Separator for electrochemical devices and method of manufacturing the same

Abstract

This disclosure provides 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 polymer columnar portion and an inorganic particle portion, the polymer columnar portion comprising a plurality of adhesive polymer columns each having a predetermined volume, the inorganic particle portion comprising inorganic particles filled between the polymer columns, 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, while another portion is in contact with the surface of the porous polymer substrate, at least one of the individual polymer columns being spaced apart from the other polymer columns by a predetermined distance, some of the polymer columns in the polymer columnar portion protruding from the surface of the inorganic particle portion, and a height (T) of the protruding polymer columns from the surface of the inorganic particle portion. p (1 μm or larger)

Description

Technical Field

[0001] This disclosure relates to separators used in electrochemical devices, such as lithium-ion secondary batteries.

[0002] This application claims priority to Korean Patent Application No. 10-2024-0043445, filed on March 29, 2024, the disclosure of which is incorporated herein by reference in its entirety. Background Technology

[0003] Non-aqueous secondary batteries, represented by 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 vehicles and other applications has been considered.

[0004] Currently manufactured lithium-ion batteries use porous polymer substrates, such as polyolefin-based polymer resins, as separator substrates to prevent short circuits between the positive and negative electrodes. However, polymer substrates suffer from low heat resistance, exhibiting shrinkage or melting at high temperatures. 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 a short circuit caused by contact between the positive and negative electrodes. This could lead to a rapid release of electrical energy, potentially causing the battery to explode or catch fire.

[0005] 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.

[0006] Meanwhile, electrode assemblies are typically manufactured via a continuous roll-to-roll process. In this paper, a lamination process is performed to press the laminated electrodes and spacers together (applying heat pressing as needed). To achieve the desired level of electrode-spacer bonding strength, sufficient lamination process time needs to be ensured; however, this can lead to reduced productivity, such as decreased production speed.

[0007] Therefore, in separators used in electrochemical devices, there is a need for ongoing research and development to ensure sufficient porosity and adhesion (between the electrode and the separator) as well as process efficiency. Summary of the Invention

[0008] Technical issues

[0009] This disclosure relates to providing a separator capable of ensuring high adhesion to electrodes and improving battery production efficiency. Furthermore, this disclosure relates to providing an electrochemical device including said separator. Other objects and advantages of this disclosure will be apparent from the means or methods set forth in the claims and combinations thereof.

[0010] Technical solution

[0011] A first 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 polymer columnar portion and an inorganic particle portion, the polymer columnar portion comprising a plurality of adhesive polymer columns each having a predetermined volume, the inorganic particle portion comprising inorganic particles filled between the polymer columns, 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, while another portion is in contact with the surface of the porous polymer substrate, at least one of the individual polymer columns being spaced apart from the other polymer columns by a predetermined distance, some of the polymer columns in the polymer columnar portion protruding from the surface of the inorganic particle portion, and a height (T) of the protruding polymer columns from the surface of the inorganic particle portion. p (1 μm or larger)

[0012] In the foregoing aspects of this disclosure, the D of the polymer column 10 D can be a polymer column 50 30% or more, and D of polymer columnar materials 90 D can be a polymer column 50 200% or less.

[0013] In the foregoing aspects of this disclosure, the D of the polymer column 50 D can be inorganic particles 50 At least twice as much.

[0014] In the foregoing aspects of this disclosure, in any of the first to third embodiments, the D of the inorganic particles 50 It can be 0.1 μm to 1.5 μm, and D of polymer columnar materials. 50 It can range from 2.0 μm to 7.0 μm.

[0015] In the above aspects of this disclosure, the thickness (T) of the inorganic particle portion i ) can be the thickness (T) of the polymer columnar portion c 85% or less.

[0016] In the above aspects of this disclosure, the thickness (T) of the inorganic particle portion i The thickness can range from 1.0 μm to 5.0 μm, and the thickness of the polymer columnar portion (T) can also vary. c The thickness can range from 2.0 μm to 7.0 μm.

[0017] In the above aspects of this disclosure, the thickness (T) of the inorganic particle portion i ) and the thickness of the polymer columnar portion (T) c It can satisfy the following equation 1.

[0018] 0.2< <0.7 Equation 1

[0019] In any of the first to seventh embodiments of this disclosure, the volume of the protruding polymer column can be 25% to 55% relative to 100% by volume of the inorganic coating.

[0020] In the above aspects of this disclosure, when the separator is pressed under temperature conditions of 25°C to 90°C and pressure conditions of 0.5 MPa to 20 MPa, the thickness difference between the inorganic particulate portion and the polymer column can be less than 1 μm.

[0021] In the foregoing aspects of this disclosure, based on the top view image of the separator, the area of ​​the polymer columnar structure exposed on the surface of the inorganic coating may be 5% to 80% relative to 100% of the surface area of ​​the inorganic coating.

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

[0023] In the foregoing aspects of this disclosure, the cross-sectional area (b) of at least one of the polymer columnar bodies included in the inorganic coating, as observed in a section at the upper 5% from the uppermost part of the inorganic coating toward its lower part, may be greater than the cross-sectional area (a) of the polymer columnar body observed in a section at the lower 5% from the lowermost part of the inorganic coating toward its surface portion.

[0024] In the above aspects of this disclosure, in the cross-section of the polymer column observed in the vertical section of the inorganic coating, the diameter (a) of the lower part of at least one of the polymer columns included in the inorganic coating is smaller than the diameter (b) of the upper part of the polymer column, and the ratio of diameter (b) to diameter (a) can be from 2 to 20.

[0025] Meanwhile, one aspect of this disclosure relates to an electrochemical device that includes a separator for the electrochemical device according to any of the foregoing aspects.

[0026] In this disclosure, each of the embodiments may be implemented independently. Alternatively, two or more of the embodiments may be implemented in combination.

[0027] Beneficial effects

[0028] The separator according to this disclosure not only has excellent adhesion to the electrodes but also ensures sufficient porosity, thereby exhibiting excellent electrical and ionic conductivity characteristics. Furthermore, the time spent on the lamination process can be reduced during electrode assembly manufacturing, thus achieving high process efficiency in battery manufacturing. Attached Figure Description

[0029] The accompanying drawings illustrate preferred embodiments of the present disclosure and are intended to provide a better understanding of the technical concept of the present disclosure together with the foregoing description of the invention. Therefore, the present disclosure should not be construed as limited to the content described in these drawings.

[0030] Figure 1 The image is a SEM image of the surface of the inorganic coating at 500x magnification before the separator manufactured in Example 1 is planarized.

[0031] Figure 2 The image is a SEM image of the surface of the inorganic coating before the separator manufactured in Example 1 is planarized, at a magnification of 2000x.

[0032] Figure 3 The image is a SEM image of the surface of the inorganic coating before the separator manufactured in Example 1 is planarized, at a magnification of 5000x.

[0033] Figure 4 The image is a SEM image of the surface of the inorganic coating after the separator manufactured in Example 1 has been planarized, at a magnification of 500x.

[0034] Figure 5 The image is a SEM image of the surface of the inorganic coating after the separator manufactured in Example 1 has been planarized, at a magnification of 5500x.

[0035] Figure 6 The image is a SEM image of the cross-section of the separator manufactured in Example 1 before planarization at a magnification of 5500x.

[0036] Figure 7 This is an SEM image of the cross-section of the separator manufactured in Example 1 after flattening, at a magnification of 5500x.

[0037] Figure 8 This is a schematic diagram showing a cross-section of a separator according to one embodiment of the present disclosure. Detailed Implementation

[0038] 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, and should be interpreted as corresponding to the technical concept of the present disclosure based on the principle that the inventor can appropriately define the concepts of the terms in order to describe his or her 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. It should be understood that various equivalent examples and modifications may exist at the time of submission.

[0039] Throughout this specification, unless otherwise stated to the contrary, a description in which a part "includes" a constituent element means that it may further include other constituent elements, and does not exclude other constituent elements.

[0040] When the meaning of reference involves inherent manufacturing and material tolerances, terms such as “about” or “substantially” used throughout this specification are used to indicate the meaning of numbers or close to said numbers and to prevent unethical infringers from unfairly using statements of precise or absolute numbers to aid in understanding the disclosure of this application.

[0041] Throughout this specification, the description of "A and / or B" means "A or B, or both".

[0042] In this specification, the D of the polymer column is... 50 This refers to the diameter at the 50th percentile point in the cumulative polymer column count distribution based on diameter. In other words, the D of the polymer column... 50 This refers to the diameter at the 50th percentile point in the cumulative polymer column count distribution based on diameter. Furthermore, the D of the polymer column... 10 This refers to the diameter at the 10th percentile point in the cumulative polymer column count distribution based on the polymer column diameter, and the D of the polymer column. 90 This refers to the diameter at the 90th percentile point in the cumulative polymer column count distribution based on the polymer column diameter. The diameter 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), and the diameter distribution is calculated by measuring the differences in the diffraction patterns based on the polymer column size as the polymer columns pass through the laser beam. 10 D50 and D 90 The diameter of the polymer column can be measured by calculating the diameter of the polymer column at the 10%, 50%, and 90% points of the cumulative polymer column count distribution based on the diameter of the polymer column in the analyzer.

[0043] The specific terminology used in the following detailed description of the invention is for convenience only and is not intended to be limiting. Terms such as “left,” “right,” “up,” and “down” may indicate directions in the relevant 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,” and related words and phrases, indicate positions and directions in the relevant figures and should not be limiting. Such terms include the words listed above, their derivatives, and words with similar meanings.

[0044] In this disclosure, the glass transition temperature (Tg) can be measured by differential scanning calorimetry (DSC) curves obtained by DSC analysis at a heating rate of 10 °C.

[0045] 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 the concepts of lithium-ion batteries, nickel-cadmium batteries, nickel-metal hydride batteries, etc.

[0046] The separator for an electrochemical device disclosed herein includes: a porous polymer substrate; and an inorganic coating covering one or both surfaces of the porous polymer substrate.

[0047] <Separator>

[0048] This disclosure includes separators.

[0049] Figure 8 This is a schematic cross-section of the separator of this disclosure, particularly showing the form of the separator before compression (where the polymer columnar parts protrude beyond the inorganic particle portion). Compression can refer to the artificial application of external force during the battery assembly process.

[0050] In one embodiment of this disclosure, the separator includes: a porous polymer substrate 10; and an inorganic coating 20 formed on at least one or both side surfaces of the porous polymer substrate. The inorganic coating 20 comprises polymer columnar portions and inorganic particle portions, the polymer columnar portions comprising a plurality of adhesive polymer columns 100 each having a predetermined volume, and the inorganic particle portions comprising inorganic particles 200 filling the spaces between the polymer columns.

[0051] Thickness of the separator (T) s The thickness can be from 5.0 μm to 30 μm, and the thickness can be appropriately adjusted within the above range. For example, the thickness can be 25.0 μm or less, 20.0 μm or less, 12.0 μm or less, or 10.0 μm or less. Furthermore, the porosity of the separator can be from approximately 30% to 80% by volume. The porosity can be appropriately adjusted within the above range. For example, the porosity can be 30% by volume or more, 35% by volume or more, 40% by volume or more, 50% by volume or more, or 55% by volume 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. Simultaneously, 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 greater, 70 seconds / 100 cc or greater, 100 seconds / 100 cc or greater, 120 seconds / 100 cc or greater, or 150 seconds / 100 cc or greater. Alternatively, the porosity can be 220 seconds / 100 cc or less, 200 seconds / 100 cc or less, or 180 seconds / 100 cc or less.

[0052] In one embodiment of this disclosure, the thickness of the separator (T) s 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 separator thickness. Alternatively, the thickness can be measured at two or more arbitrary points, and the average of these measurements can be taken as the separator thickness. 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. When measuring the separator thickness based on an average value, it is appropriate to measure the thickness based on the polymer columnar structure rather than the inorganic particulate portion.

[0053] In one embodiment of this disclosure, porosity can be calculated by determining the density (apparent density) of the object to be measured (e.g., a separator) and the net density of the object to be measured (derived from the composition ratio of the materials contained in the 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].

[0054] [Equation 2]

[0055] Porosity (volume %) = {1 - (apparent density / net density)} × 100

[0056] Meanwhile, the apparent density in the above formula can be calculated by the following [Equation 3].

[0057] [Formula 3]

[0058] 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 ])}

[0059] 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.

[0060] The term "permeability" as used in this specification refers to the time required for 100 cc of air to pass through an object whose permeability is to be measured (e.g., a separator or porous polymer substrate), and can be expressed in seconds per 100 cc. It is interchangeable with transmittance and is typically expressed as a Gurley value, etc. In one specific embodiment of this disclosure, permeability can be measured according to JIS P8117. Furthermore, the air permeability P1 measured for an object of thickness T1 can be converted to the transmittance P2 corresponding to a thickness of 20 μm using the formula P2 = (P1 × 20) / T1.

[0061] In one embodiment of this disclosure, the thickness compression ratio of the separator under compression conditions (e.g., pressure conditions of 0.5 MPa to 20 MPa, or 2.0 MPa to 8.0 MPa and temperature conditions of 25°C to 90°C, or 55°C to 65°C) can be 25% or greater and 40% or less. The compression ratio can be calculated using Equation 4 below.

[0062] [Formula 4]

[0063] Compression ratio (%) = {(Initial thickness of the separator before compression - Thickness of the separator after compression) / (Initial thickness of the separator before compression)} × 100

[0064] Furthermore, in one embodiment of this disclosure, the spacer can be planarized by pressing the protruding portion under pressure conditions (e.g., pressure conditions of 0.5 MPa to 20 MPa, 2.0 MPa to 8.0 MPa, or 2.5 MPa to 6 MPa and temperature conditions of 25°C to 90°C, or 55°C to 65°C), and thus the thickness of the inorganic coating can become uniform. Simultaneously, the pressing can be hot pressing. Such characteristics are 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, thereby preventing separation. In other words, under the conditions used for laminating the electrode and the spacer (i.e., hot pressing conditions), the polymer column can exhibit softening properties.

[0065] In this paper, 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 15 μm or less, or 5 μm to 15 μm.

[0066] <Porous polymer substrate>

[0067] A porous polymer substrate is a substrate having multiple pores formed therein, which acts as a porous ion-conducting barrier that blocks electrical contact between the negative and positive electrodes while allowing ions to pass through. These pores are interconnected, allowing gas or liquid to pass from one side surface of the substrate to the other.

[0068] Organic or inorganic materials with electrical insulating properties can be used as the materials constituting such porous polymer substrates. In particular, thermoplastic resins are preferred as the materials constituting the substrate in providing a shut-off function. Here, the shut-off function refers to the function in which, when the battery temperature rises, the thermoplastic resin melts and seals the pores of the porous substrate to block ion migration, thereby preventing thermal runaway of the battery. Thermoplastic resins with melting points below 200°C are suitable, and polyolefins are particularly preferred.

[0069] Furthermore, it may further comprise at least one of the polymeric resins (e.g., polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene ether, polyphenylene sulfide, or polyethylene naphthalate). The porous polymeric substrate may be a nonwoven fabric, a porous polymeric membrane, or a laminate of both or more thereof, but is not particularly limited thereto.

[0070] Specifically, the porous polymer substrate is any one of the following a) to e).

[0071] a) A porous membrane formed by melting / extruding a polymer resin.

[0072] b) A multilayer membrane formed by laminating two or more layers of the porous membrane in a).

[0073] c) A nonwoven web prepared by laying filaments obtained by melting / spinning polymer resin.

[0074] d) A multilayer film formed by laminating two or more layers of the nonwoven web of b), and

[0075] e) A porous composite membrane having a multilayer structure including two or more of a) to d).

[0076] In this disclosure, the thickness of the porous polymer 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, and conversely, when the thickness exceeds the above range (i.e., too thick), the resistance of the separator may increase excessively.

[0077] 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 the lower limit mentioned above, it may be difficult to ensure sufficient mechanical properties. Furthermore, when the weight-average molecular weight is greater than the upper limit mentioned above, the shut-off properties may deteriorate, or molding may become difficult. Additionally, in terms of improving manufacturing yield, the puncture strength of the porous polymer substrate can be 300 gf or greater. The puncture strength of the porous substrate is represented by the maximum puncture load (gf) measured using a Kato tech KES-G5 handheld compression tester under conditions of a needle tip curvature radius of 0.5 mm and a puncture speed of 2 mm / s. Meanwhile, the weight-average molecular weight can be measured by methods such as gel chromatography.

[0078] In one specific embodiment of this disclosure, any planar porous polymer substrate used in electrochemical devices can be used as the porous polymer substrate. For example, an insulating film with high ion permeability and mechanical strength, typically 10 nm to 200 nm pore size, and typically 2 μm to 12 μm thickness can be used.

[0079] Furthermore, the porous polymer substrate may have a porosity of 20% to 80% or 30% to 60% and an average pore size of 10 nm to 200 nm, however, the porosity and average pore size are not particularly limited thereto.

[0080] Inorganic Coatings

[0081] In this disclosure, the separator includes an inorganic coating formed on one side surface of a porous polymer substrate. The inorganic coating comprises polymer columnar portions and inorganic particle portions, the polymer columnar portions comprising a plurality of adhesive polymer columns each having a predetermined volume, and the inorganic particle portions comprising inorganic particles filling the spaces between the polymer columnar portions.

[0082] In one specific embodiment of this disclosure, the inorganic particles may be included in the inorganic coating in an amount ranging from about 50% to 95% by weight, preferably from 70% to 90% by weight, relative to 100% by weight of the inorganic coating.

[0083] Furthermore, the polymer columns can be included in an amount ranging from 5 to 30 parts by weight, preferably from 10 to 25 parts by weight, relative to 100 parts by weight of inorganic particles. When the content of polymer columns is low, it is difficult to ensure the desired level of adhesion; however, when polymer columns are included in an amount exceeding the above range, the Gurley value and / or porosity of the separator may decrease, which is undesirable.

[0084] Meanwhile, in the top view image of the inorganic coating, the total area of ​​the polymer columnar body can be 5% to 80%, 5% to 60%, or 5% to 40% relative to the total area of ​​the inorganic coating before compression, after compression, or both before and after compression. Preferably, the total area can be 10% to 35%.

[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 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 together with it, 20 nm or more, 50 nm or more, or 100 nm or more. For example, the average pore size of the inorganic coating can be from 20 nm to 800 nm. The pore size can be calculated by shape analysis using SEM images. When the pore size is smaller than the above range, the pores may be blocked due to the expansion of the binder resin in the coating, and when the pore size is outside 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. When the porosity meets the above range, it is advantageous in terms of lithium-ion permeability, and because the surface opening ratio is not too high, it is suitable for ensuring adhesion between the spacer and the electrode.

[0087] <Polymer columnar structure>

[0088] The inorganic coating may include polymer columnar portions comprising a plurality of adhesive polymer columns, each having a predetermined volume, and the polymer columns may contain polymer resin in an amount of 90% or more, 95% or more, or 99% or more, relative to 100% by weight. Preferably, the polymer columns may be made of polymer resin. Furthermore, the polymer columns have adhesive properties and can adhere to battery materials (e.g., inorganic particles or porous polymer substrates) adjacent to the polymer columns.

[0089] In this disclosure, one or more of the polymer columns may not have open-pore structures in their body. Preferably, the polymer columns do not have open-pore structures so that fluids (e.g., gases or liquids) do not flow through the polymer column body.

[0090] At least a portion of the polymer column is exposed on the surface of the inorganic coating, while another portion can contact the surface of the porous polymer substrate.

[0091] In inorganic coatings, two or more of the polymer columns can aggregate to form clusters, or individual polymer columns can be spaced apart from each other by a predetermined distance. In one embodiment of this disclosure, two or more of the polymer columns aggregated to form clusters account for 30% or less, preferably 20% or less, and more preferably 10% or less, relative to 100% of the total polymer columns. Excessive aggregation of polymer columns can cause non-uniformity of resistance in the separator. Therefore, in terms of increasing the uniformity of resistance, the polymer columns forming clusters preferably account for 10% or less relative to 100% of the total polymer columns.

[0092] 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 in the inorganic coating.

[0093] 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 the polymer column, D 50 D can be inorganic particles 50 At least twice as much.

[0094] In one embodiment of this disclosure, the polymer columnar structure D 50 It can be approximately 2.0 μm to 7.0 μm, and D 50 It can be adjusted appropriately within the above range. For example, D 50 It can be in the range of 3.0 μm to 6.0 μm. The D-type polymer columnar polymer... 50 This is reflected in the state before the separator is pressed, and preferably before the slurry is prepared.

[0095] Furthermore, in this disclosure, pressing can be performed in the range of seconds to minutes. For example, pressing can be performed in 60 seconds or 30 seconds. Since the separators according to this disclosure can be flattened in a short period of time, process efficiency can be improved.

[0096] It is typically assumed that the compression conditions correspond to the lamination process conditions of the electrodes and spacers used to manufacture the electrode assembly. This characteristic is beneficial for enhancing the adhesion between the electrodes and spacers during battery manufacturing and for ensuring close contact between the electrodes and spacers, thereby preventing separation.

[0097] In other words, when the separator according to this disclosure is applied to battery manufacturing, preferably, the thickness (T) of the inorganic coating after the electrodes and separator are laminated is... c () smaller than the D of the polymer column after lamination 50 .

[0098] Simultaneously, compared to before pressing, the planarized polymer column can have a larger area observed in the planar view. In this paper, after planarization, the major axis length of the polymer column observed in the planar view is preferably the same as the D of the polymer column before planarization. 50 10 times or less.

[0099] In this disclosure, regarding planarization by pressing, the modulus of the polymer column at room temperature is preferably from 1,000 Pa to 3,500 Pa. More preferably, the modulus is from 1,000 Pa to 3,000 Pa. Preferably, the energy storage modulus can be related to the material constituting the polymer column. Furthermore, considering the temperature conditions applied during actual battery assembly, the ratio of the polymer column's modulus at 60°C to its modulus at room temperature (modulus (60°C) / modulus (room temperature)) is 0.05 or less. More preferably, the ratio is 0.01 or greater and 0.05 or less. In one embodiment of this disclosure, the room temperature can be in the range of 20°C to 25°C. In one embodiment of this disclosure, the modulus of the polymer column at a high temperature of 55°C to 65°C (e.g., 60°C) can be in the range of 0.05 Pa to 100 Pa.

[0100] Furthermore, more preferably, when measured using a dynamic mechanical analyzer (DMA; ARES-G2, TA Instrument), the polymer columnar material may have at least one tan δ peak in the range of 45°C to 80°C. Tan δ peaks appearing below 45°C are undesirable because they may indicate adhesive properties between the wound separators, and when the temperature is above 80°C, no sudden decrease in storage modulus is observed even upon application of the temperature, making it difficult to planarize the polymer columnar material during high-temperature pressing.

[0101] In one embodiment of this disclosure, the modulus can be measured using a rheological analyzer (Dynamic Mechanical Analyzer (DMA), ARES-G2, TA Instrument). In one specific embodiment, the 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, with such a DMA, the slope of the storage modulus (G') at 45°C and at 60°C to 70°C can be measured.

[0102] In one embodiment of this disclosure, the polymer column preferably comprises a non-reactive material for lithium secondary batteries and can provide bonding strength between the separator and the electrode. Considering these aspects, the polymer column in this disclosure may comprise an acrylic polymer. For example, the acrylic material may comprise at least one repeating unit of: 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 material is not limited thereto. Meanwhile, in one specific embodiment, at least one hydrogen atom in the unit may be replaced by another substituent.

[0103] However, after the liquid electrolyte is injected, the polymer columns may dissolve and lose their adhesiveness, or the viscosity of the liquid electrolyte may increase due to the dissolved components, posing a risk of increased resistance in the lithium secondary battery. Therefore, it is preferable to have suitable solubility. For example, the solubility in organic solvents or electrolytes can be reduced by cross-linking the surface of the material constituting the polymer columns.

[0104] In one specific embodiment, after dissolving in THF (tetrahydrofuran) for 1 to 48 hours, the amount of polymer column dissolved (by weight) 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.

[0105] 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% from the uppermost part of the inorganic coating 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% from the lowermost part of the inorganic coating toward the surface portion. This characteristic of the polymer columns can correspond to cases where the polymer columns protrude from the surface of the inorganic coating and / or are planarized by pressing. Preferably, this characteristic can be confirmed in the form of polymer columns after protrusion and subsequent planarization.

[0106] In the cross-section of the polymer column observed in a vertical section of the inorganic coating, either together with or independently, the diameter (a) of the lower portion of at least one of the polymer columnar sections may be smaller than the diameter (b) of the upper portion. In one embodiment, the ratio of the upper diameter (b) to the lower diameter (a) may be greater than 1 and 20 or less, 1.2 to 20, 1.5 to 20, or 2 to 20. This characteristic of the polymer columnar section may correspond to a situation where the polymer columnar section protrudes from the surface of the inorganic coating and / or is planarized by pressing. Preferably, after planarization, this characteristic can be confirmed in the form of a polymer columnar section. In one embodiment of this disclosure, the upper diameter refers to the diameter measured at the upper 5% point from the uppermost part of the polymer columnar section towards the lower portion, and the lower diameter refers to the diameter measured at the lower 5% point from the lowermost part of the polymer columnar section towards the upper portion.

[0107] In one embodiment of this disclosure, the diameter and / or cross-sectional dimensions of the polymer column can be obtained by classifying SEM images of horizontal or vertical cross-sections of the separator into gray levels and measuring the area corresponding to a specific gray level of the polymer column. A gray level refers to the shadow value of a plurality of pixels contained in the SEM image. For example, in an SEM image with 256 gray levels containing 0 to 255 levels, the shadow value 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 having gray levels of 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 performing an EDS plot of the components on the cross-section of the electrode obtained by argon (Ar) ion milling using an energy-dispersive X-ray spectroscopy (EDS) detector of a scanning electron microscope (SEM) apparatus, followed by image processing.

[0108] 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, and then obtaining an arbitrary cross-section from it.

[0109] <Inorganic Particles>

[0110] In one specific embodiment of this disclosure, the inorganic particles are not particularly limited, as long as 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 fall within the operating voltage range of the electrochemical device in which they are used (e.g., based on Li / Li). +within the range of 0 V to 5 V) without undergoing oxidation and / or reduction reactions. In particular, the use of inorganic particles with a high dielectric constant as the inorganic particles helps increase the dissociation degree of electrolyte salts (e.g., lithium salts) in the liquid electrolyte, thereby improving the ionic conductivity of the electrolyte liquid.

[0111] For the above reasons, the inorganic particles preferably include high-dielectric inorganic particles having a dielectric constant of 5 or more, and preferably 10 or more. Non-limiting examples of inorganic particles having a dielectric constant of 5 or more include BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3 (PLZT, 0<x<1, 0<y<1), Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3 (PMN-PT), hafnium dioxide (HfO2), SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, SiC, TiO2, or a mixture thereof.

[0112] Furthermore, as the inorganic particles, inorganic particles having lithium ion transfer capability, that is, inorganic particles containing lithium element but not storing lithium and instead having a function of transporting lithium ions can be used. Non-limiting examples of inorganic particles having lithium ion transfer capability include (LiAlTiP)-based x O y glasses (0<x<4, 0<y<13), such as lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0<x<2, 0<y<3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0<x<2, 0<y<1, 0<z<3) 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), for example Li3N; SiS2-based glass (Li x Si y S z , 0<x<3, 0<y<2, 0<z<4), for example Li3PO4-Li2S-SiS2; P2S5-based glass (Li x P y S z , 0<x<3, 0<y<3, 0<z<7), for example LiI-Li2S-P2S5; or a mixture thereof.

[0113] Furthermore, the D 50 of the inorganic particles is not particularly limited, but may preferably be in the range of 0.1 μm to 1.5 μm, or 0.4 μm to 1.3 μm to form a coating with a uniform thickness and appropriate porosity. When D 50 is less than the lower limit of the above range, dispersibility may decrease, and when D 50 is greater than the upper limit of the above range, the thickness of the formed inorganic coating may increase. The D 50 of the inorganic particles is measured according to the D 50 measurement method described in the definitions of the present specification, and the D 50 of the inorganic particles present in the inorganic particle portion may also satisfy the above range.

[0114] <Polymer column portion and inorganic particle portion>

[0115] In one embodiment of the present disclosure, the inorganic coating includes a polymer column portion and an inorganic particle portion, the polymer column portion includes a plurality of adhesive polymer columns each having a predetermined volume, and the inorganic particle portion includes inorganic particles filled between the polymer columns.

[0116] The inorganic particle portion may further include a binder resin to ensure bonding strength between the inorganic particles and between the inorganic particles and the porous substrate. The inorganic particle portion has pores generated by void volumes (spaces formed between adjacent inorganic particles). The inorganic coating may have a porous structure with a predetermined porosity through the pores, allowing gas or liquid to pass from one side surface to the other side surface. The inorganic particles and the polymer columns may be bonded to each other due to the adhesive properties of the polymer columns, or may be bonded via the binder resin.

[0117] The thickness (T cThe thickness (T) can be 2.0 μm to 7.0 μm, 2.2 μm to 6.0 μm, 2.5 μm to 5.8 μm, or 3.2 μm to 5.3 μm. Due to interactions (e.g., compression by inorganic particles disposed around the polymer column in the separator), the thickness (T) of the polymer column portion... c The thickness of the polymer column portion can be greater than the diameter of the polymer column itself. When the thickness of the polymer column portion is less than the lower limit mentioned above, the difference between the thickness of the polymer column portion and the thickness of the inorganic particle portion may be small, resulting in a reduced content of protruding polymer columns, and therefore, the separator may have poor adhesion. Meanwhile, when the thickness of the polymer column portion is greater than the upper limit mentioned above, the difference between the thickness of the polymer column portion and the thickness of the inorganic particle portion may be large, and the polymer columns may separate from the inorganic coating.

[0118] In one embodiment of this disclosure, without artificial pressing after manufacturing the separator, one or more of the polymer columns may protrude above the inorganic particle portion. In other words, one or more of the polymer columns may protrude from the surface of the inorganic particle portion. In one embodiment of this disclosure, when the polymer columns protrude beyond the inorganic particle portion, the thickness (T) of the inorganic particle portion... i ) can be the thickness (T) of the polymer columnar portion c 85% or less of the inorganic particulate portion. Meanwhile, in one embodiment of this disclosure, the thickness of the inorganic particulate portion can be the D of the polymer columnar portion. 50 20% or more. Meanwhile, in one embodiment of this disclosure, the height (T) of the polymer column... c The value can be determined by cutting a cross-section of the separator sample, observing the cross-section by SEM, and then taking the value of the highest part of the polymer column.

[0119] In one specific implementation, the thickness (T) of the inorganic particle portion i The thickness (T) of the inorganic particle portion can be from 1.0 μm to 5.0 μm, from 1.5 μm to 4.0 μm, and preferably from 2.0 μm to 2.6 μm. i The thickness can preferably be 1.0 μm or greater, and within the above numerical range, adhesion to the electrodes is excellent, thus increasing the battery strength. Meanwhile, a thickness of 5.0 μm or less is advantageous in terms of battery cycle characteristics and resistance characteristics. Furthermore, the reduced thickness of the separator improves the battery's energy density when used in a battery. When the inorganic coating is applied to both surfaces of the porous polymer substrate, the thickness of the inorganic particle portion refers to the value measured for the inorganic coating applied to either surface.

[0120] In one embodiment of this disclosure, the thickness (T) of the inorganic particle portion i ) and the thickness of the polymer columnar portion (T) c It can satisfy the following equation 1.

[0121] 0.2< <0.7 Equation 1

[0122] Equation 1 can refer to T c and T i The thickness difference between them and T c The ratio. When the ratio is less than the lower limit mentioned above, the difference between the thickness of the polymer columnar portion and the thickness of the inorganic particle portion may be small, resulting in a reduced content of protruding polymer columnar portions, and therefore, the separator may have poor adhesion or poor heat resistance. Meanwhile, when the ratio is greater than the upper limit mentioned above, the difference between the thickness of the polymer columnar portion and the thickness of the inorganic particle portion may be large, and therefore, the polymer columnar portions may separate from the inorganic coating or the polymer columnar portions may have reduced uniformity, and the manufactured electrode assembly may have poor thickness uniformity.

[0123] In one embodiment of this disclosure, one or more of the polymer columns may protrude beyond a predetermined height above the surface of the inorganic coating. Hereinafter, a polymer column protruding beyond the surface of the inorganic coating refers to the thickness (T) of the polymer column portion within the inorganic coating. c The thickness of the inorganic particle portion is greater than the thickness of the inorganic particle portion (T). i ), making the height greater than the thickness of the inorganic particle portion (T). i ).

[0124] In one embodiment of this disclosure, the height (T) of the protruding polymer columnar body from the surface of the inorganic particle portion p The size is 1 μm or larger. Multiple polymer columns are embedded in the inorganic coating, causing them to expose or protrude beyond the inorganic particle portion, and the protrusion height (T) of some of the polymer columns is [not specified]. p The diameter (T) can be 1 μm or larger. For example, the height (T) of the protruding polymer column is... pThe polymer column can be greater than 1 μm and 6 μm or smaller, and can be, for example, 5 μm or smaller, 4.9 μm or smaller, 4 μm or smaller, 3 μm or smaller, 2.6 μm or smaller, 2.5 μm or smaller, 2.2 μm or smaller, or 2.1 μm or smaller, as well as greater than 1 μm, 1.5 μm or larger, or 2 μm or larger. Furthermore, some of the polymer column protruding from or exposed on the surface of the inorganic particle portion can contact the porous substrate. In this document, polymer column protruding beyond the surface of the inorganic particle portion means that the height of the polymer column is greater than the height of the inorganic particle portion.

[0125] When the height of the protruding polymer column (T) p When the content of the protruding polymer columns is less than the lower limit mentioned above, the amount of protruding polymer columns may decrease, which may cause poor adhesion of the separator. Simultaneously, when the height (T) of the protruding polymer columns... p When the height exceeds the aforementioned upper limit, the polymer column may separate from the inorganic coating. In this document, the height of the protruding polymer column can specifically refer to its height before the separator is pressed.

[0126] In one embodiment of this disclosure, the volume of the protruding polymer columns can be 25% to 55% or 30% to 50% of the inorganic coating, relative to 100% by volume. When the volume of the protruding polymer columns is less than the lower limit, the separator may have insufficient adhesion; when the volume is greater than the upper limit, the difference between the thickness of the polymer column portion and the thickness of the inorganic particle portion may be large, and the polymer columns may separate from the inorganic coating or have reduced uniformity, resulting in poor thickness uniformity of the manufactured electrode assembly. The volume of the protruding polymer columns can be measured using atomic force microscopy (AFM), which will be described later. The volume of the protruding polymer columns can be calculated using AFM by measuring the height of the protrusion and the radius and diameter of the protrusion.

[0127] In one embodiment of this disclosure, the thickness (T) of the inorganic particle 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 area where no polymer columnar bodies are located, and taking the average of these measurements as the height. For example, the thickness can be measured as the average of 2 to 10 points over an area with a side length of 50 μm or less. Alternatively, in the case of a cross-section, the thickness can be measured as the average of 2 to 10 points over a length of 50 μm or less. 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.

[0128] Furthermore, in one embodiment of this disclosure, the thickness (T) of the polymer columnar portion c The value can be determined by cutting a cross-section of the separator sample, observing the cross-section by SEM, and then taking the value of the highest part of the polymer column.

[0129] Furthermore, in one embodiment of this disclosure, the protrusion height (T) of the polymer column is... p The value can be determined by cutting a 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.

[0130] Alternatively, in one embodiment of this disclosure, the height of the protruding polymer pillars can be measured using atomic force microscopy (AFM). For example, the height of the protruding polymer pillars can be obtained by scanning the surface of a cross-sectional sample using AFM to obtain an image converted to a two-dimensional (2D) scale. Measurements yield a map in which the magnitude of resistance is represented by color intensity and the distribution of surface resistance can be visually identified by differences in hue (intensity). Specifically, height images with predetermined dimensions (e.g., 40 μm × 40 μm) are obtained using AFM. Subsequently, the inorganic coating is masked using software such as Gwyddion (S / W), and an average height value is determined. Then, the protruding polymer pillars are masked, and the maximum height of each polymer pillar is determined. Finally, the difference between the height of the protruding polymer pillars and the average height of the inorganic coating is measured.

[0131] For this purpose, a sample for atomic force microscopy (AFM) measurement is first prepared. The cross-sectional sample prepared in this process is attached to a metal disk for AFM (with the cross-section facing upwards), and a silver paste or similar material is applied to create a conductive path between the sample (excluding the milled cross-section) and the metal disk for AFM. The sample prepared as described above is loaded into the microscope, and after laser alignment, the cross-section is selected as the area for measurement using an optical microscope. Subsequently, the AFM probe is brought into contact with the cross-section of the electrode, and the current flowing through the sample between the AFM probe and the contact electrode is measured. The extended resistance is obtained from the measured current.

[0132] According to one embodiment of this disclosure, the driving conditions for a scanning extended resistance microscope (AFM) used to analyze cross-sectional samples of electrodes are as follows. There are no particular limitations on the AFM, as long as it can provide visual imaging of the resistance distribution according to the scanning extended resistance microscopy method. For example, an NX10 (Park Systems Corporation) can be used.

[0133] In one embodiment of this disclosure, the spacer can be planarized by pressing the protruding portion under pressing conditions (e.g., pressure conditions of 0.5 MPa to 20 MPa, or 2.0 MPa to 8.0 MPa, and temperature conditions of 25°C to 90°C, or 55°C to 65°C), and thus the thickness of the inorganic coating can become uniform. Simultaneously, 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, thereby preventing separation. In other words, under the conditions used for laminating the electrode and the spacer (i.e., hot pressing conditions), the polymer column can exhibit softening properties.

[0134] In one embodiment of this disclosure, when the separator is compressed under compression conditions of 0.5 MPa to 20 MPa and 25°C to 90°C, the thickness (T) of the polymer columnar portion after compression is... c The thickness of the inorganic particle portion (T) can be equal to or greater than the thickness of the inorganic particle portion. i ), and can be the thickness of the inorganic particle portion (T) i The height of the polymer columnar portion protruding from the inorganic coating after compression can be less than 1 μm, 0.8 μm or less, 0.6 μm or less, 0.5 μm or less, 0.3 μm or less, or 0.2 μm or less. In other words, the height difference between the inorganic particle portion and the polymer columnar portion decreases, causing planarization of the separator. (Refer to...) Figure 8 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 surface of the porous polymer substrate. In this disclosure, T... c It can be the same height as the polymer column with the most protrusions. Meanwhile, in this disclosure, T... p Based on the highest part of the inorganic coating relative to the inorganic particle filling portion.

[0135] As described below, the compression ratio can be mainly generated by the deformation (compression) of the polymer column.

[0136] Furthermore, in this disclosure, pressing can be performed in the range of seconds to minutes. For example, pressing can be performed in 60 seconds or 30 seconds. Since the separators according to this disclosure can be flattened in a short period of time, process efficiency can be improved.

[0137] It is typically assumed that the compression conditions correspond to the lamination process conditions of the electrodes and spacers used to manufacture the electrode assembly. This characteristic is beneficial for enhancing the adhesion between the electrodes and spacers during battery manufacturing and for ensuring close contact between the electrodes and spacers, thereby preventing separation.

[0138] Meanwhile, in this specification, planarization can mean that, under the aforementioned pressing conditions, the thickness of the inorganic particle portion and the height of the polymer columnar portion are the same, or the thickness difference between the inorganic particle portion and the polymer columnar portion is less than 1 μm, 0.8 μm or less, 0.6 μm or less, 0.5 μm or less, 0.3 μm or less, or 0.2 μm or less. In one embodiment of this disclosure, the height of the polymer columnar portion can be based on the maximum height (T) within the polymer columnar portion. c ) polymer columnar bodies.

[0139] In other words, when the separator according to this disclosure is applied to battery manufacturing, preferably, after the electrodes and separator are laminated, the thickness (T) of the inorganic coating is... c D is smaller than that of the polymer column. 50 .

[0140] Simultaneously, compared to before pressing, the planarized polymer column can have a larger area observed in the planar view. In this paper, after planarization, the major axis length of the polymer column observed in the planar view is preferably the same as the D of the polymer column before planarization. 50 At most 10 times.

[0141] In one embodiment of this disclosure, when the surface of the separator is measured in a top view using SEM, based on the top view image of the separator, the area occupied by the surface area of ​​the polymer columns exposed on the surface of the inorganic coating relative to 100% of the surface area of ​​the inorganic coating can be 5% or more, 8% or more, or 10% or more, and 80% or less, 70% or less, 60% or less, or 50% or less. Hereinafter, the area can be measured after pressing the separator under pressures of 0.5 MPa to 20 MPa, 1 MPa to 10 MPa, or 2 MPa to 8 MPa and temperatures of 25°C to 90°C, or 55°C to 65°C, or before pressing. When the surface area of ​​the polymer columns exposed on the surface of the inorganic coating meets the above ranges, the adhesiveness of the separator or the Gurley value and / or porosity of the separator can be excellent.

[0142] <Adhesive Resin>

[0143] 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.

[0144] In one embodiment of this disclosure, the adhesive resin may include a PVdF-based polymer resin. The PVdF-based polymer resin may include at least one of a homopolymer of vinylidene fluoride (i.e., polyvinylidene fluoride), a copolymer of vinylidene fluoride and monomers that can be copolymerized therewith, and mixtures thereof. In one embodiment of this disclosure, examples of monomers may include fluorinated monomers, chlorine-based monomers, etc. Non-limiting examples of fluorinated monomers may include vinyl fluoride; trifluoroethylene (TrFE); vinyl 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), etc., and may include one or more of them.

[0145] Together with or independently of the adhesive resin, the adhesive resin may also include (meth)acrylic polymer resins. (Meth)acrylic polymers contain (meth)acrylates as monomers, and non-limiting examples may include (meth)acrylic polymers containing 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 as monomers.

[0146] 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.

[0147] <Methods for manufacturing separators>

[0148] Next, a method for manufacturing the separators of this disclosure will be described. However, the following description relates to one embodiment for manufacturing the separators of this disclosure, and the method is not particularly limited thereto.

[0149] 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 polymer substrate and dried.

[0150] 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 sequentially or simultaneously introduced into the polymer solution to prepare a slurry for the inorganic coating. The binder resin is preferably a water-soluble binder resin.

[0151] The obtained separators are then dried to form a complete inorganic coating on the porous polymer substrate. In this study, to prevent deformation of the polymer columns, the drying temperature of the separators is preferably set to be 20°C higher or lower than the temperature at which the tan δ peak of the polymer column material is observed.

[0152] 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.

[0153] Existing coating methods (such as Mayer bars, die coaters, reverse roller coaters, or gravure coaters) can be used to apply the slurry. When an inorganic coating is formed on both surfaces of a porous substrate, the coating solution can be applied to each surface separately and then dried, or it can be applied to both surfaces of the porous substrate simultaneously and then dried.

[0154] Furthermore, the separators of this disclosure can also be manufactured using the following methods: preparing an inorganic coating and a porous polymer substrate separately, merging these sheet layers together, and then bonding them together by thermal bonding or adhesive. Methods for obtaining the inorganic coating as an independent sheet may include applying a slurry to a release sheet, forming the inorganic coating using the methods described above, and methods that only peel off the inorganic coating, etc.

[0155] In addition to the manufacturing method described above, any manufacturing method capable of realizing the above-described separator structure can be applied without restriction.

[0156] <Lithium secondary batteries>

[0157] This disclosure also provides a secondary battery including the aforementioned separator. The secondary battery includes: a negative electrode; a positive electrode; and a separator between the negative and positive electrodes, wherein the separator is a low-resistance separator having the aforementioned characteristics.

[0158] 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 (x is 0 to 0.33 in this paper), 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 oxides represented by O2 (in this paper, M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); and those with the chemical formula LiMn 2-x M x Lithium manganese complex oxides represented by O2 (in this document, M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (in this document, 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.

[0159] 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 oxide, 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, 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 oxides.

[0160] In a specific embodiment of the present disclosure, the conductor may be, for example, any one selected from graphite, carbon black, carbon fiber or metal fiber, metal powder, conductive whisker, conductive metal oxide, activated carbon and polyphenylene derivatives, or a mixture of two or more of these conductive materials. More specifically, the conductor may be one selected from 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.

[0161] The current collector is not particularly limited as long as it has high conductivity without causing chemical changes of the corresponding battery, and for example, stainless steel, copper, aluminum, nickel, titanium, baked carbon; or aluminum or stainless steel with surface treated with carbon, nickel, titanium, silver, etc. may be used.

[0162] As the binder resin, polymers commonly used in electrodes in the art can be used. Non-limiting examples of such binder resins may include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, poly(ethylhexyl acrylate), polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-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 and the like, but are not limited thereto.

[0163] The electrode assembly prepared as above can be inserted into a suitable housing, and an electrolyte liquid can be injected thereinto to fabricate a battery.

[0164] In the present disclosure, the electrolyte liquid comprises a compound obtained by dissolving a substance having A + B - (wherein A + comprises an alkali metal cation (for example, Li + , Na + , or K+ Ions composed of (or combinations thereof), and B - Including those composed of anions (e.g., PF6) - BF4 - Cl - ,Br - I - ClO4 - AsF6 - CH3CO2 - CF3SO3 - N(CF3SO2)2 - or C(CF2SO2)3 - An electrolyte liquid is obtained by dissolving or dissociating a salt of an ion composed of propylene carbonate (or a combination thereof) in an 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), methyl ethyl carbonate (EMC), γ-butyrolactone, ester-based compounds, or mixtures selected from one or more of these), however, the electrolyte liquid is not limited thereto.

[0165] 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.

[0166] 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.

[0167] Furthermore, this disclosure provides battery modules including batteries (including electrode assemblies) as individual cells, battery packs including battery modules, and devices including battery packs as power sources. Specific examples of such devices may include power tools that operate by receiving power via 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 e-bikes and e-scooters; electric golf carts; systems for energy storage, etc., but are not limited thereto.

[0168] In the following description, this disclosure will be described in detail with reference to embodiments to specifically illustrate this disclosure. However, embodiments of this disclosure can be modified in various other forms, and the scope of this disclosure should not be construed as limited to the embodiments described below. Embodiments of this disclosure are provided to describe this disclosure more fully to those skilled in the art.

[0169] <Example 1>

[0170] Inorganic particles (Al2O3, D) 50 Polyvinyl alcohol (approximately 0.6 μm), used as a binder resin, and carboxymethyl cellulose (Daicel Corporation, Daicel 1220), used as a dispersant resin, were introduced into water (solvent) at a ratio of 96:2:2, and a dispersion process was performed using a bead mill to obtain a mixture. Polymer particles (D...) for polymer columnar formation were then introduced into the mixture. 50 The mixture was stirred to obtain a dispersion slurry (4.1 μm thick). The concentration of solids in the dispersion slurry was 30% by weight. In the mixture, the content of polymer particles for the polymer columns was approximately 11 parts by weight relative to 100 parts by weight of inorganic particles. The dispersion slurry was applied to a porous polymer substrate (Toray Corporation, B09PJ1, 9 μm thick) using a microgravure coating method and dried 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 (single-sided) was 5.2 g / m². 2 .

[0171] Figures 1 to 3 These are SEM images (5.0 kV) of the surface of the inorganic coating on the manufactured separator at magnifications of 500x, 2000x, and 5000x, respectively. Furthermore, Figure 6 This is a SEM image of the cross-section of the inorganic coating of the manufactured separator at a magnification of 5500x. Referring to this, it is determined that polymer columns are exposed on the surface of the inorganic particle portion, with their lower ends in contact with the porous polymer substrate. Furthermore, it is determined that the individual polymer columns are spaced at predetermined distances and distributed in an island pattern.

[0172] Meanwhile, the obtained separators are pressed for 20 seconds at 2.5 MPa and 65°C using a hot press to flatten the surface. Figure 4 and Figure 5 These are SEM images of the inorganic coating surface after planarization at magnifications of 500x and 5500x, respectively. Figure 7This is a SEM image of the cross-section at 5500x magnification after the separator manufactured in Example 1 has been flattened. Referring to this, it is confirmed that the protruding portions in the polymer column are pressed and flattened.

[0173] <Examples 2 to 5>

[0174] The separators of Examples 2 to 5 were manufactured in the same manner as in Example 1, except that the content of polymer particles used for the polymer column and the amount of inorganic coating were changed, as shown in Table 2.

[0175] <Comparative Example 1>

[0176] The separator of Comparative Example 1 was manufactured in the same manner as in Example 1, except that polymer particles for polymer columns were not used.

[0177] <Comparative Example 2>

[0178] The separator of Comparative Example 2 was manufactured in the same manner as in Example 1, except that the height of the protruding polymer column was changed by adjusting the thickness of the inorganic particle portion as shown in Table 2.

[0179] [Experimental Example]

[0180] <Experimental Example 1: Solubility, Modulus, and D of Polymer Particles Used in Polymer Columnar Formations> 50 Measurement of Tg >

[0181] solubility

[0182] In each of the Examples and Comparative Examples, the polymer material to be used as the polymer column was dried at 60°C to prepare a 0.3 g sample. The sample was placed on a mesh sieve with a mesh size of 80 and dissolved in THF (tetrahydrofuran) for 24 hours, after which the weight of the remaining residue was compared with the initial weight. The solubility was calculated based on Equation 5 below. The results are summarized in Table 1 below.

[0183] [Formula 5]

[0184] Solubility (%) = {(Weight measured before immersion - Weight measured after immersion) / (Weight measured before immersion)} × 100

[0185] Modulus

[0186] Samples measuring 40 cm × 60 cm were prepared using the polymer material to be used as polymer columns in each of the Examples and Comparative Examples. The thickness of the samples was 1 mm. The modulus of the samples was measured. The modulus was measured using a rheological analyzer (Dynamic Mechanical Analyzer (DMA), ARES-G2, TA Instrument). The modulus was determined by performing temperature scan tests at a temperature condition of -60°C to 80°C and a frequency of 1.0 rad / s.

[0187] Tg

[0188] The glass transition temperature (Tg) was measured using a differential scanning calorimetry (DSC, TA Instrument) apparatus. 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. Subsequently, the sample was cooled to -30 °C and then the glass transition temperature was measured while the sample was reheated at 10 °C / min.

[0189] [Table 1]

[0190]

[0191] <Experiment Example 2: Measurement of the Thickness of the Separator>

[0192] In the embodiments 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. Simultaneously, the thickness of the inorganic particle portion (T) was also considered. i The result was determined to be the average of the values ​​measured at three arbitrary points. The results are summarized in Table 1.

[0193] <Experimental Example 3: Measurement of the height and volume ratio of protruding polymer columns>

[0194] The surface of the spacers manufactured in each of the Examples and Comparative Examples was measured using an atomic force microscope (NX10, Park Systems Corporation). Specifically, the spacers manufactured in each of the Examples and Comparative Examples were attached to a metal disk for AFM using carbon tape, and experiments were conducted according to standard operating procedures (SmartScan, SOP-0590-0k) to obtain height image data with dimensions of 40 μm × 40 μm. Image processing and analysis were then performed using an XEI S / W. The height of the protruding polymer columns relative to the inorganic coating was analyzed using a Gwyddion S / W. Experiments were conducted at three points on the spacers of each of the Examples and Comparative Examples, and the average value was calculated. Simultaneously, the volume ratio of the protruding polymer columns was determined using a Gwyddion S / W.

[0195] <Experimental Example 4: Evaluation of Dry Adhesion Between Electrode and Separator>

[0196] Manufacturing of positive and negative electrodes

[0197] By using LiNi as the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2, carbon black (as a conductor), and polyvinylidene fluoride (PVdF) (as a binder) were added to N-methylpyrrolidone (NMP) (solvent) in a weight ratio of 85:5:10 to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated onto a sheet aluminum current collector and dried to manufacture the positive electrode, resulting in a final positive electrode loading of 3.3 mAh / cm³. 2 .

[0198] A negative electrode slurry was formed by mixing artificial and natural graphite as the negative electrode active material, carbon black as the conductor, and polyvinylidene fluoride (PVdF) as the binder in a weight ratio of 75:5:20, and adding N-methylpyrrolidone (NMP) (solvent). The negative electrode slurry was then subjected to a reaction at 3.8 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.

[0199] The manufactured negative electrode is laminated between the separators, the separators are laminated onto the negative electrode, and the positive electrode is further laminated onto the separators.

[0200] Evaluation methods and results

[0201] The separator samples obtained in each embodiment and comparative example were cut into dimensions of 100 mm (length) × 25 mm (width) 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.

[0202] <Experimental Example 5: Evaluation of Wet Adhesion Between Electrode and Separator>

[0203] The separator samples obtained in each of the Examples and Comparative Examples were cut into dimensions of 100 mm (length) × 25 mm (width) to prepare individual specimens. Each specimen was laminated with a positive electrode manufactured according to the Experimental Example, and then hot-pressed at 50°C for 20 seconds to obtain a laminate. The laminate was immersed in an electrolyte solution and held for 24 hours. Afterward, each laminate was removed from the electrolyte solution and fixed to an adhesive strength measuring device (LLOYD Instrument, LF plus). The separator portion was peeled at a rate of 25 mm / min at a 180° angle at 25°C, and the corresponding strength was measured. The electrolyte solution was obtained by mixing ethylene carbonate and ethyl methyl carbonate in a volume ratio of 7:3 and contained LiPF6 at a concentration of 1 M.

[0204] <Experiment Example 6: Resistance Measurement>

[0205] The resistance of the separators in each of the Examples and Comparative Examples was measured using an impedance method. Each separator was inserted between stainless steel plates to fabricate a coin cell, and 1 M LiPF6 in an ethylene carbonate / ethyl methyl carbonate (EC / EMC, volume ratio 30:70) electrolyte was injected into it. Electrochemical impedance spectroscopy was performed on the cells at 25°C in a scan range from 100,000 Hz to 10,000 Hz using a Solaton 1470E battery testing system and a frequency response analyzer 1255B, and the resistance was measured based on the analytical results.

[0206] <Experiment Example 7: Measurement of Thermal Shrinkage>

[0207] The spacers manufactured in each of the examples and comparative examples were cut into 50 mm × 50 mm dimensions, placed between A4 sheets of paper, and then placed in a convection oven at 120°C for 1 hour. Heat shrinkage in the machine direction (MD) and transverse direction (TD) was then measured.

[0208] [Table 2]

[0209]

[0210] Examples 1 to 5 satisfy the condition that the height of the protruding polymer columns before pressing is 1 μm or greater. Therefore, compared to Comparative Examples 1 and 2, Examples 1 to 5 not only exhibit excellent adhesion to the electrodes but also ensure sufficient porosity, resulting in excellent electrical and ionic conductivity properties. Meanwhile, in Comparative Example 1, no polymer particles were used for the polymer columns, and therefore, thermal shrinkage was poor, and the dry adhesion between the negative electrode and the separator, as well as the wet adhesion between the positive electrode and the separator, were reduced.

[0211] Meanwhile, in Comparative Example 2, polymer particles were used for polymer columns; however, the height (T) of the protruding polymer columns was... p When the thickness is less than 1 μm, poor adhesion is obtained.

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 polymer columnar portion and an inorganic particle portion. The polymer columnar portion comprises a plurality of adhesive polymer columns, each having a predetermined volume. The inorganic particle portion comprises inorganic particles filling the spaces between the polymer columns. The polymer column is made of polymer material and has no pores. At least a portion of the polymer columnar structure is exposed on the surface of the inorganic coating, while another portion is in contact with the surface of the porous polymer substrate. At least one of the individual polymer columns is spaced apart from the other polymer column by a predetermined distance. Some of the polymer columnar sections in the polymer columnar portion protrude from the surface of the inorganic particle portion, and The height (T) of the protruding polymer columnar body from the surface of the inorganic particle portion p (1 μm or larger) 2. The separator according to claim 1, wherein the D of the polymer columnar body 10 D is the polymer column. 50 30% or more, and the D of the polymer column 90 D is the polymer column. 50 200% or less.

3. The separator according to claim 1, wherein the D of the polymer columnar body 50 D of the inorganic particles 50 At least twice as much.

4. The separator according to claim 1, wherein the inorganic particles have a D 50 The diameter is 0.1 μm to 1.5 μm, and the D of the polymer column is... 50 The range is from 2.0 μm to 7.0 μm.

5. The separator according to claim 1, wherein the thickness (T) of the inorganic particle portion is... i ) is the thickness (T) of the polymer columnar portion. c 85% or less.

6. The separator according to claim 1, wherein the thickness (T) of the inorganic particle portion is... i The thickness of the polymer columnar portion (T) is 1.0 μm to 5.0 μm. c The thickness ranges from 2.0 μm to 7.0 μm.

7. The separator according to claim 1, wherein the thickness (T) of the inorganic particle portion is... i ) and the thickness (T) of the polymer columnar portion c ) satisfies the following equation 1: 0.2< <0.7 Equation 1.

8. The separator according to claim 1, wherein the volume of the protruding polymer column is 25% to 55% of the volume relative to 100% by volume of the inorganic coating.

9. The separator according to claim 1, wherein when the separator is pressed under temperature conditions of 25°C to 90°C and pressure conditions of 0.5 MPa to 20 MPa, the thickness difference between the inorganic particle portion and the polymer column is less than 1 μm.

10. The separator according to claim 1, wherein, based on a top view image of the separator, the surface area of ​​the polymer column exposed on the surface of the inorganic coating accounts for 5% to 80% of the surface area of ​​the inorganic coating.

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. 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, as observed in a section at the upper 5% of the inorganic coating from the uppermost part toward its lower part, is greater than the cross-sectional area (a) of the polymer column as observed in a section at the lower 5% of the inorganic coating from the lowermost part toward its surface portion.

13. 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 diameter (a) of the lower portion of at least one of the polymer columns included in the inorganic coating is smaller than the diameter (b) of the upper portion of the polymer column, and the ratio of the diameter (b) to the diameter (a) is 2 to 20.

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

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