High-strength low-moisture high-temperature-resistant battery separator and method of making same

Abstract

This invention discloses a high-strength, low-moisture, high-temperature resistant battery separator and its preparation method. The high-strength, low-moisture, high-temperature resistant battery separator comprises a base film and a coating layer applied to the base film. The coating layer is formed by applying a high-strength, low-moisture, high-temperature resistant slurry, wherein the high-strength, low-moisture, high-temperature resistant slurry comprises glass fiber, alumina, and a titanate coupling agent. This invention achieves the purpose of improving the needle penetration strength and adhesion of the separator, as well as reducing the thermal shrinkage and water content of the separator through the synergistic effect of glass fiber, alumina, and titanate coupling agent.

Description

Technical Field

[0001] This invention belongs to the field of battery separator technology, specifically relating to a high-strength, low-moisture, high-temperature resistant battery separator and its preparation method. Background Technology

[0002] With increasingly severe environmental problems, more and more new energy projects are attracting social attention, among which electric vehicles are particularly popular. As the power source for electric vehicles, the safety and lifespan of lithium-ion batteries are not only key research areas but also major concerns for people. Lithium battery separators play an important role in this process.

[0003] Based on the above, the safety and lifespan of lithium-ion batteries have become a major focus of attention. Conventional lithium battery separators are made of PP or PE, which have low heat resistance. While coating the separator with common inorganic ceramics (alumina, boehmite, silicon dioxide, etc.) can improve heat resistance, it also significantly increases water content, leading to the decomposition of lithium salts in the electrolyte. This results in a noticeable deterioration of the battery's chemical properties (such as capacity, internal resistance, and performance), and also affects battery safety. Furthermore, existing battery separators suffer from poor adhesion. Therefore, how to improve adhesion, reduce internal resistance, and enhance battery capacity and safety while ensuring the heat resistance of the battery separator is a pressing issue that needs to be addressed. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a high-strength, low-moisture, and high-temperature resistant slurry.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned high-strength, low-moisture, and high-temperature resistant slurry.

[0006] Another objective of this invention is to provide a high-strength, low-moisture, high-temperature resistant battery separator.

[0007] Another object of the present invention is to provide a method for preparing the above-mentioned high-strength, low-moisture, high-temperature resistant battery separator.

[0008] The objective of this invention is achieved through the following technical solution.

[0009] A high-strength, low-moisture, high-temperature resistant slurry comprises: glass fiber, alumina, and titanate coupling agent, wherein the ratio of glass fiber, alumina, and titanate coupling agent by mass parts is (2-3):(5-9):(3-6).

[0010] In the above technical solution, the titanate coupling agent is a monoalkoxy type, a monoalkoxy pyrophosphate type, an integrated type, or a ligand type.

[0011] The above technical solution also includes: a dispersant and water, wherein the ratio of alumina, dispersant and water by mass is (5-9):(0.1-0.5):(81.5-89.9).

[0012] In the above technical solution, the dispersant is ammonium polyacrylate, polyvinyl alcohol, or polyethylene glycol.

[0013] In the above technical solution, the particle size of the high-strength, low-moisture, and high-temperature resistant slurry is D50: 0.3-0.7 micrometers; D90: 1.0-1.5 micrometers.

[0014] A method for preparing a high-strength, low-moisture, and high-temperature resistant slurry includes: mixing glass fiber, alumina, water, titanate coupling agent, and dispersant until homogeneous to obtain the high-strength, low-moisture, and high-temperature resistant slurry, wherein, by mass parts, the ratio of glass fiber, alumina, water, titanate coupling agent, and dispersant is (2-3):(5-9):(81.5-89.9):(3-6):(0.1-0.5).

[0015] In the above technical solution, the preparation method includes the following steps:

[0016] Step 1: Mix the dispersant, water, glass fiber and alumina, stir first and then sonicate until homogeneous to obtain the first solution;

[0017] In step 1, the step of stirring and then sonicating until homogeneous includes: first stirring at a rotation speed of 1500-3100 r / min and a revolution speed of 20-50 r / min for 10-20 min, and then sonicating at an ultrasonic frequency of 10-50 kHz for 10-20 min.

[0018] Step 2: Mix the first solution with the titanate coupling agent, and simultaneously stir and sonicate under vacuum to obtain a high-strength, low-moisture, high-temperature resistant slurry.

[0019] In step 2, the time for simultaneous stirring and sonication in a vacuum environment is 10 to 20 minutes.

[0020] In step 2, the rotation speed of the stirring is 1000-3800 r / min, and the revolution speed is 20-40 r / min.

[0021] In step 2, the ultrasonic frequency of the ultrasound is 5 to 8 kHz.

[0022] In step 2, the vacuum level of the vacuum environment is 0.06 to 0.08 kPa.

[0023] A high-strength, low-moisture, high-temperature resistant battery separator includes: a base film and a coating applied to the base film, the coating being formed by applying a high-strength, low-moisture, high-temperature resistant slurry.

[0024] In the above technical solution, the thickness of the coating is 2 to 3 μm.

[0025] The method for preparing the above-mentioned high-strength, low-moisture, high-temperature resistant battery separator includes: coating the high-strength, low-moisture, high-temperature resistant slurry onto a base film, drying it, and obtaining the high-strength, low-moisture, high-temperature resistant battery separator.

[0026] In the above technical solution, the drying time is 1 to 3 minutes and the drying temperature is 50 to 70°C.

[0027] In the above technical solution, the coating speed is 30-50 m / min.

[0028] In the above technical solution, the base film is a PE film.

[0029] A high-strength, low-moisture, high-temperature resistant battery separator includes: a base film and a coating applied to the base film, wherein the coating comprises: glass fiber, alumina and titanate coupling agent, and the ratio of glass fiber, alumina and titanate coupling agent by mass is (2-3):(5-9):(3-6).

[0030] Applications of glass fiber, alumina and titanate coupling agents in diaphragms to improve diaphragm needle punching strength and / or adhesion.

[0031] Glass fiber, alumina and titanate coupling agents are used together in diaphragms to reduce heat shrinkage and / or diaphragm water content.

[0032] This invention employs a synergistic modification of titanate coupling agent, glass fiber, and alumina. Compared with existing methods, the advantages of this invention are as follows:

[0033] 1. The titanate coupling agent used in this invention can form flexural entanglement with the organic polymer (e.g., PE) in the base membrane, improve the compatibility between the organic polymer and inorganic materials (alumina and glass fiber), and form strong intermolecular forces on the surface of organic molecules and inorganic powders, thereby improving the impact resistance of the membrane, increasing the adhesion between the coating and the membrane, and improving the membrane adhesion.

[0034] Titanate coupling agents are substances with an amphoteric structure, and their general structural formula is (RO). m Ti(OX-RY) nSome groups in the molecule can react with chemical groups on inorganic surfaces to form chemical bonds, while other groups have organophilic properties and can react chemically with organic molecules or produce strong intermolecular interactions, thus firmly combining two materials with completely different properties and making them tightly bonded together. The phosphorous oxy group in the titanate coupling agent can provide antioxidant and flame-retardant properties, and by selecting OX-, the titanate can have both coupling and adhesive properties. The long carbon alkane group in the titanate coupling agent is relatively soft and can bend and entangle with organic polymers, thereby improving the compatibility of organic and inorganic materials and increasing the impact strength of the material.

[0035] 2. When alumina and glass fiber are mixed and bonded together, it is equivalent to a portion of the alumina surface being covered by glass fiber. This reduces the specific surface area of ​​alumina, and since glass fiber has lower water absorption than alumina, it indirectly reduces the specific surface area of ​​alumina in contact with air, thus reducing the water absorption of the coated membrane. After the titanate coupling agent is mixed with alumina and glass fiber, it coats the surfaces of alumina and glass fiber. Due to the good water resistance and thixotropic properties of the titanate coupling agent, the water content of the membrane is further reduced.

[0036] 3. Glass fiber has the advantages of high temperature resistance, non-combustibility, heat insulation and low water absorption. When mixed with alumina, it can increase the density of the membrane coating. At the same time, the titanate coupling agent can tightly bond the coating and the base membrane together, enhance the coating's support for the membrane, and further enhance the membrane's heat resistance. Attached Figure Description

[0037] Figure 1 SEM image of the high-strength, low-moisture, high-temperature resistant battery separator prepared in Example 4;

[0038] Figure 2 SEM image of the battery separator prepared in Comparative Example 6;

[0039] Figure 3 SEM image of the battery separator prepared in Comparative Example 7;

[0040] Figure 4 SEM image of the battery separator prepared in Comparative Example 8;

[0041] Figure 5 SEM image of the battery separator prepared in Comparative Example 9;

[0042] Figure 6 SEM image of the battery separator prepared for Comparative Example 10. Detailed Implementation

[0043] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0044] The drug purchase sources involved in the following examples are as follows:

[0045] Titanate coupling agent: Isopropyl tris(dioctylpyrophosphoryloxy)titanate;

[0046] Glass fiber: The length of the glass fiber is 0.5–1.8 μm and the width is 0.12–0.4 μm;

[0047] Acrylic ester copolymer: butyl acrylate;

[0048] Alumina silicate fiber: The length of the alumina silicate fiber is 0.5-1.8 μm and the width is 0.12-0.4 μm;

[0049] Silane coupling agent: aminopropyltrimethoxysilane;

[0050] Ammonium polyacrylate: polyacrylamide.

[0051] In the following examples, the water used is pure water.

[0052] In the following examples, the base film is a PE film with a thickness of 9 μm.

[0053] Peel strength (the peel strength is used to characterize the adhesion): Select a flat, high-strength, low-moisture, high-temperature resistant battery separator / battery separator, cut it into samples 30mm wide and 200mm long, and flatly attach a 200mm long piece of special adhesive tape to the coating surface of the sample. Use a standard roller to press the sample three times at a uniform speed, tear off one end, and use a tensile tester to perform a peel test to obtain the peel strength.

[0054] Example 1

[0055] A method for preparing a high-strength, low-moisture, and high-temperature resistant slurry includes the following steps:

[0056] Step 1: Mix the dispersant, water, glass fiber, and alumina in a mixer. First, stir at a rotation speed of 3100 r / min and a revolution speed of 20 r / min for 10 min, then sonicate at a frequency of 50 kHz for 15 min until homogeneous to obtain the first solution. By mass, the ratio of glass fiber, alumina, water, and dispersant is 2:8:84.8:0.2. The dispersant is ammonium polyacrylate, and the particle size of alumina is D50: 0.588 μm; D90: 1.256 μm.

[0057] Step 2: Mix the first solution and the titanate coupling agent in a mixer and simultaneously stir and sonicate for 15 minutes (high-speed dispersion) in a vacuum environment with ultrasonic oscillation function (vacuum degree of 0.07 kPa) to obtain a high-strength, low-moisture, and high-temperature resistant slurry. The rotation speed of the mixer is 1000 r / min, the revolution speed is 40 r / min, the ultrasonic frequency is 5 kHz, and the ratio of titanate coupling agent to alumina in the first solution is 5:8 by mass.

[0058] Example 2

[0059] A method for preparing a high-strength, low-moisture, and high-temperature resistant slurry includes the following steps:

[0060] Step 1: Mix the dispersant, water, glass fiber, and alumina in a mixer. First, stir at a rotation speed of 2000 r / min and a revolution speed of 30 r / min for 15 min, then sonicate at an ultrasonic frequency of 30 kHz for 15 min until homogeneous to obtain the first solution. By mass parts, the ratio of glass fiber, alumina, water, and dispersant is 2.5:7.5:84.8:0.2. The dispersant is ammonium polyacrylate, and the particle size of alumina is D50: 0.543 μm; D90: 1.208 μm.

[0061] Step 2: Mix the first solution and the titanate coupling agent in a mixer and simultaneously stir and sonicate for 15 minutes (high-speed dispersion) in a vacuum environment with ultrasonic oscillation function (vacuum degree of 0.07 kPa) to obtain a high-strength, low-moisture, and high-temperature resistant slurry. The rotation speed of the mixer is 2800 r / min, the revolution speed is 30 r / min, and the ultrasonic frequency is 6 kHz. By mass, the ratio of titanate coupling agent to alumina in the first solution is 5:7.5.

[0062] Example 3

[0063] A method for preparing a high-strength, low-moisture, and high-temperature resistant slurry includes the following steps:

[0064] Step 1: Mix the dispersant, water, glass fiber, and alumina in a mixer. First, stir at a rotation speed of 1500 r / min and a revolution speed of 50 r / min for 20 min, then sonicate at an ultrasonic frequency of 50 kHz for 15 min until homogeneous to obtain the first solution. By mass, the ratio of glass fiber, alumina, water, and dispersant is 3:7:84.8:0.2. The dispersant is ammonium polyacrylate, and the particle size of alumina is D50: 0.523 μm; D90: 1.298 μm.

[0065] Step 2: Mix the first solution and the titanate coupling agent in a mixer and simultaneously stir and sonicate for 15 minutes (high-speed dispersion) in a vacuum environment with ultrasonic oscillation function (vacuum degree of 0.07 kPa) to obtain a high-strength, low-moisture, and high-temperature resistant slurry. The rotation speed of the mixer is 3800 r / min, the revolution speed is 20 r / min, and the ultrasonic frequency is 8 kHz. By mass, the ratio of titanate coupling agent to alumina in the first solution is 5:7.

[0066] Comparative Example 1

[0067] A method for preparing a lithium battery slurry includes: mixing 5 parts by mass of alumina, 89.8 parts by mass of pure water, and 0.2 parts by mass of a dispersant; first mixing in a mixer at a rotation speed of 3100 r / min and a revolution speed of 20 r / min for 10 min; then sonicating at a frequency of 50 kHz for 15 min until homogeneous; adding 5 parts by mass of an adhesive; and simultaneously sonicating under stirring conditions (rotation speed of 1000 r / min and revolution speed of 40 r / min) (ultrasound frequency of 5 kHz) for 15 min to obtain the lithium battery slurry. The adhesive is an acrylate copolymer, the dispersant is ammonium polyacrylate, and the alumina particle size is D50: 0.499 μm; D90: 1.373 μm.

[0068] Comparative Example 2

[0069] A method for preparing a lithium battery slurry includes: mixing 2 parts by mass of glass fiber, 8 parts by mass of alumina, 84.8 parts by mass of pure water, and 0.2 parts by mass of dispersant; first mixing in a mixer at a rotation speed of 3100 r / min and a revolution speed of 20 r / min for 10 min; then sonicating at a frequency of 50 kHz for 15 min until homogeneous; adding 5 parts by mass of adhesive; and simultaneously sonicating under stirring conditions (rotation speed of 1000 r / min and revolution speed of 40 r / min) (ultrasound frequency of 5 kHz) for 15 min to obtain the lithium battery slurry. The adhesive is an acrylate copolymer, the dispersant is ammonium polyacrylate, and the alumina has a particle size of D50: 0.509 μm and D90: 1.433 μm.

[0070] Comparative Example 3

[0071] A method for preparing a lithium battery slurry includes: mixing 10 parts by mass of glass fiber, 84.8 parts by mass of pure water, and 0.2 parts by mass of dispersant; first mixing in a mixer at a rotation speed of 3100 r / min and a revolution speed of 20 r / min for 10 min; then sonicating at a frequency of 50 kHz for 15 min until homogeneous; adding 5 parts by mass of titanate coupling agent; and simultaneously sonicating under stirring conditions (rotation speed of 1000 r / min and revolution speed of 40 r / min) with ultrasonic vibration (ultrasonic frequency of 5 kHz) for 15 min to obtain the lithium battery slurry, wherein the dispersant is ammonium polyacrylate.

[0072] Comparative Example 4

[0073] A method for preparing a lithium battery slurry includes: mixing 10 parts by mass of alumina, 84.8 parts by mass of pure water, and 0.2 parts by mass of a dispersant; first mixing in a mixer at a rotation speed of 3100 r / min and a revolution speed of 20 r / min for 10 min; then sonicating at a frequency of 50 kHz for 15 min until homogeneous; adding 5 parts by mass of titanate coupling agent; and simultaneously sonicating under stirring conditions (rotation speed of 1000 r / min and revolution speed of 40 r / min) with ultrasonic vibration (ultrasonic frequency of 5 kHz) for 15 min to obtain the lithium battery slurry, wherein the dispersant is ammonium polyacrylate, and the particle size of the alumina is D50: 0.509 μm; D90: 1.433 μm.

[0074] Comparative Example 5

[0075] A method for preparing a lithium battery slurry is basically the same as the method for preparing a high-strength, low-moisture, and high-temperature resistant slurry in Example 2, except that "glass fiber" is replaced with "alumina silicate fiber" and "titanium ester coupling agent" is replaced with "silane coupling agent".

[0076] Examples 4-6 and Comparative Examples 6-10

[0077] A method for preparing a battery separator includes: placing a base film on a coating machine containing a slurry with a particle size of X micrometers; coating the base film with the slurry on one side at a speed of Am / min; after coating, drawing the slurry into a drying device via a traction roller; drying at B℃ for C minutes; and obtaining a coating with a thickness of D μm on the base film to obtain the battery separator. The slurry is one of the high-strength, low-moisture, high-temperature resistant slurries prepared in Examples 1-3 and the lithium battery slurries prepared in Comparative Examples 1-5. The battery separators obtained sequentially from the high-strength, low-moisture, high-temperature resistant slurries prepared in Examples 1-3 are the high-strength, low-moisture, high-temperature resistant battery separators of Examples 4-6, and the battery separators obtained sequentially from the lithium battery slurries prepared in Comparative Examples 1-5 are the Comparative Examples 6-10. The values ​​of A, B, C, D, and X are shown in Table 1.

[0078] Table 1

[0079]

[0080] The performance parameters of the high-strength, low-moisture, high-temperature resistant battery separator prepared in Example 4 are as follows:

[0081]

[0082]

[0083] The performance parameters of the high-strength, low-moisture, high-temperature resistant battery separator prepared in Example 5 are as follows:

[0084]

[0085] The performance parameters of the high-strength, low-moisture, high-temperature resistant battery separator prepared in Example 6 are as follows:

[0086]

[0087] The performance parameters of the battery separator prepared in Comparative Example 6 are as follows:

[0088]

[0089] The performance parameters of the battery separator prepared in Comparative Example 7 are as follows:

[0090]

[0091] The performance parameters of the battery separator prepared in Comparative Example 8 are as follows:

[0092]

[0093]

[0094] The performance parameters of the battery separator prepared in Comparative Example 9 are as follows:

[0095]

[0096] The performance parameters of the battery separator prepared in Comparative Example 10 are as follows:

[0097]

[0098] The separator obtained by coating the slurry after mixing alumina and glass fiber has the advantage of being hydrophobic by glass fiber itself, which can reduce the water content of the separator. However, those skilled in the art know that high water content will lead to the decomposition of lithium salt electrolyte in the battery, resulting in a significant deterioration of the chemical characteristics of the lithium battery, such as capacity, internal resistance, and product characteristics. This invention reduces the internal resistance of the lithium battery by reducing the water content of the separator, thereby improving its battery capacity and safety. After adding titanate coupling agent, the adhesion of the separator can be improved, making the structure between the coating and the base film more stable. At the same time, the addition of titanate coupling agent can improve the stability of the powder (the powder after mixing alumina and glass fiber) at high temperature, thereby improving the impact resistance of the separator.

[0099] Because aluminosilicate fibers have relatively high water absorption, titanate coupling agents offer better flame retardancy and improved impact resistance than silane coupling agents. Figures 1-6 It can be seen that the high-strength, low-moisture, high-temperature resistant battery separator prepared in Example 4 (synergistic modification with glass fiber, alumina, and titanate coupling agent) has higher density and stability than the battery separators prepared in Comparative Examples 6-10.

[0100] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A high-strength, low-moisture, high-temperature-resistant battery separator, characterized by, include: A base film and a coating applied to the base film, the coating being made of a high-strength, low-moisture, high-temperature resistant slurry, the high-strength, low-moisture, high-temperature resistant slurry comprising: glass fiber, alumina and titanate coupling agent, wherein the ratio of glass fiber, alumina and titanate coupling agent by mass parts is (2~3):(5~9):(3~6). A method for preparing a high-strength, low-moisture, and high-temperature resistant slurry includes: mixing glass fiber, alumina, water, titanate coupling agent, and dispersant until homogeneous to obtain a high-strength, low-moisture, and high-temperature resistant slurry, wherein, by mass parts, the ratio of glass fiber, alumina, water, titanate coupling agent, and dispersant is (2~3):(5~9):(81.5~89.9):(3~6):(0.1~0.5); When alumina and glass fiber are mixed and bonded together, the specific surface area of ​​alumina is reduced. When titanate coupling agent is mixed with alumina and glass fiber, it coats the surface of alumina and glass fiber, further reducing the water content of the membrane.

2. The high-strength, low-moisture, high-temperature-resistant battery separator of claim 1, wherein, The titanate coupling agent is of the monoalkoxy type, monoalkoxy pyrophosphate type, integrated type, or ligand type.

3. The high-strength, low-moisture, high-temperature-resistant battery separator of claim 2, wherein, The dispersant is ammonium polyacrylate, polyvinyl alcohol, or polyethylene glycol.

4. A method for preparing the high-strength, low-moisture, high-temperature resistant battery separator according to any one of claims 1 to 3, characterized in that, include: The high-strength, low-moisture, and high-temperature resistant slurry is coated onto a base film and dried to obtain a high-strength, low-moisture, and high-temperature resistant battery separator.

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