Separator for electrochemical device and electrochemical device comprising same

Abstract

The separator for an electrochemical device according to an embodiment of the present invention comprises: a porous polymer substrate; and a coating layer disposed on at least one surface of the porous polymer substrate and including a polymer binder and inorganic particles, wherein the porosity of the porous polymer substrate is approximately 50-65%, inclusive.

Description

Separator for electrochemical devices and electrochemical devices containing the same

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0122192, filed September 9, 2024, and Korean Patent Application No. 10-2025-0123277, filed September 1, 2025, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a separator for an electrochemical device and an electrochemical device including the same.

[0003] Electrochemical devices convert chemical energy into electrical energy using electrochemical reactions. Recently, lithium secondary batteries have been widely used due to their high energy density and voltage, long cycle life, and wide range of applications.

[0004] Lithium secondary batteries generate electricity through a chemical reaction in which lithium ions move between the positive and negative electrodes. The lithium ions from the positive electrode move to the negative electrode, charging the battery. The lithium ions from the negative electrode return to the positive electrode, releasing energy and discharging. This requires an electrolyte, which acts as a path for the lithium ions between the positive and negative electrodes, and a separator, which prevents the two electrodes from touching each other. Generally, the four components of a lithium-ion battery are the positive electrode, negative electrode, electrolyte, and separator.

[0005] The present invention provides a separator for an electrochemical device capable of improving resistance by controlling the porosity of a porous polymer substrate while minimizing changes in the thickness of the separator.

[0006] However, the present invention is not limited to the above-mentioned characteristics, and other characteristics not mentioned will be clearly understood by those skilled in the art from the following description.

[0007] One embodiment of the present invention provides a separator for an electrochemical device, comprising: a porous polymer substrate; and a coating layer provided on at least one surface of the porous polymer substrate and including a polymer binder and inorganic particles; wherein the porosity of the porous polymer substrate is about 50% or more and 65% or less.

[0008] According to one embodiment of the present invention, the thickness of the porous polymer substrate may be about 8 ㎛ or more and 15 ㎛ or less.

[0009] According to one embodiment of the present invention, the air permeability of the porous polymer substrate may be about 30 s / 100cc or more and 90 s / 100cc or less.

[0010] According to one embodiment of the present invention, the electrical resistance (ER) of the porous polymer substrate may be about 0.1 ohm or more and 0.6 ohm or less.

[0011] According to one embodiment of the present invention, the coating layer may be provided on both sides of the porous polymer substrate.

[0012] According to one embodiment of the present invention, the thickness of the coating layer may be about 1 ㎛ or more and 5 ㎛ or less.

[0013] According to one embodiment of the present invention, the inorganic particles may include aluminum hydroxide (Al(OH)3).

[0014] According to one embodiment of the present invention, the inorganic particles may include boehmite.

[0015] According to one embodiment of the present invention, the inorganic particles may not contain alumina.

[0016] According to one embodiment of the present invention, the thickness change rate after compression of the separation membrane may be about 7% or less.

[0017] According to one embodiment of the present invention, the thickness change rate of the separation membrane after 100 cycles may be about 7% or less.

[0018] One embodiment of the present invention provides an electrochemical device comprising: an anode; a cathode; and a separator interposed between the anode and the cathode, and any one of the above-described membranes.

[0019] According to one embodiment of the present invention, the electrochemical device may be cylindrical.

[0020] A separator for an electrochemical device according to one embodiment of the present invention can improve resistance by controlling the porosity of a porous polymer substrate while minimizing changes in the thickness of the separator.

[0021] An electrochemical device according to one embodiment of the present invention can improve resistance and performance of the electrochemical device by controlling the porosity of the separator.

[0022] The following drawings attached to this specification illustrate embodiments of the present invention and, together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0023] Figure 1 is a schematic diagram of a separator for an electrochemical device according to one embodiment of the present invention.

[0024] Figure 2 is a drawing showing the structure of an electrochemical device according to one embodiment of the present invention.

[0025] In some of the accompanying drawings, corresponding components are designated by the same reference numerals. Those skilled in the art will appreciate that the drawings illustrate elements simply and clearly and are not necessarily drawn to scale. For example, to facilitate understanding of various embodiments, the dimensions of some elements depicted in the drawings may be exaggerated relative to other elements. Furthermore, elements of known technology that are useful or essential in commercially feasible embodiments may often not be depicted so as not to obscure the spirit of various embodiments of the present invention.

[0026] In this specification, when a part is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0027] In this specification, “A and / or B” means “A and B, or A or B.”

[0028] In this specification, “about,” “approximately,” and “substantially” are used to mean a range of or approximation to a numerical value or degree, taking into account inherent manufacturing and material tolerances, and are used to prevent infringers from unfairly using the disclosure, which mentions exact or absolute numbers provided to aid understanding of the present invention.

[0029] In this specification, when it is said that a component is “on”, this does not exclude other components being placed therebetween, unless otherwise specifically stated, but rather means that other components may be placed thereon.

[0030] In this specification, the characteristic of having pores means that the object includes a plurality of pores and the pores are interconnected with each other, thereby allowing gaseous and / or liquid fluids to pass from one side of the object to the other side.

[0031] In this specification, the separator has a porous characteristic including a plurality of pores, and acts as a porous ion-conducting barrier that allows ions to pass while blocking electrical contact between the cathode and the anode in an electrochemical device.

[0032] Among the components of an electrochemical device, a separator may include a polymer substrate having a porous structure located between the anode and cathode. The separator isolates the anode and cathode, preventing electrical short-circuiting between the two electrodes while simultaneously allowing electrolyte and ions to pass through. Although the separator itself does not participate in the electrochemical reaction, its physical properties, such as wettability with respect to the electrolyte, porosity, and thermal shrinkage, may affect the performance and safety of the electrochemical device.

[0033] Therefore, to enhance the physical properties of such membranes, various methods have been attempted, such as adding a coating layer to a porous polymer substrate and adding various substances to the coating layer to improve the properties of the coating layer. For example, inorganic substances may be added to the coating layer to enhance the mechanical strength of the membrane, or inorganic substances or hydrates may be added to the coating layer to enhance the flame retardancy and heat resistance of the polymer substrate.

[0034] Within the above coating layer, inorganic particles can be linked to other inorganic particles by a polymer binder to form an interstitial volume, and lithium ions can move through the interstitial volume. That is, the coating layer including the polymer binder and inorganic particles serves to prevent thermal shrinkage of the separator while also assisting the movement of lithium ions through the separator.

[0035] Meanwhile, if the porous polymer substrate used in the separator for electrochemical devices has a low porosity, the rapid charging performance and resistance performance of the electrochemical device may deteriorate. Accordingly, research is being conducted to increase the porosity of the porous polymer substrate to lower the resistance of the electrochemical device.

[0036] However, a separator for an electrochemical device including a porous polymer substrate having a high porosity has the disadvantage of a decrease in mechanical strength and an increase in thickness change of the separator, which deteriorates the performance of the electrochemical device.

[0037] Accordingly, there is a need to develop a separator that can lower the resistance of the separator by including a porous polymer substrate with high porosity, while improving the mechanical strength and minimizing changes in the thickness of the separator.

[0038] Hereinafter, an embodiment of the present invention will be described in detail with reference to the attached drawings. The drawings may be exaggerated, omitted, or schematically illustrated to explain or emphasize the contents of an embodiment of the present invention.

[0039] Hereinafter, the present invention will be described in more detail.

[0040] Figure 1 is a schematic diagram of a separator for an electrochemical device according to one embodiment of the present invention.

[0041] One embodiment of the present invention includes a separator (100) for an electrochemical device, including a porous polymer substrate (110); and a coating layer (130) provided on at least one surface of the porous polymer substrate (110) and including a polymer binder and inorganic particles; wherein the porosity of the porous polymer substrate (110) is about 50% or more and 65% or less. According to one embodiment of the present invention, the porosity refers to the ratio of the volume occupied by pores to the volume of the separator, and the porosity can be measured according to ASTM D-2873.

[0042] A separator for an electrochemical device according to one embodiment of the present invention can improve resistance by controlling the porosity of a porous polymer substrate while minimizing changes in the thickness of the separator.

[0043] The above electrochemical device separator (100) includes a porous polymer substrate (110). As described above, the electrochemical device separator (100) includes the porous polymer substrate (110), thereby allowing lithium ions to pass through while blocking electrical contact, and can implement a shutdown function at an appropriate temperature.

[0044] According to one embodiment of the present invention, the porous polymer substrate (110) may be manufactured using a polyolefin-based resin as a base resin. Examples of the polyolefin-based resin include polyethylene, polypropylene, polypentene, etc., and the porous polymer substrate may include one or more of these. A porous membrane, for example, having a large number of pores, manufactured using such a polyolefin-based resin as a base resin can provide a shutdown function at an appropriate temperature.

[0045] According to one embodiment of the present invention, the weight average molecular weight of the polyolefin resin may be about 500,000 or more and 1.5 million or less. By controlling the weight average molecular weight of the polyolefin resin within the above-described range, the compression resistance of the separator can be improved. Furthermore, when different types of polyolefin resins are mixed and used or the separator is formed with a multilayer structure made of different types of polyolefin resins, the weight average molecular weight of the polyolefin resin can be calculated by adding the weight average molecular weights according to the content ratio of each polyolefin resin.

[0046] In this specification, the weight average molecular weight (Mw) can be measured by gel permeation chromatography (GPC: gel permeation chromatography, PL GPC220, Agilent Technologies), and the measurement conditions can be set as follows.

[0047] - Column: PL Olexis (Polymer Laboratories)

[0048] - Solvent: TCB (Trichlorobenzene)

[0049] - Flow rate: 1.0 ml / min

[0050] - Sample concentration: 1.0 mg / ml

[0051] - Injection volume: 200 ㎕

[0052] - Column temperature: 160 ℃

[0053] - Detector: Agilent High Temperature RI detector

[0054] - Standard: Polystyrene (corrected with a cubic function)

[0055] According to one embodiment of the present invention, the porous polymer substrate (110) may be manufactured by a method (wet method) of mixing a polyolefin resin with a plasticizer (diluent) at a high temperature to form a single phase, separating the polymer material and the plasticizer during a cooling process, extracting the plasticizer to form pores, and then performing stretching and heat-setting.

[0056] According to one embodiment of the present invention, the average size of the pores and the maximum size of the pores of the porous polymer substrate (110) can be easily manufactured by a person skilled in the art to conform to the scope of the present invention by controlling the mixing ratio of the plasticizer, the stretching ratio, and the heat-setting treatment temperature.

[0057] According to one embodiment of the present invention, the porosity of the porous polymer substrate (110) is about 50% or more and 65% or less. Within the above-described porosity range, the thickness change of the separator according to the winding tension during charging and discharging of the electrochemical device does not increase, and the performance of the electrochemical device can be maintained. In addition, within the above-described porosity range, the ventilation time and the electrical resistance (ER) do not increase, and further, the increase in the internal resistance of the battery is suppressed, so that the rapid charging performance of the electrochemical device can be maintained. By controlling the porosity of the porous polymer substrate (110) within the above-described range, the resistance can be improved while simultaneously minimizing the compression and thickness change rate of the separator.

[0058] According to one embodiment of the present invention, the thickness of the porous polymer substrate (110) may be about 8 ㎛ to 15 ㎛. For example, the thickness of the porous polymer substrate (110) may be about 8 ㎛ to 14 ㎛, about 8 ㎛ to 13 ㎛, about 8 ㎛ to 12 ㎛, about 8 ㎛ to 11 ㎛, or about 9 ㎛ to 11 ㎛, and according to one embodiment, may be about 10 ㎛. By controlling the thickness of the porous polymer substrate within the above-described range, the energy density of the battery can be improved.

[0059] According to one embodiment of the present invention, the thickness of the porous polymer substrate can be measured by a contact measurement method using a thickness measuring device (Mitutoyo, VL-50S-B).

[0060] According to one embodiment of the present invention, the air permeability of the porous polymer substrate (110) may be about 30 s / 100cc or more and 90 s / 100cc or less. For example, the air permeability of the porous polymer substrate may be about 30 s / 100cc or more and 85 s / 100cc or less, about 30 s / 100cc or more and 80 s / 100cc or less, about 30 s / 100cc or more and 75 s / 100cc or less, about 30 s / 100cc or more and 70 s / 100cc or less, about 35 s / 100cc or more and 70 s / 100cc or less, or about 40 s / 100cc or more and 70 s / 100cc or less. Within the above-described range of permeability, the membrane thickness change rate due to membrane compression may not increase, and resistance increase may be suppressed. By controlling the permeability of the porous polymer substrate within the above-described range, resistance can be improved while simultaneously minimizing membrane compression and thickness change rate.

[0061] According to one embodiment of the present invention, the air permeability (Gurley) can be measured by the ASTM D726-94 method. The Gurley used herein is resistance to air flow, which is measured by a Gurley densometer. The air permeability value described herein is the value obtained when 100 cc of air is injected into 1 in of the sample porous support under a pressure of 12.2 in H2O. 2 The time (in seconds) it takes to pass through the cross section is expressed as the ventilation time.

[0062] According to one embodiment of the present invention, the electrical resistance (ER) of the porous polymer substrate (110) may be about 0.1 ohm or more and 0.6 ohm or less. For example, the electrical resistance (ER) of the porous polymer substrate (110) may be about 0.15 ohm or more and 0.55 ohm or less, about 0.2 ohm or more and 0.55 ohm or less, or about 0.2 ohm or more and 0.5 ohm or less. By controlling the electrical resistance (ER) of the porous polymer substrate (110) within the above-described range, the separator performance and further, the battery performance can be improved.

[0063] According to one embodiment of the present invention, the electrical resistance (ER) of the porous polymer substrate can be measured by sufficiently soaking the porous polymer substrate prepared in an electrolyte solution containing 1 M LiPF6 in a volume ratio of EC (ethylene carbonate) / EMC (ethyl methyl carbonate) = 1:2, manufacturing a coin cell using only the porous polymer substrate, and leaving it at room temperature for 1 day, using an impedance measurement method.

[0064] According to one embodiment of the present invention, the coating layer (130) is provided on at least one surface of the porous polymer substrate (110). As described above, the electrochemical device separator (100) includes the coating layer (130) provided on at least one surface of the porous polymer substrate (110), thereby improving the heat resistance of the separator, improving the mechanical properties, and preventing the separator from shrinking at high temperatures and causing an electrical short circuit in the electrode.

[0065] According to one embodiment of the present invention, the coating layer (130) includes a polymer binder and inorganic particles. As described above, since the coating layer (130) includes the polymer binder and the inorganic particles, the heat resistance of the separator is improved, the mechanical properties are improved, and the shrinkage of the separator at high temperatures and an electrical short circuit of the electrode is prevented or suppressed, and pores can be formed within the coating layer.

[0066] According to one embodiment of the present invention, the coating layer (130) may be formed by inorganic particles being bound by polymer binder particles and integrated within the layer. The pores within the coating layer may be derived from interstitial volume, which is an empty space between the inorganic particles.

[0067] According to one embodiment of the present invention, the coating layer (130) may include a plurality of pores. For example, the coating layer (130) may be a porous coating layer. According to one embodiment, the coating layer (130) may be a porous coating layer including a plurality of pores therein. As described above, since the coating layer (130) includes a plurality of pores, it can physically block the negative electrode and the positive electrode while allowing lithium ions to pass through and current to flow.

[0068] According to one embodiment of the present invention, the polymer binder in the coating layer (130) may be an acrylic binder and / or a fluorine-based binder. As described above, by selecting an acrylic binder, the polymer binder can maintain the porosity of the separator, and improve the adhesive strength between the electrode and the separator in the lamination process of the battery, thereby improving the ease of battery manufacturing, and stably implementing the stacking process. In addition, by selecting the binder particles to be a fluorine-based binder, the porosity of the separator can be maintained, and the adhesive strength can be maintained even when the coating layer is wetted by the electrolyte after battery activation. Furthermore, the stiffness of the battery can be improved, and bending of the battery can be prevented or suppressed.

[0069] According to one embodiment of the present invention, the fluorine-based binder may be a polyvinylidene-based (PVdF-based) binder. For example, the polyvinylidene-based (PVdF-based) binder may include at least one of a homopolymer of vinylidene fluoride (i.e., polyvinylidene fluoride), a copolymer of vinylidene fluoride and a monomer capable of copolymerization, and mixtures thereof.

[0070] As the above monomer, for example, a fluorinated monomer and / or a chlorinated monomer can be used. Non-limiting examples of the fluorinated monomer include vinyl fluoride; trifluoroethylene (TrFE); chlorofluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkylvinyl) ethers such as perfluoro(methylvinyl) ether (PMVE), perfluoro(ethylvinyl) ether (PEVE), and perfluoro(propylvinyl) ether (PPVE); perfluoro(1,3-dioxole); and perfluoro(2,2-dimethyl-1,3-dioxole) (PDD), and the like, and one or more of these may be included.

[0071] In addition, the polyvinylidene-based (PVdF-based) binder may be a copolymer of polyvinylidene fluoride and hexafluoropropylene. For example, it may be a polyvinylidene-based binder having a hexafluoropropylene content of about 1 wt% or more and 50 wt% or less. As described above, by selecting the polyvinylidene-based binder as a polyvinylidene-based binder having a hexafluoropropylene content of about 1 wt% or more and 50 wt% or less, the porosity of the separator can be maintained, and even if the coating layer is wetted by the electrolyte after activation of the battery, the adhesive strength can be maintained.

[0072] According to one embodiment of the present invention, the acrylic binder may be, for example, polyacrylic acid (PA), polyacrylonitrile (PAN), polyacrylamide (PAA), or a (meth)acrylic polymer, or a mixture including two or more thereof, but the present invention is not limited thereto.

[0073] At this time, the (meth)acrylic polymer means a polymer containing (meth)acrylic acid or its ester as a monomer, and may include, for example, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, ethyl (meth)acrylate, methyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, lauryl (meth)acrylate, tetradecyl (meth)acrylate, or a mixture of two or more thereof.

[0074] Additionally, the acrylic binder in this specification also includes polyacrylic acid, a polymer polymerized using acrylic acid as a monomer. This is a polymer containing carboxylic acid groups as repeating units, and can be understood as an example of the (meth)acrylic polymer of the present invention.

[0075] Therefore, the polyacrylic acid (PA, e.g., K-702, Lubrizol) used in the example corresponds to an acrylic binder according to one embodiment of the present invention, and is included in the technical scope of the present invention as an example of a polymer containing the (meth)acrylic acid or a derivative thereof.

[0076] According to one embodiment of the present invention, the average particle diameter (D50) of the polymer binder is not particularly limited, but may be about 0.1 ㎛ or more and 1 ㎛ or less in order to form a coating layer (130) with a uniform thickness and an appropriate porosity. For example, the average particle diameter (D50) of the polymer binder may be about 0.1 ㎛ or more and 0.8 ㎛ or less, about 0.1 ㎛ or more and 0.6 ㎛ or less, about 0.1 ㎛ or more and 0.4 ㎛ or less, or about 0.1 ㎛ or more and 0.2 ㎛ or less. By controlling the average particle diameter (D50) of the polymer binder within the above-described range, the dispersibility in the slurry prepared for manufacturing the coating layer can be improved, and the thickness of the formed coating layer can be reduced.

[0077] According to one embodiment of the present invention, the content of the polymer binder may be about 1 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the coating layer (130). For example, the content of the polymer binder may be about 1 part by weight or more and 9 parts by weight or less, about 1 part by weight or more and 8 parts by weight or less, about 1 part by weight or more and 7 parts by weight or less, about 1 part by weight or more and 6 parts by weight or less, about 1 part by weight or more and 5 parts by weight or less, about 1 part by weight or more and 4 parts by weight or less, or about 2 parts by weight or more and 4 parts by weight or less with respect to 100 parts by weight of the coating layer (130). By controlling the content of the polymer binder within the above-described range, the ease of assembly can be improved in the process of assembling the electrode.

[0078] According to one embodiment of the present invention, the inorganic particles have an operating voltage range (e.g., Li / Li) of the applied electrochemical device. +It may be that no oxidation and / or reduction reaction occurs at a voltage of 0 V to 5 V as a reference.

[0079] According to one embodiment of the present invention, the inorganic particles are 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), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, SiC, Al(OH)3, TiO2, zinc tin hydroxide (ZnSn(OH)6), tin-zinc oxide (Zn2SnO4, ZnSnO3), antimony trioxide (Sb2O3), antimony tetroxide (Sb2O4), antimony pentoxide (Sb2O5).

[0080] According to one embodiment of the present invention, the inorganic particles may include aluminum hydroxide (Al(OH)3). As described above, the inorganic particles include aluminum hydroxide (Al(OH)3), thereby ensuring uniformity of the coating layer, increased surface area, and thermal stability, and further minimizing the change in membrane thickness even when the membrane is pressed.

[0081] According to one embodiment of the present invention, the inorganic particles may include boehmite. For example, the boehmite may be platelet-shaped. According to one embodiment, the platelet boehmite has a two-dimensionally thin and widely spread structure and may be in the form of platelet particles. The platelet boehmite may have a relatively high specific surface area. As described above, the inorganic particles include boehmite, thereby ensuring uniformity of the coating layer, increased surface area, and thermal stability, and further minimizing membrane thickness change rate even when the membrane is pressed.

[0082] According to one embodiment of the present invention, the inorganic particles may not contain alumina (Al2O3). For example, when the inorganic particles contain alumina (Al2O3), a large number of spherical particles can be formed in a dense structure. In contrast, when boehmite is used, the plate-shaped primary particles form a porous structure in which the primary particles are aggregated, and can be flexibly deformed when pressed, and the micropores within the coating layer serve as a buffer, so that the compression resistance can be excellent.

[0083] In addition, the boehmite has a large number of hydroxyl groups (-OH) on its surface, so it can have better bonding and dispersion stability with a polymer binder.

[0084] Additionally, the boehmite can contribute to thinning by reducing the coating thickness, and its low hardness can prevent mechanical wear. In contrast, the relatively high hardness of alumina can cause mechanical wear during the coating process, limiting the ability to reduce the coating thickness.

[0085] According to one embodiment of the present invention, the average particle diameter (D50) of the inorganic particles may be about 0.1 ㎛ or more and 1 ㎛ or less. For example, the average particle diameter (D50) of the inorganic particles may be about 0.1 ㎛ or more and 1 ㎛ or less, about 0.2 ㎛ or more and 0.9 ㎛ or less, about 0.3 ㎛ or more and 0.8 ㎛ or less, about 0.4 ㎛ or more and 0.7 ㎛ or less, or about 0.4 ㎛ or more and 0.6 ㎛ or less, and according to one embodiment, may be about 0.5 ㎛. By controlling the average particle diameter (D50) of the inorganic particles within the above-described range, heat resistance of the coating layer can be secured and coating uniformity can be promoted.

[0086] In this specification, the D50 particle size refers to the particle size at the 50% point of the cumulative distribution of particle numbers according to particle size. The particle size can be measured using a laser diffraction method. Specifically, after the powder to be measured is dispersed in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500), and when the particles pass through the laser beam, the difference in the diffraction pattern according to the particle size is measured to calculate the particle size distribution. By calculating the particle diameter at the point where it becomes 50% of the cumulative distribution of particle numbers according to particle size in the measuring device, the D50 particle size can be measured.

[0087] According to one embodiment of the present invention, the content of the inorganic particles may be about 90 parts by weight or more and less than 100 parts by weight with respect to 100 parts by weight of the coating layer (130). For example, the content of the inorganic particles may be about 92 parts by weight or more and 98 parts by weight or less or about 94 parts by weight or more and 96 parts by weight or less with respect to 100 parts by weight of the coating layer (130). By controlling the content of the inorganic particles included in the coating layer (130) within the above-described range, the heat resistance of the separator can be improved, thereby ensuring the safety of the battery.

[0088] According to one embodiment of the present invention, the coating layer (130) may be provided on both sides of the porous polymer substrate (110). As described above, by including the coating layer (130) provided on both sides of the porous polymer substrate (110), the electrochemical device separator (100) can improve the heat resistance of the separator, improve the mechanical properties, and minimize the increase in the thickness change of the separator due to the winding tension during charging and discharging of the electrochemical device.

[0089] According to one embodiment of the present invention, the thickness of the coating layer (130) may be about 1 ㎛ or more and 5 ㎛ or less. For example, the thickness of the coating layer (130) may be about 1 ㎛ or more and 4 ㎛ or less, about 1 ㎛ or more and 3 ㎛ or less, or about 1.5 ㎛ or more and 2 ㎛ or less. Within the above-described range, the increase in internal resistance of the battery due to an increase in the thickness of the separator can be minimized, and coating uniformity can be secured. By controlling the thickness of the coating layer (130) within the above-described range, the coating uniformity can be secured, while at the same time, the increase in internal resistance of the battery can be minimized, and thin film can be realized.

[0090] In one embodiment of the present invention, the thickness of the coating layer (130) or the like can be measured using a contact thickness measuring device. The contact thickness measuring device can be, for example, VL-50S-B from Mitutoyo.

[0091] According to one embodiment of the present invention, the thickness change rate of the separator after compression may be about 7% or less. For example, the thickness change rate of the separator after compression may be about 1% or more and 7% or less, about 1% or more and 6.5% or less, or about 3.6% or more and 6.4% or less. If the above-described range is exceeded, the thickness change rate of the separator increases, which may cause an increase in the internal resistance of the battery.

[0092] According to one embodiment of the present invention, the thickness change rate of the separator after 100 cycles may be about 7% or less. For example, the thickness change rate of the separator after 100 cycles may be about 1% or more and 7% or less, about 1% or more and 6.7% or less, or about 4.2% or more and 6.7% or less. By keeping the thickness change rate of the separator to a minimum within the above-described range, an increase in internal resistance of the battery can be suppressed.

[0093] Referring to FIG. 2, an electrochemical device (200) according to one embodiment of the present invention includes an anode (210); a cathode (220); and a separator (100) interposed between the anode and the cathode and according to one embodiment of the present invention described above. In addition, the electrochemical device (200) according to one embodiment of the present invention may further include an electrolyte (240) and a battery case (250). In the electrochemical device (200) according to one embodiment of the present invention, any description overlapping with that of the separator (100) for the electrochemical device will be omitted.

[0094] An electrochemical device (200) according to one embodiment of the present invention can improve resistance and electrochemical device performance by controlling the porosity of the separator (100).

[0095] In one embodiment of the present invention, the electrochemical device (200) is a device that converts chemical energy into electrical energy through an electrochemical reaction, and is a concept encompassing a primary battery and a secondary battery. In the present specification, the secondary battery is capable of charging and discharging, and refers to a lithium secondary battery, a nickel-cadmium battery, a nickel-hydrogen battery, etc. The lithium secondary battery uses lithium ions as an ion conductor, and examples thereof include, but are not limited to, a non-aqueous electrolyte secondary battery including a liquid electrolyte, an all-solid-state battery including a solid electrolyte, a lithium polymer battery including a gel polymer electrolyte, and a lithium metal battery using lithium metal as an anode.

[0096] According to one embodiment of the present invention, the positive electrode (210) has a positive electrode current collector and a positive electrode active material layer including a positive electrode active material, a conductive material, and a binder resin on at least one surface of the positive electrode current collector. The positive electrode active material is a layered compound such as lithium manganese oxide (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); chemical formula LiMn1-xM xA lithium manganese composite oxide represented by O2 (wherein, M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (wherein, M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which a portion of Li in the chemical formula is replaced by an alkaline earth metal ion; a disulfide compound; or a mixture of two or more of Fe2(MoO4)3.

[0097] According to one embodiment of the present invention, the negative electrode (220) has a negative electrode current collector and a negative electrode active material layer including a negative electrode active material, a conductive material, and a binder resin on at least one surface of the current collector. The negative electrode includes carbon such as lithium metal oxide, non-graphitizable carbon, and graphite carbon as the negative electrode active material; LixFe2O3(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 of group 1, 2, and 3 of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, 및 Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료; 티타늄 산화물 중 선택된 1종 또는 2종 이상의 혼합물을 포함할 수 있다.

[0098] According to one embodiment of the present invention, the conductive material may be, for example, one selected from graphite, carbon black, carbon fibers or metal fibers, metal powders, conductive whiskers, conductive metal oxides, activated carbon, and polyphenylene derivatives, or a mixture of two or more conductive materials thereof. According to one embodiment, the conductive material may be one selected from 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, or a mixture of two or more conductive materials thereof.

[0099] According to one embodiment of the present invention, the current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, stainless steel, copper, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. can be used.

[0100] According to one embodiment of the present invention, the binder resin may be a polymer commonly used in electrodes in the art. Non-limiting examples of such binder resins include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethylmethacrylate, polyethylhexyl acrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. Examples thereof include, but are not limited to, cellulose acetatepropionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose.

[0101] According to one embodiment of the present invention, the positive electrode slurry for manufacturing the positive electrode active material layer may include a dispersant, and the dispersant may be a pyrrolidone-based compound. Specifically, it may be N-methylpyrrolidone (ADC-01, LG Chemical).

[0102] According to one embodiment of the present invention, the electrolyte (240) of the electrochemical device (200) is A + B - As a salt with the same structure, A + is Li + , Na + , K + It may include an ion composed of an alkali metal cation such as B or a combination thereof. In addition, B - is PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 - The salt containing an anion such as or a combination thereof may be dissolved or dissociated in an organic solvent consisting of 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 butyrolactone or a mixture thereof, but is not limited thereto.

[0103] According to one embodiment of the present invention, the electrochemical device (200) may be cylindrical.

[0104] For example, the separation membrane (100) according to one embodiment of the present invention can be suitable for the cylindrical electrochemical device (200) by implementing a thin film by selecting boehmite in the coating layer.

[0105] In addition, the separator (100) according to one embodiment of the present invention can minimize the change in thickness of the separator according to the winding tension during charging and discharging by selecting boehmite in the coating layer.

[0106] As described above, the electrochemical device (200) can contribute to thin film formation by selecting a cylindrical shape, while minimizing changes in the thickness of the separator due to winding tension.

[0107] According to one embodiment of the present invention, a battery module including a battery including the electrochemical device (200) as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source may be provided. Examples of the device include, but are not limited to, a power tool that is powered by an electric motor and moves; an electric vehicle 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; and a power storage system.

[0108] Hereinafter, the present invention will be described in detail using examples. However, the examples according to the present invention may be modified in various ways, and the scope of the present invention is not construed as being limited to the examples described below. The examples in this specification are provided to more fully explain the present invention to those of ordinary skill in the art.

[0109]

[0110] <Example 1>

[0111] Manufacturing of porous polymer substrates

[0112] Polyethylene resin (weight-average molecular weight: 1 million) was extruded and a porous polymer substrate was manufactured using a wet method. The total thickness of the manufactured porous polymer substrate was approximately 10 ㎛, the porosity was 55%, the air permeability was 60 s / 100 cc, and the resistance (ER) was 0.4 W.

[0113] As described above, the average size and maximum size of the pores of the porous polymer substrate can be easily manufactured by a person skilled in the art to conform to the scope of the present invention by controlling the mixing ratio of the plasticizer, the stretching ratio, and the heat-setting treatment temperature.

[0114] Coating layer formation

[0115] Boehmite with a D50 particle size of 500 nm was prepared as an inorganic particle. Polyacrylic acid (K-702, Lubrizol) with a D50 particle size of 200 nm was prepared as a polymer binder, sodium carboxymethyl cellulose (CMC-Na) (SG-L02, GL Chem) as a dispersant, and a silicone surfactant (BYK-348, BYK) were prepared.

[0116] The above-prepared inorganic particles, polymer binder, dispersant, and surfactant were added to water in a weight ratio of 95:4:0.5:0.5, and dispersed to prepare a slurry for a coating layer.

[0117] The coating layer slurry was applied to both sides of the porous polymer substrate using a doctor blade by bar coating, and dried with air at 50°C using a heat gun to form a coating layer with a thickness of 1.5 μm on each side of the porous polymer substrate.

[0118]

[0119] <Example 2>

[0120] In the above Example 1, a separator was manufactured in the same manner as in the above Example 1, except that the thickness of each coating layer was 2.0 μm.

[0121]

[0122] <Example 3>

[0123] In the above Example 1, a separation membrane was manufactured in the same manner as in the above Example 1, except that the porosity of the manufactured porous polymer substrate was 50%.

[0124]

[0125] <Example 4>

[0126] In the above Example 1, a separation membrane was manufactured in the same manner as in the above Example 1, except that the porosity of the manufactured porous polymer substrate was 60%.

[0127]

[0128] <Example 5>

[0129] In the above Example 1, a separation membrane was manufactured in the same manner as in the above Example 1, except that the porosity of the manufactured porous polymer substrate was 65%.

[0130] In the above Examples 1 to 5, boehmite having a D50 particle size of 500 nm was prepared as an inorganic particle commonly forming a coating layer, and a coating layer was formed on both sides of a porous polymer substrate. In addition, each example was manufactured by changing the porosity of the porous substrate and the thickness of the coating layer.

[0131]

[0132] <Comparative Example 1>

[0133] Manufacturing of porous polymer substrates

[0134] Polyethylene resin (weight-average molecular weight: 1 million) was extruded and a porous polymer substrate was manufactured using a wet method. The total thickness of the manufactured porous polymer substrate was approximately 10 ㎛, the porosity was 55%, the air permeability was 60 s / 100 cc, and the resistance (ER) was 0.4 W.

[0135] As described above, the average size and maximum size of the pores of the porous polymer substrate can be easily manufactured by a person skilled in the art to conform to the scope of the present invention by controlling the mixing ratio of the plasticizer, the stretching ratio, and the heat-setting treatment temperature.

[0136] Coating layer formation

[0137] Al2O3 (AES 11, Sumitomo) with a D50 particle size of 500 nm was prepared as an inorganic particle. Polyacrylic acid (K-702, Lubrizol) with a D50 particle size of 200 nm was prepared as a polymer binder, sodium carboxymethyl cellulose (CMC-Na) (SG-L02, GL Chem) was prepared as a dispersant, and a silicone surfactant (BYK-348, BYK) was prepared.

[0138] The above-prepared inorganic particles, polymer binder, dispersant, and surfactant were added to water in a weight ratio of 95:4:0.5:0.5, and dispersed to prepare a slurry for a coating layer.

[0139] The coating layer slurry was applied to one surface of the porous polymer substrate using a doctor blade by bar coating and dried with air at 50°C using a heat gun to form a coating layer with a thickness of 2.0 μm.

[0140]

[0141] <Comparative Example 2>

[0142] In the above Comparative Example 1, a separator was manufactured in the same manner as in the above Comparative Example 1, except that the thickness of the coating layer was 3.0 ㎛.

[0143]

[0144] <Comparative Example 3>

[0145] In the above Comparative Example 1, a separation membrane was manufactured in the same manner as in the above Comparative Example 1, except that boehmite having a D50 particle size of 500 nm was used as the inorganic particle.

[0146]

[0147] Comparative Example 4

[0148] In the above Comparative Example 3, a separator was manufactured in the same manner as in the above Comparative Example 3, except that the thickness of the coating layer was 3.0 μm.

[0149]

[0150] Comparative Example 5

[0151] In the above Comparative Example 1, a separator was manufactured in the same manner as in the above Comparative Example 1, except that a coating layer with a thickness of 1.0 μm was formed on each side of the porous polymer substrate.

[0152]

[0153] Comparative Example 6

[0154] In Comparative Example 5, a separator was manufactured in the same manner as in Comparative Example 5, except that the thickness of each coating layer was 1.5 μm.

[0155]

[0156] Comparative Example 7

[0157] In the above Example 1, a separator was manufactured in the same manner as in the above Example 1, except that the thickness of each coating layer was 1.0 μm.

[0158]

[0159] Comparative Example 8

[0160] In the above Example 1, a separation membrane was manufactured in the same manner as in the above Example 1, except that the porosity of the porous polymer substrate was 40%.

[0161]

[0162] Comparative Example 9

[0163] In the above Example 1, a separation membrane was manufactured in the same manner as in the above Example 1, except that the porosity of the porous polymer substrate was 45%.

[0164] In some of the comparative examples 1 to 9 above, alumina (Al2O3) having a D50 particle size of 500 nm was prepared as the inorganic particles forming the coating layer (Comparative Examples 1, 2, 5, 6), and in some comparative examples, boehmite was prepared (Comparative Examples 3, 4, 7, 8, 9). In addition, in some comparative examples, the coating layer was formed on a cross-section of the porous polymer substrate (Comparative Examples 1, 2, 3, 4), and in some comparative examples, the coating layer was formed on both sides (Comparative Examples 5, 6, 7, 8, 9).

[0165]

[0166] <Manufacturing of Cylindrical Electrochemical Devices>

[0167] Cylindrical electrochemical devices were manufactured using the electrochemical device separators of the above examples and comparative examples.

[0168] 1) Manufacturing of the anode

[0169] Cathode active material (LiNi) 0.8 Mn 0.1 Co 0.1O2), a conductive agent (carbon black), a dispersant (N-methylpyrrolidone, ADC-01, LG Chemical), and a binder resin (a mixture of PVDF-HFP and PVDF) were mixed with water in a weight ratio of 97.5:0.7:0.14:1.66 to prepare a slurry for a positive electrode active material layer with a concentration of 50 wt% of the remaining components excluding water. Next, the slurry was applied to the surface of an aluminum thin film (thickness 10 μm) and dried to manufacture a positive electrode having a positive electrode active material layer (thickness 120 μm).

[0170] 2) Manufacturing of cathode

[0171] Graphite (natural graphite and artificial graphite blend), conductive agent (carbon black), dispersant (polyvinylpyrrolidone, Junsei, Japan), and binder resin (PVDF-HFP and PVDF blend) were mixed with water in a weight ratio of 97.5:0.7:0.14:1.66 to prepare a slurry for an anode active material layer with a concentration of 50 wt% of the remaining components excluding water. Next, the slurry was applied to the surface of a copper thin film (thickness 10 μm) and dried to manufacture an anode having an anode active material layer (thickness 120 μm).

[0172] 3) Manufacturing of cylindrical electrochemical devices

[0173] The separators of the above examples and comparative examples were interposed between the above-manufactured cathodes and anodes in the order of 'separator-cathode-separator-anode' and laminated in the form of an electrode assembly.

[0174] The above laminated electrode assembly was wound into a jelly roll shape to manufacture a cylindrical electrochemical device.

[0175]

[0176] <Experimental Example>

[0177] Membrane permeability measurement

[0178] The membrane permeability (permeability, Gurley) of the above examples and comparative examples was measured by the ASTM D726-94 method. The permeability used here is the resistance to air flow, which is measured by a Gurley densometer. The permeability value described here is the value obtained when 100 cc of air flows through 1 in of the membrane under a pressure of 12.2 in H2O. 2 The time (in seconds) it takes to pass through the cross section of the tube is expressed as the ventilation time.

[0179]

[0180] Measuring the resistance of the separator

[0181] The resistance of the separator of the above examples and comparative examples was measured by sandwiching each separator substrate between SUS plates and injecting electrolyte to manufacture coin cells and measuring the resistance (ER) using the EIS method. At this time, the frequency was in the range of 100,000 to 10,000 Hz. The electrolyte was a non-aqueous solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a ratio of 3:7 and LiPF6 mixed at a concentration of 1 M.

[0182]

[0183] Measurement of thickness change rate after compression

[0184] The rate of change in thickness after compression of the membranes of the above examples and comparative examples was measured by the following method.

[0185] First, prepare a membrane specimen (2 cm wide x 2 cm long), and then measure the initial thickness (T) using a micrometer at room temperature. o ) was measured. Afterwards, compression was performed by applying a pressure of approximately 3 MPa to the membrane specimen for 5 minutes. Immediately after the pressure was removed after compression, the thickness (T1) of the membrane was measured again.

[0186] At this time, the rate of change in the thickness of the membrane after compression was calculated according to Equation 1 below:

[0187]

[0188] [Formula 1]

[0189]

[0190]

[0191]

[0192] Through this, the degree of thickness change due to mechanical compression of the membrane was measured and shown in Tables 1 and 2 below.

[0193]

[0194] Measurement of thickness change rate after 100 cycles

[0195] The change rate (%) in the thickness of the separator after the charge / discharge cycle of the separator of the above examples and comparative examples was measured by the following method.

[0196] Coin cells are assembled using the separator of the present invention, and the thickness of the separator immediately after cell assembly (T o ) was measured. Afterwards, the battery was subjected to 100 charge-discharge cycles within a voltage range of 2.5 to 4.2 V at a current density of 0.5 C in an environment of 25°C. After completion of the cycle, the separator thickness (T1) was measured.

[0197] At this time, the membrane thickness change rate (%) after 100 cycles was calculated according to the following equation 1:

[0198]

[0199] [Formula 1]

[0200]

[0201]

[0202] Through this, the thickness of the membrane measured before and after 100 cycles was compared to measure the membrane thickness change rate (%), which is shown in Tables 1 and 2 below.

[0203]

[0204] Evaluation of direct current internal resistance (DCIR) of electrochemical devices

[0205] The electrochemical devices of the above examples and comparative examples were charged at a current of 2.5 C until the SOC reached 50%. When each electrochemical device reached 50% SOC, the DCIR resistance value was calculated according to Equation 1 below and is shown in Tables 1 and 2 below.

[0206] [Formula 1]

[0207] DCIR=(V0-V1) / I (V0 = voltage before pulse, V1 = voltage 10 seconds after pulse, I = applied current)

[0208]

[0209] Example 1 Example 2 Example 3 Example 4 Example 5 Type of inorganic material Boehmite Boehmite Boehmite Boehmite Coating layer thickness (㎛) 1.5 2 1.5 1.5 1.5 Coating layer single / double-sided double-sided double-sided double-sided double-sided membrane thickness (㎛) 13 14 13 13 13 Porosity (%) 5 5 5 5 5 0 6 0 6 5 Air permeability (s / 100 cc) 6 0 6 0 6 6 4 9 4 3 ER (W) 0.4 0 4 0 5 0 3 0 2 Thickness change after compression (%) 4.2 3 6 3 7 5 4 6 4 1 00 Thickness change after cycles (%) 4.5 4 2 4 2 5 9 6 7 DCIR (W) 1.2 0 5 1 2 4 9 1 2 6 5 1 1 4 4 1 1 1 6

[0210]

[0211] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Inorganic material type Alumina Alumina Boehmite Boehmite Alumina Alumina Boehmite Boehmite Boehmite Coating layer thickness (㎛) 23 23 11.5 11.5 1.5 Coating layer single / double-sided cross-section cross-section cross-section double-sided double-sided double-sided double-sided double-sided membrane thickness (㎛) 12 13 12 13 12 13 12 13 12 13 13 Porosity (%) 5 5 5 5 5 5 5 5 5 5 5 5 4 0 4 5 Air permeability (s / 100cc) 6 0 6 0 6 0 6 0 6 0 6 0 6 0 1 1 5 10 ER (W) 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.6 8 0.6 2 Thickness after compression Change rate (%) 8.6 7.9 7.16.8 Coating uniformity not secured 6.5 Coating uniformity not secured 3.2 3.5 Thickness change rate after 100 cycles (%) 9.4 9.18.4 7.7 7.4 3.7 4.1 DCIR (W) 1.29 5 1.31 31.24 6 1.26 5 1.30 31.37 2 1.344

[0212]

[0213] According to Table 1 above, Examples 1 to 5 improved the resistance of the separator by increasing the porosity of the porous polymer substrate from the existing 30%-40% to 50%-65%, while minimizing the compression and thickness change rate of the separator. For example, the resistance (ER) of the separator in Examples 1 to 5 was at the level of 0.2W-0.5W, the thickness change rate of the separator after compression was at the level of 3.6%-6.4%, and the thickness change rate of the separator after 100 cycles was at the level of 4.2%-6.7%.

[0214] In contrast, according to Table 2, Comparative Examples 1 to 4 showed that the thickness change rate after compression and the thickness change rate after 100 cycles increased by cross-section coating the coating layer. For example, the thickness change rate of the separator after compression of Comparative Examples 1 to 4 was at the level of 6.8% to 8.6%, and the thickness change rate of the separator after 100 cycles was at the level of 7.7% to 9.4%.

[0215] According to Comparative Examples 1 and 2 and Comparative Examples 3 and 4, it can be seen that as the coating layer thickness increases among cross-sectional coatings, the battery internal resistance (DCIR) increases. For example, in Comparative Examples 1 and 2, the coating layer thicknesses were 2 mm and 3 mm, respectively, and the battery internal resistance (DCIR) was 1.295 W and 1,313 W, respectively.

[0216] According to Comparative Examples 5 and 7, even if the coating layer was formed on both sides of the porous polymer substrate, there was a problem in that it was difficult to secure coating uniformity when the coating layer thickness on each side was relatively thin at 1 ㎛.

[0217] According to Comparative Example 6, when alumina was used instead of boehmite as the inorganic material in the coating layer, the thickness change rate of the separator after compression was 6.5% compared to the example, and the thickness change rate of the separator after 100 cycles was 7.4%, indicating that the thickness change rate of the separator after 100 cycles increased. Accordingly, it can be seen that the use of boehmite is more advantageous in terms of compression resistance of the separator.

[0218] According to Comparative Examples 8 and 9, the porosity of the porous polymer substrate is relatively low at 40% and 45%, respectively, so that the ventilation time increases, the electrical resistance (ER) increases at 0.68 W and 0.62 W, ​​respectively, and further, the internal resistance of the battery increases at 1.372 W and 1.344 W, respectively, compared to other examples and comparative examples.

[0219] Therefore, the electrochemical device separator according to one embodiment of the present invention and the electrochemical device including the same can improve resistance by controlling the porosity of the porous polymer substrate and appropriately selecting the material of the coating layer, while minimizing compression and thickness change rate of the separator.

[0220] Although the present disclosure has been described above with reference to embodiments thereof, it will be understood by those skilled in the art or having ordinary knowledge in the art that various modifications and changes to the various embodiments of the present disclosure may be made without departing from the technical scope of the various embodiments of the present disclosure as set forth in the claims below. Accordingly, the technical scope of the various embodiments of the present disclosure should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

[0221] [Explanation of symbols]

[0222] 100: Separator for electrochemical devices

[0223] 110: Porous polymer substrate

[0224] 130: Coating layer

[0225] 200: Electrochemical devices

[0226] 210: Bipolar

[0227] 220: Cathode

[0228] 240: Electrolyte

[0229] 250: Battery case

Claims

1. Porous polymer substrate; and A coating layer provided on at least one surface of the porous polymer substrate and including a polymer binder and inorganic particles; A separator for an electrochemical device, wherein the porosity of the porous polymer substrate is 50% or more and 65% or less.

2. In claim 1, A separator for an electrochemical device, wherein the thickness of the porous polymer substrate is 8 ㎛ or more and 15 ㎛ or less.

3. In claim 1, A separator for an electrochemical device, wherein the porous polymer substrate has an air permeability of 30 s / 100cc or more and 90 s / 100cc or less.

4. In Claim 1, A separator for an electrochemical device, wherein the electrical resistance (ER) of the porous polymer substrate is 0.1 W or more and 0.6 W or less.

5. In claim 1, A separator for an electrochemical device, wherein the coating layer is provided on both sides of the porous polymer substrate.

6. In claim 1, A separator for an electrochemical device, wherein the thickness of the coating layer is 1 ㎛ or more and 5 ㎛ or less.

7. In Claim 1, A separator for an electrochemical device, wherein the inorganic particles used in the above coating layer include aluminum hydroxide (Al(OH)3).

8. In claim 1, A separator for an electrochemical device, wherein the inorganic particles used in the above coating layer include boehmite.

9. In Claim 7, A separator for an electrochemical device, wherein the above inorganic particles do not contain alumina.

10. In Claim 1, A separator for an electrochemical device, wherein the thickness change rate after compression of the separator is 7% or less.

11. In Claim 1, A separator for an electrochemical device, wherein the thickness change rate of the separator after 100 cycles is 7% or less.

12. An electrochemical device comprising: a positive electrode; a negative electrode; and a separator interposed between the positive electrode and the negative electrode, the separator of claim 1.

13. In claim 12, The electrochemical device is an electrochemical device having a cylindrical shape.

Images