A high-efficiency and safe lithium battery separator and its preparation method

Abstract

The present invention provides a highly efficient and safe lithium battery separator and a method for preparing the same, belonging to the field of new energy technology. Specifically, the present invention employs structural design and modification of polyimide, introducing side chains into the polyimide main chain to disrupt the regularity and symmetry of the chain segments, effectively reducing interactions between the molecular chains. Furthermore, the invention utilizes sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and a conductive medium as binders to effectively enhance the cohesion and peeling properties of the separator, thereby further improving the overall performance of lithium batteries. This method is of great significance and has broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of new energy technology, and specifically relates to an efficient and safe lithium battery separator and a preparation method thereof. Background Art

[0002] In the structure of lithium batteries, the separator is a key internal component. The performance of the separator determines the battery's interface structure and internal resistance, directly impacting characteristics such as capacity, cycle life, and safety. A high-performance separator plays a crucial role in improving the battery's overall performance. The separator's primary function is to separate the positive and negative electrodes of the battery, preventing contact and short circuits. It also allows electrolyte ions to pass through. The separator material is non-conductive, and its physical and chemical properties significantly influence battery performance.

[0003] Patent No. CN107221628A provides an efficient and safe lithium battery separator and its preparation method, which comprises dissolving PAN polymer in a first portion of DMF solvent, adding nanocellulose into a second portion of DMF solvent, and stirring and dispersing the mixture evenly; then adding PVP additive to the first portion of DMF solvent; mixing the first portion of DMF solvent and the second portion of DMF solvent evenly; subjecting the casting solution to vacuum degassing to remove bubbles in the mixed solution; and placing the mixed solution without bubbles into a film-making device to form a film. The present invention provides an efficient and safe lithium battery separator and its preparation method, and the obtained lithium battery separator has excellent mechanical strength. A lithium battery separator is provided, which is obtained by any of the above-mentioned preparation methods, and is formed by three layers, wherein the second layer has a plurality of finger-shaped holes, and the first and third layers both have a plurality of air holes. A lithium-ion battery is provided, comprising any of the above-mentioned lithium battery separators, and having better battery cycle performance.

[0004] Patent No. CN106876641A discloses a lithium battery separator, its preparation method, and its application in lithium batteries. The lithium battery separator of the present invention is an inorganic nanofiber membrane. The inorganic component can enhance the thermal dimensional stability of the lithium battery separator, making the lithium battery separator have higher heat resistance and stability; the inorganic component can improve the wettability of the lithium battery separator with the electrolyte. The inorganic nanofiber membrane has a high porosity, which can improve the electrolyte absorption rate and ion conductivity of the lithium battery separator, which is beneficial to improving the cycle and rate performance of the lithium battery. The lithium battery separator prepared by the electrospinning technology adopted in the present invention has the advantages of high temperature resistance and high porosity. The obtained lithium battery separator can withstand high temperature treatment for a long time without obvious thermal shrinkage. The process for preparing the lithium battery separator of the present invention is simple and has high productivity. The prepared lithium battery separator can meet the safety requirements of high-capacity lithium-ion batteries.

[0005] At present, with the continuous increase in battery energy density, battery safety issues are becoming increasingly prominent. The performance of the diaphragms used in today's batteries can no longer meet the requirements of high-power, high-energy-density batteries. Therefore, it is an irreversible trend to develop battery diaphragms that take into account both high-energy-density and high-safety performance. Summary of the Invention

[0006] In view of the problems described in the background technology, the inventors of the present invention have proposed an efficient and safe lithium battery separator and a preparation method thereof. This method prepares a polyimide separator for lithium batteries by structurally designing and modifying polyimide, and then using CMC and SBR as binders for spraying, thereby improving the safety and overall performance of power batteries.

[0007] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0008] An efficient and safe lithium battery separator and a preparation method thereof, characterized by comprising the following steps:

[0009] S1. Under inert atmosphere, deionized water is added to a reaction tank, and then diamine monomer, aluminum oxide, and a novel diamine monomer with a quinone structure are added to the reaction tank, and stirred for 20 to 100 minutes to obtain a first mixed solution; then the first mixed solution is cooled to below 5°C, and a dianhydride monomer is added to obtain a second mixed solution, and the system temperature is kept below 5°C and stirred for 10 to 17 hours to obtain a polyamic acid solution, and then a solvent is added and stirred for 40 to 60 minutes to obtain a polyamic acid slurry;

[0010] S2, cooling the polyamic acid slurry obtained in step S1 to 5-15° C., then coating the polyamic acid slurry on an aluminum-plastic film using a doctor blade by a casting method to obtain a preformed polyamic acid film, and sequentially passing it through two coagulation baths and an extraction bath. After the extraction is completed, the aluminum-plastic film is separated to obtain a polyamic acid film;

[0011] S3. Dry the polyamic acid film obtained in step S2, and then heat it in a vacuum oven to obtain a polyimide separator for a lithium battery.

[0012] More preferably, the diamine monomer is selected from one or more of 1,4-bis(4-aminophenoxy)benzene, 2,2′-bistrifluoromethyl-4,4′-diaminodiphenyl ether, and 1,3,5-tris(4-aminophenoxy)benzene.

[0013] Further preferably, the dianhydride monomer is selected from one or more of pyromellitic anhydride, biphenyltetracarboxylic anhydride, polyphenyl dianhydride, 1,2,4,5-pyromellitic anhydride, 3,6-bis(trifluoromethyl)-pyromellitic anhydride, 2,2-bis(3,4-dicarboxyphenyl)methane dianhydride, 3,5-bis(3,4-dicarboxyphenyl)biphenyl dianhydride, 1,4,5,8-naphthalenetetracarboxylic anhydride, binaphthalic anhydride, cyclobutane dianhydride and 1,4-bis(phenylmaleic anhydride)benzene.

[0014] More preferably, the total mass of the diamine monomer and the dianhydride monomer accounts for 10 to 30 wt % of the mass of the polyamic acid solution.

[0015] More preferably, the mass ratio of the diamine monomer: the novel diamine monomer with a benzoquinone structure: alumina: dianhydride monomer is (1-1.4): (0.1-0.5): (0.05-0.5): (1-1.5).

[0016] More preferably, the preparation method of the novel diamine monomer having a benzoquinone structure is:

[0017] 7-14 parts of 2,5-diaminobenzoquinone, 6-12 parts of maleic acid diamine, 0.004-0.6 parts of epoxycyclohexyl-cage polysilsesquioxane and 150-200 parts of DMF are added to a stirring kettle and mixed, and then 2-5 parts of triethylamine are added. The mixture is stirred at 60-70°C for 1-3 hours, and then the DMF is removed by reduced pressure distillation to obtain a new diamine monomer with a benzoquinone structure.

[0018] More preferably, the mass fraction of deionized water in the polyamic acid slurry is 70-90 wt % of the total solvent, the mass fraction of the solvent is 10-30 wt % of the total solvent, and the solvent is selected from dimethyl carbonate (DMC) or ethyl methyl carbonate (EMC).

[0019] Further preferably, the drying is specifically as follows: the polyamic acid film is first dried at 55-65°C, and then the adhesive is sprayed on the surface of the polyamic acid film with a precision high-pressure sprayer at a spraying speed of 2-5 mL / min, and after the spraying is completed, the film is dried for a second time at 100-105°C.

[0020] More preferably, the binder is selected from sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR), and the binder is sprayed on the aluminum-plastic film, with a base layer thickness of 10-12 microns and a thickness of 1-2 microns on both sides.

[0021] Further preferably, the binder preparation method is as follows:

[0022] A1: Dissolve sodium carboxymethyl cellulose (CMC) in deionized water to prepare an emulsion with a concentration of 1.0-2.5 wt%;

[0023] A2: Add conductive carbon black, and control the carbon black concentration at 0.8-1.6wt%;

[0024] A3: Add sodium carboxymethyl cellulose (CMC) and control the CMC concentration at 4-5wt%;

[0025] A4: Finally, add styrene-butadiene rubber (SBR), and control the SBR concentration at 4-5wt%.

[0026] Compared with the prior art, the present invention has the following technical effects:

[0027] 1) This method designs the structure of polyimide by introducing side chains into the main chain of the polyimide molecule to destroy the regularity and symmetry of the chain segments, effectively reducing the interaction between the molecular chains. The resulting polyimide membrane has the characteristics of high chemical stability, moderate porosity, high mechanical strength and low high-temperature thermal shrinkage, which is of great significance for improving the safety and electrochemical performance of power batteries.

[0028] 2) The present invention uses sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR) and a conductive medium as a binder, effectively improving its agglomeration and peeling properties, thereby contributing to further improvement of the comprehensive performance of the lithium battery.

[0029] 3) The introduction of epoxycyclohexyl-cage polysilsesquioxane as a crosslinking center significantly improves the mechanical strength and thermal stability of the final product. Its unique nanoscale effect and highly reactive epoxy groups effectively increase the crosslink density of the material.

[0030] 4) The units introduced through the amino-epoxy reaction not only enhance the functionality of the monomer but also improve the surface properties of the material, such as chemical resistance and electrochemical stability. For lithium battery separators, this can effectively improve their stability in the electrolyte and the overall performance of the battery. DETAILED DESCRIPTION

[0031] The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention. Unless otherwise specified, the examples are based on conventional experimental conditions. In addition, for those skilled in the art, without departing from the spirit and scope of the present invention, various modifications or improvements to the material components and dosages in these embodiments are within the scope of protection claimed in the present invention.

[0032] Example 1

[0033] An efficient and safe lithium battery separator and a preparation method thereof, characterized by comprising the following steps:

[0034] S1. Under inert atmosphere, deionized water is added to a reaction tank, and then diamine monomer, aluminum oxide, and a novel diamine monomer with a quinone structure are added to the reaction tank, and stirred for 20 minutes to obtain a first mixed solution; then the first mixed solution is cooled to below 5°C, and a dianhydride monomer is added to obtain a second mixed solution, and the system temperature is maintained below 5°C and stirred for 10 hours to obtain a polyamic acid solution, and then a solvent is added and stirred for 40 minutes to obtain a polyamic acid slurry;

[0035] S2, cooling the polyamic acid slurry obtained in step S1 to 5° C., then coating the polyamic acid slurry on an aluminum-plastic film using a doctor blade by a casting method to obtain a preformed polyamic acid film, and sequentially passing it through two coagulation baths and an extraction bath. After the extraction is completed, the aluminum-plastic film is separated to obtain a polyamic acid film;

[0036] S3. Dry the polyamic acid film obtained in step S2, and then heat it in a vacuum oven to obtain a polyimide separator for a lithium battery.

[0037] The diamine monomer is selected from 1,4-bis(4-aminophenoxy)benzene.

[0038] The dianhydride monomer is selected from pyromellitic anhydride.

[0039] The total mass of the diamine monomer and the dianhydride monomer accounts for 10 wt % of the mass of the polyamic acid solution.

[0040] The mass ratio of the diamine monomer: the novel diamine monomer with benzoquinone structure: aluminum oxide: and the dianhydride monomer is 1:0.1:0.05:1.

[0041] The preparation method of the novel diamine monomer with benzoquinone structure is as follows:

[0042] 7 g of 2,5-diaminobenzoquinone (CAS: 1521-06-8), 6 g of maleic acid diamine, 0.004 g of epoxycyclohexyl-cage polysilsesquioxane and 150 g of DMF were added to a stirring kettle and mixed. Then, 2 g of triethylamine was added and stirred at 60°C for 1 hour. Then, DMF was removed by vacuum distillation to obtain a new diamine monomer with a benzoquinone structure.

[0043] The mass fraction of deionized water in the polyamic acid slurry is 70 wt % of the total solvent, the mass fraction of the solvent is 10 wt % of the total solvent, and the solvent is selected from dimethyl carbonate (DMC).

[0044] The drying is specifically as follows: the polyamic acid film is first dried at 55°C, and then the adhesive is sprayed on the surface of the polyamic acid film with a precision high-pressure sprayer at a spraying speed of 2 mL / min, and after the spraying is completed, the film is dried again at 100°C.

[0045] The adhesive is selected from sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR). The adhesive is sprayed on the aluminum-plastic film. The base layer has a thickness of 10 microns and the thicknesses of both sides are 1 micron.

[0046] The binder preparation method is as follows:

[0047] A1: Dissolve sodium carboxymethyl cellulose (CMC) in deionized water to prepare an emulsion with a concentration of 1.0 wt%;

[0048] A2: Add conductive carbon black, and control the carbon black concentration at 0.8wt%;

[0049] A3: Sodium carboxymethyl cellulose (CMC) was added, and the CMC concentration was controlled at 4 wt%;

[0050] A4: Finally, styrene-butadiene rubber (SBR) was added, and the SBR concentration was controlled at 4 wt%.

[0051] Example 2

[0052] An efficient and safe lithium battery separator and a preparation method thereof, characterized by comprising the following steps:

[0053] S1. Under inert atmosphere, deionized water is added to a reaction tank, and then diamine monomer, aluminum oxide, and a novel diamine monomer with a benzoquinone structure are added to the reaction tank, and stirred for 50 minutes to obtain a first mixed solution; then the first mixed solution is cooled to below 5°C, and a dianhydride monomer is added to obtain a second mixed solution, and the system temperature is maintained below 5°C and stirred for 12 hours to obtain a polyamic acid solution, and then a solvent is added and stirred for 45 minutes to obtain a polyamic acid slurry;

[0054] S2, cooling the polyamic acid slurry obtained in step S1 to 5° C., then coating the polyamic acid slurry on an aluminum-plastic film using a doctor blade by a casting method to obtain a preformed polyamic acid film, and sequentially passing it through two coagulation baths and an extraction bath. After the extraction is completed, the aluminum-plastic film is separated to obtain a polyamic acid film;

[0055] S3. Dry the polyamic acid film obtained in step S2, and then heat it in a vacuum oven to obtain a polyimide separator for a lithium battery.

[0056] The diamine monomer is selected from 2,2′-bis(trifluoromethyl)-4,4′-diaminodiphenyl ether.

[0057] The dianhydride monomer is selected from 3,6-bis(trifluoromethyl)-pyromellitic dianhydride.

[0058] The total weight of the diamine monomer and the dianhydride monomer accounts for 15 wt % of the weight of the polyamic acid solution.

[0059] The mass ratio of the diamine monomer: the novel diamine monomer with benzoquinone structure: aluminum oxide: and the dianhydride monomer is 1.1:0.2:0.2:1.2.

[0060] The preparation method of the novel diamine monomer with benzoquinone structure is as follows:

[0061] 9 g of 2,5-diaminobenzoquinone (CAS: 1521-06-8), 8 g of maleic acid diamine, 0.1 g of epoxycyclohexyl-cage polysilsesquioxane and 165 g of DMF were added to a stirring kettle and mixed. Then, 3 g of triethylamine was added and stirred at 65° C. for 2 h. Then, DMF was removed by vacuum distillation to obtain a new diamine monomer with a benzoquinone structure.

[0062] The mass fraction of deionized water in the polyamic acid slurry is 80 wt % of the total solvent, the mass fraction of the solvent is 15 wt % of the total solvent, and the solvent is selected from ethyl methyl carbonate (EMC).

[0063] The drying is specifically as follows: the polyamic acid film is first dried at 55°C, and then the adhesive is sprayed on the surface of the polyamic acid film at a spraying speed of 3 mL / min using a precision high-pressure sprayer, and then dried again at 100°C after the spraying is completed.

[0064] The adhesive is selected from sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR). The adhesive is sprayed on the aluminum-plastic film. The base layer has a thickness of 10 microns and the thicknesses of both sides are 2 microns.

[0065] The binder preparation method is as follows:

[0066] A1: Dissolve sodium carboxymethyl cellulose (CMC) in deionized water to prepare a 1.5% emulsion;

[0067] A2: Add conductive carbon black, and control the carbon black concentration at 1.2wt%;

[0068] A3: Sodium carboxymethyl cellulose (CMC) was added, and the CMC concentration was controlled at 4.2 wt%;

[0069] A4: Finally, styrene-butadiene rubber (SBR) was added, and the SBR concentration was controlled at 4.2 wt%.

[0070] Example 3

[0071] An efficient and safe lithium battery separator and a preparation method thereof, characterized by comprising the following steps:

[0072] S1. Under inert atmosphere, deionized water is added to a reaction tank, and then diamine monomer, aluminum oxide, and a novel diamine monomer with a benzoquinone structure are added to the reaction tank, and stirred for 75 minutes to obtain a first mixed solution; then the first mixed solution is cooled to below 5°C, and a dianhydride monomer is added to obtain a second mixed solution, and the system temperature is maintained below 5°C and stirred for 14 hours to obtain a polyamic acid solution, and then a solvent is added and stirred for 55 minutes to obtain a polyamic acid slurry;

[0073] S2, cooling the polyamic acid slurry obtained in step S1 to 12° C., then coating the polyamic acid slurry on an aluminum-plastic film using a doctor blade by a casting method to obtain a preformed polyamic acid film, and sequentially passing it through two coagulation baths and an extraction bath. After the extraction is completed, the aluminum-plastic film is separated to obtain a polyamic acid film;

[0074] S3. Dry the polyamic acid film obtained in step S2, and then heat it in a vacuum oven to obtain a polyimide separator for a lithium battery.

[0075] The diamine monomer is selected from 1,3,5-tris(4-aminophenoxy)benzene.

[0076] The dianhydride monomer is selected from 1,4-di(phenylmaleic anhydride)benzene.

[0077] The total mass of the diamine monomer and the dianhydride monomer accounts for 25 wt % of the mass of the polyamic acid solution.

[0078] The mass ratio of the diamine monomer: the novel diamine monomer with benzoquinone structure: aluminum oxide: and the dianhydride monomer is 1.25:0.4:0.2:1.4.

[0079] The preparation method of the novel diamine monomer with benzoquinone structure is as follows:

[0080] 12 g of 2,5-diaminobenzoquinone (CAS: 1521-06-8), 10 g of maleic acid diamine, 0.3 g of epoxycyclohexyl-cage polysilsesquioxane and 180 g of DMF were added to a stirring kettle and mixed. Then, 4 g of triethylamine was added and stirred at 65° C. for 2 h. Then, DMF was removed by vacuum distillation to obtain a new diamine monomer with a benzoquinone structure.

[0081] The mass fraction of deionized water in the polyamic acid slurry is 85 wt % of the total solvent, the mass fraction of the solvent is 25 wt % of the total solvent, and the solvent is selected from dimethyl carbonate (DMC).

[0082] The drying is specifically as follows: the polyamic acid film is first dried at 65°C, then the adhesive is sprayed on the surface of the polyamic acid film with a precision high-pressure sprayer at a spraying speed of 4 mL / min, and after the spraying is completed, the film is dried again at 105°C.

[0083] The adhesive is selected from sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR). The adhesive is sprayed on the aluminum-plastic film. The base layer has a thickness of 12 microns and the thicknesses of both sides are 1 micron.

[0084] The binder preparation method is as follows:

[0085] A1: Dissolve sodium carboxymethyl cellulose (CMC) in deionized water to prepare an emulsion with a concentration of 2.0 wt%;

[0086] A2: Add conductive carbon black and control the carbon black concentration at 1.4wt%;

[0087] A3: Sodium carboxymethyl cellulose (CMC) was added, and the CMC concentration was controlled at 4.8 wt%;

[0088] A4: Finally, styrene-butadiene rubber (SBR) was added, and the SBR concentration was controlled at 4.8 wt%.

[0089] Example 4

[0090] An efficient and safe lithium battery separator and a preparation method thereof, characterized by comprising the following steps:

[0091] S1. Under inert atmosphere, deionized water is added to a reaction tank, and then diamine monomer, aluminum oxide, and a novel diamine monomer with a benzoquinone structure are added to the reaction tank, and stirred for 100 minutes to obtain a first mixed solution; then the first mixed solution is cooled to below 5°C, and a dianhydride monomer is added to obtain a second mixed solution, and the system temperature is maintained below 5°C and stirred for 17 hours to obtain a polyamic acid solution, and then a solvent is added and stirred for 60 minutes to obtain a polyamic acid slurry;

[0092] S2, cooling the polyamic acid slurry obtained in step S1 to 15° C., then coating the polyamic acid slurry on an aluminum-plastic film using a doctor blade by a casting method to obtain a preformed polyamic acid film, and sequentially passing it through two coagulation baths and an extraction bath. After the extraction is completed, the aluminum-plastic film is separated to obtain a polyamic acid film;

[0093] S3. Dry the polyamic acid film obtained in step S2, and then heat it in a vacuum oven to obtain a polyimide separator for a lithium battery.

[0094] The diamine monomer is selected from 2,2′-bis(trifluoromethyl)-4,4′-diaminodiphenyl ether.

[0095] The dianhydride monomer is selected from 1,4,5,8-naphthalenetetracarboxylic dianhydride.

[0096] The total mass of the diamine monomer and the dianhydride monomer accounts for 30 wt % of the mass of the polyamic acid solution.

[0097] The mass ratio of the diamine monomer: the novel diamine monomer with benzoquinone structure: aluminum oxide: and the dianhydride monomer is 1.4:0.5:0.4:1.2.

[0098] The preparation method of the novel diamine monomer with benzoquinone structure is as follows:

[0099] 14 g of 2,5-diaminobenzoquinone (CAS: 1521-06-8), 12 g of maleic acid diamine, 0.6 g of epoxycyclohexyl-cage polysilsesquioxane and 200 g of DMF were added to a stirring kettle and mixed. Then, 5 g of triethylamine was added and stirred at 70°C for 3 hours. Then, DMF was removed by vacuum distillation to obtain a new diamine monomer with a benzoquinone structure.

[0100] The mass fraction of deionized water in the polyamic acid slurry is 90 wt % of the total solvent, the mass fraction of the solvent is 30 wt % of the total solvent, and the solvent is selected from ethyl methyl carbonate (EMC).

[0101] The drying is specifically as follows: the polyamic acid film is first dried at 65°C, then the adhesive is sprayed on the surface of the polyamic acid film with a precision high-pressure sprayer at a spraying speed of 5 mL / min, and after the spraying is completed, the film is dried again at 105°C.

[0102] The adhesive is selected from sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR). The adhesive is sprayed on the aluminum-plastic film. The base layer has a thickness of 12 microns and the thicknesses of both sides are 2 microns.

[0103] The binder preparation method is as follows:

[0104] A1: Dissolve sodium carboxymethyl cellulose (CMC) in deionized water to prepare an emulsion with a concentration of 2.5 wt%;

[0105] A2: Add conductive carbon black, and control the carbon black concentration at 1.6wt%;

[0106] A3: Sodium carboxymethyl cellulose (CMC) was added, and the CMC concentration was controlled at 5wt%;

[0107] A4: Finally, add styrene-butadiene rubber (SBR), and control the SBR concentration at 5 wt%.

[0108] Comparative Example 1

[0109] An efficient and safe lithium battery separator and a preparation method thereof, characterized by comprising the following steps:

[0110] S1. Under inert atmosphere, deionized water is added to a reaction tank, and then a diamine monomer and aluminum oxide are added to the reaction tank, and stirred for 20 minutes to obtain a first mixed solution; then the first mixed solution is cooled to below 5°C, a dianhydride monomer is added to obtain a second mixed solution, and the system temperature is kept below 5°C and stirred for 10 hours to obtain a polyamic acid solution, and then a solvent is added and stirred for 40 minutes to obtain a polyamic acid slurry;

[0111] S2, cooling the polyamic acid slurry obtained in step S1 to 5° C., then coating the polyamic acid slurry on an aluminum-plastic film using a doctor blade by a casting method to obtain a preformed polyamic acid film, and sequentially passing it through two coagulation baths and an extraction bath. After the extraction is completed, the aluminum-plastic film is separated to obtain a polyamic acid film;

[0112] S3. Dry the polyamic acid film obtained in step S2, and then heat it in a vacuum oven to obtain a polyimide separator for a lithium battery.

[0113] The diamine monomer is selected from 1,4-bis(4-aminophenoxy)benzene.

[0114] The dianhydride monomer is selected from pyromellitic anhydride.

[0115] The total mass of the diamine monomer and the dianhydride monomer accounts for 10 wt % of the mass of the polyamic acid solution.

[0116] The mass ratio of the diamine monomer:aluminum oxide:dianhydride monomer is 1:0.05:1.

[0117] The mass fraction of deionized water in the polyamic acid slurry is 70 wt % of the total solvent, the mass fraction of the solvent is 10 wt % of the total solvent, and the solvent is selected from ethyl methyl carbonate (EMC).

[0118] The drying is specifically as follows: the polyamic acid film is first dried at 55°C, and then the adhesive is sprayed on the surface of the polyamic acid film with a precision high-pressure sprayer at a spraying speed of 2 mL / min, and after the spraying is completed, the film is dried again at 100°C.

[0119] The adhesive is selected from sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR). The adhesive is sprayed on the aluminum-plastic film. The base layer has a thickness of 10 microns and the thicknesses of both sides are 1 micron.

[0120] The binder preparation method is as follows:

[0121] A1: Dissolve sodium carboxymethyl cellulose (CMC) in deionized water to prepare an emulsion with a concentration of 1.0 wt%;

[0122] A2: Add conductive carbon black, and control the carbon black concentration at 0.8wt%;

[0123] A3: Sodium carboxymethyl cellulose (CMC) was added, and the CMC concentration was controlled at 4 wt%;

[0124] A4: Finally, styrene-butadiene rubber (SBR) was added, and the SBR concentration was controlled at 4 wt%.

[0125] Comparative Example 2

[0126] The same as Example 1, except that the diaphragm is a commercially available PE diaphragm.

[0127] Evaluation of the embodiment:

[0128] 1. The separators prepared in the embodiments and comparative examples of the present invention were used to assemble batteries, and the safety performance of the batteries (refer to GB38031-2020) was tested. The test results are shown in Table 1. The test was carried out as follows:

[0129] Lithium iron phosphate was used as the positive electrode active material, artificial graphite was used as the negative electrode active material, and the diaphragms prepared in the examples and comparative examples were used as battery diaphragms to assemble a 110Ah square aluminum shell battery. Charge and discharge tests were carried out, and the electrolyte was 1.0 mol / L LiPF6 / EC+DEC+EMC (1:1:1) electrolyte.

[0130] Table 1 Battery safety performance test results

[0131] project Overdischarge Overcharge External short circuit 150℃ thermal shock extrusion acupuncture Example 1 OK OK OK OK OK OK Example 2 OK OK OK OK OK OK Example 3 OK OK OK OK OK OK Example 4 OK OK OK OK OK OK Comparative Example 1 OK OK OK OK OK NG Comparative Example 2 OK OK OK NG OK NG

[0132] 2. The separators prepared in the embodiments of the present invention and the comparative examples were used to assemble batteries, and the electrochemical performance of the batteries was tested. The test results are shown in Table 2. The test was carried out as follows:

[0133] The positive electrode material was prepared using lithium iron phosphate and carbon black in a mass ratio of 4:1. A lithium metal sheet was used as the negative electrode material. The separators prepared in the examples and comparative examples of the present invention were used as the separator. The electrolyte was a 1.0 mol / L LiPF6 / EC+DEC+EMC (1:1:1) solution. Coin-shaped batteries were assembled and allowed to stand at room temperature for 24 hours before use. The assembled batteries were tested for charge-discharge performance at 1C, 2C, and 3C rates on a LANHE battery testing system.

[0134] Table 2 Rate cycle charge and discharge performance test results

[0135]

[0136]

[0137] It can be seen from the above specific embodiments that the polyimide separator prepared by this method has a significant effect on improving the comprehensive performance of lithium-ion batteries, especially the safety performance, and has very important significance and broad application prospects.

[0138] The above description is an example of a specific embodiment of the present invention, which is used to more clearly illustrate the inventive concept of the present invention, but is not used to limit the scope of the claims of the present invention. Based on the inventive concept of the present invention, those skilled in the art can easily modify and alter the above embodiment, and such modifications and alterations falling within the inventive concept of the present invention are included within the scope of the appended claims of the present invention.

Claims

1. A method for preparing an efficient and safe lithium battery separator, characterized by: The following steps are involved: S1. Under inert atmosphere, deionized water is added to a reaction tank, and then diamine monomer, aluminum oxide, and a novel diamine monomer with a quinone structure are added to the reaction tank, and stirred for 20 to 100 minutes to obtain a first mixed solution; then the first mixed solution is cooled to below 5°C, and a dianhydride monomer is added to obtain a second mixed solution, and the system temperature is kept below 5°C and stirred for 10 to 17 hours to obtain a polyamic acid solution, and then a solvent is added and stirred for 40 to 60 minutes to obtain a polyamic acid slurry; S2, cooling the polyamic acid slurry obtained in step S1 to 5-15° C., then coating the polyamic acid slurry on an aluminum-plastic film using a doctor blade by a casting method to obtain a preformed polyamic acid film, and sequentially passing it through two coagulation baths and an extraction bath. After the extraction is completed, the aluminum-plastic film is separated to obtain a polyamic acid film; S3, drying the polyamic acid film obtained in step S2, and then heating it in a vacuum oven to obtain a polyimide separator for a lithium battery; The preparation method of the novel diamine monomer with benzoquinone structure is as follows: 7-14 parts of 2,5-diaminobenzoquinone, 6-12 parts of maleic acid diamine, 0.004-0.6 parts of epoxycyclohexyl-cage polysilsesquioxane and 150-200 parts of DMF are added to a stirring kettle and mixed. Then, 2-5 parts of triethylamine are added and stirred at 60-70°C for 1-3 hours. Then, DMF is removed by vacuum distillation to obtain a novel diamine monomer with a benzoquinone structure.

2. The method for preparing an efficient and safe lithium battery separator according to claim 1, characterized in that: The diamine monomer is selected from one or more of 1,4-bis(4-aminophenoxy)benzene, 2,2'-bistrifluoromethyl-4,4'-diaminodiphenyl ether, and 1,3,5-tris(4-aminophenoxy)benzene.

3. The method for preparing an efficient and safe lithium battery separator according to claim 1, characterized in that: The dianhydride monomer is selected from one or more of pyromellitic anhydride, biphenyltetracarboxylic anhydride, polyphenyl dianhydride, 1,2,4,5-pyromellitic anhydride, 3,6-bis(trifluoromethyl)-pyromellitic anhydride, 2,2-bis(3,4-dicarboxyphenyl)methane dianhydride, 3,5-bis(3,4-dicarboxyphenyl)biphenyl dianhydride, 1,4,5,8-naphthalenetetracarboxylic anhydride, binaphthalic anhydride, cyclobutane dianhydride and 1,4-bis(phenylmaleic anhydride)benzene.

4. The method for preparing an efficient and safe lithium battery separator according to claim 1, characterized in that: The total mass of the diamine monomer and the dianhydride monomer accounts for 10-30wt% of the mass of the polyamic acid solution, and the mass ratio of the diamine monomer: the new diamine monomer with a benzoquinone structure: aluminum oxide: dianhydride monomer is (1-1.4): (0.1-0.5): (0.05-0.5): (1-1.5).

5. The method for preparing an efficient and safe lithium battery separator according to claim 1, characterized in that: The mass fraction of deionized water in the polyamic acid slurry is 70-90wt% of the total solvent, the mass fraction of the solvent is 10-30wt% of the total solvent, and the solvent is selected from dimethyl carbonate (DMC) or ethyl methyl carbonate (EMC).

6. The method for preparing an efficient and safe lithium battery separator according to claim 1, characterized in that: The drying is specifically as follows: the polyamic acid film is first dried at 55-65°C, then the adhesive is sprayed on the surface of the polyamic acid film with a precision high-pressure sprayer at a spraying speed of 2-5 mL / min, and after the spraying is completed, the film is dried again at 100-105°C.

7. The method for preparing an efficient and safe lithium battery separator according to claim 6, characterized in that: The adhesive is selected from sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR). The adhesive is sprayed on the aluminum-plastic film. The base layer has a thickness of 10-12 microns and the thicknesses of both sides are 1-2 microns.

8. The method for preparing an efficient and safe lithium battery separator according to claim 7, characterized in that: The binder preparation method is as follows: A1: Dissolve sodium carboxymethyl cellulose (CMC) in deionized water to prepare an emulsion with a concentration of 1.0-2.5 wt%; A2: Add conductive carbon black, and control the carbon black concentration at 0.8-1.6wt%; A3: Add sodium carboxymethyl cellulose (CMC) and control the CMC concentration at 4-5wt%; A4: Finally, add styrene-butadiene rubber (SBR), and control the SBR concentration at 4-5wt%.

9. A lithium battery separator prepared according to the preparation method according to any one of claims 1 to 8.

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