Lead tab with improved welding performance

Abstract

To provide a lead tab with improved welding performance. The present invention relates to a welding method for a welding joint, which includes a metal substrate containing aluminum and metal layers laminated on both sides of the metal substrate, the metal layers containing 70 to 99.9% by weight of chromium, and a laser welding strength of 40 kgf / mm 2 The above lead tab 10 is provided.

Description

[Technical Field]

[0001] The present invention relates to a lead tab with improved welding capabilities. [Background technology]

[0002] The secondary battery industry is in the spotlight as a core component of IT devices, along with semiconductors and displays. Recently, the use of large-capacity batteries has been increasing in applications such as electric bicycles, hybrid electric vehicles (HEVs), electric vehicles (EVs), plug-in hybrid electric vehicles (PHEVs), and energy storage systems (ESSs).

[0003] A typical secondary battery is provided with a lead tab for extracting electricity to the outside. In a secondary battery, one end of the lead tab is connected to the battery element and is sandwiched between the opposing films, and the other end protrudes outside the films.

[0004] When a secondary battery is subjected to external physical force, the bond between the lead tab and electrode tab weakens, causing a problem of partial or complete breakage. If a large current flows in a short period of time under this condition, the battery may overheat, posing a risk of fire or explosion.

[0005] To address these issues, research is ongoing into lead tabs with improved welding performance. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention relates to lead tabs with improved welding capabilities that can avoid problems caused by the limitations and drawbacks of the related art, as discussed above.

[0007] In addition to the above-described aspects of the present invention, other features and advantages of the present invention will be described hereinafter or will become apparent to those skilled in the art from such description. [Means for solving the problem]

[0008] One embodiment of the present invention includes a metal substrate containing aluminum and metal layers laminated on both sides of the metal substrate, wherein the metal layers contain 70 to 99.9 wt % of chromium and have a laser welding strength of 40 kgf / mm 2 The above lead tabs are provided. [Effects of the Invention]

[0009] According to the present invention, a lead tab with improved welding performance can be provided. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view of a secondary battery according to an embodiment of the present invention;

[0011] [Figure 2] FIG. 2 is a cross-sectional view of a lead tab according to one embodiment of the present invention.

[0012] [Figure 3] FIG. 2 is a cross-sectional view taken along II' in FIG.

[0013] [Figure 4] FIG. 1 is a conceptual diagram schematically illustrating a part of a sputtering apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiments described below are presented for illustrative purposes to help a clear understanding of the present invention, and are not intended to limit the scope of the present invention.

[0015] The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for illustrating the embodiments of the present invention are merely examples, and the present invention is not limited to the details shown in the drawings. Throughout the specification, the same components may be referred to by the same reference numerals. In describing the present invention, if it is determined that a detailed description of related publicly known art may unnecessarily obscure the gist of the present invention, such a detailed description will be omitted.

[0016] When terms such as "comprise," "have," and "perform" are used in this specification, other parts may be added unless the expression "only" is used. When an element is expressed in the singular, it includes the plural unless otherwise expressly stated. In addition, when analyzing elements, it is interpreted as including a margin of error even if there is no other explicit statement.

[0017] When describing a positional relationship, for example, when describing the positional relationship between two parts using "above," "at the top," "below," or "to the side," the expressions "immediately" or "directly" are not used, and one or more other parts may be located between the two parts.

[0018] Spatially relative terms such as "below," "beneath," "lower," "above," "upper," and the like can be used to easily describe the relationship of one element or component to other elements or components as shown in the figures. Spatially relative terms should be understood to include different orientations of elements in use or operation in addition to the orientation shown in the figures. For example, if elements shown in the figures are inverted, an element described as "below" or "beneath" another element can be positioned "above" the other element. Thus, the exemplary term "below" can encompass both an orientation of below and above. Similarly, the exemplary terms "top" or "upper" can encompass both an orientation of above and below.

[0019] When describing a temporal relationship, for example, when the temporal precedence is explained using "after," "following," "next to," or "before," the expressions "immediately" or "directly" are not used, and therefore cases where the relationship is not consecutive may also be included.

[0020] Although terms such as "first," "second," and the like are used to describe various components, these components are not limited by these terms. These terms are used only to distinguish one component from another. Therefore, a first component referred to below may be a second component within the technical concept of the present invention.

[0021] The term "at least one" should be understood to include all possible combinations of one or more associated items. For example, "at least one of the first, second, and third items" may refer to not only the first, second, or third item, but also all possible combinations of two or more of the first, second, and third items.

[0022] The features of the various embodiments of the present invention may be partially or fully combined or combined with each other, may be technically interlocked and driven in various ways, and each embodiment may be implemented independently of each other or may be implemented together in a related relationship.

[0023] FIG. 1 is a perspective view of a secondary battery 1 according to one embodiment of the present invention.

[0024] FIG. 2 is a cross-sectional view of a lead tab 10 according to one embodiment of the present invention.

[0025] FIG. 3 is a cross-sectional view taken along II' in FIG.

[0026] The type of secondary battery 1 according to an embodiment of the present invention is not particularly limited, but it may preferably be a lithium secondary battery.

[0027] 1 and 3, a secondary battery 1 according to one embodiment of the present invention includes a film-shaped positive electrode 161 and a film-shaped negative electrode 162 stacked on top of each other with a separator 163 interposed therebetween, and an electrolyte 164 disposed between the positive electrode 161 and the negative electrode 162, enabling charge and discharge through the transfer of lithium ions. The secondary battery 1, including the positive electrode 161, the negative electrode 162, and the electrolyte 164, is covered in a liquid-tight container 30. Specifically, the positive electrode 161, the negative electrode 162, and the electrolyte 164 are enclosed within the container 30 to protect them from the outside. The negative electrode 162 is formed by coating a negative electrode active material slurry on a negative electrode current collector made of copper foil for secondary batteries. The positive electrode 161 is also formed by coating a positive electrode active material slurry on a positive electrode current collector, such as aluminum.

[0028] Although not shown in the drawings, the lead tabs 10 may consist of a negative electrode lead tab and a positive electrode lead tab. More specifically, the lead tab 10 located on the left side of Fig. 1 may be a positive electrode lead tab, and the lead tab 10 located on the right side may be a negative electrode lead tab.

[0029] Referring to FIG. 1 , a sealing tape 20 is disposed on one side of an outer casing 30 of a secondary battery 1. The sealing tape 20 further improves adhesion between the lead tab 10 and the outer casing 30. The sealing tape 20 is disposed on the lead tab 10, and a portion of the sealing tape 20 adheres to the inner surface of the outer casing 30 to seal the outer casing 30. The sealing tape 20 prevents leakage of the electrolyte 164 or the like sealed inside the outer casing 30. The sealing tape 20 is also disposed between the lead tab 10 and the outer casing 30 to ensure insulation between the lead tab 10 and the outer casing 30. A polypropylene film is used as the sealing tape 20. However, an embodiment of the present invention is not limited thereto and may be made of a polymer composite.

[0030] Referring to FIG. 1, one end of the lead tab 10 is connected to either the positive electrode 161 or the negative electrode 162 , and the other end of the lead tab 10 is exposed to the outside of the exterior packaging material 30 .

[0031] 2, the lead tab 10 of the present invention includes a metal substrate 110 including aluminum (Al) and a metal layer 120 on the metal substrate 110. The metal substrate 110 and the metal layer 120 will be described in detail below.

[0032] Referring to FIG. 3, a plurality of electrode tabs 150 protruding from a positive electrode 161 are integrally joined to form a pre-welding portion 151, and a lead tab 10 is electrically connected to the upper end of the pre-welding portion 151 by welding.

[0033] For example, in the case of ultrasonic welding, when ultrasonic vibrations are applied, the lead tab 10 penetrates and adheres to the pre-welding portion 151 formed by the electrode tab 150 being integrally joined while being plastically deformed by frictional heat.

[0034] The material of the metal substrate 110 is not particularly limited, but may be aluminum or copper. According to an embodiment of the present invention, the metal substrate 110 may be made of aluminum.

[0035] According to one embodiment of the present invention, the metal substrate 110 may have a thickness of 100 to 1,000 μm, preferably 100 to 500 μm.

[0036] According to one embodiment of the present invention, the lead tab 10 may further include a metal layer 120 on the metal substrate 110 .

[0037] The metal layer 120 contains 70.0 to 99.9 wt % (w / w) of chromium (Cr).

[0038] Specifically, the metal layer 120 may be formed by a dry vacuum process. For example, the metal layer 120 may be formed by any of a sputtering process, an evaporation process, an ion plating process, and a CVD process, which are examples of the dry vacuum process. Preferably, the metal layer 120 may be formed by a sputtering process.

[0039] Typically, the lead tab further includes a protective layer containing a chromium compound to improve corrosion resistance. In this case, the protective layer is formed by chromate treatment. However, the protective layer formed by chromate treatment may have a very high oxygen fraction within the protective layer. Here, the oxygen fraction refers to the ratio of oxygen to the total number of atoms in the protective layer. A protective layer with a very high oxygen fraction may cause excessive oxidation of the metal layer in contact with the protective layer, reducing the adhesion between the lead tab and the insulating film. This may reduce the welding performance between the lead tab and the electrode tab, weakening the bond between the welded portion of the lead tab and the electrode tab, leading to partial or complete breakage. If a large current flows in this state within a short period of time, the battery may overheat, resulting in a risk of fire or explosion.

[0040] In addition, in the case of a protective layer formed by chromate treatment, trivalent chromium (Cr 3+ ) or hexavalent chromium (Cr 6+ ) may be present in part. In this case, hexavalent chromium (Cr 6+ ) may have a strong oxidizing power. As a result, the metal layer in contact with the protective layer may be excessively oxidized, which may reduce the adhesion between the lead tab and the insulating film, degrade the welding performance between the lead tab and the electrode tab, and weaken the bonding strength at the welded portion of the lead tab and the electrode tab.

[0041] Therefore, according to one embodiment of the present invention, in order to increase the adhesion between the lead tab 10 and the sealing tape 20 and improve the welding performance between the lead tab 10 and the electrode tab 150, the metal layer 120 needs to contain 70.0 to 99.9 wt% (w / w) of chromium (Cr).

[0042] According to one embodiment of the present invention, when the metal layer 120 is deposited by sputtering and contains 70.0 to 99.9 wt % chromium (Cr), the oxygen fraction in the metal layer 120 is sufficiently low to achieve the purpose, thereby increasing the adhesion between the lead tab 10 and the sealing tape 20 and improving the welding performance between the lead tab 10 and the electrode tab 150.

[0043] In addition, according to an embodiment of the present invention, when the metal layer 120 is deposited by a sputtering process and contains 70.0 to 99.9 wt % of chromium (Cr), the hexavalent chromium (Cr 6+ ) and thus the occurrence of harmful problems on the human body and environmental problems can be suppressed.

[0044] The lead tab 10 according to one embodiment of the present invention has a resistance of 40 kgf / mm 2 The laser weld strength of the lead tab 10 can be measured by welding the lead tab 10 and 30 pre-welded aluminum foils using a laser, and then gripping the welded lead tab 10 and the 30 pre-welded aluminum foils with a gripper, and measuring the tensile strength. The tensile strength measured at this time is referred to as the laser weld strength according to the present invention. A method for measuring laser weld strength according to one embodiment of the present invention will be described in detail below.

[0045] According to one embodiment of the present invention, the lead tab 10 has a resistance of 40 kgf / mm 2 When the laser welding strength is above this level, the bonding strength of the welded portion between the lead tab and the electrode tab is improved, which can suppress or prevent the problem of partial or total breakage. In this state, even if a large current flows in a short period of time, the risk of fire or explosion may be low.

[0046] On the other hand, the lead tab 10 is 40 kgf / mm 2If the laser welding strength is less than this, the bonding strength of the welded portion of the lead tab and electrode tab may decrease, causing a problem of partial or total breakage. In this state, if a large current flows within a short period of time, the battery may heat up, posing a risk of fire or explosion.

[0047] According to one embodiment of the present invention, the metal layer 120 may have a thickness of 10 to 500 nm.

[0048] If the metal layer 120 has a thickness of less than 10 nm, the metal layer 120 may be deposited unevenly, and as a result, when forming the secondary battery 1, the sealing tape 20 placed on the metal layer 120 may be deposited unevenly, which may cause a problem of leakage of the electrolyte 164 in the secondary battery 1.

[0049] Furthermore, if the thickness of the metal layer 120 exceeds 500 nm, the internal stress in the metal layer 120 increases, causing cracks. Therefore, the metal layer 120 according to an embodiment of the present invention should have a thickness of 10 to 500 nm, and preferably, a thickness of 10 to 200 nm.

[0050] A method for manufacturing the lead tab 10 according to one embodiment of the present invention will now be described in detail.

[0051] First, a metal substrate 110 is prepared.

[0052] The metal substrate 110 may have a thickness of 100 to 1,000 μm and may be made of, but is not limited to, aluminum or copper. According to an embodiment of the present invention, the metal substrate 110 may be made of aluminum.

[0053] Subsequently, a metal layer 120 may be formed on the metal substrate 110 by a sputtering process using a DC sputtering device. The metal layer 120 may have a thickness of 10 to 500 nm.

[0054] In this case, chromium (Cr) metal is used as the sputtering target.

[0055] FIG. 4 is a conceptual diagram that schematically shows a part of the sputtering apparatus 40. As shown in FIG.

[0056] According to an embodiment of the present invention, the metal layer 120 is formed on the metal substrate 110 by a process using the sputtering apparatus 40 .

[0057] According to one embodiment of the present invention, the sputtering apparatus 40 may include a chamber 13. A gas inlet 11 may be disposed on one side of the chamber 13, and a gas outlet 12 may be disposed on the other side of the chamber 13.

[0058] In this regard, although FIG. 4 shows a case where the gas inlet 11 is arranged on the left side of the chamber 13 and the gas outlet 12 is arranged on the right side of the chamber 13, one embodiment of the present invention is not limited to this, and both the gas inlet 11 and the gas outlet 12 may be arranged below the chamber 13.

[0059] The gas inlet 11 provides a path for injecting a sputtering gas from the outside of the chamber 13 into the chamber 13. Here, the sputtering gas corresponds to the gas described above, specifically, a gas used to generate plasma for the sputtering process. The sputtering gas is injected into the chamber 13 through the gas inlet 11 and ionized by a voltage applied to the chamber 13, resulting in a plasma state in which electrons, ions (e.g., Ar+ ions), and neutral gases are mixed. In one embodiment, the sputtering gas may be a mixture of argon gas and nitrogen gas, or may be oxygen or nitrogen dioxide (NO2).

[0060] 4, the gas inlet 11 may be connected to a gas flow regulator (not shown), a gas storage device (not shown), etc., disposed outside the chamber 13. The gas stored in the gas storage device may be injected into the chamber 13 through the gas inlet 11 at a flow rate regulated by the gas flow regulator.

[0061] The gas exhaust unit 12 serves to pump the air inside the chamber 13 to the outside in order to maintain a vacuum state inside the chamber 13. Although not shown in FIG. 4, the gas exhaust unit 12 is connected to a vacuum pump (not shown) so that the amount of air exhausted from the inside of the chamber 13 to the outside can be adjusted.

[0062] Inside the chamber 13, a substrate support table 23, a substrate G on the substrate support table 23, a heating member 22, a target 34, a target support table 31, and an adjustment unit 33 are arranged.

[0063] The substrate support 23 is disposed at the bottom of the chamber 13 and serves to seat the substrate G drawn into the chamber 13. In addition, a heating member 22 for heating the substrate G seated on the substrate support 23 to a predetermined temperature may be further disposed inside the substrate support 23. The heating member 22 applies a predetermined heat to the substrate G seated on the substrate support 23 to improve reactivity with the deposition material to be deposited on the substrate G.

[0064] According to one embodiment of the present invention, the substrate G on the substrate support table 23 is a metal substrate 110 .

[0065] A target 34 made of a deposition material to be deposited on the upper surface of the substrate G is disposed above the substrate support 23, and the target 34 is fixed to the upper inner wall of the chamber 13 by a target support 31. A power supply 32 for applying a voltage to the target 34 is connected to one side of the target 34, and the substrate support 31 is grounded. In addition, magnets (not shown) may be further provided behind the target 34, and these magnets serve to confine electrons generated in the chamber 13 near the target 34.

[0066] When a negative charge is applied to the target 34, it reacts with a sputtering gas such as argon (Ar) injected into the chamber 13, ionizing the sputtering gas, and the ionized sputtering gas collides with the target 34. Here, the sputtering gas ionized by a magnet attached to the backside of the target 34 continuously collides with the target 34, and the deposition material separated from the target 34 is accelerated toward the substrate G and deposited on the upper surface of the substrate G.

[0067] Subsequently, the vaporized deposition material injected into the chamber 13 moves toward the substrate G, thereby depositing a uniform metal layer 120 on the substrate G.

[0068] According to one embodiment of the present invention, the target 34 disposed on the target support 31 is chromium (Cr).

[0069] An adjustment unit 33 is disposed at the upper left side of the chamber 13. The adjustment unit 33 adjusts the pretreatment current, pretreatment pressure, pretreatment power, and film formation pressure.

[0070] The sputtering voltage according to the present embodiment refers to the voltage at the power supply unit 32 .

[0071] The present invention will be specifically described below with reference to examples and comparative examples. However, the following examples are provided to aid in understanding the present invention, and the scope of the present invention is not limited to these examples.

[0072] Example 1

[0073] A 300 μm lead tab was completed by forming a 20 nm thick metal layer on an aluminum metal substrate using a sputtering process. Chromium (Cr) metal was used as the target during the sputtering process, and the sputtering voltage was as shown in Table 1 below.

[0074] Example 2

[0075] The lead tab was completed using the same method as in Example 1, except for the sputtering voltage conditions for forming the metal layer.

[0076] Example 3

[0077] The lead tab was completed using the same method as in Example 1, except for the sputtering voltage conditions for forming the metal layer.

[0078] Example 4

[0079] The lead tab was completed using the same method as in Example 1, except for the sputtering voltage conditions for forming the metal layer.

[0080] Example 5

[0081] The lead tab was completed using the same method as in Example 1, except for the sputtering voltage conditions for forming the metal layer.

[0082] Comparative Example 1

[0083] A 300 μm lead tab was completed using the same method as in Example 1, except that a metal substrate made of aluminum was prepared, immersed in a 0.06 M chromate solution at room temperature for 20 seconds, dried at room temperature for 10 seconds, rinsed with distilled water for 10 seconds, immersed in a 0.06 M chromate solution at room temperature for 10 seconds, dried at room temperature for 10 seconds, rinsed with distilled water for 10 seconds, and dried for 15 seconds to form a protective layer with a thickness of 20 nm.

[0084] Comparative Example 2

[0085] Lead tabs were completed using the same method as in Comparative Example 1, except that when forming the protective layer, the metal substrate was immersed in a 0.06 M chromate solution at room temperature for 15 seconds, dried at room temperature for 10 seconds, rinsed with distilled water for 10 seconds, immersed in a 0.06 M chromate solution at room temperature for 10 seconds, dried at room temperature for 10 seconds, rinsed with distilled water for 10 seconds, and dried for 15 seconds to form a protective layer with a thickness of 20 nm.

[0086] Comparative Example 3

[0087] Lead tabs were completed using the same method as in Comparative Example 1, except that when forming the protective layer, the metal substrate was immersed in a 0.06 M chromate solution at room temperature for 20 seconds, dried at room temperature for 15 seconds, rinsed with distilled water for 10 seconds, immersed in a 0.06 M chromate solution at room temperature for 10 seconds, dried at room temperature for 10 seconds, rinsed with distilled water for 10 seconds, and dried for 15 seconds to form a protective layer with a thickness of 20 nm.

[0088] Comparative Example 4

[0089] Lead tabs were completed using the same method as in Comparative Example 1, except that when forming the protective layer, the metal substrate was immersed in a 0.06 M chromate solution at room temperature for 20 seconds, dried at room temperature for 10 seconds, rinsed with distilled water for 10 seconds, immersed in a 0.06 M chromate solution at room temperature for 20 seconds, dried at room temperature for 10 seconds, rinsed with distilled water for 10 seconds, and dried for 15 seconds to form a protective layer with a thickness of 20 nm.

[0090] Comparative Example 5

[0091] Lead tabs were completed using the same method as in Comparative Example 1, except that when forming the protective layer, the metal substrate was immersed in a 0.06 M chromate solution at room temperature for 20 seconds, dried at room temperature for 10 seconds, rinsed with distilled water for 10 seconds, immersed in a 0.06 M chromate solution at room temperature for 10 seconds, dried at room temperature for 5 seconds, rinsed with distilled water for 10 seconds, and dried for 15 seconds to form a protective layer with a thickness of 20 nm.

[0092] The laser welding strength of the lead tabs in Examples 1 to 5 and Comparative Examples 1 to 5, depending on whether or not a metal layer was formed by the sputtering process, is shown in Table 1 below.

[0093] Table 1

[0094] [Table 1]

[0095] i) Laser welding strength measurement

[0096] The lead tab samples manufactured in Examples 1 to 5 and Comparative Examples 1 to 5 were laser welded to 30 pre-welded aluminum foils (laser welding step), and then the tensile strength was measured.

[0097] At this time, the lead tab samples were cut into a size of 45 mm x 43 mm (width: 45 mm, length: 43 mm) from the lead tabs manufactured in Examples 1 to 5 and Comparative Examples 1 to 5, and formed to a thickness of 300 μm.

[0098] The 30 pre-welded aluminum foils have a size of 50 mm x 50 mm (width: 50 mm, length: 50 mm) and a thickness of 10 μm. They are formed by stacking 30 aluminum foils made of aluminum (Al) and performing ultrasonic welding (ultrasonic welding step).

[0099] <Ultrasonic welding step conditions>

[0100] Welding Area: 45 mm x 6 mm area (width 45 mm, length: 6 mm). Specifically, the welding area is placed on one side of the aluminum foil.

[0101] Welding Energy: 700J

[0102] Ultrasonic welding machine: Tech-SONIC US-3620SLS

[0103] <Laser welding step conditions>

[0104] Welding Area: 30 mm x 6 mm area (width: 30 mm, length: 6 mm). Specifically, the welding area is placed on one side of 30 pre-welded aluminum foils.

[0105] Welding Energy: 2250W

[0106] Time: 2ms

[0107] Laser welding machine: IPG Photonics YLS-4000 / 4000-AMB

[0108] <Tensile strength measurement conditions>

[0109] The tensile strength is measured on the welded lead tab sample and 30 sheets of pre-welded aluminum foil.

[0110] The tensile strength can be measured using an ORIENTAL™ OTT-00 Universal Testing Machine (UTM). At this time, the ultrasonically welded lead tab sample is attached to the lower fixture of the UTM, and 30 sheets of pre-welded aluminum foil are fixed to the upper fixture to evaluate the tensile strength.

[0111] Angle: 180°

[0112] Peeling speed: 30mm / min

[0113] Referring to Table 1, the following results can be seen:

[0114] In the case of the lead tabs of Examples 1 to 5 in which a metal layer was formed on a metal substrate by a sputtering process, the laser welding strength was 40 kgf / mm 2 It turns out that this is the case.

[0115] On the other hand, in the case of the lead tabs of Comparative Examples 1 to 5, in which a protective layer was formed on the metal substrate by chromate treatment without forming a metal layer by the sputtering process, the laser welding strength was 40 kgf / mm 2 It can be seen that it is less than

[0116] The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and alterations are possible within the scope of the technical subject matter of the present invention. Therefore, the scope of the present invention is expressed by the following claims, and all modifications and alterations derived from the meaning, scope, and equivalent concepts of the claims should be interpreted as being included in the scope of the present invention. [Explanation of symbols]

[0117] 1: Secondary battery

[0118] 10: Lead tab

[0119] 20: Sealing tape

[0120] 30: Exterior material

[0121] 110: Metal base material

[0122] 120: Metal layer

Claims

1. a metal substrate containing aluminum; and a metal layer laminated on both sides of the metal substrate, the metal layer comprises 70 to 99.9 wt. % chromium; Laser welding strength is 40 kgf / mm ２ That's all for the lead tab.

2. 2. The lead tab according to claim 1, wherein the thickness of the metal substrate is 100 to 1,000 μm.

3. 2. The lead tab according to claim 1, wherein the thickness of the metal layer is 10 to 500 nm.

4. The lead tab of claim 1 , wherein the metal layer is formed by a dry vacuum process.

5. The lead tab according to claim 4 , wherein the dry vacuum process includes at least one of a sputtering process, an evaporation process, an ion plating process, and a CVD process.

6. A secondary battery comprising the lead tab according to claim 1.

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