Lead tab with improved adhesion

Abstract

To provide a lead tab with improved adhesive strength. [Solution] The lead tab (10) comprises 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, having a glossiness of 60 to 100 (Gs60°), and a water contact angle of 60 to 80°.

Description

[Technical Field]

[0001] The present invention relates to a lead tab with improved adhesion. [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 film, and the other end protrudes outside the film.

[0004] In secondary batteries, surface treatment of the lead tabs is necessary to facilitate adhesion between the lead tabs and the insulating film and to prevent defects such as corrosion and peeling due to stimuli inside and outside the battery in the actual usage environment after adhesion.

[0005] Meanwhile, hexavalent chromium was used in the materials used in conventional surface treatment technology. However, the use of surface treatment methods using hexavalent chromium is currently restricted or limited worldwide due to its harmfulness to the human body and environmental issues.

[0006] To solve these problems, research is being conducted continuously into lead tabs with improved adhesion. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention relates to a lead tab with improved adhesion that can avoid problems caused by the limitations and drawbacks of the related art as described above.

[0008] 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]

[0009] One embodiment of the present invention provides a lead tab comprising a metal substrate containing aluminum and metal layers laminated on both sides of the metal substrate, the metal layers containing 70 to 99.9 wt % chromium, having a gloss of 60 to 100 (Gs60°), and a water contact angle of 60 to 80°. [Effects of the Invention]

[0010] According to the present invention, a lead tab with improved adhesion can be provided. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view of a secondary battery according to an embodiment of the present invention;

[0012] [Figure 2] FIG. 2 is a cross-sectional view of a lead tab according to one embodiment of the present invention.

[0013] [Figure 3] FIG. 2 is a cross-sectional view taken along II' in FIG.

[0014] [Figure 4] FIG. 1 is a conceptual diagram schematically illustrating a part of a sputtering apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] When describing a temporal relationship, for example, when the temporal precedence relationship is described 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] FIG. 1 is a perspective view of a secondary battery 1 according to one embodiment of the present invention.

[0025] FIG. 2 is a cross-sectional view of a lead tab 10 according to one embodiment of the present invention.

[0026] FIG. 3 is a cross-sectional view taken along II' in FIG.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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 .

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] According to one embodiment of the present invention, the lead tab 10 may further include a metal layer 120 on the metal substrate 110 .

[0038] The metal layer 120 contains 70 to 99.9 wt % (w / w) of chromium (Cr).

[0039] 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.

[0040] Generally, lead tabs further include 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, resulting in reduced adhesion between the lead tab and the insulating film.

[0041] 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, which may result in excessive oxidation of the metal layer in contact with the protective layer, thereby reducing the adhesive strength between the lead tab and the insulating film.

[0042] Therefore, according to one embodiment of the present invention, in order to increase the adhesive strength between the lead tab 10 and the sealing tape 20, the metal layer 120 should contain 70 to 99.9 weight % (w / w) of chromium (Cr).

[0043] According to one embodiment of the present invention, when the metal layer 120 is deposited by a sputtering process and contains 70 to 99.9 wt % chromium (Cr), the oxygen fraction in the metal layer 120 is sufficiently low to achieve the intended purpose, thereby increasing the adhesion between the lead tab 10 and the sealing tape 20. As a result, defects such as corrosion and peeling due to stimuli inside and outside the battery may not occur in an actual usage environment.

[0044] In addition, according to an embodiment of the present invention, when the metal layer 120 is deposited by a sputtering process and contains 70 to 99.9 wt % of chromium (Cr), the hexavalent chromium (Cr 6+ ) and thus reduce the occurrence of harmful problems for the human body and environmental problems.

[0045] The lead tab 10 according to one embodiment of the present invention may have a glossiness of 60 to 100 (Gs60°). The glossiness (Gs60°) according to one embodiment of the present invention is measured using a gloss meter (VG8000 product of Nippon Denshoku Co., Ltd.) with a light source irradiation angle of 60°. A method for measuring the glossiness (Gs60°) according to one embodiment of the present invention will be described in detail below.

[0046] According to one embodiment of the present invention, when the lead tab 10 has a glossiness of 60 to 100 (Gs60°), the bonding strength between the metal layer 120 of the lead tab 10 and the sealing tape 20 is improved, and defects such as corrosion and peeling due to stimuli inside and outside the battery may not occur in actual usage environments.

[0047] On the other hand, if the lead tab 10 has a glossiness of less than 60 (Gs60°), the surface of the metal layer 120 of the lead tab 10 becomes very rough, the bonding strength between the metal layer 120 of the lead tab 10 and the sealing tape 20 decreases, and defects such as corrosion and peeling may occur due to stimuli inside and outside the battery in the actual usage environment.

[0048] Furthermore, if the lead tab 10 has a glossiness exceeding 100 (Gs60°), the surface of the metal layer 120 of the lead tab 10 becomes very smooth, which makes it easy for uneven adhesion to occur between the metal layer 120 of the lead tab 10 and the sealing tape 20. As a result, defects such as corrosion and peeling may occur due to stimuli inside and outside the battery in the actual usage environment.

[0049] According to one embodiment of the present invention, the lead tab 10 may have a water contact angle of 60 to 80°. The water contact angle according to one embodiment of the present invention is measured using a contact angle measuring device (Phoenix-MT product by SIO Corporation). A method for measuring the water contact angle according to one embodiment of the present invention will be described in detail below.

[0050] According to one embodiment of the present invention, when the lead tab 10 has a water contact angle of 60 to 80°, the bonding strength between the metal layer 120 of the lead tab 10 and the sealing tape 20 is improved, and defects such as corrosion and peeling due to stimuli inside and outside the battery may not occur in actual usage environments.

[0051] On the other hand, if the lead tab 10 has a water contact angle of less than 60°, the surface of the lead tab 10 may be highly polarized, resulting in moisture adsorption and surface oxidation during storage or transportation. As a result, the bonding strength between the metal layer 120 of the lead tab 10 and the sealing tape 20 may be reduced, and defects such as corrosion or peeling may occur due to stimuli inside and outside the battery in the actual usage environment.

[0052] Furthermore, if the lead tab 10 has a water contact angle exceeding 80°, the metal layer 120 of the lead tab 10 will not adhere properly to the sealing tape 20, resulting in poor adhesion. As a result, defects such as corrosion and peeling may occur due to stimuli inside and outside the battery in an actual usage environment.

[0053] According to one embodiment of the present invention, the lead tab 10 may have an arithmetic mean roughness (Ra) of 0.06 to 0.15 μm, a maximum height roughness (Ry) of 0.5 to 1.0 μm, and a ten-point average roughness (Rz) of 0.4 to 0.7 μm. The arithmetic mean roughness (Ra), maximum height roughness (Ry), and ten-point average roughness (Rz) according to one embodiment of the present invention are each measured using a profiler (KOSKA Lab's Surfcorder ET3000 product). The method for measuring the arithmetic mean roughness (Ra), maximum height roughness (Ry), and ten-point average roughness (Rz) according to one embodiment of the present invention is described in detail below.

[0054] The definitions of the arithmetic mean roughness (Ra), maximum height roughness (Ry) and ten-point mean roughness (Rz) are as follows:

[0055] Arithmetic mean roughness (Ra): The arithmetic mean of the absolute values ​​of the top and bottom based on the center height value of the entire measurement section

[0056] Maximum height roughness (Ry): The distance between the highest peak and deepest valley among the five cut-off sections

[0057] 10-point average roughness (Rz): The average height of the five highest peaks and five deepest valleys in one cutoff section is calculated by averaging it over all sections.

[0058] According to one embodiment of the present invention, when the lead tab 10 has an arithmetic mean roughness (Ra) of 0.06 to 0.15 μm, a maximum height roughness (Ry) of 0.5 to 1.0 μm, and a ten-point mean roughness (Rz) of 0.4 to 0.7 μm, the bonding strength between the metal layer 120 of the lead tab 10 and the sealing tape 20 is improved, and defects such as corrosion and peeling due to stimuli inside and outside the battery may not occur in actual usage environments.

[0059] On the other hand, if the lead tab 10 has an arithmetic mean roughness (Ra) of less than 0.06 μm, a maximum height roughness (Ry) of less than 0.5 μm, or a ten-point mean roughness (Rz) of less than 0.4 μm, the area where the metal layer 120 of the lead tab 10 adheres to the sealing tape 20 is too small, reducing the bonding strength between the metal layer 120 of the lead tab 10 and the sealing tape 20, which can cause defects such as corrosion and peeling due to stimuli inside and outside the battery in an actual usage environment.

[0060] Furthermore, if the lead tab 10 has an arithmetic mean roughness (Ra) exceeding 0.15 μm, a maximum height roughness (Ry) exceeding 1.0 μm, or a ten-point mean roughness (Rz) exceeding 0.7 μm, the surface of the metal layer 120 of the lead tab 10 will become very rough, reducing the bonding strength between the metal layer 120 of the lead tab 10 and the sealing tape 20, which may result in defects such as corrosion and peeling due to stimuli inside and outside the battery in an actual usage environment.

[0061] According to one embodiment of the present invention, the lead tab 10 may have a surface energy of 41 dyne / cm or more. The surface energy according to one embodiment of the present invention is calculated by substituting the water contact angle measured according to one embodiment of the present invention according to the Owens-Wendt-geometric mean method. The method for measuring the surface energy according to one embodiment of the present invention is described in detail below.

[0062] According to one embodiment of the present invention, when the lead tab 10 has a surface energy of 41 dyne / cm or more, defects do not occur on the surface of the metal layer 120, the bonding strength between the metal layer 120 of the lead tab 10 and the sealing tape 20 is improved, and defects such as corrosion and peeling due to stimuli inside and outside the battery in actual usage environments may not occur.

[0063] On the other hand, if the lead tab 10 has a surface energy of less than 41 dyne / cm, the metal layer 120 of the lead tab 10 will not adhere properly to the sealing tape 20, resulting in poor adhesion. As a result, defects such as corrosion and peeling may occur due to stimuli inside and outside the battery in an actual usage environment.

[0064] Preferably, the lead tab 10 may have a surface energy of 41 to 60 dyne / cm, and more preferably, the lead tab 10 may have a surface energy of 41 to 50 dyne / cm.

[0065] According to one embodiment of the present invention, the lead tab 10 may have an L of 60 to 75, an a of -1 or less, and a b of -1 or less based on the Lab color system. The color system according to one embodiment of the present invention is a color system in which the L, a, and b values ​​measured with a spectrophotometer (KONICA MINOLTA, CM-5 product) are used as coordinates. Based on the Lab color system, if the L value of the surface of the lead tab 10 is 100, the surface will be white, and if it is 0, the surface will be black. In addition, as the a value increases in the positive (+) direction, the surface will be redder, and as the a value increases in the negative (-) direction, the surface will be greener. As the b value increases in the positive (+) direction, the surface will be gradually yellower, and as the b value increases in the negative (-) direction, the surface will be gradually bluer.

[0066] According to one embodiment of the present invention, when the lead tab 10 has an L of 60 to 75 based on the Lab color system, an a of -1 or less, and a b of -1 or less, the metal layer 120 arranged on the outermost surface of the lead tab 10 has a uniform surface structure, which improves the bonding strength with the sealing tape 20 and prevents defects such as corrosion and peeling due to stimuli inside and outside the battery in actual usage environments.

[0067] On the other hand, if the L, a, and b of the lead tab 10 are out of the range of 60 to 75, -1 or less, and -1 or less, respectively, based on the Lab color system, the metal layer 120 of the lead tab 10 and the sealing tape 20 will not adhere properly, resulting in a problem of reduced adhesion. As a result, defects such as corrosion and peeling may occur due to stimuli inside and outside the battery in the actual usage environment.

[0068] According to one embodiment of the present invention, the metal layer 120 may have a thickness of 10 to 500 nm.

[0069] 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.

[0070] 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.

[0071] A method for manufacturing the lead tab 10 according to one embodiment of the present invention will now be described in detail.

[0072] First, a metal substrate 110 is prepared.

[0073] 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.

[0074] 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.

[0075] In this case, chromium (Cr) metal is used as the sputtering target.

[0076] FIG. 4 is a conceptual diagram that schematically shows a part of the sputtering apparatus 40. As shown in FIG.

[0077] 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 .

[0078] 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.

[0079] 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.

[0080] 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).

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] According to one embodiment of the present invention, the substrate G on the substrate support table 23 is a metal substrate 110 .

[0086] 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.

[0087] 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.

[0088] 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.

[0089] According to one embodiment of the present invention, the target 34 disposed on the target support 31 is chromium (Cr).

[0090] 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.

[0091] The sputtering voltage according to the present embodiment refers to the voltage at the power supply unit 32 .

[0092] 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.

[0093] Example 1

[0094] After preparing a metal substrate made of aluminum, a 20 nm thick metal layer was formed on the metal substrate using a sputtering process to complete a 300 μm lead tab. Chromium (Cr) metal was used as the target during the sputtering process, and the sputtering voltage was as shown in Table 1 below.

[0095] Example 2

[0096] The lead tab was completed using the same method as in Example 1, except for the sputtering voltage conditions for forming the metal layer.

[0097] Example 3

[0098] The lead tab was completed using the same method as in Example 1, except for the sputtering voltage conditions for forming the metal layer.

[0099] Example 4

[0100] The lead tab was completed using the same method as in Example 1, except for the sputtering voltage conditions for forming the metal layer.

[0101] Example 5

[0102] The lead tab was completed using the same method as in Example 1, except for the sputtering voltage conditions for forming the metal layer.

[0103] Comparative Example 1

[0104] 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.

[0105] Comparative Example 2

[0106] 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.

[0107] Comparative Example 3

[0108] 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.

[0109] Comparative Example 4

[0110] 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.

[0111] Comparative Example 5

[0112] 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.

[0113] In Examples 1 to 5 and Comparative Examples 1 to 5, the glossiness, water contact angle, and illuminance (Ra, Ry, Rz) of the lead tabs with and without a metal layer formed by a sputtering process are shown in Table 1. In addition, in Examples 1 to 5 and Comparative Examples 1 to 5, the surface energy and chromaticity values ​​of the lead tabs with and without a metal layer formed by a sputtering process are shown in Table 2.

[0114] Table 1

[0115] [Table 1]

[0116] Table 2

[0117] [Table 2]

[0118] i) Gloss measurement

[0119] The surfaces of the lead tab 10 samples manufactured in Examples 1 to 5 and Comparative Examples 1 to 5 were measured using a gloss meter (VG8000 product of Nippon Denshoku Co., Ltd.) with the light source irradiation angle set at 60° and the surface to be measured aligned with the slit so that it faced downwards. Specifically, the gloss was measured on the surface of the metal layer 120 of the lead tab 10 sample.

[0120] At this time, the lead tab samples were cut into a size of 100 mm x 100 mm (width: 100 mm, length: 100 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.

[0121] ii) Water contact angle measurement

[0122] The surfaces of the lead tab 10 samples manufactured in Examples 1 to 5 and Comparative Examples 1 to 5 were measured using a contact angle measuring device (Phoenix-MT product by SIO Corporation) with the stage fixed so that the surface to be measured faced upward. Specifically, the water contact angle was measured on the surface of the metal layer 120 of the lead tab 10 sample.

[0123] The specific conditions are as follows:

[0124] Temperature: 25℃

[0125] Humidity: 50RH%

[0126] Drop Volume: 0.8 μl

[0127] iii) Surface energy measurement

[0128] The surface energy was determined by substituting the value of the water contact angle according to the Owens-Wendt-geometric mean method.

[0129] iv) Illuminance (Ra, Ry, Rz) measurement

[0130] The illuminance (Ra, Ry, Rz) of the surface of each of the lead tab 10 samples manufactured in Examples 1 to 5 and Comparative Examples 1 to 5 was measured using a profiler (KOSKA Lab's Surfcorder ET3000 product) with the surface to be measured facing up on a stage. Specifically, the illuminance (Ra, Ry, Rz) was measured on the surface of the metal layer 120 of each of the lead tab 10 samples.

[0131] The specific conditions are as follows:

[0132] Measurement length: 0.8 mm

[0133] Measurement speed: 0.1mm / s

[0134] v) Chromaticity value measurement

[0135] The surfaces of the lead tab 10 samples manufactured in Examples 1 to 5 and Comparative Examples 1 to 5 were measured using a spectrophotometer (KONICA MINOLTA, CM-5 product) with the surface to be measured facing downwards, aligned with the slit. Specifically, the chromaticity values ​​were measured on the surface of the metal layer 120 of the lead tab 10 sample.

[0136] The specific conditions are as follows:

[0137] Light source: xenon lamp(D65)

[0138] Viewing angle: 10 degrees

[0139] Wavelength range: 360~740nm

[0140] Wavelength spacing: 10nm

[0141] Reference:air

[0142] Referring to Table 1, the following results can be seen:

[0143] It can be seen that the lead tabs of Examples 1 to 5, in which a metal layer was formed on a metal substrate by a sputtering process, achieved the desired physical properties.

[0144] On the other hand, it can be seen that 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, were unable to achieve the desired physical properties.

[0145] 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]

[0146] 1: Secondary battery 10: Lead tab 20: Sealing tape 30: Exterior material 110: Metal base material 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; The gloss level is 60 to 100 (Gs60°), A lead tab with a water contact angle of 60 to 80 degrees.

2. The arithmetic mean roughness (Ra) is 0.06 to 0.15 μm, The maximum height roughness (Ry) is 0.5 to 1.0 μm, 2. The lead tab according to claim 1, wherein the ten-point average roughness (Rz) is 0.4 to 0.7 μm.

3. 2. The lead tab according to claim 1, wherein the surface energy is 41 dyne / cm or more.

4. 2. The lead tab according to claim 1, which has, based on the Lab color system, L of 60 to 75, a of −1 or less, and b of −1 or less.

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

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

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

8. The lead tab according to claim 7 , wherein the dry vacuum process includes at least one of a sputtering process, an evaporation process, an ion plating process, and a CVD process.

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

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