Separator for lithium secondary battery and manufacturing method thereof

Abstract

To provide a separator for an electrochemical element with excellent wettability of the electrolyte and adhesion to the electrode.SOLUTION: The separator has an organic / inorganic composite porous coating layer formed on the surface of a polymer base material. The organic / inorganic composite porous coating layer is configured such that a first region having a high content of inorganic particles and a second region having a low content of inorganic particles are arranged therein. The first region improves the wettability with the electrolyte, while the second region enables high adhesion to the electrode to be maintained.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a separator for a lithium secondary battery and a method for producing the same. This application claims priority based on Korean Patent Application No. 2022-0026842, filed on March 2, 2022, the entire contents of which are incorporated herein by reference in their entirety in the specification and drawings thereof. [Background technology]

[0002] In recent years, interest in energy storage technology has been growing. Applications are expanding to include mobile phones, camcorders, laptops, and even electric vehicles. This has led to more and more research and development efforts into electrochemical devices. Among the wide range of electrochemical devices, lithium secondary batteries have been gaining attention due to their rechargeability, high operating voltage, and significantly higher energy density.

[0003] A lithium secondary battery is manufactured by using a material into which lithium ions can be inserted and extracted as the active material of a positive electrode and a negative electrode, respectively, disposing a porous separator between the positive electrode and the negative electrode, and then injecting a liquid electrolyte. Electricity is generated or consumed by an oxidation-reduction reaction caused by the insertion and extraction of lithium ions in the negative electrode and the positive electrode.

[0004] As the porous separator, a microporous membrane made of a polyolefin material is used, or a composite separator in which a coating layer containing inorganic particles is formed on the surface of a microporous membrane in consideration of improving mechanical properties and safety is used.

[0005] On the other hand, as part of efforts to increase the energy density of batteries, the development of larger-area batteries has been considered. However, when the battery area is increased, the electrolyte does not flow smoothly to the center of the battery, and the migration of lithium ions is restricted due to a lack of electrolyte in areas that are not wetted by the electrolyte. In response, lithium is precipitated in areas where the migration of lithium ions is concentrated. For this reason, there is currently a need to develop separators that improve the inflow of electrolyte into the interior of large-area batteries. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a separator for an electrochemical element that has excellent wettability with an electrolyte and adhesive strength to an electrode.

[0007] As will be readily apparent from the following description, the objects and advantages of the present invention can be realized by any of the means or methods and combinations thereof set forth in the appended claims. [Means for solving the problem]

[0008] In order to solve the above problems, a first aspect of the present invention provides a separator for an electrochemical element according to the following embodiments.

[0009] A separator for an electrochemical element according to a first aspect includes a porous polymer substrate and a porous organic / inorganic composite coating layer formed on both surfaces or on at least one surface of the polymer substrate, the organic / inorganic composite coating layer being defined into a first region and a second region, the first region and the second region each independently containing inorganic particles and a binder material, and the separator is structurally characterized in that the content ratio of inorganic particles in the first region based on Formula 1 is higher than the content ratio of inorganic particles in the second region based on Formula 2. [Formula 1] Inorganic particle content ratio (wt%) of the first region = [amount of inorganic particles in the first region / (amount of inorganic particles in the first region + amount of binder material in the first region)] × 100 (1) [Formula 2] The content ratio (wt%) of inorganic particles in the second region = [the amount of inorganic particles in the second region / (the amount of inorganic particles in the second region + the amount of binder material in the second region)] × 100 (2)

[0010] According to a second aspect, the separator for an electrochemical element according to the first aspect may be such that the porosity of the first region in the coating layer is higher than the porosity of the second region.

[0011] According to a third aspect, the separator for electrochemical elements may be the separator for electrochemical elements according to the first or second aspect, wherein the content ratio of inorganic particles in the first region is higher than that in the second region and is 70 wt % or more and 90 wt % or less.

[0012] According to a fourth aspect, the separator for electrochemical elements may be the separator for electrochemical elements according to any one of the first to third aspects, wherein the content ratio of inorganic particles in the second region is lower than that in the first region and is 85 wt % or less.

[0013] According to a fifth aspect, the separator for an electrochemical element may be the separator for an electrochemical element according to any one of the first to fourth aspects, wherein the second region is disposed in a partial section around the first region, and at least a part of a side surface of the first region is exposed to the outside, and the second region is disposed so as to be in contact with the boundary of the first region.

[0014] According to a sixth aspect, the separator for an electrochemical element according to any one of the first to fifth aspects may be such that the second region is a single, integral region or is divided into two or more units, one of which is disposed apart from the other units.

[0015] According to a seventh aspect, the separator for electrochemical elements may be the separator for electrochemical elements according to any one of the first to sixth aspects, in which the first region is arranged in a rectangular shape inside the surface of the polymer-based material, and the second region has units arranged on one side of the first region and on another side opposite the first region, and no second region is arranged on the remaining two sides.

[0016] According to an eighth aspect, the separator may be a separator for an electrochemical element according to any one of the first to seventh aspects, wherein the separator is a rectangle having an aspect ratio of more than 1, and the second regions are respectively disposed on two shorter sides of the separator.

[0017] A second aspect of the present invention provides an electrochemical device according to the following embodiment.

[0018] An electrochemical device according to a ninth aspect relates to an electrochemical device including an electrode assembly including a positive electrode, a negative electrode, and a separator sandwiched between the positive electrode and the negative electrode, wherein the separator is one of the first to eighth aspects.

[0019] According to a tenth aspect, the electrochemical device may be the electrochemical device according to the ninth aspect, which is a lithium ion secondary battery.

[0020] A third aspect of the present invention provides a method for producing a separator according to the following embodiment.

[0021] A method for producing a separator according to an eleventh aspect is a method for producing the separator according to any one of the first to eighth aspects, and the method is carried out by a roll-to-roll process in which a long, rectangular polymer substrate is continuously supplied, and includes the steps of forming second regions having predetermined widths at both ends of the polymer substrate in a width direction (TD direction) perpendicular to the running direction (MD direction) and forming a first region between the second regions to obtain a separator strip including a composite coating layer having the first and second regions.

[0022] According to a twelfth aspect, the method for producing the separator according to the eleventh aspect may be such that the first region and the second region are formed by applying slurries for forming the first region and the second region to defined portions using a double slot die.

[0023] According to a thirteenth aspect, the method for producing the separator according to the eleventh or twelfth aspect may include cutting the separator strip to a predetermined width to obtain a separator, and exposing side surfaces of the first region at both ends in the MD direction of the polymer-based material. [Effects of the Invention]

[0024] A separator according to one aspect of the present invention includes an organic / inorganic composite porous coating layer formed on the surface of a polymer substrate, the organic / inorganic composite porous coating layer having a first region with a high content of inorganic particles and a second region with a low content of inorganic particles. The first region can improve wettability with an electrolyte, and the second region can maintain high adhesive strength with an electrode, but the effects of the present invention are not limited thereto. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a schematic diagram of a separator according to the present invention. [Figure 2]1 is a schematic diagram illustrating a method for manufacturing a separator according to the present invention. [Figure 3] 1 is a photographic image of the negative electrode surface taken out from the battery of Example 1. [Figure 4] 1 is a photographic image of the negative electrode surface removed from the battery of Example 2. [Figure 5] 1 is a photographic image of the negative electrode surface taken out from the battery of Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention will be described in detail below. Prior to this, the terms and words used in this specification and claims should not be construed as being limited to their ordinary or dictionary meanings, but should be construed as having meanings and concepts that correspond to the technical ideas of the present invention, based on the principle that the inventor himself can appropriately define the concepts of terms in order to best describe the invention. Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent the entire technical ideas of the present invention, and therefore, various equivalents and modifications that can be substituted therefor may exist at the time of filing this application.

[0027] Throughout this specification, when a part is described as "comprising" a certain component, this does not mean that other components are excluded, and that other components may also be included, unless otherwise specified.

[0028] Throughout this specification, the phrase "A and / or B" means "A or B or both."

[0029] One aspect of the present invention relates to a separator for an electrochemical element.

[0030] The electrochemical device is a device that converts chemical energy into electrical energy through an electrochemical reaction, and is a concept that encompasses both primary and secondary batteries. The secondary battery is capable of charging and discharging, and is a concept that encompasses lithium ion batteries, nickel-cadmium batteries, nickel-metal hydride batteries, etc.

[0031] In this specification, the separator serves as a porosity-conducting barrier that allows ions to pass through while blocking electrical contact between the negative and positive electrodes in an electrochemical device. Preferably, the separator has a plurality of pores formed therein, and the pores are interconnected to allow gas and / or liquid to pass from one side of the separator to the other.

[0032] A separator 100 according to one aspect of the present invention includes a porous polymer substrate 110 that includes a plurality of pores and a polymer material. The separator also includes a porous organic / inorganic composite coating layer (hereinafter referred to as coating layer 120) disposed on both surfaces or on at least one surface of the polymer substrate 110.

[0033] In one embodiment of the present invention, the coating layer may have a layered structure containing inorganic particles and a binder material, and the inorganic particles may be bound by the binder material. The coating layer has a porous structure due to spaces (interstitial volumes) formed between the inorganic particles. This porous structure may improve the separator's ability to retain electrolyte.

[0034] In one embodiment of the present invention, the coating layer may be 3 vol% to 40 vol% of the separator based on 100 vol% of the total volume of the entire separator, and simultaneously or independently, the thickness of the coating layer may be 5% to 50% of the total film thickness of the entire separator (100%).

[0035] In one embodiment of the present invention, the polymer substrate is a sheet-like porous membrane containing a polymer material and having a plurality of pores. For example, the polymer substrate may be in the form of at least one sheet selected from the group consisting of porous polymer films and nonwoven fabrics. The pores include open pores, and the open pores are interconnected to allow gas and / or liquid to pass from one side of the polymer substrate to the other.

[0036] In one embodiment of the present invention, the polymer-based material may have an air permeability of 2000 sec / 100 cc or less and a porosity of 30 vol% to 60 vol% in terms of battery output and cycle characteristics. Meanwhile, in the present invention, the polymer-based material may have a pore diameter in the range of 10 nm to 100 nm.

[0037] In the present invention, the air permeability refers to the time (seconds) required for 100 ml of air to pass through a polymer substrate or separator having a size of 1 square inch under a constant air pressure of 4.8 inches. The air permeability can be measured, for example, using an EG01-55-1MR device manufactured by Asahi Seiko Co., Ltd.

[0038] In the present invention, the term "porosity" refers to the ratio of the volume occupied by pores to the total volume, and is expressed in units of vol%. The term "porosity" can be used interchangeably with terms such as "void ratio" and "porosity." The method for measuring the porosity is not particularly limited, and according to one embodiment of the present invention, the porosity can be measured, for example, by the Brunauer-Emmett-Teller (BET) measurement method using nitrogen gas or a mercury porosimeter. Alternatively, in one embodiment of the present invention, the true density of the object to be measured can be calculated from the density (apparent density) of the object to be measured for porosity, the composition ratio of the components constituting the object, and the density of each component, and the porosity of the object can be calculated from the difference between the apparent density and the true density (net density).

[0039] In one embodiment of the present invention, the polymer substrate may have a thickness of 5 μm to 20 μm in view of achieving a thinner electrochemical device and a higher energy density. If the thickness of the polymer substrate is less than this range, the conductive barrier function may be insufficient. On the other hand, if the thickness excessively exceeds this range (i.e., is too thick), the resistance of the separator may excessively increase.

[0040] In one embodiment of the present invention, the polymer material is preferably a thermoplastic resin having a melting point of 200°C or less, and may include one or more polyolefin-based resins, from the viewpoint of providing a shutdown function. The shutdown function refers to the function of preventing thermal runaway of the battery by blocking the movement of ions between the positive and negative electrodes when the temperature of the battery rises and closing the pores of the polymer substrate by the polymer resin melting.

[0041] The polyolefin resin may include, for example, one or more selected from the group consisting of polyethylene, polypropylene, polybutene, and polypentene. In particular, the polyolefin resin may be polyethylene and / or polypropylene. In addition to the polyolefin resin, the polymer material may further include one or more selected from polymer resins such as polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalene.

[0042] Next, the inorganic particles and binder material contained in the coating layer of the separator will be described.

[0043] In one embodiment of the present invention, the inorganic particles are not particularly limited as long as they have a particle size smaller than the desired thickness of the coating layer, for example, a particle size 1 / 2 to 1 / 1,000 of the thickness of the coating layer, and are electrochemically stable. For example, the diameter of the inorganic particles may be 10 nm or more. On the other hand, the diameter of the inorganic particles may be, for example, 10 μm or less, 7 μm or less, 5 μm or less, 2 μm or less, or 1 μm or less. That is, the inorganic particles are selected to be within the operating voltage range (e.g., Li / Li) of the applied electrochemical device. + There are no particular limitations on the inorganic particles, as long as they do not undergo oxidation and / or reduction reactions at a potential of 0 to 5 V relative to the reference potential. In particular, when inorganic particles with ion-transfer ability are used, the ionic conductivity in the electrochemical device can be increased, thereby improving performance. Furthermore, when inorganic particles with a high dielectric constant are used as the inorganic particles, they can contribute to an increase in the degree of dissociation of the electrolyte salt, for example, lithium salt, in the liquid electrolyte, thereby improving the ionic conductivity of the electrolyte solution.

[0044] For the reasons mentioned above, in a specific embodiment of the present invention, the inorganic particles may include high-dielectric-constant inorganic particles having a dielectric constant of 5 or more, or 10 or more, inorganic particles having lithium ion conductivity, or a mixture thereof. Non-limiting examples of inorganic particles having a dielectric constant of 5 or more include BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT, where 0 <x<1,0<y<1である。)、Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3 (PMN-PT), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, SiC, TiO2, etc. can be used alone or in combination of two or more. In particular, the above-mentioned BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT, where 0 <x<1,0<y<1である。)、Pb(Mg 1 / 3 Nb 2 / 3 Inorganic particles such as )O3-PbTiO3 (PMN-PT) and hafnia (HfO2) not only exhibit high dielectric constant characteristics with a dielectric constant of over 100, but also possess piezoelectricity, which generates a potential difference between the two surfaces when stretched or compressed by applying a certain amount of pressure, thereby preventing internal short circuits between the electrodes due to external impacts and improving the safety of electrochemical devices. Furthermore, when the aforementioned high dielectric constant inorganic particles are mixed with inorganic particles with lithium ion transport ability, the synergistic effect can be doubled.

[0045] In a specific embodiment of the present invention, the inorganic particles having lithium ion conductivity refer to inorganic particles that contain lithium element but do not store lithium and have the function of moving lithium ions. Since the inorganic particles having lithium ion conductivity can transfer and move lithium ions due to a kind of defect existing inside the particle structure, the conductivity of lithium ions in the battery is improved, and thereby, the battery performance can be enhanced. Non-limiting examples of the inorganic particles having lithium ion conductivity include lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) x O y -based glasses such as 14Li2O - 9Al2O3 - 38TiO2 - 39P2O5 (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), lithium germanium thiophosphate such as Li 3.25 Ge 0.25 P 0.75 S4 (Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), lithium nitride such as Li3N (Li x N y , 0 < x < 4, 0 < y < 2), SiS2 - based glasses such as Li3PO4 - Li2S - SiS2 (Li[[ID=…]] x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4), P2S5 - based glasses such as LiI - Li2S - P2S5 (Li… x P y S z , 0 < x < 3, 0 < y < 3, 0 < z < 7) or mixtures thereof, and the like.

[0046] In one embodiment of the present invention, non-limiting examples of binder materials that can be used in the coating layer include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene-co-vinyl acetate, polyethylene oxide, and the like. Examples of the polymer resin include any one polymer resin selected from the group consisting of polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, and carboxyl methyl cellulose, or a mixture of two or more of these polymer resins, but are not limited thereto.

[0047] On the other hand, in a separator according to one embodiment of the present invention, the coating layer is defined into a first region and a second region, and the first region and the second region each independently contain inorganic particles and a binder material, and it may be preferable that the content ratio of the inorganic particles in the first region based on Formula 1 is higher than the content ratio of the inorganic particles in the second region based on Formula 2.

[0048] [Formula 1] Inorganic particle content ratio (wt%) of the first region = [amount of inorganic particles in the first region / (amount of inorganic particles in the first region + amount of binder material in the first region)] × 100 (1) [Formula 2] Inorganic particle content ratio (wt%) of the second region = [amount of inorganic particles in the second region / (amount of inorganic particles in the second region + amount of binder material in the second region)] × 100 (2)

[0049] 1 shows the configuration of a separator 100 according to one embodiment of the present invention. Referring to the figure, a first region 121 having a high content ratio of inorganic particles is disposed, a side portion of the first region is exposed to the outside, and second regions 122 having a low content ratio of inorganic particles are disposed on two opposing sides of the first region.

[0050] As described above, since the coating layer 120 has a first region and a second region, when the separator according to the present invention is used to manufacture an electrode, the first region promotes the flow of electrolyte into the interior of the battery, and at the same time, since the second region has a higher content of binder material than the first region, the second region can be used to achieve high adhesion between the separator and the electrode.

[0051] In one embodiment of the present invention, the inorganic particle content of the first region is higher than the inorganic particle content of the second region, and may be 70 wt% or more, 75 wt% or more, or 80 wt% or more. Alternatively, the inorganic particle content may be 90 wt% or less within the above range. Meanwhile, in a preferred embodiment of the present invention, the binder resin content of the first region is preferably greater than 10 wt%. If the binder resin content is less than this range, it is difficult to ensure the adhesive strength between the separator and the electrode required to maintain the dimensional stability and durability of the electrode assembly. In one embodiment of the present invention, the inorganic particle content of the second region is lower than the inorganic particle content of the first region, and may be less than 90 wt%, 89 wt% or less, 85 wt% or less, 80 wt% or less, or 75 wt% or less. In one embodiment of the present invention, the content of the inorganic particles may be greater than 75 wt% in the first region and less than 75 wt% in the second region, or greater than 80 wt% in the first region and less than 80 wt% in the second region.

[0052] In one embodiment of the present invention, the porosity may increase as the content of inorganic particles increases, and therefore the porosity of the first region may be higher than the porosity of the second region, while the air permeability (sec / 100cc) of the first region may be lower than that of the second region.

[0053] Next, various embodiments of the coating layer will be described by way of example, however, the provided embodiments are merely for the purpose of enhancing understanding of the present invention and are not intended to limit the scope of the present invention in any way.

[0054] In one embodiment of the present invention, the second region is preferably disposed in a section surrounding the first region, with at least a portion of the side surface of the first region exposed to the outside. The second region is also disposed so as to border the first region. In the separator according to the present invention, the first region is disposed in the coating layer to promote the inflow of the electrolyte into the interior. The first region has a low binder resin content and a high inorganic particle content, and therefore exhibits relatively weaker adhesive strength and cohesion with the electrode than the second region. In the case of the second region, the separator and electrode exhibit relatively stronger adhesion than the first region, which may hinder the electrolyte from penetrating between them. For this reason, the electrolyte flows through the first region more quickly and easily than through the second region. During battery fabrication, the top and bottom surfaces of the separator contact the electrodes, so the electrolyte flows through the sides of the separator. Therefore, if the entire area around the first region is surrounded by the second region, i.e., if the side surfaces of the first region are completely covered by the second region, it is difficult to achieve the effect of promoting the flow of electrolyte.

[0055] In one embodiment of the present invention, the second region may be formed as a single, integrated region. In another embodiment, the second region may be divided into two or more units, with one of the units being spaced apart from the other units. On the other hand, when the second region is divided into two or more units and multiple units are provided, distributing the units spaced apart from each other can ensure uniform adhesive strength with the electrodes throughout the separator.

[0056] In a specific embodiment of the present invention, the first region may be arranged in a rectangular shape inside the surface of the polymer substrate, and the second region may have units arranged on one side of the first region and the other side opposite the first region, with no second region arranged on the remaining two sides. When the second region is arranged in this shape, electrolyte inflow is promoted through the side of the first region where the second region is not arranged, enabling the electrodes and separator to be bonded with high adhesive strength at both ends of the separator's width direction or both ends of the separator's length. In one embodiment of the present invention, taking into account the side of electrolyte inflow, if the separator is rectangular with an aspect ratio greater than 1, the second region may be arranged on each of the two short sides of the separator, with the long side of the separator exposed. In one embodiment of the present invention, as described below, the separator is manufactured in a strip shape with a length in the MD direction longer than the length in the TD direction, and therefore the second region may be formed on the long side of the separator strip during the manufacturing process. However, the separator strip is cut to a predetermined width using a tool such as a cutter to obtain a separator, and the obtained separator is used to assemble a battery, so that a separator with a rectangular shape (during the manufacturing process) that is short in the MD direction and long in the TD direction can be finally provided. In this case, the second region may be disposed on the short side of the manufactured separator.

[0057] FIG. 1 is a schematic diagram illustrating a separator according to one embodiment of the present invention. Referring to the figure, the first region is formed in a rectangular shape having four sides, and the second region is disposed in a section surrounding the first region. More specifically, the second region is composed of two units, one of which is disposed so as to contact one side of the first region, and the other unit is disposed on the other side opposite the first region. Furthermore, the side surfaces of the first region are exposed on the remaining two sides where the second region is not disposed.

[0058] 2 is a schematic diagram showing a method for manufacturing a separator according to one embodiment of the present invention, which will be described with reference to the drawing.

[0059] The separator can be manufactured using a continuous process using a roll-to-roll method. Referring to FIG. 2, a long, rectangular polymer substrate 110 is continuously supplied by a traveling roll of a roll-to-roll device, and a slurry for forming a coating layer is applied to the surface of the polymer substrate. The application of the slurry can be performed using a conventional application device 300 such as a slot die. Meanwhile, the slurry is divided into a slurry for forming the first region and a slurry for forming the second region, and each slurry can be prepared by adding inorganic particles and a binder material to an appropriate solvent.

[0060] Once each slurry is prepared, the second region-forming slurry is applied to both ends of the polymer substrate in the width direction (TD) perpendicular to the running direction (MD), and the first region-forming slurry is applied to the area between the second regions. The first and second region-forming slurries can be applied simultaneously using a double slot die, or by applying the first or second region-forming slurry first and then sequentially applying the remaining slurries. For example, the first region-forming slurry can be applied to a predetermined position inside the polymer substrate, and the second region-forming slurry can be applied to both ends of the width direction where the first region-forming slurry has been applied continuously.

[0061] The applied slurry is then dried to obtain a separator strip including a composite coating layer having a first region and a second region. The drying can be performed by applying heat or air while passing through a dryer 500. The separator strip is then cut to a predetermined width using a tool such as a cutter 400 to obtain a separator. At this time, the obtained separator has the side surfaces of the first region exposed at both ends in the MD direction of the polymer substrate.

[0062] According to another aspect of the present invention, there is provided an electrochemical device in which the above-described separator for a lithium secondary battery is interposed between a positive electrode and a negative electrode.

[0063] In one embodiment of the present invention, the electrochemical device may be a lithium ion secondary battery.

[0064] In a specific embodiment of the present invention, the electrochemical device can be manufactured by injecting a non-aqueous electrolyte solution, if necessary, into an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, stacked in this order. In this case, the positive electrode, the negative electrode, and the non-aqueous electrolyte solution constituting the electrode assembly may be any of those commonly used in the manufacture of lithium secondary batteries.

[0065] In a specific embodiment of the present invention, the positive electrode may be manufactured by forming a positive electrode mixture layer on a positive electrode current collector, which may be formed by coating a positive electrode slurry containing a positive electrode active material, a binder, a conductive material, and a solvent on the positive electrode current collector, followed by drying and rolling.

[0066] In a specific embodiment of the present invention, the positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like can be used.

[0067] In one specific embodiment of the present invention, the positive electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound (intercalation compound)).

[0068] In a specific embodiment of the present invention, the positive electrode active material may include, but is not limited to, lithium transition metal oxides; lithium metal iron phosphate; lithium nickel-manganese-cobalt oxide; an oxide in which a portion of the lithium nickel-manganese-cobalt oxide is substituted with another transition metal; or two or more of these. Specifically, the positive electrode active material may include, but is not limited to, layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), or compounds substituted with one or more transition metals; 1+x Mn 2-x Lithium manganese oxides such as LiMnO4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, and Cu2V2O7; and the chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by the formula LiMnO2 (where M=Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x=0.01 to 0.3); 2-x M x Lithium manganese composite oxides represented by Li2Mn3MO8 (where M is Co, Ni, Fe, Cr, Zn, or Ta, and x is 0.01 to 0.1); lithium metal phosphate oxides represented by LiMPO4 (where M is Fe, CO, Ni, or Mn); lithium nickel-manganese-cobalt oxides represented by LiMPO4 (where M is Fe, CO, Ni, or Mn); 1+x (Ni a Co b Mn c ) 1-x O2 (x=0~0.03, a=0.3~0.95, b=0.01~0.35, c=0.01~0.5, a+b+c=1); Lithium nickel-manganese-cobalt oxide, in which a portion of the oxide is replaced by aluminum a [Ni b Co c Mn d Al e ] 1-f M1 fO2 (M1 is any one or more selected from the group consisting of Zr, B, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, F, P, and S, 0.8 ≦ a ≦ 1.2, 0.5 ≦ b ≦ 0.99, 0 < c < 0.5, 0 < d < 0.5, 0.01 ≦ e ≦ 0.1, 0 ≦ f ≦ 0.1); an oxide in which a part of lithium nickel - manganese - cobalt oxide is substituted with another transition metal Li 1+x (Ni a Co b Mn c M d ) 1-x O2 (x = 0 to 0.03, a = 0.3 to 0.95, b = 0.01 to 0.35, c = 0.01 to 0.5, d = 0.001 to 0.03, a + b + c + d = 1, M is any one selected from the group consisting of Fe, V, Cr, Ti, W, Ta, Mg, and Mo.). Disulfide compounds; Fe2(MoO4)3 and the like can be mentioned, but it is not limited only to these.

[0069] In a specific embodiment of the present invention, the positive electrode may further selectively contain a conductive material. The conductive material may be porous. Therefore, as the conductive material, any material having porosity and conductivity can be used without particular limitation. For example, a carbon - based substance having porosity can be used. As such a carbon - based substance, carbon black, graphite, graphene, activated carbon, carbon fiber, carbon nanotube (CNT), etc. can be used. Further, as the conductive material, metallic conductive materials such as metal fibers and metal meshes; metallic powders such as copper, silver, nickel, and aluminum; or organic conductive materials such as polyphenylene derivatives can also be used. The conductive material can be used alone or in combination.

[0070] In a specific embodiment of the present invention, the positive electrode may further include a binder, which may be a thermoplastic resin or a thermosetting resin. More specifically, examples of the binder that can be used include polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, and ethylene-acrylic acid copolymer, either alone or in combination. However, the binder is not necessarily limited to these, and any binder that can be used in the relevant technical field can be used.

[0071] In one specific embodiment of the present invention, the positive electrode active material may be contained in an amount of 80 wt % to 99 wt % based on the total weight of the solid content in the positive electrode slurry.

[0072] In a specific embodiment of the present invention, the solvent used in the positive electrode slurry may include an organic solvent such as N-methyl-2-pyrrolidone (NMP), and may be used in an amount that provides a suitable viscosity when the positive electrode active material and, optionally, a binder and a conductive material are included. For example, the solvent may be included so that the solids concentration in the slurry containing the positive electrode active material and, optionally, a binder and a conductive material is 50 wt % to 95 wt %, preferably 70 wt % to 90 wt %.

[0073] In one specific embodiment of the present invention, the positive electrode can be manufactured by mixing a positive electrode active material, an optional conductive material (referred to as a conductive material), and an optional binder to prepare a composition for forming a positive electrode active material layer, and then applying the composition to at least one surface of the positive electrode current collector, drying, and rolling. Alternatively, the positive electrode can be manufactured by casting the composition for forming a positive electrode active material layer on a separate support, peeling it off from the support, and laminating the resulting film on the positive electrode current collector.

[0074] In a specific embodiment of the present invention, the negative electrode may be manufactured by forming a negative electrode mixture layer on a negative electrode current collector, which may be formed by coating a negative electrode slurry containing a negative electrode active material, a binder, a conductive material, and a solvent on the negative electrode current collector, followed by drying and rolling.

[0075] In a specific embodiment of the present invention, the negative electrode active material may include lithium metal, a carbon material capable of reversibly intercalating / deintercalating lithium ions, a metal or an alloy of such a metal with lithium, a metal composite oxide, a material capable of doping and dedoping lithium, a transition metal oxide, or a mixture of two or more of these.

[0076] The carbonaceous material capable of reversibly intercalating / deintercalating lithium ions, which is an example of the negative electrode active material, may be any carbonaceous negative electrode active material commonly used in lithium ion secondary batteries, and representative examples thereof include crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite, such as amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite. Examples of the amorphous carbon include soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbide, and calcined coke.

[0077] An example of the negative electrode active material is that as the metal or an alloy of these metals and lithium, metals such as Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, Sn, or a mixture of two or more of these metals, or an alloy of these metals and lithium can be used.

[0078] An example of the negative electrode active material is that as the metal composite oxide, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, Li x Fe2O3(0≦x≦1), Li x WO2(0≦x≦1), Sn x Me 1-x Me’ y O z (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8), or a mixture of two or more of these can be used.

[0079] An example of the negative electrode active material is that as the material capable of doping and de-doping lithium, Si, SiO x (0 < x ≦ 2), Si-Y alloy (where Y is an alkali metal, alkaline earth metal, Group 13 element, Group 14 element, transition metal, rare earth element, or a mixture of two or more of these and is not Si), Sn, SnO2, Sn-Y (where Y is an alkali metal, alkaline earth metal, Group 13 element, Group 14 element, transition metal, rare earth element, or a mixture of two or more of these and is not Sn), etc. can be mentioned, and it is also possible to mix at least one of these with SiO2 and use them. Examples of the element Y include Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a mixture of two or more of these.

[0080] Examples of the negative electrode active material, which are the transition metal oxides, include lithium-containing titanium composite oxide (LTO), vanadium oxide, and lithium vanadium oxide.

[0081] In one specific embodiment of the present invention, the negative electrode active material may be contained in an amount of 80 wt % to 99 wt % based on the total weight of the solid content in the negative electrode slurry.

[0082] In a specific embodiment of the present invention, the negative electrode may optionally further include a binder. The binder is a component that aids in bonding between the active material and the current collector, or between the active material, the conductive material, and the current collector, and is typically added in an amount of 1 to 30 wt % based on the total weight of the solids in the negative electrode slurry. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0083] In a specific embodiment of the present invention, the negative electrode may optionally further include a conductive material. The conductive material is a component for further improving the conductivity of the negative electrode active material. When included, the conductive material may be added in an amount of 1 to 20 wt % based on the total weight of the solids in the negative electrode slurry. This conductive material may be the same as or different from the conductive material used in manufacturing the positive electrode. Examples of such conductive materials include carbon powders such as carbon black, acetylene black (or Denka Black), Ketjen Black, channel black, furnace black, lamp black, and summer black; graphite powders such as natural graphite, artificial graphite, and graphite with highly developed crystalline structures; conductive fibers such as carbon fiber and metal fiber; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0084] In a specific embodiment of the present invention, the solvent used in the negative electrode slurry may include water or an organic solvent such as NMP or alcohol, and may be used in an amount that provides a suitable viscosity when the negative electrode active material and, optionally, a binder and a conductive material are included. For example, the solvent may be included so that the solids concentration in the slurry containing the negative electrode active material and, optionally, a binder and a conductive material is 50 wt % to 95 wt %, preferably 70 wt % to 90 wt %.

[0085] In a specific embodiment of the present invention, when a non-aqueous electrolyte is used, the non-aqueous electrolyte may include a lithium salt and an organic solvent, and may further include additives commonly used in the art.

[0086] In one specific embodiment of the present invention, the lithium salt has Li as the cation. + Contains F as an anion - , Cl - , Br - , I - , NO3 - , N(CN)2 - , ClO4 - , BF4- , AlO4 - , AlCl4 - , PF6 - , SbF6 - , AsF6 - , BF2C2O4 - , BC4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , C4F9SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , (CF3CF2SO2)2N - Or it may contain a mixture of two or more of these.

[0087] In one specific embodiment of the present invention, the lithium salt can be used alone or in combination of two or more kinds as needed. The lithium salt can be appropriately changed within a range that is normally usable, but can be contained in the non-aqueous electrolyte at a concentration of 0.01M to 5M, 0.1M to 5M, or 0.1M to 3M.

[0088] In a specific embodiment of the present invention, the organic solvent is not particularly limited as long as it minimizes decomposition due to oxidation or other reactions during charging and discharging of the secondary battery and can exhibit the desired properties together with the additives. For example, ether-based solvents, ester-based solvents, and amide-based solvents can be used alone or in combination.

[0089] In a specific embodiment of the present invention, the ether solvent among the organic solvents may be, but is not limited to, dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, ethyl propyl ether, or a mixture of two or more thereof.

[0090] In one specific embodiment of the present invention, the ester solvent may include a cyclic carbonate compound, a linear carbonate compound, a linear ester compound, a cyclic ester compound, or a mixture of two or more thereof.

[0091] In one specific embodiment of the present invention, specific examples of the cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, fluoroethylene carbonate (FEC), or a mixture of two or more thereof.

[0092] In one embodiment of the present invention, typical examples of the linear carbonate compound that can be used include, but are not limited to, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, or a mixture of two or more of these.

[0093] In one specific embodiment of the present invention, the linear ester compound may be, for example, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, or a mixture of two or more of these, but is not limited thereto.

[0094] In one specific embodiment of the present invention, the cyclic ester compound may be, for example, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, ε-caprolactone, or a mixture of two or more of these, but is not limited thereto.

[0095] In a specific embodiment of the present invention, the cyclic carbonate-based compound is a high-viscosity organic solvent with a high dielectric constant, which effectively dissociates the lithium salt in the electrolyte. Therefore, by mixing the cyclic carbonate-based compound with a low-viscosity, low-dielectric-constant linear carbonate-based compound and a linear ester-based compound, such as dimethyl carbonate and diethyl carbonate, in an appropriate ratio, a non-aqueous electrolyte solution with high electrical conductivity can be prepared.

[0096] A lithium secondary battery separator according to one aspect of the present invention can effectively transfer lithium ions and reduce side reactions at the interface between the ion-conductive polymer separator and an electrode, thereby significantly reducing the rate of increase in the initial resistance inside the battery. As a result, a battery using the separator can exhibit improved power density characteristics and reduced irreversible capacity, thereby improving rate characteristics and shortening the time required for charging or discharging the battery, thereby improving charge / discharge life. Therefore, the separator is suitable for use in portable devices requiring fast charging speeds, such as mobile phones, laptops, digital cameras, and camcorders, electric vehicles such as hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs), and medium- to large-scale energy storage systems.

[0097] In order to deepen understanding of the present invention, examples, comparative examples and experimental examples are presented below. However, the following test examples are merely examples relating to the configuration and effects of the present invention, and the scope and effects of the present invention are not limited to these examples.

[0098] Example: Manufacture of separator [Example 1] Polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) (molecular weight (Mw) 500,000 g / mol, HFP content 15 wt%) and alumina (particle size 0.5 μm) were added to acetone in a weight ratio of 22.5:77.5 to prepare a slurry for forming the first region with a solid content of 20 wt%.

[0099] Next, PVDF-HFP (molecular weight (Mw) 500,000 g / mol, HFP content 15 wt%) and alumina (particle size 0.5 μm) were added to acetone in a weight ratio of 25:75 to prepare a slurry for forming a second region with a solid content of 20 wt%.

[0100] A polyethylene polymer film (film thickness 9 μm, porosity 45 vol%, ventilation time 60 sec / 100 cc) was prepared, and the slurries for forming the first and second regions were applied in this order as shown in Figure 1. The separator was then dried under humidified conditions of 23°C and 45% relative humidity to obtain a separator.

[0101] [Example 2] PVDF-HFP (molecular weight (Mw) 500,000 g / mol, HFP content 15 wt%) and alumina (particle size 0.5 μm) were added to acetone in a weight ratio of 20:80 to prepare a slurry for forming the first region with a solid content of 20 wt%.

[0102] Next, PVDF-HFP (molecular weight (Mw) 500,000 g / mol, HFP content 15 wt%) and alumina (particle size 0.5 μm) were added to acetone in a weight ratio of 25:75 to prepare a slurry for forming a second region with a solid content of 20 wt%.

[0103] A polyethylene polymer film (film thickness 9 μm, porosity 45 vol%, ventilation time 60 sec / 100 cc) was prepared, and the slurries for forming the first and second regions were applied in this order as shown in Figure 1. The separator was then dried under humidified conditions of 23°C and 45% relative humidity to obtain a separator.

[0104] [Comparative Example 1] PVDF-HFP (molecular weight (Mw) 500,000 g / mol, HFP content 15 wt%) and alumina (particle size 0.5 μm) were added to acetone in a weight ratio of 25:75 to prepare a slurry for forming a coating layer with a solid content of 20 wt%.

[0105] A polyethylene polymer film (film thickness 9 μm, porosity 45 vol%, ventilation time 60 sec / 100 cc) was prepared, and the slurry was applied to it. The film was then dried under humidified conditions of 23° C. and 45% relative humidity to obtain a separator.

[0106] Experimental example: Evaluation of separator properties The physical properties of the separator produced above were evaluated according to the following evaluation methods, and the results are shown in Table 1 below and FIGS. 3 to 5. [Evaluation results]

[0107] [Table 1]

[0108] [Evaluation method] 1. Ventilation time The air permeability of the separator was measured using an air permeability measuring device (EGO-IT, manufactured by Asahi Seiko Co., Ltd.) in accordance with JIS P 8117. On the other hand, in order to measure the air permeability of each of the first and second regions, after producing the separator, a sample for measuring the air permeability time was obtained by dividing the first and second regions using a knife.

[0109] 2. Electrode adhesion strength The active material [natural graphite and artificial graphite (weight ratio 5:5)], conductive material [Super P], and binder [polyvinylidene fluoride (PVDF)] were mixed in a weight ratio of 92:2:6, dispersed in water, and then coated onto copper foil with a width of 250 mm to prepare the negative electrode.

[0110] Separators were manufactured and prepared according to Examples 1 and 2 and Comparative Example 1. The prepared separator was divided into a first region and a second region using a knife.

[0111] The separator and negative electrode were stacked and sandwiched between 100 μm PET films, and then laminated using a roll lamination machine at 60°C, a pressure of 2.4 kgf / mm, and a speed of 5 m / min.

[0112] The bonded separator and negative electrode were cut into a size of 25 mm wide and 70 mm long, and the ends of the separator and negative electrode were attached to a universal material testing machine (manufactured by Instron). After that, a force was applied at a 180° angle at a measurement speed of 300 mm / min to measure the force required to peel off the negative electrode and the separator attached to the negative electrode.

[0113] 3. Check the wettability of the electrolyte (1) Manufacturing of the negative electrode Anode slurry was prepared by mixing artificial graphite as anode active material, carbon black as a conductive material, carboxymethyl cellulose (CMC) as a dispersant, and styrene-butadiene rubber (SBR, BM-L301 manufactured by Zeon Corporation) as a binder with water in a weight ratio of 95.8:1:1.2:2. The anode slurry was coated onto copper foil to a thickness of 50 μm to form a thin electrode plate, which was then dried at 135°C for at least 3 hours and pressed to prepare anodes.

[0114] (2) Manufacturing of the positive electrode A cathode slurry was prepared by mixing LiCoO2 as a cathode active material, carbon black as a conductive material, and polyvinylidene fluoride (PVDF) as a binder with N-methyl-2-pyrrolidone (NMP) in a weight ratio of 98:1:1. The cathode slurry was coated onto aluminum foil to a thickness of 20 μm to form a thin electrode plate, which was then dried at 135°C for at least 3 hours and pressed to prepare a cathode.

[0115] (3) Manufacture of lithium secondary batteries Next, the prepared separator was sandwiched between a negative electrode and a positive electrode, and then stacked to prepare a stack-type electrode assembly, which was then inserted into a pouch outer casing. An electrolyte solution prepared by dissolving 1M LiPF6 in a solvent prepared by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 30:70 was then injected to prepare a lithium secondary battery.

[0116] The secondary battery fabricated as described above was disassembled at an SOC of 60, and the negative electrode surface was observed to check for wetting. When wetting was good, the entire negative electrode surface showed a uniform state of charge (FIGS. 3 and 4). However, when wetting was poor, dark, uncharged areas were observed on the negative electrode surface (FIG. 5).

[0117] Although the present invention has been described above using limited embodiments and drawings, the present invention is not limited to these, and it goes without saying that various modifications and variations can be made by a person having ordinary knowledge in the technical field to which the present invention pertains within the technical spirit of the present invention and the scope of equivalents of the claims. [Explanation of symbols]

[0118] 100...Separator 110...Polymer base material 120...organic / inorganic composite coating layer 121...First Area 122...Second Region 300... Coating device 500...Dryer 400...Cutter

Claims

1. The present invention comprises a porous polymer substrate and a porous organic / inorganic composite coating layer formed on both surfaces or on at least one surface of the polymer substrate, the organic / inorganic composite coating layer is defined into a first region and a second region; The first region and the second region each independently contain inorganic particles and a binder material, and the content ratio of the inorganic particles in the first region based on the following formula 1 is higher than the content ratio of the inorganic particles in the second region based on the following formula 2: The separator for an electrochemical element, wherein the organic / inorganic composite coating layer has a single-layer structure in each of the first region and the second region. [Formula 1] Inorganic particle content ratio (wt%) of first region = [amount of inorganic particles in first region / (amount of inorganic particles in first region + amount of binder material in first region)] × 100 (1) [Formula 2] Content ratio (wt%) of inorganic particles in the second region = [amount of inorganic particles in the second region / (amount of inorganic particles in the second region + amount of binder material in the second region)] × 100 (2)

2. 2. The separator for an electrochemical element according to claim 1, wherein the porosity of the first region in the coating layer is higher than the porosity of the second region.

3. 2. The separator for an electrochemical element according to claim 1, wherein the content ratio of the inorganic particles in the first region is higher than that in the second region and is 70 wt % or more and 90 wt % or less.

4. 2. The separator for an electrochemical element according to claim 1, wherein the content ratio of the inorganic particles in the second region is lower than that in the first region and is 85 wt % or less.

5. 2. The separator for an electrochemical element according to claim 1, wherein the second region is disposed in a partial section around the first region, so that at least a portion of a side surface of the first region is exposed to the outside, and the second region is disposed so as to be in contact with the boundary of the first region.

6. 6. The separator for an electrochemical element according to claim 5, wherein the second region is a single, integral region or is divided into two or more units, any one of which is disposed apart from the other units.

7. 6. The separator for electrochemical elements according to claim 5, wherein the first region is arranged in a rectangular shape inside the surface of the polymer substrate, and the second region has units arranged on one side of the first region and on another side opposite the first region, and no second region is arranged on the remaining two sides.

8. 7. The separator for an electrochemical element according to claim 6, wherein the separator is rectangular with an aspect ratio of greater than 1, and the second regions are disposed on two shorter sides of the separator.

9. The battery includes an electrode assembly including a positive electrode, a negative electrode, and a separator sandwiched between the positive electrode and the negative electrode, An electrochemical element, wherein the separator is the separator according to any one of claims 1 to 8.

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

11. A method for producing the separator according to any one of claims 1 to 8, The method is carried out by a roll-to-roll process in which a long, rectangular polymer substrate is continuously supplied, A method for producing a separator for an electrochemical element, comprising the steps of forming second regions having a predetermined width at both ends of the polymer substrate in a width direction (TD direction) perpendicular to the running direction (MD direction), and forming a first region between the second regions to obtain a separator strip including a composite coating layer having the first and second regions.

12. 12. The method for producing a separator for an electrochemical element according to claim 11, wherein the first region and the second region are formed by applying slurries for forming the first region and the second region to defined portions, respectively, using a double slot die.

13. 12. The method for manufacturing a separator for an electrochemical device according to claim 11, wherein the separator strip is cut to a predetermined width to obtain a separator, and side surfaces of the first region are exposed at both ends in the MD direction of the polymer substrate.

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