Lithium secondary battery, and battery module and battery pack including same

Abstract

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 stacked; and a battery case for receiving the electrode assembly, 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 includes 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

Lithium secondary battery, battery module and battery pack including the same

[0001] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0105153, filed August 10, 2023, the entire contents of which are incorporated herein by reference.

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

[0003]

[0004] 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.

[0005] 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.

[0006] 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.

[0007] 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.

[0008] Accordingly, there is a need to supplement mechanical safety and safety against thermal propagation in cases where abnormal behavior such as thermal runaway occurs in lithium secondary batteries or large physical deformation occurs.

[0009]

[0010] The present invention is intended to solve the above problems, and provides a lithium secondary battery having excellent fire safety, heat resistance, and heat blocking effect, and a battery module and battery pack including the same.

[0011]

[0012] 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 laminated; and a battery case accommodating the electrode assembly, 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 including 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.

[0013] The thickness of the above glass layer may be 200㎛ or less.

[0014] The first metal layer and the second metal layer may each independently have a thickness of 0.2 μm to 5.0 μm.

[0015] The thickness ratio of the first metal layer or the second metal layer and the glass layer may be 1:20 to 1:1000.

[0016] The first metal layer and the second metal layer may each independently include at least one selected from the group consisting of copper, aluminum, stainless steel, and nickel.

[0017] An electrode including an electrode current collector including the above glass layer may be disposed at the outermost part of the electrode assembly.

[0018]

[0019] In another aspect, the present invention provides a battery module including a plurality of the above-described lithium secondary batteries and a battery pack including a plurality of the above-described battery modules.

[0020]

[0021] The lithium secondary battery according to the present invention includes an electrode current collector including a glass layer between two metal layers, so that when abnormal behavior such as thermal runaway occurs or when a large physical deformation occurs, the glass layer may be crushed, causing damage to the metal layer, thereby inducing an electrical short circuit between the electrodes.

[0022] Additionally, the density of the glass layer is 2.4 g / cm 3 2.9g / cm 3 It is similar to aluminum metal, but has a higher density than copper metal (density 8.96 g / cm 3 ) is smaller than that of a cathode, and especially when applied to a cathode, it is similar in weight to an electrode current collector made of only metal, so it can improve safety by thermal propagation in the event of an actual fire as well as mechanical safety while maintaining energy density per weight.

[0023] 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.

[0024]

[0025] Figure 1 is a cross-sectional view showing an electrode collector according to one embodiment of the present invention.

[0026] Figures 2 and 3 are cross-sectional views showing a lithium secondary battery according to one embodiment of the present invention.

[0027]

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] In this specification, the description of “A and / or B” means A, or B, or A and B.

[0033] In this specification, “%” means weight percent unless explicitly indicated otherwise.

[0034]

[0035] lithium secondary battery

[0036] 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, and a battery case accommodating the electrode assembly, 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 an electrode current collector including 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.

[0037] Hereinafter, the electrode current collector including the glass layer, electrode, separator, electrolyte, and battery case will be described in that order.

[0038]

[0039] (1) Electrode current collector

[0040] 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.

[0041] Accordingly, there is a need to supplement mechanical safety and safety against thermal propagation in cases where abnormal behavior such as thermal runaway occurs in lithium secondary batteries or large physical deformation occurs.

[0042]

[0043] Accordingly, the inventors of the present invention designed an electrode current collector comprising a glass layer and a first metal layer and a second metal layer disposed on both sides of the glass layer, and confirmed that when abnormal behavior such as thermal runaway occurs in the battery or a large physical deformation occurs, the glass layer is crushed and damages the metal layer, thereby inducing an electrical short circuit between the electrodes. That is, the lithium secondary battery according to the present invention can improve mechanical safety and safety due to thermal propagation in the event of an actual fire.

[0044]

[0045] Figure 1 is a cross-sectional view showing an electrode collector according to one embodiment of the present invention.

[0046] Referring to FIG. 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, and a second metal layer (13B) disposed on the other surface of the glass layer.

[0047]

[0048] (1-1) Glass layer (11)

[0049] The above glass layer (11) is an amorphous solid, and is characterized by being transparent, smooth, and easily broken. The main component of glass is silicon dioxide (SiO2), and quartz or silica is used, both of which are minerals composed of almost pure SiO2.

[0050] The electrode current collector according to the present invention includes a glass layer (11) between metal layers, so that when abnormal behavior such as thermal runaway occurs in the battery or a large physical deformation occurs, the glass layer is crushed and causes damage to the metal layer, thereby inducing an electrical short circuit between the electrodes, thereby improving safety by thermal propagation in the event of an actual fire.

[0051]

[0052] The above glass layer (11) may have a thickness of 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 increases dramatically, which increases resistance and may adversely affect the energy density. If the thickness of the glass layer (11) satisfies the above numerical range, the thickness of the glass layer can be minimized, and the battery safety due to an electrical short circuit caused by a broken glass layer affecting the electrode when the battery behaves abnormally can be greatly improved.

[0053]

[0054] (1-2) Metal layer (13A, 13B)

[0055] The first metal layer (13A) and / or the second metal layer (13B) may include at least one selected from the group consisting of copper, aluminum, stainless steel, and nickel. Although not particularly limited, when forming a positive electrode current collector, it is preferable to include aluminum, and when forming a negative electrode current collector, it is preferable to include copper. In addition, the first metal layer (13A) and / or the second metal layer (13B) 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.

[0056]

[0057] The first metal layer (13A) and / or the second metal layer (13B) may have a thickness of 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. When 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, so it is difficult to maintain the shape as an electrode, and it is difficult to control the physical properties of the electrode. On the other hand, when the thickness exceeds 5.0 μm, the resistance of the electrode increases, and the thickness and weight of the cell increase excessively, which may lower the energy density.

[0058]

[0059] The thickness ratio of the first metal layer (13A) and the glass layer (11) may be 1:20 to 1:1000, and the thickness ratio of the second metal layer (13B) and 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) and the glass layer (11) may be preferably 1:25 to 1:400, more preferably 1:50 to 1:200. When the thickness ratio of the first metal layer (13A) or the second metal layer (13B) and the glass layer (11) satisfies the above numerical range, the thickness of the glass layer can be minimized, and the battery safety due to an electrical short circuit can be greatly improved when a broken glass layer affects the electrode during abnormal battery behavior.

[0060]

[0061] Figures 2 and 3 are cross-sectional views showing a lithium secondary battery according to one embodiment of the present invention.

[0062] Referring to FIGS. 2 and 3, 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 glass layer (11) described above.

[0063] The lithium secondary battery according to the present invention may include at least one electrode current collector (10) including the above-described glass layer (11), 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 an electrode current collector (10) including the above-described glass layer (11) may be disposed at the outermost part of the electrode assembly (50). When the above-described electrode (30) is disposed at the outermost part of the electrode assembly (50), the glass layer (11) broken when the battery malfunctions may have an additional effect of penetrating the battery case housing the electrode assembly (50). Accordingly, an electrical short circuit may be induced as the electrolyte inside the battery case is lost through the damaged portion of the battery case, and safety due to thermal propagation may be improved when an actual fire occurs.

[0064]

[0065] (2) Electrode

[0066] (2-1) Bipolar

[0067] 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.

[0068]

[0069] 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.

[0070] 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.

[0071]

[0072] 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.

[0073]

[0074] 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.

[0075]

[0076] 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.

[0077] 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.

[0078]

[0079] 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.

[0080]

[0081] (2-2) Cathode

[0082] The above negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0083] 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.

[0084]

[0085] The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

[0086] 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.

[0087] 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.

[0088]

[0089] 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.

[0090]

[0091] 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.

[0092]

[0093] 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.

[0094]

[0095] (3) Membrane

[0096] 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.

[0097]

[0098] (4) Electrolyte

[0099] Examples of the electrolyte 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.

[0100] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0101] 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.

[0102]

[0103] 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.

[0104]

[0105] 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.

[0106]

[0107] (5) Battery case

[0108] The lithium secondary battery according to the present invention may optionally further include a battery case that houses the electrode assembly of the positive electrode, the separator, and the negative electrode, and a sealing member that seals the battery case.

[0109]

[0110] 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).

[0111]

[0112] Battery modules and battery packs

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117]

[0118] 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.

[0119]

[0120] Examples and Comparative Examples

[0121] Example 1

[0122] A positive electrode current collector was manufactured by forming a first metal layer and a second metal layer by physically vapor deposition (PVD) of aluminum metal to a thickness of 1 ㎛ on each side of 100 ㎛ thick Willow glass (Corning).

[0123] <Manufacturing of Lithium Secondary Batteries>

[0124] 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.

[0125] After applying the positive electrode slurry to one surface of the positive electrode current collector manufactured by the above-described method, the positive electrode was dried at 140°C and then rolled to manufacture the positive electrode.

[0126] Graphite was used as the cathode.

[0127] 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 in the center of 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.

[0128]

[0129] Example 2

[0130] <Manufacturing of positive electrode A>

[0131] A positive electrode current collector was manufactured by forming a first metal layer and a second metal layer by physically vapor deposition (PVD) of aluminum metal to a thickness of 1 ㎛ on each side of 100 ㎛ thick Willow glass (Corning).

[0132] 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.

[0133] After applying the positive electrode slurry to one surface of the positive electrode current collector manufactured by the method described in Example 1, the positive electrode A was manufactured by drying at 140°C and then rolling.

[0134] <Manufacturing of positive electrode B>

[0135] A cathode B was manufactured in the same manner as described above, except that a 15 μm thick aluminum current collector, which is a typical metal current collector, was used as the cathode current collector.

[0136] <Manufacturing of Lithium Secondary Batteries>

[0137] Graphite was used as the cathode.

[0138] As shown in Fig. 3, one side of the cathode (17) was placed on both sides of the anode B (15), the other side of the cathode (17) was placed on the anode A (10), and then a separator (19) was interposed between the anode A (10) and the cathode (17) and between the anode B (15) and the cathode (17), so that an electrode assembly was manufactured in which the anode A (10) was placed on the outermost side of the electrode assembly.

[0139] After positioning the manufactured electrode assembly in the center of the battery case, an electrolyte was injected 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.

[0140]

[0141] Comparative Example 1

[0142] A battery cell was manufactured in the same manner as in Example 1, except that a 15 μm thick aluminum current collector, which is a common metal current collector, was used as the positive electrode current collector.

[0143]

[0144] Comparative Example 2

[0145] A battery cell was manufactured in the same manner as in Example 1, except that a positive electrode current collector including a first metal layer and a second metal layer was used by physically vapor depositing aluminum metal to a thickness of 1 μm on both sides of a 6 μm thick polyethylene terephthalate (PET) sheet.

[0146]

[0147] Experimental Example 1

[0148] 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.

[0149]

[0150] 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.

[0151] 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.

[0152] 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.

[0153] 3) A nail penetration test was performed by penetrating the manufactured battery cells at a speed of 0.1 mm / s using a sharp nail type to evaluate the mechanical safety of each battery cell.

[0154]

[0155] 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△○○

[0156] From the above [Table 1], 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, respectively, in 1) the time delay effect for thermal propagation, 2) safety from physical impact, and 3) safety from nail penetration. In the case of Examples 1 and 2, the positive electrode including the positive electrode current collector including a glass layer (Willow glass) is included, and when the battery exhibits abnormal behavior due to an external heat source, physical impact, or nail penetration, the glass layer is broken and the metal layers disposed on both sides of the glass layer are damaged, thereby inducing an electrical short circuit between the electrodes, thereby improving 1) the time delay effect for thermal propagation, 2) safety from physical impact, and 3) safety from nail penetration.

[0157] In particular, in the case of Example 2, the positive electrode (positive electrode A) including a positive electrode current collector including a glass layer (Willow glass) is positioned at the outermost side of the electrode assembly, and the positive electrode current collector including a glass layer (Willow glass) is positioned on both sides of the outermost side of the electrode assembly, so that a more excellent time delay effect is exhibited for heat transfer, and also, when the positive electrode current collector is broken by physical impact or nail penetration, it pierces the battery case and releases the electrolyte to the outside of the battery case, so that even better safety can be exhibited.

[0158]

[0159]

[0160] [Explanation of symbols]

[0161] 10: Electrode current collector including a glass layer

[0162] 11: Glass layer

[0163] 13A, 13B: first metal layer, second metal layer

[0164] 15: Bipolar

[0165] 15a: Positive current collector

[0166] 15b: Positive active material layer

[0167] 17: Cathode

[0168] 17a: Negative current collector

[0169] 17b: Negative active material layer

[0170] 19: Membrane

[0171] 30: Electrode including an electrode collector including a glass layer

[0172] 50: Electrode assembly

[0173] 100: Lithium secondary battery

Claims

1. An electrode assembly having a structure in which a plurality of electrodes and a plurality of separators are alternately stacked; and a battery case accommodating the electrode assembly, 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 including 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. In claim 1, A lithium secondary battery, wherein the thickness of the glass layer is 200㎛ or less.

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

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

5. In claim 1, A lithium secondary battery, wherein the first metal layer and the second metal layer each independently include at least one selected from the group consisting of copper, aluminum, stainless steel, and nickel.

6. In claim 1, A lithium secondary battery, wherein an electrode including an electrode current collector including the glass layer is disposed at the outermost part of the electrode assembly.

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

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

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