CN114597584A - Lithium ion battery diaphragm with charging protection function and preparation method thereof - Google Patents

Lithium ion battery diaphragm with charging protection function and preparation method thereof Download PDF

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Publication number
CN114597584A
CN114597584A CN202210293232.5A CN202210293232A CN114597584A CN 114597584 A CN114597584 A CN 114597584A CN 202210293232 A CN202210293232 A CN 202210293232A CN 114597584 A CN114597584 A CN 114597584A
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coating
positive electrode
binder
raw materials
lithium ion
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CN114597584B (en
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袁海朝
徐锋
豆赛赛
苏碧海
石琳琳
白涛
胡晓梦
李钦钦
袁静
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Hebei Gellec New Energy Material Science and Technoloy Co Ltd
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Hebei Gellec New Energy Material Science and Technoloy Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/423—Polyamide resins
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention discloses a lithium ion battery diaphragm with a charging protection function and a preparation method thereof, wherein the lithium ion battery diaphragm comprises: base film, coating correspond the anodal coating of anodal one side and coating at the negative pole coating that the base film corresponds the negative pole one side, and wherein, the raw materials that form anodal coating include: organic solvents, binders and polyamides; the raw materials for forming the anode coating include: inorganic particles, a binder, a molten flame retardant, a dispersant and an organic solvent; the melt flame retardant is tetrabromobisphenol A bis (allyl) ether, tetrabromobisphenol A bis (2-hydroxyethyl) ether or tetrabromobisphenol A bis (2, 3-dibromopropyl) ether. The invention coats polymer slurry with oxidation resistance facing the positive electrode, solves the problem of strong oxidation effect on the isolating membrane caused by the collapse of the positive electrode structure, and coats slurry combining inorganic particles and a melting flame retardant facing the negative electrode.

Description

Lithium ion battery diaphragm with charging protection function and preparation method thereof
Technical Field
The invention belongs to the technical field of battery diaphragms, and particularly relates to a lithium ion battery diaphragm with a charging protection function and a preparation method thereof.
Background
For the charging problem of the lithium ion battery, some battery manufacturers avoid potential safety hazards by adding an explosion-proof safety valve and a safety helmet, but the above method does not completely solve the fundamental problem of battery charging. The diaphragm is one of the materials in the lithium battery, is a transfer station in the charging process of the lithium ion battery, and has an important position that when the lithium battery is overcharged, lithium ions in the positive electrode excessively separate out to cause the positive electrode structure to collapse, the unstable structure enables the positive electrode structure to be in a strong oxidation state to generate strong oxidation action on the isolating membrane, meanwhile, a large amount of lithium ions separated out from the positive electrode separate out on the surface of the negative electrode to form lithium dendrites, challenges are created on the mechanical strength of the diaphragm, and the two processes are accompanied by a large amount of joule heat to finally cause the isolating membrane to shrink and melt to generate internal short circuit, so that the thermal failure of a battery core is caused.
Today, most solutions to the above problems are to enhance the mechanical properties and stability of the separator by coating an inorganic coating on the separator, but the solutions have more problems, such as: the inoxidizability of the inorganic coating is relatively weak, and when the lithium battery is excessively charged, the inorganic coating is oxidized and powdered in the electrolyte, so that the impedance of the lithium battery is increased; secondly, when overcharging, a large amount of heat can be generated in the battery, even if the inorganic diaphragm does not shrink, the overcharging is still in progress, the capacity is continuously increased, the voltage is correspondingly increased, and finally, the anode and the cathode react with the electrolyte to generate excessive heat, and the battery is ignited or even explodes.
In the face of the present situation, if a functional coating separator that can solve the above problems can be developed, the solution of the charge protection problem of the lithium ion battery will be advanced.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a lithium ion battery diaphragm with a charging protection function, which can solve the problems of oxidation and powder falling of an inorganic coating in the overcharge process and strengthen the oxidation resistance and stability of the diaphragm facing to the positive electrode surface; the problem that the reaction process cannot be stopped under the condition of original characteristics of the conventional inorganic coating can be avoided, the charging process can be thoroughly cut off, and the anti-overcharge protection function is enhanced.
The invention also aims to provide a preparation method of the lithium ion battery separator with the charge protection function.
The purpose of the invention is realized by the following technical scheme.
A lithium ion battery separator with charge protection comprising: a base film, an anode coating coated on one side of the base film corresponding to the anode and a cathode coating coated on one side of the base film corresponding to the cathode, wherein,
the raw materials for forming the positive electrode coating include: organic solvents, binders and polyamides;
the raw materials for forming the anode coating comprise: inorganic particles, a binder, a molten flame retardant, a dispersant and an organic solvent;
the organic solvent is at least one of acetone, N-methyl pyrrolidone and ethanol;
the polyamide is one or a mixture of more of poly (p-phenylene terephthalamide), poly (m-phenylene isophthalamide), poly (p-benzamide) and poly (bold amine);
the inorganic particles are alumina powder, aluminum nitride powder or boehmite powder;
the melt flame retardant is tetrabromobisphenol A bis (allyl) ether, tetrabromobisphenol A bis (2-hydroxyethyl) ether or tetrabromobisphenol A bis (2, 3-dibromopropyl) ether.
In the technical scheme, the thickness of the positive coating is 1.0-1.5 μm.
In the technical scheme, the thickness of the negative electrode coating is 1.0-1.5 mu m.
In the technical scheme, the dispersant is polyacrylamide or fatty alcohol ether sodium sulfate.
In the above technical scheme, the binder is polyvinylidene fluoride, polymethyl acrylate or SBR (styrene butadiene rubber).
In the technical scheme, in the raw materials for forming the positive electrode coating, the ratio of the organic solvent to the binder to the polyamide is (10-20) in parts by mass: (1.5-3): (2-4.2); in the raw materials for forming the negative electrode coating, the ratio of inorganic particles, a binder, a molten flame retardant, a dispersant and an organic solvent is (1.8-3.5) by mass: (1.8-3.2): (0.8-1.5): (0.35-0.8): (12-22).
The preparation method of the lithium ion battery diaphragm with the charging protection function comprises the following steps:
coating positive electrode slurry on one surface of a base film opposite to a positive electrode to form the positive electrode coating, and coating negative electrode slurry on one surface of the base film opposite to a negative electrode to form the negative electrode coating, wherein the positive electrode slurry is formed by mixing raw materials for forming the positive electrode coating, and the negative electrode slurry is formed by mixing raw materials for forming the negative electrode coating.
In the technical scheme, the coating speed is 10-25 m/min, and the coating mode is gravure coating.
In the technical scheme, the coating is followed by extraction, the extracting agent is 3-methyl-1-butanol, and the extraction time is 15-25 min.
In the technical scheme, the extraction is followed by drying, and the drying temperature is 55-70 ℃.
In the above technical scheme, the method for preparing the positive electrode slurry comprises the following steps: mixing an organic solvent and a binder, stirring at a rotating speed of 1300-2000 rpm for 35-55 min to be uniform, adding the polyamide, and stirring at a rotating speed of 1200-1800 rpm for 35-50 min to be uniform; the method for preparing the cathode slurry comprises the following steps: mixing an organic solvent, a dispersing agent and a binder, stirring at the rotating speed of 1400-2000 rpm for 40-60 min until uniform, adding the inorganic particles, stirring at the rotating speed of 1200-1800 rpm for 35-50 min until uniform, adding the molten flame retardant, and stirring at the rotating speed of 1300-2000 rpm for 40-55 min until uniform.
The invention respectively faces the different polarity surfaces of the lithium battery by coating two different types of coating slurry. The slurry has the advantages that the slurry is coated with the polymer slurry with oxidation resistance facing the positive electrode, the problem of strong oxidation effect on the isolating membrane caused by collapse of the positive electrode structure is solved, the slurry combining the inorganic particles and the fused flame retardant is coated facing the negative electrode, the slurry has a flame retardant effect and strong mechanical strength, and the fused flame retardant can be fused under high-temperature overcharge and is absorbed into the ceramic particles and micropores of the diaphragm matrix, so that the function of circuit breaking is realized, the lithium ion channel of the battery under the overcharge condition is thoroughly cut off, and the safety protection effect is realized.
Drawings
Fig. 1 is an SEM image of the positive electrode coating of example 1;
fig. 2 is an SEM image of the negative electrode coating in example 1.
Detailed Description
The technical scheme of the invention is further explained by combining specific examples.
The base films used in the following examples and comparative examples were polyethylene base films having a thickness of 12 μm.
Example 1
A lithium ion battery separator with charge protection comprising: a basal membrane, an anode coating coated on one surface of the basal membrane corresponding to an anode and a cathode coating coated on one surface of the basal membrane corresponding to a cathode, wherein the thickness of the anode coating is 1 μm, the thickness of the cathode coating is 1 μm,
the raw materials for forming the positive electrode coating include: organic solvents, binders and polyamides;
the raw materials for forming the anode coating include: inorganic particles, a binder, a molten flame retardant, a dispersant and an organic solvent;
the organic solvent is acetone;
the polyamide is poly-p-phenylene terephthalamide;
the inorganic particles are alumina powder;
the melting flame retardant is tetrabromobisphenol A bis (allyl) ether, the dispersing agent is polyacrylamide, and the binder is polyvinylidene fluoride.
In the raw materials for forming the positive electrode coating, the ratio of the organic solvent to the binder to the polyamide is 12: 2: 2.5; in the raw materials for forming the negative electrode coating, the ratio of the inorganic particles, the binder, the molten flame retardant, the dispersant and the organic solvent is 2.5: 2.5: 0.8: 0.35: 13.
the preparation method of the lithium ion battery diaphragm with the charging protection function comprises the following steps:
coating the positive electrode slurry on one surface of a base film opposite to a positive electrode to form a positive electrode coating, wherein the SEM of the positive electrode coating is shown in figure 1 and is kept stand at normal temperature for 10min, the negative electrode slurry is coated on one surface of the base film opposite to a negative electrode to form a negative electrode coating, the SEM of the negative electrode coating is shown in figure 2, wherein the positive electrode slurry is formed by mixing raw materials for forming the positive electrode coating, the negative electrode slurry is formed by mixing raw materials for forming the negative electrode coating, the coating speed is 10m/min, the coating mode is gravure coating, the positive electrode slurry and the negative electrode slurry are extracted after coating is finished, the extracting agent is 3-methyl-1-butanol, the extraction time is 15min, drying is carried out after extraction, the drying temperature is 55 ℃, and the drying time is 20 min.
The method for preparing the anode slurry comprises the following steps: mixing an organic solvent and a binder in a stirring tank, stirring at the rotating speed of 1500rpm for 40min to be uniform, adding polyamide, and stirring at the rotating speed of 1300rpm for 35min to be uniform; the method for preparing the cathode slurry comprises the following steps: mixing an organic solvent, a dispersing agent and a binder in a stirring tank, stirring at 1400rpm for 40min to be uniform, adding inorganic particles, stirring at 1400rpm for 35min to be uniform, adding a molten flame retardant, and stirring at 1500rpm for 40min to be uniform.
Example 2
A lithium ion battery separator with charge protection comprising: a basal membrane, an anode coating coated on one side of the basal membrane corresponding to the anode and a cathode coating coated on one side of the basal membrane corresponding to the cathode, wherein the thickness of the anode coating is 1.2 mu m, the thickness of the cathode coating is 1.3 mu m,
the raw materials for forming the positive electrode coating include: organic solvents, binders and polyamides;
the raw materials for forming the anode coating include: inorganic particles, a binder, a molten flame retardant, a dispersant and an organic solvent;
the organic solvent is N-methyl pyrrolidone;
the polyamide is polyisophthaloyl metaphenylene diamine;
the inorganic particles are aluminum nitride powder;
the melting flame retardant is tetrabromobisphenol A bis (2-hydroxyethyl) ether, the dispersant is fatty alcohol ether sodium sulfate, and the binder is polymethyl acrylate.
In the raw materials for forming the positive electrode coating, the ratio of the organic solvent to the binder to the polyamide is 13: 2.5: 3; in the raw materials for forming the negative electrode coating, the ratio of the inorganic particles, the binder, the molten flame retardant, the dispersant and the organic solvent is 2.8: 2.7: 1: 0.4: 14.
the preparation method of the lithium ion battery diaphragm with the charging protection function comprises the following steps:
coating positive slurry on one surface of a base film opposite to a positive electrode to form a positive coating, standing at normal temperature for 10min, coating negative slurry on one surface of the base film opposite to a negative electrode to form a negative coating, wherein the positive slurry is formed by mixing raw materials for forming the positive coating, the negative slurry is formed by mixing raw materials for forming the negative coating, the coating speed of the positive slurry is 15m/min, the coating speed of the negative slurry is 17m/min, the coating mode is gravure coating, the positive slurry and the negative slurry are extracted after coating is completed, an extracting agent is 3-methyl-1-butanol, the extraction time is 20min, drying is carried out after extraction, the drying temperature is 60 ℃, and the drying time is 23 min.
The method for preparing the anode slurry comprises the following steps: mixing an organic solvent and a binder in a stirring tank, stirring for 45min at the rotating speed of 1600rpm until the mixture is uniform, then adding polyamide, and stirring for 40min at the rotating speed of 1400rpm until the mixture is uniform; the method for preparing the cathode slurry comprises the following steps: mixing an organic solvent, a dispersing agent and a binder in a stirring tank, stirring at the rotating speed of 1500rpm for 45min to be uniform, adding inorganic particles, stirring at the rotating speed of 1500rpm for 40min to be uniform, adding a molten flame retardant, and stirring at the rotating speed of 1600rpm for 45min to be uniform.
Example 3
A lithium ion battery separator with charge protection comprising: a basal membrane, an anode coating coated on one side of the basal membrane corresponding to the anode and a cathode coating coated on one side of the basal membrane corresponding to the cathode, wherein the thickness of the anode coating is 1.5 mu m, the thickness of the cathode coating is 1.5 mu m,
the raw materials for forming the positive electrode coating include: organic solvents, binders and polyamides;
the raw materials for forming the anode coating include: inorganic particles, a binder, a molten flame retardant, a dispersant and an organic solvent;
the organic solvent is ethanol;
the polyamide is poly-p-benzamide;
the inorganic particles are boehmite powder;
the melt flame retardant is tetrabromobisphenol A bis (2, 3-dibromo propyl) ether, the dispersant is polyacrylamide, and the binder is SBR (styrene butadiene rubber).
In the raw materials for forming the positive electrode coating, the ratio of the organic solvent, the binder and the polyamide is 14: 3: 3.2; in the raw materials for forming the negative electrode coating, the ratio of the inorganic particles, the binder, the molten flame retardant, the dispersant and the organic solvent is 3.2: 2.9: 1.2: 0.45: 15.
the preparation method of the lithium ion battery diaphragm with the charging protection function comprises the following steps:
coating the positive electrode slurry on one surface of a base film opposite to a positive electrode to form a positive electrode coating, standing at normal temperature for 10min, coating the negative electrode slurry on one surface of the base film opposite to a negative electrode to form a negative electrode coating, wherein the positive electrode slurry is formed by mixing raw materials for forming the positive electrode coating, the negative electrode slurry is formed by mixing raw materials for forming the negative electrode coating, the coating speed is 20m/min, the coating mode is gravure coating, the positive electrode slurry and the negative electrode slurry are extracted after coating is finished, the extracting agent is 3-methyl-1-butanol, the extraction time is 25min, drying is carried out after extraction, the drying temperature is 65 ℃, and the drying time is 25 min.
The method for preparing the anode slurry comprises the following steps: mixing an organic solvent and a binder in a stirring tank, stirring at the rotating speed of 1700rpm for 50min until the mixture is uniform, adding polyamide, and stirring at the rotating speed of 1500rpm for 45min until the mixture is uniform; the method for preparing the cathode slurry comprises the following steps: mixing an organic solvent, a dispersing agent and a binder in a stirring tank, stirring for 50min at the rotating speed of 1600rpm until the mixture is uniform, adding inorganic particles, stirring for 45min at the rotating speed of 1600rpm until the mixture is uniform, adding a molten flame retardant, and stirring for 50min at the rotating speed of 1700rpm until the mixture is uniform.
Comparative example 1
A lithium ion battery separator comprising: a basal membrane, an anode coating coated on one side of the basal membrane corresponding to the anode and a cathode coating coated on one side of the basal membrane corresponding to the cathode, wherein the thickness of the anode coating is 1 μm, the thickness of the cathode coating is 1 μm,
the raw materials for forming the positive electrode coating include: an organic solvent, a binder and inorganic particles;
the raw materials for forming the anode coating include: inorganic particles, a binder, a dispersant and an organic solvent;
the organic solvent is acetone;
the inorganic particles are alumina powder;
the dispersant is polyacrylamide, and the binder is polyvinylidene fluoride.
In the raw materials for forming the positive electrode coating, the ratio of the organic solvent, the binder and the inorganic particles is 12: 2: 2.5; in the raw material for forming the negative electrode coating, the ratio of the inorganic particles, the binder, the dispersant and the organic solvent is 2.5: 2.5: 0.35: 13.
the preparation method of the lithium ion battery diaphragm comprises the following steps:
coating the positive electrode slurry on one surface of a base film opposite to a positive electrode to form a positive electrode coating, standing at normal temperature for 10min, coating the negative electrode slurry on one surface of the base film opposite to a negative electrode to form a negative electrode coating, wherein the positive electrode slurry is formed by mixing raw materials for forming the positive electrode coating, the negative electrode slurry is formed by mixing raw materials for forming the negative electrode coating, the coating speed is 10m/min, the coating mode is gravure coating, the positive electrode slurry and the negative electrode slurry are extracted after coating is finished, the extracting agent is 3-methyl-1-butanol, the extraction time is 15min, drying is carried out after extraction, the drying temperature is 55 ℃, and the drying time is 20 min.
The method for preparing the anode slurry comprises the following steps: mixing an organic solvent and a binder in a stirring tank, stirring at the rotating speed of 1500rpm for 40min to be uniform, adding inorganic particles, and stirring at the rotating speed of 1300rpm for 35min to be uniform; the method for preparing the cathode slurry comprises the following steps: mixing the organic solvent, the dispersant and the binder in a stirring tank, stirring at 1400rpm for 40min to be uniform, adding the inorganic particles, and stirring at 1400rpm for 35min to be uniform.
Comparative example 2
A lithium ion battery separator comprising: a basal membrane, an anode coating coated on one side of the basal membrane corresponding to the anode and a cathode coating coated on one side of the basal membrane corresponding to the cathode, wherein the thickness of the anode coating is 1.2 mu m, the thickness of the cathode coating is 1.3 mu m,
the raw materials for forming the positive electrode coating include: an organic solvent, a binder and inorganic particles;
the raw materials for forming the anode coating include: inorganic particles, a binder, a dispersant and an organic solvent;
the organic solvent is N-methyl pyrrolidone;
the inorganic particles are aluminum nitride powder;
the dispersing agent is fatty alcohol ether sodium sulfate, and the binder is polymethyl acrylate.
In the raw materials for forming the positive electrode coating, the ratio of the organic solvent, the binder and the inorganic particles is 13: 2.5: 3; in the raw material for forming the negative electrode coating, the ratio of the inorganic particles, the binder, the dispersant and the organic solvent is 2.8: 2.7: 0.4: 14.
the preparation method of the lithium ion battery diaphragm comprises the following steps:
coating positive slurry on one surface of a base film opposite to a positive electrode to form a positive coating, standing at normal temperature for 10min, coating negative slurry on one surface of the base film opposite to a negative electrode to form a negative coating, wherein the positive slurry is formed by mixing raw materials for forming the positive coating, the negative slurry is formed by mixing raw materials for forming the negative coating, the coating speed of the positive slurry is 15m/min, the coating speed of the negative slurry is 17m/min, the coating mode is gravure coating, the positive slurry and the negative slurry are extracted after coating is completed, an extracting agent is 3-methyl-1-butanol, the extraction time is 20min, drying is carried out after extraction, the drying temperature is 60 ℃, and the drying time is 23 min.
The method for preparing the anode slurry comprises the following steps: mixing an organic solvent and a binder in a stirring tank, stirring for 45min at the rotating speed of 1600rpm until the mixture is uniform, then adding inorganic particles, and stirring for 40min at the rotating speed of 1400rpm until the mixture is uniform; the method for preparing the cathode slurry comprises the following steps: mixing the organic solvent, the dispersant and the binder in a stirring tank, stirring at 1500rpm for 45min to be uniform, adding the inorganic particles, and stirring at 1500rpm for 40min to be uniform.
Comparative example 3
A lithium ion battery separator comprising: a basal membrane, an anode coating coated on one side of the basal membrane corresponding to the anode and a cathode coating coated on one side of the basal membrane corresponding to the cathode, wherein the thickness of the anode coating is 1.5 mu m, the thickness of the cathode coating is 1.5 mu m,
the raw materials for forming the positive electrode coating include: organic solvents, binders, and inorganic particles;
the raw materials for forming the anode coating include: inorganic particles, a binder, a dispersant and an organic solvent;
the organic solvent is ethanol;
the inorganic particles are boehmite powder;
the dispersant is polyacrylamide, and the binder is SBR (styrene butadiene rubber).
In the raw materials for forming the positive electrode coating, the ratio of the organic solvent, the binder and the inorganic particles is 14: 3: 3.2; in the raw material for forming the negative electrode coating, the ratio of the inorganic particles, the binder, the dispersant and the organic solvent is 3.2: 2.9: 0.45: 15.
the preparation method of the lithium ion battery diaphragm comprises the following steps:
coating the positive electrode slurry on one surface of a base film opposite to a positive electrode to form a positive electrode coating, standing at normal temperature for 10min, coating the negative electrode slurry on one surface of the base film opposite to a negative electrode to form a negative electrode coating, wherein the positive electrode slurry is formed by mixing raw materials for forming the positive electrode coating, the negative electrode slurry is formed by mixing raw materials for forming the negative electrode coating, the coating speed is 20m/min, the coating mode is gravure coating, the positive electrode slurry and the negative electrode slurry are extracted after coating is finished, the extracting agent is 3-methyl-1-butanol, the extraction time is 25min, drying is carried out after extraction, the drying temperature is 65 ℃, and the drying time is 25 min.
The method for preparing the anode slurry comprises the following steps: mixing an organic solvent and a binder in a stirring tank, stirring at the rotating speed of 1700rpm for 50min until the mixture is uniform, adding inorganic particles, and stirring at the rotating speed of 1500rpm for 45min until the mixture is uniform; the method for preparing the cathode slurry comprises the following steps: mixing the organic solvent, the dispersant and the binder in a stirring tank, stirring at 1600rpm for 50min until uniform, adding the inorganic particles, and stirring at 1600rpm for 45min until uniform.
Lithium batteries with models of NCM-606090-4000 mAh were prepared by using the lithium ion battery separators obtained in the above examples 1-3 and comparative examples 1-3, respectively, and 5 lithium batteries were prepared in each example and comparative example, wherein the positive electrode material was a ternary material (NCM523) (purchased from New Endurance materials), the negative electrode material was graphite (fibrate), and the electrolyte of the electrolyte was LiPF6(the solvent is a mixture of EC (ethylene carbonate) and DMC (dimethyl carbonate), and EC: DMC ═ 1:1 by mass) is assembled into a half-cell. The cathode slurry is prepared by uniformly mixing a cathode material, a conductive agent (Keqin carbon black) and a binder SBR (styrene butadiene rubber latex) (Shenzhen Yitong) according to a mass ratio of 8:0.8:1.2, and the anode slurry is prepared by uniformly mixing a cathode material, conductive carbon black (Shenzhen Jingzhida) and a binder PVDF (Chengdu Kelong Jingzhida)) Uniformly mixing according to the mass ratio of 8:1: 1.
Coating the positive electrode slurry on a positive electrode current collector to obtain a positive electrode, wherein the positive electrode current collector is an aluminum foil, and the coating amount of the positive electrode slurry is 7mg/cm2The coating thickness of the positive electrode slurry is 40 um; coating the negative electrode slurry on a negative electrode current collector to obtain a negative electrode, wherein the negative electrode current collector is copper foil, and the coating amount of the negative electrode slurry is 6mg/cm2The coating thickness of the negative electrode slurry was 40 μm. And (3) completing formation and grading, and performing overcharge test on the prepared lithium battery, wherein the test method and the test result are as follows:
the test method comprises the following steps: the lithium battery is placed in a test box, the process flow of the test box is charged to 5.5V (rated voltage is 4.8V) at 1C, and whether the lithium battery explodes, smokes and fires is observed. The test results of 5 lithium batteries for each example and comparative example are shown in table 1.
TABLE 1
Figure BDA0003562284050000091
According to the test results, explosion and fire do not occur in the embodiment and the comparative example, the pass rate of the overcharge test in the embodiment is far higher than that of the lithium battery in the comparative example, and the lithium ion battery diaphragm obtained in the embodiment 1-3 strengthens the oxidation resistance and the overcharge resistance of the lithium battery, cuts off a lithium ion channel at high temperature in the charging process, and enhances the safety and the protection of the lithium battery.
In addition, the lithium ion battery diaphragms obtained in examples 1 to 3 and comparative examples 1 to 3 were tested for tensile strength and TMA rupture temperature, and details are shown in table 2.
TABLE 2
Figure BDA0003562284050000092
The invention has been described in an illustrative manner, and it is to be understood that any simple variations, modifications or other equivalent changes which can be made by one skilled in the art without departing from the spirit of the invention fall within the scope of the invention.

Claims (10)

1. A lithium ion battery separator having a charge protection function, comprising: a base film, an anode coating coated on one side of the base film corresponding to the anode and a cathode coating coated on one side of the base film corresponding to the cathode, wherein,
the raw materials for forming the positive electrode coating comprise: organic solvents, binders and polyamides;
the raw materials for forming the anode coating comprise: inorganic particles, a binder, a molten flame retardant, a dispersant and an organic solvent;
the organic solvent is at least one of acetone, N-methyl pyrrolidone and ethanol;
the polyamide is one or a mixture of more of poly (p-phenylene terephthalamide), poly (m-phenylene isophthalamide), poly (p-benzamide) and poly (bold amine);
the inorganic particles are alumina powder, aluminum nitride powder or boehmite powder;
the melt flame retardant is tetrabromobisphenol A bis (allyl) ether, tetrabromobisphenol A bis (2-hydroxyethyl) ether or tetrabromobisphenol A bis (2, 3-dibromopropyl) ether.
2. The lithium ion battery separator according to claim 1, wherein the thickness of the positive electrode coating layer is 1.0 to 1.5 μm, and the thickness of the negative electrode coating layer is 1.0 to 1.5 μm.
3. The lithium ion battery separator according to claim 2, wherein the dispersant is polyacrylamide or sodium fatty alcohol ether sulfate.
4. The lithium ion battery separator of claim 3, wherein the binder is polyvinylidene fluoride, polymethyl acrylate, or SBR.
5. The lithium ion battery separator according to claim 1, wherein the ratio of the organic solvent to the binder to the polyamide in the raw materials for forming the positive electrode coating is (10 to 20) in parts by mass: (1.5-3): (2-4.2); in the raw materials for forming the negative electrode coating, the ratio of inorganic particles, a binder, a molten flame retardant, a dispersant and an organic solvent is (1.8-3.5) by mass: (1.8-3.2): (0.8-1.5): (0.35-0.8): (12-22).
6. The method for preparing the lithium ion battery separator with the charge protection function according to claim 1, which comprises the following steps:
coating positive electrode slurry on one surface of a base film opposite to a positive electrode to form the positive electrode coating, and coating negative electrode slurry on one surface of the base film opposite to a negative electrode to form the negative electrode coating, wherein the positive electrode slurry is formed by mixing raw materials for forming the positive electrode coating, and the negative electrode slurry is formed by mixing raw materials for forming the negative electrode coating.
7. The method according to claim 6, wherein the coating speed is 10 to 25m/min and the coating method is gravure coating.
8. The preparation method according to claim 6, wherein the coating is followed by extraction with 3-methyl-1-butanol for 15-25 min.
9. The method according to claim 6, wherein the extraction is followed by drying at a temperature of 55 to 70 ℃.
10. The method for producing according to claim 6, characterized in that the method for producing the positive electrode slurry is: mixing an organic solvent and a binder, stirring at a rotating speed of 1300-2000 rpm for 35-55 min to be uniform, adding the polyamide, and stirring at a rotating speed of 1200-1800 rpm for 35-50 min to be uniform; the method for preparing the cathode slurry comprises the following steps: mixing an organic solvent, a dispersing agent and a binder, stirring at the rotating speed of 1400-2000 rpm for 40-60 min until uniform, adding the inorganic particles, stirring at the rotating speed of 1200-1800 rpm for 35-50 min until uniform, adding the molten flame retardant, and stirring at the rotating speed of 1300-2000 rpm for 40-55 min until uniform.
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