase separation (TIPS) method and an asynchronous double-pull process of Shanghai Enjie company, wherein the mass ratio of the two polyolefins is 50/50, the density is 0.956, the thickness is 12 mu m, the porosity is 40 percent, and the air permeability is 200sec/100 ml;
2. the PE microporous base membrane was coated by MCD type coater (available from fuji mechanical industries) with the sealer polyethylene oxide to polyethylene ratio of 5:5, melting point 92 ℃, diameter 410nm, distance 94nm from micropores. The slurry of the composition is coated on a PE microporous membrane, the coating rate of hole sealing substances is 100%, and finally, the high-safety lithium ion battery isolating membrane can be prepared after baking in an oven.
Comparative example
Selecting ND12 series PE microporous base film prepared by Shanghai Enjie company Thermally Induced Phase Separation (TIPS) method and asynchronous double-pulling process, the thickness is 12 μm, the porosity is 40%, and the air permeability is 200sec/100 ml.
The specific test method is as follows:
1. the separator obtained in the above preparation was placed in an oven set at 140 ℃.
2. And taking out the corresponding diaphragm from the oven, and manufacturing the diaphragm into the corresponding small lithium ion battery.
3. The current and voltage of the lithium ion battery were measured using a multimeter and the data obtained for examples 1, 2, 3 and comparative example are shown in table 1.
TABLE 1
| Example 1 | Example 2 | Example 3 | Comparative example | |
| current/A | 2.0 | 1.1 | 0.0 | 10.0 |
| voltage/V | 10 | 5.5 | 0 | 50 |
From the data, the hole sealing substances in the diaphragm can be automatically melted when the battery reaches a certain temperature, so that the current is blocked, and the danger is prevented. In the comparative example, since the effect of the pore sealing material is not provided, the large current passes through, and the danger is very high.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (7)
1. A lithium ion battery separator, comprising at least: the sealing material is melted before the polyolefin substrate layer and sealed in the micropores of the polyolefin substrate layer to block an electrified path of the lithium ion battery when the temperature of the lithium ion battery is increased, wherein the thickness of the polyolefin substrate layer is 9-25 mu m, the porosity is 39-40%, the longitudinal tensile strength is 180-260 MPa, the transverse tensile strength is 110-160 MPa, and the air permeability is 150-260sec/100 ml; the distance between the hole sealing object and the micropores is 94 nm; the hole sealing material is hemispherical, the diameter of the hole sealing material is 300-800nm, the melting point of the hole sealing material is 80-125 ℃, the solid content of the hole sealing material is 31-48%, the viscosity of the hole sealing material is 15-190 mPa & S, and the melting point of the polyolefin substrate layer is 135-150 ℃; the hole sealing material comprises a mixture of polyethylene oxide and polyethylene, the weight ratio of the polyethylene oxide to the polyethylene is 1:1, and the diameter of the hole sealing material is matched with that of the micropores.
2. The lithium ion battery separator according to claim 1, wherein: the polyolefin substrate layer is selected from one or more of ultrahigh molecular weight polyethylene with the weight average molecular weight of 200 ten thousand or more, linear polyethylene, branched polyethylene, high density polyethylene with the density of 0.941-0.960 g/cubic centimeter, low density polyethylene with the density of 0.915-0.940 g/cubic centimeter, crosslinked polyethylene and polypropylene;
or a mixture of at least two selected from the group consisting of the ultra high molecular weight polyethylene having a weight average molecular weight of 200 ten thousand or more, the linear polyethylene, the branched polyethylene, the high density polyethylene having a density of between 0.941 and 0.960 g/cc, the low density polyethylene having a density of between 0.915 and 0.940 g/cc, the crosslinked polyethylene, the polypropylene, and the copolymer.
3. The lithium ion battery separator according to claim 1, wherein: the polyolefin substrate layer comprises a mixture of an ultra-high molecular weight polyethylene having a weight average molecular weight of 200 ten thousand or more and a high density polyethylene having a density of 0.950 to 0.960 g/cc, the mass ratio of the ultra-high molecular weight polyethylene to the high density polyethylene being 20/60 to 60/30, the density of the mixture being 0.92 to 0.97 g/cc.
4. The lithium ion battery separator according to claim 1, wherein: the hole sealing material is formed at the upper right corner of each micropore on the polyolefin substrate layer.
5. A preparation method of a lithium ion battery separator is characterized by at least comprising the following steps:
preparing a polyolefin substrate layer with micropores by adopting a thermally induced phase separation process; forming a hole sealing object on the surface of at least one side of the polyolefin base material layer, wherein the melting point of the hole sealing object is lower than that of the polyolefin base material layer so as to ensure that the hole sealing object is melted before the polyolefin base material layer and sealed into micropores of the polyolefin base material layer when the temperature of the lithium ion battery is increased, so as to block an electrified path of the lithium ion battery; wherein the thickness of the polyolefin substrate layer is 9-25 μm, the porosity is 39-40%, the longitudinal tensile strength is 180-260 MPa, the transverse tensile strength is 110-160 MPa, and the air permeability is 150-260sec/100 ml; the distance between the hole sealing matter and the micropores is 80-120 nm; the hole sealing material is hemispherical, the diameter of the hole sealing material is 300-800nm, the melting point of the hole sealing material is 80-125 ℃, the solid content of the hole sealing material is 31-48%, the viscosity of the hole sealing material is 15-190 mPa & S, and the melting point of the polyolefin substrate layer is 135-150 ℃; the diameter of the hole sealing object is matched with that of the micropore, and the step of forming the hole sealing object on the surface of at least one side of the polyolefin substrate layer comprises the following steps:
1) weighing polyoxyethylene and polyethylene according to a weight ratio, wherein the weight ratio of the polyoxyethylene to the polyethylene is 3: 7-7: 3;
2) dissolving the polyethylene oxide and the polyethylene in a solvent, and stirring to form uniform slurry;
3) dispersing the slurry to obtain a finished product slurry;
4) and dripping the finished slurry on the polyolefin substrate layer, and drying to remove water to form a hole sealing object.
6. The method for preparing a lithium ion battery separator according to claim 5, wherein: stirring for more than 1 hour in the step 2) to form the uniform slurry, and dispersing for more than half an hour in the step 3) to obtain the finished slurry.
7. The method for preparing a lithium ion battery separator according to claim 5, wherein: the hole sealing material is formed at the upper right corner of each micropore on the polyolefin substrate layer.
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| CN103247770A (en) * | 2013-04-25 | 2013-08-14 | 东莞新能源科技有限公司 | Lithium-ion battery separator and manufacturing method thereof |
| CN103904276A (en) * | 2014-03-28 | 2014-07-02 | 东莞新能源科技有限公司 | Composite porous isolating film and electrochemical device |
| CN106784526A (en) * | 2016-12-21 | 2017-05-31 | 浙江南都电源动力股份有限公司 | A kind of ceramic coating membrane as lithium ion battery and preparation method thereof |
| CN106848162A (en) * | 2017-03-10 | 2017-06-13 | 宁德时代新能源科技股份有限公司 | Secondary battery |
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| Publication number | Publication date |
|---|---|
| CN108091806A (en) | 2018-05-29 |
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