A high temperature resistant diaphragm for lithium battery and preparation method thereof

Abstract

This application provides a high-temperature-resistant separator for lithium batteries and a method for preparing the same. The high-temperature-resistant separator comprises a polypropylene separator body; a first modified layer is disposed on one side of the polypropylene separator body; and a second modified layer is disposed on the other side of the polypropylene separator body. The first modified layer comprises the following raw materials: polyimide, cage-type polysilsesquioxane, aluminum oxide, and silica fiber; the second modified layer comprises the following raw materials: polyethylene terephthalate, arginine-modified carbon nanotubes, and zirconium oxide. By disposing the first and second modified layers on the surface of the polypropylene separator body, the separator's high-temperature resistance is enhanced.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and in particular to a high-temperature resistant diaphragm for lithium batteries and a preparation method thereof. Background Art

[0002] Lithium-ion batteries, with their high energy density, long lifespan, and lack of memory effect, are widely used in mobile phones, laptops, and electric vehicles. As their applications continue to expand, the safety of lithium-ion batteries is receiving increasing attention. Separators, as a crucial component of lithium-ion batteries, play a key role in ensuring their safety. Currently, commonly used polyolefin separators have a low melting point and poor thermal stability. If the battery temperature is too high, they can shrink or even melt, causing internal short circuits.

[0003] Application Contents

[0004] The present application has been made in view of the above-mentioned problems, and an object of the present application is to provide a high-temperature-resistant separator for a lithium battery, the separator having excellent high-temperature resistance.

[0005] Specifically as follows, the first aspect of the present application provides a high-temperature resistant diaphragm for a lithium battery, comprising a polypropylene diaphragm body;

[0006] A first modified layer is provided on one side of the polypropylene diaphragm body;

[0007] A second modified layer is provided on the other side of the polypropylene diaphragm body;

[0008] The first modified layer includes the following preparation materials:

[0009] polyimide, caged polysilsesquioxane, alumina, and silica fibers;

[0010] The second modified layer includes the following preparation materials:

[0011] Polyethylene terephthalate, arginine-modified carbon nanotubes, and zirconium oxide.

[0012] According to one of the technical solutions of this application, at least the following beneficial effects are achieved:

[0013] In the present application, a first modified layer and a second modified layer are provided on the polypropylene diaphragm film; the polyimide in the first modified layer and the polyethylene terephthalate in the second modified layer have excellent high temperature resistance, thereby improving the heat resistance of the diaphragm;

[0014] In this application, inorganic particles (zirconia, alumina and silica fibers) are added to the modified layer, and a porous modified layer is formed by the inorganic particles and the matrix polymer (polyimide or polyethylene terephthalate); at the same time, the rigidity of the inorganic particles in the porous modified layer is used to support the diaphragm, which enables the diaphragm to obtain excellent thermal stability; in this application, alumina particles and silica fibers are used to form a point-line network to further improve the thermal stability of the diaphragm; arginine-modified carbon nanotubes and zirconia are also used to form a point-line network to further improve the thermal stability of the diaphragm.

[0015] At the same time, the present application grafts arginine onto the surface of carbon nanotubes. The grafting of arginine can simultaneously introduce a large number of polar groups such as hydroxyl, carboxyl, and amide onto the surface of carbon nanotubes, which is beneficial to improving the dispersion of carbon nanotubes in the modified layer, thereby improving the stability of the point-line network; thereby further improving the thermal stability of the diaphragm.

[0016] In the present application, caged silsesquioxane is added to polyimide. The caged silsesquioxane has functional groups that can interact with amino groups, which can improve the dispersibility of the caged silsesquioxane in the polyimide, thereby promoting the dispersibility of inorganic particles in the polyimide and further improving the thermal stability of the separator.

[0017] According to some embodiments of the present application, the cage-type polysilsesquioxane is octamaleamic acid cage-type silsesquioxane.

[0018] According to some embodiments of the present application, the first modified layer includes the following raw materials in parts by weight:

[0019] 100 parts of polyimide, 4 to 6 parts of cage-type polysilsesquioxane, 1 to 3 parts of aluminum oxide and 2 to 4 parts of silicon dioxide fiber.

[0020] According to some embodiments of the present application, the raw materials for preparing the first modified layer further include a solvent.

[0021] According to some embodiments of the present application, the second modified layer includes the following raw materials in parts by weight:

[0022] 100 parts of polyethylene terephthalate, 10 to 20 parts of arginine-modified carbon nanotubes and 3 to 5 parts of zirconium oxide.

[0023] According to some embodiments of the present application, the raw materials for preparing the second modified layer further include a solvent.

[0024] According to some embodiments of the present application, the thickness of the polypropylene diaphragm body is 5 μm to 30 μm.

[0025] According to some embodiments of the present application, the thickness of the first modified layer is 1 μm to 4 μm.

[0026] According to some embodiments of the present application, the thickness of the second modified layer is 1 μm to 4 μm.

[0027] According to some embodiments of the present application, the arginine-modified carbon nanotubes include the following preparation raw materials:

[0028] Carbon nanotubes, nitric acid, thionyl chloride, and arginine.

[0029] According to some embodiments of the present application, the particle size of the aluminum oxide is 20 nm to 50 nm.

[0030] According to some embodiments of the present application, the silica fiber includes the following preparation raw materials:

[0031] PVA solution and silica sol.

[0032] According to some embodiments of the present application, the mass fraction of the PVA solution is 11% to 13%.

[0033] According to some embodiments of the present application, raw materials for preparing the silica sol include tetraethoxysilane and a catalyst.

[0034] According to some embodiments of the present application, the mass ratio of the PVA solution to the silica sol is 1:0.9 to 1.1.

[0035] The second aspect of the present application discloses a method for preparing the high-temperature resistant separator for a lithium battery according to the first aspect of the present application, comprising the following steps:

[0036] An electrostatic spinning method is adopted to form a first modified layer and a second modified layer on the surface of a polypropylene diaphragm body.

[0037] According to some embodiments of the present application, the method for preparing arginine-modified carbon nanotubes comprises the following steps:

[0038] S1, mixing carbon nanotubes and nitric acid solution and performing a hydrothermal reaction to prepare carboxylated carbon nanotubes;

[0039] S2, mixing the carboxylated carbon nanotubes and thionyl chloride and reacting them to obtain chlorinated carbon nanotubes;

[0040] S3, mixing the acyl chloride carbon nanotubes, arginine, dicyclohexylcarbodiimide and a solvent and reacting them.

[0041] According to some embodiments of the present application, the mass-to-volume ratio of the carbon nanotubes to the nitric acid solution is 1 g: 50 mL to 100 mL.

[0042] According to some embodiments of the present application, the temperature of the hydrothermal reaction in step S1 is 110°C to 130°C.

[0043] According to some embodiments of the present application, the mass-to-volume ratio of the carboxylated carbon nanotubes to thionyl chloride is 1 g: 100 mL to 200 mL.

[0044] According to some embodiments of the present application, the reaction temperature in step S2 is 80°C to 90°C.

[0045] According to some embodiments of the present application, the mass ratio of the chlorinated carbon nanotubes to arginine is 1:1-2.

[0046] According to some embodiments of the present application, the mass ratio of the chlorinated carbon nanotubes to dicyclohexylcarbodiimide is 1:0.2-0.3.

[0047] According to some embodiments of the present application, the reaction temperature in step S3 is 60°C to 70°C.

[0048] According to some embodiments of the present application, the spinning voltage selected in the electrospinning method is 5 kV to 10 kV. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present drawings or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present drawings. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0050] Figure 1 Schematic diagram of the cross-sectional structure of the high-temperature resistant diaphragm in the embodiment of the present application.

[0051] Description of Figure Numbers:

[0052] 100. Polypropylene diaphragm body; 101. First modified layer; 102. Second modified layer.

[0053] The purpose, features and advantages of this drawing will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is described and illustrated below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are merely used to explain this application and are not intended to limit this application. Based on the embodiments provided in this application, all other embodiments obtained by those of ordinary skill in the art without making any creative work are within the scope of protection of this application.

[0055] Obviously, the following descriptions are merely some examples or embodiments of the present application. Those skilled in the art can apply the present application to other similar scenarios without inventive effort. Furthermore, it is also understood that, although the effort involved in such a development process may be complex and lengthy, for those skilled in the art related to the content disclosed in the present application, changes in design, manufacturing, or production based on the technical content disclosed in the present application are merely conventional technical means and should not be construed as an insufficiency of the content disclosed in the present application.

[0056] However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters or repeated descriptions of substantially identical structures may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Furthermore, the following description is provided to enable those skilled in the art to fully understand this application and is not intended to limit the subject matter recited in the claims.

[0057] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0058] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0059] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this 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.

[0060] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating 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), indicating 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.

[0061] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0062] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0063] The properties of some raw materials in this application are as follows:

[0064] Carbon nanotubes, aspect ratio 10-30, inner diameter 10nm-20nm;

[0065] Alumina, particle size 20nm~50nm;

[0066] The structural formula of octamaleamic acid cage-shaped silsesquioxane is as follows:

[0067]

[0068] Example 1

[0069] This embodiment is a high temperature resistant diaphragm for lithium batteries. The cross-sectional results are as follows: Figure 1 As shown, it includes a polypropylene diaphragm body 100 (Celgard2500, thickness of 25 μm);

[0070] A first modified layer 101 is provided on one side of the polypropylene diaphragm body 100;

[0071] The other side of the polypropylene diaphragm body 100 is provided with a second modified layer 102;

[0072] The first modified layer 101 includes the following raw materials:

[0073] 100 parts of polyimide (soluble polyimide, PY5006T, Suzhou Pinyu Optoelectronics Technology Co., Ltd.), 5 parts of cage-type polysilsesquioxane (octamaleamic acid cage-type silsesquioxane), 2 parts of aluminum oxide, and 3 parts of silica fibers;

[0074] The second modified layer 102 includes the following raw materials:

[0075] Polyethylene terephthalate (M W is 150,000) 100 parts, arginine-modified carbon nanotubes 15 parts and zirconium oxide (D50 is 30 nm) 4 parts.

[0076] The method for preparing a high-temperature resistant separator for a lithium battery in this embodiment comprises the following steps:

[0077] S1. Preparing a first modified slurry and a second modified slurry:

[0078] First modified slurry:

[0079] Polyimide, cage-type polysilsesquioxane, alumina, silica fiber, and solvent (N,N-dimethylacetamide (DMAC) and methylpyrrolidone (NMP) in a volume ratio of 8:2 and a mass ratio of solvent to polyimide of 5:1) were uniformly mixed to prepare a first modified slurry;

[0080] Second modified slurry:

[0081] Polyethylene terephthalate (PET)W is 150,000), arginine-modified carbon nanotubes, zirconium oxide and solvent (the volume ratio of trifluoroacetic acid to dichloromethane is 8:2; the mass ratio of polyethylene terephthalate to solvent is 1:5) to prepare a second modified slurry;

[0082] S2. The first modified slurry (4 mL) was attached to one side of a polypropylene diaphragm body (width 20 cm * length 30 cm) by electrospinning to obtain a first modified layer;

[0083] The spinning parameters are:

[0084] The relative humidity was 40% and the injection speed was 0.1 mm / min;

[0085] The spinning voltage was 8 KV, the receiving distance was 15 cm, and the temperature was 25°C.

[0086] The second modified slurry (4 mL) was attached to the other surface of the polypropylene separator body by electrospinning and placed at 25° C. for 48 h to obtain a high-temperature resistant separator for lithium batteries.

[0087] The spinning parameters are:

[0088] The relative humidity was 40% and the injection speed was 0.19 mm / min;

[0089] The spinning voltage was 9 KV, the receiving distance was 15 cm, and the temperature was 25°C.

[0090] The preparation method of silica fiber in this embodiment consists of the following steps:

[0091] S1, PVA ( PVA-210) was dissolved in water (the dissolution temperature was 90°C and the dissolution time was 3 h) to prepare a PVA solution (the mass fraction of the PVA solution was 12%);

[0092] TEOS (tetraethoxysilane), H3PO4, and H2O were mixed in a molar ratio of 1:0.01:11 and stirred at 25°C for 12 h to obtain SiO2 sol;

[0093] The PVA solution and SiO2 sol were mixed in a mass ratio of 1:1 and stirred at 1000 r / min for 4 h to obtain an electrospinning solution.

[0094] S2. The electrospinning solution is spun in an electrospinning machine. The parameters of the spinning process are as follows:

[0095] The relative humidity was 40% and the spinning solution injection speed was 0.05 mm / min;

[0096] The spinning voltage was 17 kV, the receiving distance was 25 cm, and the temperature was 25°C.

[0097] After the spinning is completed, the spun product is placed in an oven at 80°C for 2 hours to dry out the moisture to obtain an electrospun product.

[0098] S3. High temperature calcination

[0099] The electrospun product was heated to 700°C at a heating rate of 1°C / min and kept warm for 3 h to obtain silica fibers.

[0100] Example 2

[0101] This embodiment is a high-temperature resistant separator for lithium batteries, which differs from Example 1 in that:

[0102] The first modified layer 101 includes the following raw materials:

[0103] 100 parts of polyimide (soluble polyimide, PY5006T, Suzhou Pinyu Optoelectronics Technology Co., Ltd.), 4 parts of cage-type polysilsesquioxane (octamaleamic acid cage-type silsesquioxane), 3 parts of aluminum oxide, and 2 parts of silica fibers;

[0104] The second modified layer 102 includes the following raw materials:

[0105] Polyethylene terephthalate (M W is 150,000) 100 parts, arginine-modified carbon nanotubes 10 parts and zirconium oxide (D50 is 30 nm) 5 parts.

[0106] The preparation method of the diaphragm in this embodiment is carried out with reference to Example 1.

[0107] Example 3

[0108] This embodiment is a high-temperature resistant separator for lithium batteries, which differs from Example 1 in that:

[0109] The first modified layer 101 includes the following raw materials:

[0110] 100 parts of polyimide (soluble polyimide, PY5006T, Suzhou Pinyu Optoelectronics Technology Co., Ltd.), 6 parts of cage-type polysilsesquioxane (octamaleamic acid cage-type silsesquioxane), 1 part of aluminum oxide, and 4 parts of silica fibers;

[0111] The second modified layer 102 includes the following raw materials:

[0112] Polyethylene terephthalate (M W is 150,000) 100 parts, arginine-modified carbon nanotubes 20 parts and zirconium oxide (D50 is 30 nm) 3 parts.

[0113] The preparation method of the diaphragm in this embodiment is carried out with reference to Example 1.

[0114] Example 4

[0115] This embodiment is a high-temperature resistant separator for lithium batteries, which differs from Example 1 in that:

[0116] The first modified layer 101 includes the following raw materials:

[0117] 100 parts of polyimide (soluble polyimide, PY5006T, Suzhou Pinyu Optoelectronics Technology Co., Ltd.), 6 parts of cage-type polysilsesquioxane (octamaleamic acid cage-type silsesquioxane), 3 parts of aluminum oxide, and 4 parts of silica fibers;

[0118] The second modified layer 102 includes the following raw materials:

[0119] Polyethylene terephthalate (M W is 150,000) 100 parts, arginine-modified carbon nanotubes 20 parts and zirconium oxide (D50 is 30 nm) 5 parts.

[0120] The preparation method of the diaphragm in this embodiment is carried out with reference to Example 1.

[0121] Example 5

[0122] This embodiment is a high-temperature resistant separator for lithium batteries, which differs from Example 1 in that:

[0123] The first modified layer 101 includes the following raw materials:

[0124] 100 parts of polyimide (soluble polyimide, PY5006T, Suzhou Pinyu Optoelectronics Technology Co., Ltd.), 4 parts of cage-type polysilsesquioxane (octamaleamic acid cage-type silsesquioxane), 1 part of aluminum oxide, and 2 parts of silica fibers;

[0125] The second modified layer 102 includes the following raw materials:

[0126] Polyethylene terephthalate (M W is 150,000) 100 parts, arginine-modified carbon nanotubes 10 parts and zirconium oxide (D50 is 30 nm) 3 parts.

[0127] The preparation method of the diaphragm in this embodiment is carried out with reference to Example 1.

[0128] Comparative Example 1

[0129] This comparative example is a separator for lithium batteries, which differs from Example 5 in that:

[0130] The first modified layer 101 includes the following raw materials:

[0131] 100 parts of polyimide (soluble polyimide, PY5006T, Suzhou Pinyu Optoelectronics Technology Co., Ltd.), 1 part of alumina and 2 parts of silica fiber.

[0132] The preparation method of the lithium battery separator in this comparative example consists of the following steps:

[0133] S1. Preparing a first modified slurry and a second modified slurry:

[0134] First modified slurry:

[0135] Polyimide, alumina, silica fiber, and solvent (N,N-dimethylacetamide (DMAC) and methyl pyrrolidone (NMP) in a volume ratio of 8:2 and a mass ratio of solvent to polyimide of 5:1) were uniformly mixed to prepare a first modified slurry;

[0136] Second modified slurry:

[0137] Polyethylene terephthalate (PET) W is 150,000), arginine-modified carbon nanotubes, zirconium oxide and solvent (the volume ratio of trifluoroacetic acid to dichloromethane is 8:2; the mass ratio of polyethylene terephthalate to solvent is 1:5) to prepare a second modified slurry;

[0138] S2. The first modified slurry (4 mL) was attached to one side of a polypropylene diaphragm body (width 20 cm * length 30 cm) by electrospinning to obtain a first modified layer;

[0139] The spinning parameters are:

[0140] The relative humidity was 40% and the injection speed was 0.1 mm / min;

[0141] The spinning voltage was 8 KV, the receiving distance was 15 cm, and the temperature was 25°C.

[0142] The second modified slurry (4 mL) was attached to the other surface of the polypropylene separator body by electrospinning and placed at 25° C. for 48 h to obtain a high-temperature resistant separator for lithium batteries.

[0143] The spinning parameters are:

[0144] The relative humidity was 40% and the injection speed was 0.19 mm / min;

[0145] The spinning voltage was 9 KV, the receiving distance was 15 cm, and the temperature was 25°C.

[0146] Comparative Example 2

[0147] This comparative example is a separator for lithium batteries, which differs from Example 5 in that:

[0148] The second modified layer 102 includes the following raw materials:

[0149] Polyethylene terephthalate (M W is 150,000) 100 parts and zirconium oxide (D50 is 30 nm) 3 parts.

[0150] The preparation method of the lithium battery separator in this comparative example consists of the following steps:

[0151] S1. Preparing a first modified slurry and a second modified slurry:

[0152] First modified slurry:

[0153] Polyimide, cage-type polysilsesquioxane, alumina, silica fiber, and solvent (N,N-dimethylacetamide (DMAC) and methylpyrrolidone (NMP) in a volume ratio of 8:2 and a mass ratio of solvent to polyimide of 5:1) were uniformly mixed to prepare a first modified slurry;

[0154] Second modified slurry:

[0155] Polyethylene terephthalate (PET) W is 150,000), zirconium oxide and solvent (the volume ratio of trifluoroacetic acid / dichloromethane is 8:2; the mass ratio of polyethylene terephthalate to solvent is 1:5) to prepare a second modified slurry;

[0156] S2. The first modified slurry (4 mL) was attached to one side of a polypropylene diaphragm body (width 20 cm * length 30 cm) by electrospinning to obtain a first modified layer;

[0157] The spinning parameters are:

[0158] The relative humidity was 40% and the injection speed was 0.1 mm / min;

[0159] The spinning voltage was 8 KV, the receiving distance was 15 cm, and the temperature was 25°C.

[0160] The second modified slurry (4 mL) was attached to the other surface of the polypropylene separator body by electrospinning and placed at 25° C. for 48 h to obtain a high-temperature resistant separator for lithium batteries.

[0161] The spinning parameters are:

[0162] The relative humidity was 40% and the injection speed was 0.19 mm / min;

[0163] The spinning voltage was 9 KV, the receiving distance was 15 cm, and the temperature was 25°C.

[0164] Comparative Example 3

[0165] This comparative example is a separator for lithium batteries, which differs from Example 5 in that:

[0166] The arginine-modified carbon nanotubes were replaced with carbon nanotubes.

[0167] The preparation method of the lithium battery separator in this comparative example consists of the following steps:

[0168] S1. Preparing a first modified slurry and a second modified slurry:

[0169] First modified slurry:

[0170] Polyimide, cage-type polysilsesquioxane, alumina, silica fiber, and solvent (N,N-dimethylacetamide (DMAC) and methylpyrrolidone (NMP) in a volume ratio of 8:2 and a mass ratio of solvent to polyimide of 5:1) were uniformly mixed to prepare a first modified slurry;

[0171] Second modified slurry:

[0172] Polyethylene terephthalate (PET) W is 150,000), carbon nanotubes, zirconium oxide and solvent (the volume ratio of trifluoroacetic acid to dichloromethane is 8:2; the mass ratio of polyethylene terephthalate to solvent is 1:5) to prepare a second modified slurry;

[0173] S2. The first modified slurry (4 mL) was attached to one side of a polypropylene diaphragm body (width 20 cm * length 30 cm) by electrospinning to obtain a first modified layer;

[0174] The spinning parameters are:

[0175] The relative humidity was 40% and the injection speed was 0.1 mm / min;

[0176] The spinning voltage was 8 KV, the receiving distance was 15 cm, and the temperature was 25°C.

[0177] The second modified slurry (4 mL) was attached to the other surface of the polypropylene separator body by electrospinning and placed at 25° C. for 48 h to obtain a high-temperature resistant separator for lithium batteries.

[0178] The spinning parameters are:

[0179] The relative humidity was 40% and the injection speed was 0.19 mm / min;

[0180] The spinning voltage was 9 KV, the receiving distance was 15 cm, and the temperature was 25°C.

[0181] Comparative Example 4

[0182] This comparative example is a separator for lithium batteries, which differs from Example 5 in that:

[0183] The silica fibers were replaced with silica powder (D50 of 30 nm).

[0184] The preparation method of the lithium battery separator in this comparative example consists of the following steps:

[0185] S1. Preparing a first modified slurry and a second modified slurry:

[0186] First modified slurry:

[0187] Polyimide, cage-type polysilsesquioxane, alumina, silica powder and solvent (N,N-dimethylacetamide (DMAC) and methylpyrrolidone (NMP) volume ratio of 8:2, solvent to polyimide mass ratio of 5:1) were mixed uniformly to prepare a first modified slurry;

[0188] Second modified slurry:

[0189] Polyethylene terephthalate (PET) W is 150,000), arginine-modified carbon nanotubes, zirconium oxide and solvent (the volume ratio of trifluoroacetic acid to dichloromethane is 8:2; the mass ratio of polyethylene terephthalate to solvent is 1:5) to prepare a second modified slurry;

[0190] S2. The first modified slurry (4 mL) was attached to one side of a polypropylene diaphragm body (width 20 cm * length 30 cm) by electrospinning to obtain a first modified layer;

[0191] The spinning parameters are:

[0192] The relative humidity was 40% and the injection speed was 0.1 mm / min;

[0193] The spinning voltage was 8 KV, the receiving distance was 15 cm, and the temperature was 25°C.

[0194] The second modified slurry (4 mL) was attached to the other surface of the polypropylene separator body by electrospinning and placed at 25° C. for 48 h to obtain a high-temperature resistant separator for lithium batteries.

[0195] The spinning parameters are:

[0196] The relative humidity was 40% and the injection speed was 0.19 mm / min;

[0197] The spinning voltage was 9 KV, the receiving distance was 15 cm, and the temperature was 25°C.

[0198] Comparative Example 5

[0199] This comparative example is a separator for lithium batteries, which differs from Example 5 in that:

[0200] The first modified layer 101 includes the following raw materials:

[0201] 100 parts of polyimide (soluble polyimide, PY5006T, Suzhou Pinyu Optoelectronics Technology Co., Ltd.), 1 part of alumina and 2 parts of silica fiber;

[0202] The second modified layer 102 includes the following raw materials:

[0203] Polyethylene terephthalate (M W is 150,000) 100 parts and zirconium oxide (D50 is 30 nm) 3 parts.

[0204] The preparation method of the lithium battery separator in this comparative example consists of the following steps:

[0205] S1. Preparing a first modified slurry and a second modified slurry:

[0206] First modified slurry:

[0207] Polyimide, alumina, silica fiber, and solvent (N,N-dimethylacetamide (DMAC) and methyl pyrrolidone (NMP) in a volume ratio of 8:2 and a mass ratio of solvent to polyimide of 5:1) were uniformly mixed to prepare a first modified slurry;

[0208] Second modified slurry:

[0209] Polyethylene terephthalate (PET) W is 150,000), zirconium oxide and solvent (the volume ratio of trifluoroacetic acid / dichloromethane is 8:2; the mass ratio of polyethylene terephthalate to solvent is 1:5) to prepare a second modified slurry;

[0210] S2. The first modified slurry (4 mL) was attached to one side of a polypropylene diaphragm body (width 20 cm * length 30 cm) by electrospinning to obtain a first modified layer;

[0211] The spinning parameters are:

[0212] The relative humidity was 40% and the injection speed was 0.1 mm / min;

[0213] The spinning voltage was 8 KV, the receiving distance was 15 cm, and the temperature was 25°C.

[0214] The second modified slurry (4 mL) was attached to the other surface of the polypropylene separator body by electrospinning and placed at 25° C. for 48 h to obtain a high-temperature resistant separator for lithium batteries.

[0215] The spinning parameters are:

[0216] The relative humidity was 40% and the injection speed was 0.19 mm / min;

[0217] The spinning voltage was 9 KV, the receiving distance was 15 cm, and the temperature was 25°C.

[0218] The performance of the diaphragms prepared in the above examples and comparative examples was tested, and the results are shown in Table 1. The test items are as follows:

[0219] Membrane rupture temperature:

[0220] The membrane rupture temperature is measured by the resistance mutation method, and the point where the resistance suddenly increases is the membrane rupture temperature;

[0221] Heat shrinkage test:

[0222] Cut the membrane to be tested into a 3cm×3cm square test sample and sandwich the sample between two glass sheets. Heat the oven to the set temperature (200℃) and keep it warm for 30 minutes. Place the sample in the oven and heat for 30 minutes. The shrinkage rate is calculated using the following equation:

[0223] Thermal shrinkage (%) = 100 × (Ai - Af) / Ai;

[0224] where Ai and Af are the initial and final areas of the relevant diaphragm, respectively.

[0225] Table 1

[0226] - Membrane rupture temperature (℃) Thermal shrinkage (%) Example 1 293 0.12 Example 2 287 0.18 Example 3 280 0.21 Example 4 289 0.17 Example 5 276 0.23 Comparative Example 1 253 1.62 Comparative Example 2 257 1.53 Comparative Example 3 259 1.49 Comparative Example 4 268 0.56 Comparative Example 5 250 2.36

[0227] As can be seen from Table 1, the separators in Examples 1 to 5 have high rupture temperatures and low thermal shrinkage rates; they have excellent high-temperature resistance, which is beneficial to improving the safety performance of lithium batteries.

[0228] In Comparative Example 1, no cage-type polysilsesquioxane was added; the dispersion effect of the inorganic particles in the polyimide was poor, resulting in poor thermal stability of the separator.

[0229] In Comparative Example 2, no arginine-modified carbon nanotubes were added; a point-line thermal insulation network could not be constructed, resulting in poor thermal stability of the diaphragm.

[0230] In Comparative Example 3, the arginine-modified carbon nanotubes were replaced with carbon nanotubes; the dispersion effect of the inorganic particles was poor, resulting in poor thermal stability.

[0231] In Comparative Example 4, the silica fibers were replaced with silica powder; a point-line thermal insulation network could not be constructed, resulting in poor thermal stability of the diaphragm.

[0232] In Comparative Example 5, cage-type polysilsesquioxane and arginine-modified carbon nanotubes are not added; the dot-line thermal insulation network cannot be constructed in the second modified layer and the inorganic particles in the first modified layer are poorly dispersed, resulting in poor thermal stability of the diaphragm.

[0233] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A high temperature resistant separator for lithium batteries, characterized in that: including a polypropylene diaphragm body; A first modified layer is provided on one side of the polypropylene diaphragm body; A second modified layer is provided on the other side of the polypropylene diaphragm body; The first modified layer includes the following preparation materials: polyimide, caged polysilsesquioxane, alumina, and silica fibers; The second modified layer includes the following preparation materials: Polyethylene terephthalate, arginine-modified carbon nanotubes, and zirconium oxide.

2. The high temperature resistant separator for lithium batteries according to claim 1, characterized in that The first modified layer includes the following raw materials in parts by weight: 100 parts polyimide, 4 to 6 parts cage-type polysilsesquioxane, 1 to 3 parts alumina, and 2 to 4 parts silica fiber; And / or, the raw materials for preparing the first modified layer further include a solvent.

3. The high temperature resistant separator for lithium battery according to claim 1, characterized in that The second modified layer includes the following raw materials in parts by weight: 100 parts of polyethylene terephthalate, 10 to 20 parts of arginine-modified carbon nanotubes, and 3 to 5 parts of zirconium oxide; And / or, the raw materials for preparing the second modified layer further include a solvent.

4. The high temperature resistant separator for lithium battery according to claim 1, characterized in that The thickness of the polypropylene diaphragm body is 5 μm to 30 μm.

5. The high temperature resistant separator for lithium battery according to claim 1, characterized in that The arginine-modified carbon nanotubes include the following preparation raw materials: Carbon nanotubes, nitric acid, thionyl chloride, and arginine.

6. The high temperature resistant separator for lithium battery according to claim 1, characterized in that The particle size of the aluminum oxide is 20 nm to 50 nm.

7. The high temperature resistant separator for lithium battery according to claim 1, characterized in that The silica fiber comprises the following preparation raw materials: PVA solution and silica sol.

8. The high temperature resistant separator for lithium battery according to claim 7, characterized in that The mass fraction of the PVA solution is 11% to 13%.

9. The high temperature resistant separator for lithium battery according to claim 7, characterized in that: The raw materials for preparing the silica sol include tetraethoxysilane and a catalyst.

10. The high temperature resistant separator for lithium battery according to claim 7, characterized in that: The mass ratio of the PVA solution to the silica sol is 1:0.9-1.

1.

11. A method for preparing a high temperature resistant separator for a lithium battery according to any one of claims 1 to 10, characterized in that: The following steps are involved: An electrostatic spinning method is adopted to form a first modified layer and a second modified layer on the surface of a polypropylene diaphragm body.

12. The preparation method according to claim 11, characterized in that The preparation method of the arginine-modified carbon nanotubes comprises the following steps: S1, mixing carbon nanotubes and nitric acid solution and performing a hydrothermal reaction to prepare carboxylated carbon nanotubes; S2, mixing the carboxylated carbon nanotubes and thionyl chloride and reacting them to obtain chlorinated carbon nanotubes; S3, mixing the acyl chloride carbon nanotubes, arginine, dicyclohexylcarbodiimide and a solvent and reacting them.

13. The preparation method according to claim 12, characterized in that The mass volume ratio of the carbon nanotubes to the nitric acid solution is 1 g: 50 mL to 100 mL.

14. The preparation method according to claim 12, characterized in that The temperature of the hydrothermal reaction in step S1 is 110°C to 130°C.

15. The preparation method according to claim 12, characterized in that: The mass volume ratio of the carboxylated carbon nanotubes to thionyl chloride is 1 g: 100 mL to 200 mL.

16. The preparation method according to claim 12, characterized in that The reaction temperature in step S2 is 80°C to 90°C.

17. The preparation method according to claim 12, characterized in that The mass ratio of the acyl chloride carbon nanotubes to arginine is 1:1-2.

18. The preparation method according to claim 12, characterized in that: The mass ratio of the chlorinated carbon nanotubes to dicyclohexylcarbodiimide is 1:0.2-0.

3.

19. The preparation method according to claim 12, characterized in that: The reaction temperature in step S3 is 60°C to 70°C.

20. The preparation method according to claim 11, characterized in that The spinning voltage selected in the electrospinning method is 5kV~10kV.

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