Copper foil capable of preventing tearing or wrinkling defects, electrode comprising same, secondary battery comprising same, and method for manufacturing same

Abstract

Provided in one embodiment of the present invention is a copper foil comprising a copper film comprising 99.9 wt% or more of copper, in which the copper film has an A value of 1.1 to 1.6. A is calculated by the following relational expression 1: [relational expression 1] A = P / Q, in relational expression 1, P is the peak intensity of the copper film at 1650 cm-1, and in relational expression 1, Q is the peak intensity of the copper film at 1460 cm-1, the peak intensity being measured by FT-IR. Provided in one embodiment of the present invention are a copper foil and a method of manufacturing the same, the copper foil comprising a copper film comprising 99.9% or more by weight of copper and having a first stress coefficient of 2.8 to 3.2, a second stress coefficient of 2.5 to 3.0, and a third stress coefficient of 3.5 to 4.5. The first stress coefficient is calculated by a relational expression 2: first stress coefficient = A / A '+ B / B' + C / C '. The second stress coefficient is calculated by a relational expression 3, wherein the relational expression 3 is that the second stress coefficient is equal to A / B + A ' / B'. The third stress coefficient is calculated through a relational expression 4; [relational expression 4] third stress coefficient = A / C + A ' / C', A in relational expression 2 being the stress at 50% elongation in MD, A 'in relational expression 2 being the stress at 50% elongation in TD, B in relational expression 2 being the stress at 10% elongation in MD, B' in relational expression 2 being the stress at 10% elongation in TD, C in relational expression 2 being the stress at 5% elongation in MD, and C in relational expression 2 being the stress at 5% elongation in MD. And C'in relational expression 2 is the stress at 5% elongation in TD, and in another embodiment of the present invention, an electrode including the copper foil, and a secondary battery including the same are provided.

Description

Technical Field

[0001] The present disclosure relates to a copper foil capable of preventing tearing or wrinkling defects of a copper foil, an electrode including the copper foil, a secondary battery including the copper foil, and a method of 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 an energy source 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 having 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 and communication devices where portability and mobility are important, lithium secondary batteries are preferred, and their application scope has also expanded to energy storage devices for hybrid vehicles and electric vehicles.

[0005] Lithium secondary batteries are reused in one charge and discharge cycle. 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 increase the operating time of the device. Therefore, in order to meet the growing expectations (needs) of consumers regarding the charge / discharge capacity of lithium secondary batteries, continuous research is required.

[0006] Such secondary batteries include an anode current collector made of a copper foil, and among copper foils, electrolytic copper foils are widely used as the anode current collector of secondary batteries. As the demand for secondary batteries increases, as the demand for high-capacity, high-efficiency, and high-quality secondary batteries increases, electrolytic copper foils that can improve the characteristics of secondary batteries are required. In particular, electrolytic copper foils that can ensure high capacity and stable capacity retention of secondary batteries are required.

[0007] As the thickness of the electrolytic copper foil used as the anode current collector of a secondary battery decreases, the amount of active material that can be included increases. However, when the thickness of the copper foil decreases, the strength of the copper foil decreases accordingly, so it is not easy to handle and the possibility of rupture increases. Therefore, in the case of ultra-thin, the tensile strength property becomes more important. In addition, in the case of metal-based and composite-based active materials that have recently attracted attention in high-capacity applications, serious volume expansion may occur, and therefore, high-strength electrolytic copper foils that can cope with this situation are required.

[0008] Meanwhile, as the copper foil becomes thinner, 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, so the capacity of the secondary battery can be increased. However, as the copper foil becomes thinner, curling occurs. Therefore, when winding the copper foil, defects such as tearing or wrinkling occur in the copper foil due to the curling at the edges, so it is difficult to manufacture a copper foil in the form of an extremely thin film. Therefore, in order to manufacture a copper foil with an extremely thin thickness, the curling of the copper foil should be prevented. Summary of the Invention Technical Objectives

[0009] Accordingly, the present disclosure relates to a copper foil capable of preventing problems caused by the limitations and disadvantages of the above 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 high strength properties by having an A value in the range of 1.1 to 1.6.

[0011] According to an embodiment of the present disclosure, there is provided a copper foil that does not curl, wrinkle, or tear during the manufacturing process by having an A value in the range of 1.1 to 1.6.

[0012] According to an embodiment of the present disclosure, there is provided a copper foil that does not wrinkle or tear by having a first stress factor value in the range of 2.8 to 3.2.

[0013] According to an embodiment of the present disclosure, there is provided a copper foil that does not wrinkle or tear by having a second stress factor value in the range of 2.5 to 3.0.

[0014] According to an embodiment of the present disclosure, there is provided a copper foil that does not wrinkle or tear by having a third stress factor value in the range of 3.5 to 4.5.

[0015] According to another embodiment of the present disclosure, there is provided an electrode for a secondary battery including a copper foil, and a secondary battery including the electrode for the secondary battery.

[0016] According to still another embodiment of the present disclosure, there is provided a method for manufacturing a copper foil in which the occurrence of curling, wrinkling, or tearing is prevented.

[0017] 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, or can be clearly understood by those skilled in the art from such a description. Technical Solutions

[0018] According to an embodiment of the present disclosure, a copper foil is provided, which includes a copper film, and the copper film includes copper with a weight percentage of 99.9% (99.9 wt%) or more. Among them, the copper film has an A value in the range of 1.1 to 1.6. "A" is calculated by the following Equation 1: [Equation 1] A = P / Q, where "P" in Equation 1 is the peak intensity at 1650 cm -1 of the copper film, and "Q" in Equation 1 is the peak intensity at 1460 cm -1 of the copper film, and the peak intensity is measured by Fourier transform infrared spectroscopy (FT-IR).

[0019] According to an embodiment of the present disclosure, a copper foil is provided, which includes a copper film, and the copper film includes copper with a weight percentage of 99.9% or more. Among them, the copper foil has a first stress factor in the range of 2.8 to 3.2, a second stress factor in the range of 2.5 to 3.0, and a third stress factor in the range of 3.5 to 4.5. The first stress factor is calculated by Equation 1: [Equation 1] First stress factor = A / A’ + B / B’ + C / C’, the second stress factor is calculated by Equation 2: [Equation 2] Second stress factor = A / B + A’ / B’, and the third stress factor is calculated by the following Equation 3: [Formula 3] Third stress factor = A / C + A’ / C’, where A in Equation 1 is the stress when the elongation in the machine direction (MD direction) is 50%, A’ in Equation 1 is the stress when the elongation in the transverse direction (TD direction) is 50%, B in Equation 1 is the stress when the elongation in the MD direction is 10%, B’ in Equation 1 is the stress when the elongation in the TD direction is 10%, C in Equation 1 is the stress when the elongation in the MD direction is 5%, and C’ in Equation 1 is the stress when the elongation in the TD direction is 5%.

[0020] 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. The formation of the copper film includes forming a copper film on a rotating anode drum by electrically connecting a cathode plate and the rotating anode drum, and the cathode plate and the rotating anode drum are arranged at intervals in the electrolyte of the electrolytic cell. Among them, 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, nickel (Ni) with a concentration of 15 ppm to 150 ppm, and lead ions (Pb with a concentration of 1 ppm to 20 ppm 2+) Hydrogen peroxide with a concentration of 1 ml / L to 10 ml / L, tungsten (W) with a concentration of 0.3 ppm to 5 ppm, and an organic additive, wherein the organic additive includes at least one of a moderator (component B), a leveling agent (component C), and an improver (component D), wherein the polishing agent (component A) includes a sulfonic acid or a metal salt thereof, the moderator (component B) includes a non-ionic water-soluble polymer, the leveling agent (component C) includes at least one of nitrogen (N) and sulfur (S), and the improver (component D) includes citric acid.

[0021] According to another embodiment of the present disclosure, an electrode for a secondary battery is provided, the electrode including a copper foil and an active material layer provided on at least one surface of the copper foil.

[0022] According to another embodiment of the present disclosure, a secondary battery is provided, including a cathode configured to provide lithium ions during charging, an anode 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

[0023] According to the present disclosure, a high-strength copper foil can be manufactured, wherein wrinkles or tears can be prevented during the manufacturing process, and the high-strength 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 productivity of the intermediate components and final products. Description of the drawings

[0024] Figure 1 is a cross-sectional view of a copper foil according to an embodiment of the present disclosure.

[0025] Figure 2 is a cross-sectional view of a copper foil according to another embodiment of the present disclosure.

[0026] Figure 3 is a cross-sectional view of an electrode for a secondary battery according to another embodiment of the present disclosure.

[0027] Figure 4 is a cross-sectional view of an electrode for a secondary battery according to another embodiment of the present disclosure.

[0028] Figure 5 is a schematic cross-sectional view of a secondary battery according to another embodiment of the present disclosure.

[0029] Figure 6 is a device for manufacturing a copper foil according to another embodiment of the present disclosure.

[0030] Figure 7 is a schematic diagram for explaining MD and TD. Detailed Embodiments

[0031] In the following, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, the embodiments described below are for illustrative purposes only to facilitate a clear understanding of the present disclosure and do not limit the scope of the present disclosure.

[0032] The shapes, sizes, ratios, angles, quantities, etc. disclosed in the accompanying drawings for describing the embodiments of the present disclosure are only illustrative. Therefore, the present disclosure is not limited to the details shown in the accompanying drawings. Throughout this specification, the same components may be denoted by the same reference numerals. When a detailed description of well-known technologies is determined to possibly obscure the gist of the present disclosure unnecessarily, the detailed description of the relevant well-known technologies will be omitted.

[0033] When using terms such as "including", "having", "consisting of", etc. described in this specification, unless the term "only" is used herein, other parts may be added. When a component is expressed in the singular form, it may include the plural form unless otherwise specified. In addition, when interpreting a component, even if not explicitly stated, it is still interpreted as including an error range.

[0034] When describing positional relationships, 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 may be located between these two parts.

[0035] To facilitate the description of the relationship between one element or component and another element or component as shown in the accompanying drawings, spatial relative terms such as "below", "beneath", "lower", "above", "upper", etc. may be used herein. It should be understood that, in addition to the orientations shown in the accompanying drawings, spatial relative terms are intended to include different orientations of the element in use or operation. For example, when the element in the accompanying 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.

[0036] When describing temporal relationships, for example, when the temporal relationship is described as "after", "subsequent", "then", "before", etc., unless "immediately" or "directly" is used, non - consecutive cases may also be included.

[0037] 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 may be the second component.

[0038] The term "at least one" should be understood to include all possible combinations of one or more related items. For example, "at least one of the first, second, and third items" can mean all combinations of two or more of the first, second, and third items as well as each of the first, second, and third items.

[0039] The features of the various embodiments of the present disclosure can be coupled or combined with each other in part or in whole, and can be linked or operated in various technologies, and each embodiment can be implemented independently of each other or can be implemented together in a related relationship.

[0040] Figure 1 is a cross-sectional view of a copper foil 110 according to an embodiment of the present disclosure.

[0041] Referring to Figure 1 , the copper foil 110 of the present disclosure includes a copper film 111 containing 99.9% or more copper by weight percentage and a protective layer 112 formed on the copper film 111. In Figure 1 In the copper foil 110 shown, the protective layer 112 is formed on one surface of the copper film 111, but the embodiments of the present disclosure are not limited thereto. Referring to Figure 2 , the protective layer 112 can be formed on each of the two surfaces of the copper film 111.

[0042] The copper film 111 can be formed on a rotating anode drum by electroplating, and has a shiny surface that is in direct contact with the rotating anode drum during the electroplating process and a matte surface opposite to the shiny surface.

[0043] The protective layer 112 is formed by electrodepositing an anti-corrosion material on the copper film 111. The anti-corrosion material can 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 increasing the lifespan of the final product including the copper foil 110 as well as the lifespan of the copper foil 110 itself.

[0044] According to an embodiment of the present disclosure, the copper film 111 has an A value in the range of 1.1 to 1.6. The A value can be obtained by measuring and calculating each of "P" and "Q" and calculating the values of the measured and calculated "P" and "Q" according to the following Equation 1.

[0045] [Equation 1]

[0046] A = P / Q

[0047] "P" in Equation 1 refers to the peak intensity at 1650 cm -1 of the copper film 111, and "Q" in Equation 1 refers to 1460 cm of the copper film 111 -1The peak intensity at this position. In this case, the peak intensity is measured by Fourier transform infrared spectroscopy (FT-IR).

[0048] 1650 cm -1 The peak intensity at this position refers to the intensity caused by the stretching vibration of C=O in the copper film 111, and the peak intensity at 1460 cm -1 refers to the intensity caused by the bending vibration of C-H in the copper film 111.

[0049] According to an embodiment of the present disclosure, the copper film 111 may have an A value in the range of 1.1 to 1.6.

[0050] When the A value of the copper film 111 is less than 1.1, the P value (the peak intensity at 1650 cm -1 of the copper film 111) is relatively small compared to the Q value (the peak intensity at 1460 cm -1 of the copper film 111), and when the P value (the peak intensity at 1650 cm -1 is small, the proportion of C=O bonds in the copper film 111 may be small. The C=O bonds in the copper film 111 are functional groups capable of achieving hydrogen bonding. Therefore, when the proportion of C=O bonds capable of achieving hydrogen bonding is small, it may be difficult to obtain a copper foil with high strength properties due to the small proportion of hydrogen bonds in the copper film 111. In addition, during the roll-to-roll manufacturing process, the copper foil 110 may be folded, or wrinkles may be formed at the lateral ends of the copper foil 110.

[0051] On the other hand, when the A value of the copper film 111 exceeds 1.6, the P value (the peak intensity at 1650 cm -1 of the copper film 111) is very large compared to the Q value (the peak intensity at 1460 cm -1 of the copper film 111), and when the P value (the peak intensity at 1650 cm- 1 is very large, the proportion of C=O bonds in the copper film 111 may be very large. When the proportion of C=O bonds capable of achieving hydrogen bonding in the copper film 111 is very large, there is a risk that the copper foil 110 has a low elongation rate, which may cause the copper foil 110 to rupture during the manufacturing process of final products such as the anode current collector of a secondary battery and a flexible printed circuit board (FPCB).

[0052] Therefore, in order to have high strength properties, the copper film 111 must have an A value in the range of 1.1 to 1.6.

[0053] According to an embodiment of the present disclosure, the copper foil 110 has a first stress factor in the range of 2.8 to 3.2. The first stress factor value can be obtained by measuring each of A, A’, B, B’, C, and C’ and substituting the measured values of A, A’, B, B’, C, and C’ into the following Equation 2.

[0054] [Equation 2]

[0055] First stress factor = A / A’ + B / B’ + C / C’

[0056] A in Equation 2 refers to the stress when the copper foil 110 is elongated by 50% in the machine direction (MD direction), A’ in Equation 2 refers to the stress when the copper foil 110 is elongated by 50% in the transverse direction (TD direction), B in Equation 2 refers to the stress when the copper foil 110 is elongated by 10% in the MD direction, B’ in Equation 2 refers to the stress when the copper foil 110 is elongated by 10% in the TD direction, C in Equation 2 refers to the stress when elongated by 5% in the MD direction, and “C’” in Equation 2 refers to the stress when elongated by 5% in the TD direction. In this case, A, A’, B, B’, C, and C’ are measured using a universal tensile testing machine (UTM).

[0057] Referring to Figure 7 , there are an MD (machine direction or length direction) and a TD (transverse or width direction), and the surface properties between the machine direction and the width direction are different. In the copper foil 110 according to an embodiment of the present disclosure, the difference in surface properties between the MD direction and the TD direction is minimized.

[0058] According to an embodiment of the present disclosure, the copper foil 110 may have a first stress factor value of 2.8 or more.

[0059] When the first stress factor value of the copper foil 110 is less than 2.8, the stress difference between the MD direction and the TD direction may be large when the copper foil 110 is stretched. As a result, wrinkles or tears may occur during the manufacture of the copper foil 110, and pinholes or curling may occur on the surface of the copper foil 110. Therefore, the processability may be reduced, and the defect rate of the secondary battery may increase.

[0060] Therefore, in order to prevent wrinkles or tears from occurring during the manufacturing process of the copper foil 110, the first stress factor value of the copper foil 110 needs to be 2.8 or more.

[0061] According to an embodiment of the present disclosure, the copper foil 110 may have a second stress factor value of 2.5 or more.

[0062] The second stress factor value can be obtained by measuring each of A, A’, B, and B’ and substituting the measured values of A, A’, B, and B’ into the following Equation 3.

[0063] [Equation 3]

[0064] Second stress factor = A / B + A’ / B’.

[0065] When the second stress factor value of the copper foil 110 is less than 2.5, a stress difference may occur in the MD and TD directions of the copper foil 110 at elongation rates of 10% and 50%. As a result, wrinkles or tears may occur during the manufacturing process of the copper foil 110, and pinholes or curling may occur on the surface of the copper foil 110. Therefore, the charge and discharge efficiency of the anode material may be reduced, or the processability may be reduced, thus increasing the defect rate of the secondary battery.

[0066] Therefore, in order to prevent wrinkles or tears from occurring during the manufacturing process of the copper foil 110, the second stress factor value of the copper foil 110 needs to be 2.5 or more.

[0067] According to an embodiment of the present disclosure, the copper foil 110 may have a third stress factor value of 3.5 or more.

[0068] The third stress factor value can be obtained by measuring each of A, A’, C, and C’ and substituting the measured values of A, A’, C, and C’ into the following Equation 4.

[0069] [Equation 4]

[0070] Third stress factor = A / C + A’ / C’.

[0071] When the third stress factor value of the copper foil 110 is less than 3.5, a stress difference may occur in the MD and TD directions of the copper foil 110 at elongation rates of 5% and 10%. As a result, wrinkles or tears may occur during the manufacturing process of the copper foil 110, and pinholes or curling may occur on the surface of the copper foil 110. Therefore, the charge and discharge efficiency of the anode material may be reduced, or the processability may be reduced, thus increasing the defect rate of the secondary battery.

[0072] Therefore, in order to prevent wrinkles or tears from occurring during the manufacturing process of the copper foil 110, the third stress factor value of the copper foil 110 needs to be 3.5 or more.

[0073] According to an embodiment of the present disclosure, the copper foil 110 may have a Vickers hardness in the range of 1.3 Hv to 1.9 Hv.

[0074] When the Vickers hardness of the copper foil is less than 1.3 Hv, during the roll-to-roll manufacturing process, folding of the copper foil 110 may be caused between two adjacent rolls, or wrinkles may occur at the lateral ends of the copper foil 110.

[0075] On the other hand, when the Vickers hardness of the copper foil 110 exceeds 1.9 Hv, there is a risk that the copper foil 110 has a low elongation rate, which may cause the copper foil 110 to break during the manufacturing process of end products such as an anode current collector of a secondary battery, an FPCB, etc. Therefore, the copper foil 110 preferably has a Vickers hardness in the range of 1.5 Hv to 1.7 Hv.

[0076] The copper foil 110 according to an embodiment of the present disclosure may have 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, manufacturing the copper foil 110 with a thickness less than 4 μm causes a reduction in workability.

[0077] On the other hand, when manufacturing a secondary battery using the 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.

[0078] The copper foil 110 according to an embodiment of the present disclosure may have a tensile strength of 45 kg / mm 2 or more. In order to suppress wrinkling and tearing of the copper foil 110, the copper foil 110 of the present disclosure has a high tensile strength of 45 kg / mm 2 or more. When the tensile strength of the copper foil 110 is less than 45 kg / mm 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.

[0079] The copper foil 110 according to an embodiment of the present disclosure may have an elongation rate of 3% to 13%.

[0080] In the case where 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, there is a high risk that the copper foil 110 will be torn because it cannot be sufficiently stretched in response to the large expansion of the volume of the high-capacity active material.

[0081] On the other hand, when the elongation rate of the copper foil 110 exceeds 13%, the copper foil 110 is easily stretched during the process of manufacturing a secondary battery with an electrode, thereby causing deformation in the electrode.

[0082] According to an embodiment of the present disclosure, the copper foil 110 may have a ten-point average roughness (Rz) of 0.7 μm to 0.9 μm.

[0083] When the secondary battery is repeatedly charged and discharged, the active material layer can 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 that the capacity retention rate and life of the secondary battery are above a specific level (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 adhesion strength between the copper foil 110 and the active material layer should be high.

[0084] Specifically, when the ten-point average roughness (Rz) of the copper foil 110 is small, the tendency of the charge and discharge efficiency of the secondary battery including the copper foil 110 to deteriorate is weakened. Therefore, according to an embodiment of the present disclosure, the copper foil 110 has a ten-point average roughness (Rz) of 0.7 μm to 0.9 μm.

[0085] When the ten-point average roughness (Rz) of the copper foil 110 is less than 0.7 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 life of the secondary battery deteriorates rapidly due to repeated charging and discharging.

[0086] On the other hand, when the ten-point average roughness (Rz) of the copper foil 110 exceeds 0.9 μm, since the contact uniformity between the copper foil 110 and the active material layer does not reach a predetermined level (that is, the coating itself is partially performed), there are multiple spaces between the copper foil 110 and the active material layer. As a result, the life of the secondary battery deteriorates rapidly due to repeated charging and discharging.

[0087] 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.

[0088] Figure 3 is a cross-sectional view of an electrode for a secondary battery according to an embodiment of the present disclosure.

[0089] As Figure 3 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.

[0090] Figure 3 shows a structure in which the active material layer 120 is formed on one surface of the copper foil 110. However, an embodiment of the present disclosure is not limited thereto, and referring to Figure 4 , the active material layer 120 may be formed on each of the two surfaces of the copper foil 110.

[0091] Typically, in a lithium secondary battery, an aluminum foil is used as a cathode current collector combined with a cathode active material, while a copper foil 110 is used as an anode current collector combined with an anode active material.

[0092] According to an embodiment of the present disclosure, an electrode 100 for a secondary battery is an anode, a copper foil 110 is used as an anode current collector, and an active material layer 120 includes an anode active material.

[0093] 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.

[0094] Figure 5 is a schematic cross-sectional view of a secondary battery according to an embodiment of the present disclosure.

[0095] Referring to Figure 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 ion-movable environment, and a separator 360 that electrically insulates the cathode 370 and the anode 340. Herein, 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 at one electrode from being unnecessarily consumed by moving through the inside of the secondary battery to the other electrode. Referring to Figure 5 , the separator 360 is disposed in the electrolyte 350.

[0096] The cathode 370 includes a cathode current collector 371 and a cathode active material layer 372, and an aluminum foil may be used as the cathode current collector 371.

[0097] The anode 340 includes an anode current collector 341 and an anode active material layer 342, and a copper foil 110 may be used as the anode current collector 341.

[0098] According to an embodiment of the present disclosure, Figure 1 the copper foil 110 disclosed in or 2 may be used as the anode current collector 341. In addition, Figure 3 the electrode 100 for a secondary battery shown in or 4 may be used as Figure 5 the anode 340 of the secondary battery shown in.

[0099] Hereinafter, a manufacturing method of the copper foil 110 of the present disclosure will be described in detail with reference to Figure 6 .

[0100] 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.

[0101] The method of the present disclosure includes forming a copper film 111 on a rotating anode drum 40 by electrically connecting a cathode plate 30 and the rotating anode drum 40, and the cathode plate and the rotating anode drum are arranged to be spaced apart from each other in an electrolyte 20 of an electrolytic cell 10.

[0102] As Figure 6 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.

[0103] The formation of the copper film 111 can be carried out by forming a seed layer through the electrical connection between the first cathode plate 31 and the rotating anode drum 40, and then growing the seed layer through the electrical connection between the second cathode plate 32 and the rotating anode drum 40.

[0104] The current density provided by each of the first cathode plate 31 and the second cathode plate 32 may be 30 to 130 ASD (A / dm 2 ).

[0105] 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, so the adhesion between the copper foil 110 and the active material layer 120 may be insufficient.

[0106] 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, so the active material may not be coated smoothly.

[0107] The surface characteristics of the copper film 111 can be changed according to the buffing or polishing degree of the surface of the rotating anode drum 40. For example, the surface of the rotating anode drum 40 can be polished using a polishing brush with a grit size of #800 to #3000.

[0108] 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.

[0109] 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, and chlorine with a concentration of 15 ppm to 25 ppm (Cl), nickel (Ni) with a concentration of 15 ppm to 150 ppm, lead ions (Pb 2+ ) with a concentration of 1 ppm to 20 ppm, hydrogen peroxide (H2O2) with a concentration of 1 ml / L to 10 ml / L, tungsten (W) with a concentration of 0.3 ppm to 5 ppm, and an organic additive.

[0110] To facilitate the formation of the copper film 111 by electroplating 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.

[0111] In one 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.

[0112] 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.

[0113] According to one 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), thereby appropriately adjusting 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 causes an increase in the total amount of elements separated from the copper film 111 during heat treatment, thereby causing a decrease in the strength of the copper foil 110 after heat treatment.

[0114] 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 may 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 introduced into the copper film 111 increases, which causes an increase in the total amount of elements detached from the copper film 111 during heat treatment. Therefore, it may not be possible to obtain the desired first to third stress factor values, and as a result, wrinkles or tears may occur, and pinholes or curling may occur on the surface of the copper foil 110.

[0115] Hydrogen peroxide (H2O2) is added in an amount of 1 ml to 10 ml per liter (L) of the electrolyte. Specifically, hydrogen peroxide (H2O2) may be added in an amount of 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 over-decomposed, and thus the effects of organic additives such as a polishing agent, a moderating agent, and a leveling agent are also inhibited.

[0116] Hydrogen peroxide (H2O2) is added in an amount of 1 ml to 10 ml per liter of the electrolyte. Specifically, hydrogen peroxide (H2O2) may be added in an amount of 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 has little effect on the decomposition of organic impurities, so the amount of carbon (C) element introduced into the copper film 111 increases, which causes an increase in the total amount of elements separated from the copper film 111 during heat treatment. Therefore, it may not be possible to obtain the desired first to third stress factor values, and as a result, wrinkles or tears may occur, and pinholes or curling may occur on the surface of the copper foil 110.

[0117] According to an embodiment of the present disclosure, the electrolyte 20 including an organic additive may further include tungsten (W). When the electrolyte 20 is treated with tungsten (W), the average size of the crystal grains included in the copper film 111 can be reduced, and the strength of the copper foil 110 can be improved. The concentration of tungsten (W) in the electrolyte 20 may be in the range of 0.3 ppm to 5 ppm. Specifically, preferably, the concentration of added tungsten (W) is 1 ppm to 4 ppm.

[0118] When the addition amount of tungsten (W) is less than 0.3 ppm, the average crystal grain size of the copper film 111 may not be small enough, and the A value of the copper film 111 becomes less than 1.1. As a result, the strength of the copper foil 110 may be reduced. In addition, during the roll-to-roll manufacturing process, folding of the copper foil 110 may occur, or wrinkles may appear at the lateral ends of the copper foil 110.

[0119] On the other hand, when the addition amount of tungsten (W) exceeds 5 ppm, impurities may increase, and the effect of the organic additive may be inhibited. As a result, the A value of the copper film 111 may fall outside the range of 1.1 to 1.6.

[0120] When the addition amount of tungsten (W) is less than 0.3 ppm, the average crystal grain size of the copper film 111 may not be small enough, and the strength of the copper foil 110 is reduced. In addition, the average crystal grain size of the copper film 111 becomes uneven, so that the desired first to third stress factor values may not be obtained. As a result, wrinkles or tears may occur, and pinholes or curls may appear on the surface of the copper foil 110.

[0121] On the other hand, when the addition amount of tungsten (W) exceeds 5 ppm, impurities may increase, and the effect of the organic additive may be inhibited. In addition, due to the excessive impurities, the stress value of the copper foil 110 may change suddenly. As a result, the desired first to third stress factor values may not be obtained, and thus, wrinkles or tears may occur, and pinholes or curls may appear on the surface of the copper foil 110.

[0122] According to an embodiment of the present disclosure, the electrolyte 20 including the organic additive may further include 1 ppm to 20 ppm of lead ions (Pb 2+ ). The concentration of lead ions (Pb 2+ ) in the electrolyte 20 is controlled to be 1 ppm to 20 ppm. In order to maintain the concentration of lead ions (Pb 2+ ), a material not including lead (Pb) may be used as the raw material input to the electrolyte 20.

[0123] 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. Therefore, the peak intensities at 1460 cm -1 and 1650 cm -1 of the copper film 111 may change, causing the A value of the copper film 111 to fall outside the range of 1.1 to 1.6.

[0124] When the concentration of lead ions (Pb 2+ ) exceeds 20 ppm, the lead ions (Pb 2+ should be removed from the electrolyte 20 by using an ion exchange filter.), and copper precipitates unevenly. Therefore, the peak intensities of the copper film 111 at 1460 cm -1 and 1650 cm -1 may change, causing the A value of the copper film 111 to fall outside the range of 1.1 to 1.6.

[0125] 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. As a result, the desired first to third stress factor values may not be obtained. Therefore, wrinkles or tears may occur, and pinholes or curling may appear on the surface of the copper foil 110.

[0126] When the concentration of lead ions (Pb 2+ ) exceeds 20 ppm, an ion exchange filter should be used to remove lead ions (Pb 2+ ) from the electrolyte 20. Due to the uneven precipitation of copper, wrinkles or tears may occur, and pinholes or curling may appear on the surface of the copper foil 110. In addition, due to the uneven precipitation of copper, the stress value of the copper foil 110 may change suddenly. As a result, the desired first to third stress factor values may not be obtained. Therefore, wrinkles or tears may occur, and pinholes or curling may appear on the surface of the copper foil 110.

[0127] According to an embodiment of the present disclosure, the electrolyte 20 including an organic additive may further include nickel (Ni) at a concentration of 15 ppm to 150 ppm. The concentration of nickel (Ni) in the electrolyte 20 is controlled within the range of 15 ppm to 150 ppm.

[0128] When the concentration of nickel (Ni) exceeds 150 ppm, the A value of the copper film 111 becomes less than 1.1. As a result, the strength of the copper foil 110 decreases, causing difficulties in manufacturing the high-strength copper foil 110.

[0129] On the other hand, when the concentration of nickel (Ni) is less than 15 ppm, the A value of the copper film 111 becomes less than 1.1. As a result, the strength of the copper foil 110 may decrease, and curling may appear on the surface of the copper foil 110.

[0130] When the concentration of nickel (Ni) exceeds 150 ppm, the strength of the copper foil 110 decreases, which may cause difficulties in manufacturing the high-strength copper foil 110. In addition, the stress value of the copper foil 110 may change suddenly. As a result, the desired first to third stress factor values may not be obtained. Therefore, wrinkles or tears may occur, and pinholes or curling may appear on the surface of the copper foil 110.

[0131] On the other hand, when the concentration of nickel (Ni) is less than 15 ppm, the surface roughness of the copper foil 110 may increase excessively, so the strength of the copper foil 110 may decrease, and curling may occur on the surface of the copper foil 110. In addition, the stress value of the copper foil 110 may change suddenly. As a result, the desired first to third stress factor values may not be obtained, and thus, wrinkles or tears may occur, and pinholes or curling may appear on the surface of the copper foil 110.

[0132] The organic additives included in the electrolyte 20 include at least one of a brightener (component A), a suppressor (component B), a leveling agent (component C), and an improver (component D). The concentration of the organic additives in the electrolyte 20 is 1 ppm to 100 ppm.

[0133] The organic additives may include two or more of a brightener (component A), a suppressor (component B), a leveling agent (component C), and an improver (component D), and may include all four components. Even in this case, the concentration of the organic additives is 100 ppm or less. When the organic additives include all of the brightener (component A), the suppressor (component B), the leveling agent (component C), and the improver (component D), the concentration of the organic additives may be 10 ppm to 100 ppm.

[0134] The brightener (component A) includes a sulfonic acid or its metal salt. The concentration of the brightener (component A) in the electrolyte 20 may be 1 ppm to 25 ppm.

[0135] The brightener (component A) can increase the charge amount of the electrolyte 20 to improve the copper electrodeposition rate, can improve the curling characteristics of the copper foil, and can improve the gloss of the copper foil 110.

[0136] When the concentration of the brightener (component A) is less than 1 ppm, the gloss of the copper foil 110 decreases, and when the concentration of the brightener (component A) exceeds 25 ppm, the roughness of the copper foil 110 may increase, and the A value of the copper film 111 becomes less than 1.1. As a result, the strength of the copper foil 110 may decrease, and folding of the copper foil 110 may occur, or wrinkles may appear at the lateral ends of the copper foil 110 during the roll-to-roll manufacturing process.

[0137] The polishing agent (Component A) can increase the charge amount in the electrolyte 20 to improve the copper electrodeposition rate, can improve the curling characteristics of the copper foil, and can improve the gloss of the copper foil 110. When the concentration of the polishing agent (Component A) is lower than 1 ppm, the gloss of the copper foil 110 decreases, and when the concentration of the polishing agent (Component A) exceeds 25 ppm, wrinkles or cracks may appear in the copper foil 110, pinholes or curling may appear on the surface of the copper foil 110, and the stress value of the copper foil 110 may change suddenly. As a result, the desired first to third stress factor values may not be obtained, and thus, wrinkles or tears may appear, and pinholes or curling may appear on the surface of the copper foil 110.

[0138] More specifically, the concentration of the polishing agent (Component A) in the electrolyte 20 can be 5 ppm to 20 ppm.

[0139] The polishing agent can include, for example, at least one selected from 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 sodium ethylenedithiodipropanesulfonate.

[0140] The moderator (Component B) includes a nonionic water-soluble polymer. The concentration of the moderator (Component B) in the electrolyte 20 can be 1 ppm to 15 ppm.

[0141] The moderator (Component B) reduces the copper electrodeposition rate to prevent the rapid increase in the roughness of the copper foil 110 and the decrease in strength. This moderator (Component B) is called an inhibitor or suppressor.

[0142] When the concentration of the moderator (Component B) is less than 1 ppm, the roughness of the copper foil 110 increases rapidly, and the A value of the copper film 111 becomes less than 1.1. As a result, the strength of the copper foil 110 may decrease, and folding of the copper foil 110 may occur, or wrinkles may appear at the lateral ends of the copper foil 110 during the roll-to-roll manufacturing process.

[0143] When the concentration of the leveling agent (Component B) is less than 1 ppm, the roughness of the copper foil 110 rapidly increases, and the strength of the copper foil 110 may decrease. As a result, wrinkles or tears may occur in the copper foil 110, and pinholes or curling may occur on the surface of the copper foil 110. In addition, the stress value of the copper foil 110 may change suddenly. As a result, the desired first to third stress factor values may not be obtained, and thus, wrinkles or tears may occur, and pinholes or curling may occur on the surface of the copper foil 110.

[0144] On the other hand, although the concentration of the leveling agent (Component B) exceeds 15 ppm, the physical properties of the copper foil 110 such as appearance, gloss, roughness, strength, and elongation hardly change. Therefore, the concentration of the leveling agent (Component B) can be adjusted in the range of 1 ppm to 10 ppm without increasing the manufacturing cost and wasting raw materials due to unnecessarily increasing the concentration of the leveling agent (Component B).

[0145] The leveling agent (Component B) may include, for example, at least one nonionic water-soluble polymer selected from polyethylene glycol (PEG), polypropylene glycol, polyethylene-polypropylene copolymer, polyglycerol, dimethyl ethers of polyethylene glycol, hydroxyethyl cellulose, polyvinyl alcohol, polyethylene glycol stearate ether, and polyglycol ether of stearyl alcohol. However, the type of the leveling agent 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 leveling agent.

[0146] The leveling agent (Component C) includes at least one of nitrogen (N) and sulfur (S). That is, the leveling agent (Component C) may contain one or more nitrogen atoms (N) or one or more sulfur atoms (S) in one molecule, and may include one or more nitrogen atoms (N) and one or more sulfur atoms (S). For example, the leveling agent (Component C) is an organic compound including at least one of nitrogen (N) and sulfur (S).

[0147] The leveling agent (Component C) prevents the generation of excessive peaks or large protrusions in the copper film 111 so that the copper film 111 can be planarized macroscopically. The concentration of the leveling agent (Component C) in the electrolyte 20 may be 1 ppm to 15 ppm.

[0148] When the concentration of the leveling agent (Component C) is lower than 1 ppm, the A value of the copper film 111 becomes less than 1.1. As a result, the strength of the copper foil 110 may decrease, and folding of the copper foil 110 may be caused, or wrinkles may occur at the lateral ends of the copper foil 110 during the roll-to-roll manufacturing process.

[0149] On the other hand, when the concentration of the leveling agent (Component C) exceeds 15 ppm, the surface roughness of the copper foil 110 increases excessively, thereby reducing the strength, and pinholes or curls may appear on the surface of the copper foil 110, making it difficult to separate the copper foil 110 from the winding machine WR after manufacturing.

[0150] When the concentration of the leveling agent (Component C) is less than 1 ppm, the strength of the copper foil 110 decreases, which may cause difficulties in manufacturing the high-strength copper foil 110. In addition, the stress value of the copper foil 110 may change suddenly. As a result, the desired first to third stress factor values may not be obtained. Therefore, wrinkles or tears may occur, and pinholes or curls may appear on the surface of the copper foil 110.

[0151] On the other hand, when the concentration of the leveling agent (Component C) exceeds 15 ppm, the surface roughness of the copper foil 110 increases excessively, the strength of the copper foil 110 decreases, and pinholes or curls may appear on the surface of the copper foil 110, making it difficult to separate the copper foil 110 from the winding machine WR after manufacturing. In addition, when the concentration of the leveling agent (Component C) exceeds 15 ppm, the stress value of the copper foil 110 may change suddenly. As a result, the desired first to third stress factor values may not be obtained.

[0152] The leveling agent (Component C) may include, for example, at least one selected from diethylthiourea, vinylthiourea, ethynylthiourea, dipropylthiourea, dibutylthiourea, N-trifluoroacetylthiourea, N-ethylthiourea, N-cyanoacetylthiourea, N-allylthiourea, o-tolylthiourea, N,N'-butylenedithiourea, thiazolidinethiol, 4-thiazolidinethiol, 4-methyl-2-pyrimidinethiol, 2-thiouracil, 3-(benzotriazole-2-mercapto)-pyrosulfuric acid, 2-mercaptopyridine, 3-(5-mercapto-1H-tetrazole)benzenesulfonic acid, 2-mercaptobenzothiazole, 2,2'-bipyridine, 4,4'-bipyridine, pyrimidine, pyridazine, pyrinoline, oxazole, 1-methylimidazole, 1-benzylimidazole, 1-methyl-2-methylimidazole, 1-benzyl-2-methylimidazole, 1-ethyl-4-methylimidazole, 1-ethyl-2-ethyl-4-hydroxymethylimidazole, N-methylpyrrole, N-ethylpyrrole, N-butylpyrrole, N-methylpyrrolidine, N-ethylpyrrolidine, N-butylpyrrolidine, purine, quinoline, isoquinoline, N-methylcarbazole, N-ethylcarbazole, and N-butylcarbazole.

[0153] The improver (Component D) may include citric acid (CA). Specifically, the electrolyte 20 may include 1 ppm to 5 ppm of citric acid (CA).

[0154] When the concentration of citric acid (CA) in the electrolyte 20 exceeds 5 ppm, the surface roughness of the copper foil 110 increases excessively. As a result, the A value of the copper film 111 becomes less than 1.1. In addition, the Vickers hardness and tensile strength of the copper foil 110 may decrease.

[0155] On the other hand, when the concentration of citric acid (CA) in the electrolyte 20 is less than 1 ppm, the A value of the copper film 111 becomes less than 1.1. As a result, the strength of the copper foil 110 may decrease, which may cause difficulties in manufacturing high-strength copper foil 110.

[0156] When the concentration of citric acid (CA) in the electrolyte 20 exceeds 5 ppm, the surface roughness of the copper foil 110 may increase excessively, which may reduce the strength of the copper foil 110 and pinholes may appear on the surface of the copper foil 110. In addition, the stress value of the copper foil 110 may change suddenly. As a result, the desired first to third stress factor values may not be obtained.

[0157] On the other hand, when the concentration of citric acid (CA) in the electrolyte 20 is less than 1 ppm, the strength of the copper foil 110 decreases, which may cause difficulties in manufacturing high-strength copper foil 110. In addition, the stress value of the copper foil 110 may change suddenly. As a result, the desired first to third stress factor values may not be obtained. Therefore, wrinkles or tears may occur, and pinholes or curls may appear on the surface of the copper foil 110.

[0158] When forming the copper film 111, the flow rate of the electrolyte 20 supplied to the electrolytic cell 10 can be 41 m 3 / h to 45 m 3 / h.

[0159] 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).

[0160] Specifically, to filter the electrolyte 20, the electrolyte 20 can be circulated at a flow rate of 35 m 3 / h to 45 m 3 / h. That is, to remove solid impurities present in the electrolyte 20 while electroplating to form the copper film 111, filtering can be performed at a flow rate of 35 m 3 / h to 45 m 3 / h. In this case, activated carbon or diatomaceous earth can be used.

[0161] To maintain the cleanliness of the electrolyte 20, the electrolyte 20 can be treated with ozone (O3).

[0162] In addition, in order to maintain the cleanliness of the electrolyte 20, the copper (Cu) wire used as the raw material for the electrolyte 20 can be cleaned.

[0163] According to an embodiment of the present disclosure, preparing the electrolyte 20 may include heat-treating a copper wire, pickling the heat-treated copper wire, water-washing the pickled copper wire, and inputting the water-washed copper wire into sulfuric acid for the electrolyte.

[0164] More specifically, in order to maintain the cleanliness of the electrolyte 20, the 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, thereby preparing the copper for manufacturing the electrolyte 20. The water-washed copper wire can be input into sulfuric acid for the electrolyte to prepare the electrolyte 20.

[0165] According to an embodiment of the present disclosure, in order to meet the characteristics of the copper foil 110, the concentration of TOC in the electrolyte 20 is controlled to be 50 ppm or less. That is, the electrolyte 20 can have a TOC concentration of 50 ppm or lower.

[0166] The thus-prepared copper film 111 can be cleaned in a cleaning tank.

[0167] For example, a pickling process for removing impurities (such as 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. The cleaning process can be omitted.

[0168] Next, a protective layer 112 is formed on the copper film 111.

[0169] Referring to Figure 6 , 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 a guide roller provided in the corrosion-resistant solution 60.

[0170] 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.

[0171] Meanwhile, the protective layer 112 may include a silane compound through silane treatment or a nitrogen compound through nitrogen treatment.

[0172] The copper foil 110 is formed by forming the protective layer 112.

[0173] At least one anode active material is selected from the following group and coated on one or both surfaces of the copper foil 110 of the present disclosure prepared by the above method to manufacture an electrode (i.e., anode) for a secondary battery of the present disclosure. The group consists of carbon, Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe metal (Me), an alloy including the metal (Me), an oxide (MeOx) of the metal (Me), and a composite of the metal (Me) and carbon.

[0174] 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 prepared 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 a pressure of 0.5 to 1.5 tons / cm 2 2.

[0175] A secondary battery can be manufactured using the electrode (anode) for a secondary battery of the present disclosure manufactured by the method described above, as well as a conventional cathode, electrolyte, and separator.

[0176] 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.

[0177] Examples 1 to 5 and Comparative Examples 1 to 5

[0178] A copper foil is prepared 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 is a copper sulfate solution. The copper ion concentration 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.

[0179] In addition, the concentrations of chlorine (Cl), nickel (Ni), lead (Pb), hydrogen peroxide, and tungsten contained in the electrolyte 20 and the concentration of the organic additive are as shown in Table 1 below.

[0180] 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 ethylenethiourea (ETU) is used as a leveling agent (component C).

[0181] A current with a current density of 60 ASD is applied between the rotating anode drum 40 and the cathode plate 30 to prepare the copper film 111. Thereafter, the copper film 111 is immersed in the corrosion-resistant solution for about two seconds to perform chromate treatment on the surface of the copper film 111, thereby forming the protective layer 112, and thus the copper foil 110 is prepared. A corrosion-resistant solution containing chromic acid as the main component is used as the corrosion-resistant solution, and the concentration of chromic acid is 5 g / L.

[0182] As a result, the copper foils of Preparation Examples 1 to 5 and Comparative Examples 1 to 5 are prepared.

[0183] [Table 1]

[0185] [Table 2]

[0187] For the copper foils of Example 1-5 and Comparative Examples 1-5 manufactured as described above, check i) peak intensity (P), ii) peak intensity (Q), iii) A(P / Q), iv) Vickers hardness, v) appearance of wrinkles / tears, and vi) appearance of cracks. Measurement of i) peak intensity (P) and ii) peak intensity (Q)

[0188] The peak intensity (P) is the peak intensity at 1650 cm of the copper film 111 -1 and the peak intensity (Q) is the peak intensity at 1460 cm of the copper film 111 -1 .

[0189] At this time, the peak intensities (P and Q) are measured by FT-IR.

[0190] iii) Measurement of A(P / Q)

[0191] The A value can be obtained by calculating the values of i) peak intensity (P) and ii) peak intensity (Q) measured according to the following Equation 1.

[0192] [Equation 1]

[0193] A = P / Q

[0194] Iv) Vickers hardness (Hv)

[0195] The Vickers hardness (Hv) is measured using a nanoindenter (HM 2000, Helmut Fischer).

[0196] Environment: temperature is (23 ± 2) °C, humidity (R.H.) is 45 ± 5%.

[0197] Indenter type: Vickers indenter (correction factor: 0.75)

[0198] Load increasing time: 10 s

[0199] Unloading increasing time: 10 s

[0200] Creep time: 3 s

[0201] Load: 0.5 mN

[0202] The Vickers hardness in Table 2 above refers to the average value obtained by measuring the Vickers hardness three times by the above method.

[0203] v) Appearance of wrinkles / tears

[0204] After 100 charge and discharge cycles, disassemble the secondary battery 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".

[0205] vi) Appearance of cracks

[0206] After 100 charge and discharge cycles, disassemble the secondary battery to observe whether cracks appear in the copper foil. When cracks appear in the copper foil, the copper foil is marked as "appeared", while when no cracks are observed, the copper foil is marked as "none".

[0207] Referring to Table 1 and Table 2, the following results can be confirmed.

[0208] Tears / wrinkles appear in the copper foil of Comparative Example 1 prepared using an electrolyte including an excessive amount of polishing agent (Component A), as well as a small amount of nickel and a small amount of lead.

[0209] Tears / wrinkles appear in the copper foil of Comparative Example 2 prepared using an electrolyte including an excessive amount of moderator (Component B) and an excessive amount of lead, as well as a small amount of tungsten.

[0210] Cracks appear in the copper foil of Comparative Example 3 prepared from an electrolyte including an excessive amount of tungsten.

[0211] Tears / wrinkles appear in the copper foil of Comparative Example 4 prepared using an electrolyte including an excessive amount of improver (Component D) and an excessive amount of nickel and a small amount of tungsten.

[0212] Tears / wrinkles appear in the copper foil of Comparative Example 5 prepared using an electrolyte including an excessive amount of leveling agent (Component C).

[0213] On the other hand, all the copper foils according to Examples 1 to 5 of the present disclosure satisfy the values within the above criteria range, and no wrinkles / tears appear and no cracks appear.

[0214] Copper foils of Examples 6 to 10 and Comparative Examples 6 to 9.

[0215] A copper foil is prepared 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 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.

[0216] In addition, the concentrations of chlorine (Cl), nickel (Ni), lead (Pb), hydrogen peroxide, and tungsten (W) and the concentration of the organic additive contained in the electrolyte 20 are as shown in Table 3 below.

[0217] 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 ethylenethiourea (ETU) is used as a leveling agent (Component C).

[0218] A current with a current density of 60 ASD is applied between the rotating anode drum 40 and the cathode plate 30 to produce a copper film 111. Subsequently, the copper film 111 is immersed in an anti-corrosion solution for about two seconds to perform chromate treatment on the surface of the copper film 111, thereby forming a protective layer 112, and thus a copper foil 110 is produced. 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.

[0219] As a result, the copper foils of Examples 6 to 10 and Comparative Examples 6 to 9 are produced.

[0220] [Table 3]

[0222] [Table 4]

[0224] For the copper foils of Examples 6 - 10 and Comparative Examples 6 - 9 manufactured as described above, check i) A, A’, B, B’, C, and C’, ii) the first stress factor, iii) the second stress factor, iv) the third stress factor, and v) the occurrence of wrinkles / tears. i) Measurement of A, A’, B, B’, C, and C’

[0225] A represents the stress of the copper foil when it is elongated by 50% in the MD direction, A’ represents the stress of the copper foil when it is elongated by 50% in the TD direction, B represents the stress of the copper foil 110 when it is elongated by 10% in the MD direction, B’ represents the stress of the copper foil 110 when it is elongated by 10% in the TD direction, C represents the stress of the copper foil when it is elongated by 5% in the MD direction, and “C’” represents the stress of the copper foil when it is elongated by 5% in the TD direction.

[0226] According to the method specified in the IPC-TM-650 Test Method Manual, a universal testing machine (UTM, INSTRON) is used to measure A, A’, B, B’, C, and C’. The width of the sample is 12.7 mm, the distance between the fixtures is 50 mm, and the measurement speed is 50 mm / min.

[0227] A is obtained by measuring the stress of the copper foil after 50% elongation in the MD direction under the same conditions as above, A’ is obtained by measuring the stress of the copper foil after 50% elongation in the TD direction under the same conditions as above, B is obtained by measuring the stress of the copper foil after 10% elongation in the MD direction under the same conditions as above, B’ is obtained by measuring the stress of the copper foil after 10% elongation in the TD direction under the same conditions as above, C is obtained by measuring the stress of the copper foil after 5% elongation in the MD direction under the same conditions as above, and C’ is obtained by measuring the stress of the copper foil after 5% elongation in the TD direction under the same conditions as above. The elongation length of the copper foil when measuring the breaking stress of the copper foil sample in the universal testing machine is defined as the maximum elongation rate, and the stress when elongated by 50% compared to the maximum elongation rate of the copper foil is defined as the stress when elongated by 50%. Similarly, the stress when elongated by 10% compared to the maximum elongation rate of the copper foil is defined as the stress when elongated by 10%, and the stress when elongated by 5% compared to the maximum elongation rate of the copper foil is defined as the stress when elongated by 5%.

[0228] ii) Calculation of the first stress factor

[0229] The value of the first stress factor can be obtained by substituting the measured values of A, A’, B, B’, C, and C’ into the following Equation 2.

[0230] [Equation 2]

[0231] First stress factor = A / A’ + B / B’ + C / C’.

[0232] iii) Calculation of the second stress factor

[0233] The value of the second stress factor can be obtained by substituting the measured values of A, A’, B, and B’ into the following Equation 3.

[0234] [Equation 3]

[0235] Second stress factor = A / B + A’ / B’.

[0236] iv) Calculation of the third stress factor

[0237] The value of the third stress factor can be obtained by substituting the measured values of A, A’, C, and C’ into Equation 4 below.

[0238] [Equation 4]

[0239] Third stress factor = A / C + A’ / C’.

[0240] v) Appearance of wrinkles / tears

[0241] After charging and discharging 100 times, the secondary battery is disassembled to observe whether wrinkles or tears appear in 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".

[0242] Referring to Tables 3 and 4, the following results can be confirmed.

[0243] Tears / wrinkles appear in the copper foil of Comparative Example 6 prepared using an electrolyte including an excessive amount of polishing agent (Component A), a small amount of nickel, a small amount of lead, and a small amount of tungsten.

[0244] Tears / wrinkles appear in the copper foil of Comparative Example 7 prepared using an electrolyte including an excessive amount of moderator (Component B), a small amount of lead, and a small amount of hydrogen peroxide.

[0245] Tears / wrinkles appear in the copper foil of Comparative Example 8 prepared using an electrolyte including an excessive amount of leveling agent (Component C), an excessive amount of hydrogen peroxide, and an excessive amount of tungsten.

[0246] Tears / wrinkles appear in the copper foil of Comparative Example 9 prepared using an electrolyte including an excessive amount of improver (Component D), an excessive amount of nickel, and an excessive amount of lead.

[0247] On the other hand, all the copper foils according to Examples 6 to 10 of the present disclosure satisfy the values within the above-mentioned standard range, thus not causing the appearance of tears / wrinkles.

[0248] 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 99.9% or more, Among them, the copper film having an A value in the range of 1.1 to 1.6, wherein, "A" is calculated by the following Equation 1, [Equation 1] A = P / Q Among them, "P" in Equation 1 is the peak intensity at 1650 cm of the copper film, and -1 and "Q" in Equation 1 is the peak intensity at 1460 cm of the copper film -1 at which point, wherein the peak intensity is measured by Fourier transform infrared spectroscopy (FT-IR).

2. The copper foil according to claim 1, wherein, The copper foil has a Vickers hardness in the range of 1.3 Hv to 1.9 Hv.

3. The copper foil according to claim 1, wherein, The copper foil has a tensile strength of 45 kgf / mm 2 or higher.

4. The copper foil according to claim 1, wherein, The copper foil has an elongation of 3% to 13%.

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

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

7. 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 formation of the copper film includes forming a copper film on the rotating anode drum by electrically connecting a cathode plate and the rotating anode drum, the cathode plate and the rotating anode drum being arranged to be spaced apart from each other in the electrolyte of the electrolytic cell, the electrolyte comprising: 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; nickel (Ni) with a concentration of 15 ppm to 150 ppm; Lead ions (Pb with a concentration of 1 ppm to 20 ppm 2+ ); hydrogen peroxide with a concentration of 1 ml / L to 10 ml / L; tungsten (W) with a concentration of 0.3 ppm to 5 ppm; and an organic additive, wherein the organic additive includes at least one of a polishing agent (component A), a moderating agent (component B), a leveling agent (component C), and an improving agent (component D), wherein the polishing agent (component A) includes a sulfonic acid or its metal salt, the moderating agent (component B) includes a non-ionic water-soluble polymer, the leveling agent (component C) includes at least one of nitrogen (N) and sulfur (S), and the improving agent (component D) includes citric acid.

8. The method according to claim 7, wherein The polishing agent (component A) has a concentration of 1 ppm to 25 ppm.

9. The method according to claim 7, wherein The moderating agent (component B) has a concentration of 1 ppm to 15 ppm.

10. The method according to claim 7, wherein, The leveling agent (component C) has a concentration of 1 ppm to 15 ppm.

11. The method according to claim 7, wherein, The improving agent (component D) has a concentration of 1 ppm to 5 ppm.

12. A copper foil, comprising a copper film, the copper film comprising copper with a weight percentage of 99.9% or more, Among them, the copper foil having a first stress factor of 2.8 or more, a second stress factor of 2.5 or more, and a third stress factor of 3.5 or more, wherein the first stress factor is calculated by Equation 2, [Equation 2] First stress factor = A / A’ + B / B’ + C / C’, the second stress factor is calculated by Equation 3, [Equation 3] Second stress factor = A / B + A’ / B’, and the third stress factor is calculated by the following Equation 4, [Equation 4] Third stress factor = A / C + A’ / C’, wherein A in Equation 2 refers to the stress when elongated by 50% in the machine direction (MD direction), A' in Equation 2 refers to the stress when elongated by 50% in the transverse direction (TD direction), B in Equation 2 refers to the stress when elongated by 10% in the MD direction, B' in Equation 2 refers to the stress when elongated by 10% in the TD direction, C in Equation 2 refers to the stress when elongated by 5% in the MD direction, and C' in Equation 2 refers to the stress when elongated by 5% in the TD direction.

13. The copper foil according to claim 12 further includes 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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