Separator for electrochemical device and electrochemical device comprising same

Abstract

The present invention relates to a separator for an electrochemical device and an electrochemical device comprising same and, particularly, to a separator for an electrochemical device and an electrochemical device comprising same, in which the separator has, on a coating layer, an adhesive layer including a hollow-particle polymer binder, enabling buffering against pressure applied during a lamination process of electrodes and separators and thus preventing damage to a porous polymer substrate and increasing breakdown voltage.

Description

Separator for electrochemical devices and electrochemical devices containing the same

[0001] The present invention claims the benefit of Korean Patent Application No. 10-2023-0043722, filed with the Korean Intellectual Property Office on April 3, 2023, and the benefit of Korean Patent Application No. 10-2023-0051173, filed with the Korean Intellectual Property Office on April 19, 2023, the entire contents of which are incorporated herein by reference. The present invention relates to a separator for an electrochemical device and an electrochemical device comprising the same, and more particularly, to a separator for an electrochemical device comprising an adhesive layer including a hollow particle-type polymer binder on a coating layer, thereby buffering pressure applied in a lamination process between an electrode and a separator, thereby preventing damage to a porous polymer substrate and improving breakdown voltage.

[0002] Among the components of electrochemical devices, the separator comprises a porous polymer substrate located between the anode and cathode. It isolates the anode and cathode, prevents electrical short-circuiting between the two electrodes, and allows the passage of electrolytes and ions. While the separator itself does not participate in electrochemical reactions, its physical properties, such as wettability with electrolyte, degree of porosity, and thermal shrinkage, influence the performance and safety of the electrochemical device.

[0003] Accordingly, various methods have been attempted to enhance the physical properties of membranes by adding a coating layer to a porous polymer substrate and by adding various substances to the coating layer to change 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.

[0004] The separator can be bonded to the electrode through a lamination process, and a binder resin can be added to the coating layer composition of the separator to secure adhesion between the electrode and the separator.

[0005] Meanwhile, conventional separators used in medium- to large-sized batteries, such as those for electric vehicles (EVs) and energy storage systems (ESSs), assemble electrodes and separators through a lamination and stacking (L&S) process. However, increasing process speed to improve productivity reduces the time required to heat the separator. Therefore, the lamination process is being improved by increasing pressure during the heating process to ensure adhesion in a short period of time.

[0006] However, the high pressure applied during the lamination process can damage the porous polymer substrate, degrading battery performance and reducing the breakdown voltage of the separator. Furthermore, it can cause Hi-pot failures and low-voltage failures.

[0007] Ultimately, research was needed on a separator that could buffer the pressure applied during the lamination process.

[0008] The technical problem to be achieved by the present invention is to provide a separator for an electrochemical device and an electrochemical device including the same, which can prevent damage to the separator even during a high-pressure lamination process for bonding an electrode and a separator by providing an adhesive layer including a polymer binder in the form of hollow particles on a coating layer.

[0009] However, the problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the description below.

[0010] One embodiment of the present invention provides a separator for an electrochemical device, comprising: a porous polymer substrate; a coating layer provided on at least one surface of the porous polymer substrate and including a first polymer binder and inorganic particles; and an adhesive layer provided on the coating layer and including a second polymer binder in the form of hollow particles.

[0011] According to one embodiment of the present invention, the density of the second polymer binder is 0.7 g / cm 3 More than 0.9 g / cm 3 It could be as follows:

[0012] According to one embodiment of the present invention, the second polymer binder may be an acrylic binder.

[0013] According to one embodiment of the present invention, the coating layer may further include a third polymer binder in the form of hollow particles.

[0014] According to one embodiment of the present invention, the sphericity of the third polymer binder is 0.6 or more, and the density of the third polymer binder particles is 1.0 g / cm 3 less than, and the density difference between the third polymer binder particles and the inorganic particles is 1.5 g / cm 3 It could be something like this.

[0015] According to one embodiment of the present invention, the third polymer binder particle may be an acrylic binder.

[0016] According to one embodiment of the present invention, the content of the inorganic particles in the coating layer may be 90 parts by weight or more with respect to 100 parts by weight of the coating layer.

[0017] According to one embodiment of the present invention, when the separation membrane is compressed by applying pressure at 90°C, 10 tons, and for 15 seconds, the thickness reduction rate of the porous polymer substrate defined by the following mathematical formula 1 may be 10% or less.

[0018] [Mathematical Formula 1]

[0019] Thickness reduction rate (%) = (Thickness of porous polymer substrate before compression - Thickness of porous polymer substrate after compression) / Thickness of porous polymer substrate before compression X 100

[0020] According to one embodiment of the present invention, when the separation membrane is compressed by applying pressure at 90°C, 10 tons, and for 15 seconds, the breakdown voltage of the porous polymer substrate may be 1000 V or more.

[0021] According to one embodiment of the present invention, when the separation membrane is compressed by applying pressure at 90°C, 10 tons, and for 15 seconds, the increase rate of air permeability of the separation membrane defined by the following mathematical expression 2 may be 15% or less.

[0022] [Equation 2]

[0023] Increase in air permeability (%) = (air permeability of the membrane after compression - air permeability of the membrane before compression) / air permeability of the membrane before compression X 100

[0024] According to one embodiment of the present invention, the increase rate of the air permeability may increase as the content of the second polymer binder increases.

[0025] According to one embodiment of the present invention, when the separator is stored at 180°C for 30 minutes, the shrinkage rate of the separator defined by the following mathematical formula 3 may be 10% or less.

[0026] [Equation 3]

[0027] Shrinkage rate (%) = (length of membrane before storage - length of membrane after storage) / length of membrane after storage

[0028] According to one embodiment of the present invention, the thickness of the adhesive layer may be 2.0 ㎛ or less.

[0029] One embodiment of the present invention provides an electrochemical device comprising a positive electrode; a negative electrode; and a separator, wherein the separator is interposed between the positive electrode and the negative electrode, and is a separator for an electrochemical device.

[0030] According to one embodiment of the present invention, a separator for an electrochemical device includes a hollow particle-type polymer binder included in an adhesive layer that can buffer pressure applied during a lamination process.

[0031] A separator for an electrochemical device according to one embodiment of the present invention can prevent damage to a porous polymer substrate through a buffering action, thereby improving the insulation breakdown voltage.

[0032] An electrochemical device according to one embodiment of the present invention can improve battery performance.

[0033] Figure 1 is a schematic diagram of a separator for an electrochemical device according to one embodiment of the present invention.

[0034] Figure 2 is a schematic diagram of an electrochemical device according to one embodiment of the present invention.

[0035] 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.

[0036] In this specification, “A and / or B” means “A and B, or A or B.”

[0037] In this specification, when it is said that a component is “provided on” a component, this does not exclude that other components are disposed in between, unless otherwise specifically stated, but rather means that other components are further disposed.

[0038] In this specification, the characteristic of having pores means that the object includes a plurality of pores and that 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.

[0039] In this specification, the separator has a porous characteristic including a large number 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.

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

[0041] One embodiment of the present invention provides a separator for an electrochemical device, comprising: a porous polymer substrate; a coating layer provided on at least one surface of the porous polymer substrate and including a first polymer binder and inorganic particles; and an adhesive layer provided on the coating layer and including a second polymer binder in the form of hollow particles.

[0042] According to one embodiment of the present invention, a separator for an electrochemical device includes a hollow particle-type polymer binder included in an adhesive layer, which can buffer the pressure applied during the lamination process. In addition, the separator for an electrochemical device according to one embodiment of the present invention can prevent damage to a porous polymer substrate through the buffering action, thereby improving the breakdown voltage.

[0043] FIG. 1 is a schematic diagram of a separator for an electrochemical device according to one embodiment of the present invention. Referring to FIG. 1, a separator (100) for an electrochemical device according to one embodiment of the present invention will be described in detail.

[0044]

[0045] According to one embodiment of the present invention, the separator (100) for an electrochemical device includes a porous polymer substrate (110). As described above, the separator (100) for an electrochemical device includes the porous polymer substrate (110), thereby allowing lithium ions to pass through while blocking electrical contact, and implementing a shutdown function at an appropriate temperature.

[0046] 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, and the like, and the porous polymer substrate may include one or more of these. A porous membrane manufactured using such a polyolefin-based resin as a base resin, i.e., a membrane having a large number of pores, is advantageous in that it provides a shutdown function at an appropriate temperature.

[0047] According to one embodiment of the present invention, the weight average molecular weight of the polyolefin resin may be 500,000 or more and 1,500,000 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.

[0048] In this specification, “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.

[0049] - Column: PL Olexis (Polymer Laboratories)

[0050] - Solvent: TCB (Trichlorobenzene)

[0051] - Flow rate: 1.0 ml / min

[0052] - Sample concentration: 1.0 mg / ml

[0053] - Injection volume: 200 ㎕

[0054] - Column temperature: 160℃

[0055] - Detector: Agilent High Temperature RI detector

[0056] - Standard: Polystyrene (corrected with a cubic function)

[0057] 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 polyolefin resin and the plasticizer during a cooling process, extracting the plasticizer to form pores, and then performing stretching and heat-setting.

[0058] According to one embodiment of the present invention, the average pore size and the maximum pore size of the electrochemical device separator (100) 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.

[0059] According to one embodiment of the present invention, the electrochemical device separator (100) includes a coating layer (130) provided on at least one surface of the porous polymer substrate (110). Specifically, the electrochemical device separator (100) includes a coating layer (130) on one surface of the porous polymer substrate (110) as shown in FIG. 1, or includes a coating layer (130) provided on both surfaces of the porous polymer substrate (110). As described above, the electrochemical device separator (100) includes a 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 of the electrode.

[0060] According to one embodiment of the present invention, the electrochemical device separator (100) includes a coating layer (130) including a first polymer binder (131, not shown) and inorganic particles (133, not shown). As described above, since the coating layer (130) includes the first polymer binder (131) and the inorganic particles (133), the heat resistance of the separator is improved, the mechanical properties are improved, the shrinkage of the separator at high temperatures is prevented, resulting in an electrical short circuit of the electrode, and pores can be formed inside the coating layer.

[0061] According to one embodiment of the present invention, the coating layer (130) may be formed by inorganic particles (133) being bound by a first polymer binder (131) and integrated within the side. The pores within the coating layer (130) may be derived from an interstitial volume, which is an empty space between the inorganic particles (133).

[0062] According to one embodiment of the present invention, the coating layer (130) may include a plurality of pores. Specifically, the coating layer may be a porous coating layer. More specifically, the coating layer may be a porous coating layer including a plurality of pores therein. As described above, by including a plurality of pores, the coating layer can physically block the negative electrode and the positive electrode while allowing lithium ions to pass through and current to flow.

[0063] According to one embodiment of the present invention, the first polymer binder (131) may be an acrylic binder, a polyvinylidene binder, or a combination thereof. By selecting the first polymer binder (131) from the above-described binders, as described above, the heat resistance of the coating layer can be improved, and the bonding strength of the inorganic particles within the coating layer can be improved.

[0064] According to one embodiment of the present invention, the first polymer binder (131) may be an acrylic binder. This can maintain the porosity of the separator, improve the adhesive strength between the electrode and the separator during the lamination process of the battery, thereby improving the ease of battery manufacturing, and stably implementing the stacking process.

[0065] According to one embodiment of the present invention, the acrylic binder is a polymer containing a carboxylic acid ester as a repeating unit, and may preferably be a (meth)acrylic acid ester or an acrylic-styrene copolymer.

[0066] According to one embodiment of the present invention, the (meth)acrylic acid ester is 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 (meth)acrylate, di(meth)acrylate, propylene glycol (meth)acrylate, Examples thereof include trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, allyl (meth)acrylate, and ethylene di(meth)acrylate, and the like may be at least one selected from these. Among these, at least one selected from methyl (meth)acrylate, ethyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate is preferable, and methyl (meth)acrylate is particularly preferable.

[0067] According to one embodiment of the present invention, the acrylic-styrene copolymer may include an acrylic binder, and the acrylic binder may be a polyacrylate. For example, the binder may be at least one selected from the group consisting of styrenebutadiene rubber, nitrile-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, and acrylate polymers, and more specifically, may be a copolymer including acrylate.

[0068] According to one embodiment of the present invention, the polyvinylidene-based binder included in the first polymer binder (131) may be a polyvinylidene fluoride (PVdF, polyvinylidene difluoride)-based binder. As described above, by selecting the polyvinylidene-based binder as a polyvinylidene fluoride-based binder, the resistance of the separator can be reduced.

[0069] According to one embodiment of the present invention, the polyvinylidene-based binder included in the first polymer binder (131) may be a polyvinylidene fluoride (PVdF, polyvinylidene difluoride)-based binder. As described above, by selecting the polyvinylidene-based binder as a polyvinylidene fluoride-based binder, the resistance of the separator can be reduced.

[0070] According to one embodiment of the present invention, the polyvinylidene-based binder may be a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-co-HFP, Poly(vinylidene fluoride-co-hexafluoropropylene)). As described above, by selecting the polyvinylidene-based binder as a copolymer of polyvinylidene fluoride and hexafluoropropylene, the dissolution of the polymer binder by the electrolyte can be minimized.

[0071] According to one embodiment of the present invention, the polyvinylidene-based binder included in the first polymer binder (131) may have a hexafluoropropylene content of 10 wt% or more. Specifically, the polyvinylidene-based binder included in the first polymer binder (131) may have a hexafluoropropylene content of 10 wt% or more and 80 wt% or less, 15 wt% or more and 75 wt% or less, 20 wt% or more and 70 wt% or less, 25 wt% or more and 65 wt% or less, 30 wt% or more and 60 wt% or less, 35 wt% or more and 55 wt% or less, or 40 wt% or more and 50 wt% or less. By controlling the content of hexafluoropropylene included in the polyvinylidene-based binder in the first polymer binder (131) within the above-described range, the resistance of the separator can be reduced. The content of the above hexafluoropropylene (HFP) monomer is 1 H-NMR and / or 19 It can be measured by F-NMR.

[0072] According to one embodiment of the present invention, the first polymer binder (131) may be a hybrid binder particle including an acrylic binder and a polyvinylidene binder. As described above, by selecting the first polymer binder (133) as a hybrid binder particle including an acrylic binder and a polyvinylidene binder, the adhesive strength with the electrode can be improved.

[0073] According to one embodiment of the present invention, the first polymer binder (131) may be in particle or liquid form. By selecting the first polymer binder (131) from the above-described ones, the porosity and air permeability of the coating layer can be controlled, the pore size of the coating layer can be controlled, and the mechanical properties of the coating layer can be improved.

[0074] According to one embodiment of the present invention, the content of the first polymer binder (131) may be 10 parts by weight or less with respect to 100 parts by weight of the coating layer. Specifically, the content of the first polymer binder (131) may be more than 0 parts by weight and less than or equal to 10 parts by weight, 1 part by weight or more and 9 parts by weight or less, 2 parts by weight or more and 8 parts by weight or less, 3 parts by weight or more and 7 parts by weight or less, or 4 parts by weight or more and 6 parts by weight or less with respect to 100 parts by weight of the coating layer (130). By controlling the content of the first polymer binder (131) within the above-described range, the mechanical properties of the coating layer (130) can be improved, the porosity of the coating layer can be maintained, and heat resistance can be improved.

[0075] According to one embodiment of the present invention, the content of the inorganic particles (133) may be 90 parts by weight or more with respect to 100 parts by weight of the coating layer (130). Specifically, the content of the inorganic particles (133) may be more than 90 parts by weight and less than 100 parts by weight, 91 parts by weight or more and 99 parts by weight or less, 92 parts by weight or more and 98 parts by weight or less, 93 parts by weight or more and 97 parts by weight or less, or 94 parts by weight or more and 96 parts by weight or less with respect to 100 parts by weight of the coating layer (130). By controlling the content of the inorganic particles (133) within the above-described range, the heat resistance and mechanical properties of the separator can be improved.

[0076] According to one embodiment of the present invention, the inorganic particles (133) that can be used in the coating layer (130) are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles that can be used in one embodiment of the present invention are those that can be used in the operating voltage range of the applied electrochemical device (e.g., Li / Li). + There are no particular limitations as long as no oxidation and / or reduction reaction occurs at a voltage of 0 V to 5 V (as a reference).

[0077] According to one embodiment of the present invention, non-limiting examples of the inorganic particles (133) include BaTiO3, Pb(Zr,Ti)O3(PZT), b 1-x La x Zr 1-y Ti y O3(PLZT, 0 <x<1, 0<y<1), Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3(PMN-PT), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, SiC, Al(OH)3, TiO2, aluminum peroxide, zinc tin hydroxide (ZnSn(OH)6), tin-zinc oxide (Zn2SnO4, ZnSnO3), antimony trioxide (Sb2O3), antimony tetroxide (Sb2O4), antimony pentoxide (Sb2O5), etc., and may include one or more of these.

[0078] According to one embodiment of the present invention, the average diameter (D) of the inorganic particles (133) 50 ) has no special limitations, but in order to form a coating layer of uniform thickness and have an appropriate porosity, it is preferably in the range of 0.3 ㎛ to 1 ㎛. Specifically, when it is less than 0.3 ㎛, the dispersibility of inorganic particles in the slurry prepared for manufacturing the coating layer may be reduced, and when it exceeds 1 ㎛, the thickness of the formed coating layer may increase.

[0079] In this specification, "D50 particle size" means 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 the cumulative distribution of particle numbers according to particle size in the measuring device becomes 50%, the D50 particle size can be measured.

[0080] According to one embodiment of the present invention, the electrochemical device separator (100) includes an adhesive layer (150) provided on the coating layer (130). As described above, since the electrochemical device separator (100) includes an adhesive layer (150) provided on the coating layer (130), adhesive strength between the electrode and the separator can be secured during the lamination process of the separator and the electrode.

[0081] According to one embodiment of the present invention, the thickness of the coating layer (130) on one side of the porous polymer substrate (110) may be 2.0 ㎛ or less. Specifically, the thickness of the coating layer (130) may be greater than 0 ㎛ and less than or equal to 2.0 ㎛, greater than or equal to 0.1 ㎛ and less than or equal to 1.9 ㎛, greater than or equal to 0.2 ㎛ and less than or equal to 1.8 ㎛, greater than or equal to 0.3 ㎛ and less than or equal to 1.7 ㎛, greater than or equal to 0.4 ㎛ and less than or equal to 1.6 ㎛, greater than or equal to 0.5 ㎛ and less than or equal to 1.5 ㎛, greater than or equal to 0.6 ㎛ and less than or equal to 1.4 ㎛, greater than or equal to 0.7 ㎛ and less than or equal to 1.3 ㎛, greater than or equal to 0.8 ㎛ and less than or equal to 1.2 ㎛, or greater than or equal to 0.9 ㎛ and less than or equal to 1.1 ㎛. By controlling the thickness of the coating layer (130) within the above-described range, the heat resistance of the separator can be improved and the energy density of the separator can be increased.

[0082] According to one embodiment of the present invention, an adhesive layer is provided, which includes a second polymer binder in the form of hollow particles. Specifically, the second polymer binder may have a particle shape and may have a hollow space formed inside the particle. The hollow space formed inside the particle may be a closed space that is not connected to the outside or a hollow space that is partially connected to the outside. As described above, since the adhesive layer includes the second polymer binder in the form of hollow particles, the hollow space formed inside the particles buffers the pressure applied during the lamination process, thereby reducing the pressure applied to the separator and preventing damage. Furthermore, by preventing damage to the separator, the breakdown voltage can be improved. In addition, the second polymer binder in the form of hollow particles is partially broken by the pressure applied during the lamination process, and the broken second polymer binder supports the pressure applied during the lamination process, thereby preventing a decrease in the thickness of the separator, thereby enabling a low thickness reduction rate. Furthermore, due to the hollow space included in the second polymer binder, the air permeability of the adhesive layer increases, and thereby the air permeability of the separator including the adhesive layer can be improved.

[0083] According to one embodiment of the present invention, the density of the second polymer binder is 0.7 g / cm 3 More than 0.9 g / cm 3 It may be as follows. As described above, by controlling the density of the second polymer binder, the size of the internal space, i.e., the empty space, contained in the hollow particle type can be controlled, and the buffering effect against the applied pressure can be improved.

[0084] According to one embodiment of the present invention, the solubility of the second polymer binder in water may be 1 g / L or less. Specifically, the solubility of the second polymer binder in water may be 0.1 g / L or less, 0.01 g / L or less, or 0.00 g / L or less. More specifically, the second polymer binder may not dissolve in water. By controlling the solubility of the second polymer binder in water within the above-described range, the second polymer binder does not dissolve in the dispersion medium in the slurry for forming the adhesive layer, thereby maintaining a hollow particle shape in the adhesive layer, thereby reducing pressure applied from the outside, and preventing damage to the separation membrane.

[0085] According to one embodiment of the present invention, the particle size (D50) of the second polymer binder in the form of hollow particles is preferably in the range of 0.3 ㎛ or more and 1 ㎛ or less. Specifically, when it is less than 0.3 ㎛, the dispersibility of the second polymer binder in the slurry prepared for producing an adhesive layer may be reduced, and when it exceeds 1 ㎛, the thickness of the formed adhesive layer may increase.

[0086] According to one embodiment of the present invention, the second polymer binder may be an acrylic binder. This can maintain the porosity of the separator, improve the adhesive strength between the electrode and the separator during the battery lamination process, thereby improving the ease of battery manufacturing, and stably implementing the stacking process.

[0087] According to one embodiment of the present invention, the acrylic binder is a polymer containing a carboxylic acid ester as a repeating unit, and may preferably be a (meth)acrylic acid ester or an acrylic-styrene copolymer.

[0088] According to one embodiment of the present invention, the (meth)acrylic acid ester is 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 (meth)acrylate, di(meth)acrylate, propylene glycol (meth)acrylate, Examples thereof include trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, allyl (meth)acrylate, and ethylene di(meth)acrylate, and the like may be at least one selected from these. Among these, at least one selected from methyl (meth)acrylate, ethyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate is preferable, and methyl (meth)acrylate is particularly preferable.

[0089] According to one embodiment of the present invention, the acrylic-styrene copolymer may include an acrylic binder, and the acrylic binder may be a polyacrylate. For example, the binder may be at least one selected from the group consisting of styrenebutadiene rubber, nitrile-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, and acrylate polymers, and more specifically, may be a copolymer including acrylate.

[0090] According to one embodiment of the present invention, the second polymer binder may be an acrylic binder that is a polymer of a mixed solution containing one selected from the group consisting of acrylamide (AA), ethylene glycol dimethacrylate (EGDMA), methyl metacrylate (MMA), butyl acrylate, and combinations thereof.

[0091] According to one embodiment of the present invention, the coating layer may further include a third polymer binder in the form of hollow particles. As described above, by further including the third polymer binder in the form of hollow particles, the coating layer can improve the energy density of the battery, control the density difference between the polymer binder particles and the inorganic particles, and improve the adhesion of the separator to the electrode by including the hollow polymer binder particles.

[0092] According to one embodiment of the present invention, the third polymer binder may be hollow. Specifically, the hollow type includes a space within, and may include a closed space or an open space connected to the outside. By selecting the third polymer binder as hollow as described above, the volume of the space can be controlled, the density of the third polymer binder can be controlled, thereby facilitating phase separation from the inorganic particles, and the third polymer binder can be provided on the surface of the separator to improve adhesion to the electrode. In addition, by implementing a low density of the third polymer binder, the energy density of the battery can be improved.

[0093] According to one embodiment of the present invention, the first polymer binder may be non-hollow. Specifically, the first polymer binder may be a particle that does not include a space inside. By implementing the first polymer binder as non-hollow as described above, even if a portion of the first polymer binder is dissolved by the dispersion medium included in the slurry for the coating layer, the particle shape can be maintained.

[0094] According to one embodiment of the present invention, the content of the third polymer binder included on the surface opposite to the surface provided with the porous polymer substrate in the coating layer may be greater than the content of the inorganic particles. Specifically, the total weight of the third polymer binders included in the surface portion of the coating layer may be greater than the total weight of the inorganic particles included in the surface portion of the coating layer. In the present specification, the surface portion of the coating layer may mean a portion that is 50% or less of the thickness of the coating layer from the surface of the coating layer. As described above, by controlling the content of the third polymer binder provided depending on the position of the coating layer, the adhesive strength between the separator and the electrode can be improved.

[0095] According to one embodiment of the present invention, the total weight of the third polymer binder included in the surface of the coating layer having the porous polymer substrate may be greater than the content of the inorganic particles. Specifically, the total weight of the third polymer binders included in the lower surface of the coating layer may be greater than the total weight of the inorganic particles included in the lower surface of the coating layer. In the present specification, the lower surface of the coating layer may mean a portion of 50% or less of the thickness of the coating layer from the surface of the coating layer where the coating layer and the porous polymer substrate are in contact. As described above, by controlling the content of the third polymer binder provided depending on the position of the coating layer, the adhesive strength of the separator and the electrode can be improved.

[0096] According to one embodiment of the present invention, the weight of the third polymer binder itself included on the surface opposite to the surface provided with the porous polymer substrate in the coating layer may be less than the weight of the inorganic particles themselves. As described above, by adjusting the weight of the inorganic particles and the third polymer binder provided depending on the position of the coating layer, the bonding force with the porous polymer substrate can be improved and the heat resistance of the separation membrane can be improved.

[0097] According to one embodiment of the present invention, the weight of the inorganic particles included on the surface of the coating layer provided with the porous polymer substrate may be greater than the weight of the third polymer binder. As described above, by adjusting the weight of the inorganic particles provided depending on the position of the coating layer, the binding force with the porous polymer substrate can be improved and the heat resistance of the separation membrane can be improved.

[0098] According to one embodiment of the present invention, the sphericity of the third polymer binder may be 0.6 or more.

[0099] In this specification, 'sphericity' may mean the ratio of the length of the major axis, which is the longest length among the lengths of the points where a straight line passing through a particle meets the surface of the particle, and the length of the minor axis, which is the shortest length, to the length of the major axis.

[0100] In this specification, “the length of the major axis and the minor axis of a particle” may be the length of the major axis and the minor axis measured by magnifying the particle and photographing it.

[0101] According to one embodiment of the present invention, the average particle diameter (D50) of the third polymer binder is 0.6 ㎛ or less. Specifically, the average particle diameter (D50) of the third polymer binder may be 0.10 ㎛ or more and 0.60 ㎛ or less, 0.15 ㎛ or more and 0.55 ㎛ or less, 0.20 ㎛ or more and 0.50 ㎛ or less, 0.25 ㎛ or more and 0.45 ㎛ or less, or 0.30 ㎛ or more and 0.40 ㎛ or less. By controlling the average particle diameter (D50) of the third polymer binder within the above-described range, the third polymer binder can improve the phase separation speed and phase separation efficiency between the third polymer binder, which is the hollow particle, and the inorganic particle in the slurry for the coating layer.

[0102] According to one embodiment of the present invention, the density of the third polymer binder is 1.0 g / cm 3 It may be less than 0.1 g / cm. Specifically, the density of the third polymer binder is 0.1 g / cm. 3 More than 0.9 g / cm 3 Below 0.2 g / cm 3 More than 0.8 g / cm 3 Below 0.3 g / cm 3 More than 0.7 g / cm 3 Less than or equal to 0.4 g / cm 3 More than 0.6 g / cm 3 It may be as follows. By controlling the density of the third polymer binder within the above-described range, the third polymer binder can be provided in an amount greater than that of the inorganic particles on the surface of the coating layer, thereby realizing weight reduction of the battery and improving energy density.

[0103] According to one embodiment of the present invention, the density difference between the third polymer binder and the inorganic particles is 1.5 g / cm 3 It may be more than that. Specifically, the density difference between the third polymer binder and the inorganic particles is 1.5 g / cm. 3 More than 10.0 g / cm 3Below 2.0 g / cm 3 More than 9.5 g / cm 3 Below 2.5 g / cm 3 More than 9.0 g / cm 3 Below 3.0 g / cm 3 More than 8.5 g / cm 3 Below 3.5 g / cm 3 More than 8.0 g / cm 3 Below 4.0 g / cm 3 More than 7.5 g / cm 3 Below 4.5 g / cm 3 More than 7.0 g / cm 3 Below 5.0 g / cm 3 More than 6.5 g / cm 3 Less than or equal to 5.5 g / cm 3 More than 6.0 g / cm 3 It may be as follows. By controlling the density difference between the third polymer binder and the inorganic particles within the above-described range, the third polymer binder can improve the phase separation speed and phase separation efficiency between the third polymer binder and the inorganic particles in the slurry for the coating layer.

[0104] According to one embodiment of the present invention, the density of the inorganic particles is 4.0 g / cm 3 It may be less than or equal to 0.1 g / cm. Specifically, the density of the inorganic particles is 0.1 g / cm. 3 More than 4.0 g / cm 3 Below 0.2 g / cm 3 Above 3.9 g / cm 3 Below 0.3 g / cm 3 More than 3.8 g / cm 3 Below 0.4 g / cm 3 More than 3.7 g / cm 3 Below 0.5 g / cm 3 More than 3.6 g / cm 3 Below 0.6 g / cm 3 More than 3.5 g / cm 3 Below 0.7 g / cm 3 More than 3.4 g / cm 3Below 0.8 g / cm 3 More than 3.3 g / cm 3 Below 0.9 g / cm 3 More than 3.2 g / cm 3 Below 1.0 g / cm 3 Above 3.1 g / cm 3 Below, 1.1 g / cm 3 More than 3.0 g / cm 3 Below 1.2 g / cm 3 More than 2.9 g / cm 3 Below, 1.3 g / cm 3 More than 2.8 g / cm 3 Below, 1.4 g / cm 3 More than 2.7 g / cm 3 Below 1.5 g / cm 3 More than 2.6 g / cm 3 Below, 1.6 g / cm 3 More than 2.5 g / cm 3 Below, 1.7 g / cm 3 More than 2.4 g / cm 3 Below, 1.8 g / cm 3 More than 2.3 g / cm 3 Below, 1.9 g / cm 3 More than 2.2 g / cm 3 Less than or equal to 2.0 g / cm 3 More than 2.1 g / cm 3 By controlling the density of the inorganic particles within the above-described range, the inorganic particles can be provided in excess of the third polymer binder particles on the surface adjacent to the porous polymer substrate in the coating layer, thereby realizing weight reduction of the battery and improving energy density.

[0105] In this specification, 'density' may mean mass per volume.

[0106] According to one embodiment of the present invention, the third polymer binder may be an acrylic binder. This can maintain the porosity of the separator, improve the adhesion between the electrode and the separator during the battery lamination process, and thus enhance the ease of battery manufacturing. Furthermore, it can stably implement the stacking process.

[0107] According to one embodiment of the present invention, the acrylic polymer is a polymer containing a carboxylic acid ester as a repeating unit, and may preferably be a (meth)acrylic acid ester or an acrylic-styrene copolymer.

[0108] According to one embodiment of the present invention, specific examples of the (meth)acrylic acid ester include 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 (meth)acrylate, di(meth)acrylate, propylene glycol (meth)acrylate, Examples thereof include trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, allyl (meth)acrylate, and ethylene di(meth)acrylate, and the like may be at least one selected from these. Among these, at least one selected from methyl (meth)acrylate, ethyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate is preferable, and methyl (meth)acrylate is particularly preferable.

[0109] According to one embodiment of the present invention, the acrylic-styrene copolymer may include an acrylic binder, and the acrylic binder may be a polyacrylate. For example, the binder may be at least one selected from the group consisting of styrenebutadiene rubber, nitrile-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, and acrylate polymers, and more specifically, may be a copolymer including acrylate.

[0110] According to one embodiment of the present invention, the total content of the first polymer binder and the third polymer binder may be 25 parts by weight or less with respect to 100 parts by weight of the coating layer. Specifically, the total content of the first polymer binder and the third polymer binder may be more than 0 part by weight and less than or equal to 25 parts by weight, 1 part by weight or more and 24 parts by weight or less, 2 parts by weight or more and 23 parts by weight or less, 3 parts by weight or more and 22 parts by weight or less, 4 parts by weight or more and 21 parts by weight or less, 5 parts by weight or more and 20 parts by weight or less, 6 parts by weight or more and 19 parts by weight or less, 7 parts by weight or more and 18 parts by weight or less, 8 parts by weight or more and 17 parts by weight or less, 9 parts by weight or more and 16 parts by weight or less, 10 parts by weight or more and 15 parts by weight or less, 11 parts by weight or more and 14 parts by weight or less, or 12 parts by weight or more and 13 parts by weight or less with respect to 100 parts by weight of the coating layer. By controlling the total content of the first polymer binder and the third polymer binder within the above-described range, the ease of assembly can be improved in the process of assembling the electrode.

[0111] According to one embodiment of the present invention, the weight ratio of the first polymer binder and the third polymer binder may be 9:1 to 1:9. Specifically, the weight ratio of the first polymer binder and the third polymer binder may be 8:1 to 1:8, 7:1 to 1:7, 6:1 to 1:6, 5:1 to 1:5, 4:1 to 1:4, 3:1 to 1:3, or 2:1 to 1:2. Preferably, the weight ratio of the first polymer binder and the third polymer binder may be 1:1. By controlling the weight ratio of the first polymer binder and the third polymer binder within the above-described range, the adhesive strength before injecting the electrolyte into the battery and the adhesive strength after injecting the electrolyte into the battery can be improved.

[0112] According to one embodiment of the present invention, when the separation membrane is compressed by applying pressure at 90°C, 10 tons, and for 15 seconds, the thickness reduction rate of the porous polymer substrate defined by the following mathematical formula 1 may be 10% or less.

[0113] [Mathematical Formula 1]

[0114] Thickness reduction rate (%) = (Thickness of porous polymer substrate before compression - Thickness of porous polymer substrate after compression) / Thickness of porous polymer substrate before compression X 100

[0115] That is, the second polymer binder in the hollow particle form is partially broken by the pressure applied during the lamination process, and the broken second polymer binder supports the pressure applied during the lamination process, thereby preventing the thickness of the separator from decreasing, thereby lowering the thickness reduction rate. Furthermore, the remaining second polymer binder that is not broken can support the pressure applied during the lamination process, thereby preventing the thickness of the separator from decreasing. Specifically, when the separator is compressed by applying pressure at 90°C, 10 tons, and 15 seconds, the thickness reduction rate of the porous polymer substrate may be more than 0% and less than or equal to 10%, more than 1% and less than or equal to 9%, more than 2% and less than or equal to 8%, more than 3% and less than or equal to 7%, or more than 4% and less than or equal to 6%. By controlling the thickness reduction rate of the porous polymer substrate within the above-described range, the breakdown voltage can be improved.

[0116] In one embodiment of the present invention, the thickness of the porous polymer substrate, the coating layer, and / or the adhesive layer, etc., can be measured using a contact-type thickness measuring device. The contact-type thickness measuring device can be, for example, VL-50S-B from Mitutoyo.

[0117] According to one embodiment of the present invention, when the separator is compressed by applying pressure at 90°C, 10 tons, and 15 seconds, the breakdown voltage of the porous polymer substrate may be 1000 V or more. Specifically, the breakdown voltage of the porous polymer substrate may be 1000 V or more and 2000 V or less, 1100 V or more and 1900 V or less, 1200 V or more and 1800 V or less, 1300 V or more and 1700 V or less, or 1400 V or more and 1600 V or less. By controlling the breakdown voltage within the above-described range, the stability and performance of the battery can be improved.

[0118] In this specification, “insulation breakdown voltage” may mean the voltage measured by increasing the voltage at a rate of 100 V / s using an AC / DC / IR hipot tester device (chroma, model 19052) and reaching 0.5 m and 3 s.

[0119] According to one embodiment of the present invention, when the separation membrane is compressed by applying pressure at 90°C, 10 tons, and for 15 seconds, the increase rate of air permeability of the separation membrane defined by the following mathematical expression 2 may be 15% or less.

[0120] [Equation 2]

[0121] Increase in air permeability (%) = (air permeability of the membrane after compression - air permeability of the membrane before compression) / air permeability of the membrane before compression X 100

[0122] Specifically, when the separator is compressed by applying pressure at 90°C, 10 tons, and 15 seconds, the increase rate of the air permeability of the separator may be more than 0% and less than or equal to 15%, more than 1% and less than or equal to 14%, more than 2% and less than or equal to 13%, more than 3% and less than or equal to 12%, more than 4% and less than or equal to 11%, more than 5% and less than or equal to 10%, more than 6% and less than or equal to 9%, or more than 7% and less than or equal to 8%. By controlling the increase rate of the air permeability of the separator within the above-described range, the ionic conductivity and the performance of the battery can be improved.

[0123] According to one embodiment of the present invention, the air permeability increase rate may increase as the content of the second polymer binder increases. Specifically, the air permeability may be improved by forming separate pores by the hollow space contained in the second polymer binder, and by controlling the air permeability increase rate as described above, ionic conductivity and battery performance may be improved.

[0124] In this specification, “membrane permeability” may be measured using EG01-55-1MR equipment from Asahi seico.

[0125] According to one embodiment of the present invention, when the separator is stored at 180°C for 30 minutes, the shrinkage rate of the separator defined by the following mathematical formula 3 may be 10% or less.

[0126] [Equation 3]

[0127] Shrinkage rate (%) = (length of membrane before storage - length of membrane after storage) / length of membrane after storage

[0128] Specifically, when the separator is stored at 180°C for 30 minutes, the shrinkage rate of the separator may be greater than 0% and less than or equal to 10%, greater than or equal to 1% and less than or equal to 9%, greater than or equal to 2% and less than or equal to 8%, greater than or equal to 3% and less than or equal to 7%, or greater than or equal to 4% and less than or equal to 6%. Furthermore, the shrinkage rate of the separator may refer to the shrinkage rate in each of the machine direction (MD) and the transverse direction (TD). By controlling the shrinkage rate of the separator within the above-described range, the heat resistance of the separator can be improved, and battery safety under high-temperature conditions can be improved.

[0129] According to one embodiment of the present invention, the thickness of the adhesive layer may be 2.0 ㎛ or less. Specifically, the thickness of the adhesive layer (150) may be greater than 0 ㎛ and less than or equal to 2.0 ㎛, greater than or equal to 0.1 ㎛ and less than or equal to 1.9 ㎛, greater than or equal to 0.2 ㎛ and less than or equal to 1.8 ㎛, greater than or equal to 0.3 ㎛ and less than or equal to 1.7 ㎛, greater than or equal to 0.4 ㎛ and less than or equal to 1.6 ㎛, greater than or equal to 0.5 ㎛ and less than or equal to 1.5 ㎛, greater than or equal to 0.6 ㎛ and less than or equal to 1.4 ㎛, greater than or equal to 0.7 ㎛ and less than or equal to 1.3 ㎛, greater than or equal to 0.8 ㎛ and less than or equal to 1.2 ㎛, or greater than or equal to 0.9 ㎛ and less than or equal to 1.1 ㎛. By controlling the thickness of the adhesive layer (150) within the above-described range, the adhesion of the separator to the electrode can be improved, the energy density of the separator can be increased, and the buffering effect against pressure applied from the outside can be improved.

[0130]

[0131] One embodiment of the present invention provides a method for manufacturing a separator for an electrochemical device, comprising the steps of: applying a slurry for a coating layer including a first polymer binder (131) and inorganic particles (135) on at least one surface of a porous polymer substrate (110); and applying a slurry for an adhesive layer including a second polymer binder (131).

[0132] The method for manufacturing an electrochemical device according to one embodiment of the present invention can easily prevent an increase in the resistance of a separator and improve the energy density of a battery by manufacturing the separator as a thin film. In the method for manufacturing a separator for an electrochemical device according to one embodiment of the present invention, any description overlapping with the description of the separator for an electrochemical device will be omitted.

[0133] According to one embodiment of the present invention, the method for manufacturing the electrochemical device includes a step of applying a slurry for a coating layer including a first polymer binder (131) and inorganic particles (135) onto at least one surface of a porous polymer substrate (110). By including the step of applying the slurry for a coating layer onto at least one surface of the porous polymer substrate as described above, a coating layer can be formed with a single application, and the content of inorganic particles in the slurry for a coating layer is excessive, thereby improving the heat resistance of the separator and facilitating evaporation of a solvent.

[0134] According to one embodiment of the present invention, prior to the step of applying the slurry for the coating layer, a polymer solution may be prepared by dissolving the first polymer binder in an appropriate solvent to prepare a slurry. The solvent is preferably one having a solubility index similar to that of the binder polymer to be used and a low boiling point. This is to facilitate uniform mixing and subsequent solvent removal. Non-limiting examples of usable solvents include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (NMP), cyclohexane, water, or mixtures thereof.

[0135] According to one embodiment of the present invention, prior to the step of applying the slurry for the coating layer, a polymer emulsion may be prepared by dispersing a first polymer binder in an appropriate dispersion medium to prepare a slurry. The dispersion medium preferably has a low boiling point. This is to facilitate uniform mixing and subsequent removal of the dispersion medium. Non-limiting examples of usable dispersion mediums include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (NMP), cyclohexane, water, or mixtures thereof.

[0136] According to one embodiment of the present invention, inorganic particles may be added and dispersed in the polymer emulsion or polymer solution. The content ratio of the inorganic particles and the polymer binder particles is as described above, and may be appropriately adjusted in consideration of the thickness, pore size, and porosity of the coating layer to be finally manufactured according to one embodiment of the present invention.

[0137] According to one embodiment of the present invention, the solid content of the slurry for the coating layer may be 10 wt% or more and 30 wt% or less. Specifically, the solid content of the slurry for the coating layer may be 11 wt% or more and 29 wt% or less, 12 wt% or more and 28 wt% or less, 13 wt% or more and 27 wt% or less, 14 wt% or more and 26 wt% or less, 15 wt% or more and 25 wt% or less, 16 wt% or more and 24 wt% or less, 17 wt% or more and 23 wt% or less, 18 wt% or more and 22 wt% or less, or 19 wt% or more and 21 wt% or less. By controlling the solid content of the slurry for the coating layer within the above-described range, an increase in the resistance of the separator can be prevented, and the separator can be manufactured into a thin film to improve the energy density of the battery.

[0138] According to one embodiment of the present invention, the method of applying the slurry for the coating layer to the surface of the porous polymer substrate (110) is not particularly limited to any one method, and a conventional method known in the art may be used. For example, various methods such as dip coating, die coating, roll coating, comma coating, or a mixture thereof may be used.

[0139] According to one embodiment of the present invention, the slurry for the coating layer may further include a third polymer binder in the form of hollow particles. As described above, the slurry for the coating layer may further include a third polymer binder in the form of hollow particles, thereby improving the energy density of the battery, controlling the difference in density between the polymer binder particles and the inorganic particles, and including the hollow polymer binder particles to improve the adhesion of the separator to the electrode.

[0140] According to one embodiment of the present invention, the method for manufacturing the electrochemical device includes a step of applying a slurry for an adhesive layer including a second polymer binder (151). By including the step of applying a slurry for an adhesive layer including a second polymer binder (151) as described above, the adhesive layer can be easily formed.

[0141] According to one embodiment of the present invention, the method for applying the slurry for the adhesive layer to the surface of the porous polymer substrate (110) is not particularly limited to any one method, and a conventional method known in the art may be used. For example, various methods such as dip coating, die coating, roll coating, comma coating, or a mixture thereof may be used.

[0142] According to one embodiment of the present invention, the slurry for the adhesive layer may further include a dispersion medium, and the dispersion medium may be water. As described above, by the slurry for the adhesive layer further including a dispersion medium, the second polymer binder can be uniformly dispersed.

[0143] According to one embodiment of the present invention, the method for manufacturing the electrochemical device may include a step of drying the slurry for the coating layer to form a coating layer. By including the step of drying the slurry for the coating layer to form a coating layer as described above, damage to the coating layer can be minimized, and the solvent or dispersion medium included in the slurry can be easily removed.

[0144] According to one embodiment of the present invention, the method for manufacturing the electrochemical device may include a step of drying the slurry for the adhesive layer to form an adhesive layer. By including the step of drying the slurry for the adhesive layer to form an adhesive layer as described above, damage to the adhesive layer can be minimized, and the dispersion medium included in the slurry can be easily removed.

[0145] According to one embodiment of the present invention, the method for manufacturing the electrochemical device may include a step of applying a slurry for a coating layer, drying the slurry for an adhesive layer, and then drying the slurry for an adhesive layer to form a coating layer and an adhesive layer, respectively. As described above, by including a step of applying a slurry for a coating layer, drying the slurry for an adhesive layer, and then drying the slurry for an adhesive layer to form a coating layer and an adhesive layer, respectively, the coating layer and the adhesive layer can be easily formed.

[0146] According to one embodiment of the present invention, the drying process appropriately sets time conditions to minimize the occurrence of surface defects in the coating layer. The drying may be performed using a drying assist device, such as a drying oven or hot air, within an appropriate range.

[0147] According to one embodiment of the present invention, the separator is interposed between the negative electrode and the positive electrode and is manufactured into an electrode assembly through a lamination process that applies heat and / or pressure to bond them. In one embodiment of the present invention, the lamination process can be performed by a roll press device including a pair of pressure rollers. That is, the negative electrode, the separator, and the positive electrode can be sequentially laminated and placed between the pressure rollers to achieve interlayer bonding. At this time, the lamination process can be performed by a hot press method.

[0148]

[0149] One embodiment of the present invention provides an electrochemical device comprising an anode (300); a cathode (500); and a separator (100), wherein the separator (100) is interposed between the anode (300) and the cathode (500), and is a separator (100) for an electrochemical device.

[0150] An electrochemical device according to one embodiment of the present invention can improve battery performance.

[0151] Figure 2 is a schematic diagram of an electrochemical device according to one embodiment of the present invention. Referring to Figure 2, the electrochemical device according to one embodiment of the present invention will be described in detail.

[0152] In this specification, the electrochemical device is a device that converts chemical energy into electrical energy through an electrochemical reaction, and is a concept encompassing primary batteries and secondary batteries. In this 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.

[0153] According to one embodiment of the present invention, the positive electrode 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.

[0154] According to one embodiment of the present invention, the negative electrode 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.

[0155] According to one embodiment of the present invention, the conductive material may be, for example, one selected from the group consisting of 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 among these. More specifically, the conductive material may be one selected from the group consisting of 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 among these.

[0156] 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.

[0157] 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.

[0158] In one embodiment of the present invention, the positive electrode slurry for producing 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).

[0159] According to one embodiment of the present invention, the content of the dispersant included in the positive electrode slurry may be more than 0 part by weight and less than or equal to 0.5 part by weight with respect to 100 parts by weight of the positive electrode slurry. Specifically, the content of the dispersant included in the positive electrode slurry may be more than 0.05 part by weight and less than or equal to 0.4 part by weight with respect to 100 parts by weight of the positive electrode slurry.

[0160] According to one embodiment of the present invention, the negative electrode slurry for producing the negative electrode active material layer may include a dispersant, and the dispersant may be a polypyrrolidone-based compound. Specifically, the dispersant may be polyvinylpyrrolidone (Polyvinylpyrrolidone, Junsei, Japan).

[0161] According to one embodiment of the present invention, the content of the dispersant included in the cathode slurry may be more than 0 part by weight and less than or equal to 0.5 part by weight with respect to 100 parts by weight of the cathode slurry. Specifically, the content of the dispersant included in the cathode slurry may be more than 0.05 part by weight and less than or equal to 0.4 part by weight with respect to 100 parts by weight of the cathode slurry.

[0162] According to one embodiment of the present invention, the electrochemical device may further include an electrolyte.

[0163] According to one embodiment of the present invention, an electrochemical device prepared as described above can be placed in an appropriate case and an electrolyte solution is injected to manufacture a battery.

[0164] According to one embodiment of the present invention, the electrolyte is A + B -As a salt with the same structure, A + is Li + , Na + , K + B containing an ion composed of an alkali metal cation or a combination thereof; - is PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 - Salts containing anions such as or combinations thereof are dissolved or dissociated in organic solvents such as 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 (γ-butyrolactone) or mixtures thereof, but are not limited thereto.

[0165] One embodiment of the present invention provides a battery module including a battery including the electrochemical element as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source. Specific examples of the device include, but are not limited to, a power tool that is powered by an electric motor; 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.

[0166] 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 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.

[0167] <Example 1>

[0168] Polyethylene resin (weight average molecular weight 900,000) was extruded and a porous polymer substrate (total thickness of approximately 9 ㎛) was manufactured using a wet method.

[0169] Al2O3 powder with a D50 particle size of 600 nm was prepared as an inorganic particle. Acrylic emulsion (CSB-130, Toyo Ink Co., Ltd.) was prepared as the first binder polymer, and sodium carboxymethyl cellulose (CMC-Na) (SG-L02, GL Chem Co., Ltd.) was prepared as the dispersant.

[0170] The above-prepared inorganic particles, first binder polymer, and dispersant were added to water in a weight ratio of 97:2:1, and then the inorganic particles were added, crushed, and dispersed to prepare a slurry for a coating layer.

[0171] The slurry for the coating layer was coated on both sides of the porous polymer substrate and dried to form a coating layer with a thickness of 1.5 μm.

[0172] To prepare a second polymer binder, a mixed solution was prepared by dissolving 6.0 mM acrylamide (AA), 24 mM ethylene glycol dimethacrylate (EGDMA), and 10 mg azobisisobutyronitrile (AIBN) in 50 mL of acetonitrile. Carboxyl-capped polystyrene beads were added to the mixed solution, which was stirred at 700 rpm. The mixture was then reacted at 43°C for 12 hours, and then at 60°C for 24 hours. Next, after aging treatment for 6 hours at a temperature of 85 ℃, centrifugation was performed, and the separated solid material was washed with alcohol. The washed solid material was used to dissolve potassium persulfate using THF to produce a hollow particle binder, which is an acrylic binder.

[0173] The second polymer binder (average particle size: 500 nm, average density: 0.8 g / cm) 3 ) was added to water and dispersed so that the solid content was 20 wt% to prepare a slurry for the adhesive layer.

[0174] The slurry for the above adhesive layer was applied by bar coating on the coating layer and then dried to form an adhesive layer with a thickness of 1 μm, thereby manufacturing a separator for an electrochemical device.

[0175]

[0176] <Comparative Example 1>

[0177] Polyethylene resin (weight average molecular weight 900,000) was extruded and a porous polymer substrate (total thickness of approximately 9 ㎛) was manufactured using a wet method.

[0178] Al2O3 powder having a D50 particle size of 600 nm was prepared as an inorganic particle. An acrylic emulsion (CSB-130, Toyo Ink Co., Ltd.) was prepared as the first binder polymer, a hollow particle-type binder as the second polymer binder prepared in Example 1, and sodium carboxymethyl cellulose (CMC-Na) (SG-L02, GL Chem Co., Ltd.) was prepared as a dispersant.

[0179] The above-prepared inorganic particles and dispersant were added to water at a weight ratio of 97:1, ball milled for 2 hours, and crushed and mixed. Thereafter, the first binder polymer and the second binder polymer were added at a weight ratio of 2:10 and mixed to prepare a slurry for a coating layer having a solid content of 25 wt%.

[0180] A separator for an electrochemical device was manufactured by coating the slurry for the coating layer on both sides of the porous polymer substrate and drying it to form a coating layer having a thickness of 2.5 μm.

[0181] <Comparative Example 2>

[0182] A separator for an electrochemical device was manufactured in the same manner as in Example 1, except that a filled particle rather than a hollow particle was used as the second polymer binder.

[0183] <Comparative Example 3>

[0184] An electrochemical device separator was manufactured in the same manner as in Example 1, except that a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP) (Slovay, solef21510) that is not hollow particle-shaped and is soluble in water was used as the second polymer binder, and that the slurry for the adhesive layer was applied on the coating layer and then separated in a humidified state to manufacture the coating layer.

[0185] Comparative Example 4

[0186] In the above Example 1, the average density of the second polymer binder is 0.6 g / cm 3 A separator for an electrochemical device was manufactured in the same manner as in Example 1 except that

[0187] Comparative Example 5

[0188] In the above Example 1, the average density of the second polymer binder is 1.0 g / cm 3 A separator for an electrochemical device was manufactured in the same manner as in Example 1 except that

[0189]

[0190] <Experimental Example 1: Measurement of Thickness Reduction Rate of Porous Polymer Substrate>

[0191] The thickness of the porous polymer substrate before and after applying pressure at 90°C, 10 tons, and 15 seconds to the membranes of Example 1 and Comparative Examples 1 to 3 was measured using a contact thickness measuring device (Mitutoyo, VL-50S-B), and the thickness reduction rate of the porous polymer substrate was calculated using the following mathematical formula 1.

[0192] [Mathematical Formula 1]

[0193] Thickness reduction rate (%) = (Thickness of porous polymer substrate before compression - Thickness of porous polymer substrate after compression) / Thickness of porous polymer substrate before compression X 100

[0194] <Experimental Example 2: Measurement of the Insulation Breakdown Voltage of a Porous Polymer Substrate>

[0195] The breakdown voltage of the porous polymer was measured after applying pressure at 90°C, 10 tons, and 15 seconds to the membranes of Example 1 and Comparative Examples 1 to 3. The measurement method was to use an AC / DC / IR hipot tester device (chroma, model 19052) to increase the pressure at a rate of 100 V / s and measure the voltage reached at 0.5 m and 3 s.

[0196] <Experimental Example 3: Measurement of the increase rate of membrane permeability>

[0197] The air permeability of the membranes of Example 1 and Comparative Examples 1 to 3 before and after applying pressure at 90°C, 10 tons, and 15 seconds to the membranes was measured using EG01-55-1MR equipment from Asahi seico, and calculated using the following mathematical formula 2.

[0198] [Equation 2]

[0199] Increase in air permeability (%) = (air permeability of the membrane after compression - air permeability of the membrane before compression) / air permeability of the membrane before compression X 100

[0200] <Experimental Example 4: Measurement of shrinkage rate of the membrane>

[0201] The membranes of Example 1 and Comparative Examples 1 to 3 were cut into a size of 50 mm (length) x 50 mm (width) to prepare test pieces, which were then kept in an oven heated to 180°C for 30 minutes, and the test pieces were then recovered and the length changes in the machine direction (MD) and the transverse direction (TD) were measured to calculate the shrinkage ratio of the membrane using the following mathematical formula 3.

[0202] [Equation 3]

[0203] Shrinkage rate (%) = (length of membrane before storage - length of membrane after storage) / length of membrane after storage

[0204] <Experimental Example 5: Dry Adhesion Measurement>

[0205] 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).

[0206] The separators of Example 1 and Comparative Examples 1 to 3 were cut into pieces of 70 mm (length) x 20 mm (width), and the prepared cathodes and separators were laminated using a press under the conditions of 60°C, 6.5 MPa, and 1 sec to produce specimens. The prepared specimens were fixed by attaching them to a glass plate using double-sided tape, and at this time, the cathodes were positioned so that they faced the glass plate. The separator portion of the specimen was peeled at an angle of 180° at a speed of 150 mm / min at 25°C, and the strength at this time was measured.

[0207]

[0208] Thickness reduction rate (%) Insulation breakdown voltage (V) Increase in air permeability (%) Shrinkage rate (MD / TD) (%) Dry adhesion (gf / 20mm) Example 16.71,550 122 / 350 Comparative example 15.01,780 3820 / 3448 Comparative example 213.48 90 213 / 357 Comparative example 313.89 00 182 / 348 Comparative example 413.71,000 134 / 551 Comparative example 54.71,950 171 / 249

[0209] Referring to Table 1 above, Example 1, which is an embodiment of the present invention, has an adhesive layer including a hollow particle-type polymer binder on a coating layer, thereby confirming that the thickness reduction rate of the porous polymer substrate is 10% or less, the insulation breakdown voltage of the porous polymer substrate is 1,550 V, the air permeability increase rate of the separator is 15% or less, and the shrinkage rate of the separator is 10% or less.

[0210] In comparison, Comparative Example 1, which only includes a coating layer and has an excessive binder content in the coating layer, showed a rapid increase in the shrinkage rate of the separator and a rapid increase in the air permeability of the separator. Furthermore, Comparative Example 2, which has an adhesive layer including a particle-type polymer binder that does not include cavities, showed an increase in the thickness reduction rate of the porous polymer substrate and an increase in the air permeability of the separator, and a decrease in the breakdown voltage of the porous polymer substrate. In addition, Comparative Example 3, which has an adhesive layer including a solution-type binder rather than a particle-type binder, showed an increase in the thickness reduction rate of the porous polymer substrate and an increase in the air permeability of the separator, and a decrease in the breakdown voltage of the porous polymer substrate.

[0211] <Reference Example 1>

[0212] Polyethylene resin (weight average molecular weight 900,000) was extruded and a porous polymer substrate (total thickness of approximately 9 ㎛, porosity of 40% by volume) was manufactured using a wet method.

[0213] A copolymer of PVdF and HFP with a degree of substitution (weight ratio of HFP in PVdF polymer) of 5 wt% as a polyvinylidene binder as a first polymer binder particle with a particle size (D50) of 500 nm, and a hollow acrylic binder, styrene-butyl acrylate (glass transition temperature of 40 ℃, sphericity of 0.95, density of 0.5 g / cm), as a third polymer binder particle with a particle size (D50) of 300 nm 3 ) and inorganic particles (Al2O3, particle size (D50) 500 nm) were added to water and dispersed to prepare a slurry for a coating layer (solid content concentration 20 wt%). The weight ratio of the first polymer binder and the third polymer binder was 1:1. Furthermore, the weight ratio of the polymer binder (the first polymer binder and the third polymer binder) and the inorganic particles was 20:80.

[0214] The dispersion 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 3 μm thick coating layer on each side, thereby manufacturing a separator with a total thickness of 15 μm. Thereafter, the adhesive strength was measured according to Experimental Example 5 and summarized in Table 2 below.

[0215] <Reference Example 2>

[0216] A separation membrane was manufactured in the same manner as in Reference Example 1, except that the particle size (D50) of the third polymer binder particle was 700 nm. Thereafter, the adhesive strength was measured according to Experimental Example 5, and the results are summarized in Table 2 below.

[0217] <Reference Example 3>

[0218] A separator was manufactured in the same manner as in Reference Example 1, except that the sphericity of the third polymer binder particles was 0.55. Thereafter, the adhesive strength was measured according to Experimental Example 5 and the results are summarized in Table 2 below.

[0219] <Reference Example 4>

[0220] In the above Reference Example 1, the third polymer binder particle is not hollow and has a density of 1.0 g / cm 3 A membrane was manufactured in the same manner as in Reference Example 1, except that the sphericity was 0.98. Thereafter, the adhesive strength was measured according to Experimental Example 5 and summarized in Table 2 below.

[0221] <Reference Example 5>

[0222] A membrane was manufactured in the same manner as in Example 1, except that the first polymer binder particles were not hollow, had a density of 1.0 g / cm3, a sphericity of 0.98, and a particle size (D50) of 700 nm. Thereafter, the adhesive strength was measured according to Experimental Example 5, and the results are summarized in Table 2 below.

[0223]

[0224] Dry Adhesion (gf / 20mm)Reference Example 140Reference Example 214Reference Example 310Reference Example 412Reference Example 511

[0225] Referring to Table 1 above, it was confirmed that Reference Example 1 according to one embodiment of the present invention has excellent adhesive strength between the negative electrode and the separator.

[0226] In this regard, in Reference Example 2, the particle size of the third polymer binder increased, making it difficult to easily separate phases in the slurry for the coating layer, and thus the adhesive strength between the negative electrode and the separator decreased.

[0227] Furthermore, in Reference Example 3, the sphericity of the third polymer binder was low, and phase separation was not easy due to surface resistance with the dispersion medium in the slurry for the coating layer, resulting in a decrease in the adhesive strength between the negative electrode and the separator.

[0228] In addition, Reference Example 4 selected the third polymer binder as a non-hollow particle rather than a hollow particle, so that the density increased and the difference in density with the inorganic material and the dispersion medium water was not large, so that phase separation did not occur easily in the slurry for the coating layer, and thus the adhesive strength between the negative electrode and the separator was reduced.

[0229] In addition, Reference Example 5 selected the third polymer binder as a non-hollow particle rather than a hollow particle, and as the particle size of the third polymer binder increased, the density increased, so that the difference in density with the inorganic material and the dispersion medium water was not large, and as the particle size increased, the resistance within the dispersion medium increased, so that phase separation did not occur easily in the slurry for the coating layer, and the adhesive strength between the negative electrode and the separator was reduced.

[0230] Ultimately, the separator for an electrochemical device according to one embodiment of the present invention can prevent damage to the separator by buffering the pressure applied during lamination by including a hollow particle-type polymer binder in the adhesive layer.

[0231] [Explanation of symbols]

[0232] 100: Separator for electrochemical devices

[0233] 110: Porous polymer substrate

[0234] 130: Coating layer

[0235] 131: First polymer binder

[0236] 133: Inorganic particles

[0237] 150: Adhesive layer

[0238] 151: Second polymer binder

[0239] 300: Bipolar

[0240] 500: negative

Claims

1. Porous polymer substrate; A coating layer provided on at least one surface of the porous polymer substrate, the coating layer including a first polymer binder and inorganic particles; and A separator for an electrochemical device comprising an adhesive layer provided on the above coating layer and including a second polymer binder in the form of hollow particles.

2. In claim 1, The density of the second polymer binder is 0.7 g / cm 3 More than 0.9 g / cm 3 A separator for an electrochemical device, comprising:

3. In claim 1, A separator for an electrochemical device, wherein the second polymer binder is an acrylic binder.

4. In claim 1, A separator for an electrochemical device, wherein the content of the inorganic particles in the coating layer is 90 parts by weight or more with respect to 100 parts by weight of the coating layer.

5. In claim 1, A separator for an electrochemical device, wherein the coating layer further comprises a third polymer binder in the form of hollow particles.

6. In claim 5, The sphericity of the third polymer binder is 0.6 or more, The density of the third polymer binder is 1.0 g / cm 3 Less than, The density difference between the third polymer binder and the inorganic particles is 1.5 g / cm 3 A separator for electrochemical devices.

7. In claim 5, A separator for an electrochemical device, wherein the third polymer binder is an acrylic binder.

8. In claim 1, When the above membrane is compressed at 90°C, 10 tons and 15 seconds, A separator for an electrochemical device, wherein the thickness reduction rate of the porous polymer substrate defined by the following mathematical formula 1 is 10% or less: [Mathematical Formula 1] Thickness reduction rate (%) = (Thickness of porous polymer substrate before compression - Thickness of porous polymer substrate after compression) / Thickness of porous polymer substrate before compression X 100.

9. In claim 1, When the above membrane is compressed at 90°C, 10 tons and 15 seconds, A separator for an electrochemical device, wherein the breakdown voltage of the porous polymer substrate is 1,000 V or more.

10. In claim 1, When the above membrane is compressed at 90°C, 10 tons and 15 seconds, A separator for an electrochemical device, wherein the increase rate of the air permeability of the separator defined by the following mathematical formula 2 is 15% or less: [Equation 2] Increase in air permeability (%) = (Air permeability of the membrane after compression - Air permeability of the membrane before compression) / Air permeability of the membrane before compression X 100.

11. In claim 10, A separator for an electrochemical device, wherein the above air permeability increase rate increases as the content of the second polymer binder increases.

12. In claim 1, When the above membrane is stored at 180°C for 30 minutes, A separator for an electrochemical device, wherein the shrinkage ratio of the separator defined by the following mathematical formula 3 is 10% or less: [Equation 3] Shrinkage rate (%) = (length of membrane before storage - length of membrane after storage) / length of membrane after storage.

13. In claim 1, A separator for an electrochemical device, wherein the thickness of the adhesive layer is 3.0 ㎛ or less.

14. Contains an anode; a cathode; and a separator; An electrochemical device wherein the separator is interposed between the anode and the cathode, and is a separator for an electrochemical device according to any one of claims 1 to 13.

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