CN113745756A - Low-closed-pore high-film-breaking polyethylene lithium battery diaphragm and preparation method thereof - Google Patents
Low-closed-pore high-film-breaking polyethylene lithium battery diaphragm and preparation method thereof Download PDFInfo
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- CN113745756A CN113745756A CN202110973572.8A CN202110973572A CN113745756A CN 113745756 A CN113745756 A CN 113745756A CN 202110973572 A CN202110973572 A CN 202110973572A CN 113745756 A CN113745756 A CN 113745756A
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- -1 polyethylene lithium Polymers 0.000 title claims abstract description 112
- 239000011148 porous material Substances 0.000 title claims abstract description 17
- 238000002360 preparation method Methods 0.000 title claims abstract description 14
- 239000004698 Polyethylene Substances 0.000 claims abstract description 101
- 229920000573 polyethylene Polymers 0.000 claims abstract description 101
- 239000005662 Paraffin oil Substances 0.000 claims abstract description 31
- 239000002994 raw material Substances 0.000 claims abstract description 30
- 239000002131 composite material Substances 0.000 claims abstract description 23
- 238000000034 method Methods 0.000 claims abstract description 21
- 238000005266 casting Methods 0.000 claims abstract description 19
- 238000000605 extraction Methods 0.000 claims abstract description 8
- 238000002844 melting Methods 0.000 claims description 22
- 230000008018 melting Effects 0.000 claims description 22
- 238000007493 shaping process Methods 0.000 claims description 11
- 238000001125 extrusion Methods 0.000 claims description 9
- 239000011259 mixed solution Substances 0.000 claims description 8
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 7
- 229910052744 lithium Inorganic materials 0.000 claims description 7
- 239000004699 Ultra-high molecular weight polyethylene Substances 0.000 claims description 4
- 229920000092 linear low density polyethylene Polymers 0.000 claims description 4
- 239000004707 linear low-density polyethylene Substances 0.000 claims description 4
- 238000010345 tape casting Methods 0.000 claims description 4
- 229920000785 ultra high molecular weight polyethylene Polymers 0.000 claims description 4
- 229920001903 high density polyethylene Polymers 0.000 claims description 2
- 239000004700 high-density polyethylene Substances 0.000 claims description 2
- 229920001684 low density polyethylene Polymers 0.000 claims description 2
- 239000004702 low-density polyethylene Substances 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 7
- 238000002156 mixing Methods 0.000 abstract description 6
- 239000000155 melt Substances 0.000 abstract description 5
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 238000013329 compounding Methods 0.000 abstract description 3
- 230000007547 defect Effects 0.000 abstract description 3
- 230000000717 retained effect Effects 0.000 abstract description 3
- 239000003085 diluting agent Substances 0.000 abstract 1
- 239000012188 paraffin wax Substances 0.000 abstract 1
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 9
- 239000012528 membrane Substances 0.000 description 5
- 239000004743 Polypropylene Substances 0.000 description 4
- 230000002457 bidirectional effect Effects 0.000 description 4
- 229920000642 polymer Polymers 0.000 description 4
- 229920001155 polypropylene Polymers 0.000 description 4
- 238000010791 quenching Methods 0.000 description 3
- 230000000171 quenching effect Effects 0.000 description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000004512 die casting Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 150000002500 ions Chemical class 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
- 238000004080 punching Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
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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
-
- 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
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Cell Separators (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
Abstract
The invention relates to a low-closed-pore high-film-breaking polyethylene lithium battery diaphragm and a preparation method thereof, belonging to the field of battery diaphragm production and manufacturing. The method comprises the step of mixing and processing two raw materials with paraffin oil by using an extruder A and an extruder B respectively to obtain two different paraffin oil-polyethylene blending systems. And (3) casting the film by using the A/B/A type three-cavity slit die head and a casting roller. And the cast film is subjected to at least four steps of biaxial stretching, diluent extraction, transverse stretching and retraction setting to obtain the polyethylene composite diaphragm. The invention adopts two polyethylene raw materials with different properties and processes the polyethylene raw materials in a three-layer compounding manner, so that the characteristics of the polyethylene raw materials in different layers are retained, the problem that the single raw material or mixed material of the biaxial stretching diaphragm in the prior art cannot give consideration to both low pore-closing temperature and high film breaking temperature is solved, and the defect of low needling strength of the composite diaphragm by a melt stretching method is overcome.
Description
Technical Field
The invention relates to the field of battery diaphragm production and manufacturing, in particular to a novel low-closed-pore high-rupture-membrane polyethylene lithium battery diaphragm and a preparation method thereof.
Background
The lithium battery diaphragm is an important component of the lithium ion battery, wherein the diaphragm base material can isolate the positive electrode and the negative electrode to prevent short circuit in the battery, and the nano-scale micropores in the diaphragm can play a role of an ion transmission channel. At present, the lithium battery diaphragm with the widest application range is mainly a polyolefin diaphragm.
The diaphragm plays an important role in the rate capability and the cycle life of the lithium battery, and is more concerned about the safety of the battery. In recent years, the improvement of the performance of the diaphragm in the industry mainly focuses on the aspects of improving the needling strength, improving the heat resistance, reducing the closed pore temperature, improving the diaphragm breaking temperature and the like.
In the lithium ion battery charge-discharge process, the temperature can rise to a certain extent, and when the battery appears the abnormity such as short circuit, the temperature can rise violently, and after reaching a certain degree, the inside obturator phenomenon that can take place of diaphragm to isolated the charge-discharge current, prevent that the temperature from further rising and taking place thermal runaway. High temperature rupture means that when the temperature of the material is too high, the membrane loses the integrity of the membrane structure due to melting.
The lower the closed pore temperature of the lithium battery diaphragm is, the higher the diaphragm breaking temperature is, and the better the safety of the battery is. Because the closed pore temperature and the rupture temperature of the diaphragm are related to the melting characteristics of the material, the closed pore temperature and the rupture temperature are relatively stable for a single material, and the preparation of the composite diaphragm by adopting two raw materials is the most effective method for simultaneously obtaining the low closed pore characteristic and the high rupture characteristic.
In the prior art, a method for preparing a polypropylene and polyethylene composite diaphragm by adopting a melt-drawing mode is available, namely two polyethylene and polypropylene raw materials are processed into a melt state, the melt is extruded by a three-channel die head, and then the three-layer polypropylene/polyethylene/polypropylene composite diaphragm is obtained by longitudinal drawing. However, this method is only a method of stretching in the machine direction and has a transverse strength of about one tenth of that in the machine direction, and thus the needle punching strength is low.
Compared with a melt unidirectional stretching method, a polyethylene diaphragm prepared by a wet bidirectional stretching method has higher needling strength, the used raw materials are single-grade polyethylene or different polyethylene raw materials are blended, the higher the melting point is, the higher the closing temperature and the breaking temperature are, and the high melting point and the low melting point can not be simultaneously achieved no matter the single-grade polyethylene or the blended polyethylene raw materials are determined by the melting points of the closing temperature and the breaking temperature, so that the diaphragm can not simultaneously obtain the characteristics of low closing and high breaking.
Disclosure of Invention
Aiming at the technical problems, the invention provides a novel low-closed-pore high-film-breaking polyethylene lithium battery diaphragm and a preparation method thereof. The polyethylene lithium battery diaphragm provided by the invention has excellent needling strength while simultaneously achieving low closed pore and high film breaking characteristics.
The term "low closed cell" as used herein means: reducing the temperature of the closed cells;
the high membrane rupture of the invention refers to: the temperature for breaking the membrane is increased.
The purpose of the invention can be realized by the following technical scheme:
the invention provides a low-closed-pore high-rupture polyethylene lithium battery diaphragm, the raw material of the diaphragm is polyethylene with two different molecular weights and structures, namely polyethylene A and polyethylene B, and the diaphragm is a polyethylene A/polyethylene B/polyethylene A three-layer composite structure.
According to a preferable technical scheme, the polyethylene A used by the outer layer of the polyethylene lithium battery diaphragm is high-density polyethylene or ultrahigh molecular weight polyethylene, and the polyethylene B used by the inner layer is low-density polyethylene or linear low-density polyethylene.
As a preferable technical scheme, the molecular weight of the polyethylene A is 80-200 ten thousand, and the molecular weight of the polyethylene B is 10-50 ten thousand.
As a preferred technical scheme, the molecular weight of the polyethylene A is 100-150 ten thousand.
As a preferred technical scheme, the molecular weight of the polyethylene B is 12-17 ten thousand.
As a preferred technical scheme, the melting point of the polyethylene A is 135-145 ℃, and the melting point of the polyethylene B is 120-127 ℃.
According to the preferable technical scheme, in the raw materials of the diaphragm, the mass ratio of polyethylene A to polyethylene B is 1-10: 1 to 10.
According to a preferable technical scheme, in the raw material of the diaphragm, the mass ratio of polyethylene A to polyethylene B is 6: 1.
the second purpose of the invention is to provide the preparation method of the polyethylene lithium battery diaphragm, which comprises the following steps:
(1) injecting paraffin oil and polyethylene A into an extruder A, extruding by using the extruder A to obtain a mixed melt A, injecting paraffin oil and polyethylene B into an extruder B, and extruding by using the extruder B to obtain a mixed melt B;
(2) and carrying out die head casting on the mixed solution A and the mixed solution B by using an A/B/A type three-cavity slit die head, and further carrying out tape casting on a film by using a tape casting roller to obtain a porous oil film.
(3) And carrying out biaxial stretching, paraffin oil removal by extraction, transverse stretching and retraction shaping on a porous oil film obtained by casting the film to obtain the polyethylene lithium battery diaphragm.
As a preferred technical scheme, the extrusion temperature of the extruder A in the step (1) is 165-210 ℃, the extrusion temperature of the extruder B is 165-210 ℃, preferably, the extrusion temperature of the extruder A is 175-185 ℃, and the extrusion temperature of the extruder B is 170-180 ℃.
According to a preferable technical scheme, in the mixed melt A in the step (1), the mass ratio of the polyethylene A to the paraffin oil is 1.3-3.5: 6.5-8.7, and preferably the mass ratio of the polyethylene A to the paraffin oil is 1: 3.
according to a preferable technical scheme, in the mixed melt B in the step (1), the mass ratio of the polyethylene B to the paraffin oil is 1.3-4.0: 6.0-8.7, preferably 3: 7.
according to a preferable technical scheme, the mass ratio of the polyethylene A to the polyethylene B in the step (1) is 1-10: 1-10; preferably, in the raw material of the separator, the mass ratio of the polyethylene A to the polyethylene B is 6: 1.
as a preferable technical scheme, before the mixed solution a and the mixed solution B in the step (2) enter an a/B/a type three-cavity slit die head for die casting, the method further comprises filtering the mixed solution a and the mixed solution B respectively.
Further, in the step (2), the mixed melt A enters two channels A at two sides of the A/B/A type three-cavity slit die head, and the mixed melt B enters a channel B in the middle of the die head, so that the composite melt is obtained.
As a preferable technical scheme, the mixed melt A equally passes through two A channels on two sides of an A/B/A type three-cavity slit die head.
As a preferable technical scheme, the casting film in the step (2) is obtained by flowing out a composite melt obtained by die head casting sheet to a casting roller for quenching, wherein the temperature of the casting roller is set to be 12-30 ℃, and preferably, the temperature of the casting roller is set to be 18-25 ℃.
As a preferred technical solution, the biaxial stretching conditions in step (3) are as follows: the method comprises longitudinal stretching and transverse stretching, wherein the temperature for longitudinal stretching is 65-137 ℃, the longitudinal stretching magnification is 3-10 times (namely the length after longitudinal stretching is 3-10 times before longitudinal stretching), the temperature for transverse stretching is 105-136 ℃, and the transverse stretching magnification is 3-10 times (the width after transverse stretching is 3-10 times before transverse stretching);
as a preferable technical scheme, the paraffin oil is removed by extraction in the step (3) by using dichloromethane.
As a preferable technical scheme, the transverse stretching operation conditions in the step (3) are as follows: the temperature range used for stretching is 100-138 ℃, and the transverse width after stretching is 130-180% before stretching.
As a preferred technical scheme, the retraction setting in the step (3) is transverse retraction setting, the temperature for the transverse retraction setting is 100-138 ℃, and the transverse retraction proportion is 5-35%; preferably, the retraction shaping also comprises longitudinal retraction shaping, the temperature for the longitudinal retraction shaping is 80-138 ℃, and the longitudinal retraction proportion is 0.1-35%.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
the invention adopts two polyethylene raw materials with different properties and processes the polyethylene raw materials in a three-layer compounding manner, so that the characteristics of the polyethylene raw materials among different layers are retained, and under the diaphragm structure, the raw material types, the raw material proportions and the preparation conditions defined by the invention, the problem that the single raw material or the mixed material of the bidirectional stretching diaphragm in the prior art cannot give consideration to both low closed pore temperature and high diaphragm breaking temperature can be effectively solved, and the defect of low needling strength of the composite diaphragm by a melt stretching method is overcome.
Drawings
FIG. 1 is a schematic view of the extrusion and die head sheet casting process of the polyethylene separator preparation method of the present invention
Detailed Description
The present invention is further illustrated by the following figures and specific examples, which are to be understood as illustrative only and not as limiting the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalent modifications thereof which may occur to those skilled in the art upon reading the present specification.
Example 1
1. Preparing raw materials:
in this example, an ultra-high-molecular-weight polyethylene having a molecular weight of 150 million was used as polyethylene A (melting point: 136.5 ℃ C., manufacturer: Korea oil; type: VH150U), and a linear low-density polyethylene having a molecular weight of 15 million was used as polyethylene B (melting point: 123 ℃ C., manufacturer: Exxon Mobil chemical, type: LL1001 BU).
2. Extruding and plasticizing:
firstly, injecting paraffin oil and polyethylene A into a double-screw extruder A, mixing and melting the polyethylene A with a melting point of 136.5 ℃ and the paraffin oil at 186.5 ℃ to obtain a mixed melt A, wherein the mass ratio of the polyethylene A to the paraffin oil in the mixed melt A is 1: 3.
simultaneously injecting paraffin oil and polyethylene B into a double-screw extruder B, mixing and melting the polyethylene B with a melting point of 123 ℃ and the paraffin oil at a temperature of 173 ℃ to obtain a mixed melt B, wherein the mass ratio of the polyethylene B to the paraffin oil in the mixed melt B is 3: 7.
the mass ratio of the polymer A to the polymer B is 6: 1.
3. die head casting: the mixed melt a and the mixed melt B obtained above are respectively filtered by using a disc filter, and then processed by using an a/B/a type three-cavity slit die head to obtain a composite melt, wherein the mixed melt a uses two a channels at two sides of the die head (the mixed melt a equally passes through the two a channels at the two sides), and the mixed melt B uses a B channel at the middle part of the die head (fig. 1), so as to obtain the composite melt.
4. Casting a film: and (3) allowing the obtained composite melt to flow out of a roller of a casting roller for quenching, wherein the temperature of the roller is 25 ℃, and a porous oil film with a polyethylene A/polyethylene B/polyethylene A three-layer composite structure is obtained, wherein the mass ratio of the polyethylene A/polyethylene B/polyethylene A three-layer composite structure is 3:1: 3.
5. And (3) bidirectional stretching: and (3) stretching the porous oil film with the three-layer composite structure in the longitudinal direction and the transverse direction by using a stretcher, wherein the longitudinal stretching temperature is 105 ℃, the length after longitudinal stretching is 7 times that before longitudinal stretching, the transverse stretching temperature is 117 ℃, and the width after transverse stretching is 7 times that before transverse stretching.
6. And (3) paraffin oil removal by extraction: after the biaxial stretching was completed, the paraffin oil in the film was removed by extraction with methylene chloride.
7. Transverse stretching and retraction setting: the film obtained through the above steps was stretched at 120 ℃ using a transverse stretcher, and the width after transverse stretching was 150% of that before stretching.
The retraction setting operation conditions are as follows: the method comprises transverse retraction and longitudinal retraction, wherein the temperature for transverse retraction and shaping is 120 ℃, the transverse retraction proportion is 15% (namely the width after transverse retraction is 85% before retraction), the temperature for longitudinal retraction and shaping is 120 ℃, the longitudinal retraction proportion is 5%, and the polyethylene lithium battery diaphragm with low closed pore and high diaphragm breaking characteristics is obtained.
Example 2
1. Preparing raw materials:
in this example, an ultra-high-molecular-weight polyethylene having a molecular weight of 150 million was used as polyethylene A (melting point: 136.5 ℃ C., manufacturer: Korea oil; type: VH150U), and a linear low-density polyethylene having a molecular weight of 18 million was used as polyethylene B (melting point: 123 ℃ C., manufacturer: Exxon Mobil chemical, type: LL1001 BU).
2. Extruding and plasticizing:
firstly, injecting paraffin oil and polyethylene A into a double-screw extruder A, mixing and melting the polyethylene A with a melting point of 136.5 ℃ and the paraffin oil at 186.5 ℃ to obtain a mixed melt A, wherein the mass ratio of the polyethylene A to the paraffin oil in the mixed melt A is 1: 3.
simultaneously injecting paraffin oil and polyethylene B into a double-screw extruder B, mixing and melting the polyethylene B with a melting point of 123 ℃ and the paraffin oil at a temperature of 173 ℃ to obtain a mixed melt B, wherein the mass ratio of the polyethylene B to the paraffin oil in the mixed melt B is 3: 7.
the mass ratio of the polymer A to the polymer B is 6: 1.
3. die head casting: the mixed melt a and the mixed melt B obtained above are respectively filtered by using a disc filter, and then processed by using an a/B/a type three-cavity slit die head to obtain a composite melt, wherein the mixed melt a uses two a channels at two sides of the die head (the mixed melt a equally passes through the two a channels at the two sides), and the mixed melt B uses a B channel at the middle part of the die head (fig. 1), so as to obtain the composite melt.
4. Casting a film: and (3) allowing the obtained composite melt to flow out of a roller of a casting roller for quenching, wherein the temperature of the roller is 25 ℃, and a porous oil film with a polyethylene A/polyethylene B/polyethylene A three-layer composite structure is obtained, wherein the mass ratio of the polyethylene A/polyethylene B/polyethylene A three-layer composite structure is 3:1: 3.
5. And (3) bidirectional stretching: the porous oil film with the three-layer composite structure is stretched in the longitudinal direction and the transverse direction by using a stretcher, the longitudinal stretching temperature is 107 ℃, the length after longitudinal stretching is 7 times that before stretching, the transverse stretching temperature is 118 ℃, and the width after transverse stretching is 7 times that before stretching.
6. And (3) paraffin oil removal by extraction: after the biaxial stretching was completed, the paraffin oil in the film was removed by extraction with methylene chloride.
7. Transverse stretching and retraction setting: the film obtained through the above steps was stretched at 120 ℃ using a transverse stretcher, and the width after transverse stretching was 150% of that before stretching.
The retraction setting operation conditions are as follows: and only performing transverse retraction, wherein the temperature for transverse retraction and shaping is 120 ℃, and the transverse retraction proportion is 15% (namely the width after transverse retraction is 85% before retraction), so that the polyethylene lithium battery diaphragm with low closed pore and high diaphragm breaking characteristics is obtained.
The comparison of the performance of the separator prepared according to the prior art with that of examples 1 and 2 according to the invention is shown in table 1:
TABLE 1 comparison of Prior Art and example 1 Performance
The invention can be seen in that two polyethylene raw materials with different properties are adopted and processed in a three-layer compounding mode, so that the characteristics of the polyethylene raw materials among different layers are retained, under the diaphragm structure, the raw material types, the raw material proportion and the preparation conditions defined by the invention, the problem that a single raw material or mixed material of a wet-process biaxial stretching diaphragm cannot give consideration to both low pore closing temperature and high film breaking temperature in the prior art can be effectively solved, and the defect of low needling strength of the melt-stretching composite diaphragm is overcome.
Claims (12)
1. The low-closed-pore high-film-breaking polyethylene lithium battery diaphragm is characterized in that raw materials of the diaphragm are polyethylene with two different molecular weights and structures, namely polyethylene A and polyethylene B, and the diaphragm is of a polyethylene A/polyethylene B/polyethylene A three-layer composite structure; preferably, the polyethylene a is high density polyethylene or ultrahigh molecular weight polyethylene, and the polyethylene B is low density polyethylene or linear low density polyethylene.
2. The separator for a lithium polyethylene battery as claimed in claim 1, wherein the molecular weight of polyethylene a is 80 to 200 ten thousand, and the molecular weight of polyethylene B is 10 to 50 ten thousand; preferably, the molecular weight of the polyethylene A is 100-150 ten thousand; preferably, the molecular weight of the polyethylene B is 12 to 17 ten thousand.
3. The separator for a lithium polyethylene battery as claimed in claim 1, wherein the melting point of the polyethylene a is 135 to 145 ℃ and the melting point of the polyethylene B is 120 to 127 ℃.
4. The polyethylene lithium battery separator as claimed in claim 1, wherein in the raw material of the separator, the mass ratio of polyethylene A to polyethylene B is 1-10: 1-10; preferably, in the raw material of the separator, the mass ratio of the polyethylene A to the polyethylene B is 6: 1.
5. a method for preparing the polyethylene lithium battery separator as claimed in claim 1, wherein the method comprises:
(1) injecting paraffin oil and polyethylene A into an extruder A, extruding by using the extruder A to obtain a mixed melt A, injecting paraffin oil and polyethylene B into an extruder B, and extruding by using the extruder B to obtain a mixed melt B;
(2) carrying out die head casting on the mixed solution A and the mixed solution B by using an A/B/A type three-cavity slit die head, and further carrying out tape casting on a film by using a tape casting roller to obtain a porous oil film;
(3) and carrying out biaxial stretching, paraffin oil removal by extraction, transverse stretching and retraction shaping on a porous oil film obtained by casting the film to obtain the polyethylene lithium battery diaphragm.
6. The method for preparing the polyethylene lithium battery separator according to claim 5, wherein the extrusion temperature of the extruder A in the step (1) is 165-210 ℃, the extrusion temperature of the extruder B is 165-210 ℃, preferably, the extrusion temperature of the extruder A is 175-195 ℃, and the extrusion temperature of the extruder B is 170-180 ℃.
7. The preparation method of the polyethylene lithium battery separator as claimed in claim 5, wherein in the mixed melt A in the step (1), the mass ratio of the polyethylene A to the paraffin oil is 1.3-3.5: 6.5-8.7; preferably, the mass ratio of the polyethylene A to the paraffin oil is 1: 3.
8. the preparation method of the polyethylene lithium battery separator as claimed in claim 5, wherein in the mixed melt B in the step (1), the mass ratio of the polyethylene B to the paraffin oil is 1.3-4.0: 6.0-8.7; preferably, the mass ratio of the polyethylene B to the paraffin oil is 3: 7.
9. the method for preparing a polyethylene lithium battery separator according to claim 5, wherein the casting roll temperature in the step (2) is 12 ℃ to 30 ℃, preferably 18 ℃ to 25 ℃.
10. The preparation method of the polyethylene lithium battery separator as claimed in claim 5, wherein the biaxial stretching operation conditions in the step (3) include longitudinal stretching and transverse stretching, the temperature for longitudinal stretching is 65 ℃ to 137 ℃, the longitudinal stretching ratio is 3 to 10 times, the temperature for transverse stretching is 105 ℃ to 136 ℃, and the transverse stretching ratio is 3 to 10 times.
11. The method for preparing a separator for a lithium polyethylene battery as claimed in claim 5, wherein the transverse stretching operation conditions in the step (3) are as follows: the temperature range used for stretching is 100-138 ℃, and the transverse width after stretching is 130-180% before stretching.
12. The preparation method of the polyethylene lithium battery diaphragm according to claim 5, wherein the retraction setting in the step (3) is transverse retraction setting, the temperature for the transverse retraction setting is 100-138 ℃, and the transverse retraction ratio is 5-35%; preferably, the retraction shaping also comprises longitudinal retraction shaping, the temperature for the longitudinal retraction shaping is 80-138 ℃, and the longitudinal retraction proportion is 0.1-35%.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115020909A (en) * | 2022-06-29 | 2022-09-06 | 上海恩捷新材料科技有限公司 | Diaphragm for lithium ion battery and preparation method thereof |
| CN115377608A (en) * | 2022-09-15 | 2022-11-22 | 河北金力新能源科技股份有限公司 | High-safety lithium battery diaphragm and preparation method thereof |
| CN116093545A (en) * | 2023-03-15 | 2023-05-09 | 中材锂膜(南京)有限公司 | Polyolefin microporous membrane and preparation method thereof, battery diaphragm and electrochemical device |
| CN117559081A (en) * | 2024-01-08 | 2024-02-13 | 中材锂膜(内蒙古)有限公司 | Ultrathin polyolefin lithium battery diaphragm, preparation method thereof and lithium ion battery |
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| CN101241984A (en) * | 2008-03-14 | 2008-08-13 | 深圳市富易达电子科技有限公司 | A compound diaphragm for lithium ion battery and its making method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115020909A (en) * | 2022-06-29 | 2022-09-06 | 上海恩捷新材料科技有限公司 | Diaphragm for lithium ion battery and preparation method thereof |
| CN115020909B (en) * | 2022-06-29 | 2024-04-05 | 江苏恩捷新材料科技有限公司 | Diaphragm for lithium ion battery and preparation method thereof |
| CN115377608A (en) * | 2022-09-15 | 2022-11-22 | 河北金力新能源科技股份有限公司 | High-safety lithium battery diaphragm and preparation method thereof |
| CN116093545A (en) * | 2023-03-15 | 2023-05-09 | 中材锂膜(南京)有限公司 | Polyolefin microporous membrane and preparation method thereof, battery diaphragm and electrochemical device |
| CN117559081A (en) * | 2024-01-08 | 2024-02-13 | 中材锂膜(内蒙古)有限公司 | Ultrathin polyolefin lithium battery diaphragm, preparation method thereof and lithium ion battery |
| CN117559081B (en) * | 2024-01-08 | 2024-04-05 | 中材锂膜(内蒙古)有限公司 | Ultrathin polyolefin lithium battery diaphragm, preparation method thereof and lithium ion battery |
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Application publication date: 20211203 |