Composite isolating membrane and preparation method thereof

Abstract

The invention relates to a composite isolating membrane and a preparation method thereof. The composite isolating membrane comprises a polyolefin porous base material and an inorganic coating, and the inorganic coating coats at least one surface of the polyolefin porous base material and comprises a plurality of inorganic particles and an adhesive resin composition. Wherein the adhesive resin composition comprises an acrylonitrile-acrylamide-acrylate copolymer with a glass transition temperature less than 0 DEG C and an amide group-containing polymer with a glass transition temperature between 150 DEG C and 200 DEG C. The composite isolating membrane disclosed by the invention has good high-temperature tolerance.

Description

Technical Field

[0001] The present invention relates to a composite separator, particularly a composite separator with high temperature stability. Background Art

[0002] With the vigorous development of consumer electronics, wearable devices, electric vehicles, industrial energy storage fields, etc., the demand for the safety and energy density of lithium-ion batteries is increasing day by day. As an important insulating porous material in the battery, the separator also has the need to further improve its physical properties. In order to further ensure the safety of lithium-ion batteries, it is necessary for the separator for lithium-ion batteries to improve its high temperature tolerance and reduce the thermal shrinkage rate at high temperatures to prevent the electrodes from contacting each other during abnormal applications and causing thermal runaway.

[0003] The separator of a lithium-ion battery uses a polyolefin material as the base material, that is, polyethylene (PE) / or polypropylene (PP). It can be mainly divided into two types: dry stretching and wet stretching. Basically, both methods melt the polymer through an extrusion process to form a film, and then manufacture suitable pores by stretching. The dry separator is usually thicker and can be produced by multi-layer stacking. It has high safety and low cost under high power. While the wet separator, due to its thin thickness, high porosity, and high pore size uniformity, is suitable for coating a ceramic coating on the surface of a polyolefin base material to form a composite separator to reduce its thermal shrinkage rate to provide safety. However, when using a resin binder to bond ceramic particles, the resin binder is prone to a decrease in strength at high temperatures, and even structural damage and thermal decomposition may occur, resulting in a significant decrease in the anti-shrinkage property of the composite separator. It is known that the anti-thermal shrinkage of the composite separator can be enhanced by increasing the thickness of the ceramic coating. However, under the trend of the thinning of the separator, the thin ceramic coating cannot resist the large shrinkage of the porous base film at high temperatures, resulting in overall shrinkage and unable to meet the anti-thermal shrinkage property at high temperatures. For example, it fails to meet the requirement of <5% at 150°C. Therefore, the thin ceramic coating is prone to cause safety concerns in use due to the decrease in heat resistance. Summary of the Invention

[0004] The present invention discloses a composite separator, particularly a composite separator with high temperature stability.

[0005] The composite separator of the present invention comprises a polyolefin porous base material and an inorganic coating coated on at least one surface of the polyolefin porous base material, wherein the inorganic coating comprises inorganic particles and a binder resin composition, the binder resin composition is 2 parts by weight to 10 parts by weight relative to every 100 parts by weight of inorganic particles, and the binder resin composition comprises an acrylonitrile-acrylamide-acrylate copolymer with a glass transition temperature (Tg) less than 0°C and an amide group-containing polymer with a glass transition temperature between 150°C and 200°C.

[0006] In the inorganic coating of the composite separator membrane of the present invention, the binder resin composition comprises 40 wt% to 85 wt% of an acrylonitrile-acrylamide-acrylate copolymer having a glass transition temperature of less than 0 °C and 15 wt% to 60 wt% of an amide group-containing polymer having a glass transition temperature between 150 °C and 200 °C.

[0007] In the composite separator membrane disclosed in the present invention, the glass transition temperature of the acrylonitrile-acrylamide-acrylate copolymer is between -40 °C and 0 °C.

[0008] In one embodiment of the composite separator membrane of the present invention, the inorganic particles used in the inorganic coating are Mg(OH) 2 , BaSO 4 , BaTiO 3 , HfO 2 , SrTiO 3 , SnO 2 , CeO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , SiO 2 , Y 2 O 3 , Al(OH) 3 , Al 2 O 3 , boehmite (AlOOH), SiC, TiO 2 or a combination thereof.

[0009] In one embodiment of the composite separator membrane of the present invention, the average particle size (D50) of the inorganic particles of the inorganic coating is between 0.1 μm and 2.0 μm.

[0010] In one embodiment of the composite separator membrane of the present invention, the inorganic coating may employ two or more inorganic particles having the same or different particle sizes.

[0011] In one embodiment of the composite separator membrane of the present invention, the thickness of the inorganic coating is between 0.1 μm and 5.0 μm.

[0012] The thermal shrinkage rate of the composite separator membrane of the present invention after heating at 150 °C for 1 hour is not more than 2% in both the longitudinal direction (MD) and the transverse direction (TD).

[0013] The peel strength between the inorganic coating of the composite separator membrane of the present invention and the polyolefin porous substrate is greater than 30 gf / cm.

[0014] In another embodiment of the present invention, a method for preparing a composite separator membrane is disclosed, which includes providing a polyolefin porous substrate, coating a slurry on one or two surfaces of the polyolefin porous substrate, wherein the slurry contains a plurality of inorganic particles, a binder resin composition, and drying the slurry to form an inorganic coating, wherein the binder resin composition contains an acrylonitrile-acrylamide-acrylate copolymer with a glass transition temperature less than 0 °C and an amide group-containing polymer with a glass transition temperature between 150 °C and 200 °C.

[0015] In the composite separator membrane of another embodiment of the present invention, it includes a polyolefin porous substrate and an inorganic coating coated on at least one surface of the porous substrate, wherein the inorganic coating contains inorganic particles, a binder resin composition, and a photoinitiator. The binder resin composition is 2 to 10 parts by weight relative to every 100 parts by weight of inorganic particles, and the photoinitiator is 0.1 to 1.5 parts by weight relative to every 100 parts by weight of inorganic particles. Wherein the binder resin composition contains an acrylonitrile-acrylamide-acrylate copolymer with a glass transition temperature (Tg) less than 0 °C and an amide group-containing polymer with a glass transition temperature between 150 °C and 200 °C.

[0016] The photoinitiator used in the inorganic coating of the composite separator membrane of the present invention is 2-isopropylthioxanthone, thioxanthone, thioxanthone derivatives, or a combination thereof.

[0017] The present invention discloses a method for preparing a composite separator membrane of another embodiment, and its steps include: providing a polyolefin porous substrate; coating a slurry on one or two surfaces of the polyolefin porous substrate, and the slurry contains a plurality of inorganic particles, a binder resin composition, water, and a photoinitiator solution; and drying the slurry and irradiating it with ultraviolet light to form an inorganic coating; wherein the binder resin composition contains an acrylonitrile-acrylamide-acrylate copolymer with a glass transition temperature less than 0 °C and an amide group-containing polymer with a glass transition temperature between 150 °C and 200 °C.

[0018] In the method for preparing the composite separator membrane disclosed in the present invention, the photoinitiator solution further contains a photoinitiator and a solvent, and the usage amount of the photoinitiator is 0.1 to 1.5 parts by weight relative to every 100 parts by weight of inorganic particles.

[0019] In the method for preparing the composite separator membrane disclosed in the present invention, the photoinitiator is 2-isopropylthioxanthone, thioxanthone, thioxanthone derivatives, or a combination thereof.

[0020] In the method for preparing the composite separator membrane disclosed in the present invention, the solvent is toluene, methanol, methyl methacrylate, ethyl acetate, 1,2-dichloroethane, acetone, water, or a combination thereof.

[0021] The above invention content aims to provide a simplified summary of the present disclosure, so that readers can have a basic understanding of the present disclosure. The invention content here is not a complete overview of the present disclosure, and its intention is not to point out the important / critical elements of the embodiments of the present invention or to define the scope of the present invention. After referring to the following embodiments, those with ordinary knowledge in the technical field to which the present invention pertains should be able to easily understand the basic spirit of the present invention and the technical means and implementation schemes adopted by the present invention. Detailed Embodiments

[0022] In order to make the disclosure of the present invention more detailed and complete, the following provides an illustrative description of the implementation schemes and specific embodiments of the present invention; however, this is not the only form for implementing or applying the specific embodiments of the present invention. The various embodiments disclosed below can be combined or replaced with each other in beneficial cases, or other embodiments can be added to one embodiment without further record or explanation.

[0023] The advantages, features, and technical methods for realizing the present invention will be described in more detail with reference to the exemplary embodiments and will be more easily understood. Moreover, the present invention can be implemented in different forms, so it should not be understood as being limited to the embodiments described herein. On the contrary, for those with ordinary knowledge in the technical field, the provided embodiments will make the present invention more thorough, comprehensive, and completely convey the scope of the present invention, and the present invention will only be limited by the appended claims.

[0024] Unless otherwise defined, all terms (including technical and scientific terms) and proper nouns used hereinafter are substantially the same as those generally understood by those skilled in the technical field to which the present invention pertains. For example, those terms defined in a general dictionary should be understood as having a meaning consistent with the content of the relevant field, and unless clearly defined hereinafter, they will not be understood in an overly idealized or overly formal sense.

[0025] The composite separator of the present invention comprises a polyolefin porous substrate and an inorganic coating coated on at least one surface of the polyolefin porous substrate, wherein the inorganic coating comprises inorganic particles and a binder resin composition, the binder resin composition is 2 parts by weight to 10 parts by weight relative to every 100 parts by weight of the inorganic particles, and the binder resin composition comprises an acrylonitrile-acrylamide-acrylate copolymer with a glass transition temperature (Tg) less than 0°C and an amide group-containing polymer with a glass transition temperature between 150°C and 200°C.

[0026] The composite separator film disclosed in the present invention can resist the shrinkage of the polyolefin porous base film at high temperatures to meet the heat shrinkage resistance at high temperatures. For example, the requirement of not more than 2% can be achieved at 150 °C. Especially when the inorganic coating is thinned, such as when the thickness is less than 5 μm and preferably less than 3 μm, the heat shrinkage rate after heating at 150 °C for 1 hour in the machine direction (MD) and the transverse direction (TD) is not more than 2%. It has only a small amount of heat shrinkage at high temperatures, which can prevent thermal runaway caused by the contact of electrodes during abnormal applications and provide good safety performance at high temperatures.

[0027] In the composite separator film of the present invention, the binder resin composition used in the inorganic coating comprises 40 wt% to 85 wt% of an acrylonitrile-acrylamide-acrylate copolymer having a glass transition temperature of less than 0 °C and 15 wt% to 60 wt% of an amide group-containing polymer having a glass transition temperature between 150 °C and 200 °C.

[0028] In the composite separator film of the present invention, the acrylonitrile-acrylamide-acrylate copolymer having a glass transition temperature of less than 0 °C in the binder resin composition used in the inorganic coating can provide a strong adhesion force between the inorganic particles and the porous substrate to strengthen the adhesion and high-temperature resistance at the interface, and its property of low glass transition temperature can provide a relatively flexible and soft inorganic coating. Furthermore, the binder resin composition contains an amide group-containing polymer having a glass transition temperature between 150 °C and 200 °C, which can form a relatively rigid network structure at high temperatures. Therefore, it can provide the high-temperature resistance of the inorganic coating and is not easily affected by the shrinkage of the porous substrate at high temperatures to strengthen the high-temperature shrinkage resistance. By using components with different glass transition temperatures in the binder resin composition of the present invention, it is avoided that the inorganic coating is too softened or too rigid and brittle at high temperatures, resulting in poor adhesion. The heat shrinkage rate of the composite separator film disclosed in the present invention after heating at 150 °C for 1 hour in the machine direction (MD) and the transverse direction (TD) is not more than 2%. Furthermore, the binder resin composition in the present invention provides good adhesion to the polyolefin porous substrate, so there is sufficient adhesion between the inorganic coating and the porous substrate, and its peel strength is greater than 30 gf / cm.

[0029] In a preferred embodiment of the present invention, the binder resin composition of the inorganic coating preferably comprises 40 wt% to 80 wt% of an acrylonitrile-acrylamide-acrylate copolymer having a glass transition temperature of less than 0 °C and 20 wt% to 60 wt% of an amide group-containing polymer having a glass transition temperature between 150 °C and 200 °C.

[0030] In a preferred embodiment of the present invention, the inorganic coating comprises 2 parts by weight to 8 parts by weight of the binder resin composition relative to every 100 parts by weight of the inorganic particles.

[0031] In the adhesive resin composition of the composite separator film of the present invention, the acrylonitrile-acrylamide-acrylate copolymer with a glass transition temperature less than 0°C is a terpolymer derived from the copolymerization of acrylonitrile monomer, acrylamide monomer and acrylate monomer. In a preferred embodiment, the glass transition temperature of the acrylonitrile-acrylamide-acrylate copolymer is between -40°C and 0°C. The acrylonitrile-acrylamide-acrylate copolymer applicable to the present invention can be a commercially available product, such as BM-950B manufactured by Zeon Corporation of Japan.

[0032] In the adhesive resin composition of the composite separator film of the present invention, the amide group-containing polymer with a glass transition temperature between 150°C and 200°C can be poly(N-vinylacetamide), amide-(meth)acrylic acid copolymer, acrylonitrile-acrylamide-(meth)acrylate copolymer, etc. The amide group-containing polymer with a glass transition temperature between 150°C and 200°C applicable to the present invention can be a commercially available product, such as the PNVA GE191 series (such as GE191-103, GE191-104, GE191-107 or GE191-108) manufactured by Showa Denko K.K. of Japan, SF168L manufactured by Shenzhen Research First New Materials Co., Ltd. of China, GR506 manufactured by Hunan Gaorui Power Materials Co., Ltd., etc.

[0033] In the composite separator film disclosed in the present invention, the inorganic particles used in the inorganic coating can be those widely used in this technical field, that is, inorganic particles having heat resistance, electrical insulation and being stable to electrolytes are sufficient, and there is no particular limitation. Suitable inorganic particles can be Mg(OH) 2 , BaSO 4 , BaTiO 3 , HfO 2 , SrTiO 3 , SnO 2 , CeO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , SiO 2 , Y 2 O 3 , Al(OH) 3 , Al 2 O 3 , boehmite (AlOOH), SiC, TiO 2 or a combination thereof, especially Al 2 O 3 , boehmite (AlOOH), SiO 2 , TiO 2 etc. are preferred.

[0034] In the inorganic coating of the composite separator film of the present invention, it is preferred that the inorganic particles adopt particles with a smaller particle size to increase the contact area with the binder and improve the adhesion between the two. Furthermore, since the size of the gaps formed between the inorganic particles affects the battery characteristics, when the particle size of the inorganic particles is too large, the gaps between the particles become too large, and short circuits caused by lithium dendrites may easily occur. Therefore, the average particle size (D50) of the inorganic particles is preferably between 0.1 μm and 2.0 μm, more preferably between 0.2 μm and 1.0 μm. In a preferred embodiment of the present invention, the inorganic coating may adopt two or more kinds of inorganic particles with the same or different particle sizes.

[0035] The inorganic coating of the composite separator film of the present invention further contains a surfactant to enhance the interfacial affinity between the inorganic coating and the polyolefin porous substrate. The wetting agent applicable to the present invention may adopt a silicone surfactant, and the usage amount of the surfactant is 0.1 parts by weight to 1.5 parts by weight relative to every 100 parts by weight of the inorganic particles, preferably 0.1 parts by weight to 1.0 parts by weight per 100 parts by weight of the inorganic particles.

[0036] The polyolefin porous substrate that can be used for the composite separator film of the present invention can be a single-layer or multi-layer polyolefin porous substrate, such as single-layer polyethylene, single-layer polypropylene, double-layer polyethylene / polypropylene, or triple-layer polypropylene / polyethylene / polypropylene, but not limited thereto. The thickness of the polyolefin porous substrate applicable to the present invention can be between about 5 μm and 30 μm, preferably between 5 μm and 20 μm, and its porosity is between about 40% and 70%, preferably between 43% and 65%.

[0037] The composite separator film of the present invention can coat the inorganic coating on one side or both sides of the polyolefin porous substrate. The thickness of the inorganic coating of the composite separator film of the present invention can be between 0.5 μm and 5 μm, preferably a single-sided or double-sided ceramic coating between 0.5 μm and 3 μm, and preferably double-sided coating.

[0038] Therefore, improving the adhesion of the composite separator film at the interface between the polyolefin porous substrate and the inorganic coating can not only strengthen the heat shrinkage resistance of the separator film, but also avoid concerns about battery safety caused by interface peeling during the charge and discharge process of the inorganic coating. In a preferred embodiment of the composite separator film of the present invention, after the inorganic coating is thinned, for example, when the thickness is less than 5 μm and preferably less than 3 μm, the peeling strength between the inorganic coating and the porous substrate is greater than 30 gf / cm.

[0039] In the inorganic coating of the composite separator film of the present invention, additives such as antistatic agents, flame retardants, antioxidants, or surface modifiers can be further included as needed.

[0040] In another embodiment of the present invention, a method for preparing a composite separator is disclosed, the steps of which include providing a polyolefin porous substrate; coating a slurry on one or two surfaces of the polyolefin porous substrate to form an inorganic coating, wherein the slurry contains a plurality of inorganic particles, a binder resin composition and water, and drying the slurry to form the inorganic coating. The binder resin composition contains an acrylonitrile-acrylamide-acrylate copolymer with a glass transition temperature less than 0 °C and an amide group-containing polymer with a glass transition temperature between 150 °C and 200 °C.

[0041] In the method for preparing the composite separator disclosed in the present invention, the slurry further contains a dispersant, the dispersant is an alkanolamine dispersant, an ammonium acrylate dispersant or a combination thereof, and the amount of the dispersant used is between 0.1 part by weight and 1.5 parts by weight relative to every 100 parts by weight of the inorganic particles.

[0042] In the method for preparing the composite separator of the present invention, the inorganic coating of the polyolefin porous substrate can be coated by methods known in the art without particular limitation, such as roll coating, knife coating, dip coating, roller coating, spin coating, slot coating and other widely used coating methods in the art.

[0043] In the composite separator of another embodiment of the present invention, it includes a polyolefin porous substrate and an inorganic coating coated on at least one surface of the porous substrate, wherein the inorganic coating contains inorganic particles, a binder resin composition and a photoinitiator. The binder resin composition is 2 parts by weight to 10 parts by weight relative to every 100 parts by weight of the inorganic particles, and the photoinitiator is 0.1 part by weight to 1.5 parts by weight relative to every 100 parts by weight of the inorganic particles. The binder resin composition contains an acrylonitrile-acrylamide-acrylate copolymer with a glass transition temperature (Tg) less than 0 °C and an amide group-containing polymer with a glass transition temperature between 150 °C and 200 °C. After the photoinitiator in the inorganic coating is irradiated with ultraviolet light, it can cause a radical reaction and crosslinking of the hydrogen-containing carbon bonds in the binder resin composition of the inorganic coating and on the surface of the polyolefin porous substrate, and further strengthen the high-temperature puncture resistance and high-temperature melting integrity of the composite separator without affecting the adhesion between the inorganic coating and the polyolefin porous substrate.

[0044] The photoinitiator used in the inorganic coating of the composite separator of the present invention is 2-isopropylthioxanthone, thioxanthone, thioxanthone derivatives or a combination thereof.

[0045] Another embodiment of the present invention discloses another method for preparing a composite separator membrane, the steps of which include: providing a polyolefin porous substrate; coating a slurry on one or two surfaces of the polyolefin porous substrate, and the slurry contains a plurality of inorganic particles, a binder resin composition, water, and a photoreaction solution; and drying the slurry and irradiating it with ultraviolet light to form an inorganic coating; wherein the binder resin composition includes an acrylonitrile-acrylamide-acrylate copolymer with a glass transition temperature less than 0 °C, and an amide group-containing polymer with a glass transition temperature between 150 °C and 200 °C.

[0046] In the method for preparing the composite separator membrane disclosed in the present invention, the photoreaction solution further includes a photoreagent and a solvent, and the usage amount of the photoreagent is 0.1 parts by weight to 1.5 parts by weight relative to every 100 parts by weight of inorganic particles.

[0047] In the method for preparing the composite separator membrane disclosed in the present invention, the photoreagent is 2-isopropyl thioxanthone, thioxanthone, a thioxanthone derivative, or a combination thereof.

[0048] In the method for preparing the composite separator membrane disclosed in the present invention, the solvent is toluene, methanol, methyl methacrylate, ethyl acetate, 1,2-dichloroethane, acetone, water, or a combination thereof.

[0049] The following examples are used to further illustrate the present invention, but the content of the present invention is not limited thereto.

[0050] Examples

[0051] The following are the raw materials used in the examples of the present invention:

[0052] SA0-030EN alumina, particle size (D50) 0.52 μm, purchased from China National United Advanced Materials Co., Ltd., Shandong

[0053] AM-BL_03 boehmite, particle size (D50) 0.35 μm, purchased from Shandong Wantai New Material Technology Co., Ltd., China

[0054] BM-950B acrylonitrile-acrylamide-acrylate copolymer emulsion, solid content 39%, glass transition temperature -30 °C, purchased from Zeon Corporation, Japan

[0055] GE191-103 poly(N-vinylacetamide) emulsion, solid content 10%, glass transition temperature 172 °C, purchased from Showa Chemical Industry Co., Ltd., Japan

[0056] SF168L acrylonitrile-acrylamide-acrylate polymer emulsion, solid content 12.5%, glass transition temperature 180 °C, purchased from Shenzhen Yanyi New Materials Co., Ltd., China

[0057] GR-506 amide-containing polyacrylate polymer emulsion, with a solid content of 20%, a glass transition temperature of 192 °C, purchased from Hunan Gaorui Power Materials Co., Ltd., China

[0058] BYK-154 ammonium polyacrylate dispersant, with a solid content of 42%, purchased from BYK Co., Germany

[0059] Angus Voltan 100 isopropanolamine dispersant, purchased from ANGUS Chemical Co., USA

[0060] BYK-ET-3061 polyether-modified silicone surfactant, purchased from BYK Co., Germany

[0061] BYK-ET-3032 styrene-maleic acid dispersant, with a solid content of 40%, purchased from BYK Co., Germany

[0062] DOUBLECURE-ITX 2-isopropylthioxanthone, purchased from Double Bond Chemical Co., Taiwan, China

[0063] Example 1

[0064] 100 g of alumina (SA0-030EN), 4.49 g of acrylonitrile-acrylamide-acrylate emulsion (BM-950B), 22 g of poly(N-vinylacetamide) emulsion (GE191-103), 0.95 g of ammonium polyacrylate dispersant (BYK-154) and 0.5 g of polyether-modified silicone surfactant (BYK-ET-3061) were added to deionized water, mixed and stirred evenly to obtain an inorganic particle slurry.

[0065] The prepared inorganic particle slurry was coated on both sides of a polyethylene porous substrate with a thickness of 9.2 μm (porosity 48%) and dried to form an inorganic coating on the porous substrate, thereby obtaining a composite separator membrane with a thickness of 12.3 μm.

[0066] The prepared composite separator membrane was tested by the testing method described hereinafter. The test results are listed in Table 1.

[0067] Thickness test: In accordance with the GB / T6672-2001 test standard, it was tested using a film thickness gauge (VL-50-B, purchased from Mitutoyo, Japan). A flat probe with a diameter of 3 mm and a pressing probe load of 0.01 N was used for the test.

[0068] Air permeability (Gurley) test: According to the ASTM D-726 specification, the tested separator membrane was cut into a size of 1 square inch, and the air permeability was obtained by measuring the time required for 100 c.c. of air to pass through the separator membrane to be tested using a Gurley air permeability tester.

[0069] Heat shrinkage test: Cut a 10×10 cm sample, and mark the initial lengths M0 and T0 in the longitudinal direction (MD) and transverse direction (TD) at the center of the sample respectively before testing. After marking, clamp the sample between two A4 papers and place it in an oven, heat it at 150 °C for 1 hour. After heating, place the sample in the same environment as the measuring instrument for 30 minutes, and then measure the longitudinal (MD) length M1 and the transverse (TD) length T1 at the center of the sample.

[0070] Longitudinal (MD) heat shrinkage rate = (M0 - M1) / M0 x 100%

[0071] Transverse (TD) heat shrinkage rate = (T0 - T1) / T0 x 100%

[0072] Mechanical strength test: Cut the test isolation films longitudinally (MD) and transversely (TD) into sizes with a width of 10 mm and a length ≥ 150 mm according to the ASTM D882-09 standard. Use a universal tensile machine to stretch at a rate of 500 mm / min, and after obtaining the maximum load value at the moment of specimen fracture, divide it by the cross-sectional area of the isolation film (specimen width × substrate thickness) to calculate the tensile strength of the isolation film longitudinally (MD) and transversely (TD) respectively.

[0073] Peel strength: Cut an 80 μm thick adhesive sheet (model 31B, purchased from Nitto) into a size of 60 mm in length and 20 mm in width, then attach it to the composite isolation film. Use a universal tensile machine to peel the adhesive sheet at a rate of 180° and 50 mm / min, and collect the peel force of the middle 50 mm length. After measuring 5 specimens for each composite isolation film, obtain its average peel strength.

[0074] Impedance measurement: Cut the isolation film into a circle with a diameter of 24 mm, soak it in a standard electrolyte solution (LiPF6 solution with a concentration of 1 M, and the solvent weight ratio is EC / DMC / EMC = 1 / 1 / 1) for 12 hours to make the electrolyte fully penetrate the isolation film, then place the isolation film between two electrodes and measure its impedance at a frequency between 1000 and 200,000.

[0075] Example 2

[0076] 100 g of alumina (SA0-030EN), 8.97 g of acrylonitrile-acrylamide-acrylate emulsion (BM-950B), 13 g of poly(N-vinylacetamide) emulsion (GE191-103), 1.55 g of ammonium polyacrylate dispersant (BYK-154), and 0.5 g of polyether-modified silicone surfactant (BYK-ET-3061) are added to deionized water, mixed and stirred evenly to obtain an inorganic particle slurry.

[0077] The prepared inorganic particle slurry was coated on both sides of a porous substrate with a thickness of 9.2 μm (porosity 48%), and dried to form an inorganic coating on the porous substrate, thereby obtaining a composite separator membrane with a thickness of 12.6 μm.

[0078] The prepared composite separator membrane was tested by the testing method described in Example 1. The test results are listed in Table 1.

[0079] Example 3

[0080] 100 g of alumina (SA0-030EN), 8.97 g of acrylonitrile-acrylamide-acrylate emulsion (BM-950B), 5.0 g of amide-containing polyacrylate polymer emulsion (GR-506), 1.43 g of ammonium polyacrylate dispersant (BYK-154), and 0.5 g of polyether-modified silicone surfactant (BYK-ET-3061) were added to deionized water, mixed, and stirred evenly to obtain an inorganic particle slurry.

[0081] The prepared inorganic particle slurry was coated on both sides of a porous substrate with a thickness of 9.2 μm (porosity 48%), and dried to form an inorganic coating on the porous substrate, thereby obtaining a composite separator membrane with a thickness of 12.4 μm.

[0082] The prepared composite separator membrane was tested by the testing method described in Example 1. The test results are listed in Table 1.

[0083] Example 4

[0084] 100 g of alumina (SA0-030EN), 8.97 g of acrylonitrile-acrylamide-acrylate emulsion (BM-950B), 12 g of amide group-containing polymer emulsion (SF168L), 0.40 g of styrene-maleic acid dispersant (BYK-ET-3032), and 0.5 g of polyether-modified silicone surfactant (BYK-ET-3061) were added to deionized water, mixed, and stirred evenly to obtain an inorganic particle slurry.

[0085] The prepared inorganic particle slurry was coated on both sides of a porous substrate with a thickness of 9.2 μm (porosity 48%), and dried to form an inorganic coating on the porous substrate, thereby obtaining a composite separator membrane with a thickness of 12.2 μm.

[0086] The prepared composite separator membrane was tested by the testing method described in Example 1. The test results are listed in Table 1.

[0087] Example 5

[0088] 100 g of alumina (SA0-030EN), 6.92 g of acrylonitrile-acrylamide-acrylate emulsion (BM-950B), 12 g of amide group-containing polymer emulsion (SF168L), 0.55 g of isoalcohol amine dispersant (Angus Voltan 100), and 0.5 g of polyether-modified silicone surfactant (BYK-ET-3061) were added to deionized water, mixed, and stirred evenly to obtain an inorganic particle slurry.

[0089] The prepared inorganic particle slurry was coated on both sides of a porous substrate with a thickness of 9.2 μm (porosity 48%), and dried to form an inorganic coating on the porous substrate, thereby obtaining a composite separator membrane with a thickness of 12.3 μm.

[0090] The prepared composite separator membrane was tested by the detection method described in Example 1. The test results are listed in Table 1.

[0091] Example 6

[0092] 75 g of alumina (SA0-030EN), 25 g of boehmite (AM-BL-03), 8.97 g of acrylonitrile-acrylamide-acrylate emulsion (BM-950B), 13 g of poly(N-vinylacetamide)-containing emulsion (GE191-103), 0.95 g of ammonium polyacrylate dispersant (BYK-154), and 0.5 g of polyether-modified silicone surfactant (BYK-ET-3061) were added to deionized water, mixed, and stirred evenly to obtain an inorganic particle slurry.

[0093] The prepared inorganic particle slurry was coated on both sides of a porous substrate with a thickness of 9.2 μm (porosity 48%), and dried to form an inorganic coating on the porous substrate, thereby obtaining a composite separator membrane with a thickness of 12.7 μm.

[0094] The prepared composite separator membrane was tested by the detection method described in Example 1. The test results are listed in Table 1.

[0095] Example 7

[0096] 50 g of alumina (SA0-030EN), 50 g of boehmite (AM-BL-03), 8.97 g of acrylonitrile-acrylamide-acrylate emulsion (BM-950B), 13 g of poly(N-vinylacetamide)-containing emulsion (GE191-103), 0.95 g of ammonium polyacrylate dispersant (BYK-154), and 0.5 g of polyether-modified silicone surfactant (BYK-ET-3061) were added to deionized water, mixed, and stirred evenly to obtain an inorganic particle slurry.

[0097] The prepared inorganic particle slurry was coated on both sides of a porous substrate with a thickness of 9.2 μm (porosity 48%), and dried to form an inorganic coating on the porous substrate, thereby obtaining a composite separator membrane with a thickness of 12.8 μm.

[0098] The prepared composite separator membrane was tested by the testing method described in Example 1. The test results are listed in Table 1.

[0099] Example 8

[0100] 100 g of alumina (SA0-030EN), 8.97 g of acrylonitrile-acrylamide-acrylate emulsion (BM-950B), 13 g of poly(N-vinylacetamide) emulsion (GE191-103), 1.55 g of ammonium polyacrylate dispersant (BYK-154), and 0.5 g of polyether-modified silicone surfactant (BYK-ET-3061) were added to deionized water, mixed and stirred evenly. Then, a photo-reaction solution uniformly mixed with 0.526 g of 2-isopropylthioxanthone and 2.63 g of methyl methacrylate solvent was added, and stirred evenly at room temperature to obtain an inorganic particle slurry.

[0101] The prepared inorganic particle slurry was coated on both sides of a polyethylene porous substrate with a thickness of 9.2 μm (porosity 48%), and dried to form an inorganic coating on the porous substrate. Then, it was exposed to a UV lamp with a radiation dose of 500 mJ / cm 2 to obtain a composite separator membrane with a thickness of 11.9 μm.

[0102] The prepared composite separator membrane was tested by the testing method described in Example 1. The test results are listed in Table 1.

[0103] Example 9

[0104] 100 g of alumina (SA0-030EN), 6.92 g of acrylonitrile-acrylamide-acrylate emulsion (BM-950B), 12 g of amide-group polymer emulsion (SF168L), 0.55 g of isopropanolamine dispersant (Angus Voltan 100), and 0.5 g of polyether-modified silicone surfactant (BYK-ET-3061) were added to deionized water, mixed and stirred evenly. Then, a photo-reaction solution uniformly mixed with 0.526 g of 2-isopropylthioxanthone and 2.63 g of methyl methacrylate solvent was added, and stirred evenly at room temperature to obtain an inorganic particle slurry.

[0105] The prepared inorganic particle slurry was coated on both sides of a porous substrate with a thickness of 9.2 μm (porosity 48%), and dried to form an inorganic coating on the porous substrate. Then, it was exposed to a UV lamp with a radiation dose of 500 mJ / cm 2Exposure was carried out with a UV lamp of radiation dose to obtain a composite isolation film with a thickness of 11.9 μm.

[0106] The obtained composite isolation film was tested by the detection method described in Example 1. The test results are listed in Table 1.

[0107] Table 1: Measurement results of the isolation film characteristics of the examples

[0108]

[0109] Although the present invention has been disclosed above by way of examples, it is not intended to limit the present invention. Any person skilled in this art should be able to make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A composite isolation membrane comprising Polyolefin porous substrate, and An inorganic coating is coated on at least one surface of the polyolefin porous substrate, wherein the inorganic coating comprises inorganic particles and a bonding resin composition, and the bonding resin composition is 2 to 10 parts by weight per 100 parts by weight of the inorganic particles. The bonding resin composition comprises an acrylonitrile-acrylamide-acrylate copolymer with a glass transition temperature less than 0°C and an amide-containing polymer with a glass transition temperature between 150°C and 200°C.

2. The composite isolation film according to claim 1, wherein the bonding resin composition comprises 40 wt % to 85 wt % of an acrylonitrile-acrylamide-acrylate copolymer having a glass transition temperature less than 0°C, and 15 wt % to 60 wt % of an amide-containing polymer having a glass transition temperature between 150°C and 200°C.

3. The composite isolation film according to claim 1, wherein the bonding resin composition comprises 40 wt % to 80 wt % of an acrylonitrile-acrylamide-acrylate copolymer having a glass transition temperature of less than 0°C, and 20 wt % to 60 wt % of an amide-containing polymer having a glass transition temperature between 150°C and 200°C. 4 . The composite isolation film according to claim 1 , wherein the glass transition temperature of the acrylonitrile-acrylamide-acrylate copolymer is between −40° C. and 0° C. The composite isolation film according to claim 1 , wherein a thickness of the inorganic coating layer is between 0.1 μm and 5.0 μm. The composite isolation film according to claim 5 , wherein the thickness of the inorganic coating layer is 0.5 μm to 3 μm. 7 . The composite isolation film according to claim 1 , wherein the amide-containing polymer having a glass transition temperature between 150° C. and 200° C. is poly(N-vinyl acetamide), amide-(meth)acrylic acid copolymer or acrylonitrile-acrylamide-(meth)acrylate copolymer. 8 . The composite isolation film according to claim 1 , wherein the inorganic coating further comprises an ammonium salt dispersant in an amount of 0.1 to 1.0 parts by weight per 100 parts by weight of the inorganic particles. 9 . The composite isolation film according to claim 1 , wherein the inorganic coating further comprises a siloxane surfactant in an amount of 0.1 to 1.0 parts by weight per 100 parts by weight of the inorganic particles.

10. The composite isolation membrane according to claim 1, wherein the inorganic particles used in the inorganic coating are Mg(OH)2, BaSO4, BaTiO3, HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al(OH)3, Al2O3, boehmite, SiC, TiO2 or a combination thereof. 11 . The composite isolation film according to claim 1 , wherein an average particle size D50 of the inorganic particles of the inorganic coating is between 0.1 μm and 2.0 μm. 12 . The composite isolation film according to claim 1 , wherein the inorganic coating layer comprises 2 to 8 parts by weight of the adhesive resin composition per 100 parts by weight of the inorganic particles. 13 . The composite isolation film according to claim 1 , wherein the inorganic coating further comprises an additive selected from an antistatic agent, a flame retardant, an antioxidant, or a surface modifier.

14. A method for preparing a composite isolation membrane, comprising the steps of: providing a polyolefin porous substrate; and Applying a slurry on one or two surfaces of the polyolefin porous substrate to form an inorganic coating, wherein the slurry comprises a plurality of inorganic particles, a bonding resin composition and water; The bonding resin composition comprises an acrylonitrile-acrylamide-acrylate copolymer with a glass transition temperature less than 0°C and an amide-containing polymer with a glass transition temperature between 150°C and 200°C.

15. The preparation method according to claim 14, wherein the slurry further comprises a dispersant and / or a surfactant. 16 . The preparation method according to claim 15 , wherein the dispersant is an alkanolamine dispersant, an ammonium acrylate dispersant or a combination thereof. 17 . The preparation method according to claim 15 , wherein the amount of the dispersant used is between 0.1 parts by weight and 1.0 parts by weight per 100 parts by weight of the inorganic particles.

18. The preparation method according to claim 15, wherein the surfactant is a siloxane surfactant. 19 . The preparation method according to claim 15 , wherein the amount of the surfactant used is between 0.1 parts by weight and 1 part by weight per 100 parts by weight of the inorganic particles.

20. A composite isolation membrane comprising Polyolefin porous substrate, and An inorganic coating is coated on at least one surface of the polyolefin porous substrate, wherein the inorganic coating comprises inorganic particles, a bonding resin composition and a photoreactant, wherein the bonding resin composition is 2 to 10 parts by weight per 100 parts by weight of the inorganic particles, and the photoreactant is 0.1 to 1.5 parts by weight per 100 parts by weight of the inorganic particles; The bonding resin composition comprises an acrylonitrile-acrylamide-acrylate copolymer with a glass transition temperature less than 0°C and an amide-containing polymer with a glass transition temperature between 150°C and 200°C. 21 . The composite isolation film according to claim 20 , wherein the photoreactive agent is 2-isopropylthioxanthone, thioxanthone, a thioxanthone derivative or a combination thereof.

22. A method for preparing a composite isolation membrane, comprising the steps of: Providing a polyolefin porous substrate; Applying a slurry on one or two surfaces of the polyolefin porous substrate, wherein the slurry comprises a plurality of inorganic particles, a bonding resin composition, water, and a photoreactive solution; and Drying the slurry and irradiating it with ultraviolet light to form an inorganic coating; The bonding resin composition comprises an acrylonitrile-acrylamide-acrylate copolymer with a glass transition temperature less than 0°C and an amide-containing polymer with a glass transition temperature between 150°C and 200°C. 23 . The preparation method according to claim 22 , wherein the photoreactive solution further comprises a photoreactive agent and a solvent, and the amount of the photoreactive agent used is 0.1 to 1.5 parts by weight per 100 parts by weight of the inorganic particles. 24 . The preparation method according to claim 23 , wherein the photoreactive agent is 2-isopropylthioxanthone, thioxanthone, a thioxanthone derivative or a combination thereof.

25. The preparation method according to claim 23, wherein the solvent is toluene, methanol, methyl methacrylate, ethyl acetate, 1,2-dichloroethane, acetone, water or a combination thereof.

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