Electrode current collector, lithium secondary battery comprising same, battery module, and battery pack

Abstract

An electrode current collector according to the present invention comprises: a polymer resin layer; a first metal layer disposed on one surface of the polymer resin layer; and a second metal layer disposed on the other surface of the polymer resin layer, wherein the first metal layer includes at least one selected from the group consisting of copper, aluminum and stainless steel, and the second metal layer includes at least four types of transition metals and a metal included in the first metal layer.

Description

Electrode current collector, lithium secondary battery, battery module and battery pack including the same This application claims the benefit of priority from Korean Patent Application No. 10-2023-0132105, filed October 04, 2023, the entire contents of which are incorporated herein by reference. The present invention relates to an electrode current collector, a lithium secondary battery including the same, a battery module, and a battery pack. As technological development and demand for electric vehicles and energy storage systems (ESS) increase, the demand for batteries as an energy source is rapidly increasing, and research is being conducted on batteries that can meet various needs. In particular, to achieve longer battery life on a single charge, batteries need to be increased in capacity, and this requires large-area electrode technology. However, the process of increasing the electrode area can degrade electrode performance, and there are concerns about thermal runaway and heat propagation to other electrodes in the event of a fire. Lithium secondary batteries can experience rapid temperature increases in the electrodes due to thermal and physical factors. Thermal factors include overcharging or overloading caused by misuse or malfunctions such as chargers. Physical factors include damage to the separator due to external impact, causing contact between the cathode and anode materials, resulting in an internal short circuit, which can cause rapid temperature increases in the electrodes. Such rapid temperature increases can cause the electrolyte and lithium to react, or hydrogen and oxygen to be generated within the battery, making the battery highly unstable. Furthermore, the electrolyte solvent can decompose, generating gas, which can ignite and potentially cause an explosion. Conventional lithium secondary batteries contain only a single metal layer as an electrode current collector. Specifically, an aluminum single metal layer is used as a positive electrode current collector, and a copper single metal layer is used as a negative electrode current collector. However, these single metal layers have extremely high electrical and thermal conductivities, which leads to extremely short times for the battery to reach high temperatures, which can lead to abnormal battery behavior, and concerns about thermal propagation due to thermal runaway. Accordingly, there have been attempts to improve safety by using an electrode current collector comprising a polymer resin layer sandwiched between two metal layers instead of the existing electrode current collector, thereby short-circuiting the electrodes in the event of a fire. However, although an electrode current collector comprising a polymer resin layer sandwiched between two metal layers can improve mechanical safety against foreign substances such as nail penetration, safety against thermal propagation in the event of an actual fire needs to be supplemented. The problem to be solved by the present invention is to provide an electrode current collector having excellent fire safety, heat resistance, and heat blocking effect. Another problem to be solved by the present invention is to provide a lithium secondary battery including the electrode collector. Another problem to be solved by the present invention is to provide a battery module and a battery pack including the lithium secondary battery. To solve the above problem, the present invention provides an electrode current collector, a lithium secondary battery including the electrode current collector, a battery module, and a battery pack. [1] The present invention provides an electrode current collector comprising: a polymer resin layer; a first metal layer disposed on one surface of the polymer resin layer; and a second metal layer disposed on the other surface of the polymer resin layer; wherein the first metal layer includes at least one selected from the group consisting of copper, aluminum, and stainless steel, and the second metal layer includes a metal included in the first metal layer and at least four transition metals, wherein the transition metals are selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Zr, Nb, Mo, Hf, Ta, and W. [2] The present invention provides an electrode current collector according to the above [1], wherein the polymer resin layer includes at least one selected from the group consisting of polyester resin, epoxy resin, phenol resin, melamine resin, urethane resin, silicone resin, EVA resin, rubber resin, acrylic resin, olefin resin, and polyetherurethane resin. [3] The present invention provides an electrode current collector according to [1] or [2], wherein the thickness of the polymer resin layer is 3 µm to 18 µm. [4] The present invention provides an electrode current collector according to any one of the above [1] to [3], wherein the second metal layer is an alloy of a metal included in the first metal layer and four or more types of transition metals. [5] The present invention provides an electrode current collector according to any one of the above [1] to [4], wherein the second metal layer includes a metal, Co, Cr, Fe, and Ni, included in the first metal layer. [6] The present invention provides an electrode current collector according to any one of [1] to [5], wherein the second metal layer includes a metal included in the first metal layer and four or more kinds of transition metals, and the weight difference between each of the four or more kinds of transition metals is within ±15%. [7] The present invention provides an electrode current collector according to any one of [1] to [6], wherein the second metal layer includes a metal included in the first metal layer and four or more kinds of transition metals in a weight ratio of 1:2 to 1:15. [8] The present invention provides an electrode current collector according to any one of [1] to [7], wherein the first metal layer and the second metal layer each have a thickness of 1 µm to 3 µm. [9] The present invention provides an electrode current collector in any one of the above [1] to [8], wherein the thickness ratio of the polymer resin layer and the first metal layer or the second metal layer is 1:1 to 1:10.

[0010] The present invention provides a lithium secondary battery comprising an electrode assembly having a structure in which a plurality of electrodes and a plurality of separators are alternately laminated, wherein the electrodes include an electrode current collector and an electrode active material layer disposed on the electrode current collector, and at least one of the plurality of electrode current collectors is an electrode current collector according to any one of [1] to [9].

[0011] The present invention provides a battery module including a plurality of lithium secondary batteries described in

[0010] above.

[0012] The present invention provides a battery pack including a plurality of battery modules described in

[0011] above. The electrode current collector according to the present invention comprises a polymer resin layer between two metal layers, and one of the metal layers is a high-entropy alloy including a metal mainly used in the current collector and four or more types of transition metals having excellent thermal stability, thereby demonstrating excellent efficiency as a current collector while maximizing safety by thermal propagation in the event of a fire. Figure 1 is a cross-sectional view schematically showing an electrode collector according to the present invention. Figures 2 and 3 are cross-sectional views each showing a lithium secondary battery including an electrode collector according to the present invention. The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided only to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Like reference numerals designate like elements throughout the specification. Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in their common sense to those of ordinary skill in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise. The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, singular forms also include plural forms, unless specifically stated otherwise. As used herein, the terms "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components in addition to the components mentioned. In this specification, when it is said that a part includes a certain component, this does not mean that other components are excluded, but rather that other components may be included, unless specifically stated otherwise. In this specification, the description of “A and / or B” means A, or B, or A and B. In this specification, “%” means weight percent unless explicitly indicated otherwise. Electrode current collector Hereinafter, the electrode current collector according to the present invention will be described. Figure 1 is a cross-sectional view schematically showing an electrode collector according to the present invention. Referring to FIG. 1, an electrode current collector (10) according to the present invention includes a polymer resin layer (11), a first metal layer (13A) disposed on one surface of the polymer resin layer, and a second metal layer (13B) disposed on the other surface of the polymer resin layer, wherein the first metal layer (13A) includes at least one selected from the group consisting of copper, aluminum, and stainless steel, and the second metal layer (13B) includes at least four transition metals. Conventional lithium secondary batteries contain only a single metal layer as an electrode current collector. Specifically, an aluminum single metal layer is used as a positive electrode current collector, and a copper single metal layer is used as a negative electrode current collector. However, these single metal layers have extremely high electrical and thermal conductivities, which leads to extremely short times for the battery to reach high temperatures, which can lead to abnormal battery behavior, and concerns about thermal propagation due to thermal runaway. Accordingly, by using an electrode current collector including a polymer resin layer sandwiched between two metal layers instead of a conventional electrode current collector, it is possible to reduce the weight compared to an electrode current collector made of metal, thereby dramatically improving the energy density per weight, and in addition, safety can be improved by causing a short circuit between the electrodes in the event of a fire. However, although the electrode current collector including a polymer resin layer interposed between two metal layers may have improved mechanical safety against foreign substances such as nail penetration, it may lack safety against thermal propagation in the event of an actual fire. The electrode current collector of the present invention can exhibit excellent heat transfer safety because the first metal layer and the second metal layer are respectively arranged on both sides of the polymer resin layer, and the second metal layer includes four or more types of transition metals that exhibit thermal stability. The electrode has a structure in which an electrode active material layer is arranged on an electrode current collector, and an electrode tab is formed to protrude from one side of the electrode, and an electrode lead is connected to the electrode tab to transmit electricity generated in the electrode to the outside. (1) Polymer resin layer The above polymer resin layer acts as a matrix resin and can prevent abnormal heat transfer between the electrode current collector and the electrode active material layer, and can also play a role in reducing the weight of the electrode current collector and alleviating external impact. The polymer resin layer may include at least one selected from the group consisting of, for example, polyester resin, epoxy resin, phenol resin, melamine resin, urethane resin, silicone resin, EVA resin, rubber resin, acrylic resin, polyolefin resin, cellulose derivative, and polyetherurethane resin. Specifically, the polymer resin layer may include at least one selected from the group consisting of polyimide (PI), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polymethylmethacrylate (PMMA), cellulose triacetate (CTA), polycarbonate (PC), polyethylene naphthalate (PEN), polyacrylonitrile (PAN), polyethylene (PE), polyamide (PA), and polypropylene (PP). In addition, the polymer resin layer may be a thermosetting resin or a photocurable resin, and preferably may include an ultraviolet-curable resin. If necessary, the polymer resin layer may include a photoinitiator such as a benzoin compound, an acetophenone compound, an acylphosphine oxide compound, a titanocene compound, a thioxanthone compound, or a peroxide compound, or a photoinitiator such as an amine or a quinone, and may additionally include a curing accelerator such as an amine-based, imidazole-based, phosphorus-based, boron-based, or phosphorus-boron-based. In addition, the polymer resin layer may include a thermal initiator such as a peroxide such as azobisnitrile, benzoyl peroxide, or acetyl peroxide. The polymer resin layer may have a thickness of 3 μm to 18 μm, preferably 3 μm to 15 μm, and more preferably 4 μm to 8 μm. When the thickness of the polymer resin layer is less than 3 μm, it is too thin, which may hinder abnormal heat transfer, and the effect of reducing the weight of the electrode current collector and alleviating external impact may be minimal. On the other hand, when the thickness exceeds 18 μm, the thickness of the cell increases dramatically, which may increase the resistance and adversely affect the energy density. When the thickness of the polymer resin layer satisfies the above numerical range, the energy density of the cell may increase while inducing an electrically disconnected state with other electrodes or maintaining physical electrical insulation. (2) Metal layer The first metal layer may include at least one selected from the group consisting of copper, aluminum, and stainless steel. Although not particularly limited, for example, when forming a positive electrode current collector, the first metal layer may include aluminum, and when forming a negative electrode current collector, the first metal layer may include copper. In addition, in one embodiment of the present invention, the first metal layer may be copper foil, aluminum foil, or stainless steel foil, when forming a positive electrode current collector, the first metal layer may be aluminum foil, and when forming a negative electrode current collector, the first metal layer may be copper foil. The second metal layer includes a metal included in the first metal layer and four or more types of transition metals, and the transition metals are selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Zr, Nb, Mo, Hf, Ta, and W. In addition, the second metal layer may be an alloy of the metal included in the first metal layer and four or more transition metals. For example, when the first metal layer includes aluminum, it may be an alloy of aluminum and four or more alloys selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Zr, Nb, Mo, Hf, Ta, and W. In addition, when the first metal layer includes copper, it may be an alloy of copper and four or more alloys selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Zr, Nb, Mo, Hf, Ta, and W. The second metal layer may include a transition metal having thermal stability together with a metal used as a conventional current collector to form a high-entropy alloy, thereby exhibiting excellent thermal stability. The high-entropy alloy may prevent heat from spreading to adjacent cells when a battery fire occurs. In one embodiment of the present invention, the second metal layer may include the metals Co, Cr, Fe, and Ni included in the first metal layer, and specifically, the second metal layer may be an alloy of the metals Co, Cr, Fe, and Ni included in the first metal layer. When the second metal layer includes Co, Cr, Fe, and Ni together with the metals included in the first metal layer, a high-entropy alloy exhibiting excellent mechanical properties is formed, thereby exhibiting excellent mechanical properties and even better thermal stability. In one embodiment of the present invention, the second metal layer may include a metal included in the first metal layer and four or more types of transition metals, and at this time, the weight difference between each of the transition metals constituting the four or more types of transition metals may be within 15 wt%. Specifically, the weight difference between each of the transition metals constituting the four or more transition metals may be within 10 wt%, more specifically within 5%, or each of the four or more transition metals may have the same weight. For example, when the weight difference between each of the transition metals constituting the four or more transition metals is within 15 wt%, the weight difference between the element having the largest weight and the element having the smallest weight among the transition metals constituting the four or more transition metals satisfies 15 wt% or less. When the weight difference between each of the transition metals constituting the four or more transition metals included in the second metal layer satisfies the above range, the four or more transition metals and the metal included in the first metal layer can smoothly form a high-entropy alloy together. In order for the four or more transition metals to be alloyed with the metal included in the first metal layer to form a multi-component high-entropy alloy, each of the alloy elements included as the four or more transition metals needs to be included in a similar content. In one embodiment of the present invention, the second metal layer may include the metal included in the first metal layer and the four or more transition metals in a weight ratio of 1:2 to 1:15, specifically, in a weight ratio of 1:3 to 1:14, and more specifically, in a weight ratio of 1:4 to 1:13.5. When the second metal layer includes the metal included in the first metal layer and the four or more transition metals in the weight ratio, both excellent conductivity required for the current collector and the desired excellent thermal stability can be achieved. In one embodiment of the present invention, the second metal layer may be formed by laminating powder of a metal included in the first metal layer and powder of four or more transition metals on the other surface of the polymer resin layer using a cold spray method. Cold spraying is a method of bonding metal powder to a surface using nitrogen or helium gas at a relatively low temperature (below the melting point of the powder), and accelerating the particles to a supersonic speed so that the particles can be embedded in the target surface, thereby forming a strong bond. Through the cold spraying, a second metal layer including the metal included in the first metal layer and four or more transition metals can be formed on the other surface of the polymer resin layer. The lamination using the cold spray can be performed by spraying a mixture of powders of the metal included in the first metal layer and powders of each of four or more transition metals using the cold spray, and at this time, the D of the powder included in the mixture 50 The silver may be 0.15 ㎛ to 0.35 ㎛, specifically 0.20 ㎛ to 0.30 ㎛, and more specifically 0.22 ㎛ to 0.28 ㎛. The first metal layer and / or the second metal layer may have fine irregularities formed on the surface, and when fine irregularities are formed on the surface, the bonding strength with the electrode combination layer can be strengthened. In addition, the first metal layer and / or the second metal layer may have various forms, such as a film, sheet, foil, net, porous body, foam, or non-woven fabric. The first metal layer and / or the second metal layer may have a thickness of 1 μm to 3 μm, specifically 1.8 μm to 2.8 μm, and more specifically 1.8 μm to 2.5 μm. When the thickness of the first metal layer and / or the second metal layer is less than 10 μm, it is too thin to function as a support, making it difficult to maintain the shape as an electrode and making it difficult to control the physical properties of the electrode. On the other hand, when the thickness exceeds 30 μm, the thickness and weight of the cell may increase excessively, which may lower the energy density. The thickness ratio of the polymer resin layer and the first metal layer and / or the second metal layer may be 1:1 to 1:10. Specifically, the thickness ratio may be 1:1.5 to 1:5, and more specifically, 1:1.5 to 1:3. When the thickness ratio of the polymer resin layer and the first metal layer and / or the second metal layer satisfies the above numerical range, there is an effect of increasing the energy density of the cell while improving the safety of the battery through electrical short-circuiting. Lithium secondary batteries, battery modules and battery packs A lithium secondary battery according to the present invention includes the electrode current collector of the present invention described above. A lithium secondary battery according to the present invention includes an electrode assembly having a structure in which a plurality of electrodes and a plurality of separators are alternately laminated, wherein the electrode includes an electrode current collector and an electrode active material layer disposed on the electrode current collector, and at least one of the plurality of electrode current collectors is the electrode current collector of the present invention described above. Figures 2 and 3 are cross-sectional views showing a lithium secondary battery including an electrode collector according to the present invention. Referring to FIGS. 2 and 3, specifically, a lithium secondary battery (100) according to the present invention includes an electrode assembly (50) in which a positive electrode (15), a separator (19), and a negative electrode (17) are sequentially laminated, the separator (19) is disposed between the positive electrode (15) and the negative electrode (17), the positive electrode (15) includes a positive electrode current collector (15a) and a positive electrode active material layer (15b) laminated on the positive electrode current collector, the negative electrode (17) includes a negative electrode current collector (17a) and a negative electrode active material layer (17b) laminated on the negative electrode current collector, and at least one of the positive electrode current collector and the negative electrode current collector is the electrode current collector (10) of the present invention described above. The lithium secondary battery (100) according to the present invention may include at least one electrode current collector (10), and preferably may include two or more. Specifically, in an electrode assembly (50) having a structure in which a plurality of electrodes and a plurality of separators are alternately laminated, an electrode (30) including the electrode current collector (10) of the present invention described above may be arranged at the outermost part of the electrode assembly (50). The lithium secondary battery (100) according to the present invention may have an outermost electrode formed of a positive electrode or a negative electrode having a structure in which a polymer resin layer is interposed between two metal layers of the present invention, or an electrode located at a central portion of the battery may be formed of a positive electrode or a negative electrode having a structure in which a polymer resin layer is interposed between two metal layers of the present invention. Since the electrode collector has been described above, a detailed description will be omitted, and only the remaining components will be described in detail below. (anode) The positive electrode current collector may include a highly conductive metal, and is not particularly limited as long as it is easily adhered to by the positive electrode active material layer and is non-reactive within the voltage range of the battery. The positive electrode current collector may be made of, for example, stainless steel, aluminum, nickel, titanium, heat-treated carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. In addition, the positive electrode current collector may typically have a thickness of 3 ㎛ to 500 ㎛, and fine unevenness may be formed on the surface of the current collector to increase the adhesion of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc. The above positive electrode active material layer may optionally include a conductive material and a binder, together with the positive electrode active material, as needed. At this time, the positive electrode active material may be included in an amount of 80 wt% to 99 wt%, more specifically 90 wt% to 98 wt%, based on the total weight of the positive electrode active material layer. The conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any particular limitation. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One of these may be used alone or a mixture of two or more may be used. The conductive material may be included in an amount of 0.01 wt% to 10 wt%, specifically 0.1 wt% to 9 wt%, and more specifically 0.1 wt% to 5 wt%, based on the total weight of the positive electrode active material layer. The above binder serves to improve the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylalcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and polymers in which hydrogens of these are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The above binder may be included in an amount of 1 wt% to 30 wt%, preferably 1 wt% to 20 wt%, and more preferably 1 wt% to 10 wt%, based on the total weight of the positive electrode active material layer. The above-mentioned positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the above-mentioned positive electrode active material is used. Specifically, the positive electrode slurry composition, prepared by dissolving or dispersing the above-mentioned positive electrode active material and optionally a binder, a conductive agent, and a dispersant in a solvent as needed, is applied onto a positive electrode current collector, followed by drying and rolling. The solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethyl formamide (DMF), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, binder, and dispersant in consideration of the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode. Alternatively, the positive electrode may be manufactured by casting the positive electrode slurry composition onto a separate support, then peeling the resulting film from the support and laminating it onto a positive electrode current collector. (Separator) The above separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without any particular restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure. (electrolyte) In addition, the electrolyte used in the present invention may include, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc. that can be used in the manufacture of a lithium secondary battery. Specifically, the electrolyte may include an organic solvent and a lithium salt. The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R represents a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable. The above lithium salt can be used without any special limitation as long as it is a compound that can provide lithium ions used in a lithium secondary battery. Specifically, the anion of the above lithium salt is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may be at least one selected from the group consisting of, and the lithium salt is LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2) 2. LiCl, LiI, or LiB(C2O4)2 can be used. The concentration of the lithium salt is preferably within the range of 0.1M to 4.0M, preferably 0.5M to 3.0M, and more preferably 1.0M to 2.0M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively. In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 to 10.0 wt% based on the total weight of the electrolyte. (cathode) The above negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector. The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, heat-treated carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 ㎛ to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc. The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material. As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, and Al alloy; metallic oxides capable of doping and dedoping lithium, such as SiOβ (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fibers, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature heat-treated carbon such as petroleum or coal tar pitch derived cokes. The above negative electrode active material may be included in an amount of 80 wt% to 99 wt%, 82 wt% to 99 wt%, or 84 wt% to 99 wt% based on the total weight of the negative electrode active material layer. The above binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof. The conductive agent is a component for further improving the conductivity of the negative electrode active material, and may be included in an amount of 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. The conductive agent is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives. The above negative electrode active material layer can be manufactured by applying and drying a negative electrode slurry composition prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the negative electrode slurry composition on a separate support, and then laminating the obtained film by peeling it off from the support on a negative electrode current collector. (battery case) In addition, the lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, the separator, and the negative electrode, and a sealing member that seals the battery container. In addition, since the lithium secondary battery according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs). In particular, to achieve longer battery life on a single charge, batteries need to be increased in capacity, and this requires large-area electrode technology. However, the process of increasing the electrode area can degrade electrode performance, and there are concerns about thermal runaway and heat propagation to other electrodes in the event of a fire. Accordingly, according to another embodiment of the present invention, a battery module including a plurality of the lithium secondary batteries and a battery pack including a plurality of the battery modules are provided. The above battery module refers to a battery assembly (assembly) in which a certain number of lithium secondary batteries are bundled and placed in a frame to protect them from external shocks, heat, vibration, etc. The above battery pack refers to the final form of a battery system installed in electric vehicles, etc. The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as power tools; electric vehicles including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems. The battery module and battery pack according to the present invention, when including a plurality of the electrode current collectors described above, can maximize safety by thermal propagation in the event of an actual fire, thereby realizing high capacity and large area of ​​the battery. Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. Examples and Comparative Examples Example 1 A first metal layer was formed by physical vapor deposition (PVD) of Al metal to a thickness of 1 ㎛ on one side of polyethylene terephthalate (PET) with a thickness of 6 ㎛. Powders of Al, Co, Cr, Fe and Ni (D) were applied to the other side of the polyethylene terephthalate (PET) using cold spray (SH Korea, Cold spray). 50 A mixture of 0.25 ㎛) in a weight ratio of 7:23.25:23.25:23.25:23.25 was cold sprayed at a nozzle inlet pressure of 3.0 MPa and a temperature of 300°C to form a second metal layer having a thickness of 2 ㎛, thereby manufacturing an electrode current collector. <Manufacturing of Lithium Secondary Batteries> A cathode slurry was prepared by mixing cathode active material (NCM65 1520), conductive agent (Li-435), and PVDF binder (KF9700, AD-c01) in a weight ratio of 96.5:1.5:2.0 in N-methylpyrrolidone. After applying the positive electrode slurry to one surface of the electrode current collector manufactured above, it was dried at 140°C and then rolled to manufacture a positive electrode. Graphite was used as the cathode. An electrode assembly was manufactured by interposing a separator between the positive and negative electrodes manufactured by the above-described method, and then positioning it inside a battery case, and then injecting an electrolyte into the case to manufacture a battery cell. The electrolyte was manufactured by dissolving 0.7 M LiPF6 in a mixed organic solvent of ethylene carbonate (EC): propylene carbonate (PC): ethyl methyl carbonate (EMC) = 2:1:7 by volume. Example 2 When forming the second metal layer, powders of Al, Co, Cr, Fe and Ni (D) are used respectively. 50 An electrode collector and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a mixture containing 0.25 ㎛) was used in a weight ratio of 13.04:21.74:21.74:21.74:21.74. Example 3 When forming the second metal layer, powders of Al, Co, Cr, Fe and Ni (D) are used respectively. 50 An electrode collector and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a mixture containing 0.25 ㎛) was used in a weight ratio of 18.4:20.4:20.4:20.4:20.4. Comparative Example 1 A lithium secondary battery was manufactured in the same manner as in Example 1, except that an electrode current collector made of aluminum metal with a thickness of 12 μm, which is a typical metal current collector, was used as the positive current collector. Comparative Example 2 An electrode current collector was manufactured by forming a first metal layer and a second metal layer by physical vapor deposition (PVD) of aluminum metal to a thickness of 2 μm on both sides of a 6 μm thick polyethylene terephthalate (PET). A lithium secondary battery was manufactured in the same manner as Example 1, except that the electrode current collector was used as a positive electrode current collector. Comparative Example 3 An electrode current collector and a lithium secondary battery were manufactured in the same manner as in Example 1, except that an electrode current collector made of copper metal with a thickness of 8 ㎛, which is a typical metal current collector, was used as a negative electrode current collector, and an electrode current collector made of aluminum metal with a thickness of 12 ㎛ was used as a positive electrode current collector. Comparative Example 4 A first metal layer and a second metal layer were formed by physically vapor depositing copper metal to a thickness of 1 μm on both sides of a 6 μm thick polyethylene terephthalate (PET) to manufacture an electrode current collector. A lithium secondary battery was manufactured in the same manner as Example 1, except that the electrode current collector was used as a negative electrode current collector and an electrode current collector made of aluminum metal with a thickness of 12 μm was used as a positive electrode current collector. Experimental Example 1 For the lithium secondary battery cells manufactured in Examples 1 to 3 and Comparative Examples 1 to 4, experiments were conducted on 1) the time delay effect on thermal propagation, 2) safety from physical impact, and 3) safety from nail penetration. The results of the experiments are shown in [Table 1] below. In this case, in [Table 1], the “◎” mark means very good, the “○” mark means good, the “△” mark means average, and the “×” mark means poor. Specifically, the experimental methods for 1) the time delay effect on thermal propagation, 2) safety from physical impact, and 3) safety from nail penetration are as follows. 1) Five of the above-mentioned manufactured battery cells are assembled into one module, and heat is applied to one battery cell at a rate of 0.5°C / sec using a heating pad. The heat to adjacent cells is measured using a thermocouple to evaluate whether there is a time delay in thermal propagation. 2) The manufactured battery cell was charged to 4.4 V at 0.2 C in CC / CV mode, and a rod with a diameter of 15.8 mm was dropped freely from a height of 610 mm to the center of the battery cell. By measuring whether the battery cell caught fire due to physical impact, the mechanical safety of each battery cell was evaluated. 3) A nail penetration test was performed by penetrating the manufactured battery cell at a speed of 0.1 mm / s using a sharp nail type, and the mechanical safety of each battery cell was evaluated based on the presence or absence of ignition of the battery cell, the amount of smoke generated, and the size of the flame at the time of ignition. 1) Time delay effect on heat propagation 2) Safety from physical impact 3) Safety from nail penetration Example 1◎◎○ Example 2◎○○ Example 3◎○○ Comparative Example 1××× Comparative Example 2△○○ Comparative Example 3××× Comparative Example 4△○○ As can be confirmed through Table 1 above, the lithium secondary batteries using the electrode current collectors of Examples 1 to 3 have a very good time delay effect for heat transfer, and also have good safety from physical impact and nail penetration. On the other hand, Comparative Example 1 using aluminum metal as a current collector and Comparative Example 3 using aluminum metal and copper metal as current collectors showed poor time delay effects for heat transfer, safety from physical impact, and safety from nail penetration. In addition, Comparative Example 2 using a current collector in which aluminum layers were formed on both sides of PET and Comparative Example 4 using a current collector in which copper layers were formed on both sides of PET showed good safety from physical impact and safety from nail penetration, but the time delay effect for heat transfer was insufficient. Through this, it was confirmed that when an electrode current collector having a first metal layer including a metal typically used as a current collector on one side of a polymer resin layer, as in Examples 1 to 3, and a second metal layer including a metal typically used as a current collector and four or more transition metals on the other side is used, the time delay effect for heat transfer of a lithium secondary battery, safety from physical impact, and safety from nail penetration can all be satisfied. In addition, through a comparison with Examples 1 and 2 and 3, it was confirmed that safety from physical impact increases as the content of four transition metals relative to the metal typically used as a current collector increases. [Explanation of symbols] 10: Electrode current collector 11: Polymer resin layer 13A, 13B: first metal layer, second metal layer 15: Bipolar 15a: Positive current collector 15b: Positive active material layer 17: Cathode 17a: Negative current collector 17b: Negative active material layer 19: Membrane 30: Electrode including electrode collector 50: Electrode assembly 100: Lithium secondary battery

Claims

1. Polymer resin layer; A first metal layer disposed on one surface of the polymer resin layer; and A second metal layer disposed on the other side of the polymer resin layer; The first metal layer comprises at least one selected from the group consisting of copper, aluminum, and stainless steel, The second metal layer includes a metal included in the first metal layer and four or more types of transition metals, The above transition metal is an electrode current collector selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Zr, Nb, Mo, Hf, Ta and W.

2. In paragraph 1, An electrode current collector, wherein the polymer resin layer comprises at least one selected from the group consisting of polyester resin, epoxy resin, phenol resin, melamine resin, urethane resin, silicone resin, EVA resin, rubber resin, acrylic resin, polyolefin resin, cellulose derivative, and polyetherurethane resin.

3. In paragraph 1, An electrode current collector, wherein the thickness of the polymer resin layer is 3 ㎛ to 18 ㎛.

4. In paragraph 1, An electrode current collector, wherein the second metal layer is an alloy of a metal included in the first metal layer and four or more types of transition metals.

5. In paragraph 1, An electrode current collector, wherein the second metal layer comprises metals, Co, Cr, Fe, and Ni, included in the first metal layer.

6. In paragraph 1, The second metal layer includes a metal included in the first metal layer and four or more types of transition metals, An electrode current collector in which the weight difference between each of the four or more transition metals constituting the above transition metals is within 15 wt%.

7. In paragraph 1, An electrode current collector, wherein the second metal layer comprises a metal included in the first metal layer and four or more types of transition metals in a weight ratio of 1:2 to 1:

15.

8. In paragraph 1, An electrode current collector wherein the first metal layer and the second metal layer each have a thickness of 1 ㎛ to 3 ㎛.

9. In paragraph 1, An electrode current collector, wherein the thickness ratio of the polymer resin layer and the first metal layer or the second metal layer is 1:1 to 1:

10.

10. An electrode assembly having a structure in which a plurality of electrodes and a plurality of separators are alternately stacked, The above electrode includes an electrode current collector and an electrode active material layer disposed on the electrode current collector, A lithium secondary battery, wherein at least one of a plurality of electrode current collectors is an electrode current collector according to any one of claims 1 to 9.

11. A battery module comprising a plurality of lithium secondary batteries described in Article 10.

12. A battery pack comprising a plurality of battery modules described in paragraph 11.

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