CN117712615A - High-porosity and high-strength diaphragm, preparation method thereof and electrochemical device - Google Patents
High-porosity and high-strength diaphragm, preparation method thereof and electrochemical device Download PDFInfo
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- CN117712615A CN117712615A CN202311654475.8A CN202311654475A CN117712615A CN 117712615 A CN117712615 A CN 117712615A CN 202311654475 A CN202311654475 A CN 202311654475A CN 117712615 A CN117712615 A CN 117712615A
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- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 238000001035 drying Methods 0.000 claims abstract description 22
- 238000000034 method Methods 0.000 claims abstract description 13
- 238000007493 shaping process Methods 0.000 claims abstract description 10
- 229920005672 polyolefin resin Polymers 0.000 claims description 53
- 239000012528 membrane Substances 0.000 claims description 30
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 claims description 27
- 239000004698 Polyethylene Substances 0.000 claims description 21
- 239000003085 diluting agent Substances 0.000 claims description 21
- -1 polyethylene Polymers 0.000 claims description 21
- 229920000573 polyethylene Polymers 0.000 claims description 21
- 238000010438 heat treatment Methods 0.000 claims description 20
- 238000001816 cooling Methods 0.000 claims description 18
- 239000005662 Paraffin oil Substances 0.000 claims description 15
- 238000002844 melting Methods 0.000 claims description 11
- 230000008018 melting Effects 0.000 claims description 11
- 238000005266 casting Methods 0.000 claims description 10
- 238000001125 extrusion Methods 0.000 claims description 9
- 238000002156 mixing Methods 0.000 claims description 9
- 238000009740 moulding (composite fabrication) Methods 0.000 claims description 9
- 238000005191 phase separation Methods 0.000 claims description 9
- 230000001360 synchronised effect Effects 0.000 claims description 8
- 239000000203 mixture Substances 0.000 claims 2
- 239000011148 porous material Substances 0.000 abstract description 4
- 238000000465 moulding Methods 0.000 abstract 1
- 230000000052 comparative effect Effects 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- 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
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
- H01M50/406—Moulding; Embossing; Cutting
-
- 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
-
- 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
- H01M50/491—Porosity
-
- 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
- H01M50/494—Tensile strength
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Cell Separators (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
Abstract
In order to solve the problem that the porosity and the strength of a diaphragm cannot be simultaneously improved in the prior art, the application provides a high-porosity and high-strength diaphragm, a preparation method thereof and an electrochemical device. The method comprises the following steps: extruding (1), molding (2), biaxial stretching (3), extracting and drying (4), transverse stretching (5), transverse stretching (6) for the second time and shaping (7). The invention also provides a high-porosity and high-strength battery diaphragm prepared by adopting the preparation method and a battery comprising the high-porosity and high-strength battery diaphragm. The porosity of the diaphragm prepared by the preparation method is improved by more than 20 percent compared with that of a conventional diaphragm, and the mechanical strength (measured by needling/gram weight) is improved by 15 percent. The average pore diameter and the maximum pore diameter are improved by more than 10nm compared with the conventional products.
Description
Technical Field
The invention belongs to the field of battery diaphragms, and particularly relates to a high-porosity and high-strength diaphragm, a preparation method thereof and an electrochemical device.
Background
In the prior art, the diaphragm porosity is generally improved by adopting a mode of reducing the transverse drawing temperature or improving the double drawing temperature, or the diaphragm strength is improved by adopting a mode of adjusting high molecular weight materials. However, the existing diaphragm products often cannot have high porosity and high strength at the same time, so that the safety and the charge and discharge rate cannot meet the actual demands. The reason for this is that the holes are both the "functional structure" required for the battery separator and cause the decrease in strength of the battery separator. The pores are defects which cause the strength of the diaphragm to be reduced, so that the high porosity and the high strength of the battery diaphragm are mutually contradicted, and the key link for solving the contradiction is the preparation process of the battery diaphragm, which determines the shape and the size distribution of the pores and also determines the structure and the performance of the battery diaphragm.
In order to improve the strength of the battery separator while maintaining high porosity, one of the methods commonly used at present is to utilize a high molecular weight material to strengthen the skeleton of the battery separator and improve the strength of the battery separator, but the casting process causes great pressure on the extruder. Therefore, a preparation method capable of simultaneously improving the porosity and the strength of the separator is required.
Disclosure of Invention
In order to solve the technical problems in the prior art, the invention provides a preparation method of a high-porosity and high-strength battery diaphragm.
It is also an object of the present invention to provide a high porosity, high strength battery separator that has a higher porosity and higher mechanical strength.
The present invention also aims to provide an electrochemical device.
A preparation method of a high-porosity and high-strength battery diaphragm, wherein the diaphragm is made of polyolefin resin;
the method comprises the following steps:
(1) Extrusion: mixing a diluent with polyolefin resin to obtain a diluent-polyolefin resin mixed system; heating and melting the diluent-polyolefin resin mixed system through an extruder to form a uniform mixed melt;
(2) And (3) forming: flowing out the mixed melt obtained in the step (1) to a casting roller for cooling, carrying out phase separation, and cooling and forming to obtain a membrane;
(3) Biaxial stretching: heating the membrane prepared in the step (2) to a temperature close to the melting point, and performing biaxial stretching to orient molecular chains, wherein the biaxial synchronous stretching is adopted, and the biaxial stretching temperature T1 is 100 ℃ less than T1 less than 125 ℃;
(4) And (3) extracting and drying: eluting the diluent remained in the membrane subjected to the biaxial stretching in the step (3) by using dichloromethane, and drying;
(5) And (3) transversely stretching: transversely stretching the dried film obtained in the step (4), wherein the transverse stretching temperature T2 is 110 ℃ less than T2 less than 140 ℃;
(6) Performing second transverse stretching, namely performing second transverse stretching on the film subjected to the transverse stretching treatment in the step (5), wherein the second transverse stretching temperature is T3, and T2-10 ℃ is less than T3 and less than T2+10 ℃;
(7) Shaping: and (3) transversely stretching the step (6) and then carrying out heat treatment to obtain the porous film, namely the high-porosity and high-strength diaphragm.
Further, the mass ratio of the polyolefin mixed resin in the diluent-polyolefin resin mixed system in the step (1) is 15% -60%; preferably, the mass ratio of the polyolefin resin in the diluent-polyolefin resin mixed system is 15-30%.
Further, the polyolefin resin in the step (1) is polyethylene; preferably, the average molecular weight of the polyethylene is 60-200 ten thousand, preferably 150 ten thousand.
Further, the diluent in the step (1) is paraffin oil.
Further, the polyolefin resin and the diluent in the step (1) are heated and melted at a temperature of 100-300 ℃.
Further, the drying temperature in the step (4) is 30-60 ℃, preferably 35-40 ℃, and most preferably 40 ℃.
Further, the step (7) is to heat treat for 20s-25s at 130 ℃ to 140 ℃.
A high-porosity and high-strength battery diaphragm is prepared by the preparation method, the porosity of the battery diaphragm is more than or equal to 45%, and the MD tensile strength is more than 1700Kgf/cm 2 TD tensile strength > 1500Kgf/cm 2 The ratio of the needling strength to the weight per unit area of the diaphragm is more than or equal to 105gfcm 2 Per gram, i.e. needling per gram weight not less than 105gfcm 2 /g。
A battery comprising the aforementioned high porosity, high strength battery separator.
The technical scheme of the invention has the beneficial effects that:
according to the method, under the condition that the tensile strength is unchanged, even the original diaphragm strength is improved, the diaphragm porosity can be greatly improved, the prepared diaphragm porosity is more than or equal to 45%, the prepared diaphragm porosity is improved by more than 20% compared with the conventional diaphragm porosity, and the mechanical strength (measured by needling/gram weight) is improved by 15%.
Detailed Description
The present invention is further illustrated by the following examples, which are not intended to limit the invention in any way.
The diluent in this example was paraffin oil, and the polyolefin resin in this example was polyethylene having a molecular weight average of 150 ten thousand (manufacturer: korean oil, model: VH 150U).
1) Extrusion: mixing paraffin oil with polyolefin resin to obtain a diluent-polyolefin resin mixed system, wherein the mass ratio of polyethylene in the diluent-polyolefin resin mixed system is 20%, and the diluent-polyolefin resin mixed system is heated and melted by an extruder to form a uniform mixed melt;
2) And (3) forming: flowing out the mixed melt obtained in the step (1) to a casting roller for cooling, carrying out phase separation, and cooling and forming to obtain a membrane;
3) Biaxial stretching: heating the membrane prepared in the step (2) to a temperature close to the melting point, and performing biaxial stretching to orient molecular chains, wherein biaxial synchronous stretching is adopted, and the biaxial stretching temperature T1 is 118 ℃.
4) And (3) extracting and drying: eluting the residual diluent in the biaxially stretched membrane in the step (3) by using dichloromethane, and drying for 10s at 40 ℃.
5) And (3) transversely stretching: and (3) transversely stretching the dried film obtained in the step (4), wherein the transverse stretching temperature T2 is 132 ℃.
6) And (3) transversely stretching the film subjected to the transverse stretching treatment in the step (5) for the second time, wherein the temperature of the transverse stretching for the second time is T3, and the temperature of T3 is 135 ℃.
7) Shaping: and (3) transversely stretching the step (7) and then carrying out heat treatment at 135 ℃ for 20s to obtain the porous film, namely the high-porosity and high-strength diaphragm.
Example 2
The diluent in this example was paraffin oil, and the polyolefin resin in this example was polyethylene having a molecular weight average of 150 ten thousand (manufacturer: korean oil, model: VH 150U).
1) Extrusion: mixing paraffin oil with polyolefin resin to obtain a diluent-polyolefin resin mixed system, wherein the mass ratio of polyethylene in the diluent-polyolefin resin mixed system is 23%, and the diluent-polyolefin resin mixed system is heated and melted by an extruder to form a uniform mixed melt;
2) And (3) forming: flowing out the mixed melt obtained in the step (1) to a casting roller for cooling, carrying out phase separation, and cooling and forming to obtain a membrane;
3) Biaxial stretching: heating the membrane prepared in the step (2) to a temperature close to the melting point, and performing biaxial stretching to orient molecular chains, wherein biaxial synchronous stretching is adopted, and the biaxial stretching temperature T1 is 120 ℃.
4) And (3) extracting and drying: eluting the residual diluent in the biaxially stretched membrane in the step (3) by using dichloromethane, and drying for 10s at 40 ℃.
5) And (3) transversely stretching: and (3) transversely stretching the dried film obtained in the step (4), wherein the transverse stretching temperature T2 is 132 ℃.
6) And (3) transversely stretching the film subjected to the transverse stretching treatment in the step (5) for the second time, wherein the temperature of the transverse stretching is T3, and the temperature of the T3 is 145 ℃.
7) Shaping: and (3) transversely stretching the step (7) and then carrying out heat treatment at 135 ℃ for 20s to obtain the porous film, namely the high-porosity and high-strength diaphragm.
Example 3
The diluent in this example was paraffin oil, and the polyolefin resin in this example was polyethylene having a molecular weight average of 150 ten thousand (manufacturer: korean oil, model: VH 150U).
1) Extrusion: mixing paraffin oil with polyolefin resin to obtain a diluent-polyolefin resin mixed system, wherein the mass ratio of polyethylene in the diluent-polyolefin resin mixed system is 18%, and the diluent-polyolefin resin mixed system is heated and melted by an extruder to form a uniform mixed melt;
2) And (3) forming: flowing out the mixed melt obtained in the step (1) to a casting roller for cooling, carrying out phase separation, and cooling and forming to obtain a membrane;
3) Biaxial stretching: heating the membrane prepared in the step (2) to a temperature close to the melting point, and performing biaxial stretching to orient molecular chains, wherein biaxial synchronous stretching is adopted, and the biaxial stretching temperature T1 is 118 ℃.
4) And (3) extracting and drying: eluting the residual diluent in the biaxially stretched membrane in the step (3) by using dichloromethane, and drying for 10s at 40 ℃.
5) And (3) transversely stretching: and (3) transversely stretching the dried film obtained in the step (4), wherein the transverse stretching temperature T2 is 132 ℃.
6) And (3) transversely stretching the film subjected to the transverse stretching treatment in the step (5) for the second time, wherein the temperature of the transverse stretching is T3, and the temperature of the T3 is 130 ℃.
7) Shaping: and (3) transversely stretching the step (7) and then carrying out heat treatment at 135 ℃ for 20s to obtain the porous film, namely the high-porosity and high-strength diaphragm.
Example 4
The diluent in this example was paraffin oil, and the polyolefin resin in this example was polyethylene having a molecular weight average of 150 ten thousand (manufacturer: korean oil, model: VH 150U).
1) Extrusion: mixing paraffin oil with polyolefin resin to obtain a diluent-polyolefin resin mixed system, wherein the mass ratio of polyethylene in the diluent-polyolefin resin mixed system is 20%, and the diluent-polyolefin resin mixed system is heated and melted by an extruder to form a uniform mixed melt;
2) And (3) forming: flowing out the mixed melt obtained in the step (1) to a casting roller for cooling, carrying out phase separation, and cooling and forming to obtain a membrane;
3) Biaxial stretching: heating the membrane prepared in the step (2) to a temperature close to the melting point, and performing biaxial stretching to orient molecular chains, wherein biaxial synchronous stretching is adopted, and the biaxial stretching temperature T1 is 118 ℃.
4) And (3) extracting and drying: eluting the residual diluent in the biaxially stretched membrane in the step (3) by using dichloromethane, and drying for 10s at 40 ℃.
5) And (3) transversely stretching: and (3) transversely stretching the dried film obtained in the step (4), wherein the transverse stretching temperature T2 is 132 ℃.
6) And (3) transversely stretching the film subjected to the transverse stretching treatment in the step (5) for the second time, wherein the temperature of the transverse stretching is T3, and the temperature of the transverse stretching is 140 ℃.
7) Shaping: and (3) transversely stretching the step (7) and then carrying out heat treatment at 135 ℃ for 20s to obtain the porous film, namely the high-porosity and high-strength diaphragm.
Comparative example 1 cancellation of second Cross-draw
The diluent in this example was paraffin oil, and the polyolefin resin in this example was polyethylene having a molecular weight average of 150 ten thousand (manufacturer: korean oil, model: VH 150U).
1) Extrusion: mixing paraffin oil with polyolefin resin to obtain a diluent-polyolefin resin mixed system, wherein the mass ratio of polyethylene in the diluent-polyolefin resin mixed system is 40%, and the diluent-polyolefin resin mixed system is heated and melted by an extruder to form a uniform mixed melt;
2) And (3) forming: flowing out the mixed melt obtained in the step (1) to a casting roller for cooling, carrying out phase separation, and cooling and forming to obtain a membrane;
3) Biaxial stretching: heating the membrane prepared in the step (2) to a temperature close to the melting point, and performing biaxial stretching to orient molecular chains, wherein biaxial synchronous stretching is adopted, and the biaxial stretching temperature T1 is 118 ℃.
4) And (3) extracting and drying: eluting the residual diluent in the biaxially stretched membrane in the step (3) by using dichloromethane, and drying for 10s at 40 ℃.
5) And (3) transversely stretching: and (3) transversely stretching the dried film obtained in the step (4), wherein the transverse stretching temperature T2 is 132 ℃.
6) Shaping: and (3) transversely stretching the step (5) and then carrying out heat treatment at 135 ℃ for 20s to obtain the porous film, namely the high-porosity and high-strength diaphragm.
Comparative example 2 transverse stretching treatment in the step (5) was omitted
The diluent in this example was paraffin oil, and the polyolefin resin in this example was polyethylene having a molecular weight average of 150 ten thousand (manufacturer: korean oil, model: VH 150U).
1) Extrusion: mixing paraffin oil with polyolefin resin to obtain a diluent-polyolefin resin mixed system, wherein the mass ratio of polyethylene in the diluent-polyolefin resin mixed system is 20%, and the diluent-polyolefin resin mixed system is heated and melted by an extruder to form a uniform mixed melt;
2) And (3) forming: flowing out the mixed melt obtained in the step (1) to a casting roller for cooling, carrying out phase separation, and cooling and forming to obtain a membrane;
3) Biaxial stretching: heating the membrane prepared in the step (2) to a temperature close to the melting point, and performing biaxial stretching to orient molecular chains, wherein biaxial synchronous stretching is adopted, and the biaxial stretching temperature T1 is 118 ℃.
4) And (3) extracting and drying: eluting the residual diluent in the biaxially stretched membrane in the step (3) by using dichloromethane, and drying for 10s at 40 ℃.
5) And (3) transversely stretching the film obtained in the step (4) after the extraction and drying treatment according to the condition of the second transverse stretching, wherein the transverse stretching temperature is T3, and the T3 is 135 ℃.
6) Shaping: and (3) transversely stretching the step (5) and then carrying out heat treatment at 135 ℃ for 20s to obtain the porous film, namely the high-porosity and high-strength diaphragm.
Comparative example 3 conventional Process
1) Extrusion: mixing paraffin oil with polyolefin resin to obtain a diluent-polyolefin resin mixed system, wherein the mass ratio of polyethylene in the diluent-polyolefin resin mixed system is 40%, and the diluent-polyolefin resin mixed system is heated and melted by an extruder to form a uniform mixed melt;
2) And (3) forming: flowing out the mixed melt obtained in the step (1) to a casting roller for cooling, carrying out phase separation, and cooling and forming to obtain a membrane;
3) And (3) extracting and drying: eluting the residual diluent in the biaxially stretched membrane in the step (3) by using dichloromethane, and drying for 20s at 20 ℃.
4) And (3) transversely stretching: transversely stretching the dried film obtained in the step (4), wherein the transverse stretching temperature T2 is 135 DEG C
5) Shaping: and (3) transversely stretching the step (4), and then carrying out heat treatment at 135 ℃ for 20s to obtain the porous film.
And (3) performance detection:
(1) The porosity test method comprises the following steps: taking a diaphragm with the specification of 10cm multiplied by 10cm, and firstly weighing the mass mu of the dry film 0 The membrane is completely soaked in absolute ethyl alcohol for a certain time, then the membrane is rapidly taken out, the absolute ethyl alcohol on the surface of the membrane is gently wiped by filter paper, and then the wet membrane is weighed with the mass mu. The porosity (. Epsilon.) of the separator can be obtained by calculation according to the formula (1). In the formula (1), ρ 0 The density of the separator material and absolute ethanol, respectively.
The needling strength test method comprises the following steps: according to the detection standard of GB/T36363-2018, the needling strength is tested by an electronic needling strength tester;
the aperture testing method comprises the following steps: the diaphragm aperture was tested using a Porolux 1000 type gas-liquid interface aperture tester from belgium Luo Mei, a special company.
TABLE 1
TABLE 2
The results show that:
example 2 increases the mass ratio of polyethylene so that the gram weight is relatively larger, the thickness of the polyethylene at the elevated stretching temperature becomes smaller, example 3 decreases the mass ratio of polyethylene, the gram weight becomes smaller, the thickness of the polyethylene at the reduced stretching temperature becomes larger, example 4 only changes the stretching temperature, needling/gram weight is one of key indexes for measuring the mechanical strength of a diaphragm, needling is in a direct proportion to the gram weight, the magnitude of the mechanical strength can be measured by the magnitude of the needling/gram weight value, the gram weight refers to the weight of the diaphragm in unit area, and the unit is g/m 2 。
Comparative examples 1 and 2 cancel the lateral stretching of step 5 or the second lateral stretching of step 6, respectively, and are low in porosity, and although the needling strength is high, the grammage is large, so that the needling/grammage value is small, showing that the combination of the two lateral stretching steps of the present application can effectively improve the mechanical strength of the separator.
Comparative example 3 is an asynchronous double-pull process, which has low porosity and high thickness and cannot meet the production requirement.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (10)
1. A preparation method of a high-porosity and high-strength battery diaphragm is characterized in that the diaphragm is made of polyolefin resin;
the method comprises the following steps:
(1) Extrusion: mixing a diluent with polyolefin resin to obtain a diluent-polyolefin resin mixed system; heating and melting the diluent-polyolefin resin mixed system through an extruder to form a uniform mixed melt;
(2) And (3) forming: flowing out the mixed melt obtained in the step (1) to a casting roller for cooling, carrying out phase separation, and cooling and forming to obtain a membrane;
(3) Biaxial stretching: heating the membrane prepared in the step (2) to a temperature close to the melting point, and performing biaxial stretching to orient molecular chains, wherein the biaxial synchronous stretching is adopted, and the biaxial stretching temperature T1 is 100 ℃ less than T1 less than 125 ℃;
(4) And (3) extracting and drying: eluting the diluent remained in the membrane subjected to the biaxial stretching in the step (3) by using dichloromethane, and drying;
(5) And (3) transversely stretching: transversely stretching the dried film obtained in the step (4), wherein the transverse stretching temperature T2 is 110 ℃ less than T2 less than 140 ℃;
(6) Performing second transverse stretching, namely performing second transverse stretching on the film subjected to the transverse stretching treatment in the step (5), wherein the second transverse stretching temperature is T3, and T2-10 ℃ is less than T3 and less than T2+10 ℃;
(7) Shaping: and (3) transversely stretching the step (6) and then carrying out heat treatment to obtain the porous film, namely the high-porosity and high-strength diaphragm.
2. The method according to claim 1, wherein the mass ratio of the polyolefin resin blend in the diluent-polyolefin resin blend system of step (1) is 15% to 60%; preferably, the mass ratio of the polyolefin resin in the diluent-polyolefin resin mixed system is 15-30%.
3. The method according to claim 1, wherein the polyolefin resin of step (1) is polyethylene; preferably, the average molecular weight of the polyethylene is 60-200 ten thousand.
4. The method of claim 1, wherein the diluent in step (1) is paraffin oil.
5. The process according to claim 1, wherein the polyolefin resin and the diluent in step (1) are heated to a melting temperature of 100℃to 300 ℃.
6. The process according to claim 1, wherein the drying temperature in step (4) is 30-60 ℃, preferably 35-40 ℃.
7. The method according to claim 1, wherein the step (7) is a heat treatment at 130 ℃ to 140 ℃ for 20s to 25s.
8. A high-porosity and high-strength battery diaphragm is characterized in that the porosity of the battery diaphragm is more than or equal to 45 percent, and the MD tensile strength is more than 1700Kgf/cm 2 TD tensile strength > 1500Kgf/cm 2 。
9. A high-porosity and high-strength battery diaphragm is characterized in that the ratio of the needling strength to the weight per unit area of the diaphragm is more than or equal to 105gfcm 2 /g。
10. An electrochemical device comprising the high porosity, high strength battery separator of any one of claims 8, 9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311654475.8A CN117712615A (en) | 2023-12-05 | 2023-12-05 | High-porosity and high-strength diaphragm, preparation method thereof and electrochemical device |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311654475.8A CN117712615A (en) | 2023-12-05 | 2023-12-05 | High-porosity and high-strength diaphragm, preparation method thereof and electrochemical device |
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| CN117712615A true CN117712615A (en) | 2024-03-15 |
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| CN202311654475.8A Pending CN117712615A (en) | 2023-12-05 | 2023-12-05 | High-porosity and high-strength diaphragm, preparation method thereof and electrochemical device |
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| Country | Link |
|---|---|
| CN (1) | CN117712615A (en) |
-
2023
- 2023-12-05 CN CN202311654475.8A patent/CN117712615A/en active Pending
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