CN117977118A - Diaphragm, preparation method thereof and method for judging crosslinking degree of diaphragm - Google Patents

Diaphragm, preparation method thereof and method for judging crosslinking degree of diaphragm Download PDF

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Publication number
CN117977118A
CN117977118A CN202311711614.6A CN202311711614A CN117977118A CN 117977118 A CN117977118 A CN 117977118A CN 202311711614 A CN202311711614 A CN 202311711614A CN 117977118 A CN117977118 A CN 117977118A
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diaphragm
crosslinking degree
photoinitiator
degree
crosslinking
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郭峥
李大伟
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Liyang Tns Electro Energy Co ltd
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Liyang Tns Electro Energy Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/494—Tensile strength
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/71—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light thermally excited
    • G01N21/73—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light thermally excited using plasma burners or torches
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/22—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material
    • G01N23/223—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material by irradiating the sample with X-rays or gamma-rays and by measuring X-ray fluorescence
    • 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
    • H01M50/417—Polyolefins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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Abstract

The invention relates to the technical field of diaphragms, in particular to a diaphragm, a preparation method thereof and a method for judging the crosslinking degree of the diaphragm. According to the diaphragm provided by the invention, the TMA rupture temperature of the diaphragm is more than or equal to 170 ℃, the tensile strength is more than or equal to 2000kgf/cm 2, and the elongation is more than or equal to 100%. The preparation method of the diaphragm comprises the following steps: sequentially dip-coating and illumination treatment are carried out on the polyolefin substrate to obtain a diaphragm; wherein the dip-coating liquid for dip-coating comprises photoinitiation, a synergistic agent and an organic solvent. The membrane has higher membrane rupture temperature and high-temperature strength. According to the preparation method of the diaphragm, the photoinitiator and the synergist are used in a combined mode, so that the initiation efficiency of the photoinitiator is improved, the crosslinking degree of the diaphragm is improved, the residue of the photoinitiator is reduced, and the performance of the diaphragm is improved.

Description

Diaphragm, preparation method thereof and method for judging crosslinking degree of diaphragm
Technical Field
The invention relates to the technical field of diaphragms, in particular to a diaphragm, a preparation method thereof and a method for judging the crosslinking degree of the diaphragm.
Background
The diaphragm is used as an important component of the lithium battery and is positioned between the positive electrode and the negative electrode of the battery, and can separate the positive electrode from the negative electrode of the battery, prevent the internal short circuit of the battery, allow lithium ions to pass through freely and ensure the charge and discharge of the battery. Polyolefin diaphragm has become one of the commercial diaphragm materials because of the advantages of high strength, good acid and alkali resistance and solvent resistance, electrochemical stability and the like. Polyolefin materials become important raw materials for commercial separators because of the advantages of low cost, high chemical stability, good electrochemical stability and the like. However, the polyolefin material has a low melting point, and is easy to fuse and rupture when the battery is abnormally overheated, so that the battery is internally short-circuited, thereby being dangerous and seriously threatening the life safety of a user. Therefore, the safety of the lithium battery can be improved by improving the rupture temperature of the diaphragm.
In order to improve the safety performance of the battery, the method adopted in the prior art comprises the following steps: (1) Various resins are doped or blended, for example, patent publication No. CN111244369A provides a battery separator comprising a polyolefin porous membrane comprising polyethylene and polypropylene resin, wherein when inorganic particles are contained, the membrane rupture temperature is above 180 ℃, and the control of the blending process and the cost increase caused by polypropylene are disadvantages of the process; (2) Silicone grafted polyethylene modified cross-links, such as the patent publication CN105576172a, the patent publication CN111108627a, the patent publication CN111108628A, and the patent publication CN111081949a disclose a method for preparing a cross-linked membrane that increases the rupture temperature, by adding an initiator, a silicone cross-linking agent, and a catalyst during the preparation of the polyethylene membrane, thereby preparing the silicone cross-linked membrane. However, the method inevitably generates gel points in the preparation process, which causes abnormal membrane surface of the membrane, and the shrinkage in the crosslinking process is serious and nonuniform.
In the prior art, more photoinitiator needs to be added in the preparation process of the diaphragm in order to improve the rupture temperature, but excessive photoinitiator is used to bring a plurality of problems, such as more migration objects, reduced weather resistance, insufficient curing thickness of a coating film and increased cost; meanwhile, the crosslinking degree is not high, and the rupture temperature is difficult to further increase.
The dip-coating process disclosed in the patent with publication number of CN115995655A and the patent with publication number of CN115377610A can realize the complete crosslinking or partial crosslinking treatment of the polyolefin porous diaphragm material by a more convenient process to obtain a product with excellent heat resistance, but reactants used in the dip-coating process have fluidity and concentration change, and continuous small changes of reaction conditions, material concentration, infiltration amount and the like in the rapid continuous production inevitably influence the quality of the product.
In view of this, the present invention has been made.
Disclosure of Invention
The first object of the invention is to provide a diaphragm with high rupture temperature and high temperature strength.
The second object of the present invention is to provide a method for preparing the above-mentioned separator, which can be used for better deep curing and reduce the residual of photoinitiator.
The third object of the present invention is to provide a method for judging the crosslinking degree of the separator, which can rapidly analyze and obtain the crosslinking degree of the separator; the membrane with certain degree of yellowing, which has excellent heat resistance, is obtained through the optimized process and the modified formula, and the membrane degree of yellowing and the degree of crosslinking have correlation, so that the membrane crosslinking treatment effect can be evaluated and detected on line in real time, and becomes an important parameter for process control.
In order to achieve the above object of the present invention, the following technical solutions are specifically adopted:
The invention provides a diaphragm, wherein TMA rupture temperature of the diaphragm is more than or equal to 170 ℃, tensile strength is more than or equal to 2000kgf/cm 2, and elongation is more than or equal to 100%.
Further, at least one of the following features (1) to (4) is included;
(1) TMA rupture temperature of the diaphragm is 195-260 ℃;
(2) The needling strength of the diaphragm is more than or equal to 40 gf/mum;
(3) The yellowness index of the diaphragm is 1% -5%;
(4) The crosslinking degree of the diaphragm is 1-75%.
Further, the TMA rupture temperature of the diaphragm is 214-260 ℃;
Preferably, TMA rupture temperature of the diaphragm is 220-260 ℃.
Further, at least one of the following features (1) to (3) is included:
(1) The yellowness index of the diaphragm is 1-1.5, and the corresponding crosslinking degree is 1% -45%;
(2) The yellowness index of the diaphragm is 1.5-4, and the corresponding crosslinking degree is 45% -55%;
(3) The yellowness index of the diaphragm is 4-5, and the corresponding crosslinking degree is 55% -75%.
The invention also provides a preparation method of the diaphragm, which comprises the following steps:
Sequentially dip-coating and illumination treatment are carried out on the polyolefin substrate to obtain the diaphragm; wherein the dip-coating liquid for dip-coating comprises a photoinitiator, a synergistic agent and an organic solvent.
The photoinitiator comprises at least one of benzophenone, thioxanthone type photoinitiators and photoinitiators 819;
preferably, the photoinitiator comprises a thioxanthone photoinitiator.
Further, at least one of the following features (1) to (3) is included;
(1) The synergist comprises ethyl 4-dimethylaminobenzoate;
(2) The mass ratio of the photoinitiator to the synergist is 1: (1-10);
(3) The mass ratio of the photoinitiator to the organic solvent is 1: (20-1000).
The invention also provides a method for judging the crosslinking degree of the diaphragm, and the crosslinking degree of the diaphragm is obtained according to the yellowing degree of the diaphragm;
Or alternatively
Obtaining the crosslinking degree of the diaphragm according to the content of the S element in the diaphragm;
Further, the membrane has a yellowness index of 0 to 1 and a corresponding degree of crosslinking of less than 1%; the yellowness index of the diaphragm is 1-1.5, and the corresponding crosslinking degree is 1% -45%; the yellowness index of the diaphragm is 1.5-4, and the corresponding crosslinking degree is 45% -55%; the yellowness index of the diaphragm is 4-5, and the corresponding crosslinking degree is 55% -75%.
Further, the content of S element in the diaphragm is 90-300 ppm, and the corresponding crosslinking degree is 50% -62%; the content of S element in the diaphragm is 300-500 ppm, and the corresponding crosslinking degree is 62% -70%; the content of S element in the diaphragm is 500-700 ppm, and the corresponding crosslinking degree is 70-73%; the content of S element in the diaphragm is 700-1000 ppm, and the corresponding crosslinking degree is 73% -75%.
Compared with the prior art, the invention has the beneficial effects that:
1. the diaphragm provided by the invention has higher rupture temperature and high-temperature strength.
2. According to the preparation method of the diaphragm, the photoinitiator and the synergist are compounded, so that the initiation efficiency of the photoinitiator is greatly improved, the crosslinking degree is improved, the residue of the photoinitiator is reduced, and the diaphragm rupture temperature and the high-temperature strength of the diaphragm are improved.
3. According to the method for judging the crosslinking degree of the diaphragm, provided by the invention, the crosslinking degree of the diaphragm can be obtained by rapid analysis according to the yellowing degree of the diaphragm or the content of S element in the diaphragm; the membrane has correlation between the yellowness and the crosslinking degree, can evaluate and detect the crosslinking treatment effect of the membrane on line in real time, and provides important parameters for process control.
Detailed Description
The technical solution of the present invention will be clearly and completely described in conjunction with the specific embodiments, but it will be understood by those skilled in the art that the examples described below are some, but not all, examples of the present invention, and are intended to be illustrative only and should not be construed as limiting the scope of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
In some embodiments of the invention, a separator is provided having a TMA rupture temperature of greater than or equal to 170 ℃, a tensile strength of greater than or equal to 2000kgf/cm 2, and an elongation of greater than or equal to 100%.
The diaphragm provided by the invention has higher rupture temperature and high-temperature strength.
In some embodiments of the invention, the TMA rupture temperature of the membrane is 195-260 ℃.
In some embodiments of the invention, the TMA rupture temperature of the membrane is 214 to 260 ℃; preferably, the TMA rupture temperature of the diaphragm is 220-260 ℃; more preferably 230 to 258 ℃.
In some embodiments of the invention, the needle punching strength of the separator is not less than 40gf/um.
In some embodiments of the invention, the membrane has a yellowness index of 1% to 5%.
In some embodiments of the invention, the separator has a degree of crosslinking of 1% to 75%.
In some embodiments of the invention, the membrane has a yellowness index of 1 to 1.5, corresponding to a degree of crosslinking of 1% to 45%;
The yellowness index of the diaphragm is 1.5-4, and the corresponding crosslinking degree is 45% -55%;
the yellowness index of the diaphragm is 4-5, and the corresponding crosslinking degree is 55% -75%.
The diaphragm provided by the invention has certain yellowness, and the diaphragm yellowness and the crosslinking degree have correlation, so that the diaphragm crosslinking treatment effect can be evaluated and detected on line in real time, and the diaphragm yellowness and the crosslinking degree become important parameters for process control.
In some embodiments of the present invention, there is also provided a method for preparing the above-mentioned separator, including the steps of:
Sequentially dip-coating and illumination treatment are carried out on the polyolefin substrate to obtain a diaphragm; wherein the dip-coating liquid for dip-coating comprises a photoinitiator, a synergist and an organic solvent.
The photoinitiator and the synergist are transferred into micropores of the polyolefin substrate and the surface of the substrate through the solution state, and cross-linking is realized through illumination treatment, so that the diaphragm with excellent performance is prepared.
According to the preparation method of the diaphragm, the photoinitiator and the synergist are used in a combined mode, so that the cost can be reduced, the initiation efficiency of the photoinitiator can be greatly improved, the deep solidification is better, the crosslinking degree of the diaphragm is greatly improved, the residue of the photoinitiator is reduced, and the rupture temperature and the high-temperature strength of the diaphragm are improved.
In some embodiments of the present invention, the photoinitiator includes at least one of benzophenone, thioxanthone type photoinitiators, and photoinitiator 819; preferably, the photoinitiator comprises a thioxanthone photoinitiator.
In some embodiments of the invention, the thioxanthone photoinitiator comprises 2 isopropyl thioxanthone (2-Isopropylthioxanthone, ITX).
In some embodiments of the invention, the synergist comprises ethyl 4-dimethylaminobenzoate (EDAB).
In some embodiments of the present invention, the polyolefin substrate comprises at least one of polyethylene, polypropylene, polybutene, polyhexene, ethylene propylene copolymer, ethylene butene copolymer, ethylene hexane copolymer.
In some embodiments of the invention, the parameters of the polyolefin substrate are: the thickness is 0.5-20 mu m, TMA rupture temperature is less than or equal to 152 ℃, impedance rupture temperature is less than or equal to 152 ℃, crosslinking degree is less than or equal to 0.5%, porosity is 20-60%, ventilation value is less than or equal to 400s/100cc, aperture is 20-80 nm, needling strength is more than or equal to 35 gf/mu m, and thermal shrinkage rate at 130 ℃ is less than or equal to 25%.
In some embodiments of the invention, the mass ratio of photoinitiator to synergist is 1: (1-10); typical but non-limiting, for example, the mass ratio of photoinitiator to synergist may be 1: 1. 1: 2. 1: 3. 1: 4. 1: 5. 1: 6. 1: 7. 1: 8. 1: 9. 1:10 or any two thereof.
In some embodiments of the invention, the mass ratio of photoinitiator to organic solvent is 1: (20-1000); typical, but not limiting, for example, the mass ratio of photoinitiator to organic solvent may be 1: 20. 1: 100. 1: 200. 1: 300. 1: 400. 1: 500. 1: 600. 1: 700. 1: 800. 1: 900. 1:1000 or any two thereof.
In some embodiments of the invention, the photoinitiator is present in the dip coating solution in an amount of 0.1wt% to 1wt% and the synergist is present in an amount of 0.05wt% to 0.5wt%; preferably, the content of the photoinitiator in the dip coating liquid is 0.5-1 wt%, and the content of the synergist is 0.25-0.5 wt%.
The problems of hole blocking and the like are easily caused when the concentration of a single component is too high. According to the invention, by adopting a mode of compounding the photoinitiator and the synergist, the formula cost can be reduced, better deep curing can be obtained, and the photoinitiator residues, especially the introduction and residues of elements except C, H, O, are reduced; the rupture temperature can be raised and the concentration required for the photoinitiator can be reduced.
In some embodiments of the present invention, the organic solvent comprises at least one of methanol, ethanol, methylene chloride, acetone, diethyl ether, petroleum ether, n-hexane, dimethylformamide, dimethylacetamide, and methylpyrrolidone.
In some embodiments of the invention, a method of preparing a polyolefin substrate comprises the steps of:
Mixing polyolefin with paraffin oil, banburying, mixing, extruding, cooling cast sheet, stretching and extracting to obtain polyolefin base material.
In some embodiments of the invention, the mass ratio of polyolefin to paraffinic oil is (2-4): 1.
In some embodiments of the present invention, the polyolefin comprises at least one of polyethylene, polypropylene, polybutene, polyhexene, ethylene propylene copolymer, ethylene butene copolymer, ethylene hexane copolymer.
In some embodiments of the invention, the dip coating is for a period of time ranging from 5 to 30 seconds.
In some embodiments of the invention, the light source for the light treatment is ultraviolet light with a wavelength of 100-400 nm and the time for the light treatment is 0.1-600 s.
In some embodiments of the invention, a lithium battery is also provided, including the separator described above.
The diaphragm rupture temperature in the lithium battery is low, the safety is poor, and the rupture of the diaphragm easily occurs when the battery is abnormally overheated, so that the internal short circuit of the battery is caused. The diaphragm provided by the invention has higher rupture temperature, and is beneficial to improving the safety performance of a lithium battery.
In some embodiments of the present invention, there is also provided a method for determining the crosslinking degree of the separator, including: obtaining the crosslinking degree of the diaphragm according to the yellowing degree of the diaphragm;
Or alternatively
Obtaining the crosslinking degree of the diaphragm according to the content of S element in the diaphragm;
The phenomenon of yellowing under the irradiation of natural sunlight and ultraviolet rays or under the actions of heat, oxygen, stress, trace moisture, improper impurity processes and the like is called yellowing. When the material absorbs light energy, a molecular chain on the absorbed part can generate carbon-carbon bond or cleavage of carbon-hydrogen bond, and the diaphragm, such as a cross-linked polyolefin diaphragm, receives ultraviolet light in the preparation process, generates free radicals and generates yellowing. The degree of crosslinking of the separator can be judged by the degree of yellowing.
Crosslinking of polyolefins generally requires polymerization of the polyolefin by addition of various photoinitiators, elements such as O, S, P contained in the photoinitiator are not contained in the polyolefin, and the amount of the photoinitiator affects the degree of crosslinking of the polyolefin. By characterizing the content of a certain element in the photoinitiator, the content of the photoinitiator can be calculated, so that the crosslinking degree of the polyolefin can be judged.
The yellowness index refers to the degree to which a colorless transparent translucent or nearly white polymeric material deviates from white, or the degree of yellowing. The standard "C" light source meets the CIE specification of the International society of illumination to irradiate materials, and the tristimulus values X, Y, Z of the color of the measured materials are calculated by the following formula: y 1 = 100 (1.28X-1.06Z)/Y.
In some embodiments of the invention, the membrane has a yellowness index of 0 to 1, corresponding to a degree of crosslinking of < 1%; the yellowness index of the diaphragm is 1 to 1.5, and the corresponding crosslinking degree is 1 to 45 percent; the yellowness index of the diaphragm is 1.5-4, and the corresponding crosslinking degree is 45% -55%; the yellowness index of the diaphragm is 4-5, and the corresponding crosslinking degree is 55% -75%.
The membrane has a yellowness index of greater than 1.5, and it can be judged that the membrane has a certain degree of crosslinking, and when the yellowness index is greater than 4, it means that the degree of crosslinking is very high.
In some embodiments of the invention, the diaphragm yellowness index is measured using an integrating sphere spectrophotometer.
In some embodiments of the invention, the content of S element in the diaphragm is 90-300 ppm, and the corresponding crosslinking degree is 50% -62%; the content of S element in the diaphragm is 300-500 ppm, and the corresponding crosslinking degree is 62% -70%; the content of S element in the diaphragm is 500-700 ppm, and the corresponding crosslinking degree is 70-73%; the content of S element in the diaphragm is 700-1000 ppm, and the corresponding crosslinking degree is 73% -75%.
In some embodiments of the invention, the content of S element in the separator is measured by inductively coupled plasma spectroscopy (ICP) or X-ray fluorescence spectroscopy.
The method for obtaining the crosslinking degree of the diaphragm according to the content of the S element in the diaphragm is suitable for the diaphragm adopting thioxanthone photoinitiator in the preparation process.
Example 1
The preparation method of the diaphragm provided by the embodiment comprises the following steps:
S1, the mass ratio is 3:1, mixing polyolefin with paraffin oil, carrying out banburying in sequence, mixing for 10min at 230 ℃, extruding, cooling a cast sheet to obtain an oil-containing substrate, carrying out biaxial stretching (stretching multiplying power is 7 times of each biaxial), and extracting to obtain a substrate;
wherein the thickness of the base material is 8.6 mu m, the TMA rupture temperature is 152 ℃, the impedance rupture temperature is 152 ℃, the crosslinking degree is 0.4%, and the porosity is 34%;
The polyolefin was polyethylene, the air permeability of the substrate was 146s/100cc, the pore diameter was 45nm, the needling strength per unit thickness was 45.9gf/μm, the heat shrinkage MD at 130℃was 16%, and the heat shrinkage TD at 130℃was 12.3%.
S2, uniformly mixing 2-isopropyl thioxanthone, 4-dimethylamino ethyl benzoate and dichloromethane to obtain a dipping and coating liquid; the dip-coating liquid is dip-coated with the base material for full contact, the dip-coating time is 5s, and after drying, ultraviolet irradiation is carried out for 10s, so as to obtain a diaphragm;
Wherein, in the dipping liquid, the content of the 2-isopropyl thioxanthone is 0.1 weight percent, and the content of the 4-dimethyl amino ethyl benzoate is 0.05 weight percent.
Example 2
The preparation method of the separator provided in this example was as described in reference to example 1, except that in step S2, the content of 2-isopropylthioxanthone in the dip-coating liquid was 0.5wt% and the content of 4-dimethylaminoethyl benzoate was 0.25wt%.
Example 3
The preparation method of the separator provided in this example was as described in reference to example 1, except that in step S2, the content of 2-isopropylthioxanthone in the dip-coating liquid was 1wt% and the content of 4-dimethylaminoethyl benzoate was 0.5wt%.
Example 4
The preparation method of the diaphragm provided by the embodiment comprises the following steps:
S1, the mass ratio is 3:1, mixing polyolefin with paraffin oil, carrying out banburying in sequence, mixing for 10min at 230 ℃, extruding, cooling a cast sheet to obtain an oil-containing substrate, carrying out biaxial stretching (stretching multiplying power is 7 times of each biaxial), and extracting to obtain a substrate;
wherein the thickness of the base material is 8.6 mu m, the TMA rupture temperature is 152 ℃, the impedance rupture temperature is 152 ℃, the crosslinking degree is 0.4%, and the porosity is 34%;
The polyolefin was polypropylene, the substrate had a gas permeation value of 90s/100cc, a pore diameter of 80nm, a needle punching strength per unit thickness of 43.5gf/μm, a heat shrinkage MD at 130℃of 16.7% and a heat shrinkage TD at 130℃of 11%.
S2, uniformly mixing 2-isopropyl thioxanthone, 4-dimethylamino ethyl benzoate and dichloromethane to obtain a dipping and coating liquid; the dip-coating liquid is dip-coated with the base material for full contact, the dip-coating time is 5s, and after drying, ultraviolet irradiation is carried out for 10s, so as to obtain a diaphragm;
Wherein, in the dipping liquid, the content of the 2-isopropyl thioxanthone is 0.5 weight percent, and the content of the 4-dimethyl amino ethyl benzoate is 0.25 weight percent.
Example 5
The preparation method of the separator provided in this embodiment is different from that in the reference embodiment 4 only in that in the step S1, the thickness of the substrate is 8.6 μm, the TMA rupture temperature is 152 ℃, the impedance rupture temperature is 152 ℃, the crosslinking degree is 0.4%, and the porosity is 34%;
The polyolefin was an ethylene propylene copolymer, the air permeability of the substrate was 245s/100cc, the pore diameter was 30nm, the needling strength per unit thickness was 45gf/μm, the heat shrinkage MD at 130℃was 15%, and the heat shrinkage TD at 130℃was 12%.
Example 6
The preparation method of the separator provided in this example was as described in reference to example 5, except that 2-isopropylthioxanthone was replaced with benzophenone.
Example 7
The preparation method of the separator provided in this example was as described in reference to example 5, except that 2-isopropylthioxanthone was replaced with photoinitiator 819.
Comparative example 1
The preparation method of the diaphragm provided by the comparative example comprises the following steps:
The mass ratio is 3:1, mixing polyolefin with paraffin oil, carrying out banburying in sequence, mixing for 10min at 230 ℃, extruding, cooling and casting to obtain an oil-containing substrate, carrying out biaxial stretching (stretching multiplying power is 7 times of each biaxial), and extracting to obtain a diaphragm;
Wherein the thickness of the diaphragm is 8.6 mu m, the TMA rupture temperature is 152 ℃, the impedance rupture temperature is 152 ℃, the crosslinking degree is 0.4%, and the porosity is 34%;
The polyolefin was polyethylene, the separator had a ventilation value of 146s/100cc, a pore diameter of 45nm, a needle punching strength per unit thickness of 45.9gf/μm, a heat shrinkage MD at 130℃of 16%, and a heat shrinkage TD at 130℃of 12.3%.
Comparative example 2
The preparation method of the diaphragm provided by the comparative example comprises the following steps:
S1, the mass ratio is 3:1, mixing polyolefin with paraffin oil, carrying out banburying in sequence, mixing for 10min at 230 ℃, extruding, cooling a cast sheet to obtain an oil-containing substrate, carrying out biaxial stretching (stretching multiplying power is 7 times of each biaxial), and extracting to obtain a substrate;
wherein the thickness of the base material is 8.6 mu m, the TMA rupture temperature is 152 ℃, the impedance rupture temperature is 152 ℃, the crosslinking degree is 0.4%, and the porosity is 34%;
the polyolefin was polyethylene, the air permeability of the substrate was 245s/100cc, the pore diameter was 30nm, the needle punching strength per unit thickness was 45gf/μm, the heat shrinkage MD at 130℃was 15%, and the heat shrinkage TD at 130℃was 12%.
S2, uniformly mixing 2-isopropyl thioxanthene and dichloromethane to obtain a dipping liquid; the dip-coating is fully contacted with the base material, the dip-coating time is 5s, and after drying, ultraviolet irradiation is carried out, the irradiation time is 10s, thus obtaining a diaphragm;
Wherein, in dip coating, the content of 2-isopropyl thioxanthone is 0.5wt%.
Comparative example 3
The preparation method of the separator provided in this comparative example was referred to comparative example 2, except that the content of 2-isopropylthioxanthone in dip coating was 1.5wt%.
Comparative example 4
The preparation method of the separator provided in this comparative example was referred to comparative example 2, except that the content of 2-isopropylthioxanthone in dip coating was 3wt%.
Test example 1
The performance of the separators produced in examples 1 to 7 and comparative examples 1 to 4 was measured, and the results are shown in Table 1.
TABLE 1
The separators prepared in example 2 and comparative example 1 were tested for their performance at various temperatures, and the results are shown in table 2.
TABLE 2
Test example 2
The results of the tests of the transmittance and yellowness index of the separators prepared in examples 1 to 7 and examples 1 to 4 are shown in table 3.
TABLE 3 Table 3
Transmittance (%) Yellowness index (%)
Example 1 53.9 3.86
Example 2 52.5 4.21
Example 3 51.2 4.83
Example 4 45.3 2.94
Example 5 40.5 4.02
Example 6 54.2 3.52
Example 7 60.8 1.35
Comparative example 1 62.7 0.81
Comparative example 2 60.5 1.30
Comparative example 3 52.3 4.18
Comparative example 4 51.9 4.13
The contents of the respective elements in example 1, example 2, example 6, example 7, comparative example 1 and comparative example 2 are shown in table 4.
TABLE 4 Table 4
O element content (ppm) S element content (ppm) P element content (ppm) Degree of crosslinking (%)
Example 1 52 94 Not detected 54.1
Example 2 261 458 Not detected 66.5
Example 6 1330 Not detected Not detected 51.2
Example 7 286 Not detected 138 42.1
Comparative example 1 Not detected Not detected Not detected 0.1
Comparative example 2 48 80 Not detected 41.2
The technical proposal of the invention is only used for illustration and not limitation; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims (10)

1. A diaphragm is characterized in that TMA rupture temperature of the diaphragm is more than or equal to 170 ℃, tensile strength is more than or equal to 2000kgf/cm 2, and elongation is more than or equal to 100%.
2. The membrane of claim 1, comprising at least one of the following features (1) to (4);
(1) TMA rupture temperature of the diaphragm is 195-260 ℃;
(2) The needling strength of the diaphragm is more than or equal to 40gf/um;
(3) The yellowness index of the diaphragm is 1% -5%;
(4) The crosslinking degree of the diaphragm is 1-75%.
3. The membrane of claim 1, wherein the TMA rupture temperature of the membrane is 214-260 ℃;
Preferably, TMA rupture temperature of the diaphragm is 220-260 ℃.
4. The membrane of claim 2, comprising at least one of the following features (1) to (3);
(1) The yellowness index of the diaphragm is 1-1.5, and the corresponding crosslinking degree is 1% -45%;
(2) The yellowness index of the diaphragm is 1.5-4, and the corresponding crosslinking degree is 45% -55%;
(3) The yellowness index of the diaphragm is 4-5, and the corresponding crosslinking degree is 55% -75%.
5. The method for producing a separator according to any one of claims 1 to 4, comprising the steps of:
Sequentially dip-coating and illumination treatment are carried out on the polyolefin substrate to obtain the diaphragm; wherein the dip-coating liquid for dip-coating comprises a photoinitiator, a synergistic agent and an organic solvent.
6. The method for producing a separator according to claim 5, wherein the photoinitiator includes at least one of benzophenone, thioxanthone type photoinitiators, and photoinitiators 819;
preferably, the photoinitiator comprises a thioxanthone photoinitiator.
7. The method of producing a separator according to claim 5, comprising at least one of the following features (1) to (3);
(1) The synergist comprises ethyl 4-dimethylaminobenzoate;
(2) The mass ratio of the photoinitiator to the synergist is 1: (1-10);
(3) The mass ratio of the photoinitiator to the organic solvent is 1: (20-1000).
8. The method for judging the crosslinking degree of the separator according to any one of claims 1 to 4, wherein the crosslinking degree of the separator is obtained based on the yellowing degree of the separator;
Or alternatively
And according to the content of the S element in the diaphragm, obtaining the crosslinking of the diaphragm.
9. The method according to claim 8, wherein the membrane has a yellowness index of 0 to 1, corresponding to a degree of crosslinking of < 1%; the yellowness index of the diaphragm is 1-1.5, and the corresponding crosslinking degree is 1% -45%; the yellowness index of the diaphragm is 1.5-4, and the corresponding crosslinking degree is 45% -55%; the yellowness index of the diaphragm is 4-5, and the corresponding crosslinking degree is 55% -75%.
10. The method according to claim 8, wherein the content of S element in the separator is 90-300 ppm, corresponding to a degree of crosslinking of 50-62%; the content of S element in the diaphragm is 300-500 ppm, and the corresponding crosslinking degree is 62% -70%; the content of S element in the diaphragm is 500-700 ppm, and the corresponding crosslinking degree is 70-73%; the content of S element in the diaphragm is 700-1000 ppm, and the corresponding crosslinking degree is 73% -75%.
CN202311711614.6A 2023-12-13 2023-12-13 Diaphragm, preparation method thereof and method for judging crosslinking degree of diaphragm Pending CN117977118A (en)

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