Separator and electrochemical element containing the same

Abstract

The present invention provides a separator in which surface adhesion is achieved within a specific temperature range. [Solution] The separator 1 includes a substrate 10, an inorganic particle layer 20 formed on at least one surface of the substrate, and an adhesive layer 30 formed on at least one of the inorganic particle layers. When the adhesive force between the probe and the separator surface is measured at a stage temperature of x°C using an atomic force microscope probe with a spring constant of 40 N / m, an average radius of 8 nm, and a scanning speed of 0.5 Hz, Fx is such that F40 is between 1 nN and 30 nN, satisfying the following equation 1. [Equation 1] F75 / F40≧5

Description

[Technical Field]

[0001] This disclosure relates to separators and electrochemical elements including the same. [Background technology]

[0002] Recently, interest in electrochemical elements and their energy storage technologies used in mobile phones, laptops, electric vehicles, and other devices has surged. In particular, research on separators, one of the key components that influence the characteristics of secondary batteries (which are electrochemical elements), is active. Separators, which are impregnated with electrolyte and function as pathways for ions, have a significant impact on the physical properties of secondary batteries.

[0003] In this regard, a method is known for improving the thermal resistance of separators by mixing inorganic particles with high thermal resistance with a binder and coating them onto a porous substrate. Research and development is underway to ensure adhesion between the separator and the electrode while sufficiently improving internal resistance. [Overview of the project] [Problems that the invention aims to solve]

[0004] One embodiment aims to provide a separator in which the surface adhesion force of the separator, measured using a probe of an atomic force microscope (AFM) with adjustable temperature, is achieved within a specific range.

[0005] Another embodiment aims to provide an electrochemical element including the separator. [Means for solving the problem]

[0006] One embodiment includes a substrate, an inorganic particle layer formed on at least one surface of the substrate, and an adhesive layer formed on at least one of the inorganic particle layers. When the adhesive force between an atomic force microscope probe with a spring constant of 40 N / m, an average radius of 8 nm, and a scanning speed of 0.5 Hz is measured at a stage temperature of x °C, and the probe is denoted as Fx, F40 is 1nN to 30nN. A separator is provided that satisfies the following equation 1. [Formula 1] F75 / F40≧5

[0007] In one embodiment, the adhesive layer may include a particulate polymer binder.

[0008] In one embodiment, the adhesive layer may include an acrylic polymer binder.

[0009] In one embodiment, the particulate polymer binder may have a core-shell structure.

[0010] In one embodiment, the glass transition temperature of the polymer contained in the core of the particulate polymer binder may be 30°C to 70°C, and / or the glass transition temperature of the polymer contained in the shell of the particulate polymer binder may be 70°C to 110°C.

[0011] In one embodiment, the glass transition temperature (Tg, c) of the polymer contained in the core and the glass transition temperature (Tg, s) of the polymer contained in the shell can satisfy the following equation 2. [Formula 2] 50℃≦(Tg, c+Tg, s) / 2≦90℃

[0012] In one embodiment, the adhesive layer may include a copolymer comprising repeating units derived from an acrylic monomer and a copolymer comprising repeating units derived from an acrylic monomer and styrene.

[0013] In one embodiment, the adhesive layer has an average particle size (D 50This may include a particulate polymer binder or a particulate acrylic polymer binder having a wavelength of 400 nm to 800 nm.

[0014] In one embodiment, F75 may be 40nN to 300nN.

[0015] In one embodiment, formula 1 can satisfy F75 / F40≧10.

[0016] In one embodiment, the adhesive layer may include a particulate polymer binder or a particulate acrylic polymer binder containing repeating units derived from a compound represented by the following chemical formula 1. [ka] In the above chemical formula 1, R 1 is hydrogen or C 1-10 It is an alkyl group, R 2 is hydrogen or C 1-20 It is a hydrocarbon group.

[0017] In one embodiment, the inorganic particle layer may include inorganic particles and a polymer binder.

[0018] In one embodiment, the inorganic particle layer has an average particle size (D 50 This may include inorganic particles with a wavelength of 100 nm to 1500 nm.

[0019] In one embodiment, the inorganic particle layer has an average particle size (D 50 This can include first inorganic particles with a wavelength of 100 nm to 500 nm and second inorganic particles with a wavelength of 500 nm to 1500 nm.

[0020] In one embodiment, the inorganic particle layer may contain inorganic particles and a polymer binder, where the weight ratio of the inorganic particles to the polymer binder may be 90:10 to 99:1.

[0021] In one embodiment, the thickness of the inorganic particle layer may be 0.5 μm to 3.0 μm.

[0022] In one embodiment, the thickness of the adhesive layer may be 0.05 μm to 2.0 μm.

[0023] Another embodiment is an electrochemical element comprising a substrate, an inorganic particle layer formed on at least one surface of the substrate, and a separator including an adhesive layer formed on at least one of the inorganic particle layers, When the adhesive force between an atomic force microscope (AFM) probe with a spring constant of 40 N / m, an average radius of 8 nm, and a scanning speed of 0.5 Hz is measured at a stage temperature of x °C, and the probe is denoted as Fx, F40 is 1nN to 30nN. The separator provides an electrochemical element that satisfies the following formula 1. [Formula 1] F75 / F40≧5

[0024] Another embodiment is an electrochemical element comprising a substrate, an inorganic particle layer formed on at least one surface of the substrate, and a separator including an adhesive layer formed on at least one of the inorganic particle layers, When C is the number of cycles at which the internal resistance of the electrochemical element increases by 30% relative to the initial resistance before the start of the charge-discharge cycle, C is 300 or more. Here, the charging and discharging process involves discharging the electrochemical element to 2.5V, then charging it from 2.5V to 4.2V at 0.5C, and finally discharging it at 0.5C, which constitutes one cycle of this process. [Effects of the Invention]

[0025] In one embodiment, the separator includes an adhesive layer on an inorganic particle layer, and the adhesive force of the separator surface, as measured using an atomic force microscope probe, is achieved within a specific range. This ensures adhesion between the separator and the electrode and effectively improves the internal resistance of the battery. [Brief explanation of the drawing]

[0026] [Figure 1] This is a schematic plan view of a secondary battery according to one embodiment. [Figure 2] This is a schematic cross-sectional view of a secondary battery according to one embodiment. [Figure 3] This figure provides a simplified diagram of a cross-section of core-shell type polymer particles contained in the adhesive layer of a separator according to one embodiment. In this specification, the particle size of the core 200 refers to the length of the portion represented by D in Figure 3, and the thickness of the shell 300 refers to the length of the portion represented by T in Figure 3. [Figure 4] A schematic structure of separator 1 according to one embodiment includes a base material 10, an inorganic particle layer 20, and an adhesive layer 30. [Modes for carrying out the invention]

[0027] The embodiments described herein can be modified into various other forms, so the technology of one embodiment is not limited to the embodiments described below. Furthermore, throughout this specification, the terms "comprising, including, containing," "equipping," "containing," or "having" a component mean, unless otherwise specifically stated to the contrary, that it may further include other components rather than excluding other components, and do not exclude any other elements, materials, or processes not listed.

[0028] Numerical ranges as used herein include lower and upper limits, all values ​​within those limits, increments logically derived from the form and width of the defined range, all limited values ​​among them, and all possible combinations of upper and lower limits of numerical ranges limited to different forms. For example, if the composition content is limited to 10% to 80% or 20% to 50%, the numerical ranges of 10% to 50% or 50% to 80% should also be interpreted as being included herein. Unless otherwise specifically defined herein, values ​​outside the defined numerical range that may arise due to experimental error or rounding of values ​​are also included in the defined numerical range.

[0029] Hereafter, unless otherwise defined in this specification, “about” may be considered as a value within 30%, 25%, 20%, 15%, 10%, 5%, 3%, 2%, 1%, or 0.5% of the expressed value.

[0030] In this specification, unless otherwise defined, “polymer” means a relatively high molecular weight molecule whose structure may include multiple repeats of units derived from low molecular weight molecules. In one embodiment, the polymer may be an alternating copolymer, a block copolymer, a random copolymer, a graft copolymer, a gradient copolymer, a branched copolymer, a crosslinked copolymer, or a copolymer containing all of these (e.g., a polymer containing more than one monomer). In other embodiments, the polymer may be a homopolymer (e.g., a polymer containing one monomer).

[0031] As used herein, the term “alkyl group” means a straight or branched radical of a carbon-saturated bond, which may be substituted with any substituent.

[0032] The present disclosure will be described in detail below (with reference to the attached drawings). However, this is illustrative only, and the present disclosure is not limited to the specific embodiments described exemplary.

[0033] One embodiment provides a separator in which the adhesion force between the separator surface and the probe, measured using the probe of an atomic force microscope (AFM) with a temperature controllable stage, is achieved at a specific temperature and within a specific range. Specifically, the separator 1 according to one embodiment includes a substrate 10, an inorganic particle layer 20 formed on at least one surface of the substrate, and an adhesive layer 30 formed on at least one of the inorganic particle layers. When the adhesive force between an atomic force microscope (AFM) probe with a spring constant of 40 N / m, an average radius of 8 nm, and a scanning speed of 0.5 Hz is measured at a stage temperature of x °C, and Fx is denoted as the adhesive force between the probe and the separator surface, F40 is between 1 nN and 30 nN, satisfying the following equation 1.

[0034] [Formula 1] F75 / F40≧5

[0035] In conventional methods of measuring adhesive strength using large-area probes, the measured adhesive strength value may vary depending on the binder concentration. However, one embodiment of the method for measuring the adhesive strength of a separator surface using an AFM probe allows for the measurement of the intrinsic adhesive strength of the binder contained in the adhesive layer by using a small-area probe (radius of approximately 8 nm). Furthermore, the stage temperature can be controlled, allowing for the analysis of changes in adhesive strength due to temperature.

[0036] In one embodiment, the adhesive force is the adhesive force between the surface of the binder contained in the adhesive layer, i.e., the outermost layer, and the probe. Specifically, the adhesive force generated when the probe leaves the surface of the separator can be calculated from the Y axis of the F / D graph, which is shown by tapping the surface of the binder contained in the adhesive layer with the probe.

[0037] A separator including an adhesive layer according to one embodiment is effective in improving battery performance because, as described above, the adhesive force using AFM is achieved, not only in terms of adhesion to the electrodes but also in effectively suppressing the increase in resistance inside the battery. Specifically, a battery including a separator according to one embodiment effectively suppresses the voltage drop of the battery by suppressing the increase in internal resistance, thereby increasing the battery life. Furthermore, by reducing the energy loss of the battery, battery efficiency is increased, and by preventing heat generation due to increased internal resistance, problems such as thermal runaway, electrolyte decomposition, fire, and explosion can be prevented.

[0038] In one embodiment, the adhesive layer may be the surface of the separator, i.e., the outermost layer, but is not necessarily limited thereto.

[0039] In one embodiment, the adhesive layer may include a particulate polymer binder or an acrylic polymer binder or a particulate acrylic polymer binder, specifically, the particulate polymer binder or particulate acrylic polymer binder may have a core-shell structure, which may be present on at least a portion of the surface of the adhesive layer.

[0040] The core-shell polymer binder can be produced by at least one method selected from the group consisting of multi-stage emulsion polymerization, seed polymerization, suspension polymerization, precipitation polymerization, interfacial polymerization, graft polymerization, and microemulsion polymerization.

[0041] In one embodiment, the glass transition temperature (Tg) of the polymer contained in the core of the particulate polymer binder or particulate acrylic polymer binder may be 30°C to 70°C, 35°C to 70°C, 30°C to 65°C, 40°C to 70°C, or 40°C to 65°C. In one embodiment, the glass transition temperature of the polymer contained in the shell of the particulate polymer binder or particulate acrylic polymer binder may be 70°C to 110°C, 70°C to 100°C, 75°C to 100°C, 75°C to 95°C, 80°C to 95°C, or 80°C to 90°C. Although not bound by any particular theory, the polymer contained in the core and / or shell having the glass transition temperature can effectively improve and / or enhance the adhesion between the separator and the electrode during the electrode fusion process.

[0042] In one embodiment, the glass transition temperature (Tg, c) of the polymer contained in the core and the glass transition temperature (Tg, s) of the polymer contained in the shell can satisfy the following equation 2.

[0043] [Formula 2] 50℃≦(Tg, c+Tg, s) / 2≦90℃

[0044] While not bound by any particular theory, the value of (Tg, c + Tg, s) / 2 in Equation 2 can tend to be similar to the electrode fusion temperature of the separator according to one embodiment. The value of (Tg, c + Tg, s) / 2 in Equation 2 and the electrode fusion temperature can satisfy the ranges of 50°C to 90°C, 55°C to 85°C, 50°C to 80°C, 60°C to 90°C, or 60°C to 80°C. When these temperature ranges are satisfied, the adhesion strength between the separator and the electrode can be effectively improved and / or enhanced in the electrode fusion process, and the blocking phenomenon, where separators adhere to each other during winding of the separator, and the phenomenon of separators adhering to each other during storage or transportation before the fusion process can be effectively prevented, and / or long-term storage is possible. Furthermore, in the separator according to one embodiment, the detachment of inorganic particles due to blocking is effectively prevented by preventing the blocking phenomenon, which is effective in preventing a decrease in battery performance due to an increase in internal resistance. Therefore, it is effective in improving battery life characteristics and energy efficiency.

[0045] In one embodiment, the adhesive layer may include an acrylic polymer binder. Specifically, the acrylic polymer binder may include repeating units derived from (meth)acrylic acid and / or (meth)acrylate, and more specifically, repeating units derived from a compound represented by the following chemical formula 1.

[0046] In one embodiment, the adhesive layer may include either a copolymer containing repeating units derived from an acrylic monomer or a copolymer containing repeating units derived from an acrylic monomer and styrene. Specifically, the adhesive layer may include either a copolymer consisting of repeating units derived from an acrylic monomer or a copolymer consisting of repeating units derived from an acrylic monomer and styrene. In one embodiment, the acrylic monomer may independently be (meth)acrylic acid and / or (meth)acrylate, and specifically, it may be a compound represented by the following chemical formula 1.

[0047] In one embodiment, the average particle size (D 50 ) of the particulate polymer binder or the particulate acrylic polymer binder may be 400 nm to 800 nm, 400 nm to 700 nm, 400 nm to 600 nm, 450 nm to 550 nm, or about 500 nm.

[0048] In one embodiment, when the particulate polymer binder or the particulate acrylic polymer binder has a core-shell structure, the average particle size (D 50 , D in FIG. 3) of the core may be 320 nm to 780 nm, 320 nm to 680 nm, 320 nm to 530 nm, 350 nm to 500 nm, 400 nm to 500 nm, or about 450 nm, and the average thickness (T in FIG. 3) of the shell may be 20 nm to 80 nm, 30 nm to 60 nm, 40 nm to 60 nm, or about 50 nm. Without being bound by a particular theory, by having the core and the shell with the average particle size or thickness within the above ranges, an adhesive layer can be uniformly formed on the inorganic particle layer, and the adhesive force between the adhesive layer and the electrode can be improved.

[0049] In one embodiment, the mass ratio of the core to the shell may be 5:5 to 9:1, 6:4 to 8:2, or about 7:3. Without being bound by a particular theory, by satisfying the above range, particles having a uniform average particle size and / or average thickness can be formed, or the separator can be effectively adhered to the electrode at the electrode fusion temperature.

[0050] In one embodiment, F40 may be 1nN to 25nN, 1nN to 20nN, 2nN to 18nN, 1nN to 18nN, or 3nN to 15nN. And / or in one embodiment, F75 may be 40nN to 300nN, 40nN to 250nN, 40nN to 230nN, 50nN to 250nN, 50nN to 230nN, 50nN to 200nN, or 60nN to 200nN. However, F40 and F75 are not necessarily limited to the above ranges, and are not particularly limited as long as their ratio F75 / F40 is 5 or greater.

[0051] In one embodiment, formula 1 can satisfy F75 / F40≧10, F75 / F40≧11, F75 / F40≧12, or F75 / F40≧13. Here, the upper limit of F75 / F40 is not particularly limited, but may be, for example, 50 or less, 40 or less, 30 or less, 25 or less, or 20 or less.

[0052] In one embodiment, the particulate polymer binder or particulate acrylic polymer binder may include repeating units derived from (meth)acrylic acid and / or (meth)acrylate, or copolymers thereof. Alternatively, the particulate polymer binder or particulate acrylic polymer binder may include repeating units derived from the following chemical formula 1.

[0053] [ka]

[0054] In the above chemical formula 1, R 1 is hydrogen or C 1-10 Alkyl alkyl group, C 1-8 Alkyl alkyl group, C 1-6 Alkyl alkyl group, C 1-5 Alkyl alkyl group, C 1-3 It may be an alkyl group, an ethyl group or a methyl group, and / or, R 2 is hydrogen, C 1-20hydrocarbon group, C 1-15 hydrocarbon group, C 1-13 hydrocarbon group, or C 1-10 It may also be a hydrocarbon group.

[0055] The hydrocarbon group includes, for example, a linear or branched alkyl group, or an alkyl group substituted or unsubstituted cycloalkyl group, and the cycloalkyl group is not limited to being a bridged ring, a spiro ring, or a fused ring. Therefore, the R 2 is hydrogen, C 1-20 Alkyl alkyl group, C 1-15 Alkyl alkyl group, C 1-12 Alkyl alkyl group, C 1-10 Alkyl alkyl group, C 1-8 Alkyl alkyl group, C 1-6 Alkyl alkyl group, C 1-5 Alkyl alkyl group, C 1-3 It is an alkyl group, an ethyl group or a methyl group, or C 1-5 Alkyl alkyl group, C 1-3 C is either substituted with one or more alkyl groups, ethyl groups, or methyl groups, or is unsubstituted. 5-20 Cycloalkyl groups, C 5-15 Cycloalkyl groups, C 6-20 Cycloalkyl groups, C 6-15 Cycloalkyl groups, C 5-12 Cycloalkyl groups, C 5-10 Cycloalkyl groups, or C 6-10 A cycloalkyl group may also be used.

[0056] Specifically, the particulate polymer binder or particulate acrylic polymer binder may contain repeating units derived from one or more selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, 1-ethylhexyl acrylate, 2-ethylhexyl acrylate, 3-ethylhexyl acrylate, isobonyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, 1-ethylhexyl methacrylate, 2-ethylhexyl methacrylate, and 3-ethylhexyl methacrylate, or may contain copolymers of one or more compounds selected from the group. Although not bound by any particular theory, acrylic polymer binders can be used in core-shell particles that satisfy the above-mentioned average particle size, thickness, and / or mass ratio, and can be effective in achieving not only electrode adhesion but also preventing an increase in the internal resistance of the battery.

[0057] In one embodiment, the inorganic particle layer may include inorganic particles and a polymer binder.

[0058] In one embodiment, the inorganic particle layer has an average particle size (D 50 It may include inorganic particles whose wavelengths are 100nm-1500nm, 100nm-1200nm, 200nm-1000nm, 200nm-800nm, 200nm-600nm, 300nm-500nm, or 200nm-400nm.

[0059] In one embodiment, the inorganic particle layer has an average particle size (D 50 The average particle size (D) of the first inorganic particles may include first inorganic particles having a size of 100 nm to 500 nm and second inorganic particles having a size of 500 nm to 1500 nm. 50 The average particle size (D) of the second inorganic particle may be 200nm to 400nm, 250nm to 350nm, or approximately 300nm. 50The wavelength may be 500nm to 1200nm, 500nm to 1000nm, 600nm to 1000nm, 600nm to 800nm, or approximately 700nm.

[0060] In one embodiment, when using two inorganic particles having different average particle sizes, the weight ratio is not particularly limited, but for example, the weight ratio of the first inorganic particles and the second inorganic particles can be mixed in a weight ratio of 10:90 to 50:50, 20:80 to 50:50, 20:80 to 40:60, or about 30:70. However, this is just an example, and the inorganic particles do not necessarily have to be mixed in the weight ratios mentioned above. Here, the first inorganic particles and the second inorganic particles may be inorganic particles of the same type, or they may be inorganic particles of different types.

[0061] In one embodiment, the inorganic particles contained in the inorganic particle layer are not particularly limited in type, as long as they are known to be electrochemically stable. For example, they may include one or more of the following: boehmite, CeO2, MgO, CaO, ZnO, Al2O3, TiO2, BaTiO3, HfO2, SrTiO3, SnO2, NiO, ZrO2, Y2O3, and / or SiC.

[0062] In one embodiment, the polymer binder can be appropriately selected by a person of the ordinary skill in the art disclosed herein from known binders to suit the purpose and circumstances. In one embodiment, the polymer binder may be a solution-type aqueous binder and may include, for example, one or more selected from the group consisting of ester polymers, amide polymers, imide polymers, acrylic polymers, acrylamide polymers, vinyl alcohol polymers, acrylonitrile polymers, polyvinyl alcohol polymers, fluorine polymers, and / or vinylpyrrolidone polymers. In one embodiment, the binder may include an acrylic polymer. Alternatively, for example, the binder may include a polymer produced from one or more monomers of any (meth)acrylamide monomer, a hydroxyl group-containing (meth)acrylic monomer, and / or a polyfunctional (meth)acrylamide monomer, and is not limited as long as it is used as a binder for an inorganic particle layer in which inorganic particles formed on the surface of the porous substrate layer of the separator are linked together by the binder to form pores.

[0063] In one embodiment, the acrylamide polymer may contain repeating units represented by the following chemical formula 2.

[0064] [ka]

[0065] In the above chemical formula 2, R 3 is hydrogen, C 1-10 Alkyl alkyl group, C 1-8 Alkyl alkyl group, C 1-5 Alkyl alkyl group, or C 1-3 It is an alkyl group.

[0066] In one embodiment, the polymer binder may further include one or more aqueous polymers selected from the group consisting of, for example, polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polyethylene glycol (PEG), polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP), and copolymers thereof.

[0067] In one embodiment, the binder (or polymer contained in the binder) may have a weight-average molecular weight (Mw) of 10,000 g / mol to 2,000,000 g / mol, 50,000 g / mol to 2,000,000 g / mol, 50,000 g / mol to 1,000,000 g / mol, 50,000 g / mol to 500,000 g / mol, 50,000 g / mol to 300,000 g / mol, 100,000 g / mol to 300,000 g / mol, or approximately 120,000 g / mol. This is merely an example, and can be appropriately selected according to experimental conditions as long as it satisfies the range of surface roughness of the separator according to this application. The weight-average molecular weight can be measured by gel permeation chromatography (GPC).

[0068] In one embodiment, the glass transition temperature of the polymer binder may be, for example, 100°C to 180°C, 110°C to 160°C, 120°C to 150°C, or 130°C to 140°C, but is not necessarily limited thereto.

[0069] In one embodiment, the weight ratio of inorganic particles to polymer binder that can be contained in the inorganic particle layer may be 90:10 to 99:1, 92:8 to 99:1, 95:5 to 99:1, 96:4 to 98:2, or about 97:3.

[0070] In one embodiment, the thickness of the inorganic particle layer may be 0.5 μm to 3.0 μm, 0.5 μm to 2.5 μm, 1.0 μm to 3.0 μm, 1.0 μm to 2.5 μm, 1.0 μm to 2.0 μm, or about 1.5 μm. In one embodiment, the inorganic particle layer can be formed on one or both sides of the porous substrate.

[0071] In one embodiment, the thickness of the adhesive layer may be 0.05 μm to 2.0 μm, 0.1 μm to 2.0 μm, 0.1 μm to 1.5 μm, 0.1 μm to 1.0 μm, 0.2 μm to 0.8 μm, or about 0.5 μm. In one embodiment, the adhesive layer may be formed on any one of the inorganic particle layers, or on both of the two inorganic particle layers formed on both sides of the porous substrate.

[0072] In one embodiment, the substrate may be a porous substrate and is not limited as long as it is commonly used in the art. For example, it may be a woven fabric, a nonwoven fabric, or a porous film. Specifically, the porous substrate may be a polyolefin such as polyethylene or polypropylene, a polyester such as polyethylene terephthalate or polybutylene terephthalate, a polyacetal, a polyamide, a polyimide, a polycarbonate, a polyetheretherketone, a polyaryletherketone, a polyetherimide, a polyamideimide, a polybenzimidazole, a polyethersulfone, a polyphenylene oxide, a cyclic olefin copolymer, a polyphenylene sulfide, a polyethylene naphthalate, a glass fiber, Teflon®, and / or polytetrafluoroethylene, and two or more of these may be used.

[0073] In one embodiment, the thickness of the porous substrate is not particularly limited and may be, for example, 1 μm to 100 μm, 1 μm to 50 μm, 1 μm to 30 μm, 5 μm to 20 μm, 5 μm to 10 μm, or about 9 μm.

[0074] Another embodiment provides a method for manufacturing the separator.

[0075] A method for manufacturing a separator according to one embodiment includes the above-described preparation step, the step of forming an inorganic particle layer on at least one surface of the substrate using an inorganic particle layer forming composition, and the step of forming an adhesive layer on at least one inorganic particle layer using an adhesive layer forming composition.

[0076] In one embodiment, the inorganic particle layer forming composition may be a slurry, and the solid content of the slurry may be, for example, 15% to 40% by weight, 20% to 40% by weight, 20% to 35% by weight, or 20% to 30% by weight.

[0077] In one embodiment, the step of forming the inorganic particle layer and / or adhesive layer may include the step of coating and drying the composition. The coating is not particularly limited, but for example, roll coating, spin coating, dip coating, bar coating, die coating, slit coating, or inkjet printing may be used. The drying can be carried out by drying with hot air, hot air, low humidity air, vacuum drying, or irradiation methods such as far-infrared radiation or electron beams. The drying temperature is not particularly limited and can be adjusted as appropriate depending on the experimental environment and purpose.

[0078] Another embodiment includes a substrate, an inorganic particle layer formed on at least one surface of the substrate, and an adhesive layer formed on at least one of the inorganic particle layers. When the adhesive force between an atomic force microscope (AFM) probe with a spring constant of 40 N / m, an average radius of 8 nm, and a scanning speed of 0.5 Hz is measured at a stage temperature of x °C, and the probe is denoted as Fx, F40 is 1nN to 30nN. An electrochemical element including a separator that satisfies the following formula 1 is provided.

[0079] [Formula 1] F75 / F40≧5

[0080] The same explanation regarding the separator described above can be applied to the aforementioned electrochemical element, and any redundant explanations will be omitted below.

[0081] Another embodiment provides an electrochemical element in which the increase in the internal resistance of the electrochemical element is effectively suppressed. Specifically, one embodiment is an electrochemical element comprising a substrate, an inorganic particle layer formed on at least one surface of the substrate, and a separator including an adhesive layer formed on at least one of the inorganic particle layers, When C is the number of cycles at which the internal resistance of the electrochemical element increases by 30% relative to the initial resistance before the start of the charge-discharge cycle, C is 300 or more. Here, the charging and discharging process involves discharging the electrochemical element to 2.5V, then charging it from 2.5V to 4.2V at 0.5C, and finally discharging it at 0.5C, which constitutes one cycle of this process.

[0082] In one embodiment, C may be 400 or more, 450 or more, 500 or more, 550 or more, or 580 or more, 800 or less, 700 or less, 650 or less, or 600 or less.

[0083] Similarly, the explanation regarding the separator described above can be applied to the electrochemical element, so any redundant explanation will be omitted below.

[0084] The electrochemical element may be any known energy storage device and is not particularly limited, but a non-limiting example is a secondary battery, or more specifically, a lithium secondary battery. A lithium secondary battery according to one embodiment may include the above-mentioned separator between the positive electrode and the negative electrode. Here, the positive electrode and the negative electrode can be any type commonly used in lithium secondary batteries and are not limited to those used in such batteries.

[0085] In one embodiment, the separator, when typically used in a battery, is assembled by arranging the negative electrode, the separator, and the positive electrode. The components of the secondary battery according to this disclosure will be described further below.

[0086] [Positive electrode] The positive electrode may include a positive electrode current collector and a positive electrode mixture layer disposed on at least one surface of the positive electrode current collector.

[0087] (Positive electrode current collector) The positive electrode current collector may include stainless steel, nickel, aluminum, titanium, or alloys thereof. The positive electrode current collector may also include aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver. The positive electrode current collector may, but is not limited thereto, be 10 μm to 50 μm in thickness.

[0088] (Positive electrode material) The positive electrode mixture layer may contain a positive electrode active material. The positive electrode active material may contain a compound capable of reversibly intercalating and deintercalating lithium ions.

[0089] According to exemplary embodiments, the positive electrode active material may include a lithium-nickel metal oxide. The lithium-nickel metal oxide may further include at least one of cobalt (Co), manganese (Mn), and aluminum (Al).

[0090] In some embodiments, the positive electrode active material or the lithium-nickel metal oxide may include a layered structure or crystalline structure represented by the following chemical formula 3.

[0091] [Chemical formula 3] Li x Ni a M b O 2+z

[0092] In chemical formula 3, 0.9 ≤ x ≤ 1.2, 0.6 ≤ a ≤ 0.99, 0.01 ≤ b ≤ 0.4, and -0.5 ≤ z ≤ 0.1 may also be true. As mentioned above, M may include Co, Mn, and / or Al.

[0093] The chemical structure represented by chemical formula 3 indicates the bonding relationships contained within the layered or crystalline structure of the positive electrode active material and does not exclude other further elements. For example, M may include Co and / or Mn, and Co and / or Mn, together with Ni, may be provided as the main active element of the positive electrode active material. Chemical formula 3 is provided to represent the bonding relationships of the said main active element and should be understood as a formula that encompasses the introduction and substitution of further elements.

[0094] In one embodiment, auxiliary elements may be further included in addition to the main active element to enhance the chemical stability of the positive electrode active material or the layered / crystalline structure. These auxiliary elements can be mixed together with the layered / crystalline structure and form bonds, and in this case, they should also be understood as being within the range of the chemical structure represented by chemical formula 3.

[0095] The auxiliary element may include, for example, at least one of Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, or Zr. The auxiliary element may act as an auxiliary active element, such as Al, together with Co or Mn, which is useful for the capacity / power activity of the positive electrode active material.

[0096] For example, the positive electrode active material or the lithium-nickel metal oxide may include a layered structure or crystalline structure represented by the following chemical formula 3-1.

[0097] [Chemical formula 3-1] Li x Ni a M1 b1 M2 b2 O 2+z

[0098] In chemical formula 3-1, M1 may include Co, Mn, and / or Al. M2 may include the aforementioned auxiliary elements. In chemical formula 3-1, 0.9 ≤ x ≤ 1.2, 0.6 ≤ a ≤ 0.99, 0.01 ≤ b1 + b2 ≤ 0.4, and -0.5 ≤ z ≤ 0.1 may also be present.

[0099] The positive electrode active material may further contain coating elements or doping elements. For example, elements substantially identical or similar to the auxiliary elements described above may be used as coating elements or doping elements. For example, one or more of the above elements may be used as coating elements or doping elements.

[0100] The coating element or doping element may be present on the surface of the lithium-nickel metal oxide particles, or may penetrate through the surface of the lithium-nickel metal oxide particles and be contained within the bonding structure represented by chemical formula 3 or chemical formula 3-1.

[0101] The positive electrode active material may include nickel-cobalt-manganese (NCM) lithium oxide. In this case, an NCM lithium oxide with an increased nickel content may be used.

[0102] Ni may be provided as a transition metal related to the output and capacity of lithium secondary batteries. Therefore, as described above, by employing a high-Ni composition in the positive electrode active material, a high-capacity positive electrode and a high-capacity lithium secondary battery can be provided.

[0103] However, as the Ni content increases, relatively, the long-term storage stability and life stability of the positive electrode or the secondary battery may decrease, and the side reactions with the electrolyte may also increase. However, according to an exemplary embodiment, by including Co, the electrical conductivity can be maintained, and by Mn, the life stability and capacity retention characteristics can be improved.

[0104] The Ni content (for example, the molar fraction of nickel among the total number of moles of nickel, cobalt, and manganese) in the NCM-based lithium oxide can be 0.6 or more, 0.7 or more, or 0.8 or more. In some embodiments, the Ni content may be 0.8 to 0.95, 0.82 to 0.95, 0.83 to 0.95, 0.84 to 0.95, 0.85 to 0.95, or 0.88 to 0.95.

[0105] In some embodiments, the positive electrode active material may include a lithium cobalt oxide-based active material, a lithium manganese oxide-based active material, a lithium nickel oxide-based active material, or a lithium iron phosphate-based (LFP) active material (for example, LiFePO4).

[0106] In some embodiments, the positive electrode active material may include, for example, a Mn-rich-based active material having a chemical structure or crystal structure represented by Chemical Formula 4, an LLO (Li rich layered oxide) / OLO (Over Lithiated Oxide)-based active material, or a Co-less-based active material.

[0107] [Chemical Formula 4] p[Li2MnO3]·(1-p)[Li q JO2]

[0108] In Chemical Formula 4, 0 < p < 1, 0.9 ≦ q ≦ 1.2, and J may include at least one element among Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, Al, Mg, and B.

[0109] (Method for manufacturing a positive electrode) For example, a positive electrode slurry may be produced by mixing the positive electrode active material in a solvent. After coating the positive electrode slurry onto a positive electrode current collector, the mixture layer may be dried and rolled to produce a positive electrode mixture layer. The coating process may be carried out by methods such as gravure coating, slot die coating, simultaneous multilayer die coating, imprinting, doctor blade coating, dip coating, bar coating, and casting, and is not limited to these. The positive electrode mixture layer may further contain a binder, and optionally further contain a conductive material, a thickener, etc. Here, the binder and conductive material are as described above.

[0110] (Positive electrode solvent) Non-limiting examples of solvents used in the production of the positive electrode slurry include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, isobutyl isobutyrate, butyl butyrate, xylene, and anisol.

[0111] (Positive electrode binder) The binder may include a non-aqueous binder and / or an aqueous binder, or a rubber-based binder and / or a fluorine-based binder, for example, polyvinylidene fluoride (PVDF), polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP), polyacrylonitrile, polymethyl methacrylate, acrylonitrile butadiene rubber (NBR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), etc. In one embodiment, a PVDF-based binder may be used as the positive electrode binder.

[0112] (Positive electrode conductive material) The conductive material may be added to enhance the conductivity and / or the mobility of lithium ions or electrons in the positive electrode mixture layer. For example, the conductive material may be a linear conductive material and / or a point conductive material, and may include, but is not limited to, carbon-based conductive materials such as graphite, carbon black, acetylene black, Ketjenblack, graphene, carbon nanotubes, VGCF (vapor-grown carbon fiber), carbon fiber, and / or metallic conductive materials such as tin, tin oxide, titanium oxide, LaSrCoO3, and LaSrMnO3.

[0113] (Positive electrode thickener / dispersant) If necessary, the cathode mixture may further contain a thickener and / or a dispersant. In one embodiment, the cathode mixture may contain a thickener such as carboxymethylcellulose (CMC).

[0114] [Negative electrode] The negative electrode may include a negative electrode current collector and a negative electrode mixture layer disposed on at least one surface of the negative electrode current collector.

[0115] (Negative electrode current collector) Non-limiting examples of negative electrode current collectors include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, and polymer substrates coated with conductive metals. The thickness of the negative electrode current collector is not limited to this, but may be, for example, 10 to 50 μm.

[0116] (Negative electrode material) The negative electrode mixture layer may contain a negative electrode active material. As the negative electrode active material, a material capable of adsorbing and desorbing lithium ions may be used. For example, the negative electrode active material may be a carbon-based material such as crystalline carbon, amorphous carbon, carbon composite, carbon fiber, lithium metal, lithium alloy, silicon (Si)-containing substance, or tin (Sn)-containing substance.

[0117] Examples of the amorphous carbon include hard carbon, soft carbon, coke, mesocarbon microbead (MCMB), mesophase pitch-based carbon fiber (MPCF), and the like.

[0118] Examples of the crystalline carbon include graphite-based carbons such as natural graphite, artificial graphite, graphitized coke, graphitized MCMB, and graphitized MPCF.

[0119] The lithium metal may be pure lithium metal or lithium metal with a protective layer formed for suppressing dendrite growth. In one embodiment, a lithium metal-containing layer deposited or coated on the negative electrode current collector may be used as the negative electrode active material layer. In one embodiment, a lithium thin film layer may be used as the negative electrode active material layer.

[0120] Examples of the elements contained in the lithium alloy include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium.

[0121] The silicon-containing substance may provide improved capacity characteristics. The silicon-containing substance may include Si, SiO x (0 < x < 2), metal-doped SiO x (0 < x < 2), silicon-carbon composite, and the like. The metal may include lithium and / or magnesium, and the metal-doped SiO x (0 < x < 2) may include metal silicate.

[0122] (Method of manufacturing the negative electrode) For example, a negative electrode slurry may be produced by mixing the negative electrode active material in a solvent. The negative electrode slurry may be coated / deposited onto a negative electrode current collector, and then dried and rolled to produce a negative electrode mixture layer. The coating process may be carried out by methods such as gravure coating, slot die coating, simultaneous multilayer die coating, imprinting, doctor blade coating, dip coating, bar coating, and casting, and is not limited to these. The negative electrode mixture layer may further contain a binder, and optionally further contain conductive materials, thickeners, and the like.

[0123] In some embodiments, the negative electrode may include a negative electrode active material layer in the form of lithium metal formed by a vapor deposition / coating process.

[0124] (Negative electrode solvent) Non-limiting examples of the solvent for the negative electrode mixture include water, pure water, deionized water, distilled water, ethanol, isopropanol, methanol, acetone, n-propanol, t-butanol, isobutyl isobutyrate, butyl butyrate, xylene, and anisole.

[0125] (Negative electrode binder / conductive material / thickener) The above-mentioned substances usable in the manufacture of the positive electrode may be used as the binder, conductive material, and thickener.

[0126] In some embodiments, rubber binders such as styrene-butadiene rubber (SBR) binders, carboxymethylcellulose (CMC), polyacrylic acid (PEDOT) binders, polyethylenedioxythiophene (poly(3,4-ethylenedioxythiophene), PEDOT) binders may be used as the negative electrode binder.

[0127] [Separator] A separator may be interposed between the positive and negative electrodes. The separator may be configured to prevent electrical short circuits between the positive and negative electrodes and to generate ion flow. Depending on the embodiment, the thickness of the separator may be 10 μm to 20 μm, but this disclosure is not limited thereto.

[0128] For example, the separator may include a porous polymer film or a porous nonwoven fabric. The porous polymer film may include polyolefin polymers such as ethylene polymer, propylene polymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer. The porous nonwoven fabric may include high-melting-point glass fibers, polyethylene terephthalate fibers, etc. The separator may also include ceramic materials. For example, inorganic particles can be coated onto the polymer film or dispersed within the polymer film to improve heat resistance.

[0129] The separator may have a single-layer or multi-layer structure including the polymer film and / or nonwoven fabric described above.

[0130] [Electrode assembly] According to exemplary embodiments, an electrode assembly may be formed by repeatedly arranging a positive electrode, a negative electrode, and a separator. In some embodiments, the electrode assembly may be of the winding, stacking, z-folding, or stack-folding type.

[0131] [Electrolyte] A lithium secondary battery may be defined by housing the electrode assembly together with the electrolyte in a case. According to an exemplary embodiment, a non-aqueous electrolyte may be used as the electrolyte.

[0132] (Lithium salt / organic solvent) The non-aqueous electrolyte contains a lithium salt, which is the electrolyte, and an organic solvent, wherein the lithium salt is, for example, Li + X - Represented by the anion (X) of the lithium salt. - ) as F - Cl - , Br - , I - NO3 - , N(CN)2 - BF4 - ClO4 - PF6 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - CF3SO3 - CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2) 2CH - (SF5)3C - (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN -and (CF3CF2SO2)2N - etc. are exemplified.

[0133] The organic solvent may contain organic compounds that have sufficient solubility in the lithium salt and additives and that do not react within the battery. The organic solvent may include, for example, at least one of carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, and aprotic solvents. Examples of the aforementioned organic solvents include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate, diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, vinylene carbonate, methyl acetate (MA), ethyl acetate (EA), n-propyl acetate (n-PA), 1,1-dimethylethyl acetate (DMEA), methyl propionate (MP), ethyl propionate (EP), fluoroethyl acetate (FEA), difluoroethyl acetate (DFEA), trifluoroethyl acetate (TFEA), and dibutyl ether (dibutyl Other substances that may be used include ether, tetraethylene glycol dimethyl ether (TEGDME), diethylene glycol dimethyl ether (DEGDME), tetrahydrofuran (THF), and 2-methyltetrahydrofuran, ethanol (ethyl alcohol), isopropyl alcohol, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, sulfolane, gamma-butyrolactone, and propylene sulfite.These may be used individually or in combination of two or more.

[0134] (Additives) The non-aqueous electrolyte may further contain additives. These additives may include, for example, cyclic carbonate compounds, fluorine-substituted carbonate compounds, sultone compounds, cyclic sulfate compounds, cyclic sulfite compounds, phosphate compounds, and borate compounds.

[0135] The aforementioned cyclic carbonate compound may include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and the like.

[0136] The fluorine-substituted cyclic carbonate compound may include fluoroethylene carbonate (FEC) and the like.

[0137] The sultone compound may include 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, etc. The cyclic sulfate compound may include 1,2-ethylene sulfate, 1,2-propylene sulfate, etc. The cyclic sulfite compound may include ethylene sulfite, butylene sulfite, etc. The phosphate compound may include lithium difluorobis-oxalato phosphate, lithium difluoro phosphate, etc. The borate compound may include lithium bis(oxalate) borate, etc.

[0138] [Solid electrolyte] In some embodiments, a solid electrolyte may be used instead of the non-aqueous electrolyte described above. In this case, the lithium secondary battery can be manufactured in the form of an all-solid-state battery. Alternatively, a solid electrolyte layer may be placed between the positive and negative electrodes instead of the separator described above.

[0139] The solid electrolyte may include sulfide site electrolytes. Non-restrictive examples include Li2S-P2S5, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-LiCl-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z. m S n(m, n are positive numbers, Z is Ge, Zn or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , (p, q are positive numbers, M is P, Si, Ge, B, Al, Ga, or In), Li 7-x PS 6-x Cl x (0 ≦ x ≦ 2), Li 7-x PS 6-x Br x (0 ≦ x ≦ 2), Li 7-x PS 6-x I x (0 ≦ x ≦ 2), etc. can be included. These can be used alone or in combination of two or more.

[0140] In one embodiment, the solid electrolyte may include, for example, oxide-based amorphous solid electrolytes such as Li2O-B2O3-P2O5, Li2O-SiO2, Li2O-B2O3, Li2O-B2O3-ZnO, etc.

[0141] [Shell structure] For example, electrode tabs (positive electrode tab and negative electrode tab) can project from the positive electrode current collector and the negative electrode current collector respectively and extend to one side of the case. The electrode tab may be fused together with the one side of the case and connected to electrode leads (positive electrode lead and negative electrode lead) extending or exposed outside the case. For example, a pouch-type case, a rectangular case, a cylindrical case, a coin-type case, etc. may be used.

[0142] Hereinafter, the examples will be further described with reference to specific experimental examples. The examples and comparative examples included in the experimental examples illustrate one embodiment and do not limit the scope of the appended claims. It is obvious to those skilled in the art that various changes and modifications to the examples are possible within the scope of the present disclosure and the scope of the technical idea, and it is needless to say that such variations and modifications belong to the scope of the appended claims.

[0143] [Test method] 1. Glass transition temperature (Tg, unit: °C) Using a differential scanning calorimetry (DSC), the heat capacity of a sample was measured by heating it at a rate of 10°C / min in the range of -100°C to 250°C. The temperature in the middle of the interval where the heat capacity of the sample changed abruptly was determined as the glass transition temperature.

[0144] 2. Electrode fusion temperature (unit: °C) Two negative electrodes and two positive electrodes were alternately placed on both sides of the separators manufactured in the examples and comparative examples. The negative and positive electrodes were then correctly aligned and folded in a Z-stack configuration. After setting the temperature of the press machine, the separators were pressed at a pressure of 1 MPa for 30 seconds. After crimping, if both the negative and positive electrodes were attached to the separator when unfolded, this temperature was defined as the electrode fusion temperature.

[0145] 3. Analysis of adhesive strength (Fx) (peak force QNM (quantitative nanomechanical), unit: nN) The adhesive force between the probe and the separator surface was measured using an atomic force microscope (AFM, Bruker) equipped with a temperature-adjustable stage, and the adhesive force at temperature x°C was expressed as Fx. Specifically, the separator was placed on a stage at temperature x, and the separator was tapped with a probe (RTESPA-300) with a spring constant of 40 N / m, an average radius of 8 nm, and a scanning speed of 0.5 Hz. The adhesive force generated when the probe leaves the separator surface was calculated from the Y axis of the F / D (load (Y axis) / distance (X axis)) graph. Specifically, in the following example, the adhesive force was measured at points where binder particles were present on the surface of the separator adhesive layer, and the average value was calculated from a total of 10 measurements. After determining the adhesive strengths F40 and F75 when the stage temperatures were 40°C and 75°C respectively, F75 / F40 was rounded to two decimal places.

[0146] 4. Measuring the number of cycles at which internal resistance increases. The number of cycles required for the internal resistance to increase by 30% relative to the initial resistance before the start of the charge-discharge cycle was defined as the number of cycles required for the internal resistance to increase, and this was performed using a battery assembled as shown below.

[0147] Cathode Manufacturing: A cathode mixture slurry was prepared by adding 92% by weight of lithium cobalt composite oxide (LiCoO2) as the cathode active material, 4% by weight of carbon black as the conductive material, and 4% by weight of polyvinylidene fluoride (PVdF) as the binder to N-methyl-2-pyrrolidone (NMP) as the solvent. The prepared slurry was coated onto a 30 μm thick aluminum (Al) thin film, dried at a temperature of 120°C, and then roll-pressed to produce a 40 μm thick cathode.

[0148] Negative electrode manufacturing: Graphite carbon, PVdF as a binder, and carbon black as a conductive agent were added to the solvent NMP at concentrations of 96% by weight, 3% by weight, and 1% by weight, respectively, to produce a negative electrode mixture slurry. The manufactured slurry was applied to a 20 μm thick copper (Cu) thin film, dried at 120°C, and pressed using a roll press to produce a 150 μm thick negative electrode.

[0149] A pouch-type battery was assembled using a stacking method, with separators manufactured between 11 positive electrodes and 12 negative electrodes. An electrolyte solution consisting of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / dimethyl carbonate (DMC) = 3:5:2 (volume ratio) in which 1M lithium hexafluorophosphate (LiPF6) was dissolved was injected into each assembled battery to produce a lithium secondary battery with a capacity of 2Ah.

[0150] The assembled batteries were charged at 4.2V CC-CV (constant current-constant voltage) using a charge-discharge cycle device, and then discharged to 2.5V. The charge-discharge cycle was measured by charging from 2.5V to 4.2V at 0.5C and discharging at 0.5C 600 times. The initial internal resistance was measured before the start of each cycle, and the internal resistance was measured again after each charge-discharge cycle. The number of cycles at which the internal resistance increased by 30% relative to the initial resistance was determined as the number of cycles required for the internal resistance to increase.

[0151] 5. Thickness measurement (unit: μm) After measuring the thickness of 10 layers of porous substrate using Mitutoyo (ID-C112X), the thickness was divided by 10 to obtain the separator thickness. After coating the porous substrate with an inorganic particle layer, the thickness was measured using the same method, and the thickness of the inorganic particle layer was subtracted from this value. After coating the inorganic particle layer with an adhesive layer, the thickness was measured using the same method, and the thickness of the adhesive layer was subtracted from the thickness of the porous substrate and the inorganic particle layer to obtain the adhesive layer thickness.

[0152] <Example 1> Average particle size (D 50 ) 29% by weight of boehmite particles with a diameter of 300 nm, average particle size (D 50 A coating slurry with a solid content of 25% by weight was prepared, containing 68% by weight of boehmite particles with a wavelength of 700 nm and 3% by weight of polyacrylamide. The coating slurry was applied to both sides of a porous polyethylene substrate with a thickness of 9 μm, and then evaporated to form inorganic particle layers with a thickness of 1.5 μm on each side.

[0153] Average particle size (D 50A dispersion of acrylic particles with a core-shell structure (concentration 3 wt%) having a particle size of 500 nm was applied to the inorganic particle layers formed on both sides, and then evaporated to form adhesive layers with a thickness of 0.5 μm on each side, thereby producing a separator. Here, the acrylic particles with a core-shell structure consist of a core (average particle size: 450 nm) containing a copolymer formed by mixing methyl methacrylate and n-butyl acrylate in a weight ratio of 70:30, and a shell containing a copolymer formed by mixing ethyl acrylate, methyl methacrylate, and styrene in a weight ratio of 12:30:58, with a weight ratio of 7:3 between the core and shell.

[0154] <Example 2> The separator was manufactured in the same manner as in Example 1, but the core-shell structured acrylic particles (average particle size: 500 nm) contained in the adhesive layer consisted of particles in which the core (average particle size: 450 nm) contained a copolymer formed by mixing methyl methacrylate, n-butyl acrylate, and ethyl acrylate in a weight ratio of 75:10:15, and the shell contained a copolymer formed by mixing ethyl acrylate, methyl methacrylate, and styrene in a weight ratio of 10:50:40.

[0155] <Example 3> The separator is manufactured in the same manner as in Example 1, but when forming the inorganic particle layer, the inorganic particles are defined as having an average particle size (D 50 The separator was manufactured using the same method, except that 97% by weight of boehmite particles with a wavelength of 300 nm was used.

[0156] <Comparative Example 1> The separator was manufactured in the same manner as in Example 1, but the core-shell structured acrylic particles (average particle size: 500 nm) contained in the adhesive layer consisted of particles in which the core (average particle size: 450 nm) contained a copolymer formed by mixing methyl methacrylate, n-butyl acrylate, and ethyl acrylate in a weight ratio of 75:10:15, and the shell contained a copolymer formed by mixing methyl methacrylate and styrene in a weight ratio of 50:50.

[0157] <Comparative Example 2> The separator was manufactured in the same manner as in Example 1, but the core-shell structured acrylic particles (average particle size: 500 nm) contained in the adhesive layer consisted of particles in which the core (average particle size: 450 nm) contained a copolymer formed by mixing methyl methacrylate, n-butyl acrylate, and ethyl acrylate in a weight ratio of 40:20:40, and the shell contained a copolymer formed by mixing ethyl acrylate and styrene in a weight ratio of 30:70.

[0158] <Comparative Example 3> The separator was manufactured in the same manner as in Example 1, but the core-shell structured acrylic particles (average particle size: 500 nm) contained in the adhesive layer consisted of particles in which the core (average particle size: 450 nm) contained a copolymer formed by mixing methyl methacrylate and n-butyl acrylate in a weight ratio of 75:25, and the shell contained a copolymer formed by mixing benzyl acrylate and styrene in a weight ratio of 10:90.

[0159] <Comparative Example 4> The separator was manufactured using the same method as in Example 1, but the core-shell structured acrylic particles (average particle size: 500 nm) contained in the adhesive layer consisted of particles in which the core (average particle size: 450 nm) contained a copolymer formed by mixing methyl methacrylate and n-butyl acrylate in a weight ratio of 60:40, and the shell contained a copolymer formed by mixing methyl methacrylate and styrene in a weight ratio of 30:70.

[0160] <Comparative Example 5> Average particle size (D 50 ) 29% by weight of boehmite particles with a diameter of 300 nm, average particle size (D 50 A coating slurry with a solid content of 25% by weight was prepared, containing 68% by weight of boehmite particles with a wavelength of 700 nm and 3% by weight of polyacrylamide. The coating slurry was applied to a porous polyethylene substrate with a thickness of 9 μm, and then evaporated to form an inorganic particle layer, thereby producing a separator.

[0161] The glass transition temperature (Tg), fusion temperature with the electrode, adhesive strength (F40, F75) at temperatures of 40°C and 75°C, and their ratio, as well as the number of cycles required for increased internal resistance, of the copolymers contained in the core-shell structure of the acrylic particles in the adhesive layer of the separators manufactured in the above examples and comparative examples were analyzed using the above test method and are shown in Table 1 below.

[0162] [Table 1]

[0163] As can be confirmed by referring to Table 1 above, in the example where the adhesive force F40 measured using an AFM probe was 30 nN or less and F75 / F40 was 5 or more, the phenomenon of increase in internal resistance was significantly improved compared to the comparative example.

[0164] The above description is merely an example of applying the principles of this disclosure, and other configurations may be included without departing from the scope of this disclosure. Although one embodiment has been described in detail above with reference to examples and experimental examples, the scope of one embodiment is not limited to any particular embodiment and should be interpreted in accordance with the appended claims. [Explanation of Symbols]

[0165] 1 Separator 10 Base material 20 Inorganic particle layer 30 Adhesive layer 100 positive electrode 105 Positive electrode current collector 107 Positive lead 110 Cathode active material layer 120 Negative electrode active material layer 125 Negative electrode current collector 127 Negative lead 130 negative electrode 140 Separator 150 Electrode assembly 160 cases 200 core particle size 300 shell thickness

Claims

1. The material comprises a substrate, an inorganic particle layer formed on at least one surface of the substrate, and an adhesive layer formed on at least one of the inorganic particle layers. When the adhesive force between an atomic force microscope (AFM) probe with a spring constant of 40 N / m, an average radius of 8 nm, and a scanning speed of 0.5 Hz is measured at a stage temperature of x°C, and the probe is denoted as Fx, F40 is 1 nN to 30 nN. A separator that satisfies equation 1 below. [Formula 1] F75 / F40≧5

2. The separator according to claim 1, wherein the adhesive layer comprises a particulate polymer binder.

3. The separator according to claim 1, wherein the adhesive layer comprises an acrylic polymer binder.

4. The separator according to claim 2, wherein the particulate polymer binder has a core-shell structure.

5. The separator according to claim 4, wherein the glass transition temperature of the polymer contained in the core of the particle-type polymer binder is 30°C to 70°C.

6. The separator according to claim 4, wherein the glass transition temperature of the polymer contained in the shell of the particulate polymer binder is 70°C to 110°C.

7. The separator according to claim 4, wherein the glass transition temperature (Tg, c) of the polymer contained in the core and the glass transition temperature (Tg, s) of the polymer contained in the shell satisfy the following formula 2. [Formula 2] 50℃≦(Tg,c+Tg,s) / 2≦90℃

8. The adhesive layer comprises a copolymer consisting of repeating units derived from an acrylic monomer, The separator according to claim 1, comprising an acrylic monomer and a copolymer consisting of repeating units derived from styrene.

9. The adhesive layer has an average particle size (D ５０ The separator according to claim 1, comprising a particulate polymer binder having a wavelength of 400 nm to 800 nm.

10. The separator according to claim 1, wherein F75 is 40 nN to 300 nN.

11. The separator according to claim 1, wherein formula 1 satisfies F75 / F40 ≥ 10.

12. The separator according to claim 1, wherein the adhesive layer comprises a particulate acrylic polymer binder containing repeating units derived from a compound represented by the following chemical formula 1. 【Chemistry 1】 In the aforementioned chemical formula 1, R １ is hydrogen or C １－１０ It is an alkyl group, R ２ is hydrogen or C １－２０ It is a hydrocarbon group.

13. The separator according to claim 1, wherein the inorganic particle layer comprises inorganic particles and a polymer binder.

14. The inorganic particle layer has an average particle size (D ５０ The separator according to claim 1, comprising inorganic particles having a wavelength of 100 nm to 1500 nm.

15. The inorganic particle layer has an average particle size (D ５０ The separator according to claim 1, comprising first inorganic particles having a length of 100 nm to 500 nm and second inorganic particles having a length of 500 nm to 1500 nm.

16. The separator according to claim 1, wherein the inorganic particle layer comprises inorganic particles and a polymer binder, and the weight ratio of the inorganic particles to the polymer binder is 90:10 to 99:

1.

17. The separator according to claim 1, wherein the thickness of the inorganic particle layer is 0.5 μm to 3.0 μm.

18. The separator according to claim 1, wherein the thickness of the adhesive layer is 0.05 μm to 2.0 μm.

19. The material comprises a substrate, an inorganic particle layer formed on at least one surface of the substrate, and a separator including an adhesive layer formed on at least one of the inorganic particle layers. When the adhesive force between an atomic force microscope (AFM) probe with a spring constant of 40 N / m, an average radius of 8 nm, and a scanning speed of 0.5 Hz is measured at a stage temperature of x°C, and the probe is denoted as Fx, F40 is 1 nN to 30 nN. The separator is an electrochemical element that satisfies the following formula 1. [Formula 1] F75 / F40≧5

20. An electrochemical element comprising a substrate, an inorganic particle layer formed on at least one surface of the substrate, and a separator including an adhesive layer formed on at least one of the inorganic particle layers, When C is the number of cycles at which the internal resistance of the electrochemical element increases by 30% relative to the initial resistance before the start of the charge-discharge cycle, C is 300 or more. The aforementioned charge and discharge process involves discharging the electrochemical element to 2.5V, then charging it from 2.5V to 4.2V at 0.5C, and finally discharging it at 0.5C, which constitutes one cycle of the electrochemical element.

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