Composite isolating membrane

Abstract

The invention discloses a composite isolating membrane, which comprises a polyolefin porous base material and an inorganic coating, and the inorganic coating is coated on at least one surface of the polyolefin porous base material and comprises a plurality of inorganic particles, adhesive resin, hydrophilic polymer metal salt and polyamide epichlorohydrin resin, wherein the use amount of the adhesive resin is between 1.5 parts by weight and 8.5 parts by weight, the use amount of the hydrophilic polymer metal salt is between 1 part by weight and 6 parts by weight, and the use amount of the polyamide epichlorohydrin resin is between 0.4 part by weight and 3 parts by weight per hundred parts by weight of the inorganic particles. The composite isolating membrane disclosed by the invention has good high-temperature tolerance.

Description

Technical Field

[0001] The present invention relates to a composite isolation membrane, in particular to a composite isolation membrane with high temperature stability. Background Art

[0002] Driven by the booming development of consumer electronics, wearable devices, electric vehicles, and industrial energy storage, lithium-ion batteries are facing increasing demands for safety and high energy density. Separators, as crucial insulating porous materials in batteries, are also facing a need for improved physical properties. To further ensure the safety of lithium-ion batteries, separators must enhance their high-temperature tolerance and reduce thermal shrinkage at high temperatures to prevent thermal runaway caused by contact between electrodes during abnormal applications.

[0003] The separator membrane of lithium-ion batteries usually uses polyolefin materials as the base material, namely polyethylene (PE) / or polypropylene (PP). Its preparation methods can be mainly divided into dry stretching and wet stretching. Both methods basically use an extrusion process to melt the polymer material to form a thin film, and then stretch it to create suitable pores. Dry separator membranes are usually thicker and can be produced in multiple layers. They are safe and low-cost at high power. Wet separator membranes are thin, have high porosity, and high pore size uniformity. They are suitable for coating a ceramic coating on the surface of the polyolefin substrate to form a composite separator membrane to reduce its thermal shrinkage rate and provide safety. However, the provision of a ceramic coating will reduce the ion conductivity of the separator membrane and may even reduce the battery cycle life. In the prior art, hydrophilic polymer metal salts, such as lithium polyacrylate (PAALi), can be added to the ceramic coating to improve the ion conductivity of the separator membrane. However, while the use of hydrophilic polymer metal salts can enhance ion conductivity, they are unable to resist the substantial shrinkage of the porous base membrane at high temperatures, such as above 160°C, and cannot meet the heat shrinkage resistance requirements at high temperatures, raising safety concerns regarding their use. Summary of the Invention

[0004] The object of the present invention is to provide a composite isolation membrane with high temperature stability.

[0005] To achieve the above-mentioned objectives, the present invention provides a composite isolation membrane comprising a polyolefin porous substrate and an inorganic coating coated on at least one surface of the polyolefin porous substrate, wherein the inorganic coating comprises a plurality of inorganic particles, a binder resin, a hydrophilic polymer metal salt, and a polyamide epichlorohydrin resin. For every hundred parts by weight of the plurality of inorganic particles, the binder resin is used in an amount ranging from 1.5 parts by weight to 8.5 parts by weight, the hydrophilic polymer metal salt is used in an amount ranging from 1 part by weight to 6 parts by weight, and the polyamide epichlorohydrin resin is used in an amount ranging from 0.4 parts by weight to 3 parts by weight.

[0006] In one embodiment of the composite isolation membrane of the present invention, the hydrophilic polymer metal salt may be, for example, lithium polyacrylate, sodium polyacrylate, lithium carboxymethyl cellulose, or lithium poly(perfluoroalkylsulfonyl)imide.

[0007] In one embodiment of the composite isolation membrane of the present invention, the weight average molecular weight of the hydrophilic polymer metal salt may be between 150,000 and 300,000.

[0008] In one embodiment of the composite isolation film of the present invention, the thickness of the inorganic coating layer may be between 0.1 μm and 5.0 μm.

[0009] In one embodiment of the composite isolation film of the present invention, the bonding resin can be, for example, one of poly-N-vinyl acetamide, acrylate-acrylonitrile copolymer, acrylonitrile-acrylamide-(meth)acrylic acid copolymer, acrylamide-acrylic acid-(meth)acrylate copolymer, (meth)acrylate-(meth)acrylic acid-acrylamide-styrene copolymer or any combination thereof.

[0010] In one embodiment of the composite isolation film of the present invention, the inorganic coating further comprises a wetting agent in an amount of 0.5 parts by weight to 3.0 parts by weight per 100 parts by weight of the plurality of inorganic particles.

[0011] In one embodiment of the composite isolation membrane of the present invention, the inorganic particles used in the inorganic coating may be, for example, one of Mg(OH)2, BaSO4, BaTiO3, HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al(OH)3, Al2O3, boehmite (AlOOH), SiC, TiO2, or any combination thereof.

[0012] In one embodiment of the composite isolation membrane of the present invention, the inorganic coating further comprises a thickener, an antistatic agent, a flame retardant, an antioxidant, a dispersant, a defoaming agent or a surface modifier.

[0013] In one embodiment of the composite isolation membrane of the present invention, the weight average molecular weight of the polyamide epichlorohydrin resin is between 200,000 and 300,000.

[0014] The composite isolation membrane of the present invention can resist the shrinkage of the polyolefin porous base membrane at high temperatures by including multiple inorganic particles, a binder resin, a hydrophilic polymer metal salt and a polyamide epichlorohydrin resin in the inorganic coating layer, thereby maintaining good high-temperature tolerance while having a high ion transfer number.

[0015] The above summary is intended to provide a simplified summary of the present invention to provide readers with a basic understanding of the present invention. This summary is not a complete overview of the present invention and is not intended to identify important or critical elements of the embodiments of the present invention or to define the scope of the present invention. After reading the detailed description below, those skilled in the art will readily understand the basic spirit of the present invention and the technical means and implementation methods employed by the present invention. DETAILED DESCRIPTION

[0016] To provide a more complete and detailed disclosure of the present invention, the following provides illustrative descriptions of the embodiments and specific examples of the present invention; however, these descriptions are not intended to be the only forms of implementing or utilizing the embodiments of the present invention. The embodiments disclosed below may be combined or substituted with one another where beneficial, and other embodiments may be added to one embodiment without further description or explanation.

[0017] The advantages, features, and technical methods achieved by the present invention will be described in more detail with reference to exemplary embodiments so as to be more easily understood. The present invention may be implemented in different forms and should not be understood as being limited to the embodiments set forth herein. On the contrary, for those skilled in the art, the provided embodiments will enable the present invention to be more thorough, comprehensive, and completely convey the scope of the present invention, and the present invention will be defined solely by the scope of the appended patent applications.

[0018] Unless otherwise defined, all terms (including technical and scientific terms) and proper nouns used herein have essentially the same meaning as generally understood by technical personnel in the field to which the present invention belongs. For example, those terms defined in commonly used dictionaries should be understood to have meanings consistent with the content of the relevant field, and will not be understood in an overly idealized or overly formal sense unless explicitly defined herein.

[0019] The composite separator membrane of the present invention comprises a polyolefin porous substrate and an inorganic coating applied to at least one surface of the polyolefin porous substrate. The polyolefin porous substrate suitable for the composite separator membrane of the present invention can be a single-layer or multi-layer polyolefin porous substrate, such as, but not limited to, a single-layer polyethylene film, a single-layer polypropylene film, a double-layer polyethylene / polypropylene film, or a triple-layer polypropylene / polyethylene / polypropylene film. The thickness of the polyolefin porous substrate suitable for the present invention can range from approximately 5 μm to 30 μm, preferably from 5 μm to 20 μm. The porosity of the polyolefin porous substrate can range from 40% to 70%, preferably from 43% to 65%.

[0020] The inorganic coating of the composite separator of the present invention can be applied to one or both sides of the polyolefin porous substrate. In one embodiment of the composite separator of the present invention, the thickness of the inorganic coating can be between 0.1 μm and 5.0 μm, and preferably a ceramic coating on one or both sides between 2.0 μm and 3.5 μm.

[0021] The inorganic coating of the composite isolation membrane of the present invention comprises a plurality of inorganic particles, a binder resin, a hydrophilic polymer metal salt, and a polyamide epichlorohydrin resin. The inorganic particles used in the inorganic coating can be those commonly used in this technical field, that is, inorganic particles that have heat resistance, electrical insulation, and electrolyte stability, and there are no special restrictions. Suitable inorganic particles can be, for example, Mg(OH)2, BaSO4, BaTiO3, HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al(OH)3, Al2O3, boehmite (AlOOH), SiC, TiO2, etc. The average particle size (D50) of the inorganic particles can be between 0.1μm and 2.0μm, and preferably between 0.15μm and 1.0μm. In one embodiment of the present invention, the inorganic coating layer may include two or more inorganic particles having the same or different particle sizes.

[0022] In the inorganic coating of the composite isolation membrane of the present invention, the adhesive resin can be one or any combination of poly-N-vinylacetamide, acrylate-acrylonitrile copolymer, acrylonitrile-acrylamide-(meth)acrylic acid copolymer, acrylamide-acrylic acid-(meth)acrylate copolymer, (meth)acrylate-(meth)acrylic acid-acrylamide-styrene copolymer, which are commonly used in this technical field. This prevents the reduced adhesion between the inorganic coating and the polyolefin porous substrate caused by the high polarity and high ionic bonds of the hydrophilic polymer metal salt. The amount of adhesive resin used can range from 1.5 to 8.5 parts by weight per 100 parts by weight of the inorganic particles, and preferably ranges from 2 to 7.5 parts by weight. Excessive amounts of adhesive resin can affect the air permeability of the isolation membrane. The adhesive resin suitable for the present invention can be selected from commercially available products, such as BM-950B manufactured by Japan's Zeon Corporation, CYJ5088A manufactured by Zhuhai Chenyu New Materials Technology Co., Ltd. in China, PNVA GE191 series (such as GE191-103, GE191-104, GE191-107 or GE191-108) manufactured by Showa Denko Corporation of Japan, SF168L manufactured by Shenzhen Yanyi New Materials Co., Ltd. in China, or GR506 manufactured by Hunan Gaorui Power Materials Co., Ltd., but are not limited thereto.

[0023] In the composite isolation membrane of the present invention, the hydrophilic polymer metal salt in the inorganic coating can dissociate to form metal ions to replenish the metal source, which can make up for the loss of battery capacity, thereby accelerating ion migration and improving battery performance. In one embodiment of the composite isolation membrane of the present invention, the hydrophilic polymer metal salt can be, for example, but not limited to, lithium polyacrylate (PAALi), sodium polyacrylate (PAANa), lithium carboxymethyl cellulose (CMCLi) or lithium poly(perfluoroalkylsulfonyl)imide (PFSILi). The weight average molecular weight of the hydrophilic polymer metal salt can be between 150,000 and 300,000, for example, 150,000, 200,000, 250,000 or 300,000. In the inorganic coating of the composite separator of the present invention, the amount of the hydrophilic polymeric metal salt used can range from 1 to 6 parts by weight, and preferably from 1.5 to 5 parts by weight, per 100 parts by weight of the inorganic particles. If the amount of the hydrophilic polymeric metal salt used is too low, it may not effectively increase the ion transference number. If the amount of the hydrophilic polymeric metal salt used is too high, it may increase the impedance of the separator, thereby affecting battery performance.

[0024] Furthermore, the inorganic coating of the composite isolation membrane of the present invention includes a polyamide epichlorohydrin resin, which undergoes a cross-linking reaction with the carboxyl groups in the hydrophilic polymer metal salt to enhance the overall strength of the isolation membrane, thereby improving thermal stability without affecting the ion migration number. When the amount of polyamide epichlorohydrin resin used is too low, the thermal stability of the isolation membrane will be insufficient. In one embodiment of the composite isolation membrane of the present invention, the amount of polyamide epichlorohydrin resin used is between 0.4 parts by weight and 3 parts by weight per hundred parts by weight of inorganic particles, and preferably between 0.45 parts by weight and 2.5 parts by weight. When the amount of polyamide epichlorohydrin resin used is too high, the uniformity of the inorganic coating will be affected.

[0025] The polyamide-epichlorohydrin resin suitable for the inorganic coating of the composite barrier film of the present invention may have a weight average molecular weight of approximately 200,000 to 300,000, such as 200,000, 220,000, 240,000, 260,000, 280,000, or 300,000, and has a structure as shown in the following formula (I):

[0026] In one embodiment of the composite isolation membrane of the present invention, suitable polyamide epichlorohydrin resins can be commercially available products, such as Polycup 172, Polycup 7700, and Polycup 2000 manufactured by Solenis Corporation of the United States, but are not limited thereto.

[0027] The composite separator disclosed herein, while containing a hydrophilic polymer metal salt in its inorganic coating, resists shrinkage of the polyolefin porous base membrane at high temperatures by adding a polyamide-epichlorohydrin resin to the inorganic coating. This allows the membrane to maintain thermal shrinkage resistance at high temperatures (e.g., 180°C) while maintaining a high ion transfer number. Therefore, even when the inorganic coating is thin, such as less than 5 μm, the thermal shrinkage after heating at 180°C for one hour can still be no greater than 2% in both the machine direction (MD) and the transverse direction (TD). This minimal thermal shrinkage at high temperatures prevents thermal runaway caused by contact between electrodes during abnormal applications, providing excellent safety performance at high temperatures. Furthermore, the adhesive resin composition of the present invention provides suitable adhesion, ensuring adequate adhesion between the inorganic coating and the polyolefin porous base membrane, such as a peel strength exceeding 10 gf / cm.

[0028] In one embodiment of the composite separator of the present invention, the inorganic coating layer may optionally further include a wetting agent to enhance interfacial compatibility between the inorganic coating layer and the polyolefin porous substrate. Suitable wetting agents for use in the present invention include silicone surfactants. The amount of the wetting agent used may range from 0.5 to 3.0 parts by weight, and preferably from 0.5 to 2.5 parts by weight, per 100 parts by weight of the inorganic particles.

[0029] In one embodiment of the composite separator of the present invention, the inorganic coating layer may further include additives such as an antistatic agent, a flame retardant, an antioxidant, a dispersant, a defoaming agent, or a surface modifier as required.

[0030] Thus, by using a polyamide-epichlorohydrin resin to enhance the thermal shrinkage resistance of the composite separator, concerns about battery safety can be avoided by avoiding the impact of heat resistance on the inorganic coating caused by the addition of hydrophilic polymer metal salts. In a preferred embodiment of the composite separator of the present invention, the thermal shrinkage rate in both the machine direction (MD) and the transverse direction (TD) after heating at 180°C for one hour remains no greater than 2%.

[0031] The following examples are used to further illustrate the present invention, but the present invention is not limited thereto.

[0032] Example

[0033] The following are the raw materials used in the embodiments of the present invention:

[0034] SA0-030EN, alumina, particle size (D50) 0.52 μm, was purchased from Shandong Guoci Functional Materials Co., Ltd., China.

[0035] PAA, Poly (acrylic acid) solution, with a concentration of 35% and a weight average molecular weight (Mw) of approximately 250,000, was purchased from Sigma-Aldrich Company, USA.

[0036] CYJ5088A, acrylate-acrylic acid-acrylamide-styrene copolymer emulsion with a solid content of 25%, was purchased from Zhuhai Chenyu New Material Technology Co., Ltd., China.

[0037] SF168L, an acrylonitrile-acrylamide-acrylic acid copolymer emulsion with a solid content of 6.25%, was purchased from Shenzhen Yanyi New Materials Co., Ltd., China.

[0038] Polycup 172, polyamide epichlorohydrin (PAE) resin, solid content of 12.5%, viscosity (25°C) of 25 cps to 75 cps, pH of 4.0 to 5.0, purchased from Solenis, USA.

[0039] Polycup 7700, a polyamide epichlorohydrin (PAE) resin, has a solid content of 12.5%, a viscosity (at 25° C.) of 30 cps to 90 cps, and a pH of 3.3 to 4.1 and was purchased from Solenis, USA.

[0040] Polycup 2000, a polyamide epichlorohydrin (PAE) resin, has a solid content of 12%, a viscosity (25° C.) less than 100 cps, and a pH value of 2.2 to 4.0, and was purchased from Solenis, USA.

[0041] BYK-ET-3030, dispersant, solid content 42%, purchased from BYK Company, Germany.

[0042] BYK-ET-3061, wetting agent, was purchased from BYK, Germany.

[0043] SF-3100, a wetting agent, was purchased from Taiwan Shichun Enterprise Co., Ltd., China.

[0044] BYK-ET-3070, a defoaming agent with a solid content of 30%, was purchased from BYK Company in Germany.

[0045] Preparation Example 1: Preparation of PAALi solution

[0046] 11.6 g of LiOH (486 mmol) was dissolved in 100 mL of deionized water, and 100 g of PAA was added, followed by stirring with a magnet for 8 hours to obtain a PAALi aqueous solution with a pH of 7 and a concentration of 22%.

[0047] Example 1

[0048] 31.36 g of aluminum oxide (SA0-030EN), 1.57 g of acrylate-acrylic acid-acrylamide-styrene copolymer emulsion (CYJ5088A), 6.27 g of acrylonitrile-acrylamide-acrylic acid copolymer emulsion (SF168L), 2.87 g of the PAALi aqueous solution of Preparation Example 1, 1.18 g of polyamide epichlorohydrin resin (Polycup 172), 0.43 g of dispersant (BYK-ET-3030), 0.51 g of defoamer (BYK-ET-3070) and 0.75 g of wetting agent (BYK-ET-3061) were added to 55.07 g of deionized water, mixed and stirred uniformly to obtain an inorganic particle slurry.

[0049] The prepared inorganic particle slurry was coated on both surfaces of a 9.2 μm thick polyethylene porous membrane (porosity 48%), and dried to form an inorganic coating on the polyethylene porous membrane, thereby obtaining a composite separator with a thickness of 12.0 μm.

[0050] The prepared composite isolation membrane was tested using the test methods described below. The test results are listed in Table 1.

[0051] Thickness test: According to the GB / T6672-2001 test standard, a film thickness tester (VL-50-B, purchased from Mitutoyo, Japan) was used. The test was performed using a flat probe with a diameter of 3 mm and a downward pressure probe load of 0.01 N.

[0052] Gurley air permeability test: According to ASTM D-726, the release film to be tested was cut into 1 square inch pieces. The air permeability was determined by measuring the time required for 100cc of air to pass through the release film using a Gurley air permeability meter.

[0053] Lithium ion migration number test:

[0054] The prepared composite separator was assembled into a button cell battery and subjected to AC impedance testing using a Biologic battery testing system at a frequency of 100 kHz to 1 Hz to measure the internal resistance. A 15 mV DC bias was applied, and the current was recorded over time for one hour. The lithium ion transference number (T+) was calculated using the following Bruce-Vincent equation.

[0055] , where V represents the applied voltage, I0 and I s Represent the initial current and steady-state current, R0 and R s They represent the initial resistance and steady-state resistance respectively.

[0056] Thermal Shrinkage Test: Cut a 10 x 10 cm sample and mark the initial lengths M0 and T0 in the machine direction (MD) and transverse direction (TD) at the center of the sample before testing. After marking, place the sample between two A4 sheets of paper in an oven and heat at 180°C for 1 hour. After heating, place the sample in the same environment as the measuring instrument for 30 minutes. Measure the machine direction (MD) length M1 and transverse direction (TD) length T1 at the center of the sample. If both the MD and TD thermal shrinkage rates are less than 2%, mark them as O. If either the MD or TD thermal shrinkage rates are greater than 2%, mark them as X.

[0057] Longitudinal direction (MD) thermal shrinkage = (M0-M1) / M0*100%

[0058] Transverse direction (TD) thermal shrinkage = (T0-T1) / T0*100%

[0059] Peel Strength: An 80μm-thick adhesive sheet (Model 31B, purchased from Nitto) was cut into pieces 60mm long and 20mm wide and attached to a composite release film. Using a universal tensile testing machine, the adhesive sheet was peeled off at a rate of 50mm / min at a 180° peel angle. The peel force was measured along the middle 50mm of the film. Five test pieces were measured for each composite release film to determine the average peel strength.

[0060] Example 2

[0061] 31.26 g of aluminum oxide (SA0-030EN), 1.56 g of acrylate-acrylic acid-acrylamide-styrene copolymer emulsion (CYJ5088A), 6.20 g of acrylonitrile-acrylamide-acrylic acid copolymer emulsion (SF168L), 2.86 g of the PAALi aqueous solution of Preparation Example 1, 2.08 g of polyamide epichlorohydrin resin (Polycup 172), 0.43 g of dispersant (BYK-ET-3030), 0.51 g of defoamer (BYK-ET-3070) and 0.75 g of wetting agent (BYK-ET-3061) were added to 54.35 g of deionized water, mixed and stirred uniformly to obtain an inorganic particle slurry.

[0062] The prepared inorganic particle slurry was coated on both surfaces of a 9.2 μm thick polyethylene porous membrane (porosity 48%), and dried to form an inorganic coating on the polyethylene porous membrane, thereby obtaining a composite separator with a thickness of 12.7 μm.

[0063] The prepared composite isolation membrane was tested using the test method described in Example 1. The test results are listed in Table 1.

[0064] Example 3

[0065] 30.69 g of aluminum oxide (SA0-030EN), 1.53 g of acrylate-acrylic acid-acrylamide-styrene copolymer emulsion (CYJ5088A), 6.14 g of acrylonitrile-acrylamide-acrylic acid copolymer emulsion (SF168L), 5.58 g of the PAALi aqueous solution of Preparation Example 1, 2.05 g of polyamide epichlorohydrin resin (Polycup 172), 0.44 g of dispersant (BYK-ET-3030), 0.51 g of defoamer (BYK-ET-3070) and 0.74 g of wetting agent (BYK-ET-3061) were added to 52.34 g of deionized water, mixed and stirred uniformly to obtain an inorganic particle slurry.

[0066] The prepared inorganic particle slurry was coated on both surfaces of a 9.2 μm thick polyethylene porous membrane (porosity 48%), and dried to form an inorganic coating on the polyethylene porous membrane, thereby obtaining a composite separator with a thickness of 12.6 μm.

[0067] The prepared composite isolation membrane was tested using the test method described in Example 1. The test results are listed in Table 1.

[0068] Example 4

[0069] 26.86 g of aluminum oxide (SA0-030EN), 1.34 g of acrylate-acrylic acid-acrylamide-styrene copolymer emulsion (CYJ5088A), 5.37 g of acrylonitrile-acrylamide-acrylic acid copolymer emulsion (SF168L), 4.88 g of the PAALi aqueous solution of Preparation Example 1, 4.48 g of polyamide epichlorohydrin resin (Polycup 7700), 0.38 g of dispersant (BYK-ET-3030) and 0.64 g of wetting agent (FS-3100) were added to 56.03 g of deionized water, mixed and stirred uniformly to obtain an inorganic particle slurry.

[0070] The prepared inorganic particle slurry was coated on both surfaces of a 9.2 μm thick polyethylene porous membrane (porosity 48%), and dried to form an inorganic coating on the polyethylene porous membrane, thereby obtaining a composite separator with a thickness of 12.5 μm.

[0071] The prepared composite isolation membrane was tested using the test method described in Example 1. The test results are listed in Table 1.

[0072] Example 5

[0073] 27.40 g of aluminum oxide (SA0-030EN), 1.37 g of acrylate-acrylic acid-acrylamide-styrene copolymer emulsion (CYJ5088A), 5.48 g of acrylonitrile-acrylamide-acrylic acid copolymer emulsion (SF168L), 4.98 g of the PAALi aqueous solution prepared in Preparation Example 1, 4.57 g of polyamide epichlorohydrin resin (Polycup 2000), 0.39 g of a dispersant (BYK-ET-3030), and 0.66 g of a wetting agent (FS-3100) were added to 55.16 g of deionized water, mixed, and stirred to obtain an inorganic particle slurry.

[0074] The prepared inorganic particle slurry was coated on both surfaces of a 9.2 μm thick polyethylene porous membrane (porosity 48%), and dried to form an inorganic coating on the polyethylene porous membrane, thereby obtaining a composite separator with a thickness of 12.4 μm.

[0075] The prepared composite isolation membrane was tested using the test method described in Example 1. The test results are listed in Table 1.

[0076] Comparative Example 1

[0077] 27.95 g of aluminum oxide (SA0-030EN), 1.40 g of acrylate-acrylic acid-acrylamide-styrene copolymer emulsion (CYJ5088A), 5.59 g of acrylonitrile-acrylamide-acrylic acid copolymer emulsion (SF168L), 5.08 g of the PAALi aqueous solution of Preparation Example 1, 0.40 g of a dispersant (BYK-ET-3030) and 0.67 g of a wetting agent (BYK-ET-3061) were added to 58.93 g of deionized water, mixed and stirred uniformly to obtain an inorganic particle slurry.

[0078] The prepared inorganic particle slurry was coated on both surfaces of a 9.2 μm thick polyethylene porous membrane (porosity 48%), and dried to form an inorganic coating on the polyethylene porous membrane, thereby obtaining a composite separator with a thickness of 12.6 μm.

[0079] The prepared composite isolation membrane was tested using the test method described in Example 1. The test results are listed in Table 1.

[0080] Table 1: Measurement results of composite isolation film characteristics of the embodiment

[0081]

[0082] The composite isolation membrane of the present invention can resist the shrinkage of the polyolefin porous base membrane at high temperatures by including multiple inorganic particles, a binder resin, a hydrophilic polymer metal salt and a polyamide epichlorohydrin resin in the inorganic coating layer, thereby maintaining good high-temperature tolerance while having a high ion transfer number.

[0083] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A composite isolation membrane, characterized in that Include: a polyolefin porous substrate; and An inorganic coating layer is coated on at least one surface of the polyolefin porous substrate, wherein the inorganic coating layer comprises a plurality of inorganic particles, a binder resin, a hydrophilic polymer metal salt, and a polyamide epichlorohydrin resin. Among them, relative to every hundred parts by weight of the plurality of inorganic particles, the usage amount of the binder resin is between 1.5 parts by weight and 8.5 parts by weight, the usage amount of the hydrophilic polymer metal salt is between 1 part by weight and 6 parts by weight, and the usage amount of the polyamide epichlorohydrin resin is between 0.4 parts by weight and 3 parts by weight.

2. The composite isolation membrane according to claim 1, wherein: The hydrophilic polymer metal salt is lithium polyacrylate, sodium polyacrylate, lithium carboxymethyl cellulose or lithium poly(perfluoroalkylsulfonyl)imide.

3. The composite isolation membrane according to claim 1, wherein: The weight average molecular weight of the hydrophilic polymer metal salt is between 150,000 and 300,000.

4. The composite isolation membrane according to claim 1, wherein The thickness of the inorganic coating is between 0.1 μm and 5.0 μm.

5. The composite isolation membrane according to claim 1, wherein: The bonding resin is one of poly-N-vinyl acetamide, acrylate-acrylonitrile copolymer, acrylonitrile-acrylamide-(meth)acrylic acid copolymer, acrylamide-acrylic acid-(meth)acrylate copolymer, (meth)acrylate-(meth)acrylic acid-acrylamide-styrene copolymer or any combination thereof.

6. The composite isolation membrane according to claim 1, wherein: The multiple inorganic particles used in the inorganic coating are one of Mg(OH)2, BaSO4, BaTiO3, HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al(OH)3, Al2O3, AlOOH, SiC, TiO2 or any combination thereof.

7. The composite isolation membrane according to claim 1, wherein: The inorganic coating further comprises a wetting agent, and the amount of the wetting agent used is 0.5 to 3.0 parts by weight per 100 parts by weight of the inorganic particles.

8. The composite isolation membrane according to claim 1, wherein: The inorganic coating further comprises a thickener, an antistatic agent, a flame retardant, an antioxidant, a dispersant, a defoaming agent or a surface modifier.

9. The composite isolation membrane according to claim 1, wherein: The weight average molecular weight of the polyamide epichlorohydrin resin is between 200,000 and 300,000.

Images