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. An embodiment of the present invention provides a copper foil comprising: a copper film having a rough surface and a smooth surface; and a protective layer on the copper film, the copper foil having a first surface in the direction of the rough surface and a second surface in the direction of the smooth surface of the copper film, and the copper foil satisfying formula 1. [Formula 1] 3.0 kgf / mm2 < = tensile strength * average coefficient of dynamic friction < = 8.0 kgf / mm2; the average dynamic friction coefficient of formula 1 refers to the average value of the dynamic friction coefficient of the first surface and the dynamic friction coefficient of the second surface.

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 having excellent strength while preventing slip during the manufacturing process, an electrode including the copper foil, a secondary battery including the electrode, and a method for manufacturing the same. Background Art

[0002] Copper foils are used in the manufacture of various products such as negative electrodes of secondary batteries and flexible printed circuit boards (FPCBs).

[0003] Generally, copper foils are produced by a roll-to-roll process in a foil manufacturing apparatus, and the process of coating an active material in the negative electrode manufacturing process of a secondary battery is also achieved by a roll-to-roll process. In recent years, in order to increase the capacity of secondary batteries, ultra-thin copper foils are used. When the thickness of the copper foil becomes less than 10 μm, a slip phenomenon often occurs between the roller and the copper foil. In the case of the slip phenomenon, wrinkles or tears occur in the copper foil and continuous processes cannot be carried out. Therefore, the workability or handleability of the electrode forming process for secondary batteries is reduced, and in severe cases, electrode manufacturing itself becomes impossible.

[0004] Therefore, it is necessary to suppress the slip of the copper foil and prevent or suppress the occurrence of wrinkles or tears in the copper foil. Summary of the Invention

[0005] Problems to be Solved by the Invention

[0006] Therefore, 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, which can solve the problems caused by the limitations and disadvantages of the related art as described above.

[0007] In addition to the viewpoints of the present invention mentioned above, other features and advantages of the present invention will be described below or can be clearly understood by those with ordinary knowledge in the technical field to which the present invention belongs from such a description.

[0008] Technical Solutions for Solving the Problems

[0009] An embodiment of the present invention provides a copper foil, including: a copper film having a rough surface and a smooth surface; and a protective layer on the copper film, the copper foil having a first surface in the direction of the rough surface of the copper film and a second surface in the direction of the smooth surface, and the copper foil satisfies the following formula 1. [Formula 1] 3.0 kgf / mm 2≤Tensile strength × Average dynamic friction coefficient≤8.0 kgf / mm 2 ; The average dynamic friction coefficient in Formula 1 refers to the average value of the dynamic friction coefficient of the first surface and the dynamic friction coefficient of the second surface.

[0010] Another embodiment of the present invention provides a method for manufacturing a copper foil, including: a step of manufacturing an electrolytic solution containing copper ions; a step of forming a copper film; and a step of forming a protective layer on the copper film, wherein the step of forming the copper film includes: a step of forming a copper film on the rotating cathode drum by applying electricity to an anode plate and a rotating cathode drum that are disposed separately from each other in the electrolytic solution in an electrolytic cell; the electrolytic solution contains: 70 to 150 g / L of copper ions; 80 to 150 g / L of sulfuric acid; 15 to 25 ppm of chlorine (Cl); and an organic additive, the organic additive includes at least one of a brightening agent (Component A), a retarder (Component B), and a leveling agent (Component C), and the leveling agent (Component C) contains a PEG-PPG derivative.

[0011] According to still another embodiment of the present invention, there is provided an electrode for a secondary battery, including: a copper foil; and an active material layer disposed on at least one surface of the copper foil.

[0012] According to still another embodiment of the present invention, there is provided a secondary battery, including: a cathode that provides lithium ions during charging; an anode that provides electrons and lithium ions during discharging; an electrolyte disposed between the cathode and the anode and providing an environment in which lithium ions can move; and a separator that electrically insulates the cathode and the anode.

[0013] Advantages of the Invention

[0014] The copper foil of the present invention prevents slip during the manufacturing process, prevents wrinkles or tears from occurring in the copper foil, and can have excellent tensile strength at the same time. Therefore, the copper foil according to one embodiment of the present invention can have excellent roll-to-roll processability, workability, or operability. Description of the Drawings

[0015] Figure 1 is a cross-sectional view of a copper foil according to an embodiment of the present invention.

[0016] Figure 2 is a cross-sectional view of an electrode for a secondary battery according to another embodiment of the present invention.

[0017] Figure 3 is a cross-sectional view of an electrode for a secondary battery according to still another embodiment of the present invention.

[0018] Figure 4Schematic cross-sectional view of a secondary battery according to another embodiment of the present invention.

[0019] Figure 5 Manufacturing apparatus for a copper foil according to another embodiment of the present invention.

[0020] Figure 6 Schematic diagram showing the circulation process of the electrolyte of the present invention.

[0021] Description of reference numerals

[0022] 100: Electrode for secondary battery

[0023] 110: Copper foil

[0024] 111: Copper film

[0025] 111a: Rough surface

[0026] 111b: Smooth surface

[0027] S1: First surface

[0028] S2: Second surface

[0029] 112: Protective layer

[0030] 120: Active material layer

[0031] 10: Electrolytic cell

[0032] 20: Electrolyte Detailed description of the embodiments

[0033] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the embodiments described below are only presented for the exemplary purpose of helping to clearly understand the present invention and do not limit the scope of the present invention.

[0034] The shapes, dimensions, 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, if it is judged that the detailed description of the relevant well-known technology may unnecessarily obscure the gist of the present invention, its detailed description will be omitted.

[0035] 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 if there is no other specific explanation, it will be interpreted as including an error range.

[0036] 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 expressions "directly" or "exactly" are used, one or more other parts may be provided between the two parts.

[0037] 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 in different directions during the use or operation of the element 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.

[0038] In the case of describing a time relationship, for example, in the case of describing the chronological relationship using "after", "then", "successively", "before", etc., unless the expressions "directly" or "exactly" are used, discontinuous cases may also be included.

[0039] 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.

[0040] The term "at least one" should be understood to include all combinations that can be prompted from more than one related item. For example, "at least one of the first item, the second item, and the third item" not only means 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.

[0041] The features of each of the multiple 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.

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

[0043] Refer to Figure 1, the copper foil 110 of the present invention includes a copper film 111 containing more than 99.9% by weight of copper. Refer to Figure 1 , the copper foil 110 of the present invention includes a copper film 111 and a protective layer 112 on the copper film 111. Figure 1 The structure in which the protective layers 112 are disposed on both sides of the copper film 111 is shown. However, an embodiment of the present invention is not limited thereto, and although not shown, the protective layer 112 may be disposed on one side of the copper film 111.

[0044] 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.

[0045] 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 the finished product including the copper foil 110.

[0046] According to an embodiment of the present invention, the copper foil 110 has a first surface S1 in the direction of the rough surface 111a of the copper film 111 and a second surface S2 in the direction of the smooth surface 111b. At this time, the copper foil 110 of an embodiment of the present invention may satisfy the following formula 1.

[0047] [Formula 1]

[0048] 3.0 kgf / mm 2 ≤ Tensile strength × Average dynamic friction coefficient ≤ 8.0 kgf / mm 2

[0049] Specifically, when the copper foil 110 of an embodiment of the present invention satisfies the formula 1, slipping is prevented during the manufacturing process, wrinkles or tears in the copper foil are prevented, and at the same time, excellent tensile strength can be obtained.

[0050] On the contrary, when the value of formula 1 is lower than 3.0 kgf / mm 2 , the tensile strength is excessively reduced, the mechanical and physical properties of the copper foil may be reduced, the average dynamic friction coefficient is excessively reduced, slipping occurs during the manufacturing process of the copper foil, and wrinkles or tears may occur in the copper foil.

[0051] In addition, when the value of formula 1 exceeds 8.0 kgf / mm 2In this case, although it is possible to prevent or suppress the occurrence of slip of the copper foil, the surface of the copper foil becomes excessively rough, and when an active material is coated on the copper foil, the coating may be uneven. In addition, even when the coefficient of kinetic friction remains at a certain value, when the tensile strength is excessively large, the brittleness of the copper foil 110 itself increases, and in the roll-to-roll process, since the copper foil 110 cannot cope with the force applied to the copper foil 110 and is stretched, tearing may occur in the copper foil 110.

[0052] At this time, the tensile strength of Equation 1 is measured using a universal testing machine (UTM) in accordance with the provisions of the IPC-TM-650 Test Method Manual. Specifically, the tensile strength of the copper foil 110 at room temperature (25 ± 3 °C) was measured using a universal testing machine from Instron. The width of the sample was 12.7 mm, the distance between the grips was 50 mm, and the measurement speed was 50 mm / minute.

[0053] In addition, the average coefficient of kinetic friction of Equation 1 refers to the average value of the coefficients of kinetic friction of the first surface S1 and the second surface S2 of the copper foil 110. Specifically, it refers to half of the sum of the coefficients of kinetic friction of the first surface S1 and the second surface S2.

[0054] At this time, the coefficients of kinetic friction of the first surface S1 and the second surface S2 of the copper foil 110 can be measured by WL2100C of WITHLAB in accordance with the provisions of ASTM D1894. Specifically, by bringing a stainless steel ball (SUS ball) into contact with the copper foil 110 and moving them relative to each other while applying a load to the stainless steel ball (SUS ball), the coefficient of kinetic friction of the copper foil 110 can be measured. At this time, a stainless steel ball (SUS ball) with a diameter of 10 mm can be used to measure the coefficient of kinetic friction of the copper foil 110 under the conditions of a speed of 150 mm / minute, a vertical load of 1.96 N (200 g), and a load cell of 29 N. The coefficient of kinetic friction is measured 3 times, and the average value is used.

[0055] According to an embodiment of the present invention, the coefficient of kinetic friction of the first surface S1 of the copper foil 110 is 0.05 to 0.15, and the coefficient of kinetic friction of the second surface S2 can be 0.1 to 0.2. Specifically, when the coefficients of kinetic friction of the first surface S1 and the second surface S2 of the copper foil 110 satisfy the above range, slip can be prevented during the manufacturing process of the copper foil, and wrinkles or tears in the copper foil can be prevented.

[0056] On the contrary, when the coefficient of kinetic friction of the first surface S1 is less than 0.05 or the coefficient of kinetic friction of the second surface S2 is less than 0.1, slip may occur during the manufacturing process of the copper foil 110, and wrinkles or tears may occur in the copper foil 110.

[0057] In addition, when the coefficient of kinetic friction of the first surface S1 exceeds 0.15 or the coefficient of kinetic friction of the second surface S2 exceeds 0.2, although slip during the manufacturing process of the copper foil 110 can be suppressed, the surface of the copper foil 110 becomes overly rough, and when an active material is coated on the copper foil, the coating may be uneven.

[0058] According to an embodiment of the present invention, the difference in the coefficient of kinetic friction between the first surface S1 and the second surface S2 of the copper foil 110 may be 0.1 or less. Specifically, when the difference in the coefficient of kinetic friction between the first surface S1 and the second surface S2 of the copper foil 110 is 0.1 or less, the difference in surface characteristics between the first surface S1 and the second surface S2 is small, and uniform coating of the active material can be achieved on both sides of the copper foil 110.

[0059] On the contrary, when the difference in the coefficient of kinetic friction between the first surface S1 and the second surface S2 of the copper foil 110 exceeds 0.1, the difference in surface characteristics between the first surface S1 and the second surface S2 becomes large, and uniform coating of the active material on both sides of the copper foil 110 may be difficult.

[0060] The copper foil 110 according to 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, which is therefore beneficial to the high-capacity of the secondary battery. However, manufacturing a copper foil 110 with a thickness less than 4 μm results in reduced workability.

[0061] On the contrary, when manufacturing a secondary battery with a copper foil 110 thicker than 35 μm, it is difficult to achieve high capacity due to the thick copper foil 110.

[0062] 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.

[0063] Figure 2 It is a cross-sectional view of the secondary battery electrode 100a according to an embodiment of the present invention. Figure 3 It is a cross-sectional view of the secondary battery electrode 100b according to another embodiment of the present invention.

[0064] As Figure 2 shown, the secondary battery electrode 100a according to 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.

[0065] Figure 2 shows a configuration in which the active material layer 120 is formed on one side of the copper foil 110. However, an embodiment of the present invention is not limited thereto. Referring to Figure 3 , the active material layer 120 may also be formed on both sides of the copper foil 110.

[0066] Generally, in a lithium secondary battery, 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.

[0067] According to an embodiment of the present invention, the secondary battery electrode 100 is a negative electrode, the copper foil 110 serves as the negative electrode current collector, and the active material layer 120 contains a negative electrode active material.

[0068] 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 at least one of, for example, Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni, and Fe, and preferably may include Si and / or Sn.

[0069] Figure 4 is a schematic cross-sectional view of a secondary battery according to an embodiment of the present invention.

[0070] Referring to Figure 4 , the secondary battery includes a positive electrode (cathode) 370, a negative electrode (anode) 340, an electrolyte (electrolyte) 350 disposed between the positive electrode 370 and the negative electrode 340 to provide an environment in which ions can move, and a separator (separator) 360 that electrically insulates the positive electrode 370 and the negative electrode 340. Here, the ions moving between the positive electrode 370 and the negative electrode 340 are, for example, lithium ions. The separator 360 separates the positive electrode 370 and the negative electrode 340 to prevent the charge generated in one electrode from moving through the inside of the secondary battery 105 to the other electrode and being wasted. Referring to Figure 4 , the separator 360 is disposed within the electrolyte 350.

[0071] The positive electrode 370 includes a positive electrode current collector 371 and a positive electrode active material layer 372, and aluminum foil (foil) may be used as the positive electrode current collector 371.

[0072] The negative electrode 340 includes a negative electrode current collector 341 and a negative electrode active material layer 342, and the copper foil 110 may be used as the negative electrode current collector 341.

[0073] According to an embodiment of the present invention, the copper foil 110 disclosed as the negative electrode current collector 341 may be used. Additionally, Figure 1 or Figure 2 orFigure 3 The electrodes 100a and 100b for secondary batteries shown can be used as Figure 4 the negative electrode 340 of the secondary battery shown.

[0074] Hereinafter, with reference to Figure 5 and Figure 6 the manufacturing method of the copper foil 110 of the present invention will be specifically described.

[0075] 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.

[0076] The method of the present invention includes a step of forming a copper film 111 on the rotating cathode drum 40 by energizing the anode plate 30 and the rotating cathode drum 40 disposed separately from each other in the electrolytic solution 20 in the electrolytic cell 10.

[0077] As exemplified in Figure 5 , the anode plate 30 may include a first anode plate 31 and a second anode plate 32 that are electrically insulated from each other.

[0078] The copper film 111 forming step 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.

[0079] The current densities provided by the first anode plate 31 and the second anode plate 32 respectively may be 30 to 130 ASD.

[0080] When the current densities provided by the first anode plate 31 and the second anode plate 32 respectively 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.

[0081] On the contrary, when the current densities provided by the first anode plate 31 and the second anode plate 32 respectively 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.

[0082] 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.

[0083] 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 can be controlled by adjusting the composition of the electrolytic solution 20.

[0084] According to an embodiment of the present invention, the electrolyte 20 may include copper ions, sulfuric acid, chlorine (Cl), and an organic additive.

[0085] In order to smoothly form the copper film 111 by electrodeposition of copper, the concentrations of copper ions and sulfuric acid in the electrolyte 20 are adjusted to 70 to 150 g / L and 80 to 150 g / L, respectively.

[0086] 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 flowing 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). This silver chloride (AgCl) can be removed by filtration.

[0087] When the concentration of chlorine (Cl) is less than 15 ppm, silver (Ag) ions cannot be smoothly removed. On the contrary, when the concentration of chlorine (Cl) exceeds 25 ppm, unnecessary reactions may occur due to excessive chlorine (Cl). Therefore, the concentration of chlorine (Cl) in the electrolyte 20 is controlled in the range of 15 to 25 ppm.

[0088] According to an embodiment of the present invention, the electrolyte 20 may include an organic additive.

[0089] The organic additive contained in the electrolyte 20 includes a brightener (component A), a retarder (component B), and a leveler (component C).

[0090] The brightener (component A) includes a sulfonic acid or its metal salt. The brightener (component A) may have a concentration of 1 to 20 ppm in the electrolyte 20.

[0091] The brightener (component A) increases the charge amount of the electrolyte 20 and thus increases the electrodeposition rate of copper, improves the curl characteristics of the copper foil, and can enhance the gloss of the copper foil 110. If the concentration of the brightener (component A) is less than 1 ppm, the gloss of the copper foil 110 decreases, and if it exceeds 20 ppm, problems such as weight change or surface roughness change may occur after dipping the copper foil 110.

[0092] The brightener may include, for example, bis-(3-sulfopropyl)-disulfide disodium salt, 3-mercapto-1-propanesulfonic acid, 3-(N,N-dimethylthiocarbamoyl)-thiopropanesulfonic acid sodium salt, 3-[(amino-iminomethyl)thio]-1-propanesulfonic acid sodium salt, o-ethyl dithiocarbonate-S-(3-sulfopropyl)-ester sodium salt, 3-(benzothiazole-2

[0093] At least one of sodium 3-mercapto-1-propanesulfonate and ethylene dithiodipropyl sulfonic acid sodium salt.

[0094] The retarder (Component B) contains a nonionic water-soluble polymer. The retarder (Component B) may have a concentration of 1 to 10 ppm in the electrolyte 20.

[0095] The retarder (Component B) reduces the rate of copper electrodeposition, thereby preventing a sharp increase in the roughness and a decrease in the strength of the copper foil 110. Such a retarder (Component B) is also referred to as an inhibitor or a suppressor.

[0096] If the concentration of the retarder (Component B) is less than 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 10 ppm, there is almost no change in the physical properties of the copper foil 110 such as appearance, gloss, roughness, strength, and elongation. Therefore, the concentration of the retarder (Component B) can be adjusted to the range of 1 to 10 ppm without unnecessarily increasing the manufacturing cost and wasting raw materials by increasing the concentration of the retarder (Component B).

[0097] The retarder (Component B) may include, for example, at least one nonionic water-soluble polymer selected from polyethylene glycol (PEG), polypropylene glycol, polyethylene-polypropylene copolymer, polyglycerol, polyethylene glycol dimethyl ether, hydroxyethyl cellulose, polyvinyl alcohol, polyethylene glycol stearate ether, and polyethylene glycol stearyl ether. However, the types of retarders are not limited thereto, and another nonionic water-soluble polymer that can be used in the manufacture of the high-strength copper foil 110 can be used as the retarder.

[0098] The leveler (Component C) contains a PEG-PPG derivative. The leveler (Component C) may have a concentration of 0.1 to 10 ppm in the electrolyte 20.

[0099] The leveler (Component C) prevents the generation of excessive peaks or large protrusions in the copper film 111, making the copper film 111 macroscopically flat. The leveler (Component C) may have a concentration of 0.1 to 10 ppm in the electrolyte 20.

[0100] Specifically, the end groups of the PEG-PPG derivative in an embodiment of the present invention are substituted with a saturated hydrocarbon or a functional group. At this time, the functional group may include at least one of a vinyl group, an acrylic group, and a bisphenol group. At this time, PEG refers to polyethylene glycol, and PPG refers to polypropylene glycol.

[0101] Specifically, in the case of a PEG-PPG copolymer, generally, hydroxyl groups (-OH) are present in the end groups, and the hydroxyl groups (-OH) present in the end groups may react with other additives added to the electrolyte, thereby reducing the physical properties of the copper foil.

[0102] At this time, when the end groups of the PEG-PPG derivative are substituted with a functional group containing at least one of a saturated hydrocarbon, a vinyl group, an acrylic group, and a bisphenol group, the end groups of the PEG-PPG derivative become stable, and the influence of various by-products in the electrolyte used for a long time may be reduced. Specifically, compared with the unsubstituted PEG-PPG derivative, it has the advantage of being able to reduce defects in electroplating such as pinholes.

[0103] If the concentration of the leveling agent (Component C) is less than 0.1 ppm, the strength of the copper foil 110 decreases, and difficulties may occur during the manufacturing process of the high-strength copper foil 110.

[0104] On the contrary, when the concentration of the leveling agent (Component C) exceeds 10 ppm, the surface roughness of the copper foil 110 excessively increases and the strength may decrease, pinholes or curls (Cu rl) occur on the surface of the copper foil 110, and difficulties may occur during the separation process of the copper foil 110 from the winding machine (WR) after the copper foil 110 is manufactured.

[0105] The leveling agent (Component C) may include, for example, at least one of PEG-PPG-isodecyl ether, PEG-PPG-glyceryl ether, PEG-PPG-butyl ether, PEG-PPG-hexylene glycol, PEG-PPG-trimethylolpropane, PEG-PPG-allylether, PEG-PPG-Methacrylate, PEG-PPG-Acylate, and PEG-PPG-bisphenol A ether.

[0106] When forming the copper film 111, the flow rate of the electrolyte 20 supplied into the electrolytic cell 10 may be 41 to 45 m 3 / hour.

[0107] Figure 6 It is a schematic diagram showing the circulation process of the electrolyte of the present invention.

[0108] According to an embodiment of the present invention, the steps of manufacturing an electrolyte may include a step of forming a second electrolyte by transferring a first electrolyte transferred from a storage tank using carbon filtration C / F, and a step of forming an electrolyte by adding a leveling agent (component C) to the filtered second electrolyte.

[0109] Specifically, the first electrolyte transferred from the storage tank may contain copper ions, sulfuric acid, chlorine, organic additives, etc.

[0110] The process of carbon filtering C / F the first electrolyte refers to the step of removing organic impurities and inorganic impurities present in the first electrolyte.

[0111] According to an embodiment of the present invention, the second electrolyte refers to the electrolyte obtained by carbon filtering the first electrolyte.

[0112] According to an embodiment of the present invention, a leveling agent (component C) may be added to the second electrolyte to form an electrolyte. The additives contained in the electrolyte have been described above and are omitted here. Specifically, the leveling agent (component C) is added after the carbon filtering C / F process.

[0113] For example, if the leveling agent (component C) is added before the carbon filtering C / F process, the leveling agent (component C) may be deteriorated and the physical properties of the copper foil may be reduced. On the contrary, if the leveling agent (component C) is added after the carbon filtering C / F process, deterioration of the leveling agent (component C) is prevented and the physical properties of the present invention are improved.

[0114] The electrolyte formed by adding the leveling agent (component C) 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.

[0115] 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.

[0116] According to an embodiment of the present invention, the steps of manufacturing the electrolyte 20 may include: a step of heat-treating the copper wire, a step of pickling the heat-treated copper wire, a step of washing the pickled copper wire, and a step of putting the washed copper wire into sulfuric acid for the electrolyte.

[0117] 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 in sequence: Heat-treat high-purity (99.9% or more) copper wire in an electric furnace at 750°C to 850°C to burn off various organic impurities attached to the copper wire, and then sequentially perform pickling of the heat-treated copper wire for 10 to 20 minutes with a 10% sulfuric acid solution and water washing of the pickled copper wire with distilled water. The water-washed copper wire can be put into sulfuric acid for the electrolyte to manufacture the electrolyte 20.

[0118] 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.

[0119] The copper film 111 manufactured in this way can be cleaned in a cleaning tank.

[0120] For example, pickling (acid cleaning) for removing impurities such as resin components or natural oxide on the surface of the copper film 111 and water washing (water cleaning) for removing the acidic solution used in pickling can be performed in sequence. The cleaning process can also be omitted.

[0121] Next, a protective layer 112 is formed on the copper film 111.

[0122] Refer to Figure 5 , and 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.

[0123] 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.

[0124] On the other hand, the protective layer 112 may include a silane compound based on silane treatment or may also include a nitrogen compound based on nitrogen treatment.

[0125] The copper foil 110 is manufactured by forming such a protective layer 112.

[0126] 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; a metal (Me) such as Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe; an alloy containing the metal (Me); an oxide (MeO x ); and a composite of the metal (Me) and carbon are coated, whereby an electrode (i.e., a negative electrode) for a secondary battery of the present invention can be manufactured.

[0127] 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 onto 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.

[0128] 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.

[0129] 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.

[0130] Examples 1-4 and Comparative Examples 1-4

[0131] 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 apart from the rotating cathode drum 40. The electrolytic solution 20 was a copper sulfate solution. The concentration of copper ions in the electrolytic solution 20 was set to 87 g / L, the concentration of sulfuric acid was set to 110 g / L, the temperature of the electrolytic solution was set to 55°C, and the current density was set to 60 ASD.

[0132] In addition, the concentration of chlorine (Cl) contained in the electrolytic solution 20 was maintained at 20 ppm, and the concentration of the organic additive was as shown in Table 1 below. At this time, after filtering the electrolytic solution using carbon, a leveling agent was added to the filtered electrolytic solution.

[0133] Among the organic additives, bis-(3-sulfopropyl)-disulfide disodium salt (SPS) was used as a brightening agent (Component A), polyethylene glycol (PEG) was used as a retarder (Component B), and PEG-PPG-isodecyl ether was used as a leveling agent (Component C).

[0134] A copper film 111 was fabricated by applying a 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.

[0135] 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.

[0136] [Table 1]

[0137]

[0138] [Table 2]

[0139]

[0140] For the copper foils of Example 1-4 and Comparative Example 1-4 fabricated in this way, i) tensile strength; ii) coefficient of kinetic friction of the first side and the second side; iii) average coefficient of kinetic friction; iv) Equation 1; and v) whether wrinkles or tears occurred were confirmed.

[0141] The copper foil was cut to obtain a 15 cm × 15 cm sample.

[0142] i) Tensile strength

[0143] The tensile strength can be measured using a universal testing machine (UTM) according to the method specified in the IPC-TM-650 Test Method Manual. Specifically, the tensile strength can be measured at room temperature (25 ± 3 °C) using a universal testing machine from Instron. The width of the sample is 12.7 mm, the distance between the grips is 50 mm, and the measurement speed is 50 mm / minute.

[0144] ii) Coefficient of kinetic friction of the first side and the second side

[0145] The coefficient of kinetic friction of the first side and the second side can be measured by WL2100C from WITHLAB according to the provisions of ASTM D1894. Specifically, a stainless steel ball (SUS ball) can be brought into contact with the sample, and while applying a load to the stainless steel ball (SUS ball), they can be moved relative to each other, thereby enabling the measurement of the coefficient of kinetic friction of both sides of the sample. At this time, a stainless steel ball (SUS ball) with a diameter of 10 mm can be used to measure the coefficient of kinetic friction under the conditions of a speed of 150 mm / minute, a vertical load of 1.96 N (200 g), and a load cell condition of 29 N. The coefficient of kinetic friction is measured 3 times, and the average value is used.

[0146] iii) Average kinetic friction coefficient

[0147] The average kinetic friction coefficient refers to the average value of the measured kinetic friction coefficients of the first and second surfaces. Specifically, it refers to half of the sum of the kinetic friction coefficients of the first and second surfaces.

[0148] iv) Whether wrinkling or tearing occurs

[0149] After 100 charge and discharge cycles, the secondary battery was disassembled to observe whether wrinkling or tearing occurred in the copper foil. The occurrence of wrinkling or tearing in the copper foil was marked as "occurred", and the non-occurrence was marked as "none".

[0150] Referring to Tables 1 and 2, no wrinkling or tearing occurred in the copper foils of Examples 1 to 4, while wrinkling or tearing occurred in the copper foils of Comparative Examples 1 to 4.

[0151] 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 expressed by the appended claims and should be interpreted to include all ways of change or deformation derived from the meaning, scope, and equivalent concepts of the claims within the scope of the present invention.

Claims

1. A copper foil, wherein include: Copper film with rough and glossy sides; as well as The protective layer on the copper film, The copper foil has a first surface in the rough surface direction of the copper film and a second surface in the smooth surface direction. The copper foil satisfies the following formula 1: Formula 1 3.0kgf / mm 2 ≤Tensile strength×average dynamic friction coefficient≤8.0kgf / mm 2 The average dynamic friction coefficient of Formula 1 refers to the average value of the dynamic friction coefficient of the first surface and the dynamic friction coefficient of the second surface.

2. The copper foil according to claim 1, wherein The dynamic friction coefficient of the first surface is 0.05 to 0.15, The dynamic friction coefficient of the second surface is 0.1 to 0.

2.

3. The copper foil according to claim 1, wherein A difference between a dynamic friction coefficient of the first surface and a dynamic friction coefficient of the second surface is 0.1 or less.

4. The copper foil according to claim 1, wherein The protective layer includes at least one of a chromium compound, a silane compound, and a nitrogen compound.

5. 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 step of forming the copper film includes: energizing an anode plate and a rotating cathode roller that are spaced apart from each other in an electrolyte in an electrolytic cell, thereby forming a copper film on the rotating cathode roller. The electrolyte comprises: 70 to 150 g / L of copper ions; 80 to 150 g / L sulfuric acid; 15 to 25 ppm chlorine Cl; and Organic additives, The organic additives include a glossing agent, i.e. component A, a speed reducer, i.e. component B, and a leveling agent, i.e. component C. The leveler, component C, comprises a PEG-PPG derivative.

6. The method for producing copper foil according to claim 5, 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 5, wherein: The terminal groups of the PEG-PPG derivatives are substituted by saturated hydrocarbons or functional groups.

8. The method for producing a copper foil according to claim 7, wherein: The functional group is at least one of a vinyl group, an acrylic group and a bisphenol group.

9. The method for producing a copper foil according to claim 5, 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 leveling agent, namely component C, to the second electrolyte solution to form the electrolyte solution.

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