Electrode current collector, and lithium secondary battery, battery module, and battery pack including this battery module
Patent Information
- Application Number
- VN1202601290
- Authority / Receiving Office
- VN · VN
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-08-22
- Filing Date
- 2024-08-21
- Publication Date
- 2026-08-03
Smart Images
Figure VN1202601290_0
Abstract
Description
Electrode current collector, lithium secondary battery, battery module and battery pack including the same This application claims the benefit of priority to Korean Patent Application No. 10-2023-0110180, filed August 22, 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, 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 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 present invention is intended to solve the above problems, and provides an electrode current collector that is not only excellent in fire safety, heat resistance, and heat blocking effect, but also lightweight and thus capable of improving energy density, an electrode assembly including the same, and a lithium secondary battery. The present invention provides an electrode current collector to solve the above problem. [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 and second metal layers include a shape memory alloy (SMA), and the shape memory alloy (SMA) is designed to apply an external force to the polymer resin layer through shape deformation when a specific temperature is exceeded. [2] The present invention provides an electrode current collector according to the above [1], wherein the shape memory alloy (SMA) includes at least one of a copper-zinc alloy, a copper-tin alloy, a magnesium-copper alloy, a nickel-titanium alloy, and a copper-aluminum-nickel alloy. [3] The present invention provides an electrode current collector, wherein the content of the shape memory alloy (SMA) in at least one of the above [1] or [2] is 20 wt% to 100 wt% based on the total weight of the metal layer. [4] The present invention provides an electrode current collector, wherein in any one or more of the above [1] to [3], the polymer resin layer further 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, and polyetherurethane resin. [5] The present invention provides an electrode current collector in which the thickness ratio of the polymer resin layer and the first metal layer or the second metal layer is 1:1 to 1:10 in any one or more of the above [1] to [4]. [6] The present invention provides an electrode current collector, wherein the polymer resin layer has a thickness of 3 µm to 18 µm in any one or more of the above [1] to [5]. [7] The present invention provides an electrode current collector, wherein in any one or more of the above [1] to [6], the first metal layer and the second metal layer each independently have a thickness of 10 µm to 30 µm. The present invention also provides a lithium secondary battery including the electrode collector. [8] The present invention provides a lithium secondary battery including 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 or more of [1] to [7]. The present invention also provides a battery module and a battery pack including the lithium secondary battery. [9] The present invention provides a battery module including a plurality of lithium secondary batteries described in [8] above.
[0010] The present invention provides a battery pack including a plurality of battery modules described in [9] above. An electrode current collector according to the present invention comprises a polymer resin layer between two metal layers, wherein the metal layer comprises a shape memory alloy (SMA). The shape memory alloy (SMA) is designed to apply an external force to the polymer resin layer through shape deformation when a certain temperature is exceeded, so that as the shape of the shape memory alloy (SMA) contracts, the polymer resin layer is additionally pressurized to induce an electrical disconnection state between the electrodes, thereby improving safety. In addition, the lithium secondary battery according to the present invention can improve not only mechanical safety against foreign substances such as nail penetration, but also safety against thermal propagation in the event of an actual fire. In addition, when the battery module and battery pack according to the present invention include a plurality of the above-described electrode current collectors, safety due to thermal propagation in the event of an actual fire is maximized, thereby enabling high capacity and large area batteries to be realized. Figure 1 is a cross-sectional view schematically showing an electrode collector according to the present invention. FIGS. 2 and 3 are each a cross-sectional view 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) and the second metal layer (13B) include a shape memory alloy (SMA). The shape memory alloy (SMA) is designed to apply an external force to the polymer resin layer through shape deformation when a specific temperature is exceeded. 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 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. Accordingly, the inventors of the present invention have designed an electrode current collector including a polymer resin layer and a first metal layer and a second metal layer including a shape memory alloy (SMA) disposed on both sides of the polymer resin layer, utilizing the property of the shape memory alloy (SMA) to return to its original shape at high temperatures. The electrode has a structure in which an electrode active material layer is arranged on an electrode current collector, an electrode tab is formed to protrude from one side of the electrode, and an electrode lead is connected to the electrode tab so as to transmit electricity generated in the electrode to the outside. The first metal layer and the second metal layer according to the present invention include a shape memory alloy (SMA), and the electrode current collector may shrink as the shape memory alloy (SMA) shrinks at high temperatures. Accordingly, the electrode tab in contact with the electrode current collector shrinks, but the electrode lead does not shrink due to being fixed by welding to a bus bar or the like. Therefore, as described above, the contracted tab induces an electrical disconnection state with the electrode lead, and has a time delay effect for thermal propagation in the event of a battery fire. In addition, the electrode current collector according to the present invention can improve safety from fire, heat resistance, and heat blocking effect. (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, for example, 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, 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), 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 and / or the second metal layer comprises a shape memory alloy (SMA). The shape memory alloy (SMA) is an alloy with strong resilience, and refers to an alloy that has the property of returning to its original shape before deformation at a high temperature even if deformed into another shape. The shape memory alloy (SMA) may be manufactured through a shape memory process using a material capable of shape memory, and the shape thus remembered has the characteristic of undergoing deformation at a high temperature. The above shape memory alloy (SMA) is designed to apply an external force to the polymer resin layer through shape deformation when a certain temperature is exceeded. Specifically, the electrode current collector according to the present invention can shrink as the shape memory alloy (SMA) shrinks in a high-temperature environment by utilizing the properties of the shape memory alloy (SMA), thereby inducing an electrical disconnection state with other electrodes, thereby providing a time delay effect for thermal propagation in the event of a battery fire. The above shape memory alloy (SMA) may include at least one of a copper-zinc alloy, a copper-tin alloy, a magnesium-copper alloy, a nickel-titanium alloy, and a copper-aluminum-nickel alloy. The content of the shape memory alloy (SMA) may be 20 wt% to 100 wt%, preferably 30 wt% to 100 wt%, and more preferably 50 wt% to 100 wt%, based on the total weight of the metal layer. When the content of the shape memory alloy (SMA) satisfies the above numerical range, the shape memory alloy (SMA) can be easily applied, and the electrode current collector can shrink to a degree that the shape memory alloy (SMA) shrinks at high temperatures when the battery behaves abnormally. This can induce an electrical disconnection state between the electrodes of the battery, thereby improving battery safety. The first metal layer and / or the second metal layer may additionally include stainless steel, aluminum, copper, nickel, titanium, heat-treated carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., in addition to the shape memory alloy (SMA), as needed, or an aluminum-cadmium alloy, and specifically, when the electrode current collector is a positive electrode, it may include aluminum, and when the electrode current collector is a negative electrode, it may include copper. In addition, the first metal layer and / or the second metal layer may form fine irregularities on the surface to strengthen the bonding strength with the electrode combination layer, and may be used in 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 10 μm to 30 μm, preferably 18 μm to 28 μm, and more preferably 18 μm to 25 μm. If 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, if 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. Preferably, the thickness ratio may be 1:1.5 to 1:5, more preferably 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 an electrode current collector (10) including the shape memory alloy (SMA) described above. The lithium secondary battery (100) according to the present invention may include at least one electrode current collector (10) including the shape memory alloy (SMA) described above, 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) including the shape memory alloy (SMA) 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 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 including a shape memory alloy (SMA) as the outermost electrode, 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 including a shape memory alloy (SMA). When the electrode (30) described above is arranged on the outermost surface of the electrode assembly (50), the electrode current collector may shrink as the shape memory alloy (SMA) shrinks at high temperatures when the battery behaves abnormally. Accordingly, the electrode tab in contact with the electrode current collector shrinks, but the electrode lead does not shrink due to being fixed by welding with a bus bar or the like. Therefore, the tab that has shrunk as described above induces an electrical disconnection state with the electrode lead, and has a time delay effect on thermal propagation in the event of a battery fire. 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 a metal to which the positive electrode active material layer can be easily adhered, but is not reactive in 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 μm to 500 μm, 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% to 99% by weight, more specifically 90% to 98% by weight, 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%, preferably 0.1 wt% to 9 wt%, and more preferably 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 Ni on both sides of 6㎛ thick polyethylene terephthalate (PET) 50 Ti 50 An electrode current collector was manufactured by forming a first metal layer and a second metal layer by physical vapor deposition (PVD) of an alloy with a thickness of 18 μm. <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 A battery cell was manufactured in the same manner as in Example 1, except that it included a plurality of electrode assemblies manufactured in the manner described above. Comparative Example 1 A battery cell was manufactured using the same method as Example 1, except that the battery cell was composed only of an electrode current collector made of 12 μm thick aluminum metal, which is a typical metal current collector. Comparative Example 2 A battery cell was manufactured in the same manner as in Example 1, except that a first metal layer and a second metal layer were formed by physically vapor deposition (PVD) of aluminum metal to a thickness of 1 μm on both sides of a 6 μm thick polyethylene terephthalate (PET) and an electrode current collector was used. Experimental Example 1 For the lithium secondary battery cells manufactured in Examples 1 and 2 and Comparative Examples 1 and 2, 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 “X” 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 made 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 the adjacent cell is measured using a thermocouple to evaluate whether there is a time delay in heat transfer. 2) The mechanical safety of each battery cell was evaluated by measuring whether the battery cell caught fire by freely dropping a rod having a diameter of 15.8 mm from a height of 610 mm into the center of the battery cell while the manufactured battery cell was fully charged to 4.4 V at 0.2 C in CC / CV mode. 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 thermal propagation 2) Safety from physical impact 3) Safety from nail penetration Example 1○○○ Example 2◎◎◎ Comparative Example 1X△X Comparative Example 2△○○ From the above [Table 1], it can be confirmed that the battery cells manufactured by Examples 1 and 2 are superior to the battery cells manufactured by Comparative Examples 1 and 2 in 1) the time delay effect for thermal propagation, 2) safety from physical impact, and 3) safety from nail penetration. [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 (10) 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 and the second metal layer include a shape memory alloy (SMA), The above shape memory alloy (SMA) is an electrode current collector designed to apply an external force to the polymer resin layer through shape deformation when a certain temperature is exceeded.
2. In claim 1, An electrode current collector, wherein the shape memory alloy (SMA) comprises at least one of a copper-zinc alloy, a copper-tin alloy, a magnesium-copper alloy, a nickel-titanium alloy, and a copper-aluminum-nickel alloy.
3. In claim 1, An electrode current collector, wherein the content of the shape memory alloy (SMA) is 20 wt% to 100 wt% based on the total weight of the metal layer.
4. In claim 1, An electrode current collector, wherein the polymer resin layer further 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, and polyetherurethane resin.
5. In claim 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.
6. In claim 1, An electrode current collector, wherein the polymer resin layer has a thickness of 3 ㎛ to 18 ㎛.
7. In claim 1, An electrode current collector, wherein the first metal layer and the second metal layer each have a thickness of 10 µm to 30 µm.
8. 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 the plurality of electrode current collectors is an electrode current collector according to any one of claims 1 to 7.
9. A battery module comprising a plurality of lithium secondary batteries described in claim 8.
10. A battery pack comprising a plurality of battery modules described in claim 9.