Separator for lithium batteries and method for its manufacture

Abstract

The present invention relates to the technical field of lithium batteries, in particular a separator for lithium batteries and a method for producing the same. The present invention discloses a method for producing a separator for lithium batteries, comprising the following steps: Step S101 “Production of a copolymer”; Step S102 “Shaping a separator”: uniformly mixing the copolymer produced in step S101 with an amino-terminated hyperbranched polyimide polymer, a sulfo-terminated hyperbranched sulfonated polyaryl ether, a nano-boron fiber, a nano-calcium carbonate, and an adhesion promoter to form a mixture, which is then milled and sieved through a sieve with 200 to 400 meshes per inch and subsequently subjected to melt extrusion and thermosetting to finally obtain a separator; Step S103 “Pore production”.The present invention further discloses a separator for lithium batteries known in the present invention. The separator for lithium batteries disclosed by the present invention exhibits high ionic conductivity, sufficient wettability with the electrolyte, excellent aging and heat resistance, as well as good mechanical properties.

Description

[0001] This application claims priority to Chinese Patent Application No. CN202211481549.8 entitled “Separator for lithium batteries and method for manufacturing the same”, filed on November 24, 2022, the entire contents of which are incorporated into the present application by reference. TECHNICAL FIELD

[0002] The present invention relates to the technical field of lithium batteries, in particular to a separator for lithium batteries and a method for producing the same. STATE OF THE ART

[0003] With the continuous progress of the modern electronics industry, the application range of energy storage devices is becoming ever broader. As an electrochemical energy storage device, batteries are widely used in many fields, such as portable smart devices and electric vehicles. As one of the more common batteries, lithium batteries are widely used in transportation, daily life, medicine, and even space exploration due to their advantages (e.g., high energy density, long cycle life, low self-discharge rate, no memory effect, stable discharge voltage, fast charging and discharging, and environmental friendliness), and have been widely accepted in the industry after nearly two decades of development.

[0004] The lithium battery separator is one of the most important internal components of lithium batteries. Its main function is to separate the positive and negative electrodes of the lithium battery, preventing the two electrodes from touching and thus causing a short circuit. Although the material of the lithium battery separator is non-conductive, it allows electrolyte ions to pass through. The performance of the separator determines the interfacial structure, internal resistance, etc., of the lithium battery, which directly affects the capacity, cycle life, safety performance, and other characteristics of the lithium battery.An ideal separator for lithium batteries should exhibit high ionic conductivity, good thermal stability, good chemical stability, and good electrochemical stability, while providing a high degree of wettability with electrolytes and excellent mechanical properties during repeated charging and discharging.

[0005] Currently, most commercial separators for lithium batteries are microporous polyolefin membranes made of polyethylene and / or polypropylene. Microporous polyolefin membranes feature low cost, controllable pore size, stable chemical stability, good mechanical strength, and good electrochemical stability. They also exhibit self-sealing performance at high temperatures, thus ensuring the safety performance of lithium-ion secondary batteries in everyday use. However, such separators suffer from excessive heat shrinkage and insufficient wettability with electrolytes.If the shrinkage rate is too high, a polyolefin membrane is prone to melting at high temperatures, resulting in large-scale short circuits and thermal runaway. Heat accumulation is exacerbated, creating high pressure inside the battery, leading to battery fire or explosion. On the other hand, since there are no polar groups in the polyolefin chain, the microporous polyolefin membrane exhibits low surface energy, strong inertness, and hydrophobicity. However, the electrolyte solution contains a large amount of polar components. Thus, the affinity between the two is low, increasing the battery resistance and affecting the battery's cycle performance and charge-discharge efficiency.

[0006] For example, Chinese Patent Application No. CN102367172B discloses a modified silica-polyolefin microporous separator for lithium-ion batteries, which is produced by the following method: a modified silica and a high / ultra-high molecular weight polyolefin are blended into a mixture, to which an ordinary polyolefin is added, and then granulated to obtain a modified masterbatch; the modified masterbatch is blended with the polyolefin, melt-blended, and extruded to form a membrane with a hard elastic structure; the membrane is continuously stretched and then thermally set at 100 to 150°C to obtain a microporous polyolefin separator for lithium-ion batteries.The microporous polyolefin separator for lithium-ion batteries according to this invention has a relatively thin thickness (less than 15 µm), relatively good strength (the longitudinal breaking strength is more than 100 MPa, the transverse breaking strength is about 8 MPa, and the elongation at break is 50%), and the porosity and pore structure of the membrane are adjustable (the porosity is greater than 50% and the pore size is 0.1 to 1 µm); and the membrane has a low thermal shrinkage rate (less than 5%). This invention can improve the thermal stability of the polymer; however, there is still the problem of insufficient wettability with electrolytes, which increases the battery resistance and impairs the battery's cycle performance and charge-discharge efficiency.

[0007] In this field, a separator for lithium batteries having high ionic conductivity, sufficient wettability with electrolytes, excellent aging resistance and heat resistance, and good mechanical properties, and a method for producing the same are still needed. CONTENT OF THE PRESENT INVENTION

[0008] The object of the present invention is to overcome the deficiencies of the prior art and to provide a separator for lithium batteries having high ionic conductivity, sufficient wettability with electrolytes, excellent aging resistance and heat resistance as well as good mechanical properties, and methods for producing the same.

[0009] To achieve the above object, the present invention provides the following technical solutions: A method for producing a separator for lithium batteries, comprising the following steps: Step S101 “Preparation of a copolymer”: Adding N-(4-cyano-3-trifluoromethylphenyl)methacrylamide, 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, allyltriphenylphosphine bromide, 7-fluoro-5-oxo-8-(4-(2-propenyl)-1-piperazinyl)-5H-thiazolo[3,2-a]quinoline-4-carboxylic acid (CAS: 84339-01-5) and an initiator to a high-boiling solvent, which is then stirred and reacted in an inert gas atmosphere for 4 to 6 hours at 65 to 75 °C and thereafter subjected to precipitation in a lithium hydroxide solution with a mass fraction of 10 to 20 wt%, wherein the precipitated polymer is washed three to six times with ethanol and finally the ethanol is removed by rotary evaporation to obtain a copolymer; Step S102 "Forming a separator": uniformly mixing the copolymer prepared by step S101 with an amino-terminated hyperbranched polyimide polymer, a sulfo-terminated hyperbranched sulfonated polyaryl ether, a nano-boron fiber, a nano-calcium carbonate, and an adhesion promoter into a mixture, which is then ground and sieved through a sieve with 200 to 400 meshes per inch, and thereafter subjected to melt extrusion and heat setting to finally obtain a separator; Step S103 "Pore Preparation": Soaking the separator prepared by step S102 in a hydrochloric acid solution having a mass fraction of 8 to 13 wt% for 18 to 32 hours, then rinsing the separator with water until the corresponding eluent is neutral, so that a separator for lithium batteries is obtained. Preferably, in step S101, the mass ratio of the N-(4-cyano-3-trifluoromethylphenyl)methacrylamide, the 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, allyltriphenylphosphine bromide, the 7-fluoro-5-oxo-8-(4-(2-propenyl)-1-piperazinyl)-5H-thiazolo[3,2-a]quinoline-4-carboxylic acid (CAS: 84339-01-5), the initiator, and the high-boiling solvent is (3 to 5):1:(0.8 to 1.2):(0.1 to 0.3):(0.06 to 0.08):(25 to 35).

[0010] Preferably, the initiator is at least one of azobisisobutyronitrile and azobisisoheptanonitrile.

[0011] Preferably, the high-boiling solvent is at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0012] Preferably, the inert gas is one of nitrogen, helium, neon and argon.

[0013] Preferably, in step S102, the mass ratio of the copolymer, the amino-terminated hyperbranched polyimide polymer, the sulfo-terminated hyperbranched sulfonated polyaryl ether, the nano-boron fiber, the nano-calcium carbonate, and the adhesion promoter is (40 to 60): (10 to 15): (15 to 20): (5 to 8): (1 to 2): (3 to 5).

[0014] Preferably, no special requirements are placed on the source of the amino-terminated hyperbranched polyimide polymer. In one embodiment of the present invention, the amino-terminated hyperbranched polyimide polymer is produced by a process according to a third embodiment of Chinese Patent Application No. CN102267940B.

[0015] Preferably, no special requirements are placed on the source of the sulfo-terminated hyperbranched sulfonated polyaryl ether. In one embodiment, the sulfo-terminated hyperbranched sulfonated polyaryl ether is prepared by a process according to a first embodiment of Chinese patent CN109546192A.

[0016] Preferably, the nano-boron fiber has an average diameter of 300 to 500 nm and an aspect ratio of (16 to 24):1; wherein the nano-calcium carbonate has a particle size of 300 to 600 nm. Preferably, the coupling agent is at least one of silane coupling agent KH550, silane coupling agent KH560, and silane coupling agent KH570.

[0017] Preferably, in step S102, the melt extrusion temperature is 340 to 400°C, the heat setting temperature is 160 to 230°C, and the heat setting time is 40 to 50 minutes.

[0018] It is preferably provided that in step S103 the mass ratio of the separator to the hydrochloric acid solution is 1:(25 to 35).

[0019] The present invention also provides a separator for lithium batteries manufactured by the manufacturing method described in the above solutions.

[0020] Due to the use of the above-mentioned technical solutions, the present invention has the following advantages over the prior art: (1) The method for producing a separator for lithium batteries provided by the present invention is characterized by a simple process, convenient operation, low requirements for equipment and reaction conditions, high production efficiency and qualification rate of the finished product, is suitable for the application of continuous mass production, and has high economic value, social value and popularization or application value. (2) In the separator for lithium batteries provided by the present invention, the component “copolymer” is prepared by copolymerization of (4-cyano-3-trifluoromethylphenyl)methacrylamide, 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, allyltriphenylphosphine bromide, 7-fluoro-5-oxo-8-(4-(2-propenyl)-1-piperazinyl)-5H-thiazolo[3,2-a]quinoline-4-carboxylic acid, so that the structure of the separator contains a cyano group, trifluoromethylphenyl group, amide group, triazone group, phenylphosphino group, fluoropiperazine, thiazole, quinoline, etc., which interact and influence each other under the joint action of electronic effect, steric hindrance effect and conjugation effect, the produced separator has excellent aging resistance and heat resistance as well as good mechanical properties.By introducing these polar groups, the wettability with electrolytes can be effectively improved. (3) In the separator for lithium batteries provided by the present invention, the epoxy group in the molecular structure of the copolymer can undergo an epoxy ring-opening reaction with the amino group on the amino-terminated hyperbranched polyimide polymer, and the sulfonic acid group on the sulfo-terminated hyperbranched sulfonated polyaryl ether can be easily bonded with the quaternary phosphonium salt structure in the molecular structure of the copolymer to form a three-dimensional network structure, combining the advantages of these components, so that the mechanical properties, heat resistance, and durability of the separator are effectively improved. (4) In the separator for lithium batteries provided by the present invention, the addition of a nano-boron fiber can improve the mechanical properties and heat resistance of the membrane, the use of nano-calcium carbonate can ensure the porosity of the membrane, and the introduction of a lithium salt structure, a quaternary phosphorus salt structure and a sulfonate anion structure into the membrane structure contributes to the improvement of the ionic conductivity. DETAILED DESCRIPTION

[0021] The present invention provides a method for producing a separator for lithium batteries, comprising the following steps: Step S101 “Preparation of a copolymer”: Adding N-(4-cyano-3-trifluoromethylphenyl)methacrylamide, 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, allyltriphenylphosphine bromide, 7-fluoro-5-oxo-8-(4-(2-propenyl)-1-piperazinyl)-5H-thiazolo[3,2-a]quinoline-4-carboxylic acid (CAS: 84339-01-5) and an initiator to a high-boiling solvent, which is then stirred and reacted in an inert gas atmosphere for 4 to 6 hours at 65 to 75 °C and thereafter subjected to precipitation in a lithium hydroxide solution with a mass fraction of 10 to 20 wt%, wherein the precipitated polymer is washed three to six times with ethanol and finally the ethanol is removed by rotary evaporation to obtain a copolymer; Step S102 "Forming a separator": uniformly mixing the copolymer prepared by step S101 with an amino-terminated hyperbranched polyimide polymer, a sulfo-terminated hyperbranched sulfonated polyaryl ether, a nano-boron fiber, a nano-calcium carbonate, and an adhesion promoter into a mixture, which is then ground and sieved through a sieve with 200 to 400 meshes per inch, and thereafter subjected to melt extrusion and heat setting to finally obtain a separator; Step S103 “Pore Preparation”: Soaking the separator prepared by step S102 in a hydrochloric acid solution having a mass fraction of 8 to 13 wt% for 18 to 32 hours, then rinsing the separator with water until the corresponding eluent is neutral, so that a separator for lithium batteries is obtained.

[0022] In the present invention, it is provided that in step S101, the mass ratio of the N-(4-cyano-3-trifluoromethylphenyl)methacrylamide, the 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, allyltriphenylphosphine bromide, the 7-fluoro-5-oxo-8-(4-(2-propenyl)-1-piperazinyl)-5H-thiazolo[3,2-a]quinoline-4-carboxylic acid (CAS: 84339-01-5), the initiator and the high-boiling solvent is preferably (3 to 5):1:(0.8 to 1.2):(0.1 to 0.3):(0.06 to 0.08):(25 to 35).

[0023] In the present invention, it is provided that the initiator is preferably at least one of azobisisobutyronitrile and azobisisoheptanonitrile.

[0024] In the present invention, it is provided that the high-boiling solvent is preferably at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone.

[0025] In the present invention, the inert gas is preferably one of nitrogen, helium, neon and argon.

[0026] In the present invention, it is provided that in step S102, the mass ratio of the copolymer, the amino-terminated hyperbranched polyimide polymer, the sulfo-terminated hyperbranched sulfonated polyaryl ether, the nano-boron fiber, the nano-calcium carbonate and the coupling agent is preferably (40 to 60): (10 to 15): (15 to 20): (5 to 8): (1 to 2): (3 to 5).

[0027] In the present invention, no special requirements are imposed on the source of the amino-terminated hyperbranched polyimide polymer. In one embodiment of the present invention, the amino-terminated hyperbranched polyimide polymer is produced by a process according to a third embodiment of Chinese Patent Application No. CN102267940B.

[0028] In the present invention, no special requirements are placed on the source of the sulfo-terminated hyperbranched sulfonated polyaryl ether. In one embodiment, the sulfo-terminated hyperbranched sulfonated polyaryl ether is prepared by a process according to a first embodiment of Chinese patent CN109546192A.

[0029] In the present invention, the nano-boron fiber has an average diameter of preferably 300 to 500 nm and an aspect ratio of preferably (16 to 24):1; wherein the nano-calcium carbonate has a particle size of preferably 300 to 600 nm.

[0030] In the present invention, it is provided that the coupling agent is preferably at least one of silane coupling agent KH550, silane coupling agent KH560 and silane coupling agent KH570.

[0031] In the present invention, it is provided that in step S102, the temperature of the melt extrusion is preferably 340 to 400°C, the temperature of the heat setting is preferably 160 to 230°C and the time duration of the heat setting is preferably 40 to 50 minutes.

[0032] In the present invention, it is provided that in step S103 the mass ratio of the separator to the hydrochloric acid solution is 1:(25 to 35).

[0033] The present invention also provides a separator for lithium batteries manufactured by the manufacturing method described in the above solutions.

[0034] In the present invention, the preparation method of the amino-terminated hyperbranched polyimide polymer is as follows: Put 0.629 g (1 mmol) of triamine monomer 2,4,6-tris[4-(4-aminophenoxy)phenyl]pyridine and 15 ml of N-methylpyrrolidone into a four-necked flask, then blow nitrogen into it, raise the temperature to 40 °C, dissolve 0.322 g (1 mmol) of 3,3',4,4'-tetracarboxylic dianhydride benzophenone in 15 ml of N-methylpyrrolidone and add it dropwise evenly into the four-necked flask over 1 to 2 hours, followed by further reacting for 12 to 16 hours;then, 10 ml of m-xylene is added, the temperature is increased to 160 to 170 °C, reflux is maintained under the action of a water separator for 5-8 hours, the reaction solution, after cooling, is discharged into ethanol, filtered, washed with deionized water and dried under vacuum at 60 °C to obtain a white, amino-terminated, hyperbranched polyimide polymer.;

[0035] In the present invention, the preparation method of the sulfo-terminated hyperbranched sulfonated polyaryl ether is as follows: Add 4.1 mmol of sulfonated 4,4'-difluorobenzophenone, 2 mmol of bisphenol A, 8 mmol of potassium carbonate, and 15 ml of N,N-dimethylacetamide (DMAc) into a container equipped with a reflux device and a water separator to prepare a reaction solution; first, the reaction solution is first refluxed at a constant temperature of 140°C for 10 hours; then, the reaction solution is subjected to a constant temperature reaction at 170°C for 10 hours; then, 1.2 mmol of 1,3,5-trihydroxybenzene is added to the reaction solution, which is then subjected to a constant temperature reaction at 170°C for 5 hours.After cooling to room temperature, the product solution in the container was added dropwise into 150 ml of hydrochloric acid solution with a concentration of 1 mol / L to conduct a precipitation reaction, obtaining a precipitate after filtration. The precipitate was dried in a vacuum oven at 100 °C for 18 hours to produce a sulfo-terminated hyperbranched sulfonated polyaryl ether. The prepared sulfo-terminated hyperbranched sulfonated polyaryl ether had a branching degree of 60%.

[0036] The present invention will be further described below in conjunction with specific embodiments. However, the scope of the present invention is not limited thereto: First embodiment

[0037] A method for producing a separator for lithium batteries, comprising the following steps: Step S101 “Preparation of a copolymer”: Adding N-(4-cyano-3-trifluoromethylphenyl)methacrylamide, 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, allyltriphenylphosphine bromide, 7-fluoro-5-oxo-8-(4-(2-propenyl)-1-piperazinyl)-5H-thiazolo[3,2-a]quinoline-4-carboxylic acid (CAS: 84339-01-5) and an initiator to a high-boiling solvent, which is then stirred and reacted in an inert gas atmosphere at 65°C for 4 hours and then subjected to precipitation in a lithium hydroxide solution with a mass fraction of 10 wt%, washing the precipitated polymer three times with ethanol and finally the ethanol is removed by rotary evaporation to obtain a copolymer; Step S102 "Forming a separator": uniformly mixing the copolymer prepared by step S101 with an amino-terminated hyperbranched polyimide polymer, a sulfo-terminated hyperbranched sulfonated polyaryl ether, a nano-boron fiber, a nano-calcium carbonate, and an adhesion promoter into a mixture, which is then ground and sieved through a 200 mesh per inch screen, and then subjected to melt extrusion and heat setting to finally obtain a separator; Step S103 “Pore Preparation”: Soaking the separator prepared by step S102 in a hydrochloric acid solution having a mass fraction of 8 wt% for 18 hours, then rinsing the separator with water until the corresponding eluent is neutral, so that a separator for lithium batteries is obtained.

[0038] In step S101, the mass ratio of the N-(4-cyano-3-trifluoromethylphenyl)methacrylamide, the 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, allyltriphenylphosphine bromide, the 7-fluoro-5-oxo-8-(4-(2-propenyl)-1-piperazinyl)-5H-thiazolo[3,2-a]quinoline-4-carboxylic acid (CAS: 84339-01-5), the initiator, and the high-boiling solvent is 3:1:0.8:0.1:0.06:25; wherein the initiator is azobisisobutyronitrile; wherein the high-boiling solvent is dimethyl sulfoxide; and wherein the inert gas is nitrogen.

[0039] In step S102, the mass ratio of the copolymer, the amino-terminated hyperbranched polyimide polymer, the sulfo-terminated hyperbranched sulfonated polyaryl ether, the nano-boron fiber, the nano-calcium carbonate, and the coupling agent is 40:10:15:5:1:3; wherein the amino-terminated hyperbranched polyimide polymer is produced by a method according to a third embodiment of Chinese Patent Application Publication CN102267940B; and wherein the sulfo-terminated hyperbranched sulfonated polyaryl ether is produced by a method according to a first embodiment of Chinese Patent Application Publication CN109546192A.

[0040] The nano-boron fiber has an average diameter of 300 nm and an aspect ratio of 16:1; the nano-calcium carbonate has a particle size of 300 nm; the coupling agent is silane coupling agent KH550; the melt extrusion temperature is 340 °C, the heat-setting temperature is 160 °C, and the heat-setting time is 40 minutes. In step S103, the mass ratio of the separator to the hydrochloric acid solution is 1:25. Second embodiment

[0041] A separator for lithium batteries and a method for producing the same are substantially the same as in the first embodiment, with the following differences: that in step S101, the mass ratio of the N-(4-cyano-3-trifluoromethylphenyl)methacrylamide, the 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, allyltriphenylphosphine bromide, the 7-fluoro-5-oxo-8-(4-(2-propenyl)-1-piperazinyl)-5H-thiazolo[3,2-a]quinoline-4-carboxylic acid (CAS: 84339-01-5), the initiator and the high-boiling solvent is 3.5:1:0.9:0.15:0.065:27; and that in step S102, the mass ratio of the copolymer, the amino-terminated hyperbranched polyimide polymer, the sulfo-terminated hyperbranched sulfonated polyaryl ether, the nano-boron fiber, the nano-calcium carbonate, and the coupling agent is 45:12:17:6:1.2:3.5. Third embodiment

[0042] A separator for lithium batteries and a method for producing the same are substantially the same as in the first embodiment, with the following differences: that in step S101, the mass ratio of the N-(4-cyano-3-trifluoromethylphenyl)methacrylamide, the 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, allyltriphenylphosphine bromide, the 7-fluoro-5-oxo-8-(4-(2-propenyl)-1-piperazinyl)-5H-thiazolo[3,2-a]quinoline-4-carboxylic acid (CAS: 84339-01-5), the initiator and the high-boiling solvent is 4:1:1:0.2:0.07:30; and that in step S102, the mass ratio of the copolymer, the amino-terminated hyperbranched polyimide polymer, the sulfo-terminated hyperbranched sulfonated polyaryl ether, the nano-boron fiber, the nano-calcium carbonate, and the coupling agent is 50:13:18:6.5:1.5:4. Fourth embodiment

[0043] A separator for lithium batteries and a method for producing the same are substantially the same as in the first embodiment, with the following differences: that in step S101, the mass ratio of the N-(4-cyano-3-trifluoromethylphenyl)methacrylamide, the 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, allyltriphenylphosphine bromide, the 7-fluoro-5-oxo-8-(4-(2-propenyl)-1-piperazinyl)-5H-thiazolo[3,2-a]quinoline-4-carboxylic acid (CAS: 84339-01-5), the initiator and the high-boiling solvent is 4.5:1:1.1:0.25:0.075:33; and that in step S102, the mass ratio of the copolymer, the amino-terminated hyperbranched polyimide polymer, the sulfo-terminated hyperbranched sulfonated polyaryl ether, the nano-boron fiber, the nano-calcium carbonate, and the coupling agent is 58:14:19:7.5:1.8:4.8. Fifth embodiment

[0044] A separator for lithium batteries and a method for producing the same are substantially the same as in the first embodiment, with the following differences: that in step S101, the mass ratio of the N-(4-cyano-3-trifluoromethylphenyl)methacrylamide, the 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, allyltriphenylphosphine bromide, the 7-fluoro-5-oxo-8-(4-(2-propenyl)-1-piperazinyl)-5H-thiazolo[3,2-a]quinoline-4-carboxylic acid (CAS: 84339-01-5), the initiator and the high-boiling solvent is 5:1:1.2:0.3:0.08:35; and that in step S102, the mass ratio of the copolymer, the amino-terminated hyperbranched polyimide polymer, the sulfo-terminated hyperbranched sulfonated polyaryl ether, the nano-boron fiber, the nano-calcium carbonate, and the coupling agent is 60:15:20:8:2:5. First comparison example

[0045] A separator for lithium batteries and a method for producing the same are substantially the same as in the first embodiment, except that no 7-fluoro-5-oxo-8-(4-(2-propenyl)-1-piperazinyl)-5H-thiazolo[3,2-a]quinoline-4-carboxylic acid is added. Second comparison example

[0046] A separator for lithium batteries and a method for producing the same are substantially the same as in the first embodiment, except that no amino-terminated hyperbranched polyimide polymer is added.

[0047] To further illustrate the advantageous technical effects of the lithium battery separators described in each embodiment, the thickness of the lithium battery separators produced in each example was controlled to 15 µm, and corresponding performance tests were conducted. For the test method, refer to the current corresponding national standard in China. The test results are shown in Table 1. The temperature resistance is expressed by the shrinkage rate. A square separator is placed in an oven at 155 °C for 2 hours, and then the shrinkage ratio of the separator is measured in TD (in the transverse direction).Regarding puncture resistance, a needle with a spherical surface (with a radius of curvature R = 0.5 mm) at one end and a diameter of 1.0 mm pierces the manufactured lithium battery separator at a speed of 2.0 mm / s. The maximum force upon piercing the separator is recorded as the puncture resistance, with the unit gF (gram force). Ionic conductivity is measured on an electrochemical workstation (Zahner IM6 EX) using a two-electrode alternating current impedance method, with the test frequency being 1 Hz to 1 MHz. Table 1 Test object Unit First implementation example Second embodiment Third embodiment Fourth embodiment Fifth embodiment First comparison example Second comparison example Temperature resistance % <0,5 <0,3 <0,2 <0,2 <0,1 0,8 1,3 Puncture resistance gF 615 618 623 630 634 599 587 Ionic conductivity mS·c m -1 4,52 4,60 4,73 4,78 4,86 4,23 4,50

[0048] From the above table, it can be seen that the separator for lithium batteries produced in the embodiments of the present invention has better mechanical properties, better temperature resistance and higher ionic conductivity than the separator produced in the comparative examples, which results from the interaction of various raw materials.

[0049] Only the preferred embodiments of the present invention are presented above. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications are also intended to fall within the scope of the present invention. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] CN 202211481549.8

[0001] CN 102367172B

[0006] CN 102267940B [0014, 0027, 0039] CN 109546192A [0015, 0028, 0039]

Claims

[1] Method for producing a separator for lithium batteries, characterized by that it includes the following steps: Step S101 “Preparation of a copolymer”: Adding N-(4-cyano-3-trifluoromethylphenyl)methacrylamide, 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, allyltriphenylphosphine bromide, 7-fluoro-5-oxo-8-(4-(2-propenyl)-1-piperazinyl)-5H-thiazolo[3,2-a]quinoline-4-carboxylic acid and an initiator to a solvent, which is then stirred and reacted in an inert gas atmosphere for 4 to 6 hours at 65 to 75°C and then subjected to precipitation in a lithium hydroxide solution with a mass fraction of 10 to 20 wt%, wherein the precipitated polymer is washed three to six times with ethanol and finally the ethanol is removed by rotary evaporation to obtain a copolymer; Step S102 "Forming a separator": uniformly mixing the copolymer prepared in step S101 with an amino-terminated hyperbranched polyimide polymer, a sulfo-terminated hyperbranched sulfonated polyaryl ether, a nano-boron fiber, a nano-calcium carbonate, and an adhesion promoter into a mixture, which is then ground and sieved through a sieve with 200 to 400 meshes per inch, and then subjected to melt extrusion and heat setting to finally obtain a separator; Step S103 “Pore Preparation”: Soaking the separator prepared in step S102 in a hydrochloric acid solution having a mass fraction of 8 to 13 wt% for 18 to 32 hours, then rinsing the separator with water until the corresponding eluent is neutral, so that a separator for lithium batteries is obtained. [2] A method of manufacturing according to claim 1, characterized bythat in step S101, the mass ratio of the N-(4-cyano-3-trifluoromethylphenyl)methacrylamide, the 1,3-bis(oxiranylmethyl)-5-(2-propenyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, allyltriphenylphosphine bromide, the 7-fluoro-5-oxo-8-(4-(2-propenyl)-1-piperazinyl)-5H-thiazolo[3,2-a]quinoline-4-carboxylic acid, the initiator and the high-boiling solvent is (3 to 5):1:(0.8 to 1.2):(0.1 to 0.3):(0.06 to 0.08):(25 to 35). [3] A method of manufacturing according to claim 1 or 2, characterized by that the initiator is at least one of azobisisobutyronitrile and azobisisoheptanonitrile. [4] A method of manufacturing according to claim 1 or 2, characterized by that the high-boiling solvent is at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone; wherein the inert gas is one of nitrogen, helium, neon and argon. [5] A method of manufacturing according to claim 1, characterized bythat in step S102, the mass ratio of the copolymer, the amino-terminated hyperbranched polyimide polymer, the sulfo-terminated hyperbranched sulfonated polyaryl ether, the nano-boron fiber, the nano-calcium carbonate and the coupling agent is (40 to 60): (10 to 15): (15 to 20): (5 to 8): (1 to 2): (3 to 5). [6] A method of manufacturing according to claim 1 or 5, characterized by that the amino-terminated hyperbranched polyimide polymer is produced by a process according to a third embodiment of Chinese Patent Application No. CN102267940B; wherein the sulfo-terminated hyperbranched sulfonated polyaryl ether is produced by a process according to a first embodiment of Chinese Patent Application No. CN109546192A. [7] A method of manufacturing according to claim 1 or 5, characterized bythat the nano-boron fiber has an average diameter of 300 to 500 nm and an aspect ratio of (16 to 24):1; wherein the nano-calcium carbonate has a particle size of 300 to 600 nm. [8] A method of manufacturing according to claim 1 or 5, characterized by that the coupling agent is at least one of Silane Coupling Agent KH550, Silane Coupling Agent KH560 and Silane Coupling Agent KH570. [9] A method of manufacturing according to claim 1, characterized by that in step S102, the melt extrusion temperature is 340 to 400°C, the heat setting temperature is 160 to 230°C and the heat setting time is 40 to 50 minutes; wherein in step S103 the mass ratio of the separator to the hydrochloric acid solution is 1:(25 to 35). [10] A separator for lithium batteries produced by the manufacturing method according to any one of claims 1 to 9. [11] Separator for lithium batteries according to claim 10 characterized by that the separator for lithium batteries has a temperature resistance of less than 0.5%, a puncture resistance of more than 615 gF and an ionic conductivity of more than 4.52 mS·cm -1 .