Self-supporting ceramic separation membrane for electrochemical devices, and electrochemical device including the same

Abstract

The present invention relates to a self-supporting ceramic separation membrane for an electrochemical element and an electrochemical element including the same. Specifically, by appropriately adjusting the content and arrangement of plate-shaped first inorganic particles and second inorganic particles which are zeolite-based inorganic substances, the heat resistance of the separation membrane is improved, electrical short circuit between electrodes is prevented to improve the safety of the battery, and the present invention relates to a self-supporting ceramic separation membrane for an electrochemical element exhibiting high cell life characteristics and an electrochemical element including the same.

Description

Technical Field

[0001] This application claims the benefit of the filing date of Patent Application No. 10-2023-0051554, filed with the Korean Intellectual Property Office on April 19, 2023, and all of its contents are incorporated herein by reference.

[0002] The present invention relates to a self-supporting ceramic separator for an electrochemical device and an electrochemical device including the same. Specifically, the present invention relates to a self-supporting ceramic separator for an electrochemical device that includes first inorganic particles and second inorganic particles, thereby improving heat resistance and exhibiting high cell life characteristics, 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, includes a polymer substrate having a porous structure, separates the positive electrode and the negative electrode, and serves to prevent an electrical short circuit between the two electrodes and to allow the electrolyte and ions to pass through. Although the separator itself is not involved in the electrochemical reaction, 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 change the physical properties of the coating layer by adding a coating layer to the porous polymer substrate and adding various substances to the coating layer in order to enhance the physical properties of the separator. 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 separator can be adhered to the electrode through a lamination process, and a polymer binder can be added to the coating layer composition of the separator to ensure the adhesive force between the electrode and the separator.

[0006] On the one hand, polyolefin-based resins, which are widely used as porous polymer substrates for electrochemical elements, shrink when exposed to high temperatures, causing the positive and negative electrodes to come into contact, resulting in an electrical short circuit between the two electrodes, heat generation, and thermal runaway due to the decomposition reaction of the electrolyte and the active material.

[0007] Therefore, research on self-supporting ceramic separator membranes that can improve heat resistance and durability, prevent electrical short circuits between electrodes, and improve battery safety and battery life characteristics by appropriately combining inorganic particles without the polyolefin-based resin, which is a porous polymer substrate, was 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 form a plate-like and dense laminated structure to prevent the transition metal eluted from the positive electrode from moving to the negative electrode surface, and to include first inorganic particles and second inorganic particles having a high specific surface area capable of gas adsorption and transition metal adsorption. On the other hand, a self-supporting ceramic separator membrane for an electrochemical element that can improve heat resistance and durability and improve battery stability and battery life characteristics due to the configuration without a porous polymer substrate, and an electrochemical element including the same are provided.

[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 self-supporting ceramic separator membrane for an electrochemical element, which includes first inorganic particles, second inorganic particles, and a polymer binder, wherein the first inorganic particles are plate-like, and the aspect ratio of the first inorganic particles is 10 or more and 300 or less.

[0011] According to one embodiment of the present invention, the separation membrane can be arranged such that one surface of the first inorganic particles faces one surface of the separation membrane.

[0012] According to one embodiment of the present invention, the separation membrane may include a first layer in which the weight of the first inorganic particles is higher than the weight of the second inorganic particles; and a second layer provided on one surface of the first layer, in which the weight of the second inorganic particles is higher than the weight of the first inorganic particles.

[0013] According to one embodiment of the present invention, the opposite surface of one surface of the first layer may be configured to face the negative electrode.

[0014] According to one embodiment of the present invention, the first inorganic particles may include one selected from the group consisting of boron nitride, boehmite, kaolin, and combinations thereof.

[0015] According to one embodiment of the present invention, the second inorganic particles are zeolite-based inorganic substances, the second inorganic particles include voids having a diameter of 0.5 nm or more and 0.9 nm or less, and the voids of the second inorganic particles can be substituted with metal ions.

[0016] According to one embodiment of the present invention, the average particle size (D50) of the second inorganic particles may be 1 μm or less.

[0017] According to one embodiment of the present invention, the thickness of the second layer may be 1 μm or more and 3 μm or less.

[0018] According to one embodiment of the present invention, the content of the first inorganic particles may be 5 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the coating layer.

[0019] According to one embodiment of the present invention, the polymer binder may be an acrylic-based binder, a polyvinylidene-based binder, or a combination thereof.

[0020] According to one embodiment of the present invention, the thickness of the separation membrane may be 7 μm or more and 15 μm or less.

[0021] According to one embodiment of the present invention, the air permeability of the separation membrane can be 170 sec / 100 cc or less.

[0022] According to one embodiment of the present invention, the resistance of the separation membrane can be 0.6 Ω or more and 1.2 Ω or less.

[0023] One embodiment of the present invention provides an electrochemical element including a positive electrode; a negative electrode; and the separation membrane interposed between the positive electrode and the negative electrode.

Effect of the Invention

[0024] The self-supporting ceramic separation membrane for an electrochemical element according to one embodiment of the present invention can suppress thermal shrinkage at high temperatures.

[0025] The self-supporting ceramic separation membrane for an electrochemical element according to one embodiment of the present invention can prevent the transition metal eluted from the positive electrode from moving to the negative electrode side, and can improve the stability of the battery and the battery life characteristics.

Brief Description of the Drawings

[0026]

Figure 1

[0027]

Figure 2

Modes for Carrying Out the Invention

[0028] 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.

[0029] In this specification, "A and / or B" means "A and B, or A or B".

[0030] In this specification, 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.

[0031] In this specification, the property of "having pores" means that a fluid in a gas phase and / or a liquid phase can pass from one side surface to the other side surface of an object through a structure in which the object includes a plurality of pores and the pores are interconnected with each other.

[0032] In this specification, a separation membrane has a porous property including a large number of pores, and serves as a porous ion-conducting barrier that allows ions to pass therethrough while blocking electrical contact between a negative electrode and a positive electrode in an electrochemical device.

[0033] Hereinafter, the present invention will be described in more detail.

[0034] One embodiment of the present invention provides a self-supporting ceramic separation membrane for an electrochemical device, which includes first inorganic particles, second inorganic particles, and a polymer binder, wherein the first inorganic particles are plate-shaped, and the aspect ratio of the first inorganic particles is 10 or more and 300 or less.

[0035] The self-supporting ceramic separation membrane for an electrochemical device according to one embodiment of the present invention can suppress thermal shrinkage at high temperatures. Further, the self-supporting ceramic separation membrane for an electrochemical device according to one embodiment of the present invention can prevent a transition metal eluted from a positive electrode from moving to the negative electrode facing surface, and can improve the stability of the battery and the battery life characteristics.

[0036] FIG. 1 is a schematic view of a self-supporting ceramic separation membrane for an electrochemical element according to an embodiment of the present invention. Referring to FIG. 1, a self-supporting ceramic separation membrane for an electrochemical element according to an embodiment of the present invention will be specifically described. FIG. 2 is a schematic view of an electrochemical element according to an embodiment of the present invention. Referring to FIG. 2, an electrochemical element according to an embodiment of the present invention will be specifically described.

[0037] According to an embodiment of the present invention, the self-supporting ceramic separation membrane 100 for the electrochemical element does not include a porous polymer substrate. Since the self-supporting ceramic separation membrane for the electrochemical element does not include the porous polymer substrate, the heat resistance of the separation membrane can be improved, and it is possible to prevent the separation membrane from shrinking at a high temperature and causing an electrical short circuit between the electrodes.

[0038] According to an embodiment of the present invention, the separation membrane 100 includes first inorganic particles, second inorganic particles, and a polymer binder. As described above, since the separation membrane includes the first inorganic particles, the second inorganic particles, and the polymer binder, the heat resistance of the separation membrane can be improved, and it is possible to prevent the separation membrane from shrinking at a high temperature and causing an electrical short circuit between the electrodes. Further, pores can be formed inside the separation membrane.

[0039] According to an embodiment of the present invention, the separation membrane 100 may include a plurality of pores. Specifically, the separation membrane may be a porous separation membrane including a plurality of pores inside. As described above, since the separation membrane includes a plurality of pores, it is possible to allow lithium ions to pass through and current to flow while physically blocking the negative electrode and the positive electrode.

[0040] According to one embodiment of the present invention, the separation membrane 100 can be formed by inorganic particles being bound by a polymer binder and accumulating within the membrane. The pores inside the separation membrane can be caused by the interstitial volume, which is the free space between the inorganic particles. Specifically, as will be described later, due to differences in the form and combination of the first inorganic particles and the second inorganic particles, there can be differences in the structure and size of the pores. Furthermore, due to the differences in the structure and size of the pores, it is possible to prevent the transition metal eluted from the positive electrode from moving to the negative electrode facing surface.

[0041] According to one embodiment of the present invention, the inorganic particles can include first inorganic particles and second inorganic particles. 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 stannate hydroxide (ZnSn(OH)6), tin-zinc oxide (Zn2SnO4, ZnSnO3), antimony trioxide (Sb2O3), antimony tetroxide (Sb2O4), antimony pentoxide (Sb2O5), zeolite A, zeolite X, zeolite Y, etc., and can include one or more of these. On the other hand, in addition to these, it can include one or more plate-shaped inorganic particles of boron nitride (BN), boehmite, and kaolin.

[0042] According to one embodiment of the present invention, the first inorganic particles are plate-shaped. As described above, since the first inorganic particles are plate-shaped, it is possible to form a dense laminated structure, thereby improving the durability of the separation membrane.

[0043] According to an embodiment of the present invention, the aspect ratio of the first inorganic particles is 10 or more and 300 or less. As described above, the first inorganic particles are plate-shaped inorganic particles, and the aspect ratio can be 10 or more and 300 or less. More specifically, the first inorganic particles are plate-shaped inorganic particles, and the aspect ratio is 20 or more and 290 or less, 30 or more and 280 or less, 40 or more and 270 or less, 50 or more and 260 or less, 60 or more and 250 or less, 70 or more and 240 or less, 80 or more and 230 or less, 90 or more and 220 or less, 100 or more and 210 or less, 110 or more and 200 or less, 120 or more and 190 or less, 130 or more and 180 or less, 140 or more and 170 or less, or 150 or more and 160 or less. In this specification, the aspect ratio can be defined as [length in the major axis direction] / [width in the direction perpendicular to the major axis direction] of the plate-shaped inorganic particles. By adjusting the aspect ratio of the first inorganic particles within the above-described range, the thickness of the coating layer can be made thinner, a dense laminated structure can be formed, and the durability of the separation membrane can be improved.

[0044] According to an embodiment of the present invention, the separation membrane can be arranged such that one surface of the first inorganic particles faces one surface of the separation membrane. As described above, the first inorganic particles are plate-shaped inorganic particles and have a long shape in the major axis direction. Therefore, by arranging them such that the major axis direction faces one surface of the separation membrane to form a dense laminated structure, the durability of the separation membrane can be improved. Also, by forming a complex pore structure, it is possible to suppress the movement of the transition metal eluted from the positive electrode to the opposite surface of the negative electrode.

[0045] According to an embodiment of the present invention, the separation membrane may include a first layer 110 having a higher weight of the first inorganic particles than the weight of the second inorganic particles; and a second layer 130 provided on one surface of the first layer and having a higher weight of the second inorganic particles than the weight of the first inorganic particles. Specifically, the first inorganic particles and the second inorganic particles may be mixed in the first layer and the second layer, but may be laminated separately into a first layer containing the first inorganic particles at a higher weight and a second layer containing the second inorganic particles at a higher weight. As described above, by laminating the first layer and the second layer separately, the second layer adsorbs gas and transition metal, and the first layer prevents the transition metal adsorbed by the second layer from moving to the opposite surface of the negative electrode, thereby suppressing the occurrence of battery short circuit.

[0046] According to an embodiment of the present invention, the opposite surface of one surface of the first layer may be configured to face the negative electrode 300. FIG. 2 is a schematic view of an electrochemical element according to an embodiment of the present invention. Referring to FIG. 2, the separation membrane may be formed by contacting a first layer containing an excessive amount of the first inorganic particles or only the first inorganic particles with the negative electrode. As described above, the second layer is provided on one surface of the first layer, and the opposite surface of one surface of the first layer is configured to face the negative electrode, so that when the transition metal eluted from the positive electrode passes through without being adsorbed by the second layer, it can be prevented from moving to the opposite surface of the negative electrode and the occurrence of battery short circuit can be suppressed.

[0047] According to an embodiment of the present invention, the first inorganic particles may include one selected from the group consisting of boron nitride, boehmite, kaolin, and combinations thereof. As described above, the first inorganic particles may be plate-shaped inorganic particles. Specifically, boron nitride (BN) having a hexagonal crystal structure, boehmite (AlOOH) having a hexagonal crystal structure, kaolin (Al2O 3· 2SiO 2·By including plate-like clay powder such as 2H2O), the first layer containing the first inorganic particles at a higher weight is arranged to face one surface of the separation membrane, and a dense laminated structure can be formed. Further, by forming a complex pore structure formed between the plate-like inorganic particles through the dense laminated structure, it is possible to suppress the transition metal eluted from the positive electrode from passing through the separation membrane and moving to the negative electrode facing surface.

[0048] According to one embodiment of the present invention, the second inorganic particles may be zeolite-based inorganic substances. Specifically, the zeolite-based inorganic substance may include one selected from the group consisting of zeolite A, zeolite X, zeolite Y, zeolite L, ZSM-5, beta-zeolite, ZSM-8, ZSM-11, and combinations thereof. The zeolite-based inorganic substance can have a high specific surface area, and preferably, the zeolite-based inorganic substance may be zeolite Y. As described above, by using a zeolite-based inorganic substance as the second inorganic particles, the ability to adsorb gases and transition metals can be improved.

[0049] According to one embodiment of the present invention, the second inorganic particles may include voids having a diameter of 0.5 nm or more and 0.9 nm or less. Specifically, the second inorganic particles include a space inside the particles, and in the internal space, the diameter may be 0.5 nm or more and 0.9 nm or less. Further, the diameter of the void may mean the longest of the lengths of two points where a straight line passing through the inside of the void intersects the surface of the void. More specifically, the voids of the second inorganic particles may have a diameter of 0.55 nm or more and 0.85 nm or less, 0.6 nm or more and 0.8 nm or less, or 0.65 nm or more and 0.75 nm or less. By adjusting the diameter of the voids within the above-described range, the ability to adsorb gases generated from a lithium-ion battery such as carbon monoxide (CO) or carbon dioxide (CO2) can be improved.

[0050] According to one embodiment of the present invention, the voids of the second inorganic particles can be replaced with metal ions. Specifically, the metal ions can be metal ions having the same or lower electronegativity as lithium ions. More specifically, the metal ions can be alkali metal ions. Preferably, the metal ion can be one selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and combinations thereof. By replacing the voids of the second inorganic particles with the metal ions selected from the above, manganese ions excessively contained in the positive electrode active material are adsorbed, and the replaced lithium ions elute into the electrolytic solution, thereby maintaining the electrical conductivity of the battery and reducing lithium dendrites generated by the accumulation of manganese, which is a transition metal moving from the positive electrode to the negative electrode, on the negative electrode.

[0051] According to one embodiment of the present invention, the average particle diameter (D50) of the second inorganic particles may be 0.3 μm or more and 1 μm or less. Specifically, the average particle diameter (D50) of the second inorganic particles may 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 second inorganic particles within the above-described range, in the slurry for the coating layer, which is an emulsion in which the polymer binder is dispersed in water, the phase separation rate and phase separation efficiency between the polymer binder and the second inorganic particles can be improved. Further, if it is less than 0.3 μm, the dispersibility of the second inorganic particles may decrease in the slurry prepared for the production of the separation membrane, and if it exceeds 1 μm, the thickness of the formed separation membrane may increase.

[0052] As used herein, the "D50 particle size" refers to the particle size at the 50% point of the cumulative distribution of the number of particles according to the particle size. The particle size 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). 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 size can be measured by calculating the particle diameter at the point where the cumulative distribution of the number of particles according to the particle size in the measuring device reaches 50%.

[0053] According to one embodiment of the present invention, the inorganic particles that can be used for the separation membrane may be electrochemically stable. That is, the inorganic particles that can be used in one embodiment of the present invention do not undergo oxidation and / or reduction reactions within the operating voltage range of the applied electrochemical device (for example, 0 V to 5 V based on Li / Li + ).

[0054] According to one embodiment of the present invention, the second layer may have a thickness of 1 μm or more and 3 μm or less. Specifically, the thickness of the second layer may be 1.1 μm or more and 2.9 μm or less, 1.2 μm or more and 2.8 μm or less, 1.3 μm or more and 2.7 μm or less, 1.4 μm or more and 2.6 μm or less, 1.5 μm or more and 2.5 μm or less, 1.6 μm or more and 2.4 μm or less, 1.7 μm or more and 2.3 μm or less, 1.8 μm or more and 2.2 μm or less, or 1.9 μm or more and 2.1 μm or less. As described above, since the average particle size (D50) of the second inorganic particles constituting the second layer is 1 μm or less, the thickness of the second layer can be adjusted within the above-described range.

[0055] According to an embodiment of the present invention, the content of the first inorganic particles may be 5 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the separation membrane. Specifically, the content of the first inorganic particles may be 6 parts by weight or more and 9 parts by weight or less, or 7 parts by weight or more and 8 parts by weight or less with respect to 100 parts by weight of the separation membrane. By adjusting the content of the first inorganic particles within the above-described range, the heat resistance of the separation membrane can be improved, and the durability of the coating layer can be improved.

[0056] According to an embodiment of the present invention, the content of the second inorganic particles may be 5 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the separation membrane. Specifically, the content of the second inorganic particles may be 6 parts by weight or more and 9 parts by weight or less, or 7 parts by weight or more and 8 parts by weight or less with respect to 100 parts by weight of the separation membrane. By adjusting the content of the second inorganic particles within the above-described range, the heat resistance of the separation membrane can be improved, and the adsorption rate of the gas and the transition metal can be improved.

[0057] According to an embodiment of the present invention, the content of the polymer binder may be 5 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the separation membrane. Specifically, the content of the polymer binder may be 6 parts by weight or more and 9 parts by weight or less, or 7 parts by weight or more and 8 parts by weight or less with respect to 100 parts by weight of the separation membrane. By adjusting the content of the 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 the activation of the battery.

[0058] According to an embodiment of the present invention, the polymer binder may be particulate or non-particulate. Specifically, as described later, the polymer binder may maintain a particulate shape without being dissolved by a dispersion medium or a solvent, or the polymer binder may be dissolved in a dispersion medium or a solvent and not maintain a particulate shape. As described above, by selecting the polymer binder to be particulate or non-particulate, the mechanical properties and porosity of the coating layer can be adjusted.

[0059] According to one embodiment of the present invention, the average particle size (D50) of the particulate polymer binder is 1.0 μm or less. Specifically, the average particle size (D50) of the particulate polymer binder particles may 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, 0.30 μm or more and 0.60 μm or less, 0.35 μm or more and 0.55 μm or less, or 0.40 μm or more and 0.50 μm or less. By adjusting the average particle size (D50) of the particulate polymer binder within the above-described range, in the inorganic slurry which is an emulsion in which the particulate polymer binder is dispersed in water, the phase separation rate and phase separation efficiency between the particulate polymer binder and the inorganic particles can be improved.

[0060] According to one embodiment of the present invention, the polymer binder may be an acrylic binder, a polyvinylidene binder, or a combination thereof.

[0061] According to one embodiment of the present invention, the polymer binder may include two or more kinds of polymer binders. As described above, by including two or more kinds of polymer binders in the polymer binder, the adhesive force of the separation membrane can be improved, the porosity of the separation membrane can be improved, the dry adhesive force in the state before injecting the electrolyte, and the wet adhesive force after injecting the electrolyte can be improved simultaneously.

[0062] According to one embodiment of the present invention, the polymer binder may include an acrylic binder. By using the acrylic binder, the porosity of the separation membrane can be maintained, the adhesive force between the electrode and the separation membrane can be improved in the lamination process of the battery, the ease of battery manufacturing can be improved, and the stacking process can be stably realized.

[0063] According to one embodiment of the present invention, the acrylic binder is a polymer containing a carboxylic acid ester as a repeating unit, and preferably may be a (meth)acrylic acid ester or an acrylic-styrene copolymer.

[0064] 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, 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, diethyl 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.

[0065] 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-based. 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-based polymers. Specifically, it may be a copolymer containing acrylate.

[0066] According to one embodiment of the present invention, the polymer binder may include 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 polymer binder 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 binding of the separation membrane can be prevented.

[0067] 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 from the manufacturing process of the separation membrane can be minimized, and the manufacturing cost of the battery can be reduced.

[0068] According to an embodiment of the present invention, the polyvinylidene-based 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 second polymer binder particles to be a polyvinylidene-based binder 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 the adhesive strength can be maintained even when the coating layer is wetted by the electrolytic solution after activation of the battery.

[0069] According to an embodiment of the present invention, the thickness of the separation membrane may be 7 μm or more and 15 μm or less, but is not particularly limited thereto. Specifically, the thickness of the separation membrane may be 8 μm or more and 14 μm or less, 9 μm or more and 13 μm or less, or 10 μm or more and 12 μm or less. The thickness can be adjusted by those skilled in the art within an appropriate range from the aspects of heat resistance and electrical resistance. As described above, since the plate-shaped first inorganic particles constituting the separation membrane are arranged so as to face one surface of the separation membrane to form a dense laminated structure, and the average particle diameter (D50) of the second inorganic particles is 1 μm or less, the thickness of the separation membrane can be adjusted within the above-described range to an appropriate range.

[0070] According to an embodiment of the present invention, the thickness of the second layer and / or the separation membrane, etc. 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.

[0071] According to an embodiment of the present invention, the air permeability of the separation membrane may be 170 sec / 100 cc or less. Specifically, the air permeability of the separation membrane may be 100 sec / 100 cc or more and 170 sec / 100 cc or less, 110 sec / 100 cc or more and 160 sec / 100 cc or less, 120 sec / 100 cc or more and 150 sec / 100 cc or less, or 130 sec / 100 cc or more and 140 sec / 100 cc or less. As described above, since the inorganic particles are plate-shaped or have a small average particle diameter (D50), it can be confirmed that the air permeability is excellent.

[0072] According to one embodiment of the present invention, the resistance of the separation membrane may be 0.6 Ω or more and 1.2 Ω or less. Specifically, the resistance of the separation membrane may be 0.7 Ω or more and 1.1 Ω or less, or 0.8 Ω or more and 1.0 Ω or less. As described above, since the inorganic particles are plate-shaped or have a small average particle size (D50), it is considered that the resistance value of the separation membrane appears low.

[0073] According to one embodiment of the present invention, the breakdown voltage of the separation membrane can be 3700 V or more. Specifically, the breakdown voltage of the separation membrane can be 3700 V or more and 5000 V or less, 3800 V or more and 4900 V or less, 3900 V or more and 4800 V or less, 4000 V or more and 4700 V or less, 4100 V or more and 4600 V or less, 4200 V or more and 4500 V or less, or 4300 V or more and 4400 V or less. As described above, since the inorganic particles are plate-shaped or have a small average particle size (D50), it can be seen that the breakdown voltage of the separation membrane appears high and the withstand voltage characteristics are excellent.

[0074] According to one embodiment of the present invention, the porosity of the separation membrane may be 30% by volume or more. Specifically, the porosity of the separation membrane may 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 separation membrane 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 opening ratio does not become too high, which is 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.

[0075] 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.

[0076] 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 separation membrane from the volume calculated in the thickness, width, and length of the separation membrane.

[0077] In one embodiment of the present invention, the porosity and pore size of the separation membrane 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 (Porosimetry analyzer; Bell Japan Inc, Belsorp-II mini). At this time, it may be advantageous to use a capillary flow porometer.

[0078] According to one embodiment of the present invention, the method for forming the separation membrane is, for example, as follows. First, a polymer solution or polymer emulsion in which a polymer binder is dissolved in a suitable solvent or dispersed in a dispersion medium is produced. As the solvent or dispersion medium, it is preferable that the solubility index is similar to the polymer binder to be used and the boiling point is low. This is to facilitate uniform mixing and subsequent removal of the solvent or dispersion medium. Non-limiting examples of solvents or dispersion media that can be used include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (NMP), cyclohexane, water, or mixtures thereof.

[0079] Next, first inorganic particles are added to and dispersed in the produced first polymer solution or first polymer emulsion to produce a first inorganic slurry. According to one embodiment of the present invention, the content ratio of the first inorganic particles to the polymer binder is as described above, and is appropriately adjusted in consideration of the thickness, pore size, and porosity of the separation membrane of the present invention finally produced.

[0080] Next, the first inorganic slurry produced above is applied to at least one side surface of the prepared PET release film and dried. The method of applying the first inorganic slurry to the surface of the PET release film is not particularly limited to any one method, and a normal 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.

[0081] Next, second inorganic particles are added to and dispersed in the second polymer solution or second polymer emulsion produced in the same manner to produce a second inorganic slurry. According to one embodiment of the present invention, the content ratio of the second inorganic particles to the polymer binder is as described above, and is appropriately adjusted in consideration of the thickness, pore size, and porosity of the separation membrane of the present invention finally produced.

[0082] Next, the second inorganic slurry produced above is applied to and dried on the first layer containing the first inorganic particles applied above. The method of applying the second inorganic slurry to the surface of the first layer is not particularly limited to any one method, and a normal 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.

[0083] In order to minimize the generation of surface defects of the separation membrane, the drying process appropriately sets the conditions of temperature and time. For the drying, drying auxiliary devices such as a drying oven or hot air can be used within an appropriate range.

[0084] After the drying process, the PET release film can be removed to manufacture the separation membrane.

[0085] According to an embodiment of the present invention, a polymer binder, namely, a first polymer binder and a second polymer binder, are dispersed in water, which is an appropriate dispersion medium together with a wetting agent, to produce a polymer emulsion, and a first and / or a second inorganic slurry can be provided. The wetting agent is one or more wetting agents in an amount of 0 to 5 parts, preferably 0 to 3 parts, per 100 parts of water, and may be present in the first and / or second inorganic slurry. A surfactant can be provided as a wetting agent, but the wetting agent can also include non-surfactants. In some embodiments, the wetting agent can be an organic solvent. When any wetting agent is present, (a plurality of) powder materials are uniformly dispersed in an aqueous dispersion of a polyvinylidene-based binder. Useful wetting agents include, but are not limited to, ionic and non-ionic surfactants, such as TRITON series (Dow) and PLURONIC series (BASF), BYK-346 (BYK Additives), and NMP, DMSO, and acetone, and include, but are not limited to, organic liquids compatible with the aqueous dispersion. As described above, by dispersing a polymer binder together with a wetting agent in water, which is an appropriate dispersion medium, to produce a polymer emulsion and providing a first and / or a second inorganic slurry, contaminants generated during the manufacturing process can be minimized.

[0086] According to an embodiment of the present invention, the separation membrane 100 is interposed between the negative electrode 300 and the positive electrode 500, and is manufactured as 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 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.

[0087] An embodiment of the present invention provides an electrochemical element including a positive electrode 500, a negative electrode 300, and a separation membrane 100 interposed between the positive electrode and the negative electrode.

[0088] The electrochemical element according to an embodiment of the present invention forms a plate-like and dense laminated structure, and includes first inorganic particles capable of preventing transition metals eluted from the positive electrode from moving to the negative electrode facing surface, and second inorganic particles having a high specific surface area and capable of gas adsorption and transition metal adsorption. However, by including a separation membrane without a porous polymer substrate, heat resistance and durability are improved, and battery stability and battery life characteristics can be improved.

[0089] 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 means a lithium secondary battery, a nickel-cadmium battery, a nickel-metal hydride battery, etc., which can be charged and discharged. Examples of the lithium secondary battery include, but are not limited to, a non-aqueous electrolyte secondary battery containing a liquid electrolyte, an all-solid battery containing a solid electrolyte, a lithium polymer battery containing a gel polymer electrolyte, and a lithium metal battery using lithium metal as a negative electrode. Battery).

[0090] According to one embodiment of the present invention, the positive electrode includes a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material, a conductive material, and a binder resin on at least one surface of the current collector. The positive electrode active material 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 Li in the chemical formula is substituted with alkaline earth metal ions; disulfide compounds; one or more mixtures of Fe2(MoO4)3 may be included.

[0091] According to one embodiment of the present invention, the negative electrode includes a negative electrode current collector and a negative electrode active material layer containing a negative electrode active material, a conductive material, and a binder resin on at least one surface of the current collector. The negative electrode uses, as the negative electrode active material, 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 zMetal composite oxides such as (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.; 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; and one or more mixtures selected from titanium oxides may be included.

[0092] 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 of the 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.

[0093] According to one 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 those obtained by surface treatment with carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel can be used.

[0094] According to one embodiment of the present invention, as the binder resin, a polymer that is usually used for electrodes in the art can be used. Non-limiting examples of such binder resins 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 is not limited thereto.

[0095] 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, ADC-01, LG Chem).

[0096] According to one embodiment of the present invention, the content of the dispersant contained in the positive electrode slurry may be more than 0 part by weight and 0.5 part 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 part by weight and 0.4 part by weight or less with respect to 100 parts by weight of the positive electrode slurry.

[0097] 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 polypyrrolidone-based compound. Specifically, the dispersant may be polyvinylpyrrolidone (Polyvinylpyrrolidone, Junsei).

[0098] According to one embodiment of the present invention, the content of the dispersant contained in the negative electrode slurry may be more than 0 part by weight and 0.5 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 more than 0.05 part by weight and 0.4 part by weight or less with respect to 100 parts by weight of the negative electrode slurry.

[0099] According to one embodiment of the present invention, the electrochemical element prepared as described above can be housed in a suitable case and filled with an electrolytic solution to manufacture a battery.

[0100] 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 composed of combinations thereof, are dissolved or dissociated in an organic solvent composed 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.

[0101] 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-powered motors; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), etc.; electric two-wheel vehicles including electric bicycles (E-bikes) and electric scooters (E-scooters); electric golf carts; power storage systems, etc., but are not limited thereto.

Example

[0102] 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.

[0103] <Example 1> As the first inorganic particles in the form of a plate, synthesized hexagonal boron nitride (hBN, hexagonal Boron Nitride) with an aspect ratio of 50 and polyacrylic acid (PAA), a dispersant, were put into NMP (N-Methyl-2-pyrrolidone), a solvent, and dispersed with a sonicator for about 30 minutes to prepare an oil-based slurry.

[0104] As a polymer binder, a first polymer binder solution containing an acrylic aqueous dispersion emulsion (Toyo ink, CSB130) and a surfactant (FC-4430, Kemis) was added to the oil-based slurry and dispersed with a sonicator for about 30 minutes to prepare a first inorganic slurry.

[0105] Thereafter, the first inorganic slurry was applied to one side of a PET release film and dried. The weight ratio of the first inorganic particles to the polymer binder was 9:1.

[0106] As the second inorganic particles, zeolite Y (SAR, silicon / aluminum ratio 1.5 or more) was put into water and dispersed, and basket milling was performed at 1400 rpm and 1800 rpm for 10 minutes and 50 minutes respectively to reduce the particle size (D50: 1 μm or less) to prepare an aqueous slurry.

[0107] As a second polymer binder solution, an acrylic aqueous dispersion emulsion (Toyo Ink Co., Ltd., CSB140) and a surfactant (BYK Co., Ltd., BYK348) were added to the aqueous slurry one hour before coating. After sonication for 30 minutes, a second inorganic slurry was prepared.

[0108] Then, the second inorganic slurry was applied to the surface of the first layer containing the first inorganic particles and dried. The weight ratio of the second inorganic particles to the polymer binder was 92:8.

[0109] Using a doctor blade, the dispersion was applied to the surface of the second layer containing the second inorganic particles by the bar coating method, and dried with a heat gun at 50°C.

[0110] After that, the PET release film was removed to produce a separation membrane with a total thickness of 13 μm.

[0111] <Example 2> A separation membrane was produced in the same manner as in Example 1, except that the aspect ratio of the first inorganic particles in the form of a plate was 200.

[0112] <Comparative Example 1> A 14-μm-thick separation membrane was produced in the same manner as in Example 1, except that in Example 1, without the first layer containing the first inorganic particles in the form of a plate, zeolite Y, which is the second inorganic particle, was added to form one layer.

[0113] <Comparative Example 2> An 11-μm-thick separation membrane was produced in the same manner as in Example 1, except that in Example 1, without the second layer containing the second inorganic particles, hexagonal boron nitride (hBN), which is the first inorganic particle in the form of a plate, was added to form one layer.

[0114] <Comparative Example 3> In Example 1, a separation membrane with a thickness of 14 μm was produced in the same manner as in Example 1, except that the aspect ratio of the first inorganic particles in the plate shape was less than 10.

[0115] <Comparative Example 4> In Example 1, a separation membrane with a thickness of 12 μm was produced in the same manner as in Example 1, except that the aspect ratio of the first inorganic particles in the plate shape exceeded 300.

[0116] <Manufacture of Electrochemical Element> 1) Manufacture of Positive Electrode A positive electrode active material (LiNi 0.8 Mn 0.1 Co 0.1 O2), a conductive material (carbon black), a dispersant (N-methylpyrrolidone, ADC-01, LG Chem), and a binder resin (a mixture of PVDF-HFP and PVDF) were mixed with water at a weight ratio of 97.5:0.7:0.14:1.66 to prepare a slurry for a positive electrode active material layer with a concentration of 50 wt% of the remaining components excluding water. Next, the slurry was applied to the surface of an aluminum thin film (thickness 10 μm) and dried to produce a positive electrode having a positive electrode active material layer (thickness 120 μm).

[0117] 2) Manufacture of Negative Electrode Graphite (a blend of natural graphite and artificial graphite), a conductive material (carbon black), a dispersant (Polyvinylpyrrolidone, Junsei), and a binder resin (a mixture of PVDF-HFP and PVDF) were mixed with water at a weight ratio of 97.5:0.7:0.14:1.66 to prepare a slurry for a negative electrode active material layer 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 produce a negative electrode having a negative electrode active material layer (thickness 120 μm).

[0118] 3) Lamination Process The fabricated negative electrode and positive electrode were laminated with the separator membranes of the examples and comparative examples interposed therebetween, and a lamination process was performed to obtain an electrode assembly. The lamination process was carried out for 10 seconds under the conditions of 70 °C and 5.2 MPa using hot pressing.

[0119] <Experimental Example 1: Air Permeability of Separator Membrane> The air permeability (air permeability time, Gurley) of the separator membranes of the examples and comparative examples was measured by the ASTM D-2873 method. The Gurley value was measured using a Gurley type densometer (No. 158) manufactured by Toyoseiki Co., Ltd. in accordance with the Gurley (JIS Gurley) measurement method of Japanese Industrial Standards. The air permeability value was represented by the time (seconds) required for 100 ml of air to pass through a cross-section of 1 in of the separator membrane under a pressure of 12.2 in H2O, that is, the air permeability time. 2 That is, it was represented by the air permeability time.

[0120] <Experimental Example 2: Resistance of Separator Membrane> The separator membranes of the examples and comparative examples were interposed between SUS to manufacture coin cells. As the electrolytic solution of the coin cells, ethylene carbonate: ethyl methyl carbonate was mixed at a volume ratio of 1:2, and LiPF6 was added at a concentration of 1 M. For each coin cell, using an analyzer (VMP3, Bio logic science instrument), the resistance was measured through the results of electrochemical impedance spectroscopy under the conditions of 25 °C, an amplitude of 10 mV, and a scan range of 0.1 hz to 1 Mhz.

[0121] <Experimental Example 3: Dielectric Breakdown Voltage of Separator Membrane> The prepared separator membrane samples of the examples and comparative examples were placed between aluminum fixtures (the diameter of the upper fixture is 30 mm, and the lower fixture is 50 × 100 mm), and the voltage at which a short circuit occurs was measured with a hi-pot tester. At this time, the measurement conditions were set to DC, a current of 0.5 mA, and a voltage increase of 100 V / s (up to 3 kV).

[0122] <Experimental Example 4: Performance Retention Rate of Electrochemical Element> To evaluate the lifespan of the electrochemical elements manufactured including the separation membranes of the Examples and Comparative Examples, each electrochemical element was charged to 4.35 V at 0.33 C and discharged to 2.0 V at 0.33 C, and this process was repeated 500 cycles, and the initial capacity and the remaining capacity were measured.

[0123] <Experimental Example 5: Gas Generation Amount of Electrochemical Element> To measure the gas generation amount of the electrochemical elements manufactured including the separation membranes of the Examples and Comparative Examples, while each electrochemical element was charged and discharged once under the conditions of 0.1 C / 0.1 C at 25 °C for formation, the generated gas amount was measured. To measure the gas generation amount of the deteriorated cell, after the cell evaluated up to 500 cycles as in Experimental Example 4 was completely discharged to 2.0 V at 0.33 C, the gas amount was measured.

[0124] <Experimental Example 6: Transition Metal Elution Amount of Electrochemical Element> To measure the elution amount of the negative electrode transition metal of the electrochemical elements manufactured including the separation membranes of the Examples and Comparative Examples, after formation was performed at SOC 30%, discharging was carried out under the conditions of a discharging current density of 0.33 C and a discharging voltage of 2.0 V, and a charge-discharge test of charging under the conditions of a charging current density of 0.33 C, a charging voltage of 4.35 V, and CC-CV (Constant Current-Constant Voltage) was carried out 500 times. After the 500-cycle test, the amount of the transition metal eluted on the negative electrode facing surface was measured.

[0125]

Table 1

[0126] Referring to Table 1 above, in Examples 1 and 2 according to an embodiment of the present invention, there were also cases where by-products that could not be adsorbed by the functional inorganic particles in the second layer could not reach the negative electrode facing surface even through the plate-like inorganic layer which is the first layer. As a result, a significantly decreased elution amount of transition metal was confirmed on the negative electrode facing surface of the electrochemical device deteriorated after 500 cycles of discharge. The maintenance rate of the performance of the electrochemical device improved with the same effect and a decreased gas generation amount were also confirmed.

[0127] On the other hand, Comparative Example 1 is a self-supporting ceramic separation membrane composed only of second inorganic particles capable of adsorbing by-products generated during the deterioration of the electrochemical device. On the negative electrode facing surface of the electrochemical device deteriorated after 500 cycles of discharge, it shows a result that the elution amount of transition metal decreased compared with a general separation membrane. Comparative Example 2 is a separation membrane composed only of plate-like inorganic particles which are first inorganic particles, and denser inorganic assembly is possible. It was expected that by complicating the path of transition metal ions, the by-products accumulated on the negative electrode facing surface would decrease. However, it is at a level inferior to Comparative Example 1. When the value of the aspect ratio of the plate-like inorganic particles is too low (AR < 10) as in Comparative Example 3, the effects that can be expected by using the plate-like inorganic particles become insufficient, and it shows inferior properties in terms of the elution amount of transition metal on the negative electrode facing surface, the maintenance rate of the performance of the electrochemical device, and the gas generation amount. When the value of the aspect ratio of the plate-like inorganic particles is too large (AR > 300) as in Comparative Example 4, the property that the plate-like inorganic particles interfere with the durability of the separation membrane becomes stronger, the breakdown voltage becomes extremely low, and it was confirmed that the maintenance rate of the performance of the electrochemical device is also at a low level.

[0128] The self-supporting ceramic separation membrane for an electrochemical device according to an embodiment of the present invention includes functional inorganic substances and plate-like inorganic substances, thereby preventing gas adsorption and the accumulation of by-products on the negative electrode facing surface during the deterioration of the electrochemical device, and it is possible to expect an improvement in the performance of the electrochemical device.

Explanation of Reference Numerals

[0129] 100: Self-supporting ceramic separation membrane for an electrochemical device 110: Layer 1 130: Layer 2 300: Negative electrode 500: Positive electrode

Claims

1. An independent ceramic separator for an electrochemical device, comprising a first inorganic particle, a second inorganic particle, and a polymer binder, wherein the first inorganic particle is plate-shaped, and an aspect ratio of the first inorganic particle is 10 or more and 300 or less.

2. The independent ceramic separator for an electrochemical device according to claim 1, wherein one surface of the first inorganic particle and one surface of the separator are arranged to face each other.

3. A first layer in which a weight of the first inorganic particle is higher than a weight of the second inorganic particle, and a second layer provided on one surface of the first layer, wherein the weight of the second inorganic particle is higher than the weight of the first inorganic particle, wherein the independent ceramic separator for an electrochemical device according to claim 1 includes the first layer and the second layer.

4. The independent ceramic separator for an electrochemical device according to claim 3, wherein an opposite surface of one surface of the first layer is configured to face a negative electrode.

5. The independent ceramic separator for an electrochemical device according to claim 1, wherein the first inorganic particle includes one selected from the group consisting of boron nitride, boehmite, kaolin, and combinations thereof.

6. The second inorganic particle is a zeolite-based inorganic material, and the second inorganic particle includes voids having a diameter of 0.5 nm or more and 0.9 nm or less, wherein the voids of the second inorganic particle are substituted with metal ions.

7. The independent ceramic separator for an electrochemical device according to claim 1, wherein an average particle diameter (D50) of the second inorganic particle is 1 µm or less.

8. The independent ceramic separator for an electrochemical device according to claim 3, wherein a thickness of the second layer is 1 µm or more and 3 µm or less.

9. The independent ceramic separator for an electrochemical device according to claim 1, wherein a content of the first inorganic particle is 5 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the separator.

10. The independent ceramic separator for an electrochemical device according to claim 1, wherein the polymer binder is an acrylic binder, a polyvinylidene binder, or a combination thereof.

11. The independent ceramic separator for an electrochemical device according to claim 1, wherein a thickness of the separator is 7 µm or more and 15 µm or less.

12. The air permeability of the separation membrane is 170 sec / 100 cc or less. The self-supporting ceramic separation membrane for an electrochemical element according to claim 1.

13. The resistance of the separation membrane is 0.6 Ω or more and 1.2 Ω or less. The self-supporting ceramic separation membrane for an electrochemical element according to claim 1.

14. An electrochemical element including a positive electrode, a negative electrode, and the separation membrane according to any one of claims 1 to 13 interposed between the positive electrode and the negative electrode.

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