Electrode lead, manufacturing method therefor, and lithium secondary battery comprising same

Abstract

The present invention relates to an electrode lead. The electrode lead is electrically connected to an electrode assembly and includes: a metal terminal; and a film layer positioned on the metal terminal and having two or more patterns intagliated on the surface thereof, wherein the two or more patterns are spaced apart from each other at equal intervals and are arranged in the horizontal direction of the film layer, and each of the two or more patterns includes a side surface and a bottom surface.

Description

Electrode lead, method for manufacturing same, and lithium secondary battery including same Cross-citation with related applications This application claims the benefit of priority from Korean Patent Application No. 10-2023-0114977, filed August 30, 2023, the entire contents of which are incorporated herein by reference. Technology field The present invention relates to an electrode lead, a method for manufacturing the same, and a lithium secondary battery including the same, and more particularly, to an electrode lead having reduced resistance and heat generation between the electrode lead and a jig, a method for manufacturing the same, and a lithium secondary battery including the same. With technological advancements and growing demand for mobile devices, demand for secondary batteries is also rapidly increasing. Among these, lithium secondary batteries are widely used as a power source for various mobile devices and other electronic products due to their high energy density, high operating voltage, and excellent storage and lifespan characteristics. A lithium secondary battery generally consists of an electrode assembly including a positive electrode, a negative electrode, and a separator, a battery case that houses the electrode assembly, an electrolyte that is poured into the battery case, and an electrode lead that electrically connects the lithium secondary battery to an external device or the secondary batteries. At this time, a lead film is attached to the interface between the electrode lead and the battery case to prevent short circuits between the electrode lead and the battery case and to seal the electrode lead and the battery case. The lead film is generally composed of a polymer for insulation and fusion with the battery case, but there is a problem that the sealing strength at the interface with the electrode lead composed of metal is reduced. As a result, the lead film is peeled off from the surface of the electrode lead, causing electrolyte to leak between the interface of the lead film and the electrode lead or moisture to infiltrate from the outside, resulting in stability problems. To solve the above problem, there are attempts to improve the sealing strength and electrolyte resistance between the electrode lead and the lead film by performing surface treatment, such as forming an oxide film on the surface of the electrode lead. However, when a film layer is formed on the surface of the electrode lead through surface treatment, the resistance of the electrode lead surface increases when the lead is charged and discharged by pressing it with a jig due to the thickness of the formed film layer, and accordingly, the amount of heat generated from the electrode lead increases, which causes a problem in that the life characteristics and stability of the lithium secondary battery deteriorate. The present invention is intended to solve the above problems, and provides an electrode lead capable of improving the sealing strength between a lead film and an electrode lead while simultaneously reducing the resistance and heat generation generated in the electrode lead during charging and discharging, a method for manufacturing the same, and a lithium secondary battery including the same. [1] The present invention provides an electrode lead electrically connected to an electrode assembly, comprising: a metal terminal; and a film layer positioned on the metal terminal and having two or more patterns engraved on a surface; wherein the two or more patterns are spaced apart at equal intervals and arranged in a horizontal direction of the film layer, and each of the patterns includes a side surface and a bottom surface. [2] The present invention provides an electrode lead in the above [1], wherein the shape of the bottom surface of the pattern is polygonal, circular, or oval. [3] The present invention provides an electrode lead in which each of the patterns has the same depth as each other in [1] or [2]. [4] The present invention provides an electrode lead in which each of the patterns has the same bottom surface area as each other in at least one of [1] to [3]. [5] The present invention provides an electrode lead in which, in at least one of the above [1] to [4], the pattern has a bottom surface and a side surface that are perpendicular to each other. [6] The present invention provides an electrode lead, wherein, in at least one of the above [1] to [5], the ratio of the bottom surface area of ​​the entire pattern to the cross-sectional area of ​​the film layer is 0.05 to 0.7, preferably 0.06 to 0.6, more preferably 0.07 to 0.5. [7] The present invention provides an electrode lead, wherein, in at least one of the above [1] to [6], the ratio of the bottom surface area of ​​the single pattern to the cross-sectional area of ​​the film layer is 0.005 to 0.010, preferably 0.0058 to 0.009, more preferably 0.006 to 0.008. [8] The present invention provides an electrode lead, wherein, in at least one of the above [1] to [7], the ratio of the depth of the pattern to the thickness of the film layer is 0.3 to 0.7, preferably 0.4 to 0.65, more preferably 0.45 to 0.6, and even more preferably 0.45 to 0.55. [9] The present invention provides an electrode lead, wherein, in at least one of the above [1] to [8], the film layer may include at least one selected from the group consisting of chromate, zirconium salt, titanium salt, and phosphate, and preferably includes chromate.

[0010] The present invention provides an electrode lead, wherein in at least one of the above [1] to [9], the metal terminal comprises at least one selected from the group consisting of aluminum, copper, nickel, and nickel-plated copper, more specifically aluminum, nickel, or a combination thereof, and even more specifically aluminum.

[0011] The present invention provides an electrode lead, wherein in at least one of the above [1] to

[0010] , the ratio of the thickness of the metal terminal to the thickness of the film layer is 10,000:1 to 500:1, preferably 6,000:1 to 500:1, and more preferably 5,000:1 to 500:1.

[0012] The present invention provides a lithium secondary battery comprising: an electrode assembly including a positive electrode, a negative electrode, and a separator; a battery case accommodating the electrode assembly; an electrolyte; an electrode tab connected to the positive electrode and the negative electrode and protruding from one side of the assembly; an electrode lead having one end connected to the electrode tab and as described above; and a lead film interposed at an interface between the electrode lead and the battery case.

[0013] The present invention provides a method for manufacturing an electrode lead, comprising a step of forming a film layer on a metal terminal by a gravure coating device, wherein the gravure coating device includes a rolling roll and a gravure roll, the gravure roll has a rough surface, the film layer has two or more patterns engraved on the surface, the two or more patterns are spaced apart at equal intervals and arranged in a horizontal direction of the film layer, and each of the patterns includes a side surface and a bottom surface.

[0014] The present invention provides a method for manufacturing an electrode lead, wherein, in the above

[0013] , the film layer may include at least one selected from the group consisting of chromate, zirconium salt, titanium salt, and phosphate, and preferably includes chromate.

[0015] The present invention provides a method for manufacturing an electrode lead, wherein, in the above

[0013] or

[0014] , each of the patterns may have the same depth and each of the patterns may have the same bottom surface area. According to the present invention, by uniformly forming an engraved pattern on a film layer located on the surface of a metal terminal of an electrode lead, the sealing strength and electrolyte resistance between the electrode lead and the lead film can be improved, while the contact resistance and heat generation generated in the electrode lead during charging and discharging can be reduced by pressing the electrode lead with a jig. Accordingly, the output characteristics, life characteristics, and stability of a lithium secondary battery can be improved. FIG. 1 is a cross-sectional view showing a schematic structure of an electrode lead according to one embodiment of the present invention. FIG. 2 is a perspective view showing a schematic structure of an electrode lead according to one embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of an electrode lead including a film layer in which two or more patterns are arranged in a horizontal direction of the film layer at unequal intervals. Figure 4 is a schematic process diagram of a gravure coating device for manufacturing an electrode lead according to one embodiment of the present invention. Figure 5 is an exploded assembly diagram of a lithium secondary battery according to the present invention. Hereinafter, the present invention will be described in more detail. Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way. The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, it should be understood that terms such as “include,” “have,” or “have” are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof. Hereinafter, the present invention will be described in detail. The precursor for a positive electrode active material according to the present invention, the method for producing the same, the positive electrode active material, the positive electrode and / or the lithium secondary battery comprise at least one or more of the following disclosed configurations, and may comprise any combination between technically possible configurations among the following configurations. electrode leads An electrode lead according to the present invention is an electrode lead electrically connected to an electrode assembly, and includes a metal terminal; and a film layer positioned on the metal terminal and having two or more patterns engraved on a surface thereof; wherein the two or more patterns are spaced apart at equal intervals and arranged in a horizontal direction of the film layer, and each of the patterns includes a side surface and a bottom surface. The above electrode lead extends from the positive and negative electrode plates included in the electrode assembly and is connected to a protruding electrode tab, so that it can function as an electrode terminal for electrically connecting a secondary battery and an external device of the secondary battery, or for electrically connecting the secondary batteries to each other. FIG. 1 is a cross-sectional view showing a schematic structure of an electrode lead according to one embodiment of the present invention, and FIG. 2 is a perspective view showing a schematic structure of an electrode lead according to one embodiment of the present invention. Referring to FIGS. 1 and 2, the electrode lead (10) includes a metal terminal (1) and a film layer (2) positioned on the metal terminal (1). Hereinafter, each configuration of the electrode lead (10) will be described in detail with reference to FIGS. 1 and 2. The above metal terminal (1) functions as a passage through which current flows when electrically connecting a lithium secondary battery and an external device of the secondary battery through an electrode lead, or when electrically connecting secondary batteries to each other. Specifically, the metal terminal (1) may include at least one selected from the group consisting of aluminum (Al), nickel (Ni), copper (Cu), nickel-plated copper, gold (Au), silver (Ag), platinum (Pt), iron (Fe), chromium (Cr), and manganese (Mn). Specifically, the metal terminal (1) may include at least one selected from the group consisting of aluminum, copper, nickel, and nickel-plated copper, and more specifically, aluminum, nickel, or a combination thereof, and even more specifically, aluminum, in that it facilitates electron movement, has no reactivity with organic solvents, and has excellent chemical stability so that oxidation or reduction does not occur even under long-term battery operation conditions. The above metal terminal (1) may be in the form of a rectangular plate, but is not limited thereto, and any form that can serve to electrically connect the secondary battery may be used without limitation. The thickness of the above metal terminal (1) may be 0.05 mm to 0.8 mm, preferably 0.1 mm to 0.7 mm, and more preferably 0.15 mm to 0.65 mm. Specifically, when the electrode lead (10) is connected to the positive electrode tab (282), the thickness of the metal terminal (1) may be 0.2 mm to 0.6 mm, preferably 0.3 mm to 0.5 mm, more preferably 0.35 mm to 0.45 mm, or 0.4 mm to 0.8 mm, preferably 0.5 mm to 0.7 mm, more preferably 0.55 mm to 0.65 mm. In addition, when the electrode lead (10) is connected to the negative electrode tab (284), the thickness of the metal terminal (1) may be 0.05 mm to 0.35 mm, preferably 0.1 mm to 0.3 mm, more preferably 0.15 mm to 0.25 mm, or 0.1 mm to 0.5 mm, preferably 0.2 mm to 0.4 mm, more preferably 0.25 mm to 0.35 mm. If the above range is satisfied, the sealing strength of the battery case can be secured, reducing concerns about electrolyte leakage and moisture infiltration. The above film layer (2) is positioned on the metal terminal (1) and serves to improve the sealing strength between the lead film and the electrode lead (10). In addition, the film layer (2) may have electrical conductivity. Since the film layer is positioned on the metal terminal and is pressed together when the electrode lead is pressed by the jig, when the film layer has electrical conductivity, the electrode lead can maintain electrical conductivity, so that current can flow smoothly through the electrode lead. Specifically, the film layer (2) may be positioned on one or both sides of the metal terminal (1). The above film layer (2) may include at least one selected from the group consisting of chromate, zirconium salt, titanium salt, and phosphate, and preferably may include chromate. The chromate may be represented by, for example, Cr2O3H2O. When the film layer includes chromate, a stable film layer can be formed on the surface of the metal terminal, and the wettability of the electrode lead surface increases, thereby improving the adhesion performance with the lead film, which is a different material. In addition, when the film layer includes chromate, the electrical conductivity of the electrode lead can be maintained. Meanwhile, when the metal terminal (1) and the lead film are in direct contact without a film layer (2), there is a problem that the sealing performance is reduced due to the weak thermal adhesion between the lead film and the metal terminal, which are different materials. As a result, peeling may occur between the lead film and the metal terminal, causing electrolyte to leak between the lead film and the metal terminal, moisture to infiltrate from the outside, and the metal terminal to corrode. Accordingly, there is a problem that the life characteristics, output characteristics, and stability of the battery are reduced. Therefore, the present invention solves this problem by forming the film layer on the surface of the metal terminal. However, when charging by pressing the electrode lead with a jig, the film layer may act as a relative resistance compared to the metal terminal, which may deteriorate the output characteristics of the battery. In addition, when the thickness of the film layer is reduced to improve the resistance problem, when a high current flows through the battery, the amount of heat generated at the contact surface between the electrode lead and the jig increases, which may deteriorate the stability and life characteristics of the battery. Accordingly, the film layer (2) according to the present invention includes two or more patterns (3) that are regularly and engraved, thereby securing adhesion to the lead film and simultaneously reducing resistance and heat generation generated between the contact surface of the electrode lead and the jig when charging and discharging by pressing the electrode lead with a jig. Specifically, the film layer (2) has two or more patterns (3) engraved on the surface. The above film layer (2) includes a pattern (3) formed with a plurality of intaglios, so that when pressing the electrode lead with a jig, the area in contact with the jig is reduced while at the same time increasing the surface area, so that the current density can be relatively lowered, thereby reducing the resistance caused by the film layer. In addition, since the film layer is formed by forming an intaglio pattern in a thin portion while maintaining the maximum thickness, the heat generated when a high current flows through the electrode lead can be reduced. Accordingly, the life characteristics, output characteristics, and stability of the lithium secondary battery can be improved. FIG. 3 is a cross-sectional view of an electrode lead including a film layer in which two or more patterns are arranged in a horizontal direction of the film layer at unequal intervals. Comparing FIGS. 1, 2 and 3, the electrode lead (10) according to the present invention has patterns (3) formed in a negative manner on the surface of the film layer (2), and the patterns (3) can be formed uniformly and regularly. Specifically, in the electrode lead according to the present invention, the two or more patterns (3) are spaced apart at equal intervals and arranged in the horizontal direction of the film layer (2). At this time, the interval means the shortest length between each edge of one pattern and another adjacent pattern on the uppermost surface of the film layer. In addition, the equal interval means that the interval is equal within an error range of ± 10%. The horizontal direction means a direction horizontal to the surface of the film layer, and specifically, a direction horizontal to the interface between the metal terminal and the film layer. Accordingly, the above two or more patterns can be regularly arranged on the surface of the film layer. In this case, when the electrode lead is fastened to the jig and current is passed through it, the current can be prevented from flowing densely in a specific area of ​​the electrode lead, thereby reducing the contact resistance and heat generation of the entire electrode lead. Meanwhile, each of the above patterns (3) includes a side surface and a bottom surface. The bottom surface is the lower surface of the pattern indented from the top surface of the film layer, and means a surface parallel to the interface between the metal terminal and the film layer, and the side surface means a surface extending from the bottom surface to the top surface of the film layer. Each of the above patterns may have the same depth. In this case, the depth of the pattern means the vertical length from the uppermost surface of the film layer to the bottom surface of the pattern. The fact that the depths of each of the above patterns are the same means that the depths are the same within the error range of ± 5%. The contact resistance between the electrode lead and the electrode jig decreases as the standard deviation of the height distribution of the intaglio pattern decreases, the pattern size decreases, and the pattern density increases. At this time, since the contact resistance changes linearly with respect to the pattern density and pattern size, but changes exponentially with respect to the standard deviation of the height distribution of the intaglio pattern, the standard deviation of the height distribution of the intaglio pattern can have the greatest influence on the contact resistance. That is, when the depths of each of the above patterns are the same, the standard deviation of the height distribution of the intaglio pattern decreases, the contact resistance decreases, and the amount of heat generated from the electrode lead decreases. Each of the above patterns (3) may have the same bottom surface area. In this case, the fact that each of the patterns has the same bottom surface area means that the bottom surface areas are the same within a margin of error of ± 5%. In this case, the patterns engraved on the surface of the film layer may have the same surface area, so that when the electrode lead is fastened to the jig and charging / discharging is performed, each of the patterns may exhibit the same current density. Accordingly, the problem of resistance particularly increasing or decreasing in a specific region of the electrode lead does not occur, and the contact resistance and heat generation amount can be reduced throughout the electrode lead. Meanwhile, the shape of the bottom surface of the above pattern (3) is not limited in form and may be, for example, a polygon, a circle, or an ellipse. The pattern (3) above may have the bottom surface and the side surface perpendicular to each other. That is, the cross-sectional area of ​​the pattern may be maintained constant without decreasing or increasing along the depth direction of the electrode lead. At this time, the depth direction refers to a direction perpendicular to the interface between the film layer and the metal terminal. In this case, even in a single pattern, the standard deviation of the height distribution of the engraved pattern may be reduced, so that the contact resistance may be reduced as described above, and when the electrode lead is fastened to the jig, the contact resistance and heat generation of the electrode lead may be further reduced. The ratio of the bottom surface area of ​​the entire pattern (3) to the cross-sectional area of ​​the film layer (2) may be 0.05 to 0.7, preferably 0.06 to 0.6, and more preferably 0.07 to 0.5. In the present specification, the cross-sectional area of ​​the film layer refers to the surface area when no pattern is formed on the film layer. When the ratio is less than 0.05, the ratio of the bottom surface area of ​​the entire pattern to the cross-sectional area of ​​the film layer is small, so that the contact resistance between the electrode lead and the jig may increase. In addition, when the ratio is greater than 0.7, the sealing strength between the electrode lead and the lead film may not be improved. Therefore, when the ratio satisfies the above range, the sealing strength between the electrode lead and the lead film can be secured by the film layer, while sufficiently reducing the amount of heat generated from the electrode lead during charge and discharge, and also reducing the contact resistance between the electrode lead and the jig. The ratio of the bottom surface area of ​​the single pattern (3) to the cross-sectional area of ​​the film layer (2) may be 0.005 to 0.010, preferably 0.0058 to 0.009, more preferably 0.006 to 0.008. When the above range is satisfied, each pattern can be formed in a small size, so that even if the bottom surface area of ​​the entire pattern is the same, the surface area of ​​the entire film layer is relatively large, so that the contact resistance between the electrode lead and the jig can be reduced. In addition, since it is possible to prevent a specific single pattern from being formed large, the current can flow uniformly throughout the electrode lead during charging and discharging, and thus the contact resistance and heat generation generated between the electrode lead and the jig can be evenly reduced. The ratio of the depth of the pattern (3) to the thickness of the film layer (2) may be 0.3 to 0.7, preferably 0.4 to 0.65, more preferably 0.45 to 0.6, and even more preferably 0.45 to 0.55. At this time, the thickness of the film layer refers to the vertical length from the uppermost surface of the film layer to the interface between the metal terminal and the film layer, and the depth of the pattern refers to the vertical length from the uppermost surface of the film layer to the bottom surface of the pattern. When the above range is satisfied, the adhesion between the film layer and the lead film can be sufficiently secured throughout the film layer, while the contact resistance caused by the film layer during charge and discharge can be sufficiently reduced, and at the same time, the amount of heat generated from the electrode lead can be reduced. Meanwhile, the thickness of the film layer (2) may be 10 nm to 60 nm, preferably 15 nm to 40 nm, and more preferably 18 nm to 30 nm. When the above range is satisfied, the adhesive strength between the electrode lead and the lead film can be improved, thereby sufficiently securing the sealing strength of the interface between the electrode lead and the lead film, thereby preventing the problem of peeling occurring at the interface. In addition, the ratio of the thickness of the metal terminal (1) to the thickness of the film layer (2) may be 10,000:1 to 500:1, preferably 6,000:1 to 500:1, and more preferably 5,000:1 to 500:1. When the above range is satisfied, the electrode leads can be smoothly electrically connected to each other or to an external device, thereby securing output characteristics, while improving the adhesive strength with the lead film by the film layer, and reducing the increase in resistance and the resulting heat generation occurring in the electrode leads. Method for manufacturing electrode leads Next, a method for manufacturing an electrode lead according to the present invention includes a step of forming a film layer on a metal terminal by a gravure coating device, wherein the gravure coating device includes a rolling roll and a gravure roll, wherein the gravure roll has a rough surface, and the film layer has two or more patterns engraved on the surface, wherein the two or more patterns are spaced apart at equal intervals and arranged in a horizontal direction of the film layer, and each of the patterns includes a side surface and a bottom surface. Figure 4 is a schematic process diagram of a gravure coating device (300) for manufacturing an electrode lead (10) according to one embodiment of the present invention. Referring to FIG. 4, the step of forming a film layer (2) on a metal terminal (1) by the gravure coating device (300) can be performed by supplying a coating liquid to the gravure roll (310) and rotating the gravure roll (310) while in contact with the metal terminal (1), thereby forming a film layer (2) on the metal terminal (1). At this time, the rolling roll (320) can be moved so that the film layer (2) is formed on the metal terminal (1) by contacting a surface other than the surface on which the film layer (2) is formed and rotating in the opposite direction to the gravure roll (310). The gravure coating device (300) includes a rolling roll (320) and a gravure roll (310). In addition, the gravure coating device (300) may further include a coating solution supply tray (330) capable of supplying a coating solution. The above gravure roll (310) has a rough surface. By the roughness formed on the surface of the gravure roll (310), two or more patterns (3) can be formed in a negative manner on the film layer (2). That is, the gravure roll (310) has the same shape and arrangement as the pattern (3), but can include a pattern in relief as the roughness, which is opposite to the pattern (3). The above coating solution may contain at least one selected from the group consisting of chromic acid, zirconium, titanium, and phosphoric acid, and preferably may contain chromic acid. Meanwhile, the metal terminal (1) may include at least one selected from the group consisting of aluminum, nickel, copper, gold, silver, platinum, iron, chromium, and manganese, and more specifically, the metal terminal may include at least one selected from the group consisting of aluminum and nickel in that it facilitates electron movement, has no reactivity with organic solvents, and has excellent chemical stability so that oxidation or reduction does not occur even under long-term battery operation conditions. The above metal terminal (1) may be in the form of a rectangular plate, but is not limited thereto, and any form that can serve to electrically connect the secondary battery may be used without limitation. The thickness of the above metal terminal (1) may be 0.05 mm to 0.8 mm, preferably 0.1 mm to 0.7 mm, and more preferably 0.15 mm to 0.65 mm. Specifically, when the electrode lead (10) is connected to the positive electrode tab (282), the thickness of the metal terminal (1) may be 0.2 mm to 0.6 mm, preferably 0.3 mm to 0.5 mm, more preferably 0.35 mm to 0.45 mm, or 0.4 mm to 0.8 mm, preferably 0.5 mm to 0.7 mm, more preferably 0.55 mm to 0.65 mm. In addition, when the electrode lead (10) is connected to the negative electrode tab (284), the thickness of the metal terminal (1) may be 0.05 mm to 0.35 mm, preferably 0.1 mm to 0.3 mm, more preferably 0.15 mm to 0.25 mm, or 0.1 mm to 0.5 mm, preferably 0.2 mm to 0.4 mm, more preferably 0.25 mm to 0.35 mm. If the above range is satisfied, the sealing strength of the battery case can be secured, reducing concerns about electrolyte leakage and moisture infiltration. Meanwhile, according to the method for manufacturing an electrode lead (10) according to the present invention, the film layer (2) is formed on the metal terminal (1). Specifically, the film layer (2) can be formed on one side or both sides of the metal terminal (1), and can serve to improve the sealing strength between the lead film and the electrode lead. The film layer (2) formed thus may include at least one selected from the group consisting of chromate, zirconium salt, titanium salt, and phosphate, and preferably may include chromate. The chromate may be represented by, for example, Cr2O3H2O. When the film layer includes chromate, a stable film layer can be formed on the surface of the metal terminal, and the wettability of the electrode lead surface increases, thereby improving the adhesion performance with the lead film, which is a different material. The above film layer (2) has two or more patterns (3) engraved on its surface. The patterns (3) can be formed in an engraved form according to the shape of the roughness formed on the surface of the gravure roll (310). Accordingly, a pattern (2) having the same number and shape as the roughness formed in relief on the surface of the gravure roll (310) can be formed in an engraved form on the film layer (2). The film layer (2) and pattern formed according to the method for manufacturing the electrode lead (10) according to the present invention are the same as those described above as the configuration of the electrode lead (10), so a detailed description thereof is omitted. lithium secondary battery According to another embodiment, a lithium secondary battery of the present invention comprises: an electrode assembly including a positive electrode, a negative electrode, and a separator; a battery case accommodating the electrode assembly; an electrolyte; an electrode tab connected to the positive electrode and the negative electrode and protruding from one side of the assembly; an electrode lead having one end connected to the electrode tab and according to any one of claims 1 to 9; and a lead film interposed at an interface between the electrode lead and the battery case. Figure 5 is an exploded assembly diagram of a lithium secondary battery according to the present invention. Hereinafter, with reference to FIG. 5, each component of the lithium secondary battery according to the present invention will be described in detail. (1) Electrode assembly The electrode assembly includes an anode, a cathode, and a separator. Referring to FIG. 5, when the lithium secondary battery is a pouch-type secondary battery, the electrode assembly (270) can be inserted into a pouch-type battery case (210) and sealed by the pouch-type battery case (210) after injecting an electrolyte (not shown). The above electrode assembly (270) can be formed by sequentially stacking an anode, a separator, and a cathode, and specifically, the electrode assembly (270) can include two types of electrodes, an anode and a cathode, and a separator interposed between the electrodes to mutually insulate the electrodes. The positive and negative electrodes may each have a structure in which an active material slurry is applied to an electrode current collector in the form of a metal foil or metal mesh containing aluminum and copper, respectively. The slurry is typically formed by stirring granular active materials, auxiliary conductors, binders, and conductive agents with the addition of a solvent. The solvent can be removed in a subsequent process. A slurry containing an electrode active material, a binder, and / or a conductive material is applied to a positive electrode current collector and a negative electrode current collector to manufacture a positive electrode and a negative electrode, and these are laminated on both sides of a separator, thereby manufacturing an electrode assembly (270) in a predetermined shape. The types of electrode assembly (270) may include, but are not limited to, a stack type, a jelly roll type, a stack and folding type, etc. (2) Battery case The above battery case may serve to house the electrode assembly. Specifically, the battery case is for housing the electrode assembly, injecting an electrolyte, and then sealing it. The battery case is manufactured from a material having a predetermined flexibility that can form a housing portion. There is no limitation on the shape thereof, but it may preferably be cylindrical, coin-shaped, square, or pouch-shaped. The upper case and the lower case constituting the battery case may be independent members, or may be substantially one member with one end connected. The exterior shape of the battery case may be manufactured in various ways, and the present invention does not limit this. For example, the battery case may be a pouch-type battery case. Referring to FIG. 5, the pouch-type battery case (210) may be manufactured by molding a pouch film laminate (220). The pouch-type battery case (210) may accommodate the electrode assembly (270) inside. The above pouch film laminate (220) may be formed by sequentially laminating a substrate layer (221), a gas barrier layer (222), and a sealant layer (223), but is not limited thereto. Specifically, the substrate layer (221) is formed on the outermost layer of the pouch film laminate (220) to protect the secondary battery from friction and collision with the outside. The substrate layer is made of a polymer and can electrically insulate the electrode assembly (270) from the outside. The above-mentioned substrate layer (221) may be made of one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, and Teflon. Among them, the substrate layer (221) is preferably made of polyethylene terephthalate (PET), nylon, or a combination thereof, which have wear resistance and heat resistance. The gas barrier layer (222) is laminated between the substrate layer (221) and the sealant layer (223) to secure the mechanical strength of the pouch, block the ingress of gas or moisture from outside the secondary battery, and prevent electrolyte leakage from inside the pouch-type battery case. The gas barrier layer (222) may be formed of a metal. For example, the gas barrier layer (222) may be a metal thin film including one or more metals selected from the group consisting of aluminum (Al), copper (Cu), stainless steel (SUS), nickel (Ni), titanium (Ti), and invar (INVAR), but is not limited thereto. The sealant layer (223) is intended to completely seal the inside of the pouch-shaped battery case by mutually thermally bonding the sealing portion when the pouch-shaped battery case containing the electrode assembly (270) on the inside is sealed. To this end, the sealant layer (223) may be formed of a material having excellent thermal bonding strength. The sealant layer (223) may be formed of a material having insulating, corrosion-resistant, and sealing properties. Specifically, since the sealant layer (223) is in direct contact with the electrode assembly (270) and / or the electrolyte (not shown) inside the pouch-shaped battery case (210), it may be formed of a material having insulating and corrosion-resistant properties. In addition, since the sealant layer (223) must completely seal the inside of the pouch-shaped battery case to block material movement between the inside and the outside, it may be formed of a material having high sealing properties (e.g., excellent thermal bonding strength). In order to secure such insulating, corrosion-resistant, and sealing properties, the sealant layer (223) may be formed of a polymer material. Specifically, the sealant layer (223) may be made of one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, and Teflon, and preferably may be made of a polyolefin resin such as polypropylene (PP) and / or polyethylene (PE). In this case, the polypropylene may be composed of cast polypropylene (CPP), acid modified polypropylene (Acid Modified Polypropylene, PPa), polypropylene-ethylene copolymer, and / or polypropylene-butylene-ethylene terpolymer. The pouch film laminate (220) can be drawn and stretched by a punch or the like to manufacture a pouch-type battery case (210). As a result, the pouch-type battery case (210) can include a cup portion (232) and a receiving portion (234). The receiving portion (234) is a place for receiving the electrode assembly (270), and can mean a receiving space formed in the shape of a pocket on the inside of the cup portion (232) as the cup portion (232) is formed. Meanwhile, the pouch-type battery case (210) may include a first case (230) and a second case (240). The first case (230) includes a receiving portion (234) capable of receiving an electrode assembly (270), and the second case (240) may cover the receiving portion (234) from above to prevent the electrode assembly (270) from falling out of the battery case. The first case (230) and the second case (240) may be manufactured with one side connected to each other, but are not limited thereto, and may be manufactured in various ways, such as being manufactured separately and separated from each other. According to another embodiment of the present invention, when forming a cup portion (242) on a pouch film laminate (220), two symmetrical cup portions (242) can be drawn and formed adjacent to each other on one pouch film laminate (220). In this case, a cup portion (242) can be formed on each of the first case (230) and the second case (240). After the electrode assembly (270) is accommodated in the receiving portion (234) provided in the cup portion (232) of the first case (230), the bridge portion (250) formed between the two cup portions (232, 242) can be folded so that the two cup portions (242) face each other. In this case, the cup portion (242) of the second case (240) can accommodate the electrode assembly (270) from above. Accordingly, since two cup portions (232, 242) accommodate one electrode assembly (270), an electrode assembly (270) having a thicker thickness can be accommodated than when there is only one cup portion. In addition, since one corner of the secondary battery is formed by folding the pouch-type battery case (210), the number of corners to be sealed can be reduced when performing a sealing process later. Accordingly, the process speed of the pouch-type secondary battery (200) can be improved, and the number of sealing processes can be reduced. The pouch-type battery case (210) can be sealed while housing the electrode assembly (270) so that a portion of the electrode lead (10) described later, i.e., the terminal portion, is exposed. Specifically, when the electrode lead (10) is connected to the electrode tab (280) of the electrode assembly (270) and the lead film (290) is attached to a portion of the electrode lead (10), the electrode assembly (270) can be housed in the receiving portion (234) provided in the cup portion (232) of the first case (230), and the second case (240) can cover the receiving portion (234) from above. Subsequently, an electrolyte (not shown) can be injected into the receiving portion (234), and the sealing portion (260) formed on the edges of the first case (230) and the second case (240) can be sealed. The sealing portion (260) can serve to seal the receiving portion (234). Specifically, the sealing portion (260) can seal the receiving portion (234) while being formed along the edge of the receiving portion (234). The temperature at which the sealing portion (260) is sealed can be 180°C to 250°C, specifically 200°C to 250°C, and more specifically 210°C to 240°C. When the sealing temperature satisfies the above numerical range, the pouch-type battery case (210) can secure sufficient sealing strength through thermal bonding. At this time, the sealing portion (260) may be formed by folding toward the receiving portion (234) to secure the energy density of the lithium secondary battery. (3) 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 the manufacture of secondary batteries. Specifically, the electrolyte may include an organic solvent and a lithium salt. As the organic solvent, any solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move may be used without particular limitation. Specifically, the organic solvent includes ester solvents such as methyl acetate, ethyl acetate, gamma-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 dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (R is a C2 to C20 linear, branched, or cyclic hydrocarbon group, which 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, carbonate solvents are preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) with high ionic conductivity and high dielectric constant that 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) is more preferable. In this case, the performance of the electrolyte can be excellent when the cyclic carbonate and the linear carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9. 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 lithium salt is F - , Cl - , Br - , I - ,O3 - , 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. It is preferable that the concentration of the lithium salt be used within the range of 0.1 to 4.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively. In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphate 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 5 wt% based on the total weight of the electrolyte. (4) Electrode tab The above electrode tab is connected to the positive and negative electrodes and protrudes from one side of the assembly. Referring to FIG. 5, the electrode tabs (280) are respectively connected to the positive and negative electrodes of the electrode assembly (270), and protrude outward from the electrode assembly, thereby providing a path for electrons to move between the inside and the outside of the electrode assembly (270). The electrode current collector included in the electrode assembly (270) may be configured with a portion where an electrode active material is applied and an end portion where the electrode active material is not applied, i.e., a non-coated portion. The electrode tabs (280) may be formed by cutting the non-coated portion or by connecting a separate conductive member to the non-coated portion by ultrasonic welding, etc. As illustrated in FIG. 5, the electrode tabs (280) may protrude in different directions of the electrode assembly (270), but are not limited thereto, and may be formed to protrude in various directions, such as protruding in parallel in the same direction from one side. (5) Electrode lead The electrode lead (10) can serve to electrically connect the secondary battery to the outside. Referring to FIG. 5, the electrode lead (10) can be electrically connected to a plurality of electrode tabs (280) extending from the current collector of each electrode of the electrode assembly (270) by welding, and can be connected, for example, by spot welding. The electrode lead (10) may be connected to the electrode assembly (270) and may protrude outside the battery case. Specifically, one end of the electrode lead (10) may be connected to the electrode assembly (270), particularly to the electrode tab (280), and the other end of the electrode lead (10) may protrude outside the battery case. The electrode lead (10) may include a positive lead (20) having one end connected to the positive tab (282) and extending in the direction in which the positive tab (282) protrudes, and a negative lead (30) having one end connected to the negative tab (282) and extending in the direction in which the negative tab protrudes. Both the positive lead (20) and the negative lead (30) may have other ends protruding to the outside of the battery case. Accordingly, electricity generated inside the electrode assembly (270) may be supplied to the outside. In addition, since the positive tab (282) and the negative tab (284) are formed to protrude in various directions, the positive lead (20) and the negative lead (30) may also extend in various directions, respectively. The positive lead (20) and the negative lead (30) may be made of different materials. For example, the positive electrode lead (20) may be made of the same aluminum (Al) material as the positive electrode collector, and the negative electrode lead (30) may be made of the same copper (Cu) material as the negative electrode collector or a nickel (Ni)-coated copper material. A portion of the electrode lead (10) protruding outside the battery case may serve as a terminal portion and be electrically connected to an external terminal. The configuration of the electrode lead (10) other than this is the same as described above, so a detailed description is omitted. (6) Lead film The above lead film prevents electricity generated from the electrode assembly from flowing into the battery case through the electrode leads, and maintains the sealing properties of the battery case. To this end, the lead film may be formed of a non-conductive material that does not conduct electricity well. Generally, the lead film is often made of an insulating tape that is easy to attach to the electrode leads and / or the innermost layer of the battery case and has a relatively thin thickness, but is not limited thereto, and any material capable of insulating the electrode leads may be used. Referring to FIG. 5, when the lithium secondary battery is a pouch-type lithium secondary battery, the lead film (290) may be arranged to surround the interface between the electrode lead (10) and the pouch-type battery case (210). For example, the first case (230), the lead film (290), the electrode lead (10), the lead film (290), and the second case (240) may be arranged in a sequentially stacked state in the sealing portion (260) region of the battery case. Specifically, the electrode lead (10) and the battery case are in contact with each other at one side, and at least a portion of the electrode lead (10) and the pouch-type battery case (210) may be surrounded by the lead film (290), and the electrode lead and the battery case may be bonded to each other. The lithium secondary battery according to the present invention is useful in portable devices such as mobile phones, laptop computers, and digital cameras, and in electric vehicles such as hybrid electric vehicles (HEVs). In addition, a battery module or battery pack including the lithium secondary battery as a unit cell can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system. The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells. Examples of the above medium and large devices include, but are not limited to, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems. Hereinafter, the present invention will be described in more detail through specific examples. Example 1 After preparing an aluminum (Al) metal terminal having a thickness of 0.4 mm, a width of 45 mm, and a length of 41 mm, a film layer containing chromate (Cr2O3H2O) having a thickness of 20 nm was formed on the surface of the metal terminal. After this, a physical etching process that applies a constant force to the surface of the film layer is performed to form a stripe-shaped negative pattern at equal intervals. The interval between the negative patterns is 4 mm, the horizontal width of the negative pattern is 0.35 mm, and the depth is 10 nm. By forming the stripe-shaped negative pattern, an electrode lead simulating the pattern formed using a gravure coating device is manufactured. Comparative Example 1 After preparing an aluminum (Al) metal terminal having a thickness of 0.4 mm, width of 45 mm, and length of 41 mm, a film layer containing chromate (Cr2O3H2O) having a thickness of 20 nm was formed on the surface of the metal terminal, and an electrode lead was manufactured without any special treatment on the surface of the oxide film layer. Comparative Example 2 After preparing an aluminum (Al) metal terminal having a thickness of 0.4 mm, a width of 45 mm, and a length of 41 mm, a film layer containing chromate (Cr2O3H2O) having a thickness of 20 nm was formed on the surface of the metal terminal. After this, an intaglio pattern was formed on the surface of the film layer through physical etching treatment. However, unlike Example 1, the force applied when forming one pattern was not maintained constant, so that the depth was not constant and the interval was irregular, thereby forming an intaglio pattern, thereby manufacturing an electrode lead simulating a case in which a gravure coating device was not used. Experimental Example 1: Resistance Measurement Evaluation When Jig Fastening After the electrode leads manufactured in Example 1 and Comparative Examples 1 and 2 were fastened to a jig, a direct current of 400 A was applied for 10 minutes, and the resistance of each electrode lead was measured by measuring the pressure difference before and after the current was applied. The measurement results are shown in Table 1 below. Surface resistance [mΩ] Example 10.09 ±0.008 Comparative example 10.24 ±0.017 Comparative example 20.14 ±0.036 Referring to Table 1 above, it can be confirmed that Example 1, in which a uniform negative pattern is formed on the surface of the film layer of the electrode lead, has a reduced surface resistance compared to Comparative Example 1, in which no pattern is formed on the surface of the film layer, and Comparative Example 2, in which an uneven negative pattern is formed. Experimental Example 2: Evaluation of electrode lead temperature measurement during jig fastening The electrode leads manufactured in Example 1 and Comparative Examples 1 and 2 were fastened to a jig at room temperature, and a direct current of 400 A was applied for 10 minutes, after which the temperature of each electrode lead was measured. The measurement results are shown in Table 2 below. Electrode lead temperature [℃] Example 164.5 Comparative Example 1101.3 Comparative Example 292.8 Referring to Table 2 above, when the same amount of direct current is passed through the electrode lead manufactured in Example 1, it can be seen that the temperature rise is lower than that of the electrode leads manufactured in Comparative Examples 1 and 2. Therefore, it can be understood that the electrode lead manufactured in Example 1 has a lower amount of heat generated between the electrode lead and the jig during charging and discharging than that of the electrode leads manufactured in Comparative Examples 1 and 2. (Explanation of symbols) 1: Metal terminal 2: Film layer 3: Pattern 10: Electrode leads 20: Positive lead 30: Negative lead 200: Secondary battery 210: Battery case 220: Pouch film laminate 221: Substrate layer 222: Gas barrier layer 223: Sealant layer 230: Case 1 232: Cup 234: Reception area 240: Case 2 242: Cup 250: Bridge section 260: Sealing part 270: Electrode assembly 280: Electrode tab 282: Positive tab 284: Negative tab 290: Lead Film 300: Gravure coating device 310: Gravure Roll 320: Rolling roll 330: Coating solution supply tray

Claims

1. An electrode lead electrically connected to the electrode assembly, metal terminals; and A film layer positioned on the metal terminal and having two or more patterns engraved on the surface; The above two or more patterns are spaced at equal intervals and arranged in the horizontal direction of the film layer, Each of the above patterns includes a side surface and a bottom surface, Electrode leads.

2. In paragraph 1, The shape of the bottom surface of the above pattern is a polygonal, circular, or oval electrode lead.

3. In paragraph 1, Each of the above patterns has electrode leads of the same depth.

4. In paragraph 1, Each of the above patterns has an electrode lead with the same bottom surface area.

5. In paragraph 1, The above pattern is an electrode lead in which the bottom surface and the side surface are perpendicular.

6. In paragraph 1, An electrode lead, wherein the ratio of the bottom surface area of ​​the entire pattern to the cross-sectional area of ​​the film layer is 0.05 to 0.

7.

7. In paragraph 1, An electrode lead, wherein the ratio of the bottom surface area of ​​the single pattern to the cross-sectional area of ​​the film layer is 0.005 to 0.

010.

8. In paragraph 1, An electrode lead, wherein the ratio of the depth of the pattern to the thickness of the film layer is 0.3 to 0.

7.

9. In paragraph 1, An electrode lead, wherein the film layer comprises at least one selected from the group consisting of chromate, zirconium salt, titanium salt, and phosphate.

10. In paragraph 1, An electrode lead, wherein the metal terminal comprises at least one selected from the group consisting of aluminum, copper, nickel, and nickel-plated copper.

11. In paragraph 1, An electrode lead having a ratio of the thickness of the metal terminal to the thickness of the film layer of 10,000:1 to 500:

1.

12. Electrode assembly including anode, cathode and separator; A battery case for storing the above electrode assembly; electrolyte; An electrode tab connected to the positive and negative electrodes and protruding from one side of the assembly; An electrode lead connected to the electrode tab and according to any one of claims 1 to 11; and A lithium secondary battery comprising a lead film interposed at the interface between the electrode lead and the battery case.

13. A step of forming a film layer on a metal terminal by a gravure coating device is included. The above gravure coating device includes a rolling roll and a gravure roll, The above gravure roll has a rough surface, The above film layer has two or more patterns engraved on the surface, The above two or more patterns are spaced at equal intervals and arranged in the horizontal direction of the film layer, Each of the above patterns includes a side surface and a bottom surface, Method for manufacturing electrode leads.

14. In paragraph 13, A method for manufacturing an electrode lead, wherein the film layer comprises at least one selected from the group consisting of chromate, zirconium salt, titanium salt, and phosphate.

15. In paragraph 13, Each of the above patterns has the same depth, A method for manufacturing electrode leads, wherein each of the above patterns has the same bottom surface area.

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