Lithium secondary battery including a heat dissipating current collector

Abstract

A lithium secondary battery according to the present invention includes an electrode assembly and a battery case that accommodates the electrode assembly. The electrode assembly includes a plurality of positive electrodes, a plurality of negative electrodes, and a plurality of separators, the positive electrodes, the separators, and the negative electrodes being stacked in order. At least one of the plurality of positive electrodes and the plurality of negative electrodes includes a heat dissipation collector and an electrode active material layer formed on at least one surface of the heat dissipation collector. The heat dissipation collector includes a heat dissipation layer, a polymer layer disposed on the heat dissipation layer, and a metal layer disposed on the polymer layer. The heat dissipation layer of the heat dissipation collector includes a passage that extends to the outside of the battery case to dissipate heat inside the battery.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0001463 filed on January 4, 2023, and Korean Patent Application No. 10-2023-0193646 filed on December 27, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a lithium secondary battery including a heat dissipation current collector, and more particularly to a lithium secondary battery including a heat dissipation current collector for dissipating heat generated inside the lithium secondary battery to the outside, thereby improving safety. [Background technology]

[0003] With the technological development and increasing demand for electric vehicles and energy storage systems (ESS), the demand for batteries as their energy source is rapidly increasing. Accordingly, research into batteries that can meet various requirements is being conducted. In particular, active research is being conducted into lithium secondary batteries, which have high energy density and excellent life and cycle characteristics as power sources for such devices.

[0004] However, in lithium secondary batteries, the temperature of the electrodes can rise suddenly due to thermal and physical factors. Thermal factors include overcharging or overloading due to misuse or a malfunctioning charger, while physical factors include damage to the separator due to external impact, which causes the negative and positive electrodes to come into contact and cause an internal short circuit. In these cases, the temperature of the electrodes can rise suddenly.

[0005] Therefore, measures are needed to prevent the phenomenon of a sudden rise in temperature of lithium secondary batteries. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention relates to a lithium secondary battery including a heat dissipating current collector for dissipating heat generated inside the lithium secondary battery to the outside, thereby improving safety. [Means for solving the problem]

[0007] In one aspect, the present invention provides a lithium secondary battery including an electrode assembly and a battery case that accommodates the electrode assembly, wherein the electrode assembly includes a positive electrode, a separator, and a negative electrode stacked in that order, at least one of the positive electrode and the negative electrode includes a heat dissipation collector and an electrode active material layer formed on at least one surface of the heat dissipation collector, the heat dissipation collector including a heat dissipation layer, a polymer layer disposed on the heat dissipation layer, and a metal layer disposed on the polymer layer, and the heat dissipation layer of the heat dissipation collector includes a passage extending to the outside of the battery case to dissipate heat inside the battery.

[0008] The heat dissipation layer may contain at least one of silicone and acrylic resin.

[0009] The heat dissipation layer may have insulating properties.

[0010] The heat dissipation layer may have a thermal conductivity (k1) of about 10 W / K·m or less.

[0011] The metal layer may comprise aluminum or copper.

[0012] The thermal conductivity (k2) of the metal layer may be about 200 W / K·m to 500 W / K·m.

[0013] The ratio (k2 / k1) of the thermal conductivity (k2) of the metal layer to the thermal conductivity (k1) of the heat dissipation layer may be about 40-200.

[0014] The polymer layer may include at least one selected from the group consisting of polyethylene terephthalate (PET), polyimide (PI), polymethyl methacrylate (PMMA), cellulose triacetate (CTA), polypropylene (PP), polyethylene (PE), polycarbonate (PC), and polyethylene naphthalate (PEN).

[0015] The ratio (t3 / t1) of the melting point (t3) of the polymer layer to the melting point (t1) of the heat-dissipating layer may be about 0.1 to 2.0.

[0016] The ratio (w2 / w1) of the thickness (w2) of the metal layer to the thickness (w1) of the heat dissipation layer may be about 0.67 or less.

[0017] The polymer layer may include a first polymer layer and a second polymer layer spaced apart from each other, and the metal layer may include a first metal layer and a second metal layer spaced apart from each other, with the first polymer layer and the first metal layer stacked in sequence on one side of the heat dissipation layer, and the second polymer layer and the second metal layer stacked in sequence on the other side of the heat dissipation layer.

[0018] The electrode assembly may include a plurality of positive electrodes, a plurality of negative electrodes, and a plurality of separators, and the electrode including the heat dissipating current collector may be disposed on the outermost side of the electrode assembly.

[0019] In another aspect, the present invention provides a lithium secondary battery electrode assembly including a positive electrode, a negative electrode, and a separator, wherein at least one of the positive electrode and the negative electrode includes a heat dissipation current collector including a heat dissipation layer having a thermal conductivity lower than that of a metal layer used as a current collector of the electrode, and the heat dissipation layer is configured to extend to the outside of the battery and to dissipate heat inside the battery to the outside of the battery.

[0020] The heat dissipation current collector may include a polymer layer and a metal layer disposed on at least one surface of the heat dissipation layer.

[0021] The polymer layer may have a melting point similar to that of the heat-dissipating layer.

[0022] In still another aspect, the present invention provides a method for manufacturing an electrode assembly for a lithium secondary battery, the electrode assembly including a positive electrode, a negative electrode, and a separator, wherein at least one of the positive electrode and the negative electrode includes a heat dissipation current collector including a heat dissipation layer having a thermal conductivity lower than the thermal conductivity of a metal layer used as a current collector of the electrode, and the heat dissipation layer extends to the outside of the battery so as to dissipate heat inside the battery to the outside of the battery.

[0023] The heat dissipation current collector may be configured to include a polymer layer and a metal layer disposed on the polymer layer on at least one surface of the heat dissipation layer.

[0024] The polymer layer may be configured to have a melting point substantially similar to that of the heat dissipation layer. [Effects of the Invention]

[0025] According to the present invention, the electrode assembly includes a heat dissipation layer having a thermal conductivity lower than that of the metal layer, so that heat in the metal layer is transferred to the heat dissipation layer and dissipated from the heat dissipation layer to the outside of the battery, thereby preventing risks such as fire of the lithium secondary battery, ensuring safety, and preventing deterioration of the lithium secondary battery.

[0026] According to the present invention, the heat dissipation layer contains silicone or acrylic, so that it is stable against secondary internal short circuits when the electrode structure is destroyed by an external impact.

[0027] According to the present invention, the melting point of the heat dissipation layer is close to that of the polymer layer, and it is possible to suppress the inflow of current to other electrodes, which is required to rapidly increase the temperature of the lithium secondary battery. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a diagram showing a lithium secondary battery according to one embodiment of the present invention; [Figure 2] 1 is a cross-sectional view showing an electrode including a heat dissipation current collector according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] In some of the accompanying drawings, corresponding components are designated by the same reference numerals. Those skilled in the art will understand that the drawings illustrate elements simply and clearly and are not necessarily drawn to scale. For example, the dimensions of some elements shown in the drawings may be exaggerated relative to other elements to facilitate understanding of various embodiments. Furthermore, elements of known technology that are useful or essential in commercially feasible embodiments may not be depicted in order to avoid obscuring the spirit of various embodiments of the present invention.

[0030] The advantages and features of the present invention, as well as methods for achieving them, will become more apparent from the following detailed description of the embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and may be embodied in a variety of different forms. The present embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art to which the invention pertains. The present invention is defined solely by the scope of the claims. Throughout the specification, the same reference numerals refer to the same elements.

[0031] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in the sense that they can be commonly understood by a person of ordinary skill in the art to which the present invention belongs. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless they are clearly and specifically defined.

[0032] The terms used in this specification are for the purpose of describing the embodiments and are not intended to limit the present invention. In this specification, the singular includes the plural unless otherwise stated in the text. The words "comprises" and / or "comprising" used in this specification do not exclude the presence or addition of one or more other elements in addition to the elements mentioned.

[0033] In this specification, when a part is said to include a certain component, this means that it may further include other components, not excluding other components, unless otherwise specified to the contrary.

[0034] In this specification, the phrase "A and / or B" means A, or B, or A and B.

[0035] In this specification, "%" means % by weight unless expressly indicated otherwise.

[0036] In this specification, "thermal conductivity" refers to the inherent property of a substance that indicates the degree to which heat is transferred from one side to another. The unit of thermal conductivity is W / K·m, which means that when there is a temperature difference of 1°C between both ends of a 1m thick plate, the rate at which heat is transferred through the 1m of the plate is 2 It means the amount of heat flowing through a

[0037] As used in this specification, the terms "about," "approximately," and "substantially" are used to mean a numerical value, a range of degree, or a value close to that range, taking into account inherent manufacturing and material tolerances, and are used to prevent infringers from unfairly taking advantage of the disclosure content in which exact or absolute numerical values ​​provided for understanding the present invention are mentioned.

[0038] When the temperature of the electrodes in a lithium secondary battery rises suddenly, the electrolyte reacts with lithium, and hydrogen and oxygen are generated inside the battery, causing the battery to become extremely unstable. This causes the electrolyte solvent to decompose, generating gas, which can ignite and lead to the battery exploding.

[0039] Conventional lithium secondary batteries have included only a single metal layer as an electrode current collector, for example, a single metal layer of aluminum as a positive electrode current collector and a single metal layer of copper as a negative electrode current collector. However, a single metal layer of aluminum or copper has relatively high electrical conductivity and thermal conductivity, but does not include a path for dissipating heat to the outside of the battery, so the time it takes for the battery to instantaneously reach a high temperature due to abnormal behavior is relatively short.

[0040] The present invention provides a lithium secondary battery with improved safety, which can release heat to the outside even when the temperature of the lithium secondary battery rises suddenly.

[0041] The lithium secondary battery according to the present invention will be described below.

[0042] Fig. 1 is a diagram showing a lithium secondary battery according to one embodiment of the present invention, and Fig. 2 is a cross-sectional view showing an electrode including a heat dissipation current collector according to one embodiment of the present invention.

[0043] 1 and 2, a lithium secondary battery includes an electrode assembly 500 and a battery case 600 that accommodates the electrode assembly. The electrode assembly 500 includes a plurality of positive electrodes 100, a plurality of negative electrodes 200, and a plurality of separators 300. The positive electrodes 100, the separators 300, and the negative electrodes 200 are stacked in order. At least one of the positive electrodes 100 and the negative electrodes 200 includes a heat-dissipating current collector 10 and an electrode active material layer formed on at least one surface of the heat-dissipating current collector 10. The heat-dissipating current collector 10 includes a heat-dissipating layer 11, a polymer layer 13 disposed on the heat-dissipating layer 11, and a metal layer 15 disposed on the polymer layer 13. The heat-dissipating layer 11 of the heat-dissipating current collector 10 includes a passage extending to the outside of the battery case 600 to discharge heat from inside the battery.

[0044] Conventional electrode current collectors including only a single metal layer have included, for example, a single metal layer of aluminum as the positive electrode current collector and a single metal layer of copper as the negative electrode current collector. However, because the metal layer has very high electrical and thermal conductivity and does not include a path for dissipating heat to the outside, abnormal battery behavior can occur, resulting in a very short time for the temperature to reach a temperature higher than normal, increasing the risk of explosion. In contrast, the heat dissipation collector 10 of the present invention includes a heat dissipation layer 11 having a lower thermal conductivity than the metal layer 15, thereby reducing the temperature rise compared to conventional electrode current collectors including only a single metal layer. In other words, the heat dissipation collector 10 of the present invention can dissipate heat generated inside the battery to the outside of the battery through the heat dissipation layer 11, thereby preventing risks such as battery fire and ensuring safety.

[0045] electrode assembly The electrode assembly 500 includes a plurality of positive electrodes 100, a plurality of negative electrodes 200, and a plurality of separators 300, and at least one of the positive electrodes 100 and the negative electrodes 200 may be an electrode 150 including the heat dissipation current collector 10. In the example of FIG. 1 , a plurality of secondary battery electrode assemblies are illustrated in a battery case 600 as one embodiment, but the present invention is not limited thereto. For example, the battery case 600 may include only two electrode assemblies, i.e., a positive electrode and a negative electrode, which are basic units constituting a lithium secondary battery, and either the positive electrode or the negative electrode may be the electrode 150 including the heat dissipation current collector 10.

[0046] (heat dissipation collector) The heat dissipation current collector 10 includes a heat dissipation layer 11, a polymer layer 13 disposed on the heat dissipation layer 11, and a metal layer 15 disposed on the polymer layer 13. The heat dissipation layer 11 of the heat dissipation current collector 10 includes a passage that extends to the outside of the battery case 600 to dissipate heat from inside the battery. Alternatively, the heat dissipation layer 11 of the heat dissipation current collector 10 may have a structure that does not extend to the outside of the battery case 600. In this case, another heat transfer material, for example, another medium having similar thermal conductivity to the heat dissipation layer 11, may be connected to the heat dissipation layer 11 inside the battery case 600 to dissipate heat to the outside.

[0047] The heat dissipation layer 11 is a component of the heat dissipation current collector 10 for dissipating heat generated inside the battery to the outside of the battery. The heat dissipation layer 11 is formed from a material having lower thermal conductivity than the metal layer 15 disposed on the polymer layer 13, and may contain, for example, at least one of silicone and acrylic resin. When the heat dissipation layer 11 contains at least one of silicone and acrylic resin, stability against internal short circuits can be ensured even if the electrode structure is destroyed by external impact.

[0048] The thermal conductivity (k1) of the heat dissipation layer 11 may be, for example, about 10 W / K·m or less, or about 1 W / K·m to 8 W / K·m, or about 2 W / K·m to 6 W / K·m.

[0049] The heat dissipation layer 11 has insulating properties, and therefore can be relatively stable against secondary internal short circuits when the electrode structure is destroyed by an external impact.

[0050] The polymer layer 13 is a component for connecting the heat dissipation layer 11 and the metal layer 15 in the heat dissipation current collector 10, and is, for example, a component disposed between the heat dissipation layer 11 and the metal layer 15. The polymer layer 13 may contain at least one selected from the group consisting of polyethylene terephthalate (PET), polyimide (PI), poly(methylmethacrylate) (PMMA), cellulose triacetate (CTA), polypropylene (PP), polyethylene (PE), polycarbonate (PC), and polyethylene naphthalate (PEN).

[0051] The ratio (t3 / t1) of the melting point (t3) of the polymer layer 13 to the melting point (t1) of the heat-dissipating layer 11 may be approximately 0.1 to 2.0, 0.1 to 1.9, or 0.1 to 1.6. When the ratio (t3 / t1) is within the above range, the difference in melting points between the heat-dissipating layer 11 and the polymer layer 13 is not large. Therefore, in the event of abnormal battery behavior, such as penetration of the metal layer 15, both the heat-dissipating layer and the polymer layer melt, thereby suppressing the inflow of current necessary for thermal runaway. On the other hand, when the difference in melting points between the heat-dissipating layer 11 and the polymer layer 13 is large and both do not melt, the energy leading to thermal runaway is continuously supplied through the metal layer 15, making it difficult to prevent risks such as fire in the lithium secondary battery. Furthermore, when the ratio (t3 / t1) exceeds approximately 2.0, the heat-dissipating layer 11, which has a low melting point, melts, making it difficult to control thermal runaway caused by an increase in battery temperature.

[0052] The metal layer 15 may contain aluminum or copper. When the metal layer 15 contains aluminum, it can generally be used as a positive electrode current collector, and when the metal layer 15 contains copper, it can generally be used as a negative electrode current collector. The metal layer 15 may be formed on the polymer layer 13 by a process such as deposition or lamination, or by a conventional bonding method.

[0053] The thermal conductivity (k2) of the metal layer 15 is approximately 200 W / K·m to 500 W / K·m, and may be, for example, 200 W / K·m to 450 W / K·m, or 220 W / K·m to 430 W / K·m.

[0054] The ratio (k2 / k1) of the thermal conductivity (k2) of the metal layer 15 to the thermal conductivity (k1) of the heat dissipation layer 11 may be about 40 to 200, for example, 50 to 150, or 50 to 120. When the ratio (k2 / k1) satisfies the above numerical range, heat generated inside the lithium secondary battery can be released to the outside, improving safety.

[0055] The ratio (w2 / w1) of the thickness (w2) of the metal layer 15 to the thickness (w1) of the heat dissipation layer 11 may be about 0.67 or less, for example, about 0.33 or less, or about 0.02 to 0.1. When the ratio (w2 / w1) satisfies the above numerical range, heat generated inside the lithium secondary battery can be released to the outside, improving safety.

[0056] In the heat dissipation collector 10, the polymer layer 13 includes a first polymer layer 13A and a second polymer layer 13B arranged at a distance from each other, and the metal layer 15 includes a first metal layer 15A and a second metal layer 15B arranged at a distance from each other around the heat dissipation layer 11, and the first polymer layer 13A and the first metal layer 15A are stacked in order on one side of the heat dissipation layer 11, and the second polymer layer 13B and the second metal layer 15B are stacked in order on the other side of the heat dissipation layer 11.

[0057] In one embodiment, the electrode 150 including the heat dissipation current collector 10 may be disposed at the outermost position of the electrode assembly 500. For example, in FIG. 1 , the electrode 150 including the heat dissipation current collector 10 is located at the top. When the electrode 150 is disposed at the outermost position of the electrode assembly 500, interference with other electrodes does not occur when forming a path for dissipating heat through a heat dissipation layer included in the heat dissipation current collector 10. Meanwhile, the position of the electrode 150 of the present invention is not limited to the outermost position as in this embodiment, and may be located at any position within the battery case 600 as long as interference with other electrodes does not occur. For example, the electrode 150 of the present invention may be located anywhere among the plurality of electrodes.

[0058] (electrode active material layer) The electrode active material layer 17 is formed by applying an active material slurry to the surface of the heat dissipation current collector, followed by drying and rolling, and is not particularly limited as long as it is used as an electrode active material layer in a normal lithium secondary battery.

[0059] The active material slurry may include an active material and a solvent.

[0060] The active material may be an active material commonly used in the art, for example, a negative electrode active material or a positive electrode active material. The negative electrode active material may include at least one selected from the group consisting of lithium metal, a carbon material capable of reversibly intercalating / deintercalating lithium ions, a metal or an alloy of such a metal and lithium, a metal composite oxide, a material capable of doping and dedoping lithium, and a transition metal oxide. The positive electrode active material may include a lithium metal oxide containing lithium and one or more metals, such as cobalt, manganese, nickel, or aluminum, which are compounds capable of reversibly intercalating and deintercalating lithium. In one embodiment, the lithium metal oxide may include lithium-manganese oxide, lithium-cobalt oxide, lithium-nickel oxide, lithium-nickel-manganese oxide, lithium-nickel-cobalt oxide, lithium-manganese-cobalt oxide, lithium-nickel-manganese-cobalt oxide, or lithium-nickel-cobalt-transition metal (M) oxide, and the lithium metal oxide may include any one or more compounds thereof.

[0061] The solvent may be a solvent commonly used in the art, such as at least one selected from the group consisting of dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethyl formamide (DMF), acetone, and water (HO). The amount of the solvent used may be an amount that dissolves or disperses the active material, binder, and conductive material, and provides a viscosity that provides excellent thickness uniformity when the slurry is subsequently applied to fabricate an electrode, taking into consideration the coating thickness and production yield of the slurry.

[0062] The active material slurry may further contain at least one of a binder and a conductive material in addition to the active material and the solvent.

[0063] The binder serves to improve adhesion between active material particles and between the active material and the current collector. The active material may be applied to either a non-aqueous binder or an aqueous binder, and the type of binder is not particularly limited. In one embodiment, the negative electrode active material of the present invention may be applied to an aqueous binder. As another example, the water-based binder may include at least one of styrene-based rubbers such as styrene-butadiene rubber (SBR), acrylate-styrene butadiene copolymer rubber (acrylate-co-SBR), and acrylonitrile-styrene butadiene copolymer rubber (acrylonitrile-co-SBR); and acrylate-based compounds such as methyl methacrylate-lithium methacrylic acid copolymer (P(MMA-co-LiMA)), alkyl acrylate-acrylonitrile-acrylic acid copolymer (P(alkyl acrylate-co-acrylonitrile-acrylic acid)), polyacrylic acid (PAA), and polyimide-based compounds.

[0064] The conductive material is a component for further improving the conductivity of the active material, and is not particularly limited as long as it does not cause chemical changes in the battery and has conductivity. For 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 fiber or metal fiber; carbon fluoride; 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 can be used.

[0065] The electrode active material layer may be coated using any slurry coating method known in the art, including, but not limited to, a slit-die method, a gravure method, a doctor blade method, a silk screen method, an offset method, a spray method, a dip method, and the like.

[0066] (positive electrode) The positive electrode 100 may include a positive electrode current collector and a positive electrode active material formed on the positive electrode current collector. The positive electrode active material is the same as the active material described above, and therefore a detailed description thereof will be omitted.

[0067] The positive electrode current collector may contain a highly conductive metal, and is not particularly limited as long as it is easily adhered to the positive electrode active material layer and is non-reactive within the battery voltage range. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, heat-treated carbon, and aluminum or stainless steel whose surfaces have been surface-treated with carbon, nickel, titanium, silver, or the like. The positive electrode current collector typically has a thickness of about 3 μm to 500 μm, and the adhesion of the positive electrode active material may be enhanced by forming fine irregularities on the surface of the current collector. The positive electrode current collector may be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0068] (Negative electrode) The negative electrode 200 may include a negative electrode current collector and a negative electrode active material formed on the negative electrode current collector. The negative electrode active material is the same as the active material described above, and therefore a detailed description thereof will be omitted.

[0069] 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 surfaces treated with carbon, nickel, titanium, silver, or the like, and aluminum-cadmium alloys can be used. The negative electrode current collector typically has a thickness of about 3 μm to 500 μm, and, like the positive electrode current collector, the surface of the current collector may be formed with fine irregularities to strengthen the binding force of the negative electrode active material. It can be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0070] (separator) The separator 300 separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used. In particular, separators with low resistance to electrolyte ion movement and excellent electrolyte humidification are preferred. For example, porous polymer films, such as those made of polyolefin-based polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminates of two or more layers thereof, can be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. To ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymeric material can also be used. The separator can be selectively used in a single-layer or multi-layer structure.

[0071] (electrolyte) The lithium secondary battery according to the present invention may further include an electrolyte. 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 manufacturing lithium secondary batteries.

[0072] The electrolyte may include an organic solvent and a lithium salt.

[0073] The organic solvent may be any solvent capable of acting as a medium through which ions involved in the electrochemical reaction of the battery can move. For example, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether and tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate. Examples of solvents that can be used include carbonate-based solvents such as ethylene carbonate (PC), alcohol-based solvents such as ethyl alcohol and isopropyl alcohol, nitriles such as R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may contain a double-bonded aromatic ring or an ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, and sulfolanes. Among these, carbonate-based solvents are preferred, and more preferred is a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) with high ionic conductivity and a high dielectric constant, which can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate).

[0074] The lithium salt can be any compound that can provide lithium ions used in lithium secondary batteries without any particular limitation. For example, the anion of the lithium salt can be 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 - The lithium salt may be at least one selected from the group consisting of: LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably in the range of 0.1 M to 4.0 M, preferably 0.5 M to 3.0 M, and more preferably 1.0 M to 2.0 M. When the lithium salt concentration is within the above range, the electrolyte has appropriate conductivity and viscosity, thereby exhibiting excellent electrolyte performance and enabling effective migration of lithium ions.

[0075] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds (e.g., difluoroethylene carbonate), pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine 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 battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. In this case, the additives may be included in an amount of about 0.1 wt % to 10.0 wt % based on the total weight of the electrolyte.

[0076] Battery case The battery case may have an internal empty space and may be formed to accommodate the electrode assembly and the electrolyte in the internal space.

[0077] Depending on the material of the battery case, the lithium secondary battery can be classified into a can-type battery in which an electrode assembly is housed in a cylindrical or rectangular metal can, and a pouch-type battery in which an electrode assembly is housed in a pouch-type case made of an aluminum laminate sheet. The lithium secondary battery according to the present invention may be a pouch-type secondary battery.

[0078] The lithium secondary battery according to the present invention may further include, in addition to the battery case 600 described above, a sealing member (not shown) for sealing the battery case 600 .

[0079] The lithium secondary battery according to the present invention may further include a positive electrode tab connected to the plurality of positive electrodes 100 and a negative electrode tab connected to the plurality of negative electrodes 200. The positive electrode tab may extend from one end of the positive electrode 100, or may be welded to one end of the positive electrode 100 or attached using a conductive adhesive. The negative electrode tab may extend from one end of the negative electrode 200, or may be welded to one end of the negative electrode 200 or attached using a conductive adhesive.

[0080] As described above, the lithium secondary battery including the heat dissipation current collector according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, and is therefore useful in portable devices such as mobile phones, notebook computers, and digital cameras, and in electric vehicles such as hybrid electric vehicles (HEVs).

[0081] Therefore, according to another embodiment of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell, and a battery pack including the same.

[0082] The 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 (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0083] Although the present invention has been described above with reference to preferred embodiments, it will be understood that those skilled in the art or those having ordinary knowledge in the art can make various modifications and changes to the present invention without departing from the spirit and technical scope of the present invention as defined in the appended claims. Therefore, the technical scope of the present invention is not limited to the contents described in the detailed description of the specification, but is determined solely by the claims.

Claims

1. an electrode assembly; and a battery case that houses the electrode assembly, The electrode assembly is formed by stacking a positive electrode, a separator, and a negative electrode in this order, At least one of the positive electrode and the negative electrode includes a heat dissipation current collector and an electrode active material layer formed on at least one surface of the heat dissipation current collector, the heat dissipation current collector includes a heat dissipation layer, a polymer layer disposed on the heat dissipation layer, and a metal layer disposed on the polymer layer; The heat dissipation layer of the heat dissipation current collector includes a passage extending to the outside of the battery case to dissipate heat inside the battery.

2. 2. The lithium secondary battery according to claim 1, wherein the heat-dissipating layer contains at least one of silicone and acrylic resin.

3. The lithium secondary battery according to claim 1 , wherein the heat dissipation layer has insulating properties.

4. 2. The lithium secondary battery according to claim 1, wherein the heat dissipation layer has a thermal conductivity (k1) of 10 W / K·m or less.

5. The lithium secondary battery according to claim 1 , wherein the metal layer comprises aluminum or copper.

6. 2. The lithium secondary battery according to claim 1, wherein the thermal conductivity (k2) of the metal layer is 200 W / K·m to 500 W / K·m.

7. 2. The lithium secondary battery according to claim 1, wherein the ratio (k2 / k1) of the thermal conductivity (k2) of the metal layer to the thermal conductivity (k1) of the heat dissipation layer is 40 to 200.

8. 2. The lithium secondary battery according to claim 1, wherein the polymer layer comprises at least one selected from the group consisting of polyethylene terephthalate (PET), polyimide (PI), polymethyl methacrylic acid (PMMA), cellulose triacetate (CTA), polypropylene (PP), polyethylene (PE), polycarbonate (PC), and polyethylene naphthalate (PEN).

9. 2. The lithium secondary battery according to claim 1, wherein the ratio (t3 / t1) of the melting point (t3) of said polymer layer to the melting point (t1) of said heat dissipation layer is 0.1 to 2.

0.

10. 2. The lithium secondary battery according to claim 1, wherein a ratio (w2 / w1) of the thickness (w2) of the metal layer to the thickness (w1) of the heat dissipation layer is 0.67 or less.

11. the polymer layer includes a first polymer layer and a second polymer layer spaced apart from each other; the metal layer includes a first metal layer and a second metal layer spaced apart from each other; 2. The lithium secondary battery according to claim 1, wherein the first polymer layer and the first metal layer are stacked in sequence on one surface of the heat dissipation layer, and the second polymer layer and the second metal layer are stacked in sequence on the other surface of the heat dissipation layer.

12. 2. The lithium secondary battery of claim 1, wherein the electrode assembly includes a plurality of positive electrodes, a plurality of negative electrodes, and a plurality of separators, and the electrode including the heat dissipation current collector is disposed on the outermost side of the electrode assembly.

13. a positive electrode, a negative electrode, and a separator; At least one of the positive electrode and the negative electrode includes a heat dissipation current collector including a heat dissipation layer having a thermal conductivity lower than that of a metal layer used as a current collector of the electrode; The heat dissipation layer is connected to the outside of the battery to dissipate heat from inside the battery to the outside of the battery.

14. The lithium secondary battery electrode assembly according to claim 13 , wherein the heat dissipation current collector includes a polymer layer on at least one surface of the heat dissipation layer, and a metal layer disposed on the polymer layer.

15. The electrode assembly of claim 14 , wherein the polymer layer has a melting point similar to that of the heat-dissipating layer.

16. a positive electrode, a negative electrode, and a separator; At least one of the positive electrode and the negative electrode is configured to include a heat dissipation current collector including a heat dissipation layer having a thermal conductivity lower than that of a metal layer used as a current collector of the electrode; The heat dissipation layer is configured to extend to the outside of the battery to dissipate heat inside the battery to the outside of the battery.

17. 17. The method of manufacturing an electrode assembly for a lithium secondary battery according to claim 16, wherein the heat dissipation collector includes a polymer layer on at least one surface of the heat dissipation layer, and a metal layer disposed on the polymer layer.

18. The method of manufacturing an electrode assembly for a lithium secondary battery according to claim 17 , wherein the polymer layer has a melting point similar to that of the heat-dissipating layer.

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