Copper foil, electrode comprising same, secondary battery comprising same, and method for manufacturing same

Abstract

An embodiment of the present invention provides a copper foil comprising: a copper layer comprising more than 99.9% by weight of copper; and a protective layer on the copper layer, and the copper foil has a tensile strength index of not more than 3.0 kgf / mm2 and an elongation index of not more than 2.1%. The tensile strength index is calculated according to the following Equation 1: (Equation 1) tensile strength index = tensile strength 2-tensile strength 1. In the formula 1, the tensile strength 1 is the tensile strength of the sample before the salt spray test, and the tensile strength 2 is the tensile strength of the sample after the salt spray test. The elongation index is calculated according to the following Equation 2: Equation 2: Equation 2: Equation 2: Equation 2: Equation 2 = Equation 2-Equation 1. In Equation 2, the elongation 1 is the elongation of the sample before the salt spray test, and the elongation 2 is the elongation of the sample after the salt spray test. The salt spray test is performed by spraying a 5 + / -1% NaCl solution on the copper foil for six cycles, 72 hours in total, where one cycle consists of spraying at a temperature of 35 + / -2 DEG C for 2 hours and then drying for 10 hours. Embodiments of the present invention provide a copper foil comprising no less than 99.9% by weight of copper, the copper foil having a first weight retention rate of no more than 0.1% and a second weight retention rate of no more than 0.3%. The first weight retention rate is calculated by the following Equation 3: (Equation 3) first weight retention rate = (weight after 5 hours of impregnation-weight before impregnation) / weight before impregnation * 100. The second weight retention rate is calculated by the following equation 4. [Equation 4] Second Weight Retention = (Weight After Impregnation for 24 hours-Weight before Impregnation) / Weight before Impregnation * 100.

Description

Technical Field

[0001] The present disclosure relates to a copper foil, an electrode including the copper foil, a secondary battery including the copper foil, and a method for manufacturing the copper foil. Background Art

[0002] A secondary battery is a type of energy conversion device that converts electrical energy into chemical energy, stores the chemical energy therein, and then converts the chemical energy back into electrical energy to generate electricity when power is needed. Secondary batteries are used as energy sources for electric vehicles and portable household appliances such as mobile phones and laptop computers. Secondary batteries are rechargeable and are therefore also referred to as rechargeable batteries.

[0003] As secondary batteries that have economic and environmental advantages compared to disposable primary batteries, there are lead-acid batteries, nickel-cadmium secondary batteries, nickel-metal hydride secondary batteries, and lithium secondary batteries.

[0004] In particular, compared to other secondary batteries, lithium secondary batteries can store a relatively large amount of energy relative to their size and weight. Therefore, in the field of information communication devices where portability and mobility are important, lithium secondary batteries are preferred, and the application range of lithium secondary batteries has also expanded to energy storage devices for hybrid vehicles and electric vehicles.

[0005] Lithium secondary batteries are reused in each cycle including charging and discharging. When a specific device operates with a fully charged lithium secondary battery, the lithium secondary battery should have a high charge / discharge capacity in order to extend the operating time of the device. Therefore, in order to meet the growing expectations (needs) of consumers for the charge / discharge capacity of lithium secondary batteries, continuous research is required.

[0006] Such secondary batteries include an anode current collector (negative electrode current collector) made of copper foil, and among copper foils, electrolytic copper foil is widely used as the anode current collector of secondary batteries. As the demand for secondary batteries increases, the demand for secondary batteries with high capacity, high efficiency, and high quality increases. Therefore, an electrolytic copper foil that can improve the characteristics of secondary batteries is required. In particular, an electrolytic copper foil that can ensure the high capacity of secondary batteries and enable secondary batteries to stably maintain their capacity and performance is required.

[0007] Meanwhile, since the thickness of the copper foil becomes smaller, the amount of active material that can be included in the same space can be increased, and the number of current collectors can be increased. Therefore, the capacity of the secondary battery can be improved. However, since the thickness of the copper foil becomes smaller, warping occurs. Therefore, when winding the copper foil, defects such as tearing or wrinkling of the copper foil occur due to the warping of the edges. Therefore, it is difficult to manufacture a copper foil in the form of a very thin film. Therefore, in order to manufacture a copper foil having a very thin thickness, warping of the copper foil should be prevented.

[0008] Meanwhile, when the copper foil is used as the anode current collector of a secondary battery, the surface of the copper foil may be easily corroded (dissolved) by the external environment. Therefore, research is continuously being conducted to ensure that the surface state of the copper foil is not easily changed by the external environment. SUMMARY OF THE INVENTION TECHNICAL OBJECTIVE

[0009] Accordingly, the present disclosure relates to a copper foil that can prevent problems caused by the limitations and disadvantages of the above-described related art, an electrode including the copper foil, a secondary battery including the copper foil, and a method for manufacturing the copper foil.

[0010] According to an embodiment of the present disclosure, there is provided a copper foil having a tensile strength index of 3.0 kgf / mm 2 or less, such that even after a salt spray test, the copper foil does not warp, wrinkle, or tear.

[0011] According to an embodiment of the present disclosure, there is provided a copper foil having an elongation rate index of 2.1% or less, such that even after a salt spray test, the copper foil does not warp, wrinkle, or tear.

[0012] According to an embodiment of the present disclosure, there is provided a copper foil having a first weight retention rate of 0.1% or less, such that even after impregnation, its surface state is maintained and wrinkling or tearing thereof is prevented.

[0013] According to another embodiment of the present disclosure, there is provided a copper foil having a second weight retention rate of 0.3% or less, such that even after impregnation, the surface state of the copper foil is maintained and wrinkling or tearing thereof is prevented.

[0014] According to still another embodiment of the present disclosure, there is provided a copper foil having a first roughness change of 0.7 μm or less, such that even after impregnation, its surface state is maintained and wrinkling or tearing thereof is prevented.

[0015] According to still another embodiment of the present disclosure, there is provided a copper foil having a second roughness change of 0.8 μm or less, such that even after impregnation, its surface state is maintained and wrinkling or tearing thereof is prevented.

[0016] According to another embodiment of the present disclosure, an electrode for a secondary battery is provided, the electrode including a copper foil, and a secondary battery including the electrode for the secondary battery is provided.

[0017] According to still another embodiment of the present disclosure, a method for manufacturing a copper foil is provided, in which the occurrence of warping, wrinkling, or tearing is prevented.

[0018] In addition to the above aspects of the present disclosure, other features and advantages of the present disclosure will be described in the following detailed description, as will be clearly understood by those skilled in the art to which the present disclosure pertains. Technical solutions

[0019] According to an embodiment of the present disclosure, a copper foil is provided, which includes a copper film and a protective layer formed on the copper film, the copper film including copper with a weight percentage of 99.9% (wt%) or more, wherein the copper foil has a tensile strength index of 3.0 kgf / mm 2 or less and an elongation index of 2.1% or less. The tensile strength index is calculated by the following Equation 1, [Equation 1] Tensile strength index = |Tensile strength 2 - Tensile strength 1|, where Tensile strength 1 in Equation 1 is the tensile strength of the sample before the salt spray test, and Tensile strength 2 in Equation 1 is the tensile strength of the sample after the salt spray test. The elongation index is calculated by the following Equation 2, [Equation 2] Elongation index = |Elongation 2 - Elongation 1|, where Elongation 1 in Equation 2 is the elongation of the sample before the salt spray test, and Elongation 2 in Equation 2 is the elongation of the sample after the salt spray test. The salt spray test is performed by spraying a 5 ± 1% NaCl solution on the copper foil for 6 cycles, a total of 72 hours, where 1 cycle means spraying the solution for 2 hours at a temperature of 35 ± 2 °C and then drying for 10 hours.

[0020] According to an embodiment of the present disclosure, a copper foil is provided, which includes a copper film, the copper film including copper with a weight percentage of 99.9% or more, wherein the copper foil has a first weight retention rate of 0.1% or less and a second weight retention rate of 0.3% or less. The first weight retention rate is calculated by the following Equation 3, [Equation 3] First weight retention rate = |(Weight after 5-hour immersion - Weight before immersion) / Weight before immersion * 100|. The second weight retention rate is calculated by the following Equation 4, [Equation 4] Second weight retention rate = |(Weight after 24-hour immersion - Weight before immersion) / Weight before immersion * 100|.

[0021] According to another embodiment of the present disclosure, a method for manufacturing a copper foil is provided. The method includes preparing an electrolyte containing copper ions, forming a copper film, and forming a protective layer on the copper film. Wherein, the formation of the copper film includes forming a copper film on a rotating anode drum by making a cathode plate and the rotating anode drum conductive. The cathode plate and the rotating anode drum are arranged to be spaced apart from each other in the electrolyte in an electrolytic cell, and the electrolyte includes copper ions with a concentration of 70 g / L to 100 g / L, sulfuric acid with a concentration of 70 g / L to 150 g / L, chlorine (Cl) with a concentration of 15 ppm to 25 ppm, lead ions (Pb 2+ ) with a concentration of 1 ppm to 100 ppm, arsenic (As) with a concentration of 0.5 ppm to 5 ppm, silver ions (Ag + ) with a concentration of 0.1 ppm to 3 ppm, hydrogen peroxide with a concentration of 1 ml / L to 10 ml / L, and an organic additive. Wherein, the organic additive includes at least one of a polishing agent (component A), a moderating agent (component B), and a roughness regulator (component C). Wherein, the polishing agent (component A) includes a sulfonic acid or its metal salt, the moderating agent (component B) includes a nonionic water-soluble polymer, and the roughness regulator (component C) includes a nitrogen-containing heterocyclic quaternary ammonium salt or its derivative.

[0022] According to still another embodiment of the present disclosure, an electrode for a secondary battery is provided. The electrode includes a copper foil and an active material layer provided on at least one surface of the copper foil.

[0023] According to still another embodiment of the present disclosure, a secondary battery is provided, including a cathode (positive electrode) configured to provide lithium ions during charging, an anode (negative electrode) configured to provide electrons and lithium ions during discharging, an electrolyte provided between the cathode and the anode to provide an environment in which lithium ions can move, and a separator configured to electrically insulate the anode and the cathode. Advantageous effects

[0024] According to the present disclosure, wrinkles or tears can be prevented during the manufacturing process of the copper foil. Even after a salt spray test, the occurrence of wrinkles or tears can be prevented and controlled, and the copper foil can be used to manufacture intermediate components and final products such as flexible printed circuit boards (FPCBs) and secondary batteries, thereby improving the production efficiency of the intermediate components and the final products.

[0025] According to the present disclosure, wrinkles or tears can be prevented during the manufacturing process of the copper foil, and even after impregnation, the surface state of the copper foil is maintained, and the occurrence of wrinkles or tears can be prevented and controlled. In addition, intermediate components and end products such as flexible printed circuit boards (FPCBs) and secondary batteries can be manufactured using the copper foil, thereby improving the production efficiency of the intermediate components and end products. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a cross-sectional view of a copper foil according to an embodiment of the present disclosure;

[0027] Figure 2 is a cross-sectional view of a copper foil according to another embodiment of the present disclosure;

[0028] Figure 3 is a photograph of a copper foil after a salt spray test according to yet another embodiment of the present disclosure;

[0029] Figure 4 is a cross-sectional view of an electrode for a secondary battery according to yet another embodiment of the present disclosure;

[0030] Figure 5 is a cross-sectional view of an electrode for a secondary battery according to yet another embodiment of the present disclosure;

[0031] Figure 6 is a schematic cross-sectional view of a secondary battery according to yet another embodiment of the present disclosure; and

[0032] Figure 7 is an apparatus for manufacturing a copper foil according to another embodiment of the present invention. DETAILED DESCRIPTION BEST MODE

[0033] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, the embodiments described below are for illustrative purposes only to assist in clearly understanding the present disclosure and do not limit the scope of the present disclosure.

[0034] The shapes, sizes, ratios, angles, quantities, etc. disclosed for describing the embodiments of the present disclosure in the drawings are only illustrative, and thus the present disclosure is not limited to the matters shown in the drawings. Throughout this specification, the same components may be denoted by the same reference numerals. When a detailed description of well-known techniques is determined to possibly obscure the gist of the present disclosure unnecessarily, the detailed description of the well-known techniques will be omitted.

[0035] When using terms such as "comprising", "having", "consisting of", etc. described in this specification, other parts can be added unless the term "only" is used herein. When a component is expressed in the singular form, it can include the plural form unless otherwise specified. In addition, when analyzing a component, even if not explicitly stated, it is still interpreted as including an error range.

[0036] When describing a positional relationship, for example, when the positional relationship between two parts is described as "above", "over", "below", "next to", etc., unless "immediately" or "directly" is used, one or more other parts can be located between these two parts.

[0037] For the convenience of describing the relationship between one element or component and another element or component as shown in the drawings, spatial relative terms such as "below", "beneath", "lower", "above", "upper", etc. can be used herein. It should be understood that, in addition to the orientation shown in the drawings, spatial relative terms are intended to include different orientations of the element in use or operation. For example, when the element in the drawing is flipped, the element described as "above" or "upper" relative to another element will become "below" or "lower" relative to another element. Therefore, the exemplary term "below" can have both above and below orientations. Similarly, the exemplary terms "above" or "upper" can include both above and below orientations.

[0038] When describing a temporal relationship, for example, when the temporal sequence relationship is described as "after", "subsequent", "then", "before", etc., unless "immediately" or "directly" is used, non - consecutive cases can also be included.

[0039] To describe various components, terms such as "first", "second", etc. are used, but these components are not limited to these terms. These terms are only used to distinguish one component from another. Therefore, within the technical spirit of the present disclosure, the first component described below can be the second component.

[0040] The term "at least one" should be understood to include all possible combinations of one or more related items. For example, the meaning of "at least one of the first, second, and third items" can represent all combinations of two or more of the first, second, and third items and each of the first, second, and third items.

[0041] The features of various embodiments of the present disclosure can be connected or combined with each other partially or wholly, and can be linked or operated technically in various ways, and each embodiment can be implemented independently of each other or can be implemented together in a related relationship.

[0042] Figure 1 is a cross - sectional view of a copper foil 110 according to an embodiment of the present disclosure.

[0043] Referring to Figure 1 , the copper foil 110 of the present disclosure includes a copper film 111 and a protective layer 112 formed on the copper film 111. The copper film 111 includes copper with a weight percentage of 99.9% or more. In Figure 1 the copper foil 110 shown, the protective layer 112 is formed on one surface of the copper film 111, but embodiments of the present disclosure are not limited thereto. Referring to Figure 2 , the protective layer 112 may be formed on each of the two surfaces of the copper film 111.

[0044] The copper film 111 may be formed on a rotating anode drum by electroplating and may have a shiny surface that is in direct contact with the rotating anode drum during the electroplating process and a matte side opposite the shiny surface.

[0045] The protective layer 112 is formed by electrodepositing an anti-corrosion material on the copper film 111. The anti-corrosion material may include at least one of a chromium compound, a silane compound, and a nitrogen compound. The protective layer 112 prevents oxidation and corrosion of the copper film 111 and improves its heat resistance, thereby extending the life of the final product including the copper foil 110 and the life of the copper foil 110 itself.

[0046] According to an embodiment of the present disclosure, the copper foil 110 has a tensile strength index of 3.0 kgf / mm 2 or less. The tensile strength index can be obtained by calculation according to Equation 1 using the tensile strength 1 and the tensile strength 2. When the tensile strength index is 3.0 kgf / mm 2 or less, wrinkles or tears can be prevented during the manufacturing process of the copper foil, and wrinkles or tears can be prevented or controlled even after a salt spray test.

[0047] [Equation 1]

[0048] Tensile strength index = |Tensile strength 2 - Tensile strength 1|

[0049] The tensile strength 1 in Equation 1 refers to the tensile strength of the sample before the salt spray test, and the tensile strength 2 in Equation 1 refers to the tensile strength of the sample after the salt spray test.

[0050] In this case, the salt spray test is performed by spraying a 5 ± 1% NaCl solution on each copper foil for 6 cycles, for a total of 72 hours, where 1 cycle means spraying for 2 hours at a temperature of 35 ± 2 °C and then drying the sprayed sample for 10 hours.

[0051] On the other hand, when the tensile strength index of the copper foil 110 exceeds 3.0 kgf / mm 2In the case where a salt spray test is performed on the copper foil 110, the change in the tensile strength of the copper foil 110 before and after the salt spray test increases. Therefore, wrinkles or tears may occur in the copper foil 110 after the salt spray test, thereby reducing the workability and increasing the defect rate of the secondary battery.

[0052] According to an embodiment of the present disclosure, the copper foil 110 has an elongation index of 2.1% or less. Using elongation 1 and elongation 2, the elongation index is obtained by calculation according to Equation 2 below. When the elongation index is 2.1% or less, the occurrence of wrinkles or tears during the copper foil manufacturing process can be prevented, and the occurrence of wrinkles or tears even after the salt spray test can be prevented or controlled.

[0053] [Equation 2]

[0054] Elongation index = |Elongation 2 - Elongation 1|

[0055] Elongation 1 in Equation 2 refers to the elongation of the sample before the salt spray test, and elongation 2 in Equation 2 refers to the elongation of the sample after the salt spray test.

[0056] In this case, the salt spray test is performed by spraying a 5 ± 1% NaCl solution on each copper foil for 6 cycles, totaling 72 hours, where 1 cycle means spraying the solution for 2 hours at a temperature of 35 ± 2°C and then drying the sprayed solution for 10 hours.

[0057] On the other hand, in the case where the elongation index of the copper foil 110 exceeds 2.1%, when a salt spray test is performed on the copper foil 110, the change in the elongation of the copper foil 110 before and after the salt spray test increases. Therefore, wrinkles or tears may occur in the copper foil 110 after the salt spray test, thereby reducing the workability and increasing the defect rate of the secondary battery.

[0058] The copper foil 110 according to an embodiment of the present disclosure has a thickness of 4 μm to 35 μm. When the copper foil 110 is used as a current collector of an electrode in a secondary battery, as the thickness of the copper foil 110 becomes smaller, more current collectors can be accommodated in the same space, which is advantageous for the high capacity of the secondary battery. However, the manufacturing of the copper foil 110 with a thickness less than 4 μm causes deterioration of workability.

[0059] On the other hand, when manufacturing a secondary battery using a copper foil 110 with a thickness exceeding 35 μm, it is difficult to achieve a high capacity due to the relatively thick copper foil 110.

[0060] The copper foil 110 according to an embodiment of the present disclosure may have 28 kg / mm 2A tensile strength 2 of 28 kg / mm² or more. The tensile strength 2 according to an embodiment of the present disclosure is the tensile strength of the sample after the salt spray test. In order to suppress wrinkling and tearing of the copper foil 110 after the salt spray test, the copper foil 110 of the present disclosure has a high tensile strength 2 of 28 kg / mm² or more. When the tensile strength of the copper foil 110 after the salt spray test is less than 28 kg / mm², during the roll-to-roll manufacturing process, folding of the copper foil 110 may occur between two adjacent rolls, or wrinkling may occur at the lateral ends of the copper foil 110. 2 A high tensile strength 2 of 28 kg / mm² or more. When the tensile strength of the copper foil 110 after the salt spray test is less than 28 kg / mm², 2 during the roll-to-roll manufacturing process, folding of the copper foil 110 may occur between two adjacent rolls, or wrinkling may occur at the lateral ends of the copper foil 110.

[0061] The copper foil 110 according to an embodiment of the present disclosure may have an elongation rate 2 of 3.0% to 12%. The elongation rate 2 according to an embodiment of the present disclosure is the elongation rate of the sample after the salt spray test. In order to suppress wrinkling and tearing of the copper foil 110 after the salt spray test, the copper foil 110 of the present disclosure has a high elongation rate 2 of 3.0% to 12%.

[0062] When the elongation rate of the copper foil 110 after the salt spray test is less than 3%, when the copper foil 110 is used as a current collector of a secondary battery, there is a high risk that the copper foil 110 will be torn because it cannot be sufficiently stretched to respond to the large expansion of the volume of the high-capacity active material.

[0063] On the other hand, when the elongation rate of the copper foil 110 after the salt spray test exceeds 12%, the copper foil 110 is easily stretched during the manufacturing process of the electrode for the secondary battery, resulting in deformation of the electrode.

[0064] According to an embodiment of the present disclosure, the copper foil 110 has a first weight retention rate of 0.1% or less. The first weight retention rate can be obtained by calculation according to the following Equation 3.

[0065] [Equation 3]

[0066] First weight retention rate = |(weight after 5-hour immersion - weight before immersion) / weight before immersion * 100|

[0067] The weight after 5-hour immersion in Equation 3 refers to the weight of the sample measured after immersing the sample in a 20% NaOH solution for 5 hours.

[0068] The weight before immersion in Equation 3 refers to the weight of the sample measured before immersing the sample in a 20% NaOH solution.

[0069] When the first weight retention rate of the copper foil 110 exceeds 0.1%, after 5 hours of impregnation, the changes in both the weight and the surface state of the copper foil 110 may increase. As a result, the copper foil 110 may not have excellent coatability on the active material, and the adhesion strength between the copper foil 110 and the active material layer may decrease. In addition, when the change in the surface state of the copper foil 110 increases, wrinkles or tears may occur.

[0070] Therefore, in order to prevent wrinkles or tears from occurring during the manufacturing process of the copper foil while maintaining the surface state, so as to prevent wrinkles or tears even after impregnation, the first weight retention rate of the copper foil 110 must be 0.1% or less.

[0071] According to one embodiment of the present disclosure, the copper foil 110 has a second weight retention rate of 0.3% or less. The second weight retention rate can be obtained by calculation according to Equation 4 below.

[0072] [Equation 4]

[0073] Second weight retention rate = |(weight after 24 hours of impregnation - weight before impregnation) / weight before impregnation * 100|

[0074] In Equation 4, the weight after 24 hours of impregnation refers to the weight of the sample measured after impregnating the sample in a 20% NaOH solution for 24 hours.

[0075] In Equation 4, the weight before impregnation refers to the weight of the sample measured before impregnating the sample in a 20% NaOH solution.

[0076] When the second weight retention rate of the copper foil 110 exceeds 0.3%, after 24 hours of impregnation, the changes in both the weight and the surface state of the copper foil 110 may increase. As a result, the copper foil 110 may not have excellent coatability on the active material, and the adhesion strength between the copper foil 110 and the active material layer may decrease. In addition, when the change in the surface state of the copper foil 110 increases, wrinkles or tears may occur.

[0077] Therefore, in order to prevent wrinkles or tears from occurring during the manufacturing process of the copper foil while maintaining the surface state, so as to prevent wrinkles or tears even after impregnation, the second weight retention rate of the copper foil 110 must be 0.3% or less.

[0078] According to an embodiment of the present disclosure, the copper foil 110 has a first roughness variation of 0.7 μm or less. The copper foil 110 may have a matte surface (M surface) and a glossy surface (S surface). According to an embodiment of the present disclosure, the copper film 111 may be formed by electroplating on the rotating anode drum 40, and has a surface (glossy surface) in contact with the rotating anode drum 40 and a surface (matte surface) opposite to the glossy surface.

[0079] The first roughness variation can be obtained by calculation according to the following Equation 5.

[0080] [Equation 5]

[0081] First roughness variation = |Surface roughness (Rz) of the matte surface after 24 hours of immersion - Surface roughness (Rz) of the matte surface before immersion|

[0082] In Equation 5, the surface roughness (Rz) of the matte surface after 24 hours of immersion refers to the ten-point average roughness (Rz) of the matte surface (M surface) of the copper foil 110 after immersing the copper foil 110 in a 20% NaOH solution for 24 hours.

[0083] In Equation 5, the surface roughness (Rz) of the matte surface before immersion refers to the ten-point average roughness (Rz) of the matte surface (M surface) of the copper foil 110 before immersion.

[0084] When the first roughness variation of the copper foil 110 exceeds 0.7 μm, the change in the surface state of the copper foil 110 after 24 hours of immersion may increase. As a result, the copper foil 110 may not have excellent coatability on the active material, and the adhesion strength between the copper foil 110 and the active material layer may decrease. In addition, when the change in the surface state of the copper foil 110 increases, wrinkles or tears may occur.

[0085] Therefore, in order to maintain the surface state of the copper foil 110 to prevent wrinkles or tears from occurring, the first roughness variation of the copper foil 110 must be 0.7 μm or less.

[0086] According to an embodiment of the present disclosure, the copper foil 110 has a second roughness variation of 0.8 μm or less.

[0087] The second roughness variation can be obtained by calculation according to the following Equation 6.

[0088] [Equation 6]

[0089] Second roughness variation = |Surface roughness (Rz) of the glossy surface after 24 hours of immersion - Surface roughness (Rz) of the glossy surface before immersion|

[0090] In Equation 6, the surface roughness (Rz) of the shiny surface after 24 hours of immersion refers to the ten-point mean roughness (Rz) of the shiny surface (S surface) of the copper foil 110 after immersing the copper foil 110 in a 20% NaOH solution for 24 hours.

[0091] In Equation 6, the surface roughness (Rz) of the shiny surface before immersion refers to the ten-point mean roughness (Rz) of the shiny surface (S surface) of the copper foil 110 before immersion.

[0092] When the change in the second roughness of the copper foil 110 exceeds 0.8 μm, the change in the surface state of the copper foil 110 after 24 hours of immersion may increase. As a result, the copper foil 110 may not have excellent coatability on the active material, and the adhesion strength between the copper foil 110 and the active material layer may decrease. In addition, when the change in the surface state of the copper foil 110 increases, wrinkles or tears may occur.

[0093] Therefore, in order to maintain the surface state of the copper foil 110 to prevent wrinkles or tears from occurring, the change in the second roughness of the copper foil 110 must be 0.8 μm or less.

[0094] According to an embodiment of the present disclosure, the copper foil 110 may have an arithmetic mean roughness (Ra) of 0.1 μm to 0.3 μm.

[0095] When the secondary battery is repeatedly charged and discharged, the active material layer may alternately contract and expand, which causes the active material layer to separate from the copper foil 110, thereby reducing the charge and discharge efficiency of the secondary battery. Therefore, in order to ensure a specific level or higher of the capacity retention rate and lifespan of the secondary battery (that is, to suppress the deterioration of the charge and discharge efficiency of the secondary battery), by making the copper foil 110 have excellent coatability on the active material, the bonding strength between the copper foil 110 and the active material layer should be high.

[0096] Specifically, when the arithmetic mean roughness (Ra) of the copper foil 110 is small, the tendency of deterioration of the charge and discharge efficiency of the secondary battery including the copper foil 110 decreases. Therefore, according to an embodiment of the present disclosure, the copper foil 110 has an arithmetic mean roughness (Ra) of 0.1 μm to 0.3 μm.

[0097] When the arithmetic mean roughness (Ra) of the copper foil 110 is less than 0.1 μm, the surface area of the copper foil 110 is relatively small, making it easy for the active material to delaminate from the copper foil 110. As a result, the lifespan of the secondary battery deteriorates rapidly due to repeated charging and discharging.

[0098] On the other hand, when the arithmetic mean roughness (Ra) of the copper foil 110 exceeds 0.3 μm, since the contact uniformity between the copper foil 110 and the active material layer does not reach a predetermined level (i.e., the coating itself is partially performed), there are multiple spaces (gaps) between the copper foil 110 and the active material layer. As a result, due to repeated charging and discharging, the rapid life deterioration of the secondary battery occurs.

[0099] Figure 3 is a photograph of a copper foil after a salt spray test according to another embodiment of the present disclosure.

[0100] Hereinafter, the electrode 100 including the copper foil 110 of the present disclosure and the secondary battery including the electrode 100 will be described in detail.

[0101] Figure 4 is a cross-sectional view of an electrode for a secondary battery according to an embodiment of the present disclosure.

[0102] As Figure 4 shown, the electrode 100 for a secondary battery according to an embodiment of the present disclosure includes the copper foil 110 and the active material layer 120 of one of the above embodiments of the present disclosure.

[0103] Figure 4 shows a configuration in which the active material layer 120 is formed on one surface of the copper foil 110. However, the present disclosure is not limited thereto, and referring to Figure 5 , the active material layer 120 may be formed on each of the two surfaces of the copper foil 110.

[0104] Generally, in a lithium secondary battery, an aluminum foil is used as a cathode current collector connected to a cathode active material, while the copper foil 110 is used as an anode current collector connected to an anode active material.

[0105] According to an embodiment of the present disclosure, the electrode 100 for a secondary battery is an anode, the copper foil 110 is used as an anode current collector, and the active material layer 120 includes an anode active material.

[0106] To ensure a high capacity of the secondary battery, the active material layer 120 of the present disclosure may be formed of a composite of carbon and a metal. The metal may include, for example, at least one of silicon (Si), germanium (Ge), tin (Sn), lithium (Li), zinc (Zn), magnesium (Mg), cadmium (Cd), cerium (Ce), nickel (Ni), and iron (Fe), and preferably may include Si and / or Sn.

[0107] Figure 6 is a schematic cross-sectional view of a secondary battery according to an embodiment of the present disclosure.

[0108] Referring to Figure 6, the secondary battery includes a cathode 370, an anode 340, an electrolyte 350 disposed between the cathode 370 and the anode 340 to provide an environment in which ions can move, and a separator 360 that electrically insulates the cathode 370 and the anode 340. Here, the ions moving between the cathode 370 and the anode 340 are, for example, lithium ions. The separator 360 separates the cathode 370 and the anode 340 to prevent the charge generated in one electrode from being wasted by moving inside the secondary battery to the other electrode. Refer to Figure 6 , the separator 360 is disposed in the electrolyte 350.

[0109] The cathode 370 includes a cathode current collector 371 and a cathode active material layer 372, and an aluminum foil can be used as the cathode current collector 371.

[0110] The anode 340 includes an anode current collector 341 and an anode active material layer 342, and the copper foil 110 can be used as the anode current collector 341.

[0111] According to an embodiment of the present disclosure, Figure 1 the copper foil 110 disclosed in or 2 can be used as the anode current collector 341. In addition, Figure 4 the electrode 100 for a secondary battery shown in or 5 can be used as Figure 6 the anode 340 of the secondary battery shown in.

[0112] Hereinafter, with reference to Figure 7 the manufacturing method of the copper foil 110 of the present disclosure will be described in detail.

[0113] The method for manufacturing the copper foil 110 of the present disclosure includes forming a copper film 111 and forming a protective layer 112 on the copper film 111.

[0114] The method of the present disclosure includes forming a copper film 111 on the rotating anode drum 40 by making the cathode plate 30 and the rotating anode drum 40 conductive, and the cathode plate and the rotating anode drum are arranged to be spaced apart from each other in the electrolyte 20 in the electrolytic cell 10.

[0115] As Figure 7 shown, the cathode plate 30 may include a first cathode plate 31 and a second cathode plate 32 that are electrically insulated from each other.

[0116] The formation of the copper film 111 can be performed by forming a seed layer through conduction between the first cathode plate 31 and the rotating anode drum 40, and then growing the seed layer through conduction between the second cathode plate 32 and the rotating anode drum 40.

[0117] The current density provided by each of the first and second cathode plates 31 and 32 may be 30 to 130 ASD (A / dm 2 ).

[0118] When the current density provided by each of the first cathode plate 31 and the second cathode plate 32 is less than 30 ASD, the surface roughness of the copper foil 110 decreases, and thus the adhesion between the copper foil 110 and the active material layer 120 may be insufficient.

[0119] On the other hand, when the current density provided by each of the first cathode plate 31 and the second cathode plate 32 exceeds 130 ASD, the surface of the copper foil 110 may be rough, and thus it may be difficult to smoothly coat the active material.

[0120] The surface characteristics of the copper film 111 can be changed according to the buffing (polishing, grinding) or polishing degree of the surface of the rotating anode drum 40. For example, a polishing brush with a grit of #800 to #3000 can be used to polish the surface of the rotating anode drum 40.

[0121] During the formation of the copper film 111, the electrolyte 20 is maintained at a temperature of 48 °C to 60 °C. More specifically, the temperature of the electrolyte 20 can be maintained at 50 °C or higher. At this time, the physical, chemical, and electrical characteristics of the copper film 111 can be controlled by adjusting the composition of the electrolyte 20.

[0122] According to an embodiment of the present disclosure, the electrolyte 20 includes copper ions with a concentration of 70 g / L to 100 g / L, sulfuric acid with a concentration of 70 g / L to 150 g / L, chlorine (Cl) with a concentration of 15 ppm to 25 ppm, lead ions (Pb 2 + ) with a concentration of 1 ppm to 100 ppm, arsenic (As) with a concentration of 0.5 ppm to 5 ppm, silver ions (Ag + ) with a concentration of 0.1 ppm to 3 ppm, hydrogen peroxide (H2O2) with a concentration of 1 ml / L to 10 ml / L, and an organic additive.

[0123] To facilitate the formation of the copper film 111 by electroplating of copper, the copper ion concentration and sulfuric acid concentration in the electrolyte 20 are adjusted within the ranges of 70 g / L to 100 g / L and 70 g / L to 150 g / L, respectively.

[0124] In an embodiment of the present disclosure, chlorine (Cl) includes all chloride ions (Cl-) and chlorine atoms present in the molecule. For example, chlorine (Cl) can be used to remove silver (Ag) ions introduced into the electrolyte 20 during the formation of the copper film 111. Specifically, chlorine (Cl) can precipitate silver (Ag) ions in the form of silver chloride (AgCl). Silver chloride (AgCl) can be removed by filtration.

[0125] When the concentration of chlorine (Cl) is less than 15 ppm, silver (Ag) ions cannot be removed well. On the other hand, when the concentration of chlorine (Cl) exceeds 25 ppm, unnecessary reactions may occur due to the excessive chlorine (Cl). Therefore, the concentration of chlorine (Cl) in the electrolyte 20 is controlled within the range of 15 ppm to 25 ppm.

[0126] According to an embodiment of the present disclosure, the electrolyte 20 including an organic additive may further include lead ions (Pb 2+ ). Specifically, the electrolyte 20 may include lead ions (Pb 2+ ) at a concentration of 1 ppm to 100 ppm. When the lead ions (Pb 2+ ) are maintained at a concentration of 1 ppm to 100 ppm, the tensile strength index according to the present disclosure can be maintained at 3.0 kgf / mm 2 or less, and the elongation index can be maintained at 2.1% or less. As a result, wrinkles or tears can be prevented during the manufacturing process of the copper foil, and wrinkles or tears can be prevented or controlled even after the salt spray test. On the other hand, when the concentration of lead ions (Pb 2+ ) is less than 1 ppm, this may reduce the effectiveness in maintaining the physical properties of the present disclosure. As a result, the tensile strength after the salt spray test decreases rapidly compared to the tensile strength before the salt spray test, causing the tensile strength index to exceed 3.0 kgf / mm 2 , and the elongation after the salt spray test decreases rapidly compared to the elongation before the salt spray test, causing the elongation index to exceed 2.1%.

[0127] In addition, when the concentration of lead ions (Pb 2+ ) exceeds 100 ppm, copper may be precipitated unevenly. As a result, the tensile strength after the salt spray test decreases rapidly compared to the tensile strength before the salt spray test, causing the tensile strength index to exceed 3.0 kgf / mm 2 , and the elongation after the salt spray test decreases rapidly compared to the elongation before the salt spray test, causing the elongation index to exceed 2.1%.

[0128] According to an embodiment of the present disclosure, the electrolyte 20 including an organic additive may further include lead ions (Pb 2+ ). Specifically, the electrolyte 20 may include lead ions (Pb 2+ ) at a concentration of 1 ppm to 100 ppm. When the lead ions (Pb 2+)When maintained at a concentration of 1 ppm to 100 ppm, the first weight retention rate according to the present disclosure can be maintained at 0.1% or less, and the second weight retention rate can be maintained at 0.3% or less. In addition, the first roughness change can be maintained at 0.7 μm or less, and the second roughness change can be maintained at 0.8 μm or less.

[0129] On the other hand, when the concentration of lead ions (Pb 2+ ) is less than 1 ppm, there may be a problem of reduced effectiveness in maintaining the physical properties of the present disclosure. Therefore, the weight of the copper foil 110 changes rapidly after impregnation, causing the first weight retention rate to exceed 0.1% and the second weight retention rate to exceed 0.3%. In addition, the surface of the copper foil 110 may be uneven, causing the first roughness change to exceed 0.7 μm and the second roughness change to exceed 0.8 μm.

[0130] In addition, when the concentration of lead ions (Pb 2+ ) exceeds 100 ppm, copper precipitates unevenly. Therefore, the weight of the copper foil 110 changes rapidly after impregnation, causing the first weight retention rate to exceed 0.1% and the second weight retention rate to exceed 0.3%. In addition, the surface of the copper foil 110 may be uneven, causing the first roughness change to exceed 0.7 μm and the second roughness change to exceed 0.8 μm.

[0131] According to an embodiment of the present disclosure, the electrolyte 20 including an organic additive may further include arsenic (As). Specifically, the electrolyte 20 may include arsenic (As) at a concentration of 0.5 ppm to 5 ppm. When arsenic (As) is maintained at a concentration of 0.5 ppm to 5 ppm, the tensile strength index according to the present disclosure can be maintained at 3.0 kgf / mm 2 or less, and the elongation rate index can be maintained at 2.1% or less. In addition, arsenic (As) acts as a promoter for accelerating the reduction reaction of copper (Cu) within a specific concentration range. However, in the electrolyte 20, arsenic (As) may exist, for example, in the trivalent or pentavalent ionic state (As 3+ or As 5+ ).

[0132] On the other hand, when the concentration of arsenic (As) is less than 0.5 ppm, the reduction reaction of copper decreases. As a result, the tensile strength after the salt spray test decreases rapidly compared to the tensile strength before the salt spray test, causing the tensile strength index to exceed 3.0 kgf / mm 2 , and the elongation rate after the salt spray test decreases rapidly compared to the elongation rate before the salt spray test, causing the elongation rate index to exceed 2.1%.

[0133] On the other hand, when the concentration of arsenic (As) exceeds 5 ppm, the reduction reaction of copper occurs excessively. As a result, the tensile strength after the salt spray test decreases rapidly compared to the tensile strength before the salt spray test, causing the tensile strength index to exceed 3.0 kgf / mm 2 , and the elongation after the salt spray test decreases rapidly compared to the elongation before the salt spray test, causing the elongation index to exceed 2.1%.

[0134] According to an embodiment of the present disclosure, the electrolyte 20 including an organic additive may further include arsenic (As). Specifically, the electrolyte 20 may include arsenic (As) at a concentration of 0.5 ppm to 5 ppm. When the concentration of arsenic (As) is maintained at 0.5 ppm to 5 ppm, the first weight retention rate according to the present disclosure can be maintained at 0.1% or less, and the second weight retention rate can be maintained at 0.3% or less. In addition, arsenic (As) acts as a promoter for accelerating the reduction reaction of copper (Cu) within a specific concentration range. However, in the electrolyte 20, arsenic (As) may exist, for example, in the trivalent or pentavalent ionic state (As3+ or As5+).

[0135] On the other hand, when the concentration of arsenic (As) is less than 0.5 ppm, the reduction reaction of copper decreases. Therefore, the weight of the copper foil 110 changes rapidly after impregnation, causing the first weight retention rate to exceed 0.1% and the second weight retention rate to exceed 0.3%. In addition, due to the reduction of the copper reduction reaction, the surface of the copper foil 110 becomes irregular, causing the first roughness change to exceed 0.7 μm and the second roughness change to exceed 0.8 μm.

[0136] In addition, when the concentration of arsenic (As) exceeds 5 ppm, the reduction reaction of copper occurs excessively. Therefore, the weight of the copper foil 110 changes rapidly after impregnation, causing the first weight retention rate to exceed 0.1% and the second weight retention rate to exceed 0.3%. In addition, due to the excessive reduction reaction of copper, the surface of the copper foil 110 becomes irregular, causing the first roughness change to exceed 0.7 μm and the second roughness change to exceed 0.8 μm.

[0137] In addition, according to an embodiment of the present disclosure, the electrolyte 20 including an organic additive may further include silver (Ag). Specifically, the electrolyte 20 may include silver (Ag) at a concentration of 0.1 ppm to 3 ppm. When the concentration of silver (Ag) is maintained at 0.1 to 3 ppm, the tensile strength index according to the present disclosure can be maintained at 3.0 kgf / mm 2 or less, and the elongation index can be maintained at 2.1% or less.

[0138] On the other hand, when the concentration of silver (Ag) is less than 0.1 ppm, the elongation rate after the salt spray test decreases rapidly compared to that before the salt spray test, resulting in an elongation rate index exceeding 2.1%.

[0139] In addition, when the concentration of silver (Ag) exceeds 3 ppm, the tensile strength after the salt spray test decreases rapidly compared to the tensile strength before the salt spray test, resulting in a tensile strength index exceeding 3.0 kgf / mm 2 .

[0140] In addition, according to an embodiment of the present disclosure, the electrolyte 20 including the organic additive may further include silver (Ag). Specifically, the electrolyte 20 may include silver (Ag) at a concentration of 0.1 ppm to 3 ppm. When the concentration of silver (Ag) is maintained at 0.1 to 3 ppm, the first weight retention rate according to the present disclosure may be maintained at 0.1% or less, and the second weight retention rate may be maintained at 0.3% or less.

[0141] On the other hand, when the concentration of silver (Ag) is less than 0.1 ppm, the first weight retention rate may exceed 0.1%, and the second weight retention rate may exceed 0.3%.

[0142] In addition, when the concentration of silver (Ag) exceeds 3 ppm, copper is unevenly electrodeposited on the rotating anode drum. Therefore, the weight of the copper foil 110 changes rapidly after impregnation, resulting in a first weight retention rate exceeding 0.1% and a second weight retention rate exceeding 0.3%. In addition, due to the uneven electrodeposition of copper, the surface of the copper foil 110 becomes irregular, resulting in a first roughness change exceeding 0.7 μm and a second roughness change exceeding 0.8 μm.

[0143] According to an embodiment of the present disclosure, the electrolyte 20 including the organic additive may further include hydrogen peroxide (H2O2). Due to the organic additive, organic impurities may be present in the electrolyte 20 for continuous electroplating, and the organic impurities can be decomposed by treating with hydrogen peroxide (H2O2) to appropriately adjust the carbon (C) content in the copper foil. As the total organic carbon (TOC) concentration in the electrolyte 20 increases, the amount of carbon (C) element introduced into the copper film 111 increases, which results in an increase in the total amount of elements separated from the copper film 111 during heat treatment, and thus causes a decrease in the strength of the copper foil 110.

[0144] According to an embodiment of the present disclosure, the electrolyte 20 including an organic additive may further include hydrogen peroxide (H2O2). Due to the organic additive, organic impurities may be present in the continuously electroplated electrolyte 20, and the organic impurities can be decomposed by treating with hydrogen peroxide (H2O2), thereby appropriately adjusting the content of carbon (C) in the copper foil. As the total organic carbon (TOC) concentration in the electrolyte 20 increases, the amount of carbon (C) element input into the copper film 111 increases, so the total amount of elements separated from the copper film 111 during heat treatment increases, which causes a change in the surface state of the copper foil 110, resulting in changes in both the weight and surface roughness of the copper foil 110 after impregnation.

[0145] The addition amount of hydrogen peroxide (H2O2) is 1 ml to 10 ml per liter of the electrolyte. Specifically, the addition amount of hydrogen peroxide (H2O2) can be 2 ml to 8 ml per liter of the electrolyte. When the addition amount of hydrogen peroxide (H2O2) is less than 1 ml / L, it is meaningless because it has little effect on the decomposition of organic impurities. When the addition amount of hydrogen peroxide (H2O2) exceeds 10 ml / L, the organic impurities are excessively decomposed, and thus the effects of organic additives such as a polishing agent, a moderating agent, and a roughness regulator are also inhibited.

[0146] The organic additive included in the electrolyte 20 includes at least one of a polishing agent (component A), a moderating agent (component B), and a roughness regulator (component C). The concentration of the organic additive in the electrolyte 20 is 1 ppm to 100 ppm.

[0147] The organic additive may include two or more of a polishing agent (component A), a moderating agent (component B), and a roughness regulator (component C), and may include all three components. Even in this case, the concentration of the organic additive is 100 ppm or less. When the organic additive includes all of a polishing agent (component A), a moderating agent (component B), and a roughness regulator (component C), the concentration of the organic additive can be 10 ppm to 100 ppm.

[0148] The polishing agent (component A) includes a sulfonic acid or a metal salt thereof. The concentration of the polishing agent (component A) in the electrolyte 20 can be 1 ppm to 15 ppm.

[0149] The polishing agent (Component A) can increase the charge amount of the electrolyte 20 to improve the copper electrodeposition rate, can improve the warpage characteristics of the copper foil, and can improve the glossiness of the copper foil 110. When the concentration of the polishing agent (Component A) is less than 1 ppm, the glossiness of the copper foil 110 decreases, and when the concentration of the polishing agent (Component A) exceeds 15 ppm, the roughness of the copper foil 110 may increase, and the strength of the copper foil 110 may decrease. As a result, the tensile strength after the salt spray test decreases rapidly compared with the tensile strength before the salt spray test, causing the tensile strength index to exceed 3.0 kgf / mm 2 .

[0150] The polishing agent (Component A) can increase the charge amount of the electrolyte 20 to improve the copper electrodeposition rate, can improve the warpage characteristics of the copper foil, and can increase the glossiness of the copper foil 110. When the concentration of the polishing agent (Component A) is less than 1 ppm, the glossiness of the copper foil 110 decreases, and when the concentration of the polishing agent (Component A) exceeds 15 ppm, the weight and surface roughness of the copper foil 110 after impregnation may change. Therefore, the weight of the copper foil 110 changes rapidly after impregnation, causing the first weight retention rate to exceed 0.1% and the second weight retention rate to exceed 0.3%. In addition, copper is electrodeposited unevenly, so the surface of the copper foil 110 becomes irregular, causing the first roughness change to exceed 0.7 μm and the second roughness change to exceed 0.8 μm.

[0151] More specifically, the concentration of the polishing agent (Component A) in the electrolyte 20 can be 5 ppm to 10 ppm.

[0152] The polishing agent can include at least one selected from, for example, bis-(3-sulfopropyl)-disulfide disodium salt, 3-mercapto-1-propanesulfonic acid, sodium 3-(N,N-dimethylthiocarbamoyl)-thiopropanesulfonate, sodium 3-[(amino-iminomethyl)thio]-1-propanesulfonate, sodium O-ethyl dithiocarbonate-S-(3-sulfopropyl) ester, sodium 3-(benzothiazole-2-mercapto)-propyl-sulfonate, and ethyldithiodipropanesulfonic acid disodium salt.

[0153] The moderating agent (Component B) includes a nonionic water-soluble polymer. The concentration of the moderating agent (Component B) in the electrolyte 20 can be 1 ppm to 15 ppm.

[0154] The moderating agent (Component B) reduces the copper electrodeposition rate to prevent the rapid increase in roughness and the decrease in strength of the copper foil 110. This moderating agent (Component B) is called an inhibitor or suppressor.

[0155] When the concentration of the moderator (component B) is less than 1 ppm, the roughness of the copper foil 110 increases rapidly, and the strength of the copper foil 110 decreases. As a result, the tensile strength after the salt spray test decreases rapidly compared with the tensile strength before the salt spray test, causing the tensile strength index to exceed 3.0 kgf / mm 2 On the other hand, although the concentration of the moderator (component B) exceeds 15 ppm, the physical properties of the copper foil 110 such as appearance, gloss, roughness, strength, elongation, etc. hardly change. Therefore, the concentration of the moderator (component B) can be adjusted in the range of 1 ppm to 15 ppm without increasing the manufacturing cost and wasting raw materials due to the unnecessary increase in the concentration of the moderator (component B).

[0156] When the concentration of the moderator (component B) is less than 1 ppm, the weight and surface roughness of the copper foil 110 after impregnation can change. Therefore, the weight of the copper foil 110 after impregnation changes rapidly, causing the first weight retention rate to exceed 0.1% and the second weight retention rate to exceed 0.3%. In addition, copper is electrodeposited unevenly, so the surface of the copper foil 110 becomes irregular, causing the first roughness change to exceed 0.7 μm and the second roughness change to exceed 0.8 μm.

[0157] The moderator (component B) can include, for example, at least one nonionic water-soluble polymer selected from polyethylene glycol (PEG), polypropylene glycol, polyethylene-polypropylene copolymer, polyglycerol, polyethylene glycol dimethyl ether, hydroxyethyl cellulose, polyvinyl alcohol, polyethylene glycol stearate ether, polyethylene glycol stearyl ether. However, the type of the moderator is not limited thereto, and other nonionic water-soluble polymers that can be used to manufacture the high-strength copper foil 110 can be used as the moderator.

[0158] The roughness regulator (component C) includes a nitrogen-containing heterocyclic quaternary ammonium salt or a derivative thereof.

[0159] The roughness regulator (component C) improves the gloss and uniformity of the copper foil 110. The concentration of the roughness regulator (component C) in the electrolyte 20 can be 1 to 15 ppm.

[0160] When the concentration of the roughness regulator (Component C) is less than 1 ppm, the effect of improving the gloss and uniformity of the copper foil 110 may not be manifested. At the same time, the elongation rate after the salt spray test decreases rapidly compared with the elongation rate before the salt spray test, resulting in the elongation rate index exceeding 2.1%. On the other hand, when the concentration of the roughness regulator (Component C) exceeds 15 ppm, the surface gloss of the copper foil 110 becomes uneven, and the surface roughness of the copper foil 110 increases rapidly, making it difficult to ensure the desired roughness range. Therefore, the strength of the copper foil 110 may decrease. As a result, the tensile strength after the salt spray test decreases rapidly compared with the tensile strength before the salt spray test, resulting in the tensile strength index exceeding 3.0 kgf / mm 2 . More specifically, the concentration of the roughness regulator (Component C) in the electrolyte 20 can be 5 ppm to 10 ppm.

[0161] When the concentration of the roughness regulator (Component C) is less than 1 ppm, the effect of improving the gloss and uniformity of the copper foil 110 may not be manifested. Therefore, the first roughness change exceeds 0.7 μm, and the second roughness change exceeds 0.8 μm.

[0162] On the other hand, when the concentration of the roughness regulator (Component C) exceeds 15 ppm, the weight and surface roughness of the copper foil 110 after impregnation may change. Therefore, the weight of the copper foil 110 after impregnation changes rapidly, resulting in the first weight retention rate exceeding 0.1% and the second weight retention rate exceeding 0.3%. In addition, copper is electrodeposited unevenly, so the surface of the copper foil 110 becomes irregular, resulting in the first roughness change exceeding 0.7 μm and the second roughness change exceeding 0.8 μm. More specifically, the concentration of the roughness regulator (Component C) in the electrolyte 20 can be 5 ppm to 10 ppm.

[0163] The roughness regulator (Component C) may include at least one of the compounds represented by the following Chemical Formulas 1 to 5.

[0164] [Chemical Formula 1]

[0165]

[0166] [Chemical Formula 2]

[0167]

[0168] [Chemical Formula 3]

[0169]

[0170] [Chemical Formula 4]

[0171]

[0172] [Chemical Formula 5]

[0173]

[0174] In Chemical Formulas 1 to 5, l1 to l4, m1 to m4, and n1 to n5 may each refer to a repeating unit, may each be an integer greater than or equal to 1, and may be the same as or different from each other.

[0175] According to one embodiment of the present disclosure, each of the compounds represented by Chemical Formulas 1 to 5 has a number-average molecular weight of 500 to 12,000.

[0176] When the number-average molecular weight of the compound represented by Chemical Formulas 1 to 5 and used as a roughness modifier is less than 500, the surface roughness of the copper foil 110 increases due to the high ratio of monomers. When the content of the roughness modifier is low, the surface roughness of the copper film 111 may increase, and thus the glossiness and uniformity of the copper film 111 may deteriorate.

[0177] When the number-average molecular weight of the compound represented by Chemical Formulas 1 to 5 exceeds 12,000, the surface roughness deviation of the copper foil 110 increases. In this case, although the concentration of other additives is adjusted, it is difficult to suppress the increase in the surface roughness deviation of the copper foil 110.

[0178] The compounds represented by Chemical Formulas 1 to 5 can be prepared by polymerization or copolymerization using, for example, dimethyldiallylammonium chloride (DDAC).

[0179] As the compound represented by Chemical Formula 1, for example, there is PAS-2451 (manufactured by Nittobo Co., Ltd., Mw = 30,000) or the like.

[0180] As the compound represented by Chemical Formula 2, for example, there is PAS-84 (manufactured by Nittobo Co., Ltd., Mw = 20,000) or the like.

[0181] As the compound represented by Chemical Formula 3, for example, there is PAS-2351 (manufactured by Nittobo Co., Ltd., Mw = 25,000) or the like.

[0182] As the compound represented by Chemical Formula 4, for example, there is PAS-A-1 (manufactured by Nittobo Co., Ltd., Mw = 5,000), PAS-A-5 (manufactured by Nittobo Co., Ltd., Mw = 4,000) or the like.

[0183] As the compound represented by Chemical Formula 5, for example, there is PAS-J-81 (manufactured by Nittobo Co., Ltd., Mw = 180,000) or the like.

[0184] When forming the copper film 111, the flow rate of the electrolyte 20 supplied to the electrolytic cell 10 can be 41 m 3 / hour to 45 m 3 / hour.

[0185] The formation of the copper film 111 may include at least one of filtering the electrolyte 20 using activated carbon, filtering the electrolyte 20 using diatomaceous earth, and treating the electrolyte 20 with ozone (O3).

[0186] Specifically, to filter the electrolyte 20, the electrolyte 20 can be circulated at a flow rate of 35 m 3 / hour to 45 m 3 / hour. That is, to remove solid impurities present in the electrolyte 20 while electroplating to form the copper film 111, filtration can be performed at a flow rate of 35 m 3 / hour to 45 m 3 / hour. In this case, activated carbon or diatomaceous earth can be used.

[0187] To maintain the cleanliness of the electrolyte 20, the electrolyte 20 can be treated with ozone (O3).

[0188] In addition, to maintain the cleanliness of the electrolyte 20, the copper (Cu) wire used as the raw material of the electrolyte 20 can be cleaned.

[0189] According to an embodiment of the present disclosure, preparing the electrolyte 20 may include heat-treating the copper wire, pickling the heat-treated copper wire, water-washing the pickled copper wire, and placing the water-washed copper wire in sulfuric acid for the electrolyte.

[0190] More specifically, to maintain the cleanliness of the electrolyte 20, a copper wire with high purity (99.9% or higher) is heat-treated in an electric furnace at a temperature of 750 °C to 850 °C to burn various organic impurities attached to the copper wire, the heat-treated copper wire is pickled with a 10% sulfuric acid solution for 10 to 20 minutes, and then the pickled copper wire is washed with distilled water to prepare the copper for manufacturing the electrolyte 20. The water-washed copper wire can be placed in sulfuric acid for the electrolyte to prepare the electrolyte 20.

[0191] According to an embodiment of the present disclosure, to meet the characteristics of the copper foil 110, the concentration of TOC in the electrolyte 20 is controlled to be 300 ppm or less. That is, the electrolyte 20 can have a TOC concentration of 300 ppm or lower.

[0192] The thus-prepared copper film 111 can be cleaned in a cleaning tank.

[0193] For example, a pickling process for removing impurities (e.g., resin components or natural oxides) on the surface of the copper film 111 and a water washing process for removing the acidic solution used for pickling can be sequentially performed. This cleaning process can be omitted.

[0194] Next, a protective layer 112 is formed on the copper film 111.

[0195] Refer to Figure 7 , the method may further include immersing the copper film 111 in the corrosion-resistant solution 60. When the copper film 111 is immersed in the corrosion-resistant solution 60, the copper film 111 can be guided by the guide roller 70 disposed in the corrosion-resistant solution 60.

[0196] As described above, the corrosion-resistant solution 60 may include at least one of a chromium compound, a silane compound, and a nitrogen compound. For example, the copper film 111 can be immersed in a potassium dichromate solution of 1 g / L to 10 g / L at room temperature for 1 to 30 seconds.

[0197] Meanwhile, the protective layer 112 may include a silane compound by silane treatment or a nitrogen compound by nitrogen treatment.

[0198] The copper foil 110 is formed by forming the protective layer 112.

[0199] Select at least one active material from the group consisting of carbon, a metal (Me) (Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe), an alloy including the metal (Me), an oxide (MeOx) of the metal (Me), and a composite of the metal (Me) and carbon, and coat the at least one active material on one or both surfaces of the copper foil 110 of the present disclosure prepared by the above method to prepare an electrode (i.e., an anode) for the secondary battery of the present disclosure.

[0200] For example, 100 parts by weight of carbon for the anode active material, 1 to 3 parts by weight of styrene-butadiene rubber (SBR), and 1 to 3 parts by weight of carboxymethyl cellulose (CMC) are mixed, and a slurry is made using distilled water as a solvent. Subsequently, the slurry is coated on the copper foil 110 with a thickness of 20 μm to 60 μm and pressed at 110°C to 130°C and a pressure of 0.5 to 1.5 tons / cm2.

[0201] A secondary battery can be manufactured using the electrode (anode) for the secondary battery of the present disclosure prepared by the above method and a conventional cathode, electrolyte, and separator.

[0202] Hereinafter, the present disclosure will be described in detail with reference to examples and comparative examples. However, the examples described below are only for understanding the present disclosure, and the scope of the present disclosure is not limited to these manufacturing examples.

[0203] Examples 1 to 6 and Comparative Examples 1 to 9

[0204] A copper foil is prepared using a foil-making machine including an electrolytic cell 10, a rotating anode drum 40 disposed within the electrolytic cell 10, and a cathode plate 30 disposed at an interval from the rotating anode drum 40. The electrolyte 20 is a copper sulfate solution. The concentration of copper ions in the electrolyte 20 is set to 87 g / L, the sulfuric acid concentration is set to 110 g / L, the electrolyte temperature is set to 55 °C, and the current density is set to 60 ASD.

[0205] In addition, the concentration of chlorine (Cl) contained in the electrolyte 20 is maintained at 20 ppm, and the concentrations of lead ions, arsenic, silver ions, hydrogen peroxide, and organic additives are as shown in Table 1 below.

[0206] Among the organic additives, bis-(3-sulfopropyl)-disulfide disodium salt (SPS) is used as a polishing agent (Component A), PEG is used as a moderating agent (Component B), and diallylmethylethyl-ammoniumethylsulfate / maleic acid copolymer (PAS-2451 TM , manufactured by Nittobo Co., Ltd. and having an Mw of 30,000) is used as a roughness regulator (Component C).

[0207] A current with a current density of 60 ASD is applied between the rotating anode drum 40 and the cathode plate 30 to prepare a copper film 111. Subsequently, the copper film 111 is immersed in an anti-corrosion solution for about two seconds to treat the surface of the copper film 111 with chromium, thereby forming a protective layer 112, and thus a copper foil 110 is prepared. An anti-corrosion solution containing chromic acid as a main component is used as the anti-corrosion solution, and the concentration of chromic acid is 5 g / L.

[0208] As a result, copper foils of Preparation Examples 1 to 6 and Comparative Examples 1 to 9 are prepared.

[0209] [Table 1]

[0211] [Table 2]

[0213] For the copper foils of Examples 1 to 6 and Comparative Examples 1 to 9 prepared as described above, check i) Tensile Strength 1, ii) Tensile Strength 2, iii) Tensile Strength Index, iv) Elongation 1, v) Elongation 2, vi) Elongation Index, and vii) Appearance of wrinkles / tears. Measurement of i) Tensile Strength 1 and ii) Tensile Strength 2

[0214] The Tensile Strength 1 of copper foil 110 is the tensile strength of the sample before the salt spray test.

[0215] The Tensile Strength 2 of copper foil 110 is the tensile strength of the sample after the salt spray test.

[0216] In this case, the salt spray test is carried out by spraying 5 ± 1% NaCl solution on each copper foil for 6 cycles, totaling 72 hours, where 1 cycle means spraying the solution for 2 hours at a temperature of 35 ± 2 °C, and then drying the sprayed solution for 10 hours.

[0217] For Tensile Strength 1, according to the provisions of the IPC-TM-650 Test Method Manual, the tensile strength of copper foil 110 is measured at room temperature using a universal testing machine (UTM).

[0218] For Tensile Strength 2, copper foil 110 is subjected to the salt spray test, and the tensile strength of copper foil 110 is measured using the same method as for Tensile Strength 1.

[0219] iii) Calculation of Tensile Strength Index

[0220] Using the measured values of i) Tensile Strength 1 and ii) Tensile Strength 2, the Tensile Strength Index is obtained by calculation according to Equation 1 below.

[0221] [Equation 1]

[0222] Tensile Strength Index = |Tensile Strength 2 - Tensile Strength 1|

[0223] iv) Measurement of Elongation 1 and v) Elongation 2

[0224] The Elongation 1 of copper foil 110 is the elongation of the sample before the salt spray test.

[0225] The Elongation 2 of copper foil 110 is the elongation of the sample after the salt spray test.

[0226] In this case, the salt spray test is carried out by spraying 5 ± 1% NaCl solution on each copper foil for 6 cycles, totaling 72 hours, where 1 cycle means spraying the solution for 2 hours at a temperature of 35 ± 2 °C, and then drying the sprayed solution for 10 hours.

[0227] For elongation rate 1, in accordance with the provisions of the IPC-TM-650 Test Method Manual, the elongation rate of copper foil 110 is measured at room temperature using a UTM.

[0228] For elongation rate 2, copper foil 110 is subjected to a salt spray test, and the elongation rate of copper foil 110 is measured using the same method as for elongation rate 1.

[0229] vi) Calculation of the elongation rate index

[0230] Using the measured values of i) elongation rate 1 and ii) elongation rate 2, the elongation rate index is obtained through the calculation according to Equation 2 below.

[0231] [Equation 2]

[0232] Elongation rate index = |Elongation rate 2 - Elongation rate 1|

[0233] vii) Appearance of wrinkles / tears

[0234] After 100 charge and discharge cycles, the secondary battery is disassembled to observe whether wrinkles or tears appear on the copper foil. When the copper foil is wrinkled or torn, the copper foil is marked as "appeared", while when the copper foil is not wrinkled or torn, the copper foil is marked as "none".

[0235] Referring to Table 1 and Table 2, the following results can be confirmed.

[0236] Tears / wrinkles appear in the copper foil of Comparative Example 1 prepared using an electrolyte containing an excessive amount of polishing agent (Component A) and a small amount of lead ions.

[0237] Tears / wrinkles appear in the copper foil of Comparative Example 2 prepared using an electrolyte containing an excessive amount of moderator (Component B) and an excessive amount of arsenic.

[0238] Tears / wrinkles appear in the copper foil of Comparative Example 3 prepared using an electrolyte containing an excessive amount of roughness regulator (Component C) and a small amount of silver (Ag).

[0239] Tears / wrinkles appear in the copper foil of Comparative Example 4 prepared using an electrolyte containing an excessive amount of lead ions, arsenic, and silver (Ag), but not containing a polishing agent (Component A).

[0240] Tears / wrinkles appear in the copper foil of Comparative Example 5 prepared using an electrolyte containing a small amount of arsenic and silver (Ag), but not containing a moderator (Component B).

[0241] Tears / wrinkles appear in the copper foil of Comparative Example 6 prepared using an electrolyte containing an excessive amount of lead ions and silver (Ag) and a small amount of arsenic, but not containing a roughness regulator (Component C).

[0242] Tears / wrinkles occurred in the copper foil of Comparative Example 7 prepared using an electrolyte containing a small amount of a polishing agent (Component A) and arsenic (As).

[0243] Tears / wrinkles occurred in the copper foil of Comparative Example 8 prepared using an electrolyte containing a small amount of a moderator (Component B) and an excessive amount of arsenic (As).

[0244] Tears / wrinkles occurred in the copper foil of Comparative Example 9 prepared using an electrolyte containing a small amount of a surface roughness regulator (Component C) and an excessive amount of arsenic (As).

[0245] Examples 7 to 10 and Comparative Examples 10 to 13

[0246] A copper foil was produced using a foil-making machine including an electrolytic cell 10, a rotating anode drum 40 disposed in the electrolytic cell 10, and a cathode plate 30 disposed at a distance from the rotating anode drum 40. The electrolyte 20 was a copper sulfate solution. The copper ion concentration in the electrolyte 20 was set to 87 g / L, the sulfuric acid concentration was set to 110 g / L, the electrolyte temperature was set to 55 °C, and the current density was set to 60 ASD.

[0247] In addition, the concentration of chlorine (Cl) contained in the electrolyte 20 was maintained at 20 ppm, and the concentrations of lead ions, arsenic, silver ions, hydrogen peroxide, and organic additives were as shown in Table 3 below.

[0248] Among the organic additives, bis-(3-sulfopropyl)-disulfide disodium salt (SPS) was used as a polishing agent (Component A), PEG was used as a moderator (Component B), and diallylmethylethylammonium ethyl sulfate / maleic acid copolymer (PAS-2451 TM , manufactured by Nittobo Co., Ltd., with Mw of 30000) was used as a surface roughness regulator (Component C).

[0249] A current with a current density of 60 ASD was applied between the rotating anode drum 40 and the cathode plate 30 to prepare a copper film 111. Subsequently, the copper film 111 was immersed in an anti-corrosion solution for about two seconds to treat the surface of the copper film 111 with chromium, thereby forming a protective layer 112, and thus a copper foil 110 was prepared. An anti-corrosion solution containing chromic acid as a main component was used as the anti-corrosion solution, and the concentration of chromic acid was 5 g / L.

[0250] As a result, copper foils of Examples 7 to 10 and Comparative Examples 10 to 13 were prepared.

[0251] [Table 3]

[0253] [Table 4]

[0255] [Table 5]

[0257] For the copper foils of Examples 7 to 10 and Comparative Examples 10 to 13 prepared as described above, measure and calculate i) the weight before impregnation, ii) the weight after 5 hours of impregnation, iii) the weight after 24 hours of impregnation, iv) the first weight retention rate, v) the second weight retention rate, vi) the surface roughness (Rz) of the matte surface before impregnation, vii) the surface roughness (Rz) of the glossy surface before impregnation, viii) the surface roughness (Rz) of the matte surface after 24 hours of impregnation, ix) the surface roughness (Rz) of the glossy surface after 24 hours of impregnation, x) the first roughness change, and xi) the second roughness change, and xii) check for the occurrence of wrinkles / tears. Cut the samples of copper foil 110 into 5 mm * 5 mm, dry them in an oven at 50 °C for 24 hours, and then perform a pretreatment process to cool the samples in a desiccator.

[0258] i) Measurement of the weight before impregnation

[0259] The weight of the copper foil 110 before impregnation refers to the weight of the sample measured before immersing the sample in a 20% NaOH solution.

[0260] ii) Measurement of the weight after 5 hours of impregnation

[0261] The weight of the copper foil 110 after 5 hours of impregnation refers to the weight of the sample measured after immersing the sample in a 20% NaOH solution for 5 hours.

[0262] Perform impregnation in a 20% NaOH solution for 5 hours, and measure the sample weight after drying at room temperature for 2 hours after impregnation.

[0263] iii) Measurement of the weight after 24 hours of impregnation

[0264] The weight of the copper foil 110 after 24 hours of impregnation refers to the weight of the sample measured after immersing the sample in a 20% NaOH solution for 24 hours.

[0265] Perform impregnation in a 20% NaOH solution for 24 hours, and measure the sample weight after drying at room temperature for 2 hours after impregnation.

[0266] iv) Calculation of the first weight retention rate and v) the second weight retention rate

[0267] The first weight retention rate can be obtained by calculation according to Equation 3 below, using the measured value of i) the weight before impregnation and the measured value of ii) the weight after 5 hours of impregnation.

[0268] [Equation 3]

[0269] First weight retention rate = |(weight after 5 hours of impregnation - weight before impregnation) / weight before impregnation * 100|

[0270] The second weight retention rate can be obtained by calculation according to Equation 4 below, using the measured value of i) the weight before impregnation and the measured value of iii) the weight after 24 hours of impregnation.

[0271] [Equation 4]

[0272] Second weight retention rate = |(weight after 24 hours of impregnation - weight before impregnation) / weight before impregnation * 100|

[0273] vi) Measurement of the surface roughness (Rz) of the matte surface before impregnation and vii) the surface roughness (Rz) of the glossy surface before impregnation

[0274] The surface roughness (Rz) of the matte surface before impregnation and the surface roughness (Rz) of the glossy surface before impregnation respectively refer to the ten-point mean roughness (Rz) of the matte surface (M surface) and the glossy surface (S surface) of the copper foil 110 before impregnation.

[0275] The surface roughness (Rz) of the matte surface before impregnation and the surface roughness (Rz) of the glossy surface before impregnation can be measured respectively from a 5 mm * 5 mm sample according to the specifications of JIS B 0601 - 1994 using a surface roughness measuring device (M300, MahrSurf).

[0276] After 24 hours of impregnation, viii) measurement of the surface roughness (Rz) of the matte surface and ix) the surface roughness (Rz) of the glossy surface

[0277] The surface roughness (Rz) of the matte surface after 24 hours of impregnation refers to the ten-point mean roughness (Rz) of the matte surface (M surface) of the copper foil 110 after impregnating the copper foil 110 in a 20% NaOH solution for 24 hours, and the surface roughness (Rz) of the glossy surface after 24 hours of impregnation refers to the ten-point mean roughness (Rz) of the glossy surface (S surface) of the copper foil 110 after impregnating the copper foil 110 in a 20% NaOH solution for 24 hours.

[0278] The impregnation for measuring the surface roughness (Rz) is the same as the impregnation process for measuring iii) the weight after 24 hours of impregnation. After impregnation, the sample is dried at room temperature for 2 hours, and then the surface roughness is measured in the same manner as vi) the surface roughness (Rz) of the matte surface before impregnation and vii) the surface roughness (Rz) of the glossy surface before impregnation.

[0279] x) Calculation of the first roughness change and xi) the second roughness change

[0280] Using the measured values of vi) the surface roughness (Rz) of the matte surface before impregnation and viii) the surface roughness (Rz) of the matte surface after 24 hours of impregnation, the first roughness change can be obtained by calculation according to Equation 5 below.

[0281] [Equation 5]

[0282] First roughness change = |Surface roughness (Rz) of the matte surface after 24 hours of impregnation - Surface roughness (Rz) of the matte surface before impregnation|

[0283] Using the measured values of vii) the surface roughness (Rz) of the glossy surface before impregnation and ix) the surface roughness (Rz) of the glossy surface after 24 hours of impregnation, the second roughness change can be obtained by calculation according to Equation 6 below.

[0284] [Equation 6]

[0285] Second roughness change = |Surface roughness (Rz) of the glossy surface after 24 hours of impregnation - Surface roughness (Rz) of the glossy surface before impregnation|

[0286] xii) Appearance of wrinkles / tears

[0287] After 100 charge and discharge cycles, the secondary battery is disassembled to observe whether wrinkles or tears appear on the copper foil. When the copper foil is wrinkled or torn, the copper foil is marked as "appeared", while when the copper foil is not wrinkled or torn, the copper foil is marked as "none".

[0288] Referring to Tables 4, 5, and 6, the following results can be confirmed.

[0289] Tears / wrinkles appear in the copper foil of Comparative Example 10 prepared using an electrolyte containing an excessive amount of polishing agent (Component A) and arsenic, as well as a small amount of lead ions.

[0290] Tears / wrinkles appear in the copper foil of Comparative Example 11 prepared using an electrolyte containing a moderator (Component B) and a small amount of arsenic, as well as an excessive amount of silver ions.

[0291] Tears and wrinkles appeared in the copper foil of Comparative Example 12 prepared using an electrolyte including a roughness modifier (Component C) and an excessive amount of lead ions.

[0292] Tears / wrinkles appeared in the copper foil of Comparative Example 13 prepared using an electrolyte including an excessive amount of lead ions and hydrogen peroxide.

[0293] On the other hand, all of the copper foils according to Examples 7 to 10 of the present disclosure satisfy the values within the above-mentioned standard range, and thus tears / wrinkles did not appear in the copper foil.

[0294] It will be apparent to those skilled in the art that the above present disclosure is not limited to the above embodiments and the accompanying drawings, and various substitutions, modifications, and variations can be made to the present disclosure without departing from the spirit and scope of the present disclosure. Therefore, the scope of the present disclosure is defined by the appended claims, and all changes and modifications derived from the meaning, scope, and equivalent concepts of the claims are intended to fall within the scope of the present disclosure.

Claims

1. A copper foil, comprising: A copper film, the copper film comprising copper with a weight percentage of not less than 99.9%; And A protective layer, the protective layer being formed on the copper film, Among them, the copper foil has a tensile strength index not exceeding 3.0 kgf / mm 2 and an elongation rate index not exceeding 2.1%. Wherein, the tensile strength index is calculated by the following Equation 1, [Equation 1] Tensile strength index = |Tensile strength 2 - Tensile strength 1| Wherein, the tensile strength 1 in Equation 1 is the tensile strength of the sample before the salt spray test, and The tensile strength 2 in Equation 1 is the tensile strength of the sample after the salt spray test, The elongation index is calculated by the following Equation 2, [Equation 2] Elongation index = |Elongation 2 - Elongation 1| Wherein, the elongation 1 in Equation 2 is the elongation of the sample before the salt spray test, and The elongation 2 in Equation 2 is the elongation of the sample after the salt spray test, and The salt spray test is performed by spraying a 5 ± 1% NaCl solution on the copper foil for 6 cycles, totaling 72 hours, wherein 1 cycle means spraying the solution for 2 hours at a temperature of 35 ± 2°C, followed by drying for 10 hours.

2. The copper foil according to claim 1, wherein, The tensile strength 2 is not less than 28 kgf / mm 2 .

3. The copper foil according to claim 1, wherein The elongation 2 is in the range of 3.0% to 12%.

4. The copper foil according to claim 1, further comprising a protective layer formed on the copper film.

5. The copper foil according to claim 4, wherein The protective layer comprises at least one of a chromium compound, a silane compound, and a nitrogen compound.

6. A method for manufacturing a copper foil, the method comprising: Preparing an electrolyte containing copper ions; Forming a copper film; And Forming a protective layer on the copper film, Wherein, the forming of the copper film includes Forming the copper film on the rotating anode drum by making the cathode plate and the rotating anode drum conductive, the cathode plate and the rotating anode drum being arranged to be spaced apart from each other in the electrolyte in the electrolytic cell, and The electrolyte comprises: Copper ions with a concentration of 70 g / L to 100 g / L; Sulfuric acid with a concentration of 70 g / L to 150 g / L; Chlorine (Cl) with a concentration of 15 ppm to 25 ppm; Lead ions (Pb 2+ ) with a concentration of 1 ppm to 100 ppm; Arsenic (As) with a concentration of 0.5 ppm to 5 ppm; Silver ions (Ag with a concentration of 0.1 ppm to 3 ppm + ); Hydrogen peroxide with a concentration of 1 ml / L to 10 ml / L; and An organic additive, Wherein, the organic additive comprises at least one of a polishing agent (Component A), a moderating agent (Component B), and a roughness regulator (Component C), Wherein, the polishing agent (Component A) comprises a sulfonic acid or its metal salt, The moderating agent (Component B) comprises a non-ionic water-soluble polymer, and The roughness regulator (Component C) comprises a nitrogen-containing heterocyclic quaternary ammonium salt or its derivative.

7. The method according to claim 6, wherein The polishing agent (Component A) has a content of 1 ppm to 25 ppm.

8. The method according to claim 6, wherein, The moderating agent (Component B) has a content of 1 ppm to 15 ppm.

9. The method according to claim 6, wherein The roughness regulator has a content of 1 ppm to 15 ppm.

10. A copper foil, comprising a copper film, the copper film comprising copper with a weight percentage of not less than 99.9%, Among them, The copper foil has a first weight retention rate of not more than 0.1% and a second weight retention rate of not more than 0.3%, Wherein, the first weight retention rate is calculated by the following Equation 3, [Equation 3] The first weight retention rate = |(weight after 5-hour immersion - weight before immersion) / weight before immersion * 100|, and the second weight retention rate is calculated by the following Equation 4: [Equation 4] Second weight retention rate = |(weight after 24-hour immersion - weight before immersion) / weight before immersion * 100|.

11. The copper foil according to claim 10, wherein, The copper film includes a matte surface and a gloss surface, and the copper film has a first roughness variation of not more than 0.7 μm. Wherein, the first roughness variation is calculated by the following Equation 5: [Equation 5] First roughness variation = |surface roughness (Rz) of the matte surface after 24-hour immersion - surface roughness (Rz) of the matte surface before immersion|.

12. The copper foil according to claim 10, wherein, The copper film includes a matte surface and a gloss surface, and has a second roughness variation of not more than 0.8 μm. Wherein, the second roughness variation is calculated by the following Equation 6: [Equation 6] Second roughness variation = |surface roughness (Rz) of the gloss surface after 24-hour immersion - surface roughness (Rz) of the gloss surface before immersion|.

13. The copper foil according to claim 10, further comprising a protective layer formed on the copper film.

14. The copper foil according to claim 13, wherein, The protective layer includes at least one of a chromium compound, a silane compound, and a nitrogen compound.

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