CN113169418B - Polyimide microsphere slurry, composite diaphragm and lithium ion battery - Google Patents
Polyimide microsphere slurry, composite diaphragm and lithium ion battery Download PDFInfo
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- CN113169418B CN113169418B CN201980074392.7A CN201980074392A CN113169418B CN 113169418 B CN113169418 B CN 113169418B CN 201980074392 A CN201980074392 A CN 201980074392A CN 113169418 B CN113169418 B CN 113169418B
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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
- H01M50/443—Particulate material
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention relates to the technical field of preparation of lithium ion battery diaphragms, and discloses polyimide microsphere slurry, a composite diaphragm and a lithium ion battery. The slurry comprises polyimide microspheres, a water-based adhesive, a wetting agent and deionized water, wherein the polyimide microspheres are prepared from polyamino polymer, diamine and dianhydride. The composite diaphragm prepared from the slurry has the advantages of good thermal stability, excellent puncture resistance and good air permeability, and compared with a ceramic coating diaphragm, the surface density of the coating is lower, and relatively, the specific capacity of a lithium battery containing the composite diaphragm is higher.
Description
Technical Field
The invention relates to the technical field of preparation of lithium ion battery diaphragms, in particular to polyimide microsphere slurry, a composite diaphragm prepared from the slurry and a lithium ion battery comprising the composite diaphragm.
Background
The lithium ion battery has the characteristics of high specific energy, long cycle life and no memory effect, and has the advantages of safety, reliability, rapid charge and discharge and the like, and becomes a research hotspot of a novel power supply technology in recent years. The lithium ion battery comprises an anode, a cathode, a diaphragm and an electrolyte, wherein the diaphragm is used as a barrier between the anode and the cathode, plays a vital role in the performance of the lithium ion battery, the performance of the diaphragm directly influences the capacity and the cycle of the battery, particularly the important factors influencing the safety performance of the battery, and the coating on the surface of the diaphragm is an effective method for improving the safety of the diaphragm.
In order to improve the heat resistance of the diaphragm, ceramic particles are usually added into the diaphragm coating slurry, however, as the ceramic is used as an inorganic material, no stress conduction exists among the ceramic particles, so that the mechanical strength of the ceramic coating diaphragm is seriously reduced; and the compatibility of the inorganic material of the ceramic particles and the organic diaphragm base film is poor, so that the ceramic particles are easy to fall off, namely fall off powder, the high temperature resistance of the ceramic coating diaphragm is reduced, and the performance of the battery is influenced. On the other hand, the ceramic used for coating has higher density, and the weight of the coated diaphragm is increased to a certain extent, so that the specific capacity of the lithium ion battery is reduced.
Polyimide (PI) is a high-performance organic high-molecular material, integrates the advantages of excellent dielectric property, high-temperature resistance, mechanical property, chemical stability and the like, and is one of high-molecular polymers with the most application prospect. CN108346765A discloses a polyimide coated composite lithium battery separator, but since the polyimide solution is coated in the preparation process, it is easy to cause the pore blocking of the polyolefin separator substrate, so the air permeability of the obtained composite lithium battery separator is poor.
Disclosure of Invention
Summary of the invention:
the present invention aims to solve at least one of the following problems:
(1) In the existing ceramic coating diaphragm, the compatibility of the ceramic coating and a base material is poor, so that ceramic particles are easy to fall off, namely powder falls off, and the high-temperature resistance of the ceramic coating diaphragm is reduced;
(2) In the existing ceramic coating diaphragm, the coated ceramic has higher density, and the weight of the coating diaphragm is increased to a certain extent, so that the specific capacity of the lithium ion battery is reduced;
(3) In the existing polyimide coating diaphragm, the pore of the polyolefin diaphragm substrate is easily blocked, and the air permeability of the obtained composite lithium battery diaphragm is poor.
In order to solve the technical problems, the invention provides polyimide microsphere slurry, a composite diaphragm prepared from the slurry and a lithium battery comprising the composite diaphragm.
Specifically, the technical scheme adopted by the invention is as follows:
in a first aspect, the invention provides polyimide microsphere slurry, which comprises polyimide microspheres, a water-based adhesive, a wetting agent and deionized water, wherein the components in parts by weight are as follows: 1-50 parts of polyimide microspheres, 1-20 parts of water-based adhesive, 1-20 parts of wetting agent and the balance of deionized water, wherein the sum of the components is 100 parts by weight; the polyimide microspheres are prepared from polyamino polymer, diamine and dianhydride.
Preferably, the polyamino polymer is one or a combination of more than one of diamino polyethylene glycol, polylysine and polyethyleneimine, and the polymerization degree of the polyamino polymer is 100< n < 400.
Preferably, the molar ratio of the polyamino polymer to the diamine in the polyimide microspheres is 1: 100-500.
<xnotran> , , ,4,4' - ,4,4' - (4- ) ,1,3- (4- ) ,3- (3- ) ,1,4- (4- ) ,1,3- (3- ) ,2,6- ,4,4' - ,4,4' - -3,3' - ,4,4' - -2,2' - ,1,2- ,2,2- , ,1,4- ,4- -1,2- ,2- -1,4- ,2- -1,3- ,1,3- ,3,6- , [1,1' - ] -2,2' - ,4,4' - ,4,4' - ,3,3' - -4,4' - ,3,3' - ,2,7- ,3,3' - ,2,5- (4- ) ,2,2- (4- ) , </xnotran> 2, 2-bis (3-aminophenyl) hexafluoropropane and 2,2' -bis (trifluoromethyl) diaminobiphenyl.
Preferably, the dianhydride is bisphenol A type diether dianhydride, pyromellitic dianhydride, 4' -oxydiphthalic anhydride, 4' -terephthaloyloxydiphthalic anhydride, 3',4,4' -biphenyltetracarboxylic dianhydride, 3',4' -benzophenonetetracarboxylic dianhydride, hexafluoro dianhydride, 2, 3',4' -biphenyltetracarboxylic dianhydride, 1,2,3, 4-cyclopentanetetracarboxylic dianhydride, 1,2,4, 5-cyclohexanetetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride, 3,4' -oxydiphthalic anhydride, hydrogenated biphenyltetracarboxylic dianhydride, 3',4' -diphenylsulfonetetracarboxylic dianhydride, 5- [2- (1, 3-dioxoisobenzofuran-5-yl) propan-2-yl ] isobenzofuran-1, 3-dione.
Preferably, the aqueous binder is one or more of styrene-butadiene latex, styrene-acrylic latex, pure benzene latex, polymethyl methacrylate, polybutyl methacrylate, polyethylacrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate or polyurethane.
Preferably, the wetting agent is one or more of butyl sodium naphthalene sulfonate, isopropyl sodium naphthalene sulfonate, aryl sodium naphthalene sulfonate, sodium dodecyl benzene sulfonate and sodium alkyl sulfate.
In a second aspect, the present invention provides a preparation method of the polyimide microsphere slurry, including the following steps:
adding the polyimide microspheres into deionized water, stirring and grinding to obtain a primary mixed solution;
and adding the water-based adhesive and the wetting agent into the primary mixed liquid, and stirring and dispersing to obtain the polyimide microsphere slurry.
In a third aspect, the invention provides a composite diaphragm, which comprises a base film and a polyimide microsphere coating coated on the base film, wherein the polyimide microsphere coating is formed by coating the polyimide microsphere slurry on one side or two sides of the base film and drying.
Preferably, the base film layer is one of a PP film, a PE film, and a PP and PE multilayer composite film.
Finally, the invention also provides a lithium ion battery, which comprises the composite diaphragm.
The invention has the beneficial effects that:
(1) In the polyimide microsphere slurry provided by the invention, because the polyamino polymer has good hydrophilicity and is positioned on the surface of the microsphere in an aqueous solution, a surfactant is not required to be added, and the stability of the microsphere can be maintained.
(2) According to the composite diaphragm provided by the invention, the polyimide microspheres are used as an organic polymer material, the affinity with a lithium ion battery diaphragm base film which is also an organic polymer is strong, the interface bonding force between the polyimide microsphere coating and a polyolefin base film is good, powder falling is not easy to occur, the polyimide microspheres can resist high temperature of more than 400 ℃, the long-term use temperature range is-200-300 ℃, no obvious melting point exists, the high temperature resistance of the polyolefin lithium ion battery diaphragm can be improved, the size shrinkage of the polyolefin lithium ion battery diaphragm at high temperature is reduced, meanwhile, the polyimide microspheres have excellent mechanical properties, the puncture resistance of the lithium ion battery diaphragm can be improved, lithium dendrites generated in the use process of the lithium ion battery can be prevented from puncturing the diaphragm, and the safety performance of the lithium ion battery is guaranteed.
(3) Compared with an inorganic ceramic coating, the polyimide microsphere coating of the composite diaphragm provided by the invention has lower density, and correspondingly, the obtained composite diaphragm has lower surface density, and the specific capacity of a lithium ion battery is relatively improved.
(4) According to the composite diaphragm provided by the invention, the polyimide in the polyimide microsphere coating is distributed on two sides of the polyolefin base film in a microspherical shape, so that the composite diaphragm is not easy to cause hole blocking and has good air permeability.
The invention comprises the following details:
the invention provides polyimide slurry, a composite diaphragm prepared from the slurry and a lithium battery comprising the composite diaphragm, aiming at the technical problems of poor caking property, easy shedding, low specific volume of the lithium battery, poor air permeability of the existing polyimide coated diaphragm and the like.
In a first aspect, the invention provides a polyimide microsphere slurry, which comprises polyimide microspheres, a water-based adhesive, a wetting agent and deionized water, wherein the components in parts by weight are as follows: 1-50 parts of polyimide microspheres, 1-20 parts of water-based adhesive, 1-20 parts of wetting agent and the balance of deionized water, wherein the sum of the components is 100 parts by weight; the polyimide microspheres are prepared from polyamino polymer, diamine and dianhydride. The composite diaphragm prepared from the polyimide slurry according to the proportion has good comprehensive performance, and can well overcome the defects of the existing diaphragm.
According to some embodiments of the present invention, the polyamino polymer is one or a combination of more than one of diamino polyethylene glycol, polylysine and polyethyleneimine, and the specific structure is as shown below.
In the polyimide microsphere slurry, the polyamino polymer has good hydrophilicity and is positioned on the surface of the microsphere in an aqueous solution, and a surfactant is not required to be added, so that the stability of the microsphere can be maintained.
According to some embodiments of the invention, the polyamino polymer has a degree of polymerization n of 100< n < 400. If the molecular chain of the polyamino polymer is too short, the surface stability of the microspheres is poor, the microspheres are easy to aggregate and sink in water, and if the molecular chain of the polyamino polymer is too long, the obtained polyimide is especially easy to dissolve in water, and the microspheres are difficult to form.
According to some embodiments of the present invention, the molar ratio of polyamino polymer to diamine in the polyimide microspheres is 1:50 to 500. If the content of the polyamino polymer is too high, the hydrophilicity of polyimide molecular chains is too strong, microspheres are not easily formed in water, and if the content is too low, the polyimide microspheres in the obtained aqueous slurry are unstable. The particle size of the polyimide microspheres in this molar ratio range is about 0.1 to 5 μm, and a slurry containing the same is more suitable for preparing a coated lithium battery separator.
In some embodiments, the molar ratio of polyamino polymer to diamine in the polyimide microspheres is from 1:50 to 350.
In some embodiments, the molar ratio of polyamino polymer to diamine in the polyimide microspheres is 1: 60 to 350.
In other embodiments, the molar ratio of polyamino polymer to diamine in the polyimide microspheres is from 1: 100 to 350, for example: 1: 100, 1: 120, 1: 140, 1: 160, 1: 180, 1: 200, 1: 220, 1: 240, 1: 260, 1: 280, 1: 300, 1: 320, 1: 350, and the like.
According to some embodiments of the present invention, the molar ratio of the sum of the content of polyamino polymers and diamines to dianhydride in the polyimide microspheres is 1: 1.
The structure of the diamine and dianhydride is not particularly limited, and other diamines and dianhydrides commonly used in the art to achieve the same or equivalent effects may be used in the present invention, in addition to the diamines and dianhydrides exemplified in the present invention.
<xnotran> , , (MPD), 4,4' - (ODA), 4,4' - (4- ) ,1,3- (4- ) ,3- (3- ) (DADPE), 1,4- (4- ) (TPE-Q), 1,3- (3- ) (APB), 2,6- ,4,4' - ,4,4' - -3,3' - ,4,4' - -2,2' - ,1,2- ,2,2- , ,1,4- ,4- -1,2- ,2- -1,4- ,2- -1,3- ,1,3- ,3,6- , [1,1' - ] -2,2' - ,4,4' - ,4,4' - ,3,3' - -4,4' - ,3,3' - ,2,7- ,3,3' - , </xnotran> 2, 5-bis (4-aminophenoxy) biphenyl, 2-bis (4-aminophenyl) hexafluoropropane, 2-bis (3-aminophenyl) hexafluoropropane, 2' -bis (trifluoromethyl) diaminobiphenyl, or a combination of one or more thereof.
In some embodiments, the diamine is one or a combination of more than one of p-phenylenediamine, 4 '-diaminodiphenyl ether, 4' -bis (4-aminophenoxy) biphenyl, m-phenylenediamine, 1, 3-bis (4-aminophenoxy) benzene.
According to some embodiments of the invention the dianhydride is bisphenol a type diether dianhydride (BPADA), pyromellitic dianhydride (PMDA), 4' -oxydiphthalic anhydride (ODPA), 4' -terephthaloxydiphthalic anhydride (triphendiether dianhydride, HQDPA), 3',4' -biphenyltetracarboxylic dianhydride (BPDA), 3',4' -benzophenonetetracarboxylic dianhydride (BTDA), hexafluoro dianhydride (6 FDA), 2, 3',4' -biphenyltetracarboxylic dianhydride, 1,2,3, 4-cyclopentanetetracarboxylic dianhydride, 1,2,4, 5-cyclohexanetetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride, 3,4' -oxydiphthalic anhydride, hydrogenated biphenyltetracarboxylic dianhydride, 3',4' -diphenylsulfonetetracarboxylic dianhydride, 5- [2- (1, 3-dioxoisobenzofuran-5-yl) propan-2-yl ] isobenzofuran-1, 3-dione, or a combination of one or more thereof.
In some embodiments, the dianhydride is one or a combination of more than one of bisphenol a type diether dianhydride, pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, and biphenyl tetracarboxylic dianhydride.
According to some embodiments of the present invention, the method for preparing the polyimide microsphere comprises the following steps:
(1) Adding the polyamino polymer into deionized water, and adjusting the pH value to dissolve the polyamino polymer to obtain a polyamino polymer solution;
(2) Respectively dissolving diamine and dianhydride in an organic solvent to obtain a diamine solution and a dianhydride solution;
(3) Adding the diamine solution and the dianhydride solution prepared in the step (2) into the polyamino polymer solution prepared in the step (1), and performing ultrasonic dispersion to form an emulsion;
(4) Stirring the emulsion obtained in the step (3) for reaction, and heating to volatilize the organic solvent to form an aqueous solution of the polyamide acid microspheres;
(5) And (5) drying the aqueous solution of the polyamide acid microspheres obtained in the step (4), and imidizing to obtain the polyimide microspheres.
According to some embodiments of the invention, the molar ratio of polyamino polymer to diamine in step (1) is from 1:50 to 500.
In some embodiments, the molar ratio of polyamino polymer to diamine in step (1) is from 1: 100 to 350, for example: 1: 100, 1: 120, 1: 140, 1: 160, 1: 180, 1: 200, 1: 220, 1: 240, 1: 260, 1: 280, 1: 300, 1: 320, 1: 350, and the like.
In other embodiments of the present invention, the molar ratio of polyamino polymer to diamine in step (1) may also be 1: 60, 1: 80, 1: 150, 1: 210, 1: 270, 1: 310, and the like.
According to some embodiments of the present invention, the deionized water is added in the step (1) in an amount of 50 to 100 parts by mass. In some embodiments, the deionized water is added in the step (1) in an amount of 50 parts by mass.
In other embodiments of the present invention, the deionized water may be added in the step (1) in an amount of 60 parts by mass, 70 parts by mass, 80 parts by mass, 90 parts by mass, 100 parts by mass, or the like.
According to some embodiments of the invention, the dissolving of the polyamino polymer in deionized water is performed under weakly basic conditions. The pH can be adjusted by adding an inorganic base such as NaOH or an organic base.
In some embodiments, the pH adjustment in step (1) is in the range of 8 to 10, for example: 8. 8.5, 9, 9.5, 10, etc.
The diamines and dianhydrides have the structure as described in the present invention.
In the preparation method provided by the invention, the grain diameter controllability of the polyimide microspheres can be realized by changing the dosage proportion of the polyamino polymer to the diamine and dianhydride polymerization monomers.
In the preparation method provided by the invention, the selection of the organic solvent in the step (2) is very critical. The dianhydride and diamine monomers are soluble in organic solvents, while the resulting polyamic acid is insoluble in organic solvents from which microspheres precipitate after the polyamic acid is formed.
Preferably, the organic solvent is a low-toxicity, low-boiling solvent.
According to some embodiments of the invention, the organic solvent in step (2) is one or more of methanol, tetrahydrofuran, ethanol, ethyl acetate, acetone, dichloromethane, and chloroform.
In some embodiments, the organic solvent in step (2) is ethyl acetate.
According to some embodiments of the present invention, the organic solvent is added in an amount of 10 to 20 parts by mass in step (2).
In some embodiments, the organic solvent is added in an amount of 10 parts by mass in step (2).
In another embodiment of the present invention, the amount of the organic solvent added may be: 12 parts by mass, 14 parts by mass, 15 parts by mass, 17 parts by mass, 18 parts by mass, 20 parts by mass, and the like.
According to some embodiments of the invention, the temperature of the ultrasonic dispersion in the step (3) is 5 to 30 ℃, and the time of the ultrasonic dispersion is 10 to 60min. In the range of the ultrasonic condition, the emulsion has good dispersibility, and is beneficial to obtaining the polyimide microspheres with high particle size uniformity.
In some embodiments, the temperature of the ultrasonic dispersion in step (3) is 25 ℃.
In some embodiments, the time of the ultrasonic dispersion in step (3) is 20 to 40min, such as 20min, 25min, 30min, 35min, 40min, and the like.
In other embodiments of the present invention, the time for the ultrasonic dispersion in step (3) may be 10min, 15min, 45min, 50min, 55min, 60min, and the like.
According to some embodiments of the invention, the stirring in step (4) is at a rate of 300 to 3000r/min. Within this stirring rate range, a polyimide emulsion having good dispersibility can be produced.
In some embodiments, the stirring in step (4) is at a rate of 3000r/min.
According to some embodiments of the invention, the temperature of the reaction in step (4) is 20 to 25 ℃ and the reaction time is 24 hours.
According to some embodiments of the invention, the temperature at which the heating in step (4) volatilizes the organic solvent is 40 to 60 ℃, for example: 40 deg.C, 45 deg.C, 50 deg.C, 55 deg.C, 60 deg.C, etc.
In the preparation method provided by the present invention, the imidization procedure is not particularly limited, and imidization procedures commonly used in the art can be used in the present invention.
According to some embodiments of the invention, the imidization procedure in step (5) is: 100-120 ℃/1h, 200-220 ℃/1h, 300-320 ℃/1h and 350-370 ℃/1h.
In the preparation method, the diamine and dianhydride-containing volatile solvent is ultrasonically dispersed in the aqueous solution to form an oil-in-water emulsion, the diamine, the dianhydride and the polyamino polymer in water react to form the polyamic acid microspheres, and the hydrophilic polyamino polymer can keep the stability of the microspheres in the aqueous solution in an oil-water interface of the emulsion.
When the polyimide microspheres obtained by the preparation method are used for preparing the diaphragm coating slurry, the hydrophilic polyamino polymer exists on the surfaces of the microspheres, so that the stability of the microspheres in the slurry can be ensured, and the coating slurry with good dispersibility can be obtained without adding a surfactant for assistance.
The water-based binder can improve the binding force between the polymer slurry and the surface of the base membrane, thereby improving the stability of the diaphragm structure.
According to some embodiments of the invention, the aqueous binder is one or a combination of more than one of styrene-butadiene latex, styrene-acrylic latex, pure benzene latex, polymethyl methacrylate, polybutyl methacrylate, polyethyl acrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate or polyurethane. But not limited to, the above-listed aqueous binders, and other aqueous binders commonly used in the art to achieve the same or equivalent effects may also be used in the present invention.
The wetting agent can improve the wetting property of the polyimide slurry on the surface of the base film and promote the polyimide slurry to spread on the surface of the base film.
According to some embodiments of the invention, the wetting agent is one or a combination of more than one of sodium butylnaphthalene sulfonate, sodium isopropylnaphthalene sulfonate, sodium arylnaphthalene sulfonate, sodium dodecylbenzene sulfonate, and sodium alkyl sulfate. The wetting agent can remarkably improve the wetting effect of the polyimide sizing agent on the surface of the base film. But are not limited to, the above-listed wetting agents, and other wetting agents commonly used in the art to achieve the same or equivalent effects may also be used in the present invention.
The invention also provides a preparation method of the polyimide microsphere slurry, which comprises the following steps:
adding the polyimide microspheres into deionized water, stirring and grinding to obtain a primary mixed solution;
and adding the water-based adhesive and the wetting agent into the primary mixed liquid, and stirring and dispersing to obtain the polyimide microsphere slurry.
According to some embodiments of the present invention, the method for preparing polyimide microsphere slurry comprises the following steps:
adding the polyimide microspheres into deionized water, stirring and grinding for 0.5-48 h at the speed of 100-6000 r/min to obtain a primary mixed solution; and adding the water-based adhesive and the wetting agent into the primary mixed liquid, and continuously stirring and dispersing for 0.5-24 h at the speed of 100-6000 r/min to obtain the polyimide microsphere slurry.
The polyimide microspheres, aqueous binder and wetting agent are selected as described herein.
Fig. 1 is a Transmission Electron Microscope (TEM) image of the polyimide microsphere-I slurry obtained in the embodiment of the present invention, and it can be seen that the polyimide microspheres are uniformly dispersed in the slurry without agglomeration.
The invention also provides a composite diaphragm which comprises a base film and a polyimide microsphere coating coated on the base film, wherein the polyimide microsphere coating is formed by coating the polyimide slurry on one side or two sides of the base film and drying.
The microstructure of the composite diaphragm is shown in figure 2, the coating on the surface of the composite diaphragm contains uniformly arranged polyimide spherical particles, and the polyimide particles are arranged neatly and are relatively loose, so that the ventilation loss caused by the blockage of holes on the surface of the polyolefin diaphragm by the coating is reduced.
According to some embodiments of the invention, the base film layer is one of a Polyethylene (PE) film, a polypropylene (PP) film, a PP and PE multilayer composite film.
In some embodiments of the present invention, the thickness of the base film is 5 to 50 μm, the thickness of the polyimide microsphere coating is 0.1 to 6 μm, the prepared separator is not too thick, the too thick separator easily causes too large resistance, which is not beneficial to rapid charging and discharging of the battery, and simultaneously reduces the winding times of the separator, increases the volume of the battery, and causes the decrease of charging and discharging capacity.
In some embodiments of the present invention, the polyimide composite separator may be obtained by coating the obtained polyimide slurry on one or both sides of the base film using any suitable coating method known in the art, such as any one of coating methods using dip coating, brush coating, knife coating, or micro gravure coating, and then drying using any suitable drying equipment and drying conditions in the art, for example, drying in a vacuum drying oven at 50 to 90 ℃ for 0.5 to 2 hours. The preparation method does not need to change the existing coating equipment and is easy to popularize. And water is used as a solvent for preparing the polyimide slurry, so that the production process is environment-friendly, high in safety and low in production cost.
The invention also provides a lithium ion battery which comprises the composite diaphragm. The composite diaphragm prepared by the invention has good thermal stability, good puncture resistance and good air permeability, and compared with a ceramic coating diaphragm, the specific capacity of the lithium battery is reduced less.
Drawings
FIG. 1 shows a TEM image of a polyimide microsphere-I slurry;
fig. 2 shows an SEM image of a composite separator prepared according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments.
Preparing polyimide microspheres:
polyimide microspheres-I
(1) Adding 0.8 part of diamino polyethylene glycol (with the molecular weight of 5000g/mol and n = 113) into 50 parts of deionized water, and adjusting the pH value to 10 by using NaOH to fully dissolve the diamino polyethylene glycol to obtain a diamino polyethylene glycol aqueous solution;
(2) Respectively dissolving 5 parts of 4,4 '-diaminodiphenyl ether and 8 parts of benzophenone tetracarboxylic dianhydride in 10 parts of ethyl acetate to obtain an ethyl acetate solution of 4,4' -diaminodiphenyl ether and an ethyl acetate solution of benzophenone tetracarboxylic dianhydride; wherein the mol ratio of the diamino polyethylene glycol to the 4,4' -diamino diphenyl ether is 1: 156;
(3) Simultaneously adding the ethyl acetate solution of 4,4' -diaminodiphenyl ether and the ethyl acetate solution of benzophenone tetracarboxylic dianhydride obtained in the step (2) into the aqueous solution of the diaminopolyethylene glycol obtained in the step (1), and performing ultrasonic dispersion for 20min at 25 ℃ to form emulsion;
(4) Reacting the emulsion obtained in the step (3) at the stirring speed of 3000r/min at 25 ℃ for 24h, heating the reaction solution to 50 ℃ to completely volatilize the organic solvent, and then forming an aqueous solution of polyamic acid microspheres;
(5) And (5) drying the aqueous solution of the polyamic acid microspheres obtained in the step (4) at 100 ℃ for 24 hours to obtain microsphere powder, putting the microsphere powder into a high-temperature oven, and heating and imidizing according to the programs of 105 ℃/1 hour, 200 ℃/1 hour and 300 ℃/1 hour to obtain the polyimide microspheres-I. The particle size is about 1 μm.
Polyimide microspheres-II
(1) Adding 0.4 part of diamino polyethylene glycol (with the molecular weight of 5000g/mol and n = 113) into 50 parts of deionized water, and adjusting the pH value to 10 by using NaOH to fully dissolve the diamino polyethylene glycol to obtain a diamino polyethylene glycol aqueous solution;
(2) Respectively dissolving 5 parts of 4,4 '-diaminodiphenyl ether and 8 parts of benzophenone tetracarboxylic dianhydride in 10 parts of ethyl acetate to obtain an ethyl acetate solution of 4,4' -diaminodiphenyl ether and an ethyl acetate solution of benzophenone tetracarboxylic dianhydride; wherein the mol ratio of the diamino polyethylene glycol to the 4,4' -diamino diphenyl ether is 1: 312.
(3) Simultaneously adding the ethyl acetate solution of 4,4' -diaminodiphenyl ether and the ethyl acetate solution of benzophenone tetracarboxylic dianhydride obtained in the step (2) into the aqueous solution of the diaminopolyethylene glycol obtained in the step (1), and performing ultrasonic dispersion for 20min at 25 ℃ to form emulsion;
(4) Reacting the emulsion obtained in the step (3) at the stirring speed of 3000r/min at 25 ℃ for 24h, heating the reaction solution to 50 ℃, and volatilizing the organic solvent completely to form an aqueous solution of polyamic acid microspheres;
(5) And (3) drying the aqueous solution of the polyamic acid microspheres obtained in the step (4) at 100 ℃ for 24 hours to obtain microsphere powder, putting the microsphere powder into a high-temperature oven, and heating and imidizing according to the procedures of 105 ℃/1 hour, 200 ℃/1 hour and 300 ℃/1 hour to obtain the polyimide microspheres-II. The particle size is about 2.5 μm.
Polyimide microspheres-III
(1) Respectively dissolving 5 parts of 4,4 '-diaminodiphenyl ether and 5 parts of benzophenone tetracarboxylic dianhydride in 10 parts of ethyl acetate to obtain an ethyl acetate solution of 4,4' -diaminodiphenyl ether and an ethyl acetate solution of benzophenone tetracarboxylic dianhydride;
(2) Simultaneously adding the ethyl acetate solution of 4,4' -diaminodiphenyl ether and the ethyl acetate solution of benzophenone tetracarboxylic dianhydride obtained in the step (1) into water with the pH value of 10, and performing ultrasonic dispersion for 20min at the temperature of 25 ℃ to form emulsion;
(3) Reacting the emulsion obtained in the step (3) at the stirring speed of 3000r/min at 25 ℃ for 24h, heating the reaction solution to 50 ℃, and volatilizing the organic solvent completely to form an aqueous solution of polyamic acid microspheres;
(4) And (3) drying the aqueous solution of the polyamic acid microspheres obtained in the step (4) at 100 ℃ for 24 hours to obtain microsphere powder, putting the microsphere powder into a high-temperature oven, and heating and imidizing according to the procedures of 105 ℃/1 hour, 200 ℃/1 hour and 300 ℃/1 hour to obtain polyimide microsphere powder, so as to obtain polyimide microspheres-III. The particle size is about 10 μm.
Example 1:
stirring and dispersing 20 parts of polyimide microsphere I into 75 parts of deionized water at 3000r/min for 4 hours, then adding 3 parts of water-based adhesive styrene-butadiene latex and 2 parts of wetting agent sodium aryl naphthalene sulfonate, continuously stirring for 2 hours, and uniformly dispersing to obtain polyimide microsphere I slurry.
And coating the slurry on one side of a 12-micron PE-based film layer at the coating speed of 30m/min and the coating thickness of 50 microns, and drying at 80 ℃ for 10min to obtain the lithium battery diaphragm with the single-side coating thickness of 2 microns.
And then coating the slurry on the other side of the PE base film at the coating speed of 30m/min and the coating thickness of 50 microns, and drying at 80 ℃ for 10min to obtain the double-sided polyimide composite lithium battery diaphragm with the single-side coating thickness of 2 microns.
Example 2:
stirring and dispersing 30 parts of polyimide microsphere I into 65 parts of deionized water at 3000r/min, stirring and dispersing for 4 hours, then adding 3 parts of aqueous adhesive styrene-butadiene latex and 2 parts of wetting agent sodium aryl naphthalene sulfonate, continuously stirring for 2 hours, and uniformly dispersing to obtain polyimide microsphere I slurry.
And coating the slurry on one side of a 12-micron PE-based film layer at the coating speed of 30m/min and the coating thickness of 75 microns, and drying at 90 ℃ for 10min to obtain the lithium battery diaphragm with the thickness of 2.5 microns on one side.
And then coating the slurry on the other side of the PE base film at the coating speed of 30m/min and the coating thickness of 75 microns, and drying at 90 ℃ for 10min to obtain the double-sided polyimide composite lithium battery diaphragm with the thickness of 2.5 microns on the single side.
Example 3:
and stirring and dispersing 30 parts of polyimide microsphere-II into 65 parts of deionized water at 3000r/min, stirring and dispersing for 4 hours, then adding 3 parts of aqueous adhesive styrene-butadiene latex and 2 parts of wetting agent sodium aryl naphthalene sulfonate, continuously stirring for 2 hours, and uniformly dispersing to obtain polyimide microsphere-II slurry.
And coating the slurry on one side of a 12-micron PE (polyethylene) base film layer at the coating speed of 30m/min and the coating thickness of 65 microns, and drying at 90 ℃ for 10min to obtain the lithium battery diaphragm with the single-side coating thickness of 2.5 microns.
And then coating the other side of the PE base film with the slurry at the coating speed of 30m/min and the coating thickness of 75 microns, and drying at 90 ℃ for 10min to obtain the double-sided polyimide composite lithium battery diaphragm with the single-side coating thickness of 2.5 microns.
Example 4:
stirring and dispersing 40 parts of polyimide microsphere-II into 55 parts of deionized water at 3000r/min, stirring and dispersing for 4 hours, then adding 3 parts of water-based adhesive styrene-butadiene latex and 2 parts of wetting agent sodium aryl naphthalene sulfonate, continuously stirring for 2 hours, and dispersing uniformly to obtain polyimide microsphere-II slurry.
And coating the slurry on one side of a 12-micron PE-based film layer at the coating speed of 30m/min and the coating thickness of 75 microns, and drying at 90 ℃ for 15min to obtain the lithium battery diaphragm with the single-side coating thickness of 4 microns.
And then coating the slurry on the other side of the PE base film at the coating speed of 30m/min and the coating thickness of 75 microns, and drying at 90 ℃ for 15min to obtain the double-sided polyimide composite lithium battery diaphragm with the thickness of 4 microns on the single side.
Comparative example 1:
under nitrogen atmosphere, 5.00g (0.025 mol) of ODA and 5.56g (0.0255 mol) of BTDA were weighed out, and 100mL of DMA was measured C Adding into a reaction container, and mechanically stirring in an ice-water bath for 24 hours; then 11mL of acetic anhydride and 15mL of triethylamine were added to the mixture to perform chemical imidization. And after 48 hours, precipitating the obtained polymer by using ethanol, fully washing the polymer by using ethanol and deionized water, drying the polymer in a drying oven at 100 ℃ overnight, and then drying the polymer in vacuum at 150 ℃ for 24 hours to obtain the light yellow PI product.
0.8g of the solid polyimide obtained above, 2.5g of PEG2000, 2.5g of polyvinylpyrrolidone (PVP) and 44.2g of DMAc were mixed, and mechanically stirred in an oil bath at 80 ℃ until the polyimide and the pore-forming agent were completely dissolved, to obtain a casting solution of PI. After the stirring was stopped, the mixture was defoamed in an oil bath at 80 ℃ for 60min.
Spreading a 12-micron PE (polyethylene) base film on a clean glass plate flatly, pouring a proper amount of defoamed polyimide film casting solution on the PE base film, scraping the film by using a scraper, staying in the air for 1min, slowly immersing in a DMAc (DMAc and water volume ratio is 3: 2) at a constant speed to carry out NIPs (nickel-nitrogen oxides) film formation, removing the PE film with the polyimide after 3min, soaking in water for 12h, taking out, and drying to obtain a lithium battery diaphragm product with the thickness of one-side coating of 2 microns.
Comparative example 2:
under nitrogen atmosphere, 5.00g (0.025 mol) ODA and 5.56g (0.0255 mol) BTDA are weighed out, and 100mL DMA is measured out C Adding into a reaction container, and mechanically stirring in an ice-water bath for 24 hours; then adding 11mL of acetic anhydride and 15mL of triethylamine for chemical imidization. And after 48 hours, precipitating the obtained polymer by using ethanol, fully washing the polymer by using ethanol and deionized water, drying the polymer in a drying oven at 100 ℃ overnight, and then drying the polymer in vacuum at 150 ℃ for 24 hours to obtain the light yellow PI product.
30 parts of polyimide powder is dispersed into 65 parts of deionized water with stirring at 3000r/min, and the mixture is dispersed with stirring for 4 hours. 3 parts of water-based adhesive styrene-butadiene latex and 2 parts of wetting agent sodium aryl naphthalene sulfonate are added into the polyimide aqueous solution, and polyimide slurry is obtained.
And coating the slurry on one side of a 12-micron PE-based film layer at the coating speed of 30m/min and the coating thickness of 50 microns, and drying at 80 ℃ for 10min to obtain the lithium battery diaphragm with the single-side coating thickness of 2 microns.
And then coating the slurry on the other side of the PE base film at the coating speed of 30m/min and the coating thickness of 50 microns, and drying at 80 ℃ for 10min to obtain the double-sided polyimide composite lithium battery diaphragm with the single-side coating thickness of 2 microns.
Comparative example 3:
fully stirring and grinding 30 parts of alumina ceramic, 2 parts of surfactant and 60 parts of deionized water for 2 hours, then adding 5 parts of aqueous adhesive and 3 parts of wetting agent, uniformly dispersing, and continuously stirring for 2 hours to obtain alumina ceramic slurry.
And coating the slurry on one side of a 12-micron PE (polyethylene) base film layer at the coating speed of 30m/min and the coating thickness of 50 microns, and drying at 80 ℃ for 10min to obtain the lithium battery diaphragm with the single-side coating thickness of 2 microns.
And then coating the slurry on the other side of the PE base film at the coating speed of 30m/min and the coating thickness of 50 microns, and drying at 80 ℃ for 10min to obtain the double-sided ceramic composite lithium battery diaphragm with the single-side coating thickness of 2 microns.
Comparative example 4:
and stirring and dispersing 30 parts of polyimide microsphere-III into 65 parts of deionized water at 3000r/min for 4 hours, adding 3 parts of water-based adhesive styrene-butadiene latex and 2 parts of wetting agent sodium aryl naphthalene sulfonate, continuously stirring for 2 hours, and uniformly dispersing to obtain polyimide microsphere-III slurry. And coating the slurry on one side of a 12-micron PE-based film layer at the coating speed of 30m/min and the coating thickness of 75 microns, and drying at 90 ℃ for 10min to obtain the lithium battery diaphragm with the thickness of 2.5 microns on one side.
And then coating the other side of the PE base film with the slurry at the coating speed of 30m/min and the coating thickness of 75 microns, and drying at 90 ℃ for 10min to obtain the double-sided polyimide composite lithium battery diaphragm with the single-side coating thickness of 2.5 microns.
Performance testing and evaluation
The composite separators obtained in examples 1 to 4 and comparative examples 1 to 4 were subjected to air permeability, coating peel strength, puncture strength, heat shrinkage and surface density tests, the specific test methods were as follows, and the test results are shown in table 1.
a. Air permeability
The air permeability of the composite membrane was tested using a Gurley 4110 air permeability tester.
b. Peel strength and puncture resistance of coatings
The peel strength and puncture resistance of the coating of the composite diaphragm are tested by a universal tensile testing machine, and the adopted standard is GB/T1040.32-2006 plastic tensile property test.
c. Thermal shrinkage rate
The composite separator was cut into a film sample of 100X 100mm, and the longitudinal length (MD) thereof was measured Front part ) And transverse length (TD) Front side ) Baking in a vacuum oven at 120 deg.C for 1h, taking out the membrane sample, cooling to room temperature, and measuring its longitudinal length (MD) again Rear end ) And transverse length (TD) Rear end ) The heat shrinkage δ was calculated as follows:
δ MD ＝(MD front side -MD Rear end )/MD Front part ×100％
δ TD ＝(TD Front side -TD Rear end )/TD Front side ×100％
d. Areal density
And (3) overlapping the composite diaphragm into 6 stacks, flattening, pressing and removing air in the diaphragm. And cutting the stacked diaphragms according to the cutting sample plate, and measuring the lengths and the widths of the cut samples every other stack to obtain the areas S1, S2 and S3 of 3 samples.
The 3 samples were weighed to obtain M1, M2, and M3 weights, respectively.
According to the formula: the surface density = weight (M)/area (S), and 3 surface densities were obtained, and the surface density of the separator was obtained by taking the average value.
Table 1: properties of composite separator
As can be seen from table 1, compared with the ceramic-coated separator, the composite separator with the polyimide microsphere coating prepared in the embodiment of the present invention has significantly improved coating peel strength, lower Gurley value, better air permeability, lower surface density of the separator, and is expected to obtain a lithium battery with higher specific capacity. Compared with the common polyimide coating membrane, the membrane has lower Gurley value and better air permeability under the condition of equivalent other performances.
On the other hand, when the polyamino polymer is not added, if the surfactant is not used for auxiliary dispersion, the obtained slurry has poor dispersibility of the polyimide microspheres, the polyimide microspheres are easy to agglomerate, the dispersion on the surface of the base material is uneven and the adhesion is poor, the puncture resistance and the peel strength of the obtained composite diaphragm are reduced, the Gurley value is high, and the air permeability is not ideal.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (8)
1. The polyimide microsphere slurry for the composite diaphragm is characterized in that the slurry is coated on one side or two sides of a base film of the composite diaphragm; the slurry comprises polyimide microspheres, a water-based adhesive, a wetting agent and deionized water, and comprises the following components in parts by weight: 1 to 50 parts of polyimide microspheres, 1 to 20 parts of aqueous adhesive, 1 to 20 parts of wetting agent and the balance of deionized water, wherein the sum of the components is 100 parts by weight; the preparation method of the polyimide microspheres comprises the following steps:
(1) Adding the polyamino polymer into deionized water, and adjusting the pH value to dissolve the polyamino polymer to obtain a polyamino polymer solution;
(2) Dissolving diamine and dianhydride in an organic solvent respectively to obtain a diamine solution and a dianhydride solution;
(3) Adding the diamine solution and the dianhydride solution prepared in the step (2) into the polyamino polymer solution prepared in the step (1), and performing ultrasonic dispersion to form an emulsion;
(4) Stirring the emulsion obtained in the step (3) for reaction, and heating to volatilize the organic solvent to form an aqueous solution of the polyamide acid microspheres;
(5) Drying the aqueous solution of the polyamic acid microsphere obtained in the step (4), and imidizing to obtain the polyimide microsphere;
wherein the polyamino polymer is at least one of diamino polyethylene glycol, polylysine and polyethyleneimine, and the polymerization degree of the polyamino polymer is 100-n-400; the molar ratio of the polyamino polymer to the diamine in the polyimide microspheres is 1 to 50 to 500.
2. <xnotran> 1 , , , ,4,4' - ,4,4' - (4- ) ,1,3- (4- ) ,3- (3- ) ,1,4- (4- ) ,1,3- (3- ) ,2,6- ,4,4' - ,4,4' - -3,3' - ,4,4' - -2,2' - ,1,2- ,2,2- , ,1,4- ,4- -1,2- ,2- -1,4- ,2- -1,3- ,1,3- ,3,6- , [1,1' - ] -2,2' - ,4,4' - ,4,4' - ,3,3' - -4,4' - ,3,3' - ,2,7- ,3,3' - ,2,5- (4- ) ,2,2- (4- ) ,2,2- (3- ) , </xnotran> At least one of 2,2' -bis (trifluoromethyl) diaminobiphenyl; the dianhydride is bisphenol A type diether dianhydride, pyromellitic dianhydride, 4' -oxydiphthalic anhydride, 4' -terephthaloyl diphthalic anhydride, 3',4,4' -biphenyltetracarboxylic dianhydride, 3',4' -benzophenonetetracarboxylic dianhydride, hexafluoro dianhydride, 2, 3',4' -biphenyltetracarboxylic dianhydride, 1,2,3, 4-cyclopentanetetracarboxylic dianhydride, 1,2,4, 5-cyclohexanetetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride, 3,4' -oxydiphthalic anhydride, hydrogenated biphenyltetracarboxylic dianhydride, 3',4' -diphenylsulfonetetracarboxylic dianhydride, 5- [2- (1, 3-dioxoisobenzofuran-5-yl) propan-2-yl ] isobenzofuran-1, 3-dione.
3. The polyimide microsphere slurry for composite membranes according to claim 1, wherein the aqueous binder is at least one of styrene-butadiene latex, styrene-acrylic latex, pure benzene latex, polymethyl methacrylate, polybutyl methacrylate, polyethyl acrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, or polyurethane.
4. The polyimide microsphere slurry for composite membranes according to claim 1, wherein the wetting agent is at least one of sodium butylnaphthalene sulfonate, sodium isopropylnaphthalene sulfonate, sodium arylnaphthalene sulfonate, sodium dodecylbenzene sulfonate and sodium alkyl sulfate.
5. The method for preparing the polyimide microsphere slurry for the composite membrane according to any one of claims 1 to 4, wherein the method comprises the following steps:
adding the polyimide microspheres into deionized water, stirring and grinding to obtain a primary mixed solution;
and adding the water-based adhesive and the wetting agent into the primary mixed liquid, and stirring and dispersing to obtain the polyimide microsphere slurry.
6. A composite membrane, which is characterized by comprising a base membrane and a polyimide microsphere coating coated on the base membrane, wherein the polyimide microsphere coating is formed by coating the polyimide microsphere slurry for the composite membrane, which is disclosed by any one of claims 1 to 4, on one side or two sides of the base membrane and drying the coated base membrane.
7. The composite separator according to claim 6, wherein the base film layer is one of a PP film, a PE film, and a PP and PE multilayer composite film.
8. A lithium ion battery comprising the composite separator of claim 6 or 7.
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| CN113921990A (en) * | 2021-09-26 | 2022-01-11 | 安徽国风塑业股份有限公司 | High-heat-resistance and high-breakdown-resistance lithium battery microporous diaphragm and preparation method thereof |
| CN113956658B (en) * | 2021-10-21 | 2024-01-30 | 北京宇程科技有限公司 | Polyimide/titanium dioxide composite microsphere and preparation method thereof |
| CN114497899A (en) * | 2022-02-11 | 2022-05-13 | 北京宇程科技有限公司 | High-temperature-resistant polymer microsphere coated modified composite diaphragm and preparation method thereof |
| CN114361706A (en) * | 2021-12-29 | 2022-04-15 | 上海恩捷新材料科技有限公司 | Coated diaphragm and preparation method thereof |
| JP2024512851A (en) * | 2022-03-09 | 2024-03-21 | 江▲蘇▼▲硅▼▲時▼代材料科技有限公司 | Separator film and method of manufacturing separator film |
| CN114709558A (en) * | 2022-03-25 | 2022-07-05 | 中材锂膜有限公司 | High-heat-resistance polyamide-imide composite diaphragm and preparation method thereof |
| CN114614201A (en) * | 2022-03-29 | 2022-06-10 | 河北金力新能源科技股份有限公司 | Zebra coating diaphragm and preparation method thereof |
| CN114883746A (en) * | 2022-05-11 | 2022-08-09 | 北京化工大学常州先进材料研究院 | Novel polyimide microsphere slurry and coating diaphragm thereof |
| CN115441123B (en) * | 2022-10-14 | 2024-03-08 | 贺州学院 | High-liquid-absorption and high-flame-retardance battery diaphragm and preparation method thereof |
| CN115636976B (en) * | 2022-11-02 | 2023-09-05 | 天能新能源(湖州)有限公司 | Polyimide diaphragm for lithium battery and preparation method thereof |
| CN115627000B (en) * | 2022-11-02 | 2023-11-10 | 天能新能源(湖州)有限公司 | High-temperature-resistant polyimide diaphragm, preparation method thereof and application thereof in preparation of lithium ion battery |
| CN116315447B (en) * | 2023-05-04 | 2023-08-01 | 合肥长阳新能源科技有限公司 | Polyimide porous microsphere coated diaphragm for lithium battery and preparation method thereof |
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