Separator for electrochemical device and electrochemical device comprising same

Abstract

The present invention provides a separator for an electrochemical device and an electrochemical device comprising same, wherein lifespan characteristics are improved by obtaining adhesion between the separator and an electrode, a low-resistance electrode adhesive layer is achieved, and electrolyte wettability can be improved. The separator for an electrochemical device according to an embodiment of the present invention comprises: an olefin polymer porous support; an inorganic hybrid porous layer formed on at least one surface of the olefin polymer porous support; and an electrode adhesive layer formed on one surface of the inorganic hybrid porous layer, the one surface of the inorganic hybrid porous layer not being in contact with the olefin polymer porous support, wherein the electrode adhesive layer includes at least one adhesive portion and at least one uncoated portion on which the adhesive portion is not formed, the total coverage of the adhesive portion is 20-60% of the total area of the inorganic hybrid porous layer, and the minor axis length of the adhesive portion is at most twice the thickness of the separator.

Description

Separator for electrochemical devices and electrochemical devices containing the same

[0001] The present invention relates to a separator for an electrochemical device and an electrochemical device including the same.

[0002] This application claims priority to Korean Application No. 10-2023-0175900, filed December 6, 2023, the entire disclosure of which is incorporated herein by reference.

[0003] Interest in energy storage technology has been growing steadily. As its applications expand to include energy storage for mobile phones, camcorders, laptops, and even electric vehicles, research and development efforts on electrochemical devices are becoming increasingly concrete. Among these, the development of secondary batteries, energy storage devices that can be recharged and discharged based on electrochemical principles, is a focus of attention. Recent research and development efforts are focused on novel electrode and battery designs to improve capacity density and specific energy.

[0004] Among them, lithium secondary batteries are rapidly increasing in demand as an energy source due to technological development and increasing demand for mobile devices, and their use as a power source for electric vehicles (EVs) and hybrid electric vehicles (HEVs) has recently become a reality, becoming a major growth driver for the secondary battery market.

[0005] These secondary batteries are structured to have a rechargeable electrode assembly of a positive electrode / separator / negative electrode structure mounted on a battery case, and the positive and negative electrodes are manufactured by applying an electrode active material, etc. to one or both sides of a metal current collector and drying and rolling them.

[0006] Among these, the separator is one of the important elements that determines the lifespan of a secondary battery, and plays a role in electrically insulating the positive and negative electrodes. In order to be used as a separator, it is desirable to have high ion permeability, excellent mechanical strength, and stability against the electrolyte, such as allowing the electrolyte to pass smoothly.

[0007] However, the conventionally used separator has insufficient adhesive strength with the electrode due to its material properties, and thus has problems such as partial lifting or wrinkles occurring at the interface depending on the manufacturing process. To solve this problem, a mixture of binder polymers was coated on a porous substrate to form an adhesive layer. However, in this case, there was a problem that the formation of an additional adhesive layer made it difficult for the electrolyte to pass through, and the adhesive layer itself acted as a resistor, which deteriorated the output and cycle characteristics of the battery.

[0008]

[0009] Accordingly, the problem to be solved by the present invention is to solve the above-mentioned problem, and to provide a separator for an electrochemical device and an electrochemical device including the same, which can improve the lifespan characteristics by securing the adhesive strength between the separator and the electrode, while implementing an electrode adhesive layer with low resistance and improving the electrolyte impregnation property.

[0010]

[0011] The present inventors have discovered that the above problem can be solved through the following electrochemical device separator and electrochemical device including the same.

[0012] According to the first implementation example,

[0013] As a separator for electrochemical devices,

[0014] The above separation membrane comprises an olefin polymer porous support; and an inorganic hybrid porous layer formed on at least one surface of the olefin polymer porous support;

[0015] An electrode adhesive layer formed on one surface of an inorganic hybrid porous layer that is not in contact with the above olefin polymer porous support;

[0016] The electrode adhesive layer includes at least one adhesive portion and at least one non-adhesive portion on which the adhesive portion is not formed,

[0017] The total area (coverage) of the above adhesive portion is 20 to 60% of the total area of ​​the inorganic hybrid porous layer,

[0018] The present invention relates to a separator for an electrochemical device, wherein the short-axis length of the above-mentioned adhesive portion is less than twice the thickness of the above-mentioned separator.

[0019] According to the second embodiment, in the first embodiment,

[0020] The above-mentioned adhesive portion relates to a separator for an electrochemical device, characterized in that it has an irregular island shape.

[0021] According to the third embodiment, in the first embodiment or the second embodiment,

[0022] The present invention relates to a separator for an electrochemical device, characterized in that the adhesive portion in the electrode adhesive layer is irregularly distributed.

[0023] According to the fourth embodiment, in any one of the first to third embodiments,

[0024] The above electrode adhesive layer relates to a separator for an electrochemical device, characterized in that it includes a water-dispersed particle-type binder.

[0025] According to the fifth embodiment, in any one of the first to fourth embodiments,

[0026] The present invention relates to a separator for an electrochemical device, characterized in that the electrode adhesive layer further includes a wetting agent.

[0027] According to the sixth embodiment, in any one of the first to fifth embodiments,

[0028] The present invention relates to a separator for an electrochemical device, characterized in that the electrode adhesive layer does not contain a fluorine-based binder.

[0029] According to the seventh embodiment, in any one of the first to sixth embodiments,

[0030] The above electrode adhesive layer has a loading amount per unit area of ​​0.16 g / m based on the cross-section. 2 0.5 g / m 2 It relates to a separator for an electrochemical device characterized by:

[0031] According to the 8th implementation example,

[0032] In an electrochemical device comprising an anode, a cathode, and a separator interposed between the anode and the cathode,

[0033] The above separator relates to an electrochemical device, wherein the separator is an electrochemical device separator according to any one of the first to seventh embodiments.

[0034] According to the ninth embodiment, in the eighth embodiment,

[0035] The present invention relates to an electrochemical device characterized in that the electrochemical device is a lithium secondary battery.

[0036] According to the implementation example of Re10,

[0037] In a method for manufacturing a separator for an electrochemical device according to any one of the first to seventh embodiments,

[0038] Step of preparing an olefin polymer porous support;

[0039] A step of forming an inorganic mixed porous layer by applying a slurry containing inorganic particles, a first binder polymer, and a solvent on at least one surface of the above olefin polymer porous support and then drying it; and

[0040] A step of forming an electrode adhesive layer by applying a slurry containing a water-dispersed particle binder and an aqueous solvent to one surface of an inorganic mixed porous layer that is not in contact with the above olefin polymer porous support and then drying the same;

[0041] It relates to a method for manufacturing a separator for an electrochemical device including .

[0042]

[0043] The separator according to the present invention exhibits excellent adhesion to the electrode. These characteristics prevent partial lifting or wrinkling at the separator-electrode interface, thereby enhancing safety even under high-temperature conditions.

[0044] In addition, the electrode adhesive layer formed on one surface of the separator does not interfere with ion conduction between the electrode and the inorganic hybrid porous layer, so the resistance increase rate is low and the life characteristics are excellent.

[0045] In addition, the electrode adhesive layer according to the present invention can secure adhesive strength while simultaneously securing electrolyte impregnation properties and resistance characteristics by including a predetermined adhesive portion and a non-adhesive portion. In addition, uniformity in the movement of lithium ions can be secured.

[0046]

[0047] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the contents of the invention described above, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0048] Figure 1 is a surface SEM image of a separation membrane according to Example 1.

[0049] Figure 2 is an image of the surface SEM image of the separation membrane according to Example 1 analyzed using an image analysis tool.

[0050] Figure 3 is a surface SEM image of a separation membrane according to Example 2.

[0051] Figure 4 is a surface SEM image of a separation membrane according to Comparative Example 1.

[0052] Hereinafter, the present invention will be described in detail. Prior to this, the terms and words used in this specification and claims should not be interpreted as limited to their conventional or dictionary meanings. Rather, they should be interpreted with meanings and concepts that conform to the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the term to best explain his or her invention. Accordingly, the configurations described in the embodiments described in this specification are merely the most preferred embodiments of the present invention and do not represent the entire technical spirit of the present invention. Therefore, it should be understood that various equivalents and modified examples may exist as of the time of this application.

[0053]

[0054] Throughout this specification, when it is said that a part “includes” or “contains” a component, this does not mean that other components are excluded, but rather that other components may be included or provided.

[0055] Throughout this specification, the description of “A and / or B” means “A or B or both.”

[0056]

[0057] The inventors of the present invention have developed a separator that secures adhesive strength between a separator and an electrode by providing a predetermined electrode adhesive layer on the outermost layer of the separator, and at the same time, has low resistance and improved electrolyte impregnation properties within a secondary battery.

[0058]

[0059] A separator for an electrochemical device according to one embodiment of the present invention,

[0060] An olefin polymer porous support; and an inorganic hybrid porous layer formed on at least one surface of the olefin polymer porous support;

[0061] An electrode adhesive layer formed on one surface of an inorganic hybrid porous layer that is not in contact with the above olefin polymer porous support;

[0062] The electrode adhesive layer includes at least one adhesive portion and at least one non-adhesive portion on which the adhesive portion is not formed,

[0063] The total area (coverage) of the above adhesive portion is 20 to 60% of the total area of ​​the inorganic hybrid porous layer,

[0064] The shortened length of the above-mentioned adhesive portion is less than twice the thickness of the above-mentioned separator.

[0065]

[0066] electrode adhesive layer

[0067] The above electrode adhesive layer is formed on at least one surface of the inorganic hybrid porous layer that is not in contact with the olefin polymer porous support, and can serve to adhere the separator and the electrode.

[0068] The electrode adhesive layer includes one or more adhesive portions and at least one non-adhesive portion on which the adhesive portion is not formed.

[0069] The above-mentioned bonding portion refers to a portion where slurry for forming an electrode adhesive layer is applied, and the one or more bonding portions or a plurality of bonding portions may be formed spaced apart from each other on at least one surface of the inorganic hybrid porous layer. The non-coated portion refers to a portion where the slurry for forming an electrode adhesive layer is not applied, i.e., a portion where no bonding portion is formed, and refers to a portion where the surface of at least one surface of the inorganic hybrid porous layer is exposed.

[0070] The above adhesive portion may have an irregular island shape. This means that a single adhesive portion has a shape that is not fixed in a certain form, and a plurality of adhesive portions are formed spaced apart from each other, and the single adhesive portion may exhibit an island shape.

[0071] The above adhesive portions may be distributed irregularly, which means that the distance between single adhesive portions having an irregular island shape is not constant.

[0072] For example, referring to Fig. 1, the bold portion of Fig. 1 represents the bonding portion, and the light portion represents the unbonded portion. In Fig. 1, it can be seen that the bonding portion has an irregular island shape and is irregularly distributed.

[0073]

[0074] The total area (coverage) of the above-mentioned adhesive portion is 20 to 60% of the total area of ​​the above-mentioned inorganic hybrid porous layer. When the area satisfies this range, adhesive strength can be secured while simultaneously securing electrolyte impregnation and resistance characteristics.

[0075] The total area of ​​the above-mentioned adhesive portion can be obtained by observing the cross-section of the electrode adhesive layer with a scanning electron microscope (SEM) or an optical microscope, obtaining an image, and then using an image analysis tool. Specifically, after the manufactured separator is laminated in the order of release film / separator / cathode / separator / anode, it is heated at 85°C for 30 seconds and pressurized at 10 kg / cm2. 2 The pressure is applied to compress the membrane. Afterwards, the manufactured membrane is separated from the release film, and the surface of the membrane that was in contact with the release film is observed using an electron microscope. The image obtained in this way can be used to distinguish the adhesive layer domain using machine learning or deep learning methods.

[0076]

[0077] The short-axis length of the above-mentioned bonding portion is less than twice the thickness of the separator. If the short-axis length of the above-mentioned bonding portion exceeds twice the thickness of the separator, the bonded interface may be excessive, resulting in uneven movement of lithium ions, which may cause problems such as poor electrolyte penetration and lithium plating during charging.

[0078] The short axis length of the above-mentioned bonding portion refers to the length obtained by measuring the shortest straight line distance among the straight lines connecting the center to the end of a single bonding portion among the bonding portion domains after recognizing the bonding portion domain using an image analysis tool. The thickness of the separator, which is a reference, refers to the sum of the thicknesses of the olefin polymer porous support, the inorganic hybrid porous layer, and the electrode bonding layer. Specifically, the short axis length of the bonding portion can be obtained by obtaining an image by observing the cross-section of the electrode bonding layer using a scanning electron microscope (SEM) or an optical microscope, and then measuring the short axis length of each single bonding portion in all bonding layer regions observed in the image, and then calculating the average.

[0079] For example, the short-axis length of the adhesive portion may be in the range of 1 to 25 μm, 3 to 20 μm, or 5 to 15 μm.

[0080] According to a specific embodiment of the present invention, the adhesive portion may have an irregular island shape with a short axis length of no more than twice the thickness of the separator. By having such an irregular island shape, when the electrolyte is injected from one edge of the jelly roll, which is an electrode / separator laminate, a path is secured through which the electrolyte can penetrate the interface and reach the opposite edge, while at the same time securing the effect of securing adhesive strength between the electrode and the separator.

[0081]

[0082] The above adhesive layer may include a water-dispersed particle-type binder.

[0083] The above-mentioned water-dispersed particle-type binder may be in a mutually bonded form, and by including the binder, pores and / or passages may be formed within the electrode adhesive layer. Accordingly, the movement of Li ions is easy, so that the resistance increase rate is low and the life characteristics are excellent. In addition, since the binder does not penetrate into the pores of the porous layer, the porosity of the inorganic hybrid porous layer is not affected, and the binder content of the adhesive layer within the separator can be minimized. Specifically, since the binder does not penetrate into the pores of the inorganic hybrid porous layer, the binder is substantially absent from the surface of the olefin polymer porous support, so that even though an adhesive layer is formed, the resistance increase rate is low and the electrolyte impregnation property is excellent.

[0084] It can be confirmed that the binder is not substantially present on the surface of the above olefin polymer porous support by analyzing the surface of the above olefin polymer porous support through an IR spectrum.

[0085] The above-mentioned water-dispersed particle-type binder may include a styrene-butadiene polymer, an acrylic polymer, or two or more thereof.

[0086] The above styrene-butadiene polymer may mean one containing a styrene monomer-derived repeating unit and a butadiene monomer repeating unit.

[0087] The above acrylic polymer may refer to a polymer compound including a polymerization unit derived from a (meth)acrylate monomer, or a polymer compound including a repeating unit of a monomer in which some of the substituents include a (meth)acryloyl group. For example, the acrylic binder resin may include, as a monomer, an acrylic acid alkyl ester and / or a methacrylic acid alkyl ester having an alkyl group of 1 to 8 carbon atoms. The acrylic acid alkyl ester may include, for example, at least one selected from methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butylacrylate, isobutylacrylate, cyclohexylacrylate, and 2-ethylhexylacrylate. In addition, as the methacrylic acid alkyl ester, at least one selected from, for example, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, and 2-ethylhexyl methacrylate may be included. However, it is not particularly limited thereto.

[0088] The above electrode adhesive layer may not contain a fluorine-based binder in response to international per- and polyfluoroalkyl substance (PFAS) regulations.

[0089]

[0090] The above electrode adhesive layer may additionally include a wetting agent capable of swelling the particulate binder.

[0091] The above wetting agent can melt the surface of the aqueous particle-type binder in the electrode adhesive layer, thereby causing the bonding portion of the electrode adhesive layer to exhibit an irregular island shape and have a short-axis length within a predetermined range.

[0092] The above swelling agent may include a linear carbonate compound, a cyclic carbonate compound, an ester compound, or two or more thereof.

[0093] Specific examples of the linear carbonate compounds may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate, ethylpropyl carbonate, and the like.

[0094] Specific examples of the above cyclic carbonate compounds may include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, or halides thereof.

[0095] Specific examples of the above ester compounds may include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, ε-caprolactone, etc., but are not particularly limited thereto.

[0096] Specifically, the swelling agent may be dimethyl carbonate (DMC), ethylene carbonate (EC), or a mixture thereof.

[0097]

[0098] The electrode adhesive layer has a loading amount per unit area of ​​0.16 g / m based on the cross-section. 2 0.5 g / m 2 , 0.20 g / m 2 0.45 g / m 2 It can have a range of . By satisfying the above loading amount within the above range, adhesive strength can be secured while simultaneously securing electrolyte impregnation and resistance characteristics.

[0099]

[0100] Olefin polymer porous support

[0101] The above olefin polymer porous support can be any planar olefin polymer porous support commonly used in secondary batteries, such as a porous polymer film substrate formed of various polymers or a porous non-woven fabric substrate.

[0102] The porous polymer film substrate may be a porous polymer film made of an olefin polymer such as polyethylene or polypropylene, and such an olefin polymer porous polymer film substrate exhibits a shutdown function at a temperature of, for example, 80 to 130°C.

[0103] At this time, the porous polymer film may be formed of an olefin polymer such as polyethylene, polypropylene, polybutylene, polypentene, etc., such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene, or a polymer or a derivative thereof, either alone or in combination of two or more thereof.

[0104] Representative examples of olefin polymer porous polymer films that can be applied as such porous polymer films include, but are not limited to, wet polyethylene series (Asahi-Kasei E-Materials, Toray, SK IE Technology, Shanghai Energy, Senior, Sinoma, Entek), dry polypropylene series (Shenzhen Senior, Cangzhou Mingzhu), and dry polypropylene / polyethylene multilayer structure series (Polypore, Ube).

[0105] In addition, the porous polymer film substrate may be manufactured by forming a film shape using various polymers such as polyester in addition to olefin polymers. In addition, the porous polymer film substrate may be formed in a structure in which two or more film layers are laminated, and each film layer may be formed of a polymer such as the above-mentioned olefin polymer, polyester, etc. alone, or a polymer obtained by mixing two or more types thereof.

[0106] In addition, the porous polymer film substrate and the porous nonwoven fabric substrate may be formed of polymers such as polyethyleneterephthalate, polybutyleneterephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide, polyethylenenaphthalene, etc., either singly or as a mixture thereof, in addition to the above olefin polymers.

[0107] The thickness of this olefin polymer porous support is not particularly limited, but may be 1 ㎛ or more, 3 ㎛ or more, 15 ㎛ or less, or 10 ㎛ or less. When the thickness satisfies this range, the problem of acting as a resistance layer while maintaining mechanical properties can be improved.

[0108] There are no particular limitations on the pore size and porosity of the above olefin polymer porous support, but the porosity may be in the range of 10 to 95%, and the pore size (diameter) may be in the range of 0.1 to 50 ㎛. When the pore size and porosity satisfy these ranges, the problem of acting as a resistance layer is prevented, and mechanical properties can be maintained.

[0109]

[0110] Inorganic hybrid porous layer

[0111] The above-mentioned inorganic hybrid porous layer can be formed on at least one surface of the olefin polymer porous support, and includes a binder polymer and an inorganic filler. The above-mentioned inorganic hybrid porous layer, as a component layer of the separator, functions as an insulating layer that prevents short circuiting between the positive and negative electrodes, and at the same time, can prevent the olefin polymer porous support from direct contact with lithium metal.

[0112] The porosity of the above-mentioned inorganic hybrid porous layer may be in the range of 5 to 95%, but is not limited thereto. The thickness of the above-mentioned inorganic hybrid porous layer may be 1 ㎛ or more, 1.5 ㎛ or more, 15 ㎛ or less, or 10 ㎛ or less. When the thickness satisfies this range, heat resistance can be improved, the occurrence of short circuits can be suppressed, a thin film of the separator can be achieved, and at the same time, excellent insulating properties can be achieved.

[0113] The surface contact angle of the above-mentioned inorganic hybrid porous layer with respect to water may be 30 degrees or less. By having a contact angle within the above range, the coating processability of the electrode adhesive layer can be improved. The surface contact angle with respect to water is a value obtained by measuring the angle between the surface of the porous layer and water at 25°C using a contact angle meter. Specifically, the surface contact angle with respect to water may be a value obtained by measuring the angle between the surface of the above-mentioned inorganic hybrid porous layer and water.

[0114]

[0115] In the above-described inorganic hybrid porous layer, the inorganic fillers are filled and in contact with each other and are bound to each other by the binder polymer, thereby forming an interstitial volume between the inorganic fillers, and the interstitial volume between the inorganic fillers becomes an empty space to form pores. That is, the binder polymer attaches the inorganic fillers to each other so that they can maintain a state in which they are bound to each other, for example, the binder polymer connects and fixes the inorganic fillers. In addition, the pores of the above-described inorganic hybrid porous layer are pores formed by the interstitial volume between the inorganic fillers becoming an empty space, and this is a space defined by the inorganic fillers that are substantially in contact in a closed packed or densely packed structure by the inorganic fillers.

[0116]

[0117] The above inorganic filler has the function of forming micropores by enabling the formation of empty spaces between inorganic fillers and also acts as a kind of spacer that can maintain a physical shape, and since it has the property of not changing physical properties even at high temperatures of generally 200°C or higher, the formed organic / inorganic composite porous film has excellent heat resistance.

[0118] Therefore, in a lithium secondary battery including the above separator, even if the olefin polymer porous support is ruptured inside the battery due to excessive conditions caused by internal or external factors such as high temperature, overcharge, or external impact, it is difficult for the two electrodes to be completely short-circuited due to the inorganic mixed porous layer, and even if a short-circuit occurs, the short-circuited area is prevented from expanding significantly, thereby improving the safety of the battery.

[0119] The above inorganic filler is not particularly limited as long as it is electrochemically stable. That is, the inorganic filler that can be used in the present invention is not particularly limited as long as it does not undergo oxidation and / or reduction reactions within the operating voltage range of the applied battery (e.g., 0 to 5 V based on Li / Li+). Examples of such inorganic fillers include alumina (Al2O3), fumed alumina, aluminum hydroxide (Al(OH)3), magnesium hydroxide (Mg(OH)2), boehmite (AlOOH), barium titanate (BaTiO3), or a mixture of two or more thereof.

[0120] The average particle diameter (D50) of the above-mentioned inorganic filler is preferably in the range of 20 nm to 700 nm for the formation of an inorganic hybrid porous layer of uniform thickness and an appropriate porosity thereof. Specifically, it may be in the range of 100 nm to 500 nm. When the average particle diameter (D50) of the above-mentioned inorganic filler satisfies this range, the dispersibility of the slurry for the inorganic hybrid porous layer is maintained, making it easy to control the properties of the separator, and problems such as excessive increase in the thickness of the separator, resulting in a decrease in mechanical properties, or excessively large pore sizes causing internal short circuits during battery charging and discharging can be prevented. In addition, the packing density can increase, which can contribute to the thermal shrinkage rate, and excellent high heat resistance can be exhibited at the particle size in the above range.

[0121] In the present invention, the average particle diameter (D50) of the inorganic filler can be defined as the particle diameter at 50% of the particle diameter distribution. The average particle diameter (D50) of the inorganic filler in the present invention can be measured by, for example, electron microscopy using a scanning electron microscopy (SEM) or a field emission scanning electron microscopy (FE-SEM), or by using a laser diffraction method. When measuring by the laser diffraction method, more specifically, after the inorganic filler is dispersed in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), and ultrasonic waves of about 28 kHz are irradiated at an output of 60 W, and then the average particle diameter (D50) at 50% of the particle diameter distribution in the measuring device can be calculated.

[0122] Additionally, the inorganic filler may be a primary particle, which is a single particle, or a secondary particle formed as an aggregate of primary particles.

[0123]

[0124] The above binder polymer is not particularly limited as long as it can provide bonding force between inorganic fillers, bonding force between the inorganic mixed porous layer and the olefin polymer porous support, and bonding force between the inorganic mixed porous layer and the electrode. For example, binder resins include polyvinylidene fluoride-co-hexafluoropropylene (PVdF), polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, and cyanoethylflurane. Any one binder polymer selected from the group consisting of (cyanoethylpullulan), cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, or a mixture of two or more thereof, may be used, but is not limited thereto.In addition, heat-resistant polymers having a high Tm (150°C or higher or 180°C or higher) such as polyacetal, polysulfone (PSF), polyethersulfone (PES), polyetherimide (PEI), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyacrylamide (PAAm), polyarylate (PA), polycarbonate, polyamideimide (PAI), polyimide (PI), polyamide, wholly aromatic polyamide (aramid), polyphenylene oxide, polybutylene terephthalate, polyethylene terephthalate, polyether ketone, or a mixture of two or more thereof may be used, but are not limited thereto.

[0125] The content of the above binder polymer may be 0.1 to 10% based on the total weight of the inorganic hybrid porous layer. Specifically, the content of the binder polymer may be 0.1% or more, 1% or more, 3% or more, 10% or less, or 8% or less based on the total weight of the inorganic hybrid porous layer. When the binder polymer is included in the above content range, not only can the heat resistance characteristics be improved, but also the resistance of the separator can be reduced, and there is an advantage in that the energy density of the battery can be increased.

[0126]

[0127] A secondary battery according to the present invention comprises a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes. The electrode applicable to the present invention is not particularly limited, and an electrode active material can be manufactured in a form in which it is bound to an electrode current collector using a conventional method known in the art.

[0128] Non-limiting examples of the positive electrode active material among the above electrode active materials include conventional positive electrode active materials that can be used in the positive electrode of a conventional lithium secondary battery, and in particular, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a lithium composite oxide combining these is preferably used.

[0129] Non-limiting examples of the negative electrode active material include conventional negative electrode active materials that can be used in the negative electrode of a conventional lithium secondary battery, and in particular, lithium metal or lithium alloy, carbon, petroleum coke, activated carbon, graphite, or other carbons, and lithium adsorbents are preferable.

[0130] Non-limiting examples of positive current collectors include foils made of aluminum, nickel, or combinations thereof, and non-limiting examples of negative current collectors include foils made of copper, gold, nickel, or copper alloys, or combinations thereof.

[0131]

[0132] A method for manufacturing a separation membrane according to one embodiment of the present invention,

[0133] Step of preparing an olefin polymer porous support;

[0134] A step of applying a slurry containing an inorganic filler, a first binder polymer, and a solvent on the above olefin polymer porous support and then drying it to form an inorganic hybrid porous layer; and

[0135] A step of forming an electrode adhesive layer by applying a slurry containing a water-dispersed particle binder and an aqueous solvent to one surface of an inorganic mixed porous layer that is not in contact with the above-mentioned olefin polymer porous support and then drying the slurry.

[0136]

[0137] In the method for manufacturing the above-mentioned separation membrane, the description of the olefin polymer porous support, the inorganic mixed porous layer, and the electrode adhesive layer will be based on the description of the separation membrane above.

[0138] Specifically, when forming the electrode adhesive layer, a slurry for forming an electrode adhesive layer is prepared by mixing a water-dispersed particle-type binder and an aqueous solvent, and then this is applied to one surface of the inorganic mixed porous layer that is not in contact with the olefin polymer porous support.

[0139] The method of applying the above slurry is not limited to any method that can be generally used in the field to which the present invention belongs, such as slot die coating, roll coating, bar coating, spray coating, gravure coating, microgravure coating, etc.

[0140] The above aqueous solvent may include at least one selected from water, methanol, ethanol, propyl alcohol, butyl alcohol, butanediol, ethylene glycol, propylene glycol, and tripropylene glycol.

[0141]

[0142] Hereinafter, the present invention will be described in detail using examples. However, the examples according to the present invention may be modified in various ways, 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 more fully explain the present invention to those of average skill in the art.

[0143]

[0144] Example

[0145] [Manufacturing of membranes]

[0146] Example 1

[0147] 1) A polyethylene base film (Toray B09PJ1 thickness: 9 um) was prepared.

[0148] 2) A slurry of alumina Al2O3 (Daehan Ceramics Co., Ltd., ALK-S1): acrylic binder polymer (Toyo Co., Ltd., CSB-400): dispersant CMC (GL Chem, SG-L02) = 96:2:2 (weight ratio) mixed with water as a solvent was applied to both sides at a thickness of 1.5 μm to prepare a ceramic coating separator.

[0149] 3) On one side of the ceramic coating separator, a first water-dispersed particle-type binder (ZEON, BM2570, D50=500 nm) and a second water-dispersed particle-type binder (Hansol Chemical, HES-40, D50=800 nm) were mixed at a ratio of 50:50 (wt%) using water as a solvent to prepare an electrode adhesive layer slurry. At this time, the solid content of the slurry was 2.5 parts by weight based on 100 parts by weight of the slurry. The slurry was applied by a microgravure coating method and dried with hot air in a drying oven controlled to 60°C or lower to form a double-sided electrode adhesive layer. At this time, the loading amount of the electrode adhesive layer was a total of 0.45 g / m on both sides. 2 This was it.

[0150] The surface SEM image of the above-mentioned manufactured separator after the pressing process was as shown in Fig. 1, and the adhesive layer domain obtained through image analysis and machine learning was as shown in Fig. 2.

[0151]

[0152] [Manufacturing of secondary batteries]

[0153] LiCoO2 97.5 wt%, multi-walled carbon nanotubes (MWCNT, LG Chem) 1.0 wt% as a conductive material, and polyvinylidene fluoride (PVdF, Kureha, 9700) 1.5 wt% were mixed and added to an N-methyl-2-pyrrolidone solvent, and stirred for 30 minutes using a mechanical stirrer to prepare a positive electrode active material slurry. The slurry was applied to a thickness of about 80 μm on a 20 μm thick aluminum current collector using a doctor blade, dried in a hot air dryer at 100°C for 0.5 hour, and then dried again under vacuum at 120°C for 4 hours, and rolled to a porosity of 21.5% to prepare a positive electrode.

[0154] A slurry of a negative electrode active material was prepared by mixing 96.5 wt% of artificial graphite particles (LC1, Shanshan) with an average particle size of 16 μm, 2.3 wt% of styrene-butadiene rubber (SBR) binder (ZEON), and 1.2 wt% of carboxymethyl cellulose (CMC, Daicel, 2200) and adding them to distilled water and stirring them for 60 minutes using a mechanical stirrer. The slurry was applied to a thickness of about 80 μm on an 8 μm thick copper current collector using a doctor blade, dried in a hot air dryer at 100°C for 0.5 hour, and then dried again under vacuum at 120°C for 4 hours, and roll pressing to a porosity of 24.2% to prepare a negative electrode.

[0155]

[0156] An electrode assembly was manufactured by interposing a separator between the positive and negative electrodes manufactured above, and then embedded in an electrode case, and an organic electrolyte solution in which 1M LiPF6 was dissolved in a 3 / 7 (volume ratio) mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) was injected to manufacture a secondary battery.

[0157]

[0158] Example 2

[0159] A separator was manufactured in the same manner as in Example 1, except that an electrode adhesive layer slurry was manufactured using only a water-dispersed particle binder (ZEON, BM2570, D50=500 nm) in water as a solvent on one side of the ceramic coating separator prepared in 2) of the above Example 1. At this time, the loading amount of the electrode adhesive layer was 0.5 g / m in total on both sides. 2 This was the surface SEM image of the above-mentioned manufactured membrane after the pressing process, as shown in Fig. 3.

[0160] A secondary battery was manufactured in the same manner as in Example 1, except that the separator manufactured in Example 2 was used.

[0161]

[0162] Example 3

[0163] A separator was manufactured in the same manner as in Example 1, except that an electrode adhesive layer slurry was manufactured using only a water-dispersed particle binder (ZEON, BM2510, D50=500 nm) in water as a solvent on one side of the ceramic coating separator prepared in 2) of the above Example 1. At this time, the loading amount of the electrode adhesive layer was 0.5 g / m2 for both sides. 2 This was it.

[0164] A secondary battery was manufactured in the same manner as in Example 1, except that the separator manufactured in Example 3 was used.

[0165]

[0166] Comparative Example 1

[0167] The total loading amount of the electrode adhesive layer on both sides is 0.31 g / m 2 And, except that the solid content of the slurry was 2.0 parts by weight based on 100 parts by weight of the slurry, the separator was manufactured in the same manner as in Example 1. At this time, the total area of ​​the bonding portion of the electrode adhesive layer was 19.3% of the total area of ​​the inorganic hybrid porous layer. The surface SEM image of the manufactured separator after the pressing process was as shown in Fig. 4.

[0168] A secondary battery was manufactured in the same manner as in Example 1, except that the separator manufactured in Comparative Example 1 was used.

[0169]

[0170] Comparative Example 2

[0171] The total loading amount of the electrode adhesive layer on both sides is 1.09 g / m 2 And, the solid content of the slurry was 3.5 parts by weight based on 100 parts by weight of the slurry, and the separator was manufactured in the same manner as in Example 1. At this time, the total area of ​​the bonding portion of the electrode adhesive layer was 100% of the total area of ​​the inorganic mixed porous layer.

[0172] A secondary battery was manufactured in the same manner as in Example 1, except that the separator manufactured in Comparative Example 2 was used.

[0173]

[0174] Comparative Example 3

[0175] The loading amount of the electrode adhesive layer is 0.50 g / m 2 And, the electrode adhesive layer was pattern-coated by etching the pattern in a 45-degree diagonal direction on a microgravure roll, and was manufactured in the same manner as the separator of Example 1. At this time, the pattern of the microgravure roll was alternately arranged with a coated portion of 500 μm and an uncoated portion of 500 μm in length.

[0176] A secondary battery was manufactured in the same manner as in Example 1, except that the separator manufactured in Comparative Example 3 was used.

[0177]

[0178] Evaluation Results

[0179] The properties of the separators and secondary batteries manufactured in Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated, and the results are shown in Table 1 below.

[0180]

[0181] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Membrane thickness (㎛) 10.5 10.6 10.2 10.5 10.3 10.5 Cathode / membrane adhesion (gf / 25mm) 27 33 26 12 4 7 23 Resistance (ohm) 0.8 3 0.8 5 0.8 5 0.8 10.9 9 0.8 8 Ratio of total area of ​​bonding area (Coverage) to total area of ​​inorganic hybrid porous layer (%) 38.1 5 0.2 4 9.5 19.3 10 0 3 0.5 Loading amount per unit area of ​​electrode adhesive layer (based on double-sided, g / m) 2 )0.450.50.50.311.090.5Short-term length of adhesive (㎛)9.212.313.58.5n / a270Capacity retention rate (%, 500 cycles)94.092.292.793.390.188.2

[0182] [Membrane thickness]

[0183] The coated membrane was cut to a 50x50mm size using a die-cutting machine, and its thickness was measured using a MITUTOYO VL-50S-B. Five measurements were taken per sample, and the average value was recorded.

[0184]

[0185] [Adhesion]

[0186] The coated separator (25 mm wide x 13 cm long) and electrode are placed between A4 papers and pressed for 10 seconds at a temperature of 60°C and a pressure of 1000 kg using a heat press device to bond them together. Then, the bonded electrode and separator are peeled off by applying force in a 180° direction using a UTM device to measure the electrode adhesion of the separator.

[0187]

[0188] [resistance]

[0189] The coated separator is cut using a puncher to fit the coin cell structure below, and then assembled according to the structure below. At this time, the electrolyte is prepared by adding 1M lithium salt LiPF6 and 2 wt% VC to a solvent mixed in a volume ratio of EC:EMC = 30:70. After dropping 4-5 drops, it is placed in a coin cell compressor and the cap is completely sealed. After aging at room temperature for 3 hours, the resistance is measured.

[0190]

[0191] [Total area (coverage) of the adhesive part and the short-axis length of the adhesive part among the electrode adhesive layers]

[0192] After the manufactured separator is laminated in the order of release film / separator / cathode / separator / anode, heat of 85℃ and 10kg / cm for 30 seconds 2Apply pressure to compress. Afterwards, the release film and the peeled separator were collected, and the surface of the electrode adhesive layer that was in contact with the release film was observed using a scanning electron microscope (SEM) or an optical microscope to obtain an image, and then machine learning was used to obtain the total area of ​​the adhesive from the adhesive domain in the electrode adhesive layer.

[0193] Additionally, in all bonding areas within the electrode bonding layer, the short-axis length of each single bonding portion was measured and then averaged to obtain the short-axis length of the bonding portion. At this time, the short-axis length was measured as the shortest straight-line distance among the straight lines connecting the center to the end of a single bonding portion.

[0194]

[0195] [Capacity retention rate]

[0196] The secondary batteries manufactured in Examples 1 to 3 and Comparative Examples 1 to 3 were charged at 1C to 4.4 V under constant current / constant voltage (CC / CV) conditions at 25°C, and then charged to 1 / 20 C under constant voltage (CV). After charging was completed, there was a 10-minute rest period, and then discharged again at 1C to 3.0 V under constant current (CC) conditions. This was counted as one cycle, and 500 cycles were repeated. The capacity retention rate was measured as the ratio of the capacity at the 500th cycle to the capacity at the second cycle during the charge / discharge process.

Claims

1. As a separator for electrochemical devices, The above separation membrane comprises an olefin polymer porous support; and an inorganic hybrid porous layer formed on at least one surface of the olefin polymer porous support; An electrode adhesive layer formed on one side of an inorganic hybrid porous layer that is not in contact with the above olefin polymer porous support; The electrode adhesive layer comprises at least one adhesive portion and at least one non-adhesive portion on which the adhesive portion is not formed, The total area (coverage) of the above adhesive portion is 20 to 60% of the total area of ​​the inorganic hybrid porous layer, A separator for an electrochemical device, wherein the short-axis length of the above-mentioned adhesive portion is less than twice the thickness of the above-mentioned separator.

2. In paragraph 1, A separator for an electrochemical device, characterized in that the above-mentioned adhesive portion has an irregular island shape.

3. In paragraph 1, A separator for an electrochemical device, characterized in that the adhesive portion in the electrode adhesive layer is irregularly distributed.

4. In paragraph 1, A separator for an electrochemical device, characterized in that the electrode adhesive layer comprises a water-dispersed particle-type binder.

5. In paragraph 4, A separator for an electrochemical device, characterized in that the electrode adhesive layer further includes a wetting agent.

6. In paragraph 1, A separator for an electrochemical device, characterized in that the electrode adhesive layer does not contain a fluorine-based binder.

7. In paragraph 1, The electrode adhesive layer has a loading amount per unit area of ​​0.16 g / m based on the cross-section. 2 0.5 g / m 2 A separator for an electrochemical device, characterized by:

8. In an electrochemical device including an anode, a cathode, and a separator interposed between the anode and the cathode, An electrochemical device, wherein the above separator is a separator for an electrochemical device according to any one of claims 1 to 7.

9. In paragraph 8, An electrochemical device, characterized in that the electrochemical device is a lithium secondary battery.

10. In a method for manufacturing a separator for an electrochemical device according to any one of clauses 1 to 7, A step for preparing an olefin polymer porous support; A step of applying a slurry containing inorganic particles, a first binder polymer, and a solvent on at least one surface of the above olefin polymer porous support and then drying it to form an inorganic hybrid porous layer; and A step of forming an electrode adhesive layer by applying a slurry containing a water-dispersed particle binder and an aqueous solvent to one surface of an inorganic hybrid porous layer not in contact with the above olefin polymer porous support and then drying the same; A method for manufacturing a separator for an electrochemical device comprising:

Images