Lithium titanate coating lithium battery diaphragm and preparation method thereof

Abstract

The invention discloses a lithium titanate coating lithium battery diaphragm and a preparation method thereof, the lithium titanate coating lithium battery diaphragm comprises a base membrane and a coating on the base membrane, the coating comprises lithium titanate, a first substance and ethoxyamine hydrochloride, the first substance is at least one of ethylene propylene diene monomer, chloroprene rubber and vinyl ether acrylate, and the ethoxyamine hydrochloride is at least one of ethylene propylene diene monomer, chloroprene rubber and vinyl ether acrylate. The ratio of the lithium titanate to the first substance to the ethoxyamine hydrochloride in parts by mass is (5-20): (0.5-3.8): (0.1-1.5). The lithium titanate, the first substance and the ethoxyamine hydrochloride cooperate to improve the breakdown voltage, the ionic conductivity and the binding power of the diaphragm, and meanwhile, the moisture content and the electrostatic content of the diaphragm are reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery separators, and particularly relates to a lithium-ion battery separator with a lithium titanate coating and a preparation method thereof. Background Art

[0002] With the rapid development of social economy and the continuous improvement of people's demand for quality of life, relying on traditional fossil fuels for energy supply can no longer meet the actual production needs. It is necessary to find renewable clean energy that is environmentally friendly and inexpensive, and to design efficient energy storage devices. Since Sony released the first lithium-ion battery product (lithium cobalt oxide cathode with carbon anode) for small portable electronic devices in 1991, lithium-ion batteries with long cycle life and high energy density have attracted great attention in the industrial and academic fields, and have gradually been widely used in portable electronic devices, power tools, large and small robots, electric vehicles, stationary energy storage units, smart grids, etc. Currently, lithium resources are relatively abundant. The characteristics of lithium such as low reduction potential, light mass, and small ionic radius enable lithium-based batteries to have high battery potential, relatively high mass specific capacity, and relatively high power density. These advantages enable lithium-ion batteries to dominate consumer batteries, power batteries, and large-scale energy storage for many years to come.

[0003] In a lithium-ion battery, the separator is mainly used to separate the electrodes. Its microporous structure only allows lithium ions in the electrolyte to pass through (blocking electrons), realizing the transmission of lithium ions between the electrodes through the electrolyte. As the "third electrode" of a lithium-ion battery, the separator is a key material that ensures the safety of the battery system and affects the battery performance, and needs to have characteristics such as high strength, heat resistance, flame retardancy, high porosity, uniformity, low moisture, and good wettability. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a lithium-ion battery separator with a lithium titanate coating.

[0005] Another object of the present invention is to provide a preparation method of the above-mentioned lithium-ion battery separator with a lithium titanate coating.

[0006] Another object of the present invention is to provide a slurry.

[0007] The object of the present invention is achieved by the following technical solutions.

[0008] A lithium-ion battery separator with a lithium titanate coating includes: a base film and a coating on the base film. The coating includes: lithium titanate (LTO), a first substance, and ethoxyamine hydrochloride. The first substance is at least one of ethylene propylene diene monomer rubber, neoprene, and vinyl ether acrylate. By mass, the ratio of lithium titanate, the first substance, and ethoxyamine hydrochloride is (5 - 20):(0.5 - 3.8):(0.1 - 1.5).

[0009] In the above technical solution, the first substance is preferably ethylene propylene diene monomer (EPDM).

[0010] In the above technical solution, by mass parts, the ratio of lithium titanate, the first substance, and ethoxyamine hydrochloride is preferably (11 - 13):(1.5 - 3):(0.5 - 1.5).

[0011] In the above technical solution, the method for preparing lithium titanate includes the following steps:

[0012] Step 1: Mix the lithium source, titanium source, and the second solvent until homogeneous to obtain a dispersion liquid. Among them, by mole parts, the ratio of lithium in the lithium source to titanium in the titanium source is (4.2 - 4.8):(4.8 - 5.3);

[0013] In Step 1, the second solvent is one or a mixture of several of isopropanol, acetone, and absolute ethanol.

[0014] In Step 1, the lithium source is one or a mixture of two of lithium hydroxide and lithium carbonate.

[0015] In Step 1, the titanium source is one or a mixture of several of titanium dioxide, titanium tetrabromide, and tetrabutyl titanate.

[0016] In Step 1, the ratio of the mole parts of lithium in the lithium source to the mass parts of the second solvent is (200 - 300):(150 - 200), where the unit of mole parts is mmol and the unit of mass parts is g.

[0017] Step 2: Dry the dispersion liquid to obtain a white powder, and calcine the white powder in a nitrogen or inert gas atmosphere at 750 - 1000 °C for 8 - 24 h to obtain lithium titanate.

[0018] In Step 2, before drying, grind the dispersion liquid until homogeneous. The grinding is carried out by ball milling, the ball milling time is 8 - 14 h, and the ball - to - material ratio is (10 - 30):(0.2 - 1.5).

[0019] In Step 2, the drying temperature is 40 - 70 °C, and the drying time is 14 - 18 h.

[0020] The above - mentioned preparation method of the lithium titanate - coated lithium battery separator includes: coating a slurry on a base film to obtain a precursor of the lithium titanate - coated lithium battery separator, extracting, dehydrating, and obtaining a coating on the base film to obtain the lithium titanate - coated lithium battery separator.

[0021] In the above technical solution, the extraction is carried out using an extraction liquid, specifically: the lithium titanate-coated lithium-ion battery separator precursor is successively passed through extraction liquids with decreasing extractant concentration. The extractant is N-methylpyrrolidone (NMP). The extraction liquids with decreasing extractant concentration are successively: the first extraction liquid, the second extraction liquid, the third extraction liquid, and the fourth extraction liquid. The first extraction liquid, the second extraction liquid, and the third extraction liquid are each a mixture of the extractant and water, and the fourth extraction liquid is water.

[0022] In the above technical solution, the concentration of the extractant in the first extraction liquid is 65 - 80 wt%, the concentration of the extractant in the second extraction liquid is 40 - 60 wt%, and the concentration of the extractant in the third extraction liquid is 20 - 40 wt%.

[0023] In the above technical solution, the dehydration is carried out by drying at 50 - 60 °C for 6 - 12 min.

[0024] A slurry includes: lithium titanate, a first substance, ethoxyamine hydrochloride, and a first solvent. By mass, the ratio of lithium titanate, the first substance, and ethoxyamine hydrochloride is (5 - 20):(0.5 - 3.8):(0.1 - 1.5).

[0025] In the above technical solution, by mass, the ratio of lithium titanate, the first substance, and ethoxyamine hydrochloride is preferably (11 - 13):(1.5 - 3):(0.5 - 1.5).

[0026] In the above technical solution, the first solvent is N-methylpyrrolidone (NMP).

[0027] In the above technical solution, by mass, the ratio of ethoxyamine hydrochloride and the first solvent is (0.1 - 1.5):(74.7 - 94.4).

[0028] In the above technical solution, by mass, the ratio of ethoxyamine hydrochloride and the first solvent is preferably (0.5 - 1.5):(84 - 86).

[0029] The method for preparing the above slurry includes: mixing lithium titanate, the first substance, ethoxyamine hydrochloride, and the first solvent until uniform to obtain the slurry.

[0030] In the above technical solution, lithium titanate, the first substance, ethoxyamine hydrochloride, and the first solvent are mixed and stirred at 30 - 45 °C until uniform.

[0031] In the above technical solution, lithium titanate, the first substance, ethoxyamine hydrochloride, and the first solvent are mixed and stirred at 30 - 45 °C at a speed of 350 - 400 r / min for 3 - 5 h until uniform.

[0032] Application of lithium titanate, ethylene propylene diene monomer (EPDM) and ethoxyamine hydrochloride in synergistically improving breakdown voltage, ionic conductivity and / or diaphragm adhesion force of a diaphragm.

[0033] Application of lithium titanate, ethylene propylene diene monomer (EPDM) and ethoxyamine hydrochloride in synergistically reducing air permeability value, thermal shrinkage rate, moisture content and / or static electricity content of a diaphragm.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] The present invention synergistically improves the breakdown voltage, ionic conductivity and adhesion force of a diaphragm by using lithium titanate, a first substance (the first substance is at least one of ethylene propylene diene monomer (EPDM), chloroprene rubber and vinyl ether acrylate) and ethoxyamine hydrochloride, and simultaneously reduces the moisture content and static electricity content of the diaphragm. Description of the Drawings

[0036] Figure 1 Surface SEM of the diaphragm prepared from the slurry of Example 1.

[0037] Figure 2 Cross-section SEM of the diaphragm prepared from the slurry of Example 1. Detailed Description of the Invention

[0038] The technical solutions of the present invention will be further described below with reference to specific embodiments.

[0039] The sources of raw materials in the following embodiments are as follows:

[0040] Titanium dioxide, purity 99.5%, Arlanxeo;

[0041] Lithium carbonate, purity 99%, Tianjin Hengxing Chemical Reagent Manufacturing Co., Ltd.;

[0042] Ethoxyamine hydrochloride, purity 99.9%, molecular weight 97.54, Shanghai Aladdin Co., Ltd.;

[0043] N-methylpyrrolidone (NMP), purity 99.5%, Tianjin Hengxing Chemical Reagent Manufacturing Co., Ltd.;

[0044] Ethylene propylene diene monomer (EPDM), Hebei Jierui Rubber Products Co., Ltd., Mooney viscosity 80 Pa·s, molecular weight distribution index (polydispersity index, PDI) 4.5.

[0045] The models and manufacturers of the equipment involved in the following embodiments and comparative examples are as follows:

[0046] Scanning electron microscope, Sigma 300, Carl Zeiss AG, Germany;

[0047] Japan AsahiSeiko Asahi Seiko air permeability meter, model: EH01-551MR;

[0048] Japan Shimadzu stretching machine, model: AGS-X (100N);

[0049] Electrochemical workstation, CHI660E, Shanghai Chenhua Instrument Co., Ltd.;

[0050] Electrostatic instrument, FMX-004, Schrader;

[0051] Coulometric moisture tester, WKT-A9, VicoMetco.

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

[0053] In the following examples, water is deionized water.

[0054] Examples 1 to 5

[0055] A method for preparing slurry comprises: dispersing lithium titanate, a first substance and ethoxylated amine hydrochloride in a first solvent, stirring at 35°C and 380 r / min for 4 hours until uniform, to obtain slurry, wherein the ratio of lithium titanate, the first substance and ethoxylated amine hydrochloride is X by weight, the ratio of ethoxylated amine hydrochloride to the first solvent is Y by weight, the first substance is ethylene propylene diene monomer rubber, and the first solvent is N-methylpyrrolidone (NMP).

[0056] The method for preparing lithium titanate comprises the following steps:

[0057] Step 1, mixing a lithium source, a titanium source and a second solvent until uniform to obtain a dispersion, wherein, in terms of the amount of substance, the ratio of lithium in the lithium source to titanium in the titanium source is 4.4:5.0, the ratio of the amount of substance of lithium in the lithium source to the mass fraction of the second solvent is 280:180, the unit of the amount of substance is mmol, the unit of the mass fraction is g, the second solvent is isopropanol, the lithium source is lithium carbonate (powder), and the titanium source is titanium dioxide (powder);

[0058] Step 2, the dispersion is placed in a ball mill and subjected to high-speed ball milling (the ball milling time is 12 hours, and the ball-to-material ratio of the ball milling is 15:1) until it is uniform, and dried in a 60°C forced air drying oven for 16 hours to obtain a white powder. The white powder is calcined at 950°C for 16 hours under a nitrogen atmosphere, and ground to obtain lithium titanate (powder). The particle size of the lithium titanate (powder) is D90=1.03 μm.

[0059] The X and Y values ​​are shown in Table 1.

[0060] Table 1

[0061] Slurry X Y Example 1 12：2：1 1：85 Example 2 12：3.5：1 1：83.5 Example 3 12：2：0.3 0.3：85.7 Example 4 8：2：1 1：89 Example 5 16：1.2：0.3 0.3：82.5

[0062] Example 6

[0063] A method for preparing a slurry is basically the same as that of Example 1, except that: in Example 1, "ethylene propylene diene monomer rubber" is replaced with "vinyl ether acrylate, CAS No. 86273-46-3".

[0064] Comparative Example 1

[0065] A method for preparing a slurry includes: dispersing the lithium titanate and ethylene propylene diene monomer rubber obtained in Example 1 in a first solvent, and stirring at a speed of 380 r / min at 35 °C for 4 h until uniform to obtain a slurry. By mass fraction, the ratio of lithium titanate, ethylene propylene diene monomer rubber and the first solvent is 12:2:86, and the first solvent is N-methylpyrrolidone (NMP).

[0066] Comparative Example 2

[0067] A method for preparing a slurry includes: dispersing the lithium titanate and ethoxyamine hydrochloride obtained in Example 1 in a first solvent, and stirring at a speed of 380 r / min at 35 °C for 4 h until uniform to obtain a slurry. By mass fraction, the ratio of lithium titanate, ethoxyamine hydrochloride and the first solvent is 12:1:87, and the first solvent is N-methylpyrrolidone (NMP).

[0068] Comparative Example 3

[0069] A method for preparing a slurry includes: dispersing ethylene propylene diene monomer rubber and ethoxyamine hydrochloride in a first solvent, and stirring at a speed of 380 r / min at 35 °C for 4 h until uniform to obtain a slurry. By mass fraction, the ratio of ethylene propylene diene monomer rubber, ethoxyamine hydrochloride and the first solvent is 2:1:97, and the first solvent is N-methylpyrrolidone (NMP).

[0070] Examples 7-12 and Comparative Examples 4-6

[0071] A method for preparing a separator, comprising: double-sidedly coating a slurry on a base film to obtain a separator precursor, extracting, dehydrating (drying in an oven at 60 °C for 10 min), obtaining a coating with a single-sided thickness of 3 μm on the base film to obtain a separator, wherein the extraction is carried out using an extraction liquid, specifically: passing the separator precursor through a first extraction liquid, a second extraction liquid, a third extraction liquid, and a fourth extraction liquid in sequence, with the extraction agent concentration decreasing from high to low. The extraction agent is N-methylpyrrolidone (NMP). The first extraction liquid, the second extraction liquid, and the third extraction liquid are each a mixture of the extraction agent and water, and the fourth extraction liquid is water. The concentration of the extraction agent in the first extraction liquid is 70 wt%, the concentration of the extraction agent in the second extraction liquid is 50 wt%, and the concentration of the extraction agent in the third extraction liquid is 30 wt%. The slurry is one of the slurries prepared in Examples 1 to 6 and Comparative Examples 1 to 3, and when the slurry of Comparative Example 2 is used to prepare the separator, material loss occurs during the extraction process.

[0072] Table 2

[0073] Separator Slurry used for preparing the separator Example 7 Example 1 Example 8 Example 2 Example 9 Example 3 Example 10 Example 4 Example 11 Example 5 Example 12 Example 6 Comparative Example 4 Comparative Example 1 Comparative Example 5 Comparative Example 2 Comparative Example 6 Comparative Example 3

[0074] The diaphragms prepared in the above-mentioned examples and comparative examples were subjected to air permeability tests, breakdown voltage tests, thermal shrinkage tests, water content tests, static electricity content tests, ionic conductivity tests, and adhesion tests, successively obtaining air permeability values, breakdown voltages, thermal shrinkage rates, moisture contents, static electricity contents, ionic conductivities, and diaphragm adhesion forces. Among them, the diaphragm was evenly tested at 10 points (the distance between two adjacent "points" is 10 cm) on a Japanese Asahi Seiko air permeability meter, and the average value of these 10 points was taken to obtain the air permeability value of the diaphragm; the diaphragm was laid flat on the test conductive plate of a withstand voltage insulation analyzer, and 50 breakdown points were tested (the distance between two adjacent "breakdown points" is 5 cm), and the average value of these 50 breakdown points was taken to obtain the breakdown voltage; the diaphragm was cut into a size of 4 cm × 6 cm, and its area change in an oven at 180 °C for 1 h was measured to obtain the thermal shrinkage rate; the diaphragm was cut into small pieces 3 cm long, rolled up with tweezers and placed in the coulomb titration cell of a coulombic moisture analyzer (150 mL of anode solution was filled in the coulomb titration cell. The method for preparing the anode solution includes: mixing 0.5 g of KI, 0.6 g of NaN3, and 5 mL of glacial acetic acid and diluting to 1000 mL with deionized water.). After standing for 10 min, the data value of the moisture content was directly read on the display screen of the coulombic moisture analyzer after 10 min, thereby obtaining the moisture content of the diaphragm; a static electricity meter was used to evenly test 5 points on the diaphragm (the distance between two adjacent "points" is 50 cm), and the average value of these 5 points was calculated to obtain the static electricity voltage value as the static electricity content; the test temperature for ionic conductivity was 25 °C and the relative humidity was 100% RH (the test method refers to the ionic conductivity test method in the national standard "Polyolefin Diaphragms for Lithium-Ion Batteries" (standard number: GB / T 36363-2018)); the diaphragm was cut into a shape of 25 mm × 60 mm, and a 3M tape was used to paste on the coating of the diaphragm. The force used to tear the 3M tape and the coating by a Japanese Shimadzu tensile machine was the diaphragm adhesion force. The test results are shown in Table 3.

[0075] Table 3

[0076]

[0077] From the above tests, it can be seen that the introduction of LTO, ethylene propylene diene monomer, and ethoxyamine hydrochloride can synergistically improve the diaphragm adhesion force, breakdown voltage, and ionic conductivity, while reducing the moisture content and static electricity content of the diaphragm.

[0078] The diaphragm prepared from the slurry of Example 1 was subjected to microscopic scanning, as Figure 1 and Figure 2 shown, the LTO distribution is relatively uniform, and the overall diaphragm is relatively dense.

[0079] The above is an exemplary description of the present invention. It should be noted that any simple deformation, modification, or equivalent substitution that can be made by those skilled in the art without creative efforts falls within the protection scope of the present invention without departing from the core of the present invention.

Claims

1. A lithium-ion battery separator with a lithium titanate coating, characterized in that, Comprising: A base film and a coating on the base film, the coating comprising: lithium titanate, a first substance, and ethoxyamine hydrochloride, the first substance being at least one of ethylene propylene diene monomer rubber, chloroprene rubber, and vinyl ether acrylate, and by mass parts, the ratio of lithium titanate, the first substance, and ethoxyamine hydrochloride is (5 to 20):(0.5 to 3.8):(0.1 to 1.5).

2. A slurry, characterized in that, Comprising: Lithium titanate, a first substance, ethoxyamine hydrochloride, and a first solvent, and by mass parts, the ratio of lithium titanate, the first substance, and ethoxyamine hydrochloride is (5 to 20):(0.5 to 3.8):(0.1 to 1.5).

3. The slurry according to claim 2, wherein The first solvent is N-methylpyrrolidone.

4. The slurry according to claim 2, wherein By mass parts, the ratio of ethoxyamine hydrochloride to the first solvent is (0.1 to 1.5):(74.7 to 94.4).

5. A preparation method of a lithium titanate-coated lithium-ion battery separator, characterized in that, Comprising: Coating the slurry according to any one of claims 2 to 4 on the base film to obtain a precursor of a lithium-ion battery separator with a lithium titanate coating, extracting, dehydrating, and obtaining a coating on the base film to obtain a lithium-ion battery separator with a lithium titanate coating.

6. A method for preparing the slurry according to any one of claims 2 to 4, characterized in that, Comprising: Mixing lithium titanate, a first substance, ethoxyamine hydrochloride, and the first solvent until homogeneous to obtain a slurry.

7. Application of lithium titanate, ethylene propylene diene monomer rubber, and ethoxyamine hydrochloride in synergistically improving the breakdown voltage of the separator.

8. Application of lithium titanate, ethylene propylene diene monomer rubber, and ethoxyamine hydrochloride in synergistically reducing the air permeability value, thermal shrinkage rate, moisture content, and / or static charge content of the separator.

9. Application of lithium titanate, ethylene propylene diene monomer rubber, and ethoxyamine hydrochloride in synergistically improving the adhesion of the separator.

10. Application of lithium titanate, ethylene propylene diene monomer rubber, and ethoxyamine hydrochloride in synergistically improving the ionic conductivity of the separator.

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