CN114094280A - Preparation method of diaphragm, diaphragm and lithium ion battery - Google Patents

Preparation method of diaphragm, diaphragm and lithium ion battery Download PDF

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Publication number
CN114094280A
CN114094280A CN202111307354.7A CN202111307354A CN114094280A CN 114094280 A CN114094280 A CN 114094280A CN 202111307354 A CN202111307354 A CN 202111307354A CN 114094280 A CN114094280 A CN 114094280A
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pmma
coating
slurry
gas
base film
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杨润
赖旭伦
孙先维
符宽
晋沛沛
金庆波
陈杰
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Huizhou Liwei Electronic Technology Co ltd
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Huizhou Liwei Electronic Technology 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • 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
    • H01M50/42—Acrylic resins
    • 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
    • H01M50/431—Inorganic material
    • H01M50/434—Ceramics
    • 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
    • H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
    • 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
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Materials Engineering (AREA)
  • Composite Materials (AREA)
  • Ceramic Engineering (AREA)
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Abstract

The invention provides a preparation method of a diaphragm, the diaphragm and a lithium ion battery, which comprises the following steps: s1, preparing ceramic coating slurry; s2, mixing PMMA, a wetting agent, a thickening agent and a solvent to prepare PMMA coating slurry, and adding the ceramic coating slurry into the PMMA coating slurry to mix to obtain mixed slurry; and S3, introducing gas to the bottom of the mixed slurry, wherein the flow rate of the introduced gas is 1.6-2.0 m/S, the gas velocity is 30-50 m/S, coating the mixed slurry with the gas on at least one surface of the base film, and drying at 40-60 ℃ to obtain the PMMA coating, the ceramic coating and the diaphragm of the base film which are sequentially stacked. Compared with the prior art, the method utilizes bubble buoyancy to bring PMMA particles to the surface of the ceramic coating, achieves the purpose of coating twice through one-time coating, and simultaneously solves the problem that the thickness and the areal density of the PMMA coating are difficult to control.

Description

Preparation method of diaphragm, diaphragm and lithium ion battery
Technical Field
The invention relates to the field of lithium batteries, in particular to a preparation method of a diaphragm, the diaphragm and a lithium ion battery.
Background
The lithium ion battery consists of a positive electrode, a negative electrode, electrolyte and a diaphragm. The diaphragm plays the role of insulating, blocking the positive and negative electrodes and preventing short circuit, and has direct influence on the safety performance and cost of the battery. With the wide application of mobile phones, notebook computers and some portable digital devices in the market, the diaphragm is required to be thinner and thinner on the premise of ensuring safety, and the diaphragm and the pole piece are required to have certain adhesion, so that the deformation and the softness of the battery are reduced.
Polymethyl methacrylate, abbreviated as PMMA, also called acrylic or organic glass, has high tensile strength and impact strength, and has certain cohesiveness at high temperature and high pressure. At present, PMMA and alumina are compounded by adopting a secondary coating process, and in Chinese patent application CN201620974312.7, a 1-4 mu m alumina coating is coated on the surface of a base film, and then a 0.3-1.0 mu m PMMA coating is coated. However, since the density of PMMA is low, the thickness and the surface density of the PMMA coating layer are difficult to control, and the secondary coating process is complicated and consumes certain manpower and material resources, which is not convenient for industrial production and application. For example, chinese patent application CN201710042274.0 discloses a PMMA and its copolymer mixed coating membrane, but in this method, since the density of PMMA particles is slightly higher than that of water, it is difficult to ensure that the PMMA particles are mostly located on the surface of the ceramic coating, which results in easy deformation and softening of the lithium battery.
In view of the above, it is necessary to provide a technical solution to the above problems.
Disclosure of Invention
One of the objects of the present invention is: the preparation method of the diaphragm can solve the problem that the production process is difficult to control due to small thickness and surface density increment of the existing PMMA coating, can achieve the effect of secondary coating by adopting a primary coating process, and can obviously reduce the production cost.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method of making a separator comprising the steps of:
s1, preparing ceramic coating slurry;
s2, mixing PMMA, a wetting agent, a thickening agent and a solvent to prepare PMMA coating slurry, and adding the ceramic coating slurry into the PMMA coating slurry to mix to obtain mixed slurry;
and S3, introducing gas to the bottom of the mixed slurry, wherein the flow rate of the introduced gas is 1.6-2.0 m/S, the gas velocity is 30-50 m/S, coating the mixed slurry with the gas on at least one surface of the base film, and drying at 40-60 ℃ to obtain the PMMA coating, the ceramic coating and the diaphragm of the base film which are sequentially stacked.
Preferably, in step S1, the preparation method of the ceramic coating slurry comprises: mixing the inorganic filler, the thickening agent and the solvent, ball-milling for 1-3 h, and then adding the binder for mixing to obtain the ceramic coating slurry.
Preferably, the particle diameter D of the inorganic filler500.9 to 1.2 μm; particle size D of PMMA500.3 to 0.6 μm.
Preferably, in step S2, the PMMA coating paste is prepared by: and mixing and stirring the wetting agent, the thickening agent and the solvent for 1-2 hours, adding the PMMA emulsion, and stirring together to obtain PMMA coating slurry.
Preferably, in step S3, the gas is at least one of air, inert gas, oxygen, and nitrogen.
Preferably, in step S3, the running speed of the base film is 40-50 m/min.
Preferably, in step S3, the mixed slurry with gas is dried in an oven with gradually increased temperature.
Preferably, the temperature gradient is 3-5 ℃.
Another object of the present invention is to provide a separator produced by the method for producing a separator described in any one of the above.
The invention also provides a lithium ion battery, which comprises a positive plate, a negative plate and a diaphragm arranged between the positive plate and the negative plate, wherein the diaphragm is the diaphragm.
Compared with the prior art, the invention has the beneficial effects that: according to the preparation method provided by the invention, gas is introduced into the mixed slurry containing PMMA and inorganic filler, the gas flow is controlled to be 1.6-2.0 m/s, the gas speed is 30-50 m/s, the generated continuous stable bubbles with proper size can be adhered to PMMA particles with good hydrophobicity to form a bubble-PMMA particle polymer, the PMMA particles are brought to the surface of the ceramic coating under the action of bubble buoyancy, the purpose of coating twice is achieved through one-time coating, meanwhile, the problem that the PMMA coating is difficult to control due to small thickness and surface density increment of the PMMA coating is solved, and the production cost is reduced.
Drawings
FIG. 1 is an SEM image of PMMA particles.
FIG. 2 is a photograph of an aggregation of bubble-PMMA particles.
FIG. 3 is an analysis chart of the stress condition of the interface between PMMA particles and bubbles.
FIG. 4 is an SEM image of PMMA particles floating on the surface of the ceramic coating.
FIG. 5 is a graph showing wet bond strength curves of example 1 of the present invention and comparative example 1.
Detailed Description
The invention provides a preparation method of a diaphragm, which comprises the following steps:
s1, preparing ceramic coating slurry;
s2, mixing PMMA, a wetting agent, a thickening agent and a solvent to prepare PMMA coating slurry, and adding the ceramic coating slurry into the PMMA coating slurry to mix to obtain mixed slurry;
and S3, introducing gas to the bottom of the mixed slurry, wherein the flow rate of the introduced gas is 1.6-2.0 m/S, the gas velocity is 30-50 m/S, coating the mixed slurry with the gas on at least one surface of the base film, and drying at 40-60 ℃ to obtain the PMMA coating, the ceramic coating and the diaphragm of the base film which are sequentially stacked.
Polymethyl methacrylate (PMMA) has the following advantages: 1) the swelling degree in the electrolyte is low, the electrolyte is less absorbed, and the electrochemical performance of the lithium ion battery is good; 2) the adhesive has adhesiveness at a certain temperature and pressure, the adhesion between the diaphragm and the pole piece can be improved, and the hardness of the produced lithium ion battery is high.
The PMMA particles are approximately spherical in shape, and as shown in fig. 1, have a low density (slightly higher than that of water), and have a high surface hydrophobicity, so that they are easily adhered to the surface of the bubbles and have a low desorption probability.
The bubbles are used as a carrier, have strong hydrophobicity, are very easy to collide with PMMA particles with good hydrophobicity in the slurry, such as PMMA particle aggregates with the density smaller than that of water are formed after adhesion, and the PMMA particles can gather at the bottom of the bubbles due to the action of gravity, as shown in figure 2, a picture shot by a high-speed camera can clearly show that the PMMA particles gather at the bottom of the bubbles, and the bubbles can float upwards due to the action of buoyancy, so that the PMMA particles are taken to the surface of the ceramic coating, the bubbles are broken in the subsequent drying process, the outermost layer is the PMMA coating, the inner layer is the diaphragm of the ceramic coating, the effect of replacing two layers is achieved, the controllability of the PMMA particles is guaranteed, and the production cost is also remarkably reduced.
As shown in FIG. 3, the force analysis of the interface between PMMA particles and bubbles shows that van der Waals repulsion F exists between PMMA particles and bubblesWRepulsive force F to static electricityElWhile a large hydrophobic attraction F existssy. Only when the attractive force between PMMA particles and bubbles is greater than the repulsive force (F)sy＞FW+FEl) The bubbles can approach the PMMA particles and further press the hydration layer on the surface of the PMMA particles, and the particles adhere to the bubbles and float upwards. According to the method for floating the PMMA particles by utilizing the bubbles, during inflation, the hydration film on the surfaces of the PMMA particles with higher hydrophobicity is influenced, the wetting agent is desorbed from the surfaces of the PMMA particles under the action of the bubbles, the van der Waals attractive force among the PMMA particles is recovered, the PMMA particles float on the surface layer of the coating along with the bubbles, and then the bubbles are broken, so that the aim of floating the PMMA particles on the surface of the ceramic coating can be achieved controllably.
In addition, the PMMA particles can form an alternate form by utilizing the steric hindrance between the bubbles and be coated on the surface of the ceramic coating, so that the wet adhesion strength of the lithium battery diaphragm and the pole piece can be enhanced, and the stability and the safety of the lithium battery during use can be effectively improved.
The inventor verifies through a plurality of times of research experiments that the flow rate and the speed of the introduced gas are controlled within the range, the flow rate and the speed of the introduced gas have an interaction effect, bubbles which are stable continuously and have proper sizes can be generated under the condition, and the bubbles can carry PMMA particles to float upwards. Specifically, when the gas flow is too small, the number of generated bubbles is small, so that the floating number of PMMA is small; when the air flow is too large, a large amount of air bubbles in the slurry may explode at the surface of the coating layer, affecting the appearance of the coating film. When the gas velocity is low, the floating velocity of bubbles injected into the slurry is low, and the floating rate of PMMA is influenced; when the gas speed is high, the bubbles are easy to crush after being extruded.
Preferably, in step S1, the preparation method of the ceramic coating slurry comprises: mixing the inorganic filler, the thickening agent and the solvent, ball-milling for 1-3 h, and then adding the binder for mixing to obtain the ceramic coating slurry. Wherein, the inorganic filler can be at least one of aluminum oxide, aluminum hydroxide, boehmite, magnesium hydroxide and magnesium oxide. The thickener can be sodium carboxymethylcellulose (CMC), and the solvent can be deionized water; the binder can be any one of polyvinylidene fluoride, polyamide, polyacrylonitrile, polyacrylate and polyacrylic acid.
Preferably, the particle diameter D of the inorganic filler500.9 to 1.2 μm; the PMMParticle diameter D of A500.3 to 0.6 μm. PMMA with smaller particle size is adopted, and can collide with bubbles better to be adhered to the lower ends of the bubbles to form bubble-PMMA particle aggregates with the bubbles, so that the bubbles float on the surface of the ceramic coating.
Preferably, in step S2, the PMMA coating paste is prepared by: and mixing and stirring the wetting agent, the thickening agent and the solvent for 1-2 hours, adding the PMMA emulsion, and stirring together to obtain PMMA coating slurry. The wetting agent can be methyl cellulose, and is adsorbed on the surfaces of PMMA particles in the mixing process, so that van der Waals attractive force among the PMMA particles gradually disappears, and then the van der Waals attractive force is converted into stronger repulsive force, so that the PMMA particles in the slurry are well dispersed. The solvent may be deionized water and the thickener may be CMC.
Preferably, in step S3, the gas is at least one of air, inert gas, oxygen, and nitrogen. More preferably, the gas is air, the air is used as a gas phase, and the air can be vertically filled into the material box through a one-way valve air pipe arranged at the bottom of the material box of the slurry, so that the air brings the PMMA particles away to the surface of the ceramic coating.
Preferably, in step S3, the running speed of the base film is 40-50 m/min. The base film through the operating speed matches with the gas flow, the gas speed and the drying temperature that let in, and bubble in the assurance coating that can be better can not break in advance, just breaks out inefficacy through 40 ~ 60 ℃ of drying temperature after it takes away from the surface of ceramic coating with PMMA granule.
Preferably, in step S3, the mixed slurry with gas is dried in an oven with gradually increased temperature.
Preferably, the temperature gradient is 3-5 ℃. For example, 5-section oven is adopted for drying, and the mixed slurry is dried by the oven with the temperature gradient of 5 ℃ in sequence of 40 ℃, 45 ℃, 50 ℃, 55 ℃ and 60 ℃.
The second aspect of the present invention is a separator produced by the production method for a separator described in any one of the above.
The third aspect of the invention provides a lithium ion battery, which comprises a positive plate, a negative plate and a diaphragm arranged between the positive plate and the negative plate, wherein the diaphragm is the diaphragm.
In order to make the technical solutions and advantages of the present invention clearer, the present invention and its advantages will be described in further detail below with reference to the following detailed description and the accompanying drawings, but the embodiments of the present invention are not limited thereto.
Example 1
A method of making a separator comprising the steps of:
s1, mixing and stirring 60 parts of deionized water, 30 parts of alumina and 4 parts of CMC uniformly, then ball-milling for 1-3 hours in a ball mill, and finally adding 6 parts of a binder to obtain alumina slurry;
s2, mixing and stirring 40 parts of deionized water, 1.5 parts of methyl cellulose wetting agent and 5 parts of CMC for 1-2 hours, and then adding 3.5 parts of polymethyl methacrylate emulsion and uniformly stirring to obtain PMMA coating slurry; then adding the alumina slurry into the PMMA coating slurry to be uniformly mixed to obtain mixed slurry;
s3, taking air as a gas phase, vertically filling the air into the material box through a check valve air pipe arranged at the bottom of the material box, controlling the air flow to be 1.8m/S and the air speed to be 40m/S, coating the mixed slurry with the air on at least one surface of the base film, wherein the running speed of the base film is 45m/min, and then drying the base film in a 5-section drying oven at 40-60 ℃, wherein the temperature gradient is 5 ℃, so that the PMMA coating, the ceramic coating and the diaphragm of the base film which are sequentially stacked are obtained.
The properties of alumina compared to PMMA are shown in table 1 below.
TABLE 1
Figure BDA0003340624980000061
Example 2
The difference from embodiment 1 is step S3.
S3, taking air as a gas phase, vertically filling the air into the material box through a check valve air pipe arranged at the bottom of the material box, controlling the air flow to be 1.8m/S and the air speed to be 30m/S, coating the mixed slurry with the air on at least one surface of the base film, wherein the running speed of the base film is 45m/min, and then drying the base film in a 5-section drying oven at the temperature of 40-60 ℃, wherein the temperature gradient is 5 ℃, so that the PMMA coating, the ceramic coating and the diaphragm of the base film which are sequentially stacked are obtained.
The rest is the same as embodiment 1, and the description is omitted here.
Example 3
The difference from embodiment 1 is step S3.
S3, taking air as a gas phase, vertically filling the air into the material box through a check valve air pipe arranged at the bottom of the material box, controlling the air flow to be 1.8m/S and the air speed to be 50m/S, coating the mixed slurry with the air on at least one surface of the base film, wherein the running speed of the base film is 45m/min, and then drying the base film in a 5-section drying oven at the temperature of 40-60 ℃, wherein the temperature gradient is 5 ℃, so that the PMMA coating, the ceramic coating and the diaphragm of the base film which are sequentially stacked are obtained.
The rest is the same as embodiment 1, and the description is omitted here.
Example 4
The difference from embodiment 1 is step S3.
S3, taking air as a gas phase, vertically filling the air into the material box through a check valve air pipe arranged at the bottom of the material box, controlling the air flow to be 1.8m/S and the air speed to be 70m/S, coating the mixed slurry with the air on at least one surface of the base film, wherein the running speed of the base film is 45m/min, and then drying the base film in a 5-section drying oven at the temperature of 40-60 ℃, wherein the temperature gradient is 5 ℃, so that the PMMA coating, the ceramic coating and the diaphragm of the base film which are sequentially stacked are obtained.
The rest is the same as embodiment 1, and the description is omitted here.
Example 5
The difference from embodiment 1 is step S3.
S3, taking air as a gas phase, vertically filling the air into the material box through a check valve air pipe arranged at the bottom of the material box, controlling the air flow to be 1.6m/S and the air speed to be 30m/S, coating the mixed slurry with the air on at least one surface of the base film, wherein the running speed of the base film is 45m/min, and then drying the base film in a 5-section drying oven at the temperature of 40-60 ℃, wherein the temperature gradient is 5 ℃, so that the PMMA coating, the ceramic coating and the diaphragm of the base film which are sequentially stacked are obtained.
The rest is the same as embodiment 1, and the description is omitted here.
Example 6
The difference from embodiment 1 is step S3.
S3, taking air as a gas phase, vertically filling the air into the material box through a check valve air pipe arranged at the bottom of the material box, controlling the air flow to be 1.6m/S and the air speed to be 50m/S, coating the mixed slurry with the air on at least one surface of the base film, wherein the running speed of the base film is 45m/min, and then drying the base film in a 5-section drying oven at the temperature of 40-60 ℃, wherein the temperature gradient is 5 ℃, so that the PMMA coating, the ceramic coating and the diaphragm of the base film which are sequentially stacked are obtained.
The rest is the same as embodiment 1, and the description is omitted here.
Example 7
The difference from embodiment 1 is step S3.
S3, taking air as a gas phase, vertically filling the air into the material box through a check valve air pipe arranged at the bottom of the material box, controlling the air flow to be 2.0m/S and the air speed to be 20m/S, coating the mixed slurry with the air on at least one surface of the base film, wherein the running speed of the base film is 45m/min, and then drying the base film in a 5-section drying oven at the temperature of 40-60 ℃, wherein the temperature gradient is 5 ℃, so that the PMMA coating, the ceramic coating and the diaphragm of the base film which are sequentially stacked are obtained.
The rest is the same as embodiment 1, and the description is omitted here.
Example 8
The difference from embodiment 1 is step S3.
S3, taking air as a gas phase, vertically filling the air into the material box through a check valve air pipe arranged at the bottom of the material box, controlling the air flow to be 2.0m/S and the air speed to be 60m/S, coating the mixed slurry with the air on at least one surface of the base film, wherein the running speed of the base film is 45m/min, and then drying the base film in a 5-section drying oven at the temperature of 40-60 ℃, wherein the temperature gradient is 5 ℃, so that the PMMA coating, the ceramic coating and the diaphragm of the base film which are sequentially stacked are obtained.
The rest is the same as embodiment 1, and the description is omitted here.
Example 9
The difference from embodiment 1 is step S3.
S3, taking air as a gas phase, vertically filling the air into the material box through a check valve air pipe arranged at the bottom of the material box, controlling the air flow to be 1.8m/S and the air speed to be 40m/S, coating the mixed slurry with the air on at least one surface of the base film, wherein the running speed of the base film is 30m/min, and then drying the base film in a 5-section drying oven at 40-60 ℃, wherein the temperature gradient is 5 ℃, so that the PMMA coating, the ceramic coating and the diaphragm of the base film which are sequentially stacked are obtained.
The rest is the same as embodiment 1, and the description is omitted here.
Example 10
The difference from embodiment 1 is step S3.
S3, taking air as a gas phase, vertically filling the air into the material box through a check valve air pipe arranged at the bottom of the material box, controlling the air flow to be 1.8m/S and the air speed to be 40m/S, coating the mixed slurry with the air on at least one surface of the base film, wherein the running speed of the base film is 60m/min, and then drying the base film in a 5-section drying oven at 40-60 ℃, wherein the temperature gradient is 5 ℃, so that the PMMA coating, the ceramic coating and the diaphragm of the base film which are sequentially stacked are obtained.
The rest is the same as embodiment 1, and the description is omitted here.
Comparative example 1
A method of making a separator comprising the steps of:
s1, mixing and stirring 60 parts of deionized water, 30 parts of alumina and 4 parts of CMC uniformly, then ball-milling for 1-3 hours in a ball mill, and finally adding 6 parts of a binder to obtain alumina slurry; coating the aluminum oxide slurry on at least one surface of a base film, and drying to obtain an aluminum oxide coating;
s2, mixing and stirring 40 parts of deionized water, 1.5 parts of methyl cellulose wetting agent and 5 parts of CMC for 1-2 hours, and then adding 3.5 parts of polymethyl methacrylate emulsion and uniformly stirring to obtain PMMA coating slurry; coating the PMMA coating slurry on the surface of the aluminum oxide coating far away from the base film, and drying to obtain a PMMA coating; the preparation of the separator was completed.
The separators obtained in example 1 and comparative example 1 were subjected to performance tests.
The test results are shown in FIGS. 4 to 5.
As can be seen from the SEM image of fig. 4, PMMA particles are uniformly distributed on the surface of the alumina coating, and it can be seen that the diaphragm prepared by the present invention can pull most of PMMA particles to the surface of the alumina coating by floating bubbles through the action force between the bubbles and particles, thereby solving the problems of the current two-time coating tedious process and difficulty in controlling the thickness and surface density of the PMMA coating.
In addition, as can be seen from the wet adhesion strength graph of fig. 5, the test curves of the diaphragm obtained by the preparation method of the present invention and the preparation method of the comparative example 1 are basically overlapped, which shows that the bubbles used by the present invention pull most of PMMA particles to the surface of the alumina coating, the difference between the adhesion of the PMMA coating to the pole piece and the secondary coating of the comparative example 1 is not large, and the stability of the diaphragm and the lithium ion battery is ensured.
In addition, performance tests are also carried out on the diaphragms obtained in the embodiments 1 to 10, and it is found that when the flow rate of the introduced gas is controlled to be 1.6 to 2.0m/s and the gas speed is controlled to be 30 to 50m/s, the size of the generated bubbles is suitable, continuous and stable, the more PMMA particles are taken away to the surface of alumina, and the controllability of the PMMA coating is ensured. When the gas flow is too small, the amount of the generated bubbles is small, so that the amount of the PMMA floating upwards is small; when the air flow is too large, a large amount of air bubbles in the slurry may burst at the surface of the coating rather than being broken at the drying stage, greatly affecting the appearance of the coating film. In addition, when the gas velocity is small, the floating velocity of bubbles injected into the slurry is low, and the floating rate of PMMA is influenced; when the gas speed is high, the bubbles are easy to crush after being extruded.
Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims (10)

1. A method for preparing a separator, comprising the steps of:
s1, preparing ceramic coating slurry;
s2, mixing PMMA, a wetting agent, a thickening agent and a solvent to prepare PMMA coating slurry, and adding the ceramic coating slurry into the PMMA coating slurry to mix to obtain mixed slurry;
and S3, introducing gas to the bottom of the mixed slurry, wherein the flow rate of the introduced gas is 1.6-2.0 m/S, the gas velocity is 30-50 m/S, coating the mixed slurry with the gas on at least one surface of the base film, and drying at 40-60 ℃ to obtain the PMMA coating, the ceramic coating and the diaphragm of the base film which are sequentially stacked.
2. The method for preparing a separator according to claim 1, wherein in step S1, the ceramic coating slurry is prepared by: mixing the inorganic filler, the thickening agent and the solvent, ball-milling for 1-3 h, and then adding the binder for mixing to obtain the ceramic coating slurry.
3. The method for producing a separator according to claim 2, wherein the particle diameter D of the inorganic filler500.9 to 1.2 μm; particle size D of PMMA500.3 to 0.6 μm.
4. The method for preparing a separator according to claim 1, wherein in step S2, the PMMA coating paste is prepared by: and mixing and stirring the wetting agent, the thickening agent and the solvent for 1-2 hours, adding the PMMA emulsion, and stirring together to obtain PMMA coating slurry.
5. The method for producing a separator according to claim 1, wherein in step S3, the gas is at least one of air, an inert gas, oxygen, and nitrogen.
6. The method of manufacturing a separator according to claim 1, wherein in step S3, the running speed of the base film is 40 to 50 m/min.
7. The method for preparing a separator according to claim 6, wherein the mixed slurry with gas is dried in an oven with gradually increased temperature in step S3.
8. The method for producing a separator according to claim 7, wherein the temperature gradient is 3 to 5 ℃.
9. A separator produced by the method for producing a separator according to any one of claims 1 to 8.
10. A lithium ion battery comprising a positive plate, a negative plate and a separator interposed between said positive plate and said negative plate, wherein said separator is the separator of claim 9.
CN202111307354.7A 2021-11-05 2021-11-05 Preparation method of diaphragm, diaphragm and lithium ion battery Pending CN114094280A (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106784533A (en) * 2017-01-20 2017-05-31 东莞市卓高电子科技有限公司 A kind of production technology containing PMMA and its copolymer coated barrier film
CN108963153A (en) * 2018-07-10 2018-12-07 珠海恩捷新材料科技有限公司 A kind of lithium ion battery separator and preparation method thereof
CN110957452A (en) * 2019-09-25 2020-04-03 东莞赣锋电子有限公司 Preparation method of coating diaphragm containing PMMA and PEEK
CN111793414A (en) * 2020-07-10 2020-10-20 普罗旺斯科技（深圳）有限公司 Antibacterial heat dissipation coating and preparation method thereof

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106784533A (en) * 2017-01-20 2017-05-31 东莞市卓高电子科技有限公司 A kind of production technology containing PMMA and its copolymer coated barrier film
CN108963153A (en) * 2018-07-10 2018-12-07 珠海恩捷新材料科技有限公司 A kind of lithium ion battery separator and preparation method thereof
CN110957452A (en) * 2019-09-25 2020-04-03 东莞赣锋电子有限公司 Preparation method of coating diaphragm containing PMMA and PEEK
CN111793414A (en) * 2020-07-10 2020-10-20 普罗旺斯科技（深圳）有限公司 Antibacterial heat dissipation coating and preparation method thereof

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Application publication date: 20220225