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

Abstract

To provide copper foil that does not curl, wrinkle or tear during a manufacturing process.SOLUTION: The copper foil comprises a copper film containing 99.9 wt.% or more of copper, and has an R value in the range from 2.0 to 3.5, where R is calculated by the formula 1, [formula 1] R=log(WA / WB) / log(tA / tB), where WA in the formula 1 is calculated using the formula 2, [formula 2] WA=[XA0+(XA45)X2+XA90] / 4, WB in the formula 1 is calculated using the formula 3, [formula 3] WB=[XB0+(XB45)X2+XB90] / 4, tA in the formula 1 represents the thickness of a specimen before a tensile test, tB in the formula 1 represents the thickness of the specimen after the tensile test, XA0, XA45 and XA90 in the formula 2 represent widths of central portions of specimens collected in directions of 0°, 45° and 90° in a stretching direction before stretching, and XB0, XB45 and XB90 in the formula 3 represent widths of the central portions of the specimens collected in directions of 0°, 45° and 90° in the stretching direction after the stretching.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Secondary batteries are a type of energy conversion device that converts electrical energy into chemical energy, stores it, and then converts the chemical energy back into electrical energy when electricity is needed, generating electricity. They are used as a power source in portable home appliances such as mobile phones and laptops, as well as electric vehicles. Secondary batteries are also called rechargeable batteries because they can be recharged.

[0003] Secondary batteries, which have economical and environmental advantages over disposable primary batteries, include lead-acid batteries, nickel-cadmium secondary batteries, nickel-metal hydride secondary batteries, and lithium secondary batteries.

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

[0005] Lithium secondary batteries are used repeatedly through a cycle of charging and discharging. When a device is operated with a fully charged lithium secondary battery, the lithium-ion secondary battery must have a high charge / discharge capacity to extend the operating time of the device. Therefore, there is a continuous demand for research to meet the ever-increasing expectations (needs) of users regarding the charge / discharge capacity of lithium secondary batteries.

[0006] Such secondary batteries include a negative electrode current collector made of copper foil, and among copper foils, electrolytic copper foil is widely used as the negative electrode current collector of secondary batteries. As the demand for secondary batteries increases, the demand for high-capacity, high-efficiency, and high-quality secondary batteries also increases. secondary There is a demand for electrolytic copper foils that can improve battery characteristics, particularly for electrolytic copper foils that can increase the capacity of secondary batteries and ensure stable capacity maintenance and performance.

[0007] On the other hand, thinner copper foils allow for a larger amount of active material to be contained in the same space, and therefore, the number of current collectors can be increased, resulting in an increased capacity of secondary batteries. However, thinner copper foils tend to curl, which can cause defects such as foil rupture or wrinkles due to edge curling during winding, making it difficult to manufacture very thin copper foils. Therefore, to manufacture very thin copper foils, it is necessary to prevent copper foil curl. Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, the present invention relates to a copper foil that can avoid the problems caused by the limitations and shortcomings of the related art, an electrode including the same, a secondary battery including the same, and a method for manufacturing the same.

[0009] One embodiment of the present invention provides a copper foil having an R value in the range of 2.0 to 3.5, which prevents curling, wrinkling, or bursting during the manufacturing process.

[0010] Another embodiment of the present invention provides a secondary battery electrode including such a copper foil, and a secondary battery including such a secondary battery electrode.

[0011] Yet another embodiment of the present invention provides a method for manufacturing a copper foil that is free from curling, wrinkling, or bursting.

[0012] In addition to the above-mentioned aspects of the present invention, other features and advantages of the present invention will be described below or will be apparent to those skilled in the art from such description. [Means for solving the problem]

[0013] One embodiment of the present invention provides a copper foil including a copper film containing 99.9 wt % or more copper, and having an R value in the range of 2.0 to 3.5. The R is calculated by the following formula 1, [Formula 1] R = log(WA / WB) / log(tA / tB), and the WA in formula 1 is calculated by the following formula 2, [Formula 2] WA = [XA0 + (XA45)] × 2+XA90] / 4WB in the above formula 1 is calculated by the following formula 3, [Formula 3]WB=[XB0+(XB45) × 2+XB90] / 4 In formula 1, tA represents the thickness of the test piece before the tensile test, tB represents the thickness of the test piece after the tensile test, XA0, XA45, and XA90 in formula 2 represent the widths of the center of the test piece in the tensile direction before tensioning, taken in the 0°, 45°, and 90° directions, and XB0, XB45, and XB90 in formula 3 represent the widths of the center of the test piece in the tensile direction after tensioning, taken in the 0°, 45°, and 90° directions.

[0014] Another embodiment of the present invention includes the steps of preparing an electrolyte containing copper ions, forming a copper film, and forming a protective layer on the copper film, wherein the step of forming the copper film includes applying current to a positive electrode plate and a rotating cathode drum that are spaced apart from each other in an electrolyte in an electrolytic cell, thereby forming the copper film on the rotating cathode drum, and the electrolyte includes 70 to 100 g / L of copper ions, 70 to 150 g / L of sulfuric acid, 15 to 25 ppm of chlorine (Cl), 1 to 100 ppm of chlorine (Cl), lead (Pb), 0.3-5 ppm tungsten (W), 1-10 ml / L hydrogen peroxide, and an organic additive, the organic additive including at least one of a brightener (component A), a moderator (component B), and a labeling agent (component C), the brightener (component A) including sulfonic acid or a metal salt thereof, the moderator (component B) including a non-ionic water-soluble polymer, and the labeling agent (component C) including at least one of nitrogen (N) and sulfur (S).

[0015] According to yet another embodiment of the present invention, there is provided an electrode for a secondary battery, comprising: a copper foil; and an active material layer disposed on at least one surface of the copper foil.

[0016] According to yet another embodiment of the present invention, there is provided a secondary battery including: a cathode that provides lithium ions during charging; an anode that provides electrons and lithium ions during discharging; an electrolyte disposed between the cathode and the anode to provide an environment in which the lithium ions can move; and a separator that electrically insulates the cathode and the anode. [Effects of the Invention]

[0017] According to the present invention, the occurrence of wrinkles or ruptures during the manufacturing process of copper foil is prevented, and by using such copper foil to manufacture intermediate parts and final products such as flexible printed circuit boards (FPCBs) and secondary batteries, the productivity of not only the intermediate parts but also the final products can be improved. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a cross-sectional view of a copper foil according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of a copper foil according to another embodiment of the present invention. [Figure 3] FIG. 4 is a cross-sectional view of an electrode for a secondary battery according to still another embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view of an electrode for a secondary battery according to still another embodiment of the present invention. [Figure 5] 10 is a schematic cross-sectional view of a secondary battery according to yet another embodiment of the present invention. [Figure 6] 10 is a diagram showing a copper foil manufacturing apparatus according to still another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiments described below are merely provided for illustrative purposes to facilitate a clear understanding of the present invention and do not limit the scope of the present invention.

[0020] 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. The same components may be designated by the same reference numerals throughout the specification. In describing the present invention, if it is determined that a detailed description of related prior art may unnecessarily obscure the gist of the present invention, such a detailed description will be omitted.

[0021] When words such as "comprise," "have," and "consist of" 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 interpreting an element, it is interpreted as including a margin of error even if there is no other express statement.

[0022] In describing a positional relationship, for example, when the positional relationship between two parts is described using expressions such as "above," "on top of," "below," or "beside," one or more other parts may be located between the two parts as long as the expressions "immediately" or "directly" are not used.

[0023] Spatially relative terms such as "below," "beneath," "lower," "above," and "upper" may be used to easily describe the relationship of one element or component to another element or component as illustrated in the drawings. Spatially relative terms should be understood to encompass different orientations of elements in use or operation in addition to the orientation depicted in the drawings. For example, if an element depicted in the drawings is turned over, an element described as "below" or "beneath" another element may be positioned "above" the other element. Thus, the exemplary term "below" can encompass both an orientation of below and an orientation of above. Similarly, the exemplary terms "above" or "upper" can encompass both an orientation of above and below.

[0024] When describing a temporal relationship, for example, when the temporal sequence is described using "after," "following," "next," or "before," it can also include cases where the sequence is not consecutive, as long as the expressions "immediately" or "directly" are not used.

[0025] Although terms such as "first," "second," etc. are used to describe various components, these components are not limited by these terms. These terms are used merely 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.

[0026] The term "at least one" should be understood to include all possible combinations of one or more of the 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, respectively, but also all possible combinations of items that can be present from two or more of the first, second, and third items.

[0027] The features of the various embodiments of the present invention may be partially or fully combined or combined with each other, and various technical interlocking and driving mechanisms may be possible, and each embodiment may be implemented independently of the others, or may be implemented together in a related relationship.

[0028] FIG. 1 is a cross-sectional view of a copper foil 110 according to an embodiment of the present invention.

[0029] Referring to Fig. 1, the copper foil 110 of the present invention includes a copper film 111 containing 99.9% or more by weight of copper and a protective layer 112 on the copper film 111. In the copper foil 110 shown in Fig. 1, the protective layer 112 is formed on one side of the copper film 111, but the present invention is not limited thereto. Referring to Fig. 2, the protective layer 112 may be formed on both sides of the copper film 111.

[0030] The copper film 111 can be formed on the rotating cathode drum through electroplating, and has a shiny surface that directly contacts the rotating cathode drum during the electroplating process and a matte surface on the opposite side.

[0031] The protective layer 112 is formed by electrodepositing an anticorrosion material on the copper film 111. The anticorrosion 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 heat resistance, thereby extending the lifespan of the copper foil 110 itself as well as the lifespan of the final product including the copper foil 110.

[0032] According to one embodiment of the present invention, the copper foil 110 has an R value in the range of 2.0 to 3.5. The R value can be obtained by measuring and calculating WA, WB, tA, and tB, respectively, and calculating the measured and calculated values ​​of WA, WB, tA, and tB using the following Equation 1:

[0033] [Formula 1]

[0034] R = log(WA / WB) / log(tA / tB)

[0035] In the above formula 1, tA means the thickness of the test piece before the tensile test, and tB in the above formula 1 means the thickness of the test piece after the tensile test.

[0036] The WA and WB can be calculated using the following Equations 2 and 3. First, copper foil 110 is cut in three directions (0°, 45°, and 90°) in the MD direction, and an axial tensile test is performed on each cut copper foil at a UTM tensile test speed of 5 mm / min. The tensile test is performed using a universal testing machine (UTM) until the cut copper foil grows 15% after tension compared to before tension. The widths of the central portion in the tensile direction of the cut copper foil before and after the tensile test can then be measured to calculate XA0, XA45, XA90, XB0, XB45, and XB90 using the following Equations 2 and 3.

[0037] [Formula 2]

[0038] WA=[XA0+(XA45) × 2+XA90] / 4

[0039] [Formula 3]

[0040] WB=[XB0+(XB45) × 2+XB90] / 4

[0041] In the above formula 2, XA0, XA45, and XA90 mean the width of the center of the tensile direction of the test specimens taken in the 0°, 45°, and 90° directions before tensioning.

[0042] In the formula 3, XB0, XB45, and XB90 mean the width of the center of the tensile direction after tensioning the test specimens taken in the 0°, 45°, and 90° directions.

[0043] According to one embodiment of the present invention, the copper foil 110 may have an R value in the range of 2.0 to 3.5.

[0044] If the R value of the copper foil 110 is less than 2.0, the change in thickness of the copper foil 110 is large compared to the change in width of the copper foil 110, which may cause wrinkles or ruptures during the manufacturing process of the copper foil 110, thereby reducing workability and increasing the defect rate of secondary batteries.

[0045] On the other hand, if the R value of the copper foil 110 exceeds 3.5, the variation in width of the copper foil 110 is large compared to the variation in thickness of the copper foil 110, which may cause wrinkles or ruptures during the manufacturing process of the copper foil 110, thereby reducing workability and increasing the defective rate of secondary batteries.

[0046] The copper foil 110 according to an embodiment of the present invention may have a thickness of 4 to 35 μm. When the copper foil 110 is used as a current collector of an electrode in a secondary battery, a thinner copper foil 110 is advantageous for increasing the capacity of the secondary battery because more current collectors can be accommodated in the same space. However, manufacturing a copper foil 110 with a thickness of less than 4 μm reduces workability.

[0047] On the other hand, when a secondary battery is manufactured using a copper foil 110 having a thickness exceeding 35 μm, it becomes difficult to realize a high capacity due to the thick copper foil 110 .

[0048] The copper foil 110 according to an embodiment of the present invention has a thickness of 45 kg / mm 2 In order to prevent the copper foil 110 from wrinkling and bursting, the copper foil 110 of the present invention has a tensile strength of 45 kg / mm 2 The copper foil 110 has a high tensile strength of 45 kg / mm ​​or more. 2 If it is less than this, the copper foil 110 may be folded between two adjacent rolls during the roll-to-roll manufacturing process, or wrinkles may be formed at the left and right edges of the copper foil 110 during the roll-to-roll manufacturing process.

[0049] The copper foil 110 according to an embodiment of the present invention may have an elongation ratio of 3 to 13%.

[0050] If the elongation rate of the copper foil 110 is less than 3%, when the copper foil 110 is used as a current collector of a secondary battery, the copper foil 110 does not stretch sufficiently to accommodate the large volume expansion of the high-capacity active material, and there is a high risk of the copper foil 110 bursting.

[0051] On the other hand, if the elongation rate of the copper foil 110 exceeds 13%, the copper foil 110 may easily elongate during the process of manufacturing an electrode for a secondary battery, which may cause deformation of the electrode.

[0052] According to an embodiment of the present invention, the copper foil 110 may have a ten-point average roughness (Rz) of 0.7 to 0.9 μm.

[0053] As the secondary battery is repeatedly charged and discharged, the active material layer alternately contracts and expands, which causes separation between the active material layer and the copper foil 110, reducing the charge and discharge efficiency of the secondary battery. Therefore, in order for the secondary electrode to maintain a certain level of capacity retention and lifespan (i.e., to prevent a reduction in the charge and discharge efficiency of the secondary battery), the copper foil 110 must have excellent coating properties on the active material, thereby ensuring high adhesive strength between the copper foil 110 and the active material layer.

[0054] Specifically, the smaller the ten-point average roughness (Rz) of the copper foil 110, the less the charge / discharge efficiency of a secondary battery including the copper foil 110 tends to decrease. Therefore, according to one embodiment of the present invention, the copper foil 110 has a ten-point average roughness (Rz) of 0.7 to 0.9 μm.

[0055] If the ten-point average roughness (Rz) of the copper foil 110 is less than 0.7, the surface area of ​​the copper foil 110 is relatively small, so the active material is easily detached from the copper foil 110, resulting in a rapid decrease in the lifespan of the secondary battery due to repeated charging and discharging.

[0056] On the other hand, if the ten-point average roughness (Rz) of the copper foil 110 exceeds 0.9, the contact uniformity between the copper foil 110 and the active material layer does not reach a certain level, resulting in numerous spaces between the copper foil 110 and the active material layer (i.e., the coating itself is not completely formed), which results in a rapid decrease in the lifespan of the secondary battery due to repeated charging and discharging.

[0057] The electrode 100 including the copper foil 110 of the present invention and the secondary battery including this electrode 100 will be specifically described below.

[0058] FIG. 3 is a cross-sectional view of an electrode for a secondary battery according to one embodiment of the present invention.

[0059] As illustrated in FIG. 3, a secondary battery electrode 100 according to an embodiment of the present invention includes a copper foil 110 and an active material layer 120 according to any one of the above-described embodiments of the present invention.

[0060] 3 illustrates a configuration in which the active material layer 120 is formed on one side of the copper foil 110. However, the present invention is not limited thereto, and as shown in FIG. 4, the active material layer 120 may be formed on both sides of the copper foil 110.

[0061] In a lithium secondary battery, aluminum foil is generally used as a positive electrode current collector combined with a positive electrode active material, and copper foil 110 is generally used as a negative electrode current collector combined with a negative electrode active material.

[0062] According to one embodiment of the present invention, the secondary battery electrode 100 is a negative electrode, the copper foil 110 is used as a negative electrode current collector, and the active material layer 120 includes a negative electrode active material.

[0063] To ensure high capacity of the secondary battery, the active material layer 120 of the present invention may be formed of a composite of carbon and metal, for example, the metal may include at least one of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni, and Fe, preferably Si and / or Sn.

[0064] FIG. 5 is a schematic cross-sectional view of a secondary battery according to an embodiment of the present invention.

[0065] 5, 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 from the anode 340. Here, the ions that move between the cathode 370 and the anode 340 are, for example, lithium ions. The separator 360 separates the cathode 370 from the anode 340 to prevent charges generated at one electrode from moving to the other electrode through the interior of the secondary battery 105 and being wasted. Referring to FIG. 5, the separator 360 is disposed within the electrolyte 350.

[0066] The positive electrode 370 includes a positive electrode current collector 371 and a positive electrode active material layer 372, and the positive electrode current collector 371 may be aluminum foil.

[0067] The negative electrode 340 includes a negative electrode current collector 341 and a negative electrode active material layer 342, and the negative electrode current collector 341 may be made of copper foil 110.

[0068] According to one embodiment of the present invention, the copper foil 110 shown in FIG. 1 or 2 may be used as the negative electrode current collector 341. Also, the secondary battery electrode 100 shown in FIG. 3 or 4 may be used as the negative electrode 340 of the secondary battery shown in FIG. 5.

[0069] Hereinafter, a method for manufacturing the copper foil 110 of the present invention will be described in detail with reference to FIG.

[0070] The method for manufacturing the copper foil 110 of the present invention includes the steps of forming a copper film 111 and forming a protective layer 112 on the copper film 111 .

[0071] The method of the present invention includes a step of forming a copper film 111 on a rotating cathode drum 40 by passing an electric current through a positive electrode plate 30 and a rotating cathode drum 40 that are arranged spaced apart from each other in an electrolyte 20 in an electrolytic cell 10.

[0072] As illustrated in FIG. 6, the positive electrode plate 30 can include first and second positive electrode plates 31, 32 that are electrically insulated from each other.

[0073] The copper film 111 formation step can be performed by forming a seed layer by passing current between the first positive electrode plate 31 and the rotating cathode drum 40, and then growing the seed layer by passing current between the second positive electrode plate 32 and the rotating cathode drum 40.

[0074] The current density provided by the first and second positive electrode plates 31, 32, respectively, may be 30 to 130 ASD.

[0075] If the current density provided by each of the first and second positive electrode plates 31, 32 is less than 30 ASD, the surface roughness of the copper foil 110 is low, and the adhesive strength between the copper foil 110 and the active material layer 120 may not be sufficient.

[0076] On the other hand, if the current density provided by each of the first and second positive electrode plates 31 and 32 exceeds 130 ASD, the surface of the copper foil 110 may be rough, making it difficult to coat the active material smoothly.

[0077] The surface characteristics of the copper film 111 may vary depending on the degree of buffing or polishing of the surface of the rotating cathode drum 40. For example, the surface of the rotating cathode drum 40 may be polished with an abrasive brush having a grit size of #800 to #3000.

[0078] During the formation of the copper film 111, the electrolyte 20 is maintained at a temperature of 48 to 60° C. More specifically, the temperature of the electrolyte 20 may be maintained at 50° C. or higher. At this time, the physical, chemical, and electrical properties of the copper film 111 may be controlled by adjusting the composition of the electrolyte 20.

[0079] According to one embodiment of the present invention, the electrolyte 20 contains 70-100 g / L of copper ions, 70-150 g / L of sulfuric acid, 15-25 ppm of chlorine (Cl), 1-10 ml / L of hydrogen peroxide (H2O2) and organic additives.

[0080] In order to ensure smooth formation of copper film 111 by electrodeposition of copper, the concentrations of copper ions and sulfuric acid in electrolytic solution 20 are adjusted to 70 to 100 g / L and 70 to 150 g / L, respectively.

[0081] In one embodiment of the present invention, chlorine (Cl) is a chloride ion (Cl - ) and all chlorine atoms present in the molecule. Chlorine (Cl) can be used to remove silver (Ag) ions that flow 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). Such silver chloride (AgCl) can be removed by filtration.

[0082] If the chlorine (Cl) concentration is less than 15 ppm, silver (Ag) ions are not removed smoothly. On the other hand, if the chlorine (Cl) concentration exceeds 25 ppm, unwanted reactions may occur due to the excess chlorine (Cl). Therefore, the chlorine (Cl) concentration in the electrolyte 20 is controlled within the range of 15 to 25 ppm.

[0083] According to one embodiment of the present invention, the electrolyte solution 20 containing the organic additives contains lead ions (Pb 2+ Specifically, the electrolyte 20 may further contain 1 to 100 ppm of lead ions (Pb 2+ ) can contain lead ions (Pb 2+ ) is maintained in the range of 1 to 100 ppm, the R value according to the present invention can be maintained in the range of 2.0 to 3.5.

[0084] On the other hand, lead ions (Pb 2+ If the concentration of ) is less than 1 ppm, the effect of maintaining the physical properties of the present invention may be reduced, and as a result, the R value may fall outside the range of 2.0 to 3.5.

[0085] In addition, lead ions (Pb 2+ If the concentration of ) exceeds 100 ppm, copper will be deposited unevenly, which may cause a sudden change in the thickness and width of the copper foil before and after the tensile test, resulting in a problem where the R value falls outside the range of 2.0 to 3.5.

[0086] According to an embodiment of the present invention, the organic additive-containing electrolyte 20 may further contain tungsten (W). Specifically, the electrolyte 20 may contain 0.3 to 5 ppm of tungsten (W). When the tungsten (W) content is maintained at 0.3 to 5 ppm, the R value according to the present invention may be maintained in the range of 2.0 to 3.5.

[0087] On the other hand, if the tungsten (W) concentration is less than 0.3 ppm, the average crystalline particle size of the copper film 111 will not be constant, which may result in a sudden change in the thickness and width of the copper foil before and after the tensile test, resulting in a problem where the R value falls outside the range of 2.0 to 3.5.

[0088] In addition, if the tungsten (W) concentration exceeds 5 ppm, the amount of impurities increases, which can cause a sudden change in the thickness and width of the copper foil before and after the tensile test, resulting in a problem where the R value falls outside the range of 2.0 to 3.5.

[0089] According to one embodiment of the present invention, the organic additive-containing electrolyte 20 may further contain hydrogen peroxide (H2O2). Organic impurities exist in the electrolyte 20 used for continuous plating due to the organic additives. Treating the electrolyte with hydrogen peroxide (H2O2) decomposes the organic impurities, thereby appropriately adjusting the carbon (C) content within the copper foil. The higher the TOC concentration in the electrolyte 20, the greater the amount of carbon (C) elements that flow into the copper film 111. This increases the total amount of elements that are released from the copper film 111 during heat treatment, resulting in a decrease in the strength of the copper foil 110 after heat treatment.

[0090] The amount of hydrogen peroxide (H2O2) to be added is 1 to 10 ml per L of electrolyte. Specifically, it is preferable to add 2 to 8 ml per L of electrolyte. If the amount of hydrogen peroxide (H2O2) added is less than 1 ml / L, it is meaningless because it has almost no effect on decomposing organic impurities. If the amount of hydrogen peroxide (H2O2) added is more than 10 ml / L, organic impurities are excessively decomposed, and the effects of organic additives such as brighteners, moderators, and labeling agents are also suppressed.

[0091] The organic additives contained in the electrolyte 20 include at least one of a brightener (component A), a moderator (component B), and a labeling agent (component C). The organic additives in the electrolyte 20 have a concentration of 1 to 100 ppm.

[0092] The organic additive may contain two or more of the brightener (component A), the moderator (component B), and the labeling agent (component C), or may contain all three components. Even in such cases, the concentration of the organic additive is 100 ppm or less. When the organic additive contains all of the brightener (component A), the moderator (component B), and the labeling agent (component C), the organic additive may have a concentration of 10 to 100 ppm.

[0093] The brightener (component A) contains sulfonic acid or a metal salt thereof. The brightener (component A) may have a concentration of 1 to 25 ppm in the electrolyte solution 20.

[0094] The brightener (Component A) increases the charge of the electrolyte 20, thereby increasing the copper electrodeposition rate and improving the curl characteristics of the copper foil, thereby enhancing the gloss of the copper foil 110. If the concentration of the brightener (Component A) is less than 1 ppm, the gloss of the copper foil 110 decreases, and surface defects of the copper foil 110 may occur, causing the R-value to fall outside the range of 2.0 to 3.5. If the concentration of the brightener (Component A) exceeds 25 ppm, the roughness of the copper foil 110 may increase, reducing its strength, which may result in abrupt changes in the thickness and width of the copper foil before and after the tensile test, causing the R-value to fall outside the range of 2.0 to 3.5.

[0095] More specifically, the brightener (component A) may have a concentration of 5 to 20 ppm in the electrolytic solution 20.

[0096] The brightener may include, for example, at least one of bis-(3-sulfopropyl)-disulfide disodium salt, 3-mercapto-1-propanesulfonic acid, 3-(N,N-dimethylthiocarbamoyl)-thiopropanesulfonate sodium salt, 3-[(amino-iminomethyl)thio]-1-propanesulfonate sodium salt, o-ethyldithiocarbonate-S-(3-sulfopropyl)-ester sodium salt, 3-(benzothiazolyl-2-mercapto)-propyl-sulfonic acid sodium salt, and ethylenedithiodipropylsulfonic acid sodium salt.

[0097] The moderator (component B) includes a non-ionic water-soluble polymer. The moderator (component B) may have a concentration of 1 to 10 ppm in the electrolyte solution 20.

[0098] The moderator (component B) reduces the copper electrodeposition rate to prevent a rapid increase in roughness and a decrease in strength of the copper foil 110. Such a moderator (component B) is also called a suppressor.

[0099] If the concentration of the moderator (component B) is less than 1 ppm, the roughness of the copper foil 110 may increase sharply, resulting in a decrease in the strength of the copper foil 110. This may result in a sudden change in the thickness and width of the copper foil before and after the tensile test, causing the R value to fall outside the range of 2.0 to 3.5. On the other hand, even if the concentration of the moderator (component B) exceeds 10 ppm, there is almost no change in the physical properties of the copper foil 110, such as the appearance, gloss, roughness, strength, and elongation rate. Therefore, the concentration of the moderator (component B) can be adjusted to the range of 1 to 10 ppm, without increasing the concentration of the moderator (component B) unnecessarily, which would increase manufacturing costs and waste raw materials.

[0100] The moderator (component B) may include at least one non-ionic water-soluble polymer selected from the group consisting of polyethylene glycol (PEG), polypropylene glycol, polyethylene polypropylene copolymer, polyglycerin, polyethylene glycol dimethyl ether, hydroxyethylene cellulose, polyvinyl alcohol, stearic acid polyglycol ether, and stearyl alcohol polyglycol ether. However, the type of moderator is not limited thereto, and other non-ionic water-soluble polymers that can be used in manufacturing the high-strength copper foil 110 may be used as the moderator.

[0101] The labeling agent (component C) contains at least one of nitrogen (N) and sulfur (S). That is, the labeling agent (component C) can contain one or more nitrogen atoms (N) or one or more sulfur atoms (S) in one molecule, or it may contain one or more nitrogen atoms (N) and one or more sulfur atoms (S). For example, the labeling agent (component C) is an organic compound containing at least one of nitrogen (N) and sulfur (S).

[0102] The labeling agent (component C) prevents excessively high peaks or excessively large protrusions from being formed on the copper film 111, thereby making the copper film 111 macroscopically flat. The labeling agent (component C) may have a concentration of 1 to 10 ppm in the electrolyte solution 11.

[0103] If the concentration of the labeling agent (component C) is less than 1 ppm, the strength of the copper foil 110 decreases, making it difficult to manufacture a high-strength copper foil 110. This can lead to a sudden change in the thickness and width of the copper foil before and after the tensile test, resulting in an R-value outside the range of 2.0 to 3.5. On the other hand, if the concentration of the labeling agent (component C) exceeds 10 ppm, the surface roughness of the copper foil 110 increases excessively, reducing its strength. Pinholes and curls can form on the surface of the copper foil 110, making it difficult to separate the copper foil 110 from the winder (WR) after manufacturing. As a result, a sudden change in the thickness and width of the copper foil before and after the tensile test can occur, resulting in an R-value outside the range of 2.0 to 3.5.

[0104] Examples of the labeling agent (component C) include diethylthiourea, ethylenethiourea, acetylenethiourea, dipropylthiourea, dibutylthiourea, N-trifluoroacetylthiourea, N-ethylthiourea, N-cyanoacetylthiourea, N-allylthiourea, o-tolylthiourea, and N,N'-butylenethiourea. thiourea, thiazolidinethiol, 4-thiazolinethiol, 4-methyl-2-pyrimidinethiol, 2-thiouracil, 3-(benzotriazole-2-mercapto)-propanesulfonic acid, 2-mercaptopyridine, 3(5-mercapto-1H-tetrazole)benzenesulfonate, 2-mercaptobenzothiazole, dimethylpyridine, 2,2'-bipyridine, 4,4'-bipyridine, pyrimidine, The compound may include at least one of pyridazine, pyrimidine, pyrinoline, oxazole, thiazole, 1-methylimidazole, 1-benzylimidazole, 1-methyl-2-methylimidazole, 1-benzyl-2-methylimidazole, 1-ethyl-4-methylimidazole, 1-ethyl-2-ethyl-4-methylol, N-methylpyrrole, N-ethylpyrrole, N-butylpyrrole, N-methylpyrroline, N-ethylpyrroline, N-butylpyrroline, pyrimidine, purine, quinoline, isoquinoline, N-methylcarbazole, N-ethylcarbazole, and N-butylcarbazole.

[0105] When the copper film 111 is formed, the flow rate of the electrolyte 20 supplied into the electrolytic cell 10 is 41 to 45 m / s. 3 / hour.

[0106] The step of forming the copper film 111 may include at least one of a step of filtering the electrolyte solution 20 using activated carbon, a step of filtering the electrolyte solution 20 using diatomaceous earth, and a step of treating the electrolyte solution 20 with ozone (O3).

[0107] Specifically, for filtering the electrolyte 20, the electrolyte 20 is filtered to a depth of 35 to 45 m. 3 That is, during the electroplating for forming the copper film 111, the electrolyte 20 may be circulated at a flow rate of 35 to 45 m / hour to remove solid impurities present in the electrolyte 20. 3 Filtration can be performed at a flow rate of 1000 kJ / hour. Activated carbon or diatomaceous earth can be used.

[0108] To maintain the cleanliness of the electrolyte 20, the electrolyte 20 may be treated with ozone (O3).

[0109] In addition, to ensure the cleanliness of the electrolyte 20, the copper wire that is the raw material for the electrolyte 20 can be washed.

[0110] According to one embodiment of the present invention, the step of preparing the electrolyte 20 may include the steps of heat-treating a copper wire, pickling the heat-treated copper wire, rinsing the pickled copper wire with water, and immersing the rinsed copper wire in sulfuric acid for the electrolyte.

[0111] More specifically, in order to maintain the purity of the electrolyte 20, a high-purity (99.9% or higher) copper wire is heat-treated in an electric furnace at 750°C to 850°C to burn off various organic impurities adhering to the copper wire, and the heat-treated copper wire is pickled using a 10% sulfuric acid solution for 10 to 20 minutes, and the pickled copper wire is then washed using distilled water, thereby producing copper for producing the electrolyte 20. The washed copper wire can be introduced into sulfuric acid for the electrolyte to produce the electrolyte 20.

[0112] According to one embodiment of the present invention, the concentration of total organic carbon (TOC) in the electrolyte 20 is controlled to 50 ppm or less to satisfy the characteristics of the copper foil 110. That is, the electrolyte 20 may have a total organic carbon (TOC) concentration of 50 ppm or less.

[0113] The copper film 111 thus produced can be cleaned in a cleaning bath.

[0114] For example, acid cleaning may be performed to remove impurities, such as resin components or natural oxide, from the surface of the copper film 111, and water cleaning may be performed to remove the acid solution used in the acid cleaning. The cleaning process may be omitted.

[0115] Next, a protective layer 112 is formed on the copper film 111 .

[0116] 6, the method may further include the step of immersing the copper film 111 in an anticorrosion solution 60. When the copper film 111 is immersed in the anticorrosion solution 60, the copper film 111 may be guided by a guide roll 70 disposed in the anticorrosion solution 60.

[0117] As described above, the anticorrosive solution 60 may contain at least one of a chromium compound, a silane compound, and a nitrogen compound. For example, the copper film 111 may be immersed in a 1 to 10 g / L potassium dichromate solution at room temperature for 1 to 30 seconds.

[0118] On the other hand, the protective layer 112 may contain a silane compound obtained by silane treatment, or may contain a nitrogen compound obtained by nitrogen treatment.

[0119] By forming such a protective layer 112, the copper foil 110 is produced.

[0120] The electrode for a secondary battery (i.e., anode) of the present invention can be manufactured by coating one or both sides of the copper foil 110 of the present invention manufactured by the above-mentioned method with one or more negative electrode active materials selected from the group consisting of carbon; metal (Me) of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe; alloys containing the metal (Me); oxides (MeOx) of the metal (Me); and composites of the metal (Me) and carbon.

[0121] For example, 100 parts by weight of carbon for the negative electrode active material is mixed with 1 to 3 parts by weight of styrene butadiene rubber (SBR) and 1 to 3 parts by weight of carboxymethyl cellulose (CMC), and then distilled water is used as a solvent to prepare a slurry. The slurry is then applied to the copper foil 110 with a doctor blade to a thickness of 20 to 60 μm, and the applied slurry is applied at 110 to 130° C. with a pressure of 0.5 to 1.5 ton / cm. 2 Press with a pressure of .

[0122] A secondary battery can be manufactured by utilizing the secondary battery electrode (negative electrode) of the present invention manufactured by the above method, together with a conventional positive electrode, electrolyte, and separator.

[0123] The present invention will be described in detail below through examples and comparative examples. However, the following examples are merely provided to aid in understanding the present invention, and the scope of the present invention is not limited to these examples.

[0124] Examples 1-4 and Comparative Examples 1-7

[0125] Copper foil was produced using a foil-making machine including an electrolytic cell 10, a rotating cathode drum 40 disposed in the electrolytic cell 10, and a positive electrode plate 30 disposed spaced apart from the rotating cathode 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 to 110 g / L, the electrolyte temperature to 55° C., and the current density to 60 ASD.

[0126] In addition, chlorine (Cl) and lead (Pb) contained in the electrolyte 20 2+), the concentration of tungsten (W) and the concentration of the organic additive are as shown in Table 1 below.

[0127] Among the organic additives, bis-(3-sulfopropyl)-disulfide disodium salt (SPS) was used as the brightener (component A), polyethylene glycol (PEG) was used as the moderator (component B), and ethylenethiourea (ETU) was used as the labeling agent (component C).

[0128] A current density of 60 ASD was applied between the rotating cathode drum 40 and the positive electrode plate 30 to produce a copper film 111. Next, the copper film 111 was immersed in an anti-rust solution for about 2 seconds to chromate the surface of the copper film 111 and form a protective layer 112, thereby producing a copper foil 110. A chromic acid-based anti-rust solution was used as the anti-rust solution, and the concentration of chromic acid was 5 g / L.

[0129] As a result, copper foils of Examples 1-4 and Comparative Examples 1-7 were produced.

[0130] [Table 1]

[0131] [Table 2]

[0132] For the copper foils of Examples 1-4 and Comparative Examples 1-7 thus prepared, i) WA, ii) WB, iii) tA, iv) tB, v) R value, vi) tensile strength, vii) elongation and viii) Rz value were measured and calculated, and ix) the occurrence of wrinkles / rupture was confirmed.

[0133] i) WA, ii) WB measurement

[0134] The WA and WB of the copper foil 110 are calculated using the following Equations 2 and 3.

[0135] [Formula 2]

[0136] WA=[XA0+(XA45) × 2+XA90] / 4

[0137] [Formula 3]

[0138] WB=[XB0+(XB45) × 2+XB90] / 4

[0139] Copper foil 110 is cut in three directions (0°, 45°, and 90°) from the MD direction, and each cut copper foil is subjected to an axial tensile test at a UTM tensile test speed of 5 mm / min. The tensile test is performed until the cut copper foil grows 15% after tension compared to before tension. The widths of the central portion in the tension direction of the cut copper foil before and after the tensile test are measured, and XA0, XA45, XA90, XB0, XB45, and XB90 can be calculated using the following Equations 2 and 3.

[0140] In this regard, XA0, XA45, and XA90 in the formula 2 refer to the widths of the center of the tensile direction of the test specimens taken at 0°, 45°, and 90° directions before tensioning, and XB0, XB45, and XB90 in the formula 3 refer to the widths of the center of the tensile direction of the test specimens taken at 0°, 45°, and 90° directions after tensioning.

[0141] iii) tA, iv) tB measurement

[0142] tA is the measured thickness of the test piece before the tensile test, and tB is the measured thickness of the test piece after the tensile test.

[0143] At this time, the tensile test was carried out using a universal testing machine (UTM).

[0144] v)R calculation

[0145] The R value can be obtained by calculating the measured i) WA, ii) WB, iii) tA and iv) tB values ​​using the following formula 1.

[0146] [Formula 1]

[0147] R = log(WA / WB) / log(tA / tB)

[0148] vi) Tensile strength measurement

[0149] The tensile strength is measured using a universal testing machine (UTM), where the sample width is 12.7 mm, the grip distance is 50 mm, and the test speed is 50 mm / min.

[0150] vii) Stretching ratio measurement

[0151] The elongation rate was measured using a universal testing machine (UTM) in accordance with the IPC-TM-650 Test Method Manual. Specifically, the elongation rate was measured using an Instron universal testing machine. The width of the sample for elongation rate measurement was 12.7 mm, the grip distance was 50 mm, and the measurement speed was 50 mm / min.

[0152] viii) 10-point surface roughness (Rz) measurement

[0153] The surface roughness (Rz) of the copper foil was measured at 10 points using a surface roughness measuring instrument (M300, Mahr) in accordance with JIS B 0601-2001 standard.

[0154] ix) Presence or absence of wrinkles / bursts

[0155] After 100 charge / discharge cycles, the secondary battery was disassembled and observed for wrinkles or ruptures in the copper foil. If wrinkles or ruptures occurred in the copper foil, it was marked as "occurred," and if not, it was marked as "none."

[0156] Referring to Tables 1 and 2, the following results can be seen.

[0157] Contains excessive amounts of brightener (component A) and lead ions (Pb 2+The copper foil of Comparative Example 1, which was manufactured using an electrolyte containing trace amounts of tungsten (W) and copper foil containing copper (Cu), experienced bursting / wrinkling.

[0158] Contains excessive amounts of moderator (component B) and lead ions (Pb 2+ The copper foil of Comparative Example 2, which was manufactured using an electrolyte containing trace amounts of tungsten (W) and copper foil containing copper (Cu), experienced rupture / wrinkling.

[0159] Contains excessive amounts of labeling agent (component C) and lead ions (Pb 2+ The copper foil of Comparative Example 3, which was manufactured using an electrolyte containing trace amounts of tungsten (W) and copper foil containing copper (Cu), experienced rupture / wrinkling.

[0160] Contains a small amount of brightener (component A) and lead ions (Pb 2+ The copper foil of Comparative Example 4, which was manufactured using an electrolyte containing excessive amounts of tungsten (W) and hydrogen peroxide, experienced rupture / wrinkling.

[0161] It contains a small amount of moderator (component B) and contains lead ions (Pb 2+ ), and the copper foil of Comparative Example 5, which was manufactured using an electrolyte containing an excessive amount of tungsten (W) and a trace amount of hydrogen peroxide, experienced rupture / wrinkling.

[0162] Contains trace amounts of labeling agent (component C) and lead ions (Pb 2+ The copper foil of Comparative Example 6, which was manufactured using an electrolyte containing excessive amounts of tungsten (W) and copper foil of Comparative Example 6, experienced rupture / wrinkling.

[0163] The copper foil of Comparative Example 7, which was manufactured using an electrolyte containing trace amounts of brightener (component A) and tungsten (W) and excessive amounts of moderator (component B) and labeling agent (component C), experienced rupture / wrinkling.

[0164] The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it will be apparent to those skilled in the art that various substitutions, modifications, and changes can be made without departing from the scope of the present invention. Therefore, the scope of the present invention is expressed by the following claims, and all modifications and variations derived from the meaning, scope, and equivalents of the claims should be construed as being included in the scope of the present invention. [Explanation of symbols]

[0165] 100: Electrode for secondary batteries 110: Copper foil 111: Copper film 120: Active material layer 10: Electrolytic cell 20: Electrolyte

Claims

1. A copper film containing 99.9% by weight or more of copper, A copper foil having an R value in the range of 2.0 to 3.5, The copper foil is used as a current collector of a secondary battery, The R is calculated by the following formula 1: [Formula 1] R=log(WA / WB) / log(tA / tB) WA in the above formula 1 is calculated by the following formula 2: [Formula 2] WA=[XA0+(XA45)×2+XA90] / 4 The WB in Equation 1 is calculated using Equation 3 below: [Formula 3] WB=XB0+(XB45)×2+XB90] / 4 tA in Equation 1 means the thickness of the test piece before the tensile test, tB in Equation 1 means the thickness of the test piece after the tensile test, In the formula 2, XA0, XA45, and XA90 mean the widths of the central part of the tensile direction of the test specimens taken in the 0°, 45°, and 90° directions before tensioning, In the formula 3, XB0, XB45, and XB90 mean the width of the center of the tensile direction after tensioning the test piece taken in the 0°, 45°, and 90° directions.

2. 45 kgf / mm ２ The copper foil according to claim 1, having a tensile strength of at least 1000 kJ / cm2.

3. The copper foil of claim 1 having an elongation of 3 to 13%.

4. The copper foil of claim 1, having a 10-point average roughness (Rz) of 0.7 to 0.9 μm.

5. The copper foil of claim 1 further comprising a protective layer on said copper film.

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

7. preparing an electrolyte solution containing copper ions; forming a copper film; and forming a protective layer on the copper film; The copper foil is used as a current collector of a secondary battery, The step of forming the copper layer includes: forming a copper film on a rotating cathode drum by passing current through a positive electrode plate and a rotating cathode drum that are spaced apart from each other in an electrolyte solution in an electrolytic cell; The electrolyte solution is 70-100 g / L copper ions; 70-150 g / L sulfuric acid; 15-25 ppm chlorine (Cl); 1 to 100 ppm lead ions (Pb ２＋ ); 0.3 to 5 ppm tungsten (W); 1-10 ml / L hydrogen peroxide; and organic additives; The organic additives include a brightener (component A), a moderator (component B), and a labeling agent (component C); The brightener (component A) contains a sulfonic acid or a metal salt thereof, The moderator (component B) contains a nonionic water-soluble polymer, The method for producing copper foil, wherein the labeling agent (component C) contains at least one of nitrogen (N) and sulfur (S).

8. The method for producing copper foil according to claim 7, wherein the brightener (component A) has a content of 1 to 25 ppm.

9. The method for producing copper foil according to claim 7, wherein the moderator (component B) has a content of 1 to 10 ppm.

10. The method for producing copper foil according to claim 7, wherein the labeling agent (component C) has a content of 1 to 10 ppm.

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