CN116207446B - Lithium battery diaphragm with low short circuit rate and preparation method thereof - Google Patents
Lithium battery diaphragm with low short circuit rate and preparation method thereof Download PDFInfo
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- CN116207446B CN116207446B CN202310497572.4A CN202310497572A CN116207446B CN 116207446 B CN116207446 B CN 116207446B CN 202310497572 A CN202310497572 A CN 202310497572A CN 116207446 B CN116207446 B CN 116207446B
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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
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
- H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
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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
-
- 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
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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
- H01M50/409—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
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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
- H01M50/491—Porosity
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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 provides a lithium battery diaphragm with low short circuit rate and a preparation method thereof; the lithium battery diaphragm with low short circuit rate comprises an intermediate layer and two surface layers, wherein the intermediate layer is provided with a first surface and a second surface positioned opposite to the first surface; the two surface layers are respectively attached to the first surface and the second surface; the surface layer is polyolefin resin with crystallinity of 20-30%, isotacticity of not less than 98 and melt index of 2-4g/10 min. According to the method, polyolefin with certain crystallinity, isotacticity and melt index is selected as the surface layer of the lithium battery diaphragm, so that the surface of the lithium battery diaphragm has the characteristic of low hardness, and in the process, if the surface layer is subjected to the external force effects such as extrusion and friction, the surface layer can be subjected to the characteristic of low hardness by the surface layer, the damage phenomenon of the surface is reduced through elastic deformation and stress relaxation, the occurrence of weak points is reduced, the overall pressure resistance of the lithium battery diaphragm is improved, and the short circuit risk is reduced.
Description
Technical Field
The invention relates to the field of lithium batteries, in particular to a lithium battery diaphragm with low short circuit rate and a preparation method thereof.
Background
The lithium ion battery has the characteristics of high energy density, good safety, long cycle life and the like, is widely applied to the fields of power, energy storage, 3C and the like, is commercialized and mature, and becomes an indispensable product in daily life work and commercial activities. The safety performance of the lithium battery is one of the most important basic performances of various consumer groups, and the diaphragm has the functions of isolating the anode and the cathode and conducting ions in a lithium battery system, so that unsafe factors such as short circuit and the like of the lithium battery can be effectively prevented.
In lithium battery products, the yield in the product manufacturing process is an important factor affecting the cost, the higher the yield is, the lower the product cost is, and the lower the yield is, the cost of the lithium battery product is affected, so how to improve the yield is one of the directions of attention in the field.
Short circuit generated in the preparation process of the lithium battery is a common factor which mainly causes the bad effect of the lithium battery product, and the diaphragm is used as one of four main materials of a lithium battery system and is closely related to whether the battery is short-circuited or not. In particular, the separator is easily damaged during the production process to form a weak point, and at this time, the weak point is easily broken down under a certain voltage, resulting in a short circuit. The above problems are technical problems to be solved in the art.
Disclosure of Invention
The invention provides a lithium battery diaphragm with low short circuit rate and a preparation method thereof, which can effectively reduce the short circuit rate of the diaphragm assembled into a battery.
According to a first aspect, the present application provides a lithium battery separator with a low short circuit rate, comprising:
an intermediate layer and two surface layers, the intermediate layer having a first surface and a second surface opposite the first surface; the two surface layers are respectively attached to the first surface and the second surface;
the surface layer is polyolefin resin with crystallinity of 20-30%, isotacticity of not less than 98 and melt index of 2-4g/10 min.
In an alternative embodiment, the intermediate layer is a polyolefin resin having a crystallinity of not less than 42%, an isotacticity of 90 to 95, and a melt index of 0.5 to 2g/10min.
In an alternative embodiment, the surface layer is a polypropylene-based resin; and/or
The middle layer is polypropylene resin.
In an alternative embodiment, the sum of the thicknesses of the surface layers is 20% -50% of the total thickness.
In an alternative embodiment, the porosity of the lithium battery separator is 35% -55%.
In an alternative embodiment, the total thickness of the intermediate layer and the two surface layers is 10-25 μm.
According to a second aspect, the present application provides a method for preparing the lithium battery separator with low short circuit rate, comprising the following steps:
the raw materials of the surface layer and the raw materials of the middle layer are processed through coextrusion and cooled, so that the surface layer is attached to the two opposite sides of the middle layer, and a casting film is obtained;
annealing the casting film;
and sequentially stretching and heat setting the annealed casting film to obtain the lithium battery diaphragm.
In an alternative embodiment, the step of co-extrusion processing and cooling:
the extrusion temperature of the surface layer is 250-300 ℃; and/or
The extrusion temperature of the middle layer is 190-230 ℃; and/or
The cooling temperature is 70-100 ℃.
In an alternative embodiment, the step of annealing the cast film: the annealing temperature is 135-150 ℃ and the annealing time is 10-16h.
In an alternative embodiment, the stretching step includes: cold drawing at a drawing rate of 1.1-1.5 and a temperature of 80-100deg.C, and hot drawing at a drawing rate of 1.6-2.4 and a hot drawing temperature of 135-153 deg.C; and/or
The temperature of the heat setting is 150-165 ℃.
The beneficial effects of this application lie in: according to the method, polyolefin with certain crystallinity, isotacticity and melt index is selected as the surface layer of the lithium battery diaphragm, so that the surface of the lithium battery diaphragm has the characteristic of low hardness, and in the process, if the surface layer is subjected to the external force effects such as extrusion and friction, the surface layer can be subjected to the characteristic of low hardness by the surface layer, the damage phenomenon of the surface is reduced through elastic deformation and stress relaxation, the occurrence of weak points is reduced, the overall pressure resistance of the lithium battery diaphragm is improved, and the short circuit risk is further reduced.
Drawings
Fig. 1 is a schematic view of a layered structure according to an embodiment of the present application.
Reference numerals: a surface layer 1 and an intermediate layer 2.
Detailed Description
The invention will be described in further detail below with reference to the drawings by means of specific embodiments. Wherein like elements in different embodiments are numbered alike in association. In the following embodiments, numerous specific details are set forth in order to provide a better understanding of the present application. However, one skilled in the art will readily recognize that some of the features may be omitted, or replaced by other elements, materials, or methods in different situations. In some instances, some operations associated with the present application have not been shown or described in the specification to avoid obscuring the core portions of the present application, and may not be necessary for a person skilled in the art to describe in detail the relevant operations based on the description herein and the general knowledge of one skilled in the art.
Furthermore, the described features, operations, or characteristics of the description may be combined in any suitable manner in various embodiments. Also, various steps or acts in the method descriptions may be interchanged or modified in a manner apparent to those of ordinary skill in the art. Thus, the various orders in the description and drawings are for clarity of description of only certain embodiments, and are not meant to be required orders unless otherwise indicated.
The numbering of the components itself, e.g. "first", "second", etc., is used herein merely to distinguish between the described objects and does not have any sequential or technical meaning. The terms "coupled" and "connected," as used herein, are intended to encompass both direct and indirect coupling (coupling), unless otherwise indicated.
In one aspect, the application discloses a lithium battery separator with low short circuit rate, which comprises an intermediate layer 2 and two surface layers 1; specifically, the intermediate layer 2 has a first surface and a second surface, where the first surface and the second surface are opposite to each other, and as shown in fig. 1, the upper surface of the intermediate layer 2 is exemplified as the first surface, and the lower surface of the intermediate layer 2 is exemplified as the second surface; the two surface layers 1 are respectively attached to the first surface and the second surface, i.e., when the first surface and the second surface of the intermediate layer 2 are respectively the upper surface and the lower surface of the intermediate layer 2, the surface layers 1 are respectively located on the upper side and the lower side of the intermediate layer 2. The three-layer diaphragm with the A/B/A structure can be formed, wherein the A layer is the surface layer 1, and the B layer is the middle layer 2.
In the embodiment disclosed in the present application, the surface layer 1 is selected from a polyolefin resin having a crystallinity of 20% -30%, an isotacticity of not less than 98, and a melt index of 2-4g/10min, for example, the polyolefin resin may be a polypropylene resin, which may be modified or unmodified polypropylene meeting the parameter requirements, and the present application is not limited specifically.
Because the crystallinity, isotacticity and melt index of polypropylene all can influence the hardness of material to a certain extent, this application is through selecting as the surface layer 1 of lithium battery diaphragm with the polyolefin that the crystallinity is lower relatively, the isotacticity is higher relatively and have certain melt index for the surface of lithium battery diaphragm has certain elasticity and lower hardness, and then in the course, when the surface of like lithium battery diaphragm receives extrusion, friction etc. effect, the lithium battery diaphragm can carry out elastic deformation and stress relaxation through the surface layer 1 on its surface to effectively reduce the damage phenomenon on surface, reduce the short circuit risk.
In some alternative designs, the intermediate layer 2 may be a polyolefin resin having a crystallinity of not less than 42%, an isotacticity of 90-95, and a melt index of 0.5-2g/10min, and as such, a modified or unmodified polypropylene resin may be used, which is not particularly limited herein.
Since the crystallinity, isotacticity and melt index of polypropylene all affect the pore diameter of the material to a certain extent, the application can enable the middle layer 2 to form a small pore diameter structure by selecting polyolefin with relatively higher crystallinity, relatively lower isotacticity and certain melt index as the middle layer 2 of the lithium battery diaphragm, the pore diameter in the lithium battery diaphragm is mainly used for enabling lithium ions to better pass through the diaphragm and reach the opposite positive electrode or negative electrode, and if the pore diameter structure of the middle layer 2 is too large, active substances except lithium ions also pass through the diaphragm, so that the internal short circuit of a battery using the lithium battery diaphragm is caused; therefore, the present application can further improve the pressure resistance of the lithium battery separator by reducing the pore diameter of the intermediate layer 2.
In some alternative designs, the thickness of the surface layer 1 and the total thickness of the surface layer 1 may be 20% -50%, the thickness of the surface layer 1 may be the same or different, and preferably, the thickness of the surface layers 1 is the same; for example, when the thickness of the lithium battery separator is 14 μm, the sum of the thicknesses of the above-mentioned surface layers 1 may be between 2.8 μm and 7 μm, and the thickness of each surface layer 1 may be between 1.4 μm and 3.5 μm.
In some alternative designs, the overall porosity of the resulting lithium battery separator is 35-55%, and the specific porosity can be controlled during the stretching stage.
In some alternative designs the total thickness of the intermediate layer 2 and the two surface layers 1 is 10-25 μm, which thickness can be controlled during the extrusion and stretching stages.
The application also provides a preparation method of the lithium battery diaphragm with low short circuit rate, which comprises the following steps:
step S1: the raw materials of the surface layer 1 and the raw materials of the middle layer 2 are put into a co-extrusion device for melting, and then are extruded by a die head of the co-extrusion device to obtain prefabricated films of which the surface layer 1 is attached to the two opposite sides of the middle layer 2, and the prefabricated films are cooled to obtain a casting film;
specifically, in this step, the a material constituting the surface layer 1 and the B material constituting the intermediate layer 2 are respectively fed into a coextrusion apparatus, and the a material and the B material are melted; illustratively, the above-mentioned material A may be extruded through two skin outlets of a die under the condition of 250-300℃and the above-mentioned material B may be extruded through a middle outlet of the die under the condition of 190-230℃to form a three-layer-structured prefabricated film of A/B/A.
Then the prefabricated film is cooled by a casting cooling roller, specifically, the cooling temperature of the casting cooling roller can be set between 70 ℃ and 100 ℃, for example, the surface temperature of the casting cooling roller can be set to 70 ℃ or 100 ℃; after cooling the prefabricated film, a casting film can be obtained.
In this step, the above-mentioned material A is polyolefin resin particles having a crystallinity of 20% to 30%, an isotacticity of not less than 98, and a melt index of 2 to 4g/10min, for example, polypropylene resin particles are used as the material A in the present application; the material B is polyolefin resin particles having a structural crystallinity of not less than 42%, an isotacticity of 90 to 95 and a melt index of 0.5 to 2g/10min, for example, polypropylene resin particles are used as the material B in the present application.
Step S2: the casting film prepared by step S1 is annealed.
Specifically, in this step, the casting film may be rolled up and then put into an oven for annealing treatment; for example, after the casting film is cooled, the casting film may be wound into a roll shape, wherein the winding length is 2000-4000m and the winding width is 1-2m, and then the oven temperature is set to 135-150 ℃ and annealed for 10-16h.
It will be appreciated that the annealing temperature is inversely proportional to the annealing time, and in particular, a shorter annealing time may be used when the annealing temperature is higher, whereas a longer annealing time may be required when the annealing temperature is lower; for example, when the oven temperature is set to 150 ℃, the annealing time can be controlled to about 10 hours, whereas when the oven temperature is set to 135 ℃, the annealing time needs to be set to about 16 hours.
Step S3: and sequentially stretching and heat setting the annealed casting film to obtain the lithium battery diaphragm.
In this step, the casting film after the completion of annealing is stretched and heat-set, thereby forming a porous structure inside thereof; specifically, the stretching may be sequentially performed by cold stretching and hot stretching; illustratively, when cold drawing is performed, it may be performed under the conditions of a draw ratio of 1.1 to 1.5 and a temperature of 80 to 100 ℃; the hot drawing may be performed under conditions of a draw ratio of 1.6 to 2.4 and a temperature of 135 to 150 ℃.
Finally, after stretching, carrying out heat setting on the casting film, namely, carrying out heat treatment on the diaphragm at high temperature, reducing the heat shrinkage rate of the diaphragm, and improving the dimensional stability, thereby obtaining the lithium battery diaphragm; illustratively, the heat setting described above may be at a temperature of 150-165 ℃.
In order to further illustrate the effects of the present application, the present application also provides the following more specific embodiments.
Control example:
preparing a material A, wherein the material A is polypropylene resin particles with isotacticity of 96, crystallinity of 34 and melt index of 2.0g/10 min; a material B was prepared, which was polypropylene resin particles having an isotacticity of 98, a crystallinity of 38% and a melt index of 1.0g/10min.
Adding the material A and the material B into a coextrusion device, and forming a prefabricated film with an A/B/A structure through coextrusion (wherein a layer A is formed by extruding the material A and a layer B is formed by extruding the material B); wherein the extrusion processing temperature of the layer A is 230 ℃, and the extrusion processing temperature of the layer B is 220 ℃; cooling the prefabricated film by a casting roller at 85 ℃ to form a casting film, then rolling 2500m, and annealing for 15 hours at 143 ℃; then longitudinally stretching, wherein the cold stretching temperature is 85 ℃, the stretching multiplying power is 1.3, the hot stretching temperature is 153 ℃, and the stretching multiplying power is 2.1; after the completion of the stretching, heat setting was performed at 163 ℃.
Finally, the lithium battery diaphragm with the thickness of 14 mu m and the porosity of 39% is prepared, the lithium battery diaphragm comprises an intermediate layer 2 made of a material B and a surface layer 1 which is positioned on the upper surface and the lower surface of the intermediate layer 2 and made of a material A, wherein the surface layer 1 accounts for 30% of the total thickness of the lithium battery diaphragm.
Example 1:
referring to the method disclosed in the comparative example, three sets of lithium battery separators, labeled sample 1, sample 2, and sample 3, respectively, were prepared.
In the sample 1, the raw material adopted by the surface layer is polypropylene with the isotacticity of 98, the crystallinity of 20 percent and the melt index of 2.0g/10 min; the intermediate layer adopts polypropylene with the raw materials of 98 percent of isotacticity, 38 percent of crystallinity and 1.0g/10min of melt index; the rest preparation steps and process parameters are the same as those of the comparative example.
The final sample 1 had a thickness of 14 μm, a porosity of 39% and a surface layer 1 of 30% of the total thickness of the lithium battery separator.
In the sample 2, the raw material adopted by the surface layer is polypropylene with the isotacticity of 96, the crystallinity of 34 and the melt index of 2.0g/10 min; the intermediate layer is made of polypropylene with 94 isotacticity and 42 crystallinity and 1.0g/10min melt index, and the rest preparation steps and process parameters are the same as those of the comparative example.
The thickness of the finally obtained sample 2 was 14 μm, the porosity was 39%, and the proportion of the surface layer 1 to the total thickness of the lithium battery separator was 30%.
Wherein, in sample 3, the adopted raw materials are consistent with sample 1; in preparation, the preparation procedure was as described in reference to comparative example 1, with the difference that: in the preparation process, the prefabricated film with the A/B/A structure is formed by increasing the extrusion temperature of the A layer to 260 ℃ while the other process parameters are kept unchanged.
The final sample 3 had a thickness of 14 μm, a porosity of 39% and a surface layer 1 of 30% of the total thickness of the lithium battery separator.
Each performance of the above-described control and samples 1 to 3 was tested.
Wherein, the thickness is measured by a Mark thickness gauge; the ventilation value is tested by a Gurley ventilation instrument; the porosity is calculated by a mass method; the pore diameter is tested by adopting a PMI tester, the testing principle is the bubble point method principle, and the measured pore diameter is the pore diameter value at the narrowest part in the diaphragm pore structure; the voltage withstand value is tested by adopting a voltage withstand tester, the lithium battery diaphragm is placed under the condition of simulating positive and negative electrodes, the voltage is gradually increased, the diaphragm breaks down finally, the voltage value corresponding to the breakdown is the voltage withstand value, wherein the higher the voltage withstand value is, the stronger the short-circuit resistance of the diaphragm can be reflected; the hardness test of the lithium battery diaphragm adopts a nano comprehensive mechanical property tester, which is based on a nano mechanical microscopic probe system and can carry out nano indentation hardness test.
The final test results are shown in table 1:
TABLE 1
| Sample of | Thickness/. Mu.m | Porosity/% | Pore size/nm | Ventilation value/(S/100 ml) | hardness/MPa | Withstand voltage value/KV |
| Comparative example | 14 | 39.2 | 33.3 | 238 | 25.3 | 1.5 |
| Sample 1 | 14 | 39.6 | 33.8 | 247 | 11 | 1.8 |
| Sample 2 | 14 | 39.4 | 28.5 | 252 | 14.3 | 1.7 |
| Sample 3 | 14 | 38.8 | 32.5 | 244 | 10.2 | 1.9 |
From the above experimental data, it can be seen that the pressure resistance values of sample 1, sample 2 and sample 3 are all improved compared with the comparative examples.
Comparing the comparative example with the sample 1, it can be seen that the porosity and pore size of the sample 1 are not greatly different from those of the comparative example, but the surface hardness is more reduced. It is revealed that the hardness of the lithium battery separator can be reduced by reducing the crystallinity of the surface layer 1 and increasing the isotacticity thereof, thereby increasing the withstand voltage value.
Comparing sample 2 with sample 1 and the control, it can be seen that the hardness of sample 2 is reduced less than that of sample 1, but the pore size at the narrowest point is reduced more than that of the control. It can be shown that the pore diameter of the lithium battery separator can be effectively reduced by reducing the isotacticity and crystallinity of the raw material of the intermediate layer 2, thereby improving the pressure resistance.
Comparing sample 3 with sample 1, it was found that the pressure resistance of sample 3 was further improved as compared with sample 1, and the hardness was further reduced as compared with sample 1. It can be shown that, in the production process, the extrusion temperature of the surface layer 1 is increased, and the hardness of the lithium battery separator can be further reduced, thereby increasing the withstand voltage value.
Example 2:
preparing a material A, wherein the material A is polypropylene with the isotacticity of 98, the crystallinity of 22 and the melt index of 2.0g/10 min; a material B was prepared, which had an isotacticity of 93, a crystallinity of 45% and a melt index of 1.0g/10min.
Adding the material A and the material B into a co-extrusion device, and forming a prefabricated film with an A/B/A structure through co-extrusion; wherein the extrusion processing temperature of the layer A is 260 ℃ and the extrusion processing temperature of the layer B is 220 ℃; cooling the prefabricated film by a casting roller at 85 ℃ to form a casting film, then rolling 2500m, and annealing for 15 hours at 143 ℃; then longitudinally stretching, wherein the cold stretching temperature is 85 ℃, the stretching multiplying power is 1.3, the hot stretching temperature is 153 ℃, and the stretching multiplying power is 2.1; after the completion of the stretching, heat setting was performed at 163 ℃.
The lithium battery diaphragm with the thickness of 14 mu m and the porosity of 39% is finally prepared and comprises an intermediate layer 2 made of a material B and a surface layer 1 made of a material A and positioned on the upper surface and the lower surface of the intermediate layer 2, wherein the surface layer 1 accounts for 30% of the total thickness of the lithium battery diaphragm. The performance of example 2 was then tested with reference to the method disclosed in example 1, and the results are shown in table 2:
TABLE 2
| Sample of | Thickness/. Mu.m | Porosity/% | Pore size/nm | Ventilation value/(S/100 ml) | hardness/MPa | Withstand voltage value/KV |
| Example 2 | 14 | 38.9 | 27.2 | 256 | 11.3 | 2.1 |
As can be seen from the above experimental results, the withstand voltage value finally obtained in this example 2 is higher than that of the control example and samples 1 to 3; it is shown that the withstand voltage value of the lithium battery separator can be greatly improved by reducing the pore diameter of the intermediate layer while reducing the hardness.
Example 3:
preparing a layer A material, wherein the layer A material is polypropylene with the isotacticity of 98, the crystallinity of 30 and the melt index of 4.0g/10 min; a layer B material was prepared, which had an isotacticity of 95, a crystallinity of 42% and a melt index of 2g/10min.
Adding the layer A material and the layer B material into a co-extrusion device, and forming a prefabricated film with an A/B/A structure through co-extrusion; wherein the extrusion processing temperature of the layer A is 300 ℃, and the extrusion processing temperature of the layer B is 230 ℃; cooling the prefabricated film by a casting roller at the temperature of 100 ℃ to form a casting film, then rolling 2500m, and then annealing for 10 hours at the temperature of 150 ℃; then longitudinally stretching, wherein the cold stretching temperature is 100 ℃, the stretching multiplying power is 1.5, the hot stretching temperature is 150 ℃, and the stretching multiplying power is 2.4; after the completion of the stretching, heat setting was performed at 165 ℃.
Example 4:
preparing a layer A material, wherein the layer A material is polypropylene with the isotacticity of 98, the crystallinity of 20 and the melt index of 2.0g/10 min; a layer B material was prepared, which had an isotacticity of 90, a crystallinity of 42% and a melt index of 0.5g/10min.
Adding the layer A material and the layer B material into a co-extrusion device, and forming a prefabricated film with an A/B/A structure through co-extrusion; wherein the extrusion processing temperature of the layer A is 250 ℃, and the extrusion processing temperature of the layer B is 190 ℃; cooling the prefabricated film by a casting roller at 70 ℃ to form a casting film, then rolling 2500m, and then annealing for 16 hours at 135 ℃; then longitudinally stretching, wherein the cold stretching temperature is 80 ℃, the stretching multiplying power is 1.1, the hot stretching temperature is 135 ℃, and the stretching multiplying power is 1.6; after the stretching was completed, heat setting was performed at 150 ℃.
The foregoing description of the invention has been presented for purposes of illustration and description, and is not intended to be limiting. Several simple deductions, modifications or substitutions may also be made by a person skilled in the art to which the invention pertains, based on the idea of the invention.
Claims (9)
1. A lithium battery separator with a low short circuit rate, comprising:
an intermediate layer and two surface layers, the intermediate layer having a first surface and a second surface opposite the first surface; the two surface layers are respectively attached to the first surface and the second surface;
the middle layer is polyolefin resin with crystallinity not lower than 42%, isotacticity of 90-95 and melt index of 0.5-2g/10 min; the surface layer is polyolefin resin with crystallinity of 20-30%, isotacticity of not less than 98 and melt index of 2-4g/10 min.
2. The low short circuit rate lithium battery separator according to claim 1, wherein the surface layer is a polypropylene-based resin; and/or
The middle layer is polypropylene resin.
3. The low short circuit rate lithium battery separator of claim 1 wherein the sum of the thicknesses of the surface layers is 20% to 50% of the total thickness.
4. The low short circuit rate lithium battery separator of claim 1 wherein the porosity of the lithium battery separator is 35% to 55%.
5. The low short circuit rate lithium battery separator according to claim 1, wherein the total thickness of the intermediate layer and the two surface layers is 10-25 μm.
6. A method for preparing the lithium battery separator with low short circuit rate according to any one of claims 1 to 5, comprising the steps of:
the raw materials of the surface layer and the raw materials of the middle layer are processed through coextrusion and cooled, so that the surface layer is attached to the two opposite sides of the middle layer, and a casting film is obtained;
annealing the casting film;
and sequentially stretching and heat setting the annealed casting film to obtain the lithium battery diaphragm.
7. The method for preparing a lithium battery separator according to claim 6, wherein in the step of co-extrusion processing and cooling:
the extrusion temperature of the surface layer is 250-300 ℃; and/or
The extrusion temperature of the middle layer is 190-230 ℃; and/or
The cooling temperature is 70-100 ℃.
8. The method for preparing a lithium battery separator according to claim 6, wherein in the step of annealing the cast film: the annealing temperature is 135-150 ℃ and the annealing time is 10-16h.
9. The method for preparing a lithium battery separator according to claim 6, wherein the step of sequentially stretching and heat-setting the annealed cast film comprises: cold drawing at a drawing rate of 1.1-1.5 and a temperature of 80-100deg.C, and hot drawing at a drawing rate of 1.6-2.4 and a hot drawing temperature of 135-153 deg.C; and/or
The temperature of the heat setting is 150-165 ℃.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310497572.4A CN116207446B (en) | 2023-05-06 | 2023-05-06 | Lithium battery diaphragm with low short circuit rate and preparation method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310497572.4A CN116207446B (en) | 2023-05-06 | 2023-05-06 | Lithium battery diaphragm with low short circuit rate and preparation method thereof |
Publications (2)
| Publication Number | Publication Date |
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| CN116207446A CN116207446A (en) | 2023-06-02 |
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Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20010068785A (en) * | 2000-01-10 | 2001-07-23 | 성재갑 | Microporous membrane of high crystalline polypropylene and preparation method thereof |
| EP2303576A1 (en) * | 2008-07-16 | 2011-04-06 | ExxonMobil Oil Corporation | Matte surface multilayer films having improved sealing properties, their methods of manufacture, and articles made therefrom |
| DE102010018374A1 (en) * | 2010-04-26 | 2011-10-27 | Treofan Germany Gmbh & Co. Kg | Highly porous separator film |
| DE102011121606A1 (en) * | 2011-12-20 | 2013-06-20 | Treofan Germany Gmbh & Co. Kg | Highly porous separator film with coating and shut-off function |
| KR20170033545A (en) * | 2015-09-17 | 2017-03-27 | 롯데케미칼 주식회사 | Polypropylene lithium ion battery separator for high wettability of electrolyte |
| CN106680469A (en) * | 2016-12-27 | 2017-05-17 | 北方华锦化学工业集团有限公司 | Evaluation method of special polypropylene resin for lithium battery diaphragm |
| JP2017185647A (en) * | 2016-04-01 | 2017-10-12 | 三菱ケミカル株式会社 | Laminated porous film and method for producing the same |
| CN114188658A (en) * | 2021-11-15 | 2022-03-15 | 深圳中兴新材技术股份有限公司 | Thin film, preparation method thereof and battery |
| CN115534464A (en) * | 2022-10-24 | 2022-12-30 | 广东德冠薄膜新材料股份有限公司 | High-gloss and high-transparency BOPP film and preparation method and application thereof |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100406689B1 (en) * | 2001-03-05 | 2003-11-21 | 주식회사 엘지화학 | Multicomponent composite film for electrochemical device and method for preparing the same |
| JP5807388B2 (en) * | 2010-05-26 | 2015-11-10 | 東レ株式会社 | Porous polypropylene film |
| JP2014197541A (en) * | 2013-03-05 | 2014-10-16 | ユニチカ株式会社 | Coating material for lithium ion secondary battery separator, lithium ion secondary battery separator, and lithium ion secondary battery |
| KR101672815B1 (en) * | 2013-12-17 | 2016-11-04 | 주식회사 엘지화학 | A separator for electrochemical device |
| JP2016033897A (en) * | 2014-07-31 | 2016-03-10 | 日本碍子株式会社 | Separator for lithium air battery and lithium air battery |
| CN104979513B (en) * | 2015-05-25 | 2017-08-22 | 武汉惠强新能源材料科技有限公司 | A kind of three-layer co-extruded lithium ion battery separator and its production method |
| JP2018076476A (en) * | 2016-11-10 | 2018-05-17 | 有限会社ケー・イー・イー | High temperature low heat shrinkable polyolefin multilayer microporous film and method for producing the same |
| EP3607598A4 (en) * | 2017-04-06 | 2020-12-30 | Asahi Kasei Kabushiki Kaisha | Separator for lithium-ion secondary battery |
| CN109192902B (en) * | 2018-07-10 | 2021-11-23 | 深圳中兴新材技术股份有限公司 | Preparation method of multi-stage safety protection lithium battery diaphragm and lithium battery diaphragm |
| CN110391384B (en) * | 2019-07-19 | 2022-11-08 | 深圳中兴新材技术股份有限公司 | Preparation method of high-rigidity lithium ion battery diaphragm and diaphragm prepared by preparation method |
| DE112020005551T5 (en) * | 2019-11-13 | 2022-08-25 | Gs Yuasa International Ltd. | NON-AQUEOUS ELECTROLYTE ENERGY STORAGE DEVICE |
| WO2022255443A1 (en) * | 2021-06-04 | 2022-12-08 | 株式会社Ｇｓユアサ | Separator for lead-acid battery, and lead-acid battery including same |
-
2023
- 2023-05-06 CN CN202310497572.4A patent/CN116207446B/en active Active
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20010068785A (en) * | 2000-01-10 | 2001-07-23 | 성재갑 | Microporous membrane of high crystalline polypropylene and preparation method thereof |
| EP2303576A1 (en) * | 2008-07-16 | 2011-04-06 | ExxonMobil Oil Corporation | Matte surface multilayer films having improved sealing properties, their methods of manufacture, and articles made therefrom |
| DE102010018374A1 (en) * | 2010-04-26 | 2011-10-27 | Treofan Germany Gmbh & Co. Kg | Highly porous separator film |
| DE102011121606A1 (en) * | 2011-12-20 | 2013-06-20 | Treofan Germany Gmbh & Co. Kg | Highly porous separator film with coating and shut-off function |
| KR20170033545A (en) * | 2015-09-17 | 2017-03-27 | 롯데케미칼 주식회사 | Polypropylene lithium ion battery separator for high wettability of electrolyte |
| JP2017185647A (en) * | 2016-04-01 | 2017-10-12 | 三菱ケミカル株式会社 | Laminated porous film and method for producing the same |
| CN106680469A (en) * | 2016-12-27 | 2017-05-17 | 北方华锦化学工业集团有限公司 | Evaluation method of special polypropylene resin for lithium battery diaphragm |
| CN114188658A (en) * | 2021-11-15 | 2022-03-15 | 深圳中兴新材技术股份有限公司 | Thin film, preparation method thereof and battery |
| CN115534464A (en) * | 2022-10-24 | 2022-12-30 | 广东德冠薄膜新材料股份有限公司 | High-gloss and high-transparency BOPP film and preparation method and application thereof |
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