Separator for cylindrical electrochemical device and cylindrical electrochemical device comprising same

Abstract

The separator for a cylindrical electrochemical device of the present invention comprises: 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 polymer binder included in the coating layer includes an electrolyte-resistant polymer binder and an adhesive polymer binder, and the peel strength of the separator is about 150 gf / cm or more.

Description

Separator for a cylindrical electrochemical device and a cylindrical electrochemical device including the same

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0142798 filed October 18, 2024 and Korean Patent Application No. 10-2025-0149382 filed October 16, 2025, and all contents disclosed in the documents of said Korean patent applications are incorporated herein as part of this specification.

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

[0003] Electrochemical devices convert chemical energy into electrical energy using electrochemical reactions; recently, lithium-ion batteries, which offer high energy density and voltage, long cycle life, and applicability to various fields, are widely used.

[0004] A lithium secondary battery may include an electrode assembly manufactured with a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes, and the electrode assembly may be manufactured by housing it in a case together with an electrolyte.

[0005] The present invention provides a separator for a cylindrical electrochemical device that includes an electrolyte-resistant polymer binder in the coating layer of the separator, thereby having high peel strength and minimizing damage to the separator, and a cylindrical electrochemical device including the same.

[0006] However, the present invention is not limited to the characteristics mentioned above, and other unmentioned characteristics 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 a cylindrical electrochemical device comprising: a porous polymer substrate; and a coating layer provided on at least one surface of the porous polymer substrate and comprising a polymer binder and inorganic particles, wherein the polymer binder included in the coating layer comprises an electrolyte-resistant polymer binder and a binding polymer binder, and has a peel strength of about 150 gf / cm or more.

[0008] The content of the inorganic particles included in the coating layer may be about 90 parts by weight or more and 99 parts by weight or less per 100 parts by weight of the coating layer.

[0009] The content of the polymer binder included in the coating layer may be about 1 part by weight or more and 10 parts by weight or less per 100 parts by weight of the coating layer.

[0010] The content of the electrolyte-resistant polymer binder included in the coating layer may be about 0.5 parts by weight or more and 5 parts by weight or less per 100 parts by weight of the coating layer.

[0011] The electrolyte-resistant polymer binder included in the coating layer may comprise polyacrylamide (PAM), styrene-co-acrylonitrile copolymer (SAN), polyether ether ketone (PEEK), polyether sulfone (PES), and one or more selected from these.

[0012] The content of the binding polymer binder included in the coating layer may be about 1 part by weight or more and 8 parts by weight or less per 100 parts by weight of the coating layer.

[0013] The content ratio of the electrolyte-resistant polymer binder and the binding polymer binder included in the coating layer may be about 1:2 to 2:1.

[0014] The electrolyte solubility of the electrolyte-resistant polymer binder included in the coating layer may be about 0% or more and 10% or less.

[0015] The degree of electrolyte swelling of the electrolyte-resistant polymer binder included in the coating layer may be about 0% or more and 20% or less.

[0016] The thickness of the coating layer may be about 1 μm or more and 3 μm or less.

[0017] According to one embodiment of the present invention, a cylindrical electrochemical element is provided, comprising: an anode; a cathode; and a separator interposed between the anode and the cathode and any one of the aforementioned separators.

[0018] A separator for a cylindrical electrochemical device according to one embodiment of the present invention can increase peel strength and secure electrolyte resistance by including an electrolyte-resistant polymer binder in the coating layer.

[0019] A cylindrical electrochemical device according to one embodiment of the present invention includes an electrolyte-resistant polymer binder in the coating layer to prevent damage to the separator and thereby improve battery life characteristics.

[0020] The following drawings attached to this specification illustrate embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0021] FIG. 1 is a schematic diagram showing separator damage occurring during the winding process of a cylindrical electrochemical element of a comparative example according to one embodiment of the present invention.

[0022] FIG. 2 is a schematic diagram showing membrane damage and byproduct growth after electrolyte injection into a membrane of a comparative example according to one embodiment of the present invention.

[0023] FIG. 3 is a schematic diagram of a separator for a cylindrical electrochemical device according to one embodiment of the present invention.

[0024] FIG. 4 is a schematic diagram showing the process after the electrolyte is injected into the separator according to one embodiment of the present invention.

[0025] FIG. 5 is a schematic diagram showing a winding process of a cylindrical electrochemical element according to one embodiment of the present invention.

[0026] FIG. 6 is an SEM image showing the surface of the separator membrane of Example 1 according to one embodiment of the present invention.

[0027] FIG. 7 is an SEM image showing the surface of the separator membrane of Example 2 according to one embodiment of the present invention.

[0028] FIG. 8 is an SEM image showing the surface of the separator membrane of Comparative Example 1 according to one embodiment of the present invention.

[0029] FIG. 9 is an SEM image showing the surface of the separator membrane of Comparative Example 2 according to one embodiment of the present invention.

[0030] In parts of the attached drawings, corresponding components are given the same reference numerals. Those skilled in the art understand that the drawings are intended to illustrate elements simply and clearly and are not necessarily drawn to scale. For example, to aid in understanding various embodiments, the dimensions of some elements depicted in the drawings may be exaggerated compared to others. Additionally, elements of known technology that are useful or essential in commercially viable embodiments may often be omitted so as not to hinder the spirit of the various embodiments of the present invention.

[0031] In this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0032] In this specification, "A and / or B" means "A and B, or A or B".

[0033] In this specification, "about," "approximately," and "substantially" are used to mean a range of numerical or degree (e.g., ±5%) or an approximation thereof, taking into account inherent manufacturing and material tolerances, and are used to prevent an infringer from unfairly exploiting the disclosure in which precise or absolute figures provided to aid in understanding the invention are mentioned.

[0034] In this specification, when a component is described as being "on" one component, this means that, unless specifically stated otherwise, other components may be placed in between, without excluding the placement of other components.

[0035] In this specification, the characteristic of having pores means that a gaseous and / or liquid fluid can pass from one side to the other side of the object through a structure in which the object includes a plurality of pores and said pores are interconnected.

[0036] In this specification, the separator has porous characteristics including a plurality of pores and acts as a porous ion-conducting barrier that blocks electrical contact between the cathode and the anode in an electrochemical device while allowing ions to pass through.

[0037] In this specification, "Wet state" may mean a state in which the separator is impregnated with at least a portion of the electrolyte, and "Dry state" may mean a dry state in which the separator is not impregnated by the electrolyte.

[0038] In this specification, "electrolyte resistance" may mean a property in which the binder does not swell or dissolution when in contact with an electrolyte, and exhibits adhesive strength or mechanical strength as its original physical properties.

[0039] Among the components of an electrochemical device, the separator may comprise a polymer substrate having a porous structure located between the anode and the cathode. The separator isolates the anode and the cathode to prevent an electrical short circuit between the two electrodes, while simultaneously allowing the electrolyte and ions to pass through. Although the separator itself does not participate in electrochemical reactions, its physical properties, such as wettability to the electrolyte, porosity, and thermal shrinkage rate, can affect the performance and safety of the electrochemical device.

[0040] Therefore, to enhance the physical properties of such separation membranes, various methods are being attempted to improve the properties of the coating layer by adding a coating layer to a porous polymer substrate and adding various materials to the coating layer. For example, inorganic materials may be added to the coating layer to improve the mechanical strength of the separation membrane, or inorganic materials or hydrates may be added to the coating layer to improve the flame retardancy and heat resistance of the polymer substrate.

[0041] Within the coating layer, inorganic particles can be connected to other inorganic particles by a polymer binder to form an interstitial volume, and lithium ions can move through the interstitial volume. For example, a coating layer containing a polymer binder and inorganic particles serves to prevent thermal shrinkage of the separator while simultaneously facilitating the movement of lithium ions through the separator.

[0042] Meanwhile, cylindrical, prismatic, and pouch-type battery cells are known as types of secondary battery cells. In the case of a cylindrical battery cell, an insulating separator is interposed between the positive and negative electrodes, and this is wound to form a jellyroll-shaped electrode assembly, which is then inserted into a battery can and an electrolyte is injected to constitute a battery.

[0043] FIG. 1 is a schematic diagram showing damage to the separator occurring during the winding process of a cylindrical electrochemical element according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing damage to the coating layer (130) of the separator (100) and growth of by-products after the injection of the electrolyte (E) into the separator of a comparative example according to one embodiment of the present invention.

[0044] Referring to FIGS. 1 and 2, a cylindrical electrochemical element of a comparative example according to one embodiment of the present invention comprises a separator (100), a positive electrode (200), and a negative electrode (300). The separator (100) comprises a porous polymer substrate (110) and a coating layer (130) provided on both sides of the porous polymer substrate (100). When assembling such a cylindrical battery cell, the separator coating layer (130) at the step difference portion may be damaged due to the tension applied to the separator (100) by the winding process and the step difference at the ends of the positive electrode (200) and the negative electrode (300). Due to such damage to the coating layer (130), by-products generated during cell operation after the injection of the electrolyte may grow between the coating layer (130) of the damaged separator (100), or lithium plating may occur, causing a decrease in the lifespan of the battery. In addition, the coating layer (130) of the step portion may swell or dissolve not only during cell assembly but also during cell operation after the electrolyte injection, which may cause damage to the separator (100) due to physical impact. For this reason, if the coating layer (130) of the separator (100) is damaged and by-products grow after the electrolyte (E) injection, it may cause a decrease in the battery's lifespan.

[0045] The present invention provides a technology for preventing damage to the coating layer (130) of the separator (100) due to a step difference between the positive electrode (200) and the negative electrode (300) ends during cylindrical battery cell assembly and cell operation.

[0046] FIG. 3 is a schematic diagram of a separator (100) for a cylindrical electrochemical device according to one embodiment of the present invention.

[0047] One embodiment of the present invention comprises a cylindrical electrochemical device separator (100) comprising: a porous polymer substrate (110); and a coating layer (130) provided on at least one surface of the porous polymer substrate (110) and comprising a polymer binder and inorganic particles, wherein the polymer binder included in the coating layer (130) comprises an electrolyte-resistant polymer binder and a binding polymer binder, and the peel strength of the separator (100) is about 150 gf / cm or more.

[0048] A separator (100) for a cylindrical electrochemical device according to one embodiment of the present invention can increase peel strength and secure electrolyte resistance by including an electrolyte-resistant polymer binder in the coating layer (130).

[0049] The above-described separator (100) for an electrochemical device includes a porous polymer substrate (110). As described above, by including the porous polymer substrate (110) in the separator (100) for an electrochemical device, it is possible to block electrical contact while allowing lithium ions to pass through, and at the same time, implement a shutdown function at an appropriate temperature. The shutdown function is a function that prevents thermal runaway by blocking the current flow through the separator blocking the pores when the battery overheats. When the internal temperature of the battery rises above a certain temperature, the separator melts and blocks the pores, thereby blocking contact between the positive and negative electrodes and stopping the current flow.

[0050] 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 polyolefin-based resins include polyethylene, polypropylene, polypentene, etc., and may include one or more of these. A porous separator having a plurality of pores manufactured using such a polyolefin-based resin as a base resin can provide a shutdown function at an appropriate temperature.

[0051] According to one embodiment of the present invention, the weight-average molecular weight of the polyolefin resin may be about 500,000 to 1,500,000. 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 using a mixture of different types of polyolefin resins or forming a separator 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.

[0052] In the present specification, the weight-average molecular weight (Mw) may be measured by gel permeation chromatography (GPC: gel permeation chromatography, PL GPC220, Agilent Technologies), and according to one embodiment, the measurement conditions may be set as follows.

[0053] - Column: PL Olexis (Polymer Laboratories)

[0054] - Solvent: TCB (Trichlorobenzene)

[0055] - Flow rate: 1.0 ml / min

[0056] - Sample concentration: 1.0 mg / ml

[0057] - Injection volume: 200 µl

[0058] - Column temperature: 160 ℃

[0059] - Detector: Agilent High Temperature RI detector

[0060] - Standard: Polystyrene (corrected by a cubic function)

[0061] According to one embodiment of the present invention, the porous polymer substrate (110) may be manufactured by a method (wet method) in which a polyolefin-based resin is mixed with a plasticizer (diluent) at a high temperature to form a single phase, the polymer material and the plasticizer are separated during the cooling process, the plasticizer is extracted to form pores, and then stretched and heat-set.

[0062] 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 adjusting the mixing ratio of the plasticizer, the stretching ratio, and the heat-setting treatment temperature.

[0063] According to one embodiment of the present invention, the thickness of the porous polymer substrate (110) may be about 8 μm or more and 15 μm or less. For example, the thickness of the porous polymer substrate (110) may be about 8 μm or more and 14 μm or less, 8 μm or more and 13 μm or less, 8 μm or more and 12 μm or less, 8 μm or more and 11 μm or less, or 9 μm or more and 11 μm or less, and according to one embodiment, it may be 10 μm. By controlling the thickness of the porous polymer substrate (110) within the above-described range, the energy density of the battery can be improved.

[0064] According to one embodiment of the present invention, the thickness of the porous polymer substrate (110) can be measured by a contact measurement method using, for example, a thickness gauge (Mitutoyo, VL-50S-B).

[0065] According to one embodiment of the present invention, the porosity of the porous polymer substrate (110) may be about 10 volume% or more and 90 volume% or less. For example, the porosity of the porous polymer substrate (110) may be about 10 volume% or more and 90 volume% or less, 20 volume% or more and 80 volume% or less, 30 volume% or more and 70 volume% or less, or 40 volume% or more and 60 volume% or less. By controlling the porosity of the porous polymer substrate within the above-described range, the lithium ion separator permeability can be controlled.

[0066] 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, by including the coating layer (130) provided on at least one surface of the porous polymer substrate (110) in the separator (100) for the electrochemical device, the heat resistance of the separator is improved, mechanical properties are improved, and electrical short circuits at the electrodes can be prevented as the separator (100) shrinks at high temperatures.

[0067] According to one embodiment of the present invention, the coating layer (130) comprises a polymer binder and inorganic particles. As described above, by the coating layer (130) comprising the polymer binder and the inorganic particles, the heat resistance of the separator is improved, mechanical properties are improved, the separator shrinks at high temperatures to prevent electrical short circuits from occurring at the electrodes, and pores can be formed within the coating layer (130).

[0068] 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 accumulated within the layer. Pores within the coating layer (130) may originate from interstitial volumes, which are empty spaces between the inorganic particles.

[0069] 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 that includes a plurality of pores inside. As described above, by the coating layer (130) including a plurality of pores, it is possible to physically block the negative electrode and the positive electrode while allowing lithium ions to pass through and current to flow.

[0070] According to one embodiment of the present invention, the thickness of the coating layer (130) formed on one side of the porous polymer substrate (110) may be about 1 μm or more and 3 μm or less. At the thickness within the above-described range, the heat resistance and adhesion of the coating layer (130) may be improved, the increase in resistance may be suppressed, and the overall thickness of the separator (100) may be reduced, which may have a positive effect on battery assembly.

[0071] In one embodiment of the present invention, the thickness of the coating layer (130), etc., can be measured by applying a contact-type thickness gauge. For example, the contact-type thickness gauge may use the VL-50S-B from Mitutoyo.

[0072] According to one embodiment of the present invention, the inorganic particles usable in the coating layer (130) are not particularly limited as long as they are electrochemically stable. For example, the inorganic particles usable in one embodiment of the present invention are within the operating voltage range of the electrochemical element to which they are applied (e.g., Li / Li + It is not particularly limited as long as oxidation and / or reduction reactions do not occur at a standard of 0 V to 5 V.

[0073] According to one embodiment of the present invention, non-limiting examples of the inorganic particles include BaTiO3, Pb(Zr,Ti)O3(PZT), and Pb 1-x La x Zr 1-y Ti y O3(PLZT, 0 <x<1, 0<y<1), Pb(Mg1 / 3 Nb 2 / 3 Examples include O3-PbTiO3(PMN-PT), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, SiC, boehmite (AlO(OH)), 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.

[0074] According to one embodiment of the present invention, the average particle size (D50) of the inorganic particles is not subject to any particular limitation, but may be approximately 0.1 μm or more and 1 μm or less for the formation of a coating layer (130) of uniform thickness and appropriate porosity. For example, the average particle size (D50) of the inorganic particles may be approximately 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. At the average particle size (D50) of the above range, the dispersibility of the inorganic particles in the slurry prepared for manufacturing the coating layer (130) may be improved, and the thickness of the coating layer formed may be reduced.

[0075] In this specification, "D50 particle size" refers to the particle size at the 50% point of the cumulative distribution of the number of particles according to particle size. The particle size can be measured using a laser diffraction method. For example, after dispersing the powder to be measured in a dispersion medium, it 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 particle size as the particles pass through a laser beam, thereby calculating the particle size distribution. The D50 particle size can be measured by calculating the particle diameter at the point that is 50% of the cumulative distribution of the number of particles according to particle size in the measuring device.

[0076] According to one embodiment of the present invention, the content of the inorganic particles may be about 90 parts by weight or more and 99 parts by weight or less with respect to 100 parts by weight of the coating layer (130). For example, the content of the inorganic particles with respect to 100 parts by weight of the coating layer (130) may be about 90 parts by weight or more and 98 parts by weight or less, 90 parts by weight or more and 97 parts by weight or less, 90 parts by weight or more and 96 parts by weight or less, 90 parts by weight or more and 95 parts by weight or less, 90 parts by weight or more and 94 parts by weight or less, or 90 parts by weight or more and 93 parts by weight or less. With the inorganic particle content within the above-described range, heat resistance can be improved, and the binder content can be maintained at an appropriate level, so peel strength and electrolyte resistance are excellent, and the detachment of the coating layer during assembly and damage to the coating layer (130) during cycling can be reduced, thereby improving the capacity retention rate. In this way, by controlling the content of the inorganic particles included in the coating layer (130) within the above-described range, the safety of the battery can be ensured by improving the heat resistance of the separator (100), and at the same time, the binder content can be controlled so that, for example, damage to the coating layer (130) can be prevented during the winding process.

[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 per 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, 1 part by weight or more and 8 parts by weight or less, 1 part by weight or more and 7 parts by weight or less, 2 parts by weight or more and 7 parts by weight or less, or 2 parts by weight or more and 6 parts by weight or less per 100 parts by weight of the coating layer (130). In the above-described range of content, the binding strength and electrolyte resistance of the coating layer (130) can be improved, and the increase in resistance of the separator (100) can be suppressed or the capacity retention rate of the battery can be improved.

[0078] According to one embodiment of the present invention, the polymer binder included in the coating layer (130) of the separator (100) includes an electrolyte-resistant polymer binder. As described above, the electrolyte resistance of the battery can be improved by including an electrolyte-resistant polymer binder in the coating layer (130) of the separator (100).

[0079] According to one embodiment of the present invention, the content of the electrolyte-resistant polymer binder may be about 0.5 parts by weight or more and 5 parts by weight or less per 100 parts by weight of the coating layer. For example, the content of the electrolyte-resistant polymer binder may be about 1 part by weight or more and 5 parts by weight or less, 1 part by weight or more and 4.5 parts by weight or less, 1 part by weight or more and 4 parts by weight or less, 1.5 parts by weight or more and 4 parts by weight or less, or 2 parts by weight or more and 4 parts by weight or less per 100 parts by weight of the coating layer. In the above-described range of content, the resistance of the separator is reduced and the binder is sufficient to hold the coating layer (130), so the binding strength of the coating layer (130) is improved or the electrolyte resistance of the separator (100) is improved.

[0080] According to one embodiment of the present invention, the electrolyte-resistant polymer binder may comprise polyacrylamide (PAM), styrene-co-acrylonitrile copolymer (SAN), polyether ether ketone (PEEK), polyether sulfone (PES), and one or more selected from these. By selecting the electrolyte-resistant polymer binder within the above-described range, the electrolyte resistance of the separator (100) can be increased, and damage to the coating layer (130) can be prevented or suppressed, thereby increasing the capacity retention rate of the battery.

[0081] Poly(acrylic acid)-based binders used in the coating layer of conventional separators can swell and dissolve in the electrolyte, and the separator can be damaged by physical impact after the electrolyte is injected. By selecting the electrolyte-resistant polymer binder within the range described above, it does not swell significantly even after the electrolyte is injected, thereby minimizing damage to the separator (100).

[0082] According to one embodiment of the present invention, the polymer binder comprises a binding polymer binder. As described above, by including the binding polymer binder, the polymer binder can improve the binding force between inorganic particles within the coating layer (130) and the binding force between the porous polymer substrate (110) and the coating layer (130).

[0083] According to one embodiment of the present invention, the binding polymer binder may be an acrylic binder, a polyvinylidene binder, or a combination thereof. The combination of the acrylic binder and the polyvinylidene binder may be a mixture of the acrylic binder and the polyvinylidene binder, a copolymer containing the acrylic repeating unit and the polyvinylidene repeating unit, or a copolymer of the acrylic binder and the polyvinylidene binder. Additionally, the polyvinylidene binder may be a copolymer of polyvinylidene fluoride (PVdF) and hexafluoropropylene (HFP). By selecting the above-described binding polymer binder, the porosity of the separator can be maintained, and the binding force between the porous polymer substrate (110), the coating layer (130), and the inorganic particles within the coating layer (130) can be improved during the winding process of the battery, thereby making it easier to manufacture the battery and improving the detachment of the coating layer (130) during the manufacturing process. Furthermore, the porosity of the separator (100) can be maintained, and the adhesive force can be maintained even if the coating layer (130) is wetted by the electrolyte after the activation of the battery.

[0084] According to one embodiment of the present invention, the acrylic binder may be a polymer comprising a carboxylic acid ester as a repeating unit, for example, a (meth)acrylic acid ester or an acrylic-styrene copolymer.

[0085] According to one embodiment of the present invention, the (meth)acrylic acid ester is (meth)acrylate methyl, (meth)acrylate ethyl, (meth)acrylate n-propyl, (meth)acrylate i-propyl, (meth)acrylate n-butyl, (meth)acrylate i-butyl, (meth)acrylate n-amyl, (meth)acrylate i-amyl, (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, di(meth)acrylate ethylene glycol, di(meth)acrylate propylene glycol. Examples include tri(meth)acrylate trimethylolpropane, tetra(meth)acrylate pentaerythritol, hexa(meth)acrylate dipentaerythritol, (meth)acrylate allyl, di(meth)acrylate ethylene, etc., and one or more selected from these may be used. Among these, one or more selected from (meth)acrylate methyl, (meth)acrylate ethyl, and (meth)acrylate 2-ethylhexyl may be used, or (meth)acrylate methyl.

[0086] According to one embodiment of the present invention, the acrylic-styrene copolymer may include an acrylic binder, and the acrylic binder may be of the polyacrylate type. For example, the binder may be one or more selected from styrene-butyl acrylate, styrene-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, and acrylate-based polymers, and may be, for example, a copolymer containing acrylate.

[0087] According to one embodiment of the present invention, the polyvinylidene-based binder may be a polyvinylidene-based binder having a hexafluoropropylene (HFP) content of about 1 wt% or more and 50 wt% or less. For example, the hexafluoropropylene (HFP) content in the polyvinylidene-based binder may be about 1 wt% or more and 50 wt% or less, 2 wt% or more and 45 wt% or less, 3 wt% or more and 40 wt% or less, 4 wt% or more and 35 wt% or less, 5 wt% or more and 30 wt% or less, 7 wt% or more and 25 wt% or less, and 10 wt% or more and 20 wt% or less. As described above, by selecting the polyvinylidene-based binder as a polyvinylidene-based binder having a hexafluoropropylene content of about 1% by weight or more and 50% by weight or less, the porosity of the separator (100) can be maintained, and the adhesive strength can be maintained even if the coating layer (130) is wetted by the electrolyte after activation of the battery. In this specification, the degree of substitution of the polyvinylidene-based binder may refer to the weight ratio containing hexafluoropropylene.

[0088] According to one embodiment of the present invention, the average particle size (D50) of the binding polymer binder is not subject to any particular limitation, but may be in the range of about 0.1 μm or more and 1 μm or less for the formation of a coating layer (130) of uniform thickness and appropriate porosity. For example, the average particle size (D50) of the polymer binder may be about 0.1 μm or more and 0.8 μm or less, 0.1 μm or more and 0.6 μm or less, 0.1 μm or more and 0.4 μm or less, or 0.1 μm or more and 0.2 μm or less. By controlling the average particle size (D50) of the binding polymer binder within the above-described range, dispersibility in the slurry prepared for manufacturing the coating layer (130) can be improved, and the thickness of the coating layer (130) formed can be reduced.

[0089] According to one embodiment of the present invention, the content of the binding polymer binder may be about 1 part by weight or more and 8 parts by weight or less per 100 parts by weight of the coating layer (130). For example, the content of the binding polymer binder may be about 1 part by weight or more and 7 parts by weight or less, 1 part by weight or more and 6 parts by weight or less, 1 part by weight or more and 5 parts by weight or less, 1 part by weight or more and 4 parts by weight or less, or 2 parts by weight or more and 4 parts by weight or less per 100 parts by weight of the coating layer (130). In the above-described range of content, the binding force between the porous polymer substrate (110), the coating layer (130), and the inorganic particles within the coating layer (130) can be improved during the winding process of the battery, and the resistance of the separator (100) can be reduced.

[0090] According to one embodiment of the present invention, the content ratio of the electrolyte-resistant polymer binder and the binding polymer binder may be about 1:2 to 2:1. For example, the content ratio of the electrolyte-resistant polymer binder and the binding polymer binder may be about 1:2 to 1:5 or 2:1 to 5:1. In the above-described range of content ratios, the increase in resistance and decrease in electrolyte resistance of the separator (100) can be suppressed.

[0091] According to one embodiment of the present invention, the solubility of the electrolyte-resistant polymer binder in the electrolyte (E) may be approximately 0% or more and 10% or less. The solubility in the electrolyte (E) may refer to a physical property indicating how much of the polymer is dissolved in the electrolyte (E). For example, to measure the solubility of the electrolyte-resistant polymer binder in the electrolyte (E), the weight of the electrolyte-resistant polymer binder in a dry state may be measured, and then the solubility in the electrolyte (E) may be measured by dissolving the electrolyte-resistant polymer binder in the electrolyte (E) and then measuring the weight of the electrolyte-resistant polymer binder remaining undissolved. When the solubility of the electrolyte-resistant polymer binder in the electrolyte (E) is maintained within the range described above, the amount of binder dissolved in the electrolyte (E) decreases, thereby suppressing damage to the coating layer (130) and improving battery performance.

[0092] According to one embodiment of the present invention, the degree of swelling of the electrolyte (E) of the electrolyte-resistant polymer binder may be approximately 0% or more and 20% or less. The degree of swelling of the electrolyte (E) may refer to a physical characteristic indicating how much the polymer expands when in contact with the electrolyte (E). For example, to measure the degree of swelling of the electrolyte (E) of the electrolyte-resistant polymer binder, the weight of the electrolyte-resistant polymer binder in a dry state may be measured, and then the degree of swelling of the electrolyte (E) may be measured by immersing the electrolyte-resistant polymer binder in the electrolyte (E) and then measuring the weight of the swollen polymer binder. When the degree of swelling of the electrolyte (E) of the electrolyte-resistant polymer binder maintains the range described above, the increase of the binder swelling in the electrolyte (E) is suppressed, thereby reducing damage to the coating layer and improving battery performance.

[0093] FIG. 4 is a schematic diagram showing the process after the electrolyte (E) is injected into the separator (100) according to one embodiment of the present invention.

[0094] According to one embodiment of the present invention, the peel strength of the separator (100) for the cylindrical electrochemical device is about 150 gf / cm or more. For example, the peel strength of the separator (100) for the cylindrical electrochemical device may be approximately 150 gf / cm or more and 300 gf / cm or less, 160 gf / cm or more and 290 gf / cm or less, 160 gf / cm or more and 280 gf / cm or less, 160 gf / cm or more and 270 gf / cm or less, 160 gf / cm or more and 260 gf / cm or less, 160 gf / cm or more and 250 gf / cm or less, 170 gf / cm or more and 240 gf / cm or less, 180 gf / cm or more and 230 gf / cm or less, 190 gf / cm or more and 220 gf / cm or less, or 190 gf / cm or more and 210 gf / cm or less. When the peel strength of the above-described separator (100) is maintained within the range described above, the bonding strength between the porous polymer substrate (110) and the coating layer (130) is secured, thereby reducing the probability that the coating layer (130) will detach from the porous polymer substrate (130), and the capacity retention rate can be improved by smoothly providing a pathway for lithium ions during charging and discharging.

[0095] At this time, the peel strength of the separator (100) refers to the force required to peel off the coating layer (130) and the porous polymer substrate (110) by applying an adhesive tape to the surface of the coating layer of the separator (100) with a size of 7 cm X 2 cm, mounting the end portion of the separator (100) on a UTM device (LLOYD Instrument LF Plus), and applying a force at 180° at a measurement speed of 300 mm / min.

[0096] In the case of a cylindrical electrochemical device, the electrode assembly is housed in a cylindrical can, so the adhesive strength between the electrode and the separator (100) is not required significantly, and since the performance of the battery is not affected even with minimal adhesive strength, the binder content can be reduced compared to a stacked battery.

[0097] According to one embodiment of the present invention, a method for manufacturing a film for a cylindrical electrochemical device may include the steps of: preparing a porous polymer substrate (110); applying a slurry for a coating layer containing an electrolyte-resistant polymer binder to at least one surface of the porous polymer substrate (110) to form a coating layer (130); and drying a separator (100) coated with the coating layer (130). The porous polymer substrate (110), the electrolyte-resistant polymer binder, and the coating layer (130) are as described above.

[0098] According to one temporary state of the present invention, the method of coating the slurry for the coating layer onto the porous polymer substrate (110) may use a conventional coating method, and various methods such as bar coating, dip coating, die coating, roll coating, comma coating, or a combination thereof may be used.

[0099] One embodiment of the present invention includes a cylindrical electrochemical element comprising: an anode (200); a cathode (300); and a separator (100) interposed between the anode (200) and the cathode (300).

[0100] A cylindrical electrochemical device according to one embodiment of the present invention may include an electrolyte-resistant polymer binder in the coating layer (130) to prevent or suppress damage to the separator and thereby improve battery life characteristics.

[0101] According to one embodiment of the present invention, the positive electrode (200) comprises a positive electrode current collector and a positive electrode active material layer comprising 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 is a layered compound such as a lithium manganese complex 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 Mn2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7, etc.; 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 ~ 0.3); chemical formula LiMn1-xM x It may include a lithium manganese complex oxide represented by O2 (where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which part of the Li of the chemical formula is substituted with alkaline earth metal ions; a disulfide compound; and one or more of Fe2(MoO4)3.

[0102] According to one embodiment of the present invention, the cathode (300) comprises a cathode current collector and a cathode active material layer comprising a cathode active material, a conductive material, and a binder resin on at least one surface of the current collector. The cathode comprises, as the cathode active material, carbon such as lithium metal oxide, non-graphitizable carbon, or graphite-based carbon; 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, Group 1, 2, and 3 elements 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.

[0103] According to one embodiment of the present invention, the conductive material may be, for example, any one selected from graphite, carbon black, carbon fiber or metal fiber, metal powder, conductive whiskers, conductive metal oxide, activated carbon, and polyphenylene derivative, or a mixture of two or more of these conductive materials. For example, the conductive material may be one selected from natural graphite, artificial graphite, super-p, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, Denka black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide, or a mixture of two or more of these conductive materials.

[0104] 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. may be used.

[0105] According to one embodiment of the present invention, the binder resin may be a polymer commonly used in the industry for electrodes. 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 include acetatepropionate), cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, but are not limited thereto.

[0106] According to one embodiment of the present invention, the anode slurry for manufacturing the anode active material layer may include a dispersant, and the dispersant may be a pyrrolidone-based compound. Specifically, it may be N-methylpyrrolidone (N-methylpyrrolidone, ADC-01, LG Chem).

[0107] According to one embodiment of the present invention, the electrochemical element may further include an electrolyte (E) containing an electrolyte, and the electrolyte is A + B - As a salt with a structure like that, A + is Li + , Na + , K + It may include alkali metal cations such as or ions composed of a combination thereof. In addition, B - is PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 - A salt comprising an anion such as or a combination thereof may be dissolved or dissociated in an organic solvent comprising 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), ethylmethyl carbonate (EMC), gamma butyrolactone, or a mixture thereof, but is not limited thereto.

[0108] According to one embodiment of the present invention, the electrochemical device may be a cylindrical electrochemical device comprising a separator (100), an anode (200), and a cathode (300) according to the above description. In this case, the separator (100) described above may be interposed between the anode (200) and the cathode (300) in the order of 'separator-cathode-separator-anode', stacked in the form of an electrode assembly, and then wound into a jelly roll shape to form an electrode assembly, and the cylindrical electrochemical device may be manufactured by inserting the above into a battery can.

[0109] FIG. 5 is a schematic diagram showing a winding process of a cylindrical electrochemical device according to one embodiment of the present invention. Referring to FIG. 5, in the case of a separator (100) to which a coating layer (130) according to one embodiment of the present invention is applied, damage to the coating layer (130) as in the comparative example does not occur even if winding tension is applied during the winding process due to the step difference between the anode (200) and the cathode (300), so the reduction in the lifespan of the battery can be suppressed. In addition, damage to the coating layer (130) due to the step difference is suppressed even when the cell is operated after injecting the electrolyte (E), so the reduction in the lifespan of the battery can be further suppressed.

[0110] Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention is not to be interpreted as being limited to the embodiments described below. The embodiments of this specification are provided to more completely explain the present invention to those with average knowledge in the art.

[0111]

[0112] <Example 1>

[0113] Manufacturing of porous polymer substrates

[0114] A polyethylene resin (weight-average molecular weight 1 million) was extruded, and a porous polymer substrate (total thickness about 10 μm, porosity 45%, air permeability 80 s / 100cc, ER 0.5 ohm) was prepared by a wet method.

[0115] Formation of a coating layer

[0116] Al2O3 powder 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 binding polymer binder, PAM (MP15, Songkang, Tg: 160 ℃, Mw: 500,000, electrolyte swelling degree: 0%, electrolyte solubility: 0%) was prepared as an electrolyte-resistant polymer binder, sodium carboxymethyl cellulose (CMC-Na) (SG-L02, GL Chem) was prepared as a dispersant, and a polysiloxane-based material was prepared as a wetting agent.

[0117] A slurry for a coating layer was prepared by adding the above-prepared inorganic particles, a binding polymer binder, an electrolyte-resistant polymer binder, a dispersant, and a wetting agent to water in a weight ratio of 90:4:2:3:1 and then dispersing them.

[0118] A coating layer slurry was applied to one surface of the porous polymer substrate using a doctor blade in a bar coating method, and a coating layer with a thickness of 2 μm was formed by drying with a heat gun at 50°C.

[0119]

[0120] <Example 2>

[0121] In the above Example 1, a separator was prepared in the same manner as in Example 1, except that the electrolyte-resistant polymer binder used was PES (Poly(oxy-1,4-phenylenesulfonyl-1,4-phenylene), Sigma Aldrich, electrolyte swelling degree: 5%, electrolyte solubility: 0%), and the inorganic particles, binding polymer binder, electrolyte-resistant polymer binder, dispersant, and wetting agent were in a weight ratio of 90:2:4:3:1.

[0122]

[0123] <Example 3>

[0124] In the above Example 1, a separator was prepared in the same manner as in Example 1, except that SAN (Poly(styrene-co-acrylonitrile), sigma Aldrich, Mw: 185,000, electrolyte swelling degree: 5%, electrolyte solubility: 5%, Tg: 100 ℃) was used as the electrolyte-resistant polymer binder, and the inorganic particles, binding polymer binder, electrolyte-resistant polymer binder, dispersant, and wetting agent were in a weight ratio of 90:2:4:3:1.

[0125]

[0126] <Example 4>

[0127] In the above Example 1, a separator was prepared in the same manner as in Example 1, except that the electrolyte-resistant polymer binder used was PEEK (Poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene), Sigma Aldrich, Tg: 150°C, electrolyte swelling degree: 5%, electrolyte solubility: 5%), and the inorganic particles, binding polymer binder, electrolyte-resistant polymer binder, dispersant, and wetting agent were in a weight ratio of 90:2:4:3:1.

[0128]

[0129] <Example 5>

[0130] In the above Example 1, a separator was prepared in the same manner as in Example 1, except that the thickness of the coating layer was 1 μm.

[0131]

[0132] <Example 6>

[0133] In the above Example 1, a separator was prepared in the same manner as in Example 1, except that the thickness of the coating layer was 3 μm.

[0134]

[0135] <Comparative Example 1>

[0136] In the above Example 1, a separator was prepared in the same manner as in Example 1, except that PAA (ASR-2006ES1_T1, Aekyung Co., Ltd., Tg: 40 ℃, electrolyte swelling degree: 1,000%, electrolyte solubility: 70%) was used as the electrolyte-resistant polymer binder, and the inorganic particles, binding polymer binder, electrolyte-resistant polymer binder, dispersant, and wetting agent were in a weight ratio of 90:2:4:3:1.

[0137]

[0138] <Comparative Example 2>

[0139] In the above Example 1, a separator was prepared in the same manner as in Example 1, except that the electrolyte-resistant polymer binder used was PAM (MP15, Songgang Co., Ltd., Tg: 160 ℃, Mw: 500,000, electrolyte swelling degree: 0%, electrolyte solubility: 0%), and the inorganic particles, binding polymer binder, electrolyte-resistant polymer binder, dispersant, and wetting agent were mixed in a weight ratio of 93.7:2:0.3:3:1.

[0140]

[0141] <Comparative Example 3>

[0142] In the above Example 1, a separator was prepared in the same manner as in Example 1, except that the electrolyte-resistant polymer binder used was PAM (MP15, Songgang Co., Ltd., Tg: 160 ℃, Mw: 500,000, electrolyte swelling degree: 0%, electrolyte solubility: 0%), and the inorganic particles, binding polymer binder, electrolyte-resistant polymer binder, dispersant, and wetting agent were in a weight ratio of 90:1:6:2:1.

[0143]

[0144] <Comparative Example 4>

[0145] In the above Example 1, a separator was prepared in the same manner as in Example 1, except that the electrolyte-resistant polymer binder used was PVA (polyvinyl alcohol, Sigma Aldrich, Tg: 50 °C, Mw: 100,000, electrolyte swelling degree: 500 %, electrolyte solubility: 50%), and the inorganic particles, binding polymer binder, electrolyte-resistant polymer binder, dispersant, and wetting agent were in a weight ratio of 90:2:4:3:1.

[0146]

[0147] <Comparative Example 5>

[0148] In the above Example 1, a separator was prepared in the same manner as in Example 1, except that the thickness of the coating layer was 4 μm.

[0149]

[0150] <Manufacturing of Cylindrical Electrochemical Devices>

[0151] Cylindrical electrochemical devices were each manufactured using the separator membranes for cylindrical electrochemical devices of the above examples and comparative examples.

[0152] 1) Manufacture of the anode

[0153] Cathode active material (LiNi 0.8 Mn 0.1 Co 0.1 O2), a conductive material (carbon black), a dispersant (N-methylpyrrolidone, ADC-01, LG Chem), 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 an anode active material layer with a concentration of 50 wt% of the components excluding water. Next, the slurry was applied to the surface of an aluminum thin film (thickness 10 μm) and dried to manufacture an anode having an anode active material layer (thickness 120 μm).

[0154] 2) Preparation of the cathode

[0155] Graphite (a blend of natural graphite and artificial graphite), a conductive material (carbon black), a dispersant (Polyvinylpyrrolidone, Junsei, Japan), 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 negative electrode active material layer with a concentration of 50 wt% of the components excluding water. Next, the slurry was applied to the surface of a copper thin film (thickness 10 μm) and dried to manufacture a negative electrode having a negative electrode active material layer (thickness 120 μm).

[0156] 3) Fabrication of cylindrical electrochemical devices

[0157] The separators of the above examples and comparative examples were interposed between the above-manufactured cathode and anode in the order of 'separator-cathode-separator-anode' and stacked in the form of an electrode assembly.

[0158] The above-mentioned stacked electrode assembly was wound into a jelly roll shape to form an electrode assembly, and this was inserted into a battery can to manufacture a cylindrical electrochemical device.

[0159]

[0160] <Experimental Example>

[0161] Measurement of electrolyte swelling degree

[0162] The degree of electrolyte swelling (%) of the electrolyte-resistant polymer binder of the above examples and comparative examples can be measured using Formula 1 below.

[0163] [Equation 1]

[0164] Swelling degree (%) = {(W1 - W0) / W0} X 100

[0165] W0 above represents the weight of the polymer material before immersion in the electrolyte, and W1 represents the weight of the swollen polymer material after 24 hours of immersion in the electrolyte. The electrolyte is a mixture of ethylene carbonate and ethyl-methyl carbonate in a mass ratio of 3:7, containing LiPF6 in an amount of 1 mol / liter.

[0166]

[0167] Electrolyte solubility measurement

[0168] The electrolyte solubility (%) of the electrolyte-resistant polymer binder of the above examples and comparative examples can be measured using Formula 2 below.

[0169] [Equation 2]

[0170] Solubility (%) = {(W0 - W r ) / W0} X 100

[0171] The above W0 represents the weight of the polymer material before dissolution in the electrolyte, and W r represents the weight of the polymer material remaining undissolved after 24 hours following the dissolution of the electrolyte. The electrolyte is a mixture of ethylene carbonate and ethyl-methyl carbonate in a mass ratio of 3:7, containing LiPF6 in an amount of 1 mol / liter.

[0172]

[0173] Peel strength measurement

[0174] For the separator membranes of the above examples and comparative examples, a 7 cm x 2 cm specimen of the separator membrane was prepared to measure the peel strength. After attaching an adhesive tape to the surface of the coating layer of the prepared separator membrane, the end portion of the separator membrane was mounted on a UTM device (LLOYD Instrument LF Plus). The force required to peel off the coating layer and the porous polymer substrate was measured by applying force at a UTM device angle of 180° and a measurement speed of 300 mm / min.

[0175]

[0176] Measurement of capacity retention rate

[0177] For the electrochemical elements of the above examples and comparative examples, charge cycles were performed by charging at 25°C at 1 C until the voltage reached 4.2 V, and discharging at a constant current of 1 C until the voltage reached 3.0 V, and the capacity retention rate was measured after 100 cycles and 500 cycles, respectively.

[0178]

[0179] Separator surface image

[0180] FIGS. 6 and 7 are Scanning Electron Microscope (SEM) images showing the membrane surfaces of Examples 1 and 2 according to one embodiment of the present invention, respectively. FIGS. 8 and 9 are SEM images showing the membrane surfaces of Comparative Examples 1 and 2 according to one embodiment of the present invention, respectively.

[0181] According to the images in FIGS. 6 and 7, it can be seen that the separators of Examples 1 and 2 of the present invention have excellent electrolyte resistance, which can suppress damage to the coating layer and minimize cracks on the surface of the separator. Furthermore, according to FIGS. 8 and 9, it can be seen that in the case of Comparative Examples 1 and 2, the electrolyte resistance is inferior, causing damage to the coating layer and cracks on the surface of the separator.

[0182]

[0183] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Electrolyte Resistance Binder Type PAMPESSAN PEEK PAMPAM Electrolyte Swelling Degree (%) 0 5 5 5 00 Electrolyte Solubility (%) 0 5 5 00 Content (wt%) 2 4 4 2 2 Peel Strength (gf / cm) 2 0 2 0 2 0 2 0 2 0 18 0 2 3 0 Separator Unit Resistance (ohm) 0 8 0 8 0 8 8 0 8 7 8 8 5 00 Cycles 9 0 9 19 0 9 0 9 9 0

[0184]

[0185] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Electrolyte Resistance Binder Type PAAPAMPAMPVAPAM Electrolyte Swelling Degree (%) 1000005000 Electrolyte Solubility (%) 7000500 Content (wt%) 50.3642 Peel Strength (gf / cm) 705035070250 Separator Unit Resistance (ohm) 0.80.61.00.80.9 Capacity Retention Rate (%) 100 Cycles 8585908598500 Cycles 7065807090

[0186]

[0187] According to Table 1 above, Examples 1 to 6 included an electrolyte-resistant binder in the coating layer of the separator, which increased the peel strength of the separator, ensured electrolyte resistance to prevent damage to the coating layer during assembly, minimized resistance, and increased the capacity retention rate. For example, the peel strength of the separator in Examples 1 to 6 showed a relatively even distribution in the range of 180 gf / cm² to 230 gf / cm². In addition, the capacity retention rate in Examples 1-6 was 90% or higher for both 100 cycles and 500 cycles.

[0188] In addition, Examples 1, 5, and 6 confirmed that resistance can be minimized and capacity retention rate increased while controlling the thickness of the coating layer.

[0189] According to Table 2 above, the capacity retention rate in the comparative examples was mostly 90% or less.

[0190] For example, it can be seen that Comparative Example 1 uses a binder with inferior electrolyte resistance, resulting in lower peel strength and lower capacity retention rate compared to the Example. Comparative Example 2 has a very low content of electrolyte-resistant binder, so it can be seen that the resistance value of the individual separator is lower than that of the Example; however, it can be seen that the peel strength and electrolyte resistance are inferior, causing coating layer detachment during assembly and coating layer damage during cycling, which leads to a decrease in capacity retention rate. Furthermore, according to FIG. 9, it can be seen that surface cracks of the separator occurred due to coating layer damage caused by inferior electrolyte resistance. Comparative Example 3 has an increased content of electrolyte-resistant binder, resulting in an increased resistance value of the individual separator and very high peel strength; consequently, it cannot smoothly provide a pathway for lithium ions during charging and discharging, resulting in an inferior capacity retention rate. Comparative Example 4 has an increased coating layer thickness, which increases peel strength, but it can be seen that resistance also increased, resulting in inferior performance.

[0191] Accordingly, a separator for a cylindrical electrochemical device according to one embodiment of the present invention and a cylindrical electrochemical device including the same can maintain a high capacity retention rate by including an electrolyte-resistant polymer binder in the coating layer, thereby increasing peel strength while minimizing damage to the separator.

[0192] Although the foregoing has been described with reference to the embodiments of the present disclosure, a person skilled in the art or having ordinary knowledge in the art will understand that various modifications and changes can be made to the various embodiments of the present disclosure 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 determined by the claims.

[0193] [Explanation of the symbol]

[0194] 100: Separator for electrochemical devices

[0195] 110: Porous polymer substrate

[0196] 130: Coating layer

[0197] 200: Anode

[0198] 300: Cathode

[0199] E: Electrolyte

Claims

1. Porous polymer substrate; and A coating layer provided on at least one surface of the above-mentioned porous polymer substrate and comprising a polymer binder and inorganic particles; comprising The polymer binder included in the coating layer comprises an electrolyte-resistant polymer binder and a binding polymer binder, A separator for a cylindrical electrochemical device having a peel strength of 150 gf / cm or more.

2. In Claim 1, A separator for a cylindrical electrochemical device, wherein the content of the inorganic particles included in the coating layer is 90 parts by weight or more and 99 parts by weight or less per 100 parts by weight of the coating layer.

3. In Claim 1, A separator for a cylindrical electrochemical device, wherein the content of the polymer binder included in the coating layer is 1 part by weight or more and 10 parts by weight or less per 100 parts by weight of the coating layer.

4. In Claim 1, A separator for a cylindrical electrochemical device, wherein the content of an electrolyte-resistant polymer binder included in the coating layer is 0.5 parts by weight or more and 5 parts by weight or less per 100 parts by weight of the coating layer.

5. In Claim 1, A separator for a cylindrical electrochemical device, wherein the electrolyte-resistant polymer binder included in the coating layer comprises polyacrylamide (PAM), styrene-co-acrylonitrile copolymer (SAN), polyether ether ketone (PEEK), polyether sulfone (PES), and one or more selected from these.

6. In Claim 1, A separator for a cylindrical electrochemical device, wherein the content of the binding polymer binder included in the coating layer is 1 part by weight or more and 8 parts by weight or less per 100 parts by weight of the coating layer.

7. In Claim 1, A separator for a cylindrical electrochemical device, wherein the content ratio of the electrolyte-resistant polymer binder and the binding polymer binder included in the coating layer is 1:2 to 2:

1.

8. In Claim 1, A separator for a cylindrical electrochemical device, wherein the electrolyte solubility of the electrolyte-resistant polymer binder included in the coating layer is 0% or more and 10% or less.

9. In Claim 1, A separator for a cylindrical electrochemical device, wherein the electrolyte swelling degree of the electrolyte-resistant polymer binder included in the coating layer is 0% or more and 20% or less.

10. In Claim 1, A separator for a cylindrical electrochemical device, wherein the thickness of the coating layer is 1 μm or more and 3 μm or less.

11. A cylindrical electrochemical element comprising: an anode; a cathode; and a separator of claim 1 interposed between the anode and the cathode.

Images