Separator for electrochemical device and electrochemical device including the same

Abstract

The present disclosure relates to a separator for an electrochemical device and an electrochemical device including the same, and more specifically, to a separator for an electrochemical device, the present invention relates to a separator for an electrochemical device and an electrochemical device comprising the same, and more particularly, to a separator for an electrochemical device capable of improving heat resistance and reducing resistance of a battery by providing an adhesive layer containing a polyvinyl acetate-based resin on a coating layer, and an electrochemical device comprising the same.

Description

Technical Field

[0001] The present disclosure claims the benefit of the filing date of Korean Patent Application No. 10-2023-0026495 filed on February 28, 2023, in the Korean Intellectual Property Office, and the benefit of the filing date of Korean Patent Application No. 10-2024-0007842 filed on January 18, 2024, in the Korean Intellectual Property Office, all of which are included in the present disclosure. The present disclosure relates to a separator for an electrochemical device and an electrochemical device including the same, and more particularly to a separator for an electrochemical device and an electrochemical device including the same: the separator for an electrochemical device can improve heat resistance by providing an adhesive layer containing a polyvinyl acetate-based resin on a coating layer, and reduce the resistance of a battery. Background Art

[0002] In the components of an electrochemical device, a separator including a polymer substrate having a porous structure located between the positive electrode and the negative electrode plays the role of separating the positive electrode and the negative electrode, preventing electrical short circuits between the two electrodes, and allowing electrolyte and ions to pass therethrough. The separator itself does not participate in the electrochemical reaction, but physical properties such as wettability to the electrolyte, degree of porosity, and thermal shrinkage affect the performance and safety of the electrochemical device.

[0003] Therefore, in order to enhance the physical properties of the separator, various methods have been tried to change the physical properties of the coating by adding a coating to a porous polymer substrate and adding various materials to the coating. For example, an inorganic material can be added to the coating to improve the mechanical strength of the separator, or an inorganic material or hydrate can be added to the coating to improve the flame retardancy and heat resistance of the polymer substrate.

[0004] The separator may be attached to the electrode through a lamination process, and a binder resin may be added to the separator coating slurry to ensure adhesion between the electrode and the separator.

[0005] Meanwhile, existing separators used in medium and large batteries such as electric vehicles (EV) and energy storage systems (ESS) are bonded by a coating method for lamination and stacking assembly processes via humidified phase separation. Due to this, a high content of poly (vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) is required; however, separators containing a high content of PVdF-HFP have the problem that they have reduced heat resistance, and since the particle size tends to increase in a slurry containing a binder, the separator is difficult to thin, and it is difficult to ensure energy density. In addition, in the case of an oil-based binder, there is a problem that since the electrolyte has solubility, when the binder is excessively dissolved in the electrolyte, it increases the viscosity of the electrolyte while reducing ionic conductivity, thereby increasing resistance or deteriorating battery performance.

[0006] In the case where the separator includes a high content of inorganic particles in the coating, it has excellent heat resistance due to the high content of inorganic materials, and the separator can be thinned. However, such a separator including a coating with a high content of inorganic particles has a problem that it cannot be laminated during the assembly process of manufacturing a battery because there is no adhesive layer on the surface.

[0007] Therefore, there is a need to study separators that can reduce resistance and be thinner while ensuring adhesion. Summary of the invention

[0008] Technical issues

[0009] An object of the present disclosure is to provide a separator for an electrochemical device and an electrochemical device including the same, wherein the separator for an electrochemical device overcomes the disadvantages of the prior art, in particular, realizes that the viscosity of the electrolyte in the battery is at a low level, and improves the performance of the battery and makes the separator thinner, wherein an adhesive layer containing a polyvinyl acetate-based resin is provided on the coating, and the amount of the binder dissolved in the electrolyte is controlled. This can be achieved by adjusting the content of the polyvinyl acetate-based resin provided in the coating, and through this, the viscosity of the electrolyte in the battery is at a low level, while being able to improve the performance of the battery and make the separator thinner.

[0010] However, objects to be solved by the present disclosure are not limited to those mentioned, and other objects not mentioned will be clearly understood from the following description by those skilled in the art.

[0011] Technical Solution

[0012] In a first embodiment of the present disclosure, there is provided a separator for an electrochemical device, comprising: a porous polymer substrate; a coating, wherein the coating is disposed on at least one surface of the porous polymer substrate, and the coating comprises a first polymer binder and inorganic particles; and an adhesive layer, wherein the adhesive layer is disposed on the coating, and the adhesive layer comprises a second polymer binder, wherein the second polymer binder comprises a polyvinyl acetate-based resin, wherein the amount of the second polymer binder per unit area of ​​the adhesive layer is greater than 0 g / m 2 and equal to or less than 1.5g / m 2 In this regard, the area is the area seen from a plan view on the separator, ie, from a view perpendicular to the substrate, coating and adhesive layer.

[0013] According to the second embodiment of the present disclosure, in the first embodiment, the amount of the second polymer binder per unit area of ​​the adhesive layer may be 0.1 g / m 2 Up to 1.4g / m 2 .

[0014] According to the third embodiment of the present disclosure, in the second embodiment or the third embodiment, the content of the inorganic particles in the coating layer may be 90 parts by weight or more based on 100 parts by weight of the coating layer.

[0015] According to a fourth embodiment of the present disclosure, in any one of the first to third embodiments, the second polymer binder may be in a granular form.

[0016] According to a fifth embodiment of the present disclosure, in any one of the first to fourth embodiments, the adhesive layer may further include a third polymer binder, wherein the third polymer binder includes a polyvinylidene-based binder.

[0017] According to a sixth embodiment of the present disclosure, in any one of the first to fifth embodiments, the polyvinylidene-based binder may be a copolymer of polyvinylidene fluoride and hexafluoropropylene.

[0018] According to a seventh embodiment of the present disclosure, in any one of the first to sixth embodiments, a weight ratio of the second polymer binder to the third polymer binder in the adhesive layer may be 99:1 to 50:50.

[0019] According to an eighth embodiment of the present disclosure, in any one of the first to seventh embodiments, the thickness of the coating layer may be greater than 0 μm and 2.0 μm or less.

[0020] According to a ninth embodiment of the present disclosure, in any one of the first to eighth embodiments, the resistance of the separator may be 0.8Ω or less.

[0021] In a tenth embodiment of the present disclosure, an electrochemical device is provided, which includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the separator is interposed between the positive electrode and the negative electrode and the separator is a separator for an electrochemical device according to any one of the first to ninth embodiments.

[0022] According to an eleventh embodiment of the present disclosure, in the tenth embodiment, the solubility of the second polymer binder in the electrolyte may be 50 (weight / weight) % or more and 80 (weight / weight) % or less at room temperature.

[0023] Beneficial Effects

[0024] The separator for an electrochemical device according to the present disclosure can improve the energy density of a battery by thinning the separator, and a coating layer including a high content of inorganic particles can achieve adhesive strength in the process of manufacturing a battery by providing an adhesive layer.

[0025] The electrochemical device according to the present disclosure can maintain the viscosity of the electrolyte at a low level by adjusting the solubility of the polymer binder included in the adhesive layer in the electrolyte, and can maintain the surface resistance of the battery at a low level while improving the ion conductivity of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of a separator for an electrochemical device according to one embodiment of the present disclosure.

[0027] Figure 2 is a schematic diagram of a separator for an electrochemical device according to one embodiment of the present disclosure.

[0028] Figure 3 is a schematic diagram of a separator for an electrochemical device according to one embodiment of the present disclosure.

[0029] Figure 4 is a schematic diagram of a separator for an electrochemical device according to one embodiment of the present disclosure.

[0030] Figure 5 is a schematic diagram of an electrochemical device according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0031] Hereinafter, multiple embodiments of the present disclosure will be described in detail so that those skilled in the art to which the present disclosure belongs can easily implement the present disclosure. However, these are merely examples given for illustrative purposes, and the scope of the present disclosure is not intended to be limited to the following.

[0032] Unless otherwise limited, the detailed description of the defined or specified elements can be applied to all inventions and is not limited to the description of a specific invention. That is, the present disclosure also relates to a combination of embodiments, even if they are disclosed separately. In addition, unless otherwise explicitly stated, throughout the detailed description and the appended claims, the singular includes the plural.

[0033] As used herein, unless otherwise expressly stated, when a part "includes" a certain component, it means that it may also include other components without excluding other components. However, unless otherwise expressly stated, "include" or "comprising" etc. include "essentially including" and "consisting of...".

[0034] As used herein, the term "consisting essentially of" has the meaning of "consisting of at least 70%, preferably "consisting of at least 80%, most preferably "consisting of at least 90%". If referring to the amount of a component in a material mixture, the % is the % by weight relative to the total weight of the respective mixture. For example, a material consisting essentially of polyethylene comprises polyethylene in an amount of at least 70 % by weight relative to the total weight of the material.

[0035] Additionally, the terms "about," "substantially," and "approximately" as used herein are used in the sense of being at or approximately at when taking into account manufacturing and material tolerances inherent in the conditions being stated, and are used to prevent unscrupulous infringers from taking unfair advantage of the present disclosure (where precise or absolute numbers are stated to aid in understanding the present disclosure).

[0036] As used herein, "A and / or B" means "A and B, or A or B."

[0037] As used herein, unless otherwise specifically stated, when described as being disposed “on” a component, this means that other components may also be disposed, rather than excluding other components disposed therebetween. However, unless otherwise explicitly stated, “on” encompasses the meaning of “directly on”, i.e., the situation where no other components may also be disposed therebetween.

[0038] As used herein, the feature of "having pores" means that the target object includes a plurality of pores and allows gaseous and / or liquid fluids to pass from one side of the object to the other side through a structure connecting the pores to each other.

[0039] As used herein, the separator has a porous property including many pores, and it serves as a porous ion-conducting barrier that prevents electrical contact between a negative electrode and a positive electrode in an electrochemical device and allows ions to pass therethrough.

[0040] Hereinafter, the present disclosure will be described in more detail.

[0041] In one embodiment of the present disclosure, a separator 100 for an electrochemical device is provided. The separator 100 includes: a porous polymer substrate 110, a coating 130 and an adhesive layer 150. The coating 130 is disposed on, preferably directly disposed on, at least one surface of the porous polymer substrate 110. In addition, the coating contains, substantially contains, or consists of a first polymer binder 131 (not shown) and inorganic particles 133 (not shown). The adhesive layer 150 is disposed on, preferably directly disposed on the coating 130. In addition, the adhesive layer contains, substantially contains, or consists of a second polymer binder 151. The second polymer binder contains, substantially contains, or consists of a resin based on polyvinyl acetate (PVAc). The amount of the second polymer binder 151 per unit area of ​​the adhesive layer 150 is greater than 0 g / m 2 and equal to or less than 1.5g / m 2 .

[0042] The separator 100 for an electrochemical device according to one embodiment of the present disclosure may be thinned to improve the energy density of a battery, and the coating layer 130 including a high content of inorganic particles may achieve adhesive strength in a process of manufacturing a battery by providing the adhesive layer 150 .

[0043] Figure 1 is a schematic diagram of a separator 100 for an electrochemical device according to one embodiment of the present disclosure. Figure 2 is a schematic diagram of a separator 100 for an electrochemical device according to one embodiment of the present disclosure. Figure 1 1 is a schematic diagram of a separator 100 for an electrochemical device in which a coating layer 130 and an adhesive layer 150 are provided on one surface of the separator 100 for an electrochemical device. Figure 2 is a schematic diagram of a separator 100 for an electrochemical device in which a coating layer 130 and an adhesive layer 150 are provided on each of both surfaces of the separator 100 for an electrochemical device. Figure 1 and Figure 2 , a separator 100 for an electrochemical device according to an exemplary embodiment of the present disclosure will be described in detail.

[0044] According to one embodiment of the present disclosure, the separator 100 for an electrochemical device includes the porous polymer substrate 110. As described above, in the separator 100 for an electrochemical device, the porous polymer substrate 110 allows lithium ions to pass therethrough while blocking electrical contact and implements a shutdown function at an appropriate temperature.

[0045] According to one embodiment of the present disclosure, the porous polymer substrate 110 can be manufactured using a polyolefin-based resin as a base resin, that is, the porous polymer substrate 110 can include, substantially include, or consist of a polyolefin-based resin. For example, the polyolefin-based resin can include, substantially include polyethylene, polypropylene, polypentene, etc.; or consist of them, and can include, substantially include one or more of these; or consist of one or more of these. From the perspective of imparting a shutdown function at an appropriate temperature, a porous (i.e., having a plurality of pores) separator prepared using such a polyolefin-based resin as a base resin is advantageous.

[0046] According to one embodiment of the present disclosure, the weight average molecular weight of the polyolefin-based resin may be 500,000 or more and 1,500,000 or less. By adjusting the weight average molecular weight of the polyolefin-based resin within the above range, the compression resistance of the separator can be improved. In addition, when different types of polyolefin-based resins are used by mixing or the separator is formed into a multilayer structure having different types of polyolefin-based resins, the weight average molecular weight of the polyolefin-based resin can be calculated by adding the weight average molecular weights according to the content ratio of each polyolefin-based resin.

[0047] As used herein, "weight average molecular weight (Mw)" can be measured by gel permeation chromatography (GPC, PLGPC220, Agilent Technologies), and the measurement conditions can be set as follows.

[0048] -Column: Polymer Laboratories (PL) Olexis

[0049] -Solvent: Trichlorobenzene (TCB)

[0050] -Flow rate: 1.0mL / min

[0051] -Sample concentration: 1.0mg / ml

[0052] -Injection volume: 200 μL

[0053] - Column temperature: 160℃

[0054] -Detector: Agilent high temperature RI detector

[0055] - Standard: polystyrene (calibrated with cubic function).

[0056] According to one embodiment of the present disclosure, the porous polymer substrate 110 can be prepared by a method (wet method) in which a polyolefin-based resin and a diluent are kneaded at a high temperature to make a single phase, the polyolefin resin and the diluent are subjected to phase separation during cooling, and the diluent is extracted to form pores, and the resultant is subjected to stretching and heat setting.

[0057] According to one embodiment of the present disclosure, the separator 100 for an electrochemical device can be easily prepared by a person skilled in the art by adjusting the mixing ratio of the diluent, the stretching ratio, the temperature of the heat setting treatment, etc. so that the average pore size and the maximum pore size can meet the range of the present disclosure.

[0058] According to one embodiment of the present disclosure, the thickness of the porous polymer substrate 110 may be 1 μm or more and 50 μm or less. The thickness of the porous polymer substrate may be 2 μm or more, 3 μm or more, 4 μm or more, 5 μm or more, 6 μm or more, 7 μm or more, or 8 μm or more. The thickness of the porous polymer substrate may be 45 μm or less, 40 μm or less, 35 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, or 15 μm or less. Specifically, the thickness of the porous polymer substrate may be 2 μm or more and 45 μm or less, 3 μm or more and 40 μm or less, 4 μm or more and 35 μm or less, 5 μm or more and 30 μm or less, 6 μm or more and 25 μm or less, 7 μm or more and 20 μm or less, or 8 μm or more and 15 μm or less. By adjusting the thickness of the porous polymer substrate within the above range, the energy density of the battery can be improved.

[0059] According to one embodiment of the present disclosure, the porosity of the porous polymer substrate 110 may be 10% by volume or more and 90% by volume or less. The porosity of the porous polymer substrate may be 10% by volume or more, 20% by volume or more, 30% by volume or more, or 40% by volume or more. The porosity of the porous polymer substrate may be 90% by volume or less, 80% by volume or less, 70% by volume or less, or 60% by volume or less. Specifically, the porosity of the porous polymer substrate may be 10% by volume or more and 90% by volume or less, 20% by volume or more and 80% by volume or less, 30% by volume or more and 70% by volume or less, or 40% by volume or more and 60% by volume or less. By adjusting the porosity of the porous polymer substrate within the above range, the permeability of lithium ions through the separator may be controlled.

[0060] According to the present disclosure, the porosity may correspond to a value obtained by subtracting a volume converted by the weight and density of each component of the porous polymer substrate 110 and / or the coating 130 from a volume calculated by the thickness, width, and length of the porous polymer substrate 110 and / or the coating 130 .

[0061] According to the present disclosure, the porosity and pore size of the porous polymer substrate 110 and / or the coating 130 can be measured by a BET 6-point method via a nitrogen adsorption flow method using a scanning electron microscope (SEM) image, a mercury porosimeter, or a capillary flow porosimeter or a porosimetry analyzer (Bell Japan Inc, Belsorp-II mini). At this time, the use of a capillary flow porosimeter may be provided.

[0062] According to one embodiment of the present disclosure, the separator 100 for an electrochemical device includes a coating 130 disposed on, preferably directly disposed on, at least one surface of a porous polymer substrate 110. Specifically, the separator 100 for an electrochemical device includes a coating 130 disposed on, preferably directly disposed on, one side of the porous polymer substrate 110, such as Figure 1 As shown, or including a coating 130 disposed on, preferably directly disposed on, both sides of the porous polymer substrate 110, such as Figure 2 As described above, by including the coating layer 130 disposed on at least one surface of the porous polymer substrate 110, the separator 100 for an electrochemical device can improve the heat resistance and mechanical properties of the separator and prevent electrical short circuits from occurring in electrodes due to shrinkage of the separator at high temperatures.

[0063] According to one embodiment of the present disclosure, the separator 100 for an electrochemical device includes a coating 130, the coating 130 comprising, substantially comprising, or consisting of a first polymer binder 131 (not shown) and inorganic particles 133 (not shown). As described above, by including the first polymer binder 131 and the inorganic particles 133, the coating 130 can improve the heat resistance and mechanical properties of the separator and prevent electrical short circuits from occurring in the electrode due to shrinkage of the separator at high temperatures, and pores can be formed inside the coating.

[0064] According to one embodiment of the present disclosure, the coating 130 may include a plurality of pores. Specifically, the coating may be a porous coating. More specifically, the coating may be a porous coating including a plurality of pores therein. As described above, by including a plurality of pores, the coating 130 enables the flow of current by allowing lithium ions to flow therethrough while physically blocking the negative electrode and the positive electrode.

[0065] According to an embodiment of the present disclosure, the coating layer 130 may be formed such that the inorganic particles 133 are attached to the first polymer binder 131 and accumulated within the coating layer. The pores inside the coating layer 130 may originate from the interstitial volume, which is the empty space between the inorganic particles 133.

[0066] According to one embodiment of the present disclosure, the first polymer binder 131 may be an acrylic binder, a polyvinylidene binder, or a combination thereof. The first polymer binder 131 may be an acrylic binder. As described above, by selecting the first polymer binder 131, the heat resistance of the coating layer may be improved and the bonding strength of the inorganic particles in the coating layer may be improved.

[0067] According to one embodiment of the present disclosure, the acrylic binder included or substantially included in or forming the first polymer binder 131 is a polymer including carboxylic acid ester as a repeating unit, and it may be preferably (meth)acrylate or acrylic-styrene copolymer.

[0068] According to one embodiment of the present disclosure, examples of (meth)acrylates that may form the first polymer binder or be included in the first polymer binder may be methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, hydroxymethyl (meth)acrylate, hydroxyethyl (meth)acrylate, ethylene glycol (meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, allyl (meth)acrylate, ethylene di(meth)acrylate, and the like, and may be one or more selected from these. Among these, one or more selected from methyl (meth)acrylate, ethyl (meth)acrylate and 2-ethylhexyl (meth)acrylate are preferred, and methyl (meth)acrylate is particularly preferred.

[0069] According to one embodiment of the present disclosure, the acrylic-styrene copolymer that can form the first polymer binder or be included in the first polymer binder can be an acrylic binder, and the acrylic binder can be a polyacrylate-based binder. For example, the acrylic binder can be one or more selected from styrene butadiene rubber, nitrile rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, and an acrylate-based polymer, and specifically, can be a copolymer containing acrylate.

[0070] According to an embodiment of the present disclosure, the polyvinylidene-based binder included in or forming the first polymer binder 131 may be a polyvinylidene fluoride (PVdF)-based binder. As described above, by selecting a polyvinylidene fluoride-based binder as the polyvinylidene-based binder, the resistance of the separator may be reduced.

[0071] According to one embodiment of the present disclosure, the first polymer binder 131 may be in a granular or liquid form. According to the above description, by selecting the first polymer binder 131, the size of the pores of the coating can be controlled and the mechanical properties of the coating can be improved, while controlling the porosity and air permeability of the coating.

[0072] According to one embodiment of the present disclosure, the polyvinylidene fluoride (PVdF)-based binder contained in or forming the first polymer binder 131 may have a content of hexafluoropropylene (HFP) of 10 wt % or more. Specifically, the polyvinylidene fluoride-based binder contained in the first polymer binder 131 may have a content of hexafluoropropylene (HFP) in an amount of 10 wt % or more and 80 wt % or less, 15 wt % or more and 75 wt % or less, 20 wt % or more and 70 wt % or less, 25 wt % or more and 65 wt % or less, 30 wt % or more and 60 wt % or less, 35 wt % or more and 55 wt % or less, or 40 wt % or more and 50 wt % or less. By adjusting the content of hexafluoropropylene contained in the polyvinylidene fluoride-based binder in the first polymer binder 131 within the above range, the resistance of the separator can be reduced. The content of HFP monomer in the polyvinylidene fluoride (PVdF) based binder can be determined by 1 H-NMR and / or 19 Confirmed by F-NMR.

[0073] According to one embodiment of the present disclosure, the content of the first polymer binder 131 may be 10 parts by weight or less relative to 100 parts by weight of the coating. The content of the first polymer binder 131 may be greater than 0 parts by weight, 1 part by weight or greater, 2 parts by weight or greater, 3 parts by weight or greater, or 4 parts by weight or greater relative to 100 parts by weight of the coating. The content of the first polymer binder 131 may be 9 parts by weight or less, 8 parts by weight or less, 7 parts by weight or less, or 6 parts by weight or less relative to 100 parts by weight of the coating. Specifically, the content of the first polymer binder 131 may be greater than 0 parts by weight and equal to or less than 10 parts by weight, equal to or greater than 1 part by weight and equal to or less than 9 parts by weight, equal to or greater than 2 parts by weight and equal to or less than 8 parts by weight, equal to or greater than 3 parts by weight and equal to or less than 7 parts by weight, or equal to or greater than 4 parts by weight and equal to or less than 6 parts by weight relative to 100 parts by weight of the coating 130. By adjusting the content of the first polymer binder 131 within the above range, the mechanical properties of the coating 130 can be improved, the porosity of the coating can be maintained, and the heat resistance can be improved. The content of the first polymer binder in the coating can be determined by the amount of the first polymer binder in the composition used to prepare the coating, such as the slurry.

[0074] According to one embodiment of the present disclosure, the average diameter (D 50 ) is not particularly limited, but is preferably within a range of 0.1 μm or more and 1 μm or less in order to form a coating layer 130 having a uniform thickness and having an appropriate porosity. The average diameter (D 50 ) may be 0.2 μm or more, 0.3 μm or more, 0.4 μm or more, or 0.5 μm or more. The average diameter (D 50 ) may be 0.9 μm or less, 0.8 μm or less, 0.7 μm or less, or 0.6 μm or less. Specifically, the average diameter (D 50 ) may be 0.2 μm or more and 0.9 μm or less, 0.3 μm or more and 0.8 μm or less, 0.4 μm or more and 0.7 μm or less, or 0.5 μm or more and 0.6 μm or less. By setting the average diameter (D 50 ) within the above range, the dispersibility in the slurry prepared for coating preparation can be improved and the thickness of the coating to be formed can be reduced. 50)" means the diameter (particle diameter) at the 50% point in the cumulative distribution of the number of particles according to the particle diameter. The average particle diameter can be determined by using a laser diffraction method. Specifically, a material to be determined is dispersed in a dispersion medium, and the resulting dispersion is introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac S3500) to determine the difference in diffraction patterns according to particle sizes when particles pass through a laser beam, thereby providing a particle size distribution. 50 The particle size can be measured by calculating the particle size at a point where the cumulative distribution of the number of particles according to the particle size in the measuring device becomes 50%.

[0075] According to one embodiment of the present disclosure, the content of the inorganic particles 133 in the coating 130 may be 90 parts by weight or more based on 100 parts by weight of the coating 130. The content of the inorganic particles 133 in the coating 130 may be 90 parts by weight or more, 91 parts by weight or more, 92 parts by weight or more, 93 parts by weight or more, or 94 parts by weight or more relative to 100 parts by weight of the coating 130. The content of the inorganic particles 133 in the coating 130 may be less than 100 parts by weight, 99 parts by weight or less, 98 parts by weight or less, 97 parts by weight or less, or 96 parts by weight or less relative to 100 parts by weight of the coating 130. Specifically, the content of the inorganic particles 133 in the coating 130 may be 90 parts by weight or more and less than 100 parts by weight, 91 parts by weight or more and 99 parts by weight or less, 92 parts by weight or more and 98 parts by weight or less, 93 parts by weight or more and 97 parts by weight or less, or 94 parts by weight or more and 96 parts by weight or less, relative to 100 parts by weight of the coating 130. By adjusting the content of the inorganic particles 133 within the above range, the heat resistance and mechanical properties of the separator can be improved. The content of the inorganic particles in the coating can be determined by the amount of the inorganic particles in the composition used to prepare the coating, such as the slurry.

[0076] According to one embodiment of the present disclosure, the inorganic particles 133 that can be used in the coating layer 130 are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles that can be used in one embodiment of the present disclosure are not particularly limited as long as they are electrochemically stable at the operating voltage of the electrochemical device to which they are applied (e.g., based on Li / Li + It is sufficient that no oxidation and / or reduction reaction occurs within the range of 0V to 5V.

[0077] For example, when inorganic particles with a high dielectric constant are used, the inorganic particles help to improve the dissociation of electrolyte salts (e.g., lithium salts) in liquid electrolytes, thereby improving the ionic conductivity of the electrolyte solution. For the above reasons, the inorganic particles can be inorganic particles with a dielectric constant greater than or equal to 5, inorganic particles with lithium ion transport capability, or a mixture thereof.

[0078] According to one embodiment of the present disclosure, non-limiting examples of the inorganic particles 133 may 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, Mg(OH)2, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, SiC, Al(OH)3, TiO2, aluminum peroxide, zinc tin hydroxide (ZnSn(OH)6), tin zinc oxide (Zn2SnO4, ZnSnO3), antimony trioxide (Sb2O3), antimony tetroxide (Sb2O4), antimony pentoxide (Sb2O5), etc., and may include one or more of these.

[0079] According to one embodiment of the present disclosure, the average diameter (D 50 ) is not particularly limited, but in order to form a coating layer of uniform thickness and appropriate porosity, it is preferably in the range of 0.3 μm or more and 1 μm or less, for example, 0.5 μm to 0.7 μm, for example, about 0.6 μm. Specifically, when the particle size is less than 0.3 μm, the dispersibility of the inorganic particles in the slurry prepared for preparing the coating layer may be deteriorated, and when the particle size exceeds 1 μm, the thickness of the formed coating layer may increase.

[0080] As used herein, “D 50 "Particle size" means the particle size at the 50% point of the cumulative distribution of the number of particles according to the particle size. The particle size can be measured using a laser diffraction method. Specifically, after a powder to be measured is dispersed in a dispersion medium, the resultant is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500) to measure the difference in diffraction patterns according to the particle size when the particles pass through a laser beam, thereby calculating the particle size distribution. 50 The particle size can be measured by calculating the particle size at a point where the cumulative distribution of the number of particles according to the particle size in the measuring device becomes 50%.

[0081] According to one embodiment of the present disclosure, the separator 100 for an electrochemical device includes an adhesive layer 150 disposed, preferably directly disposed, on the coating layer 130. As described above, by including the adhesive layer 150 disposed on the coating layer 130, the separator 100 for an electrochemical device can ensure the adhesive strength between the electrode and the separator during the lamination process of the separator and the electrode.

[0082] According to one embodiment of the present disclosure, the adhesive layer 150 includes, substantially includes, or consists of a second polymer binder 151; the second polymer binder 151 includes, substantially includes, or consists of a polyvinyl acetate-based resin. More specifically, the adhesive layer 150 may be polyvinyl acetate, i.e., may consist of polyvinyl acetate. As described above, by including the second polymer binder 151 containing a polyvinyl acetate-based resin, the adhesive layer 150 may obtain dry bonding strength with the electrode.

[0083] According to one embodiment of the present disclosure, the amount of the second polymer binder 151 per unit area of ​​the adhesive layer 150 is greater than 0 g / m 2 and equal to or less than 1.5g / m 2 The amount of the second polymer binder 151 per unit area of ​​the adhesive layer 150 may be 0.1 g / m 2 or larger, 0.2g / m 2 or larger, 0.3g / m 2 or larger, 0.5g / m 2 or larger, 0.8g / m 2 or greater, or 0.9g / m 2 The amount of the second polymer binder 151 per unit area of ​​the adhesive layer 150 may be 1.4 g / m 2 or less, 1.3g / m 2 or less, 1.2g / m 2 or less, 1.1g / m 2 or less or 1.0g / m 2 Specifically, the amount of the second polymer binder 151 per unit area of ​​the adhesive layer 150 may be 0.1 g / m 2 or larger and 1.5g / m 2 or less, 0.2g / m 2 or larger and 1.4g / m 2 or less, 0.5g / m 2 or greater and 1.3g / m 2 or less, 0.8g / m 2 or greater and 1.2g / m 2 or less, or 0.9g / m 2 or greater and 1.1 g / m2 For example, the amount of the second polymer binder 151 per unit area of ​​the adhesive layer 150 may be 0.2 g / m 2 or greater and 1.0g / m 2 or less. By reducing the amount of the second polymer binder 151 dissolved by the electrolyte by adjusting the content of the second polymer binder 151 per unit area of ​​the adhesive layer 130 within the above range, the viscosity of the electrolyte can be reduced, and thus, the resistance of the separator can be reduced and the adhesive strength can be improved. The amount of the second polymer binder in the adhesive layer can be determined by the amount of the second polymer binder in the composition used to prepare the adhesive layer, such as the slurry.

[0084] According to one embodiment of the present disclosure, the second polymer binder 151 may be in a granular form, that is, may be formed of various second polymer binder particles 151. As described above, by selecting the second polymer binder 151 in a granular form, the porosity of the separator may be improved.

[0085] According to one embodiment of the present disclosure, the average diameter (D 50 ) is not particularly limited, but is preferably within a range of 0.1 μm or more and 1 μm or less in order to form the adhesive layer 130 having a uniform thickness and having an appropriate porosity. The average diameter (D 50 ) may be 0.2 μm or more, 0.3 μm or more, 0.4 μm or more, or 0.5 μm or more. The average diameter (D 50 ) may be 0.9 μm or less, 0.8 μm or less, 0.7 μm or less, or 0.6 μm or less. Specifically, the average diameter (D 50 ) may be 0.2 μm or more and 0.9 μm or less, 0.3 μm or more and 0.8 μm or less, 0.4 μm or more and 0.7 μm or less, or 0.5 μm or more and 0.6 μm or less. By setting the average diameter (D 50 ) is adjusted within the above range, the dispersibility in the slurry prepared for the adhesive layer preparation can be improved and the thickness of the adhesive layer to be formed can be reduced. In this specification, "D 50 The "particle size" refers to the particle size at the 50% point of the cumulative distribution of the number of particles according to the particle size. Specifically, after the powder to be measured is dispersed in a dispersion medium, the resultant is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500) to measure the difference in the diffraction pattern according to the particle size when the particle passes through the laser beam, thereby calculating the particle size distribution.50 The particle size can be measured by calculating the particle size at a point where the cumulative distribution of the number of particles according to the particle size in the measuring device becomes 50%.

[0086] Figure 3 is a schematic diagram of a separator 100 for an electrochemical device according to one embodiment of the present disclosure. Figure 4 is a schematic diagram of a separator 100 for an electrochemical device according to one embodiment of the present disclosure. Specifically, Figure 3 1 is a schematic diagram of a separator 100 for an electrochemical device provided with a coating layer 130 and an adhesive layer 150 on one side thereof, wherein the adhesive layer 150 includes a third polymer binder 153 . Figure 4 1 is a schematic diagram of a separator 100 for an electrochemical device having a coating layer 130 and an adhesive layer 150 disposed on both sides, wherein the adhesive layer 150 includes a third polymer binder 153. Figure 3 and Figure 4 , a separator 100 for an electrochemical device according to an exemplary embodiment of the present disclosure will be described in detail.

[0087] According to one embodiment of the present disclosure, the adhesive layer 150 may further include a third polymer binder 153 containing, substantially containing, or consisting of a polyvinylidene-based binder. As described above, by further including the third polymer binder 153 containing, substantially containing, or consisting of a polyvinylidene-based binder, the resistance increase caused by the electrolyte may be minimized and the wet adhesive strength may be improved.

[0088] According to one embodiment of the present disclosure, the polyvinylidene-based binder can have a content of hexafluoropropylene (HFP) of 40 wt % or less. The polyvinylidene-based binder can have a content of hexafluoropropylene greater than 0 wt % or more, 5 wt % or more, 10 wt % or more, or 15 wt % or more. The polyvinylidene-based binder can have a content of hexafluoropropylene of 40 wt % or less, 35 wt % or less, 30 wt % or less, or 25 wt % or less.

[0089] Specifically, the polyvinylidene-based binder may have a content of hexafluoropropylene in a range of greater than 0 wt % and equal to or less than 40 wt %, equal to or greater than 5 wt % and equal to or less than 35 wt %, equal to or greater than 10 wt % and equal to or less than 30 wt %, or equal to or greater than 15 wt % and equal to or less than 25 wt %. By maintaining the porosity of the separator by adjusting the content of hexafluoropropylene contained in the polyvinylidene-based binder within the above range, the resistance of the separator may be improved.

[0090] According to one embodiment of the present disclosure, the polyvinylidene-based binder may be a polyvinylidene fluoride (PVdF)-based binder. As described above, by selecting the polyvinylidene-based binder as a polyvinylidene fluoride-based binder such as polyvinylidene fluoride, the porosity of the separator may be maintained, thereby improving the resistance of the separator.

[0091] According to one embodiment of the present disclosure, the polyvinylidene fluoride-based binder may be a copolymer of polyvinylidene fluoride and hexafluoropropylene (poly(vinylidene fluoride-co-hexafluoropropylene); PVdF-co-HFP). As described above, by selecting the polyvinylidene fluoride-co-hexafluoropropylene-based binder as a copolymer of polyvinylidene fluoride and hexafluoropropylene, the dissolution of the third polymer binder by the electrolyte may be minimized and the wet adhesive strength may be improved.

[0092] Adhesive layer 150 may consist essentially of or consist of the second polymeric binder and the third polymeric binder.

[0093] According to one embodiment of the present disclosure, in the adhesive layer 150, the weight ratio between the second polymer binder 151 and the third polymer binder 153 may be in the range of 99:1 to 50:50. Specifically, in the adhesive layer 150, the weight ratio between the second polymer binder 151 and the third polymer binder 153 may be in the range of 95:5 to 55:45, 90:10 to 60:40, 85:15 to 65:35, or 80:20 to 70:30, for example, about 70:30. By adjusting the weight ratio between the second polymer binder 151 and the third polymer binder 153 in the adhesive layer 150 within the above range, the dry adhesive strength can be improved while preventing the increase in the resistance of the separator caused by the electrolyte.

[0094] As used herein, dry adhesion strength can be measured in such a manner that the separator is cut into 70 mm (length) × 25 mm (width), the prepared negative electrode and separator are laminated to prepare a sample using a press at 60°C, 6.5 MPa and 1 second, the prepared sample is fixed to a glass plate by attaching it using a double-sided tape, and after the negative electrode is set to face the glass plate, the film portion of the sample is peeled off at an angle of 180° at a rate of 150 mm / min at 25°C, and the strength at this time is measured.

[0095] As used herein, wet adhesion strength can be measured in such a manner that the separator is cut into 70 mm (length) × 25 mm (width), the prepared negative electrode and separator are laminated using a press at 60°C, 6.5 MPa and 1 second to prepare a sample, the prepared sample is loaded into a battery box together with the electrolyte and kept for 4 hours to impregnate the sample with the electrolyte (ethylene carbonate and ethyl methyl carbonate are mixed in a volume ratio of 7:3 and prepared to have a concentration of 1M LiPF6), then, the sample is taken out of the box and fixed to a glass plate by attaching it using a double-sided tape, at this time, after the negative electrode is set to face the glass plate, the film portion of the sample is peeled off at an angle of 90° at a rate of 200 mm / min at 25°C, and the strength at this time is measured.

[0096] According to one embodiment of the present disclosure, the combined amount of the second polymer binder 151 and the third polymer binder 153 per unit area of ​​the adhesive layer 150 may be greater than 0 g / m 2 and equal to or less than 1.5g / m 2 The combined amount of the second polymer binder 151 and the third polymer binder 153 per unit area of ​​the adhesive layer 150 may be 0.1 g / m 2 or larger, 0.2g / m 2 or larger, 0.3g / m 2 or larger, 0.5g / m 2 or larger, 0.8g / m 2 or greater, or 0.9g / m 2 The combined amount of the second polymer binder 151 and the third polymer binder 153 per unit area of ​​the adhesive layer 150 may be 1.4 g / m 2 or less, 1.3g / m 2 or less, 1.2g / m 2 or less, 1.1g / m 2 or less or 1.0g / m 2 Specifically, the combined amount of the second polymer binder 151 and the third polymer binder 150 per unit area of ​​the adhesive layer 150 may be 0.1 g / m 2 or larger and 1.5g / m 2 or less, 0.3g / m 2 or larger and 1.4g / m 2 or less, 0.5g / m 2 or greater and 1.3g / m 2 or less, 0.7g / m 2 or greater and 1.2g / m 2 or less, or 0.9g / m 2 or greater and 1.1 g / m 2or less. By reducing the amount of the second polymer binder dissolved by the electrolyte by adjusting the combined amount of the second polymer binder and the third polymer binder per unit area of ​​the adhesive layer within the above range, the viscosity of the electrolyte can be reduced, and by doing so, the resistance of the separator can be reduced and the adhesive strength can be improved. The combined amount of the second polymer binder and the third polymer binder in the adhesive layer can be determined by the amount of the second polymer binder and the third polymer binder in the composition used to prepare the adhesive layer, such as the slurry.

[0097] According to one embodiment of the present disclosure, the thickness of the coating 130 on either side of the porous polymer substrate 110 may be greater than 0 μm and 2.0 μm or less. The thickness of the coating 130 on either side of the porous polymer substrate 110 may be 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, 0.4 μm or more, 0.5 μm or more, 0.6 μm or more, 0.7 μm or more, 0.8 μm or more, 0.9 μm or more, 1.0 μm or more, 1.1 μm or more, 1.2 μm or more, 1.3 μm or more, or 1.4 μm or more. The thickness of the coating 130 on either side of the porous polymer substrate 110 may be equal to or less than 2.0 μm, equal to or less than 1.9 μm, equal to or less than 1.8 μm, equal to or less than 1.7 μm, or equal to or less than 1.6 μm. Specifically, the thickness of the coating 130 may be greater than 0 μm and equal to or less than 2.0 μm, 0.1 μm or greater and equal to or less than 1.9 μm, 0.2 μm or greater and equal to or less than 1.8 μm, 0.3 μm or greater and equal to or less than 1.7 μm, 0.4 μm or greater and equal to or less than 1.6 μm, 0.5 μm or greater and equal to or less than 1.5 μm, 0.6 μm or greater and equal to or less than 1.4 μm, 0.7 μm or greater and equal to or less than 1.3 μm, 0.8 μm or greater and equal to or less than 1.2 μm, 0.9 μm or greater and equal to or less than 1.1 μm, for example, about 1.5 μm. By adjusting the thickness of the coating 130 within the above range, the heat resistance of the separator can be improved and the energy density of the separator can be increased.

[0098] According to one embodiment of the present disclosure, the thickness of the adhesive layer 150 may be greater than 0 μm and 1.0 μm or less. The thickness of the adhesive layer 150 may be 0.1 μm or greater, 0.2 μm or greater, 0.3 μm or greater, or 0.4 μm or greater. The thickness of the adhesive layer 150 may be equal to or less than 1.0 μm, equal to or less than 0.9 μm, equal to or less than 0.8 μm, equal to or less than 0.7 μm, or equal to or less than 0.6 μm. Specifically, the thickness of the coating 130 may be greater than 0 μm and equal to or less than 1.0 μm, 0.1 μm or greater and equal to or less than 0.9 μm, 0.2 μm or greater and equal to or less than 0.8 μm, 0.3 μm or greater and equal to or less than 0.7 μm, 0.4 μm or greater and equal to or less than 0.6 μm, for example, about 0.5 μm.

[0099] In one embodiment of the present disclosure, the thickness of the polymer substrate and / or coating and / or adhesive layer can be measured by applying a contact thickness gauge. As a contact thickness gauge, for example, Mitutoyo's VL-50S-B can be used.

[0100] According to one embodiment of the present disclosure, the resistance of the separator 100 for an electrochemical device may be equal to or less than 0.85Ω. The resistance of the separator 100 for an electrochemical device may be greater than 0Ω, 0.10Ω or greater, 0.15Ω or greater, 0.20Ω or greater, 0.25Ω or greater, 0.30Ω or greater, 0.35Ω or greater, 0.40Ω or greater, or 0.50Ω or greater. The resistance of the separator 100 for an electrochemical device may be equal to or less than 0.85Ω, equal to or less than 0.80Ω, equal to or less than 0.75Ω, equal to or less than 0.70Ω, equal to or less than 0.65Ω, equal to or less than 0.60Ω, equal to or less than 0.55Ω, or equal to or less than 0.50Ω. Specifically, the resistance of the separator for electrochemical device may be greater than 0Ω and equal to or less than 0.90Ω, 0.05Ω or greater and equal to or less than 0.85Ω, 0.10Ω or greater and equal to or less than 0.80Ω, 0.15Ω or greater and equal to or less than 0.75Ω, 0.20Ω or greater and equal to or less than 0.70Ω, 0.25Ω or greater and equal to or less than 0.65Ω, 0.30Ω or greater and equal to or less than 0.60Ω, 0.35Ω or greater and equal to or less than 0.55Ω, or 0.40Ω or greater and equal to or less than 0.50Ω. By adjusting the resistance of the separator for electrochemical device within the above range, battery performance can be improved.

[0101] As used herein, "resistance" may mean that a coin cell is manufactured by interposing a separator between SUS and injecting an electrolyte in which LiPF6 is mixed at a concentration of 1M in a non-aqueous solvent (in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a ratio of 3:7), thereby measuring resistance (ER) by an EIS method. In particular, the frequency may be in the range of 100,000 Hz to 10,000 Hz.

[0102] According to an embodiment of the present disclosure, the second polymer binder can be a particle type, a solution type, and a combination thereof. In this specification, "particle type" can be defined as the second polymer binder maintaining a particle phase by not being dissolved by the electrolyte embedded in the battery. In this specification, "solution type" can be defined as the second polymer binder maintaining a particle phase by being dissolved by the electrolyte embedded in the battery. By selecting the type of the second polymer binder in the above, the dry adhesion and wet adhesion of the electrode are improved respectively.

[0103] According to an embodiment of the present disclosure, an adhesive layer is disposed on the partial coating layer 130. Specifically, the second polymer binder is disposed on the partial coating layer 130. As described above, by disposing the adhesive layer on the partial coating layer 130, dry adhesion and wet adhesion to the electrode are improved, respectively.

[0104] According to an embodiment of the present disclosure, based on the total area of ​​the coating, the adhesive layer is set to an area greater than 0% and less than 100%. Specifically, based on the total area of ​​the coating, the second polymer binder is set to an area greater than 0% and less than 100%. Specifically, based on the total area of ​​the coating, the second polymer binder is set to an area greater than 0% and less than 100%. Specifically, based on the total area of ​​the coating, the second polymer binder is set to 1% or more and 99% or less, 5% or more and 95% or less, 10% or more and 90% or less, 15% or more and 85% or less, 20% or more and 80% or less, 25% or more and 75% or less, 30% or more and 70% or less, 35% or more and 65% or less, 40% or more and 60% or less, or 45% or more and 55% or less. The area where the second polymer binder is set on the coating is adjusted within the above range, and the dry adhesion and wet adhesion of the electrode are improved respectively.

[0105] According to an embodiment of the present disclosure, the second polymer binder can be disposed on a portion of the coating by spraying, rod coating, spin coating or dip coating. The method for disposing the second polymer binder is selected as described above, and the second polymer binder is easily disposed on the coating. In one embodiment of the present disclosure, a method for preparing a separator for an electrochemical device is provided, the method comprising applying a coating slurry comprising a first polymer binder 131 and inorganic particles 135 on at least one surface of a porous polymer substrate 110 to form a coating; and applying an adhesive layer slurry comprising a second polymer binder to form an adhesive layer.

[0106] The method for preparing an electrochemical device according to one embodiment of the present disclosure can easily prevent the increase in resistance of the separator by preparing the separator as a thin film and can improve the energy density of the battery. In the description related to the method for preparing a separator for an electrochemical device according to one embodiment of the present disclosure, those repeated with the separator for an electrochemical device will be omitted here.

[0107] According to one embodiment of the present disclosure, the method of preparing an electrochemical device includes a step of applying a coating slurry including a first polymer binder 131 and inorganic particles 135 on at least one surface of a porous polymer substrate 110. As described above, by including the step of applying the coating slurry on at least one surface of the porous polymer substrate, a coating can be formed by a single application, the heat resistance of the separator is improved due to the presence of excess inorganic particles in the coating slurry, and the solvent (i.e., the solvent that may be included in the coating slurry in addition to the first polymer binder 131 and the inorganic particles 135) is easily evaporated. The coating slurry may substantially include or consist of the first polymer binder 131, the inorganic particles 135, and the solvent.

[0108] According to an embodiment of the present disclosure, the method can be carried out as follows: before the step of applying the coating slurry, the first polymer binder can be dispersed in a suitable dispersion medium to prepare a polymer emulsion to prepare a slurry. As a solvent, it is preferred to use a solvent having a solubility index similar to that of the binder polymer and having a low boiling point. This is to promote uniform mixing and subsequent solvent removal. Non-limiting examples of usable solvents can include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (NMP), cyclohexane, water, mixtures thereof, etc. As used herein, a dispersion medium is a medium used in the process of preparing a slurry and can refer to a solvent.

[0109] According to one embodiment of the present disclosure, inorganic particles can be added and dispersed in the polymer emulsion. The content ratio of the inorganic particles to the polymer binder particles is as described above, and can be appropriately adjusted considering the thickness, pore size and porosity of the coating finally prepared according to an exemplary embodiment of the present disclosure.

[0110] According to one embodiment of the present disclosure, the coating slurry may be dispersed by adding the first polymer binder and the inorganic particles to water as a dispersion medium (solvent).

[0111] According to one embodiment of the present disclosure, the coating slurry may further include a dispersant. The coating slurry may substantially include or consist of a first polymer binder 131, inorganic particles 135, a solvent and a dispersant. Specifically, the coating slurry may include sodium carboxymethylcellulose (SG-L02, GL Chem Co.) as a dispersant. As described above, the coating slurry may improve the dispersibility of the coating slurry by further including a dispersant.

[0112] According to one embodiment of the present disclosure, the content of the dispersant in the coating slurry may be 0.5 parts by weight or more and 2 parts by weight or less relative to 100 parts by weight of the total content of the first polymer binder, the inorganic particles and the dispersant. Within the above range, the dispersibility of the coating slurry may be improved by adjusting the content of the dispersant.

[0113] According to one embodiment of the present disclosure, in the coating slurry, based on the total content of 100 parts by weight of the first polymer binder, inorganic particles and dispersant, the content of inorganic particles can be 90 parts by weight or more. Based on the total content of 100 parts by weight of the first polymer binder, inorganic particles and dispersant, the content of inorganic particles in the coating slurry can be 90 parts by weight or more, 91 parts by weight or more, 92 parts by weight or more, 93 parts by weight or more, or 94 parts by weight or more. Based on the total content of 100 parts by weight of the first polymer binder, inorganic particles and dispersant, the content of inorganic particles in the coating slurry can be less than 100 parts by weight, 99 parts by weight or less, 98 parts by weight or less, 97 parts by weight or less, or 96 parts by weight or less. Specifically, based on 100 parts by weight of the total content of the first polymer binder, the inorganic particles and the dispersant, the content of the inorganic particles in the coating slurry may be 90 parts by weight or more and less than 100 parts by weight, 91 parts by weight or more and 99 parts by weight or less, 92 parts by weight or more and 98 parts by weight or less, 93 parts by weight or more and 97 parts by weight or less, or 94 parts by weight or more and 96 parts by weight or less. By adjusting the content of the inorganic particles 133 within the above range, the heat resistance and mechanical properties of the separator can be improved.

[0114] According to one embodiment of the present disclosure, based on the total content of 100 parts by weight of the first polymer binder, the inorganic particles and the dispersant, the content of the first polymer binder in the slurry can be 10 parts by weight or less. Based on the total content of 100 parts by weight of the first polymer binder, the inorganic particles and the dispersant, the content of the first polymer binder in the coating slurry can be greater than 0 parts by weight, 1 part by weight or more, 2 parts by weight or more, 3 parts by weight or more, 4 parts by weight or more. Based on the total content of 100 parts by weight of the first polymer binder, the inorganic particles and the dispersant, the content of the first polymer binder in the coating slurry can be equal to or less than 10 parts by weight, equal to or less than 9 parts by weight, equal to or less than 8 parts by weight, equal to or less than 7 parts by weight, or equal to or less than 6 parts by weight. Specifically, based on 100 parts by weight of the total content of the first polymer binder, the inorganic particles and the dispersant, the content of the first polymer binder in the coating slurry may be greater than 0 parts by weight and equal to or less than 10 parts by weight, greater than or equal to 1 part by weight and equal to or less than 9 parts by weight, greater than or equal to 2 parts by weight and equal to or less than 8 parts by weight, greater than or equal to 3 parts by weight and equal to or less than 7 parts by weight, or greater than or equal to 4 parts by weight and equal to or less than 6 parts by weight. By adjusting the content of the first polymer binder 131 within the above range, the mechanical properties of the coating 130 can be improved, the porosity of the coating can be maintained, and the heat resistance can be improved.

[0115] According to one embodiment of the present disclosure, the method of applying the coating slurry to the surface of the porous polymer substrate 110 is not particularly limited to any one method, and conventional methods known in the art can be used. For example, various methods such as dip coating, die coating, roller coating, comma coating, combinations thereof, etc. can be used.

[0116] According to one embodiment of the present disclosure, the method for preparing an electrochemical device includes the step of applying a slurry for an adhesive layer including a second polymer binder 151. As described above, the adhesive layer can be easily formed by including the step of applying a slurry for an adhesive layer including the second polymer binder 151, and the loading amount of the second polymer binder (the total weight of the second polymer binder and / or the third polymer binder included in the adhesive layer) can be easily adjusted.

[0117] According to one embodiment of the present disclosure, the method of applying the adhesive layer slurry to the surface of the porous polymer substrate 110 is not particularly limited to any one method, and conventional methods known in the art can be used. For example, various methods such as dip coating, die coating, roll coating, comma coating, combinations thereof, etc. can be used.

[0118] According to one embodiment of the present disclosure, the adhesive layer slurry may further include a solvent, and the solvent may be water. As described above, by further including a solvent, the adhesive layer slurry may more uniformly disperse the second polymer binder and the third polymer binder.

[0119] The adhesive layer slurry may essentially comprise or consist of the second polymer binder and a solvent.The adhesive layer slurry may essentially comprise or consist of the second polymer binder, the third polymer binder, and a solvent.

[0120] According to one embodiment of the present disclosure, based on 100 parts by weight of the adhesive layer slurry, the content of the second polymer binder in the adhesive layer slurry can be 1 part by weight or more and 99 parts by weight or less. Based on 100 parts by weight of the adhesive layer slurry, the content of the second polymer binder in the adhesive layer slurry can be 10 parts by weight or more, 20 parts by weight or more, 30 parts by weight or more, or 40 parts by weight or more. Based on 100 parts by weight of the adhesive layer slurry, the content of the second polymer binder in the adhesive layer slurry can be 90 parts by weight or less, 80 parts by weight or less, 70 parts by weight or less, or 60 parts by weight or less. Specifically, based on 100 parts by weight of the adhesive layer slurry, the content of the second polymer binder in the adhesive layer slurry can be 10 parts by weight or more and 90 parts by weight or less, 20 parts by weight or more and 80 parts by weight or less, 30 parts by weight or more and 70 parts by weight or less, or 40 parts by weight or more and 60 parts by weight or less. By adjusting the content of the second polymer binder within the above range, the viscosity of the electrolyte may be reduced, and by doing so, the resistance of the separator may be reduced and the adhesive strength may be improved.

[0121] According to one embodiment of the present disclosure, the solid content of the adhesive layer slurry can be 10 weight % or more and 30 weight % or less. The solid content of the adhesive layer slurry can be 11 weight % or more, 12 weight % or more, 13 weight % or more, 14 weight % or more, 15 weight % or more, 16 weight % or more, 17 weight % or more, 18 weight % or more, or 19 weight % or more. The solid content of the adhesive layer slurry can be 29 weight % or less, 28 weight % or less, 27 weight % or less, 26 weight % or less, 25 weight % or less, 24 weight % or less, 23 weight % or less, 22 weight % or less, or 21 weight % or less. Specifically, the solid content of the adhesive layer slurry can be 11% by weight or more and 29% by weight or less, 12% by weight or more and 28% by weight or less, 13% by weight or more and 27% by weight or less, 14% by weight or more and 26% by weight or less, 15% by weight or more and 25% by weight or less, 16% by weight or more and 24% by weight or less, 17% by weight or more and 23% by weight or less, 18% by weight or more and 22% by weight or less, or 19% by weight or more and 21% by weight or less. By adjusting the solid content of the adhesive layer slurry within the above range, the second polymer binder and the third polymer binder set on the coating can be easily applied, and the content to be set can be easily adjusted.

[0122] According to one embodiment of the present disclosure, a method for preparing an electrochemical device may include a step of preparing a coating layer by drying the coating layer slurry (i.e., a slurry for coating) after applying the coating layer slurry to one or both surfaces of a porous polymer substrate. As described above, by including a step of drying the coating layer slurry to provide a coating layer, damage to the coating layer can be minimized and the solvent contained in the slurry can be easily removed.

[0123] According to one embodiment of the present disclosure, the temperature of the drying process of the coating may be 25°C or higher and 75°C or lower. Specifically, the temperature of the drying process of the coating may be 30°C or higher and 70°C or lower, 35°C or higher and 65°C or lower, 40°C or higher and 60°C or lower, or 45°C or higher and 55°C or lower. By adjusting the temperature of the drying process of the coating within the above range, denaturation of the porous polymer substrate can be prevented and the dispersion medium can be effectively removed.

[0124] According to one embodiment of the present disclosure, a method for preparing an electrochemical device may include the following steps: drying the adhesive layer slurry to provide an adhesive layer. As described above, by including the step of drying the adhesive layer slurry to prepare the adhesive layer, damage to the adhesive layer can be minimized and the solvent contained in the slurry can be easily removed.

[0125] According to one embodiment of the present disclosure, the temperature of the drying process of the adhesive layer may be 25° C. or higher and 75° C. or lower. Specifically, the temperature of the drying process of the adhesive layer may be 30° C. or higher and 70° C. or lower, 35° C. or higher and 65° C. or lower, 40° C. or higher and 60° C. or lower, or 45° C. or higher and 55° C. or lower. By adjusting the temperature of the drying process of the adhesive layer within the above range, the denaturation of the porous polymer substrate can be prevented and the solvent can be effectively removed.

[0126] According to one embodiment of the present disclosure, the method for preparing an electrochemical device may include the step of forming a coating layer and an adhesive layer by drying the coating slurry and the adhesive layer slurry immediately after applying the adhesive layer slurry. As described above, by including the step of forming a coating layer and an adhesive layer by drying the coating slurry and the adhesive layer slurry immediately after applying the adhesive layer slurry in the method for preparing an electrochemical device, the coating layer and the adhesive layer can be easily formed.

[0127] According to one embodiment of the present disclosure, in the drying process, the time conditions are appropriately set to minimize the surface defects of the coating. For drying, a drying auxiliary device (eg, a drying furnace or hot air) may be used within an appropriate range.

[0128] According to one embodiment of the present disclosure, the separator is prepared into an electrochemical device by a lamination process, in which the negative electrode and the positive electrode are inserted and combined by applying heat and / or pressure. In one embodiment of the present disclosure, the lamination process can be carried out by a rolling device including a pair of pressure rollers. That is, interlayer bonding can be achieved by sequentially stacking the negative electrode, the separator, and the positive electrode and embedding them between the pressure rollers. In particular, the lamination process can be carried out by hot pressing.

[0129] In one embodiment of the present disclosure, an electrochemical device 1000 is provided, wherein the electrochemical device 1000 includes a positive electrode 300; a negative electrode 500; a separator 100; and an electrolyte, wherein the separator 100 is interposed between the positive electrode 300 and the negative electrode 500, and the separator 100 is a separator 100 for an electrochemical device according to the present invention.

[0130] The electrochemical device according to one embodiment of the present disclosure can achieve the viscosity of the electrolyte by adjusting the solubility of the polymer binder included in the adhesive layer in the electrolyte, and can achieve the surface resistance of the battery at a low level while improving the ion conductivity of the battery.

[0131] Figure 5 is a schematic diagram of an electrochemical device 1000 according to an exemplary embodiment of the present disclosure. Figure 5, an electrochemical device 1000 according to an exemplary embodiment of the present disclosure will be described in detail.

[0132] In one embodiment of the present disclosure, an electrochemical device is a device that converts chemical energy into electrical energy by an electrochemical reaction, and it is a concept covering both primary batteries and secondary batteries. As used herein, a secondary battery can be charged and discharged, and refers to a lithium secondary battery, a nickel-cadmium battery, a nickel-hydrogen battery, etc. A lithium secondary battery uses lithium ions as an ion conductor, and examples of lithium secondary batteries may include a non-aqueous electrolyte secondary battery containing a liquid electrolyte, an all-solid-state battery containing a solid electrolyte, a lithium polymer battery containing a gel polymer electrolyte, a lithium metal battery using lithium metal as a negative electrode, etc., but are not limited thereto.

[0133] According to one embodiment of the present disclosure, the positive electrode is provided with a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material, a conductive material and a binder resin on at least one surface of the current collector. The positive electrode active material may include one or a mixture of two or more of the following: a layered compound (e.g., lithium manganese composite oxide (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), etc.), or a compound substituted by one or more transition metals; lithium manganese oxide (e.g., chemical formula Li 1+x Mn 2-x O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2, etc.); lithium copper oxide (e.g., Li2CuO2); vanadium oxide (e.g., LiV3O8, LiV3O4, V2O5, Cu2V2O7, etc.); 1-x M x Ni-site lithium nickel oxide represented by O2 (wherein M is Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x is 0.01 to 0.3); represented by the chemical formula LiMn 1-x M x Lithium manganese composite oxides represented by Li2Mn3MO8 (wherein M is Co, Ni, Fe, Cr, Zn or Ta, and x is 0.01 to 0.1) or Li2Mn3MO8 (wherein M is Fe, Co, Ni, Cu or Zn); LiMn2O4 in which part of the Li in the chemical formula is replaced by alkaline earth metal ions; disulfide compounds; and Fe2(MoO4)3.

[0134] According to an embodiment of the present disclosure, the negative electrode is provided with a negative electrode current collector and a negative electrode active material layer containing a negative electrode active material, a conductive material, and a polymer binder on at least one surface of the current collector. The negative electrode may contain, as the negative electrode active material, one or a mixture of two or more of the following: carbon such as non-graphitized carbon and graphite-based carbon; metal composite oxides (e.g., Li x Fe2O3(0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me' y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements in Group I, Group II, and Group III of the periodic table, halogens; 0<x≤1; 1≤y≤3; 1≤z≤8), etc.); lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; metal oxides (e.g., SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, etc.); conductive polymers (e.g., polyacetylene, etc.); Li-Co-Ni-based materials; and titanium oxides.

[0135] According to an embodiment of the present disclosure, the conductive material may be, for example, any one or a mixture of two or more conductive materials selected from the following: graphite, carbon black, carbon fiber or metal fiber, metal powder, conductive whisker, conductive metal oxide, activated carbon, and polyphenylene derivative. More specifically, the conductive material may be one or a mixture of two or more conductive materials selected from the following: natural graphite, artificial graphite, super-P, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black, denka black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide.

[0136] According to an embodiment of the present disclosure, the current collector is not particularly limited as long as it has high conductivity and does not cause chemical changes in the electrochemical device, 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.

[0137] According to one embodiment of the present disclosure, as a polymer binder resin, a polymer 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, polyethylhexyl acrylate, polybutyl acrylate, polyacrylonitrile, polyvinyl pyrrolidone, 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, etc., but are not limited thereto.

[0138] As used herein, the positive electrode slurry for preparing the positive electrode active material layer may include a dispersant, and the dispersant may be a pyrrolidone-based compound, specifically, N-methylpyrrolidone (ADC-01, LG Chem).

[0139] According to one embodiment of the present disclosure, the content of the dispersant contained in the positive electrode slurry may be greater than 0 parts by weight and equal to or less than 0.5 parts by weight based on 100 parts by weight of the positive electrode slurry. Specifically, the content of the dispersant contained in the positive electrode slurry may be greater than 0.05 parts by weight and equal to or less than 0.4 parts by weight based on 100 parts by weight of the positive electrode slurry.

[0140] According to one embodiment of the present disclosure, the negative electrode slurry for preparing the negative electrode active material layer may include a dispersant, and the dispersant may be a polypyrrolidone-based compound. Specifically, the dispersant may be polyvinyl pyrrolidone (Junsei Co., Ltd, Japan).

[0141] According to one embodiment of the present disclosure, the content of the dispersant contained in the negative electrode slurry may be greater than 0 parts by weight and equal to or less than 0.5 parts by weight based on 100 parts by weight of the negative electrode slurry. Specifically, the content of the dispersant contained in the negative electrode slurry may be greater than 0.05 parts by weight and equal to or less than 0.4 parts by weight based on 100 parts by weight of the negative electrode slurry.

[0142] According to one embodiment of the present disclosure, the electrochemical device prepared as described above may be incorporated into a suitable case, and a battery may be manufactured by injecting an electrolyte.

[0143] According to one embodiment of the present disclosure, the electrolyte is + B - A salt of the structure + Alkali metal cations (e.g., Li + 、Na + and K + ) or an ion composed of a combination thereof, B- For anions (e.g., PF6 - 、BF4 - , Cl - Br - ,I - 、ClO4 - 、AsF6 - 、CH3CO2 - CF3SO3 - 、N(CF3SO2)2 - 、C(CF2SO2)3 - , which is dissolved or dissociated in 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), gamma (γ)-butyrolactone or an organic solvent consisting of a mixture thereof, but is not limited thereto.

[0144] According to one embodiment of the present disclosure, at room temperature (25° C.), the solubility of the second polymer binder in the electrolyte may be 50 (weight / weight)% or more and 80 (weight / weight)% or less. The solubility of the second polymer binder in the electrolyte is defined as the amount of the second polymer binder dissolved by 100 g of the electrolyte at room temperature (solute=second polymer binder, solvent=electrolyte). At room temperature (25° C.), the solubility of the second polymer binder in the electrolyte can be 51 (wt / wt)% or greater, 52 (wt / wt)% or greater, 53 (wt / wt)% or greater, 54 (wt / wt)% or greater, 55 (wt / wt)% or greater, 56 (wt / wt)% or greater, 57 (wt / wt)% or greater, 58 (wt / wt)% or greater, 59 (wt / wt)% or greater, 60 (wt / wt)% or greater, 61 (wt / wt)% or greater, 62 (wt / wt)% or greater, 63 (wt / wt)% or greater, or 64 (wt / wt)% or greater. At room temperature (25° C.), the solubility of the second polymer binder in the electrolyte can be 79 (wt / wt)% or less, 78 (wt / wt)% or less, 77 (wt / wt)% or less, 76 (wt / wt)% or less, 75 (wt / wt)% or less, 74 (wt / wt)% or less, 73 (wt / wt)% or less, 72 (wt / wt)% or less, 71 (wt / wt)% or less, 70 (wt / wt)% or less, 69 (wt / wt)% or less, 68 (wt / wt)% or less, 67 (wt / wt)% or less, or 66 (wt / wt)% or less.Specifically, at room temperature, the solubility of the second polymer binder in the electrolyte may be 51 (wt / wt)% or more and 79 (wt / wt)% or less, 52 (wt / wt)% or more and 78 (wt / wt)% or less, 53 (wt / wt)% or more and 77 (wt / wt)% or less, 54 (wt / wt)% or more and 76 (wt / wt)% or less, 55 (wt / wt)% or more and 75 (wt / wt)% or less, 56 (wt / wt)% or more and 74 (wt / wt)% or less, 57 (wt / wt)% or more and 78 (wt / wt)% or less, 58 (wt / wt)% or more and 79 (wt / wt)% or less, 59 (wt / wt)% or more and 71 (wt / wt)% or less, 51 (wt / wt)% or more and 72 (wt / wt)% or less, 52 (wt / wt)% or more and 73 (wt / wt)% or less, 53 (wt / wt)% or more and 74 (wt / wt)% or less, 54 (wt / wt)% or more and 76 (wt / wt)% or less, 73 (wt / wt)% or less, 58 (wt / wt)% or more and 72 (wt / wt)% or less, 59 (wt / wt)% or more and 71 (wt / wt)% or less, 60 (wt / wt)% or more and 70 (wt / wt)% or less, 61 (wt / wt)% or more and 69 (wt / wt)% or less, 62 (wt / wt)% or more and 68 (wt / wt)% or less, 63 (wt / wt)% or more and 67 (wt / wt)% or less, or 64 (wt / wt)% or more and 66 (wt / wt)% or less. By adjusting the solubility of the second polymer binder in the electrolyte within the above range, the increase in electrolyte viscosity caused by the dissolution of the second polymer in the electrolyte can be prevented, and the resistance and ionic conductivity of the separator can be improved.

[0145] According to one embodiment of the present disclosure, at room temperature (25° C.), the solubility of the third polymer binder in the electrolyte may be 50 (weight / weight)% or more and 80 (weight / weight)% or less. The solubility of the third polymer binder in the electrolyte is defined as the amount of the third polymer binder dissolved by 100 g of the electrolyte at room temperature (solute=third polymer binder, solvent=electrolyte). At room temperature (25°C), the solubility of the third polymer binder in the electrolyte can be 51 (wt / wt)% or greater, 52 (wt / wt)% or greater, 53 (wt / wt)% or greater, 54 (wt / wt)% or greater, 55 (wt / wt)% or greater, 56 (wt / wt)% or greater, 57 (wt / wt)% or greater, 58 (wt / wt)% or greater, 59 (wt / wt)% or greater, 60 (wt / wt)% or greater, 61 (wt / wt)% or greater, 62 (wt / wt)% or greater, 63 (wt / wt)% or greater, 64 (wt / wt)% or greater. At room temperature (25°C), the solubility of the third polymer binder in the electrolyte can be 79 (wt / wt)% or less, 78 (wt / wt)% or less, 77 (wt / wt)% or less, 76 (wt / wt)% or less, 75 (wt / wt)% or less, 74 (wt / wt)% or less, 73 (wt / wt)% or less, 72 (wt / wt)% or less, 71 (wt / wt)% or less, 70 (wt / wt)% or less, 69 (wt / wt)% or less, 68 (wt / wt)% or less, 67 (wt / wt)% or less, or 66 (wt / wt)% or less.Specifically, at room temperature, the solubility of the third polymer binder in the electrolyte may be 51 (wt / wt)% or more and 79 (wt / wt)% or less, 52 (wt / wt)% or more and 78 (wt / wt)% or less, 53 (wt / wt)% or more and 77 (wt / wt)% or less, 54 (wt / wt)% or more and 76 (wt / wt)% or less, 55 (wt / wt)% or more and 75 (wt / wt)% or less, 56 (wt / wt)% or more and 74 (wt / wt)% or less, 57 (wt / wt)% or more and 73 (wt / wt)% or less, 58 (wt / wt)% or more and 72 (wt / wt)% or less, 59 (wt / wt)% or more and 71 (wt / wt)% or less, 60 (wt / wt)% or more and 70 (wt / wt)% or less, 61 (wt / wt)% or more and 69 (wt / wt)% or less, 62 (wt / wt)% or more and 68 (wt / wt)% or less, 63 (wt / wt)% or more and 67 (wt / wt)% or less, 64 (wt / wt)% or more and 66 (wt / wt)% or less. By adjusting the solubility of the third polymer binder in the electrolyte within the above range, the increase in electrolyte viscosity caused by the dissolution of the third polymer in the electrolyte can be prevented, and the resistance and ion conductivity of the separator can be improved.

[0146] In one embodiment of the present disclosure, a battery module, a battery pack including the battery module, and a device including the battery pack as a power source are provided, wherein the battery module includes a battery including an electrode assembly as a unit cell. Specific examples of the device may include an electric tool driven by an electric motor; an electric vehicle (EV), including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), etc.; an electric two-wheeled vehicle, including an electric bicycle (E-bike) and an electric scooter (E-scooter); an electric golf cart; a power storage system, etc., but are not limited thereto.

[0147] Embodiments of the invention

[0148] Hereinafter, the embodiments will be described in detail to illustrate the present disclosure in detail. However, the embodiments according to the present disclosure can be modified in various forms, and the scope of the present disclosure should not be interpreted as being limited to the following detailed embodiments. The embodiments of the present disclosure are provided to more completely illustrate the present disclosure to people with ordinary knowledge in the art.

[0149] <Example 1>

[0150] A polyethylene resin (weight average molecular weight: 900,000) was extruded, and a porous polymer substrate (total thickness: about 9 μm, porosity: 40% by volume) was prepared by a wet process.

[0151] As inorganic particles, prepare D 50 Al2O3 powder with a particle size of 600 nm. Acrylic emulsion (CSB-130, Toyo Ink Co.) was prepared as a first binder polymer, and sodium carboxymethylcellulose (CMC-Na) (SG-L02, GL Chem Co.) was prepared as a dispersant.

[0152] After the prepared inorganic particles, the first binder polymer, and the dispersant were added to water as a dispersion medium at a weight ratio of 97:2:1, the inorganic particles were pulverized and dispersed to prepare a coating slurry.

[0153] Both surfaces of the porous polymer substrate are coated with the coating slurry respectively and dried to form coating layers.

[0154] As a second polymer binder, polyvinyl acetate was added to water as a solvent and dispersed so that the solid content became 20% by weight to prepare a slurry for an adhesive layer.

[0155] The adhesive layer was applied to the coating layer by bar coating so that the polyvinyl acetate (average diameter (D 50 ): 500nm) becomes 1.0g / m 2 , and then dried to form an adhesive layer to manufacture a separator for an electrochemical device.

[0156] <Example 2>

[0157] A separator for an electrochemical device was manufactured in the same manner as in Example 1 above, except that in Example 1 above, the slurry for the adhesive layer was applied by bar coating so that the loading amount of polyvinyl acetate became 0.5 g / m 2 , and then dried to form an adhesive layer.

[0158] <Example 3>

[0159] A separator for an electrochemical device was manufactured in the same manner as in Example 1 above, except that in Example 1 above, the slurry for the binder layer was applied by spraying so that the loading amount of polyvinyl acetate became 0.2 g / m 2 , and then dried to form an adhesive layer.

[0160] <Example 4>

[0161] The separator for an electrochemical device was manufactured in the same manner as in Example 1 above, except that in Example 1 above, polyvinyl acetate (PVAc) (i.e., the second polymer binder) and a copolymer of polyvinylidene fluoride (PVdF) and hexafluoropropylene (HFP) (BG4430 of Arkema) (i.e., the third polymer binder) were mixed in a weight ratio of 70:30 and added to water (i.e., the solvent) to prepare a slurry for the adhesive layer, and the slurry for the adhesive layer was coated by rod coating so that the total loading amount of polyvinyl acetate (PVAc) and the copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP) became 0.5 g / m 2 , and then dried to form an adhesive layer.

[0162] <Example 5>

[0163] A separator for an electrochemical device was manufactured in the same manner as in Example 1 above, except that in Example 1 above, the adhesive layer was formed such that the second polymer binder was provided to 50% area based on the total area of ​​the coating layer.

[0164] <Comparative Example 1>

[0165] A polyethylene resin (weight average molecular weight 900,000) was extruded, and a porous polymer substrate (total thickness about 9 μm) was prepared by a wet process.

[0166] Preparation 50 Al2O3 powder with a particle size of 600 nm was used as inorganic particles. A copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP) (Solef21510, Solvay Co.) was prepared as a binder polymer, and sodium carboxymethylcellulose (CMC-Na) (SG-L02, GL Chem Co.) was prepared as a dispersant.

[0167] After adding the prepared inorganic particles, binder polymer, and dispersant to acetone at a weight ratio of 78:20:2, a coating slurry was prepared by dissolving the polymer binder.

[0168] The coating slurry was applied to both sides of the porous polymer substrate so that the loading amount became 3.2 g / m 2 , and then a wet phase separation method is used to form a coating to produce a separator for an electrochemical device.

[0169] <Comparative Example 2>

[0170] A separator for an electrochemical device was manufactured in the same manner as in Example 1 above, except that in Example 1 above, acrylate (ADS11, LGC Co.) (ie, acrylic resin) was used as the second polymer binder.

[0171] <Comparative Example 3>

[0172] A separator for an electrochemical device was manufactured in the same manner as in Example 1 above, except that in Example 1 above, only a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP) (LBG4430LX, Arkema Co.) was used as the second polymer binder.

[0173] <Comparative Example 4>

[0174] A separator for an electrochemical device is manufactured in the same manner as in Example 1 above, except that as the second polymer binder, a mixture in which acrylate (ADS11, LGC Co.) (i.e., acrylic resin) and a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP) (LBG4430LX, Arkema Co.) are mixed in a weight ratio of 5:5 is used in Example 1 above.

[0175] <Comparative Example 5>

[0176] A separator for an electrochemical device was manufactured in the same manner as in Example 1 above, except that in Example 1 above, polyolefin wax (Chemipal W700, Mitsui Chemicals, Co., Ltd.) was used as the second polymer binder.

[0177] <Comparative Example 6>

[0178] A separator for an electrochemical device was manufactured in the same manner as in Example 1 above, except that in Example 1 above, the slurry for the binder layer was applied by bar coating so that the loading amount of polyvinyl acetate became 1.5 g / m 2 , and then dried to form an adhesive layer.

[0179] <Manufacturing of Electrochemical Device>

[0180] 1) Preparation of positive electrode

[0181] The positive electrode active material (LiNi 0.8 Mn 0.1 Co 0.1O2), a conductive material (carbon black), a dispersant (N-methylpyrrolidone, ADC-01, LG Chem) and a binder resin (PVDF-HFP and PVDF mixed) were mixed with water in a weight ratio of 97.5:0.7:0.14:1.66 to prepare a positive electrode active material layer slurry having a concentration of 50 wt % of the remaining components except water. Then, the slurry was applied to the surface of an aluminum film (thickness 10 μm) and dried to prepare a positive electrode having a positive electrode active material layer (thickness 120 μm).

[0182] 2) Preparation of negative electrode

[0183] Graphite (a blend of natural graphite and artificial graphite), a conductive material (carbon black), a dispersant (polyvinyl pyrrolidone, Junsei Co., Japan) and a binder resin (a mixture of PVDF-HFP and PVDF) were mixed with water at a weight ratio of 97.5:0.7:0.14:1.66 to prepare a slurry for a negative electrode active material layer having a concentration of 50 wt % of the remaining components except water. Then, the slurry was applied to the surface of a copper film (thickness of 10 μm) and dried to prepare a negative electrode having a negative electrode active material layer (thickness of 120 μm).

[0184] 3) Lamination process

[0185] An electrode assembly was obtained by laminating the prepared negative electrode and positive electrode with the separators of the examples and comparative examples interposed therebetween and performing a lamination process The lamination process was performed using a hot press at 70° C. and 5.2 MPa for 10 seconds.

[0186] <Experimental Example 1: Measurement of heat shrinkage at 180°C>

[0187] The specimens were prepared by cutting each separator of Examples 1 to 5 and Comparative Examples 1 to 5 into a size of 50 mm (length) × 50 mm (width), keeping the specimens in an oven heated to 180°C for 30 minutes, then recovering the specimens, and measuring the changes in length in the machine direction (MD) and the transverse direction (TD), and calculating the heat shrinkage rate by the following equation 1, and the results are summarized in the following Table 1.

[0188] [Equation 1]

[0189] Thermal shrinkage at 180°C (%) = {(value before shrinkage - value after shrinkage) / value before shrinkage} × 100

[0190] <Experimental Example 2: Measurement of dry adhesive strength>

[0191] The samples were prepared by cutting each separator of Examples 1 to 5 and Comparative Examples 1 to 5 into a size of 70 mm (length) × 25 mm (width), and laminating the prepared negative electrode and separator for 1 second using a press at 60°C and 6.5 MPa. The prepared sample was fixed by attaching to a glass plate using a double-sided tape, and in particular, the negative electrode was placed facing the glass plate. The separator portion of each sample was peeled off at an angle of 180° at a speed of 150 mm / min at 25°C, and the strength at this time was measured, and the results are summarized in Table 1 below.

[0192] <Experimental Example 3: Measurement of wet adhesive strength>

[0193] The samples were prepared by cutting each separator of Examples 1 to 5 and Comparative Examples 1 to 5 into a size of 70 mm (length) × 25 mm (width), and laminating the prepared negative electrode and separator for 1 second using a press at 60 ° C and 6.5 MPa. Each of the prepared samples was loaded into a battery box with an electrolyte and kept therein for 4 hours to impregnate the sample with the electrolyte. As an electrolyte, a mixture of ethylene carbonate and ethyl methyl carbonate in which LiPF6 was made into a concentration of 1M with a volume ratio of 7:3 was used. Then, each sample was taken out of the box and fixed by attaching it to a glass plate using double-sided tape. In particular, the negative electrode was placed facing the glass plate. The separator portion of each sample was peeled off at an angle of 90 ° at a speed of 200 mm / min at 25 ° C, and the strength at this time was measured, and the results are summarized in Table 1 below.

[0194] <Experimental Example 4: Measurement of Viscosity of Electrolyte>

[0195] In the electrode assemblies including the separators of Examples 1 to 5 and Comparative Examples 1 to 5, the viscosity of the electrolyte was measured at 25°C using a Brookfield LVDV-II+Pro viscometer (cone and plate type, 90% torque, rotor #42, sample loading: 1 mL), and the results are summarized in Table 1 below.

[0196] <Experimental Example 5: Measurement of ionic conductivity>

[0197] In the electrode assemblies including the separators of Examples 1 to 5 and Comparative Examples 1 to 5, the ion conductivity of the electrolyte was measured at 25° C. using a multiparameter meter of Mettler Toledo, and the results are summarized in Table 1 below.

[0198] <Experimental Example 6: Measurement of Resistance of Separator>

[0199] As for resistance, each separator was interposed between SUS and an electrolyte was injected to make a coin cell, and the resistance (ER) was measured by an EIS method, and the results are summarized in the following Table 1. In particular, the frequency was set in the range of 10,000 Hz to 100,000 Hz. The electrolyte was a mixture in which LiPF6 was mixed to a concentration of 1 M in a non-aqueous solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a ratio of 3:7.

[0200] <Experimental Example 7: Measurement of Cycle Capacity Retention Rate at Room Temperature>

[0201] The electrochemical devices using the separators of Examples 1 to 5 and Comparative Examples 1 to 5 were charged / discharged once at 0.1C in a voltage range of 3.0V to 4.4V in a chamber at 25°C using an electrochemical charger and a discharger, and their life characteristics were measured when charging at 1.0C and discharging at 1.0C for 200 cycles. In particular, the ratio of the discharge capacity after 200 cycles to the discharge capacity after one cycle was expressed as a capacity retention rate by calculation using the following equation 2, and the results of the life characteristics are summarized in the following Table 1.

[0202] The capacity retention ratio was calculated by the following Equation 2.

[0203] [Equation 2]

[0204] Capacity retention rate (%) = (discharge capacity after 200 cycles / discharge capacity after one cycle) × 100

[0205] [Table 1]

[0206]

[0207] Referring to Table 1, it is determined that the polyvinyl acetate-based resin is included in the adhesive layer and the content of the second polymer binder per unit area of ​​the adhesive layer is greater than 0 g / m 2 and equal to or less than 1.2g / m 2 In the separators of Examples 1 to 4, the resistance of the separator was 0.75Ω or less, and the capacity retention rate under room temperature cycle was 80% or more.

[0208] In contrast, in the separator of Comparative Example 1 (which is a separator using a humidified phase separation method without a separate adhesive layer), the thermal shrinkage rate is high, while in the separator of Comparative Example 2 containing only an acrylic resin in the adhesive layer, the separator of Comparative Example 3 containing only a copolymer of polyvinylidene fluoride and hexafluoropropylene, and the separator of Comparative Example 4 containing both an acrylic resin and a copolymer of polyvinylidene fluoride and hexafluoropropylene, the resistance of the separator increases, while the capacity retention rate under room temperature cycling decreases.

[0209] In addition, in the separator of Comparative Example 5 containing polyolefin wax in the adhesive layer, both the dry adhesion strength and the wet adhesion strength decreased, while in the separator of Comparative Example 6 containing an excess of polyvinyl acetate-based resin, the resistance of the separator increased and the capacity retention rate under room temperature cycling decreased.

[0210] Finally, a separator for an electrochemical device according to an embodiment of the present disclosure is characterized in that it contains a polyvinyl acetate-based resin in the adhesive layer, and can improve battery performance by reducing membrane resistance, and improve capacity retention under room temperature cycles by adjusting the content of the polyvinyl acetate-based resin.

[0211] [Explanation of Reference Numerals]

[0212] 100: Separators for electrochemical devices

[0213] 110: Porous polymer substrate

[0214] 130: Coating

[0215] 131: First polymer binder

[0216] 133: Inorganic particles

[0217] 150: Adhesive layer

[0218] 151: Second polymer binder

[0219] 300: Positive

[0220] 500: Negative

[0221] 1000: Electrochemical Devices

Claims

1. A separator for an electrochemical device, comprising: a porous polymer substrate; a coating, wherein the coating is disposed on at least one surface of the porous polymer substrate and the coating comprises a first polymeric binder and inorganic particles; and an adhesive layer, wherein the adhesive layer is disposed on the coating layer and the adhesive layer comprises a second polymeric binder, wherein the second polymeric binder comprises a polyvinyl acetate-based resin; The amount of the second polymer binder per unit area of ​​the adhesive layer is greater than 0 g / m 2 and equal to or less than 1.5g / m 2 .

2. The separator for an electrochemical device according to claim 1, wherein the amount of the second polymer binder per unit area of ​​the adhesive layer is 0.1 g / m 2 Up to 1.4g / m 2 . 3 . The separator for an electrochemical device according to claim 1 , wherein a content of the inorganic particles in the coating layer is 90 parts by weight or more relative to 100 parts by weight of the coating layer. The separator for an electrochemical device according to claim 1 , wherein the second polymer binder is in a granular form. 5 . The separator for an electrochemical device according to claim 1 , wherein the adhesive layer further comprises a third polymer binder, wherein the third polymer binder comprises a polyvinylidene-based binder. 6 . The separator for an electrochemical device according to claim 5 , wherein the polyvinylidene-based binder is a copolymer of polyvinylidene fluoride and hexafluoropropylene. 7 . The separator for an electrochemical device according to claim 5 , wherein a weight ratio of the second polymer binder to the third polymer binder in the adhesive layer is 99:1 to 50:

50. 8 . The separator for an electrochemical device according to claim 1 , wherein a thickness of the coating layer is greater than 0 μm and 2.0 μm or less. 9 . The separator for an electrochemical device according to claim 1 , wherein the electric resistance of the separator is 0.8Ω or less. 10 . An electrochemical device comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the separator is interposed between the positive electrode and the negative electrode, and the separator is a separator for an electrochemical device according to any one of the preceding claims. 11 . The electrochemical device according to claim 10 , wherein the solubility of the second polymer binder in the electrolyte is 50 (w / w) % or more and 80 (w / w) % or less at room temperature.

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