Separator for lithium secondary battery and manufacturing method for the same

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 manufacturing the same. This application claims priority based on Korean Patent Application No. 2022-0026842 filed on March 2, 2022, and all of the contents disclosed in the specification and drawings of the application are incorporated into this application.

Background Art

[0002] In recent years, interest in energy storage technology has been increasing. The application fields are expanding to mobile phones, camcorders, notebook computers, and even the energy of electric vehicles. Along with this, efforts in research and development related to electrochemical elements are becoming more concrete. Among various electrochemical elements, lithium secondary batteries, which can be charged and discharged, have a high operating voltage, and have a much larger energy density, are in the spotlight.

[0003] A lithium secondary battery is manufactured by using substances into which lithium ions can be inserted and desorbed as the active materials of the positive electrode and the 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 the redox reaction accompanying the insertion and desorption 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 the microporous membrane is used in consideration of improving mechanical physical properties and safety.

[0005] On one hand, as part of efforts to increase the energy density of batteries, the development of large-area batteries is being considered. However, when the area of the battery is increased, the flow of the electrolyte into the central part inside the battery is not smooth. In the parts not wetted by the electrolyte, the movement of lithium ions is restricted due to the lack of electrolyte. On the contrary, there is a problem that lithium is precipitated from the parts where the movement of lithium ions is concentrated. For this reason, at present, there is a demand for the development of a separator with improved electrolyte flow characteristics even inside large-area batteries. Summary of the Invention Problems to be Solved by the Invention

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

[0007] It will be easily understood that the objects and advantages of the present invention can be achieved by the means or methods and combinations thereof shown in the claims. Means for Solving the Problems

[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 aspect.

[0009] The separator for an electrochemical element according to the first aspect includes a porous polymer substrate and a porous organic / inorganic composite coating layer formed on both surfaces or at least one surface of the polymer substrate. The organic / inorganic composite coating layer is defined in 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 Formula 1 is higher than the content ratio of the inorganic particles in the second region based on Formula 2, which is a constitutive feature. [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)

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

[0011] According to the third aspect, it may be a separator for an electrochemical element described in the first aspect or the 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 the fourth aspect, it may be a separator for an electrochemical element described in any one of the first aspect to the third aspect, 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 the fifth aspect, it may be a separator for an electrochemical element described in any one of the first aspect to the fourth aspect, wherein the second region is arranged in a partial section around the first region and at least a part of the side surface of the first region is exposed to the outside, and the second region is arranged so as to be in contact with the boundary of the first region.

[0014] According to the sixth aspect, it may be a separator for an electrochemical element described in any one of the first aspect to the fifth aspect, wherein the second region is a single integrated region or is divided into two or more units, and any one unit is arranged separately from the other units.

[0015] According to the seventh aspect, the first region is arranged in a rectangular shape inside the surface of the polymer substrate, and the second region is arranged with units on any one side of the first region and the other side facing it, respectively. The separator for an electrochemical element according to any one of the first aspect to the sixth aspect, in which the second region is not arranged on the remaining two sides, may be used.

[0016] According to the eighth aspect, the separator is a rectangle with an aspect ratio greater than 1, and the second region is arranged on each of the two short sides of the separator. The separator for an electrochemical element according to any one of the first aspect to the seventh aspect may be used.

[0017] The second aspect of the present invention provides an electrochemical element according to the following aspect.

[0018] The electrochemical element according to the ninth aspect relates to an electrochemical element 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 as described in any one of the first aspect to the eighth aspect.

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

[0020] The third aspect of the present invention provides a method for manufacturing a separator according to the following aspect.

[0021] The method for manufacturing a separator according to the 11th aspect is a method for manufacturing the separator described in any one of the 1st to 8th aspects, and the method is performed by a roll-to-roll process of continuously supplying a long strip-shaped polymer substrate, and a second region having a predetermined width is formed at each of both ends in the width direction (TD direction) perpendicular to the running direction (MD direction) of the polymer substrate, and a first region is formed between the second regions to obtain a separator strip including a composite coating layer having the first region and the second region.

[0022] According to the 12th aspect, the formation of the first region and the second region may be a method for manufacturing the separator described in the 11th aspect, in which the formation of the first region and the second region is performed by applying slurries for forming the first region and the second region to defined parts using a double slot die.

[0023] According to the 13th aspect, the separator strip may be cut to a predetermined width to obtain a separator, which may be a method for manufacturing the separator described in the 11th aspect or the 12th aspect in which the side surfaces of the first region are exposed at both ends in the MD direction of the polymer substrate.

Advantages of the Invention

[0024] The separator according to one aspect of the present invention has an organic / inorganic composite porous coating layer formed on the surface of a polymer substrate, and in the organic / inorganic composite porous coating layer, a first region with a high content of inorganic particles and a second region with a low content of inorganic particles are arranged. The wettability of the electrolyte is improved by the first region, and the high adhesive force with the electrode can be maintained by the second region, but the effects of the present invention are not limited thereto.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0026] Hereinafter, the present invention will be described in detail. Prior to this, terms and words used in this specification and the claims are not to be construed as limited to their ordinary or dictionary meanings. The inventor himself interprets them in accordance with the meaning and concept corresponding to the technical idea of the present invention in accordance with the principle that he can appropriately define the concept of the terms in order to explain the invention in the best way. Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention. At the time of this application, there can be various equivalents and modifications that can replace these.

[0027] Throughout this specification, when a certain part states that a certain component "includes", this means, unless otherwise specified, that it does not exclude other components and may further include other components.

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

[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 encompasses the concepts of primary batteries and secondary batteries. The secondary battery is capable of charging and discharging, and encompasses concepts such as lithium-ion batteries, nickel-cadmium batteries, nickel-metal hydride batteries, etc.

[0031] In this specification, the separator serves as an ion-conducting barrier that allows ions to pass through while blocking electrical contact between the negative electrode and the positive electrode in the electrochemical device. A plurality of pores are formed inside the separator, and the pores are interconnected, and it is preferable that gas and / or liquid can pass from one side surface to the other side surface of the separator.

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

[0033] In one embodiment of the present invention, the coating layer includes inorganic particles and a binder material, and the inorganic particles may have a layered structure bound by the binder material. The coating layer has a porous structure resulting from the spaces (interstitial volumes) formed between the inorganic particles. Such a porous structure has the effect of improving the electrolyte retention capacity of the separator.

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

[0035] In one embodiment of the present invention, the polymer substrate includes a polymer material and is a sheet-like porous film having a plurality of pores. For example, the polymer substrate may have a form including one or more selected from among porous polymer films and non-woven fabrics, each in one or more sheets. The pores include open pores, and the open pores are interconnected so that gas and / or liquid can pass through from one side surface to the other side surface of the polymer substrate.

[0036] In one embodiment of the present invention, from the aspect of the output and cycle characteristics of the battery, the polymer substrate may have an air permeability of 2000 sec / 100 cc or less and a porosity of 30 vol% to 60 vol%. On the other hand, in the present invention, the polymer substrate may have a pore diameter in the range of 10 nm to 100 nm.

[0037] In the present invention, the air permeability means 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 porosity means the ratio of the volume occupied by pores to the total volume, and vol% is used as its unit, and it can be used interchangeably with terms such as void fraction and porosity. In the present invention, the measurement of the porosity is not particularly limited, and according to one embodiment of the present invention, for example, it can be measured by the Brunauer-Emmett-Teller (BET) measurement method using nitrogen gas or the mercury porosimeter method. Alternatively, in one embodiment of the present invention, the true density of the measurement object is calculated from the density (apparent density) of the measurement object of the porosity, the composition ratio of the components constituting the object, and the density of each component, and the porosity of the measurement object can be calculated from the difference between the apparent density and the true density.

[0039] In one embodiment of the present invention, from the aspect of thinning and increasing the energy density of the electrochemical device, the polymer substrate can have a thickness of 5 μm to 20 μm. When the thickness of the polymer substrate is less than the above numerical range, the function of the conductive barrier is insufficient. On the contrary, when the above range is exceeded excessively (that is, when it is too thick), the resistance of the separator may increase excessively.

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

[0041] The polyolefin resin may contain, for example, any 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. Further, the polymer material may further contain any one or more selected from among polymer resins such as polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalene, together with the polyolefin resin.

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

[0043] In one embodiment of the present invention, the inorganic particles have a particle size smaller than the layer thickness of the desired coating layer, for example, a particle size of 1 / 2 to 1 / 1,000 times the layer thickness of the coating layer, and are not particularly limited as long as they are electrochemically stable. For example, the diameter of the inorganic particles can be 10 nm or more. On the other hand, for example, the diameter of the inorganic particles can be 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 not particularly limited as long as oxidation and / or reduction reactions do not occur in the operating voltage range of the applied electrochemical element (for example, 0 to 5 V based on Li / Li + In particular, when using inorganic particles with ion transfer ability, the ionic conductivity in the electrochemical element can be increased to improve performance. Also, when using inorganic particles with a high dielectric constant as the inorganic particles, it can contribute to an increase in the dissociation degree of electrolyte salts in the liquid electrolyte, such as lithium salts, and improve the ionic conductivity of the electrolyte solution.

[0044] For the reasons described 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).), 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).), Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3 (PMN-PT), inorganic particles such as hafnia (HfO2) not only exhibit high dielectric constant characteristics with a dielectric constant of 100 or more, but also generate charges when a certain pressure is applied and stretched or compressed, resulting in a potential difference between both surfaces. By having piezoelectricity, it is possible to prevent the occurrence of internal short circuits of both electrodes due to external shocks and improve the safety of the electrochemical device. In addition, when the above-mentioned high dielectric constant inorganic particles and inorganic particles having lithium ion conductivity are used in combination, these synergistic effects 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 transmit 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 improved. 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 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 the binder material that can be used for the coating layer include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose. Any one of the polymer resins selected from the group consisting of these or a mixture of two or more of these can be mentioned. However, it is not particularly limited to these.

[0047] On the other hand, in the separator according to one embodiment of the present invention, the coating layer is defined in 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 Formula 1 may preferably be 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) [Equation 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] FIG. 1 shows the form of the separator 100 according to an embodiment of the present invention. Referring to the figure, a first region 121 with a high content ratio of inorganic particles is arranged, a part of the side surface of the first region is exposed to the outside, and second regions 122 with a low content ratio of inorganic particles are arranged on two opposite sides of the first region.

[0050] Thus, by providing the coating layer 120 with the first region and the second region, when the separator according to the present invention is used in the manufacture of an electrode, the first region promotes the flow of the electrolyte into the battery. At the same time, since the second region has a higher content of the binder material than the first region, a high adhesive force between the separator and the electrode can be achieved using the second region.

[0051] In one embodiment of the present invention, the content ratio of the inorganic particles in the first region is higher than the content ratio of the inorganic particles in the second region, and can be 70 wt% or more, 75 wt% or more, or 80 wt% or more. On the other hand, the content of the inorganic particles can be 90 wt% or less within the range satisfying the above range. On the other hand, in a preferred embodiment of the present invention, it is preferable that the content of the binder resin in the first region exceeds 10 wt%. When the content of the binder resin does not satisfy the above range, it is difficult to ensure the adhesive force required for maintaining the form stability and durability of the electrode assembly in the separator and the electrode. In one embodiment of the present invention, the content ratio of the inorganic particles in the second region is lower than the content ratio of the inorganic particles in the first region, and can 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 can exceed 75 wt% in the first region and be 75 wt% or less in the second region. Alternatively, the content of the inorganic particles can exceed 80 wt% in the first region and be 80 wt% or less in the second region.

[0052] On the other hand, in one embodiment of the present invention, the porosity can increase as the content range of the inorganic particles increases. Therefore, the porosity of the first region can be higher than the porosity of the second region. On the other hand, the air permeability (sec / 100cc) can be lower in the first region than in 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 deepening the understanding of the present invention, and the scope of the present invention is not limited thereto in any way.

[0054] In one embodiment of the present invention, it is preferable that the second region is arranged in a partial section around the first region and at least a part of the side surface of the first region is exposed to the outside. Further, the second region is arranged so as to be in contact with the boundary of the first region. In the separator according to the present invention, the first region is arranged in the coating layer to promote the flow of the electrolytic solution into the inside. Since the first region has a low content of the binder resin and a high content of the inorganic particles, the adhesive force and the adhesion force to the electrode are relatively low compared to the second region. In the case of the second region, since the separator and the electrode exhibit a relatively higher adhesion force compared to the first region, there is a possibility that it may interfere with the penetration of the electrolytic solution therebetween. For such reasons, the flow of the electrolytic solution through the first region is relatively faster and easier than the flow through the second region. When manufacturing the battery, since the top surface and the bottom surface of the separator come into contact with the electrodes, the flow of the electrolytic solution is performed through the side surface of the separator. Therefore, when the entire section around the first region is surrounded by the second region, that is, when the side surface of the first region is entirely covered by the second region, it is difficult to exert the effect of promoting the flow of the electrolytic solution.

[0055] Also, in one embodiment of the present invention, the second region may be formed as a single integrated region. In another embodiment, the second region is divided into two or more units, and one of the units may be arranged apart from the other remaining units. On the other hand, when the second region is divided into two or more units and a plurality of them are provided, by separating and distributing the units from each other, it is possible to ensure a uniform adhesion force to the electrode over the entire separator.

[0056] In a specific embodiment of the present invention, the first region is arranged in a rectangular shape inside the surface of the polymer substrate, and in the second region, units are arranged on one side of any one side of the first region and the other side facing this side, respectively, and the second region may not be arranged on the remaining two sides. When the second region is arranged in such a shape, the flow-in of the electrolytic solution is promoted through the side surface of the first region where the second region is not arranged, and the electrode and the separator can be bonded with high adhesive force at all of both ends in the width direction or both ends in the longitudinal direction of the separator. In an embodiment of the present invention, considering the side surface of the flow-in of the electrolytic solution, when the separator is a rectangle with an aspect ratio greater than 1, the second region may be arranged on two short sides of the separator so that the long side of the separator is exposed. In an embodiment of the present invention, as will be described later, when the separator is manufactured, it is manufactured in a strip shape in which the length manufactured in the MD direction is longer than the length manufactured in the TD direction. Therefore, during the manufacturing process, the second region can be formed on the long side of the separator strip. However, since the manufactured separator strip is cut to a predetermined width using an instrument such as a cutter to obtain a separator, and the separator thus obtained is used for battery assembly, finally, a separator in a rectangular shape with a short MD direction (during the manufacturing process) and a long TD direction can be provided. At this time, the second region may be arranged on the short side of the manufactured separator.

[0057] FIG. 1 schematically shows a separator according to an embodiment of the present invention. Referring to this figure, the first region is formed in a rectangular shape having four sides, and the second region is arranged in a partial section around the first region. More specifically, the second region is composed of two units, and one of these units is arranged so as to be in contact with any one side of the first region, and the remaining unit is arranged on the other side facing this side. Further, the side surfaces of the first region are exposed on the remaining two sides where the second region is not arranged.

[0058] Figure 2 schematically illustrates a method for manufacturing a separator according to an embodiment of the present invention. A method for manufacturing a separator will be described with reference to this figure.

[0059] The separator can be manufactured by a continuous process of a roll-to-roll method. Referring to Figure 2, a long strip-shaped polymer substrate 110 is continuously supplied by a running roll of a roll-to-roll apparatus, 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 by a normal coating apparatus 300 such as a slot die. On the other hand, the slurry is divided into a slurry for forming a first region and a slurry for forming a second region and prepared respectively, and each slurry can be manufactured by introducing inorganic particles and a binder material into an appropriate solvent.

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

[0061] Thereafter, the applied slurry is 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 heat or blowing while passing through a dryer 500. Thereafter, the separator is obtained by cutting the separator strip to a predetermined width using an instrument such as a cutter 400. At this time, in the obtained separator, the side surfaces of the first region are 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 element 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 element may be a lithium-ion secondary battery.

[0064] In a specific embodiment of the present invention, the electrochemical element can be manufactured by injecting a non-aqueous electrolyte, as necessary, into an electrode assembly in which a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode are laminated in this order. At this time, as the positive electrode, negative electrode, and non-aqueous electrolyte constituting the electrode assembly, any of those commonly used in the manufacture of lithium secondary batteries can be used.

[0065] In a specific embodiment of the present invention, the positive electrode can be manufactured by forming a positive electrode mixture layer on a positive electrode current collector. The positive electrode mixture layer can be formed by coating a positive electrode slurry containing a positive electrode active material, a binder, a conductive material, a solvent, etc. on the positive electrode current collector and then 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, fired carbon, or a material obtained by surface-treating the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. can be used.

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

[0068] In a specific embodiment of the present invention, examples of the positive electrode active material include lithium transition metal oxides; lithium metal iron phosphate; lithium nickel-manganese-cobalt oxide; oxides in which a part of the lithium nickel-manganese-cobalt oxide is substituted with other transition metals; or two or more of these may be included, but it is not limited thereto. Specifically, the positive electrode active material is, for example, a layered compound such as 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 O4 (where x is 0 to 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3), Ni-site type lithium nickel oxide represented by; chemical formula LiMn 2-x M x O2 (where M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1) or lithium manganese composite oxide represented by Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); lithium metal phosphate LiMPO4 (where M = Fe, CO, Ni, or Mn); lithium nickel-manganese-cobalt oxide Li 1+x (Ni a Co b Mn c ) 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, a + b + c = 1); an oxide in which a part of the lithium nickel-manganese-cobalt oxide is substituted with aluminum, Li a [Ni b Co c Mn d Al e 1-f M1 f ​O2 (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 are not limited thereto at all.

[0069] In a specific embodiment of the present invention, the positive electrode may further selectively include 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 selectively include a binder. As the binder, a thermoplastic resin or a thermosetting resin can be used. More specifically, as the binder, 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, ethylene-acrylic acid copolymer, etc. can be used alone or in combination, but are not necessarily limited thereto. Any material that can be used as a binder in the relevant technical field can be used.

[0071] In a specific embodiment of the present invention, the positive electrode active material may be contained at 80% to 99% by weight 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 can be used in an amount that provides a preferable viscosity when the positive electrode active material and optionally a binder and a conductive material are included. For example, it may be included such that the concentration of the solid content in the slurry containing the positive electrode active material and optionally a binder and a conductive material is 50% to 95% by weight, preferably 70% to 90% by weight.

[0073] In a specific embodiment of the present invention, the positive electrode can be manufactured by mixing a positive electrode active material, a conductive material (referred to as a conductive material), and optionally a binder to produce 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. As another method, it is also possible to manufacture the positive electrode by casting the composition for forming the positive electrode active material layer on a separate support, peeling the film obtained by peeling the support from the support, and laminating (laminating) the film on the positive electrode current collector.

[0074] In a specific embodiment of the present invention, the negative electrode can be manufactured by forming a negative electrode binder layer on a negative electrode current collector. The negative electrode binder layer can be formed by coating a negative electrode slurry containing a negative electrode active material, a binder, a conductive material, a solvent, etc. on the negative electrode current collector and then 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 these metals and 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] As an example of the negative electrode active material, the carbon material capable of reversibly intercalating / deintercalating lithium ions can be used without particular limitation as long as it is a carbon-based negative electrode active material generally used in lithium-ion secondary batteries. Representative examples thereof include crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flaky, 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, calcined coke, and the like.

[0077] As an example of the negative electrode active material, 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] As an example of the negative electrode active material, as the metal composite oxide, there are 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] As an example of the negative electrode active material, as the material capable of doping and undoping lithium, there are 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., 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] An example of the negative electrode active material, examples of the transition metal oxide include lithium-containing titanium composite oxide (LTO), vanadium oxide, lithium vanadium oxide, and the like.

[0081] In a specific embodiment of the present invention, the negative electrode active material may be contained at 80% to 99% by weight 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 further selectively include a binder. The binder is a component that assists in the binding between the active material and the current collector, or between the active material, the conductive material, and the current collector, and is usually added at 1% to 30% by weight based on the total weight of the solid content in the negative electrode slurry. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, 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 further selectively contain a conductive material. The conductive material is a component for further improving the conductivity of the negative electrode active material, and when contained, it can be added at 1 to 20% by weight based on the total weight of the solid content in the negative electrode slurry. As such a conductive material, the same or different conductive materials used in the production of the positive electrode can be used. For example, carbon powders such as carbon black, acetylene black (or Denka black), Ketjen black, channel black, furnace black, lamp black, or summer black; graphite powders such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers and metal fibers; 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; conductive materials such as polyphenylene derivatives, etc. can be used.

[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 can be used in an amount that provides a preferable viscosity when the negative electrode active material and optionally a binder and a conductive material, etc. are included. For example, it can be included such that the concentration of the solid content in the slurry containing the negative electrode active material and optionally a binder and a conductive material is 50% to 95% by weight, preferably 70% to 90% by weight.

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

[0086] In a specific embodiment of the present invention, the lithium salt contains Li as a cation + and 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 a specific embodiment of the present invention, the lithium salt can be used singly or, if necessary, in a mixture of two or more. The lithium salt can be appropriately changed within the usually usable range, but can be contained in a non-aqueous electrolyte at a concentration of 0.01 M to 5 M or 0.1 M to 5 M or 0.1 M to 3 M.

[0088] In a specific embodiment of the present invention, the organic solvent is not particularly limited as long as decomposition due to oxidation reaction or the like is suppressed as much as possible during the charge and discharge process of the secondary battery and it can exhibit the desired characteristics together with the additive. For example, ether solvents, ester solvents, amide solvents, etc. can be used alone or in a mixture of two or more.

[0089] In a specific embodiment of the present invention, among the organic solvents, as the ether solvent, dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, ethyl propyl ether, or a mixture of two or more of these can be used, but it is not limited thereto.

[0090] In a 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 of these.

[0091] In a 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 of these.

[0092] In a specific embodiment of the present invention, specific examples of the linear carbonate compound include 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, and typically any of these can be used, but it is not limited thereto.

[0093] In a specific embodiment of the present invention, specific examples of the linear ester compound include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, or a mixture of two or more of these, and typically any of these can be used, but it is not limited thereto.

[0094] In a specific embodiment of the present invention, as specific examples of the cyclic ester compound, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, ε-caprolactone, or a mixture of two or more thereof can be used, but it is not limited thereto.

[0095] In a specific embodiment of the present invention, the cyclic carbonate compound is a high-viscosity organic solvent and has a high dielectric constant, so that the lithium salt in the electrolyte is sufficiently dissociated. Therefore, by mixing such a cyclic carbonate compound with a low-viscosity and low-dielectric-constant linear carbonate compound and linear ester compound such as dimethyl carbonate and diethyl carbonate in an appropriate ratio, a non-aqueous electrolyte having high electrical conductivity can be produced.

[0096] The separator for a lithium secondary battery according to one aspect of the present invention can effectively transfer lithium ions, reduce side reactions between the separator for a lithium secondary battery containing an ion-conductive polymer substance and the electrode, and significantly reduce the increase rate of the initial resistance inside the battery. As a result, a battery using this can improve the output density characteristics of the battery and improve the rate characteristics as the irreversible capacity decreases, so that the required time for charging or discharging the battery is shortened and the charge-discharge life is improved. Therefore, it is suitably used for portable devices such as mobile phones, notebook computers, digital cameras, camcorders, etc., which require a high charging speed, in the field of electric vehicles such as hybrid electric vehicles (HEV) and plug-in hybrid electric vehicles (PHEV), and in medium- and large-sized energy storage systems.

[0097] Hereinafter, in order to deepen the understanding of the content of the present invention, examples, comparative examples, and experimental examples are presented. However, the following test examples are merely one test example regarding the configuration and effects of the present invention, and the scope of rights and effects of the present invention are not limited thereto.

[0098] Example. Manufacture of Separator [Example 1] Polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) (molecular weight (Mw) 5,000,000 g / mol, HFP content 15 wt%) and alumina (particle size 0.5 μm) were added to acetone at a weight ratio of 22.5:77.5 to prepare a slurry for forming a first region with a solid content of 20 wt%.

[0099] Next, PVDF-HFP (molecular weight (Mw) 5,000,000 g / mol, HFP content 15 wt%) and alumina (particle size 0.5 μm) were added to acetone at a weight ratio of 25:75 to prepare a slurry for forming a second region with a solid content of 20 wt%.

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

[0101] [Example 2] PVDF-HFP (molecular weight (Mw) 5,000,000 g / mol, HFP content 15 wt%) and alumina (particle size 0.5 μm) were added to acetone at a weight ratio of 20:80 to prepare a slurry for forming a first region with a solid content of 20 wt%.

[0102] Next, PVDF-HFP (molecular weight (Mw) 5,000,000 g / mol, HFP content 15 wt%) and alumina (particle size 0.5 μm) were added to acetone at a weight ratio of 25:75 to prepare a slurry for forming a second region with a solid content of 20 wt%.

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

[0104] [Comparative Example 1] PVDF-HFP (molecular weight (Mw) 5,000,000 g / mol, HFP content 15 wt%) and alumina (particle size 0.5 μm) were put into acetone at a weight ratio of 25:75 to prepare a slurry for forming a coating layer with a solid content of 20 wt%.

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

[0106] Experimental Example. Physical Property Evaluation of Separator The physical properties of the separator manufactured above were evaluated according to the following evaluation methods, and the results are shown in Table 1 and Figures 3 to 5 below. [Evaluation Results]

[0107] [Table 1]

[0108] [Evaluation Methods] 1. Air Permeability Time The air permeability of the separator was measured using an air permeability measuring instrument (manufactured by Asahi Seiko Co., Ltd., EGO-IT) in accordance with JIS P8117. On the other hand, in order to measure the air permeability of the first and second regions respectively, after manufacturing the separator, a measurement sample of the air permeability time was obtained by a method of dividing the first region and the second region using a knife.

[0109] 2. Electrode Adhesion An active material [natural graphite and artificial graphite (weight ratio 5:5)], a conductive material [super P], and a binder [polyvinylidene fluoride (PVDF)] were mixed at a weight ratio of 92:2:6, dispersed in water, and then coated on a copper foil with a width of 250 mm to manufacture a negative electrode.

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

[0111] After overlapping the prepared separator and the negative electrode, they were sandwiched between 100-μm PET films and then laminated using a roll lamination machine. At this time, lamination was performed using a roll lamination machine under the conditions of 60 °C, a pressure of 2.4 kgf / mm, and a speed of 5 m / min.

[0112] The laminated separator and negative electrode were cut into a size of 25 mm in width and 70 mm in length. After attaching the end portions of the separator and the negative electrode to a universal material testing machine (manufactured by Instron), a force was applied at 180° at a measurement speed of 300 mm / min to measure the force required to peel off the separator attached to the negative electrode from the negative electrode.

[0113] 3. Confirmation of wettability of electrolyte (1) Manufacture of negative electrode Artificial graphite as a negative electrode active material, carbon black as a conductive material, carboxymethyl cellulose (CMC) as a dispersant, and styrene-butadiene rubber (SBR, BM-L301 manufactured by Nippon Zeon Co., Ltd.) as a binder were mixed with water at a weight ratio of 95.8:1:1.2:2 to produce a negative electrode slurry. The negative electrode slurry was coated on a copper foil (Cu-foil) to a thickness of 50 μm to form a thin electrode plate shape, and then dried at 135 °C for 3 hours or more and then pressed to manufacture a negative electrode.

[0114] (2) Manufacture of positive electrode LiCoO2 as a positive electrode active material, carbon black as a conductive material, and polyvinylidene fluoride (PVDF) as a binder were mixed with N-methyl-2-pyrrolidone (NMP) at a weight ratio of 98:1:1 to produce a positive electrode slurry. The positive electrode slurry was coated on an aluminum foil to a thickness of 20 μm to form a thin electrode plate shape, and then dried at 135 °C for 3 hours or more and then pressed to manufacture a positive electrode.

[0115] (3) Manufacture of Lithium Secondary Battery Next, after sandwiching the manufactured separator between the negative electrode and the positive electrode, they were laminated to prepare a stacked electrode assembly, which was inserted into a pouch exterior material, and an electrolytic solution in which 1M LiPF6 was dissolved in a solvent obtained by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) at a volume ratio of 30:70 was injected to manufacture a lithium secondary battery.

[0116] The secondary battery manufactured as described above was disassembled in a state of SOC 60 to observe the negative electrode surface and observe wetting. When the wetting is good, although a uniform charge state is shown over the entire surface of the negative electrode (Figs. 3 and 4), when the wetting is poor, uncharged dark portions are observed from the negative electrode surface (Fig. 5).

[0117] As described above, the present invention has been described with reference to limited embodiments and drawings, but the present invention is not limited thereto, and it goes without saying that various modifications and variations are possible within the equivalent scope of the technical idea and claims of the present invention by those having ordinary knowledge in the technical field to which the present invention pertains.

Explanation of Reference Numerals

[0118] 100...Separator 110...Polymer Base Material 120...Organic / Inorganic Composite Coating Layer 121...First Region 122...Second Region 300...Coating Device 500...Dryer 400...Cutter

Claims

Claim 1 A separator for an electrochemical device, comprising a porous polymer substrate and a porous organic / inorganic composite coating layer formed on both surfaces or at least one surface of the polymer substrate, wherein 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. [Formula 1] Content ratio of inorganic particles in the first region (wt%) = [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] Content ratio of inorganic particles in the second region (wt%) = [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) Claim 2 The separator for an electrochemical device according to claim 1, wherein the porosity of the first region in the coating layer is higher than the porosity of the second region. Claim 3 The separator for an electrochemical device 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. Claim 4 The separator for an electrochemical device 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. Claim 5 The separator for an electrochemical device according to claim 1, wherein the second region is arranged in a partial section around the first region and at least a part of the side surface of the first region is exposed to the outside, and the second region is arranged so as to be in contact with the boundary of the first region. Claim 6 The separator for an electrochemical device according to claim 5, wherein the second region is a single integrated region or is divided into two or more units, and any one unit is arranged separately from the other units. Claim 7 The separator for an electrochemical device according to claim 5, wherein the first region is arranged in a rectangular shape inside the surface of the polymer substrate, and units are arranged on each of one side of the first region and the other side facing it, and the second region is not arranged on the remaining two sides. Claim 8 The separator is a rectangle with an aspect ratio greater than 1, and the second region is disposed on each of the two short sides of the separator. The separator for an electrochemical element according to claim 6.

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

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

11. A method for manufacturing the separator according to any one of claims 1 to 8, The method is performed by a roll-to-roll process of continuously supplying a long strip-shaped polymer substrate, forming a second region having a predetermined width at each of both ends in the width direction (TD direction) perpendicular to the running direction (MD direction) of the polymer substrate, and forming a first region between the second regions to obtain a separator strip including a composite coating layer having the first region and the second region. The method for manufacturing a separator for an electrochemical element includes the step of

12. The formation of the first region and the second region is performed by applying slurries for forming the first region and the second region to defined portions using a double slot die. The method for manufacturing a separator for an electrochemical element according to claim 11.

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

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