Diaphragm with self-stratifying coating, preparation method thereof, and related secondary battery and electric device

Abstract

The invention discloses a diaphragm with a self-layering coating, a preparation method of the diaphragm and a related secondary battery and an electric device. The battery diaphragm comprises a base membrane and a coating arranged on at least one surface of the base membrane, the coating is obtained by coating slurry once, the slurry comprises an amino-modified organosilicon polymer, an amino-modified inorganic filler and epoxy resin, the content of the amino-modified organosilicon polymer on the upper surface of the coating is recorded as V1, and the content of the amino-modified inorganic filler on the lower surface of the coating is recorded as V2. The content on the lower surface of the coating is recorded as V2 and V1gt; v2. According to the embodiment of the invention, the heat resistance and cohesiveness of the base membrane can be improved at the same time through one-time coating, and the heat shrinkage resistance of the diaphragm is improved through the amino-modified organosilicon polymer, the amino-modified inorganic filler and the epoxy resin.

Description

Technical Field

[0001] The present application belongs to the field of battery technology, and in particular relates to a diaphragm with a self-stratifying coating, a preparation method thereof, and related secondary batteries and electrical devices. Background Art

[0002] At present, in order to take into account the heat resistance and bonding strength of the coated separator, two coatings are often required. That is, first a layer of heat-resistant inorganic filler is roller-coated on the surface of the base film to ensure a small thermal shrinkage rate, and then large particle glue is roller-coated or PVDF is sprayed to improve the adhesion of the separator, so as to resist the risk of positive and negative short circuits that are prone to occur when the temperature rises during use due to external impact.

[0003] But it is obvious that the double coating has a higher production cost. In addition, the inorganic particles of the coating are mostly connected by adhesives. When the external temperature continues to increase, the base film tends to shrink more and the adhesive molecular chain moves more easily, which makes the heat shrinkage resistance ineffective. Summary of the invention

[0004] The embodiments of the present application provide a diaphragm with a self-stratifying coating, a preparation method thereof, and related secondary batteries and electrical devices, which can improve the heat resistance and adhesion of the base film through a single coating, and improve the anti-thermal shrinkage performance of the diaphragm through amino-modified silicone polymers, amino-modified inorganic fillers and epoxy resins.

[0005] In the first aspect, an embodiment of the present application provides a diaphragm with a self-stratifying coating, comprising a base film and a coating arranged on at least one surface of the base film, wherein the coating is obtained by one-time coating of a slurry, the slurry comprising an amino-modified silicone polymer, an amino-modified inorganic filler and an epoxy resin, the content of the amino-modified silicone polymer on the upper surface of the coating is denoted as V1, the content on the lower surface of the coating is denoted as V2, and V1>V2.

[0006] In any embodiment of the present application, the thickness of the upper surface of the coating is 0.1% to 20% of the thickness of the coating, and the thickness of the lower surface of the coating is 0.1% to 20% of the thickness of the coating.

[0007] In any embodiment of the present application, the surface content of the amino-modified organosilicon polymer in the coating can be characterized by the energy spectrum silicon element, and other characterization methods that can accurately identify the content of the amino-modified organosilicon polymer in the coating can also be used.

[0008] In any embodiment of the present application, the amino-modified organic silicon polymer, the amino-modified inorganic filler and the epoxy resin are bonded to form a three-dimensional network cross-linked structure in the coating through the reaction of the amino group and the epoxy group.

[0009] In any embodiment of the present application, the mass ratio of the amino-modified silicone polymer, the amino-modified inorganic filler and the epoxy resin is (2-10):1800:(80-120), wherein the mass of the amino-modified silicone polymer is based on the mass of the raw material KH550 / KH560 added in the preparation of the amino-modified silicone polymer.

[0010] In any embodiment of the present application, the amino-modified silicone polymer includes an amino-modified silicone pressure-sensitive adhesive.

[0011] In any embodiment of the present application, the amino-modified inorganic filler includes at least one of silane-modified alumina, silane-modified boehmite, silane-modified magnesium hydroxide, silane-modified silica, silane-modified titanium dioxide, silane-modified zirconia, silane-modified hydrotalcite and silane-modified montmorillonite.

[0012] In any embodiment of the present application, the epoxy resin includes a bisphenol A epoxy resin, and the type of the bisphenol A epoxy resin includes at least one of E-20, E-21, E-42, E-44, E-51 and E-54.

[0013] In any embodiment of the present application, the coating further comprises a curing agent, and the curing agent comprises an amine curing agent.

[0014] In any embodiment of the present application, the amine curing agent includes at least one of aliphatic amine, modified alicyclic amine curing agent, cardanol-modified aliphatic amine curing agent and polyamide curing agent.

[0015] In any embodiment of the present application, the thickness of the coating layer is 1-6 μm.

[0016] In any embodiment of the present application, the diaphragm satisfies at least one of the following conditions (1) to (4): (1) the longitudinal heat shrinkage of the diaphragm at 150°C and 1 hour is 0.80% to 1.10%; (2) the transverse heat shrinkage of the diaphragm at 150°C and 1 hour is 0.40% to 0.60%; (3) the bonding strength of the diaphragm is 50 to 70 N / m; (4) the air permeability of the diaphragm is 160 to 190 s / 100cc.

[0017] In the second aspect, an embodiment of the present application provides a method for preparing a battery separator, comprising the following steps: preparing a slurry, mixing an amino-modified silicone polymer, an amino-modified inorganic filler and an epoxy resin in a solvent in a predetermined proportion to form a slurry; applying the slurry on at least one surface of a base film to form a coating and drying to obtain a separator.

[0018] In any embodiment of the present application, in preparing the slurry, the solvent includes at least one of xylene, n-butanol, methyl isobutyl ketone, butanone, acetone, tetrahydrofuran, butyl acetate and ethyl acetate.

[0019] In any embodiment of the present application, the slurry further includes a curing agent, and the mass ratio of the curing agent to the epoxy resin is (6-10):(60-120).

[0020] In any embodiment of the present application, in the preparation of the slurry, the preparation method of the amino-modified silicone polymer includes: after mixing the materials containing the coupling agent and the solvent, adjusting the pH of the mixed solution to 2-4, and raising the temperature of the mixed solution to 40-80°C, condensing and refluxing for 4-8 hours, and then distilling under reduced pressure at 50-80°C to obtain polysiloxane; mixing the polysiloxane, silicone polymer, and solvent according to a preset ratio, reacting at 90-120°C for 2-5 hours, and then adding a polymer initiator, and reacting for 0.5-3 hours to obtain an amino-modified silicone polymer.

[0021] In any embodiment of the present application, the mass ratio of polysiloxane to silicone polymer is (2-8):(80-220).

[0022] In any embodiment of the present application, the organic silicon polymer includes at least one of a hydroxyl-terminated silicone rubber and an organic silicon resin.

[0023] In any embodiment of the present application, the number average molecular weight of the hydroxyl-terminated silicone rubber is 50,000 to 200,000.

[0024] In any embodiment of the present application, the silicone resin is a polyalkyl silicone resin, preferably a polymethyl silicone resin, and more preferably a methyl MQ resin.

[0025] In any embodiment of the present application, the number average molecular weight of the methyl MQ resin is 1000-8000.

[0026] In any embodiment of the present application, the M / Q value of the methyl MQ resin is 0.2-1.

[0027] In any embodiment of the present application, the polymer initiator is a free radical initiator.

[0028] In any embodiment of the present application, the preparation method of the amino-modified inorganic filler includes: mixing the inorganic filler, the coupling agent and the solvent according to a preset ratio, reacting at 40 to 70° C. for 20 to 50 minutes, and then reacting at 120 to 170° C. for 10 to 30 minutes to obtain the amino-modified inorganic filler.

[0029] In any embodiment of the present application, the mass ratio of the inorganic filler to the coupling agent is 1800:(15-20).

[0030] In any embodiment of the present application, the coupling agent includes KH-550 and / or KH560.

[0031] In any embodiment of the present application, in coating, the coating method includes roller coating or spray coating.

[0032] In any embodiment of the present application, during coating, the thickness of the base film is not limited and can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or 16 μm.

[0033] In any embodiment of the present application, during coating, the coating vehicle speed is 40 to 150 m / min.

[0034] In any embodiment of the present application, the winding method can be at least one of PET release film winding, deviation correction winding, adhesive strip attachment winding, and slitting and post-winding.

[0035] In a third aspect, an embodiment of the present application provides a secondary battery, which includes the above-mentioned diaphragm or the diaphragm prepared by the above-mentioned preparation method.

[0036] In the third and fourth aspects, an embodiment of the present application provides an electrical device, which includes the above-mentioned secondary battery.

[0037] The diaphragm with self-stratifying coating, the preparation method thereof, and the related secondary battery and electric device of the embodiment of the present application can be coated with a coating containing amino-modified silicone polymer and epoxy resin at one time, and the amino-modified silicone polymer and epoxy resin can achieve self-stratification due to their different surface energies. The amino-modified silicone polymer is gathered on the upper surface of the coating, and the epoxy resin is gathered on the lower surface of the coating, so that the base film can have good heat resistance and good adhesion between the coating and the base film after one coating, thereby reducing the number of coatings and saving costs. The invention aims to achieve the purpose of the present invention; and through the bonding reaction between the amino groups contained in the amino-modified silicone polymer and the amino-modified inorganic filler and the epoxy group contained in the epoxy resin, a three-dimensional network cross-linking structure is formed between the amino-modified silicone polymer, the amino-modified inorganic filler and the epoxy resin, and the chemical bond between the inorganic filler and the epoxy resin (adhesive) replaces the traditional van der Waals force, thereby enhancing the interaction force between the inorganic filler molecules, reducing the movement of the inorganic filler molecules caused by the increase in external temperature, thereby improving the stability of the inorganic filler, and then improving the heat shrinkage resistance of the diaphragm. DETAILED DESCRIPTION

[0038] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the scheme of the present application will be further described below. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0039] In the following description, many specific details are set forth to facilitate a full understanding of the present disclosure, but the present application may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present application, rather than all of the embodiments.

[0040] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] If not otherwise specified, all embodiments and optional embodiments of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of the present application.

[0042] Unless otherwise specified, all technical features and optional technical features of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of the present application.

[0043] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0044] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0045] Unless otherwise specified, this application adopts conventional test methods or test methods recommended by the instrument.

[0046] Typically, a secondary battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator. The separator is arranged between the positive electrode sheet and the negative electrode sheet, and its main function is to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass freely to form a loop.

[0047] With the application and promotion of secondary batteries, people often need to coat twice in order to take into account the heat resistance and bonding strength of the diaphragm. First, a layer of heat-resistant inorganic filler is rolled on the surface of the base film to ensure a small thermal shrinkage rate, and then the adhesion of the diaphragm is improved by rolling large particle glue, spraying PVDF, etc., so as to resist the risk of positive and negative short circuits that are easy to occur when the temperature rises during use, thereby increasing the production cost. The inorganic filler in the heat-resistant layer can bring heat resistance to the diaphragm. In order to make the inorganic filler molecules bond to each other, adhesives, such as commonly used acrylates, are usually used to bond the inorganic filler molecules to each other with van der Waals forces. However, with the increase in temperature, on the one hand, high temperature will accelerate the movement between the molecular chains of the binder, destroy the van der Waals forces between the inorganic filler molecules, and make the inorganic filler layer lose its support effect on the base film, resulting in obvious thermal shrinkage on a macro scale; on the other hand, high temperature will also increase the shrinkage tendency of the base film, and may lose its support for the coating. As a result, the positive and negative electrodes inside the battery are in direct contact, resulting in internal short circuits, thereby increasing the safety risks of secondary batteries.

[0048] In order to solve the above problems, the inventors of the present application surprisingly found during the research process that by providing a coating including an amino-modified silicone polymer, an amino-modified inorganic filler and an epoxy resin on the surface of the base film, and making the surface energy of the amino-modified silicone polymer lower than the surface energy of the epoxy resin, the diaphragm can have good heat resistance and good adhesion between the coating and the base film through a single coating, and the heat shrinkage resistance of the diaphragm can be improved by establishing a three-dimensional cross-linked structure among the silicone polymer, the inorganic filler and the epoxy resin.

[0049] Diaphragm

[0050] An embodiment of the present application provides a diaphragm with a self-stratifying coating, comprising a base film and a coating arranged on at least one (which may be one or two) surface of the base film, wherein the coating is obtained by one-time coating of a slurry, the slurry comprising an amino-modified silicone polymer, an amino-modified inorganic filler and an epoxy resin, the content of the amino-modified silicone polymer on the upper surface of the coating is denoted as V1, and the content on the lower surface of the coating is denoted as V2, and V1>V2.

[0051] In the present application, the surface content of the amino-modified organosilicon polymer in the coating can be characterized by the silicon element of the energy spectrum, and other characterization methods that can accurately identify the content of the amino-modified organosilicon polymer in the coating can also be used.

[0052] In the present application, the silicon content of the energy spectrum of the upper surface or the lower surface of the coating can be detected using methods known in the art.

[0053] Due to the difference in surface energy between amino-modified silicone polymer and epoxy resin, self-stratification occurs. When a self-stratifying coating containing amino-modified silicone polymer, amino-modified inorganic filler and epoxy resin is coated on a base film, as the solvent evaporates, the amino-modified silicone polymer migrates to the upper surface of the diaphragm and the epoxy resin migrates to the lower surface of the diaphragm. The amino-modified silicone polymer on the upper surface of the diaphragm can provide good adhesion between the diaphragm and the electrode, and because it is concentrated on the upper surface of the diaphragm, it will not block the pores of the base film on the lower surface of the diaphragm, so that the diaphragm has a good porosity; the epoxy resin on the lower surface of the diaphragm can provide bonding strength between the inorganic fillers and adhesion between the coating and the base film, and the coating in the present application also has good heat resistance.

[0054] The thickness of the upper surface of the coating is 0.1% to 20% of the thickness of the coating, and the thickness of the lower surface of the coating is 0.1% to 20% of the thickness of the coating.

[0055] The inventors found in the process of studying the heat resistance and coating process of the diaphragm that in order to take into account both the heat resistance and bonding strength of the diaphragm, people often need to coat twice. In order to make the inorganic filler molecules bond to each other, adhesives, such as commonly used acrylates, are usually used to bond the inorganic filler molecules to each other by van der Waals force. However, increasing the number of coating processes will increase production costs, and acrylate adhesives will lead to poor heat resistance of the diaphragm.

[0056] The inventors found in further research that a coating containing an amino-modified silicone polymer and an epoxy resin can be applied once, and the amino-modified silicone polymer and the epoxy resin can be self-stratified into an adhesive layer and a heat-resistant layer due to their different surface energies, so that the base film can improve the heat resistance and adhesion of the diaphragm at the same time after one coating, thereby achieving the purpose of reducing the number of coatings and saving costs; and through the bonding reaction between the amino groups contained in the amino-modified silicone polymer and the amino-modified inorganic filler and the epoxy group contained in the epoxy resin, a three-dimensional network cross-linked structure is formed between the amino-modified silicone polymer, the amino-modified inorganic filler and the epoxy resin, and the chemical bond between the inorganic filler and the epoxy resin (adhesive) replaces the traditional van der Waals force, thereby enhancing the interaction between the inorganic filler molecules, reducing the movement of the inorganic filler molecules caused by the increase in external temperature, thereby improving the stability of the inorganic filler, and then improving the heat shrinkage resistance of the diaphragm.

[0057] The present application has no particular restrictions on the material of the base film, and any known base film with good chemical stability and mechanical stability can be selected. For example, the base film may include at least one of a porous polyolefin-based resin film (e.g., at least one of polyethylene, polypropylene, and polyvinylidene fluoride), a porous glass fiber, and a porous non-woven fabric. The base film may be a single-layer film or a multi-layer composite film. When the base film is a multi-layer composite film, the materials of each layer may be the same or different.

[0058] In some embodiments, the amino-modified silicone polymer, the amino-modified inorganic filler and the epoxy resin are bonded to form a three-dimensional network cross-linked structure in the coating through the reaction of the amino group and the epoxy group.

[0059] The three-dimensional network cross-linked structure refers to a network cross-linked structure composed of multiple cross-linked polymer chains in three-dimensional space. In the present application, the amino-modified organosilicon polymer, the amino functional group in the amino-modified inorganic filler and the epoxy functional group in the epoxy resin are bonded to form the three-dimensional network cross-linked structure, so that the organosilicon polymer, the inorganic filler and the epoxy resin are connected by chemical bonds, and the chemical bonds are not easy to break at high temperatures, thereby improving the stability of the organosilicon polymer, the inorganic filler and the epoxy resin at high temperatures, and further improving the heat resistance of the diaphragm.

[0060] In some embodiments, the mass ratio of the amino-modified silicone polymer, the amino-modified inorganic filler and the epoxy resin is (2-10):1800:(80-120), preferably, the mass ratio of the amino-modified silicone polymer, the amino-modified inorganic filler and the epoxy resin is (2-8):1800:(90-110), and more preferably (3-6):1800:100, for example, it can be 3:1800:100, 3.75:1800:100, 4:1800:100, 5:1800:100, 5.3:1800:100, 6:1800:100 or 8:1800:100, wherein the mass of the amino-modified silicone polymer is based on the mass of the raw material KH550 / KH560 added in the preparation of the amino-modified silicone polymer.

[0061] In some embodiments, the amino-modified silicone polymer includes an amino-modified silicone pressure-sensitive adhesive.

[0062] In some embodiments, the amino-modified inorganic filler includes at least one of silane-modified alumina, silane-modified boehmite, silane-modified magnesium hydroxide, silane-modified silica, silane-modified titanium dioxide, silane-modified zirconia, silane-modified hydrotalcite, and silane-modified montmorillonite. Preferably, the amino-modified inorganic filler is silane-modified boehmite.

[0063] In some embodiments, the epoxy resin includes a bisphenol A epoxy resin, and the type of the bisphenol A epoxy resin includes at least one of E-20, E-21, E-42, E-44, E-51 and E-54.

[0064] In some embodiments, the coating further comprises a curing agent, and the curing agent comprises an amine curing agent. In the present application, the curing agent can cure and harden the coating in the coating, and can form a relatively hard protective film after the coating is cured for a certain period of time. At the same time, the curing agent can also increase the hardness and wear resistance of the coating, improve the adhesion and chemical resistance of the coating, and extend the service life of the coating.

[0065] In some embodiments, the amine curing agent includes at least one of aliphatic amine, modified alicyclic amine curing agent, cardanol modified aliphatic amine curing agent and polyamide curing agent. Preferably, the amine curing agent includes aliphatic amine, more preferably polyamine, and even more preferably ethylenediamine.

[0066] In some embodiments, the thickness of the coating is 1 to 6 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or 6 μm. The coating of the present application can significantly improve the heat resistance of the separator, thereby allowing a thinner porous base film to be selected, thereby helping to improve the energy density of the secondary battery.

[0067] In some embodiments, the longitudinal heat shrinkage of the separator at 150° C. for 1 h is 0.80% to 1.10% (for example, 0.91%, 0.94%, 0.98%, 1.02% or 1.07%).

[0068] In some embodiments, the transverse heat shrinkage of the separator at 150° C. for 1 h is 0.40% to 0.60% (for example, 0.41%, 0.44%, 0.51%, 0.53% or 0.56%).

[0069] The separator of the present application has low thermal shrinkage in both the transverse and longitudinal directions at a high temperature of 150° C., thereby improving the safety performance of the secondary battery.

[0070] In some embodiments, the adhesive strength of the diaphragm is 50-70 N / m (eg, 50 N / m, 54 N / m, 59 N / m, 63 N / m, or 68 N / m).

[0071] In some embodiments, the air permeability of the membrane is 160-190 s / 100 cc (for example, 162 s / 100 cc, 169 s / 100 cc, 175 s / 100 cc, 178 s / 100 cc, or 186 s / 100 cc).

[0072] The separator of the present application has good air permeability, thereby being able to improve ion conductivity and secondary battery capacity performance characteristics.

[0073] In the present application, the average particle size of a material has a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, a scanning electron microscope, a transmission electron microscope, or a particle size distribution instrument can be used to measure a material or a diaphragm to obtain an image, and a plurality of (e.g., more than 10) test particles can be randomly selected from the image, and the average value of the shortest diagonal length of the particles can be calculated as the average particle size.

[0074] In this application, the specific surface area of ​​a material has a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, it can be tested by nitrogen adsorption specific surface area analysis test method with reference to GB / T 19587-2017, and calculated by BET (Brunauer Emmett Teller) method. Alternatively, the nitrogen adsorption specific surface area analysis test can be performed by Tri-Star 3020 specific surface area pore size analysis tester of Micromeritics, USA.

[0075] In the present application, the heat shrinkage rate, bonding strength and air permeability of the separator have the meanings known in the art and can be measured by methods known in the art. For example, they can all be tested with reference to the standard GB / T36363-2018.

[0076] It should be noted that the coating parameters (such as thickness, etc.) of the above-mentioned diaphragm are the coating parameters of one side of the base film. When the coating is provided on both sides of the base film, the coating parameters on either side satisfy the present application and are considered to fall within the protection scope of the present application.

[0077] Preparation method

[0078] A method for preparing a battery separator comprises the following steps: S1, preparing a slurry, mixing an amino-modified silicone polymer, an amino-modified inorganic filler and an epoxy resin in a solvent in a predetermined proportion to prepare a slurry; S2, coating the slurry on at least one (may be one or two) surfaces of a base film to form a coating and drying to obtain a separator.

[0079] In some embodiments, in step S1, the solvent includes at least one of xylene, n-butanol, methyl isobutyl ketone, butanone, acetone, tetrahydrofuran, butyl acetate and ethyl acetate.

[0080] In some embodiments, in step S1, the slurry further includes a curing agent, and the mass ratio of the curing agent to the epoxy resin is (6-10): (60-120), preferably, the mass ratio of the curing agent to the epoxy resin is (7-9): (90-110), and more preferably (7-9): 100, for example, it can be 8: 100, 8: 110, 8: 120, 6: 100, 6: 110 or 6: 120. Optionally, the mass ratio of the curing agent to the epoxy resin is 8: 100.

[0081] In some embodiments, in step S1, the preparation method of the amino-modified silicone polymer includes: S11, after mixing the materials containing the coupling agent and the solvent, adjusting the pH of the mixed solution to 2-4, preferably, pH=3, and raising the temperature of the mixed solution to 40-80°C, preferably, the temperature of the mixed solution to 60°C, reacting by condensation reflux for 4-8h, and then distilling under reduced pressure at 50-80°C to obtain polysiloxane; S12, mixing the polysiloxane and the silicone polymer according to a preset ratio, reacting at 90-120°C for 2-5h, and then adding a polymer initiator, and reacting for 0.5-3h to obtain the amino-modified silicone polymer.

[0082] In the present application, coupling agent KH-550 or coupling agent KH560 is firstly hydrolyzed to obtain polysiloxane, and then hydroxyl-terminated silicone rubber, silicone resin and polymer initiator are added to react to obtain amino-modified silicone pressure-sensitive adhesive solution.

[0083] In some embodiments, the mass ratio of polysiloxane to silicone polymer is (2-8): (80-220), preferably, the mass ratio of polysiloxane to silicone polymer is (2-6): (80-120), and more preferably (2-5): (90-110), for example, it can be 2:90, 3:90, 4:90, 5:90, 2:100, 3:100, 4:100, 5:100, 2:110, 3:110, 4:110 or 5:110. In S12, the silicone polymer includes at least one (one or two) of terminal hydroxyl silicone rubber and silicone resin. The number average molecular weight of the terminal hydroxyl silicone rubber is 50,000 to 200,000 (for example, it can be 50,000, 80,000, 100,000, 120,000, 140,000, 160,000, 180,000, 200,000), preferably 80,000 to 150,000, and more preferably 100,000. The silicone resin is a polyalkyl silicone resin, preferably a polymethyl silicone resin, and more preferably a methyl MQ resin. The number average molecular weight of the methyl MQ resin is 1000 to 8000 (for example, 1000, 2000, 3000, 4000, 5000, 6000, 7000 or 8000), preferably 1000 to 5000, and more preferably 2000. The M / Q value of the methyl MQ resin is 0.2 to 1 (for example, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1), preferably 0.2 to 0.8, and more preferably 0.6. The solvent is xylene, and the polymer initiator is a free radical initiator, more preferably a peroxide initiator, and even more preferably BPO. In S12, in order to better obtain an amino-modified silicone polymer, the silicone polymer and polysiloxane can be dissolved in a solvent, reacted at a preset temperature for a preset time, and then a solution containing a polymer initiator is added, and the reaction is continued to obtain an amino-modified silicone pressure-sensitive adhesive solution. At this time, the mass ratio of polysiloxane, terminal hydroxyl silicone rubber and silicone resin is: (2-10): (30-100): (50-130), preferably, the mass ratio of polysiloxane, terminal hydroxyl silicone rubber and silicone resin is: (2-8): (30-80): (50-130), more preferably (3-6): (40-80): (60-120), for example, it can be 2:40:60, 3:40:60, 3.75:40:60, 4:40:60, 5:40:60, 5.3:70:105, 6:60:90, 6:80:120.

[0084] In some embodiments, it is more preferred that the diaphragm has better bonding strength and smaller thermal shrinkage value (MD and TD), and the mass ratio of polysiloxane, terminal hydroxyl silicone rubber and silicone resin is: (2-10): (30-100): (90-130), preferably (5-6): (60-80): (105-120).

[0085] In some embodiments, it is more preferred that the diaphragm has a lower permeability value, and the mass ratio of polysiloxane, terminal hydroxyl silicone rubber and silicone resin is: (2-10): (30-80): (60-80), preferably (3-4): (40-50): (60-80).

[0086] In some embodiments, it is more preferred that the diaphragm has a lower air permeability, a higher bonding strength and a smaller thermal shrinkage value (MD and TD), and the mass ratio of polysiloxane, terminal hydroxyl silicone rubber and silicone resin is: (4-8): (30-80): (70-100), preferably 6:60:90.

[0087] In some embodiments, in step S1, the preparation method of the amino-modified inorganic filler includes: S13, mixing the inorganic filler, the coupling agent and the solvent according to a preset ratio, reacting at 40-70°C for 20-50 minutes, and then reacting at 120-170°C for 10-30 minutes to obtain the amino-modified inorganic filler.

[0088] In some embodiments, the mass ratio of the inorganic filler to the coupling agent is 1800:(15-20) (for example, 1800:15, 1800:16, 1800:17, 1800:18, 1800:19 or 1800:20), preferably 1800:(16-19).

[0089] In S13, in order to better obtain the amino-modified inorganic filler, the inorganic filler and the solvent may be fully mixed first, and then a preset content of the coupling agent may be added.

[0090] In some embodiments, the coupling agent includes KH-550 and / or KH560.

[0091] In some embodiments, in coating, the coating method includes roller coating or spray coating.

[0092] In some embodiments, during coating, the thickness of the base film is not limited and can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or 16 μm.

[0093] In some embodiments, during coating, the coating vehicle speed is 40 to 150 m / min, for example, it can be 40 m / min, 50 m / min, 60 m / min, 70 m / min, 80 m / min, 90 m / min, 100 m / min, 110 m / min, 120 m / min, 130 m / min, 140 m / min or 150 m / min.

[0094] In some embodiments, the winding method can be at least one of PET release film winding, deviation correction winding, adhesive strip winding, and winding after slitting.

[0095] Some parameters such as raw materials and their contents used in the preparation method of the diaphragm of the present application can refer to the diaphragm of the embodiment of the present application, and will not be repeated here.

[0096] Secondary battery

[0097] A secondary battery comprises the battery separator mentioned above or the battery separator prepared by the preparation method mentioned above.

[0098] Secondary batteries, also known as rechargeable batteries or storage batteries, refer to batteries that can be recharged to activate active materials and continue to be used after the battery is discharged. Generally, secondary batteries include electrode assemblies and electrolytes. The electrode assemblies include positive electrode sheets, negative electrode sheets, and separators. The separators are arranged between the positive electrode sheets and the negative electrode sheets, and mainly play the role of preventing the positive and negative electrodes from short-circuiting, while allowing active ions to pass through.

[0099] The present application has no particular limitation on the type of secondary battery. For example, the secondary battery may be a lithium ion battery, a sodium ion battery, etc. In particular, the secondary battery may be a lithium ion secondary battery.

[0100] The secondary battery of the present application includes a diaphragm of an embodiment of the present application or a diaphragm prepared by a method of an embodiment of the present application, wherein the diaphragm is spaced between the positive electrode sheet and the negative electrode sheet. Optionally, at least one side of the diaphragm close to the negative electrode sheet has a coating of the present application. Thus, the secondary battery of the present application can take into account high energy density, high thermal safety performance and long service life.

[0101]

Positive electrode

[0102] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material. For example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0103] When the secondary battery of the present application is a lithium-ion battery, the positive electrode active material may include but is not limited to at least one of a lithium-containing transition metal oxide, a lithium-containing phosphate and their respective modified compounds. Examples of the lithium transition metal oxide may include but are not limited to at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and their respective modified compounds. Examples of the lithium-containing phosphate may include but are not limited to at least one of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon and their respective modified compounds.

[0104] As an example, the positive electrode active material for lithium ion batteries may include LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.85 Co 0.15 Al 0.05 At least one of O2, LiFePO4, and LiMnPO4.

[0105] When the secondary battery of the present application is a sodium ion battery, the positive electrode active material may include but is not limited to at least one of sodium-containing transition metal oxides, polyanion materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian blue materials.

[0106] As an example, the positive electrode active material for sodium ion batteries may include NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, NaNi 1 / 2 Ti 1 / 2 O2、NaNi 1 / 2 Mn 1 / 2 O2、Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2、NaNi 1 / 3 Co 1 / 3 Mn 1 / 3At least one of O2, NaFePO4, NaMnPO4, NaCoPO4, and Prussian blue materials.

[0107] In the present application, the modified compound of each positive electrode active material mentioned above may be a compound obtained by doping and / or surface coating the positive electrode active material.

[0108] In some embodiments, the positive electrode film layer may further include a positive electrode conductive agent. The present application has no particular restrictions on the type of the positive electrode conductive agent. As an example, the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. In some embodiments, based on the total mass of the positive electrode film layer, the mass percentage of the positive electrode conductive agent is ≤5%.

[0109] In some embodiments, the positive electrode film layer may also optionally include a positive electrode binder. The present application has no particular restrictions on the type of the positive electrode binder. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylic resin. In some embodiments, based on the total mass of the positive electrode film layer, the mass percentage of the positive electrode binder is ≤5%.

[0110] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0111] The positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder and any other components in a solvent and stirring them uniformly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0112]

Negative electrode

[0113] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material. For example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0114] The negative electrode active material may be a negative electrode active material for a secondary battery known in the art. As an example, the negative electrode active material may include but is not limited to at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based film material, tin-based film material and lithium titanate. The silicon-based film material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite and silicon alloy material. The tin-based film material may include at least one of elemental tin, tin oxide and tin alloy material.

[0115] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. The present application has no particular restrictions on the type of the negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the total mass of the negative electrode film layer, the mass percentage of the negative electrode conductive agent is ≤5%.

[0116] In some embodiments, the negative electrode film layer may also optionally include a negative electrode binder. The present application has no particular restrictions on the type of the negative electrode binder. As an example, the negative electrode binder may include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA) and carboxymethyl chitosan (CMCS). In some embodiments, based on the total mass of the negative electrode film layer, the mass percentage of the negative electrode binder is ≤5%.

[0117] In some embodiments, the negative electrode film layer may further include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc. In some embodiments, based on the total mass of the negative electrode film layer, the mass percentage of the other additives is ≤2%.

[0118] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0119] The negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional auxiliary agents in a solvent and stirring them uniformly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0120] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate described in the present application also includes a conductive primer layer (for example, composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In some other embodiments, the negative electrode plate described in the present application also includes a protective layer covering the surface of the negative electrode film layer.

[0121]

Electrolyte

[0122] During the charge and discharge process of the secondary battery, active ions are embedded and released back and forth between the positive electrode and the negative electrode, and the electrolyte plays a role in conducting active ions between the positive electrode and the negative electrode. The present application has no particular restrictions on the type of electrolyte, which can be selected according to actual needs.

[0123] The electrolyte solution includes an electrolyte salt and a solvent. The types of the electrolyte salt and the solvent are not specifically limited and can be selected according to actual needs.

[0124] When the secondary battery of the present application is a lithium ion battery, as an example, the electrolyte salt may include but is not limited to at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0125] When the secondary battery of the present application is a sodium ion battery, as an example, the electrolyte salt may include but is not limited to at least one of sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalatoborate (NaDFOB), sodium dioxalatoborate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluorobis(oxalatophosphate) (NaDFOP) and sodium tetrafluorooxalatophosphate (NaTFOP).

[0126] As an example, the solvent may include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE).

[0127] In some embodiments, the electrolyte may further include additives, for example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, additives that improve battery low temperature power performance, etc.

[0128] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be made into an electrode assembly through a winding process and / or a lamination process.

[0129] In some embodiments, the secondary battery may include an outer package, which may be used to package the electrode assembly and the electrolyte.

[0130] In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).

[0131] The preparation method of the secondary battery of the present application is well known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte can be assembled to form a secondary battery. As an example, the positive electrode sheet, the separator and the negative electrode sheet can be formed into an electrode assembly through a winding process and / or a lamination process, and the electrode assembly is placed in an outer package, and the electrolyte is injected after drying, and a secondary battery is obtained through vacuum packaging, standing, forming, shaping and other processes.

[0132] In some embodiments of the present application, the secondary batteries according to the present application can be assembled into a battery module. The battery module can contain multiple secondary batteries, and the specific number can be adjusted according to the application and capacity of the battery module.

[0133] Electrical devices

[0134] An electrical device, comprising the above-mentioned secondary battery. The electrical device comprises at least one of the secondary battery, battery module or battery pack of the present application. The secondary battery, battery module or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0135] Example 1

[0136] (1) Preparation of amino-modified silicone polymers

[0137] ① Use acetic acid to prepare a solution with a pH of 3 by adding 0.3 parts by mass of water.

[0138] ② Add 3 parts by mass of KH-550 and 4.5 parts by mass of tetrahydrofuran to the aqueous acetic acid solution in ①, stir evenly and heat to 60°C, and condense and reflux for 6 hours.

[0139] ③ After the reaction is completed, distill under reduced pressure at 65°C to remove the solvent and water to obtain a viscous liquid polysiloxane.

[0140] ④ Dissolve the prepared polysiloxane, 40 parts by mass of terminal hydroxyl silicone rubber (number average molecular weight 100,000) and 60 parts by mass of methyl MQ resin (number average molecular weight 2000, M / Q value: 0.6) in 40 parts by mass of xylene and stir in a reactor at 110°C for 3 hours.

[0141] ⑤ Add a solution containing 1.5 parts by mass of BPO dissolved in 3.5 parts by mass of xylene and stir for 1 hour to obtain an amino-modified silicone pressure-sensitive adhesive solution.

[0142] (2) Preparation of amino-modified inorganic fillers

[0143] 1800 parts by mass of boehmite was placed in deionized water, stirred and dispersed evenly, and then 17 parts by mass of KH-550 was added. After reacting at 60°C for 30 minutes, the temperature was raised to 150°C, and the reaction was continued for 15 minutes. The filtered product was then placed in an oven and dried at 110°C for 4 hours. After being ground into powder, silane-modified boehmite was obtained.

[0144] (3) The amino-modified silicone pressure-sensitive adhesive solution obtained in step (1), the silane-modified boehmite obtained in step (2), 100 parts by mass of E-51, and 8 parts by mass of ethylenediamine curing agent are added to 2500 parts by mass of a mixed solvent (a solution with a mass ratio of xylene to n-butanol of 7:3), and stirred evenly to obtain a self-stratifying slurry.

[0145] (4) The self-stratified slurry obtained in step (3) is double-sidedly coated on a 7 μm PE base film by roller coating using a double-release and double-retracting double-sided coating line, and finally dried (the solvent is condensed and refluxed for reuse) to form a coating. The coating speed is 100 m / min, the coating thickness is 2 μm, and a PET release film is used for rewinding to prevent the diaphragm from sticking.

[0146] The EDS spectrometer was used to detect the silicon content on the upper and lower surfaces of the coating, where V1>V2.

[0147] Example 2-5, Comparative Example 1-2

[0148] The experimental steps of Examples 2-5 and Comparative Examples 1-2 are basically the same as those of Example 1, except that the mass fractions of the coupling agent in step (1) and step (2), and the hydroxyl-terminated silicone rubber and methyl MQ resin in step (1) are different, as shown in Table 1.

[0149] Table 1: Formula mass fraction and coating speed table

[0150]

[0151] Data Analysis:

[0152] 1. Air permeability test method: Use a digital Wangyan air permeability tester to test the air permeability of the diaphragm.

[0153] 2. Heat shrinkage test method: Take a 15cm*15cm block diaphragm, mark it as MD along the coating direction, mark it as TD in the vertical direction, draw two perpendicular line segments in the MD and TD directions, and record the length as L0 and T0. Place the sample flat on two A4 papers and put it in an oven, and keep it at 150℃ for 1h. Take out the sample after heating, and test the length of the two line segments in the MD and TD directions after returning to room temperature, and record the length as L1 and T1. The formula for calculating the heat shrinkage of the diaphragm is as follows: MD%=(L0-L1) / L0*100%, TD%=(T0-T1) / T0*100%.

[0154] 3. Adhesion strength test method: First, fold the coated surface together, then use A4 paper to clamp the coated film and send it into the laminator. The laminator temperature is 100℃ and the speed is set to 1. After that, use a 2.5cm×30cm tooling mold to cut the sample, and finally test it on a tensile test machine at a speed of 50mm / min. The average value is taken after three tests.

[0155] The test results are shown in Table 2:

[0156] Table 2

[0157]

[0158]

[0159] By comparing Examples 1-5, it can be found that as the mass fraction of silicone increases, the bonding performance becomes greater and greater, and finally remains unchanged, the heat resistance is also improved to a certain extent, but the air permeability becomes worse and worse. This is because the enrichment degree of the silicone pressure-sensitive adhesive in the upper layer is constantly increasing, and the support becomes stronger, but too much adhesive will cause pore blockage, which reduces the air permeability of the diaphragm.

[0160] By comparing Example 1 and Comparative Example 1, it can be found that when the coating vehicle speed reaches 180 m / min, the slurry has no time to be stratified due to the too fast drying speed, and the silicone resin cannot be enriched in the upper layer, and the bonding strength is greatly reduced.

[0161] Comparing Example 1 and Comparative Example 2, the non-crosslinked separator without KH550 modification has a substantially unchanged adhesive property, but a significantly reduced heat resistance because the coating layer has no support from crosslinking points, and the supporting effect on the base film is also reduced.

[0162] The above is only a specific implementation of the present application. Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working processes of the systems, modules and units described above can refer to the corresponding processes in the aforementioned method embodiments, and will not be repeated here. It should be understood that the protection scope of the present application is not limited to this. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in this application, and these modifications or replacements should be included in the protection scope of this application.

Claims

1. A battery separator, comprising a base film and a coating disposed on at least one surface of the base film, It is characterized in that The coating is obtained by coating the slurry once, wherein the slurry comprises an amino-modified organic silicon polymer, an amino-modified inorganic filler and an epoxy resin, and the content of the amino-modified organic silicon polymer on the surface of the coating is denoted as V. 1 , the content on the lower surface of the coating is recorded as V 2 , V 1 >V 2 .

2. The battery separator according to claim 1, It is characterized in that The amino-modified organic silicon polymer, the amino-modified inorganic filler and the epoxy resin are bonded to form a three-dimensional network cross-linked structure in the coating layer through the reaction of amino groups and epoxy groups.

3. The battery separator according to claim 1, It is characterized in that The mass ratio of the amino-modified organosilicon polymer, the amino-modified inorganic filler and the epoxy resin is (2-10):1800:(80-120); and / or, The amino-modified organosilicon polymer includes an amino-modified organosilicon pressure-sensitive adhesive; The amino-modified inorganic filler comprises at least one of silane-modified alumina, silane-modified boehmite, silane-modified magnesium hydroxide, silane-modified silica, silane-modified titania, silane-modified zirconia, silane-modified hydrotalcite and silane-modified montmorillonite; The epoxy resin includes bisphenol A epoxy resin, and the type of the bisphenol A epoxy resin includes at least one of E-20, E-21, E-42, E-44, E-51 and E-54.

4. The battery separator according to claim 1, It is characterized in that The coating further comprises a curing agent, and the curing agent comprises an amine curing agent; optionally, the amine curing agent comprises at least one of a fatty amine, a modified alicyclic amine curing agent, a cardanol-modified fatty amine curing agent and a polyamide curing agent.

5. The battery separator according to claim 1, It is characterized in that The coating has a thickness of 1 to 6 μm; The thickness of the upper surface of the coating is 0.1% to 20% of the thickness of the coating, and the thickness of the lower surface of the coating is 0.1% to 20% of the thickness of the coating.

6. The battery separator according to claim 1, It is characterized in that The diaphragm satisfies at least one of the following conditions (1) to (4): (1) The longitudinal heat shrinkage of the diaphragm at 150° C. for 1 hour is 0.80% to 1.10%; (2) The transverse heat shrinkage of the diaphragm at 150° C. for 1 hour is 0.40% to 0.60%; (3) The bonding strength of the diaphragm is 50 to 70 N / m; (4) The air permeability of the diaphragm is 160 to 190 s / 100 cc.

7. A method for preparing a battery separator, It is characterized in that The following steps are involved: preparing a slurry by mixing an amino-modified organic silicon polymer, an amino-modified inorganic filler and an epoxy resin in a solvent according to a predetermined ratio to prepare a slurry; The slurry is coated on at least one surface of a base film to form a coating layer and dried to obtain a battery separator.

8. The preparation method according to claim 7, It is characterized in that In preparing the slurry, the solvent includes at least one of xylene, n-butanol, methyl isobutyl ketone, butanone, acetone, tetrahydrofuran, butyl acetate and ethyl acetate; and / or, The slurry further includes a curing agent, and the mass ratio of the curing agent to the epoxy resin is (6-10): (60-120); and / or, In preparing the slurry, the preparation method of the amino-modified organosilicon polymer includes: After mixing the materials containing coupling agent and solvent, adjusting the pH of the mixed solution to 2-4, raising the temperature of the mixed solution to 40-80°C, reacting by condensation reflux for 4-8h, and then distilling under reduced pressure at 50-80°C to obtain polysiloxane; mixing the polysiloxane, organosilicon polymer and solvent according to a preset ratio, reacting at 90-120°C for 2-5h, adding a polymer initiator, and reacting for 0.5-3h to obtain the amino-modified organosilicon polymer; and / or, The mass ratio of the polysiloxane to the organosilicon polymer is (2-8):(80-220); and / or, The preparation method of the amino-modified inorganic filler comprises: The inorganic filler, coupling agent and solvent are mixed according to a preset ratio, reacted at 40-70° C. for 20-50 minutes, and then reacted at 120-170° C. for 10-30 minutes to obtain the amino-modified inorganic filler; and / or, The coupling agent includes KH-550 and / or KH560, and the mass ratio of the inorganic filler to the coupling agent is 1800:(15-20); and / or, In coating, the coating method includes roller coating or spray coating. 9 . A secondary battery comprising the battery separator according to claim 1 or the battery separator prepared by the preparation method according to claim 7 .

10. An electric device comprising the secondary battery according to claim 9.

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