CN113972434A - Lithium battery diaphragm and preparation method thereof - Google Patents
Lithium battery diaphragm and preparation method thereof Download PDFInfo
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- CN113972434A CN113972434A CN202111095237.9A CN202111095237A CN113972434A CN 113972434 A CN113972434 A CN 113972434A CN 202111095237 A CN202111095237 A CN 202111095237A CN 113972434 A CN113972434 A CN 113972434A
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- diaphragm
- lithium battery
- nucleating agent
- preparing
- casting sheet
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 21
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 21
- 238000002360 preparation method Methods 0.000 title claims abstract description 11
- 239000002667 nucleating agent Substances 0.000 claims abstract description 31
- 238000001816 cooling Methods 0.000 claims abstract description 29
- 238000005266 casting Methods 0.000 claims abstract description 24
- 238000000605 extraction Methods 0.000 claims abstract description 21
- 238000002156 mixing Methods 0.000 claims abstract description 12
- 238000001035 drying Methods 0.000 claims abstract description 7
- 239000003960 organic solvent Substances 0.000 claims abstract description 5
- 229920000098 polyolefin Polymers 0.000 claims abstract description 5
- 238000005406 washing Methods 0.000 claims abstract description 4
- 239000006185 dispersion Substances 0.000 claims abstract description 3
- 238000001125 extrusion Methods 0.000 claims abstract description 3
- 239000002994 raw material Substances 0.000 claims abstract description 3
- 238000007493 shaping process Methods 0.000 claims abstract description 3
- 238000010345 tape casting Methods 0.000 claims abstract description 3
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical group ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 claims description 30
- 238000000034 method Methods 0.000 claims description 17
- 229910052751 metal Inorganic materials 0.000 claims description 11
- 239000002184 metal Substances 0.000 claims description 11
- 239000000203 mixture Substances 0.000 claims description 11
- FBPFZTCFMRRESA-FSIIMWSLSA-N D-Glucitol Natural products OC[C@H](O)[C@H](O)[C@@H](O)[C@H](O)CO FBPFZTCFMRRESA-FSIIMWSLSA-N 0.000 claims description 10
- 239000000600 sorbitol Substances 0.000 claims description 10
- QIQXTHQIDYTFRH-UHFFFAOYSA-N octadecanoic acid Chemical compound CCCCCCCCCCCCCCCCCC(O)=O QIQXTHQIDYTFRH-UHFFFAOYSA-N 0.000 claims description 7
- 229910019142 PO4 Inorganic materials 0.000 claims description 5
- CJZGTCYPCWQAJB-UHFFFAOYSA-L calcium stearate Chemical compound [Ca+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O CJZGTCYPCWQAJB-UHFFFAOYSA-L 0.000 claims description 5
- 239000008116 calcium stearate Substances 0.000 claims description 5
- 235000013539 calcium stearate Nutrition 0.000 claims description 5
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 5
- 239000010452 phosphate Substances 0.000 claims description 5
- GUJOJGAPFQRJSV-UHFFFAOYSA-N dialuminum;dioxosilane;oxygen(2-);hydrate Chemical compound O.[O-2].[O-2].[O-2].[Al+3].[Al+3].O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O GUJOJGAPFQRJSV-UHFFFAOYSA-N 0.000 claims description 4
- 229910052901 montmorillonite Inorganic materials 0.000 claims description 4
- FBPFZTCFMRRESA-JGWLITMVSA-N D-glucitol Chemical compound OC[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO FBPFZTCFMRRESA-JGWLITMVSA-N 0.000 claims description 3
- 235000021355 Stearic acid Nutrition 0.000 claims description 3
- OQCDKBAXFALNLD-UHFFFAOYSA-N octadecanoic acid Natural products CCCCCCCC(C)CCCCCCCCC(O)=O OQCDKBAXFALNLD-UHFFFAOYSA-N 0.000 claims description 3
- 229910017059 organic montmorillonite Inorganic materials 0.000 claims description 3
- 239000008117 stearic acid Substances 0.000 claims description 3
- XOOUIPVCVHRTMJ-UHFFFAOYSA-L zinc stearate Chemical group [Zn+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O XOOUIPVCVHRTMJ-UHFFFAOYSA-L 0.000 claims description 3
- 239000005264 High molar mass liquid crystal Substances 0.000 claims description 2
- 125000003118 aryl group Chemical group 0.000 claims description 2
- XXHCQZDUJDEPSX-KNCHESJLSA-L calcium;(1s,2r)-cyclohexane-1,2-dicarboxylate Chemical compound [Ca+2].[O-]C(=O)[C@H]1CCCC[C@H]1C([O-])=O XXHCQZDUJDEPSX-KNCHESJLSA-L 0.000 claims description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 abstract description 9
- 230000003068 static effect Effects 0.000 description 19
- 239000005662 Paraffin oil Substances 0.000 description 18
- 239000004699 Ultra-high molecular weight polyethylene Substances 0.000 description 12
- 239000003963 antioxidant agent Substances 0.000 description 12
- 230000003078 antioxidant effect Effects 0.000 description 12
- 239000012752 auxiliary agent Substances 0.000 description 12
- 229920000785 ultra high molecular weight polyethylene Polymers 0.000 description 12
- 239000000843 powder Substances 0.000 description 9
- 238000004458 analytical method Methods 0.000 description 5
- 238000000113 differential scanning calorimetry Methods 0.000 description 5
- 238000009998 heat setting Methods 0.000 description 5
- 239000000155 melt Substances 0.000 description 5
- 238000002844 melting Methods 0.000 description 5
- 230000008018 melting Effects 0.000 description 5
- 229920003023 plastic Polymers 0.000 description 5
- 239000004033 plastic Substances 0.000 description 5
- 238000005070 sampling Methods 0.000 description 5
- 230000037303 wrinkles Effects 0.000 description 5
- 239000004705 High-molecular-weight polyethylene Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000002425 crystallisation Methods 0.000 description 3
- 230000008025 crystallization Effects 0.000 description 3
- YWEWWNPYDDHZDI-JJKKTNRVSA-N (1r)-1-[(4r,4ar,8as)-2,6-bis(3,4-dimethylphenyl)-4,4a,8,8a-tetrahydro-[1,3]dioxino[5,4-d][1,3]dioxin-4-yl]ethane-1,2-diol Chemical group C1=C(C)C(C)=CC=C1C1O[C@H]2[C@@H]([C@H](O)CO)OC(C=3C=C(C)C(C)=CC=3)O[C@H]2CO1 YWEWWNPYDDHZDI-JJKKTNRVSA-N 0.000 description 2
- FMZUHGYZWYNSOA-VVBFYGJXSA-N (1r)-1-[(4r,4ar,8as)-2,6-diphenyl-4,4a,8,8a-tetrahydro-[1,3]dioxino[5,4-d][1,3]dioxin-4-yl]ethane-1,2-diol Chemical compound C([C@@H]1OC(O[C@@H]([C@@H]1O1)[C@H](O)CO)C=2C=CC=CC=2)OC1C1=CC=CC=C1 FMZUHGYZWYNSOA-VVBFYGJXSA-N 0.000 description 2
- OYFUVZBROQZLCL-UHFFFAOYSA-K aluminum;4-tert-butylbenzoate;hydroxide Chemical compound [OH-].[Al+3].CC(C)(C)C1=CC=C(C([O-])=O)C=C1.CC(C)(C)C1=CC=C(C([O-])=O)C=C1 OYFUVZBROQZLCL-UHFFFAOYSA-K 0.000 description 2
- 239000011575 calcium Substances 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 229940087101 dibenzylidene sorbitol Drugs 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910052755 nonmetal Inorganic materials 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 229920001903 high density polyethylene Polymers 0.000 description 1
- 239000004700 high-density polyethylene Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 238000005191 phase separation Methods 0.000 description 1
- 230000002035 prolonged effect Effects 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
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
-
- 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
Abstract
The invention discloses a lithium battery diaphragm and a preparation method thereof, wherein the preparation method of the lithium battery diaphragm comprises the following steps: step 1, adding a nucleating agent into a polyolefin and white oil system; the addition proportion of the nucleating agent is between 50 and 5000 ppm; step 2, preparing a casting sheet by high-temperature dispersion, mixing and plasticization of a double-screw raw material system mixed with a nucleating agent through oral die extrusion, wherein one surface of the casting sheet is in contact with a cooling roller, and the temperature of the cooling roller is between 10 and 50 ℃; cooling and forming the other side of the casting sheet in other modes; the cooled tape casting sheet is subjected to preliminary extraction washing and drying by an organic solvent; and 3, stretching, extracting and shaping the casting sheet obtained in the step 2 to obtain the diaphragm with the two surfaces having consistent performance. The invention achieves the purpose of improving the consistency of two surfaces of the diaphragm by improving the production formula of the diaphragm and matching with the improvement of the production process flow of the existing wet diaphragm.
Description
Technical Field
The invention belongs to the technical field of lithium battery diaphragm production, and particularly relates to a lithium battery diaphragm and a preparation method thereof.
Background
In the prior art, one surface of a casting sheet is fully contacted with a metal cooling roller for rapid cooling in the production of the casting sheet, and the other surface of the casting sheet is cooled by a back cooling roller or an air cooling and liquid cooling mode. However, the heat transfer coefficient of the non-metal roller is far from that of the metal material of the main cooling roller, or the back cooling roller is only in line contact with the high-temperature surface of the casting sheet, so that the two surface properties of the diaphragm have certain difference, and the use performance of the diaphragm in a battery is influenced.
The important reason for the difference is that only one surface of the diaphragm is in full contact with the metal cooling roller in the production process of the cast sheet, the cooling speed is high, the polyolefin and the white oil component are subjected to rapid phase separation, the polyolefin crystallinity is low, the contact time of the other surface of the diaphragm and the surface of the metal roller is short or the other surface of the diaphragm and the surface of the metal roller are cooled only by a non-metal medium, the cooling time of a high-temperature melt is prolonged, and the problem of high crystallization is caused. Meanwhile, the phase splitting speed is inconsistent due to inconsistent cooling speed, so that the difference of the two-sided performance is further aggravated; in particular, the friction coefficients of both surfaces are low or the difference between the friction coefficients of both surfaces is large.
Disclosure of Invention
Aiming at the defects of the existing problems, the invention aims to provide a lithium battery diaphragm and a preparation method thereof; the aim of improving the consistency of two surfaces of the diaphragm is achieved by improving the production formula of the diaphragm and matching with the improvement of the production process flow of the existing wet diaphragm.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a preparation method of a lithium battery diaphragm comprises the following steps:
step 1, adding a nucleating agent into a polyolefin and white oil system; the addition ratio of the nucleating agent is between 50 and 5000ppm, preferably between 500 and 5000 ppm;
step 2, preparing a casting sheet by high-temperature dispersion, mixing and plasticization of a double-screw raw material system mixed with a nucleating agent through oral die extrusion, wherein one surface of the casting sheet is in contact with a cooling roller, and the temperature of the cooling roller is between 10 and 50 ℃; the other surface of the casting sheet is cooled and formed by other modes, such as air cooling, water cooling, oil cooling, metal roller limited contact cooling and the like; the cooled tape casting sheet is subjected to preliminary extraction washing and drying by an organic solvent;
the cast sheets were tested: testing the crystallinity of two surfaces after extraction and drying, wherein the difference of the crystallinity of the two surfaces is less than 5 percent;
and 3, stretching, extracting and shaping the casting sheet obtained in the step 2 to obtain the diaphragm with the two surfaces having consistent performance.
The difference of the static friction coefficients of the two surfaces is less than 20 percent, and the static friction coefficient of at least one surface is more than or equal to 1.
The preparation method integrally changes the crystallization performance of the matrix through the formula, reduces the difference of the crystallinity of two surfaces, eliminates the defects possibly caused by the formula through process improvement, and finally achieves the effect of consistent performance of the two surfaces of the diaphragm
In step 2 of the invention, the content of the nucleating agent in the casting sheet is lower than 100ppm, and the reason that the primary extraction washing is needed is that: in the process of casting sheet forming, the nucleation function of the needed nucleating agent function is realized, a small amount of auxiliary agents such as the nucleating agent and the like are migrated to the surface of the casting sheet, and a production line is polluted to a certain extent if the auxiliary agents are not cleaned; after extraction, the casting sheet is clean, the subsequent production and processing links are not polluted, and the working pressure of the subsequent extraction is effectively relieved.
In a preferred embodiment of the present invention, in step 2, the organic solvent is dichloromethane.
Preferably, the extraction time is greater than or equal to 30 s.
As a preferred embodiment of the present application, the nucleating agent is selected from and not limited to the following components:
(1R,2S) -rel-1, 2-cyclohexanedicarboxylic acid calcium salt, Stearic Acid (SA) and its stearate, sorbitol and its derivatives; montmorillonite, TMP series aryl phosphate nucleating agent and organic phosphate nucleating agent; poly 4-methoxy-4' -acryloyloxybenzoic acid phenyl ester (PMAPAB) polymer liquid crystal nucleating agents and the like.
Preferably, the stearate is selected from zinc stearate (ZnSt)2) Or calcium stearate (CaSt)2)。
Preferably, the sorbitol and its derivatives are selected from any one or more of p-dimethyl dibenzylidene sorbitol (MDBS), dibenzylidene sorbitol (DBS), bis (p-ethyl dibenzylidene) sorbitol (EDBS), di-p-chlorobenzylidene sorbitol (CDBS), sorbitol nucleating agent (TM-3).
Preferably, the montmorillonite is organic montmorillonite.
Preferably, the organic phosphate nucleating agent is selected from any one or more of NA-10, NA-11 and NA-21.
More preferably, the nucleating agent is dimethyl dibenzylidene sorbitol and calcium stearate, and the weight parts of the nucleating agent are as follows: 2, the mixture ratio is used.
The invention also protects the lithium battery diaphragm prepared by the preparation method of the lithium battery diaphragm.
Advantageous effects
Compared with the prior art, the lithium battery diaphragm and the preparation method thereof provided by the invention have the following beneficial effects: firstly, the difference between two surfaces of the diaphragm is obviously improved by adding the nucleating agent; secondly, the pollution of the nucleating agent to the subsequent process is avoided through the primary extraction.
After the nucleating agent is added, the crystallinity of two surfaces of the casting sheet is improved, the crystallization of one surface of the casting sheet, which is not in contact with the main cooling roller, is further refined, the friction coefficient of the casting sheet is basically consistent with that of the other surface of the casting sheet, and the friction force is improved.
Detailed Description
The present invention will be described in further detail with reference to examples. The reagents or instruments used are not indicated by manufacturers, and are regarded as conventional products which can be purchased in the market.
Comparative example 1
The method comprises the steps of adding 0.2 part by weight of antioxidant (Irg1010 (gasoline refining)) and 0.1 part by weight of antioxidant (P168 (gasoline refining)) into 14 parts by weight of ultra-high molecular weight polyethylene powder (GUR4032, Takolnisanius) and 86 parts by weight of paraffin oil (68#, Zhejiang Zhengxin), and mixing the components in sequence.
The gel was extruded using a T die, the temperature of the extruded melt was controlled at 220 ℃, then rapidly cooled on a constant temperature metal counter roll with a surface temperature of 10 ℃ and rolled into a sheet with a thickness of 1.5 mm.
After extraction, the sheet was subjected to DSC analysis to obtain the difference in crystallinity between both sides of the sheet. At the time of sampling, a skin sample having a surface of 0.1mm or less was sampled and analyzed. The analysis result showed that the difference in crystallinity between both sides was 5.1%.
The treated sheet was stretched. The composition is rapidly stretched at about 1 ℃ below the melt melting point, wherein stretching is performed simultaneously at 10 times in both the Machine Direction (MD) and the Transverse Direction (TD). The uniformity of the temperature field needs to be controlled during stretching, and the temperature difference between different points of the temperature field in the stretching area is less than 0.5 ℃. The stretched diaphragm is thin and easy to wrinkle in a non-tensioned state, so the diaphragm needs to be tensioned under the action force of less than 1% of the tensile strength of the diaphragm, and the diaphragm is drawn in for extraction to extract paraffin oil in the diaphragm. Then carrying out constant-temperature hot air at 40 ℃ to take out the residual dichloromethane in the diaphragm, and carrying out heat setting treatment at 130 ℃ to finally obtain the diaphragm.
The friction coefficient of the obtained diaphragm is tested according to a GB-T10006-1988 plastic and sheet friction coefficient measuring method, the diaphragm is divided into a surface A and a surface B, and the surface A is slightly higher in static friction coefficient; the static friction coefficient of the surface A and the surface A is 1.6, and the dynamic friction coefficient is 0.5; the static friction coefficient of the surface B and the surface B is 0.9, and the dynamic friction coefficient is 0.4. The difference of the static friction coefficients of the two surfaces is larger and is more than 20 percent.
Comparative example 2
The ultra-high molecular weight polyethylene powder (GUR4032, Taconi Sealanib) 14 parts by weight and paraffin oil (68#, Zhejiang Zhenjin) 86 parts by weight were mixed in the same order with an antioxidant (Irg1010 (gasoline parkerization)) 0.2 parts by weight and an antioxidant (P168 (gasoline parkerization)) 0.1 parts by weight, based on 100 parts by weight of the total of the high molecular weight polyethylene and the paraffin oil. Firstly, the ultra-high molecular weight polyethylene powder and the antioxidant are uniformly mixed by using a high-speed mixer, and the mixing uniformity is determined by detecting the content of the auxiliary agent through infrared rays. And putting the ultra-high molecular weight polyethylene material mixed with the antioxidant and paraffin oil into a double-screw extruder for mixing, and finally preparing mixture melt gel.
The gel was extruded using a T die, the temperature of the extruded melt was controlled at 220 ℃, then rapidly cooled on a constant temperature metal counter roll with a surface temperature of 10 ℃ and rolled into a sheet with a thickness of 1.5 mm.
After extraction, the sheet was subjected to DSC analysis to obtain the difference in crystallinity between both sides of the sheet. At the time of sampling, a skin sample having a surface of 0.1mm or less was sampled and analyzed. The analysis result showed that the difference in crystallinity between both sides was 5.0%.
The treated sheet was stretched. The composition is rapidly stretched at about 1 ℃ below the melt melting point, and is stretched at 10 times in the Machine Direction (MD) and then at 100 times in the Transverse Direction (TD). The uniformity of the temperature field needs to be controlled during stretching, and the temperature difference between different points of the temperature field in the stretching area is less than 0.5 ℃. The stretched diaphragm is thin and easy to wrinkle in a non-tensioned state, so the diaphragm needs to be tensioned under the action force of less than 1% of the tensile strength of the diaphragm, and the diaphragm is drawn in for extraction to extract paraffin oil in the diaphragm. Then the residual dichloromethane in the diaphragm is taken out by constant temperature hot air at 40 ℃, and then is stretched by 1.3 times in the Transverse Direction (TD) and is subjected to heat setting treatment at 130 ℃ to finally obtain the diaphragm.
The friction coefficient of the obtained diaphragm is tested according to a GB-T10006-1988 plastic and sheet friction coefficient measuring method, the diaphragm is divided into a surface A and a surface B, and the surface A is slightly higher in static friction coefficient; the static friction coefficient of the surface A and the surface A is 0.5, and the dynamic friction coefficient is 0.3; the static friction coefficient of the surface B and the surface B is 0.5, and the dynamic friction coefficient is 0.4. The friction on both sides is less than 1 and there is less difference.
Example 1
The ultra-high molecular weight polyethylene powder (GUR4032, Taconi Sealanib) 14 parts by weight, paraffin oil (68#, Zhejiang Zhengxin) 86 parts by weight, 100 parts by weight of the total of the high molecular weight polyethylene and paraffin oil, 0.2 parts by weight of antioxidant (Irg1010 (gasoline parkerization)), 0.1 parts by weight of antioxidant (P168 (gasoline parkerization)), 0.05 parts by weight of dimethyl dibenzylidene sorbitol (99% purity, Wuhan Fengtai Winto technologies Co., Ltd.), and 0.02 parts by weight of calcium stearate (Ca 6.5 + -0.5%, Shanghai Mirui chemical technology Co., Ltd.) were sequentially mixed. Firstly, the ultra-high molecular weight polyethylene powder and the auxiliary agent are uniformly mixed by using a high-speed mixer, and the mixing uniformity is determined by detecting the content of the auxiliary agent through infrared rays. And putting the ultra-high molecular weight polyethylene material mixed with the auxiliary agent and paraffin oil into a double-screw extruder for mixing, and finally preparing mixture melt gel.
The gel was extruded using a T die, the temperature of the extruded melt was controlled at 220 ℃, then rapidly cooled on a constant temperature metal counter roll with a surface temperature of 10 ℃ and rolled into a sheet with a thickness of 1.5 mm.
Drawing the sheet, immersing the sheet in a dichloromethane extraction container for not less than 30s, and drying the surface of the sheet by using hot air at 45 ℃. The sheet was subjected to DSC analysis after extraction to obtain the difference in crystallinity on both sides of the sheet. At the time of sampling, a skin sample having a surface of 0.1mm or less was sampled and analyzed. The analysis result showed that the difference in crystallinity between both sides was 0.5%.
The treated sheet was stretched. The composition is rapidly stretched at about 1 ℃ below the melt melting point, wherein stretching is performed simultaneously at 10 times in both the Machine Direction (MD) and the Transverse Direction (TD). The uniformity of the temperature field needs to be controlled during stretching, and the temperature difference between different points of the temperature field in the stretching area is less than 0.5 ℃. The stretched diaphragm is thin and easy to wrinkle in a non-tensioned state, so the diaphragm needs to be tensioned under the action force of less than 1% of the tensile strength of the diaphragm, and the diaphragm is drawn in for extraction to extract paraffin oil in the diaphragm. Then carrying out constant-temperature hot air at 40 ℃ to take out the residual dichloromethane in the diaphragm, and carrying out heat setting treatment at 130 ℃ to finally obtain the diaphragm.
The friction coefficient of the obtained diaphragm is tested according to a GB-T10006-1988 plastic and sheet friction coefficient measuring method, the diaphragm is divided into a surface A and a surface B, and the surface A is slightly higher in static friction coefficient; the static friction coefficient of the surface A and the surface A is 1.8, and the dynamic friction coefficient is 0.9; the static friction coefficient of the surface B and the surface B is 1.7, and the dynamic friction coefficient is 0.8. The difference in the friction coefficients of the two surfaces is small.
Example 2
28 parts by weight of high-density polyethylene powder (VH035, KPIC), 72 parts by weight of paraffin oil (68#, Zhejiang Zhenjin), 0.2 parts by weight of antioxidant (Irg1010 (gasoline parkerization)), 0.1 part by weight of antioxidant (P168 (gasoline parkerization)), 0.03 parts by weight of nucleating agent (Sandostab 4030, Craine), and organic montmorillonite(s) (Katsuma Kagaku Co., Ltd.) were added to 100 parts by weight of the total of the high-molecular weight polyethylene and paraffin oil
I.30P，NANOCOR&Weiweizhu) 0.03 parts by weight, and they were mixed in order. Firstly, the ultra-high molecular weight polyethylene powder and the auxiliary agent are uniformly mixed by using a high-speed mixer, and the mixing uniformity is determined by detecting the content of the auxiliary agent through infrared rays. And putting the ultra-high molecular weight polyethylene material mixed with the auxiliary agent and paraffin oil into a double-screw extruder for mixing, and finally preparing mixture melt gel.
The gel was extruded using a T die, the temperature of the extruded melt was controlled at 210 ℃, then rapidly cooled on a constant temperature metal counter roll with a surface temperature of 10 ℃ and rolled into a sheet with a thickness of 1.6 mm.
Drawing the sheet, immersing the sheet in a dichloromethane extraction container for not less than 30s, and drying the surface of the sheet by using hot air at 45 ℃. The sheet was subjected to DSC analysis after extraction to obtain the difference in crystallinity on both sides of the sheet. At the time of sampling, a skin sample having a surface of 0.1mm or less was sampled and analyzed. The analysis result showed that the difference in crystallinity between both sides was 0.5%.
The treated sheet was stretched. The composition is rapidly stretched at about 1 ℃ below the melt melting point, wherein stretching is performed simultaneously at 10 times in both the Machine Direction (MD) and the Transverse Direction (TD). The uniformity of the temperature field needs to be controlled during stretching, and the temperature difference between different points of the temperature field in the stretching area is less than 0.5 ℃. The stretched diaphragm is thin and easy to wrinkle in a non-tensioned state, so the diaphragm needs to be tensioned under the action force of less than 1% of the tensile strength of the diaphragm, and the diaphragm is drawn in for extraction to extract paraffin oil in the diaphragm. Then carrying out constant-temperature hot air at 40 ℃ to take out the residual dichloromethane in the diaphragm, and carrying out heat setting treatment at 130 ℃ to finally obtain the diaphragm.
The friction coefficient of the obtained diaphragm is tested according to a GB-T10006-1988 plastic and sheet friction coefficient measuring method, the diaphragm is divided into a surface A and a surface B, and the surface A is slightly higher in static friction coefficient; the static friction coefficient of the surface A and the surface A is 1.9, and the dynamic friction coefficient is 0.9; the static friction coefficient of the surface B and the surface B is 1.8, and the dynamic friction coefficient is 0.9. The difference in the friction coefficients of the two surfaces is small.
Example 3
The ultra-high molecular weight polyethylene powder (GUR4022, Ticona Sealanib) 15 parts by weight, paraffin oil (68#, Zhejiang Zhengxin) 85 parts by weight, and 100 parts by weight of the total of the high molecular weight polyethylene and paraffin oil were mixed with 0.2 part by weight of antioxidant (Irg1010 (gasoline parkerization)), 0.1 part by weight of antioxidant (P168 (gasoline parkerization)), 0.03 part by weight of nucleating agent (Sandostab 4030, Craine), and 0.02 part by weight of calcium stearate (Ca 6.5 + -0.5%, Shanghai Mirey chemical technology Co., Ltd.) in this order. Firstly, the ultra-high molecular weight polyethylene powder and the auxiliary agent are uniformly mixed by using a high-speed mixer, and the mixing uniformity is determined by detecting the content of the auxiliary agent through infrared rays. And putting the ultra-high molecular weight polyethylene material mixed with the auxiliary agent and paraffin oil into a double-screw extruder for mixing, and finally preparing mixture melt gel.
The gel was extruded using a T die, the temperature of the extruded melt was controlled at 220 ℃, then rapidly cooled on a constant temperature metal counter roll with a surface temperature of 10 ℃ and rolled into a sheet with a thickness of 1.5 mm.
Drawing the sheet, immersing the sheet in a dichloromethane extraction container for not less than 30s, and drying the surface of the sheet by using hot air at 45 ℃. After the sheet is extracted, DSC analysis can be carried out to obtain the crystallinity difference of the two sides of the sheet. At the time of sampling, a skin sample having a surface of 0.1mm or less was sampled and analyzed. The analysis result showed that the difference in crystallinity between both sides was 0.3%.
The treated sheet was stretched. The composition is rapidly stretched at about 1 ℃ below the melt melting point, and is stretched at 10 times in the Machine Direction (MD). Further, stretching was performed at 10 times in the Transverse Direction (TD). The uniformity of the temperature field needs to be controlled during stretching, and the temperature difference between different points of the temperature field in the stretching area is less than 0.5 ℃. The stretched diaphragm is thin and easy to wrinkle in a non-tensioned state, so the diaphragm needs to be tensioned under the action force of less than 1% of the tensile strength of the diaphragm, and the diaphragm is drawn in for extraction to extract paraffin oil in the diaphragm. Then the residual dichloromethane in the diaphragm is taken out by constant temperature hot air at 40 ℃, and then is stretched by 1.3 times in the Transverse Direction (TD) and is subjected to heat setting treatment at 130 ℃ to finally obtain the diaphragm.
The friction coefficient of the obtained diaphragm is tested according to a GB-T10006-1988 plastic and sheet friction coefficient measuring method, the diaphragm is divided into a surface A and a surface B, and the surface A is slightly higher in static friction coefficient; the static friction coefficient of the surface A and the surface A is 1.2, and the dynamic friction coefficient is 0.6; the coefficient of static friction between the surface B and the surface B is 1.0, and the coefficient of dynamic friction is 0.5. The friction coefficient difference between the two surfaces is small, and the static friction coefficient of the surface A is larger than 1.
The protection of the present invention is not limited to the above embodiments. Variations and advantages that may occur to those skilled in the art may be incorporated into the invention without departing from the spirit and scope of the inventive concept and the scope of the appended claims is intended to be protected.
Claims (9)
1. A preparation method of a lithium battery diaphragm is characterized by comprising the following steps:
step 1, adding a nucleating agent into a polyolefin and white oil system; the addition proportion of the nucleating agent is between 50 and 5000 ppm;
step 2, preparing a casting sheet by high-temperature dispersion, mixing and plasticization of a double-screw raw material system mixed with a nucleating agent through oral die extrusion, wherein one surface of the casting sheet is in contact with a cooling roller, and the temperature of the cooling roller is between 10 and 50 ℃; cooling and forming the other side of the casting sheet in other modes; the cooled tape casting sheet is subjected to preliminary extraction washing and drying by an organic solvent;
and 3, stretching, extracting and shaping the casting sheet obtained in the step 2 to obtain the diaphragm with the two surfaces having consistent performance.
2. The method for preparing a lithium battery separator according to claim 1, wherein in the step 2, the other cooling means is selected from any one of air cooling, water cooling, oil cooling and metal roller limited contact cooling.
3. The method for preparing a lithium battery separator according to claim 1, wherein the organic solvent is dichloromethane in the step 2.
4. The method for preparing a lithium battery separator as claimed in claim 1, wherein the nucleating agent is selected from a mixture of any one or more of the following components: (1R,2S) -rel-1, 2-cyclohexane dicarboxylic acid calcium salt, stearic acid and stearate thereof, sorbitol and derivatives thereof; montmorillonite, TMP series aryl phosphate nucleating agent and organic phosphate nucleating agent; poly 4-methoxy-4' -acryloyloxybenzoic acid phenyl ester (PMAPAB) polymer liquid crystal nucleating agent.
5. The method for preparing a lithium battery separator according to claim 4, wherein the stearate is selected from zinc stearate or calcium stearate.
6. The method for preparing a lithium battery separator according to claim 4, wherein the sorbitol and the derivatives thereof are selected from one or more of p-dimethyl dibenzylidene sorbitol, di (p-ethyl dibenzylidene) sorbitol, di-p-chlorobenzylidene sorbitol, and sorbitol nucleating agents.
7. The method for preparing a lithium battery separator according to claim 4, wherein the montmorillonite is an organic montmorillonite.
8. The method for preparing a lithium battery separator according to claim 4, wherein the organophosphate-based nucleating agent is selected from any one or more of NA-10, NA-11, and NA-21.
9. A lithium battery separator prepared by the method for preparing a lithium battery separator as claimed in any one of claims 1 to 8.
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| CN116864916A (en) * | 2023-07-18 | 2023-10-10 | 河北金力新能源科技股份有限公司 | Extremely thin high-strength lithium ion battery diaphragm and preparation method thereof |
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