Lithium-ion rechargeable battery, battery module containing the same, and battery pack

Abstract

The lithium secondary battery according to the present invention is a lithium secondary battery comprising an electrode assembly having a structure in which a plurality of electrodes and a plurality of separators are alternately stacked, and a battery case housing the electrode assembly, wherein the electrode comprises 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 comprising a glass layer, a first metal layer disposed on one surface of the glass layer, and a second metal layer disposed on the other surface of the glass layer.

Description

[Technical Field]

[0001] This invention claims priority under Korean Patent Application No. 10-2023-0105153, filed on 10 August 2023, and all content disclosed in the said Korean Patent Application is incorporated herein by reference.

[0002] The present invention relates to a lithium secondary battery, a battery module containing the same, and a battery pack. [Background technology]

[0003] With the increasing technological development and demand for electric vehicles and energy storage systems (ESS), the demand for batteries as their energy source is rapidly increasing. Consequently, research is being conducted on batteries that can meet a variety of requirements.

[0004] In particular, to enable longer usage times on a single charge, batteries need to be made with higher capacity, and increasing capacity requires the technology to enlarge the electrode area. However, the performance of the electrodes may decrease during the process of enlarging their area, and in the event of a fire, there is a risk of thermal runaway and thermal propagation to other electrodes.

[0005] In lithium-ion batteries, the electrode temperature can rise rapidly due to thermal and physical factors. Thermal factors include overcharging and overloading due to misuse or malfunction of chargers, while physical factors include damage to the separator due to external impact, which can cause an internal short circuit when the negative and positive electrode materials come into contact, potentially leading to a rapid rise in electrode temperature. When the electrode temperature rises rapidly in this way, the electrolyte and lithium react, and hydrogen and oxygen are generated inside the battery, making the battery extremely unstable. This can lead to the decomposition of the electrolyte solvent, generating gases, and these decomposition gases can ignite, potentially causing the battery to explode.

[0006] Conventional lithium-ion batteries contained only a single metal layer as the electrode current collector; specifically, a single metal layer of aluminum was used as the positive electrode current collector, and a single metal layer of copper was used as the negative electrode current collector. However, because such single metal layers have very high electrical and thermal conductivity, the time it takes for them to reach high temperatures instantaneously due to abnormal battery behavior is very short, raising concerns about thermal runaway and thermal propagation.

[0007] Therefore, there is a need for enhanced mechanical safety and thermal propagation safety in the event of abnormal behavior such as thermal runaway or significant physical deformation in lithium secondary batteries. [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The present invention aims to solve the above-mentioned problems and provides a lithium secondary battery, a battery module containing the same, and a battery pack that are excellent in terms of safety from fire, heat resistance, and thermal insulation effect. [Means for solving the problem]

[0009] In one aspect, 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 stacked, and a battery case housing the electrode assembly, wherein the electrode comprises 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 comprising a glass layer, a first metal layer disposed on one side of the glass layer, and a second metal layer disposed on the other side of the glass layer.

[0010] The thickness of the glass layer may be 200 μm or less.

[0011] The first metal layer and the second metal layer may each independently have a thickness of 0.2 μm to 5.0 μm.

[0012] The thickness ratio of the first metal layer or the second metal layer to the glass layer may be 1:20 to 1:1000.

[0013] The first metal layer and the second metal layer may each independently contain one or more materials selected from the group consisting of copper, aluminum, stainless steel, and nickel.

[0014] An electrode including the current collector containing the glass layer may be placed on the outermost part of the electrode assembly.

[0015] In other aspects, the present invention provides a battery module comprising a plurality of the above-described lithium secondary batteries, and a battery pack comprising a plurality of the battery modules. [Effects of the Invention]

[0016] The lithium secondary battery according to the present invention includes an electrode current collector containing a glass layer between two metal layers. Therefore, in the event of abnormal behavior such as thermal runaway or large physical deformation, the glass layer is pulverized, damaging the metal layer and inducing an electrical short circuit between the electrodes.

[0017] Furthermore, the density of the glass layer is 2.4 g / cm³. 3 ~2.9g / cm 3 It is similar to aluminum metal, but copper metal (density 8.96 g / cm³) 3 Because it is smaller than ( ), especially when applied to the negative electrode, its weight is similar to that of an electrode current collector made only of metal, and while maintaining energy density per unit weight, it can improve not only mechanical safety but also safety due to thermal propagation in the event of an actual fire.

[0018] In addition, when the above-described electrode current collector includes a plurality of elements, the battery module and the battery pack according to the present invention can maximize the safety due to thermal propagation in the event of an actual fire, and can achieve high capacity and large area of the battery.

Brief Description of the Drawings

[0019] [Figure 1] It is a cross-sectional view showing an electrode current collector according to an embodiment of the present invention. [Figure 2] It is a cross-sectional view showing a lithium secondary battery according to an embodiment of the present invention. [Figure 3] It is a cross-sectional view showing a lithium secondary battery according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0020] Advantages and features of the present invention, and methods for achieving them, will become clear by referring 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 can be realized in various different forms. These embodiments are provided so that the disclosure of the present invention is complete and to fully convey the scope of the invention to those with ordinary knowledge in the technical field to which the present invention pertains. The present invention is defined only by the scope of the claims. Throughout the specification, the same reference numerals denote the same components.

[0021] Unless otherwise defined, all terms (including technical and scientific terms) used in this specification can be used in a meaning commonly understood by those with ordinary knowledge in the technical field to which the present invention pertains. Also, terms defined in commonly used dictionaries are not ideally or excessively interpreted unless specifically defined otherwise.

[0022] The terms used herein are for illustrative purposes only and are not intended to limit the invention. In this specification, singular nouns include plural nouns unless otherwise specified in the text. The terms “comprises” and / or “comprising” as used in this specification do not preclude the presence or addition of one or more other components in addition to the components mentioned.

[0023] In this specification, when a part is said to include a component, this means that, unless otherwise stated to the contrary, it may include other components rather than excluding them.

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

[0025] In this specification, "%" means weight percent unless otherwise explicitly indicated.

[0026] Lithium-ion rechargeable battery The lithium secondary battery according to the present invention is a lithium secondary battery comprising an electrode assembly having a structure in which a plurality of electrodes and a plurality of separators are alternately stacked, and a battery case housing the electrode assembly, wherein the electrode comprises 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 comprising a glass layer, a first metal layer disposed on one surface of the glass layer, and a second metal layer disposed on the other surface of the glass layer.

[0027] The following describes the electrode current collector including the glass layer, the electrodes, the separator, the electrolyte, and the battery case in that order.

[0028] (1) Electrode current collector Conventional lithium-ion batteries contained only a single metal layer as the electrode current collector; specifically, a single metal layer of aluminum was used as the positive electrode current collector, and a single metal layer of copper was used as the negative electrode current collector. However, because such single metal layers have very high electrical and thermal conductivity, the time it takes for the battery to reach high temperatures instantaneously due to abnormal battery behavior is very short, raising concerns about thermal runaway and thermal propagation.

[0029] Therefore, there is a need for enhanced mechanical safety and thermal propagation safety in the event of abnormal behavior such as thermal runaway or significant physical deformation in lithium secondary batteries.

[0030] Therefore, the inventors have devised an electrode current collector comprising a glass layer and a first metal layer and a second metal layer arranged on both sides of the glass layer. They have confirmed that this has the effect of inducing an electrical short circuit between electrodes when the battery experiences abnormal behavior such as thermal runaway or large physical deformation, by causing damage to the metal layers while the glass layer is shattered. In other words, the lithium secondary battery according to the present invention can improve mechanical safety and safety through thermal propagation in the event of an actual fire.

[0031] Figure 1 is a cross-sectional view showing an electrode current collector according to one embodiment of the present invention.

[0032] Referring to Figure 1, an electrode current collector 10 according to one embodiment of the present invention includes a glass layer 11, a first metal layer 13A disposed on one surface of the glass layer 11, and a second metal layer 13B disposed on the other surface of the glass layer 11.

[0033] (1-1) Glass layer 11 The aforementioned glass layer 11 is an amorphous solid, characterized by being transparent, smooth, and brittle. The main component of glass is silicon dioxide (SiO2), and quartz or silica sand are used, both of which are minerals consisting of nearly pure SiO2.

[0034] The electrode current collector according to the present invention includes a glass layer 11 between metal layers. When abnormal behavior occurs in the battery, such as thermal runaway, or when large physical deformation occurs, the glass layer 11 is pulverized, damaging the metal layers and inducing an electrical short circuit between the electrodes. This improves safety in the event of an actual fire by preventing thermal propagation.

[0035] The thickness of the glass layer 11 may be 200 μm or less, preferably 50 μm to 200 μm, and more preferably 50 μm to 100 μm. If the thickness of the glass layer 11 exceeds 200 μm, the thickness of the cell will increase dramatically, which may increase resistance and adversely affect the energy density. When the thickness of the glass layer 11 satisfies the above numerical range, the thickness of the glass layer 11 can be minimized, while in the event of abnormal behavior in the battery, the broken glass layer 11 will affect the electrodes, significantly improving battery safety by preventing electrical short circuits.

[0036] (1-2) Metal layer 13A, 13B The first metal layer 13A and / or the second metal layer 13B may contain one or more materials selected from the group consisting of copper, aluminum, stainless steel, or nickel. While not particularly limited, it is preferable to include aluminum when forming a positive electrode current collector, and to include copper when forming a negative electrode current collector. Furthermore, the first metal layer 13A and / or the second metal layer 13B may have fine irregularities formed on its surface to strengthen the bonding force with the electrode bonding layer, and can be used in various forms such as films, sheets, foils, meshes, porous materials, foams, and nonwoven fabrics.

[0037] The thickness of the first metal layer 13A and / or the second metal layer 13B may be 0.2 μm to 5.0 μm, preferably 0.5 μm to 2.0 μm, and more preferably 0.5 μm to 1.0 μm. If the thickness of the first metal layer 13A and / or the second metal layer 13B is less than 0.2 μm, it is too thin to function as a support, making it difficult to maintain the shape of the electrode and difficult to control the physical properties of the electrode. On the other hand, if the thickness exceeds 5.0 μm, the resistance of the electrode increases, the thickness and weight of the cell increase excessively, and there is a risk that the energy density will decrease.

[0038] The thickness ratio of the first metal layer 13A to the glass layer 11 may be 1:20 to 1:1000, and the thickness ratio of the second metal layer 13B to the glass layer 11 may be 1:20 to 1:1000. The thickness ratio of the first metal layer 13A or the second metal layer 13B to the glass layer 11 may preferably be 1:25 to 1:400, and more preferably 1:50 to 1:200. When the thickness ratio of the first metal layer 13A or the second metal layer 13B to the glass layer 11 satisfies the above numerical range, the thickness of the glass layer 11 can be minimized, while in the event of abnormal behavior in the battery, the broken glass layer 11 can affect the electrodes, significantly improving battery safety by preventing electrical short circuits.

[0039] Figures 2 and 3 are cross-sectional views showing a lithium secondary battery according to one embodiment of the present invention.

[0040] Referring to Figures 2 and 3, the 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 stacked in order, the separator 19 being positioned between the positive electrode 15 and the negative electrode 17, the positive electrode 15 including a positive electrode current collector 15a and a positive electrode active material layer 15b stacked on the positive electrode current collector 15a, the negative electrode 17 including a negative electrode current collector 17a and a negative electrode active material layer 17b stacked on the negative electrode current collector 17a, and at least one of the positive electrode current collector 15a and the negative electrode current collector 17a is an electrode current collector 10 including the glass layer 11 described above.

[0041] The lithium secondary battery according to the present invention includes at least one electrode current collector 10 containing the glass layer 11 described above, and preferably 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 stacked, an electrode 30 containing the electrode current collector 10 containing the glass layer 11 described above can be placed on the outermost part of the electrode assembly 50. When the electrode 30 described above is placed on the outermost part of the electrode assembly 50, when abnormal behavior occurs in the battery, the shattered glass layer 11 can further rupture the battery case housing the electrode assembly 50. This allows the electrolyte inside the battery case to disappear through the damaged part of the battery case, inducing an electrical short circuit, and improving safety through thermal propagation in the event of an actual fire.

[0042] (2) Electrode (2-1) Positive electrode The positive electrode current collector may contain a highly conductive metal and is not particularly limited as long as the positive electrode active material layer adheres to it easily and it is unreactive within the battery voltage range. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, heat-treated carbon, or aluminum or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc. The positive electrode current collector usually has a thickness of about 3 μm to 500 μm, and the adhesion strength of the positive electrode active material may be increased by forming fine irregularities on the surface of the current collector. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, and nonwoven fabric.

[0043] The positive electrode active material layer may, if necessary, selectively contain a conductive material and a binder along with the positive electrode active material.

[0044] In this case, the positive electrode active material may be included in an amount of 80% to 99% by weight, more specifically 90% to 98% by weight, relative to the total weight of the positive electrode active material layer.

[0045] The conductive material is used to impart conductivity to the electrodes and is not particularly limited as long as it does not cause chemical changes in the battery it is used in. 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 and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these may be used alone, or a mixture of two or more. The conductive material may be included in an amount of 0.01% to 10% by weight, preferably 0.1% to 9% by weight, and more preferably 0.1% to 5% by weight, relative to the total weight of the positive electrode active material layer.

[0046] The binder plays a role in improving 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), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and polymers in which the hydrogen atoms of these materials are substituted with Li, Na, or Ca, or various copolymers thereof. One of these can be used alone, or a mixture of two or more. The binder may be present in an amount of 1% to 30% by weight, preferably 1% to 20% by weight, and more preferably 1% to 10% by weight, relative to the total weight of the positive electrode active material layer.

[0047] The positive electrode may be manufactured by a conventional method for manufacturing a positive electrode, except that the positive electrode active material described above is used. Specifically, it can be manufactured by coating a positive electrode slurry composition, prepared by dissolving or dispersing the positive electrode active material and, if necessary, a binder, conductive material, and dispersant selectively in a solvent, onto a positive electrode current collector, followed by drying and rolling.

[0048] The solvent can be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water. One of these can be used alone, or a mixture of two or more. The amount of solvent used should be sufficient to dissolve or disperse the cathode active material, conductive material, binder, and dispersant, and to have a viscosity that allows for excellent thickness uniformity during subsequent coating for cathode manufacturing, taking into account the coating thickness and production yield of the slurry.

[0049] Alternatively, the positive electrode may be manufactured by casting the positive electrode slurry composition onto another support, peeling it off the support, and then laminating the resulting film onto the positive electrode current collector.

[0050] (2-2) Negative electrode The negative electrode includes a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0051] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, heat-treated carbon, copper or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. The negative electrode current collector usually has a thickness of 3 μm to 500 μm, and, similar to the positive electrode current collector, the bonding force of the negative electrode active material may be strengthened by forming fine irregularities on the surface of the current collector. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, and nonwoven fabric.

[0052] The negative electrode active material layer selectively includes a binder and a conductive material together with the negative electrode active material.

[0053] As the negative electrode active material, compounds capable of reversible intercalation and deintercalation of lithium can be used. Specific examples 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 alloys, Sn alloys, or Al alloys; metallic oxides capable of doping and dedoping with lithium, such as SiOβ (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the aforementioned metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites. Any one or a mixture of two or more of these can be used. A metallic lithium thin film may also be used as the negative electrode active material. Furthermore, both low-crystallinity carbon and high-crystallinity carbon can be used as the carbon material. Typical examples of low-crystalline carbon include soft carbon and hard carbon, while typical examples of high-crystalline carbon include amorphous, plate-like, flaky, spherical, or fibrous natural or artificial graphite, 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.

[0054] The negative electrode active material may be present in an amount of 80% to 99% by weight, 82% to 99% by weight, or 84% to 99% by weight, based on the total weight of the negative electrode active material layer.

[0055] The binder is a component that helps to bond the conductive material, active material, and current collector, and is usually added in an amount of 0.1% to 10% by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0056] The conductive material is a component for further improving the conductivity of the negative electrode active material and may be included in an amount of 1% to 30% by weight, 1% to 20% by weight, or 1% to 10% by weight relative to the total weight of the negative electrode active material layer. The conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive, and may be used as an example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fibers or metal fibers; carbon fluoride; metal powders such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive materials such as polyphenylene derivatives.

[0057] The negative electrode active material layer may be manufactured by coating a negative electrode slurry composition, which is prepared by dissolving or dispersing a negative electrode active material and a binder and conductive material selectively in a solvent, onto a negative electrode current collector and drying it, or by casting the negative electrode slurry composition onto another support, peeling it off the support, and then laminating the resulting film onto the negative electrode current collector.

[0058] (3) Separator The separator separates the negative and positive electrodes and provides a passage for lithium ions to move. It can be used without particular limitations as long as it is one that is commonly used as a separator in lithium secondary batteries, and is particularly preferred if it has low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity. Specifically, porous polymer films, such as porous polymer films made from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers thereof can be used. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, coated separators containing ceramic components or polymeric substances may be used to ensure heat resistance or mechanical strength, and may be used selectively as a single-layer or multi-layer structure.

[0059] (4) Electrolyte Examples of electrolytes used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0060] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0061] The organic solvent can be any solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move, and is not particularly limited. Specifically, the organic solvents 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; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propylene Carbonate solvents such as carbonate (PC); alcoholic solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and may include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred.

[0062] The lithium salt is not particularly limited as long as it can provide lithium ions used in a lithium secondary battery and can be used without limitation. Specifically, as the anion of the lithium salt, 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 one or more selected from the group consisting of (CF3CF2SO2)2N - may be used, and the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. The concentration of the lithium salt is preferably used within the range of 0.1 M to 4.0 M, more preferably 0.5 M to 3.0 M, and even more preferably 1.0 M to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0063] In addition to the components of the electrolyte, the electrolyte may further contain one or more additives for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity, such as haloalkylene carbonate compounds like difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be present in an amount of 0.1% to 10.0% by weight relative to the total weight of the electrolyte.

[0064] (5) Battery case The lithium secondary battery according to the present invention may further optionally include a battery case for housing the electrode assembly comprising the positive electrode, separator, and negative electrode, and a sealing member for sealing the battery case.

[0065] Furthermore, the lithium secondary battery according to the present invention exhibits excellent discharge capacity, output characteristics, and capacity retention rate stably, making it useful in portable devices such as mobile phones, notebook computers, and digital cameras, as well as in the electric vehicle field, such as hybrid electric vehicles (HEVs).

[0066] Battery modules and battery packs Accordingly, according to another embodiment of the present invention, a battery module comprising a plurality of the lithium secondary batteries and a battery pack comprising a plurality of the battery modules are provided.

[0067] The battery module refers to a battery assembly in which a certain number of lithium secondary batteries are grouped together and placed in a frame to protect them from external shocks, heat, vibrations, etc. The battery pack refers to the final form of a battery system installed in an electric vehicle or the like.

[0068] The aforementioned battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0069] When the battery module and battery pack according to the present invention include multiple electrode current collectors, safety due to thermal propagation in the event of an actual fire is maximized, and the battery can be made to have a higher capacity and a larger surface area.

[0070] Hereinafter, embodiments of the present invention will be described in detail so that those with ordinary skill in the art to which the present invention pertains can easily implement it. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0071] Examples and Comparative Examples Example 1 A positive electrode current collector was manufactured by physically vapor-depositing (PVD) aluminum metal to a thickness of 1 μm on both sides of a 100 μm thick willow glass (Corning Corporation) to form a first metal layer and a second metal layer.

[0072] <Manufacturing of lithium-ion secondary batteries> A cathode slurry was prepared by mixing a cathode active material (NCM65 1520), a conductive material (Li-435), and a PVDF binder (KF9700, AD-c01) in a weight ratio of 96.5:1.5:2.0 in N-methylpyrrolidone.

[0073] After applying the positive electrode slurry to one surface of the positive electrode current collector manufactured by the method described above, the positive electrode was manufactured by drying it at 140°C and then rolling it.

[0074] Graphite was used for the negative electrode.

[0075] After manufacturing an electrode assembly by interposing a separator between the positive and negative electrodes produced by the method described above, the assembly was placed in the center of the battery case, and an electrolyte was injected into the case to produce a battery cell. The electrolyte was prepared by dissolving 0.7 M LiPF6 in a mixed organic solvent consisting of ethylene carbonate (EC):propylene carbonate (PC):ethyl methyl carbonate (EMC) in a volume ratio of 2:1:7.

[0076] Example 2 <Manufacturing of positive electrode A> A positive electrode current collector was manufactured by physically vapor-depositing (PVD) aluminum metal to a thickness of 1 μm on both sides of a 100 μm thick willow glass (Corning Corporation) to form a first metal layer and a second metal layer.

[0077] A cathode slurry was prepared by mixing a cathode active material (NCM65 1520), a conductive material (Li-435), and a PVDF binder (KF9700, AD-c01) in a weight ratio of 96.5:1.5:2.0 in N-methylpyrrolidone.

[0078] After applying the positive electrode slurry to one surface of the positive electrode current collector manufactured by the method described above in Example 1, the positive electrode A was manufactured by drying it at 140°C and then rolling it.

[0079] <Manufacturing of positive electrode B> Positive electrode B was manufactured in the same manner as described above, except that a 15 μm thick aluminum current collector, a common metal current collector, was used as the positive electrode current collector.

[0080] <Manufacturing of lithium-ion secondary batteries> Graphite was used for the negative electrode.

[0081] In the configuration shown in Figure 3, one side of the negative electrode 17 is placed facing both sides of the positive electrode B15, and the positive electrode A10 is placed facing the other side of the negative electrode 17. Then, a separator 19 is interposed between the positive electrode A10 and the negative electrode 17, and between the positive electrode B15 and the negative electrode 17, thereby manufacturing an electrode assembly in which the positive electrode A10 is placed on the outermost side of the electrode assembly.

[0082] After positioning the manufactured electrode assembly in the center of the battery case, an electrolyte solution was injected into the case to produce a battery cell. The electrolyte solution was prepared by dissolving 0.7 M LiPF6 in a mixed organic solvent consisting of ethylene carbonate (EC):propylene carbonate (PC):ethyl methyl carbonate (EMC) in a volume ratio of 2:1:7.

[0083] Comparative Example 1 A battery cell was manufactured in the same manner as in Example 1, except that a 15 μm thick aluminum current collector, a common metal current collector, was used as the positive electrode current collector.

[0084] Comparative Example 2 A battery cell was manufactured in the same manner as in Example 1, except that a 1 μm thick layer of aluminum metal was physically vapor-deposited (PVD) onto both sides of a 6 μm thick polyethylene terephthalate (PET) sheet, and a positive electrode current collector containing a first metal layer and a second metal layer was used.

[0085] Experimental Example 1 Experiments were conducted on the lithium secondary battery cells manufactured in Examples 1-2 and Comparative Examples 1-2 regarding 1) the time delay effect on thermal propagation, 2) safety against physical impact, and 3) safety against nail penetration. The experimental results are shown in Table 1 below. In Table 1, "◎" indicates very good, "○" indicates good, "△" indicates average, and "X" indicates poor.

[0086] Specifically, the experimental methods for 1) the time delay effect on thermal propagation, 2) safety against physical impact, and 3) safety against nail penetration are as follows.

[0087] 1) The five manufactured battery cells were combined into a single module, and heat was applied to one of the battery cells at a rate of 0.5°C / sec using a heating pad. The heat transferred to adjacent cells was measured using thermocouples, and the presence or absence of a time delay in heat transfer was evaluated.

[0088] 2) The manufactured battery cells were fully charged to 4.4V at 0.2C in CC / CV mode. The presence or absence of ignition in the battery cells was measured by free-dropping a 15.8mm diameter rod from a height of 610mm into the center of each battery cell, and the mechanical safety of each battery cell was evaluated.

[0089] 3) The manufactured battery cells were subjected to a nail-penetration experiment using a sharp nail type at a speed of 0.1 mm / s to evaluate the mechanical safety of each battery cell.

[0090] [Table 1]

[0091] From Table 1 above, it can be confirmed that the battery cells manufactured in Examples 1 and 2, respectively, are superior to the battery cells manufactured in Comparative Examples 1 and 2 in terms of 1) time delay effect against thermal propagation, 2) safety against physical impact, and 3) safety against nail penetration. Examples 1 and 2 include a positive electrode containing a positive electrode current collector containing a glass layer (willow glass). When abnormal battery behavior occurs due to an external heat source, physical impact, or nail penetration, the glass layer breaks, damaging the metal layers arranged on both sides of the glass layer and inducing an electrical short circuit between the electrodes. This improves 1) time delay effect against thermal propagation, 2) safety against physical impact, and 3) safety against nail penetration.

[0092] In particular, in Example 2, the positive electrode (positive electrode A) including a positive electrode current collector containing a glass layer (willow glass) is positioned on the outermost part of the electrode assembly. By positioning positive electrode current collectors containing glass layers (willow glass) on both sides of the outermost part of the electrode assembly, a superior time delay effect against heat propagation is achieved. Furthermore, when the positive electrode current collector is shattered by physical impact or nail penetration, it breaks the battery case and releases the electrolyte to the outside of the battery case, thus providing even greater safety. [Explanation of Symbols]

[0093] 10 Electrode current collector including a glass layer 11 glass layer 13A, 13B 1st metal layer, 2nd metal layer 15 Positive electrode 15a Positive electrode current collector 15b Positive electrode active material layer 17 Negative electrode 17a Negative electrode current collector 17b Negative electrode active material layer 19 Separator 30 Electrode containing a glass layer, including an electrode current collector. 50 electrode assembly 100 Lithium-ion rechargeable batteries

Claims

1. A lithium secondary battery comprising an electrode assembly having a structure in which multiple electrodes and multiple separators are alternately stacked, and a battery case housing the electrode assembly, The electrode comprises an electrode current collector and an electrode active material layer disposed on the electrode current collector. A lithium secondary battery in which at least one of the plurality of electrode current collectors is an electrode current collector comprising a glass layer, a first metal layer disposed on one surface of the glass layer, and a second metal layer disposed on the other surface of the glass layer.

2. The lithium secondary battery according to claim 1, wherein the thickness of the glass layer is 200 μm or less.

3. The lithium secondary battery according to claim 1, wherein the first metal layer and the second metal layer each independently have a thickness of 0.2 μm to 5.0 μm.

4. The lithium secondary battery according to claim 1, wherein the thickness ratio of the first metal layer or the second metal layer to the glass layer is 1:20 to 1:1000.

5. The lithium secondary battery according to claim 1, wherein the first metal layer and the second metal layer each independently contain one or more selected from the group consisting of copper, aluminum, stainless steel, and nickel.

6. The lithium secondary battery according to claim 1, wherein the electrode, which includes the electrode current collector including the glass layer, is arranged on the outermost part of the electrode assembly.

7. A battery module comprising a plurality of lithium secondary batteries as described in claim 1.

8. A battery pack comprising a plurality of battery modules as described in claim 7.

Images