Electrochemical device separator and electrochemical device comprising same

Abstract

The present invention relates to an electrochemical device separator in which LATP particles having excellent ion conductivity are included in a porous coating layer, and an electrochemical device comprising same. The degree of aluminum substitution of the LATP particles is adjusted such that the lithium ion conductivity and lifespan characteristics of the electrochemical device are improved.

Description

Separator for an electrochemical device and an electrochemical device equipped with the same

[0001] The present invention claims the benefit of the filing dates of Korean Patent Application No. 10-2024-0157436 filed with the Korean Intellectual Property Office on November 7, 2024, and Korean Patent Application No. 10-2025-0000713 filed with the Korean Intellectual Property Office on January 3, 2025, the entire contents of which are incorporated into the present invention.

[0002] The present invention relates to a separator for an electrochemical device and an electrochemical device equipped with the same.

[0003] Electrochemical devices convert chemical energy into electrical energy using electrochemical reactions; recently, lithium-ion batteries, which offer high energy density and voltage, long cycle life, and applicability to various fields, are widely used.

[0004] A lithium secondary battery may include an electrode assembly manufactured with a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes, and the electrode assembly may be manufactured by housing it in a case together with an electrolyte. The positive electrode may provide lithium ions, and the lithium ions may move to the negative electrode by passing through a separator made of a porous material. The negative electrode may use lithium metal or a carbon-based active material, such as one having an electrochemical reaction potential close to that of lithium metal and capable of inserting and extracting lithium ions.

[0005] NASICON is a superionic conductor containing sodium (Na), and Na 1+x Zr2Si x P 3-x O 12(0 <x<3)로 표현될 수 있다. NASICON은 서로 모서리를 공유하는 ZrO6팔면체와 PO4 / SiO4사면체 구조를 포함하는 특유의 구조를 가지며, 소듐 이온이 상기 팔면체와 상기 사면체의 공극 또는 이들 사이의 공극을 이동하면서 높은 이온 전도성을 나타낼 수 있다. 최근에는 NASICON에서 Na, Zr 및 / 또는 Si가 다른 등가의 원소로 대체된 NASICON 유사 구조를 갖는 화합물로서 LATP의 리튬 이온 전도성, 기계적 안정성 및 열적 안정성에 주목하여 이를 전기화학소자용 분리막에 적용하기 위한 연구가 이루어지고 있다.

[0006] The present invention aims to provide a separator for an electrochemical device having excellent ion conductivity using LATP, and an electrochemical device having excellent resistance and lifespan characteristics including said separator.

[0007] One embodiment of the present invention comprises a porous substrate and LATP (Li 1+x Al x Ti 2-x (PO4)3) The present invention provides a separator for an electrochemical device comprising particles and a polymer binder, and a porous coating layer formed on one surface of the porous substrate, wherein x is a real number from 0.2 to 0.4.

[0008] The above LATP particles may have an average particle size (D50) of 1 to 3 μm.

[0009] The thickness of the porous coating layer may be 1 to 3.5 μm.

[0010] The polymer binder is a non-particulate acrylic binder, and the porous coating layer may contain 15 weight percent or less of the polymer binder.

[0011] The above polymer binder may have a glass transition temperature of 0°C or lower.

[0012] One embodiment of the present invention comprises an anode, a cathode, and a separator disposed between the anode and the cathode, wherein the separator is a cylindrical electrochemical device that is a separator for an electrochemical device according to one embodiment of the present invention.

[0013] The porous coating layer can be positioned to face the anode.

[0014] The above separation membrane is formed on the other side of the above porous substrate and further comprises a second porous coating layer comprising inorganic particles and a polymer binder, wherein the inorganic particles may be different from the LATP particles.

[0015] The above electrochemical device may be a lithium secondary battery.

[0016] The separator for an electrochemical device according to the present invention includes lithium metal phosphate, which has excellent ion conductivity, and uses inorganic particles with a high dielectric constant to have low moisture content and can reduce the gas generation rate in the electrochemical device.

[0017] Hereinafter, each component of the present invention is described in more detail so that a person skilled in the art to which the present invention pertains can easily implement it; however, this is merely an example, and the scope of the rights of the present invention is not limited by the following.

[0018] The term “comprising” as used herein is used when listing materials, compositions, devices, and methods useful for the present invention, and is not limited to the examples listed.

[0019] As used herein, "about" and "substantially" are used to mean a range of numerical values ​​or degrees or approximations thereof, taking into account inherent manufacturing and material tolerances, and are used to prevent an infringer from unfairly exploiting the disclosure in which precise or absolute figures provided to aid in understanding the invention are mentioned.

[0020] As used in this specification, "electrochemical device" may refer to a primary battery, a secondary battery, a supercapacitor, etc.

[0021] Unless otherwise specifically stated, "particle size" as used in this specification refers to D50, which is the particle size corresponding to 50% of the cumulative distribution of the number of particles according to particle size.

[0022]

[0023] One embodiment of the present invention comprises a porous substrate, and LATP (Li 1+x Al x Ti 2-x (PO4)3) The present invention provides a separator for an electrochemical device comprising particles and a polymer binder, and a porous coating layer formed on one surface of the porous substrate, wherein x is a real number from 0.2 to 0.4.

[0024] The porous substrate electrically insulates the anode and cathode to prevent short circuits while providing pores through which lithium ions can pass. The porous substrate may be resistant to the electrolyte of an electrochemical device, which is an organic solvent. For example, the porous substrate may include, but is not limited to, polyolefin-based materials such as polyethylene, polypropylene, and polybutene; polyvinyl chloride, polyethylene terephthalate, polycycloolefin, polyethersulfone, polyamide, polyimide, polyimideamide, polyaramid, polycycloolefin, nylon, polytetrafluoroethylene, and copolymers or mixtures thereof. Preferably, the porous substrate may include a polyolefin-based polymer, which may have excellent slurry applicability for forming a porous coating layer and be advantageous for manufacturing a thin-thickness separator.

[0025] The porous substrate may have a single-layer or multi-layer structure. The porous substrate may include two or more polymer resin layers with different melting points (Tm) to provide a shutdown function during high-temperature runaway of the battery. For example, the porous substrate may include a polypropylene layer with a relatively high melting point and a polyethylene layer with a relatively low melting point. Preferably, the porous substrate may have a three-layer structure laminated in the order of polypropylene, polyethylene, and polypropylene. The polyethylene layer may prevent thermal runaway of the battery by shutting down the pores as it melts as the temperature of the battery rises above a predetermined temperature.

[0026] The thickness of the porous substrate may be 1 μm or more and 100 μm or less. Specifically, the thickness of the porous substrate may be 10 μm or more and 90 μm or less, 20 μm or more and 80 μm or less, 30 μm or more and 70 μm or less, or 40 μm or more and 60 μm or less. Preferably, the thickness of the porous substrate may be 1 μm or more and 30 μm or less. More preferably, the thickness of the porous substrate may be 5 μm or more and 15 μm or less, or 7 μm or more and 13 μm or less. By controlling the thickness of the porous substrate within the above-described range, the volume of the electrochemical device can be minimized while electrically insulating the anode and the cathode, thereby increasing the amount of active material included in the electrochemical device.

[0027] The porous substrate may include pores with an average diameter of 0.01 μm or more and 1 μm or less. Specifically, the size of the pores included in the porous substrate may be 0.01 μm or more and 0.09 μm or less, 0.02 μm or more and 0.08 μm or less, 0.03 μm or more and 0.07 μm or less, or 0.04 μm or more and 0.06 μm or less. Preferably, the size of the pores may be 0.02 μm or more and 0.06 μm or less. By controlling the pore size of the porous substrate within the above-described range, the air permeability and ion conductivity of the entire separation membrane being manufactured can be controlled.

[0028] The porous substrate may have an air permeability of 10 s / 100cc or more and 100 s / 100cc or less. Specifically, the air permeability of the porous substrate may be 10 s / 100cc or more and 90 s / 100cc or less, 20 s / 100cc or more and 80 s / 100cc or less, 30 s / 100cc or more and 70 s / 100cc or less, or 40 s / 100cc or more and 60 s / 100cc or less. Preferably, the air permeability of the porous substrate may be 50 s / 100cc or more and 70 s / 100cc or less. When the air permeability of the porous substrate is within the range described above, the air permeability of the manufactured separator may be provided within a range suitable for securing the output and cycle characteristics of the electrochemical device.

[0029] The above air permeability (s / 100cc) refers to the time (in seconds) required for 100cc of air to pass through a porous substrate or membrane of a predetermined area under constant pressure. The above air permeability may be measured using a Gurley densometer in accordance with ASTM D 726-58, ASTM D726-94, or JIS-P8117. For example, using a Gurley 4110N instrument, air at a pressure of 0.304 kPa or 1.215 kN / m 2 100cc of air under water pressure is 1 square inch (or 6.54 cm²) 2 The time it takes for ) to pass through a sample can be measured. For example, using the Asahi Seico EG01-55-1MR instrument, the time it takes for 100cc of air to pass through a 1 square inch sample under constant pressure of 4.8 inches of water at room temperature can be measured.

[0030] The porous substrate may have a porosity of 10 vol% or more and 60 vol% or less. Specifically, the porosity of the porous substrate may be 15 vol% or more and 55 vol% or less, 20 vol% or more and 50 vol% or less, 25 vol% or more and 45 vol% or less, or 30 vol% or more and 40 vol% or less. Preferably, the porosity of the porous substrate may be 30 vol% or more and 50 vol% or less. When the porosity of the porous substrate is within the range described above, the ion conductivity of the manufactured separator may be provided within a range suitable for securing the output and cycle characteristics of the electrochemical device.

[0031] The above porosity refers to the ratio of the volume of pores to the total volume of the porous substrate. The above porosity can be measured by methods known in the art. For example, it can be measured by the BET (Brunauer Emmett Teller) measurement method using nitrogen gas adsorption, the capillary flow porometer, or the water or mercury infiltration method.

[0032] The porous coating layer comprises LATP particles, which are lithium metal phosphate, and a polymer binder. The porous coating layer may be formed by coating a coating slurry comprising LATP particles, a polymer binder, and a dispersion medium onto one surface of the porous substrate. The porous coating layer comprises an interstitial volume formed by connecting the LATP particles by the polymer binder, which adheres to the porous substrate while allowing lithium ions to pass through, thereby preventing thermal shrinkage of the porous substrate.

[0033] The coating slurry described above may include a dispersion medium to dissolve or disperse at least a portion of the polymer binder and to disperse the LATP particles. The coating slurry may be used in which the LATP particles and the polymer binder are uniformly dispersed by adjusting the type and content of the dispersion medium. For example, the dispersion medium may be one selected from the group consisting of water, ethanol, acetone, isopropyl alcohol (IPA), dimethylacetamide (DMAc), dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), acetonitrile, and combinations thereof. Preferably, the dispersion medium may be a mixture of water and isopropyl alcohol or water. A porous coating layer in which the LATP particles and the polymer binder are uniformly dispersed can be formed using the above-described type of dispersion medium.

[0034] The coating slurry may further include additives such as dispersants, surfactants, defoaming agents, and flame retardants to improve dispersibility and flame retardancy and to improve the uniformity of the formed porous coating layer. For example, the dispersant may include one or more selected from the group consisting of polyacrylic acid, oil-soluble polyamines, oil-soluble amine compounds, fatty acids, fatty alcohols, sorbitan fatty acid esters, tannic acid, and pyrogallic acid. By using a dispersant of the type described above, the stability of the coating slurry can be improved and the uniformity of the porous coating layer formed by the coating slurry can be ensured.

[0035] Based on the total weight of the coating slurry, the additive may be included in an amount of 0% by weight or more and 5% by weight or less. Specifically, the content of the additive may be 0.01% by weight or more and 4% by weight or less, 0.1% by weight or more and 3% by weight or less, or 1% by weight or more and 2% by weight or less. Preferably, the content of the additive may be 1% by weight or more and 5% by weight or less. By controlling the content of the additive within the above-described range, uniform dispersion and stability of the inorganic particles included in the coating slurry can be achieved.

[0036] The thickness of the porous coating layer may be 1 μm or more and 3.5 μm or less. Specifically, the thickness of the porous coating layer may be 1 μm or more, 1.5 μm or more, 2 μm or more, 2.5 μm or more, 3 μm or more, or 3.5 μm or less, 3 μm or less, 2.5 μm or less, 2 μm or less, or 1.5 μm or less. The porous coating layer may include LATP particles of a particle size to be described later, thereby minimizing shrinkage of the porous substrate even within the thickness range described above, and thus providing advantages in improving the resistance, energy density, and lifespan characteristics of the electrochemical device.

[0037] The above polymer binder can bind LATP particles contained in the porous coating layer and impart adhesion to the porous coating layer. The above polymer binder may be a non-particulate acrylic binder that does not dissolve in the dispersion medium of the coating slurry but does not maintain a particulate form.

[0038] The polymer binder may have a glass transition temperature (Tg) of 0°C or lower. Specifically, the polymer binder may be a non-particle type binder with a glass transition temperature (Tg) of 0°C or lower. A particle type polymer binder may be placed between the LATP particles to inhibit the establishment of ion conduction pathways through adjacent LATP particles, thereby reducing ion conductivity. A polymer binder satisfying the above glass transition temperature range can improve the binding between LATP particles and the binding strength between the porous coating layer and the porous substrate, and can provide stability to an electrochemical device including the separator. If the glass transition temperature of the polymer binder falls outside the above range, sufficient binding strength for LATP particles with relatively large particle sizes cannot be secured, and the porous coating layer may detach from the porous substrate.

[0039] The porous coating layer may contain the polymer binder in an amount of 15 weight% or less. The dispersion medium included in the coating slurry may be removed by drying or heating after the formation of the porous coating layer. Preferably, the porous coating layer may be composed of the LATP particles and the polymer binder. The polymer binder may be included in an amount of 1 weight% or more, 5 weight% or more, 10 weight% or more, or 15 weight% or less, 10 weight% or less, or 5 weight% or less, based on the total weight of the porous coating layer, and within the above-described range, it may bind the LATP particles and maintain the bonding between the porous coating layer and the porous substrate.

[0040] The above LATP particles are Li 1+x Al x Ti 2-xIt may be an inorganic compound represented by (PO4)3. The above x may be the degree of aluminum substitution in the LATP particles, and the above x may be a real number between 0.2 and 0.4. As the above x changes, one or more of the crystal structure and the number, shape, and arrangement of grain boundaries within the LATP particles may change. Lithium ions can move along the interstitial volume of the porous coating layer, but can also move through the interior of the LATP particles. Therefore, the porous coating layer containing the above LATP particles and the separator equipped therewith may exhibit improved ion conductivity. Lithium ions move within the LATP particles with crystallographic directionality. If the degree of aluminum substitution deviates from the range described above, the ion conductivity may decrease as the number of grain boundaries on the movement path through which lithium ions must pass increases due to increased crystallographic inconsistency.

[0041] The above LATP particles may be spherical or amorphous particles with an average particle size (D50) of 1 to 3 μm. Within the above-described range, the movement of lithium ions through the LATP particles is not obstructed, allowing for high ion conductivity. In the case of LATP particles with a particle size smaller than the above-described range, boundaries between particles may be over-formed or non-uniform grain boundaries may be formed due to aggregation between particles. Additionally, LATP particles with a particle size larger than the above-described range may have a low overall density, resulting in insufficient contact between particles and causing stagnation of lithium ion movement at the grain boundaries. Thus, if the particle size deviates from the above-described range, it affects the overall density, grain boundary uniformity, and the number of grain boundaries, thereby hindering the establishment of lithium ion diffusion pathways and causing a decrease in lithium ion conductivity in the separator. Therefore, LATP particles within the above-described range form an efficient lithium ion conduction network and allow the electrolyte to effectively penetrate into the spaces between the LATP particles, thereby maximizing the contact area between the electrolyte and the LATP particles.

[0042] The separator for the electrochemical device described above can ensure the movement of lithium ions through LATP particles contained in the porous coating layer, in addition to the movement of lithium ions through the interstitial volume formed in the porous coating layer. The separator has improved ion conductivity and can provide improved lifespan characteristics by preventing stagnation of lithium ion movement.

[0043] The separator for the electrochemical device described above may further include a second porous coating layer formed on the other side of the porous substrate. When the separator includes the second porous coating layer, the porous coating layer and the second porous coating layer may be arranged with the porous substrate in between. The second porous coating layer can prevent thermal shrinkage of the porous substrate, thereby improving the stability of the separator.

[0044] The second porous coating layer may include inorganic particles and a polymer binder. The type of inorganic particles is not limited as long as they are different from the LATP particles. Electrochemically stable or flame-retardant inorganic particles may be used. For example, the inorganic particles may be HfO2, SnO2, ZnO, ZrO2, SiO2, Y2O3, Al2O3, Al(OH)3, SiC, AlOOH, TiO2, Sb2O3, Sb2O4, Sb2O5, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, Zn2SnO4, ZnSnO3, ZnSn(OH)6, H3BO3, HBO2, and mixtures thereof.

[0045] The polymer binder used in the second porous coating layer may be the same as or different from the polymer binder of the porous coating layer described above.

[0046] The second porous coating layer may contain the inorganic particles and the polymer binder in a weight ratio of 60:40 to 95:5. Within the range described above, the second porous coating layer may prevent thermal shrinkage of the porous substrate and may not impede the effect of improving ion conductivity resulting from the use of the porous coating layer.

[0047]

[0048] Another embodiment of the present invention provides a method for manufacturing a separator for an electrochemical device, comprising the steps of forming a coating layer by coating one surface of a porous substrate with a coating slurry comprising LATP particles, a polymer binder, and a dispersion medium, and manufacturing a separator by drying the coating layer to remove the dispersion medium. Any content overlapping with that described in the description of the separator for an electrochemical device is replaced by the description of the preceding embodiment.

[0049] The step of forming the coating layer involves coating one side of a porous substrate with a coating slurry comprising LATP particles, a polymer binder, and a dispersion medium. For example, the coating may be formed by methods such as a bar coater, wire bar coater, roll coater, spray coater, spin coater, inkjet coater, screen coater, reverse coater, gravure coater, knife coater, slot die coater, hot melt coater, comma coater, direct metering coater, etc., but is not limited thereto. Preferably, the step of forming the coating layer may involve coating a cross-section of the porous substrate with the coating slurry using a bar coater or a slot die coater.

[0050] The step of forming the coating layer may further include the step of corona discharge treatment of at least one surface of the porous substrate. After the corona discharge treatment step, the coating slurry may be coated onto the porous substrate. The step of corona discharge treatment of at least one surface of the porous substrate prevents a decrease in the bonding strength between the surface of the porous substrate and the surface of the coating layer at high temperatures, and prevents a decrease in the bonding strength between the surface of the polymer substrate and the surface of the coating layer due to the electrolyte.

[0051] The corona discharge treatment may involve treating at least one surface of the porous substrate with a voltage of 0.1 kV or more and 10 kV or less in air. Specifically, the corona discharge treatment may involve treating with a voltage of 0.2 kV or more and 9 kV or less, 0.3 kV or more and 8 kV or less, 0.4 kV or more and 7 kV or less, 0.5 kV or more and 6 kV or less, 0.6 kV or more and 5 kV or less, 0.7 kV or more and 4 kV or less, 0.8 kV or more and 3 kV or less, 0.9 kV or more and 2 kV or less, or 1.0 kV or more and 2 kV or less in air. Preferably, the corona discharge treatment may involve treating with a voltage of 1.8 kV in air. By adjusting the applied voltage of the corona discharge treatment within the above-described range, an appropriate number of functional groups can be formed on the surface of the polymer substrate, and damage to the surface of the polymer substrate can be prevented.

[0052] The step of forming the coating layer may further include coating the other side of the porous substrate with a second coating slurry comprising the inorganic particles, a polymer binder, and a dispersion medium. The separator for the electrochemical device may include a porous coating layer formed by the coating slurry on one side and a second porous coating layer formed by the second coating slurry on the other side. The coating method or means of the second coating slurry may be the same as or different from the coating of the coating slurry. The second coating slurry may be applied to the porous substrate simultaneously with the coating slurry, or applied after the coating slurry has been applied.

[0053] The step of manufacturing a separation membrane by removing the dispersion medium may involve drying or heating the coating layer to evaporate the dispersion medium contained within the coating layer. The dispersion medium removal step may be performed at a temperature that allows only the dispersion medium contained within the coating layer to evaporate without deforming the polymer binder contained within the coating layer. For example, the dispersion medium removal step may involve heating the coating layer to a predetermined temperature, provided that the surface temperature of the coating layer does not exceed 60°C. When heating the coating layer under these conditions, thermal energy may first be used to heat the dispersion medium to cause a phase change, and may not be used to deform the polymer binder.

[0054]

[0055] Another embodiment of the present invention provides a cylindrical electrochemical device comprising an anode, a cathode, and a separator disposed between the anode and the cathode, wherein the separator is a separator for an electrochemical device according to the above-described embodiment.

[0056] The porous coating layer of the separator for the electrochemical device is formed on one surface of the porous substrate, and the porous coating layer may be positioned to face the anode. When the LATP particles come into contact with the cathode, they may cause side reactions to generate gas or impurities, thereby degrading the stability and performance of the electrochemical device. The porous coating layer is positioned in close proximity to the anode active material containing lithium, so that side reactions are reduced while the effect of improving ion conductivity can be maximized.

[0057] The anode and the cathode may each have an electrode active material applied and dried to at least one surface of a current collector. The current collector may be made of a material that is conductive without causing chemical changes in the electrochemical device. For example, the current collector for the anode may be aluminum, nickel, titanium, calcined carbon, stainless steel; or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc., but is not limited thereto. For example, the current collector for the cathode may be copper, nickel, titanium, calcined carbon, stainless steel; or copper or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc., but is not limited thereto. The current collector may be in various forms such as a metal sheet, film, foil, net, porous body, foam, etc.

[0058] The above-described positive electrode comprises a positive current collector and a positive active material layer comprising a positive active material, a conductive material, and a binder resin on at least one surface of the current collector. The positive active material is a layered compound such as a lithium manganese complex oxide (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 ~ 0.3); chemical formula LiMn 1-x M xIt may include a lithium manganese complex oxide represented by O2 (where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which part of the Li of the chemical formula is substituted with alkaline earth metal ions; a disulfide compound; and one or more of Fe2(MoO4)3.

[0059] The above-mentioned cathode comprises a cathode current collector and a cathode active material layer comprising a cathode active material, a conductive material, and a binder resin on at least one surface of the current collector. The above-mentioned cathode comprises, as the cathode active material, carbon such as lithium metal oxide, non-graphitizable carbon, or graphite-based carbon; LixFe2O3 (0≤x≤1), Li x WO2(0≤x≤1), Si, SiO x (0 <x<2), SiC, Si 합금 등의 실리콘계 재료; Sn x Me 1-x Me y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, 2, and 3 elements of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, 및 Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료; 티타늄 산화물 중 선택된 1종 또는 2종 이상의 혼합물을 포함할 수 있다.

[0060] The conductive material may be any one selected from the group consisting of graphite, carbon black, carbon fiber or metal fiber, metal powder, conductive whiskers, conductive metal oxides, carbon nanotubes, activated carbon, and polyphenylene derivatives, or a mixture of two or more of these conductive materials. The carbon nanotubes have a graphite sheet having a cylindrical shape with a nano-sized diameter, and sp 2 It has a bonded structure and exhibits conductive or semiconductor properties depending on the angle and structure at which the graphite plane is rolled. Carbon nanotubes can be classified into single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and multi-walled carbon nanotubes (MWCNT) depending on the number of bonds forming the walls, and these carbon nanotubes can be appropriately selected according to the application of the dispersion. More specifically, it may be one type selected from the group consisting of natural graphite, artificial graphite, super-p, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, Denka black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide, or a mixture of two or more of these conductive materials.

[0061] As the above binder resin, a binder resin commonly used in the electrodes of electrochemical devices can be used. Non-limiting examples of such binder resins include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethylmethacrylate, polyethylhexyl acrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. Examples include acetatepropionate), cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, but are not limited thereto.

[0062] 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 - A salt comprising an anion such as or a combination thereof may be dissolved or dissociated in an organic solvent comprising 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), ethylmethyl carbonate (EMC), gamma butyrolactone, or a mixture thereof, but is not limited thereto.

[0063] The electrochemical device comprising the above electrode assembly may be a lithium secondary battery. The battery may be used as a unit cell, a battery module comprising the unit cell, a battery pack comprising the battery module, or a device comprising the battery pack as a power source. Examples of such devices include small devices such as computers, mobile phones, and power tools; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs) that are powered by an electric motor; electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters (E-scooters); electric golf carts; and medium-to-large devices such as power storage systems, but are not limited thereto.

[0064]

[0065] The present invention will be explained in more detail below through specific embodiments and experimental examples. The following embodiments and experimental examples are intended to illustrate the present invention, and the present invention is not limited by the following embodiments and experimental examples.

[0066] Example 1

[0067] Preparation of the first coating slurry

[0068] Li as lithium metal phosphate in water at room temperature (25℃) 1.3 Al 0.3 Ti 1.7 A coating slurry was prepared by adding (PO4)3(LATP) particles (average particle size 2 μm) and a water-soluble polymer binder in the weight ratios listed in the table below and stirring for 120 minutes.

[0069] Preparation of the second coating slurry

[0070] A coating slurry was prepared by adding a polyacrylate-based dispersant to water at room temperature, adding alumina and the above-mentioned non-particulate binder, and stirring for 120 minutes.

[0071] Preparation of porous substrate

[0072] As a porous substrate (MI: 0.2 g / 10 min, T m A polyethylene film with a thickness of 9 μm was used, having a temperature of 135°C, a porosity of 45%, and an average pore size of 45 nm.

[0073] Manufacturing of separation membranes

[0074] A first coating slurry (thickness 3 μm) was coated on one side of the porous substrate using a doctor blade on a polyethylene film to form a porous coating layer, and a second coating slurry (thickness 3 μm) was coated on the other side to form a second porous coating layer. A low-temperature air flow was applied to the polyethylene film having the porous coating layer formed thereon to produce a separator with a total thickness of 15 μm.

[0075] Manufacturing of electrochemical devices

[0076] After weighing the lithium active material (NCM622), conductive material (Super P), and binder (PVdF) in a weight ratio of 93:5:2, they were added to N-methylpyrrolidone (NMP) and mixed to prepare an anode active material slurry. The anode active material slurry was coated to a thickness of 100 μm onto a 20 μm thick aluminum foil, and then rolled and dried to produce a circular anode with a diameter of 12 mm.

[0077] The cathode was fabricated as a 0.3 mm thick lithium thin film in a circular shape with a diameter of 10 mm.

[0078] The positive electrode, the separator, and the negative electrode were sequentially stacked within a CR2032 coin-type battery case. Specifically, a porous coating layer formed from the first coating slurry was positioned to face the positive electrode. The electrode assembly was wound and housed within the coin-type battery case, and an electrolyte solution was prepared by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 50:50 and dissolving LiPF6 to a concentration of 1.0 M, and then injecting the solution to manufacture a coin-type electrochemical device.

[0079] Comparative Example 1

[0080] Li as lithium metal phosphate in the preparation of the first coating slurry above 1.3 Al 0.3 Ti 1.7 Except for using (PO4)3(LATP) particles (average particle size 0.6 μm), a separator for an electrochemical device was prepared in the same manner as in Example 1, and an electrochemical device including the separator was prepared.

[0081] Comparative Example 2

[0082] Li as lithium metal phosphate in the preparation of the first coating slurry above 1.4 Al 0.3 Ti 1.6 Except for using (PO4)3(LATP) particles (average particle size 0.6 μm), a separator for an electrochemical device was prepared in the same manner as in Example 1, and an electrochemical device including the separator was prepared.

[0083] Comparative Example 3

[0084] Li as lithium metal phosphate in the preparation of the first coating slurry above 1.5 Al 0.5 Ti 1.5 Except for using (PO4)3(LATP) particles (average particle size 0.6 μm), a separator for an electrochemical device was prepared in the same manner as in Example 1, and an electrochemical device including the separator was prepared.

[0085] Comparative Example 4

[0086] Li as lithium metal phosphate in the preparation of the first coating slurry above 1.6 Al 0.6 Ti 1.4 Except for using (PO4)3(LATP) particles (average particle size 0.6 μm), a separator for an electrochemical device was prepared in the same manner as in Example 1, and an electrochemical device including the separator was prepared.

[0087]

[0088] Experimental Example.

[0089] Verification of ion conductivity of the separator

[0090] The charge transfer resistance (R-) of the electrochemical devices of the above examples and comparative examples was measured through Electrochemical Impedance Spectroscopy (EIS) of the copper-type cell using a Potentiostat (VSP classic, Bio-Logic). ct ) was measured and shown in Table 1.

[0091] Cycle capacity retention rate measurement

[0092] The electrochemical devices of the above examples and comparative examples were charged and discharged three times at 0.2C in a 25°C chamber in a voltage range of 2.8 V to 4.5 V, and then the life characteristics were measured for 30 cycles while performing 1.0C charging and 1.0C discharging, and the results are shown in Table 1 below. At this time, the life characteristics were expressed as a capacity retention rate calculated by the ratio of the discharge capacity after 30 cycles to the discharge capacity at the first discharge.

[0093] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 LATP(Li 1+x Al x Ti 2-x(PO4)3) Degree of Al substitution of particles (x) 0.3 0.3 0.4 0.5 0.6 Average LATP particle size (D50, μm) 20.6 0.6 0.6 0.6 LATP particle:polymer binder weight ratio 97.5:2.5 97.5:2.5 97.5:2.5 97.5:2.5 97.5:2.5 Polymer binder (type) Non-particulate Non-particulate Non-particulate Non-particulate Non-particulate Porous coating layer containing LATP Facing electrode Anode Anode Anode Anode R ct (Ω)46.03435.8489.7511.5922.5 Capacitance Retention(%)52.443.033.037.837.0

Claims

1. Porous substrate; and LATP(Li 1+x Al x Ti 2-x (PO4)3) particles and a polymer binder, and a porous coating layer formed on one surface of the porous substrate, A separator for an electrochemical device, wherein x is a real number from 0.2 to 0.

4.

2. In Paragraph 1, The above LATP particles are separators for electrochemical devices having an average particle size (D50) of 1 to 3 μm.

3. In Paragraph 1, A separator for an electrochemical device, wherein the thickness of the porous coating layer is 1 to 3.5 μm.

4. In Paragraph 1, The above polymer binder is a non-particulate acrylic binder, and A separator for an electrochemical device, wherein the porous coating layer comprises 15 weight percent or less of the polymer binder.

5. In Paragraph 1, The above polymer binder is a separator for an electrochemical device having a glass transition temperature of 0°C or lower.

6. Includes an anode, a cathode, and a separator disposed between the anode and the cathode, and The above separator is a cylindrical electrochemical device, which is a separator for an electrochemical device according to any one of claims 1 to 5.

7. In Paragraph 6, A cylindrical electrochemical device in which the porous coating layer is positioned to face the anode.

8. In Paragraph 6, The above separator is formed on the other side of the porous substrate and further comprises a second porous coating layer comprising inorganic particles and a polymer binder, A cylindrical electrochemical device in which the above-mentioned inorganic particles are different from the above-mentioned LATP particles.