Method for manufacturing a separation membrane, a separation membrane manufactured by the method, and an electrochemical element containing the separation membrane.

Abstract

The present invention relates to a method for producing a separation membrane, a separation membrane produced by the method, and an electrochemical device including the separation membrane. The method for producing a separation membrane according to an embodiment of the present invention includes the steps of (S1) preparing a slurry including inorganic particles, a binder polymer, and a solvent, (S2) dispersing the inorganic particles in the slurry, the dispersion being performed using two types of dispersing devices, a contact dispersing machine and a non-contact dispersing machine, the contact dispersing machine including beads having an average particle size of 200 times or more the average particle size (D50) of the inorganic particles, and (S3) applying the slurry to at least one surface of a polymeric porous support and drying it. The present invention provides a method for producing a separation membrane that uniformly disperses inorganic particles in a slurry, and the separation membrane produced by this method has excellent physical properties due to less aggregation of inorganic particles and less surface protrusion defects in appearance.

Description

[Technical Field]

[0001] The present invention relates to a separation membrane usable in electrochemical elements such as lithium secondary batteries, a method for manufacturing the separation membrane, and an electrochemical element containing the separation membrane.

[0002] This application claims priority based on Korean Patent Application No. 10-2022-0019173, filed on 14 February 2022, and all contents disclosed in the specification and drawings of said application are incorporated into this application. [Background technology]

[0003] Recently, interest in energy storage technologies has been growing. With applications expanding to mobile phones, camcorders, laptops, and even electric vehicles, efforts to research and develop electrochemical devices are becoming increasingly concrete. In this regard, electrochemical devices are a highly regarded field, with particular interest focused on rechargeable secondary batteries and high-energy-density lithium-ion batteries. Furthermore, ensuring safety is a key consideration in the development of such secondary batteries.

[0004] In lithium-ion secondary batteries currently in production, a porous polymer support made of polyolefin polymer resin is used as the separation membrane substrate to prevent short circuits between the positive and negative electrodes. However, this porous polymer support has the problem of low heat resistance as it shrinks or melts at high temperatures. Therefore, if the battery becomes hot due to internal or external stimuli, there is a high possibility that the positive and negative electrodes will come into contact and short-circuit due to the shrinkage or melting of the separation membrane, which can cause a rapid release of electrical energy and potentially lead to the battery exploding or catching fire.

[0005] Therefore, to solve these problems, a method is widely used in which an inorganic composite void layer, in which inorganic particles and a binder polymer are mixed, is formed on at least one surface of a porous polymer support in order to improve its heat resistance.

[0006] In the process of manufacturing a slurry for forming an inorganic composite void layer, such a separation membrane causes inorganic particles and binder particles to aggregate and form composite particles. Further, problems such as the aggregation of inorganic particles in the slurry, a decrease in air permeability, and an increase in resistance value occur. In an attempt to solve this problem, in the conventional separation membrane manufacturing process, a milling step is performed to crush, mix, and disperse the inorganic particles in the slurry for forming an inorganic composite void layer. However, it is difficult to ensure the dispersibility of inorganic particles in the conventional milling step.

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide a method for manufacturing a separation membrane capable of uniformly dispersing inorganic particles in a slurry for forming an inorganic composite void layer.

[0008] Another object of the present invention is to provide a separation membrane having excellent physical properties and an electrochemical device including the separation membrane.

[0009] Other objects and advantages of the present invention can be easily understood to be achievable by the means or methods described in the claims and combinations thereof.

Means for Solving the Problems

[0010] The present inventors have found that the above-described problems can be solved through the following method for manufacturing a separation membrane, the separation membrane manufactured by the method, and an electrochemical device including the separation membrane.

[0011] The first embodiment is as follows. (S1) Preparing a slurry containing inorganic particles, a binder polymer, and a solvent; (S2) Dispersing the inorganic particles in the slurry, wherein the dispersion is performed using both a contact-type disperser and a non-contact-type disperser, and the contact-type disperser includes beads having an average particle size of 200 times or more the average particle size (D50) of the inorganic particles. The present invention relates to a method for producing a separation membrane, comprising the steps of (S3) applying the slurry to at least one surface of a porous polymer support and drying it.

[0012] The second embodiment is, in the first embodiment, The present invention relates to a method for manufacturing a separation membrane, wherein the contact-type disperser contains beads having an average particle size 2000 to 4000 times the average particle size (D50) of the inorganic particles.

[0013] The third embodiment is, in the first embodiment or the second embodiment, The present invention relates to a method for manufacturing a separation membrane, wherein the dispersion is first performed using a contact-type disperser, and then further dispersed using a non-contact disperser.

[0014] The fourth embodiment is, in the third embodiment, The present invention relates to a method for producing a separation membrane, wherein, after dispersion using the aforementioned contact-type disperser, the particle size distribution (PSD) of inorganic particles in the slurry is such that the proportion of inorganic particles having a particle size 10 times or more than the average particle size (D50) of the inorganic particles is 5% or less.

[0015] The fifth embodiment is one of the first to fourth embodiments, The present invention relates to a method for manufacturing a separation membrane, wherein the contact-type disperser employs a bead mill, ball mill, spike mill, basket mill, attrition mill, or two or more of these dispersion methods.

[0016] The sixth embodiment is one of the first to fifth embodiments, This invention relates to a method for manufacturing a separation membrane, wherein the non-contact disperser is a high-pressure homogenizer.

[0017] The seventh embodiment is one of the six embodiments, This invention relates to a method for manufacturing a separation membrane, wherein dispersion using the aforementioned non-contact disperser is performed under pressure conditions of 5 MPa to 200 MPa.

[0018] The eighth embodiment is one of the seventh embodiments, The present invention relates to a method for manufacturing a separation membrane in which the average particle size (D50) of the beads is 0.5 mm or larger.

[0019] The ninth embodiment is one of the eight embodiments, The present invention relates to a method for producing a separation membrane, wherein the beads are zirconia beads, alumina beads, yttria-stabilized zirconia (YSZ) beads, titania beads, or two or more of these.

[0020] The 10th embodiment is one of the 1st to 9th embodiments, This invention relates to a method for producing a separation membrane in which the average particle size of the inorganic particles is 0.01 μm to 1.0 μm.

[0021] The 11th embodiment relates to a separation membrane manufactured by the method of any one of the 1st to 10th embodiments.

[0022] The twelfth embodiment relates to an electrochemical element comprising a positive electrode, a negative electrode, and a separation membrane of the eleventh embodiment interposed between the positive electrode and the negative electrode.

[0023] The 13th embodiment is described in the 12th embodiment, This invention relates to an electrochemical element in which the aforementioned electrochemical element is a lithium secondary battery. [Effects of the Invention]

[0024] According to one embodiment of the present invention, a contact dispersion method and a non-contact dispersion method are utilized as methods for dispersing inorganic particles in a slurry. This makes it possible to suppress the generation of secondary particles, remove coarse inorganic particles, disperse fine inorganic particles, and provide a method for manufacturing a separation membrane with improved dispersibility of inorganic particles.

[0025] Furthermore, according to one embodiment of the present invention, it is possible to provide a separation membrane with reduced surface protrusion defects and excellent physical properties, and an electrochemical element including the separation membrane.

[0026] The drawings accompanying this specification illustrate preferred embodiments of the present invention and serve to further illustrate the technical idea of ​​the invention along with its content; therefore, the present invention should not be construed as being limited solely to what is depicted in the drawings. On the other hand, the shapes, sizes, scales, or ratios of elements in the drawings accompanying this specification may be exaggerated to emphasize a clearer explanation. [Brief explanation of the drawing]

[0027] [Figure 1] This shows the particle size distribution of the slurry dispersed according to Example 1. [Figure 2] This shows the particle size distribution of the slurry dispersed according to Comparative Example 1. [Figure 3] This shows the results of observing the protrusions of the separation membrane produced by Comparative Example 1 using SEM. [Modes for carrying out the invention]

[0028] The present invention will now be described in detail. Terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary and dictionary meanings, but rather in a manner and concept corresponding to the technical idea of ​​the present invention, in accordance with the principle that the inventor himself can appropriately define the concept of a term in order to best describe the invention.

[0029] Throughout this specification, when a part “includes” other components, unless otherwise specified, it means that it may include other components rather than excluding them.

[0030] Throughout this specification, the phrase "A and / or B" means "A, B, or both."

[0031] The separation membrane is manufactured by applying and drying an inorganic composite void layer-forming slurry to a polymer porous support to form an inorganic composite void layer. If the slurry particles in the inorganic composite void layer-forming slurry are not uniformly dispersed, the inorganic particles in the inorganic composite void layer will aggregate, leading to problems such as increased resistance or decreased air permeability of the separation membrane. Conventionally, to solve this problem, a milling process has been performed as a contact dispersion method in the manufacturing process of the inorganic composite void layer-forming slurry. However, even after the milling process, there is a problem in that the dispersibility of inorganic particles in the inorganic composite void layer-forming slurry decreases. In particular, when performing the milling process, it is necessary to adjust the average particle size of the beads considering the particle size of the fine inorganic particles in order to achieve the desired particle distribution and for the convenience of process control.

[0032] On the other hand, non-contact dispersion methods are not used in the technical field for manufacturing separation membranes. However, the inventors have found that by utilizing a non-contact dispersion method in the manufacturing of separation membranes, a strong shear force can be applied to the fluid phase, thereby uniformly dispersing inorganic particles in the slurry.

[0033] In particular, the inventors have discovered a method for manufacturing a separation membrane that allows for the uniform dispersion of inorganic particles during the manufacturing of the separation membrane by appropriately utilizing contact-type dispersion methods and non-contact-type dispersion methods, thereby suppressing the generation of secondary particles, removing coarse inorganic particles, and dispersing fine inorganic particles.

[0034] A method for manufacturing a separation membrane according to one embodiment of the present invention is: (S1) A step of preparing a slurry containing inorganic particles, a binder polymer, and a solvent, (S2) A step of dispersing inorganic particles in the slurry, The aforementioned dispersion is carried out using both a contact-type disperser and a non-contact disperser. The contact-type disperser includes a step of including beads having an average particle size 200 times or more than the average particle size (D50) of the inorganic particles, (S3) The step of applying the slurry to at least one surface of a polymer porous support and drying it.

[0035] In step (S1), a slurry containing inorganic particles, a binder polymer, and a solvent is prepared.

[0036] In a specific embodiment of the present invention, the slurry may be such that the inorganic particles are dispersed in the solvent and the binder polymer is dissolved in the solvent.

[0037] In a specific embodiment of the present invention, the inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles that can be used in the present invention are not particularly limited as long as oxidation and / or reduction reactions do not occur within the operating voltage range of the electrochemical device to be applied (for example, 0 to 5V with respect to the Li / Li

[0040] , reference). In particular, when using inorganic particles with a high dielectric constant as the inorganic particles, it is possible to contribute to an increase in the dissociation degree of electrolyte salts in the liquid electrolyte, such as lithium salts, and improve the ionic conductivity of the electrolyte solution.

[0038] For the reasons described above, the inorganic particles can be inorganic particles with a dielectric constant of 5 or more, inorganic particles having lithium ion transfer ability, or a mixture thereof.

[0039] The inorganic particles with a dielectric constant of 5 or more are one or more selected from the group consisting of Al2O3, SiO2, ZrO2, AlO(OH), TiO2, BaTiO3, Pb(Zr x Ti 1-x )O3 (PZT, 0 < x < 1), Pb 1-x La x Zr 1-y Ti y O3 (PLZT, 0 < x < 1, 0 < y < 1), (1 - x)Pb(Mg 1 / 3 Nb 2 / 3 )O3 - xPbTiO3 (PMN - PT, 0 < x < 1), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZO3, and SiC, and can be a mixture of one or more thereof.

[0040] The inorganic particles having the lithium ion conduction ability are lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) x O y -based glass (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), lithium germanium thiophosphate (Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), lithium nitride (Li x N y , 0 < x < 4, 0 < y < 2), SiS2-based glass (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4), and P2S5-based glass (Li x P y S z , 0 < x < 3, 0 < y < 3, 0 < z < 7), and may be one or a mixture of two or more selected from the group consisting of.

[0041] Also, the average particle diameter (D50) of the inorganic particles is not particularly limited, but for the formation of a coating layer having a uniform thickness and an appropriate porosity, those having an average particle diameter of 0.01 μm or more and 0.5 μm or more can be used, and those having an average particle diameter of 10 μm or less, 5 μm or less, or 1 μm or less can also be used. The numerical range of the average particle diameter can be any combination of the above upper and lower limits. In the present invention, the average particle diameter (D50) means the particle diameter at the 50% point of the cumulative particle number distribution according to the particle diameter.

[0042] In one specific embodiment of the present invention, the binder polymer may be one that is commonly used in the industry to form an inorganic composite void layer when manufacturing separation membranes. In particular, the glass transition temperature (T) g Polymers with a temperature range of -200 to 200°C can be used, which can improve the mechanical properties such as flexibility and elasticity of the ultimately formed inorganic composite void layer. Such binder polymers effectively act as binders, linking and stably fixing inorganic particles together, thereby contributing to preventing a decrease in the mechanical properties of the separation membrane into which the inorganic composite void layer is introduced.

[0043] Furthermore, while the binder polymer does not necessarily need to possess ion-conducting ability, using a polymer with ion-conducting ability can further improve the performance of the electrochemical element. Therefore, the binder polymer can be one with the highest possible dielectric constant. In fact, the degree of dissociation of salt in the electrolyte depends on the dielectric constant of the electrolyte solvent, so the higher the dielectric constant of the binder polymer, the better the degree of dissociation of salt in the electrolyte can be. Such binder polymers can have dielectric constants in the range of 1.0 to 100 (measurement frequency = 1 kHz), and can be particularly high or low.

[0044] In addition to the functions described above, the binder polymer may exhibit a high degree of swelling of the electrolyte by gelling when impregnated in a liquid electrolyte. As a result, the solubility index of the binder polymer, i.e., the Hildebrand solubility index, is 15-45 MPa. 1 / 2 , 15~25MPa 1 / 2 , or 30-45 MPa 1 / 2 This is within the range. Therefore, hydrophilic polymers with more polar groups can be used than hydrophobic polymers such as polyolefins. The solubility index is 15 MPa. 1 / 2 Less than or 45 MPa 1 / 2 This is because, if the amount exceeds the limit, it will not swell easily with the liquid electrolyte used in normal batteries.

[0045] Non-limiting examples of such binder polymers include, but are not limited to, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichloroethylene, polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, ethylene vinyl acetate copolymer, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethylcellulose, cyanoethyl sucrose, pullulan, and carboxymethylcellulose.

[0046] The weight ratio of the inorganic particles to the binder polymer is, for example, 50:50 to 99:1, more specifically 70:30 to 95:5. When the content ratio of inorganic particles to binder polymer satisfies the above range, the problem of reduced pore size and porosity of the formed inorganic composite void layer due to a high binder polymer content can be prevented, and the problem of weakened peel resistance of the formed inorganic composite void layer due to a low binder polymer content can also be resolved.

[0047] The method for producing a separation membrane according to one embodiment of the present invention may further include, in addition to the inorganic particles and binder polymers described above, other additives such as dispersants as components of the inorganic composite void layer.

[0048] In one specific embodiment of the present invention, the solvent is not particularly limited, as long as it is a liquid capable of dissolving the binder polymer and is commonly used in the industry.

[0049] Non-limiting examples of the solvent include acetone, tetrahydrofuran, methylene chloride, chloroform, trimethyl phosphate, triethyl phosphate, methyl ethyl ketone (MEK), toluene, hexane, cyclohexane, dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), or mixtures of two or more of these, preferably acetone. Non-limiting examples of the solvent also include aqueous solvents such as water, methanol, ethanol, ethylene glycol, diethylene glycol, glycerol, or mixtures of two or more of these.

[0050] Next, in step (S2), two types of dispersion devices, a contact-type disperser and a non-contact-type disperser, are used to disperse the inorganic particles in the slurry. In this invention, by appropriately utilizing the contact-type disperser and the non-contact-type disperser, inorganic particles can be uniformly dispersed in the slurry.

[0051] In one specific embodiment of the present invention, inorganic particles in a slurry can be dispersed first using a contact-type disperser, and then dispersed again using a non-contact homogenizer. After removing coarse inorganic particles with the contact-type disperser, a more uniform particle size can be achieved with the non-contact homogenizer, and sufficient shear force can be applied to the inorganic particles within the non-contact homogenizer, making it easier to disperse fine inorganic particles.

[0052] After dispersion using the aforementioned contact-type disperser, the particle size distribution (PSD) of inorganic particles in the slurry can be observed to show that the proportion of inorganic particles with a particle size 10 times or more than the average particle size (D50) of the inorganic particles may be 5% or less.

[0053] The aforementioned contact-type disperser is a general term for a device that can crush and disperse inorganic particles by physical impact between the beads and the inorganic particles inside a device containing a slurry and beads containing inorganic particles. For example, the aforementioned contact-type disperser may be a bead mill, ball mill, spike mill, basket mill, attrition mill, or one that employs two or more of these dispersion methods.

[0054] For example, the contact-type disperser may be a bead mill disperser that applies the bead mill dispersion method. The term "bead mill disperser" generally refers to a device capable of dispersing inorganic particles while crushing them using the bead mill method. The type of bead mill disperser is not particularly limited as long as it is one that is commonly used in this industry.

[0055] On the other hand, the contact-type disperser of the present invention includes beads having an average particle size of 200 times or more the average particle size (D50) of the inorganic particles. Specifically, the average particle size of the beads may be 200 to 4000 times, or 2000 to 4000 times, the average particle size of the inorganic particles. Furthermore, the average particle size of the beads may be 200 times or more the average particle size of the inorganic particles, and 0.5 mm or more, specifically 0.5 mm to 1.5 mm. By including beads that satisfy the above predetermined average particle size range in the bead mill disperser, a desired particle distribution can be achieved, and sufficient impact force can be applied to the inorganic particles, thereby suppressing the generation of secondary particles. In addition, the dispersed inorganic particles and beads can be easily separated. In particular, when using beads with a particle size smaller than the presented average particle size, process control becomes difficult, and there is a risk that problems will occur in the quality of the separation membrane due to the generation of secondary particles that were not completely crushed due to insufficient impact force.

[0056] The type of beads is not particularly limited, but those capable of colliding with inorganic particles in the slurry and improving the dispersibility of those inorganic particles are preferred. For example, the beads may be zirconia beads, alumina beads, yttria-stabilized zirconia (YSZ) beads, titania beads, or two or more of these.

[0057] In the present invention, the non-contact disperser may be a high-pressure homogenizer.

[0058] The aforementioned high-pressure homogenizer is a device that homogenizes a substance by applying high pressure to a microchannel, thereby applying a strong shear force to the substance passing through it. By homogenizing a slurry with a high-pressure homogenizer, inorganic particles within the slurry can be uniformly dispersed. This offers advantages over contact dispersion methods using beads, particularly in that it allows for the dispersion of fine particles that are difficult to physically impact due to the size limitations of the beads used in contact dispersion machines.

[0059] The dispersion using the high-pressure homogenizer described above can be carried out by applying a high pressure of 5 MPa or more, or a high pressure in the range of 5 MPa to 200 MPa, more preferably in the range of 10 MPa to 50 MPa to the fluid. By performing the dispersion under such conditions, sufficient dispersion force is provided to enable the dispersion of secondary particles, while at the same time ensuring the durability of the device.

[0060] Subsequently, in step (S3), the slurry is applied to and dried on at least one surface of the polymer porous support.

[0061] The method for coating the inorganic composite void layer-forming composition onto the polymer porous support is not particularly limited, but it is preferable to use slot coating or dip coating methods. Slot coating is a method in which the composition supplied through a slot die is applied to the entire surface of the substrate, and the thickness of the coating layer can be adjusted by the flow rate supplied by a metering pump. Dip coating is a method in which the substrate is coated by immersing it in a tank filled with the composition, and the thickness of the coating layer can be adjusted by the concentration of the composition and the speed at which the substrate is withdrawn from the composition tank. For more accurate control of the coating thickness, the composition may be measured after immersion using a Mayer bar or the like.

[0062] By drying the polymer porous support coated with the inorganic composite void layer formation composition using a dryer such as an oven, an inorganic composite void layer is formed on at least one surface of the polymer porous support.

[0063] In the inorganic composite void layer, the inorganic particles are packed together and in contact with each other, and are bound together by the binder polymer. This creates an interstitial volume between the inorganic particles, and this interstitial volume between the inorganic particles becomes an empty space, forming pores.

[0064] In other words, the binder polymer adheres to the inorganic particles in such a way that it maintains their bonded state; for example, the binder polymer connects and fixes the inorganic particles together. Furthermore, the pores in the inorganic composite void layer are pores formed by interstitial volumes between the inorganic particles, and these may be spaces that are substantially limited by the inorganic particles in contact with each other in a packed structure (closed packed or densely packed) of inorganic particles.

[0065] In the electrode assembly according to the present invention, the porous polymer support may specifically be a porous polymer film substrate or a porous polymer nonwoven fabric substrate.

[0066] The porous polymer film substrate may be a porous polymer film made of polyolefin such as polyethylene or polypropylene, and such a polyolefin porous polymer film substrate exhibits a shutdown function at temperatures of, for example, 80°C to 130°C.

[0067] In this case, the polyolefin porous polymer film can be formed from polyethylene such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene, or from polyolefin polymers such as polypropylene, polybutylene, and polypentene, either individually or as a mixture of two or more of these polymers.

[0068] Furthermore, the porous polymer film substrate may be manufactured by forming it into a film using various polymers other than polyolefins, such as polyester. The porous polymer film substrate may also be formed in a structure in which two or more film layers are laminated, and each film layer may be formed from a single polymer such as polyolefin or polyester, or from a polymer obtained by mixing two or more of these polymers.

[0069] Furthermore, the porous polymer film substrate and porous nonwoven fabric substrate can be formed from polymers other than the polyolefin-based polymers mentioned above, such as polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalate, either individually or in mixtures thereof.

[0070] The thickness of the polymer porous support is not particularly limited, but is more specifically 1 μm to 100 μm, and more specifically 5 μm to 50 μm. The pore size and porosity present in the polymer porous support are also not particularly limited, but are preferably 0.01 μm to 50 μm and 10% to 95%, respectively.

[0071] Another embodiment of the present invention is a separation membrane manufactured by a manufacturing method according to one embodiment of the present invention. Because the inorganic particles in the inorganic composite void layer do not aggregate, the pore distribution formed in the interstitial volume between inorganic particles is uniform, resulting in low resistance and preventing internal short circuits caused by undispersed coarse powder.

[0072] An electrochemical element according to yet another embodiment of the present invention includes a positive electrode, a negative electrode, and a separation membrane interposed between the positive electrode and the negative electrode. The separation membrane is a separation membrane manufactured by the separation membrane manufacturing method described above.

[0073] Such electrochemical elements include all elements that perform electrochemical reactions, and specifically include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors such as supercapacitor elements. In particular, lithium secondary batteries, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries, are preferred among the secondary batteries.

[0074] The positive and negative electrodes used with the separation membrane of the present invention are not particularly limited and can be manufactured in a form in which the electrode active material is bonded to an electrode current collector by conventional methods known in the art. Among the electrode active materials, non-limiting examples of the positive electrode active material include conventional positive electrode active materials used in the positive electrodes of conventional electrochemical elements, and it is particularly preferable to use lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or lithium composite oxides that combine these. Non-limiting examples of the negative electrode active material include conventional negative electrode active materials used in the negative electrodes of conventional electrochemical elements, and it is particularly preferable to use lithium adsorbent materials such as lithium metal or lithium alloy, carbon, petroleum coke, activated carbon, graphite, or other carbon compounds. Non-limiting examples of the positive electrode current collector include foil made from aluminum, nickel, or combinations thereof, and non-limiting examples of the negative electrode current collector include foil made from copper, gold, nickel, or copper alloy, or combinations thereof.

[0075] The electrolyte used in the electrochemical element of the present invention is A + B - A salt with a structure like this, + Li + na + , K+ It contains alkali metal cations such as B, or ions consisting of combinations thereof. - PF6 - BF4 - Cl - , Br - , I - ClO4 - AsF6 - CH3CO2 - CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 - Salts containing anions such as these, or ions consisting of combinations thereof, may be dissolved or dissociated in organic solvents consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), gamma-butyrolactone (γ-butyrolactone), or mixtures thereof, but are not limited to these.

[0076] The injection of the electrolyte can be carried out at an appropriate stage in the battery manufacturing process, depending on the manufacturing process of the final product and the required physical properties. That is, it can be injected before battery assembly or at the final stage of battery assembly.

[0077] The present invention will be described in detail below with reference to specific examples. However, the examples of the present invention can be modified into many other forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples of the present invention are provided to give a more complete explanation of the present invention to a person of average knowledge in the industry.

[0078] [Examples] The separation membranes for each example and comparative example were manufactured using the following method.

[0079] <Example 1> 1) At room temperature, Al2O3 inorganic particles (manufactured by Korea Ceramics, ALK-N1, average particle size 280 nm), polyvinylidene fluoride (PVDF) binder polymer, and cyanoethyl pullulan were added to acetone and stirred to prepare a slurry. The weight ratio of the inorganic particles:PVDF:cyanoethyl pullulan:acetone was 23:6:1:70.

[0080] 2) The slurry was put into a bead mill disperser. Zirconia beads with an average particle size of 0.6 mm were used in the bead mill disperser, and the slurry was dispersed at 50°C for 3 hours.

[0081] After dispersion using a bead mill disperser, further dispersion was performed using a high-pressure homogenizer under a pressure of 20 MPa.

[0082] 3) A slurry dispersed on one surface of a polyethylene porous film SW811G (Senior, 11 μm thick, 48% porosity) was applied and then dried to produce a separation membrane.

[0083] <Example 2> A separation membrane was manufactured in the same manner as in Example 1, except that zirconia beads with an average particle size of 1.0 mm were used in the bead mill disperser.

[0084] <Comparative Example 1> A separation membrane was manufactured in the same manner as in Example 1, except that zirconia beads with an average particle size of 0.8 mm were used in the bead mill disperser and a high-pressure homogenizer was not applied.

[0085] <Comparative Example 2> A separation membrane was manufactured in the same manner as in Example 1, except that zirconia beads with an average particle size of 0.1 mm were used in the bead mill disperser.

[0086] <Comparative Example 3> The slurry was prepared in the same manner as in Example 1, except that a high-pressure homogenizer was used alone. However, continuous production was impossible because inorganic particles that could not be dispersed during the manufacturing process clogged the flow path of the high-pressure homogenizer.

[0087] <Experimental Results>

[0088] [Table 1]

[0089] (1) Slurry particle size and particle size exceedance ratio (%) -The particle size distribution of the dispersed slurry was measured, and D50 and D90 were calculated from the particle size distribution graph relative to volume. Figures 1 and 2 show the particle size distribution graphs of the slurries dispersed according to Example 1 and Comparative Example 1.

[0090] D50 represents the particle size that accounts for 50% of the volume from the maximum particle size relative to the total volume of the graph, and D90 represents the particle size that accounts for 90% of the volume from the maximum particle size relative to the total volume of the graph. In other words, when the graph is divided into 10 equal parts based on the cumulative distribution of particle size, these represent the particle sizes corresponding to the 5 / 10 and 9 / 10 positions.

[0091] -The particle size exceeding the standard ratio in Table 1 represents the proportion of inorganic particles in the slurry whose particle size is 10 times or more than the average particle size (D50) of the inorganic particles, based on the particle size distribution (PSD) of the inorganic particles.

[0092] (2) Evaluation method for appearance (surface protrusions) A 1m x 1m separation membrane was collected, and its quality was determined by visually inspecting the area for any protrusions. (Judgment criteria: OK: No protrusions, NG: Protrusions are visible to the naked eye)

Claims

1. (S1) A step of preparing a slurry containing inorganic particles, a binder polymer and a solvent, (S2) A step in which inorganic particles are dispersed in the slurry, The aforementioned dispersion is carried out using both a contact-type disperser and a non-contact disperser. The contact-type disperser includes a step of including beads having an average particle size 200 times or more than the average particle size (D50) of the inorganic particles, A method for producing a separation membrane, comprising the steps of (S3) applying the slurry to at least one surface of a porous polymer support and drying it, The contact-type disperser includes beads having an average particle size 2000 to 4000 times the average particle size (D50) of the inorganic particles. The non-contact disperser is a high-pressure homogenizer, A manufacturing method in which, after dispersion using the contact-type disperser and the non-contact disperser, the proportion of inorganic particles having a particle size 10 times or more than the average particle size (D50) of the inorganic particles in the slurry is 5% or less in the particle size distribution (PSD) of the inorganic particles.

2. The method for manufacturing a separation membrane according to claim 1, wherein the dispersion is first performed using a contact-type disperser, and then dispersed using a non-contact disperser.

3. The method for producing a separation membrane according to claim 1, wherein the contact-type disperser is a bead mill, a ball mill, a spike mill, a basket mill, an attrition mill, or two or more of these dispersion methods.

4. The method for manufacturing a separation membrane according to claim 1, wherein the dispersion using the non-contact disperser is performed under pressure conditions of 5 MPa to 200 MPa.

5. The method for producing a separation membrane according to claim 1, wherein the average particle size (D50) of the beads is 0.5 mm or more.

6. The method for producing a separation membrane according to claim 1, wherein the beads are zirconia beads, alumina beads, yttria-stabilized zirconia (YSZ) beads, titania beads, or two or more of these.

7. The method for producing a separation membrane according to claim 1, wherein the average particle size of the inorganic particles is 0.01 μm to 1.0 μm.

8. A separation membrane manufactured by the manufacturing method described in any one of claims 1 to 7.

9. An electrochemical element comprising a positive electrode, a negative electrode, and a separation membrane according to claim 8 interposed between the positive electrode and the negative electrode.

10. The electrochemical element according to claim 9, wherein the electrochemical element is a lithium secondary battery.

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