Lithium secondary battery comprising heat-dissipating current collector

Abstract

The present invention relates to a lithium secondary battery, the lithium secondary battery comprising: an electrode assembly; and a battery case configured to accommodate the electrode assembly. The electrode assembly includes a plurality of positive electrodes, a plurality of separators, and a plurality of negative electrodes stacked in this order, and at least one of the plurality of positive electrodes and the plurality of negative electrodes includes a heat-dissipating current collector and an electrode active material layer formed on at least one surface of the heat-dissipating 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, and the heat dissipation layer of the heat dissipation current collector includes a channel extending to the outside of the battery case and configured to discharge heat inside the battery.

Description

Technical Field

[0001] This application is based on and claims priority to Korean Patent Application No. 10-2023-0001463, filed with the Korean Intellectual Property Office on January 4, 2023, and Korean Patent Application No. 10-2023-0193646, filed with the Korean Intellectual Property Office on December 27, 2023. The disclosures of the Korean patent applications are incorporated herein by reference in their entirety.

[0002] The present invention relates to a lithium secondary battery including a heat-dissipating current collector, and more particularly, to a lithium secondary battery including a heat-dissipating current collector that improves safety by discharging heat generated inside the lithium secondary battery to the outside. Background Art

[0003] With the increase in the development of technologies and demands for electric vehicles and energy storage systems (ESSs), the demand for batteries as an energy source is rapidly increasing. Therefore, research on batteries that can meet various needs is underway. In particular, active research is being conducted on lithium secondary batteries, which have a high energy density and excellent life and cycle characteristics as a power source for the above devices.

[0004] However, in lithium secondary batteries, the temperature of the electrodes may rise rapidly due to thermal factors and physical factors. Due to thermal factors (such as overcharging or overloading caused by, for example, misuse of the lithium secondary battery and malfunction of the charger), and due to physical factors (when the separator is damaged due to, for example, external impact, the negative electrode material and the positive electrode material come into contact with each other, and an internal short circuit occurs), the temperature of the electrodes may rise rapidly.

[0005] Therefore, measures are needed to address the rapid rise in the temperature of lithium secondary batteries. Summary of the Invention

[0006] Technical problem

[0007] The present invention relates to a lithium secondary battery including a heat-dissipating current collector to improve safety by discharging heat generated inside the lithium secondary battery to the outside.

[0008] Technical solution

[0009] In one aspect, the present invention provides a lithium secondary battery including:

[0010] an electrode assembly; and

[0011] a battery case configured to accommodate the electrode assembly.

[0012] The electrode assembly includes a positive electrode, a separator, and a negative electrode stacked in sequence, and

[0013] At least one of the positive electrode and the negative electrode includes a heat-dissipating current collector and an electrode active material layer formed on at least one surface of the heat-dissipating current collector.

[0014] The heat-dissipating current collector includes a heat-dissipating layer, a polymer layer provided on the heat-dissipating layer, and a metal layer provided on the polymer layer, and

[0015] The heat-dissipating layer of the heat-dissipating current collector includes a channel that extends to the outside of the battery case and is configured to discharge the heat inside the battery.

[0016] The heat-dissipating layer may include at least one of polysiloxane and an acrylic resin.

[0017] The heat-dissipating layer may have an insulating property.

[0018] The thermal conductivity (k1) of the heat-dissipating layer may be about 10 W / K∙m or less.

[0019] The metal layer may include aluminum or copper.

[0020] The thermal conductivity (k2) of the metal layer may be about 200 W / K∙m to 500 W / K∙m.

[0021] The ratio (k2 / k1) of the thermal conductivity (k2) of the metal layer to the thermal conductivity (k1) of the heat-dissipating layer may be about 40 to 200.

[0022] The polymer layer may include at least one selected from polyethylene terephthalate (PET), polyimide (PI), polymethyl methacrylate (PMMA), cellulose triacetate (CTA), polypropylene (PP), polyethylene (PE), polycarbonate (PC), and polyethylene naphthalate (PEN).

[0023] 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.

[0024] The ratio (w2 / w1) of the thickness (w2) of the metal layer to the thickness (w1) of the heat-dissipating layer may be about 0.67 or less.

[0025] The polymer layer may include a first polymer layer and a second polymer layer arranged to be spaced apart from each other, and the metal layer may include a first metal layer and a second metal layer arranged to be spaced apart from each other. The first polymer layer and the first metal layer may be sequentially stacked on one surface of the heat-dissipating layer, and the second polymer layer and the second metal layer may be sequentially stacked on the other surface of the heat-dissipating layer.

[0026] 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 is disposed at the outermost position of the electrode assembly.

[0027] In another aspect, the present invention provides a lithium secondary battery electrode assembly, which comprises:

[0028] a positive electrode;

[0029] a negative electrode; and

[0030] a separator.

[0031] At least one of the positive electrode and the negative electrode includes a heat dissipation current collector, the heat dissipation current collector includes a heat dissipation layer, the heat dissipation layer has a lower thermal conductivity than the metal layer serving as the current collector of the corresponding electrode, and

[0032] the heat dissipation layer extends to the outside of the battery and is configured to discharge the heat inside the battery to the outside of the battery.

[0033] The heat dissipation current collector may include a polymer layer on at least one surface of the heat dissipation layer and a metal layer provided on the polymer layer.

[0034] The polymer layer may have a melting point substantially similar to that of the heat dissipation layer.

[0035] In yet another aspect, the present invention provides a method for manufacturing a lithium secondary battery electrode assembly, the lithium secondary battery electrode assembly including a positive electrode, a negative electrode, and a separator. The method includes:

[0036] Configuring at least one of the positive electrode and the negative electrode to include a heat dissipation current collector, the heat dissipation current collector including a heat dissipation layer having a lower thermal conductivity than the metal layer serving as the current collector of the corresponding electrode; and

[0037] Configuring the heat dissipation layer to extend to the outside of the battery and discharge the heat inside the battery to the outside of the battery.

[0038] The heat dissipation current collector may be configured to include a polymer layer on at least one surface of the heat dissipation layer and a metal layer provided on the polymer layer.

[0039] The polymer layer may be configured to have a melting point substantially similar to that of the heat dissipation layer.

[0040] Beneficial effect

[0041] According to the present invention, since the electrode assembly includes a heat dissipation layer having a lower thermal conductivity than the metal layer, the heat from the metal layer is transferred to the heat dissipation layer, and the heat dissipation layer discharges the heat to the outside of the battery. Therefore, risks such as the ignition of a lithium secondary battery can be prevented, thereby ensuring safety and preventing the deterioration of the lithium secondary battery.

[0042] According to the present invention, by including a polysiloxane or an acrylic resin, when the electrode structure collapses due to an external impact, the heat dissipation layer can stably resist a secondary internal short circuit.

[0043] According to the present invention, since the heat dissipation layer has a melting point substantially similar to that of the polymer layer, current flowing into the other electrode (which is required for the temperature of the lithium secondary battery to rapidly increase) can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 FIG. is a view showing a lithium secondary battery according to an embodiment of the present invention.

[0045] Figure 2 FIG. is a cross-sectional view of an electrode including a heat dissipation current collector according to an embodiment of the present invention.

[0046] In the several views of the drawings, the same reference numerals denote the same components. Those skilled in the art should understand that the elements in the drawings are simply and clearly shown and do not necessarily need to be drawn to scale. For example, the dimensions of some elements in the figures may be exaggerated relative to other elements to help improve the understanding of the various embodiments. Also, common but well-understood elements that are useful or necessary in a commercially viable embodiment are generally not depicted, thus facilitating a less obstructed view of these various embodiments. DETAILED DESCRIPTION

[0047] Advantages and features of the present invention and methods for achieving these advantages and features will become clear by referring to the embodiments described in detail below and the drawings. However, the present invention is not limited to the embodiments to be described below, but can be implemented in various different forms. These embodiments are provided only to ensure that the present invention is fully disclosed and to fully inform those of ordinary skill in the art to which the present invention pertains of the scope of the present invention. The present invention is defined only by the claims. Throughout the specification, the same reference numerals denote the same components.

[0048] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used with the meaning commonly understood by those of ordinary skill in the art to which the present invention pertains. In addition, terms defined in commonly used dictionaries will not be ideally or overly interpreted unless clearly and specifically defined.

[0049] The terms used herein are for describing the embodiments and are not intended to limit the present invention. As used herein, unless otherwise specified in the phrase, the singular also includes the plural. As used herein, "comprising" and / or "including" do not exclude the presence or addition of one or more other components in addition to the recited components.

[0050] Unless otherwise specifically stated, when a part described herein includes a certain component, this means that other components may also be included, rather than excluding them.

[0051] As used herein, the description "A and / or B" means A, or B, or A and B.

[0052] In this text, unless otherwise clearly stated, "%" means weight percentage.

[0053] In this text, "thermal conductivity" means an inherent property of a material, which represents the degree to which heat is transferred from one side to other places. The unit of thermal conductivity is W / K∙m, which means that when the temperature difference between both ends is 1 °C, the heat flowing through a 1 m thick plate per second for 1 m 2 is the amount of heat.

[0054] As used herein, considering unique manufacturing and material tolerances, the terms "about", "approximately" and "substantially" are used to mean a range of values or degrees, or their approximate values, and are used to prevent infringers from unfairly taking advantage of the described content (where precise or absolute values are mentioned, thus helping to understand the present invention).

[0055] When the temperature of the electrode in a lithium secondary battery rises rapidly, due to the reaction between the electrolyte and lithium or the generation of hydrogen and oxygen inside the battery, the battery may become very unstable, the solvent in the electrolyte may decompose to generate gas, and the decomposition gas of the solvent may catch fire, resulting in battery explosion.

[0056] Conventional lithium secondary batteries only include a single metal layer as the electrode current collector. For example, a single metal layer of aluminum is used as the positive electrode current collector, and a single metal layer of copper is used as the negative electrode current collector. However, since the single metal layer of aluminum or copper has relatively high electrical conductivity and thermal conductivity, and does not include a channel through which heat is discharged to the outside of the battery, the time taken to reach a high temperature instantaneously due to abnormal behavior of the battery is relatively short.

[0057] The present invention provides a lithium secondary battery that has improved safety by discharging heat to the outside even when the temperature of the lithium secondary battery rises rapidly.

[0058] Hereinafter, the lithium secondary battery according to the present invention will be described.

[0059] Figure 1 is a diagram showing a lithium secondary battery according to an embodiment of the present invention. Figure 2 is a cross-sectional view showing an electrode including a heat dissipation current collector according to an embodiment of the present invention.

[0060] Reference Figure 1 and Figure 2, the lithium secondary battery includes an electrode assembly 500 and a battery case 600 that houses the electrode assembly. The electrode assembly 500 includes a plurality of positive electrodes 100, a plurality of separators 300, and a plurality of negative electrodes 200 stacked in sequence. At least one of the plurality of positive electrodes 100 and the plurality of negative electrodes 200 includes a heat dissipation current collector 10 and an electrode active material layer formed on at least one surface of the heat dissipation current collector 10. 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, and the heat dissipation layer 11 of the heat dissipation current collector 10 includes a channel that extends to the outside of the battery case 600 to discharge the heat inside the battery.

[0061] In the case of a conventional electrode current collector that includes only a single metal layer, for example, a single metal layer containing aluminum is used as the positive electrode current collector, and a single metal layer containing copper is used as the negative electrode current collector. However, in this case, since there is no channel for dissipating heat to the outside when the metal layer has a very high electrical conductivity and thermal conductivity, and only a single metal layer is included, the time taken to instantaneously reach a high temperature compared to the normal temperature due to abnormal behavior of the battery is very short, and there is a high risk of explosion. On the contrary, by including a heat dissipation layer 11 having a lower thermal conductivity than the thermal conductivity of the metal layer 15, the heat dissipation current collector 10 according to the present invention can have a lower rising temperature compared to a conventional electrode current collector that includes only a single metal layer. That is, the heat dissipation current collector 10 according to the present invention can discharge the heat generated inside the battery to the outside of the battery via the heat dissipation layer 11, thereby preventing risks such as battery ignition and ensuring safety.

[0062] Electrode assembly

[0063] The electrode assembly 500 may include 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 electrode 100 and the negative electrode 200 may be an electrode 150 that includes a heat dissipation current collector 10. Figure 1 The example shows a plurality of secondary battery electrode assemblies inside the battery case 600 according to one embodiment, but the present invention is not limited thereto. For example, the battery case 600 may include only the basic units constituting the lithium secondary battery, for example, two electrode assemblies of a positive electrode and a negative electrode, where the positive electrode or the negative electrode may be an electrode 150 that includes the above heat dissipation current collector 10.

[0064] (Heat dissipation current collector)

[0065] 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 channel that extends to the outside of the battery case 600 to discharge the heat inside the battery. On the other hand, the heat dissipation layer 11 of the heat dissipation current collector 10 can be configured as a structure that does not extend to the outside of the battery case 600. In this case, a separate heat transfer material, such as a separate medium having a thermal conductivity substantially similar to that of the heat dissipation layer 11, can be connected to the heat dissipation layer 11 inside the battery case 600 to discharge the heat to the outside.

[0066] The heat dissipation layer 11 is configured to discharge the heat generated inside the battery from the heat dissipation current collector 10 to the outside of the battery. The heat dissipation layer 11 is made of a material having a lower thermal conductivity than the metal layer 15 disposed on the polymer layer 13, and may include at least one of, for example, polysiloxane and acrylic resin. When the heat dissipation layer 11 includes at least one of polysiloxane and acrylic resin, even if the electrode structure collapses due to an external impact, the stability against internal short circuit can be ensured.

[0067] The thermal conductivity (k1) of the heat dissipation layer 11 is, 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.

[0068] By having insulating properties, when the electrode structure collapses due to an external impact, the heat dissipation layer 11 can relatively stably resist secondary internal short circuit.

[0069] The polymer layer 13 is configured to connect the heat dissipation layer 11 and the metal layer 15 in the heat dissipation current collector 10 to each other. For example, the polymer layer 13 is disposed between the heat dissipation layer 11 and the metal layer 15. The polymer layer 13 may include at least one selected from polyethylene terephthalate (PET), polyimide (PI), poly(methyl methacrylate) (PMMA), cellulose triacetate (CTA), polypropylene (PP), polyethylene (PE), polycarbonate (PC), and polyethylene naphthalate (PEN).

[0070] The ratio (t3 / t1) of the melting point (t3) of the polymer layer 13 to the melting point (t1) of the heat dissipation layer 11 is about 0.1 to 2.0, 0.1 to 1.9, or 0.1 to 1.6. When the ratio (t3 / t1) satisfies the above numerical range, since the difference in melting points between the heat dissipation layer 11 and the polymer layer 13 is not large, when the battery exhibits an abnormality, for example, when the metal layer 15 is penetrated, the heat dissipation layer and the polymer layer melt together, thereby being able to suppress the inflow of current required for thermal runaway. On the contrary, when the difference in melting points between the heat dissipation layer 11 and the polymer layer 13 is large and the heat dissipation layer and the polymer layer do not melt together, the energy causing thermal runaway is continuously supplied via the metal layer 15, which may make it difficult to prevent risks such as the ignition of a lithium secondary battery. In addition, when the ratio (t3 / t1) exceeds about 2.0, there is a problem that thermal runaway becomes uncontrollable due to the rise in battery temperature caused by the melting of the heat dissipation layer 11 with a low melting point.

[0071] The metal layer 15 may include aluminum or copper. When the metal layer 15 includes aluminum, the metal layer can generally be used as a positive electrode current collector, and when the metal layer 15 includes copper, the metal layer can generally be used as a negative electrode current collector. The metal layer 15 can be formed on the polymer layer 13 through processes such as deposition or lamination, or can be formed by a conventional bonding method.

[0072] The thermal conductivity (k2) of the metal layer 15 is about 200 W / K∙m to 500 W / K∙m, for example, 200 W / K∙m to 450 W / K∙m, or 220 W / K∙m to 430 W / K∙m.

[0073] 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 can be about 40 to 200, for example, 50 to 150, or 50 to 120. When the ratio (k2 / k1) satisfies the above numerical range, the heat generated inside the lithium secondary battery is discharged to the outside, thereby being able to improve safety.

[0074] The ratio (w2 / w1) of the thickness (w2) of the metal layer 15 to the thickness (w1) of the heat dissipation layer 11 can 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, the heat generated inside the lithium secondary battery is discharged to the outside, thereby being able to improve safety.

[0075] In the heat-dissipating current collector 10, the polymer layer 13 may include a first polymer layer 13A and a second polymer layer 13B, and the metal layer 15 may include a first metal layer 15A and a second metal layer 15B that are arranged to be spaced apart from each other with respect to the heat-dissipating layer 11. The first polymer layer 13A and the first metal layer 15A may be sequentially stacked on one surface of the heat-dissipating layer 11, and the second polymer layer 13B and the second metal layer 15B may be sequentially stacked on the other surface of the heat-dissipating layer 11.

[0076] According to one embodiment, the electrode 150 including the heat-dissipating current collector 10 may be disposed at the outermost position of the electrode assembly 500. For example, in Figure 1 , the electrode 150 including the heat-dissipating current collector 10 may be located at the top position. When the electrode 150 is disposed at the outermost position of the electrode assembly 500, interference with other electrodes may not occur when forming a channel for dissipating heat through the heat-dissipating layer included in the heat-dissipating current collector 10. On the other hand, as long as interference with other electrodes does not occur, the electrode 150 is not limited to being disposed at the outermost position as in this embodiment, and may be located at any position within the battery case 600, for example. For example, the electrode 150 of the present invention may be disposed at any position between a plurality of electrodes.

[0077] (Electrode active material layer)

[0078] Except for the fact that the electrode active material layer 17 is formed by coating an active material slurry on the surface of the above-described heat-dissipating current collector and then drying and calendering the active material slurry, the electrode active material layer 17 may be used without particular limitation as long as it is generally used as an electrode active material layer in a lithium secondary battery.

[0079] The active material slurry may include an active material and a solvent.

[0080] 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 lithium metal, a carbon material capable of reversibly intercalating / deintercalating lithium ions, a metal or an alloy of these metals and lithium, a metal composite oxide, a material capable of doping / dedoping lithium, and a transition metal oxide. The positive electrode active material is a compound capable of reversibly intercalating / deintercalating lithium and may include, for example, a lithium metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel, and aluminum. According to one embodiment, the lithium metal oxide may include, for example, a lithium-manganese-based oxide, a lithium-cobalt-based oxide, a lithium-nickel-based oxide, a lithium-nickel-manganese-based oxide, a lithium-nickel-cobalt-based oxide, a lithium-manganese-cobalt-based oxide, a lithium-nickel-manganese-cobalt-based oxide, or a lithium-nickel-cobalt-transition metal (M) oxide, and may include one or more than two of these compounds.

[0081] The solvent can be a solvent commonly used in the art and can include at least one selected from dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, and water (H2O). Considering the coating thickness of the slurry and the manufacturing yield, the solvent is used in an amount sufficient to dissolve or disperse the active material, binder, and conductive material and having a viscosity capable of exhibiting excellent thickness uniformity when applied to subsequent electrode manufacturing.

[0082] The active material slurry may further include at least one of a binder and a conductive material, as well as the active material and the solvent.

[0083] The binder is used to improve the adhesion between active material particles and the adhesion between the active material and the current collector. The active material can be applied to both non-aqueous binders and aqueous binders, and there is no particular limitation on the type of binder. As an example, the negative electrode active material in the present invention can be applied to an aqueous binder. As another example, the aqueous binder may include at least one of the following: styrene-based rubbers such as styrene-butadiene rubber (SBR), acrylate-styrene butadiene copolymer rubber (acrylate-co-SBR), or acrylonitrile-styrene butadiene copolymer rubber (acrylonitrile-co-SBR), and acrylate compounds such as methyl methacrylate-lithium methacrylate copolymer (P(MMA-co-LiMA)), alkyl acrylate-acrylonitrile-acrylic acid copolymer (P(alkyl acrylate-co-acrylonitrile-acrylic acid)), polyacrylic acid (PAA), or polyimide series.

[0084] The conductive material is a component for further improving the conductivity of the active material, and the conductive material is not particularly limited as long as it has conductivity and does not cause chemical changes in the battery. As examples, the following can be used: graphite, such as natural graphite or artificial graphite; carbon black, such as acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal cracking carbon black; conductive fibers, such as carbon fibers or metal fibers; fluorocarbons; metal powders, such as aluminum powder 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.

[0085] For the coating of the electrode active material layer, any slurry coating method known in the art can be used without limitation. For example, a die slot method, a gravure printing method, a doctor blade method, a screen printing method, an offset printing method, a spraying method, or an impregnation method can be used.

[0086] (Positive electrode)

[0087] The positive electrode 100 may include a positive electrode current collector and a positive electrode active material formed on the positive electrode current collector. Since the positive electrode active material is the same as the above-mentioned active material, its detailed description will be omitted.

[0088] The positive electrode current collector may include a highly conductive metal and is not particularly limited as long as the positive electrode active material layer can easily adhere to it and is not reactive within the voltage range of the battery. As the positive electrode current collector, for example, stainless steel, aluminum, nickel, titanium, heat-treated carbon, or aluminum or stainless steel surface-treated with, for example, carbon, nickel, titanium, or silver can be used. In addition, the positive electrode current collector generally may have a thickness of about 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to improve the adhesion of the positive electrode active material. For example, the positive electrode current collector can be used in various forms such as films, sheets, foils, meshes, porous materials, foams, and non-woven materials.

[0089] (Negative electrode)

[0090] The negative electrode 200 may include a negative electrode current collector and a negative electrode active material formed on the negative electrode current collector. Since the negative electrode active material is the same as the above-mentioned active material, its detailed description will be omitted.

[0091] The negative electrode current collector is not particularly limited as long as it has high conductivity and does not cause chemical changes in the battery. As the negative electrode current collector, for example, copper, stainless steel, aluminum, nickel, titanium, heat-treated carbon, or copper, stainless steel, or aluminum-cadmium alloy surface-treated with, for example, carbon, nickel, titanium, or silver can be used. In addition, the negative electrode current collector generally may have a thickness of about 3 μm to 500 μm, and like the positive electrode current collector, fine irregularities may be formed on the surface of the current collector to enhance the binding force of the negative electrode active material. For example, the negative electrode current collector can be used in various forms such as films, sheets, foils, meshes, porous materials, foams, and non-woven materials.

[0092] (Separator)

[0093] The separator 300 separates the negative electrode and the positive electrode from each other and provides a moving channel for lithium ions. Any separator can be used without particular limitation as long as it is commonly used in lithium secondary batteries. In particular, a separator having low resistance to the movement of ions in the electrolyte and having excellent electrolyte moisturizing ability can be used. For example, a porous polymer membrane such as a porous polymer membrane made of a polyolefin polymer or a laminated structure of two or more layers of the above porous polymer membrane can be used. The polyolefin polymer is such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer. In addition, a conventional porous nonwoven fabric such as a nonwoven fabric made of, for example, high melting point glass fiber or polyethylene terephthalate fiber can be used. In addition, a coated separator containing a ceramic component or a polymer material can be used to ensure heat resistance or mechanical strength, and can optionally be used in a single-layer or multi-layer structure.

[0094] (Electrolyte)

[0095] The lithium secondary battery according to the present invention may further include an electrolyte. Examples of the electrolyte used in the present invention include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used to manufacture lithium secondary batteries, and are not limited thereto.

[0096] The electrolyte may contain an organic solvent and a lithium salt.

[0097] The organic solvent can be used without particular limitation as long as it can be used as a medium through which ions participating in the electrochemical reaction of the battery can move. For example, as the organic solvent, for example, ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene or fluorobenzene; carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), or propylene carbonate (PC); alcohol solvents such as ethanol and isopropyl alcohol; nitriles such as R-CN (R is a straight-chain, branched-chain, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may contain a double bond, an aromatic ring, or an ether bond); amides such as dimethylformamide; or dioxolanes such as 1,3-dioxolane; or sulfolane can be used. Among them, carbonate solvents are preferred, and a mixture of a cyclic carbonate having high ionic conductivity and high dielectric constant (e.g., ethylene carbonate or propylene carbonate) and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) that can improve the charge / discharge performance of the battery is more preferred.

[0098] A lithium salt can be used without particular limitation as long as it is a compound capable of providing lithium ions for use in a lithium secondary battery. For example, the anion of the lithium salt can be at least one selected from the following anions: 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 - , and as the lithium salt, for example, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, 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 can be used in the range of 0.1 M to 4.0 M, 0.5 M to 3.0 M, or 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 that excellent electrolyte performance can be achieved and lithium ions can move effectively.

[0099] In addition to the electrolyte components, for the purpose of, for example, improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity, the electrolyte can further contain, for example, at least one additive such as a carbonic acid haloalkyl ester compound (e.g., difluoroethylene carbonate), pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, (poly)glycol dimethyl ether, hexamethylphosphoric triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol or aluminum trichloride. Here, based on the total weight of the electrolyte, the content of the additive can be about 0.1 wt% to 10.0 wt%.

[0100] Battery case

[0101] The battery case has an empty space therein and can be configured to accommodate an electrode assembly and an electrolyte in the inner space.

[0102] Depending on the material of the battery case, lithium secondary batteries can be classified into: can-type batteries, in which the electrode assembly is built into a cylindrical or square metal can; or pouch-type batteries, in which the electrode assembly is built into a pouch-shaped case of an aluminum laminate. The lithium secondary battery according to the present invention can be a pouch-type secondary battery.

[0103] In addition to the above battery case 600, the lithium secondary battery according to the present invention may optionally include a sealing member (not shown) for sealing the battery case 600.

[0104] The lithium secondary battery according to the present invention may further include a positive electrode tab connected to a plurality of positive electrodes 100 and a negative electrode tab connected to a plurality of negative electrodes 200. The positive electrode tab may extend and protrude from one end of the positive electrode 100, may be welded to one end of the positive electrode 100, or may be bonded to one end of the positive electrode using a conductive adhesive. The negative electrode tab may extend and protrude from one end of the negative electrode 200, may be welded to one end of the negative electrode 200, or may be bonded to the negative electrode using a conductive adhesive.

[0105] As described above, the lithium secondary battery including a heat-dissipating current collector according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate. Therefore, the lithium secondary battery can be used in fields of portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0106] Therefore, another embodiment of the present invention provides a battery module including the lithium secondary battery as a unit cell and a battery pack including the battery module.

[0107] The battery module or the battery pack can be used as a power source for at least one of medium and large-sized devices such as power tools, electric vehicles (EVs) (such as hybrid electric vehicles or plug-in hybrid electric vehicles (PHEVs)), and energy storage systems.

[0108] Although the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art or those with ordinary knowledge in the art should understand that various modifications and changes can be made to the present invention without departing from the gist and technical scope of the present invention described in the appended claims. Therefore, the technical scope of the present invention should be determined by the claims and is not limited to the content described in the detailed description of the specification.

Claims

1. A lithium secondary battery, the lithium secondary battery comprising: An electrode assembly; and A battery case configured to accommodate the electrode assembly, Wherein the electrode assembly includes a positive electrode, a separator, and a negative electrode stacked in sequence, Wherein 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, Wherein the heat dissipation current collector includes a heat dissipation layer, a polymer layer provided on the heat dissipation layer, and a metal layer provided on the polymer layer, and Wherein the heat dissipation layer of the heat dissipation current collector includes a channel extending to the outside of the battery case and configured to discharge the heat inside the battery.

2. The lithium secondary battery according to claim 1, wherein the heat dissipation layer includes at least one of polysiloxane and acrylic resin.

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

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

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

6. The lithium secondary battery according to claim 1, wherein the metal layer has a thermal conductivity (k2) of about 200 W / K∙m to 500 W / K∙m.

7. 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 about 40 to 200.

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

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

0.

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

11. The lithium secondary battery according to claim 1, wherein the polymer layer includes a first polymer layer and a second polymer layer arranged to be spaced apart from each other, Wherein the metal layer includes a first metal layer and a second metal layer arranged to be spaced apart from each other, and 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. The lithium secondary battery according to 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 at the outermost position of the electrode assembly.

13. A lithium secondary battery electrode assembly, the lithium secondary battery electrode assembly comprising: a positive electrode; a negative electrode; and a separator, wherein at least one of the positive electrode and the negative electrode comprises a heat dissipating current collector, the heat dissipating current collector comprising a heat dissipating layer having a lower thermal conductivity than the metal layer of the current collector used as the corresponding electrode, and wherein the heat dissipating layer is connected to the outside of the battery and configured to discharge the heat inside the battery to the outside of the battery.

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

15. The lithium secondary battery electrode assembly according to claim 14, wherein the polymer layer has a melting point substantially similar to the melting point of the heat dissipating layer.

16. A method of manufacturing a lithium secondary battery electrode assembly, the lithium secondary battery electrode assembly comprising a positive electrode, a negative electrode and a separator, the method comprising: configuring at least one of the positive electrode and the negative electrode to comprise a heat dissipating current collector, the heat dissipating current collector comprising a heat dissipating layer having a lower thermal conductivity than the metal layer of the current collector used as the corresponding electrode; and configuring the heat dissipating layer to extend to the outside of the battery and discharge the heat inside the battery to the outside of the battery.

17. The method according to claim 16, the method further comprising: configuring the heat dissipating current collector to comprise a polymer layer on at least one surface of the heat dissipating layer and a metal layer provided on the polymer layer.

18. The method according to claim 17, the method further comprising: configuring the polymer layer to have a melting point substantially similar to the melting point of the heat dissipating layer.

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