CN116073072A - Battery diaphragm and preparation method and application thereof - Google Patents

Battery diaphragm and preparation method and application thereof Download PDF

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Publication number
CN116073072A
CN116073072A CN202310111130.1A CN202310111130A CN116073072A CN 116073072 A CN116073072 A CN 116073072A CN 202310111130 A CN202310111130 A CN 202310111130A CN 116073072 A CN116073072 A CN 116073072A
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powder
battery
stretching
bentonite
wollastonite
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请求不公布姓名
苏航
李阳兴
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Anhui Deyi Energy Technology Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/403—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
    • 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
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/417—Polyolefins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/431—Inorganic material
    • 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
    • H01M50/431—Inorganic material
    • H01M50/434—Ceramics
    • H01M50/437—Glass
    • 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
    • H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/494—Tensile strength
    • 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 belongs to the technical fields of advanced inorganic nonmetallic materials and electronic core industry, relates to a battery component, in particular to a lithium ion battery component, and particularly relates to a battery diaphragm, a preparation method and application thereof. Uniformly mixing wollastonite, bentonite, a silane coupling agent, titanate and absolute ethyl alcohol, regulating the pH to be acidic, and heating to 80-120 ℃ for modification reaction to obtain modified porcelain powder; mixing the modified porcelain powder with glass powder and polyolefin to obtain mixed powder, and carrying out melt extrusion, stretching, extraction and shaping on the mixed powder and paraffin oil to obtain the modified porcelain powder. The battery diaphragm provided by the invention can not only avoid combustion and explosion of the lithium battery caused by temperature rise, but also improve the tensile property and puncture resistance of the battery diaphragm, and remarkably improve the safety of the lithium battery.

Description

Battery diaphragm and preparation method and application thereof
Technical Field
The invention belongs to the technical fields of advanced inorganic nonmetallic materials and electronic core industry, relates to a battery component, in particular to a lithium ion battery component, and particularly relates to a battery diaphragm, a preparation method and application thereof.
Background
The disclosure of this background section is only intended to increase the understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art already known to those of ordinary skill in the art.
At present, a microporous film mainly made of polyolefin materials is adopted as a commercial lithium battery diaphragm, the greatest problem of the materials is that the melting point is relatively low, and when the internal heat of the battery rises sharply, the diaphragm breaks the film to cause internal short circuit and thermal runaway of the lithium battery, and finally the combustion and explosion of the lithium battery are initiated. The characteristic of low melting point of polyolefin is the root cause for influencing the safety of lithium battery separator, and how to effectively improve the limitation of polyolefin material is the key for developing high-safety lithium battery separator.
The inventor researches know that the main ways to improve the safety of the lithium battery separator are structural compounding, mixing and/or adding a coating layer, however, the inventor further researches find that the above ways are limited in improving the safety of the lithium battery separator, do not break the limitation of the polyolefin material, and meanwhile, the safety is improved while other performances of the separator such as puncture resistance and air permeability are sacrificed. Therefore, how to improve the safety of the lithium battery separator under the premise of ensuring other performances is a technical problem which needs to be solved at present.
Disclosure of Invention
In order to improve the safety performance of a lithium battery diaphragm and avoid the influence on other aspects of performance while improving the safety performance, the invention aims to provide a battery diaphragm, a preparation method and application thereof.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
on the one hand, the preparation method of the battery diaphragm comprises the steps of uniformly mixing wollastonite, bentonite, a silane coupling agent, titanate and absolute ethyl alcohol or fluorine-free pure water or isopropanol, adjusting pH to be acidic, heating to 80-120 ℃ and carrying out modification reaction to obtain modified porcelain powder; mixing the modified porcelain powder with glass powder and polyolefin to obtain mixed powder, and carrying out melt extrusion, stretching, extraction and shaping on the mixed powder and paraffin oil to obtain the modified porcelain powder;
the polyolefin is preferably polyethylene or polypropylene;
wherein, the mass ratio of wollastonite to bentonite is 2-6:0.5-1.5, the mass ratio of silane coupling agent to titanate is 2-8:2-6, and the total mass ratio of wollastonite to bentonite and the total mass ratio of silane coupling agent to titanate is 5-10:0.5-1;
the mass ratio of the modified porcelain powder to the glass powder to the polyolefin is 8-15:2-7:78-90.
According to the invention, the modified porcelain powder, the glass powder and the polyolefin are prepared into the uniformly dispersed diaphragm material through melt extrusion, stretching, extraction and shaping, and when the temperature is low, the mechanical strength of the polyolefin can support the diaphragm porous structure, and the diaphragm keeps normal work; when the temperature is increased, the polyolefin is softened, and the mechanical strength of the modified porcelain powder continuously provides a supporting function, so that the interval between the anode and the cathode is ensured; when the temperature continues to rise, the glass powder is melted and wrapped and bridged with the modified porcelain powder, holes formed by melting polyolefin are filled, and the isolation of the anode and the cathode is continuously maintained; when the temperature is further increased, the glass powder which is completely thermally decomposed and melted into a liquid phase by the polyolefin is continuously increased to be bridged and bonded with the ceramic powder component, and the glass powder and the ceramic powder component are subjected to eutectic reaction to form a hard ceramic framework to keep the positive electrode and the negative electrode isolated.
Meanwhile, researches show that the modified porcelain powder after the modification reaction of the silane coupling agent and the titanate can improve the combination property with polyolefin, and the tensile property and the puncture resistance of the prepared diaphragm material are obviously improved by adding the silane coupling agent and the titanate in the proportion.
In another aspect, a battery separator is obtained by the above-described method of preparation.
In a third aspect, the use of a battery separator as described above in a lithium ion battery.
The beneficial effects of the invention are as follows:
in the battery diaphragm prepared by the invention, inorganic components are melted into liquid phase after the temperature reaches a certain interval in the process of rapidly rising the heat of the battery, and the ceramic powder material is bridged and coated to promote the occurrence of ceramic reaction while filling the melting gap of the polyolefin material, so that an inorganic ceramic layer is generated between the positive electrode and the negative electrode to prevent short circuit, the occurrence of combustion and explosion of the lithium battery caused by continuous temperature rising is avoided, and the safety of the lithium battery is obviously improved. In addition, the addition of the modified porcelain powder increases the combination property of the porcelain powder and polyolefin, thereby further improving the tensile property and puncture resistance of the battery diaphragm.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
FIG. 1 is a diagram of a ceramic mechanism of a battery separator prepared in an embodiment of the invention, wherein the diagram comprises a polyethylene matrix 1, modified porcelain powder (wollastonite) 2, modified porcelain powder (bentonite) 3, glass powder 4, glass powder 5 and a pore structure;
FIG. 2 is a Scanning Electron Microscope (SEM) image before and after sintering of a battery separator prepared according to an embodiment of the present invention, a is before sintering, and b is after sintering;
FIG. 3 is a thermogravimetric analysis (TGA) curve of a battery separator prepared according to an embodiment of the present invention;
FIG. 4 is a graph showing puncture performance of a battery separator prepared according to an embodiment of the present invention;
fig. 5 is a tensile strength curve of a battery separator prepared according to an embodiment of the present invention.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present invention. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
In view of the difficulty in ensuring the safety and the puncture resistance of the conventional lithium ion battery diaphragm, the invention provides a battery diaphragm, and a preparation method and application thereof.
According to a typical embodiment of the invention, a preparation method of a battery diaphragm is provided, wollastonite, bentonite, a silane coupling agent, titanate and absolute ethyl alcohol are uniformly mixed, pH is adjusted to be acidic, and the mixture is heated to 80-120 ℃ for modification reaction to obtain modified porcelain powder; mixing the modified porcelain powder with glass powder and polyolefin to obtain mixed powder, and carrying out melt extrusion, stretching, extraction and shaping on the mixed powder and paraffin oil to obtain the modified porcelain powder;
wherein, the mass ratio of wollastonite to bentonite is 2-6:0.5-1.5, the mass ratio of silane coupling agent to titanate is 2-8:2-6, and the total mass ratio of wollastonite to bentonite and the total mass ratio of silane coupling agent to titanate is 5-10:0.5-1;
the mass ratio of the modified porcelain powder to the glass powder to the polyolefin is 8-15:2-7:78-90.
In some embodiments, wollastonite D 50 Bentonite with particle size of 100-150 mu mD of (2) 50 The grain diameter is 100-150 mu m.
In some embodiments, the silane coupling agent is a silane coupling agent KH560.
In some embodiments, wollastonite, bentonite, a silane coupling agent, titanate, and absolute ethanol are mixed uniformly and then the pH is adjusted to 4 to 5. The battery diaphragm prepared by using the modified porcelain powder subjected to the conditional modification reaction as a raw material has better performance. The pH is adjusted by hydrochloric acid.
In some embodiments, the reaction time is from 5 to 7 hours in the modification reaction. In the reaction process, the rotating speed is 200-500 r/min.
In some embodiments, the mass ratio of wollastonite to bentonite to absolute ethanol is 5-10:1-3.
The polyolefin is polyethylene, polypropylene or a mixture thereof. In some embodiments, the polyolefin is polyethylene. The polyethylene preferably has a viscosity average molecular weight of 80 to 150W, i.e. (0.8 to 1.5). Times.10 6 。
In some embodiments, the glass frit is a low temperature glass frit. From SiO 2 、P 2 O 5 、B 2 O 3 、Li 2 O、ZnO、BaO、K 2 O、Na 2 The invention is prepared by melting and copolymerizing inorganic materials such as O, etc., and the melting of the low-temperature glass powder is carried out in the range of 200-280 ℃.
In some embodiments, the mass ratio of the mixed powder to the paraffin oil is 20-40:60-80.
In some embodiments, during melt extrusion, the extruder temperature is in the range of 180-220 ℃, the rotational speed is 90-150 rpm/min, the molten material is cast into sheets through a die outlet with a gap of 1.5-2.5 mm, the sheets are pulled through a cooling roll to cool the sheets, the roll speed is 4-8 m/min, and the roll temperature is 15-20 ℃.
In some embodiments, stretching employs asynchronous biaxially stretching or synchronous biaxially stretching.
In some embodiments, the stretching temperature is 90-130 ℃, and the stretching magnification is 6-15 times.
In some embodiments, the paraffinic oil is extracted with methylene chloride.
In some embodiments, the extract is then stretched and set again. The stretching temperature and the shaping temperature are 90-130 ℃, and the stretching multiplying power is 1-5 times.
Specifically, the steps are as follows:
1. modifying the porcelain powder: mixing wollastonite with the particle size D50 of 100-150 mu m with bentonite, absolute ethyl alcohol, a silane coupling agent KH560 and titanate, regulating the pH value to 4-5 by using an HCl solution, controlling the temperature to be in the range of 80-120 ℃ and the rotating speed to be 200-500 r/min, heating and stirring for 5-7 h, and vacuum drying after the completion to obtain modified porcelain powder; wherein the mass ratio of wollastonite to bentonite is (2-6) (0.5-1.5), the mass ratio of KH560 to titanate is (2-8) (2-6), the mass ratio of wollastonite/bentonite, absolute ethyl alcohol and KH 560/titanate is (5-10) (1-3) (0.5-1);
2. mixing the modified porcelain powder prepared in the step 1, low-temperature glass powder and polyethylene with viscosity average molecular weight of 80-150W by a high-speed stirrer, and discharging after mixing for 1-2 hours; wherein the mass ratio of the porcelain powder to the glass powder to the polyethylene is (8-15) to (2-7): (78-90);
3. adding the mixed material obtained in the step 2 and paraffin oil into a double-screw extruder through a metering system to melt, wherein the ratio of the mixed material to the paraffin oil is (20-40): (60-80), the temperature interval of the extruder is 180-220 ℃, the rotating speed is 90-150 rpm/min, the molten material is cast into sheets through a die head outlet with a gap of 1.5-2.5 mm, the sheets are pulled to be cooled into sheets through a cooling roller, the roller speed is 4-8 m/min, and the roller temperature is 15-20 ℃;
4. drawing the sheet obtained in the step 3 into an asynchronous biaxial stretching or synchronous biaxial stretching device, wherein the stretching temperature is 90-130 ℃, and the stretching multiplying power is 6-15 times;
5. immersing the material obtained in the step 4 into a device containing dichloromethane to extract paraffin oil, and drying the material at 35-45 ℃ after extraction;
6. drawing the material obtained in the step 5 into a transverse drawing device, drawing and shaping the material into a film with the thickness of 2-16 mu m, wherein the drawing temperature and shaping temperature are 90-130 ℃, and the drawing multiplying power is 1-5 times;
7. and (3) pulling the material obtained in the step (6) into a winding device for winding.
In another embodiment of the present invention, there is provided a battery separator obtained by the above-described preparation method.
Specifically, the thickness is 2 to 16. Mu.m.
In a third aspect, the use of a battery separator as described above in a lithium ion battery.
Specifically, the lithium ion battery is composed of a positive electrode, an electrolyte, the battery separator, and a negative electrode. The positive electrode is a positive electrode of a conventional lithium ion battery, and the positive electrode material of the positive electrode can be lithium cobaltate, lithium manganate, lithium nickelate, lithium iron phosphate, lithium manganese phosphate, nickel-manganese-cobalt ternary material and the like. The electrolyte is conventional lithium ion battery electrolyte, and the electrolyte of the electrolyte can be lithium hexafluorophosphate (LiPF 6 ) Lithium perchlorate (LiClO) 4 ) Lithium tetrafluoroborate (LiBF) 4 ) Etc. The negative electrode is a conventional lithium ion battery negative electrode, and the negative electrode material of the negative electrode can be graphite, a silicon material, an alloy material and the like.
In order to enable those skilled in the art to more clearly understand the technical scheme of the present invention, the technical scheme of the present invention will be described in detail below with reference to specific examples and comparative examples.
Embodiment one:
taking particle diameter D 50 2.4kg of wollastonite with the particle size of 100-150 mu m and 0.6kg of bentonite are added into a reaction kettle, 23.5kg of absolute ethyl alcohol, 1.8kg of silane coupling agent KH560 and 1.2kg of titanate are added, hydrochloric acid is added to adjust the pH value to 4.5 at the temperature of 90 ℃, and the mixture is stirred for 6 hours and then taken out for drying, so that the modified porcelain powder is obtained. 3kg of modified porcelain powder, 25.5kg of polyethylene with the viscosity average molecular weight of 100w and 1.5kg of glass powder are taken, added into a high-speed stirrer, stirred for 60min at the rotating speed of 350r/min, and taken out. 30kg of uniformly mixed materials and 70kg of paraffin oil are added into a double-screw extruder for melt co-extrusion, the extrusion temperature is 195 ℃, the rotating speed is 100r/min, the lip clearance of an extrusion die head is 2.0mm, and the casting sheet is cooled by a cooling roller to prepare a casting sheet with the thickness of 1.7 mm. And synchronously and bidirectionally (transversely and longitudinally) stretching the casting sheet and shaping the casting sheet into a thinner sheet, wherein the stretching multiplying powers are respectively 9.5 times in two directions. Immersion in CH after stretching 2 Cl 2 Extracting in an extraction tank to form holes and drying. After drying, the separator was subjected to transverse stretching again and set into a 10 μm film, wherein the stretching ratio was 1.23.
The ceramic mechanism of the battery diaphragm prepared by the embodiment is shown in figure 1, and when the temperature is lower than 140 ℃, the mechanical strength of the polyethylene matrix can support the diaphragm porous structure, and the diaphragm keeps normal operation; when the temperature is increased to 140-180 ℃, the molecular orientation of the polyethylene matrix is destroyed to soften, and the mechanical strength of the porcelain powder continuously provides a supporting function to keep the anode and the cathode from contacting; when the temperature is raised to about 180-200 ℃, the polyethylene matrix is melted and broken, at the moment, the glass powder is melted and wrapped and bridged with the porcelain powder, and the holes formed by the melting of the polyethylene are filled to keep the isolation of the anode and the cathode; the temperature is further increased, the polyolefin matrix is completely thermally decomposed, the glass powder melted into a liquid phase is continuously increased to be bridged and bonded with the ceramic powder component, and the glass powder and the ceramic powder component are subjected to eutectic reaction to form a hard ceramic framework to keep the positive electrode and the negative electrode isolated.
The battery separator was sintered at 500 ℃ for 1 hour under nitrogen atmosphere, and SEM images before and after sintering are shown in fig. 2. FIG. 2a shows that the modified porcelain powder and the glass powder (indicated by arrows) have better compatibility, and the interface between the particles and the matrix is blurred, which indicates that the modified porcelain powder and the polyethylene matrix realize better combination. Fig. 2b shows that the polyethylene matrix is completely decomposed after high temperature sintering of the material, and the residual ceramic powder is bonded together after melting of the glass frit to form a ceramic skeleton structure, which provides further spacing between the anode and cathode of the battery.
Embodiment two:
taking particle diameter D 50 3.6kg of wollastonite with the particle size of 100-150 mu m and 0.9kg of bentonite are added into a reaction kettle, 38.25kg of absolute ethyl alcohol, 1.35kg of silane coupling agent KH560 and 0.9kg of titanate are added, hydrochloric acid is added to adjust the pH value to 4.5 at the temperature of 90 ℃, and the mixture is stirred for 6 hours and then taken out for drying, so that the modified porcelain powder is obtained. 10kg of modified porcelain powder, 24kg of polyethylene with the viscosity average molecular weight of 100w and 5kg of glass powder are taken, added into a high-speed stirrer, stirred for 60min and taken out. Adding 30kg of uniformly mixed materials and 70kg of paraffin oil into a double-screw extruder for melt co-extrusion at the extrusion temperature of 195 ℃ and rotatingThe speed is 100r/min, the lip clearance of the extrusion die head is 2.0mm, and the casting sheet is cooled by a cooling roller to prepare a casting sheet with the thickness of 1.7 mm. And synchronously and bidirectionally (transversely and longitudinally) stretching the casting sheet and shaping the casting sheet into a thinner sheet, wherein the stretching multiplying powers are respectively 9.5 times in two directions. Immersion in CH after stretching 2 Cl 2 The extraction tank is used for extracting and forming holes and drying. After drying, the separator was subjected to transverse stretching again and set into a 10 μm film, wherein the stretching ratio was 1.23.
Comparative example:
30kg of polyethylene with viscosity average molecular weight of 100w and 70kg of paraffin oil are added into a double-screw extruder for melt co-extrusion, the extrusion temperature is 195 ℃, the rotating speed is 100r/min, the lip clearance of an extrusion die head is 2.0mm, and the casting sheet is cooled by a cooling roller to prepare a casting sheet with thickness of 1.7 mm. And synchronously and bidirectionally (transversely and longitudinally) stretching the casting sheet and shaping the casting sheet into a thinner sheet, wherein the stretching multiplying powers are respectively 9.5 times in two directions. Immersing into CH after stretching 2 Cl 2 And (5) extracting to form holes in the extraction tank and drying. After completion of the drying, the film was stretched again in the transverse direction and set to a 10 μm film, wherein the stretching ratio was 1.23.
The performance pairs of the examples and comparative examples are shown in table 1.
Table 1 comparison of the properties of examples and comparative examples
Figure BDA0004076950850000091
Note that: the tensile strength detection method is referred to GB/T1040.3-2006, the needling strength detection method is referred to GB/T6672-2001, and the thermal shrinkage detection method is referred to GB/T135 l9-2016.
As can be seen from Table 1, under the condition that the thickness, the air permeability and the porosity are basically consistent, the tensile strength and the puncture strength of the diaphragm are improved after the modified porcelain powder and the glass powder are added, and meanwhile, the heat shrinkage performance of the diaphragm is obviously improved due to the addition of inorganic materials.
The TGA curves of the examples and comparative examples are shown in fig. 3, in which the uncramified polyethylene separator starts to decompose at about 400 c, reaches a maximum decomposition rate at about 445 c, and substantially completely decomposes at 480 c. After the modified porcelain powder is added, a small amount of decomposition is carried out at 380-420 ℃ in the first embodiment and the second embodiment, and mainly wollastonite and crystal water in bentonite absorb heat and escape, polyethylene at 420 ℃ starts to be thermally decomposed, the maximum decomposition speed is reached at about 465 ℃, the thermal decomposition of the polyethylene is completed at 500 ℃, and the improvement of the decomposition temperature of the polyethylene and the temperature at the maximum decomposition speed show that the addition of the modified porcelain powder can effectively improve the thermal stability of the polyethylene material and the safety performance of a lithium battery diaphragm.
The puncture performance curves of the examples and the comparative examples are shown in fig. 4, the puncture resistance of the polyethylene is obviously improved after the modified porcelain powder is added, and compared with the diaphragms with two different modified porcelain powder ratios, the puncture resistance of the diaphragms is improved along with the improvement of the modified porcelain powder ratio, which shows that the combination property of the modified porcelain powder and the polyethylene is improved, and the puncture resistance of the polyethylene matrix is enhanced by the improvement of the combination property.
The tensile strength curves of the examples and the comparative examples are shown in fig. 5, and the tensile strength and the elongation rate of the polyethylene are improved after the modified porcelain powder is added, which shows that the combination property of the surface groups of the modified porcelain powder and polyethylene molecules is improved, the combination property is improved, the toughness of the polyethylene molecular chain is enhanced, but the tensile strength starts to be reduced after the adding proportion of the ceramic material exceeds a certain proportion. The reason for this may be that the addition of too much modified porcelain powder reduces the uniformity of the system and reduces the overall tensile strength of the separator.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A preparation method of a battery diaphragm is characterized in that wollastonite, bentonite, a silane coupling agent, titanate and absolute ethyl alcohol are uniformly mixed, the pH value is regulated to be acidic, and the mixture is heated to 80-120 ℃ for modification reaction to obtain modified porcelain powder; and mixing the modified porcelain powder with glass powder and polyolefin to obtain mixed powder, and carrying out melt extrusion, stretching, extraction and shaping on the mixed powder and paraffin oil to obtain the modified porcelain powder.
2. The method for producing a battery separator according to claim 1, wherein wollastonite D 50 D of bentonite with particle size of 100-150 mu m 50 The grain diameter is 100-150 mu m;
or, the silane coupling agent is a silane coupling agent KH560;
or, the polyolefin is polyethylene;
preferably, the mass ratio of the wollastonite to the bentonite is 2-6:0.5-1.5, the mass ratio of the silane coupling agent to the titanate is 2-8:2-6, and the total mass ratio of the wollastonite to the bentonite and the total mass ratio of the silane coupling agent to the titanate are 5-10:0.5-1;
preferably, the mass ratio of the modified porcelain powder to the glass powder to the polyolefin is 8-15:2-7:78-90.
3. The method for preparing a battery separator according to claim 1, wherein wollastonite, bentonite, a silane coupling agent, titanate and absolute ethyl alcohol are uniformly mixed and then the pH is adjusted to 4-5.
4. The method for preparing a battery separator according to claim 1, wherein the mass ratio of wollastonite to bentonite to absolute ethanol is 5-10:1-3.
5. The method for preparing the battery diaphragm according to claim 1, wherein the mass ratio of the mixed powder to the paraffin oil is 20-40:60-80.
6. The method for producing a battery separator according to claim 1, wherein during melt extrusion, the extruder temperature is in the range of 180 to 220 ℃, the rotation speed is 90 to 150rpm/min, the molten material is cast into a sheet through a die outlet with a gap of 1.5 to 2.5mm, the sheet is drawn through a cooling roll to be cooled into a sheet, the roll speed is 4 to 8m/min, and the roll temperature is 15 to 20 ℃.
7. The method for preparing a battery separator according to claim 1, wherein the stretching is asynchronous biaxial stretching or synchronous biaxial stretching;
or the stretching temperature is 90-130 ℃, and the stretching multiplying power is 6-15 times.
8. The method for preparing a battery separator according to claim 1, wherein the separator is stretched and shaped again after extraction.
9. A battery separator, characterized by being obtained by the production method according to any one of claims 1 to 8.
10. Use of the battery separator of claim 9 in a lithium ion battery.
CN202310111130.1A 2023-02-01 2023-02-01 Battery diaphragm and preparation method and application thereof Pending CN116073072A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117578028A (en) * 2024-01-16 2024-02-20 深圳索理德新材料科技有限公司 Ceramic coating material, ceramic coating diaphragm and preparation method of ceramic coating diaphragm

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117578028A (en) * 2024-01-16 2024-02-20 深圳索理德新材料科技有限公司 Ceramic coating material, ceramic coating diaphragm and preparation method of ceramic coating diaphragm

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