CN109860483B - Separator coating liquid and manufacturing method thereof, separator and manufacturing method thereof, and secondary battery - Google Patents
Separator coating liquid and manufacturing method thereof, separator and manufacturing method thereof, and secondary battery Download PDFInfo
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- CN109860483B CN109860483B CN201910135040.XA CN201910135040A CN109860483B CN 109860483 B CN109860483 B CN 109860483B CN 201910135040 A CN201910135040 A CN 201910135040A CN 109860483 B CN109860483 B CN 109860483B
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Abstract
The invention belongs to the technical field of secondary batteries, and relates to a diaphragm coating liquid and a manufacturing method thereof, a diaphragm and a manufacturing method thereof, and a secondary battery. The invention provides a preparation method of a diaphragm coating liquid, which comprises the following steps: providing a first dispersion liquid formed by polyetherimide solution, a binder and a pore-forming agent, providing a second dispersion liquid formed by inorganic particles, a dispersing agent and an organic solvent, mixing the first dispersion liquid and the second dispersion liquid, and separating to obtain the diaphragm coating liquid. The method can retain the original stability of the polyetherimide solution to the maximum extent, and simultaneously, the method enables the diaphragm coating solution to have good thermal shrinkage performance by adding inorganic particles. The separator coating solution prepared by the above method can improve the performance of the base film as a whole. In addition, the invention also provides a diaphragm containing the diaphragm coating liquid, a manufacturing method thereof and a secondary battery.
Description
Technical Field
The invention belongs to the technical field of secondary batteries, and particularly relates to a diaphragm coating liquid and a manufacturing method thereof, a diaphragm and a manufacturing method thereof, and a secondary battery.
Background
The separator is a porous membrane that separates the positive and negative poles of the battery and allows only certain specific ions to pass through. In the structure of the battery, the separator is one of the most critical materials, and the performance of the separator determines the interface structure, internal resistance and the like of the battery, and directly influences the capacity, cycle and safety performance of the battery. The separator with excellent performance plays an important role in improving the comprehensive performance of the battery.
In the prior art, the diaphragm has low stability and large thermal shrinkage, and is easy to cause short circuit of a battery and cause safety problems.
In view of this, the present invention is particularly proposed to solve at least one of the above-mentioned problems.
Disclosure of Invention
The first purpose of the invention is to provide a method for preparing a diaphragm coating solution, which can keep the original stability of a polyetherimide solution to the maximum extent and simultaneously enable the diaphragm coating solution to have good heat shrinkage performance by adding inorganic particles.
A second object of the present invention is to provide a separator coating liquid prepared by the above method, which can improve the properties of a base film as a whole.
A third object of the present invention is to provide a separator including the above separator coating liquid, which has a small thermal shrinkage rate and high mechanical strength.
The fourth purpose of the invention is to provide a manufacturing method of the diaphragm, which is simple to operate and has strong feasibility.
A fifth object of the present invention is to provide a secondary battery including the above separator, which has good safety performance.
In order to achieve the purpose, the invention adopts the technical scheme that:
according to an aspect of the present invention, there is provided a method of manufacturing a separator coating liquid, including:
providing a first dispersion of a polyetherimide solution, a binder, and a pore former;
providing a second dispersion of inorganic particles, a dispersant and an organic solvent;
mixing the first dispersion liquid and the second dispersion liquid, and separating to obtain a membrane coating liquid;
wherein the mass of the polyetherimide solution accounts for 5-10% of the total mass of the diaphragm coating liquid;
the mass of the inorganic particles accounts for 15-30% of the total mass of the diaphragm coating liquid.
As a further preferable technical scheme, the mass of the pore-forming agent accounts for 5% -15% of the total mass of the diaphragm coating liquid;
preferably, the mass of the binder accounts for 1% -3% of the total mass of the diaphragm coating liquid;
preferably, the mass of the dispersing agent accounts for 0.5-3% of the total mass of the diaphragm coating liquid.
As a further preferable technical solution, the inorganic particles include any one of alumina, barium titanate, magnesium hydroxide, or silica, or a combination of at least two thereof;
preferably, the organic solvent comprises any one of N-methylpyrrolidone, dimethylacetamide, N-dimethylformamide, or dimethyl phthalate, or a combination of at least two thereof;
preferably, the pore-forming agent comprises any one of dimethyl carbonate, ethyl acetate, cyclohexane or dimethyl phosphate or a combination of at least two of the above;
preferably, the binder comprises any one or a combination of at least two of polyvinylidene fluoride, polyvinylpyrrolidone or polyvinyl alcohol;
preferably, the dispersant comprises vinyl bis stearamide and/or oxidized polyethylene wax.
In a further preferred embodiment, the polyetherimide solution comprises polyetherimide and a dissolving agent, wherein the dissolving agent comprises any one or a combination of at least two of N-methylpyrrolidone, dimethylacetamide, N-dimethylformamide or dimethyl phthalate.
As a further preferred technical solution, the polyetherimide is a pretreated polyetherimide, and the pretreatment comprises drying;
preferably, the temperature of the drying is 110-150 ℃;
preferably, the drying time is 2-4 h.
According to another aspect of the invention, the diaphragm coating liquid is prepared by adopting the preparation method of the diaphragm coating liquid.
According to another aspect of the present invention, there is provided a separator comprising a base film and a coating liquid layer formed of the separator coating liquid;
preferably, the base film comprises polyethylene or polypropylene.
According to another aspect of the present invention, there is provided a method for manufacturing the separator, including: and coating the diaphragm coating liquid on the surface of the base film to perform pore-forming curing and post-treatment.
As a further preferred technical solution, the pore-forming solidification mode includes extraction, and the extracted extractant includes an inorganic extractant and/or an organic extractant;
preferably, the inorganic extractant comprises water;
preferably, the organic extractant comprises any one of or a combination of at least two of N-methylpyrrolidone, dimethylacetamide, N-dimethylformamide or dimethyl phthalate;
preferably, the number of extractions is 2-4.
According to another aspect of the present invention, there is provided a secondary battery comprising the separator or the separator obtained by the method for manufacturing the separator.
Compared with the prior art, the invention has the beneficial effects that:
1. the method for preparing the diaphragm coating solution can retain the original stability of the polyetherimide solution to the maximum extent, and meanwhile, the diaphragm coating solution has good heat shrinkage performance by adding the inorganic particles.
2. The diaphragm coating liquid provided by the invention is prepared by adopting the method. The diaphragm coating liquid can effectively reduce the heat shrinkage rate of the base film, and can improve the performance of the base film.
3. The diaphragm provided by the invention comprises the coating liquid layer formed by the diaphragm coating liquid, and has small thermal shrinkage rate and high mechanical strength.
4. The manufacturing method of the diaphragm provided by the invention is simple to operate and strong in feasibility, and the function of improving the heat shrinkage rate of the base film by the diaphragm coating liquid is exerted to the maximum.
5. The secondary battery provided by the invention comprises the diaphragm, and the diaphragm has high stability and low thermal shrinkage rate, so that the safety performance of the secondary battery is greatly improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is an SEM picture of a separator obtained by coating a polyethylene-based film with a separator coating solution provided in example 1 of the present invention.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to embodiments and examples, but those skilled in the art will understand that the following embodiments and examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. Those who do not specify the conditions are performed according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are conventional products which are not indicated by manufacturers and are commercially available.
It should be noted that:
in the present invention, all the embodiments and preferred methods mentioned herein can be combined with each other to form a new technical solution, if not specifically stated.
In the present invention, all the technical features mentioned herein and preferred features may be combined with each other to form a new technical solution, if not specifically stated.
The "ranges" disclosed herein may have one or more lower limits and one or more upper limits, respectively, in the form of lower limits and upper limits.
In the present invention, unless otherwise specified, the individual reactions or operation steps may or may not be performed in sequence. Preferably, the methods herein are performed sequentially.
Unless otherwise defined, technical and scientific terms used herein have the same meaning as is familiar to those skilled in the art. In addition, any methods or materials similar or equivalent to those described herein can also be used in the present invention.
In a first aspect, in at least one embodiment, there is provided a method of making a separator coating liquid, comprising:
providing a first dispersion of a polyetherimide solution, a binder, and a pore former;
providing a second dispersion of inorganic particles, a dispersant and an organic solvent;
mixing the first dispersion liquid and the second dispersion liquid, and separating to obtain a membrane coating liquid;
wherein, the mass of the polyetherimide solution accounts for 5-10% of the total mass of the diaphragm coating solution;
the mass of the inorganic particles accounts for 15-30% of the total mass of the diaphragm coating liquid.
Aiming at the problems of low stability and large thermal shrinkage rate of a battery diaphragm in the prior art, the invention provides a preparation method of a diaphragm coating liquid, which can retain the original stability of a polyetherimide solution to the maximum extent and simultaneously enables the diaphragm coating liquid to have good thermal shrinkage performance by adding inorganic particles.
Polyetherimide (PEI) is amber transparent solid, has inherent flame retardance and low smoke without adding any additive, has an oxygen index of 47%, a combustion grade of UL94-V-0 grade and a density of 1.28-1.42g/cm3. PEI has very strong high temperature stability and even non-reinforced PEI still has good toughness and strength. PEI also has very low shrinkage, good flame retardancy, chemical resistance, and mechanical properties. In addition, the glass transition temperature of PEI is very high, which reaches 215 ℃, and PEI can be used for a long time at the working temperature of 160-180 ℃. Therefore, the heat-resistant diaphragm coating solution is prepared by using the excellent thermal stability and mechanical properties of PEI, and the safety performance of the base film is further improved.
The inorganic particles are added into the diaphragm coating liquid, so that the skeleton structure of the base film can be increased, the supporting effect is achieved, and the heat shrinkage performance of the base film is improved.
It is understood that the polyetherimide must be formed into a polyetherimide solution before the polyetherimide can better exhibit its high stability characteristics; the binder has the function of enabling the prepared diaphragm coating liquid to be better attached to the surface of the base film; the dispersant has the function of better dispersing inorganic particles in an organic solvent, so that the prepared diaphragm coating liquid is more uniform; the pore-forming agent has the function of enabling the prepared diaphragm coating liquid to generate pores in the subsequent diaphragm preparation process, and the pores ensure that ions can smoothly pass through the diaphragm to generate electrochemical reaction.
The proper proportion of the polyetherimide to the inorganic particles in the diaphragm coating liquid can ensure that the performance of the manufactured diaphragm coating liquid is optimal. Typically, but not by way of limitation, the mass of the polyetherimide solution comprises the total mass of the separator coating fluid, and may be, for example, 5%, 6%, 7%, 8%, 9%, or 10%; the mass of the inorganic particles may be 15%, 17%, 19%, 20%, 22%, 25%, 27%, or 30% by mass of the total mass of the separator coating liquid, for example.
In a preferred embodiment, the mass of the pore-forming agent accounts for 5-15% of the total mass of the diaphragm coating liquid;
preferably, the mass of the binder accounts for 1-3% of the total mass of the diaphragm coating liquid;
preferably, the mass of the dispersant accounts for 0.5-3% of the total mass of the separator coating liquid.
Typically, but not by way of limitation, the mass of the pore former may be 5%, 8%, 9%, 10%, 12%, 13%, or 15% of the total mass of the separator coating solution, for example; the mass of the binder accounts for the total mass of the separator coating liquid, and can be 1%, 2% or 3%; the mass of the dispersant accounts for 0.5%, 1%, 1.5%, 2% or 3% of the total mass of the diaphragm coating liquid.
It should be noted that the content of the pore-forming agent, the binder and the dispersant in the total mass of the separator coating liquid also provides a favorable guarantee for improving the performance of the separator coating liquid.
In a preferred embodiment, the inorganic particles comprise any one of or a combination of at least two of alumina, barium titanate, magnesium hydroxide, or silica;
preferably, the organic solvent comprises any one or a combination of at least two of N-methylpyrrolidone, dimethylacetamide, N-dimethylformamide, or dimethyl phthalate;
preferably, the pore-forming agent comprises any one of dimethyl carbonate, ethyl acetate, cyclohexane or dimethyl phosphate or a combination of at least two of the two;
preferably, the binder comprises any one or a combination of at least two of polyvinylidene fluoride, polyvinylpyrrolidone or polyvinyl alcohol;
preferably, the dispersant comprises vinyl bis stearamide and/or oxidized polyethylene wax.
By adding the inorganic particles, the diaphragm coating liquid has good heat shrinkage performance, and the performance of the base film is improved. Typically, but not by way of limitation, the inorganic particles may be alumina, may be barium titanate, may be magnesium hydroxide, and may also be silica.
N-Methyl pyrrolidone (NMP) is a colorless transparent oil, an organic solvent with a slight amine odor. The lithium ion battery has low volatility, good thermal stability and chemical stability, can volatilize along with water vapor, and is widely applied to industries such as lithium batteries, medicines, pesticides, pigments, cleaning agents, insulating materials and the like.
Dimethylacetamide (DMAC) is a colorless and transparent organic solvent, and can be mixed with water, alcohols, ethers, esters, and other solvents.
N, N-Dimethylformamide (DMF) is colorless and transparent, is an organic solvent with wide application range, and has good dissolving capacity and chemical stability for various organic compounds and inorganic compounds.
Dimethyl phthalate (DMP) is a yellowish oily organic solvent, slightly aromatic, miscible with organic solvents such as ethanol and diethyl ether, and insoluble in water and petroleum ether.
It should be noted that the organic solvent may be other organic solvents commonly used in the art, as long as the organic solvent has similar properties to the above four organic solvents or the organic solvent formed by mixing the organic solvents.
The present invention is not particularly limited with respect to the types of pore-forming agent, binder and dispersant. Typically, but not by way of limitation, the pore-forming agent may be selected from dimethyl carbonate, ethyl acetate, cyclohexane, dimethyl phosphate, or a mixture of dimethyl carbonate and ethyl acetate; the binder can be selected from polyvinylidene fluoride, polyvinylpyrrolidone and polyvinyl alcohol; the dispersant can be selected from vinyl bis stearamide, oxidized polyethylene wax and a mixture of the vinyl bis stearamide and the oxidized polyethylene wax.
In a preferred embodiment, the polyetherimide solution comprises polyetherimide and a dissolution agent comprising any one of, or a combination of at least two of, N-methylpyrrolidone, dimethylacetamide, N-dimethylformamide, or dimethyl phthalate.
It is understood that polyetherimides are solids and require dissolution in a solvent to develop their high stability characteristics. Typically, but not by way of limitation, the dissolving agent may be selected from N-methylpyrrolidone, dimethylacetamide, N-dimethylformamide or dimethyl phthalate.
In a preferred embodiment, the polyetherimide is a polyetherimide that has been pretreated, the pretreatment comprising drying;
preferably, the temperature for drying is 110-;
preferably, the drying time is 2-4 h.
It is understood that the purpose of the pretreatment is to remove water possibly contained in the polyetherimide so as to ensure that the subsequent manufacturing process of the diaphragm coating liquid is smoothly carried out. Typically, but not by way of limitation, moisture that may be contained in the polyetherimide is removed by drying. The drying time can be 2h, 3h or 4 h; the drying temperature may be 110 ℃, 120 ℃, 130 ℃, 140 ℃ or 150 ℃.
In a second aspect, in at least one embodiment, a separator coating solution is provided, which is prepared by the above-mentioned method for preparing a separator coating solution.
The diaphragm coating liquid prepared by the method can effectively reduce the thermal shrinkage rate of the base film and can improve the performance of the base film.
In a third aspect, there is provided in at least one embodiment a separator comprising a base film and a coating liquid layer formed of the above separator coating liquid;
preferably, the base film comprises polyethylene or polypropylene.
The diaphragm coating liquid provided by the invention has the advantages of small thermal shrinkage rate, high mechanical strength and good comprehensive performance.
The separator provided by the present invention mainly comprises a base film and a coating liquid layer formed on the surface of the base film by the separator coating liquid, and the material of the base film is not particularly limited, and typically, but not limited, the base film may be polyethylene or polypropylene.
The invention is described in further detail below primarily with reference to polyethylene as an example, however, it is to be understood that the base film includes, but is not limited to, polyethylene.
In a fourth aspect, in at least one embodiment, there is provided a method for manufacturing the above diaphragm, including: and coating the diaphragm coating liquid on the surface of the base film to perform pore-forming curing and post-treatment.
The manufacturing method of the diaphragm provided by the invention is simple to operate and strong in feasibility, and can exert the function of improving the heat shrinkage rate of the base film of the diaphragm coating liquid to the maximum.
The post-treatment means that the separator after pore-forming and curing is dried for use. Typically, but not by way of limitation, the temperature of the oven drying may be 50 ℃, 60 ℃ or 70 ℃; the drying time can be 7h, 8h or 9 h.
In a preferred embodiment, the pore-forming solidification comprises extraction, and the extracted extractant comprises an inorganic extractant and/or an organic extractant;
preferably, the inorganic extractant comprises water;
preferably, the organic extractant comprises any one of or a combination of at least two of N-methylpyrrolidone, dimethylacetamide, N-dimethylformamide or dimethyl phthalate;
preferably, the number of extractions is 2-4.
The pore-forming and curing are intended to cause some pores in the separator coating solution applied to the base film and to cause the polyetherimide, which has been previously present in a liquid form, to adhere to the surface of the base film, thereby exerting its high stability.
The invention has no special requirement on the pore-forming solidification mode as long as the aim is achieved. For example, the pore-forming solidification mode is selected for extraction, and the number of extraction can be 2, 3 or 4, which is typical but not limited; the desired extractant may be an inorganic solvent, such as water; or an organic solvent such as N-methylpyrrolidone, dimethylacetamide, dimethyl phthalate or N, N-dimethylformamide; or the organic solvent and the inorganic solvent can be prepared according to a certain proportion and then used.
In a fifth aspect, in at least one embodiment, there is provided a secondary battery comprising the above separator or the separator obtained by the above method for producing a separator.
The secondary battery provided by the invention has the separator with high stability and low thermal shrinkage, so that the safety performance of the secondary battery is greatly improved. The secondary battery includes a lithium ion battery, a sodium ion battery, a lithium sulfur battery, a potassium ion battery, or the like.
The present invention will be further described with reference to specific examples, comparative examples, experimental examples and the accompanying drawings.
Example 1
The embodiment provides a manufacturing method of a diaphragm coating liquid, which comprises the following steps:
(1) 75g of polyetherimide was dried at a temperature of 110 ℃ for 3h, and then at a temperature of 50 ℃, the dried polyetherimide was dissolved in 1.92L of N-methylpyrrolidone to obtain a polyetherimide solution;
(2) adding 30g of polyvinylidene fluoride powder into the polyetherimide solution, stirring until the polyvinylidene fluoride powder is dissolved, then adding 150g of dimethyl carbonate, and stirring until the separated polyetherimide is dissolved to obtain a first dispersion liquid;
(3) adding 1.5g of vinyl bis stearamide into 300mL of N-methyl pyrrolidone, uniformly stirring, then adding 450g of alumina particles, and fully dispersing to obtain a second dispersion liquid;
(4) mixing the first dispersion liquid and the second dispersion liquid, stirring uniformly to obtain a mixed liquid, filtering the mixed liquid (with a sieve of 80-120 meshes), and discharging to obtain a membrane coating liquid;
the mass of the polyetherimide solution accounts for 5% of the total mass of the diaphragm coating liquid, the mass of the alumina particles accounts for 15% of the total mass of the diaphragm coating liquid, the mass of the dimethyl carbonate accounts for 5% of the total mass of the diaphragm coating liquid, the mass of the polyvinylidene fluoride accounts for 1% of the total mass of the diaphragm coating liquid, and the mass of the vinyl bis-stearamide accounts for 0.5% of the total mass of the diaphragm coating liquid.
Example 2
The embodiment provides a manufacturing method of a diaphragm coating liquid, which comprises the following steps:
(1) 300g of polyetherimide was oven dried at a temperature of 150 ℃ for 2h, and then the oven dried polyetherimide was dissolved in 600mL of dimethylacetamide at a temperature of 60 ℃ to give a polyetherimide solution;
(2) adding 90g of polyvinylpyrrolidone powder into the polyetherimide solution, stirring until the polyvinylpyrrolidone powder is dissolved, then adding 450mL of ethyl acetate, and stirring until the separated polyetherimide is dissolved to obtain a first dispersion liquid;
(3) adding 90g of oxidized polyethylene wax into 600mL of N-methylpyrrolidone, uniformly stirring, then adding 900g of barium titanate particles, and fully dispersing to obtain a second dispersion liquid;
(4) mixing the first dispersion liquid and the second dispersion liquid, stirring uniformly to obtain a mixed liquid, filtering the mixed liquid (with a sieve of 80-120 meshes), and discharging to obtain a membrane coating liquid;
wherein the mass of the polyetherimide solution accounts for 10% of the total mass of the diaphragm coating liquid, the mass of the barium titanate particles accounts for 30% of the total mass of the diaphragm coating liquid, the mass of the ethyl acetate accounts for 15% of the total mass of the diaphragm coating liquid, the mass of the polyvinylpyrrolidone accounts for 3% of the total mass of the diaphragm coating liquid, and the mass of the oxidized polyethylene wax accounts for 3% of the total mass of the diaphragm coating liquid.
Example 3
The embodiment provides a manufacturing method of a diaphragm coating liquid, which comprises the following steps:
(1) 240g of polyetherimide was dried at a temperature of 130 ℃ for 4h, and then at a temperature of 80 ℃ the dried polyetherimide was dissolved in 1.4L of dimethylacetamide to give a polyetherimide solution;
(2) adding 60g of polyvinyl alcohol powder into the polyetherimide solution, stirring until the polyvinyl alcohol powder is dissolved, then adding 300g of dimethyl phosphate, and stirring until the separated polyetherimide is dissolved to obtain a first dispersion liquid;
(3) adding 30g of vinyl bis stearamide into 400mL of dimethyl phthalate, uniformly stirring, then adding 600g of silicon dioxide particles, and fully dispersing to obtain a second dispersion liquid;
(4) mixing the first dispersion liquid and the second dispersion liquid, stirring uniformly to obtain a mixed liquid, filtering the mixed liquid (with a sieve of 80-120 meshes), and discharging to obtain a membrane coating liquid;
wherein the mass of the polyetherimide solution accounts for 8% of the total mass of the diaphragm coating liquid, the mass of the silica particles accounts for 20% of the total mass of the diaphragm coating liquid, the mass of the dimethyl phosphate accounts for 10% of the total mass of the diaphragm coating liquid, the mass of the polyvinyl alcohol accounts for 2% of the total mass of the diaphragm coating liquid, and the mass of the vinyl bis-stearamide accounts for 1% of the total mass of the diaphragm coating liquid.
Example 4
This example provides the same preparation method as example 1 except that the amount of the polyetherimide solution in step (1) was changed to 300g so that the mass of the polyetherimide solution was 10% of the total mass of the separator coating solution.
Example 5
This example provides a method for preparing a membrane coating liquid, which includes the same steps as in example 1, except that the amount of alumina particles in step (3) is changed to 900g, so that the mass of the alumina particles accounts for 30% of the total mass of the membrane coating liquid.
Example 6
This example provides a method for preparing a separator coating solution, which includes the same preparation steps as in example 1, except that 450g of alumina particles was replaced with 450g of barium titanate particles in step (3) such that the mass of the barium titanate particles was 5% of the total mass of the separator coating solution.
Example 7
This example provides a method for preparing a separator coating solution, which includes the same preparation steps as in example 1, except that 450g of alumina particles in step (3) are replaced with 450g of magnesium hydroxide particles, such that the mass of the magnesium hydroxide particles is 5% of the total mass of the separator coating solution.
Example 8
This example provides a method for preparing a separator coating solution, which includes the same steps as in example 1, except that the amount of polyvinylidene fluoride powder in step (2) is changed to 90g, so that the mass of polyvinylidene fluoride accounts for 3% of the total mass of the separator coating solution.
Example 9
This example provides a method for preparing a separator coating solution, which comprises the same steps as in example 1, except that the amount of dimethyl carbonate in step (2) was changed to 450g, so that the mass of dimethyl carbonate was 15% of the total mass of the separator coating solution.
Example 10
This example provides a method for preparing a separator coating solution, which comprises the same steps as in example 1, except that the amount of vinyl bis stearamide in step (3) was changed to 90g, so that the mass of vinyl bis stearamide accounted for 3% of the total mass of the separator coating solution.
Comparative example 1
This comparative example provides a method for producing a separator coating liquid, which comprises the same production steps as in example 1 except that, in step (1) and step (2), polyvinylidene fluoride powder was added to N-methylpyrrolidone, and the mixture was stirred until the polyvinylidene fluoride powder was dissolved, and then 150g of dimethyl carbonate was added, and the mixture was stirred until the polyether imide precipitated was dissolved, to obtain a first dispersion liquid.
Comparative example 2
This comparative example provides a method of manufacturing a separator coating liquid, which has the same manufacturing steps as example 1 except that no alumina particles are added in step (3).
Comparative example 3
The comparative example provides a method for preparing a separator coating solution, which comprises the same preparation steps as in example 1 except that step (1) is omitted, polyvinylidene fluoride powder is added into N-methylpyrrolidone in step (2), and alumina particles are not added in step (3).
Examples of the experiments
(1) Preparing extraction liquid
Respectively mixing N-methylpyrrolidone and deionized water in a volume ratio of 3: 2. 1: 1. 2: 3 to obtain a first extract, a second extract and a third extract.
(2) Making a diaphragm
The membrane coating solutions obtained in the above examples 1 to 10 and comparative examples 1 to 3 were respectively coated on a polyethylene-based membrane at a speed of 8 to 15m/min, and then sequentially extracted by a first extraction solution, a second extraction solution and a third extraction solution for 3 times, washed with deionized water, and then dried at 60 ℃ for 8 hours to finally obtain a membrane. Fig. 1 is an SEM picture of a separator obtained by coating a polyethylene-based film with a separator coating solution according to example 1 of the present invention; table 1 is a table comparing parameters of separators obtained by coating the separator coating liquids provided in examples 1 to 10 and comparative examples 1 to 3 of the present invention on a polyethylene-based film with those of the polyethylene-based film.
Table 1 comparative table of parameters of separators obtained by coating the separator coating liquids provided in examples 1 to 10 and comparative examples 1 to 3 on a polyethylene-based film with respect to the polyethylene-based film
Note: each of the separators and the polyethylene base films obtained in this example were gray or white in appearance
As can be seen from Table 1, the preparation method of the separator coating solution provided by the invention can maximally retain the original stability of the polyetherimide solution, and the separator coating solution has good heat shrinkage performance by adding the inorganic particles. Compared with a polyethylene base film, the thermal shrinkage rate of the diaphragm provided by the invention is reduced by 50%, and the needling strength is enhanced by 5%.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (9)
1. A method for manufacturing a diaphragm coating liquid is characterized by comprising the following steps:
(1) 300g of polyetherimide was dried at a temperature of 110 ℃ for 3h, and then at a temperature of 50 ℃, the dried polyetherimide was dissolved in 1.92L of N-methylpyrrolidone to obtain a polyetherimide solution;
(2) adding 30g of polyvinylidene fluoride powder into the polyetherimide solution, stirring until the polyvinylidene fluoride powder is dissolved, then adding 150g of dimethyl carbonate, and stirring until the separated polyetherimide is dissolved to obtain a first dispersion liquid;
(3) adding 1.5g of vinyl bis stearamide into 300mL of N-methyl pyrrolidone, uniformly stirring, then adding 450g of alumina particles, and fully dispersing to obtain a second dispersion liquid;
(4) mixing the first dispersion liquid and the second dispersion liquid, stirring the mixture to be uniform to obtain a mixed liquid, and filtering the mixed liquid by using a 80-120-mesh sieve to obtain a membrane coating liquid;
the mass of the polyetherimide solution accounts for 10% of the total mass of the diaphragm coating liquid, the mass of the alumina particles accounts for 15% of the total mass of the diaphragm coating liquid, the mass of the dimethyl carbonate accounts for 5% of the total mass of the diaphragm coating liquid, the mass of the polyvinylidene fluoride accounts for 1% of the total mass of the diaphragm coating liquid, and the mass of the vinyl bis-stearamide accounts for 0.5% of the total mass of the diaphragm coating liquid.
2. A separator coating liquid characterized by being produced by the method for producing a separator coating liquid according to claim 1.
3. A separator comprising a base film and a coating liquid layer formed from the separator coating liquid of claim 2;
the base film comprises polyethylene or polypropylene.
4. A method of making a membrane according to claim 3, comprising: and coating the diaphragm coating liquid on the surface of the base film to perform pore-forming curing and post-treatment.
5. The method of claim 4, wherein the pore-forming solidification comprises extraction, and the extraction agent comprises an inorganic extraction agent and/or an organic extraction agent.
6. The method of manufacturing a separator according to claim 5, wherein the inorganic extractant includes water.
7. The method for manufacturing a separator according to claim 5, wherein the organic extractant includes any one of N-methylpyrrolidone, dimethylacetamide, N-dimethylformamide, or dimethyl phthalate, or a combination of at least two thereof.
8. The method for producing a separator according to claim 5, wherein the number of times of extraction is 2 to 4.
9. A secondary battery comprising the separator according to claim 3 or the separator produced by the method for producing a separator according to any one of claims 4 to 8.
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| 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 |
| CN104037378A (en) * | 2014-05-28 | 2014-09-10 | 中国乐凯集团有限公司 | Secondary lithium-ion battery separator and application thereof |
| DE102014001025A1 (en) * | 2014-01-27 | 2015-07-30 | Li-Tec Battery Gmbh | Electrochemical cell |
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| CN109301134A (en) * | 2018-10-31 | 2019-02-01 | 河北金力新能源科技股份有限公司 | Diaphragm coating paste and preparation method thereof, lithium ion battery separator and preparation method thereof and lithium ion battery |
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