Separator for electrochemical devices and method for manufacturing the same

Abstract

The separator according to the present disclosure not only has excellent adhesion to the electrode, but also ensures sufficient porosity, thereby exhibiting excellent electrical resistance and ion conductivity characteristics. Furthermore, the separator is in close contact with the electrode, without a gap at the interface therebetween, thereby ensuring excellent long-term life characteristics of the battery. Furthermore, the time taken for the lamination process during the electrode assembly manufacturing can be reduced, thereby enabling high processing efficiency in the battery manufacturing.

Description

Technical Field

[0001] This application claims priority to Korean Patent Application No. 10-2023-0194079, filed on December 28, 2023. This disclosure relates to separators for electrochemical devices, such as lithium-ion secondary batteries. Background Technology

[0002] Non-aqueous secondary batteries, such as lithium-ion batteries, are widely used as power sources for portable electronic devices such as laptops, mobile phones, digital cameras, and camcorders. Furthermore, in recent years, due to their high energy density, their application in automobiles and other fields is also being considered.

[0003] In currently manufactured lithium-ion batteries, porous polymer substrates, such as polyolefin-based polymer resins, are used as separator substrates to prevent short circuits between the positive and negative electrodes. However, these polymer substrates have the problem of shrinking or melting at high temperatures, exhibiting low heat resistance. Therefore, when the battery temperature rises to a high level due to internal or external stimuli, the separator may shrink or melt, increasing the likelihood of the positive and negative electrodes coming into contact with each other, leading to a short circuit. Consequently, electrical energy may be released rapidly, potentially causing the battery to explode or catch fire.

[0004] Therefore, to address these issues, methods are widely used to improve heat resistance by forming a porous filler layer containing a mixture of inorganic particles and binder resin on at least one surface of a polymer substrate. However, the heat-resistant layer needs sufficient porosity to ensure ion transport pathways and electrolyte impregnation. The pores in the heat-resistant layer originate from the interstitial volume between the inorganic particles. As the binder resin content increases, the interstitial volume becomes blocked by the binder resin, making it difficult to ensure sufficient porosity. On the other hand, when the binder resin content is insufficient, the electrodes and separators cannot adhere tightly to each other, and the electrodes and separators may separate during battery manufacturing or operation.

[0005] Meanwhile, electrode assemblies are typically manufactured via a continuous roll-to-roll process, and in this paper, a lamination process is performed to press the laminated electrodes and spacers (hot pressing is applied as needed). To achieve the desired level of electrode-spacer bonding strength, sufficient lamination process time needs to be ensured; however, this may lead to reduced productivity, such as reduced production speed.

[0006] Therefore, in separators for electrochemical devices, continuous research and development are needed to ensure sufficient porosity and adhesion (between the electrode and the separator) as well as processing efficiency. Summary of the Invention

[0007] Technical issues

[0008] This disclosure aims to provide a separator capable of ensuring high adhesion to the electrodes and improving battery production efficiency. Furthermore, this disclosure aims to provide an electrochemical device including said separator. It will be readily apparent that other objects and advantages of this disclosure can be achieved by the means or methods set forth in the claims, or combinations thereof.

[0009] Technical solution

[0010] One aspect of this disclosure relates to a separator for an electrochemical device, the separator comprising: a porous polymer substrate; and an inorganic coating covering one or both surfaces of the porous polymer substrate, wherein the inorganic coating comprises a plurality of adhesive polymer columns, each having a predetermined volume, the polymer columns being made of a polymer material and non-porous, at least a portion of the polymer columns being exposed on the surface of the inorganic coating and another portion thereon being in contact with the surface of the porous substrate, at least one of the polymer columns being spaced apart from another polymer column at a predetermined distance, the space between the polymer columns being filled with inorganic particles, and the thickness compression ratio of the separator under compression conditions of 1.5 MPa to 4.0 MPa and 45°C to 65°C being 25% or greater and 95% or less. The compression ratio can be calculated using the following [Equation 1].

[0011] [Equation 1]

[0012] Compression ratio (%) = {(Initial thickness of the separator before compression - Thickness of the separator after compression) / (Initial thickness of the separator before compression)} × 100

[0013] In the foregoing aspects of this disclosure, the storage modulus of the polymer column can be 100 Pa or greater and 3,500 Pa or less.

[0014] In any of the foregoing aspects of this disclosure, the storage modulus of the polymer column at 60°C may be 0.05 Pa or greater and 50 Pa or less.

[0015] In any of the foregoing aspects of this disclosure, the thickness (T) of the inorganic particle filling portion i ) can be a polymer columnar structure D 50 85% or less.

[0016] In any of the foregoing aspects of this disclosure, the D of the polymer columnar material 10 D 50 30% or more, and D of polymer columnar materials 90 D 50 200% or less.

[0017] In any of the foregoing aspects of this disclosure, based on a top view of the separator, the area occupied by the polymer columnar body may be 10% to 50% relative to 100% of the surface area of ​​the inorganic coating.

[0018] In any of the foregoing aspects of this disclosure, when the separator is pressed under compression conditions of 1.5 MPa to 4.0 MPa and 45°C to 65°C, the thickness difference of the separator before and after compression may be 4 μm or greater, and the thickness of the separator after compression may be 5 μm to 20 μm.

[0019] In any of the foregoing aspects of this disclosure, when the separator is pressed under compression conditions of 1.5 MPa to 4.0 MPa and 45°C to 65°C, the thickness (T) of the separator after compression is... s ) can be T i <T s <T i ×1.1, and the protruding thickness of the polymer column from the inorganic particle filling portion after compression can be 1 μm or less.

[0020] In any of the foregoing aspects of this disclosure, the cross-sectional area (b) of at least one of the polymer columns included in the inorganic coating, observed in a section at the upper 5% of the inorganic coating from the uppermost part toward its lower part, may be greater than the cross-sectional area (a) of the polymer column observed in a section at the lower 5% of the inorganic coating from the lowermost part toward its surface portion.

[0021] In any of the foregoing aspects of this disclosure, in the cross-section of the polymer column observed in the vertical section of the inorganic coating, the lower diameter (a) of at least one of the polymer columns included in the inorganic coating is smaller than the upper diameter (b) of the polymer column, and the ratio of diameter (b) to diameter (a) can be from 2 to 20.

[0022] In any of the foregoing aspects of this disclosure, the inorganic coating may have a porous structure formed by the interstitial volume between inorganic particles.

[0023] Furthermore, one embodiment of this disclosure can provide an electrochemical device including a separator for an electrochemical device according to any of the foregoing aspects.

[0024] In this disclosure, each of the above embodiments can be implemented independently. Alternatively, two or more of the above embodiments can be implemented in combination.

[0025] Beneficial effects

[0026] The separator according to this disclosure not only exhibits excellent adhesion to the electrodes but also ensures sufficient porosity, thereby demonstrating excellent electrical and ionic conductivity characteristics. Furthermore, the separator is in close contact with the electrodes, with no gaps at the interface, thus ensuring excellent long-term battery life characteristics. In addition, the time spent on the lamination process during electrode assembly manufacturing can be reduced, thereby achieving high processing efficiency in battery manufacturing. Attached Figure Description

[0027] The accompanying drawings illustrate preferred embodiments of this disclosure and are intended to provide a better understanding of the technical concept of this disclosure in conjunction with the foregoing description of the invention. Therefore, this disclosure should not be construed as limited to the matters described in these drawings. Furthermore, for purposes of clarity, the shapes, dimensions, scales, or proportions of elements in the drawings included in this specification may be enlarged.

[0028] Figure 1 This is a diagram schematically illustrating one embodiment of the separators in this disclosure.

[0029] Figure 2a SEM images of the surface of the inorganic coating of the separator manufactured in Example 1 are shown, and Figure 2b The SEM image of its cross-section is shown.

[0030] Figure 3a SEM images of the surface of the inorganic coating on the separator manufactured in Example 1 after pressing are shown, and Figure 3b The SEM image of its cross-section is shown.

[0031] Figure 4 SEM images of the surface of the inorganic coating of the separator manufactured in Comparative Example 2 are shown.

[0032] Figure 5 SEM images of the surface of the inorganic coating of the separator manufactured in Comparative Example 2 after pressing are shown. Detailed Implementation

[0033] The present disclosure will be described in detail below. Prior to this, the terms or words used in this specification and claims should not be construed as limited to their ordinary or dictionary meanings, but rather should be interpreted as corresponding to the technical concept of the present disclosure based on the principle that the inventors can appropriately define the concepts of the terms in order to describe their own invention in the best possible way. Therefore, the embodiments described in this specification and the constructions shown in the accompanying drawings are merely one of the most preferred embodiments of the present disclosure and do not fully represent the technical concept of the present disclosure. Consequently, it should be understood that various equivalents and modifications may exist at the time of submission.

[0034] Throughout this specification, unless otherwise stated to the contrary, a description in which a part “includes” a component means that it may also include other components, and does not exclude other components.

[0035] Furthermore, terms such as “about” or “substantially” used throughout this specification, when there are inherent manufacturing and material tolerances in the meanings mentioned, are used to indicate values ​​or close to those values, and are intended to prevent unethical infringers from unfairly exploiting the disclosure of precise or absolute values ​​presented to aid in understanding this application.

[0036] Throughout this specification, the description of "A and / or B" means "A or B or both".

[0037] Throughout this specification, particle size D 50 This refers to the particle size at the 50th percentile point in the cumulative particle count distribution based on particle size. In other words, D 50 This refers to the particle size at the 50% point of the cumulative particle count distribution based on particle size. Furthermore, D... 10 This refers to the particle size at the 10% point in the cumulative particle count distribution based on particle size, and D. 90 This refers to the particle size at the 90th percentile point in the cumulative particle count distribution based on particle size. Particle size can be measured using laser diffraction. Specifically, the powder to be measured is dispersed in a dispersion medium and then introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac S3500). The particle size distribution is calculated by measuring the differences in the diffraction patterns based on particle size as the particles pass through the laser beam. 10 D 50 and D 90 The particle size can be measured by calculating the particle size at the 10%, 50%, and 90% points of the cumulative particle count distribution based on particle size in the analyzer.

[0038] The specific terminology used in the following detailed description of the invention is merely for convenience and is not intended to be limiting. Terms such as “left,” “right,” “up,” and “down” may indicate directions in the referenced figures and should not be limiting. Terms such as “inward” and “outward” respectively indicate directions toward or away from the geometric center of the designated device, system, and its components. Terms such as “front,” “back,” “up,” and “down,” as well as related words and phrases, indicate positions and orientations in the referenced figures and should not be limiting. Such terms include the words listed above, their derivatives, and words with similar meanings.

[0039] In this disclosure, the glass transition temperature (Tg) can be measured by a DSC curve obtained by differential scanning calorimetry (DSC) at a heating rate of 10 °C / min.

[0040] This disclosure relates to separators for electrochemical devices and electrochemical devices including the same. In this disclosure, an electrochemical device is a device that converts chemical energy into electrical energy through an electrochemical reaction, and includes the concepts of primary batteries and secondary batteries. Secondary batteries are rechargeable and encompass concepts such as lithium-ion batteries, nickel-cadmium batteries, and nickel-metal hydride batteries.

[0041] Separator

[0042] In one embodiment of this disclosure, the separator includes a porous substrate 10 and an inorganic coating 20 formed on at least one or both side surfaces of the porous substrate. Figure 1 This is a schematic cross-section of a separator in this disclosure, in which inorganic particles 200 and polymer columnar bodies 100 are disposed. Figure 1 Specifically, the form of the separator before compression (pressing) during the separator manufacturing process is shown, where polymer columnar bodies protrude beyond the inorganic particle filling portion. Compression can refer to the artificial application of external force during the battery assembly process.

[0043] The total thickness of the spacer can be from 5.0 μm to 30 μm, and the thickness can be appropriately adjusted within the above range. For example, the total thickness can be 25.0 μm or less, 20.0 μm or less, 15.0 μm or less, 12.0 μm or less, or 10.0 μm or less. In one embodiment of this disclosure, the spacer can be introduced during the manufacture of the electrode assembly and, after being flattened by a pressing process such as lamination, can have a thickness of 15.0 μm or less, 14.0 μm or less, 13.0 μm or less, 12.0 μm or less, 11.0 μm or less, or 10.0 μm or less. Furthermore, the porosity of the spacer can be from about 25 vol% to 80 vol%. The porosity can be appropriately adjusted within the above range. For example, the porosity can be 30 vol% or more, 35 vol% or more, 40 vol% or more, 50 vol% or more, or 55 vol% or more. Alternatively, the porosity can be 70% by volume or less, 65% by volume or less, 60% by volume or less, or 55% by volume or less. Meanwhile, the permeability of the separator can be in the range of approximately 50 seconds / 100 cc or more and approximately 250 seconds / 100 cc or less. The permeability can be appropriately adjusted within the above range. For example, the permeability can be 60 seconds / 100 cc or more, 70 seconds / 100 cc or more, 100 seconds / 100 cc or more, 120 seconds / 100 cc or more, or 150 seconds / 100 cc or more. Alternatively, the permeability can be 220 seconds / 100 cc or less, 200 seconds / 100 cc or less, or 180 seconds / 100 cc or less.

[0044] In one embodiment of this disclosure, the thickness of the separator can be determined by cutting a cross-section of the separator sample, observing the cross-section using SEM, and taking the thickness at the thickest point as the thickness of the separator. Alternatively, the thickness can be measured at two or more arbitrary points, and the average of these measurements can be taken as the thickness of the separator. When the thickness is measured at four or more points, the lowest and / or highest values ​​can be excluded, and the average of the remaining values ​​can be taken.

[0045] In one embodiment of this disclosure, porosity can be calculated by determining the density (apparent density) of the test object, such as a separator, and the net density of the test object based on the composition ratio of the materials contained in the test object and the density of each component, and then calculating the difference between the apparent density and the net density. For example, porosity can be calculated using the following [Equation 2].

[0046] [Equation 2]

[0047] Porosity (volume %) = {1 - (apparent density / net density)} × 100

[0048] Meanwhile, the apparent density in the above equation can be calculated by the following [Equation 3].

[0049] [Equation 3]

[0050] Apparent density (g / cm³) 3 = {Weight of the object to be measured [g] / (Thickness of the object to be measured [cm] × Area of ​​the object to be measured [cm²])} 2 ])}

[0051] Alternatively, porosity or pore size can be measured using the BELSORP (BET device) of BEL JAPAN Co., Ltd. with an adsorbed gas such as nitrogen, or by methods such as mercury porosimetry or capillary flow porosimetry.

[0052] As used in this specification, the term "permeability" refers to the time required for 100 cc of air to pass through an object whose permeability is being measured (e.g., a separator or porous substrate), and can be expressed in seconds per 100 cc. It is interchangeable with transmittance and is typically expressed as a Gurely value, etc. In one specific embodiment of this disclosure, permeability can be measured according to JIS P8117. Furthermore, the air transmittance P1 measured for an object of thickness T1 can be converted to the transmittance P2 corresponding to an object thickness of 20 μm using the equation P2 = (P1 × 20) / T1.

[0053] Compression ratio of the separator

[0054] In one embodiment of this disclosure, the thickness compression ratio of the separator under pressing conditions of 1.5 MPa to 4.0 MPa and 45°C to 65°C can be 25% or greater and 95% or less. Within the above range, the thickness compression ratio of the separator can preferably be 75% or less, 60% or less, 50% or less, or 40% or less. The compression ratio can be calculated using the following [Equation 1].

[0055] [Equation 1]

[0056] Compression ratio (%) = {(Initial thickness of the separator before compression - Thickness of the separator after compression) / (Initial thickness of the separator before compression)} × 100

[0057] In this disclosure, the initial thickness of the separator before compression refers to the thickness of the separator after manufacturing, in a state without manual pressing. The compression ratio and the thickness difference before and after compression refer to the thickness difference and ratio before and after compression when the separator, after manufacturing and in a state without manual pressing, is compressed. The thickness of the separator is based on measurements of the thickest portion of the separator before and after compression. The thickness of the separator is referenced... Figure 1 describe.

[0058] Furthermore, in one embodiment of this disclosure, when the separator is pressed under compression conditions of 1.5 MPa to 4.0 MPa and 45°C to 65°C, the thickness difference of the separator before and after compression can be 4 μm or greater. Meanwhile, the thickness of the separator after compression can be 5 μm to 20 μm.

[0059] In one embodiment of this disclosure, when the separator is pressed under compression conditions of 1.5 MPa to 4.0 MPa and 45°C to 65°C, the height (T) of the polymer column after compression is... c The thickness of the inorganic particle filling portion can be equal to or greater than the thickness of the inorganic particle filling portion, and can be 1.1 times or less than 1.1 times the thickness of the inorganic particle filling portion. In one specific embodiment, T c The thickness of the inorganic particle filling portion can be 1.07 times or less, or 1.05 times or less. Furthermore, the protrusion height (T) of the polymer columnar structure in the inorganic coating after compression... p () can be 1 μm or smaller, or less than 1 μm.

[0060] When the separator is not artificially pressed after manufacturing, one or more of the polymer columns may protrude above the inorganic particle filling portion. In other words, one or more of the polymer columns may protrude from the surface of the inorganic particle filling portion.

[0061] As described below, the compression ratio can be primarily caused by the deformation (compression) of the polymer column.

[0062] Meanwhile, in one embodiment of this disclosure, the height (T) of the inorganic particle filling portion... i The thickness can be determined by cutting a cross-section of the separator specimen, observing the cross-section using SEM, and then measuring the thickness at two or more arbitrary points in the region where no polymer columnar structure is present, taking the average of these measurements as the height. When measuring the thickness at four or more points, the lowest and / or highest values ​​can be excluded, and the average of the remaining values ​​can be taken.

[0063] Furthermore, in one embodiment of this disclosure, the height (T) of the polymer column is... cThe value can be determined by cutting the cross-section of the separator sample, observing the cross-section through SEM, and then taking the value of the highest part of the polymer column.

[0064] Furthermore, in one embodiment of this disclosure, the protrusion height (T) of the polymer column is... p The value can be determined by cutting the cross-section of the separator sample, observing the cross-section by SEM, and then taking the value of the part with the largest gap between the inorganic particle filling part and the polymer column.

[0065] Porous substrate

[0066] A porous substrate, acting as a porous ion conduction barrier that allows ions to pass through while simultaneously blocking the electrical contact between the negative and positive electrodes, refers to a substrate in which multiple pores are formed. These pores are interconnected, allowing gas or liquid to flow from one side surface of the substrate to another.

[0067] As the material constituting such a porous substrate, organic or inorganic materials with electrical insulating properties can be used. In particular, thermoplastic resins are preferred as the material constituting the substrate in order to provide a shut-off function. In this document, the shut-off function refers to the function that, when the battery temperature rises, the thermoplastic resin melts and closes the pores of the porous substrate to prevent ion migration, thereby preventing thermal runaway of the battery. Thermoplastic resins with a melting point below 200°C are suitable, and polyolefins are particularly preferred.

[0068] In addition, it may contain at least one of the following polymer resins: for example, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene ether, polyphenylene sulfide, or polyvinyl naphthalene. The porous substrate may be a nonwoven fabric, a porous polymer membrane, or a laminate of two or more thereof, but is not particularly limited thereto.

[0069] Specifically, the porous polymer substrate is any one of the following a) to e).

[0070] a) A porous membrane formed by melting / extruding a polymer resin.

[0071] b) Multilayer membranes formed by laminating two or more porous membranes from a)

[0072] c) Nonwoven webs prepared by laying filaments obtained by melting / spinning polymer resin.

[0073] d) Multilayer films formed by laminating two or more layers of nonwoven webs from b), and

[0074] e) A porous composite membrane having a multilayer structure including two or more of a) to d).

[0075] In this disclosure, the thickness of the porous substrate can be in the range of 3 μm to 12 μm or 5 μm to 12 μm. When the thickness does not reach the above values, the conductive barrier is not functional enough; conversely, when the thickness exceeds the above range (i.e., too thick), the resistance of the separator may increase excessively.

[0076] In one embodiment of this disclosure, the weight-average molecular weight (Mw) of the polyolefin can be from 100,000 to 5,000,000. For example, the molecular weight (Mw) can be 200,000 or greater, 500,000 or greater, 700,000 or greater, or 1,000,000 or greater. Alternatively, the molecular weight can be 4,000,000 or less, 3,000,000 or less, 2,500,000 or less, 2,000,000 or less, or 1,500,000 or less. The unit for molecular weight (Mw) can be g / mol. When the weight-average molecular weight is less than 100,000, it may be difficult to ensure sufficient mechanical properties. Furthermore, when the weight-average molecular weight is greater than 5,000,000, the shut-off properties may deteriorate, or molding may become difficult. Additionally, in terms of improving manufacturing yield, the puncture strength of the porous substrate can be 300 gf or greater. The puncture strength of the porous substrate is represented by the maximum puncture load (gf) measured by puncture testing using a Kato tech KES-G5 portable compression tester under conditions of a needle tip curvature radius of 0.5 mm and a puncture speed of 2 mm / s.

[0077] In one specific embodiment of this disclosure, any planar porous polymer substrate for electrochemical devices can be used as the porous polymer substrate. For example, an insulating film with high ion permeability and mechanical strength, a pore size typically from 10 nm to 200 nm, and a thickness typically from 2 μm to 12 μm can be used. Meanwhile, the porous substrate can have a porosity of 20 vol% to 60 vol% or 30 vol% to 60 vol% and a pore size of 10 nm to 200 nm; however, the porosity and pore size are not particularly limited thereto.

[0078] Inorganic coating

[0079] In this disclosure, the separator comprises an inorganic coating formed on one side surface of a porous substrate. The inorganic coating comprises a plurality of polymer columnar structures and a plurality of inorganic particles.

[0080] In one specific embodiment of this disclosure, the inorganic coating may contain inorganic particles in an amount ranging from about 50% to 95% by weight, and preferably from about 70% to 90% by weight, relative to 100% by weight of the inorganic coating. Furthermore, polymer columnar particles may be included in an amount ranging from 10% to 40% by weight, and preferably from 20% to 35% by weight, relative to 100 parts by weight of the inorganic particles.

[0081] When the content of polymer columns in the inorganic coating is low, it is difficult to ensure the desired level of adhesion. However, when polymer columns are included in amounts exceeding the above range, the Gurley value and / or porosity of the separator may decrease, which is undesirable.

[0082] Meanwhile, in the planar image of the inorganic coating, the total area of ​​the polymer columnar structure can be 10% to 80%, and preferably 10% to 50%, based on the total area of ​​the inorganic coating. The total area of ​​the polymer columnar structure can correspond to the area before compression, the area after compression, or the area before and after compression.

[0083] In inorganic coatings, two or more of the polymer columns may aggregate to form clusters, or individual polymer columns may be spaced apart from each other at predetermined intervals. In one embodiment of this disclosure, the aggregated polymer columns that form clusters comprise 30% or less, preferably 20% or less, and more preferably 10% or less, relative to 100% of the total polymer columns. Excessive aggregation of the polymer columns can lead to non-uniform resistance in the separators. Therefore, for improving resistance uniformity, the aggregated polymer columns preferably comprise 10% or less relative to 100% of the total polymer columns.

[0084] In one embodiment of this disclosure, the polymer columns are preferably spaced apart from other polymer columns at a predetermined distance without direct contact, and are distributed in an island pattern within the inorganic coating. A plurality of polymer columns are embedded in the inorganic coating such that they are exposed or protrude beyond the surface of the inorganic coating, and some of the polymer columns may have a protrusion height T greater than 1 μm. p For example, T p The diameter can be greater than 1 μm and 10 μm or less, and for example, 7 μm or less, 5 μm or less, or 3 μm or less. Furthermore, some of the polymer columns exposed on or protruding from the inorganic coating surface can contact the porous substrate. In this document, "polymer column protruding beyond the inorganic coating surface" refers to the height (T) of the polymer column within the inorganic coating. c The height of the inorganic particle filling part is greater than (T).i This results in a height greater than that of the inorganic particle filling portion.

[0085] In one embodiment of this disclosure, the average pore size of the inorganic coating can be from 20 nm to 1,000 nm. In one embodiment of this disclosure, the pore size of the inorganic particle-filled portion can be measured. Within the above range, the average pore size of the inorganic coating can be 800 nm or less, or 500 nm or less, and independently or in conjunction with this, can be 20 nm or greater, 50 nm or greater, or 100 nm or greater. For example, the average pore size of the inorganic coating can be from 20 nm to 800 nm. The pore size can be calculated using shape analysis from SEM images. When the pore size is smaller than the above range, the pores may become clogged due to the expansion of the binder resin in the coating, while when the pore size exceeds the above range, there are problems such as difficulty in using it as an insulating layer and deterioration of self-discharge characteristics after manufacturing a secondary battery.

[0086] In one embodiment of this disclosure, the porosity of the inorganic coating (porosity in the state comprising polymer columnar structures) is preferably 30 vol% to 80 vol%. The porosity can be appropriately adjusted within the above range. For example, the porosity can be 35 vol% or more, 40 vol% or more, or 45 vol% or more. Alternatively, the porosity can be 75 vol% or less, 70 vol% or less, or 65 vol% or less. A porosity of 30% or more is advantageous in terms of lithium-ion permeability, and when the porosity is 80% or less, the surface opening ratio is not too high, which is suitable for ensuring adhesion between the spacer and the electrode.

[0087] polymer columnar body

[0088] Relative to 100% by weight of polymer columns, the polymer columns may contain polymer resin in amounts of 90% by weight or more, 95% by weight or more, or 99% by weight or more. Preferably, the polymer columns may be formed from polymer resin. Furthermore, the polymer columns have adhesive properties and can adhere to battery materials adjacent to the polymer columns, such as inorganic particles or porous substrates.

[0089] In this disclosure, the polymer column may not have open cell pores in its body. Preferably, the polymer column does not have open cell pores, so that fluids such as gases or fluids do not flow through the polymer column body.

[0090] As described above, at least a portion of one or more of the polymer columns is exposed or protrudes beyond the surface of the inorganic coating, while another portion may contact the surface of the porous substrate.

[0091] In one embodiment of this disclosure, the polymer columnar structure D 10 It can be D 50 30% or more, and its D 90 It can be D 50 200% or less. Together with or independently of this, the D of the polymer columnar material... 50 D can be inorganic particles 50 At least twice as much.

[0092] In one embodiment of this disclosure, the polymer columnar structure D 50 It can be from about 2.5 μm to 7.5 μm or from 3.0 μm to 7.0 μm, and preferably, the D 50 It can be in the range of 3.5 μm to 6.5 μm. The D-type polymer columnar polymer... 50 This reflects the state before pressing the separator, and preferably the state before slurry preparation.

[0093] In one embodiment of this disclosure, the storage modulus (G') of the polymer column at room temperature is preferably between 100 Pa and 3,500 Pa. For example, within the above range, the storage modulus can be 1,500 Pa or greater, or 2,000 Pa or greater. Preferably, the storage modulus can be related to the material forming the polymer column. In one embodiment of this disclosure, the room temperature can be in the range of 20°C to 25°C.

[0094] Furthermore, considering the temperature conditions during actual battery assembly, the ratio of the polymer column's storage modulus at 60°C to its modulus at room temperature (G'(60°C) / G'(room temperature)) is greater than 0 and less than 0.01. For example, this ratio can be less than 0.01. In one embodiment of this disclosure, the polymer column's storage modulus at high temperatures (55°C to 80°C or 60°C to 80°C) can be in the range of 0.05 Pa to 50 Pa. For example, the storage modulus can be the storage modulus at 60°C. During the electrode assembly manufacturing process, the lamination process used to laminate the electrodes and spacers is typically conditioned to about 60°C to 80°C, and herein, as the storage modulus decreases, the polymer column is pressed, thereby flattening the spacers. Furthermore, at room temperature, preferably with an increased storage modulus, sufficient bonding strength with the electrodes can be ensured.

[0095] Together with or independently of this, when measured using a dynamic mechanical analyzer (DMA) device, the polymer columnar material can exhibit at least one tan δ peak in the ranges of 45°C to 70°C, 45°C to 75°C, or 45°C to 80°C. When these ranges are met, the polymer columnar material deforms during the lamination process of bonding the spacer to the electrode, thereby ensuring close contact between the electrode and the spacer and guaranteeing the desired level of electrode-spacer adhesion.

[0096] In one embodiment of this disclosure, the storage modulus and tan δ peak can be measured using a rheological analyzer (Dynamic Mechanical Analyzer (DMA)). For example, TA Instruments' ARES-G2 can be used. In a specific embodiment, the storage modulus can be determined by performing a temperature scan test at a temperature condition of -60°C to 80°C and a frequency of 1.0 rad / s. Furthermore, the tan δ peak can be determined by calculating the ratio of the loss modulus to the storage modulus from the moduli measured above (storage modulus and loss modulus).

[0097] Furthermore, in one embodiment of this disclosure, when a pressure of 0.5 MPa or greater and 20.0 MPa or less (e.g., 2.0 MPa to 8.0 MPa) is applied, one or more of the polymer columns can be flattened by pressing the protruding portions, and the thickness of the inorganic coating can be uniform. The pressing can be hot pressing. This characteristic is beneficial for enhancing the adhesion between the electrode and the spacer during electrode assembly manufacturing and for ensuring close contact between the electrode and the spacer, preventing separation. In other words, the polymer columns can exhibit softening properties under the conditions used for laminating the electrode and the spacer (i.e., hot pressing conditions).

[0098] The pressure can be appropriately adjusted within the above range, and can be, for example, from 1.0 MPa to 8.0 MPa, or 4 MPa or less. When the applied pressure is low, the temperature can be adjusted to improve processability. For example, when pressing with a force of 4 MPa or less, the temperature can be adjusted within the above range. Furthermore, after compression under the above conditions, the protrusion height (T) of the polymer column... p The particle size can be 1 μm or smaller, or even less than 1 μm. In other words, the height difference between the inorganic particle filling and the polymer column is reduced, thus making the separator flatter. (See reference...) Figure 1 In this public disclosure, T c This refers to the total height of the inorganic coating (one side), and is based on the highest point of the inorganic coating from the porous substrate. In this disclosure, T... c This can be used to highlight the height of the polymer column.

[0099] Meanwhile, in this public disclosure, Tp The highest part based on the inorganic coating, starting from the inorganic particle filling portion.

[0100] Furthermore, in this disclosure, pressing can be performed within a range of seconds to minutes. For example, pressing can be performed within 60 seconds or 30 seconds. Since the separator according to this disclosure can be flattened in a short period of time, processing efficiency can be improved.

[0101] In this specification, "flattening" means that, under the aforementioned pressing conditions, the thickness of the inorganic particle filling portion is the same as the height of the polymer column, or the height difference between the inorganic particle filling portion and the polymer column is 1 μm or less, preferably less than 0.5 μm, and more preferably less than 0.3 μm. In one embodiment of this disclosure, the height of the polymer column can be based on the polymer column with the maximum height. In other words, when the separator according to this disclosure is applied to battery manufacturing, it is preferable that, after laminating the electrode and the separator, the thickness of the inorganic coating is less than the D of the polymer column. 50 .

[0102] Simultaneously, compared to before pressing, the flattened polymer column observed in the planar view can have a larger area. In this paper, the major axis length of the polymer column observed in the planar view after flattening is preferably D of the polymer column before flattening. 50 10 times or less.

[0103] Meanwhile, in one specific embodiment, the amount (by weight) of the polymer column dissolved in THF (tetrahydrofuran) for 1 to 48 hours can be 55% or less, preferably 35% or less, more preferably 25% or less, even more preferably 22% or less, and most preferably 20% or less.

[0104] After the electrolyte is injected during battery manufacturing, the polymer columns may dissolve and lose their adhesiveness, or the viscosity of the electrolyte may increase due to the dissolved components, leading to an increased risk of resistance in the lithium secondary battery. Therefore, it is necessary to reduce the solubility in the electrolyte by cross-linking the surface of the material forming the polymer columns.

[0105] In one embodiment of this disclosure, the polymer column having the above-described properties preferably comprises a material that is non-reactive in lithium secondary batteries and provides bonding strength between the separator and the electrode. Considering these aspects, in this disclosure, the polymer column may comprise an acrylic polymer. The polymer column may comprise an acrylic polymer in amounts such as 10% or more, 30% or more, 50% or more, 70% or more, or 90% or more, relative to 100% by weight. In one embodiment of this disclosure, the acrylic polymer may comprise at least one repeating unit from the following: acrylate-based acrylates, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, and stearyl methacrylate. However, the acrylic polymer is not limited thereto. Furthermore, in one specific embodiment, at least one hydrogen atom in the unit may be replaced by an additional substituent. In one embodiment of this disclosure, the acrylic polymer may contain the repeating unit described above in amounts of 30% or more, 50% or more, 70% or more, or 90% or more, relative to 100% by weight of the acrylic polymer.

[0106] Meanwhile, in one embodiment of this disclosure, the weight-average molecular weight of the acrylic polymer can be from about 20,000 to 800,000.

[0107] In one embodiment of this disclosure, the cross-sectional area (b) of at least one of the polymer columns observed in a section at the upper 5% of the inorganic coating from the uppermost part toward the lower part can be greater than the cross-sectional area (a) of the polymer column observed in a section at the lower 5% of the inorganic coating from the lowermost part toward the surface portion. This characteristic of the polymer columns can correspond to the polymer columns protruding from the surface of the inorganic coating and / or flattening by pressing. Preferably, this characteristic can be defined in the form of the polymer columns after protrusion and subsequent flattening.

[0108] Together with or independently of this, in a cross-section of the polymer column observed in a vertical section of the inorganic coating, the lower diameter (a) of at least one of the polymer columns may be smaller than the upper diameter (b). In one embodiment, the ratio of the upper diameter (b) to the lower diameter (a) may be greater than 1 and less than 20, 1.2 to 20, 1.5 to 20, or 2 to 20. This characteristic of the polymer column may correspond to the polymer column protruding from the surface of the inorganic coating and / or being flattened by pressing. Preferably, this characteristic can be determined in the form of the polymer column after flattening. In one embodiment of this disclosure, the upper diameter refers to the diameter measured at 5% of the uppermost point of the polymer column towards the lower part, and the lower diameter refers to the diameter measured at 5% of the lowermost point of the polymer column towards the upper part.

[0109] In one embodiment of this disclosure, the height, diameter, and / or cross-sectional dimensions of the polymer column can be calculated from SEM images of the horizontal or vertical cross-section of the separator. Figure 2b An SEM image of a cross-section of the separator according to Embodiment 1 of this disclosure is shown, in which the dimensions of the individual components can be identified. As another method of using the SEM image, the SEM image is divided into gray levels, and the area corresponding to a specific gray level corresponding to the polymer column can be measured. A gray level refers to the brightness of multiple pixels contained in the SEM image. For example, in an SEM image with 256 gray levels having levels from 0 to 255, the brightness can be in the range of 0 to 255. In a specific embodiment of this disclosure, the gray level of the polymer column can be in the range of 10 to 50, and the gray level of the inorganic particles can be in the range of 160 to 220. Therefore, in an SEM image of any cross-section of the separator, the region of the polymer column can be defined and defined by pixels with gray levels from 10 to 50, and its length and area can be calculated. In this disclosure, cross-sectional SEM images of the electrode can be obtained by energy-dispersive X-ray spectroscopy (EDS) mapping of the components on the cross-section of the electrode obtained by argon (Ar) ion milling using an EDS detector of a scanning electron microscope (SEM) apparatus, followed by image processing.

[0110] In another specific embodiment of this disclosure, the diameter or area of ​​the polymer column can be calculated by three-dimensional modeling of the separator and / or inorganic coating, thereby obtaining an arbitrary cross-section.

[0111] Inorganic particle filling part

[0112] In the inorganic coating of the separator, the spaces between the polymer columns can be filled with inorganic particles or a mixture of inorganic particles and binder resin. In this specification, the portion filled with inorganic particles, mixtures, etc., is referred to as the "inorganic particle-filled portion." The inorganic particle-filled portion may also contain binder resin to ensure the bonding strength between the inorganic particles and between the inorganic particles and the porous substrate. The inorganic particle-filled portion has pores created by interstitial volumes (spaces formed between adjacent inorganic particles). The inorganic coating can have a porous structure with a predetermined porosity due to these pores, thereby allowing gas or liquid to flow from one side surface to another. The inorganic particles and polymer columns can be bonded to each other due to adhesive properties or via binder resin.

[0113] In one embodiment of this disclosure, the thickness T of the inorganic particle filling portion i D can be used for polymer columnar structures before the separator is flattened. 50 85% or less. For example, thickness T i It can range from 5% to 40%. In one specific implementation, T i The thickness can range from 1.0 μm to 5 μm, and can be appropriately adjusted within this range. i It can be, for example, 4 μm or smaller, 3 μm or smaller, or 2 μm or smaller. T i The thickness can preferably be 1.0 μm or greater, and within the above-mentioned numerical range, it exhibits excellent adhesion to the electrodes, thus improving the cell strength of the battery. Meanwhile, a thickness of 5.0 μm or less is advantageous in terms of battery cycle characteristics and resistance characteristics. When the inorganic coating is disposed on both surfaces of the porous substrate, the thickness of the inorganic particle-filled portion refers to the value measured for the inorganic coating disposed on either surface.

[0114] In one embodiment of this disclosure, the height (thickness, T) of the inorganic particle filling portion (one side) is... i The thickness can be determined by cutting a cross-section of the separator specimen, observing the cross-section using SEM, and then measuring the thickness at two or more arbitrary points in the area where no polymer columnar structure is present, taking the average of these measurements as the height. When measuring the thickness at four or more points, the lowest and / or highest values ​​can be excluded, and the average of the remaining values ​​can be taken.

[0115] Furthermore, in one embodiment of this disclosure, the height of the inorganic particle filling portion tends to increase as it approaches the polymer column. This trend can be more pronounced in the region surrounding the polymer column. In other words, outside the surrounding region, the height of the inorganic particle filling portion can gradually increase from any point on the inorganic particle filling portion toward the polymer column, and this height can increase relatively sharply from the boundary of the surrounding region toward the polymer column. In one embodiment of this disclosure, the surrounding region can refer to a portion with a width of approximately 2 μm extending from the boundary between the inorganic particle filling portion and the polymer column toward the inorganic particle filling portion.

[0116] Inorganic particles

[0117] In one specific embodiment of this disclosure, the inorganic particles are not particularly limited, provided they are electrochemically stable. In other words, there are no particular limitations on the inorganic particles that can be used in this disclosure, as long as they do not undergo oxidation and / or reduction reactions within the operating voltage range of the electrochemical device in which they are used (e.g., 0 V to 5 V based on Li / Li+). In particular, using inorganic particles with a high dielectric constant helps to increase the degree of dissociation of electrolyte salts, such as lithium salts, in the electrolyte, thereby improving the ionic conductivity of the electrolyte.

[0118] For the reasons stated above, inorganic particles preferably include high-dielectric inorganic particles with a dielectric constant of 5 or greater, and more preferably 10 or greater. Non-limiting examples of inorganic particles with a dielectric constant of 5 or greater include BaTiO3, Pb(Zr,Ti)O3 (PZT), and b... 1-x La x Zr 1-y Ti y O3 (PLZT, 0) <x<1,0<y<1)、Pb(Mg 1 / 3 Nb 2 / 3 Hafnium dioxide (HfO2), SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, SiC, TiO2 or mixtures thereof.

[0119] Furthermore, as inorganic particles, inorganic particles with lithium-ion transfer capabilities can be used; that is, inorganic particles that contain lithium but do not store lithium but instead have the function of transporting lithium ions. Non-limiting examples of inorganic particles with lithium-ion transfer capabilities include those based on (LiAlTiP). x O yglass (0 < x < 4, 0 < y < 13), such as lithium phosphate (Li3PO4); lithium titanium phosphate (LixTiy(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) or 14Li2O - 9Al2O3 - 38TiO2 - 39P2O5; lithium germanium thiophosphate (Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), such as lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3) or Li 3.25 Ge 0.25 P 0.75 S4; lithium nitride (Li x N y , 0 < x < 4, 0 < y < 2), such as Li3N; SiS2-based glass (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4), such as Li3PO4 - Li2S - SiS2; P2S5-based glass (Li x P y S z , 0 < x < 3, 0 < y < 3, 0 < z < 7), such as LiI - Li2S - P2S5; or a mixture thereof.

[0120] In addition, there is no particular limitation on the average particle size of the inorganic particles, but it can be preferably in the range of 0.1 μm to 1.5 μm to form a coating with a uniform thickness and appropriate porosity. When the average particle size is less than 0.1 μm, the dispersibility may decrease, and when the average particle size is greater than 1.5 μm, the thickness of the formed coating may increase.

[0121] According to a non-limiting embodiment of the present disclosure, the diameter (D 50 ) of the inorganic particles can be appropriately adjusted within the range of 0.1 μm to 1.5 μm, and for example, it can be within the range of 200 nm to 1 μm.

[0122] Adhesive resin

[0123] Furthermore, as mentioned above, the inorganic coating may also contain a binder resin to supplement the bonding strength. In the inorganic coating, the inorganic particles and the binder resin may be included in a weight ratio of 70:30 to 99.9:0.1 or 70:30 to 99:1.

[0124] In one embodiment of this disclosure, the adhesive resin may comprise a PVdF-based polymer resin. The PVdF-based polymer resin may include at least one of the following: a homopolymer of vinylidene fluoride (i.e., polyvinylidene fluoride), a copolymer of vinylidene fluoride and monomers thereto, and mixtures thereof. In one embodiment of this disclosure, examples of said monomers may include fluorinated monomers, chlorine-based monomers, etc. Non-limiting examples of fluorinated monomers may include: vinyl fluoride; trifluoroethylene (TrFE); chlorofluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers, such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE), and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-m-dioxane); perfluoro(2,2-dimethyl-1,3-m-dioxane) (PDD); and so on, and may include one or more of them.

[0125] Together with or independently of this, the adhesive resin may also comprise a (meth)acrylate polymer resin. The (meth)acrylate polymer comprises (meth)acrylates as monomers, and non-limiting examples may include the following (meth)acrylate polymers comprising the following monomers: butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, ethyl (meth)acrylate, methyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, tert-butyl (meth)acrylate, amyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, lauryl (meth)acrylate, or tetradecyl (meth)acrylate.

[0126] Furthermore, in one embodiment of this disclosure, the inorganic coating may also contain additives, such as dispersants and / or thickeners, in an amount ranging from 1% to 3% by weight relative to 100% by weight of the inorganic coating. In one embodiment of this disclosure, one or more of the following may be suitably selected and used as additives: polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), ethyl hydroxyethyl cellulose (EHEC), methyl cellulose (MC), carboxymethyl cellulose (CMC), hydroxyalkyl methyl cellulose, and cyanoethylene polyvinyl alcohol.

[0127] Method for manufacturing separators

[0128] Next, a method for manufacturing the separators of this disclosure will be described. However, the following description relates to one embodiment of manufacturing the separators of this disclosure, and the method is not particularly limited thereto.

[0129] Specifically, inorganic particles are first introduced into a suitable solvent to prepare a mixture. Then, polymer particles for polymer columns are introduced into the mixture to prepare a slurry for the inorganic coating. The slurry is then applied to a porous substrate and dried.

[0130] In one embodiment of this disclosure, when the inorganic coating also comprises a binder resin, a polymer solution is prepared by dissolving the binder resin in a solvent. Inorganic particles and polymer particles for polymer columns can then be introduced sequentially or simultaneously into the polymer solution to prepare a slurry for the inorganic coating. The binder resin is preferably a water-soluble binder resin or a material having high affinity for the polymer particles for the polymer columns.

[0131] The obtained separators are then dried to integrally form an inorganic coating on the porous substrate. In this study, to prevent deformation of the polymer columnar material, the drying temperature of the separators is preferably set to be no more than 20°C higher than the observed glass transition temperature (Tg) of the polymer columnar material.

[0132] When preparing the slurry, water or an aqueous solvent containing water can be used as the solvent. Furthermore, when there are limitations in terms of drying speed and temperature, methanol, ethanol, isopropanol, etc., which have lower boiling points than water, can be used as a co-solvent.

[0133] The slurry can be applied using existing coating methods such as Mayer bars, die coaters, reverse roller coaters, or gravure coaters. Simultaneously, drying can be performed using common methods for solvent removal. Examples of drying methods include natural drying, forced-air drying, warm or hot air drying, high-temperature drying, convection drying, etc., however, the drying methods are not limited to these.

[0134] In addition to the manufacturing methods described above, any manufacturing method capable of realizing the above-mentioned separator structure can be applied without restriction.

[0135] This disclosure also provides a secondary battery including the aforementioned separator. The battery includes: a negative electrode; a positive electrode; and a separator located between the negative and positive electrodes, and the separator has the aforementioned characteristics.

[0136] In this disclosure, the positive electrode comprises a positive current collector and a positive active material layer comprising a positive active material, a conductor, and a binder resin on at least one side surface of the current collector. The positive active material may include one or a mixture of two or more of the following: layered compounds, such as lithium manganese composite oxides (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), or lithium nickel oxide (LiNiO2), or compounds substituted with one or more transition metals; lithium manganese oxides, such as those with the chemical formula Li... 1+x Mn 2-x O4 (here, x is 0 to 0.33), LiMnO3, LiMn2O3 or LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxide, such as LiV3O8, LiFe3O4, V2O5 or Cu2V2O7; and LiNi 1-x M x Ni-site type lithium nickel oxide represented by O2 (here, M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); by chemical formula LiMn 2-x M x Lithium manganese complex oxides represented by O2 (here, M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (here, M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which some Li in the chemical formula is replaced by alkaline earth metal ions; disulfide compounds; and Fe2(MoO4)3.

[0137] In this disclosure, the negative electrode comprises a negative electrode current collector and a negative electrode active material layer comprising a negative electrode active material, a conductor, and a binder resin on at least one side surface of the current collector. The negative electrode may contain a mixture of one, two, or more of the following as the negative electrode active material: lithium metal oxide; carbon, such as non-graphitizable carbon or graphite-based carbon; metal composite oxides, such as Li... x Fe2O3 (0≤x≤1), Li x WO2 (0≤x≤1) and Sn x Me 1-x Me' y O z(Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, an element of Group 1, Group 2 or Group 3 of the periodic table, a halogen; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8); lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; 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.

[0138] In a specific embodiment of the present disclosure, the conductor can be, for example, any one selected from the following: graphite, carbon black, carbon fiber or metal fiber, metal powder, conductive whiskers, conductive metal oxides, activated carbon, and polyphenylene derivatives, or a mixture of two or more of these conductive materials. More specifically, the conductor can be one selected from the following: natural graphite, artificial graphite, super p, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, Denka black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide, or a mixture of two or more of these conductive materials.

[0139] The current collector is not particularly limited as long as it has high conductivity and does not cause chemical changes to the corresponding battery, and for example, stainless steel; copper; aluminum; nickel; titanium; calcined carbon; or aluminum or stainless steel whose surface is treated with carbon, nickel, titanium, silver, etc. can be used; and so on.

[0140] As the binder resin, polymers commonly used in electrodes in the art can be used. Non-limiting examples of such binder resins can include polyvinylidene fluoride-copoly-hexafluoropropylene, polyvinylidene fluoride-copoly-trichloroethylene, polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-copoly-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, etc., but are not limited thereto.

[0141] ] The electrode assembly prepared as above can be inserted into a suitable housing, and an electrolyte can be injected therein to manufacture a battery.

[0142] In the present disclosure, the electrolyte includes by having such as A + B - (where A + includes an alkali metal cation such as Li + , Na + or K+ or combinations thereof, ions, and B - Including anions such as PF6 - BF4 - Cl - ,Br - I - ClO4 - AsF6 - CH3CO2 - CF3SO3 - N(CF3SO2)2 - Or C(CF2SO2)3 - An electrolyte is obtained by dissolving or dissociating a salt of an ion (or a combination thereof) in an organic solvent, said organic solvent including 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 (g-butyrolactone), ester-based compounds, or mixtures selected from one or more of these, however, the electrolyte is not limited thereto.

[0143] Furthermore, in one specific embodiment of this disclosure, the organic solvent may comprise an ester-based compound. The ester-based compound may preferably be included in an amount of 30% or more, 50% or more, 60% or more, or 65% or more, relative to 100% by weight of the organic solvent.

[0144] In one specific embodiment of this disclosure, the ester-based compound may include at least one selected from: isobutyl propionate, isoamyl propionate, isobutyl butyrate, isopropyl propionate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl butyrate, ethyl butyrate, propyl butyrate, and butyl butyrate.

[0145] Furthermore, this disclosure provides a battery module including a battery having the electrode assembly 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 this device may include: power tools that operate by receiving power from an electric motor; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), etc.; electric two-wheeled bicycles, including electric bicycles (E-bikes) and electric scooters (E-scooters); electric golf carts; systems for energy storage; and so on, but are not limited thereto.

[0146] The present disclosure will be described in detail below with reference to embodiments in order to specifically describe the present disclosure. However, embodiments based on the present disclosure may be modified in various other forms, and the scope of the present disclosure should not be construed as limited to the embodiments described below. Embodiments of the present disclosure are provided to describe the present disclosure more fully to those skilled in the art.

[0147] Example

[0148] Measurement of the thickness of the separator

[0149] In the examples and comparative examples, the thickness of the separator was determined by cutting a cross-section of the separator sample, observing the cross-section using SEM, and then taking the thickness at the thickest point as the thickness of the separator. Based on the thickest point among the measured points, the thickness of the separator was measured before and after compression to calculate the compression ratio, and the results are summarized in Table 2 below. Meanwhile, the thickness of the inorganic particle filling portion was determined as the average of the values ​​measured at three arbitrary points.

[0150] Measurement of the solubility of polymer columnar materials

[0151] The polymer material to be used as the polymer column in each of the comparative and examples was dried at 60°C to prepare a 0.3 g sample. The sample was placed on an 80 mesh sieve and dissolved in THF (tetrahydrofuran) for 24 hours, after which the weight of the remaining residue was compared with the initial weight. Solubility was calculated based on the following [Equation 4]. The results are summarized in Table 1 below.

[0152] [Equation 4]

[0153] Solubility (%) = {(Weight measured before impregnation - Weight measured after impregnation) / (Weight measured before impregnation)} × 100

[0154] Measurement of storage modulus of polymer columnar materials

[0155] Samples measuring 40 mm × 6 mm were prepared using the polymer material to be used as polymer columns in each of the comparative and examples. The sample thickness was 1 mm. The storage modulus of the samples was measured. The storage modulus was measured using a rheological analyzer (Dynamic Mechanical Analyzer (DMA), ARES-G2, TA Instrument). The storage modulus was determined by performing temperature scan tests at a temperature range of -60°C to 80°C and a frequency of 1.0 rad / s. The results are summarized in Table 1 below. In addition, the storage modulus and loss modulus were determined during the measurement, and the tan δ peak was determined from them.

[0156] [Table 1]

[0157]

[0158] Example 1

[0159] Inorganic particles (Al2O3, D) 50 An acrylic emulsion (Toyo Corporation, CSB-130) and carboxymethyl cellulose (Daicel Corporation, Daicel 1220), approximately 0.6 μm in size, serving as a binder resin, were introduced into a solution of water and ethanol (95:5) at a ratio of 96:2:2, and dispersed using a bead mill to obtain a mixture. Polymer particles (acrylic polymer A24, D) for polymer columnar formation were then introduced into the mixture. 50 4.22 μm, G' 2,623 Pa@25℃, Tg 47.2℃), and the resulting mixture was stirred to obtain a dispersion slurry. The concentration of solid contents in the dispersion slurry was 30% by weight. In the mixture, the content of polymer particles for polymer columns was approximately 25 parts by weight relative to 100 parts by weight of inorganic particles. The dispersion slurry was applied to a porous substrate (Senior SW807I, thickness 7.0 μm) using a microgravure coating method and dried at 60℃ to obtain a separator. Furthermore, the opposite surface was coated and dried in the same manner to obtain a double-sided coated separator. In the separator, the loading of the inorganic coating (one side) was 6.8 g / m² based on both sides of the porous substrate. 2 .

[0160] Figure 2a SEM images of the obtained separator surface are shown, as well as Figure 2bA SEM image of its cross-section is shown. Referring to this, polymer columns are exposed on the surface of the inorganic coating. Furthermore, numerous polymer columns are identified as being spaced at predetermined distances and distributed in an island pattern.

[0161] Meanwhile, the obtained separator was pressed for 20 seconds at 3.5 MPa and 60°C using a hot press, and the compression ratio of the separator was determined. Figure 3a SEM images of the separator surface after compression are shown, as well as Figure 3b An SEM image of its cross-section is shown. Referring to this, it is determined that the protruding portions within the polymer column are compressed and flattened.

[0162] Simultaneously, using SEM images of the separator from Example 1, the ratio between the lower diameter (a) and the upper diameter (b) of the polymer column before and after pressing was determined, and the values ​​are summarized in Table 2. Measurements were taken on both surfaces of the separator, and the results for the upper and lower surfaces are described in Table 2. Referring to this, it was determined that the b / a ratio was greater than 2 both before and after pressing.

[0163] [Table 2]

[0164]

[0165] Example 2

[0166] Inorganic particles (Al2O3, D) 50 An acrylic emulsion (Toyo Corporation, CSB-130) and carboxymethyl cellulose (Daicel Corporation, Daicel 1220), approximately 0.6 μm in diameter, serving as a binder resin, were introduced into a solution of water and ethanol (95:5) at a ratio of 96:2:2, and dispersed using a bead mill to obtain a mixture. A polymer (A24, D) for polymer columnar formation was then introduced into the mixture. 50 4.22 μm, G' 2,623 Pa@25℃, Tg 47.2℃), and the resulting mixture was stirred to obtain a dispersion slurry. The concentration of solid contents in the dispersion slurry was 30% by weight. In the mixture, the content of polymer particles for polymer columns was approximately 30 parts by weight relative to 100 parts by weight of inorganic particles. The dispersion slurry was applied to a porous substrate (Senior SW807I, thickness 7.0 μm) using a microgravure coating method and dried at 80℃ to obtain a separator. Furthermore, the opposite surface was coated in the same manner and dried to obtain a double-sided coated separator. In the separator, the loading of the inorganic coating (one side) was 6.9 g / m² based on both sides of the porous substrate. 2 .

[0167] Meanwhile, the obtained separator was pressed for 20 seconds at 3.5 MPa and 60°C using a hot press, and the compression ratio of the separator was determined.

[0168] Comparative Example 1

[0169] Inorganic particles (Al2O3, D) 50 An acrylic emulsion (Toyo Corporation, CSB-130) and carboxymethyl cellulose (Daicel Corporation, Daicel 1220), approximately 0.6 μm thick, serving as an adhesive resin, were introduced into a solution of water and ethanol (95:5) at a ratio of 96:2:2, and the mixture was stirred to obtain a mixture. The mixture was applied to a porous substrate (Asahi Corporation, ND506, 6.0 μm thick) using a microgravure coating method and dried at 80°C.

[0170] Meanwhile, the obtained separator was pressed for 20 seconds using a hot press at 3.5 MPa and 60°C, and the compression ratio of the separator was determined.

[0171] Comparative Example 2

[0172] The separator was manufactured in the same manner as in Example 2, except that an acrylic polymer A15 (D) for polymer columns was used. 50 3.84 μm, G' 1,381 Pa@25℃, Tg 59.3℃).

[0173] Figure 4 SEM images of the obtained separator surface are shown. Referring to these images, polymer columns are exposed on the surface of the inorganic coating. Furthermore, numerous polymer columns are identified as being spaced at predetermined distances and distributed in an island pattern.

[0174] Meanwhile, the obtained separator was pressed for 20 seconds at 3.5 MPa and 60°C using a hot press, and the compression ratio of the separator was determined. Figure 5 An SEM image of the separator surface after compression is shown. Referring to this, it is determined that the protruding portions of the polymer columnar structure were not compressed and maintained their height.

[0175] Comparative Example 3

[0176] The separator was manufactured in the same manner as in Example 2, except that an acrylic polymer A25 (D) for polymer columns was used. 50 3.92 μm, G' 25.2 Pa@25℃, Tg 41.1℃).

[0177] Meanwhile, the obtained separator was pressed for 20 seconds at 3.5 MPa and 60°C using a hot press, and the compression ratio of the separator was determined.

[0178] For the separators manufactured in the embodiments and comparative examples, the separator thickness and other parameters are summarized in Table 3 below.

[0179] [Table 3]

[0180]

[0181] Manufacturing of the positive electrode

[0182] A positive electrode active material slurry was prepared by adding LiCoO2 (as the positive electrode active material), carbon black (as the conductor), and polyvinylidene fluoride (PVdF) (as the binder) to the solvent N-methylpyrrolidone (NMP) in a weight ratio of 96:2:2. The positive electrode active material slurry was coated onto a sheet-like aluminum current collector and dried to achieve a final positive electrode loading of 3.8 mAh / cm³. 2 The positive electrode active material layer.

[0183] Manufacturing of negative electrode

[0184] A negative electrode slurry was formed by mixing artificial graphite as the negative electrode active material, carbon black as the conductor, carboxymethyl cellulose as the dispersant, and styrene-butadiene emulsion as the binder in a weight ratio of 96:0.5:1.5:2.0, and then adding the mixture to water as a solvent. The negative electrode slurry was then used at a concentration of 4.0 mAh / cm³. 2 The loading amount is coated onto a copper current collector and dried to manufacture a negative electrode in which a layer of negative electrode active material is formed.

[0185] Evaluation of the adhesion between the negative electrode and the separator

[0186] The separator samples obtained in each of the Examples and Comparative Examples were cut into 100 mm (length) × 25 mm (width) dimensions to prepare individual specimens. Each specimen was laminated with a negative electrode and then hot-pressed at 70°C for 20 seconds to obtain a laminate. The laminate was fixed to an adhesive strength measuring device (LLOYD Instrument, LF plus), and the separator portion was peeled off at a rate of 25 mm / min at a 180° angle at 25°C, and the corresponding strength was measured.

[0187] Referring to Table 4 below, the spacer in Comparative Example 2 did not adhere to the electrode. Meanwhile, at the same pressing time, Examples 1 and 2 exhibited higher adhesion compared to Comparative Example 1. Therefore, it is determined that the spacer according to this disclosure exhibits excellent adhesion and allows for reduced lamination time, which is also advantageous in terms of processability.

[0188] Methods for measuring resistance

[0189] The resistance of the separators in each of the Examples and Comparative Examples was measured using impedance spectroscopy. Separators were inserted between stainless steel plates to fabricate a coin cell, and an electrolyte of 1 M LiPF6 in ethylene carbonate / ethyl methyl carbonate (EC / EMC, volume ratio 30:70) was injected into it. Electrochemical impedance spectroscopy was performed on the cells at 25°C using a Solaton 1470E battery testing system and a 1255B frequency response analyzer in a scan range of 100,000 Hz to 10,000 Hz, and the resistance was measured based on the analytical results. Referring to Table 4 below, suitable resistance values ​​for battery operation were determined for Examples 1 and 2.

[0190] [Table 4]

[0191]

[0192] Molecular weight measurement

[0193] Molecular weight (weight-average molecular weight / number-average molecular weight) was measured by gel permeation chromatography (GPC). An Agilent Technologies PL GPC220 was used, and the measurement conditions are as follows.

[0194] - Column (Manufacturer, Model): 2×TSKgel SupermultiporeHZ-M+TSKgel SuperHZ-2500

[0195] - Eluent: THF

[0196] - Temperature: 40℃

[0197] - Flow rate: 1.0 mL / min

[0198] - Injection volume and sample concentration: 30 μl, and 1 mg / mL to 10 mg / mL

[0199] - Standard material: Polystyrene

[0200] - Detector: RI

[0201] Measurement of glass transition temperature

[0202] The glass transition temperature (Tg) was measured using a differential scanning calorimeter (DSC, TA Instrument). Each obtained sample (10 mg to 15 mg) was cooled from ambient temperature to -30 °C and then heated to 200 °C at 10 °C / min. The samples were then cooled to -30 °C and reheated at 10 °C / min while the glass transition temperature was measured.

[0203] [Figure Labels]

[0204] 10 Porous Substrates

[0205] 20 Inorganic Coating

[0206] 100 polymer columnar bodies

[0207] 200 inorganic particles

[0208] T s Thickness of the separator

[0209] T p The protrusion height of the polymer column

[0210] T i The height of the inorganic particle filling section, T c Height of inorganic coating

Claims

1. A separator for an electrochemical device, the separator comprising: Porous polymer substrate; and An inorganic coating covering one or both surfaces of the porous polymer substrate. The inorganic coating comprises a plurality of adhesive polymer columns, each having a predetermined volume, and the polymer columns are made of a polymer material and are non-porous. At least a portion of the polymer columnar structure is exposed on the surface of the inorganic coating, and another portion is in contact with the surface of the porous substrate. At least one of the polymer columns is spaced apart from the other polymer column by a predetermined distance. The spaces between the polymer columns are filled with inorganic particles, and The thickness compression ratio of the separator under pressing conditions of 1.5 MPa to 4.0 MPa and 45°C to 65°C is 25% or greater and 95% or less, and the compression ratio is calculated by the following [Equation 1]: [Equation 1] Compression ratio (%) = {(Initial thickness of the separator before compression - Thickness of the separator after compression) / (Initial thickness of the separator before compression)} × 100.

2. The separator according to claim 1, wherein the polymer column has a storage modulus of 100 Pa or greater and 3,500 Pa or less at room temperature.

3. The separator according to claim 1, wherein the polymer column has a storage modulus of 0.05 Pa or greater and 50 Pa or less at 60°C.

4. The separator according to claim 1, wherein the thickness (T) of the inorganic particle filling portion... i ) is the D of the polymer column. 50 85% or less.

5. The separator according to claim 1, wherein the D of the polymer columnar body 10 D 50 30% or more, and the D of the polymer column 90 D 50 200% or less.

6. The separator according to claim 1, wherein, based on a top view of the separator, the area occupied by the polymer column is 10% to 50% relative to 100% of the surface area of ​​the inorganic coating.

7. The separator according to claim 1, wherein when the separator is pressed under compression conditions of 1.5 MPa to 4.0 MPa and 45°C to 65°C, the thickness difference of the separator before and after compression is 4 μm or greater, and the thickness of the separator after compression is 5 μm to 20 μm.

8. The separator according to claim 1, wherein when the separator is pressed under compression conditions of 1.5 MPa to 4.0 MPa and 45°C to 65°C, the thickness (T) of the separator after compression is... s ) equal to or greater than T i and equal to or less than T i ×1.1(T) i <T s <T i ×1.1), and the protruding thickness of the polymer column from the inorganic particle filling portion after the compression is 1 μm or less.

9. The separator according to claim 1, wherein the cross-sectional area (b) of at least one of the polymer columns included in the inorganic coating, observed in a section at 5% of the upper portion of the inorganic coating toward its lower portion, is greater than the cross-sectional area (a) of the polymer column observed in a section at 5% of the lower portion of the inorganic coating toward its surface portion.

10. The separator according to claim 1, wherein in the cross-section of the polymer column observed in the vertical section of the inorganic coating, the lower diameter (a) of at least one of the polymer columns included in the inorganic coating is smaller than the upper diameter (b) of the polymer column, and the ratio of the diameter (b) to the diameter (a) is 2 to 20.

11. The separator according to claim 1, wherein the inorganic coating has a porous structure formed by the interstitial volume between the inorganic particles.

12. An electrochemical device comprising the separator according to claim 1.

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