Separator for electrochemical devices and electrochemical device comprising the same

Abstract

The present disclosure relates to a separator for an electrochemical device, in which an adhesive layer including a binder and a coagulant is formed on a coating layer, in which the binder is able to exist in the form of secondary particles having a particle diameter of greater than 1 μm and 5 μm or less in the adhesive layer due to the effect of the coagulant, thereby resulting in a low coverage of the adhesive layer on the coating layer, and thereby providing a separator not only having a low resistance but also having excellent electrolyte wettability.

Description

Technical Field

[0001] This disclosure is based on and claims priority to Korean Patent Application No. 10-2024-0105160 filed with the Korean Intellectual Property Office on August 7, 2024, and Korean Patent Application No. 10-2025-0104415 filed with the Korean Intellectual Property Office on July 30, 2025, the disclosure of which is incorporated herein by reference in its entirety.

[0002] This disclosure relates to a separator for an electrochemical device and an electrochemical device including the separator. Background Technology

[0003] Electrochemical devices use electrochemical reactions to convert chemical energy into electrical energy. Recently, lithium-ion batteries, which have high energy density, high voltage, long cycle life, and can be used for a variety of applications, have been widely used.

[0004] In components of such an electrochemical device, the separator may comprise a porous polymer substrate with a porous structure located between the positive and negative electrodes. The separator serves to isolate the positive and negative electrodes, preventing electrical short circuits between the two electrodes and allowing the passage of electrolytes and ions. Although the separator itself does not participate in the electrochemical reaction, its physical properties, such as its wettability with the electrolyte, porosity, and thermal shrinkage, may affect the performance and safety of the electrochemical device.

[0005] Therefore, in order to enhance the physical properties of such separators, various methods have been explored, including adding coatings to porous polymer substrates and adding various materials to the coatings to improve their performance. For example, inorganic materials can be added to the coating to improve the mechanical strength of the separator, or inorganic materials or hydrates can be added to improve the flame retardancy and heat resistance of the porous polymer substrate.

[0006] In the coating, inorganic particles can be linked to other inorganic particles via a polymer binder to form an interstitial volume, through which lithium ions can move. That is, the coating containing the polymer binder and inorganic particles prevents thermal shrinkage of the separator while simultaneously facilitating the movement of lithium ions through the separator.

[0007] Simultaneously, to ensure adhesion between the separator and the electrode, the separator coating can be further coated with an adhesive layer containing a binder. In this case, when the coating is coated with an adhesive layer with an increased binder loading, the adhesive strength of the adhesive layer can be improved due to the high binder content; however, the coverage of the adhesive layer on the coating may become excessive, potentially increasing the separator's resistance. Furthermore, since the binder has a lower electrolyte affinity compared to inorganic particles, the electrolyte wettability of the separator may also decrease, thereby delaying the manufacturing process time of the separator and the electrochemical device.

[0008] Therefore, there is a need to develop a novel separator for electrochemical devices that exhibits excellent electrolyte wettability and low resistance, due to the low coverage of the adhesive layer on the coating surface while possessing excellent adhesion. Summary of the Invention

[0009] Technical issues

[0010] One object of this disclosure is to provide a separator for an electrochemical device, the separator having low resistance, wherein the average secondary particle size (D) of the binder is reduced by an agglomerating agent within the adhesive layer. 50 The thickness must be greater than 1 μm and less than 5 μm to achieve an adhesive layer coverage of 5% to 80% on the coating, thereby giving the separator low resistance.

[0011] Technical solution

[0012] To achieve the above objectives, this disclosure provides a separator for an electrochemical device, the separator comprising: a porous polymer substrate; a coating disposed on at least one surface of the porous polymer substrate and comprising inorganic particles; and an adhesive layer disposed on the coating and comprising a binder and an agglomerant, wherein the binder has an average secondary particle size (D2). 50 The adhesive layer comprises a particulate binder with a particle size greater than 1 μm and 5 μm or smaller, wherein the binder is a (co)polymer containing at least one functional group selected from the group consisting of hydroxyl, amino, amide and carboxyl groups, the agglomerator is a (co)polymer containing at least one functional group selected from the group consisting of amide, amino, hydroxyl and carboxyl groups, and the adhesive layer is distributed with a coverage of 5% or more and 80% or less of the surface area corresponding to the coating.

[0013] In the separator of the electrochemical device, the average primary particle size (D) of the binder 50 It can be 1 μm or smaller.

[0014] The agglomerant may be a (co)polymer with a weight-average molecular weight of 1,000 g / mol or greater and 50,000 g / mol or less.

[0015] The weight ratio between the binder and the agglomerate can be 1:0.1 or greater and 1:1.5 or less.

[0016] The adhesive layer may be distributed with a coverage of 40% or more and 70% or less of the surface area corresponding to the coating.

[0017] The adhesive may be a (co)polymer comprising at least one monomer selected from the group consisting of vinyl alcohol, acrylic acid, methacrylic acid, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, dimethylaminoethyl methacrylate, acrylamide, glucose, and ethyleneamine.

[0018] The polymerizing agent may be a (co)polymer comprising at least one monomer selected from the group consisting of acrylamide, vinylamine, acrylic acid, methacrylic acid, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, dimethylaminoethyl methacrylate, glucose, and vinyl alcohol.

[0019] The thickness of the adhesive layer can be 0.5 μm or greater and 5 μm or less.

[0020] The thickness of the coating can be 0.5 μm or greater and 3 μm or less.

[0021] This disclosure provides an electrochemical device including a positive electrode, a negative electrode, and a separator for the electrochemical device, wherein the separator for the electrochemical device is located between the positive electrode and the negative electrode.

[0022] Beneficial effects

[0023] In the separator for an electrochemical device according to the present disclosure, the binder in the adhesive layer exists in the form of secondary particles with a diameter greater than 1 μm and 5 μm or smaller. Therefore, the coverage of the adhesive layer on the coating can be as low as 5% to 80%, thereby providing excellent electrolyte wettability of the separator and smooth movement of lithium ions through the separator, resulting in low resistance of the separator.

[0024] Furthermore, the method for manufacturing an electrochemical device according to this disclosure has economic advantages because by using a separator with excellent wettability, the time required for the steps of injecting and impregnating the electrode assembly with electrolyte can be reduced. Attached Figure Description

[0025] Figure 1 (a) is a conceptual diagram of the separator of the electrochemical device according to the present disclosure, and Figure 1 (b) is a conceptual diagram of a conventional separator used in electrochemical devices, in which the adhesive layer does not contain agglomerates and only contains adhesives.

[0026] Figure 2This is an image of the adhesive layer of the separator for an electrochemical device in Example 1, taken using a scanning electron microscope in backscattered electron (BSE) mode. In the image, gray area A represents the adhesive, white area B represents inorganic particles, and black area C represents pores.

[0027] Figure 3 This is an image of the adhesive layer of the separator used in the electrochemical device of Comparative Example 1, taken using a scanning electron microscope in backscattered electron (BSE) mode. In the image, gray area A represents the adhesive, white area B represents inorganic particles, and black area C represents pores. Detailed Implementation

[0028] The various components of this disclosure will be described in more detail below to enable those skilled in the art to readily implement it. However, this is merely illustrative, and the scope of this disclosure is not limited to the following.

[0029] The term "comprising" as used herein is used to list materials, compositions, apparatus, and methods that can be used in this disclosure, but is not limited to the examples listed.

[0030] The terms “about” and “substantially” as used herein are used to mean “at or near the stated value given manufacturing and material tolerances” and are intended to prevent unethical infringers from improperly using the precise or absolute values ​​given in this disclosure to aid in understanding this disclosure.

[0031] In this specification, when it is mentioned that a component is "on" a certain component, it means that the possibility of other components being placed between it is not excluded, but rather that other components may be further placed between it, unless otherwise specifically stated.

[0032] As used in this article, "electrochemical device" can refer to primary batteries, secondary batteries, supercapacitors, etc. More specifically, the electrochemical device can be a lithium-ion secondary battery, and can be pouch-shaped, cylindrical, prismatic, or button-shaped, but its specific shape is not limited to these.

[0033] As used herein, the term "electrode" is intended to encompass both "positive" and "negative" electrodes, and can refer to an electrode obtained by coating an electrode active material onto at least one surface of a conductive material and then drying it, a process that does not cause a chemical change in the electrochemical device. The types of conductive and electrode active materials are not limited, as long as they are suitable for use in an electrochemical device.

[0034] As used herein, "separator" can generally refer to a functional separator in which a porous coating comprising inorganic materials and a binder is formed on at least one surface of a porous polymer substrate (e.g., a polyolefin substrate or nonwoven fabric). However, in this specification, it can refer to a separator in which a coating comprising inorganic materials is formed on at least one surface of the porous polymer substrate, and an adhesive layer comprising a binder is formed on the coating. Furthermore, the separator possesses porous characteristics by comprising multiple pores and functions as a porous ion-conducting barrier to allow ions to pass through while preventing electrical contact between the negative and positive electrodes in an electrochemical device.

[0035] In this specification, "having pores" means that the material includes a plurality of pores, such that gaseous and / or liquid fluids can be transferred from one side of the material to the other through a communication structure between the pores.

[0036] In this specification, "average particle size (D)" 50 ") or average particle size (D 50 The particle size distribution (D) refers to the particle size at which the cumulative particle size distribution reaches 50% of the total particle size. This diameter can be measured using laser diffraction. Specifically, the particle size distribution is calculated by dispersing the powder in a dispersion medium, introducing the dispersion into a commercially available laser diffraction particle size analyzer (e.g., Microtrac S3500), and measuring the difference in diffraction pattern as the particles pass through a laser beam. The particle size (D) can be measured by calculating the particle size at 50% of the cumulative particle size distribution as a function of particle size in the analyzer. 50 The primary and secondary particle sizes of the binder measured in this specification refer to the average particle size measured in a slurry state where primary or secondary particles are mixed with solvent.

[0037] As used herein, “coverage” refers to the percentage of a specific surface area covered by another material or layer. For example, the coverage of an adhesive layer relative to a coating surface area refers to the percentage of the area covered by the adhesive layer on one surface of the coating relative to the total area of ​​the coating surface. This coverage can be measured by the following method: On one surface of a separator coated with the adhesive layer, scanning electron microscope images at magnifications of approximately 10x to 10,000x are acquired for five regions, and image analysis software is used to distinguish the contrast of the adhesive contained in the adhesive layer, the inorganic materials contained in the coating, and the presence of pores in the adhesive layer or the coating. Next, the area occupied by the adhesive, the inorganic materials, and the pores is calculated, and the coverage of the adhesive layer is measured by averaging the percentage of the area distributed by the adhesive relative to the total area.

[0038] The term "particle-type binder" as used in this article refers to a binder that retains the original shape of the particles when dispersed in a solvent. Conversely, "solution-type binder" refers to a binder that loses its original particle shape and exists in a solution state when dispersed in a solvent.

[0039] As used herein, “primary particle” refers to the original particle that forms another type of particle or larger particle. With respect to the binder of this disclosure, the primary particle is a relatively small particle unit consisting only of repeating units comprising monomers containing hydroxyl, amino, amide, and carboxyl groups.

[0040] As used herein, "secondary particles" refers to physically distinguishable particles formed by combining, aggregating, or assembling multiple primary particles using an aggregator. Regarding the binder of this disclosure, the binder secondary particles refer to composite particles in which the aggregator and the binder primary particles are bonded together through intermolecular interactions (e.g., hydrogen bonds), and the secondary particles are particles with a volume approximately five times that of the primary particles.

[0041] In this specification, the “thickness” of the coating or adhesive layer can be measured using a known thickness gauge. For example, the thickness of the coating or adhesive layer can be determined by measuring the average thickness using a commercially available thickness gauge (Mitutoyo, VL-50S-B) with a 5 mm diameter probe.

[0042] This disclosure will be described in more detail below.

[0043] This disclosure provides a separator for an electrochemical device.

[0044] According to one embodiment of this disclosure, a separator for an electrochemical device comprises: a porous polymer substrate; a coating disposed on at least one surface of the porous polymer substrate and comprising inorganic particles; and an adhesive layer disposed on the coating and comprising a binder and an agglomerant, wherein the binder has an average secondary particle size (D0). 50 The adhesive layer comprises a particulate binder with a particle size greater than 1 μm and 5 μm or smaller, wherein the binder is a (co)polymer containing at least one functional group selected from the group consisting of hydroxyl, amino, amide and carboxyl groups, the agglomerator is a (co)polymer containing at least one functional group selected from the group consisting of amide, amino, hydroxyl and carboxyl groups, and the adhesive layer is distributed with a coverage of 5% or greater and 80% or less of the surface area corresponding to the coating.

[0045] The separator for the electrochemical device can be a separator in which a coating containing inorganic particles is disposed on one or both surfaces of the porous polymer substrate, and an adhesive layer containing a binder and an agglomerator is disposed on the other surface of the coating, which is not in contact with the porous polymer substrate. In the case of a separator for an electrochemical device with a coating disposed on both surfaces of the porous polymer substrate, the adhesive layer may be disposed on the other surface of at least one of the coatings. For example, in the case of a separator with a coating disposed on both surfaces of the porous polymer substrate, the adhesive layer may be disposed on the other surface of one of the coatings, or the adhesive layer may be disposed on the other surfaces of both coatings respectively. Furthermore, in the case of a separator with a coating disposed on one surface of the porous polymer substrate, the adhesive layer may be disposed on the other surface of the coating. The separator for the electrochemical device can minimize the thermal shrinkage problem of the porous polymer substrate through the coating, thereby exhibiting excellent heat resistance; at the same time, due to the adhesive layer, the separator can also have excellent adhesion to the electrode.

[0046] In a separator used in an electrochemical device, multiple primary binder particles can be aggregated by an aggregator within the adhesive layer, thus allowing the binder to have an average particle size (D). 50 The particles are larger than 1 μm and exist in the form of secondary particles of 5 μm or smaller. Therefore, the adhesive layer can have excellent adhesive strength and low coverage on the coating. Thus, within the low-coverage adhesive layer, lithium ions can move smoothly through areas where the adhesive is absent, resulting in lower resistance of the separator. Furthermore, unlike conventional separators coated with high-coverage adhesive layers, the electrolyte can easily penetrate into the coating and the porous polymer substrate through areas where the adhesive is absent, thus also resulting in excellent electrolyte wettability of the separator. Figure 1As shown, in a separator for an electrochemical device according to one embodiment of the present disclosure, a plurality of primary binder particles in the adhesive layer can exist as secondary particles aggregated from the primary particles by the agglomerating agent. As a result, the area of ​​the coating not covered by the adhesive layer can be large. Therefore, unlike the adhesive layer of a conventional separator for an electrochemical device, which has a high adhesive layer coverage due to the absence of an agglomerating agent, the adhesive layer in the separator for an electrochemical device according to the present disclosure can have a lower coverage on the coating.

[0047] See Figure 2 As can be seen, in the adhesive layer of Example 1, because the adhesive is agglomerated into secondary particles by the agglomerating agent, the inorganic particles (white area B) and pores (black area C) of the coating are exposed in approximately 40% of the total area of ​​the coating that are not covered by the adhesive (gray area A). On the other hand, see... Figure 3 As can be seen, in the adhesive layer of Comparative Example 1, there is no agglomerating agent, therefore the adhesive particles uniformly cover approximately 90% of the total coating area. In other words, it can be seen that the coverage of the adhesive layer in the separator for an electrochemical device according to this disclosure is low.

[0048] The binder has an average secondary particle size (D) 50 A particulate binder with a particle size greater than 1 μm and a particle size of 5 μm or smaller. Specifically, the average secondary particle size of the binder can be greater than 1 μm, 1.5 μm or larger, 2 μm or larger, 2.5 μm or larger, or 3 μm or larger, and can also be 5 μm or smaller, 4.5 μm or smaller, 4 μm or smaller, 3.5 μm or smaller, or 3 μm or smaller. When the average secondary particle size (D) of the binder... 50 When the above range is met, a relatively small number of secondary particles can exist within the adhesive layer of the same area. Therefore, the adhesive secondary particles are sparsely distributed on the coating, and thus the coverage of the adhesive layer on the coating can be as low as approximately 5% to 80%. If the average secondary particle size (D) of the adhesive... 50If the average secondary particle size of the binder is 1 μm or smaller, exceeding the aforementioned range, a large number of secondary particles can be uniformly distributed in the same area of ​​the adhesive layer due to their small size. Consequently, the secondary particles can be densely packed on the coating, resulting in a very small area of ​​the coating without the binder, and therefore a high coverage of the adhesive layer. Therefore, in this case, the resistance of the separator may be high, and its electrolyte wettability may also be poor. Furthermore, if the average secondary particle size of the binder is greater than 5 μm, exceeding the aforementioned range, the thickness of the separator may become excessive, thus relatively reducing the electrode volume within a limited battery volume. As a result, the energy density of the electrochemical device including the separator may decrease.

[0049] The binder can be a particulate (co)polymer. Therefore, when the primary binder particles aggregate to form secondary particles, the particle uniformity of the secondary particles can be improved, resulting in excellent adhesion between the separator and the electrode. Furthermore, since the binder maintains its particulate form, sufficient space can exist between the binder particles, allowing lithium ions to move effectively through this space.

[0050] The agglomerant can be a solution-type (co)polymer. When the agglomerant is a solution-type (co)polymer, it can penetrate into the binder in a dissolved state, thereby effectively forming hydrogen bonds between the functional groups of the agglomerant and the functional groups of the binder, thus obtaining secondary particles of the binder with a secondary particle size within the above-mentioned range.

[0051] The binder is a polymer or copolymer containing at least one functional group selected from the group consisting of hydroxyl, amino, amide, and carboxyl groups, and the agglomerant is a polymer or copolymer containing at least one functional group selected from amide, amino, hydroxyl, and carboxyl groups. Therefore, the hydroxyl and other functional groups in the binder can form hydrogen bonds with the amide and other functional groups in the agglomerant, thereby allowing the binder to be aggregated into secondary particles with a particle size within the aforementioned range. Furthermore, when the binder and the agglomerant are used together, the degree of hydrogen bonding between the binder and the agglomerant varies with the content of the agglomerant, making it advantageous to precisely control the coverage of the adhesive layer. Specifically, the binder can be a polymer or copolymer containing hydroxyl groups, and the agglomerant can be a polymer or copolymer containing amide groups.

[0052] The adhesive layer is distributed with a coverage rate corresponding to 5% or more and 80% or less of the surface area of ​​the coating. Specifically, the coverage rate of the adhesive layer can be 5% or more, 10% or more, 20% or more, 30% or more, 40% or more, or 50% or more, and can also be 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, or 30% or less. More specifically, the adhesive layer can be distributed with a coverage rate corresponding to 40% or more and 70% or less of the surface area of ​​the coating. When the coverage rate of the adhesive layer meets the above ranges, the adhesive strength of the adhesive layer can be excellent, and at the same time, there can be a sufficiently large area on the coating surface that is not covered by the adhesive, so that lithium ions can move smoothly, and therefore the resistance of the separator can be low. In addition, the electrolyte can easily penetrate into the coating and the porous polymer substrate through the areas where the adhesive is not present, so the electrolyte wettability of the separator can also be excellent. Conversely, if the coverage of the adhesive layer exceeds the upper limit of the aforementioned range, the amount of lithium ions penetrating the coating and the adhesive layer may be significantly reduced, resulting in potentially higher resistance of the separator. Furthermore, due to the low electrolyte affinity of the adhesive, excessively high coverage may significantly reduce the electrolyte wettability of the separator. Additionally, if the coverage of the adhesive layer is below the lower limit of the aforementioned range, the adhesive content in the adhesive layer may be too low, leading to potentially poor adhesion between the separator and the electrode.

[0053] According to one embodiment of this disclosure, the average primary particle size (D) of the adhesive 50 The primary particle size can be 1 μm or smaller. Specifically, the average primary particle size of the binder can be 1 μm or smaller, 0.9 μm or smaller, 0.8 μm or smaller, 0.6 μm or smaller, 0.4 μm or smaller, or 0.2 μm or smaller, and can also be 50 nm or larger, 100 nm or larger, 150 nm or larger, 200 nm or larger, or 250 nm or larger. When the average primary particle size of the binder meets the above ranges, the size of the secondary particles formed by the primary particles of the binder agglomerating with the agglomerating agent can also meet the above ranges. Furthermore, the primary particles of the binder can have excellent dispersibility, so that lithium ions can move smoothly through the adhesive layer, and the adhesive layer can also be maintained at a small thickness.

[0054] According to one embodiment of this disclosure, the agglomerant can be a (co)polymer with a weight-average molecular weight of 1,000 g / mol or greater and 50,000 g / mol or less. Specifically, the weight-average molecular weight of the agglomerant (co)polymer can be 1,000 g / mol or greater, 3,000 g / mol or greater, 5,000 g / mol or greater, or 10,000 g / mol or greater, and can also be 50,000 g / mol or less, 30,000 g / mol or less, 10,000 g / mol or less, or 5,000 g / mol or less. When the weight-average molecular weight of the agglomerant (co)polymer meets the above ranges, the agglomerant can contain a sufficient number of amide, amino, hydroxyl, or carboxyl groups, such that it can effectively form hydrogen bonds with the binder, resulting in easy acquisition of binder secondary particles with the above particle size. Furthermore, when the weight-average molecular weight of the agglomerant meets the above-mentioned range, it has the following advantages: due to the low viscosity of the adhesive layer slurry containing the agglomerant, the adhesive layer can be easily formed on the coating, thus making it easy to form the adhesive layer with the desired coverage.

[0055] According to one embodiment of this disclosure, the weight ratio between the binder and the agglomerant can be 1:0.1 or greater, 1:0.2 or greater, 1:0.3 or greater, 1:0.4 or greater, 1:0.5 or greater, 1:0.6 or greater, 1:0.7 or greater, 1:0.8 or greater, 1:0.9 or greater, or 1:1 or greater, and can also be 1:1.5 or less, 1:1.3 or less, 1:1.1 or less, 1:0.9 or less, 1:0.7 or less, or 1:0.5 or less. When the weight ratio between the binder and the agglomerant meets the above ranges, the binder can agglomerate into secondary particles having a particle size within the above ranges, thus allowing an adhesive layer with low coverage to be formed on the coating. Furthermore, when the weight ratio between the binder and the agglomerant meets the above ranges, the peel strength of the adhesive layer can be improved, and the resistance of the separator can also be reduced.

[0056] According to one embodiment of this disclosure, the binder can be a (co)polymer comprising at least one monomer selected from the group consisting of vinyl alcohol, acrylic acid, methacrylic acid, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, dimethylaminoethyl methacrylate, acrylamide, glucose, and ethyleneamine. When the binder (co)polymer comprises at least one monomer selected from the above list, the functional groups such as hydroxyl, amino, amide, or carboxyl groups contained in the binder readily form hydrogen bonds with the functional groups of the agglomerator, thus the binder can be readily aggregated into secondary particles with a particle size within the above range. For example, when the binder is polyacrylic acid (PAA) containing acrylic acid as a monomer, the hydroxyl groups of the binder can form hydrogen bonds with the functional groups of the agglomerator, thereby readily obtaining secondary binder particles with a particle size within the above range.

[0057] According to one embodiment of this disclosure, the agglomerant can be a (co)polymer comprising at least one monomer selected from the group consisting of acrylamide, vinylamine, dimethylaminoethyl methacrylate, acrylic acid, methacrylic acid, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, glucose, and vinyl alcohol. When the agglomerant (co)polymer comprises at least one monomer selected from the above list, the functional groups such as amide, amino, hydroxyl, or carboxyl groups contained in the agglomerant readily form hydrogen bonds with the functional groups of the binder, thus the binder can be readily aggregated into secondary particles with a particle size within the above range. For example, when the agglomerant is polyacrylamide (PAM) containing acrylamide as a monomer, the amide groups of the agglomerant readily form hydrogen bonds with the functional groups of the binder, thereby easily obtaining secondary binder particles with a particle size within the above range.

[0058] According to one embodiment of this disclosure, the thickness of the adhesive layer can be 0.5 μm or greater and 5 μm or less. Specifically, the thickness of the adhesive layer can be 0.5 μm or greater, 1 μm or greater, 1.5 μm or greater, or 2 μm or greater, or it can be 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less. When the thickness of the adhesive layer meets the above ranges, the adhesion between the separator and the electrode can be excellent, and the resistance of the separator can also be low because the adhesive layer does not significantly increase the total thickness of the separator. Furthermore, when the thickness of the adhesive layer meets the above ranges, the electrolyte wettability of the separator can also be excellent.

[0059] According to one embodiment of this disclosure, the thickness of the coating can be 0.5 μm or greater and 3 μm or less. Specifically, the thickness of the coating can be 0.5 μm or greater, 1 μm or greater, 1.5 μm or greater, or 2 μm or greater, and can also be 3 μm or less, 2.5 μm or less, or 2 μm or less. When the coating thickness meets the above ranges, the insulation and thermal stability of the separator can be improved, while the total thickness of the separator can be reduced, thereby minimizing the volume of the electrochemical device. As a result, the amount of active material contained in the electrochemical device can be increased, thereby increasing the energy density of the electrochemical device.

[0060] According to one embodiment of this disclosure, the thickness of the separator for the electrochemical device can be 10 μm or more and 30 μm or less. Specifically, the thickness of the separator for the electrochemical device can be 10 μm or more, 12 μm or more, 14 μm or more, 16 μm or more, 18 μm or more, or 20 μm or more, and can also be 30 μm or less, 27 μm or less, 25 μm or less, 23 μm or less, 21 μm or less, 20 μm or less, or 18 μm or less. When the thickness of the separator for the electrochemical device meets the above ranges, the separator can electrically isolate the positive and negative electrodes, and at the same time, the volume of the electrochemical device can be minimized. Therefore, the amount of active material contained in the electrochemical device can be increased, thereby increasing the energy density of the electrochemical device.

[0061] According to one embodiment of this disclosure, the inorganic particles may not undergo oxidation and / or reduction reactions within the operating voltage range of the electrochemical device (e.g., 0V to 5V relative to Li / Li⁺). Specifically, the inorganic particles may be selected from BaTiO₃, Pb(Zr,Ti)O₃(PZT), b 1-x La x Zr1-y Ti y O3(PLZT, 0) <x<1,0<y<1)、Pb(Mg 1 / 3 Nb 2 / 3 At least one of the following groups: O3-PbTiO3 (PMN-PT), hafnium dioxide (HfO2), SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, SiC, Al(OH)3, TiO2, aluminum peroxide, zinc-tin hydroxide (ZnSn(OH)6), zinc-tin oxide (Zn2SnO4, ZnSnO3), antimony trioxide (Sb2O3), antimony tetroxide (Sb2O4), and antimony pentoxide (Sb2O5).

[0062] According to one embodiment of this disclosure, the average particle size (D) of the inorganic particles 50 The average particle size (D) of the inorganic particles can be 0.3 μm or larger and 1 μm or smaller. Specifically, the average particle size (D) of the inorganic particles is... 50 The average particle size can be 0.3 μm or larger, 0.4 μm or larger, or 0.5 μm or larger, and can also be 1 μm or smaller, 0.8 μm or smaller, or 0.6 μm or smaller. When the average particle size of the inorganic particles meets the above ranges, the dispersibility of the inorganic particles in the coating slurry can be excellent, so that a coating with a uniform thickness can be formed.

[0063] According to one embodiment of this disclosure, the coating may further comprise a second binder in addition to the inorganic particles, for stably fixing the inorganic particles by connecting them to each other. The second binder may be the same as or different from the binder contained in the adhesive layer, and may be, for example, selected from polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, ethylene-co-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. At least one of the following groups: propionate, cyanoethyl amylopectin, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, amylopectin, carboxyl methyl cellulose, acrylonitrile-styrene-styrene copolymer, polyimide, and styrene-butadiene rubber.

[0064] According to one embodiment of this disclosure, the weight ratio of the inorganic particles to the second binder (inorganic particles: second binder) can be from 50:50 to 99:1, specifically from 70:30 to 95:5. When the content ratio of the inorganic particles to the second binder meets the above range, the thermal safety performance of the separator can be improved, and due to the increased gaps formed between the inorganic particles, the pore size and porosity can be increased, thereby improving the performance of the final battery.

[0065] According to one embodiment of this disclosure, the porous polymer substrate can be a porous membrane in which multiple pores are formed, electrically isolating the positive and negative electrodes to prevent short circuits between them. For example, when the electrochemical device is a lithium secondary battery, the porous polymer substrate can be an ion conduction barrier that allows lithium ions to pass through while simultaneously preventing electrical contact between the positive and negative electrodes. At least some of the pores can form a three-dimensional network connecting the surface and interior of the porous polymer substrate, through which fluid can pass.

[0066] The porous polymer substrate may contain materials that are physically and chemically stable to the electrolyte as an organic solvent. For example, the porous polymer substrate may contain resins selected from, but not limited to, polyolefins such as polyethylene, polypropylene, and polybutene; polyvinyl chloride; polyethylene terephthalate; polycyclic olefins; polyethersulfone; polyamide; polyimide; polyamide-imide; nylon; polytetrafluoroethylene; and copolymers or mixtures thereof. Preferably, polyolefin resins may be used. Polyolefin resins can be processed to relatively small thicknesses and can be easily coated with a slurry, thus making them suitable for manufacturing electrochemical devices with higher energy densities.

[0067] The porous polymer substrate can have a single-layer or multi-layer structure. It may comprise two or more layers of polyolefin resin with different melting points (Tm) to provide a shut-off function in the event of high-temperature thermal runaway. For example, the porous polymer substrate may comprise a polypropylene layer with a relatively high melting point and a polyethylene layer with a relatively low melting point. Preferably, the porous polymer substrate may have a three-layer structure consisting of polypropylene, polyethylene, and polypropylene stacked sequentially. When the battery temperature rises above a predetermined temperature, the polyethylene layer can melt, thereby sealing the pores and preventing thermal runaway of the battery.

[0068] According to one embodiment of this disclosure, the thickness of the porous polymer substrate can be 4 μm or greater and 15 μm or less. Specifically, the thickness of the porous polymer substrate can be 4 μm or greater, 5 μm or greater, 6 μm or greater, 7 μm or greater, 8 μm or greater, 9 μm or greater, or 10 μm or greater, and can also be 15 μm or less, 13 μm or less, 11 μm or less, 9 μm or less, or 7 μm or less. By controlling the thickness of the porous polymer substrate within the above ranges, the volume of the electrochemical device can be minimized while electrically isolating the positive and negative electrodes, thereby increasing the amount of active material contained in the electrochemical device.

[0069] According to one embodiment of this disclosure, the porous polymer substrate may include pores with an average particle size greater than 0.01 μm and 1 μm or smaller. Specifically, the size of the pores contained in the porous polymer substrate may be 0.01 μm or larger, 0.02 μm or larger, 0.03 μm or larger, or 0.04 μm or larger, and may also be 1 μm or smaller, 0.09 μm or smaller, 0.08 μm or smaller, 0.07 μm or smaller, or 0.06 μm or smaller. Preferably, the pore size may be 0.02 μm or larger and 0.06 μm or smaller. By controlling the pore size of the porous polymer substrate within the above ranges, the air permeability and ionic conductivity of the entire manufactured separator can be controlled.

[0070] The air permeability of the porous polymer substrate can be 10 s / 100cc or greater and 100 s / 100cc or less. Specifically, the air permeability of the porous polymer substrate can be 10 s / 100cc or greater and 90 s / 100cc or less, 20 s / 100cc or greater and 80 s / 100cc or less, 30 s / 100cc or greater and 70 s / 100cc or less, or 40 s / 100cc or greater and 60 s / 100cc or less. Preferably, the air permeability of the porous polymer substrate can be 50 s / 100cc or greater and 70 s / 100cc or less. When the air permeability of the porous polymer substrate is within the above range, the air permeability of the manufactured separator can be within a range suitable for ensuring the output and cycle characteristics of the electrochemical device. Air permeability (s / 100cc) refers to the time (in seconds) required for 100cc of air to pass through a predetermined area of ​​porous polymer substrate or separator under constant pressure. This air permeability can be measured using a Gurley densometer according to ASTM D 726-58, ASTM D726-94, or JIS-P8117. For example, a Gurley 4110 N device can be used at an air pressure of 0.304 kPa or 1.215 kN / m³. 2 Measure the pressure of 100cc of air passing through 1 square inch (or 6.54 cm) under water pressure. 2 The time required to pass a sample. For example, the Asahi Seiko EG01-55-1MR apparatus can be used to measure the time required for 100 cc of air to pass through a 1 square inch sample at a constant pressure of 4.8 inches of water at room temperature.

[0071] The porosity of the porous polymer substrate can be 10 vol% or greater and 60 vol% or less. Specifically, the porosity of the porous polymer substrate can be 10 vol% or greater, 20 vol% or greater, 30 vol% or greater, 40 vol% or greater, or 50 vol% or greater, and can also be 60 vol% or less, 50 vol% or less, or 40 vol% or less. Preferably, the porosity of the porous polymer substrate can be 30 vol% or greater and 50 vol% or less. When the porosity of the porous polymer substrate is within the above range, the ionic conductivity of the manufactured separator can be within a range suitable for ensuring the output and cycling characteristics of the electrochemical device. The porosity refers to the volume percentage of pore volume to the total volume of the porous polymer substrate. The porosity can be measured by methods known in the art. For example, it can be measured using the BET (Brunauer-Emmett-Teller) method with nitrogen adsorption, the capillary flow porosity method, or the water or mercury infiltration porosity method.

[0072] This disclosure provides a method for manufacturing an electrochemical device.

[0073] The method of manufacturing the electrochemical device may include a method of manufacturing the separator for the electrochemical device. In the method of manufacturing the separator for the electrochemical device according to one embodiment of the present disclosure, descriptions overlapping with the description of the separator for the electrochemical device will be omitted.

[0074] According to one embodiment of this disclosure, the method of manufacturing an electrochemical device may include: (S10) forming a coating by applying a coating slurry containing inorganic particles to at least one surface of a porous polymer substrate; (S20) forming an adhesive layer by applying an adhesive layer slurry containing a binder and an aggregator onto the coating; (S30) manufacturing an electrode assembly by inserting a separator for the electrochemical device manufactured in step (S20) between a positive electrode and a negative electrode; and (S40) housing the electrode assembly in a battery casing and then impregnating the electrode assembly by injecting a liquid electrolyte into the battery casing, wherein the binder has an average secondary particle size (D) of 2000-2000 mm. 50 A particulate binder with a particle size greater than 1 μm and 5 μm or smaller, wherein the binder is a (co)polymer containing at least one functional group selected from the group consisting of hydroxyl, amino, amide and carboxyl groups, and the agglomerator is a (co)polymer containing at least one functional group selected from the group consisting of amide, amino, hydroxyl and carboxyl groups.

[0075] Specifically, steps (S10) and (S20) can be steps in manufacturing a separator for an electrochemical device, and step (S10) is a step in forming a coating on at least one surface of the porous polymer substrate during the manufacturing of the separator for the electrochemical device. Step (S20) can be a step in forming an adhesive layer on the coating. The separator for an electrochemical device according to this disclosure can be manufactured by steps (S10) and (S20).

[0076] Specifically, the method for forming the coating or adhesive layer in steps (S10) and (S20) is not particularly limited to any one method and can be performed using conventional methods known in the art. For example, various methods such as bar coating, dip coating, die coating, roll coating, comma coating, or combinations thereof can be used. For example, the method for forming the coating in step (S10) can be by applying a coating slurry to a porous polymer substrate using gravure coating or slot die coating, followed by drying; the method for forming the adhesive layer in step (S20) can be by applying an adhesive layer slurry to the coating using gravure coating or slot die coating, followed by drying.

[0077] Step (S30) may involve placing the separator of the electrochemical device of this disclosure, manufactured in steps (S10) and (S20), between the negative and positive electrodes to manufacture an electrode assembly. The positive and negative electrodes may be as follows.

[0078] According to one embodiment of this disclosure, the positive electrode may include: a positive electrode current collector; and a positive electrode active material layer, the positive electrode active material layer being disposed on at least one surface of the positive electrode current collector and comprising a positive electrode active material, a conductive material, and a binder resin. The positive electrode active material may include a mixture of one or more layered compounds selected from layered compounds, such as lithium manganese oxide (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), etc., or compounds substituted with one or more transition metals; [The last part, "Li," appears to be a continuation of the previous sentence and is left untranslated.] 1+x Mn 2-x Lithium manganese oxides represented by O4 (where x is 0 to 0.33), such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxides (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, and Cu2V2O7; and lithium NiO4. 1-x M x O2 represents Ni-type lithium nickel oxides (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 to 0.3); LiMn 1-x M xO2 (where M=Co, Ni, Fe, Cr, Zn or Ta, and x=0.01 to 0.1) or Li2Mn3MO8 (where M=Fe, Co, Ni, Cu or Zn); LiMn2O4, in which a part of Li in the formula is substituted with an alkaline earth metal ion; disulfide compounds; and Fe2(MoO4)3.

[0079] According to one embodiment of the present disclosure, the negative electrode may include: a negative electrode current collector; and a negative electrode active material layer, which is disposed on at least one surface of the negative electrode current collector and includes a negative electrode active material, a conductive material, and a binder resin. The negative electrode may include, as the negative electrode active material, one or a mixture of two or more selected from lithium metal oxides; carbon materials such as non-graphitizable carbon and graphite-based carbon; metal composite oxides such as LixFe2O3 (0≤x≤1), Li x WO2 (0≤x≤1) and Sn x Me 1-x Me' y O z (Me=Mn, Fe, Pb or Ge; Me'=Al, B, P, Si, an element of Group 1, 2 or 3 of the periodic table, or a halogen; 0<x≤1; 1≤y≤3; 1≤z≤8); lithium metal; lithium alloys; silicon-based alloys; tin-based alloys; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4 and Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; and titanium oxide.

[0080] According to one embodiment of the present disclosure, the conductive material may be, for example, any one or a mixture of two or more conductive materials selected from the group consisting of graphite, carbon black, carbon fiber, metal fiber, metal powder, conductive whiskers, conductive metal oxide, activated carbon, and polyphenylene derivatives. More specifically, the conductive material may be a mixture of one or two or more conductive materials selected from the group consisting of natural graphite, artificial graphite, Super P, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, Denka black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide.

[0081] According to one embodiment of the present disclosure, the current collector is not particularly limited as long as it has high conductivity and does not cause chemical changes in the battery, and examples thereof include stainless steel, copper, aluminum, nickel, titanium, calcined carbon, and aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver and the like.

[0082] According to one embodiment of this disclosure, polymers commonly used in electrodes in the art can be used as binder resins. Non-limiting examples of such binder resins include, but are not limited to, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylylene, polymethyl methacrylate, polyetylexyl acrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyacrylate, cellulose acetate, cellulose acetatebutyrate, and cellulose acetatepropionate. Acetatepropionate, cyanoethyl amylopectin (pullulan), cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, amylopectin, and carboxyl methyl cellulose.

[0083] According to one embodiment of this disclosure, the positive electrode slurry used to form the positive electrode active material layer may contain a dispersant, wherein the dispersant may be a pyrrolidone compound. Specifically, the dispersant may be N-methylpyrrolidone (ADC-01, LG Chem Corporation).

[0084] According to one embodiment of this disclosure, based on 100 parts by weight of the positive electrode slurry, the content of the dispersant in the positive electrode slurry can be greater than 0 parts by weight and less than 0.5 parts by weight. Specifically, based on 100 parts by weight of the positive electrode slurry, the content of the dispersant in the positive electrode slurry can be greater than 0.05 parts by weight and less than 0.4 parts by weight.

[0085] According to one embodiment of this disclosure, the negative electrode slurry used to form the negative electrode active material layer may contain a dispersant, wherein the dispersant may be a polypyrrolidone compound. Specifically, the dispersant may be polyvinylpyrrolidone (Junsei Co., Ltd.).

[0086] According to one embodiment of this disclosure, based on 100 parts by weight of the negative electrode slurry, the content of the dispersant in the negative electrode slurry can be greater than 0 parts by weight and less than 0.5 parts by weight. Specifically, based on 100 parts by weight of the negative electrode slurry, the content of the dispersant in the negative electrode slurry can be greater than 0.05 parts by weight and less than 0.4 parts by weight.

[0087] Step (S40) may involve housing the electrode assembly in a battery housing and then impregnating the electrode and separator by injecting a liquid electrolyte into the battery housing. Because the separator for an electrochemical device according to the present disclosure is used in step (S40), it has the advantage of requiring a shorter impregnation time compared to conventional separators including those with a high adhesive layer coverage. Therefore, the method for manufacturing an electrochemical device according to the present disclosure has a shorter overall manufacturing time compared to conventional manufacturing methods, thus offering an economic advantage.

[0088] According to one embodiment of this disclosure, examples of the electrolyte include, but are not limited to, electrolytes formed by dissolving or dissociating salts having an A⁺B⁻ structure in an organic solvent, wherein A⁺ comprises ions selected from alkali metal cations (e.g., Li⁺, Na⁺, and K⁺) or combinations thereof, and B⁻ comprises anions selected from anions (e.g., PF6⁻, BF4⁻, Cl⁻, Br⁻, I⁻, ClO4⁻, AsF6⁻, CH3CO2⁻, CF3SO3⁻, N(CF3S) The organic solvent is selected from propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), γ-butyrolactone (γ-butyrolactone), or mixtures thereof.

[0089] This disclosure provides an electrochemical device.

[0090] The electrochemical device may include the separator described above for an electrochemical device according to the present disclosure, and may be manufactured by the method described above for manufacturing an electrochemical device. In an electrochemical device according to one embodiment of the present disclosure, the portions overlapping with the description of the separator for an electrochemical device and the method for manufacturing an electrochemical device will be omitted.

[0091] According to one embodiment of this disclosure, the electrochemical device may include a positive electrode, a negative electrode, and a separator according to this disclosure, wherein the separator may be located between the positive electrode and the negative electrode. Because the electrochemical device of this disclosure includes the separator described above, the electrolyte wettability of the separator is improved, and the resistance of the separator is also low; therefore, the battery performance of the electrochemical device can be excellent.

[0092] The electrochemical device is a device that converts chemical energy into electrical energy through an electrochemical reaction, and includes both primary and secondary batteries. The secondary battery is capable of charging and discharging, and refers to lithium secondary batteries, nickel-cadmium batteries, nickel-metal hydride batteries, etc. The lithium secondary battery uses lithium ions as the ion conductor, and examples include, but are not limited to: non-aqueous electrolyte secondary batteries containing a liquid electrolyte, all-solid-state batteries containing a solid electrolyte, lithium polymer batteries containing a gel polymer electrolyte, and lithium metal batteries using lithium metal as the negative electrode.

[0093] One embodiment of this disclosure may provide a battery module including a battery containing the electrochemical device as a unit cell; a battery pack including the battery module; and a device including the battery pack as a power source. Specific examples of the device include, but are not limited to: power tools that are moved by a battery motor; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles, including electric bicycles (E-bikes) and electric scooters (E-scooters); electric golf carts; and energy storage systems.

[0094] The present disclosure will be described in detail below with reference to embodiments. However, embodiments of the present disclosure can be modified in various different forms, and the scope of the present disclosure should not be construed as limited to the embodiments described below. The embodiments of this specification are provided to explain the present disclosure more fully to those skilled in the art.

[0095] Examples and Comparative Examples

[0096] Manufacturing of separators for electrochemical devices

[0097] <Example 1>

[0098] Polyethylene resin (weight average molecular weight: 900,000 g / mol) was extruded and a porous polymer substrate (total thickness: approximately 9 μm, porosity: 40 vol%) was manufactured from the resin using a wet process.

[0099] Preparation of average particle size (D) 50Al₂O₃ powder with a wavelength of 600 nm was used as inorganic particles. Particulate polyacrylic acid binder was prepared as a second binder for the coating, and sodium carboxymethyl cellulose (CMC-Na) was prepared as a dispersant. The inorganic particles, the second binder, and the dispersant were added to water in a weight ratio of 92:5:3. The inorganic particles were then pulverized and dispersed to prepare a coating slurry. The coating slurry was applied to both surfaces of the porous polymer substrate using a doctor blade via a rod coating method, and then dried in air at 50°C using a hot air gun to form a coating on both surfaces of the porous polymer substrate.

[0100] To form the adhesive layer, 4 g of particulate polyacrylic acid (average primary particle size (D)) was prepared. 50 A binder (250 nm) was used as the binder, and 1 g of solution-type polyacrylamide (weight average molecular weight: 5,000 g / mol) was prepared as the agglomerant. The binder and the agglomerant were added and dispersed in 95 g of water as a solvent at a weight ratio of 1:0.25, thereby preparing an adhesive layer slurry. At this time, the diameter (D) of the secondary particles of the binder formed by aggregation was... 50 The value is 2 μm.

[0101] The adhesive slurry is applied to the surface of either of the two coatings using a doctor blade via a bar coating method, and then air-dried at 50°C using a hot air gun to form an adhesive layer on the coating. The same process is performed on the other coating, thereby providing an adhesive layer on both sides of the porous polymer substrate, thus creating a separator for an electrochemical device.

[0102] <Example 2>

[0103] Except for the preparation of the adhesive layer slurry using 4 g of the binder and 2 g of the agglomerant, the separator for the electrochemical device was manufactured in the same manner as in Example 1.

[0104] <Example 3>

[0105] Except for the preparation of the adhesive layer slurry using 4 g of the binder and 4 g of the agglomerant, the separator for the electrochemical device was manufactured in the same manner as in Example 1.

[0106] <Example 4>

[0107] Except for using granular polyvinyl alcohol as a binder to prepare the adhesive layer slurry, the separator for the electrochemical device was manufactured in the same manner as in Example 1.

[0108] <Example 5>

[0109] Except for the use of solution-type polyethyleneamine (weight average molecular weight: 5,000 g / mol) as an agglomerant to prepare the adhesive layer slurry, the separator for the electrochemical device was manufactured in the same manner as in Example 1.

[0110] <Comparative Example 1>

[0111] Except that the adhesive layer slurry is prepared without the use of agglomerating agents, the separator for the electrochemical device is manufactured in the same manner as in Example 1.

[0112] <Comparative Example 2>

[0113] In addition to using polyvinylidene fluoride (primary particle size (D) 50 In addition to preparing the adhesive layer slurry by adding and dispersing polyacrylamide (weight average molecular weight: 5,000 g / mol) in water as a solvent at a weight ratio of 1:0.25 as a binder, a separator for an electrochemical device was manufactured in the same manner as in Example 1.

[0114] <Measuring the resistance of the partition>

[0115] The separators of each embodiment and comparative example were sandwiched between SUS plates to manufacture button cells. An electrolyte containing 1 M LiPF6 and a mixture of ethylene carbonate and methyl ethyl carbonate in a 1:2 volume ratio was injected into the button cells. To measure the resistance of the button cells, electrochemical impedance spectroscopy was performed using a VMP3 (BioLogic Science Instruments) at 25°C, with an amplitude of 10 mV and a scan range of 0.1 Hz to 1 MHz. The results are shown in Tables 1 and 2 below.

[0116] <Measurement of Adhesive Layer Coverage>

[0117] On one surface of a partition coated with the adhesive layer, scanning electron microscopy (SEM, BSE mode) images at 1000x magnification were acquired for five different regions. From these images, image analysis software was used to distinguish the contrast of the adhesive contained in the adhesive layer, the inorganic materials contained in the coating, and the pores present in the adhesive layer and the coating. The area occupied by the adhesive, inorganic materials, and pores was then calculated, and the coverage of the adhesive layer was measured by averaging the percentage of the area distributed by the adhesive to the total area. Figure 2 and Figure 3Images of the adhesive layers of Example 1 and Comparative Example 1, taken using a scanning electron microscope (SEM) in BSE mode, are shown below. Gray area A represents the adhesive contained in the adhesive layer, while white area B and black area C represent inorganic particles and pores contained in the coating, respectively. The coverage of the adhesive layer on the coating was calculated by measuring the percentage of the total area occupied by the gray area using image analysis software. In Example 1, the coverage of the adhesive layer according to this calculation method was 61%, and in Comparative Example 1, the coverage of the adhesive layer was 90%.

[0118] [Table 1]

[0119]

[0120] [Table 2]

[0121]

[0122] Manufacturing of electrode components

[0123] Using the separators for electrochemical devices manufactured in the examples and comparative examples, positive electrode components and electrode components are manufactured.

[0124] 1) Manufacturing of the positive electrode

[0125] The positive electrode active material (LiNi) 0.8 Mn 0.1 Co 0.1 O2), conductive material (carbon black), dispersant (N-methylpyrrolidone, ADC-01, LG Chem Corporation), and binder resin (a mixture of PVDF-HFP and PVDF) were mixed with water at a weight ratio of 97.5:0.7:0.14:1.66 to prepare a positive electrode active material layer slurry with a concentration of 50 wt% for components other than water. Next, the slurry was coated onto the surface of an aluminum film (thickness: 10 μm) and dried to manufacture a positive electrode with a positive electrode active material layer (thickness: 120 μm).

[0126] 2) Manufacturing of the negative electrode

[0127] Graphite (a blend of natural and artificial graphite), conductive material (carbon black), dispersant (N-methylpyrrolidone, Junsei Co., Ltd., Japan), and binder resin (a mixture of PVDF-HFP and PVDF) were mixed with water at a weight ratio of 97.5:0.7:0.14:1.66 to prepare a negative electrode active material layer slurry with a concentration of 50 wt% for components other than water. Next, the slurry was coated onto the surface of a copper thin film (thickness: 10 μm) and dried to manufacture a negative electrode with a negative electrode active material layer (thickness: 120 μm).

[0128] 3) Lamination process

[0129] The positive and negative electrodes were each cut into 5 cm × 5 cm dimensions, and the separators and PET films of each embodiment and comparative example were each cut into 10 cm × 10 cm dimensions. Next, the positive electrode / separator / PET film were stacked, and then the stack was hot-pressed at 60°C and 6.5 MPa for 1 second to manufacture the positive electrode assembly. In the same manner, the negative electrode / separator / PET film was stacked and then laminated to obtain the negative electrode assembly. To prevent electrolyte from permeating between the PET film and separator in both the negative and positive electrode assemblies, and to ensure that the electrolyte only permeates to the interface between each electrode and separator, the ends of the PET film and separator in each assembly were sealed with polyimide tape.

[0130] Measurement of electrolyte immersion time

[0131] The laminated positive electrode assembly was immersed in a bath containing 10 mL of electrolyte for evaluation. The electrolyte contained 1 M LiPF6 and a mixture of ethylene carbonate and methyl ethyl carbonate in a 1:2 volume ratio. The negative electrode assembly was evaluated in the same manner. Based on the fact that the separator becomes transparent after being immersed in the electrolyte, the time required for the entire separator to be immersed was measured as the electrolyte immersion time, and the results are shown in Table 3 below.

[0132] [Table 3]

[0133]

[0134] As shown in Tables 1 and 2 above, it can be confirmed that for the separators of the embodiments, the diameter of the secondary binder particles formed by hydrogen bonds between the binder and the agglomerator is greater than 1 μm and 5 μm or smaller, thus the coverage of the adhesive layer on the coating satisfies 5% to 80%. On the other hand, it can be confirmed that in the separator of Comparative Example 1, where the adhesive layer does not contain an agglomerator, and in the separator of Comparative Example 2, where the adhesive layer contains an agglomerator but the binder does not contain functional groups such as hydroxyl, carboxyl, amide, or amino groups, and thus no hydrogen bonds are formed, the diameter of the secondary binder particles in the adhesive layer is 1 μm or smaller, thus the coverage of the adhesive layer on the coating exceeds 80%.

[0135] Therefore, it can be confirmed that for the separators of Examples 1 to 5, the coverage of the adhesive layer is low, so lithium ions can move smoothly through the adhesive layer, resulting in a resistance of less than 1 Ω for all separators, while the separators of Comparative Examples 1 and 2 have a resistance of more than 1 Ω due to the high coverage of the adhesive layer.

[0136] Furthermore, as shown in Table 3, in the positive and negative electrode assemblies including the separators of each embodiment, the adhesive layer coverage of the separator is low, so the electrolyte can flow smoothly through the pores of the adhesive layer, resulting in a short electrolyte immersion time for the separator. On the other hand, in the case of the separator in the comparative example, the adhesive layer coverage is high, so the electrolyte cannot flow smoothly through the pores of the adhesive layer, resulting in a long electrolyte immersion time for the separator. Thus, it can be confirmed that in the case of the electrode assembly including the separators of each embodiment, the electrolyte wettability of the separator is excellent.

[0137] In summary, compared with conventional separators, the separator of this disclosure has the following advantages: low coverage of the adhesive layer, resulting in lower resistance, and excellent electrolyte wettability.

[0138] [Explanation of reference numerals in the attached figures]

[0139] 1: Binder; 2: Inorganic particles

[0140] 10: Porous polymer substrate; 20: Coating

[0141] 30: Adhesive layer; A: Adhesive

[0142] B: Inorganic particles; C: Pores

Claims

1. A separator for an electrochemical device, comprising: Porous polymer substrate; A coating, wherein the coating is disposed on at least one surface of the porous polymer substrate and comprises inorganic particles; as well as An adhesive layer, disposed on the coating and comprising an adhesive and an aggregator. The binder has an average secondary particle size (D) 50 Particulate binders with a particle size greater than 1 μm and 5 μm or smaller. The binder is a (co)polymer containing at least one functional group selected from the group consisting of hydroxyl, amino, amide, and carboxyl groups. The polymerizing agent is a (co)polymer containing at least one functional group selected from the group consisting of amide, amino, hydroxyl, and carboxyl groups, and The adhesive layer is distributed with a coverage of 5% or more and 80% or less of the surface area corresponding to the coating.

2. The separator for an electrochemical device according to claim 1, wherein the average primary particle size (D) of the binder is... 50 () is 1 μm or smaller.

3. The separator for an electrochemical device according to claim 1, wherein the agglomerant is a (co)polymer with a weight-average molecular weight of 1,000 g / mol or greater and 50,000 g / mol or less.

4. The separator for an electrochemical device according to claim 1, wherein the weight ratio between the binder and the agglomerator is 1:0.1 or greater and 1:1.5 or less.

5. The separator for an electrochemical device according to claim 1, wherein the adhesive layer is distributed with a coverage of 40% or more and 70% or less of the surface area corresponding to the coating.

6. The separator for an electrochemical device according to claim 1, wherein the binder is a (co)polymer comprising at least one monomer selected from the group consisting of vinyl alcohol, acrylic acid, methacrylic acid, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, dimethylaminoethyl methacrylate, acrylamide, glucose, and ethyleneamine.

7. The separator for an electrochemical device according to claim 1, wherein the agglomerant is a (co)polymer comprising at least one monomer selected from the group consisting of acrylamide, vinylamine, acrylic acid, methacrylic acid, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, dimethylaminoethyl methacrylate, glucose, and vinyl alcohol.

8. The separator for an electrochemical device according to claim 1, wherein the thickness of the adhesive layer is 0.5 μm or greater and 5 μm or less.

9. The separator for an electrochemical device according to claim 1, wherein the coating has a thickness of 0.5 μm or greater and 3 μm or less.

10. An electrochemical device, comprising: Positive electrode; Negative electrode; And a separator for an electrochemical device according to any one of claims 1 to 9, The separator for the electrochemical device is located between the positive electrode and the negative electrode.

Images