Separation membrane for electrochemical device, and electrochemical device including the same

Abstract

The present invention relates to a separation membrane for an electrochemical element and an electrochemical element including the same. Specifically, it includes an adhesive layer provided facing a silicon-based negative electrode, and the silicon-based negative electrode and the adhesive layer each contain a polyacrylamide (PAM)-based binder, thereby improving the adhesive force with the silicon-based negative electrode, suppressing the swelling of the electrochemical element to which the silicon-based negative electrode is applied, and improving the stability of the electrochemical element. The present invention relates to a separation membrane for an electrochemical element and an electrochemical element including the same.

Description

Technical Field

[0001] This application claims the benefit of the filing date of Patent Application No. 10-2023-0052786, filed with the Korean Intellectual Property Office on April 21, 2023, and all of its content is incorporated herein by reference.

[0002] The present invention relates to a separator for an electrochemical device and an electrochemical device including the same. Specifically, the present invention provides an adhesive layer provided to face a silicon-based negative electrode, and the silicon-based negative electrode and the adhesive layer each contain a polyacrylamide (PAM)-based binder, thereby improving the adhesive force with the silicon-based negative electrode, suppressing swelling of the electrochemical device to which the silicon-based negative electrode is applied, and improving the stability of the electrochemical device. The present invention relates to a separator for an electrochemical device and an electrochemical device including the same.

Background Art

[0003] Among the components of an electrochemical device, the separator is located between the positive electrode and the negative electrode and includes a polymer substrate having a porous structure. The separator separates the positive electrode and the negative electrode and plays a role in preventing an electrical short circuit between the two electrodes and allowing the electrolyte and ions to pass through. The separator itself is not involved in the electrochemical reaction, but physical properties such as wettability with respect to the electrolyte, degree of porosity, and thermal shrinkage rate affect the performance and safety of the electrochemical device.

[0004] Therefore, various methods have been attempted to add a coating layer to the porous polymer substrate to enhance the physical properties of the separator and add various substances to the coating layer to change the physical properties of the coating layer. As an example, an inorganic substance may be added to the coating layer to improve the mechanical strength of the separator, or an inorganic substance or hydrate may be added to the coating layer to improve the flame retardancy and heat resistance of the polymer substrate.

[0005] The separation membrane can be adhered to the electrode through a lamination process, and a binder resin can be added to the coating layer composition of the separation membrane to ensure the adhesive force between the electrode and the separation membrane.

[0006] On the other hand, among the negative electrode active materials used in the negative electrode of the electrochemical device, silicon-based active materials are attracting attention for having a capacity about 10 times higher than that of carbon-based active materials, and there is an advantage that a high energy density can be realized even with a thin electrode due to the high capacity. However, silicon-based active materials have problems of volume expansion accompanying charge and discharge and deterioration of life characteristics due to this.

[0007] Therefore, research on a separation membrane that can improve the adhesive force with a silicon-based negative electrode, suppress the swelling of an electrochemical device to which a silicon-based negative electrode is applied, and improve the stability of the electrochemical device has been necessary.

Summary of the Invention

Problems to be Solved by the Invention

[0008] The technical problem to be achieved by the present invention is to include an adhesive layer provided facing a silicon-based negative electrode, wherein the silicon-based negative electrode and the adhesive layer each contain a polyacrylamide (PAM)-based binder, thereby improving the adhesive force with the silicon-based negative electrode, suppressing the swelling of an electrochemical device to which the silicon-based negative electrode is applied, and providing a separation membrane for an electrochemical device that can improve the stability of the electrochemical device, and an electrochemical device including the same.

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

Means for Solving the Problems

[0010] One embodiment of the present invention provides a separator including an adhesive layer provided to face a silicon-based negative electrode. The silicon-based negative electrode includes a silicon-based negative electrode active material and a first polymer binder, the adhesive layer includes a second polymer binder, and each of the first polymer binder and the second polymer binder is a polyacrylamide (PAM)-based binder, and provides a separator for an electrochemical device.

[0011] According to one embodiment of the present invention, the content of the first polymer binder may be 12 parts by weight or less with respect to 100 parts by weight of the silicon-based negative electrode.

[0012] According to one embodiment of the present invention, the content of the second polymer binder may be 50 parts by weight or less with respect to 100 parts by weight of the adhesive layer. According to one embodiment of the present invention, the silicon-based negative electrode active material is one or more selected from the group consisting of Si, SiO x (0 < x < 2), Si-Y alloy, and Si-C composite, where Y is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, or a combination thereof, and may not be Si.

[0013] According to one embodiment of the present invention, it may include a porous polymer substrate; a coating layer provided on at least one surface of the porous polymer substrate; and an adhesive layer provided between the silicon-based negative electrode and the coating layer.

[0014] According to one embodiment of the present invention, the coating layer may include inorganic particles and a third polymer binder.

[0015] According to one embodiment of the present invention, the average particle diameter (D50) of the inorganic particles may be 0.3 μm or more and 1.0 μm or less.

[0016] According to one embodiment of the present invention, the third polymer binder may be an acrylic-based binder, a polyvinylidene-based binder, or a combination thereof.

[0017] According to one embodiment of the present invention, the dry adhesive force of the adhesive layer can be 50 gf / 25 mm or more.

[0018] According to one embodiment of the present invention, the wet adhesive force of the adhesive layer can be 10 gf / 25 mm or more and 30 gf / 25 mm or less.

[0019] One embodiment of the present invention provides an electrochemical element including a positive electrode; a silicon-based negative electrode; and the separator disposed between the positive electrode and the silicon-based negative electrode.

Advantages of the Invention

[0020] The separator for an electrochemical element according to one embodiment of the present invention can improve the adhesive force with a silicon-based negative electrode.

[0021] The separator for an electrochemical element according to one embodiment of the present invention can suppress the swelling of an electrochemical element to which a silicon-based negative electrode is applied and improve the stability of the electrochemical element.

Brief Description of the Drawings

[0022]

Figure 1

Modes for Carrying Out the Invention

[0023] In this specification, when a certain part says that a certain component "includes", unless otherwise stated to the contrary, it does not exclude other components, but means that it may further include other components.

[0024] In this specification, "A and / or B" means "A and B, or A or B".

[0025] As used herein, when it is said that a certain component is "provided above" another component, this does not exclude the possibility that other components may be disposed therebetween, and means that other components may be further disposed, unless otherwise stated to the contrary.

[0026] As used herein, the property of "having pores" means that the object contains a plurality of pores, and a fluid in the gas phase and / or liquid phase can pass from one side surface to the other side surface of the object through a structure in which the pores are interconnected with each other.

[0027] As used herein, a "separator membrane" is a membrane having a porous property including a large number of pores, and serves as a porous ion-conducting barrier that allows ions to pass through while blocking electrical contact between the negative electrode and the positive electrode in an electrochemical device.

[0028] Hereinafter, the present invention will be described in more detail.

[0029] One embodiment of the present invention provides a separator membrane for an electrochemical device including an adhesive layer provided facing a silicon-based negative electrode, wherein the silicon-based negative electrode includes a silicon-based negative electrode active material and a first polymer binder, the adhesive layer includes a second polymer binder, and the first polymer binder and the second polymer binder are polyacrylamide (PAM)-based binders.

[0030] The separator membrane for an electrochemical device according to one embodiment of the present invention can improve the adhesive force with a silicon-based negative electrode. Further, the separator membrane for an electrochemical device according to one embodiment of the present invention can suppress the swelling of an electrochemical device to which a silicon-based negative electrode is applied, and improve the stability of the electrochemical device.

[0031] FIG. 1 is a schematic diagram of a separator membrane for an electrochemical device according to one embodiment of the present invention. Referring to FIG. 1, the separator membrane 100 for an electrochemical device, which is one embodiment of the present invention, will be specifically described.

[0032] According to one embodiment of the present invention, the electrochemical element includes a silicon-based negative electrode. Among the negative electrode active materials used for the negative electrode of the electrochemical element, the silicon-based active material has an advantage that it can realize a high energy density even with a thin electrode due to its high capacity in that it has a capacity about 10 times higher than that of the carbon-based active material. However, since the silicon-based active material has a problem of volume expansion accompanying charge and discharge, the present invention was devised to suppress this.

[0033] According to one embodiment of the present invention, the separator 100 for the electrochemical element includes an adhesive layer 150 provided to face the silicon-based negative electrode. Specifically, the adhesive layer 150 may be adhered to the silicon-based negative electrode or may be located between the silicon-based negative electrode and the coating layer 130 of the separator or the porous polymer substrate 110. As described above, by including the adhesive layer provided so that the separator for the electrochemical element faces the silicon-based negative electrode, the adhesive force with the silicon-based negative electrode can be improved, swelling of the electrochemical element to which the silicon-based negative electrode is applied can be suppressed, and the stability of the electrochemical element can be improved.

[0034] According to one embodiment of the present invention, the silicon-based negative electrode includes a silicon-based negative electrode active material and a first polymer binder. As described above, by including the silicon-based negative electrode active material and the first polymer binder in the silicon-based negative electrode, the volume expansion and / or shrinkage of the silicon-based negative electrode active material can be sufficiently alleviated while improving the electrode adhesive force.

[0035] According to one embodiment of the present invention, the silicon-based negative electrode includes a silicon-based negative electrode active material. Specifically, the silicon-based negative electrode may include a silicon-based compound as the silicon-based negative electrode active material. Non-limiting examples of the silicon-based compound include Si, SiO x(0 < x < 2), Si-Y (where Y is an alkali metal, alkaline earth metal, Group 13 element, Group 14 element, transition metal, rare earth element, or a combination thereof, and is not Si) alloys, Si-C composites, etc. can be mentioned, and one or more of these can be included.

[0036] According to one embodiment of the present invention, the silicon-based negative electrode includes a first polymer binder. As described above, by including the first polymer binder in the silicon-based negative electrode, the adhesive force with the separator can be improved by the interaction with the second polymer binder included in the adhesive layer.

[0037] According to one embodiment of the present invention, the adhesive layer 150 includes a second polymer binder. As described above, by including the second polymer binder in the adhesive layer, the adhesive force with the silicon-based negative electrode can be improved by the interaction with the first polymer binder.

[0038] According to one embodiment of the present invention, each of the first polymer binder and the second polymer binder is a polyacrylamide (PAM) - based binder. Specifically, the polyacrylamide (PAM) - based binder can be derived from one or more monomers selected from the group consisting of acrylamide, n - methylolacrylamide, n - butoxymethylacrylamide, methacrylamide, n - methylolmethacrylamide, and n - butoxymethylmethacrylamide. By using a polyacrylamide (PAM: polyacryl amide) - based binder as the first polymer binder and the second polymer binder, stronger stress can be exerted by hydrogen bonds or covalent bonds between the silicon-based negative electrode and the adhesive layer to improve the adhesive force, and the volume expansion and / or shrinkage of the silicon-based negative electrode active material can be sufficiently alleviated.

[0039] According to an embodiment of the present invention, each of the first polymer binder and the second polymer binder may further include an aqueous binder. More specifically, the aqueous binder may include one selected from the group consisting of polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), and copolymers thereof. As described above, by each of the first polymer binder and the second polymer binder further including an aqueous binder, stronger stress can be exerted by hydrogen bonds or covalent bonds between the silicon-based negative electrode and the adhesive layer, thereby improving the adhesive force.

[0040] According to an embodiment of the present invention, the content of the first polymer binder may be 12 parts by weight or less with respect to 100 parts by weight of the silicon-based negative electrode. Specifically, the content of the first polymer binder with respect to 100 parts by weight of the silicon-based negative electrode may be 7 parts by weight or more and 12 parts by weight or less, 7.5 parts by weight or more and 11.5 parts by weight or less, 8 parts by weight or more and 11 parts by weight or less, 8.5 parts by weight or more and 10.5 parts by weight or less, or 9 parts by weight or more and 10 parts by weight or less. By adjusting the content of the first polymer binder within the above-described range, the volume expansion and / or shrinkage of the silicon-based negative electrode active material can be sufficiently alleviated while improving the electrode adhesive force.

[0041] According to an embodiment of the present invention, the content of the second polymer binder may be 50 parts by weight or less with respect to 100 parts by weight of the adhesive layer. Specifically, the content of the second polymer binder with respect to 100 parts by weight of the adhesive layer may be 40 parts by weight or more and 50 parts by weight or less, 41 parts by weight or more and 49 parts by weight or less, 42 parts by weight or more and 48 parts by weight or less, 43 parts by weight or more and 47 parts by weight or less, or 44 parts by weight or more and 46 parts by weight or less. By adjusting the content of the second polymer binder within the above-described range, the adhesive force with the silicon-based negative electrode can be improved.

[0042] According to one embodiment of the present invention, the silicon-based negative electrode active material is one or more selected from the group consisting of Si, SiO x (0 < x < 2), Si-Y alloy, and Si-C composite, wherein Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth element, or a combination thereof, and may not be Si. Specifically, when the silicon-based negative electrode active material is included in the negative electrode, the energy density and rapid charging performance can be improved.

[0043] According to one embodiment of the present invention, the separator 100 for the electrochemical device may include a porous polymer substrate 110; a coating layer 130 provided on at least one surface of the porous polymer substrate; and an adhesive layer 150 provided between the silicon-based negative electrode and the coating layer. As described above, by including the porous polymer and the coating layer in the separator for the electrochemical device, lithium ions can pass through while blocking electrical contact, and the heat resistance and mechanical properties can be improved. Further, by including the adhesive layer provided between the silicon-based negative electrode and the coating layer in the separator for the electrochemical device, the adhesive force with the silicon-based negative electrode can be improved.

[0044] According to one embodiment of the present invention, the separator 100 for the electrochemical device may include a porous polymer substrate 110 and an adhesive layer 150 provided between the silicon-based negative electrode and the porous polymer substrate. Specifically, when the coating layer is not provided or there is a coating layer provided only on one surface of the porous polymer substrate, as described above, by including the porous polymer substrate and the adhesive layer provided between the silicon-based negative electrode and the porous polymer substrate, the adhesive force with the silicon-based negative electrode can be improved.

[0045] According to an embodiment of the present invention, the separation membrane 100 for the electrochemical element may include a porous polymer substrate 110. As described above, by including a porous polymer substrate in the separation membrane for the electrochemical element, it is possible to allow lithium ions to pass through while blocking electrical contact, and to embody a shutdown function at an appropriate temperature.

[0046] According to an embodiment of the present invention, the porous polymer substrate may include a polyolefin-based resin. Specifically, the porous polymer substrate may be manufactured using a polyolefin-based resin as a base resin. More specifically, examples of the polyolefin-based resin include polyethylene, polypropylene, polypentene, etc., and one or more of these may be included. A porous separation membrane having a large number of pores, i.e., manufactured using such a polyolefin-based resin as a base resin, can be provided with a shutdown function at an appropriate temperature.

[0047] According to an embodiment of the present invention, the weight average molecular weight of the polyolefin-based resin may be 500,000 or more and 1,500,000 or less. By adjusting the weight average molecular weight of the polyolefin-based resin within the above-described range, the compression resistance of the separation membrane can be improved. Further, when mixing and using different polyolefin-based resins or forming a separation membrane in a multilayer structure composed of different polyolefin-based resins, the weight average molecular weight of the polyolefin-based resin can be calculated by adding the weight average molecular weights corresponding to the content ratios of the respective polyolefin-based resins.

[0048] In this specification, the "weight average molecular weight (Mw)" can be measured by gel permeation chromatography (GPC: PL GPC220, Agilent Technologies), and the measurement conditions can be set as follows.

[0049] - Column: PL Olexis (Polymer Laboratories) - Solvent: TCB (Trichlorobenzene) - Flow rate: 1.0 ml / min - Sample concentration: 1.0 mg / ml - Injection volume: 200 μl - Column temperature: 160 °C - Detector: Agilent High Temperature RI detector - Standard: Polystyrene (corrected by a cubic function) According to one embodiment of the present invention, the porous polymer substrate can be manufactured by a dry method or a wet method. Specifically, the porous polymer substrate can be manufactured by a method (dry method) in which a film made of a polyolefin resin is stretched in one direction and then stretched in a direction perpendicular to the one direction. Alternatively, the porous polymer substrate can be manufactured by a method (wet method) in which a polyolefin resin is kneaded with diluents at a high temperature to form a single phase, the polymer material and the diluent are phase-separated during the cooling process, the diluent is extracted to form pores, and then stretching and heat setting treatments are performed.

[0050] According to one embodiment of the present invention, the average size and the maximum size of the pores of the porous polymer substrate can be easily manufactured by adjusting the mixing ratio of the diluent, the stretching ratio, the temperature of the heat setting treatment, etc., so that those skilled in the art can meet the scope of the present invention.

[0051] According to one embodiment of the present invention, the separation membrane 100 for an electrochemical element may include a coating layer 130 provided on at least one surface of the porous polymer substrate 110. Specifically, the separation membrane for an electrochemical element includes a coating layer provided on one or both surfaces of the porous polymer substrate. As described above, by including a coating layer provided on at least one surface of the porous polymer substrate in the separation membrane for an electrochemical element, the heat resistance of the separation membrane can be improved, the mechanical properties can be improved, and it is possible to prevent the separation membrane from shrinking at a high temperature and causing an electrical short circuit to the electrode.

[0052] According to one embodiment of the present invention, the coating layer may include inorganic particles and a third polymer binder. As described above, by including inorganic particles and a third polymer binder in the coating layer, the heat resistance of the separation membrane can be improved, the mechanical properties can be improved, and it is possible to prevent the separation membrane from shrinking at high temperatures and causing an electrical short circuit to the electrode.

[0053] According to one embodiment of the present invention, the content of the third polymer binder in the coating layer may be 10 parts by weight or less. Specifically, the content of the third polymer binder with respect to 100 parts by weight of the coating layer may be more than 0 parts by weight and 10 parts by weight or less, 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. By adjusting the content of the third polymer binder within the above-described range, the porosity of the separation membrane can be maintained, and the adhesive force can be maintained even when the coating layer is wetted by the electrolyte after activation of the battery.

[0054] According to one embodiment of the present invention, the coating layer 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 that includes a plurality of pores inside. As described above, by including a plurality of pores in the coating layer, it is possible to allow lithium ions to pass through and current to flow while physically blocking the negative electrode and the positive electrode.

[0055] According to one embodiment of the present invention, the coating layer may be formed by inorganic particles being bound by a third polymer binder and accumulated within the layer. The pores inside the coating layer may be due to the interstitial volume, which is the empty space between the inorganic particles.

[0056] According to one embodiment of the present invention, the thickness of the coating layer can be formed to be 1 μm to 20 μm with respect to any one of the porous polymer substrates, but it is not particularly limited thereto. The thickness can be adjusted by those skilled in the art within an appropriate range from the viewpoints of heat resistance and electrical resistance.

[0057] In one embodiment of the present invention, the thickness of the polymer substrate, the coating layer and / or the separation membrane can be measured by applying a contact thickness measuring instrument. As the contact thickness measuring instrument, for example, VL-50S-B manufactured by Mitutoyo can be used.

[0058] According to one embodiment of the present invention, the inorganic particles that can be used in the coating layer 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 not particularly limited as long as oxidation and / or reduction reactions do not occur within the operating voltage range of the applied electrochemical device (for example, 0 V to 5 V based on Li / Li + .

[0059] According to one embodiment of the present invention, non-limiting examples of the inorganic particles include BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3 (PLZT, 0 <x <1, 0 <y <1), Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3 (PMN-PT), 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), zeolite-based compounds, etc. can be mentioned, and one or two or more of these can be included.

[0060] According to one embodiment of the present invention, the average particle diameter (D50) of the inorganic particles can be 0.3 μm or more and 1.0 μm or less. Specifically, the average particle diameter (D50) of the inorganic particles can be 0.4 μm or more and 0.9 μm or less, 0.5 μm or more and 0.8 μm or less, or 0.6 μm or more and 0.7 μm or less. By adjusting the average particle diameter (D50) of the inorganic particles within the above-described range, in the slurry for a coating layer which is an emulsion in which the third polymer binder particles are dispersed in water, the phase separation rate and phase separation efficiency between the third polymer binder particles and the inorganic particles can be improved. Further, when it is less than 0.3 μm, the dispersibility of the inorganic particles may decrease in the slurry for a coating layer which is a slurry prepared for the production of the coating layer, and when it exceeds 1 μm, the thickness of the formed coating layer may increase.

[0061] In the present specification, the "D50 particle diameter" means the particle diameter at the 50% point of the cumulative distribution of the number of particles according to the particle diameter. The particle diameter can be measured using the laser diffraction method. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (for example, 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. The D50 particle diameter can be measured by calculating the particle diameter at the point where the cumulative distribution of the number of particles according to the particle diameter in the measuring device reaches 50%.

[0062] According to one embodiment of the present invention, the third polymer binder can be in a particulate or non-particulate form. Specifically, as described later, the third polymer binder may maintain its particle shape without being dissolved by a dispersion medium or a solvent, and the third polymer binder may be dissolved in a dispersion medium or a solvent and not maintain its particle shape. As described above, by selecting the third polymer binder from particulate or non-particulate forms, the mechanical properties and porosity of the coating layer can be adjusted.

[0063] According to one embodiment of the present invention, the average particle size (D50) of the particulate third polymer binder is 1.0 μm or less. Specifically, the average particle size (D50) of the particulate third polymer binder can be 0.10 μm or more and 0.90 μm or less, 0.15 μm or more and 0.85 μm or less, 0.20 μm or more and 0.70 μm or less, 0.25 μm or more and 0.65 μm or less, or 0.30 μm or more and 0.50 μm or less. By adjusting the average particle size (D50) of the particulate third polymer binder within the above-described range, in the slurry for a coating layer which is an emulsion in which the particulate third polymer binder is dispersed in water, the phase separation rate and phase separation efficiency between the particulate third polymer binder and the inorganic particles can be improved.

[0064] According to one embodiment of the present invention, the third polymer binder may include one or more polymer binders. As described above, by including one or more polymer binders in the third polymer binder, the adhesion of the coating layer can be improved, the porosity of the coating layer can be improved, and the dry adhesion in the state before injecting the electrolytic solution and the wet adhesion after injecting the electrolytic solution can be improved simultaneously.

[0065] According to one embodiment of the present invention, the third polymer binder may be an acrylic binder, a polyvinylidene binder, or a combination thereof. As described above, by using an acrylic binder, a polyvinylidene binder, or a combination thereof as the third polymer binder, the porosity of the separation membrane can be maintained, and the adhesion can be maintained even when the coating layer is wetted by the electrolytic solution after activation of the battery.

[0066] According to an embodiment of the present invention, the third polymer binder may be an acrylic binder. By using the acrylic binder as the third polymer binder, the porosity of the separation membrane can be maintained, and in the lamination process of the battery, the adhesion between the electrode and the separation membrane can be improved, thereby improving the ease of battery manufacturing and enabling the stacking process to be stably realized.

[0067] According to an embodiment of the present invention, the acrylic binder is a polymer containing carboxylic acid ester as a repeating unit, and preferably may be (meth)acrylic acid ester or an acrylic-styrene copolymer.

[0068] According to an 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, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, allyl (meth)acrylate, ethylene di(meth)acrylate, etc., and may be one or more selected from these. Among these, it is preferably one or more selected from methyl (meth)acrylate, ethyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, and particularly preferably methyl (meth)acrylate.

[0069] 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 one or more selected from the group consisting of styrene-butadiene rubber, nitril-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, and acrylate polymers, and specifically, it may be a copolymer containing acrylate.

[0070] According to one embodiment of the present invention, the third polymer binder may be a polyvinylidene-based binder. Specifically, according to one embodiment of the present invention, the polyvinylidene-based binder may be a copolymer of polyvinylidene fluoride and hexafluoropropylene. As described above, by selecting the binder resin to be a polyvinylidene-based binder, the porosity of the separation membrane can be maintained, and the adhesive force can be maintained even when the coating layer is wetted by the electrolyte after the activation of the battery. Furthermore, the stiffness of the battery can be improved, and the bending of the separation membrane can be prevented.

[0071] According to one embodiment of the present invention, the polyvinylidene-based binder may be an aqueous binder. Specifically, by selecting the polyvinylidene-based binder to be an aqueous binder, the pollutants discharged in the manufacturing process of the separation membrane can be minimized, and the manufacturing cost of the battery can be reduced.

[0072] According to one embodiment of the present invention, the third polymer binder may be a polyvinylidene-based binder having a hexafluoropropylene content of 1% by weight or more and 50% by weight or less. As described above, by selecting the third polymer binder from polyvinylidene-based binders having a hexafluoropropylene content of 1% by weight or more and 50% by weight or less, the porosity of the separation membrane can be maintained, and even if the coating layer is wetted by the electrolytic solution after activation of the battery, the adhesive force can be maintained. According to one embodiment of the present invention, the porosity of the coating layer can be 30% by volume or more. Specifically, the porosity of the coating layer can be 30% by volume or more and 70% by volume or less, 32% by volume or more and 68% by volume or less, 34% by volume or more and 66% by volume or less, 36% by volume or more and 64% by volume or less, 38% by volume or more and 62% by volume or less, 40% by volume or more and 60% by volume or less, 42% by volume or more and 58% by volume or less, 44% by volume or more and 56% by volume or less, 46% by volume or more and 54% by volume or less, or 48% by volume or more and 52% by volume or less. By adjusting the porosity of the coating layer within the above-described range, the movement of ions in the separation membrane can be maintained, and an increase in the resistance of the separation membrane can be prevented. Specifically, when the porosity is 70% by volume or less, mechanical properties that can withstand the pressing process of adhering to the electrode can be ensured, and the surface aperture ratio does not become too high, making it suitable for ensuring the adhesive force. On the other hand, when the porosity is 30% by volume or more, it is advantageous from the viewpoint of ion permeability.

[0073] In this specification, "porosity" means the ratio of the volume occupied by pores to the total volume, and volume% is used as its unit, and it can be used interchangeably with terms such as void fraction and porosity.

[0074] In this specification, the porosity corresponds to the value obtained by subtracting the volume converted from the weight and density of each constituent component of the coating layer from the volume calculated in the thickness, width, and length of the coating layer.

[0075] In one embodiment of the present invention, the porosity and pore size of the coating layer can be measured by the BET six-point method by the nitrogen gas adsorption flow method using a scanning electron microscope (SEM) image, a mercury porosimeter, a capillary flow porometer, or a porosimetry analyzer (Bell Japan Inc, Belsorp-II mini). At this time, it may be advantageous to use a capillary flow porometer.

[0076] According to one embodiment of the present invention, the separation membrane 100 for the electrochemical element may include an adhesive layer 150 provided between the silicon-based negative electrode and the coating layer 130. As described above, by including the adhesive layer provided between the separation membrane for the electrochemical element and the coating layer, the adhesion force with the silicon-based negative electrode can be improved, swelling of the electrochemical element to which the silicon-based negative electrode is applied can be suppressed, and the stability of the electrochemical element can be improved.

[0077] According to one embodiment of the present invention, the adhesive layer includes a second polymer binder. The content of the second polymer binder in the adhesive layer can be 50 parts by weight or less. Specifically, the content of the second polymer binder with respect to 100 parts by weight of the adhesive layer can be 40 parts by weight or more and 50 parts by weight or less, 41 parts by weight or more and 49 parts by weight or less, 42 parts by weight or more and 48 parts by weight or less, 43 parts by weight or more and 47 parts by weight or less, or 44 parts by weight or more and 46 parts by weight or less. By adjusting the content of the second polymer binder within the above-described range, the adhesion force with the silicon-based negative electrode can be improved.

[0078] According to one embodiment of the present invention, the thickness of the adhesive layer can be formed to have a thickness of 1 μm to 20 μm on the side in contact with the porous polymer base material of the coating layer and the other side, but it is not particularly limited thereto. The thickness can be adjusted by those skilled in the art within an appropriate range from the aspect of the adhesion force with the electrode.

[0079] In one embodiment of the present invention, the thickness of the adhesive layer can be measured by applying a contact thickness measuring instrument. For example, VL-50S-B of Mitutoyo can be used as the contact thickness measuring instrument.

[0080] In this specification, "Wet adhesive force" may mean the adhesive force in a state where the electrolyte is injected into the battery. "Dry adhesive force" may mean the adhesive force in a state before injecting the electrolyte into the battery.

[0081] According to one embodiment of the present invention, the Dry adhesive force of the adhesive layer can be 50 gf / 25 mm or more. Specifically, the Dry adhesive force of the adhesive layer can be 50 gf / 25 mm or more and 150 gf / 25 mm or less, 60 gf / 25 mm or more and 140 gf / 25 mm or less, 70 gf / 25 mm or more and 130 gf / 25 mm or less, 80 gf / 25 mm or more and 120 gf / 25 mm or less, or 90 gf / 25 mm or more and 110 gf / 25 mm or less. By adjusting the Dry adhesive force of the adhesive layer within the above-mentioned range, swelling of the electrochemical device to which the silicon-based negative electrode is applied can be suppressed, and the stability of the electrochemical device can be improved.

[0082] According to one embodiment of the present invention, the Wet adhesive force of the adhesive layer can be 10 gf / 25 mm or more and 30 gf / 25 mm or less. Specifically, the Wet adhesive force of the adhesive layer can be 12 gf / 25 mm or more and 28 gf / 25 mm or less, 14 gf / 25 mm or more and 26 gf / 25 mm or less, 16 gf / 25 mm or more and 24 gf / 25 mm or less, or 18 gf / 25 mm or more and 22 gf / 25 mm or less. By adjusting the Wet adhesive force of the adhesive layer within the above-mentioned range, swelling of the electrochemical device to which the silicon-based negative electrode is applied can be suppressed, and the stability of the electrochemical device can be improved.

[0083] One embodiment of the present invention provides a method for manufacturing a separator for an electrochemical device, including: mixing a slurry for a coating layer including a third polymer binder and inorganic particles (S10); applying the slurry for the coating layer onto at least one surface of a porous polymer substrate and drying to form a coating layer (S30); mixing a slurry for an adhesive layer including a second polymer binder (S50); and applying the slurry for the adhesive layer onto one surface of the coating layer and drying to form an adhesive layer (S70).

[0084] The method for manufacturing a separator for an electrochemical device according to one embodiment of the present invention can maintain adhesion in a lamination process with an electrode, maintain adhesion after activation of the battery, improve stiffness, or prevent bending of a pouch-type cell.

[0085] According to one embodiment of the present invention, the method for manufacturing a separator for an electrochemical device includes mixing a slurry for a coating layer including a third polymer binder and inorganic particles (S10). As described above, by including the step of mixing a slurry for a coating layer including a third polymer binder and inorganic particles (S10), a coating layer can be easily formed on the separator.

[0086] According to one embodiment of the present invention, in the method for manufacturing a separator for an electrochemical device, the third polymer binder can be dispersed in water, which is a suitable dispersion medium, to produce a polymer emulsion and provide a slurry for a coating layer. Alternatively, the third polymer binder can be dissolved in water, which is a suitable solvent, to produce a polymer solution and provide a slurry for a coating layer. As described above, by dispersing or dissolving the third polymer binder in a suitable dispersion medium or solvent to produce a polymer emulsion or a polymer solution and providing a slurry for a coating layer, contaminants generated during the manufacturing process can be minimized.

[0087] According to one embodiment of the present invention, inorganic particles can be added and dispersed in the polymer emulsion or the polymer solution. The content ratio of the inorganic particles and the third polymer binder is about 95:5, and it is appropriately adjusted in consideration of the thickness, pore size, and porosity of the coating layer according to one embodiment of the present invention finally produced.

[0088] According to one embodiment of the present invention, the method for manufacturing the separation membrane for an electrochemical element includes a step (S30) of applying and drying the slurry for the coating layer on at least one surface of a porous polymer substrate to provide a coating layer.

[0089] According to one embodiment of the present invention, the method for manufacturing the separation membrane for an electrochemical element includes a step of applying the slurry for the coating layer on at least one surface of a porous polymer substrate. As described above, by including the step of applying the slurry for the coating layer on at least one surface of a porous polymer substrate, a coating layer can be formed by one application. Due to the separation between the inorganic particles and the polymer binder particles in the slurry for the coating layer, in the portion close to the porous polymer substrate, there is an excess of inorganic particles, and in the far portion facing the porous polymer substrate, there is an excess of polymer binder particles, which can improve the adhesive force with the adhesive layer and can improve the porosity of the separation membrane.

[0090] 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 is not particularly limited to any one method, and a conventional method known in the art can be used. For example, various methods such as dip coating, die coating, roll coating, comma coating, or a mixed method thereof can be used.

[0091] According to one embodiment of the present invention, the method for manufacturing the separation membrane for an electrochemical element includes a step of drying the slurry for the coating layer to provide the coating layer. As described above, by including the step of drying the slurry for the coating layer to provide the coating layer, damage to the coating layer can be minimized, and the dispersion medium or solvent contained in the slurry can be easily removed.

[0092] According to one embodiment of the present invention, in the drying step, time conditions are appropriately set in order to minimize the generation of surface defects in the coating layer. For the drying, drying auxiliary devices such as a drying oven or hot air can be used within an appropriate range.

[0093] According to one embodiment of the present invention, the method for manufacturing the separation membrane for an electrochemical element includes a step (S50) of mixing a slurry for an adhesive layer containing a second polymer binder. As described above, by including the step (S50) of mixing the slurry for the adhesive layer containing the second polymer binder, an adhesive layer can be easily formed on the separation membrane.

[0094] According to one embodiment of the present invention, the second polymer binder may be dispersed in water, which is an appropriate dispersion medium, to produce a polymer emulsion, and the slurry for the adhesive layer may be provided. Alternatively, the second polymer binder may be dissolved in water, which is an appropriate solvent, to produce a polymer solution, and the slurry for the adhesive layer may be provided. As described above, by dispersing or dissolving the second polymer binder in an appropriate dispersion medium or solvent to produce a polymer emulsion or a polymer solution and providing the slurry for the adhesive layer, contaminants generated during the manufacturing process can be minimized.

[0095] According to one embodiment of the present invention, other compositions can be added and dispersed in the polymer emulsion or the polymer solution. The content ratio of the second polymer binder to other compositions is 45:55, and it is appropriately adjusted in consideration of the thickness and adhesive strength of the adhesive layer according to one embodiment of the present invention finally manufactured.

[0096] According to one embodiment of the present invention, the method for manufacturing the separation membrane for an electrochemical element includes a step (S70) of applying the slurry for the adhesive layer onto one surface of the coating layer and drying it to provide an adhesive layer.

[0097] According to one embodiment of the present invention, the method for manufacturing the separation membrane for an electrochemical element includes a step of applying the slurry for the adhesive layer onto one surface of the coating layer. As described above, by including the step of applying the slurry for the adhesive layer onto one surface of the coating layer, the adhesive layer can be formed by a single application. Among the slurry for the adhesive layer, in the portion close to the coating layer, other compositions including an acrylic binder are present in excess, and in the portion far from the coating layer facing the coating layer, the second polymer binder is present in excess, which can improve the adhesive force with the silicon-based negative electrode.

[0098] According to one embodiment of the present invention, the method of applying the slurry for the adhesive layer onto the surface of the coating layer is not particularly limited to any one method, and a conventional method known in the art can be used. For example, various methods such as dip coating, die coating, roll coating, comma coating, or a mixed method thereof can be used.

[0099] According to one embodiment of the present invention, the method for manufacturing the separation membrane for an electrochemical element includes a step of drying the slurry for the adhesive layer to provide an adhesive layer. As described above, by including the step of drying the slurry for the adhesive layer to provide an adhesive layer, damage to the adhesive layer can be minimized, and the dispersion medium or solvent contained in the slurry can be easily removed.

[0100] According to one embodiment of the present invention, for the drying process, time conditions are appropriately set in order to minimize the occurrence of surface defects in the adhesive layer. For the drying, drying auxiliary devices such as a drying oven or hot air can be used within an appropriate range.

[0101] According to an embodiment of the present invention, the separation membrane 100 is interposed between a silicon-based negative electrode and a positive electrode and is manufactured into an electrochemical element by a lamination process in which heat and / or pressure is applied for binding. In an 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 silicon-based negative electrode, the separation membrane, and the positive electrode are sequentially laminated, and this is inserted between the pressure rollers to achieve interlayer binding. At this time, the lamination process can be performed by a hot pressing method.

[0102] An embodiment of the present invention provides an electrochemical element including a positive electrode; a silicon-based negative electrode; and the separation membrane interposed between the positive electrode and the silicon-based negative electrode.

[0103] The electrochemical element according to an embodiment of the present invention can suppress volume expansion accompanying charge and discharge of a silicon-based active material, suppress deterioration of life characteristics due to this, and improve stability.

[0104] In the present invention, the electrochemical element is a device that converts chemical energy into electrical energy by an electrochemical reaction, and is a concept including a primary battery and a secondary battery. In this specification, the secondary battery is capable of charging and discharging, and means a lithium secondary battery, a nickel-cadmium battery, a nickel-metal hydride battery, and the like. The lithium secondary battery uses lithium ions as an ion conductor, and examples include a non-aqueous electrolyte secondary battery including a liquid electrolyte, an all-solid battery including a solid electrolyte, a lithium polymer battery including a gel polymer electrolyte, and a lithium metal battery using lithium metal as a negative electrode, but is not limited thereto.

[0105] ​According to one embodiment of the present invention, the adhesive layer included in the separation membrane is provided on the silicon-based negative electrode. As described above, by providing the adhesive layer included in the separation membrane on the silicon-based negative electrode, it is possible to suppress the volume expansion accompanying charge and discharge of the silicon-based active material and the resulting deterioration of the life characteristics, and improve the stability.

[0106] According to one embodiment of the present invention, the positive electrode includes 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 current collector. The positive electrode active material includes layered compounds such as lithium manganese composite oxides (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), and compounds substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x O4 (where x is 0 to 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3), Ni-site type lithium nickel oxide represented by; chemical formula LiMn 1-x M x O2 (where M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1), or lithium manganese composite oxide represented by Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which part of the chemical formula Li is substituted with alkaline earth metal ions; disulfide compounds; one or a mixture of two or more of Fe2(MoO4)3 may be included.

[0107] According to one embodiment of the present invention, the negative electrode includes 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 active material is Si, SiO xIt may contain one or more silicon-based negative electrode active materials selected from the group consisting of (0 < x < 2), Si-Y alloy, and Si-C composite. Further, as the negative electrode active material, the negative electrode includes carbon such as lithium metal oxide, graphitizable carbon, graphite-based carbon; Li x Fe2O3(0 ≦ x ≦ 1), Li x WO2(0 ≦ x ≦ 1), Sn x Me 1-x Me’ y O z (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8), etc. metal composite oxides; lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; it may further contain one or a mixture of two or more selected from titanium oxides.

[0108] According to one embodiment of the present invention, the conductive material may be, for example, any one selected from the group consisting of graphite, carbon black, carbon fiber or metal fiber, metal powder, conductive whisker, conductive metal oxide, activated carbon, and polyphenylene derivative, or a mixture of two or more of these conductive materials. More specifically, it may be one or a mixture of two or more conductive materials selected from the group consisting of 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.

[0109] According to an embodiment of the present invention, the current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery. For example, stainless steel, copper, aluminum, nickel, titanium, fired carbon, or a material obtained by surface-treating the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. can be used.

[0110] According to one embodiment of the present invention, the negative electrode active material layer may further contain a binder resin. As the binder resin, polymers commonly used for electrodes in the art can be used. Non-limiting examples of such binder resins further contained in the negative electrode active material layer include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polyethylhexyl acrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetatepropionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, but are not limited thereto.

[0111] According to one embodiment of the present invention, as the binder resin contained in the positive electrode active material layer, a polymer that is usually used for electrodes in the art can be used. Non-limiting examples of such binder resins contained in the positive electrode active material layer include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polyethylhexyl acrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetatepropionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, etc., and the like are not limited thereto.

[0112] According to one embodiment of the present invention, the positive electrode slurry for manufacturing the positive electrode active material layer may contain a dispersant, and the dispersant may be a pyrrolidone-based compound. Specifically, it may be N-methylpyrrolidone (N-methylpyrrolidone, HPD-01, LG Chem).

[0113] According to one embodiment of the present invention, the content of the dispersant contained in the positive electrode slurry may be more than 0 parts by weight and 0.5 parts by weight or less with respect to 100 parts by weight of the positive electrode slurry. Specifically, the content of the dispersant contained in the positive electrode slurry may be more than 0.05 parts by weight and 0.4 parts by weight or less with respect to 100 parts by weight of the positive electrode slurry.

[0114] According to one embodiment of the present invention, the negative electrode slurry for manufacturing the negative electrode active material layer may contain a dispersant, and the dispersant may be a CMC dispersant (SWCNT, Ocsial, Tuball dispersion).

[0115] According to one embodiment of the present invention, the content of the dispersant contained in the negative electrode slurry may be more than 0 parts by weight and 1.0 part by weight or less with respect to 100 parts by weight of the negative electrode slurry. Specifically, the content of the dispersant contained in the negative electrode slurry may be 0.1 part by weight or more and 0.9 part by weight or less, 0.2 part by weight or more and 0.8 part by weight or less, 0.3 part by weight or more and 0.7 part by weight or less, or 0.4 part by weight or more and 0.6 part by weight or less with respect to 100 parts by weight of the negative electrode slurry.

[0116] According to one embodiment of the present invention, the electrochemical element prepared as described above can be manufactured into a battery by being enclosed in a suitable case and injecting an electrolytic solution.

[0117] According to one embodiment of the present invention, the electrolytic solution is a salt having a structure such as A + B - wherein A + is an alkali metal cation such as Li + , Na + , K + or an ion composed of a combination thereof, and B - is PF6- , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 - Salts containing anions such as these, or ions consisting of combinations thereof, are dissolved or dissociated in an organic solvent consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), gamma-butyrolactone (γ-butyrolactone), or mixtures thereof, but are not limited thereto.

[0118] One embodiment of the present invention provides a battery module 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 power tools powered by battery motors; electric vehicles including electric vehicles (EV), hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), etc.; electric two-wheel vehicles including electric bicycles (E-bike) and electric scooters (E-scooter); electric golf carts; power storage systems, etc., but are not limited thereto.

Examples

[0119] Hereinafter, examples will be given to specifically describe the present invention in detail. However, the examples according to the present invention can be deformed into various different forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples in this specification are provided to more fully explain the present invention to those with average knowledge in the industry.

[0120] <Example 1> <Manufacture of the separation membrane> Prepare a porous polymer substrate (total thickness of about 10 μm, porosity of 40% by volume) manufactured by the wet method.

[0121] As the particulate third polymer binder, an acrylic binder with a particle size of 150 nm (Toyo Co., CSB-140, glass transition temperature -25 °C), a PAA (Polyacrylic acid) dispersant (Dow Chemical Co., CK-702), a wetting agent (BYK Co., BYK-348), and inorganic particles (Al2O3, particle size 500 nm) were added to water and dispersed to prepare a slurry for the coating layer (solid content concentration 35% by weight). The weight ratio of the third polymer binder to the inorganic particles was 4.6:95.4.

[0122] The slurry for the coating layer was applied to both sides of the porous polymer substrate by the bar coating method using a doctor blade, and dried with a 50 °C wind using a heat gun to form a coating layer with a thickness of 1.5 μm on each side.

[0123] The solution-type PAM-based binder (Myungwon Co., SBS-04), which is the second polymer binder, styrene-butyl acrylate (LG Chem., ADS-11, glass transition temperature 40 °C) with a particle size of 500 nm, and a PAA (Polyacrylic acid) dispersant (Dow Chemical, CK-702) were put into water and dispersed to prepare a slurry for the adhesive layer (solid content concentration: 5 wt%). The weight ratio of the second polymer binder to the other composition particles was set to 45:55.

[0124] On the surface of the coating layer, the slurry for the adhesive layer was applied on both sides by the bar coating method using a doctor blade, and dried with a 50 °C air flow using a heat gun to form an adhesive layer with a thickness of 0.5 μm on each side, thereby manufacturing a separator membrane with a total thickness of 14 μm.

[0125] <Manufacture of Electrochemical Element> 1) Manufacture of positive electrode The positive electrode active material (LiNi 0.8 Mn 0.1 Co 0.1 O2), a conductive material (LBCNT, BT1003M, LG Chem.), a dispersant (N-methylpyrrolidone, HPD-01, LG Chem.), and a PVDF binder resin (KF9700, Solvay) were mixed with NMP at a weight ratio of 97.5:0.7:0.14:1.66 to prepare a slurry for the positive electrode active material layer with a concentration of 76.5 wt% of the remaining components excluding NMP. Next, the slurry was applied to the surface of an aluminum thin film (thickness: 12 μm) and dried to manufacture a positive electrode having a loading of 4.52 mAh / cm 2

[0126] 2) Manufacture of negative electrode ​Silicon particles (Elkem, M702), PAM-based binder (Arakawa, BUH0452), conductive material (Imerys, SFG-6L), conductive material (SWCNT, Ocsial, Tuball dispersion), and CMC dispersant (SWCNT, Ocsial, Tuball dispersion) were mixed with water at a weight ratio of 80:9.4:9.6:0.4:0.6 to prepare a slurry for the negative electrode active material layer with a concentration of 25 wt% of the remaining components excluding water. Next, the slurry was applied to the surface of a copper thin film (thickness 8 μm) and dried to produce a negative electrode with a negative electrode loading of 8 mAh / cm 2 having a negative electrode loading of 8 mAh / cm

[0127] <Comparative Example 1> <Manufacture of Separator> A separator was manufactured in the same manner as in Example 1.

[0128] <Manufacture of Electrochemical Element> In the manufacture of the negative electrode of Example 1, an electrochemical element was manufactured in the same manner as in Example 1, except that an SBR binder (LG Chem, M37) was used instead of the PAM-based binder.

[0129] <Comparative Example 2> <Manufacture of Separator> In the adhesive layer of Example 1, a separator was manufactured in the same manner as in Example 1, except that an acrylic binder, LBG-4430LX (Arkema, particle size 250 mm), was used instead of the PAM-based binder.

[0130] <Manufacture of Electrochemical Element> An electrochemical element was manufactured in the same manner as in Example 1.

[0131] <Comparative Example 3> <Manufacture of Separator> In the adhesive layer of Example 1, a separation membrane was produced in the same manner as in Example 1, except that LBG-4430LX (Arkema, particle size 250 mm), an acrylic binder, was used instead of the PAM-based binder.

[0132] <Manufacture of Electrochemical Element> In the manufacture of the negative electrode of Example 1, an electrochemical element was produced in the same manner as in Example 1, except that an SBR binder (LG Chem, M37) was used instead of the PAM-based binder.

[0133] <Comparative Example 4> <Manufacture of Separation Membrane> A separation membrane was produced in the same manner as in Example 1.

[0134] <Manufacture of Electrochemical Element> In Example 1, graphite (a blend of artificial graphite / natural graphite, P20T / LSN-1, Zichen / BTR), an SBR binder (LG Chem, M37), a conductive material (carbon black, Super-C65), and a dispersant (CMC DAICEL 2200, DAICEL Japan) were mixed with water at a weight ratio of 80.3 / 19.7:2.3:1.05:0.5 to prepare a slurry for a negative electrode active material layer with a concentration of 50 wt% of the remaining components excluding water. Next, the slurry was applied to the surface of a copper thin film (thickness 6 μm) and dried to produce a negative electrode having a negative electrode loading of 5.5 mAh / cm 2 An electrochemical element was produced in the same manner as in Example 1, except for this. Specifically, different from Example 1, graphite was used as the negative electrode active material, and an SBR binder (LG Chem, M37) was used instead of the PAM-based binder to produce the negative electrode.

[0135] <Experimental Example 1: Air Permeability of Separation Membrane> The air permeability refers to the time it takes for 100 cc of air to permeate through an object to be measured for air permeability, such as a separation membrane and a porous polymer substrate, and the unit can be seconds (second) / 100 cc. The air permeability can be expressed by a Gurley value or the like. In the present invention, the air permeability was measured in accordance with JIS P8117. <Experimental Example 2: Dry Adhesion Force between Negative Electrode and Separation Membrane> The negative electrodes and separation membranes of the examples and comparative examples prepared by cutting the separation membranes of the examples and comparative examples into 70 mm (length) × 25 mm (width) were laminated using a press under the conditions of 60 °C, 6.5 MPa, and 1 second to prepare test pieces. The prepared test pieces were attached and fixed to a glass plate using double-sided tape, and at this time, the negative electrodes were arranged so as to face the glass plate. The separation membrane portion of the test piece was peeled at an angle of 180° at a speed of 150 mm / min at 25 °C, and the adhesion force of the negative electrodes of the examples and comparative examples at this time was measured.

[0136] <Experimental Example 3: Wet Adhesion Force between Negative Electrode and Separation Membrane> The negative electrodes and separation membranes of the examples and comparative examples prepared by cutting the separation membranes of the examples and comparative examples into 70 mm (length) × 25 mm (width) were laminated using a press under the conditions of 60 °C, 6.5 MPa, and 1 second to prepare test pieces. The prepared test pieces were placed in a battery case together with an electrolytic solution and maintained for 4 hours to impregnate the test pieces with the electrolytic solution. The electrolytic solution used was prepared by mixing ethylene carbonate and ethyl methyl carbonate at a volume ratio of 7:3 and a concentration of LiPF6 1M. Then, after the test pieces were taken out of the case, they were attached and fixed to a glass plate using double-sided tape, and at this time, the negative electrodes were arranged so as to face the glass plate. The separation membrane portion of the test piece was peeled at an angle of 90° at a speed of 200 mm / min at 25 °C, and the adhesion force of the negative electrodes of the examples and comparative examples at this time was measured.

[0137] <Experimental Example 4: Swelling Degree of Electrochemical Element> The electrochemical elements of the examples and comparative examples were laminated to fabricate small full cells of the 2 Ah class. The thickness of each cell thus manufactured in the initial full discharge state was measured with a vernier caliper at 25°C. Thereafter, after performing cycle evaluation at 25°C, the thickness of the cell after 600 cycles was measured to measure the change in the thickness of the cell before and after cycling. When the initial thickness of the cell was T1 and the thickness of the cell after 600 cycles was T2, the swelling degree of the electrochemical element was calculated according to the following formula 1. [Formula 1] Swelling degree (%) = (T2 - T1) / T1 * 100

[0138]

Table 1

[0139] On the other hand, it was confirmed that in Comparative Examples 1 to 3, the PAM-based binder was not contained in the negative electrode or the adhesive layer, and the adhesion force between the negative electrode and the separator decreased rapidly compared to Example 1. Also, the swelling degree of the electrochemical element showed a higher value compared to Example 1.

[0140] In Comparative Example 4, graphite which is not a silicon-based negative electrode active material was used as the negative electrode active material, the PAM-based binder was not contained in the negative electrode, and it was confirmed that the adhesion force between the negative electrode and the separator decreased rapidly compared to Example 1. However, it was confirmed that in Comparative Example 4, by using graphite which does not cause volume expansion accompanying charge and discharge as the negative electrode active material, the swelling degree of the electrochemical element was excellent compared to Example 1.

[0141] Therefore, the separator of the electrochemical device according to an embodiment of the present invention includes an adhesive layer provided between a silicon-based negative electrode and a coating layer. The silicon-based negative electrode and the adhesive layer each contain a polyacrylamide (PAM)-based binder, thereby improving the adhesive force with the silicon-based negative electrode, suppressing the swelling of the electrochemical device to which the silicon-based negative electrode is applied, and improving the stability of the electrochemical device.

Explanation of Symbols

[0142] 100: Separator for Electrochemical Device 110: Porous Polymer Substrate 130: Coating Layer 150: Adhesive Layer

Claims

1. In a separator for an electrochemical element including an adhesive layer provided to face a silicon-based negative electrode, the silicon-based negative electrode includes a silicon-based negative electrode active material and a first polymer binder, the adhesive layer includes a second polymer binder, and each of the first polymer binder and the second polymer binder is a polyacrylamide (PAM)-based binder. A separator for an electrochemical element.

2. The separator for an electrochemical element according to Claim 1, wherein the content of the first polymer binder is 12 parts by weight or less with respect to 100 parts by weight of the silicon-based negative electrode.

3. The separator for an electrochemical element according to Claim 1, wherein the content of the second polymer binder is 50 parts by weight or less with respect to 100 parts by weight of the adhesive layer.

4. The silicon-based negative electrode active material is one or more selected from the group consisting of Si, SiO ｘ (0 < x < 2), Si-Y alloy, and Si-C composite, The separator for an electrochemical element according to Claim 1, wherein Y is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, or a combination thereof, and is not Si.

5. A porous polymer substrate, a coating layer provided on at least one surface of the porous polymer substrate, and an adhesive layer provided between the silicon-based negative electrode and the coating layer, The separator for an electrochemical element according to Claim 1, comprising.

6. The separator for an electrochemical element according to Claim 5, wherein the coating layer includes inorganic particles and a third polymer binder.

7. The separator for an electrochemical element according to Claim 6, wherein the average particle diameter (D50) of the inorganic particles is 0.3 μm or more and 1.0 μm or less.

8. The separator for an electrochemical element according to Claim 6, wherein the third polymer binder is an acrylic-based binder, a polyvinylidene-based binder, or a combination thereof.

9. The separator for an electrochemical element according to Claim 1, wherein the dry adhesive strength of the adhesive layer is 50 gf / 25 mm or more.

10. The separator for an electrochemical element according to Claim 1, wherein the wet adhesive strength of the adhesive layer is 10 gf / 25 mm or more and 30 gf / 25 mm or less.

11. An electrochemical element including a positive electrode, a silicon-based negative electrode, and the separator for an electrochemical element according to any one of Claims 1 to 10 disposed between the positive electrode and the silicon-based negative electrode.

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