High-heat-resistant powder having adhesive outer layer, secondary battery separator using same, and manufacturing method therefor

Abstract

The present invention relates to a method for improving thermal resistance of a secondary battery separator, the thermal resistance of the secondary battery separator being improved without a binder and slurry process. By using a method of coating a binder with powder in which an outer layer is formed on inorganic particles, the physical properties of a separator can be improved, and performance including battery stability can be improved.

Description

High-heat resistant powder with an adhesive outer layer, a secondary battery separator using the same, and a method for manufacturing the same

[0001] The present invention relates to a powder having an outer layer, a secondary battery separator including the powder having an outer layer, and a method for manufacturing the same. More specifically, it relates to improving battery performance by improving the heat resistance of the separator without the addition of an additional binder and a slurry manufacturing process.

[0002] A secondary battery refers to a battery that can be reused by charging a discharged battery with current supplied from an external power source.

[0003] Recently, rechargeable batteries are being utilized as a core material in portable electronic devices such as laptops and smartphones, as well as in electric vehicles. As industries incorporating these rechargeable batteries grow, their utility is also increasing.

[0004] The main components of a secondary battery include a separator, cathode material, anode material, and electrolyte. The separator of a lithium-ion secondary battery is a porous material that blocks direct contact between the two electrodes and acts as a pathway for lithium ions; the resistance, lifespan characteristics, and stability of the secondary battery can be determined by the separator's porosity and other factors.

[0005] When a separator membrane undergoes thermal shrinkage at high temperatures, it can cause a fire. To prevent this, inorganic particles are coated to improve the thermal and mechanical properties of the membrane. In this case, a binder and slurry manufacturing process is used to coat the inorganic particles onto the membrane.

[0006] However, when binders are used, the cohesive force of inorganic particles is low, and there are concerns about environmental pollution caused by the use of solvents. Therefore, there is a need for technology that improves the stability and performance of batteries without binder and slurry manufacturing processes.

[0007] [Prior Art Literature]

[0008] [Patent Literature]

[0009] (Patent Document 1) Republic of Korea Published Patent Application No. 10-2022-0024179

[0010] The present invention relates to a powder having an outer layer, a secondary battery separator comprising the powder having an outer layer, and a method for manufacturing the same. More specifically, it relates to improving battery performance by enhancing the heat resistance of the separator without the addition of a binder or a slurry manufacturing process. The purpose is to provide the powder and a separator with excellent thermal and mechanical properties coated with the powder, and to provide a battery with high safety using the separator.

[0011] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other problems not mentioned but intended to be solved will be clearly understood by those skilled in the art to which the present invention belongs from the content to be described below.

[0012] One aspect of the present invention is an inorganic particle surface-modified with a surface modifier; and

[0013] Includes an outer layer;

[0014] The above surface modifier includes double bonds, and

[0015] The above outer layer surrounds the inorganic particles surface-modified by the surface-modifying agent,

[0016] Provides powder.

[0017] Another aspect of the present invention is a first step of surface-modifying inorganic particles with a surface modifier; and

[0018] A second step of polymerizing a monomer into the surface modifier to form an outer layer surrounding the inorganic particles; comprising

[0019] The above surface modifier includes double bonds,

[0020] A method for manufacturing powder is provided.

[0021] Another aspect of the present invention is that the powder is coated on one or more surfaces,

[0022] Provides a separation membrane.

[0023] In addition, including the above-mentioned separator,

[0024] Provides a secondary battery.

[0025] When using the powder of the present invention, the separator can be coated with a powder containing inorganic particles without a binder and slurry manufacturing process. In addition, the coated separator has excellent thermal and mechanical performance, and the battery manufactured using the separator of the present invention has excellent stability.

[0026] Figure 1 illustrates the process of manufacturing powder by surface-modifying inorganic particles with a surface modifier and forming an outer layer on the surface-modified inorganic particles.

[0027] Figure 2 shows a separation membrane coated with powder having an outer layer formed thereon.

[0028] Figures 3a and 3b are scanning electron microscope (SEM) images of boehmite before surface modification in Preparation Example 1 and boehmite after surface modification in Preparation Example 1 and after forming an outer layer in Preparation Example 2, respectively.

[0029] Figures 4a and 4b are scanning electron microscope (SEM) images of a separator coated according to Comparative Example 2 of the present invention and a separator coated according to Example 1 of the present invention, respectively.

[0030] Hereinafter, the operation and effects of the invention will be described in more detail through specific embodiments and drawings. However, these embodiments are merely examples of the invention and do not define the scope of the invention.

[0031] Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0032] Therefore, it should be understood that the configuration of the embodiments described in this specification is merely one of the most preferred embodiments of the present invention and does not represent all of the technical ideas of the present invention, and that various equivalents and modifications that can replace them may exist at the time of filing this application.

[0033] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0034] Where various parameters in this specification are given as an enumeration of ranges, preferred ranges, preferred upper limits, and preferred lower limits, it should be understood that any pair of any upper range limit or preferred value and any lower range limit or preferred value specifically discloses all ranges formed by any pair of any upper range limit or preferred value, regardless of whether the range is disclosed separately.

[0035] Where a range of numerical values ​​is mentioned in this specification, unless otherwise described, the range is intended to include its endpoint and all integers and fractions within the range.

[0036] The scope of the present invention is not intended to be limited to specific values ​​mentioned when defining the scope.

[0037] In the present specification, "a to b" and "a~b" indicating numerical ranges are defined as ≥a and ≤b.

[0038] Embodiments of the present invention have been described in detail below, but the present invention is not limited thereto.

[0039]

[0040] A powder according to one aspect of the present invention comprises: inorganic particles surface-modified with a surface modifier; and an outer layer; wherein the surface modifier comprises double bonds, and the outer layer may surround the inorganic particles surface-modified with the surface modifier.

[0041] The diameter of the above powder may be 0.1 μm or more and 3 μm or less. More preferably, it may be 0.15 μm or more and 2 μm or less.

[0042] For example, the diameter of the powder may be 0.2 μm or more and 1 μm or less.

[0043] If the size of the powder exceeds that of the present invention, there may be a problem in that the coating thickness formed on the separator becomes too thick, and if it falls below that of the present invention, there may be a problem in that the pores of the separator become clogged.

[0044] The above inorganic particles may collectively refer to particles composed of compounds that do not contain carbon or particles composed of simple compounds that contain carbon.

[0045] In one embodiment of the present invention, the inorganic particles are lithium aluminum titanium phosphate (LiAlTi(PO4)3), lithium lanthanum titanate (LiLa2TiO3), silica (SiO2), Al2O3, AlOOH, Al2O3·H2O, It may be Al2O3·2H2O, TiO2, ZrO2, ZnO, NiO, CaO, SnO2, Y2O3, MgO, BaTiO3, CaTiO3, SrTiO3, SiC, Li3PO4, Pb(Zr,Ti)O3(PZT), (Pb,La)(Zr,Ti)O3(PLZT) and mixtures thereof.

[0046] The above inorganic particles have no special size restrictions, but for example, the average particle size

[0047] It may be 0.05 μm to 0.5 μm, and more preferably 0.08 μm to 0.3 μm. If the average particle size of the inorganic particles is less than the above preferred range, dispersibility may be reduced, and if it exceeds the above preferred range, the thickness of the coating layer after coating may increase, and mechanical properties may be degraded.

[0048] In addition, the above-mentioned inorganic particles have no particular restrictions on shape and may be, for example, spherical, plate-shaped, elliptical, or irregular.

[0049] For example, boehmite (alumina oxide, AlO(OH)) can be used as the above inorganic particles, or a combination of boehmite and pseudoboehmite (Al2O3·H2O) can be used.

[0050] The above surface modifier may refer to a coupling agent, and the coupling agent may refer to a substance used for the purpose of increasing the bonding strength between materials of different properties. In the present invention, it may be used for the purpose of forming the outer layer on the inorganic particles.

[0051] The above surface modifier may include chromium (Cr), silicon (Si), titanium (Ti) and / or aluminum (Al).

[0052] In addition, the surface modifier may include a functional group capable of reacting with the surface of the inorganic particle. The functional group may include a hydroxyl group (-OH), an alkoxy group (-OR), an aldehyde group (-CHO), a carbonyl group (>C=O), a carboxyl group (-COOH), an amine group (-NH2), a halide (-X), or a combination thereof.

[0053] The above surface modifier may include one or more double bonds. In this case, the double bond may refer to a bond formed by the sharing of two pairs of electrons, which is a type of covalent bond. Specifically, it may be a carbon-carbon double bond.

[0054] For example, the surface modifier may be a silane-based coupling agent, and the silane-based coupling agent may include a methacrylate containing an alkoxy group and a double bond.

[0055] In one embodiment of the present invention, the surface modifier may be epoxy silane, vinyl silane, 3-(trimethoxysilyl)propyl methacrylate (MPS), triethoxyvinyl silane (TEVS), or trimethylvinyl silane (TMVS), or a combination thereof.

[0056] In one embodiment of the present invention, the weight of the surface modifier may be 0.05 weight% or more and 5 weight% or less based on 100 weight% of the total weight of the powder.

[0057] For example, the weight of the surface modifier may be 0.06 wt% or more and 4.9 wt% or less, 0.07 wt% or more and 4.8 wt% or less, 0.08 wt% or more and 4.7 wt% or less, or 0.09 wt% or more and 4.6 wt% or less, based on 100 wt% of the total weight of the powder.

[0058] If the weight of the surface modifier exceeds that of the present invention, there may be problems such as polymer reactions between surface modifiers or growth exceeding the particle size, and if the weight of the surface modifier falls below that of the present invention, complete surface modification may not be achieved, and as a result, the outer layer may not be sufficiently formed.

[0059] In one embodiment of the present invention, the outer layer may be formed by grafting a monomer onto the surface modifier.

[0060] For example, when the surface modifier surface modifies the inorganic particle, the double bond site of the surface modifier may be located at the outermost edge of the surface of the inorganic particle. After surface modification, if the monomer is graft polymerized with the surface modifier, the monomer may be graft polymerized at the double bond of the surface modifier. The monomer polymerized with the surface modifier may be polymerized into a hairy structure.

[0061] The above-mentioned grafting polymerization may refer to a grafting from method, a grafting through method, a grafting to method, or a combination thereof.

[0062] At this time, to graft polymerize the monomer with the surface modifier, a conventional free radical polymerization technique may be used.

[0063] For example, emulsion polymerization techniques can be used as free radical polymerization techniques.

[0064] Emulsion polymerization can refer to a method of polymerizing monomers by emulsifying them in water and using a water-soluble initiator.

[0065] The above monomer may include one or more double bonds. In this case, the double bond may refer to a bond formed by the sharing of two pairs of electrons, which is a type of covalent bond. Specifically, it may refer to a carbon-carbon double bond.

[0066] In one embodiment of the present invention, the outer layer may include an acrylate-based monomer unit, a styrene-based monomer unit, and a monomer unit including a hydrophilic functional group.

[0067] For example, the outer layer may include butyl acrylate, styrene, and 2-hydroxyethyl acrylate.

[0068] In addition, the outer layer may further include acrylic acid-based monomer units, acrylonitrile-based monomer units, acrylamide-based monomer units, vinyl acetate-based monomer units, monomer units containing conjugated double bonds, or a combination thereof.

[0069] In addition, monomers of each series can be combined to form monomer units.

[0070] For example, the monomer units of the above acrylate series are methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, isopropyl acrylate, isopropyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, It may be formed by polymerizing tert-butyl acrylate, tert-butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, or a combination thereof.

[0071] For example, the above-mentioned styrene series monomer unit can be formed by polymerizing styrene.

[0072] For example, the monomer unit containing the above hydrophilic functional group may be formed by polymerizing (meth)acrylic acid, acrylonitrile, acrylamide, hydroxyethyl (meth)acrylate, (meth)acrylic acid ethylene glycol ester, or a combination thereof.

[0073] For example, the above acrylic acid series monomer unit may be formed by polymerizing methacrylic acid, methyl methacrylic acid, or a combination thereof.

[0074] For example, the above-mentioned acrylonitrile-based monomer unit may be formed by polymerizing acrylonitrile, methacrylonitrile, or a combination thereof.

[0075] For example, the above-mentioned acrylamide series monomer unit can be formed by polymerizing acrylamide.

[0076] For example, the above vinyl acetate series monomer unit can be formed by polymerizing vinyl acetate.

[0077] In addition, monomer units containing conjugated double bonds may be formed by polymerizing 1,3-butadiene, 1,3-pentadiene, isoprene, or a combination thereof.

[0078] In one embodiment of the present invention, based on 100 parts by weight of the total weight of the surface-modified inorganic particles, the acrylate-based monomer unit may be 1.0 parts by weight or more and 3.0 parts by weight or less, the styrene-based monomer unit may be 0.5 parts by weight or more and 2.5 parts by weight or less, and the monomer unit containing a hydrophilic functional group may be 0.05 parts by weight or more and 0.35 parts by weight or less.

[0079] For example, based on 100 parts by weight of the total weight of the surface-modified inorganic particles, the acrylate-based monomer unit may be 1.2 parts by weight or more and 2.8 parts by weight or less, 1.4 parts by weight or more and 2.6 parts by weight or less, 1.5 parts by weight or more and 2.4 parts by weight or less, or 1.6 parts by weight or more and 2.2 parts by weight or less.

[0080] If the content of the above-mentioned acrylate-based monomer unit exceeds the present invention, the heat resistance and air permeability characteristics of the separator may be reduced, and if it falls below the present invention, there may be a problem of reduced adhesion to the separator.

[0081] For example, based on 100 parts by weight of the total weight of the surface-modified inorganic particles, the styrene-based monomer unit may be 0.7 parts by weight or more and 2.3 parts by weight or less, 1.0 parts by weight or more and 2.0 parts by weight or less, 1.2 parts by weight or more and 1.8 parts by weight or less, or 1.2 parts by weight or more and 1.6 parts by weight or less.

[0082] If the content of the above-mentioned styrene-based monomer unit exceeds that of the present invention, the adhesion to the separator may be reduced, and if it falls below that, the heat resistance and chemical resistance properties may be reduced.

[0083] For example, based on 100 parts by weight of the total weight of the surface-modified inorganic particles, the monomer unit containing the hydrophilic functional group may be 0.07 parts by weight or more and 0.33 parts by weight or less, 0.1 parts by weight or more and 0.3 parts by weight or less, or 0.15 parts by weight or more and 0.25 parts by weight or less.

[0084] If the content of the monomer unit containing the above-mentioned hydrophilic functional group exceeds that of the present invention, the heat resistance may be reduced, and if it falls below that of the present invention, the adhesion to the separator may be lowered, and the secondary battery manufactured using the same may have reduced ion conductivity and battery resistance characteristics.

[0085] In one embodiment of the present invention, the weight ratio of the acrylate-based monomer unit and the styrene-based monomer unit (weight of acrylate-based monomer unit: weight of styrene-based monomer unit) may be 1.1 to 2:1.

[0086] For example, the weight ratio of the acrylate-based monomer unit and the styrene-based monomer unit may be 1.15:1, 1.2:1, 1.3:1, 1.357:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, or 1.9:1.

[0087] If the weight of the acrylate-based monomer unit relative to the weight of the styrene-based monomer unit exceeds that of the present invention, the heat resistance and air permeability characteristics of the separation membrane may be reduced, and if it falls below that, there may be a problem of reduced adhesion to the separation membrane.

[0088] In one embodiment of the present invention, the outer layer may include a cross-linkable monomer. Due to the cross-linkable monomer, cross-links and / or branches may be formed between monomers included in the outer layer.

[0089] The crosslinkable monomer included in the outer layer may include two or more double bonds. Additionally, the number of crosslinkable monomers may be one or multiple, and each crosslinkable monomer may represent a compound of the same type or a compound of a different type.

[0090] The above-mentioned crosslinkable monomer can be directly polymerized with a surface modifier, can be polymerized with the monomer, and can be polymerized with other crosslinkable monomers.

[0091] The above-mentioned crosslinkable monomer may include multiple identical or different types of functional groups within a single monomer, and each functional group may mean a vinyl group (-CH=CH2), a hydroxyl group (-OH), an alkoxy group (-OR), an aldehyde group (-CHO), a carbonyl group (-C=O), a carboxyl group (-COOH), an amine group (-NH2), a halide (-X), or a combination thereof, but is not limited thereto.

[0092] In one embodiment of the present invention, the crosslinkable monomer may be neopentyl glycol di(methyl)acrylate, dicyclopentanyl (methyl)acrylate, 1,6-hexanediol diacrylate (HDDA), divinyl benzene, ethylene glycol di(meth)acrylate, divinyl adipate, trimethylolpropane trimethacrylate (TMPTMA), N,N'-methylenebisacrylamide (MBAA), or a combination thereof.

[0093] For example, the outer layer may additionally include butyl acrylate, styrene, and 2-hydroxyethyl acrylate monomers, as well as divinylbenzene monomer.

[0094] The content of the above-mentioned crosslinkable monomer may be 0.05 parts by weight or more and 0.5 parts by weight or less, based on 100 parts by weight of the total weight of the inorganic particles surface-modified by the above-mentioned surface modifier.

[0095] For example, the content of the crosslinkable monomer may be 0.06 parts by weight or more and 0.4 parts by weight or less, 0.07 parts by weight or more and 0.3 parts by weight or less, or 0.08 parts by weight or more and 0.2 parts by weight or less, based on 100 parts by weight of the total weight of the inorganic particles surface-modified by the surface modifier.

[0096] If the content of the above-mentioned crosslinkable monomer exceeds that of the present invention, there may be a problem of reduced adhesion to the separator, and if the content of the above-mentioned crosslinkable monomer falls below that of the present invention, there may be a problem of reduced chemical resistance to the electrolyte.

[0097] In one embodiment of the present invention, the outer layer may be included in an amount of 0.5% or more and 5% or less based on 100% by weight of the total weight of the powder.

[0098] For example, the weight of the outer layer may be 0.5% or more and 4.5% or less, 0.7% or more and 4.3% or less, 0.8% or more and 4.0% or less, or 0.9% or more and 3.5% or less, based on 100% of the total weight of the powder.

[0099] If the weight of the outer layer is less than 0.5% by weight based on 100% by weight of the total weight of the powder, there may be a problem in that the outer layer surrounds only a part of the inorganic particles surface-modified with a surface modifier, and if it exceeds 5% by weight, there may be a problem in that side reactions between monomers excluding the surface modifier increase or the outer layer becomes excessively thick.

[0100] For example, the surface of the inorganic particles can be surface modified using 0.05 parts by weight or more and 5 parts by weight or less of a surface modifier based on 100 parts by weight of the inorganic particles, and a powder with an outer layer formed can be produced using 1 part by weight or more and 10 parts by weight or less of a monomer based on 100 parts by weight of the inorganic particles.

[0101] A method for manufacturing a powder according to another aspect of the present invention may include: a first step of surface-modifying the inorganic particles with a surface modifier; and a second step of polymerizing a monomer into the surface modifier to form an outer layer surrounding the inorganic particles.

[0102] In addition, the surface modifier may include double bonds. In this case, the double bond may refer to a bond formed by the sharing of two pairs of electrons, which is a type of covalent bond. Specifically, it may refer to a carbon-carbon double bond.

[0103] A separation membrane according to another aspect of the present invention may have the powder of the present invention coated on one or more surfaces.

[0104] For example, a coating layer can be formed on one or both sides of the separation membrane using the powder of the present invention.

[0105] The above powder comprises inorganic particles surface-modified with a surface modifier; and an outer layer; wherein the surface modifier comprises double bonds, and the outer layer surrounds the inorganic particles surface-modified with the surface modifier.

[0106] In one embodiment of the present invention, the thickness of the coating layer may be 1 μm or more and 6 μm or less, respectively.

[0107] For example, the thickness of the coating layer may be 1 μm or more and 5 μm or less, 2 μm or more and 5 μm or less, 2 μm or more and 4 μm or less, or 3 μm or more and 4 μm or less.

[0108] If the thickness of the coating layer exceeds 6 μm, the thickness of the separator becomes too thick, which can reduce the energy density of the battery and increase resistance.

[0109] In addition, if the thickness of the coating layer is less than 1 μm, there may be a problem in that the heat resistance of the separator is reduced.

[0110] When a coating layer is formed on one or both sides of the separation membrane using the powder of the present invention, it can exhibit an adhesive strength equal to or greater than that of a separation membrane coated by mixing a powder without an outer layer with an organic material.

[0111] To ensure excellent battery characteristics, the coating layer must be uniformly coated while simultaneously requiring strong adhesion to the substrate.

[0112] The electrode adhesion of the separator can reduce the defect rate that occurs when loading electrodes during battery assembly, minimize void formation, and improve ion conductivity within the electrolyte.

[0113] Adhesion can be improved when a separation membrane is coated using a powder formed with an outer layer of the present invention. Since the improvement in the adhesion of the powder implies an increase in adhesion between the inorganic particles and the substrate, this implies that the heat resistance characteristics of the separation membrane can be improved by increasing the amount of inorganic particles.

[0114] Currently, polyolefin-based films are widely used as separators, but polyolefins have the disadvantage of severe thermal shrinkage at high temperatures and poor mechanical properties.

[0115] That is, in order to suppress thermal shrinkage caused by high temperature of polyolefin-based separators and battery instability caused by dendrites, an outer layer of inorganic particles is formed and coated on one or both sides of a porous separator substrate, thereby providing the function of suppressing the shrinkage rate of the substrate with inorganic particles without a separate binder and slurry manufacturing process, and at the same time, a safer separator can be manufactured through the coating layer.

[0116] Conventional emulsion binders have the problem of low heat resistance, but the separator coated with the above powder can have the effect of improving heat resistance by more than 30%. This can improve the safety of the separator and the battery.

[0117] If the permeability of the separator is excessively high, ions may not be able to sufficiently pass through the battery manufactured with the separator, and in this case, the efficiency of the battery may be reduced.

[0118] The degree of electrolyte swelling can refer to the extent to which the separator absorbs the electrolyte.

[0119] If the degree of electrolyte swelling is small, the battery performance can be excellent, and if the degree of electrolyte swelling is excessively large, the electrolyte in the battery may be depleted.

[0120] Meanwhile, if the degree of electrolyte swelling is excessively small, the battery resistance may be low, and battery performance may decrease.

[0121] A method for manufacturing a separation membrane according to one aspect of the present invention may form a coating layer by applying powder onto one or both sides of the separation membrane.

[0122] In one embodiment of the present invention, the coating may mean dip coating, die coating, gravure coating and / or comma coating, but is not limited thereto.

[0123] At this time, since the separator of the present invention forms a coating layer by applying the powder, it may not include a separate binder. In addition, in manufacturing the separator and / or battery of the present invention, a slurry process may not be included.

[0124] When manufacturing separators and batteries including the above-mentioned binder, environmental pollution may be caused by the use of organic solvents. Meanwhile, when manufacturing separators and batteries using only a surface modifier without an outer layer, a problem of low cohesion may occur.

[0125] A secondary battery according to another aspect of the present invention may include a separator having a coating layer formed on one or both sides of the separator using powder.

[0126] When the above separator is used in a secondary battery, lithium ions can be transferred not only through the separator substrate but also through the porous active layer, and thermal stability can be improved.

[0127] In addition, the secondary battery may include a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte.

[0128] The above secondary battery can be manufactured according to conventional methods known in the art, and as an example thereof, the electrode and the separator are assembled and then an electrolyte is injected into the assembly to manufacture it.

[0129] There are no significant limitations on the electrodes to be applied together with the above-mentioned separator; however, the cathode active material may be any conventional cathode active material that can be used for the cathode of a secondary battery. Non-limiting examples include lithium intercalation materials such as lithium manganese oxide (lithiated magnesium oxide), lithium cobalt oxide, lithium nickel oxide, or composite oxides formed by combinations thereof. Additionally, the anode active material may be any conventional anode active material that can be used for the anode of a conventional electrochemical device. Non-limiting examples include lithium metal or lithium alloys, as well as lithium intercalation materials such as carbon, petroleum coke, activated carbon, graphite, or other carbons. The anode and cathode are configured by attaching the aforementioned positive active material and negative active material to a positive current collector, i.e., a foil manufactured from aluminum, nickel, or a combination thereof, and a negative current collector, i.e., a foil manufactured from copper, gold, nickel, or a copper alloy, or a combination thereof, respectively.

[0130] The above electrolyte is A + B - As a salt with a structure like that, A + is Li + , Na + , K + It includes alkali metal cations such as or ions composed of combinations thereof, and B - is PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 -, N(CF3SO2)2 - , C(CF2SO2)3 - It is preferable that a salt containing anion such as or a combination thereof is dissolved and dissociated in an organic solvent composed of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), gamma-butyrolactone (GBL), or a mixture thereof.

[0131] In addition to the general winding process, the process of applying the above separator to a battery may include stacking and folding of the separator and electrode.

[0132] The present invention will be explained in more detail below using manufacturing examples and embodiments, but the present invention is not limited thereto.

[0133]

[0134] [Preparation Example 1] Surface modification of inorganic particles

[0135] Inorganic particles (boehmite, AlOOH) and 20 parts by weight of distilled water were added to a reaction vessel based on 100 parts by weight of the inorganic particles and dispersed by high-speed stirring.

[0136] While injecting high-purity nitrogen gas (N2) into the above reaction vessel, 0.1 parts by weight of 3-(trimethoxysilyl)propyl methacrylate (MPS) was added based on 100 parts by weight of the above inorganic particles and stirred at 90°C for 1 hour.

[0137] To wash away impurities, unreacted materials, and reaction residues, the product was washed with distilled water (DW) and ethanol (EtOH).

[0138]

[0139] Subsequently, a reaction vessel containing 3-(trimethoxysilyl)propyl methacrylate was stirred and dried at 60°C for 12 hours to produce surface-modified inorganic particles (boehmite, AlOOH).

[0140]

[0141] [Preparation Example 2] Formation of an outer layer by polymerizing a monomer into a surface modifier

[0142] An outer layer was formed on the surface-modified boehmite prepared according to Preparation Example 1 in the following manner.

[0143] The surface-modified inorganic particles and 120 parts by weight of distilled water were placed in a reaction vessel based on 100 parts by weight of the surface-modified inorganic particles, and high-purity nitrogen gas (N2) was injected while stirring at high speed to disperse them.

[0144] In the reaction vessel, based on 100 parts by weight of the total weight of the surface-modified inorganic particles, 1.9 parts by weight of butyl acrylate (BA), 1.4 parts by weight of styrene, 0.2 parts by weight of 2-hydroxy ethyl acrylate, 0.1 parts by weight of divinyl benzene, and 0.1 parts by weight of potassium persulfate (KPS) were added.

[0145] Afterwards, the reaction vessel was emulsion polymerized at 80°C for 4 hours to form an outer layer on the surface-modified inorganic particles.

[0146] A manufacturing process in which the surface of inorganic particles is modified through Manufacturing Example 1 and the outer layer of the powder is formed using Manufacturing Example 2 is schematically illustrated in FIG. 1.

[0147]

[0148] [Example 1]

[0149] Inorganic particles were surface modified using Preparation Example 1, and powder with an outer layer formed using Preparation Example 2 was coated onto a separator.

[0150] At this time, no separate binder was added during the process of coating the separator with the above powder.

[0151] The above separator is a polyolefin porous substrate (polyethylene (PE), polypropylene (PP), etc.) and was hot-air dried by jet blowing at a temperature of 50 to 80°C after dip bar coating.

[0152] A separation membrane coated with powder according to Example 1 is schematically illustrated in FIG. 2.

[0153]

[0154] [Comparative Example 1]

[0155] The separator was not coated with separate inorganic particles or binders. The separator is the same as the separator (polyolefin porous substrate) used for coating in Example 1.

[0156]

[0157] [Comparative Example 2]

[0158] A separation membrane was coated in the same manner as in Example 1, except that inorganic particles (boehmite, AlOOH) without surface modification and an outer layer were used, and a general emulsion binder made of polyacrylate was used.

[0159] At this time, the separation membrane was coated using a slurry prepared by mixing the inorganic particles (boehmite, AlOOH) without surface modification and an outer layer formed above and the general emulsion binder above in a weight ratio of 8:2 based on solid content using a ball mill method.

[0160]

[0161] [Comparative Example 3]

[0162] The separator was coated in the same manner as in Example 1, except that divinylbenzene was not added.

[0163]

[0164] [Comparative Example 4]

[0165] A separation membrane was coated in the same manner as in Example 1, except that 2-hydroxyethyl acrylate was not added, and 2.1 parts by weight of butyl acrylate (BA) was added based on 100 parts by weight of the total weight of the surface-modified inorganic particles.

[0166]

[0167] Table 1 below shows whether the monomers of the outer layer of Example 1 and Comparative Examples 1 to 4 are cross-linked and whether they contain hydrophilic functional groups.

[0168]

[0169] Whether crosslinked Whether hydrophilic functional groups are included Example 100 Comparative Example 1-- Comparative Example 200 Comparative Example 3XO Comparative Example 4OX

[0170]

[0171] Comparative Example 1 does not have a separate coating formed on the separator. Examples and Comparative Example 2 contain divinylbenzene as a crosslinking agent, so crosslinking between monomers of the outer layer is formed, and contain 2-hydroxyethyl acrylate as a hydrophilic functional group. Comparative Example 3 does not contain a crosslinking agent, so crosslinking is not formed, and Comparative Example 4 does not add a monomer containing a hydrophilic functional group.

[0172]

[0173] [Evaluation Example 1] Evaluation of coating layer adhesion (Peel test)

[0174] A tape with a width of 18 mm and a length of 30 mm was attached to the separator prepared by the method of Example 1 and Comparative Examples 1 to 4, and then pressed 5 times with a hand roller. The separator with the attached tape was mounted on a Universal Testing Machine (UTM) (1 kgf Load cell), one part of the separator was fixed to the upper clip of the tensile strength tester, and the tape attached to one side of the separator was fixed to the lower clip, and the 180° peel strength was measured at a speed of 100 mm / min.

[0175] Five specimens were prepared for each example and comparative example to measure the peel strength, and the average values ​​are shown in Table 2 below.

[0176]

[0177] Adhesion strength (N) Example 1 10.8 Comparative Example 1 - Comparative Example 29.3 Comparative Example 3 12.8 Comparative Example 49.7

[0178]

[0179] Comparative Example 1 could not test the adhesion of the coating layer because the separator was not coated.

[0180] It was confirmed that the adhesive strength of Example 1 was superior to that of Comparative Example 2, where the slurry was prepared and adhered without forming an outer layer, and Comparative Example 4, where a powder was used that did not contain a monomer containing a hydrophilic functional group.

[0181] As in Comparative Example 3, when divinylbenzene was not included as a crosslinking agent, it exhibited higher adhesive strength than Example 1. However, Comparative Example 3 had the problem of having a higher heat shrinkage rate compared to Example 1.

[0182]

[0183] [Evaluation Example 2] Scanning Electron Microscope (SEM) verification of powder with an outer layer formed

[0184] The surface of the inorganic particles was modified using Preparation Example 1, and the appearance of the powder with an outer layer formed using Preparation Example 2 was observed using a scanning electron microscope.

[0185] Figure 3 (a) shows a scanning electron microscope image of boehmite before surface modification in Preparation Example 1, and Figure 3 (b) shows a scanning electron microscope image of boehmite that was surface modified by Preparation Example 1 and formed an outer layer by Preparation Example 2.

[0186] Observations using a scanning electron microscope confirmed that a polymerized outer layer had been formed.

[0187]

[0188] [Evaluation Example 3] Scanning Electron Microscope (SEM) Confirmation of Separator Coated with Powder Forming an External Layer

[0189] Surface modification of inorganic particles was performed using Preparation Example 1, and the surface of a separation membrane coated with powder having an outer layer formed using Preparation Example 2 was observed.

[0190] Figure 4 (a) shows a scanning electron microscope image of the separator coated according to Comparative Example 2, and Figure 4 (b) shows a scanning electron microscope image of the separator coated according to Example 1.

[0191] In contrast to Fig. 4 (a), it was observed that the surface of the separator in Fig. 4 (b) was uneven and had changed color to white or light gray.

[0192]

[0193] [Evaluation Example 4] Evaluation of thermal shrinkage rate (Dry heat resistance)

[0194] A sample with dimensions of 5 x 5 cm was prepared using a separator prepared by the method of the example and comparative example, and the sample was placed in a 150°C oven for 1 hour, after which the shrinkage rate was measured and the results are shown in Table 3 below.

[0195]

[0196] Classification Heat Shrinkage Rate (Dry Heat Resistance) (MD / TD) (%) Example 1 26 / 28 Comparative Example 167 / 68 Comparative Example 2 36 / 37 Comparative Example 3 32 / 35 Comparative Example 4 32 / 32

[0197]

[0198] The thermal shrinkage rate of the separator in Example 1 was 26 / 28 (MD / TD)%, which is smaller than that of Comparative Examples 1 to 4, and it was confirmed that the heat resistance was superior compared to Comparative Examples 1 to 4.

[0199] At this time, it was also confirmed that the thermal shrinkage rate of Comparative Example 2 was lower than that of Comparative Example 1, which was not coated with separate inorganic particles or binders.

[0200] In addition, through Comparative Examples 3 and 4, it was confirmed that the outer layer of the powder containing crosslinks and hydrophilic functional groups affects the excellent heat resistance properties.

[0201]

[0202] [Evaluation Example 5] Evaluation of membrane air permeability

[0203] The air permeability of the separator prepared by the methods of the example and comparative example was measured using an air permeability measuring device to determine the time (in seconds) required for 100 cc of air to pass through. The change in air permeability was measured based on the air permeability of the uncoated separator (Comparative Example 1) and is shown in Table 4 below.

[0204]

[0205] Classification Change in air permeability (seconds, sec) Example 1 △11 (119) Comparative Example 1 - (108) Comparative Example 2 △24 (132) Comparative Example 3 △17 (125) Comparative Example 4 △15 (123)

[0206]

[0207] Although the air permeability of Example 1 was reduced by about 10% compared to Comparative Example 1, which was not coated, it was superior compared to Comparative Examples 2 to 4. In other words, it was found that the separator prepared according to Example 1 exhibited superior air permeability compared to a separator coated using a general emulsion binder.

[0208] In addition, through Comparative Examples 3 and 4, it was confirmed that the outer layer of the powder containing crosslinks and hydrophilic functional groups has an effect on excellent air permeability.

[0209]

[0210] [Evaluation Example 6] Evaluation of Electrolyte Swelling Degree

[0211] A total of 15 samples were prepared by cutting the separator membranes of Example 1 and Comparative Examples 1 to 4 into three pieces each measuring 5 cm x 5 cm, and the weight of each sample was measured.

[0212] The prepared sample was placed in a vial, 30 ml of electrolyte was added to impregnate the prepared sample with the electrolyte, and the opening of the vial was sealed with Teflon tape.

[0213] At this time, the above electrolyte was prepared by adding lithium hexafluorophosphate (LiPF6) to a solution of ethylene carbonate (EC) and diethyl carbonate (DEC) mixed in a weight ratio of 3:7 (EC:DEC=3:7) to a concentration of 1 M.

[0214] After storing the vial containing the sample and electrolyte in a 60°C oven for 24 hours, the sample containing the electrolyte was removed and its weight measured.

[0215] The degree of electrolyte swelling was calculated based on the difference in weight of the sample before and after impregnation in the electrolyte using Equation 1 below, and the average value of the degree of electrolyte swelling of three samples per sample is shown in Table 5 below.

[0216]

[0217] <Equation 1>

[0218] Electrolyte Swelling Degree (%) = [(Weight of film containing electrolyte - Weight of film before electrolyte impregnation) / Weight of film before electrolyte impregnation] * 100 (%)

[0219]

[0220] Classification Electrolyte Swelling Degree (%) Example 1 187 Comparative Example 1 180 Comparative Example 2 195 Comparative Example 3 203 Comparative Example 4 193

[0221]

[0222] It was confirmed that the separator of Example 1 had a higher degree of swelling than Comparative Example 1, but a lower degree of swelling than Comparative Examples 2 to 4.

[0223] Accordingly, according to Evaluation Examples 5 to 7, Example 1 was superior to Comparative Examples 2 to 4 in terms of thermal shrinkage rate, air permeability, and electrolyte swelling.

[0224] In addition, considering that the separator of Example 1 has an appropriate degree of electrolyte swelling, it was confirmed that an overall excellent separator and secondary battery can be manufactured without a binder and slurry manufacturing process.

[0225]

[0226] The scope of the present invention is defined by the claims set forth below rather than by the detailed description above, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the present invention.

[0227] When using the powder of the present invention, the separator can be coated with a powder containing inorganic particles without a binder and slurry manufacturing process. In addition, the coated separator has excellent thermal and mechanical performance, and the battery manufactured using the separator of the present invention has excellent stability.

Claims

1. Inorganic particles surface-modified with a surface modifier; and Includes an outer layer; The above surface modifier includes double bonds, and The above outer layer surrounds the inorganic particles surface-modified by the surface-modifying agent, Powder.

2. In Paragraph 1, The above-mentioned inorganic particles are lithium aluminum titanium phosphate (LiAlTi(PO4)3), lithium lanthanum titanate (LiLa2TiO3), silica (SiO2), Al2O3, AlOOH, and Al2O3·H2O , Al2O3·2H2O, TiO2, ZrO2, ZnO, NiO, CaO, SnO2, Y2O3, MgO, BaTiO3, CaTiO3, SrTiO3, SiC, Li3PO4, Pb(Zr,Ti)O3(PZT), (Pb,La)(Zr,Ti)O3(PLZT), or combinations thereof, comprising Powder.

3. In Paragraph 1, The above surface modifier comprises epoxy silane, vinyl silane, 3-(trimethoxysilyl)propyl methacrylate (MPS), triethoxyvinyl silane (TEVS), or trimethylvinyl silane (TMVS), or a combination thereof. Powder.

4. In Paragraph 1, The weight of the surface modifier is 0.05 weight% or more and 5 weight% or less, based on 100 weight% of the total weight of the powder. Powder.

5. In Paragraph 1, The above outer layer is formed by grafting and polymerizing monomers onto the surface modifier, Powder.

6. In Paragraph 1, The above outer layer comprises acrylate-based monomer units, styrene-based monomer units, and monomer units including hydrophilic functional groups, Powder.

7. In Paragraph 6, Based on 100 parts by weight of the total weight of the inorganic particles surface-modified with the above surface modifier, The above acrylate-based monomer unit is 1.0 part by weight or more and 3.0 part by weight or less, The above styrene-based monomer unit is 0.5 parts by weight or more and 2.5 parts by weight or less, The monomer unit containing the above hydrophilic functional group is 0.05 parts by weight or more and 0.35 parts by weight or less, Powder.

8. In Paragraph 6, A weight ratio of the above acrylate-based monomer unit and the above styrene-based monomer unit (weight of acrylate-based monomer unit:weight of styrene-based monomer unit) of 1.1 to 2:1, Powder.

9. In Paragraph 1, The above outer layer further comprises a crosslinkable monomer, Powder.

10. In Paragraph 9, Based on 100 parts by weight of the total weight of the inorganic particles surface-modified by the surface modifier, the weight of the crosslinkable monomer is 0.05 parts by weight or more and 0.5 parts by weight or less, Powder.

11. In Paragraph 1, The above outer layer is included in an amount of 0.5 weight% or more and 5 weight% or less, based on 100 weight% of the total weight of the powder, Powder.

12. A first step of surface modifying inorganic particles with a surface modifier; and A second step of polymerizing a monomer into the surface modifier to form an outer layer surrounding the inorganic particles; comprising The above surface modifier includes double bonds, Method for manufacturing powder.

13. Powder of any one of claims 1 to 11 coated on one or more surfaces, Separator.

14. Including the separator of paragraph 13, Secondary battery.

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