CN106898720B - Lithium ion battery diaphragm and preparation method thereof - Google Patents
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- CN106898720B CN106898720B CN201710229730.2A CN201710229730A CN106898720B CN 106898720 B CN106898720 B CN 106898720B CN 201710229730 A CN201710229730 A CN 201710229730A CN 106898720 B CN106898720 B CN 106898720B
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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
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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
- H01M10/42—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
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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
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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
- H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
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- H—ELECTRICITY
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- 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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Abstract
The invention relates to a lithium ion battery diaphragm, which comprises a polyolefin microporous membrane and a functional coating, wherein at least one surface of the functional coating is coated on the polyolefin microporous membrane, and the functional coating is composed of aromatic polyamide, gel polymer and metal hydroxide and has the performances of high temperature resistance, combustion resistance, easy adhesion with a battery pole piece and the like; the fusing temperature of the lithium ion battery diaphragm is more than or equal to 210 ℃, the limiting oxygen index is more than or equal to 23%, and the lithium ion battery diaphragm has good bonding property with a battery pole piece in the hot-pressing process of the battery. The preparation method is simple, the operation is simple and convenient, and the use stability of the whole battery can be obviously improved.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a lithium ion battery diaphragm and a preparation method thereof.
Background
The separator, which is one of the four major materials of a lithium ion battery, is a key internal layer component in the lithium ion battery, although not involved in the electrochemical reaction in the battery. The diaphragm has the main functions of isolating the positive electrode and the negative electrode and preventing electrons from passing through, and simultaneously allowing ions to pass through, so that the lithium ions are rapidly transmitted between the positive electrode and the negative electrode in the charging and discharging process. The performance of the diaphragm determines the interface structure, internal resistance and the like of the battery, directly influences the capacity, circulation, safety performance and other characteristics of the battery, and the diaphragm with excellent performance plays an important role in improving the comprehensive performance of the battery.
The polyolefin microporous membrane has the characteristics of excellent mechanical and chemical stability and low price, so that the polyolefin microporous membrane is widely applied in the initial development stage of the lithium ion battery and becomes the mainstream direction of the lithium ion battery diaphragm. However, the material property limits the further improvement of the comprehensive performance of the lithium ion battery, and the safety of the battery is influenced. The performance of the diaphragm cannot be comprehensively improved by using a simple organic material or a ceramic inorganic particle modified diaphragm, and the organic-inorganic composite modified diaphragm serving as a novel functional material can just meet the harsh use requirement of a lithium ion battery.
Chinese patent 201410445356.6 discloses a four-layer composite diaphragm with high thermal safety and strong electrolyte retention capability, which is obtained by compounding PP and PE and then sequentially coating aqueous ceramic slurry and aqueous PVDF slurry on the surface of a composite substrate. In the chinese patent 201310497095.8, an oxide coating, an aramid resin coating and a PVDF-HEP copolymer layer are sequentially coated outside a PP or PE separator to improve the mechanical properties and heat resistance of the separator. Although the method of coating the heat-resistant resin and the ceramic slurry on the polyolefin microporous membrane can improve the safety performance of the separator, it is still very different from the viewpoint of flame retardancy. Meanwhile, the method of coating for many times is adopted, so that the manufacturing process is relatively complex, the cost is high, and the batch stability is poor.
Disclosure of Invention
In view of the above, the invention provides a lithium ion battery separator modified by aromatic polyamide, gel polymer and metal hydroxide together, which is used for solving the problems of poor heat resistance, poor flame retardance and poor adhesion with a battery pole piece in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme:
a lithium ion battery diaphragm comprises a polyolefin microporous membrane and a functional coating coated on at least one surface of the polyolefin microporous membrane, wherein the functional coating is a microporous structure formed by aromatic polyamide, gel polymer and metal hydroxide, the fusing temperature of the lithium ion battery diaphragm is more than or equal to 210 ℃, and the limiting oxygen index is more than or equal to 23%.
In the lithium ion battery diaphragm, the thickness of the functional coating is 1-5 μm.
In the lithium ion battery diaphragm, the aromatic polyamide is m-aramid or p-aramid with the number average molecular weight of 5-30 ten thousand.
The gel polymer of the lithium ion battery diaphragm is one or more of polytetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene copolymer and fluorine-containing polymer with the number average molecular weight of 10-30 ten thousand.
In the lithium ion battery diaphragm, the metal hydroxide is aluminum hydroxide or magnesium hydroxide with the particle size of 0.5-1.2 mu m.
In the lithium ion battery diaphragm, the polyolefin microporous membrane is one of a polyethylene membrane, a polypropylene membrane and a polyethylene-polypropylene composite membrane; the thickness of the polyolefin microporous membrane is 5-25 mu m.
The preparation method of the lithium ion battery diaphragm comprises the following steps:
a: preparing a coating liquid: respectively dissolving aromatic polyamide and gel polymer with a certain mass ratio in a solvent, then mixing the aromatic polyamide and the gel polymer, adding metal hydroxide after uniformly mixing, and obtaining a coating liquid with the solid content of 10-25% after high-speed shearing and stirring; the mass ratio of the aromatic polyamide to the gel polymer is as follows: 90:10-10: 90; the mass ratio of the organic matter consisting of the aromatic polyamide and the gel polymer to the metal hydroxide is 20: 80-5: 95; the solvent is any one of N, N-dimethylformamide, N-dimethylacetamide and N-methylpyrrolidone;
b: coating: coating the coating liquid prepared in the step 1 on one or two surfaces of the polyolefin microporous membrane by taking the polyolefin microporous membrane as a coating base material to obtain a film A containing a coating;
c: immersing the film A into a coagulating bath for 5-35 s to obtain a film B, wherein the coagulating bath is a mixed solvent consisting of water and an organic solvent, and the organic solvent is one or more of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, ethylene glycol, dimethyl sulfoxide and absolute ethyl alcohol;
d: and (3) immersing the film B in water, standing for 5-35 s, removing the organic solvent on the surface of the film, and drying at 30-80 ℃ to obtain the lithium ion battery diaphragm.
In a preferable scheme, the content of the organic solvent in the coagulating bath in the step c accounts for 20-40% of the total mass, wherein the content of any one organic solvent does not exceed 30% of the total mass of the coagulating bath.
Compared with the prior art, the invention has the following advantages:
(1) the functional coating of the lithium ion battery diaphragm is added with metal hydroxide, the metal hydroxide is subjected to dehydration reaction at 200-400 ℃, combined water is released while oxides are generated, a large amount of latent heat is absorbed, the surface temperature of combustible materials is reduced, and the flame retardant function of the lithium ion battery diaphragm is improved.
(2) The functional coating of the lithium ion battery diaphragm is composed of aromatic polyamide, metal hydroxide and gel polymer, and when the functional coating is applied to a battery, the aromatic polyamide cannot melt when the temperature reaches 350-450 ℃; the metal hydroxide is subjected to dehydration reaction at 200-400 ℃, and releases combined water while generating oxides, so that a large amount of latent heat is absorbed, and the surface temperature of combustible materials is reduced; the gel polymer can enable the diaphragm to be tightly attached to the electrode, so that the thermal stability of the diaphragm is improved; the obtained lithium ion battery diaphragm has the advantages of battery deformation prevention, high flame retardance, good adhesion with a battery pole piece and improvement on the overall safety of the battery.
(3) According to the invention, by controlling the solid content, organic matter content and inorganic particle content of the functional coating, the obtained lithium ion battery diaphragm has the performances of high temperature resistance, combustion resistance, easy adhesion with a battery pole piece and the like, the fusing temperature of the lithium ion battery diaphragm is not less than 210 ℃, the limiting oxygen index is not less than 23%, and the lithium ion battery diaphragm has good adhesion with the battery pole piece in the hot pressing process of the battery.
(4) The lithium ion battery diaphragm containing the functional coating can be obtained by a one-time coating, pore-forming and shaping technology, and compared with a multiple coating technology, the preparation method is simple, the operation is simple and convenient, and the batch stability is good.
(5) In the preparation method of the multi-functional layer, the technical problems that the metal hydroxide is directly added and dispersed in the oil phase and hydrolysis reaction does not occur are solved by controlling the adding sequence and the content ratio of the raw materials, and the technical effects that the prepared slurry can be dispersed and a finished product can be obtained by one-time coating are realized.
Drawings
Fig. 1 is an SEM photograph of a functional coating modified lithium ion battery separator in example 1 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited thereto.
The lithium ion battery diaphragm of the invention is composed of polyolefin microporous membrane base material and functional coating coated on one side or two sides of the polyolefin microporous membrane base material.
Polyolefin microporous membrane base material
The polyolefin microporous membrane used in the invention is one of a polyethylene membrane, a polypropylene membrane and a polyethylene-polypropylene composite membrane; the thickness of the polyolefin microporous membrane is 5-25 μm, preferably 7-20 μm, and more preferably 9-12 μm.
Second, functional coating
The aromatic polyamide used in the invention is meta-aramid or para-aramid; the number average molecular weight is 5 to 30 ten thousand, preferably 15 to 25 ten thousand. The aromatic amine is high-temperature resistant, the aromatic polyamide is used on the diaphragm, and the polyamide cannot melt when the temperature reaches 350-450 ℃, so that short circuit between the anode and the cathode of the battery is avoided.
The gel polymer used in the invention is one or any combination of polytetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene copolymer and fluorine-containing polymer; the number average molecular weight of the gel polymer is 10 to 30 ten thousand, preferably 15 to 20 ten thousand. The gel polymer is beneficial to the infiltration of electrolyte, can be rapidly fused in the lithium ion battery, enables the diaphragm and the pole piece to be tightly attached, enhances the hardness of the battery, and prevents the deformation of the battery.
The metal hydroxide used in the invention is one of aluminum hydroxide or magnesium hydroxide, preferably magnesium hydroxide; the particle size is 0.5 to 1.2 μm, preferably 0.7 to 1 μm. The metal hydroxide is subjected to dehydration reaction at 200-400 ℃, the reaction is endothermic, combined water is released while oxides are generated, a large amount of latent heat is absorbed, the surface temperature of combustible materials is reduced, and the lithium ion battery diaphragm has a flame retardant function.
The functional coating of the lithium ion battery diaphragm is combined by aromatic polyamide, metal hydroxide and gel polymer, the high temperature resistance of the aromatic polyamide is fully exerted by optimizing the molecular weight and matching the contents of the aromatic polyamide and the metal hydroxide with the gel polymer, the high temperature resistance of the aromatic polyamide is not melted when the temperature reaches 350-450 ℃, and the thermal stability of the diaphragm can be improved; the metal hydroxide is subjected to dehydration reaction at 200-400 ℃, the reaction is endothermic, combined water is released while oxides are generated, a large amount of latent heat is absorbed, the surface temperature of combustible materials is reduced, and the lithium ion battery diaphragm has a flame retardant function; the gel polymer can enable the diaphragm to be tightly attached to the electrode, so that the battery is prevented from deforming, and therefore the safety of the whole battery can be remarkably improved and the attachment of the diaphragm and a battery pole piece can be improved by the combined use of the aromatic polyamide, the gel polymer and the metal hydroxide. The fusing temperature of the lithium ion battery diaphragm obtained by the invention is more than or equal to 210 ℃, the limiting oxygen index is more than or equal to 23%, and the lithium ion battery diaphragm has good bonding property with a battery pole piece in the hot-pressing process of the battery.
Preparation method of functional coating modified lithium ion battery diaphragm
The invention adopts a wet coating method to prepare the functional coating modified lithium ion battery diaphragm, and the wet coating method is a known method for preparing a microporous membrane or a microporous coating.
(1) Respectively dissolving aromatic polyamide and gel polymer with a certain mass ratio in a solvent, then mixing the aromatic polyamide and the gel polymer, adding metal hydroxide after uniformly mixing, and obtaining the coating liquid after high-speed shearing and stirring. Wherein the solid content of the coating liquid is 10-25%.
(2) And (2) coating the coating liquid prepared in the step (1) on the surface of the polyolefin microporous membrane by taking the polyolefin microporous membrane as a coating substrate to obtain the film A containing the multifunctional coating.
The method for applying the coating liquid to the surface of the polyolefin microporous membrane is not particularly limited as long as the coating liquid can achieve a desired coating thickness and coating uniformity. The optional method comprises the following steps: gravure coating method, microgravure coating method, reverse roll coating method, transfer roll coating method, dip coating method, bar coating method, extrusion coating method, screen printing, spray coating method, and the like.
The coating liquid may be applied to one side or both sides of the polyolefin microporous membrane, preferably to both sides of the polyolefin microporous membrane.
(3) Immersing the film A into a coagulating bath for 5s to 35s to obtain a film B. Wherein the coagulating bath is a mixed solvent composed of water and one or more selected from N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, ethylene glycol, dimethyl sulfoxide and anhydrous ethanol.
And (3) immersing the film B in water, standing for 5-35 s, removing the organic solvent on the surface of the film, and drying at 30-80 ℃ to obtain the lithium ion battery diaphragm containing the functional coating.
Wherein the mass ratio of the aromatic polyamide to the gel polymer in the step (1) is 90:10-10: 90; the mass ratio of the inorganic particles (metal hydroxide) to the organic matters (aromatic polyamide and gel polymer) is as follows: 5: 95-80: 20.
Wherein the solvent in the step (1) is any one of N, N-dimethylformamide, N-dimethylacetamide and N-methylpyrrolidone.
Wherein the thickness of the lithium ion battery diaphragm functional coating in the step (3) is 1-5 μm. This thickness refers to the total thickness of the coating, and if double-sided, refers to the total thickness of the double-sided dry coating being within this range. The excessive thickness of a plurality of coatings easily causes the excessive increase rate of the ventilation value and the waste of chemical engineering cost.
The functional coating dry film is composed of aromatic polyamide, gel polymer and metal hydroxide, and the lithium ion battery diaphragm containing the functional coating can be obtained by a one-time coating pore-forming shaping technology. The coated dry film has a low build-up of gas permeability values and uniformly distributed pore sizes.
The coating liquid has a solid content of 10-25%, is suitable for coating, and forms a dry coating with a thickness of 1-5 μm. The dry coating thickness of the invention is 1-5 μm.
In combination with the above, the present invention provides the following preferred embodiments, the main technical parameters of which are listed in table 1 and detailed as follows:
example 1
(1) 90 g of m-aramid with the molecular weight of 20 ten thousand and 10 g of PVDF with the molecular weight of 15 ten thousand are respectively dissolved in 473.67 g of DMAc, then the m-aramid and the PVDF are mixed uniformly, 5.26 g of magnesium hydroxide is added, and the coating liquid is obtained after high-speed shearing and stirring. At this time, the solid content of the coating liquid is 10%, and the mass ratio of the inorganic particles to the organic matter is 5: 95.
(2) The coating liquid was coated on the surface of a PE base film having a thickness of 9 μm by a micro gravure coating method to obtain a double-coated film A.
(3) Immersing film a in water: EG: and (4) performing 10s in a coagulating bath with the DMAc being 80:15:5 to obtain a film B containing the microporous structure coating.
(4) And (3) immersing the film B in water, standing for 15s, removing the organic solvent on the surface of the film, and drying at 70 ℃ to obtain the lithium ion battery diaphragm containing the functional coating.
The SEM photographs of the coating layer of the separator are shown in fig. 1, and the specification and performance test data of the separator are shown in table 1.
Example 2
(1) 40 g of meta-aramid with the molecular weight of 30 ten thousand and 60 g of PVDF with the molecular weight of 15 ten thousand are respectively dissolved in 583.33 g of DMF, then the meta-aramid with the molecular weight of 30 ten thousand and the PVDF are mixed uniformly, 400 g of magnesium hydroxide is added, and the coating liquid is obtained after high-speed shearing and stirring. At this time, the solid content of the coating liquid is 30%, and the mass ratio of the inorganic particles to the organic matter is 80: 20.
(2) The coating liquid was coated on the surface of a PE base film having a thickness of 9 μm by a micro gravure coating method to obtain a double-coated film A.
(3) Immersing film a in water: EG: and (4) performing 10s in a coagulating bath with the DMAc being 60:25:15 to obtain a film B containing the microporous structure coating.
(4) And (3) immersing the film B in water, standing for 15s, removing the organic solvent on the surface of the film, and drying at 70 ℃ to obtain the lithium ion battery diaphragm containing the functional coating.
Example 3
(1) Respectively dissolving 10 g of para-aramid with the molecular weight of 15 ten thousand and 90 g of PVDF with the molecular weight of 10 ten thousand in 300 g of DMAc, then mixing the para-aramid with the DMAc and the PVDF, adding 100 g of aluminum hydroxide after uniformly mixing, and obtaining the coating liquid after high-speed shearing and stirring. At this time, the solid content of the coating liquid was 25%, and the mass ratio of the inorganic particles to the organic matter was 50: 50.
(2) The coating liquid was coated on the surface of a PE base film having a thickness of 5 μm by a micro gravure coating method to obtain a single-side coated film A.
(3) Immersing film a in water: EG was 70:30 in a coagulation bath for 15 seconds, and a film B containing a coating layer having a microporous structure was obtained.
(4) And (3) immersing the film B in water, standing for 20s, removing the organic solvent on the surface of the film, and drying at 75 ℃ to obtain the lithium ion battery diaphragm containing the functional coating.
Example 4
(1) Respectively dissolving 50 g of meta-aramid fiber with the molecular weight of 5 ten thousand and 50 g of PVDF with the molecular weight of 20 ten thousand in 214.29 g of DMF, then mixing the two, adding 42.86 g of magnesium hydroxide after uniformly mixing, and obtaining the coating liquid after high-speed shearing and stirring. At this time, the solid content of the coating liquid was 25%, and the mass ratio of the inorganic particles to the organic matter was 30: 70.
(2) The coating liquid was coated on the surface of a PE base film having a thickness of 12 μm by a micro gravure coating method to obtain a single-side coated film A.
(3) Immersing film a in water: EG: EtOH 65:20:15 in a coagulation bath for 15s, resulting in film B containing a coating with a microporous structure.
(4) And (3) immersing the film B in water, standing for 15s, removing the organic solvent on the surface of the film, and drying at 70 ℃ to obtain the lithium ion battery diaphragm containing the functional coating.
Example 5
(1) Respectively dissolving 75 g of meta-aramid with the molecular weight of 25 ten thousand and 25 g of PVDF with the molecular weight of 25 ten thousand in 250 g of DMAc, then mixing the meta-aramid with the DMAc and the PVDF, adding 25 g of magnesium hydroxide after uniformly mixing, and obtaining the coating liquid after high-speed shearing and stirring. At this time, the solid content of the coating liquid is 20%, and the mass ratio of the inorganic particles to the organic matter is 20: 80.
(2) And coating the coating liquid on the surface of a PP (polypropylene) base film with the thickness of 20 mu m by adopting a micro-gravure coating method to obtain a double-sided coating film A.
(3) Immersing film a in water: and the EtOH is 75:25 for 10s in a coagulating bath, and a film B containing the coating with the microporous structure is obtained.
(4) And (3) immersing the film B in water, standing for 10s, removing the organic solvent on the surface of the film, and drying at 60 ℃ to obtain the lithium ion battery diaphragm containing the functional coating.
Example 6
(1) Respectively dissolving 80 g of meta-aramid fiber with the molecular weight of 10 ten thousand and 20 g of PVDF with the molecular weight of 17 ten thousand in 566.66 g of NMP, then mixing the meta-aramid fiber with the NMP and the NMP, adding 100 g of aluminum hydroxide after uniformly mixing, and obtaining the coating liquid after high-speed shearing and stirring. At this time, the solid content of the coating liquid was 15%, and the mass ratio of the inorganic particles to the organic matter was 50: 50.
(2) And (3) coating the coating liquid on the surface of a PP/PE/PP composite three-layer film with the thickness of 25 mu m by adopting a micro-gravure coating method to obtain a double-sided coating film A.
(3) Immersing film a in water: NMP: and the EtOH is 80:15:5 for 15s in a coagulating bath to obtain a film B containing the coating with the microporous structure.
(4) And (3) immersing the film B in water, standing for 15s, removing the organic solvent on the surface of the film, and drying at 70 ℃ to obtain the lithium ion battery diaphragm containing the functional coating.
Comparative example 1
(1) 100 g of PVDF having a molecular weight of 15 ten thousand is dissolved in 1800 g of DMAc, and then 100 g of magnesium hydroxide is added, followed by high-speed shearing and stirring to obtain a coating liquid. At this time, the solid content of the coating liquid was 10%, and the mass ratio of the inorganic particles to the organic matter was 50: 50.
(2) The coating liquid was coated on the surface of a PE base film having a thickness of 9 μm by a micro gravure coating method to obtain a single-side coated film A.
(3) Immersing film a in water: EG: and the EtOH is 60:15:25 for 20s in a coagulating bath, so as to obtain a film B containing the coating with the microporous structure.
(4) And (3) immersing the film B in water, standing for 15s, removing the organic solvent on the surface of the film, and drying at 65 ℃ to obtain the lithium ion battery diaphragm containing the functional coating.
Comparative example 2
(1) 100 g of m-aramid having a molecular weight of 20 ten thousand was dissolved in 900 g of DMAc to obtain a coating liquid, and the solid content of the coating liquid at this time was 10%.
(2) The coating liquid was coated on the surface of a PE base film having a thickness of 9 μm by a micro gravure coating method to obtain a single-side coated film A.
(3) Immersing film a in water: EG: and (4) performing 10s in a coagulating bath with the DMAc being 70:15:15 to obtain a film B containing the microporous structure coating.
(4) And (3) immersing the film B in water, standing for 15s, removing the organic solvent on the surface of the film, and drying at 70 ℃ to obtain the lithium ion battery diaphragm containing the functional coating.
The above description is only for the best mode of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Those skilled in the art will appreciate that the invention may be practiced without these specific details.
TABLE 1
Note: the coating thickness 2+2 was double coated with a thickness of 2 microns on each side.
As can be seen from the table above, the limit oxygen index of the obtained diaphragm is up to more than 23% by adopting the technical scheme of the invention, which shows that the flame retardant property effect is obvious.
The test methods for the properties in the table are as follows:
1. thickness: testing according to GB/T6672-2001 method
2. Fusing temperature: tested according to GB/T19466-2004 method
3. Limiting oxygen index: according to JIS-K7201-3: 2008, testing the method.
Claims (6)
1. A method for preparing a lithium ion battery diaphragm comprises a polyolefin microporous membrane and a functional coating coated on at least one surface of the polyolefin microporous membrane, and is characterized in that the functional coating is a microporous structure composed of aromatic polyamide, gel polymer and metal hydroxide, the fusing temperature of the lithium ion battery diaphragm is more than or equal to 210 ℃, and the limiting oxygen index is more than or equal to 23%; the metal hydroxide is aluminum hydroxide or magnesium hydroxide with the particle size of 0.5-1.2 mu m;
the preparation method comprises the following steps:
a: preparing a coating liquid: respectively dissolving aromatic polyamide and gel polymer in a solvent according to a mass ratio, then mixing the aromatic polyamide and the gel polymer, adding metal hydroxide after uniformly mixing, and obtaining a coating liquid with a solid content of 10-25% after high-speed shearing and stirring; the mass ratio of the aromatic polyamide to the gel polymer is as follows: 90:10-10: 90; the mass ratio of the organic matter consisting of the aromatic polyamide and the gel polymer to the metal hydroxide is 95: 5-20: 80; the solvent is any one of N, N-dimethylformamide, N-dimethylacetamide and N-methylpyrrolidone;
b: coating: coating the coating liquid prepared in the step a on one or two surfaces of the polyolefin microporous membrane by taking the polyolefin microporous membrane as a coating base material to obtain a film A containing a coating;
c: immersing the film A into a coagulating bath for 5s-35s to obtain a film B, wherein the coagulating bath is a mixed solvent consisting of water and an organic solvent, and the organic solvent is one or more of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, ethylene glycol, dimethyl sulfoxide or absolute ethyl alcohol;
d: and (3) immersing the film B in water, standing for 5-35 s, removing the organic solvent on the surface of the film, and drying at 30-80 ℃ to obtain the lithium ion battery diaphragm.
2. The method for preparing a lithium ion battery separator according to claim 1, wherein the functional coating has a thickness of 1 to 5 μm.
3. The method for preparing the lithium ion battery separator according to claim 2, wherein the aromatic polyamide is m-aramid or p-aramid having a number average molecular weight of 5 to 30 ten thousand.
4. The method for preparing the lithium ion battery separator according to claim 3, wherein the gel polymer is one or more of polytetrafluoroethylene, polyvinylidene fluoride or polyvinylidene fluoride-hexafluoropropylene copolymer with the number average molecular weight of 10-30 ten thousand.
5. The method for preparing the lithium ion battery separator according to claim 4, wherein the polyolefin microporous membrane is one of a polyethylene membrane, a polypropylene membrane and a polyethylene-polypropylene composite membrane; the thickness of the polyolefin microporous membrane is 5-25 mu m.
6. The method for preparing the lithium ion battery separator according to claim 5, wherein the content of the organic solvent in the coagulation bath in the step c accounts for 20-40% of the total mass of the coagulation bath, and the content of any one organic solvent does not exceed 30% of the total mass of the coagulation bath.
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| CN107293813B (en) * | 2017-07-12 | 2023-05-26 | 成都启特安全技术有限责任公司 | Battery self-destruction system |
| CN107452921B (en) * | 2017-07-20 | 2019-06-18 | 清华大学 | A kind of preparation method of p-aramid fiber nanofiber composite lithium ion cell diaphragm |
| CN111370625A (en) * | 2020-03-22 | 2020-07-03 | 华南理工大学 | Aramid fiber phase-transition coating lithium ion battery diaphragm and preparation method thereof |
| CN112194978A (en) * | 2020-08-25 | 2021-01-08 | 河北金力新能源科技股份有限公司 | High-heat-resistant coating slurry, high-temperature-resistant diaphragm for lithium battery and preparation method of high-temperature-resistant diaphragm |
| CN112290165A (en) * | 2020-11-05 | 2021-01-29 | 青岛蓝科途膜材料有限公司 | Lithium ion battery diaphragm, preparation method and lithium ion battery |
| CN118448814B (en) * | 2024-05-31 | 2024-10-29 | 沧州明珠隔膜科技有限公司 | Ceramic diaphragm with stable safety and preparation method thereof |
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| CN104377330A (en) * | 2014-11-09 | 2015-02-25 | 中国乐凯集团有限公司 | Gel polymer modified lithium ion battery diagraph and preparing method and application thereof |
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