CN112002863A - Preparation method of battery diaphragm - Google Patents
Preparation method of battery diaphragm Download PDFInfo
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- CN112002863A CN112002863A CN202010907306.0A CN202010907306A CN112002863A CN 112002863 A CN112002863 A CN 112002863A CN 202010907306 A CN202010907306 A CN 202010907306A CN 112002863 A CN112002863 A CN 112002863A
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- stretching
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention discloses a preparation method of a battery diaphragm, which comprises the following steps: step S1: preparing materials, namely preparing polyolefin and a plasticizer; step S2: cooling the mixed materials, and pouring the polyolefin and the plasticizer into a double-screw extruder for mixing to obtain a mixture; cooling the oil-containing substrate by the cooling roller; step S3: stretching, namely stretching the oil-containing substrate 7 times transversely and stretching the oil-containing substrate 7 times longitudinally to obtain an oil-containing film, and extracting and drying the oil-containing film; step S4: secondary stretching, namely stretching the film in two directions, wherein the stretching multiplying power is 0.5-3 times of that of transverse stretching and longitudinal stretching; step S5: performing heat setting treatment, namely performing heat setting treatment on the stretched film to obtain a matrix; step S6: coating, namely coating the coating on the surface of the substrate to obtain the diaphragm with the thickness of 50nm-100 nm. And (3) carrying out secondary stretching on the film, wherein the stretching ratio is 2 times of that of transverse stretching and longitudinal stretching, the coating thickness of the coating is 50-100nm, the micropore diameter of the matrix is enlarged again, the film breaking temperature is higher, and the performance of the lithium ion battery is better.
Description
Technical Field
The invention relates to the technical field of lithium ion battery diaphragms, in particular to a preparation method of a battery diaphragm.
Background
With the exhaustion of fossil energy and the increasing pressure of environmental pollution, countries around the world have vigorously advocated the application of new energy technologies. Therefore, the lithium ion battery plays a key role in new energy technology as an important energy storage product, and has the advantages of high energy density, multiple cycle times, no memory effect and the like.
Lithium ion battery includes positive pole, negative pole, sets up positive pole with electrolyte and setting on the negative pole are in positive pole with diaphragm between the negative pole has seted up the micropore on the diaphragm, and has coated on the diaphragm and scribbled the coating, however, among the prior art, the micropore aperture is less to lead to the coating effect not good, and then lead to the diaphragm rupture of membranes temperature lower, lithium ion battery's thermal stability is relatively poor.
Disclosure of Invention
Therefore, a method for preparing a battery separator with high film breaking temperature is needed.
The technical scheme adopted by the invention for solving the technical problems is as follows: a preparation method of a battery separator comprises the following steps:
step S1: preparing materials, namely preparing polyolefin and a plasticizer;
step S2: cooling the mixed materials, and respectively pouring the polyolefin and the plasticizer into a double-screw extruder for mixing to obtain a uniform mixture; extruding the mixture through a die head lip of a double-screw extruder, and cooling the mixture through a cooling roller to form an oil-containing substrate;
step S3: stretching, namely transversely stretching the oil-containing substrate by 7 times and longitudinally stretching the oil-containing substrate by 7 times to obtain an oil-containing film, and extracting and drying the oil-containing film;
step S4: performing secondary stretching, namely performing biaxial stretching on the film subjected to extraction drying, wherein the stretching ratio is 0.5-3 times of that of the transverse stretching and the longitudinal stretching;
step S5: heat setting treatment, namely performing heat setting treatment on the stretched film so as to eliminate the stress in the film and further obtain a matrix;
step S6: and coating, namely coating the coating on the surface of the substrate by using a chemical vapor deposition method, wherein the coating thickness is 50nm-100nm, so that the large-aperture diaphragm is obtained.
Further, the stretch ratio is 2.
Further, the coating thickness was 100 nm.
Furthermore, the substrate is provided with micropores, and the pore diameter of the micropores of the substrate is 60nm-150 nm.
Further, the pore diameter of the micropores of the matrix is 91 nm.
Further, the first surface and the second surface are oppositely arranged, and the coating is coated on the first surface and the second surface.
Further, the coating is made of one or more materials of alumina, silica, boehmite, and the like.
Further, the plasticizer is one or a combination of several of paraffin oil, mineral oil, soybean oil, wax and dibutyl phthalate.
Further, the polyolefin has a molecular weight of 1.0 x 105-3.0*106。
The invention has the beneficial effects that: according to the preparation method of the battery diaphragm, the film is stretched for the second time, the stretching magnification is 2 times of the transverse stretching and the longitudinal stretching, and the coating thickness of the coating is 50-100nm, so that the micropore aperture of the matrix is enlarged again, the film breaking temperature is high, and the performance of the lithium ion battery is good.
Drawings
The invention is further illustrated by the following figures and examples.
FIG. 1 is a schematic structural view of a large pore size battery separator of the present invention;
FIG. 2 is a flow chart of a method of making the battery separator of FIG. 1;
figure 3 is a graph comparing the results of the performance tests on the large pore size battery separator shown in figure 1.
The names and the numbers of the parts in the figure are respectively as follows:
Detailed Description
The present invention will now be described in detail with reference to the accompanying drawings. This figure is a simplified schematic diagram, and merely illustrates the basic structure of the present invention in a schematic manner, and therefore it shows only the constitution related to the present invention.
Example 1
Referring to fig. 1 to 3, the present invention provides a method for preparing the battery separator, including the steps of:
step S1: preparing materials, namely preparing polyolefin and plasticizer. The polyolefin has a molecular weight of 1.0 x 105-3.0*106. In other embodiments, not shown, the polyolefin in the matrix 1 may also be a polypropylene material or a polyethylene material. In this embodiment, the plasticizer is one or a combination of several of paraffin oil, mineral oil, soybean oil, wax and dibutyl phthalate.
Step S2: mixing and cooling, namely respectively pouring polyolefin and plasticizer into a double-screw extruder, and mixing for 5-25 min, wherein the temperature in the double-screw extruder is 170-220 ℃, so as to obtain a uniform mixture; after the mixture is extruded through a die lip of a double-screw extruder, the mixture is cooled through a cooling roller to form an oil-containing substrate.
Step S3: and (3) stretching, namely transversely stretching the oil-containing substrate 7 times and longitudinally stretching the oil-containing substrate 7 times at the temperature of 110-135 ℃ to obtain an oil-containing film, and extracting and drying the oil-containing film.
Step S4: and (3) secondary stretching, namely performing biaxial stretching on the film subjected to extraction drying, wherein the stretching ratio is 2 times of that of the transverse stretching and the longitudinal stretching. Preferably, the stretch ratio is 0.5 to 3.
Step S5: and (3) performing heat setting treatment, namely performing heat setting treatment on the stretched film so as to eliminate the stress in the film, thereby obtaining the matrix 1. Furthermore, the substrate 1 has micropores, and the pore diameter of the micropores of the substrate 1 is 60nm-150 nm. In the present embodiment, the pore diameter of the micropores of the substrate 1 is 91 nm.
Step S6: coating, coating the coating layer 2 on the surface of the substrate 1 by using a chemical vapor deposition method, and the coating thickness of the coating layer 2 is 100nm, thereby obtaining a large-aperture separator. In the present embodiment, the coating layer 2 is made of one or more materials of alumina, silica, boehmite, and the like. Further, the substrate 1 includes a first surface 11 and a second surface 12, and the first surface 11 and the second surface 12 are oppositely disposed.
Example 2
The preparation method of the battery diaphragm provided by the second embodiment of the invention is different from the preparation method of the battery diaphragm of the first embodiment in that: in the present embodiment, in step S6, the coating layer 2 is applied to the first surface 11 and the second surface 12 of the substrate 1 by using a chemical vapor deposition method, and the coating thickness is 50 nm.
Example 3
The preparation method of the battery diaphragm provided by the third embodiment of the invention is different from the preparation method of the battery diaphragm of the first embodiment in that: in the present embodiment, in step S6, the coating layer 2 is applied to the first surface 11 and the second surface 12 of the substrate 1 by using a chemical vapor deposition method, and the coating thickness is 70 nm.
Referring again to fig. 3, MD is the mechanical stretching direction and TD is the direction perpendicular to the mechanical stretching direction.
In the preparation methods of the battery separators provided in embodiments 1 to 3 of the present invention, the film is secondarily stretched, the stretching ratio is 2 times of the transverse stretching and the longitudinal stretching, and the coating thickness of the coating layer 2 is 50 to 100nm, so that the pore diameter of the micropores of the substrate 1 is enlarged again, and thus the moving speed of lithium ions can be increased, and the performance of the lithium ion battery is better.
Example 4
Referring to fig. 3, a method for manufacturing a battery separator according to a fourth embodiment of the present invention is different from the method for manufacturing a battery separator according to the first embodiment in that: in this embodiment, the oil-containing film is biaxially stretched at a stretch ratio of 2 times in the transverse direction and 1 time in the longitudinal direction in step S4, and the pore diameter of the substrate 1 is 73nm when the substrate 1 after the heat setting treatment of the stretched oil-containing film is used in step S5.
According to the preparation method of the battery diaphragm provided by the fourth embodiment of the invention, the oil-containing film is subjected to biaxial stretching, the stretching magnification is 2 times of that of the transverse stretching and 1 time of that of the longitudinal stretching, and the stretched oil-containing film is subjected to heat setting treatment to form the base body 1, at the moment, the aperture of the micropores of the base body 1 is 73nm, so that the magnification of secondary stretching is different, the diaphragm breaking temperature is higher, and the performance of the lithium ion battery is better.
Comparative example 1
Referring to fig. 3, the method for preparing the battery separator according to the first comparative example of the present invention is different from the method for preparing the battery separator according to the first example in that: in the present embodiment, steps S4 and S6 are omitted, and secondary drawing and coating are not performed. Directly heating the film after primary stretching to form the matrix 1 after the heat setting treatment, wherein the aperture of the micropores of the matrix 1 is 42 nm.
According to the preparation method of the battery diaphragm provided by the comparative example, the film is not subjected to secondary stretching and coating, the substrate 1 after the primary stretching and oil-containing substrate is subjected to heat setting treatment is directly subjected to heat setting treatment, and the pore diameter of the micropores of the substrate 1 is 42nm, so that compared with the preparation method of the battery diaphragm in the example I, the preparation method of the battery diaphragm in the comparative example has the advantages that the pore diameter of the micropores is obviously reduced, the air permeability is improved, the porosity is seriously reduced, the heat shrinkage rate of the substrate 1 is seriously improved, the diaphragm breaking temperature is reduced to 154 ℃, the coating effect is poor, the diaphragm breaking temperature is lower, and the heat stability of a lithium ion battery is poor.
In example four, the stretching ratio of the secondary stretching was changed from 2 to 1 times the stretching ratio in example one, and the film rupture temperature was slightly lowered, but the film rupture temperature was higher than that in comparative example one, and the thermal stability of the lithium ion battery was better.
Comparative example 2
Referring to fig. 3, the method for manufacturing the battery separator according to the second comparative example of the present invention is different from the method for manufacturing the battery separator according to the first example in that: in this embodiment, step S4 is omitted, and the primary stretched oil-containing sheet is directly subjected to heat setting treatment to obtain a substrate 1, in which case the pore diameter of the pores of the substrate 1 is 40 nm.
According to the preparation method of the battery diaphragm provided by the second comparative example, the oil-containing film is not stretched for the second time, the substrate 1 after the primary stretching and the heat setting treatment of the oil-containing substrate are directly carried out, and the aperture of the micropores of the substrate 1 is 40nm, so that compared with the preparation method of the battery diaphragm in the first example, the preparation method of the battery diaphragm in the second comparative example has the advantages that the aperture of the micropores is obviously reduced, the air permeability is improved, the porosity is obviously reduced, the heat shrinkage rate of the substrate 1 is obviously improved, the diaphragm breaking temperature is reduced to 154 ℃, the coating effect is poor, the diaphragm breaking temperature is lower, and the heat stability of the lithium ion battery is poor.
In example four, the stretching ratio of the secondary stretching was changed from 2 to 1 times the stretching ratio in example one, and the film rupture temperature was slightly lowered, but the film rupture temperature was higher and the thermal stability of the lithium ion battery was better than that in comparative example two.
Comparative example 3
Referring to fig. 3, a method for manufacturing a battery separator according to a third comparative example of the present invention is different from the first example in that: in the present embodiment, step S6 is omitted.
According to the preparation method of the battery diaphragm provided by the third comparative example, the coating 2 is not coated on the substrate 1, so that compared with the preparation method of the battery diaphragm in the first example, although the pore diameter of the micropores in the comparative example is increased, the porosity is increased due to the fact that the coating is not coated on the substrate 1, the air permeability is reduced, the porosity is increased, the heat shrinkage rate of the substrate 1 is greatly improved, the diaphragm breaking temperature is reduced to 156 ℃, the air permeability is poor, the heat shrinkage rate of the diaphragm is high, and the heat stability of the lithium ion battery is poor.
In example four, the stretching ratio of the secondary stretching was changed from 2 to 1 times the stretching ratio in example one, and the film rupture temperature was slightly lowered, but the film rupture temperature was higher and the thermal stability of the lithium ion battery was better than that in comparative example three.
In summary, the effect of performing the secondary drawing in example four is better than that of performing no secondary drawing and coating in comparative example one, that of performing no secondary drawing in comparative example two, and that of performing no coating in comparative example three.
In light of the foregoing description of preferred embodiments in accordance with the invention, it is to be understood that numerous changes and modifications may be made by those skilled in the art without departing from the scope of the invention. The technical scope of the present invention is not limited to the contents of the specification, and must be determined according to the scope of the claims.
Claims (9)
1. A preparation method of a battery diaphragm is characterized by comprising the following steps: the method for preparing the large-aperture battery diaphragm comprises the following steps:
step S1: preparing materials, namely preparing polyolefin and a plasticizer;
step S2: cooling the mixed materials, and respectively pouring the polyolefin and the plasticizer into a double-screw extruder for mixing to obtain a uniform mixture; extruding the mixture through a die head lip of a double-screw extruder, and cooling the mixture through a cooling roller to form an oil-containing substrate;
step S3: stretching, namely transversely stretching the oil-containing substrate by 7 times and longitudinally stretching the oil-containing substrate by 7 times to obtain an oil-containing film, and extracting and drying the oil-containing film;
step S4: performing secondary stretching, namely performing biaxial stretching on the film subjected to extraction drying, wherein the stretching ratio is 0.5-3 times of that of the transverse stretching and the longitudinal stretching;
step S5: heat setting treatment, namely performing heat setting treatment on the stretched film so as to eliminate the stress in the film and further obtain a matrix;
step S6: and coating, namely coating the coating on the surface of the substrate by using a chemical vapor deposition method, wherein the coating thickness is 50nm-100nm, so that the large-aperture diaphragm is obtained.
2. The method of preparing a battery separator as defined in claim 1, wherein: the draw ratio was 2.
3. The method of preparing a battery separator as defined in claim 2, wherein: the coating thickness was 100 nm.
4. The method of preparing a battery separator as defined in claim 1, wherein: the substrate is provided with micropores, and the pore diameter of the micropores of the substrate is 60nm-150 nm.
5. The method of preparing a battery separator as defined in claim 4, wherein: the pore diameter of the micropores of the matrix is 91 nm.
6. The method of preparing a battery separator as defined in claim 1, wherein: the substrate comprises a first surface and a second surface, the first surface and the second surface are oppositely arranged, and the coating is coated on the first surface and the second surface.
7. The method of preparing a battery separator as defined in claim 6, wherein: the coating is made of one or more materials of alumina, silica, boehmite and the like.
8. The method of preparing a battery separator as defined in claim 1, wherein: the plasticizer is one or a combination of several of paraffin oil, mineral oil, soybean oil, wax and dibutyl phthalate.
9. The method of preparing a battery separator according to claim 8, wherein: the polyolefin has a molecular weight of 1.0 x 105-3.0*106。
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|---|---|---|---|
| CN202010907306.0A CN112002863A (en) | 2020-09-02 | 2020-09-02 | Preparation method of battery diaphragm |
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| CN202010907306.0A CN112002863A (en) | 2020-09-02 | 2020-09-02 | Preparation method of battery diaphragm |
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| CN112002863A true CN112002863A (en) | 2020-11-27 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113629355A (en) * | 2021-08-06 | 2021-11-09 | 溧阳月泉电能源有限公司 | All-polymer high-temperature-resistant diaphragm and preparation method thereof |
| CN114683507A (en) * | 2020-12-28 | 2022-07-01 | 溧阳月泉电能源有限公司 | Preparation method of high-wettability diaphragm |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114683507A (en) * | 2020-12-28 | 2022-07-01 | 溧阳月泉电能源有限公司 | Preparation method of high-wettability diaphragm |
| CN113629355A (en) * | 2021-08-06 | 2021-11-09 | 溧阳月泉电能源有限公司 | All-polymer high-temperature-resistant diaphragm and preparation method thereof |
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