Organic polyimide fiber lithium ion battery separator and preparation method and application thereof

Abstract

The application discloses an organic polyimide fiber lithium ion battery diaphragm and a preparation method and application thereof. The organic polyimide fiber lithium ion battery diaphragm comprises a base film and a coating layer on the base film, and the coating layer comprises polyimide, organic supramolecule, carboxymethyl cellulose and polymethyl methacrylate. The mass ratio of the polyimide, the organic supramolecule, the carboxymethyl cellulose and the polymethyl methacrylate is 20:(1-2):1:2, and the number average molecular weight of the polyimide is 32132-34227 g / mol. The organic polyimide fiber lithium ion battery diaphragm has the advantages of high ionic conductivity, high tensile strength, high film breaking temperature and low friction coefficient.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery separators, and particularly relates to an organic polyimide fiber lithium ion battery separator and a preparation method and application thereof. BACKGROUND

[0002] With the charging rate of new energy vehicles becoming faster and faster, the high-voltage and high-current charging scheme relied on by the new energy vehicles has higher and higher requirements for the high film breaking temperature and high performance of the lithium ion battery separator. Although the existing ceramic coating can improve the heat resistance of the separator, it is limited by the packing density and packing height, so that the film breaking temperature of the separator is limited. Moreover, the ceramic cannot be bonded to the base film, and the peeling strength is improved by adding a bonding agent. The use of the ceramic coated separator has the above limitations.

[0003] In this case, a polyimide coated separator emerges as the times require. Polyimide, as a fiber material with high thermal decomposition temperature, can enhance the film breaking temperature of the separator. The polyimide has strong chemical stability, so that the separator prepared therefrom has good corrosion resistance. However, the performance of the polyimide coated separator in the prior art still needs to be further improved. For example, patent CN118315761A merely mentions polyimide as a polymer separator material layer, and only describes the preparation process of the separator, without explaining the improvement of the performance of the separator by adding polyimide from the aspects of monomer purification and polymerization. SUMMARY

[0004] In view of the deficiencies in the prior art, the purpose of the present application is to provide an organic polyimide fiber lithium ion battery separator.

[0005] Another purpose of the present application is to provide a preparation method of the organic polyimide fiber lithium ion battery separator.

[0006] Another purpose of the present application is to provide a slurry.

[0007] The purpose of the present application is achieved by the following technical solutions.

[0008] An organic polyimide fiber lithium ion battery separator comprises a base film and a coating layer on the base film, and the coating layer comprises polyimide (PI), organic supramolecule, carboxymethyl cellulose and polymethyl methacrylate. The mass ratio of polyimide (PI), organic supramolecule, carboxymethyl cellulose and polymethyl methacrylate is 20:(1-2):1:2. The number average molecular weight of polyimide (PI) is 32132-34227 g / mol, and the structural formula of polyimide (PI) is:

[0009] The method for obtaining the organic supramolecule includes: using resorcinol and 1,3-bis(1,3-dioxolan-2-yl)propane as substrates, normal propyl alcohol as a solvent, morpholine as a template agent, and obtaining the organic supramolecule precursor under the catalysis of hydrochloric acid, purification, drying, and obtaining the organic supramolecule, wherein the ratio of resorcinol, 1,3-bis(1,3-dioxolan-2-yl)propane and morpholine is 4:(1-2):(0.01-0.02) in terms of mass fraction.

[0010] In the technical scheme, the polyimide (PI) is obtained by polycondensation of a first substance and a second substance, the first substance is A monomer with a purity of 99.4-99.6%, and the A monomer is 4-amino-N-(4-aminophenyl)-2-(trifluoromethyl)benzamide;

[0011] The second substance is B monomer with a purity of 99.3-99.5%, and the B monomer is 6-(1,3-dioxo-1,3-dihydroisobenzofuran-5-yl)-4-(trifluoromethyl) phthalic anhydride.

[0012] In the technical scheme, the method for obtaining the polyimide (PI) includes: mixing the first substance, the second substance and a first solvent, and performing polycondensation reaction at 0-5 ℃ for 8-10 h to obtain a precursor polyimide acid, adding an imidization catalyst, and performing imidization reaction at 80-85 ℃ for 8-10 h, washing, and drying to obtain the polyimide (PI), wherein the ratio of the A monomer in the first substance, the B monomer in the second substance and the imidization catalyst is 1:(1.00-1.05):0.11 in terms of mass fraction.

[0013] In the technical scheme, the A monomer with a purity of 80-94.3% is purified by gradient recrystallization of a low-polarity organic solvent to obtain the first substance, and the B monomer with a purity of 90-95.3% is purified by high-temperature melt crystallization to obtain the second substance.

[0014] In the technical scheme, the method (gradient recrystallization) for obtaining the first substance includes: mixing a low-polarity organic solvent and the A monomer to be purified, stirring at room temperature for 30-60 min, heating to 77-78 ℃, refluxing at 77-78 ℃ for 30-60 min, cooling to 60-61 ℃, maintaining at 60-61 ℃ for 30-60 min, cooling to 40-41 ℃, maintaining at 40-41 ℃ for 1-2 h, cooling to room temperature, filtering, and drying to obtain the first substance, wherein the A monomer to be purified is the A monomer with a purity of 80-94.3%, the ratio of the volume fraction of the low-polarity organic solvent to the mass fraction of the A monomer to be purified is 1:(0.17-0.18), the unit of the volume fraction is L, and the unit of the mass fraction is kg.

[0015] In the technical scheme, the method for obtaining the second substance is: adding the B monomer with a purity of 90-95.3% into a melt crystallizer, first increasing the temperature to 190-191 ℃ at a rate of 2-3 ℃ / min, then increasing the temperature to 195-196 ℃ at a rate of 0.2-0.3 ℃ / min, maintaining the temperature at 195-196 ℃ for 1-1.5 hours, decreasing the temperature to 190-191 ℃ at a rate of 0.1-0.2 ℃ / min, then decreasing the temperature to 189 ℃ at a rate of 0.05-0.1 ℃ / min (at 189 ℃, the crystals begin to slowly precipitate), and decreasing the temperature to 160-161 ℃ at a rate of 9-15 ℃ / h, to obtain the second substance.

[0016] In the technical scheme, the imination catalyst is a mixture of phthalic anhydride and isoquinoline.

[0017] In the technical scheme, the first solvent is N-methyl pyrrolidone (NMP) (water content ≤2000 ppm) or N,N-dimethylacetamide (DMAC) (water content ≤2000 ppm), and the ratio of the volume fraction of the first solvent to the amount-of-substance fraction of the A monomer in the first substance is 1:(1-1.1), the unit of the volume fraction is L, and the unit of the amount-of-substance fraction is mol.

[0018] In the method for obtaining the first substance, the low-polarity organic solvent is ethyl acetate, and the water content of the ethyl acetate is ≤2000 ppm.

[0019] In the method for obtaining the organic supramolecule, the ratio of the volume fraction of the n-propanol to the amount-of-substance fraction of the resorcinol is 1:(4-4.5), the unit of the volume fraction is L, and the unit of the amount-of-substance fraction is mol.

[0020] In the technical scheme, the method for obtaining the organic supramolecule is: mixing n-propanol, resorcinol, 1,3-bis(1,3-dioxolan-2-yl)propane and morpholine, stirring at 0-5 ℃ for 1-2 hours until uniform, adding hydrochloric acid, continuing to stir at 0-5 ℃ for 1-2 hours, heating to 100-105 ℃ and reacting at 100-105 ℃ for 48-64 hours, to obtain an organic supramolecule precursor, purifying, drying, to obtain the organic supramolecule.

[0021] In the method for obtaining the organic supramolecule, the ratio of the volume fraction of the hydrochloric acid to the amount-of-substance fraction of the resorcinol is (0.81-0.85):16, the unit of the volume fraction is L, and the unit of the amount-of-substance fraction is mol.

[0022] In the method for obtaining the organic supramolecule, the concentration of HCl in the hydrochloric acid is 10-12 mol / L.

[0023] The preparation method of the organic polyimide fiber lithium ion battery diaphragm comprises the following steps: coating slurry on at least one side of a base film, drying, so that the base film is bonded with a coating layer, and obtaining the organic polyimide fiber lithium ion battery diaphragm, wherein the slurry comprises polyimide (PI), organic supramolecule, a second solvent, carboxymethyl cellulose and polymethyl methacrylate.

[0024] In the technical scheme, the second solvent is N-methyl pyrrolidone (NMP) (water content ≤2000 ppm) or N,N-dimethylformamide (DMF) (water content ≤2000 ppm).

[0025] In the technical scheme, the coating method is a grooved roller coating or a matrix point coating.

[0026] A slurry comprises polyimide (PI), organic supramolecule, a second solvent, carboxymethyl cellulose and polymethyl methacrylate, and the mass ratio of polyimide (PI), organic supramolecule, carboxymethyl cellulose and polymethyl methacrylate is 20: (1-2): 1: 2.

[0027] In the technical scheme, the volume fraction of the second solvent and the mass fraction of the carboxymethyl cellulose are in a ratio of 1: (0.05-0.055), wherein the unit of the volume fraction is L, and the unit of the mass fraction is kg.

[0028] A method for preparing the slurry comprises the following steps: mixing polyimide (PI), organic supramolecule, a second solvent, carboxymethyl cellulose and polymethyl methacrylate until uniform, and obtaining the slurry.

[0029] In the technical scheme, polyimide (PI), organic supramolecule, a second solvent, carboxymethyl cellulose and polymethyl methacrylate are mixed at a self-rotation speed of 1800-2000 r / min and a revolution speed of 30-40 r / min for 1-1.5 h until uniform, and the slurry is obtained.

[0030] Application of polyimide (PI), organic supramolecule, carboxymethyl cellulose and polymethyl methacrylate in synergistically improving the ion conductivity, tensile strength and / or bonding performance of a diaphragm.

[0031] Compared with the prior art, the organic polyimide fiber lithium ion battery diaphragm has the following advantages:

[0032] The organic polyimide fiber lithium-ion battery separator of this invention possesses advantages such as high ionic conductivity, high tensile strength, high membrane breakage temperature, and low coefficient of friction. The side chain groups and organic supramolecular structures in polyimide (PI) increase steric hindrance, and the multiple cavities of the organic supramolecular structures facilitate the free shuttle of lithium ions, resulting in excellent ionic conductivity of the separator. Furthermore, the semi-trapezoidal structure and aromatic rings of polyimide (PI) itself give it excellent thermodynamic and mechanical properties. This leads to excellent mechanical strength of the separator and a higher membrane breakage temperature. Moreover, polyimide (PI) has high physical and chemical stability, and its structure is not easily destroyed, resulting in a low coefficient of friction for the coating. The organic supramolecular structures contain a large number of hydroxyl groups, which can enhance intermolecular van der Waals forces and form intermolecular hydrogen bonds, further enhancing the adhesion performance of the organic polyimide fiber lithium-ion battery separator. Attached Figure Description

[0033] Figure 1 To obtain the reaction formulas for the first and second substances;

[0034] Figure 2 This is the reaction formula for the synthesis of polyimide (PI). Detailed Implementation

[0035] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0036] The molecular weight of 4-amino-N-(4-aminophenyl)-2-(trifluoromethyl)benzamide is 295.26.

[0037] The molecular weight of 6-(1,3-dioxo-1,3-dihydroisobenzofuran-5-yl)-4-(trifluoromethyl)phthalic anhydride is 379.22.

[0038] The molecular weight of resorcinol is 110.11.

[0039] The molecular weight of 1,3-bis(1,3-dioxocycloalkyl-2-yl)propane is 188.25.

[0040] The hot press can be pressurized to 1000kg and heated to 80℃, and there is no limit to the model.

[0041] Hot-pressing positive electrode tab adhesion strength: the size of the cut separator is 25*150mm, and the size of the positive electrode tab is 25*150mm; the temperature of the hot press is adjusted to 80℃, and the pressure is 1000KG. The separator and the positive electrode tab are preheated for 1s using a hot press, and hot-pressed for 1s. The hot-pressing positive electrode tab adhesion strength is tested using an electronic tensile testing machine. The separator and the positive electrode tab are peeled off until the tensile distance of the electronic tensile testing machine is 50mm, the speed of the electronic tensile testing machine is 300mm / min, and the peeling degree is 180°. The hot-pressing positive electrode tab adhesion strength = the peeling force divided by the tensile distance of the electronic tensile testing machine. The peeling force is the average value of the force collected by the electronic tensile testing machine during the peeling of the separator and the positive electrode tab. The hot-pressing positive electrode tab adhesion strength is calculated according to the data between 10-40mm of tensile distance, i.e. hot-pressing positive electrode tab adhesion strength = peeling force between 10-40mm of tensile distance divided by 30mm. The positive electrode tab is a ternary lithium nickel cobalt aluminum lithium carbonate (LiNi 0.8 Co 0.15 Al 0.05 O2) tab.

[0042] Hot-pressing negative electrode tab adhesion strength: the test method is basically the same as that of "hot-pressing positive electrode tab adhesion strength", except that the "positive electrode tab" is replaced by "negative electrode tab". The negative electrode tab is a carbon-based graphite tab (carbon content 91%).

[0043] Friction coefficient: determined according to GB 10006-88 method.

[0044] Ionic conductivity: determined according to GBT 36363-2018 method. The test temperature is 40℃, and the relative humidity is 45-50%.

[0045] The number average molecular weight of polyimide (PI) is determined according to (GB / T 31816-2015 Determination of molecular weight and its distribution of water treatment agent by gel permeation chromatography).

[0046] Membrane breaking temperature: determined according to GB / T 36800.1-2018.

[0047] The base film is a wet polyethylene film, and the thickness of the base film is 7.1μm, and the air permeability is 71 Sec / 100ml (it should be noted that other thickness of base film can also be used).

[0048] Examples 1-3

[0049] A method for preparing a slurry, comprising: mixing polyimide (PI), organic supramolecule, second solvent, carboxymethyl cellulose and polymethyl methacrylate in a polymerization reactor (Zhenhong Chemical Machinery Co., Ltd.) to be uniform at a self-rotation speed of 2000 r / min and a revolution speed of 40 r / min for 1 h to obtain the slurry, wherein the second solvent is Y, the ratio of the polyimide (PI), the organic supramolecule, the carboxymethyl cellulose and the polymethyl methacrylate is X in terms of mass fraction, the ratio of the volume fraction of the second solvent to the mass fraction of the carboxymethyl cellulose is 1:0.05, the unit of the volume fraction is L, and the unit of the mass fraction is kg.

[0050] As shown in Figure 2 , the method for obtaining the polyimide (PI) comprises: adding a first substance, a second substance and a first solvent into a polymerization reactor, performing polycondensation reaction at 0 ℃ for 10 h to obtain a precursor polyamic acid, adding an imidization catalyst, performing imidization reaction at 80 ℃ for 8 h, washing, vacuum drying to obtain the polyimide (PI) in powder form (the number average molecular weight (Mn) is 34227 g / mol), wherein the first substance is A monomer with a purity of 99.6%, the A monomer is 4-amino-N-(4-aminophenyl)-2-(trifluoromethyl)benzamide, the second substance is B monomer with a purity of 99.5%, the B monomer is 6-(1,3-dioxo-1,3-dihydroisobenzofuran-5-yl)-4-(trifluoromethyl) phthalic anhydride, the ratio of the A monomer in the first substance, the B monomer in the second substance and the imidization catalyst is 1:1.05:0.11 in terms of substance amount fraction, the imidization catalyst is a mixture of phthalic anhydride and isoquinoline (the ratio of the phthalic anhydride to the isoquinoline is 0.1:0.01 in terms of substance amount fraction), the first solvent is N-methyl pyrrolidone (NMP) (the water content is 1800 ppm), the ratio of the volume fraction of the first solvent to the substance amount fraction of the A monomer in the first substance is 1:1, the unit of the volume fraction is L, and the unit of the substance amount fraction is mol.

[0051] As shown in Figure 1 , the method (gradient recrystallization) for obtaining the first substance comprises: adding 1 L of ethyl acetate (water content: 1800 ppm) and 170 g of A monomer to be purified into a crystallization purifier, stirring at room temperature for 30 min, heating to 77 ℃, refluxing at 77 ℃ for 30 min, cooling to 60 ℃ at a rate of 0.5 ℃ / min and maintaining at 60 ℃ for 0.5 h, cooling to 40 ℃ at a rate of 1 ℃ / min and maintaining at 40 ℃ for 1 h, and finally cooling to 25 ℃ at a rate of 2 ℃ / min, suction filtering and vacuum drying to obtain the first substance, wherein the A monomer to be purified has a purity of 94.3%.

[0052] As shown in Figure 1The method for obtaining the second substance is shown as follows: the B monomer with a purity of 95.3% is added into a melt crystallizer, the temperature is raised to 191 ℃ at a rate of 2 ℃ / min, then the temperature is raised to 195 ℃ at a rate of 0.2 ℃ / min and maintained at 195 ℃ for 1 h, the temperature is lowered to 190 ℃ at a rate of 0.1 ℃ / min, then the temperature is lowered to 189 ℃ at a rate of 0.05 ℃ / min, the crystals start to slowly precipitate at 189 ℃, the temperature is lowered to 160 ℃ at a rate of 9 ℃ / h, the crystals after melt crystallization are scraped out by a cooling rod scraper, and the second substance is obtained.

[0053] The method for obtaining the organic supramolecule is shown as follows: n-propanol is added into a synthesis reactor, then resorcinol, 1,3-bis(1,3-dioxolan-2-yl)propane and morpholine are added, the mixture is stirred at 0 ℃ for 1 h until uniform, hydrochloric acid (the concentration of HCl in the hydrochloric acid is 12 mol / L) is pumped in, the mixture is continuously stirred at 0 ℃ for 1 h, the temperature is raised to 100 ℃ and the mixture is reacted at 100 ℃ for 48 h, the organic supramolecule precursor is obtained, the organic supramolecule precursor is purified (10 L of CH3OH and the organic supramolecule precursor are mixed in a beaker, the mixture is stirred until uniform, the turbid liquid in the beaker is poured into a centrifuge tube, the centrifuge tube is centrifuged at a speed of 8000 r / min for 5 min, the powder is obtained at the bottom of the centrifuge tube, 1 L of methanol is added into the powder, and the mixture is stirred and washed for 4 times (30 min each time)), and the powder is vacuum dried to obtain the organic supramolecule in powder form. The ratio of resorcinol, 1,3-bis(1,3-dioxolan-2-yl)propane and morpholine is 4:1:0.01 in terms of the amount of substance, the ratio of the volume fraction of hydrochloric acid to the amount of substance of resorcinol is 0.81:16, the unit of the volume fraction is L, and the unit of the amount of substance is mol, and the ratio of the volume fraction of n-propanol to the amount of substance of resorcinol is 1:4, the unit of the volume fraction is L, and the unit of the amount of substance is mol.

[0054] X and Y are shown in Table 1.

[0055] Table 1

[0056]

[0057] Example 4

[0058] A method for preparing a slurry, comprising: mixing polyimide (PI), organic supramolecule, second solvent, carboxymethyl cellulose and polymethyl methacrylate in a polymerization reactor (Zhenhong Chemical Machinery Co., Ltd.) to be uniform at a self-rotation speed of 1800 r / min and a revolution speed of 30 r / min for 1.5 h to obtain the slurry, wherein the second solvent is N-methyl pyrrolidone (NMP) (water content 2000 ppm), the ratio of polyimide (PI), organic supramolecule, carboxymethyl cellulose and polymethyl methacrylate is 20:2:1:2 by mass fraction, and the ratio of the volume fraction of the second solvent to the mass fraction of carboxymethyl cellulose is 1:0.05, the unit of the volume fraction is L, and the unit of the mass fraction is kg.

[0059] The method for obtaining polyimide (PI) comprises: adding a first substance, a second substance and a first solvent into a polymerization reactor, performing polycondensation reaction at 5 ℃ for 8 h to obtain precursor polyamic acid, adding imidization catalyst, performing imidization reaction at 85 ℃ for 10 h, washing, and vacuum drying to obtain polyimide (PI) in powder form (the number average molecular weight (Mn) is 32132 g / mol), wherein the first substance is A monomer with a purity of 99.4%, the A monomer is 4-amino-N-(4-aminophenyl)-2-(trifluoromethyl)benzamide; the second substance is B monomer with a purity of 99.3%, the B monomer is 6-(1,3-dioxo-1,3-dihydroisobenzofuran-5-yl)-4-(trifluoromethyl) phthalic anhydride, the ratio of the A monomer in the first substance, the B monomer in the second substance and the imidization catalyst is 1:1.00:0.11 by mass fraction, the imidization catalyst is a mixture of phthalic anhydride and isoquinoline (the ratio of phthalic anhydride to isoquinoline is 0.1:0.01 by mass fraction), the first solvent is N,N-dimethylacetamide (DMAC) (water content 1800 ppm), and the ratio of the volume fraction of the first solvent to the mass fraction of the A monomer in the first substance is 1:1.1, the unit of the volume fraction is L, and the unit of the mass fraction is mol.

[0060] The method (gradient recrystallization) for obtaining the first substance comprises: adding 1 L of ethyl acetate (water content 2000 ppm) and 180 g of the A monomer to be purified into a crystallization purifier, stirring at room temperature for 60 min, heating to 78 ℃, refluxing at 78 ℃ for 60 min, cooling to 61 ℃ at a rate of 0.5 ℃ / min and maintaining at 61 ℃ for 1 h, cooling to 41 ℃ at a rate of 1 ℃ / min and maintaining at 41 ℃ for 2 h, and finally cooling to 25 ℃ at a rate of 2 ℃ / min, and then performing suction filtration and vacuum drying to obtain the first substance. The A monomer to be purified has a purity of 80%.

[0061] The method for obtaining the second substance is: adding B monomer with a purity of 90.0% into a melt crystallizer, first increasing the temperature to 190°C at a rate of 3°C / min, then increasing the temperature to 196°C at a rate of 0.3°C / min and maintaining the temperature at 196°C for 1.5 hours, decreasing the temperature to 191°C at a rate of 0.2°C / min, then decreasing the temperature to 189°C at a rate of 0.1°C / min, and slowly starting to precipitate crystals at 189°C, decreasing the temperature to 160°C at a rate of 15°C / h, and scraping off the melt-crystallized crystals by using a cooling rod scraper to obtain the second substance.

[0062] The method for obtaining the organic supramolecule is: first adding n-propanol into a synthesis reactor, then adding resorcinol, 1,3-bis(1,3-dioxolan-2-yl)propane and morpholine, stirring at 5°C for 2 hours until uniform, pumping in hydrochloric acid (the concentration of HCl in the hydrochloric acid is 10 mol / L), continuing to stir at 5°C for 1 hour, heating to 105°C and reacting at 105°C for 64 hours to obtain an organic supramolecule precursor, purifying (mixing 10 L of CH3OH and the organic supramolecule precursor in a beaker, stirring until uniform, pouring the turbid liquid in the beaker into a centrifuge tube, centrifuging at a speed of 8000 r / min for 5 minutes, obtaining powder at the bottom of the centrifuge tube, adding 1 L of methanol to the powder, and stirring and washing the powder for 4 times (30 minutes each time)), and vacuum drying to obtain the organic supramolecule in powder form. The ratio of resorcinol, 1,3-bis(1,3-dioxolan-2-yl)propane and morpholine is 4:1:0.02 in terms of the number of moles, the ratio of the volume of hydrochloric acid to the number of moles of resorcinol is 0.85:16, the unit of the volume is L, and the unit of the number of moles is mol, and the ratio of the volume of n-propanol to the number of moles of resorcinol is 1:4.5, the unit of the volume is L, and the unit of the number of moles is mol.

[0063] Example 5

[0064] A method for preparing an organic polyimide fiber lithium ion battery separator includes: pumping the slurry prepared in Example 1 into a grooved roller coating structure through a slurry pump, coating on both sides of a base film, drying, obtaining a coating layer with a single side thickness of 5 microns on the base film, and obtaining an organic polyimide fiber lithium ion battery separator.

[0065] The ion conductivity of the organic polyimide fiber lithium ion battery separator prepared in Example 5 is 1.98 mS / cm, the tensile strength (TD) is 570 Mpa, the tensile strength (MD) is 520 Mpa, the film breaking temperature is 185°C, and the friction coefficient is 0.08. The hot-pressed positive electrode sheet adhesion strength is 15.9 N / m, and the hot-pressed negative electrode sheet adhesion strength is 15.0 N / m.

[0066] Example 6

[0067] A preparation method of the organic polyimide fiber lithium ion battery separator, comprising: pumping the slurry prepared in Example 1 into a matrix point coating structure through a slurry pump, coating on both sides of the base film, drying, obtaining a coating layer with a single side thickness of 5 microns on the base film, and obtaining the organic polyimide fiber lithium ion battery separator. The shape of the point coating dots on the organic polyimide fiber lithium ion battery separator is circular, the diameter of the point coating dots is 380 μm, the point coating dots are arranged in a matrix, and the spacing of the point coating dots is 500 μm.

[0068] The ion conductivity of the organic polyimide fiber lithium ion battery separator prepared in Example 6 is 1.93 mS / cm, the friction coefficient is 0.06, the hot-pressed positive electrode sheet bonding strength is 16.8 N / m, the hot-pressed negative electrode sheet bonding strength is 17.1 N / m, the tensile strength (TD) is 470 Mpa, the tensile strength (MD) is 420 Mpa, and the film breaking temperature is 165℃.

[0069] Example 7

[0070] A preparation method of the organic polyimide fiber lithium ion battery separator, comprising: pumping the slurry prepared in Example 3 into a matrix point coating structure through a slurry pump, coating on both sides of the base film, drying, obtaining a coating layer with a single side thickness of 5 microns on the base film, and obtaining the organic polyimide fiber lithium ion battery separator.

[0071] The ion conductivity of the organic polyimide fiber lithium ion battery separator prepared in Example 7 is 1.84 mS / cm, the tensile strength (TD) is 550 Mpa, the tensile strength (MD) is 490 Mpa, the film breaking temperature is 182℃, the friction coefficient is 0.05, the hot-pressed positive electrode sheet bonding strength is 13.5 N / m, and the hot-pressed negative electrode sheet bonding strength is 11.9 N / m.

[0072] Example 8

[0073] A preparation method of the organic polyimide fiber lithium ion battery separator, comprising: pumping the slurry prepared in Example 2 into a matrix point coating structure through a slurry pump, coating on both sides of the base film, drying, obtaining a coating layer with a single side thickness of 5 microns on the base film, and obtaining the organic polyimide fiber lithium ion battery separator.

[0074] The ion conductivity of the organic polyimide fiber lithium ion battery separator prepared in Example 8 is 1.89 mS / cm, the tensile strength (TD) is 540 Mpa, the tensile strength (MD) is 480 Mpa, the film breaking temperature is 184℃, the friction coefficient is 0.06, the hot-pressed positive electrode sheet bonding strength is 14.1 N / m, and the hot-pressed negative electrode sheet bonding strength is 12.7 N / m.

[0075] Example 9

[0076] A preparation method of the organic polyimide fiber lithium ion battery diaphragm, comprising: pumping the slurry prepared in Example 4 into a concave roller coating structure through a slurry pump, coating on both sides of the base film, drying, obtaining a coating layer with a single side thickness of 5 microns on the base film, and obtaining the organic polyimide fiber lithium ion battery diaphragm.

[0077] The ion conductivity of the organic polyimide fiber lithium ion battery diaphragm prepared in Example 9 is 1.88 mS / cm, the tensile strength (TD) is 550 Mpa, the tensile strength (MD) is 498 Mpa, the film breaking temperature is 180℃, and the friction coefficient is 0.09. The hot-pressed positive electrode sheet adhesion strength is 14.1 N / m, and the hot-pressed negative electrode sheet adhesion strength is 12.3 N / m.

[0078] Example 10

[0079] A preparation method of the organic polyimide fiber lithium ion battery diaphragm, comprising: pumping the slurry prepared in Example 4 into a matrix point coating structure through a slurry pump, coating on both sides of the base film, drying, obtaining a coating layer with a single side thickness of 5 microns on the base film, and obtaining the organic polyimide fiber lithium ion battery diaphragm. The shape of the point coating dots on the organic polyimide fiber lithium ion battery diaphragm is circular, the diameter of the point coating dots is 380 microns, the point coating dots are arranged in a matrix, and the spacing between the point coating dots is 500 microns.

[0080] The ion conductivity of the organic polyimide fiber lithium ion battery diaphragm prepared in Example 10 is 1.83 mS / cm, the friction coefficient is 0.07, the hot-pressed positive electrode sheet adhesion strength is 15.8 N / m, the hot-pressed negative electrode sheet adhesion strength is 15.1 N / m, the tensile strength (TD) is 450 Mpa, the tensile strength (MD) is 410 Mpa, and the film breaking temperature is 163℃.

[0081] Comparative Example 1

[0082] A preparation method of a lithium ion battery separator, comprising: using a grooved roller coating structure to coat the slurry in Comparative Example 1 on one side of a base film, drying, and obtaining a PVDF coating layer with a thickness of 4 microns on the base film to obtain a lithium ion battery separator. The method for preparing the slurry in Comparative Example 1 is: mixing conventional PVDF (melting point 151 ℃, particle size D50 = 7 μm), N-methyl pyrrolidone (NMP) (water content 1800 ppm), carboxymethyl cellulose and polymethyl methacrylate in a polymerization reactor (Zhenhong Chemical Machinery Co., Ltd.) to stir for 1 h at a self-rotation speed of 2000 r / min and a revolution speed of 40 r / min until uniform, to obtain the slurry. In the slurry, the ratio of conventional PVDF, carboxymethyl cellulose and polymethyl methacrylate is 22:1:2 by mass fraction, and the ratio of the volume fraction of NMP to the mass fraction of carboxymethyl cellulose is 1:0.05. The unit of the volume fraction is L, and the unit of the mass fraction is kg. The conventional PVDF is purchased from Zhonghua Blue Sky Fluorochem Ltd.

[0083] The ion conductivity of the lithium ion battery separator of Comparative Example 1 is 0.90 mS / cm, the tensile strength (TD) is 150 Mpa, the tensile strength (MD) is 190 Mpa, the film breaking temperature is 146 ℃, and the friction coefficient is 0.45. The hot-pressed positive electrode tab adhesion strength is 4.5 N / m, and the hot-pressed negative electrode tab adhesion strength is 3.8 N / m.

[0084] Comparative Example 2

[0085] A preparation method of a lithium ion battery separator, which is basically the same as that of Example 5, except that the slurry is different. The method for preparing the slurry in Comparative Example 2 is: replacing the "first substance" in Example 1 with "A monomer with a purity of 94.3%", and replacing the "second substance" with "B monomer with a purity of 95.3%". That is, Comparative Example 2 is not purified, but is used directly. The number average molecular weight (Mn) of PI obtained in Comparative Example 2 is 29689 g / mol.

[0086] The single-sided coating thickness of the lithium ion battery separator prepared in Comparative Example 2 is 4.5 microns, the ion conductivity of Comparative Example 2 is 1.48 mS / cm, the tensile strength (TD) is 370 Mpa, the tensile strength (MD) is 320 Mpa, the film breaking temperature is 170 ℃, and the friction coefficient is 0.15. The hot-pressed positive electrode tab adhesion strength is 9.2 N / m, and the hot-pressed negative electrode tab adhesion strength is 10.0 N / m.

[0087] Comparative Example 3

[0088] A preparation method of a lithium ion battery separator is substantially the same as that of Example 5, except that the slurry is different. The method for preparing the slurry of Comparative Example 3 is: replacing the "first substance" of the slurry in Example 5 with "4,4'-diaminodiphenyl ether (ODA)", and replacing the "second substance" with "pyromellitic dianhydride", both of which are not purified, the purity of 4,4'-diaminodiphenyl ether (ODA) is 80%, and the purity of pyromellitic dianhydride is 90%. The number average molecular weight (Mn) of PI obtained by Comparative Example 3 is 28235 g / mol.

[0089] The single-side coating thickness of the lithium ion battery separator prepared by Comparative Example 3 is 4 microns, the ionic conductivity of Comparative Example 3 is 1.38 mS / cm, the tensile strength (TD) is 368 Mpa, the tensile strength (MD) is 330 Mpa, the film breaking temperature is 159℃, and the friction coefficient is 0.17. The hot-pressed positive electrode tab adhesion strength is 8.3 N / m, and the hot-pressed negative electrode tab adhesion strength is 5.2 N / m.

[0090] Comparative Example 4

[0091] A preparation method of a lithium ion battery separator is substantially the same as that of Example 5, except that the slurry is different. The slurry of Comparative Example 4 is substantially the same as the slurry of Example 5, except that no organic supramolecule is added to the slurry of Comparative Example 4. The ratio of polyimide (PI), carboxymethyl cellulose and polymethyl methacrylate is 20:1:2 by mass fraction.

[0092] The single-side coating thickness of the lithium ion battery separator prepared by Comparative Example 4 is 5 microns, the ionic conductivity of Comparative Example 4 is 0.98 mS / cm, the tensile strength (TD) is 565 Mpa, the tensile strength (MD) is 515 Mpa, the film breaking temperature is 180℃, and the friction coefficient is 0.12. The hot-pressed positive electrode tab adhesion strength is 14.8 N / m, and the hot-pressed negative electrode tab adhesion strength is 13.9 N / m.

[0093] The above describes the present application by way of example, it should be noted that without departing from the core of the present application, any simple modification, modification or other equivalent replacement which can not cost the creative labor of those skilled in the art falls within the protection scope of the present application.

Claims

1. An organic polyimide fiber lithium ion battery separator, characterized by, The application relates to an organic polyimide fiber lithium ion battery diaphragm, which comprises a base film and a coating layer on the base film, wherein the coating layer comprises polyimide, organic supermolecule, carboxymethyl cellulose and polymethyl methacrylate, and the mass ratio of the polyimide, the organic supermolecule, the carboxymethyl cellulose and the polymethyl methacrylate is 20: (1-2) : 1: 2, and the number average molecular weight of the polyimide is 32000-35000 g / mol. The polyimide is obtained by polycondensation of a first substance and a second substance, the first substance is A monomer with a purity of 99.4-99.6%, and the A monomer is 4-amino-N-(4-aminophenyl)-2-(trifluoromethyl) benzamide; the second substance is B monomer with a purity of 99.3-99.5%, and the B monomer is 6-(1,3-dioxo-1,3-dihydroisobenzofuran-5-yl)-4-(trifluoromethyl) phthalic anhydride. The method for obtaining the organic supermolecule comprises the following steps: taking resorcinol and 1,3-bis(1,3-dioxolan-2-yl)propane as substrates, normal propyl alcohol as a solvent, morpholine as a template agent, and obtaining an organic supermolecule precursor under the catalysis of hydrochloric acid, purifying and drying to obtain the organic supermolecule, the mass ratio of the resorcinol, the 1,3-bis(1,3-dioxolan-2-yl)propane and the morpholine is 4: (1-2) : (0.01-0.02), and the molecular weight of the 1,3-bis(1,3-dioxolan-2-yl)propane is 188.

25. The method for obtaining the polyimide comprises the following steps: mixing the first substance, the second substance and a first solvent, carrying out polycondensation reaction at 0-5 DEG C for 8-10 hours to obtain a precursor polyimide acid, adding an imidization catalyst, carrying out imidization reaction at 80-85 DEG C for 8-10 hours, washing and drying to obtain the polyimide, and the mass ratio of the A monomer in the first substance, the B monomer in the second substance and the imidization catalyst is 1: (1.00-1.05) : 0.

11.

2. The organic polyimide fibrous lithium-ion battery separator according to claim 1, characterized in that, The imidization catalyst is a mixture of phthalic anhydride and isoquinoline.

3. The organic polyimide fibrous lithium-ion battery separator according to claim 2, characterized in that, The application also discloses a preparation method of the organic polyimide fiber lithium ion battery diaphragm.

4. The method for producing the organic polyimide fiber lithium ion battery separator according to any one of claims 1 to 3, characterized by, The application also discloses a preparation method of the organic polyimide fiber lithium ion battery diaphragm. The application also discloses a preparation method of the organic polyimide fiber lithium ion battery diaphragm.

5. A slurry characterized in that, The application also discloses a preparation method of the organic polyimide fiber lithium ion battery diaphragm. The application also discloses a preparation method of the organic polyimide fiber lithium ion battery diaphragm. ​ The method for obtaining the organic supramolecule comprises: taking resorcinol and 1,3-bis(1,3-dioxolan-2-yl)propane as substrates, normal propyl alcohol as a solvent, morpholine as a template agent, and obtaining an organic supramolecule precursor under the catalysis of hydrochloric acid, purifying, drying, and obtaining the organic supramolecule; the ratio of resorcinol, 1,3-bis(1,3-dioxolan-2-yl)propane and morpholine is 4:(1-2):(0.01-0.02) in terms of the mass fraction; the molecular weight of the 1,3-bis(1,3-dioxolan-2-yl)propane is 188.

25.

6. Process for the preparation of the slurry according to claim 5, characterized in that, Comprise: The polyimide, the organic supramolecule, the second solvent, the carboxymethyl cellulose and the polymethyl methacrylate are mixed to be uniform to obtain a slurry.

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