Separation membrane for electrochemical elements and electrochemical elements equipped therewith

Abstract

The present invention relates to a separator for an electrochemical device, comprising a porous polymer substrate and a porous coating layer formed on at least one surface of the porous polymer substrate, the porous coating layer comprising a water-based polymer binder, inorganic particles and an organic filler, the organic filler having an adhesive force within a temperature range in which the electrochemical device is used.

Description

[Technical Field]

[0001] This invention claims the interests of the applicant of Korean Patent Application No. 10-2022-0093927, filed with the Korean Intellectual Property Office on July 28, 2022, and all of its contents are included in this invention.

[0002] The present invention relates to a separation membrane for an electrochemical element and an electrochemical element equipped therewith, and more particularly to a separation membrane that is dimensionally stable in an electrolyte-impregnated state and at high temperatures. [Background technology]

[0003] Electrochemical devices convert chemical energy into electrical energy using electrochemical reactions. In recent years, lithium-ion batteries, which have high energy density and voltage, long cycle life, and can be used in various fields, have become widely used.

[0004] A lithium secondary battery may include an electrode assembly manufactured from a positive electrode, a negative electrode, and a separator membrane placed between the positive and negative electrodes, wherein the electrode assembly may be manufactured housed in a case together with an electrolyte. The separator membrane is placed between the positive and negative electrodes to insulate them, and a porous coating layer containing a polymer binder and inorganic particles may be included on at least one surface of a porous polymer substrate. The inorganic particles can be linked with other inorganic particles by the polymer binder to form an interstitial volume, through which lithium ions can move. In addition to fixing the inorganic particles, the polymer binder can provide adhesion to the porous coating layer, which can adhere to the porous polymer substrate and the electrodes, respectively.

[0005] The porous coating layer containing a polymer binder and inorganic particles can prevent the thermal shrinkage of the porous polymer substrate, and the separation membrane including the porous coating layer exhibits excellent dimensional stability in a dry state without an electrolyte. However, in a wet state where the separation membrane is impregnated with an electrolyte, the polymer binder may swell due to the electrolyte, or the separation membrane may be exposed to a high temperature of about 130 °C or higher according to the operation of the lithium secondary battery including the separation membrane, which may reduce the adhesive force of the polymer binder. In such a high-temperature wet state, the adhesive force of the porous coating layer becomes low, and the separation membrane shrinks significantly. In particular, in a cylindrical battery in which the electrode assembly is wound and inserted into a case under tension applied to the electrode assembly, the adhesive force between the electrode and the separation membrane is relatively low, so the content of the polymer binder is low, and there is a problem that the dimensional stability in the wet state becomes lower.

[0006] Therefore, research has been conducted on a separation membrane for ensuring dimensional stability under high-temperature and wet-state conditions while keeping the content of the polymer binder in the porous coating layer relatively low.

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide a separation membrane for an electrochemical device with a reduced dimensional change rate in a high-temperature wet state.

Means for Solving the Problems

[0008] One aspect of the present invention is a separation membrane for an electrochemical device including a porous polymer substrate and a porous coating layer formed on at least one surface of the porous polymer substrate, wherein the porous coating layer includes an aqueous polymer binder, inorganic particles, and an organic filler, and the organic filler generates an adhesive force within the operating temperature range of the electrochemical device.

[0009] The aqueous polymer binder may be one or more selected from the group consisting of styrene-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, and acrylate-containing polymers.

[0010] The inorganic particles are Li3PO4, Li x Ti y (PO4)3 (0 < x < 2, 0 < y < 3), Li x Al y Ti z (PO4)3 (0 < x < 2, 0 < y < 1, 0 < z < 3), Li x La y TiO3 (0 < x < 2, 0 < y < 3), Li x Ge y P z S w (0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), Li x N y (0 < x < 4, 0 < y < 2), Li x Si y S z (0 < x < 3, 0 < y < 2, 0 < z < 4), Li x P y S z (0 < x < 3, 0 < y < 3, 0 < z < 7), Li7La3Zr2O 12 , BaTiO3, BaSO4, 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), HfO2, Sb2O3, Sb2O4, Sb2O5, SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, Zn2SnO4, ZnSnO3, ZnSn(OH)6, ZrO2, Y2O3, SiO2, Al2O3, AlOOH, Al(OH)3, SiC, TiO2, H3BO3 and HBO2, and may be one or more selected from the group.

[0011] The average particle size of the organic filler may be smaller than the average particle size of the inorganic particles.

[0012] The organic filler may have an average particle size (D50) of 50 nm to 500 nm.

[0013] The glass transition temperature of the organic filler may be higher than that of the aqueous polymer binder.

[0014] The operating temperature range of the electrochemical element is 90°C to 130°C, and the glass transition temperature of the organic filler may fall within this operating temperature range.

[0015] The organic filler may be one or more selected from the group consisting of polyurethane, polyethylene, polypropylene, polystyrene, ethylene vinyl alcohol, and polyester.

[0016] The porous coating layer may contain the inorganic particles and the organic filler in a weight ratio of 5:1 to 35:1.

[0017] The porous coating layer may have a higher content of the organic filler than the content of the aqueous polymer binder.

[0018] The porous coating layer may contain 1% to 5% by weight of the aqueous polymer binder relative to the total weight of the porous coating layer.

[0019] The porous coating layer is formed by applying and drying a slurry containing the aqueous polymer binder, inorganic particles, organic filler, and dispersion medium onto the porous polymer substrate, and the slurry may have a solid content of 20% to 50% by weight.

[0020] The porous coating layer may have an air permeability of 100s / 100cc to 150s / 100cc.

[0021] A concentration gradient of the organic filler can be formed across the cross-section of the porous coating layer.

[0022] The organic filler may be present in a larger quantity on the side of the porous polymer substrate opposite the porous polymer substrate than on the surface of the porous coating layer facing the porous polymer substrate.

[0023] Another aspect of the present invention provides an electrochemical element comprising a positive electrode, a negative electrode, and a separation membrane disposed between the positive electrode and the negative electrode, wherein the separation membrane may be a separation membrane for an electrochemical element according to one aspect of the present invention.

[0024] When the separation membrane is impregnated in the electrolyte, its adhesive force to the positive electrode or the negative electrode can be 1 gf / 20 mm to 20 gf / 20 mm.

[0025] The separation membrane may have a shrinkage rate of 5% or less in the TD direction when impregnated with the electrolyte and at 130°C to 180°C.

[0026] The electrochemical element may be a lithium secondary battery. [Effects of the Invention]

[0027] The separation membrane for electrochemical elements according to the present invention provides excellent adhesion to electrodes even in a wet state impregnated with an electrolyte, by incorporating an organic filler into the porous coating layer.

[0028] Furthermore, the present invention provides a separation membrane for electrochemical elements that exhibits excellent dimensional stability in a high-temperature wet state. [Modes for carrying out the invention]

[0029] The following describes in more detail each component of the present invention so that it can be easily implemented by a person with ordinary skill in the art to which the present invention belongs. However, this is merely an example, and the scope of the rights of the present invention is not limited to the following.

[0030] As used herein, the term “including” is used to enumerate useful materials, compositions, apparatus, and methods in the present invention, and is not limited to the examples listed.

[0031] As used herein, “about” and “substantially” are used to mean within or near the range of numerical values ​​or degrees, taking into account inherent manufacturing and material tolerances, and are used to prevent infringers from unfairly exploiting disclosures that refer to precise or absolute numerical values ​​provided to aid in understanding the invention.

[0032] As used herein, "electrochemical elements" may refer to primary batteries, secondary batteries, supercapacitors, and the like.

[0033] As used herein, "particle size" means D50, which is the particle size that accounts for 50% of the cumulative distribution of particle numbers by particle size, unless otherwise specified.

[0034] One embodiment of the present invention provides a separation membrane for an electrochemical element, comprising a porous polymer substrate and a porous coating layer formed on at least one surface of the porous substrate. The porous coating layer comprises a water-based polymer binder, inorganic particles, and an organic filler, wherein the organic filler can generate adhesive force within the operating temperature range of the electrochemical element.

[0035] The porous polymer substrate provides pores that allow lithium ions to pass through while electrically insulating the positive and negative electrodes to prevent short circuits. The porous polymer substrate can be resistant to the electrolyte of an electrochemical element, which is an organic solvent. For example, the porous polymer substrate may include, but is not limited to, polymer resins such as polyethylene, polypropylene, polybutene and other polyolefins, polyvinyl chloride, polyethylene terephthalate, polycycloolefin, polyethersulfone, polyamide, polyimide, polyimidamide, polyaramid, polycycloolefin, nylon, polytetrafluoroethylene, and copolymers or mixtures thereof. Preferably, the porous polymer substrate contains a polyolefin polymer, which may be advantageous for slurry application for forming a porous coating layer and for producing thin separation films.

[0036] The thickness of the porous polymer substrate can be 1 μm to 100 μm. Specifically, the thickness of the porous polymer substrate can be 10 μm to 90 μm, 20 μm to 80 μm, 30 μm to 70 μm, or 40 μm to 60 μm. Preferably, it can be 1 μm to 30 μm, more preferably 15 μm to 30 μm, or 8 μm to 13 μm. By adjusting the thickness of the porous polymer substrate within the above range, it is possible to minimize the volume of the electrochemical element while electrically insulating the positive and negative electrodes, thereby increasing the amount of active material contained in the electrochemical element.

[0037] The porous polymer substrate may contain pores with an average diameter of 0.01 μm to 10 μm. Specifically, the size of the pores in the porous polymer substrate may be 1 μm to 9 μm, 2 μm to 8 μm, 3 μm to 7 μm, or 4 μm to 6 μm. By adjusting the size of the pores in the porous polymer substrate within the aforementioned ranges, a coating slurry containing inorganic particles, organic fillers, and an aqueous polymer binder can be uniformly coated, and the permeability and ionic conductivity of the entire separation membrane produced can be adjusted.

[0038] A slurry can be applied to at least one surface of the porous polymer substrate and dried to form a porous coating layer, which will be described later. The slurry may contain inorganic particles, a polymer binder, a dispersion medium, and the like. To improve the impregnation of the electrolyte before applying the slurry, the porous polymer substrate may be subjected to surface treatments such as plasma treatment or corona discharge.

[0039] The separation membrane for the electrochemical element may include the porous polymer substrate and a porous coating layer formed on at least one surface of the porous polymer substrate. The porous coating layer may include a water-based polymer binder, inorganic particles, and an organic filler. A porous coating layer can be formed by applying and drying a slurry containing a water-based polymer binder, inorganic particles, and an organic filler to at least one surface of the porous polymer substrate.

[0040] The porous coating layer may include inorganic particles to improve the mechanical properties and insulating properties of the porous polymer substrate, and a polymer binder to improve the adhesion between the electrode and the separation membrane. The polymer binder can bind adjacent inorganic particles together and maintain the binding. The inorganic particles can bind to adjacent inorganic particles to provide an interstitial volume, which is a void between the inorganic particles, through which lithium ions can move.

[0041] As the polymer binder, an aqueous polymer binder may be used, eliminating the need to use a separate solvent for dispersing the organic filler during slurry production. The slurry can be produced by dispersing the polymer binder, inorganic particles, and organic filler in a dispersion medium, and a porous coating layer can be formed with a single coating using the slurry. For example, the aqueous polymer binder may be one or more selected from the group consisting of styrene-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, and acrylate-containing polymers. Preferably, the aqueous polymer binder may be an acrylate-based polymer.

[0042] The inorganic particles may form a uniform thickness in the porous coating layer and may not undergo redox reactions within the operating voltage range of the electrochemical element to which they are applied. For example, the inorganic particles may have one or more properties among lithium ion transport capability, piezoelectricity, and flame retardancy.

[0043] Inorganic particles with lithium ion transport capability contain lithium but do not store lithium; instead, they have the ability to transport lithium ions. These inorganic particles can transport and move lithium ions through a type of defect present within their particle structure. Consequently, the lithium ion conductivity within electrochemical elements is improved, thereby enhancing the performance of those elements.

[0044] For example, inorganic particles with lithium ion transport capability include Li3PO4 and Li x Ti y (PO4)3(0 <x<2、0<y<3)、Li x Al y Ti z (PO4)3(0 <x<2、0<y<1、0<z<3)、Li x La y TiO3(0 <x<2、0<y<3)、Li xGe y P z S w (0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), lithium nitride such as Li3N (Li x N y , 0 < x < 4, 0 < y < 2), SiS2 - based glass such as Li3PO4 - Li2S - SiS2 (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4), P2S5 - based glass such as LiI - Li2S - P2S5 (Li x P y S z , 0 < x < 3, 0 < y < 3, 0 < z < 7), LLZO - based such as Li7La3Zr2O 12 and may be one or more selected from the group consisting of these and their mixtures, but is not limited thereto.

[0045] Inorganic particles having piezoelectricity mean substances that are insulators under normal pressure but conduct electricity due to changes in their internal structure when a certain pressure is applied. The inorganic particles can exhibit a high dielectric constant characteristic with a dielectric constant of 100 or more, and when a certain pressure is applied and they are stretched or compressed, charges are generated, and one side becomes positively charged and the opposite side becomes negatively charged, thereby generating a potential difference between the two sides. When internal short - circuiting between the positive and negative electrodes occurs due to external impacts such as local crush or nail, the inorganic particles coated on the separator not only prevent the direct contact between the positive and negative electrodes, but also, due to the piezoelectricity of the inorganic particles, a potential difference is generated within the particles, and thereby electron transfer between the positive and negative electrodes, that is, a flow of fine current occurs, which can achieve a gentle reduction in the voltage of the electrochemical device and an improvement in safety thereby.

[0046] For example, piezoelectric inorganic particles include BaTiO3, BaSO4, Pb(Zr, Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti yO3(PLZT)(0 <x<1、0<y<1)、Pb(Mg 1 / 3 Nb 2 / 3 ) may be one or more selected from the group consisting of O3-PbTiO3 (PMN-PT), HfO2 (hafnia), and mixtures thereof, but is not limited thereto.

[0047] Flame-retardant inorganic particles can add flame-retardant properties to separation membranes and prevent a rapid rise in temperature inside electrochemical elements.

[0048] For example, flame-retardant inorganic particles may be one or more selected from the group consisting of Sb2O3, Sb2O4, Sb2O5, SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, Zn2SnO4, ZnSnO3, ZnSn(OH)6, ZrO2, Y2O3, SiO2, Al2O3, AlOOH, Al(OH)3, SiC, TiO2, H3BO3, HBO2, and mixtures thereof, but are not limited to these.

[0049] The average particle size (D50) of the inorganic particles can be between 700 nm and 1500 nm, and may be larger than the average particle size of the organic filler. Specifically, the average particle size of the inorganic particles may be between 800 nm and 1400 nm, between 900 nm and 1300 nm, or between 1000 nm and 1200 nm. If the average particle size of the inorganic particles is smaller than 700 nm, a polymer binder is required for bonding between the inorganic particles, which is disadvantageous from the viewpoint of electrical resistance. If the average particle size of the inorganic particles exceeds 1500 nm, the uniformity of the coating layer surface decreases, and particles protruding after coating may damage the separation membrane and electrodes during lamination, causing a short circuit. If the average particle size of the inorganic particles is smaller than the average particle size of the organic filler, the organic filler has difficulty moving to the surface of the porous coating layer during formation of the porous coating layer, which reduces the electrode adhesion strength of the separation membrane and causes thermal shrinkage at high temperatures and in a wet state.

[0050] The organic filler is contained in the porous coating layer and can provide adhesion to the electrode. In this invention, compared to polymer binders whose adhesive strength may decrease due to the electrolyte, by including an excess amount of the organic filler, excellent adhesion to the electrode can be ensured even at high temperatures and in wet conditions.

[0051] By using an organic filler with a glass transition temperature higher than that of the aqueous polymer binder, the adhesive strength can be maintained even under high-temperature conditions of 90°C to 130°C and above 130°C, which are the operating temperature ranges for electrochemical elements. Preferably, the glass transition temperature of the organic filler may fall within the operating temperature range of the electrochemical element. For example, the organic filler may have a glass transition temperature of 80°C to 180°C, and the aqueous polymer binder may have a glass transition temperature of -20°C to 80°C.

[0052] The organic filler may be resistant to the electrolyte, which is an organic solvent, and may not dissolve or swell even when the separation membrane is impregnated with the electrolyte. For example, the organic filler may be one or more selected from the group consisting of polyurethane, polyethylene, polypropylene, polystyrene, ethylene vinyl alcohol, and polyester. Preferably, the organic filler may be polyurethane, ethylene vinyl alcohol, or polyester.

[0053] The organic filler may be used in powder form with an average particle size (D50) of 50 nm to 500 nm. Specifically, the organic filler may have an average particle size of 100 nm to 450 nm, 150 nm to 400 nm, or 200 nm to 350 nm. Preferably, the organic filler may have an average particle size of 300 nm to 500 nm. Within this range, since the average particle size of the organic filler is smaller than the average particle size of the inorganic particles, it can migrate between the inorganic particles and be distributed on the surface of the porous coating layer, and can be densely distributed on the surface of the porous coating layer, maintaining adhesion to the electrode even in a wet state where the separation membrane is impregnated with electrolyte. If the average particle size of the organic filler exceeds this range, the dispersibility of the organic filler decreases, and it becomes impossible to obtain a slurry in which the solid content is uniformly dispersed.

[0054] The porous coating layer may contain the inorganic particles and the organic filler in a weight ratio of 5:1 to 35:1. Preferably, the porous coating layer may contain the inorganic particles and the organic filler in a weight ratio of 5:1 to 32:1. If the inorganic particles are present in excess of the ratio, the separation membrane will be impregnated with the electrolyte and will not be able to maintain adhesion to the electrode. If the organic filler is present in excess of the ratio, the permeability of the separation membrane will decrease and the electrical resistance will increase.

[0055] The porous coating layer may contain an excess amount of the inorganic particles and the organic filler compared to the aqueous polymer binder. Specifically, the porous coating layer may have a greater content of inorganic particles than of the organic filler. The porous coating layer may have a greater content of inorganic particles than of the aqueous polymer binder. More specifically, the porous coating layer may have a greater content of organic filler than of the aqueous polymer binder. The porous coating layer may contain 1% to 5% by weight of the aqueous polymer binder relative to the total weight of the porous coating layer. If the content of the aqueous polymer binder is less than 1% by weight, interstitial volume is not formed through bonding between inorganic particles, making lithium ion transfer difficult and increasing electrical resistance. If the content of the aqueous polymer binder exceeds 5% by weight, the separation membrane may become impregnated with the electrolyte, reducing the adhesive strength of the polymer binder, which may cause the porous coating layer and the porous polymer substrate to peel off, or the separation membrane and the electrode to peel off.

[0056] The porous coating layer can be manufactured by applying and drying a slurry containing a water-based polymer binder, inorganic particles, an organic filler, and a dispersion medium onto the porous polymer substrate. The slurry may contain 20% to 50% by weight of solids relative to the total weight of the slurry, and within this range, the porous coating layer may have an air permeability of 100 s / 100 cc to 150 s / 100 cc.

[0057] During the process of applying the slurry to the porous polymer substrate and drying it, a concentration gradient of organic fillers can be formed across the cross-section of the porous coating layer. Organic fillers with a small average particle size can migrate between inorganic particles during the drying process of the dispersion medium, and the porous coating layer may be present in greater quantities on the side opposite the porous polymer substrate than on the surface facing the porous polymer substrate. Preferably, the organic fillers may be present in the greatest quantity on the surface of the porous coating layer located opposite the porous polymer substrate. The organic fillers present on the surface of the porous coating layer can provide adhesion to the electrode even when the separation membrane is impregnated in the electrolyte.

[0058] The thickness of the porous coating layer may be 0.5 μm to 5 μm. Specifically, the thickness of the porous coating layer may be 1 μm to 4.5 μm, 1.5 μm to 3 μm, or 2 μm to 2.5 μm. Preferably, the thickness of the porous coating layer may be 2 μm to 5 μm. By adjusting the thickness of the porous coating layer within the above range, shrinkage of the porous polymer substrate can be minimized, and stable adhesion to the porous polymer substrate can be achieved.

[0059] The porous coating layer may further contain a dispersant to further improve the dispersibility of inorganic particles. The dispersant works to maintain a uniform dispersion state of inorganic particles within the polymer binder during slurry production. For example, the dispersant can be one or more selected from oil-soluble polyamines, oil-soluble amine compounds, fatty acids, fatty alcohols, sorbitan fatty acid esters, tannic acid, and pyrogallolic acid. If the slurry contains a dispersant, the porous coating layer may contain the dispersant in an amount of 5% by weight or less.

[0060] The separation membrane, when impregnated in the electrolyte, or when impregnated in the electrolyte at a temperature of 130°C to 180°C, may have a wet adhesion force of 1 gf / 20 mm to 20 gf / 20 mm to the electrode. Preferably, the wet adhesion force may be 5 gf / 20 mm to 20 gf / 20 mm. Within this range, the separation membrane may exhibit a shrinkage rate of 5% or less in the TD direction (width direction). If the wet adhesion force is less than 1 gf / 20 mm, the stiffness of the electrode assembly including the separation membrane will be low, leading to assembly problems and bending problems due to the shrinkage of the separation membrane during the manufacture of the electrochemical element. If it exceeds 20 gf / 20 mm, the impregnation of the electrolyte into the separation membrane may be hindered, and lithium dendrites may precipitate on the surface of the separation membrane.

[0061] Another embodiment of the present invention provides an electrochemical element comprising a positive electrode, a negative electrode, a separation membrane disposed between the positive electrode and the negative electrode, and an electrolyte, wherein the separation membrane is a separation membrane for an electrochemical element according to the above embodiment.

[0062] The positive electrode and the negative electrode may have an active material coated and dried on at least one surface of their respective current collectors. The active material is not limited as long as it can be used in electrochemical elements such as lithium secondary batteries.

[0063] For example, the positive electrode active material is lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2); chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented as O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 to 0.3); chemical formula LiMn 2-x M xO2 (where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 - 0.1), or a 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 an alkaline earth metal ion; a disulfide compound; it can contain, but is not limited to, Fe2(MoO4)3, etc.

[0064] For example, the negative electrode active material is carbon such as graphitizable carbon, graphite-based carbon; Li x Fe2O3 (0 ≦ x ≦ 1), LixWO2 (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) and other 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, etc. can be included, but are not limited to this.

[0065] For the current collector, a material having conductivity without causing a chemical change in the electrochemical element can be used. For example, the current collector for the positive electrode can be aluminum, nickel, titanium, fired carbon, stainless steel; those obtained by surface treatment of the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc., but is not limited to this. For example, the current collector for the negative electrode can be copper, nickel, titanium, fired carbon, stainless steel; those obtained by surface treatment of the surface of copper or stainless steel with carbon, nickel, titanium, silver, etc., but is not limited to this. The current collector can be in various forms such as a thin metal plate, film, foil, net, porous body, foam, etc.

[0066] The electrolyte may be a non-aqueous electrolyte containing a lithium salt, and may contain a lithium salt, a non-aqueous organic solvent, an organic solid electrolyte, an inorganic solid electrolyte, and the like.

[0067] Examples of non-aqueous organic solvents that can be used include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyropionate, and ethyl propionate.

[0068] Examples of organic solid electrolytes that can be used include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polyagitation lysine, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, and polymerization agents containing ionic dissociation groups.

[0069] Examples of inorganic solid electrolytes that can be used include lithium nitrides, halides, and sulfates such as Li3N, LiI, Li5NI2, Li3NLiI-LiOH, LiSiO4, LiSiO4-LiI-LiOH, Li2SiS3, Li4SiO4, Li4SiO4-LiI-LiOH, and Li3PO4-Li2S-SiS2.

[0070] The lithium salt is a substance that is readily soluble in the non-aqueous electrolyte, such as LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB 10 Cl 10LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, (CF3SO2)2NLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium 4-phenylborate, imide, etc. may be used.

[0071] The electrochemical element can be manufactured by inserting a positive electrode, a negative electrode, a separation membrane, and an electrolyte into a case or pouch and sealing it. For example, the electrochemical element may be a cylindrical, prismatic, coin-type, or pouch-type lithium secondary battery. Preferably, the electrochemical element may be a cylindrical or pouch-type lithium secondary battery.

[0072] The lithium secondary battery can be used in small devices such as computers, mobile phones, and power tools, either as a unit cell in packs or modules; in medium to large devices such as power tools powered by battery-powered motors; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters; electric golf carts; and power storage systems.

[0073] The present invention will be described in more detail below through specific examples and experimental cases. The following examples and experimental cases are for illustrative purposes only and do not limit the present invention to the following examples and experimental cases.

[0074] Example 1 [Preparing the slurry] At room temperature (25°C), 35.1 g of alumina with an average particle size of 1000 nm was prepared as inorganic particles, 3.2 g of polyurethane emulsion with an average particle size of 500 nm (Basekorea, 35% solids) was prepared as an organic filler, and 1.8 g of acrylate-based binder (Toyo Chemical, 40% solids) with a Tg of -20°C and an average particle size of 150 nm was prepared as a polymer binder. 68.5 g of aqueous dispersion medium was prepared by mixing water and ethyl alcohol in a weight ratio of 95:5. Alumina, polyurethane emulsion, and acrylate-based binder were added, and the mixture was dispersed for 120 minutes using a paint shaker to produce a slurry in which the inorganic particles, organic filler, and aqueous polymer binder were mixed in a weight ratio of 95:3:2.

[0075] [Preparation of porous polymer substrate] As the porous polymer substrate, a polyethylene film (PE, JGP) measuring 30 cm x 20 cm with a thickness of 9 μm was used.

[0076] [Manufacturing of separation membranes] The slurry was coated onto both sides of a polyethylene film using a knife coater, and the process of drying it in an oven at 60°C for 20 minutes was repeated twice to form porous coating layers with each coating having a thickness of 3 μm, thereby producing a separation membrane with an overall thickness of approximately 15 μm.

[0077] Example 2 The separation membrane was manufactured in the same manner as in Example 1, except that during slurry preparation, 29.5 g of alumina, 16.8 g of polyurethane emulsion (35% solids), and 3.7 g of acrylate-based binder (40% solids) were used to mix inorganic particles, organic fillers, and a water-based polymer binder in a weight ratio of 80:16:4.

[0078] Comparative Example 1 The separation membrane was manufactured in the same manner as in Example 1, except that during slurry preparation, 30 g of alumina and 3.5 g of acrylate-based binder (40% solids content) were used to mix inorganic particles and a water-based polymer binder in a weight ratio of 95:5.

[0079] Comparative Example 2 The separation membrane was manufactured in the same manner as in Example 1, except that during slurry preparation, 25.8 g of alumina, 14.7 g of polyurethane emulsion (35% solids), and 14.7 g of acrylate-based binder (40% solids) were used to mix the organic filler, inorganic particles, and aqueous polymer binder in a weight ratio of 70:14:16.

[0080] Experimental Example 1. Confirmation of the permeability (Gurley) of the separation membrane. The air permeability measuring device used was the EG01-55-1MR model from Asahi Seiko.

[0081] The separation membranes produced in Examples 1-2 and Comparative Examples 1-2 were fixed to the upper and lower hollow tips of an air permeability measuring device. The time it took for 100cc of air to pass through the separation membrane substrate via a set differential pressure applied to the upper and lower tips was measured to determine the air permeability, and the results are shown in Table 1 below.

[0082] Experimental Example 2. Confirmation of Wet Adhesion Strength of Separation Membranes The wet adhesion strength of the separation membranes produced in the examples and comparative examples to the electrodes was confirmed.

[0083] For the positive electrode, a slurry containing the positive electrode active material is applied to both sides of an aluminum current collector measuring 5 cm x 5 cm and 10 μm thick at a rate of 200 g / m². 2 The product used was manufactured by applying and drying the material.

[0084] For the negative electrode, a slurry containing the negative electrode active material is applied to both sides of a copper current collector measuring 5 cm x 5 cm and 6 μm thick at a rate of 100 g / m². 2 The product used was manufactured by applying and drying the material.

[0085] After placing a 5cm x 5cm separation membrane between the positive and negative electrodes, the temperature and humidity were set to 100°C and 7kgf / cm², similar to the winding tension conditions of a cylindrical battery. 2 The membrane was pressurized to a certain pressure and inserted into an aluminum pouch measuring 7 cm x 10 cm. 1 g of electrolyte (EC:EMC weight ratio 3:7) was injected into the pouch, and the pouch was sealed. The sealed pouch was kept in an oven at 130°C for 30 minutes, after which the pouch was disassembled and the adhesion strength (wet adhesion strength) between the separation membrane and the electrode was measured.

[0086] The adhesion strength between the separation membrane and the electrode was measured using an Instron UTM device in a 180° peel test at a rate of 200 mm / min, and is shown in Table 1 below.

[0087] Experimental Example 3. Confirmation of dimensional stability of separation membrane The separation membranes that underwent the peel test in Experimental Example 2 were collected, and the shrinkage rate in the TD direction was measured and recorded in Table 1 below.

[0088] [Table 1]

Claims

1. A separation membrane for an electrochemical element comprising a porous polymer substrate and a porous coating layer formed on at least one surface of the porous polymer substrate, The porous coating layer is It contains a water-based polymer binder, inorganic particles, and organic fillers. The porous coating layer is The content of the organic filler is greater than the content of the aqueous polymer binder. The aforementioned organic filler is The glass transition temperature is between 80°C and 180°C. A separation membrane for an electrochemical element, wherein the content of the aqueous polymer binder relative to the total weight of the porous coating layer is 1% to 5% by weight.

2. The aqueous polymer binder is A separation membrane for an electrochemical element according to claim 1, which is one or more selected from the group consisting of styrene-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, and an acrylate-containing polymer.

3. The inorganic particles are, Li ３ 2O ４ 、 ｘ Ti ｙ (2O ４ ) ３ (0<8<2、0<y<3),L- ｘ Al ｙ Ti ｚ (2O ４ ) ３ (0<x<2、0<y<1、0<z<3), L- ｘ Lạ ｙ TiO ３ (0<8<2、0<y<3),L- ｘ Ge ｙ P ｚ S ｗ (0<x<4、0<y<1、0<z<1、0<w<5), L. ｘ N ｙ (0<8<4、0<y<2), L- ｘ Si ｙ S ｚ (0<x<3、0<y<2、0<z<4), L. ｘ P ｙ S ｚ (0<x<3、0<y<3、0<z<7), L- ７ Lạ ３ Zr ２ O １２ 、BTT9O ３ 、BBO ４ 、Pb(Zr、Ti)O ３ (PZT), Pb １－ｘ Lạ ｘ Zr １－ｙ Ti ｙ O ３ (>^ZT、0<8<1、0<y<1), Pb(Mg １／３ Nb ２／３ )O ３ -PbTiO ３ (PMN-PT), HfO ２ 、Sb ２ O ３ 、Sb ２ O ４ 、Sb ２ O ５ 、SrTiO ３ 、SnO ２ 、CeO ２ 、MgO、Mg(OH) ２ , NiO, CaO, ZnO, Zn ２ SnO ４ ZnSnO ３ , ZnSn(OH) ６ , ZrO ２ , Y ２ O ３ SiO ２ Al ２ O ３ , AlOOH, Al(OH) ３ SiC, TiO ２ H ３ BO ３ and HBO ２ A separation membrane for an electrochemical element according to claim 1, which is one or more selected from the group consisting of the following.

4. The separation membrane for an electrochemical element according to claim 1, wherein the average particle size (D50) of the organic filler is smaller than the average particle size (D50) of the inorganic particles.

5. The aforementioned organic filler is A separation membrane for an electrochemical element according to claim 1, wherein the average particle size (D50) is 50 nm to 500 nm.

6. The separation membrane for an electrochemical element according to claim 1, wherein the glass transition temperature of the organic filler is higher than the glass transition temperature of the aqueous polymer binder.

7. The aforementioned organic filler is A separation membrane for an electrochemical element according to claim 1, which is one or more selected from the group consisting of polyurethane, polyethylene, polypropylene, polystyrene, ethylene vinyl alcohol, and polyester.

8. The porous coating layer is The separation membrane for an electrochemical element according to claim 1, comprising the inorganic particles and the organic filler in a weight ratio of 5:1 to 35:

1.

9. The porous coating layer is A separation membrane for an electrochemical element according to claim 1, wherein the air permeability is 100 s / 100 cc to 150 s / 100 cc.

10. The separation membrane for an electrochemical element according to claim 1, wherein the concentration gradient of the organic filler is formed across the cross-section of the porous coating layer.

11. The aforementioned organic filler is The separation membrane for an electrochemical element according to claim 10, wherein the porous coating layer is present in a larger quantity on the side opposite the porous polymer substrate than on the surface facing the porous polymer substrate.

12. An electrochemical element comprising a positive electrode, a negative electrode, and a separation membrane disposed between the positive electrode and the negative electrode, The separation membrane is an electrochemical element according to any one of claims 1 to 11.

13. The electrochemical element according to claim 12, wherein the separation membrane has an adhesive strength of 1 gf / 20 mm to 20 gf / 20 mm to the positive electrode or the negative electrode after being impregnated in an electrolyte and held at a temperature of 130°C to 180°C for 30 minutes.

14. The electrochemical element according to claim 12, wherein the separation membrane has a shrinkage rate in the TD direction of 5% or less after being impregnated in an electrolyte and held at a temperature of 130°C to 180°C for 30 minutes.

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