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

Abstract

The invention relates to a copper foil, an electrode comprising the copper foil, a secondary battery comprising the electrode, and a manufacturing method thereof. One embodiment of the present invention provides a copper foil which is a copper film having a rough surface and a smooth surface, the amount of hydrogen vacancies at a depth of 30 nm to 45 nm in the rough surface being 80 to 250 counts, and the amount of hydrogen vacancies at a depth of 30 nm to 45 nm in the smooth surface being 3 to 20 counts. The amount of hydrogen vacancies is the number of hydrogen ions measured at a certain sputtering depth, which is far away from the rough surface and the smooth surface, by using TOF-SIMS (Time of Flight-Spondy Ion Mass Spectrometry).

Description

Technical Field

[0001] The present invention relates to a copper foil, an electrode including the copper foil, a secondary battery including the electrode, and a method for manufacturing the same. Specifically, the present invention relates to a copper foil in which the occurrence of curl is prevented, an electrode including the copper foil, a secondary battery including the electrode, and a method for manufacturing the same. Background Art

[0002] A secondary battery is a type of energy conversion device that converts electrical energy into chemical energy and stores it, and then converts the chemical energy back into electrical energy to generate electricity when power is needed. Secondary batteries are used not only in portable household appliances such as mobile phones and laptops, but also as an energy source for electric vehicles. Since secondary batteries can be recharged repeatedly, they are also called rechargeable batteries.

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

[0004] In particular, compared to other secondary batteries, lithium secondary batteries can store relatively more 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 is also expanding to energy storage devices for hybrid electric vehicles and electric vehicles.

[0005] Lithium secondary batteries are repeatedly used with charging and discharging as one cycle. When operating a device with a fully charged lithium secondary battery, in order to increase the operating time of the device, the lithium-ion secondary battery should have a high charge / discharge capacity. Therefore, there is a continuous need to conduct research to meet the growing needs of consumers for the charge / discharge capacity of lithium secondary batteries.

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

[0007] On the other hand, as the thickness of the copper foil becomes thinner, the amount of active material that can be included in the same space increases, and the number of current collectors can be increased, thereby increasing the capacity of the secondary battery. However, as the copper foil becomes thinner, curling occurs, and thus, when winding the copper foil, defects such as tearing or wrinkling of the copper foil occur due to curling of the edge portion. Therefore, it is difficult to manufacture a copper foil in the form of a very thin film. Accordingly, in order to manufacture a copper foil having a very thin thickness, curling of the copper foil must be prevented. Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] Accordingly, the present invention relates to a copper foil capable of preventing problems caused by the limitations and disadvantages of the related art as described above, an electrode including the copper foil, a secondary battery including the electrode, and a method for manufacturing the same.

[0010] One embodiment of the present invention provides a copper foil in which wrinkles or tearing are prevented, wherein the amount of hydrogen vacancies at a depth of 30 nm to 45 nm in the rough surface is 80 to 250 counts, and the amount of hydrogen vacancies at a depth of 30 nm to 45 nm in the smooth surface is 3 to 20 counts.

[0011] One embodiment of the present invention provides a copper foil in which wrinkles or tearing are prevented, wherein the amount of hydrogen vacancies at a depth of 60 nm to 75 nm in the rough surface is 15 to 60 counts, and the amount of hydrogen vacancies at a depth of 60 nm to 75 nm in the smooth surface is 1.0 to 10 counts.

[0012] Another embodiment of the present invention provides an electrode for a secondary battery including such a copper foil and a secondary battery including such an electrode for a secondary battery.

[0013] Still another embodiment of the present invention provides a method for manufacturing a copper foil in which curling, wrinkling, or tearing is prevented.

[0014] In addition to the viewpoints of the present invention mentioned above, other features and advantages of the present invention will be clearly understood from the following description or by those of ordinary skill in the technical field to which the present invention pertains.

[0015] Technical Solutions for Solving the Problems

[0016] An embodiment of the present invention provides a copper foil, which is a copper film having a rough surface and a smooth surface. The amount of hydrogen vacancies at a depth of 30 nm to 45 nm in the rough surface is 80 to 250 counts, and the amount of hydrogen vacancies at a depth of 30 nm to 45 nm in the smooth surface is 3 to 20 counts. The amount of hydrogen vacancies refers to the number of hydrogen ions measured by TOF-SIMS (Time Of Flight-Secondary Ion Mass Spectrometry) at a certain sputtering depth away from the rough surface and the smooth surface.

[0017] Another embodiment of the present invention provides a method for manufacturing a copper foil, including: a step of manufacturing an electrolyte containing copper ions; a step of forming a copper film; and a step of forming a protective layer on the copper film. The step of forming the copper film includes: a step of applying electricity to an anode plate and a rotating cathode drum disposed separately from each other in the electrolyte in an electrolytic cell to form a copper film on the rotating cathode drum. The electrolyte contains: 70 to 150 g / L of copper ions; 80 to 150 g / L of sulfuric acid; 15 to 25 ppm of chlorine (Cl); 1 to 15 ppm of collagen; 0.1 to 5 ppm of gelatin; and an organic additive, and the organic additive includes at least one of a brightening agent (component A) and a retarder (component B). The brightening agent (component A) contains a sulfonic acid or its metal salt, and the retarder (component B) contains a nonionic water-soluble polymer.

[0018] Advantages of the Invention

[0019] According to the present invention, the amount of hydrogen vacancies at a depth of 30 nm to 45 nm in the rough surface of the copper foil is 80 to 250 counts, and the amount of hydrogen vacancies at a depth of 30 nm to 45 nm in the smooth surface is 3 to 20 counts, thereby preventing wrinkles or tears from occurring during the manufacturing process of the copper foil. Using such a copper foil to manufacture semi-finished products and finished products such as flexible printed circuit boards (FPCBs) and secondary batteries can improve the productivity of the semi-finished products and even the finished products. Description of the Drawings

[0020] Figure 1 is a cross-sectional view of a copper foil according to an embodiment of the present invention.

[0021] Figure 2 is a cross-sectional view of a copper foil according to another embodiment of the present invention.

[0022] Figure 3 is a cross-sectional view of a copper foil according to another embodiment of the present invention.

[0023] Figure 4 is a cross-sectional view of an electrode for a secondary battery according to another embodiment of the present invention.

[0024] Figure 5 It is a cross-sectional view of an electrode for a secondary battery according to another embodiment of the present invention.

[0025] Figure 6 It is a schematic cross-sectional view of a secondary battery according to another embodiment of the present invention.

[0026] Figure 7 It is a manufacturing apparatus for a copper foil according to another embodiment of the present invention.

[0027] Figure 8 It is a schematic diagram showing the circulation process of the electrolyte of the present invention.

[0028] Description of Reference Numerals

[0029] 100: Electrode for secondary battery

[0030] 110, 110a, 110b, 110c: Copper foil

[0031] 111: Copper film

[0032] 111a: Rough surface

[0033] 111b: Smooth surface

[0034] 112: Protective layer

[0035] 120: Active material layer

[0036] 10: Electrolytic cell

[0037] 20: Electrolyte Detailed Description of Embodiments

[0038] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiments described below are merely presented for the exemplary purpose of helping to clearly understand the present invention and do not limit the scope of the present invention.

[0039] The shapes, sizes, ratios, angles, quantities, etc. disclosed in the drawings for explaining the embodiments of the present invention are exemplary, and thus the present invention is not limited to the matters shown in the drawings. Throughout the specification, the same constituent elements may be denoted by the same reference numerals. When explaining the present invention, in cases where it is judged that a detailed description of related well-known technologies may unnecessarily obscure the gist of the present invention, the detailed description thereof is omitted.

[0040] When using expressions such as "including", "having", "composed of", etc. mentioned in this specification, unless the expression "only" is used, other parts may be added. When a constituent element is expressed in the singular, unless otherwise specifically stated, it includes the plural. And, when interpreting a constituent element, even without other specific explanations, it is interpreted as including an error range.

[0041] When describing a positional relationship, for example, in the case of describing the positional relationship between two parts using expressions such as "on", "above", "below", "beside", etc., unless the expression "directly" or "exactly" is used, one or more other parts may be provided between the two parts.

[0042] Spatial relative terms such as "below", "beneath", "lower", "above", "upper", etc. can be used to easily describe the relative relationship between one element or component and other elements or components as shown in the figure. Spatial relative terms should be understood to include terms for different directions of the element during use or operation in addition to the directions shown in the drawings. For example, in the case of flipping the element shown in the drawing, the element described as "below" or "beneath" another element can be placed "above" another element. Therefore, the exemplary term "below" can include all directions of below and above. Similarly, the exemplary terms "above" or "upper" can include all directions of above and below.

[0043] In the case of describing a time relationship, for example, in the case of describing the time sequence relationship using "after", "subsequent to", "successively", "before", etc., unless the expression "directly" or "exactly" is used, discontinuous cases may also be included.

[0044] Although first, second, etc. are used to describe various components, these components are not limited to these terms. These terms are only used to distinguish one component from another. Therefore, the first component mentioned below may also be the second component within the technical concept of the present invention.

[0045] The term "at least one" should be understood to include all combinations that can be prompted from more than one related item. For example, the meaning of "at least one of the first item, the second item, and the third item" not only refers to each of the first item, the second item, or the third item, but may also refer to the combination of all items prompted by two or more of the first item, the second item, and the third item.

[0046] The features of the various embodiments of the present invention can be partially or fully combined or combined with each other, and can be variously linked and driven technically. Each embodiment can be implemented independently of each other or can be implemented together in an associated relationship.

[0047] Figure 1 It is a cross-sectional view of the copper foil 110a of an embodiment of the present invention.

[0048] Refer toFigure 1 , the copper foil 110a of the present invention includes a copper film 111 containing 99.9 wt% or more of copper. Refer to Figure 2 , the copper foil 110b of the present invention includes a copper film 111 and a protective layer 112 on the copper film 111. Figure 2 shows a configuration in which the protective layer 112 is disposed on one side of the copper film 111. However, an embodiment of the present invention is not limited thereto, and the protective layer 112 may be disposed on both sides of the copper film 111 (refer to Figure 3 ).

[0049] The copper film 111 can be formed on a rotating cathode drum by electroplating, and can have a smooth surface 111b that is in direct contact with the rotating cathode drum during the electroplating process and a rough surface 111a on the opposite side thereof.

[0050] 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 not only extending the life of the copper foil 110 itself but also extending the life of a finished product including the copper foil 110.

[0051] The copper foil 110 described below may correspond to Figures 1 to 3 the copper foils 110a, 110b, and 110c.

[0052] According to an embodiment of the present invention, the copper foil 110 includes a copper film 111 having a rough surface 111a and a smooth surface 111b. In the rough surface 111a, the amount of hydrogen vacancies at a depth of 30 nm to 45 nm may be 80 to 250 counts, and in the smooth surface 111b, the amount of hydrogen vacancies at a depth of 30 nm to 45 nm may be 3 to 20 counts.

[0053] At this time, the amount of hydrogen vacancies refers to the number of hydrogen ions measured by TOF-SIMS (Time Of Flight-Secondary Ion Mass Spectrometry) at a certain sputtering depth away from the rough surface and the smooth surface.

[0054] Specifically, when the amount of hydrogen vacancies at a depth of 30 nm to 45 nm in the rough surface 111a is 80 to 250 counts, and the amount of hydrogen vacancies at a depth of 30 nm to 45 nm in the smooth surface 111b is 3 to 20 counts, the surface characteristics of the rough surface 111a and the smooth surface 111b of the copper film 111 are stabilized, preventing wrinkles or tears from occurring in the copper foil 110 and preventing curling (Curl).

[0055] Conversely, when the amount of hydrogen vacancies at a depth of 30 nm to 45 nm in the rough surface 111a falls outside the range of 80 to 250 counts, or the amount of hydrogen vacancies at a depth of 30 nm to 45 nm in the smooth surface 111b falls outside the range of 3 to 20 counts, the difference in surface characteristics between the rough surface 111a and the smooth surface 111b becomes larger, a rather bending problem occurs during the manufacturing process, wrinkles or tears may occur in the copper foil 110, and curling (Curl) may occur.

[0056] In addition, according to an embodiment of the present invention, the amount of hydrogen vacancies at a depth of 60 nm to 75 nm in the rough surface 111a may be 15 to 60 counts, and the amount of hydrogen vacancies at a depth of 60 nm to 75 nm in the smooth surface 111b may be 1.0 to 10 counts.

[0057] Specifically, when the amount of hydrogen vacancies at a depth of 60 nm to 75 nm in the rough surface 111a is 15 to 60 counts, and the amount of hydrogen vacancies at a depth of 60 nm to 75 nm in the smooth surface 111b is 1.0 to 10 counts, wrinkles or tears are prevented from occurring in the copper foil 110 and curling (Curl) is prevented.

[0058] Conversely, when the amount of hydrogen vacancies at a depth of 60 nm to 75 nm in the rough surface 111a falls outside the range of 15 to 60 counts, or the amount of hydrogen vacancies at a depth of 60 nm to 75 nm in the smooth surface 111b falls outside the range of 1.0 to 10 counts, the difference in surface characteristics between the rough surface 111a and the smooth surface 111b becomes larger, a rather bending problem occurs during the manufacturing process, wrinkles or tears may occur in the copper foil 110, and curling (Curl) may occur.

[0059] According to an embodiment of the present invention, the depth of the hydrogen component in the rough surface 111a of the copper film 111 may be 35 nm or less.

[0060] At this time, the depth of the hydrogen component refers to the depth of the position in the rough surface 111a where the number of hydrogen ions measured by TOF-SIMS is 200 counts or more. Specifically, it is the distance from the surface of the rough surface 111a to the position where the number of measured hydrogen ions is 200 counts or more.

[0061] When the depth of the hydrogen component in the rough surface 111a of the copper film 111 is 35 nm or more, hydrogen penetrates into a deeper region based on the rough surface 111a of the copper film 111, which may cause differences in surface characteristics between the rough surface 111a and the smooth surface 111b. As a result, quite bent problems may occur during the manufacturing process, wrinkles or tears may occur in the copper foil 110, and curling (Curl) may occur.

[0062] The copper foil 110 of an embodiment of the present invention has 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, the thinner the thickness of the copper foil 110, the more current collectors can be accommodated in the same space. Therefore, it is beneficial to increase the capacity of the secondary battery. However, manufacturing a copper foil 110 with a thickness less than 4 μm will result in reduced workability.

[0063] On the contrary, when manufacturing a secondary battery using a copper foil 110 with a thickness exceeding 35 μm, it is difficult to achieve a high capacity due to the relatively thick copper foil 110.

[0064] Hereinafter, the electrode 100 including the copper foil 110 of the present invention and the secondary battery including the electrode 100 will be specifically described.

[0065] Figure 4 It is a cross-sectional view of the secondary battery electrode 100a of an embodiment of the present invention. Figure 5 It is a cross-sectional view of the secondary battery electrode 100b of another embodiment of the present invention.

[0066] As Figure 4 shown, the secondary battery electrode 100a of an embodiment of the present invention includes any one of the copper foils 110 in the above-described embodiments of the present invention and the active material layer 120.

[0067] Figure 4 shows a configuration in which the active material layer 120 is formed on one surface of the copper foil 110. However, an embodiment of the present invention is not limited thereto. Referring to Figure 5 , the active material layer 120 may also be formed on both surfaces of the copper foil 110.

[0068] Generally, in a lithium secondary battery, an aluminum foil (foil) is used as the positive electrode current collector combined with the positive electrode active material, and the copper foil 110 is used as the negative electrode current collector combined with the negative electrode active material.

[0069] According to an embodiment of the present invention, the secondary battery electrode 100 is a negative electrode, the copper foil 110 serves as a negative electrode current collector, and the active material layer 120 contains a negative electrode active material.

[0070] To ensure the high capacity of the secondary battery, the active material layer 120 of the present invention may be formed of a composite of carbon and a metal. The metal may include, for example, at least one of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni, and Fe, and preferably may include Si and / or Sn.

[0071] Figure 6 is a schematic cross-sectional view of a secondary battery according to an embodiment of the present invention.

[0072] Referring to Figure 6 , the secondary battery includes a cathode 370, an anode 340, an electrolyte 350 disposed between the cathode 370 and the anode 340 to provide an environment in which ions can move, and a separator 360 that electrically insulates the cathode 370 and the anode 340. Here, the ions moving between the cathode 370 and the anode 340 are, for example, lithium ions. The separator 360 separates the cathode 370 and the anode 340 to prevent the charge generated in one electrode from being uselessly consumed by moving inside the secondary battery 105 to the other electrode. Referring to Figure 6 , the separator 360 is disposed within the electrolyte 350.

[0073] 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.

[0074] The anode 340 includes an anode current collector 341 and an anode active material layer 342, and the copper foil 110 may be used as the anode current collector 341.

[0075] According to an embodiment of the present invention, the copper foil 110 disclosed may be used as the anode current collector 341. Additionally, Figures 1 to 3 the secondary battery electrodes 100a, 100b shown in Figure 4 or Figure 5 may be used as the anode 340 of the secondary battery shown in Figure 5 .

[0076] Hereinafter, with reference to Figure 7 and Figure 8 the manufacturing method of the copper foil 110 of the present invention will be specifically described.

[0077] The manufacturing method of the copper foil 110 of the present invention includes a step of forming a copper film 111 and a step of forming a protective layer 112 on the copper film 111.

[0078] The method of the present invention includes a step of forming a copper film 111 on the rotating cathode drum 40 by energizing an anode plate 30 and a rotating cathode drum 40 which are disposed apart from each other in an electrolytic solution 20 in an electrolytic cell 10.

[0079] As Figure 7 illustrated in, the anode plate 30 may include a first anode plate 31 and a second anode plate 32 which are electrically insulated from each other.

[0080] The step of forming the copper film 111 may be performed as follows: a seed layer is formed by energization between the first anode plate 31 and the rotating cathode drum 40, and then the seed layer is grown by energization between the second anode plate 32 and the rotating cathode drum 40.

[0081] The current densities respectively provided by the first anode plate 31 and the second anode plate 32 may be 30 to 130 ASD.

[0082] In the case where the current densities respectively provided by the first anode plate 31 and the second anode plate 32 are lower than 30 ASD, the surface roughness of the copper foil 110 is low, and thus the adhesion between the copper foil 110 and the active material layer 120 may be insufficient.

[0083] On the contrary, in the case where the current densities respectively provided by the first anode plate 31 and the second anode plate 32 exceed 130 ASD, the surface of the copper foil 110 is rough, and thus the coating of the active material may not be achieved smoothly.

[0084] The surface characteristics of the copper film 111 may vary depending on the surface polishing or grinding degree of the rotating cathode drum 40. For example, a grinding brush having a grit of #800 to #3000 may be used to grind the surface of the rotating cathode drum 40.

[0085] During the formation of the copper film 111, the electrolytic solution 20 is maintained at a temperature of 40 to 60 °C. More specifically, the temperature of the electrolytic solution 20 may be maintained above 50 °C. At this time, the physical, chemical, and electrical characteristics of the copper film 111 may be controlled by adjusting the composition of the electrolytic solution 20.

[0086] According to an embodiment of the present invention, the electrolytic solution 20 may contain copper ions, sulfuric acid, chlorine (Cl), collagen, gelatin, and an organic additive.

[0087] In order to smoothly form the copper film 111 by electro-deposition of copper, the copper ion concentration and the sulfuric acid concentration in the electrolytic solution 20 are respectively adjusted to 70 to 150 g / L and 80 to 150 g / L.

[0088] In an embodiment of the present invention, chlorine (Cl) includes chloride ions (Cl -) and all of the chlorine atoms present in the molecule. For example, 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 cause silver (Ag) ions to precipitate in the form of silver chloride (AgCl). This silver chloride (AgCl) can be removed by filtration.

[0089] When the concentration of chlorine (Cl) is less than 15 ppm, silver (Ag) ions cannot be removed smoothly. On the contrary, 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 in the range of 15 to 25 ppm.

[0090] According to an embodiment of the present invention, the electrolyte 20 may contain collagen and gelatin. Specifically, the electrolyte 20 may contain 1 to 15 ppm of collagen and 0.1 to 5 ppm of gelatin.

[0091] The collagen and gelatin of an embodiment of the present invention are added to adjust the amount of hydrogen vacancies on the rough surface and the smooth surface of the copper film of the present invention. In order to obtain the physical properties of the amount of hydrogen vacancies of the present invention, the electrolyte 20 needs to contain 1 to 15 ppm of collagen and 0.1 to 5 ppm of gelatin.

[0092] More preferably, the collagen and gelatin contained in the electrolyte 20 need to be added in a concentration ratio of 10:1 to 3:1. At this time, the collagen may have a molecular weight of 2000 to 10000, and the gelatin may have a molecular weight of 10000 to 100000.

[0093] When the concentration ratio of the collagen and gelatin contained in the electrolyte 20 deviates from the above range, the gelatin with a larger molecular weight may increase excessively, and there may be a problem that the strength becomes excessively large. When the collagen with a smaller molecular weight increases excessively compared to the gelatin, there may also be a problem that the strength is excessively reduced.

[0094] According to an embodiment of the present invention, the electrolyte 20 may contain an organic additive.

[0095] The organic additive contained in the electrolyte 20 contains at least one of a brightener (component A) and a retarder (component B).

[0096] The organic additive may contain more than one of a brightener (component A) and a retarder (component B), or may contain all of the two components.

[0097] The brightener (component A) contains a sulfonic acid or its metal salt. The brightener (component A) may have a concentration of 1 to 15 ppm in the electrolyte 20.

[0098] The brightener (Component A) increases the charge amount of the electrolyte 20, thereby increasing the copper electrodeposition rate, improving the curl characteristics of the copper foil, and 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. If it exceeds 15 ppm, problems such as weight change or surface roughness change may occur after impregnating the copper foil 110.

[0099] The brightener may include, for example, at least one of 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 ethylene dithiodi propyl sulfonic acid sodium salt.

[0100] The retarder (Component B) contains a non-ionic water-soluble polymer. The retarder (Component B) may have a concentration of 0.1 to 15 ppm in the electrolyte 20.

[0101] The retarder (Component B) reduces the copper electrodeposition rate, thereby preventing a sharp increase in the roughness and a decrease in the strength of the copper foil 110. This retarder (Component B) is also referred to as an inhibitor or a suppressor.

[0102] If the concentration of the retarder (Component B) is less than 0.1 ppm, problems such as a sharp increase in the roughness of the copper foil 110 and a change in the surface state of the copper foil 110 may occur. On the contrary, even if the concentration of the retarder (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 retarder (Component B) can be adjusted to the range of 0.1 to 15 ppm without unnecessarily increasing the manufacturing cost and wasting raw materials by increasing the concentration of the retarder (Component B).

[0103] The retarder (Component B) may include, for example, at least one non-ionic 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 ether of stearic acid, and polyethylene glycol ether of stearyl alcohol. However, the types of retarders are not limited thereto, and another non-ionic water-soluble polymer that can be used for the manufacture of the high-strength copper foil 110 can be used as the retarder.

[0104] When forming the copper film 111, the flow rate of the electrolyte 20 supplied into the electrolytic cell 10 can be 41 to 45 m3 per hour.

[0105] Figure 8 It is a schematic diagram showing the circulation process of the electrolyte of the present invention.

[0106] According to an embodiment of the present invention, the steps of manufacturing the electrolyte may include the step of forming a second electrolyte by using carbon filtration C / F to transfer the first electrolyte from the storage tank, and the step of adding collagen and gelatin to the filtered second electrolyte to form the electrolyte.

[0107] Specifically, the first electrolyte transferred from the storage tank may contain copper ions, sulfuric acid, chlorine, organic additives, etc.

[0108] The process of using carbon filtration C / F for the first electrolyte refers to the step of removing organic impurities and inorganic impurities present in the first electrolyte.

[0109] According to an embodiment of the present invention, the second electrolyte refers to the electrolyte obtained by carbon filtering the first electrolyte.

[0110] According to an embodiment of the present invention, collagen and gelatin may be added to the second electrolyte to form the electrolyte. The additives contained in the electrolyte have been described above and are omitted. Specifically, collagen and gelatin are added after the carbon filtration C / F process. When collagen and gelatin are added after the carbon filtration C / F process, it prevents the deterioration of collagen and gelatin and has the effect of improving the physical properties of the present invention.

[0111] The electrolyte formed by adding collagen and gelatin is filled in the electrolytic cell 10, and a copper foil is manufactured using a foil making machine including a rotating cathode drum 40 disposed in the electrolytic cell 10 and an anode plate 30 disposed at a distance from the rotating cathode drum 40.

[0112] In addition, for the purity of the electrolyte 20, the copper wire (Cu wire) used as the raw material of the electrolyte 20 may be cleaned.

[0113] According to an embodiment of the present invention, the steps of manufacturing the electrolyte 20 may include: the step of heat-treating the copper wire, the step of pickling the heat-treated copper wire, the step of washing the pickled copper wire, and the step of putting the washed copper wire into sulfuric acid for the electrolyte.

[0114] More specifically, in order to maintain the purity of the electrolyte 20, copper for manufacturing the electrolyte 20 can be produced through the following process: High-purity (above 99.9%) copper wire is heat-treated in an electric furnace at 750°C to 850°C to burn off various organic impurities attached to the copper wire. Then, the copper wire heat-treated for 10 to 20 minutes is pickled with a 10% sulfuric acid solution, and the pickled copper wire is washed with distilled water. The washed copper wire can be put into sulfuric acid for the electrolyte to manufacture the electrolyte 20.

[0115] According to an embodiment of the present invention, in order to meet the characteristics of the copper foil 110, the concentration of total organic carbon (TOC) in the electrolyte 20 is controlled below 300 ppm. That is, the electrolyte 20 can have a total organic carbon (TOC) concentration below 300 ppm.

[0116] The copper film 111 manufactured in this way can be cleaned in a cleaning tank.

[0117] For example, pickling (acid cleaning) for removing impurities on the surface of the copper film 111, such as resin components or natural oxide films, and water cleaning (water cleaning) for removing the acidic solution used in pickling can be performed in sequence. The cleaning process can also be omitted.

[0118] Next, a protective layer 112 is formed on the copper film 111.

[0119] Referring to Figure 7 , it 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, it can be guided by a guide roll disposed in the anticorrosion solution 60.

[0120] As described above, the anticorrosion solution 60 may contain 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 to 10 g / L at room temperature for 1 to 30 seconds.

[0121] On the other hand, the protective layer 112 may include a silane compound based on silane treatment or a nitrogen compound based on nitrogen treatment.

[0122] The copper foil 110 is manufactured by forming such a protective layer 112.

[0123] On one or both sides of the copper foil 110 of the present invention manufactured by the method described above, one or more negative electrode active materials selected from the group consisting of carbon; metals (Me) such as Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe; alloys containing the metal (Me); oxides (MeO x ); and composites of the metal (Me) and carbon are coated, thereby enabling the manufacture of an electrode (i.e., a negative electrode) for a secondary battery of the present invention.

[0124] For example, after mixing 1 to 3 parts by weight of styrene-butadiene rubber (SBR) and 1 to 3 parts by weight of carboxymethyl cellulose (CMC) in 100 parts by weight of carbon as the negative electrode active material carbon, distilled water is used as a solvent to prepare a slurry. Then, the slurry is applied to the copper foil 110 with a thickness of 20 to 60 μm using a doctor blade, and pressed at a pressure of 0.5 to 1.5 ton / cm 2 at 110 to 130 °C.

[0125] A secondary battery can be manufactured using a conventional positive electrode, electrolyte, and separator together with the electrode (negative electrode) for a secondary battery of the present invention manufactured by the above method.

[0126] Hereinafter, the present invention will be specifically described through examples and comparative examples. However, the following examples are only for helping to understand the present invention, and the scope of the rights of the present invention is not limited to these examples.

[0127] Examples 1-4 and Comparative Examples 1-4

[0128] A copper foil was manufactured using a foil-making machine including an electrolytic cell 10, a rotating cathode drum 40 disposed in the electrolytic cell 10, and an anode plate 30 disposed at a distance 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 was set to 110 g / L, the temperature of the electrolyte was set to 55 °C, and the current density was set to 60 ASD.

[0129] In addition, the chlorine (Cl) concentration contained in the electrolyte 20 was maintained at 20 ppm, and the concentrations of collagen, gelatin, and organic additives were as shown in Table 1 below. At this time, after filtering the electrolyte using carbon, collagen and gelatin were added to the filtered electrolyte.

[0130] Among the organic additives, sodium bis-(3-sulfopropyl)-disulfide (SPS) was used as a brightening agent (Component A), polyethylene glycol (PEG) was used as a retarder (Component B), and the molecular weights of collagen and gelatin were 3500 and 10000, respectively.

[0131] A copper film 111 was fabricated by applying an electric current at a current density of 60 ASD between a rotating cathode drum 40 and an anode plate 30. Subsequently, the copper film 111 was immersed in an anti-rust solution for approximately 2 seconds, and chromate treatment was performed on both sides of the copper film 111 to form a protective layer 112, thereby fabricating a copper foil. An anti-rust solution mainly composed of chromic acid was used as the anti-rust solution, and the concentration of chromic acid was 5 g / L.

[0132] As a result, copper foils of Example 1-4 and Comparative Example 1-4 were fabricated. At this time, the thickness of the fabricated copper foil was 8 μm.

[0133] [Table 1]

[0134]

[0135] [Table 2]

[0136]

[0137] [Table 3]

[0138]

[0139] [Table 4]

[0140]

[0141] [Table 5]

[0142]

[0143] [Table 6]

[0144]

[0145] For the copper foils of Example 1-4 and Comparative Example 1-4 fabricated in this manner, i) the amount of hydrogen vacancies according to the depth of the rough surface and the smooth surface; ii) the depth of the hydrogen component on the rough surface; and iii) whether curling (Curl) occurred were confirmed.

[0146] The copper foil was cut to obtain a 2 cm × 2 cm sample. After removing the protective layer on the copper film, the amount of hydrogen vacancies and the depth of the hydrogen component were measured on the rough surface and the smooth surface of the copper film, respectively. At this time, in order to remove the protective layer on the copper film, it was immersed in a sulfuric acid solution with a concentration of 10% for 30 seconds, and after performing water cleaning with distilled water for 30 seconds to remove the acidic solution, it was dried.

[0147] i) Measuring the amount of hydrogen vacancies according to the depth of the rough surface and the smooth surface

[0148] The amount of hydrogen vacancies according to the depths of the rough surface and the smooth surface refers to the number of hydrogen ions measured by TOF-SIMS (Time Of Flight-Secondary Ion Mass Spectrometry) at a certain sputtering depth away from the rough surface and the smooth surface of the copper film, respectively.

[0149] At this time, it is possible to measure the amount of hydrogen vacancies according to each depth to obtain a graph.

[0150] The specific sputtering conditions and analysis conditions are as follows.

[0151] Sputtering conditions:

[0152] - SpI (sputtering ion): Cs

[0153] - Energy: 3 keV

[0154] - Current: 26.0 nA

[0155] - Area: 300×300 μm 2

[0156] - SpIDD: 5.41E+16 ions / cm 2

[0157] Analysis conditions:

[0158] - PI (primary ion): Bi3

[0159] - Energy: 25 keV

[0160] - Current: 0.300 pA

[0161] - Area: 100×100 μm 2

[0162] - PIDD: 3.83E+12 ions / cm 2

[0163] ii) Depth of the hydrogen component of the rough surface

[0164] The depth of the hydrogen component of the rough surface refers to the depth at the position where the number of hydrogen ions measured by TOF-SIMS on the rough surface is 200 counts or more.

[0165] Specifically, in the graph of the amount of hydrogen vacancies measured in i), the depth up to the position where the number of hydrogen ions (count s) is 200 counts or more is calculated.

[0166] The case of "not measurable" indicated in Table 6 means that the position where the number of hydrogen ions is 200 counts or more is too deep from the rough surface to be measured.

[0167] iii) Whether Curl occurs

[0168] After 100 charge and discharge cycles, the secondary battery was disassembled to observe whether wrinkles or tears occurred in the copper foil. The occurrence of wrinkles or tears in the copper foil was indicated as "occurred", and the non-occurrence was indicated as "none".

[0169] Referring to Tables 1 to 6, Curl did not occur in the copper foils of Examples 1 to 4, while Curl occurred in the copper foils of Comparative Examples 1 to 4.

[0170] The present invention described above is not limited to the foregoing embodiments and drawings. It is obvious that those with ordinary knowledge in the technical field to which the present invention pertains can make various substitutions, deformations, and changes without departing from the technical idea of the present invention. Therefore, the scope of the present invention is defined by the appended claims and should be interpreted to include all manners of changes or deformations derived from the meaning, scope, and equivalent concepts of the claims.

Claims

1. A copper foil, wherein: It is a copper film with a rough surface and a smooth surface. The amount of hydrogen vacancies at a depth of 30 nm to 45 nm in the rough surface is 80 to 250 counts, The amount of hydrogen vacancies at a depth of 30 nm to 45 nm in the optical plane is 3 to 20 counts, The hydrogen vacancy amount refers to the number of hydrogen ions measured at a certain sputtering depth away from the rough surface and the smooth surface using time-of-flight secondary ion mass spectrometry TOF-SIMS.

2. The copper foil according to claim 1, wherein The amount of hydrogen vacancies at a depth of 60 nm to 75 nm in the rough surface is 15 to 60 counts, The amount of hydrogen vacancies at a depth of 60 nm to 75 nm in the optical plane is 1.0 to 10 counts.

3. The copper foil according to claim 1, wherein The depth of the hydrogen component of the rough surface is less than 35nm, The depth of the hydrogen component in the rough surface refers to the depth of a position where the number of hydrogen ions measured by TOF-SIMS in the rough surface is 200 counts or more.

4. The copper foil according to claim 1, wherein The invention also includes a protection layer disposed on the copper film.

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

6. A method for producing a copper foil, wherein: include: The step of preparing an electrolyte solution containing copper ions; a step of forming a copper film; as well as forming a protective layer on the copper film, The steps of forming the copper film include: The step of applying electricity to the anode plate and the rotating cathode drum which are arranged apart from each other in the electrolyte in the electrolytic cell to form a copper film on the rotating cathode drum, The electrolyte comprises: 70 to 150 g / L of copper ions; 80 to 150 g / L sulfuric acid; 15 to 25 ppm of chlorine; 1 to 15 ppm collagen; 0.1 to 5 ppm gelatin; and Organic additives, The organic additive comprises at least one of a brightener, i.e., component A, and a speed reducer, i.e., component B, wherein the brightener, i.e., component A, comprises sulfonic acid or a metal salt thereof, The moderator, Component B, includes a nonionic water-soluble polymer.

7. The method for producing a copper foil according to claim 6, wherein: The collagen and the gelatin were added at a ratio of 10:1 to 3:1 based on concentration.

8. The method for producing a copper foil according to claim 6, wherein: The steps of manufacturing the electrolyte include: A step of filtering the first electrolyte transferred from the storage tank with carbon to form a second electrolyte; and A step of adding the collagen and the gelatin to the second electrolyte to form the electrolyte.

9. The method for producing a copper foil according to claim 6, wherein: The collagen has a molecular weight of 2,000 to 10,000, The gelatin has a molecular weight of 10,000 to 100,000.

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