CN108807818B - Aromatic polyamide composite diaphragm and preparation method thereof - Google Patents
Aromatic polyamide composite diaphragm and preparation method thereof Download PDFInfo
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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
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
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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
- 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
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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
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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
- H01M50/409—Separators, membranes or diaphragms characterised by the material
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- 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
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Abstract
The invention discloses an aromatic polyamide composite diaphragm and a preparation method thereof, wherein the composite diaphragm consists of a base film and a coating, and the coating is arranged on one surface or two surfaces of the base film; the coating is formed by coating, washing and drying an aromatic polyamide casting solution; the aromatic polyamide casting solution is prepared by combining the following raw materials in parts by weight: aromatic polyamide fiber: 1-6 parts of a first solvent: 70-95 parts of pore-forming agent: 3-20 parts of cosolvent: 2-8 parts; the first solvent is one or more of NMP, DMF, DMAC or DMSO; the pore-forming agent is an organic alcohol compound; the cosolvent is KOH or CaCl2One or more of LiCl or pyridine. The obtained composite diaphragm has high thermal stability and good air permeability, and can be applied to production in a large scale.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to an aromatic polyamide composite diaphragm and a preparation method thereof.
Background
In recent years, with the vigorous development of new energy automobiles, the demand of lithium batteries is increasing in a blowout manner, and lithium battery separators, which are one of the core components of lithium batteries, are also developing at a high speed. At present, commercial lithium battery diaphragms are mainly made of polyolefin materials, have high porosity, high tensile strength and high acid-base resistance, but have poor temperature resistance, the melting point of the polyolefin diaphragms is 160 ℃ or lower, and when the temperature reaches the melting point of the polyolefin diaphragms, the diaphragms can undergo large-area thermal shrinkage to cause contact short circuit of positive and negative electrodes, so that thermal runaway of batteries is caused to cause safety accidents; meanwhile, the natural hydrophobicity and low surface energy of the polyolefin material make the polyolefin material difficult to be wetted by the electrolyte, and the application of the polyolefin material in the lithium battery is limited.
A plurality of battery enterprises begin to enter the field of coating and modifying the diaphragm, and the current commercialized composite diaphragm is mainly a ceramic coating diaphragm, but generally has the defects of poor thermal stability, easy precipitation of the main component of alumina of ceramic slurry due to inorganic particles, and stirring before film coating, and is not beneficial to large-scale production. And the aromatic polyamide polymers (PPTA, PMIA, PBA, PSA and the like) have the advantages of high temperature resistance, ultrahigh strength, acid and alkali resistance, light weight, insulation, aging resistance, long life cycle and the like, so that the aromatic polyamide polymers are used as coating materials, and the obtained aromatic polyamide coating diaphragm has the advantages of good thermal stability, good air permeability, high porosity, excellent wettability, long service life and the like.
At present, when a lithium ion battery diaphragm coated with aromatic polyamide is prepared, organic solvents such as DMF (dimethyl formamide), DMAc (dimethyl formamide), NMP (N-methyl pyrrolidone), DMSO (dimethyl sulfoxide) and the like are mostly used for matching with a cosolvent to dissolve the aromatic polyamide, then an inorganic particle pore-forming agent is added to obtain an aromatic polyamide casting solution, and then the aromatic polyamide coating lithium ion battery diaphragm is obtained through coating, washing and drying. However, inorganic particle pore-forming agents are difficult to disperse in organic solvents, influence the uniformity of coatings and pore-forming, and cannot be used for large-scale production.
Disclosure of Invention
The invention aims to provide an aromatic polyamide composite diaphragm and a preparation method thereof, which are used for solving the problems that an inorganic particle pore-forming agent in a lithium ion battery diaphragm coated by the existing aromatic polyamide is difficult to disperse in an organic solvent, influences the uniformity of a coating and pore-forming and cannot be used for large-scale production.
In order to achieve the purpose, the technical scheme of the invention is as follows:
the aromatic polyamide composite diaphragm consists of a base film and a coating, wherein the coating is arranged on one surface or two surfaces of the base film; the coating is formed by coating, washing and drying an aromatic polyamide casting solution;
the aromatic polyamide casting solution is prepared by combining the following raw materials in parts by weight: aromatic polyamide fiber: 1-6 parts of a first solvent: 70-95 parts of pore-forming agent: 3-20 parts of cosolvent: 2-8 parts; the pore-forming agent is an organic alcohol compound.
In one embodiment, the first solvent is one or more of NMP, DMF, DMAC, or DMSO; the cosolvent is KOH or CaCl2One or more of LiCl or pyridine; the organic alcohol compound is one or more of methanol, ethanol, ethylene glycol, propylene glycol, hexylene glycol, glycerol, tripropylene glycol and polypropylene glycol.
In one embodiment, the aromatic polyamide fiber is one or more of poly (p-phenylene terephthalamide) fiber, poly (m-phenylene isophthalamide) fiber, poly (benzamide) fiber or poly (phenylsulfone-terephthalamide) fiber; the aromatic polyamide fiber has a molecular weight of 5000-100000.
In one embodiment, the base film is one of a polyethylene film, a polypropylene/polyethylene composite film, a polyvinylidene fluoride film, a polyimide film, a polyethylene nonwoven fabric film, a polypropylene nonwoven fabric film, a polyimide nonwoven fabric film; the thickness of the base film is 5-30 mu m, the porosity is 30-80%, and the air permeability is 50-300 s/100 cc.
The preparation method for preparing the composite diaphragm comprises the following steps:
a. adding a cosolvent into a first solvent, heating and stirring until the cosolvent is completely dissolved, then adding aromatic polyamide fibers under the condition of heating and stirring, and continuously heating and stirring until the aromatic polyamide fibers are completely dissolved to obtain a fiber dissolved solution;
b. under the condition of heating and stirring, slowly adding a pore-forming agent into the fiber dissolving solution, and continuously heating and stirring until the mixture is uniformly mixed to obtain an aromatic polyamide casting solution;
c. coating one or two surfaces of a base film with the aromatic polyamide casting film liquid, then placing the base film in a gel bath to convert the liquid phase of the aromatic polyamide casting film into a film, and sequentially washing and drying the film at high temperature to obtain the aromatic polyamide composite diaphragm; the gel bath is one of deionized water or mixed liquid comprising the deionized water and a second solvent, and the second solvent is formed by mixing a first solvent and a pore-forming agent.
In one embodiment, in the step b, the preparation temperature of the aromatic polyamide casting solution is 50-80 ℃.
In one embodiment, in the step b, the stirring speed for preparing the aromatic polyamide casting solution is 300 to 2000 rpm.
In one embodiment, when the gel bath is a mixed solution including deionized water and a second solvent, the mass part ratio of the deionized water to the second solvent is (0.5:1) - (5:1), and the mass part ratio of the first solvent to the pore-forming agent in the second solvent is consistent with the mass part ratio of the first solvent to the pore-forming agent in the aromatic polyamide casting solution.
In one embodiment, the composite separator has a thickness of 11 to 30 μm and an air permeability of 50 to 500s/100 cc.
In one embodiment, the composite separator has a thickness of 11 to 25 μm and an air permeability of 100 to 160s/100 cc.
The invention has the following advantages:
the invention relates to an aromatic polyamide coated lithium ion battery diaphragm, which consists of a lithium ion battery base film and coatings on one side or two sides of the base film. The lithium ion battery base membrane is a microporous polyolefin membrane such as polyethylene, polypropylene and a polyethylene-polypropylene composite membrane, the coating is obtained by coating, washing and drying an aromatic polyamide membrane casting solution, and the aromatic polyamide membrane casting solution is composed of aromatic polyamide fibers, a good solvent of the aromatic polyamide fibers, a cosolvent and a pore-forming agent. The aromatic polyamide casting solution of the composite diaphragm has good stability; the casting solution has simple raw materials, introduces hydrophilic organic alcohol pore-forming agent to replace inorganic particle pore-forming agent, and improves the uniformity of the coating and the pore-forming uniformity; the obtained composite diaphragm has high thermal stability and good air permeability, and can be applied to production in a large scale.
Drawings
Fig. 1 is an SEM image of the composite lithium ion battery separator in example 1 of the present invention.
Detailed Description
The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
Example 1
The aromatic polyamide composite diaphragm consists of a base film and a coating, wherein the coating is arranged on one surface or two surfaces of the base film; the coating is formed by coating, washing and drying an aromatic polyamide casting solution;
the aromatic polyamide casting solution is prepared by combining the following raw materials in parts by weight: aromatic polyamide fiber: 1 part of first solvent: 91.2 parts of pore-forming agent: 4.8 parts of cosolvent: 4 parts of a mixture; the first solvent is NMP; the pore-forming agent is tripropylene glycol; the cosolvent is LiCl.
The preparation method of the aromatic polyamide composite membrane comprises the following steps:
a. adding 4 parts of cosolvent LiCl into 91.2 parts of first solvent NMP, heating and stirring until the cosolvent LiCl is completely dissolved, adding 1 part of poly-p-phenylene terephthalamide fiber while stirring at a high speed, heating and stirring for 1 hour, completely dissolving the poly-p-phenylene terephthalamide fiber to obtain a fiber dissolving solution, slowly adding 4 parts of tripropylene glycol while stirring, heating and stirring for 1 hour, and obtaining the aromatic polyamide casting solution.
b. Preparing a gel bath solution: 80 parts of deionized water, 76 parts of NMP and 4 parts of tripropylene glycol are mixed and heated to 40-50 ℃ to obtain a gel bath solution for later use.
c. Selecting a polyethylene diaphragm with the thickness of 12 microns as a base film, coating the aramid fiber membrane casting solution on one side of the base film in a bar coating mode at the coating speed of 15m/min, evaporating for 20s in the air, immersing in a gel bath for phase conversion for 1min, taking out, immersing in deionized water, washing for 2min, and drying in an oven at the temperature of 60 ℃ to obtain the aromatic polyamide coated lithium ion battery diaphragm. The thickness of the composite diaphragm is 14 microns, the air permeability is 160s/100cc, and the obtained composite lithium ion battery diaphragm is analyzed by a scanning electron microscope, as shown in figure 1, the diaphragm is found to be uniform in pore forming, high in porosity, free of large-area pore-free areas and beneficial to transmission of lithium ions.
Example 2
The aromatic polyamide composite diaphragm consists of a base film and a coating, wherein the coating is arranged on one surface or two surfaces of the base film; the coating is formed by coating, washing and drying an aromatic polyamide casting solution;
the aromatic polyamide casting solution is prepared by combining the following raw materials in parts by weight: aromatic polyamide fiber: 1.2 parts, first solvent: 73 parts of pore-forming agent: 3.8 parts of cosolvent: 3.2 parts of a mixture; the first solvent is NMP; the pore-forming agent is tripropylene glycol; the cosolvent is LiCl.
The preparation method of the aromatic polyamide composite membrane comprises the following steps:
a. weighing 3.2 parts of cosolvent LiCl, adding into 73 parts of first solvent NMP, heating and stirring until the cosolvent LiCl is completely dissolved, adding 1.2 parts of poly-p-phenylene terephthalamide fiber while stirring at a high speed, heating and stirring for 1 hour, completely dissolving the poly-p-phenylene terephthalamide fiber to obtain a fiber dissolving solution, slowly adding 3.8 parts of tripropylene glycol while stirring, heating and stirring for 1 hour, and obtaining the aromatic polyamide casting solution.
b. Preparing a gel bath solution: 80 parts of deionized water, 76 parts of NMP and 4 parts of tripropylene glycol are mixed and heated to 40-50 ℃ to obtain a gel bath solution for later use.
c. Selecting a polyethylene diaphragm with the thickness of 12 microns as a base film, coating the aramid fiber membrane casting solution on one side of the base film in a bar coating mode at the coating speed of 15m/min, evaporating for 20s in the air, immersing in a gel bath for phase conversion for 1min, taking out, washing with deionized water for 2min, and drying in an oven at the temperature of 60 ℃ to obtain the aromatic polyamide coated lithium ion battery diaphragm. The composite membrane had a thickness of 14 μm and an air permeability of 147s/100 cc.
Example 3
The aromatic polyamide composite diaphragm consists of a base film and a coating, wherein the coating is arranged on one surface or two surfaces of the base film; the coating is formed by coating, washing and drying an aromatic polyamide casting solution;
the aromatic polyamide casting solution is prepared by combining the following raw materials in parts by weight: aromatic polyamide fiber: 2.09 parts of a first solvent: 95 parts of pore-forming agent: 4.75 parts of cosolvent: 4.18 parts; the first solvent is NMP; the pore-forming agent is tripropylene glycol; the cosolvent is LiCl.
The preparation method of the aromatic polyamide composite membrane comprises the following steps:
a. weighing 4.18 parts of cosolvent LiCl, adding into 95 parts of first solvent NMP, heating and stirring until the cosolvent LiCl is completely dissolved, adding 2.09 parts of poly-p-phenylene terephthalamide fiber while stirring at a high speed, heating and stirring for 1 hour, completely dissolving the poly-p-phenylene terephthalamide fiber to obtain a fiber dissolving solution, slowly adding 4.75 parts of tripropylene glycol while stirring, heating and stirring for 1 hour, and obtaining the aromatic polyamide casting solution.
b. Preparing a gel bath solution: 76 parts of deionized water, 72.2 parts of NMP and 3.8 parts of tripropylene glycol are mixed and heated to 40-50 ℃ to obtain a gel bath solution.
c. Selecting a polyethylene diaphragm with the thickness of 12 microns as a base film, coating the aramid fiber membrane casting solution on one side of the base film in a bar coating mode at the coating speed of 15m/min, evaporating for 20s in the air, immersing in a gel bath for phase conversion for 1min, taking out, washing with deionized water for 2min, and drying in an oven at the temperature of 60 ℃ to obtain the aromatic polyamide coated lithium ion battery diaphragm. The composite membrane had a thickness of 14 μm and an air permeability of 165s/100 cc.
Example 4
The aromatic polyamide composite diaphragm consists of a base film and a coating, wherein the coating is arranged on one surface or two surfaces of the base film; the coating is formed by coating, washing and drying an aromatic polyamide casting solution;
the aromatic polyamide casting solution is prepared by combining the following raw materials in parts by weight: aromatic polyamide fiber: 1 part of first solvent: 86 parts of pore-forming agent: 9.6 parts of cosolvent: 4 parts of a mixture; the first solvent is DMAC; the pore-forming agent is tripropylene glycol; the cosolvent is CaCl2。
The preparation method of the aromatic polyamide composite membrane comprises the following steps:
a. weighing 4 parts of cosolvent CaCl2Adding the mixture into 86 parts of first solvent DMAC, heating and stirring until the mixture is completely dissolved, adding 1 part of poly-p-phenylene terephthalamide fiber while stirring at a high speed, heating and stirring for 1 hour, completely dissolving the poly-p-phenylene terephthalamide fiber to obtain a fiber dissolved solution, slowly adding 9.6 parts of tripropylene glycol while stirring, heating and stirring for 1 hour to obtain the aromatic polyamide casting solution.
b. Preparing a gel bath solution: 128 parts of deionized water, 28.8 parts of DMAC and 3.2 parts of tripropylene glycol are mixed to give a gel bath solution.
c. Selecting a polyethylene diaphragm with the thickness of 12 microns as a base film, coating the aramid fiber membrane casting solution on one side of the base film in a bar coating mode at the coating speed of 15m/min, evaporating for 20s in the air, immersing in a gel bath for phase conversion for 1min, taking out, washing with deionized water for 2min, and drying in an oven at the temperature of 60 ℃ to obtain the aromatic polyamide coated lithium ion battery diaphragm. The composite membrane had a thickness of 16 μm and an air permeability of 182s/100 cc.
Example 5
The aromatic polyamide composite diaphragm consists of a base film and a coating, wherein the coating is arranged on one surface or two surfaces of the base film; the coating is formed by coating, washing and drying an aromatic polyamide casting solution;
the aromatic polyamide casting solution is prepared by combining the following raw materials in parts by weight: aromatic polyamide fiber: 1 part of first solvent: 91.2 parts of pore-forming agent: 4.8 parts of cosolvent: 4 parts of a mixture; the first solvent is DMAC; the pore-forming agent is tripropylene glycol; the cosolvent is CaCl2。
The preparation method of the aromatic polyamide composite membrane comprises the following steps:
a. weighing 4 parts of cosolvent CaCl2Adding the mixture into 91.2 parts of first solvent DMAC, heating and stirring until the mixture is completely dissolved, adding 1 part of poly-p-phenylene terephthalamide fiber while stirring at a high speed, heating and stirring for 1 hour, completely dissolving the poly-p-phenylene terephthalamide fiber to obtain a fiber dissolved solution, slowly adding 4.8 parts of tripropylene glycol while stirring, heating and stirring for 1 hour to obtain aromaticA polyamide casting solution.
b. Preparing a gel bath solution: 128 parts of deionized water, 30 parts of DMAc and 1.6 parts of tripropylene glycol are mixed to obtain a gel bath solution.
c. Selecting a polyethylene diaphragm with the thickness of 12 microns as a base film, coating the aramid fiber membrane casting solution on one side of the base film in a bar coating mode at the coating speed of 15m/min, evaporating for 20s in the air, immersing in a gel bath for phase conversion for 1min, taking out, washing with deionized water for 2min, and drying in an oven at the temperature of 60 ℃ to obtain the aromatic polyamide coated lithium ion battery diaphragm. The composite membrane had a thickness of 16 μm and an air permeability of 187s/100 cc.
Example 6
The aromatic polyamide composite diaphragm consists of a base film and a coating, wherein the coating is arranged on one surface or two surfaces of the base film; the coating is formed by coating, washing and drying an aromatic polyamide casting solution;
the aromatic polyamide casting solution is prepared by combining the following raw materials in parts by weight: aromatic polyamide fiber: 1.5 parts, first solvent: 76.8 parts of pore-forming agent: 19.2 parts of cosolvent: 4 parts of a mixture; the first solvent is NMP; the pore-forming agent is tripropylene glycol; the cosolvent is LiCl.
The preparation method of the aromatic polyamide composite membrane comprises the following steps:
a. weighing 4 parts of cosolvent LiCl, adding into 76.8 parts of first solvent NMP, heating and stirring until the cosolvent LiCl is completely dissolved, adding 1.5 parts of poly-p-phenylene terephthalamide fiber while stirring at a high speed, heating and stirring for 1 hour, completely dissolving the poly-p-phenylene terephthalamide fiber to obtain a fiber dissolving solution, slowly adding 19.2 parts of tripropylene glycol while stirring, heating and stirring for 1 hour, and obtaining the aromatic polyamide casting solution.
b. Preparing a gel bath solution: 80 parts of deionized water, 64 parts of NMP and 16 parts of tripropylene glycol are mixed and heated to 40-50 ℃ to obtain a gel bath solution for later use.
c. Selecting a polyethylene diaphragm with the thickness of 12 microns as a base film, coating the aramid fiber membrane casting solution on one side of the base film in a bar coating mode at the coating speed of 15m/min, evaporating for 20s in the air, immersing in a gel bath for phase conversion for 1min, taking out, washing with deionized water for 2min, and drying in an oven at the temperature of 60 ℃ to obtain the aromatic polyamide coated lithium ion battery diaphragm. The composite membrane had a thickness of 14 μm and an air permeability of 196s/100 cc.
Example 7
The aromatic polyamide composite diaphragm consists of a base film and a coating, wherein the coating is arranged on one surface or two surfaces of the base film; the coating is formed by coating, washing and drying an aromatic polyamide casting solution;
the aromatic polyamide casting solution is prepared by combining the following raw materials in parts by weight: aromatic polyamide fiber: 6 parts of a first solvent: 86 parts of pore-forming agent: 9.6 parts of cosolvent: 4 parts of a mixture; the first solvent is NMP; the pore-forming agent is tripropylene glycol; the cosolvent is LiCl.
The preparation method of the aromatic polyamide composite membrane comprises the following steps:
a. weighing 4 parts of cosolvent LiCl, adding into 86 parts of first solvent NMP, heating and stirring until the cosolvent LiCl is completely dissolved, adding 6 parts of poly-p-phenylene terephthalamide fiber while stirring at a high speed, heating and stirring for 1 hour, completely dissolving the poly-p-phenylene terephthalamide fiber to obtain a fiber dissolving solution, slowly adding 9.6 parts of tripropylene glycol while stirring, heating and stirring for 1 hour, and obtaining the aromatic polyamide casting solution.
b. Preparing a gel bath solution: 80 parts of deionized water, 72 parts of NMP and 8 parts of tripropylene glycol are mixed and heated to 40-50 ℃ to obtain a gel bath solution for later use.
c. Selecting a polyethylene diaphragm with the thickness of 12 microns as a base film, coating the aramid fiber membrane casting solution on one side of the base film in a bar coating mode at the coating speed of 15m/min, evaporating for 20s in the air, immersing in a gel bath for phase conversion for 1min, taking out, washing with deionized water for 2min, and drying in an oven at the temperature of 60 ℃ to obtain the aromatic polyamide coated lithium ion battery diaphragm. The composite membrane had a thickness of 14 μm and an air permeability of 283s/100 cc.
Example 8
The aromatic polyamide composite diaphragm consists of a base film and a coating, wherein the coating is arranged on one surface or two surfaces of the base film; the coating is formed by coating, washing and drying an aromatic polyamide casting solution;
the aromatic polyamide casting solution is prepared by combining the following raw materials in parts by weight: aromatic polyamide fiber: 2 parts of a first solvent: 88 parts of pore-forming agent: 9.8 parts of cosolvent: 2 parts of (1); the first solvent is NMP; the pore-forming agent is tripropylene glycol; the cosolvent is LiCl.
The preparation method of the aromatic polyamide composite membrane comprises the following steps:
a. weighing 2 parts of cosolvent LiCl, adding into 88 parts of first solvent NMP, heating and stirring until the cosolvent LiCl is completely dissolved, adding 2 parts of poly-p-phenylene terephthalamide fiber while stirring at a high speed, heating and stirring for 1 hour, completely dissolving the poly-p-phenylene terephthalamide fiber to obtain a fiber dissolving solution, slowly adding 9.8 parts of tripropylene glycol while stirring, heating and stirring for 1 hour, and obtaining the aromatic polyamide casting solution.
b. Preparing a gel bath solution: 80 parts of deionized water, 72 parts of NMP and 8 parts of tripropylene glycol are mixed and heated to 40-50 ℃ to obtain a gel bath solution for later use.
c. Selecting a polyethylene diaphragm with the thickness of 12 microns as a base film, coating the aramid fiber membrane casting solution on one side of the base film in a bar coating mode at the coating speed of 15m/min, evaporating for 20s in the air, immersing in a gel bath for phase conversion for 1min, taking out, washing with deionized water for 2min, and drying in an oven at the temperature of 60 ℃ to obtain the aromatic polyamide coated lithium ion battery diaphragm. The composite membrane had a thickness of 14 μm and an air permeability of 356s/100 cc.
Example 9
The aromatic polyamide composite diaphragm consists of a base film and a coating, wherein the coating is arranged on one surface or two surfaces of the base film; the coating is formed by coating, washing and drying an aromatic polyamide casting solution;
the aromatic polyamide casting solution is prepared by combining the following raw materials in parts by weight: aromatic polyamide fiber: 2 parts of a first solvent: 87 parts of pore-forming agent: 4.6 parts of cosolvent: 8 parts of a mixture; the first solvent is NMP; the pore-forming agent is tripropylene glycol; the cosolvent is LiCl.
The preparation method of the aromatic polyamide composite membrane comprises the following steps:
a. weighing 8 parts of cosolvent LiCl, adding into 87 parts of first solvent NMP, heating and stirring until the cosolvent LiCl is completely dissolved, adding 2 parts of poly-p-phenylene terephthalamide fiber while stirring at a high speed, heating and stirring for 1 hour, completely dissolving the poly-p-phenylene terephthalamide fiber to obtain a fiber dissolving solution, slowly adding 4.6 parts of tripropylene glycol while stirring, heating and stirring for 1 hour, and obtaining the aromatic polyamide casting solution.
b. Preparing a gel bath solution: 80 parts of deionized water, 76 parts of NMP and 4 parts of tripropylene glycol are mixed and heated to 40-50 ℃ to obtain a gel bath solution for later use.
c. Selecting a polyethylene diaphragm with the thickness of 12 microns as a base film, coating the aramid fiber membrane casting solution on one side of the base film in a bar coating mode at the coating speed of 15m/min, evaporating for 20s in the air, immersing in a gel bath for phase conversion for 1min, taking out, washing with deionized water for 2min, and drying in an oven at the temperature of 60 ℃ to obtain the aromatic polyamide coated lithium ion battery diaphragm. The composite membrane had a thickness of 14 μm and an air permeability of 325s/100 cc.
Example 10
The aramid coated lithium ion battery separators obtained in examples 1-9 and the base films used in the examples were tested for their performance and the comparative data are shown in table 1:
as can be seen from the data in the above table, the air permeability of the composite membrane obtained by coating the aromatic polyamide coating on the polyolefin membrane is increased by 20-60 s/100cc compared with that of the base membrane, and the thermal shrinkage performance is far better than that of the base membrane, such as the thermal shrinkage at 140 ℃ in example 7 is only 2%, so that the thermal stability of the membrane is greatly improved, and the safety performance of the battery is ensured.
Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.
Claims (6)
1. The aromatic polyamide composite diaphragm is characterized by consisting of a base film and a coating, wherein the coating is arranged on one surface or two surfaces of the base film; the coating is formed by coating, washing and drying an aromatic polyamide casting solution;
the aromatic polyamide casting solution is prepared by combining the following raw materials in parts by weight: aromatic polyamide fiber: 1-6 parts of a first solvent: 70-95 parts of pore-forming agent: 3-20 parts of cosolvent: 2-8 parts; the pore-forming agent is an organic alcohol compound; the organic alcohol compound is tripropylene glycol;
the preparation method of the composite diaphragm comprises the following steps:
a. adding a cosolvent into a first solvent, heating and stirring until the cosolvent is completely dissolved, then adding aromatic polyamide fibers under the condition of heating and stirring, and continuously heating and stirring until the aromatic polyamide fibers are completely dissolved to obtain a fiber dissolved solution;
b. under the condition of heating and stirring, slowly adding a pore-forming agent into the fiber dissolving solution, and continuously heating and stirring until the mixture is uniformly mixed to obtain an aromatic polyamide casting solution; the preparation temperature of the aromatic polyamide membrane casting solution is 50-80 ℃, and the stirring speed when the aromatic polyamide membrane casting solution is prepared is 300-2000 rpm;
c. coating one or two surfaces of a base film with the aromatic polyamide casting film liquid, then placing the base film in a gel bath to convert the liquid phase of the aromatic polyamide casting film into a film, and sequentially washing and drying the film at high temperature to obtain the aromatic polyamide composite diaphragm; the gel bath is one of deionized water or mixed liquid comprising the deionized water and a second solvent, and the second solvent is formed by mixing a first solvent and a pore-forming agent;
the gel bath is a mixed solution of deionized water and a second solvent, the mass part ratio of the deionized water to the second solvent is (0.5:1) - (5:1), and the mass part ratio of the first solvent to the pore-forming agent in the second solvent is consistent with the mass part ratio of the first solvent to the pore-forming agent in the aromatic polyamide membrane casting solution.
2. The aromatic polyamide composite membrane according to claim 1, wherein the first solvent is one or more of NMP, DMF, DMAC, or DMSO; the cosolvent is KOH or CaCl2One or more of LiCl or pyridine.
3. The aromatic polyamide composite separator according to claim 1, wherein the aromatic polyamide fiber is one or more of poly (p-phenylene terephthalamide) fiber, poly (m-phenylene isophthalamide) fiber, poly (p-benzamide) fiber, or poly (phenylsulfone-terephthalamide) fiber; the aromatic polyamide fiber has a molecular weight of 5000-100000.
4. The aromatic polyamide composite separator according to claim 1, wherein the base film is one of a polyethylene film, a polypropylene/polyethylene composite film, a polyvinylidene fluoride film, a polyimide film, a polyethylene nonwoven fabric film, a polypropylene nonwoven fabric film, and a polyimide nonwoven fabric film; the thickness of the base film is 5-30 mu m, the porosity is 30-80%, and the air permeability is 50-300 s/100 cc.
5. The aromatic polyamide composite separator according to claim 1, wherein the composite separator has a thickness of 11 to 30 μm and an air permeability of 50 to 500s/100 cc.
6. The aromatic polyamide composite separator according to claim 5, wherein the composite separator has a thickness of 11 to 25 μm and an air permeability of 100 to 160s/100 cc.
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| US20230042242A1 (en) * | 2019-12-27 | 2023-02-09 | Panasonic Intellectual Property Management Co., Ltd. | Lithium secondary battery |
| CN111370625A (en) * | 2020-03-22 | 2020-07-03 | 华南理工大学 | Aramid fiber phase-transition coating lithium ion battery diaphragm and preparation method thereof |
| CN111603946A (en) * | 2020-05-21 | 2020-09-01 | 杭州科百特科技有限公司 | Nylon membrane and preparation method and application thereof |
| CN111603948B (en) * | 2020-05-21 | 2023-06-30 | 杭州科百特科技有限公司 | Nylon membrane and preparation method and application thereof |
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| US6447958B1 (en) * | 1998-04-27 | 2002-09-10 | Sumitomo Chemical Co., Ltd. | Non-aqueous electrolyte battery separator |
| CN103242556A (en) * | 2013-04-17 | 2013-08-14 | 广东精进能源有限公司 | Method for preparing aramid composite diaphragm |
| CN103531736A (en) * | 2013-10-27 | 2014-01-22 | 中国乐凯集团有限公司 | High-heat-resistance lithium-ion battery diaphragm and preparation method thereof |
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| US6447958B1 (en) * | 1998-04-27 | 2002-09-10 | Sumitomo Chemical Co., Ltd. | Non-aqueous electrolyte battery separator |
| CN103242556A (en) * | 2013-04-17 | 2013-08-14 | 广东精进能源有限公司 | Method for preparing aramid composite diaphragm |
| CN103531736A (en) * | 2013-10-27 | 2014-01-22 | 中国乐凯集团有限公司 | High-heat-resistance lithium-ion battery diaphragm and preparation method thereof |
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