Copper foil, electrode comprising the same, secondary battery comprising the same, and method of manufacturing the same

Abstract

To provide a copper foil that has excellent strength and prevents slippage during the manufacturing process, an electrode containing the same, a secondary battery containing the same, and a manufacturing method thereof.SOLUTION: There is provided a copper foil that includes a copper film having a matte surface and a shiny surface, and a protective layer disposed on the copper film, wherein the copper film has a first surface in a direction of the matte surface and a second surface in a direction of the shiny surface, and Equation 1 below is satisfied. 3.0 kgf / mm2≤tensile strength×average kinetic friction coefficient≤8.0 kgf / mm2. [Equation 1] The average kinetic friction coefficient in Equation 1 means an average value of kinetic friction coefficients of the first surface and the second surface.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a copper foil, an electrode containing the same, a secondary battery containing the same, and a method for manufacturing the same. Specifically, the present invention relates to a copper foil, an electrode containing the same, a secondary battery containing the same, and a method for manufacturing the same, which prevent slip during the manufacturing process and have excellent strength.

Background Art

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

[0003] Generally, copper foils are produced in a roll-to-roll process in a foil manufacturing apparatus, and the process of coating an active material during the manufacturing process of the negative electrode of a secondary battery is also performed in a roll-to-roll process. Recently, ultra-thin copper foils are used due to the increase in the capacity of secondary batteries. However, when the thickness of the copper foil becomes thinner than 10 μm, a slip phenomenon frequently occurs between the roll and the copper foil. When the slip phenomenon occurs, wrinkles or tearing occurs in the copper foil, making the continuous process impossible. As a result, the workability or handleability of the electrode formation process for secondary batteries decreases, and in severe cases, the manufacturing of the electrode 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 tearing in the copper foil.

Summary of the Invention

Problems to be Solved by the Invention

[0005] Therefore, the present invention relates to a copper foil, an electrode containing the same, a secondary battery containing the same, and a method for manufacturing the same, which can prevent problems caused by the limitations and disadvantages of the related art as described above.

[0006] In addition to the aspects of the present invention mentioned above, other features and advantages of the present invention will be described below, or will be clearly understood by those having ordinary knowledge in the technical field to which the present invention pertains from such description.

Means for Solving the Problems

[0007] One embodiment of the present invention provides a copper foil including a copper film having a matte surface and a shiny surface; and a protective layer on the copper film, the copper film having a first surface in the direction of the matte surface and a second surface in the direction of the shiny surface, and satisfying the following formula 1. [Formula 1] 3.0 kgf / mm 2 ≦Tensile strength × Average coefficient of kinetic friction ≦ 8.0 kgf / mm 2 The average coefficient of kinetic friction in Formula 1 means the average value of the coefficients of kinetic friction of the first surface and the second surface.

[0008] Another embodiment of the present invention includes the steps of manufacturing an electrolytic solution containing copper ions; forming a copper film; and forming a protective layer on the copper film. The step of forming the copper film includes the step of forming a copper film on the rotating negative electrode drum by energizing a positive electrode plate and a rotating negative electrode drum arranged to be separated 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 brightener (Component A), a retarder (Component B), and a leveling agent (Component C). The leveling agent (Component C) includes a PEG-PPG derivative, and provides a method for manufacturing a copper foil.

[0009] 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.

[0010] 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 that provides an environment in which lithium ions can move; and a separator that electrically insulates the cathode and the anode.

Advantages of the Invention

[0011] The copper foil according to the present invention can prevent slip during the manufacturing process, prevent wrinkles or tears from occurring in the copper foil, and at the same time can have excellent tensile strength. Therefore, the copper foil according to one embodiment of the present invention can have excellent roll-to-roll processability, workability or handleability.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0013] 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 illustrative purposes to assist in a clear understanding of the present invention and do not limit the scope of the present invention.

[0014] The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for explaining the embodiments of the present invention are exemplary, so the present invention is not limited to the matters illustrated in the drawings. Throughout the specification, the same components may be referred to by the same reference numerals. In explaining the present invention, when it is determined that a specific explanation of related known technologies may unnecessarily obscure the gist of the present invention, the detailed explanation thereof will be omitted.

[0015] When terms such as "including", "having", "consisting of", etc. mentioned in this specification are used, other parts may be added as long as the expression "only" is not used. When a component is expressed in the singular, it includes a plurality unless otherwise explicitly stated. Also, in the interpretation of components, it is interpreted to include the error range even without separate explicit description.

[0016] In the case of an explanation of the positional relationship, for example, when the positional relationship between both parts is explained by "on", "above", "below", "beside", etc., one or more other parts can be located between both parts as long as the expressions "immediately" or "directly" are not used.

[0017] Spatially relative terms such as "below", "beneath", "lower", "above", "upper", etc. can be used to easily describe the correlation between one element or component and another element or component as shown in the drawings. Spatially relative terms should be understood as terms including different directions of elements during use or operation in addition to the directions shown in the drawings. For example, when the element shown in the drawing is turned over, the element described as "below" or "beneath" another element can be placed "above" the other element. Therefore, the exemplary term "below" can include all directions of up and down. Similarly, the exemplary terms "above" or "on" can include all directions of up and down.

[0018] In the case of an explanation regarding the relationship of time, for example, when the temporal precedence relationship is explained using expressions such as "after ~", "subsequent to ~", "next to ~", "before ~", etc., cases where the expressions "immediately" or "directly" are not used and which are not continuous can also be included.

[0019] The first, second, etc. are used to describe various components, but these components are not limited by these terms. These terms are merely used to distinguish one component from another. Therefore, the first component mentioned below may be the second component within the technical idea of the present invention.

[0020] The term "at least one" should be understood to include all combinations that can be presented from one or more related items. For example, the meaning of "at least one of the first item, the second item, and the third item" may mean not only each of the first item, the second item, or the third item alone but also all combinations of two or more items that can be presented from among the first item, the second item, and the third item.

[0021] The respective features of the various embodiments of the present invention can be partially or entirely combined or combined with each other, enabling various technical linkages and drives, and each embodiment may be implemented independently of each other or may be implemented together in a related relationship.

[0022] FIG. 1 is a cross-sectional view of a copper foil 110 according to an embodiment of the present invention.

[0023] Referring to FIG. 1, the copper foil 110a of the present invention includes a copper film 111 containing 99.9 wt% or more of copper. Referring to FIG. 1, the copper foil 110 of the present invention includes a copper film 111 and a protective layer 112 on the copper film 111. FIG. 1 shows a configuration in which protective layers 112 are disposed on both surfaces of the copper film 111. However, an embodiment of the present invention is not limited thereto, and although not shown, a protective layer 112 may be disposed on one surface of the copper film 111.

[0024] The copper film 111 may be formed on the rotating negative electrode drum through electroplating, and may have a shiny surface 111b that is in direct contact with the rotating negative electrode drum during the electroplating process and a matte surface 111a on the opposite side thereof.

[0025] The protective layer 112 is formed by electrodepositing an anticorrosion material on the copper film 111. The anticorrosion material may include at least one of a chromium compound, a silane compound, and a nitrogen compound. The protective layer 112 prevents oxidation and corrosion of the copper film 111 and improves heat resistance, thereby extending the lifespan of the copper foil 110 as well as the lifespan of the final product including the same.

[0026] According to an embodiment of the present invention, the copper foil 110 has a first surface S1 in the direction of the matte surface 111a of the copper film 111 and a second surface S2 in the direction of the shiny surface 111b. At this time, the copper foil 110 according to an embodiment of the present invention can satisfy the following formula 1.

[0027] [Formula 1] 3.0 kgf / mm 2 ≦ Tensile strength x Average coefficient of kinetic friction ≦ 8.0 kgf / mm 2 Specifically, when the copper foil 110 according to an embodiment of the present invention satisfies the formula 1, slip is prevented during the manufacturing process, wrinkles or tears are prevented from occurring in the copper foil, and at the same time, it can have excellent tensile strength.

[0028] On the other hand, when the value of formula 1 is less than 3.0 kgf / mm 2 the tensile strength may become excessively low, the mechanical properties of the copper foil may deteriorate, the average coefficient of kinetic friction may become excessively low, slip may occur during the manufacturing process of the copper foil, and wrinkles or tears may occur in the copper foil.

[0029] Also, when the value of formula 1 is 8.0 kgf / mm 2In the case of exceeding, the occurrence of slip of the copper foil can be prevented or suppressed. However, the surface of the copper foil becomes excessively rough, and when coating the copper foil with an active material, the coating may become non-uniform. Further, even if the coefficient of kinetic friction maintains a constant value, when the tensile strength is excessively large, the brittleness of the copper foil 110 increases, and the copper foil 110 may not stretch in response to the force applied to the copper foil 110 during the roll-to-roll process, resulting in tearing of the copper foil 110.

[0030] At this time, the tensile strength in Equation 1 was measured by a universal testing machine (UTM) according to 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 of 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 / min.

[0031] Also, the average coefficient of kinetic friction in Equation 1 means 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 means half of the sum of the coefficients of kinetic friction of the first surface S1 and the second surface S2.

[0032] 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 a Withlab WL2100C according to the provisions of ASTM D1894. Specifically, a stainless steel ball (SUS ball) is brought into contact with the copper foil 110, and while applying a load to the stainless steel ball (SUS ball), they are moved relative to each other to measure the coefficient of kinetic friction of the copper foil 110. At this time, a stainless steel ball (SUS ball) with a diameter of 10 mm is used, and the coefficient of kinetic friction of the copper foil 110 can be measured under the conditions of a speed of 150 mm / min, a vertical load of 1.96 N (200 g), and a load cell of 29 N. The coefficient of kinetic friction is measured three times, and the average value is used.

[0033] According to an embodiment of the present invention, the coefficient of kinetic friction of the first surface S1 of the copper foil 110 may be 0.05 to 0.15, and the coefficient of kinetic friction of the second surface S2 may 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 ranges, slip can be prevented during the manufacturing process of the copper foil, and wrinkles or tears can be prevented from occurring in the copper foil.

[0034] On the other hand, 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.

[0035] Also, 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, even if the occurrence of slip can be suppressed during the manufacturing process of the copper foil 110, the surface of the copper foil 110 becomes excessively rough, and when the active material is coated on the copper foil, the coating may become non-uniform.

[0036] According to an embodiment of the present invention, the difference in the coefficients 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 coefficients 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 the surface characteristics between the first surface S1 and the second surface S2 is small, so a uniform coating of the active material on both sides of the copper foil 110 may be possible.

[0037] On the other hand, when the difference in the coefficients of kinetic friction between the first surface S1 and the second surface S2 of the copper foil 110 exceeds 0.1, the difference in the surface characteristics between the first surface S1 and the second surface S2 becomes large, and it becomes difficult to uniformly coat the active material on both sides of the copper foil 110.

[0038] According to one embodiment of the present invention, the copper foil 110 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 advantageous for increasing the capacity of the secondary battery. However, manufacturing the copper foil 110 with a thickness of less than 4 μm causes a decrease in workability.

[0039] On the other hand, when manufacturing a secondary battery with a copper foil 110 having a thickness exceeding 35 μm, it becomes difficult to realize a high capacity due to the thick copper foil 110.

[0040] 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.

[0041] FIG. 2 is a cross-sectional view of the electrode 100a for a secondary battery according to one embodiment of the present invention. FIG. 3 is a cross-sectional view of the electrode 100b for a secondary battery according to another embodiment of the present invention.

[0042] As shown in FIG. 2, the electrode 100a for a secondary battery according to one embodiment of the present invention includes any one of the copper foils 110 and the active material layer 120 of the above-described embodiments of the present invention.

[0043] FIG. 2 shows a configuration in which the active material layer 120 is formed on one surface of the copper foil 110. However, one embodiment of the present invention is not limited thereto, and referring to FIG. 3, the active material layer 120 can also be formed on both surfaces of the copper foil 110.

[0044] In a lithium secondary battery, an aluminum foil is generally used as a positive electrode current collector that binds to a positive electrode active material, and the copper foil 110 is generally used as a negative electrode current collector that binds to a negative electrode active material.

[0045] According to one embodiment of the present invention, the electrode 100 for the secondary battery is a negative electrode, the copper foil 110 is used as a negative electrode current collector, and the active material layer 120 includes a negative electrode active material.

[0046] In order to guarantee the high capacity of the secondary battery, the active material layer 120 of the present invention can be formed of a composite of carbon and metal. The metal may include, for example, at least one of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni, and Fe, preferably Si and / or Sn.

[0047] FIG. 4 is a schematic cross-sectional view of a secondary battery according to an embodiment of the present invention.

[0048] Referring to FIG. 4, 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 at one electrode from being wasted by moving to the other electrode through the inside of the secondary battery 105. Referring to FIG. 4, the separator 360 is disposed in the electrolyte 350.

[0049] The cathode 370 includes a cathode current collector 371 and a cathode active material layer 372, and an aluminum foil can be used as the cathode current collector 371.

[0050] The anode 340 includes an anode current collector 341 and an anode active material layer 342, and a copper foil 110 can be used as the anode current collector 341.

[0051] According to an embodiment of the present invention, the copper foil 110 shown in FIG. 1 can be used as the anode current collector 341. Further, the electrodes 100a and 100b for secondary batteries shown in FIG. 2 or FIG. 3 can be used for the anode 340 of the secondary battery shown in FIG. 4.

[0052] Hereinafter, the manufacturing method of the copper foil 110 of the present invention will be specifically described with reference to FIGS. 5 and 6.

[0053] The method for manufacturing 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.

[0054] The method of the present invention includes a step of forming a copper film 111 on the rotating negative electrode drum 40 by energizing a positive electrode plate 30 and a rotating negative electrode drum 40 which are arranged to be separated from each other in the electrolytic solution 20 in the electrolytic cell 10.

[0055] As shown in FIG. 5, the positive electrode plate 30 may include first and second positive electrode plates 31 and 32 which are electrically insulated from each other.

[0056] The step of forming the copper film 111 can be performed by forming a seed layer by energization between the first positive electrode plate 31 and the rotating negative electrode drum 40, and then growing the seed layer by energization between the second positive electrode plate 32 and the rotating negative electrode drum 40.

[0057] The current density provided by the first and second positive electrode plates 31 and 32 respectively can be 30 to 130 ASD.

[0058] When the current density provided by the first and second positive electrode plates 31 and 32 respectively is less than 30 ASD, since the surface roughness of the copper foil 110 is low, the adhesion between the copper foil 110 and the active material layer 120 may not be sufficient.

[0059] On the other hand, when the current density provided by the first and second positive electrode plates 31 and 32 respectively exceeds 130 ASD, the surface of the copper foil 110 becomes rough, and the coating of the active material may not be smooth.

[0060] The surface characteristics of the copper film 111 can be changed depending on the surface buff finish or polishing degree of the rotating negative electrode drum 40. For example, the surface of the rotating negative electrode drum 40 can be polished with a polishing brush having a particle size (Grit) of #800 to #3000.

[0061] During the formation process 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 can be maintained at 50 °C or higher. At this time, by adjusting the composition of the electrolytic solution 20, the physical, chemical, and electrical properties of the copper film 111 can be controlled.

[0062] According to an embodiment of the present invention, the electrolytic solution 20 may contain copper ions, sulfuric acid, chlorine (Cl), and an organic additive.

[0063] To facilitate the formation of the copper film 111 by electroplating of copper, the copper ion concentration and the sulfuric acid concentration in the electrolytic solution 20 are adjusted to 70 to 150 g / L and 80 to 150 g / L, respectively.

[0064] In an embodiment of the present invention, chlorine (Cl) includes all chlorine ions (Cl - ) and chlorine atoms present in the molecule. Chlorine (Cl) can be used, for example, to remove silver (Ag) ions that have flowed into the electrolytic solution 20 during the formation process of the copper film 111. Specifically, chlorine (Cl) can precipitate silver (Ag) ions in the form of silver chloride (AgCl). Such silver chloride (AgCl) can be removed by filtration.

[0065] When the concentration of chlorine (Cl) is less than 15 ppm, the removal of silver (Ag) ions is not smoothly performed. On the other hand, 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 electrolytic solution 20 is controlled within the range of 15 to 25 ppm.

[0066] According to an embodiment of the present invention, the electrolytic solution 20 may contain an organic additive.

[0067] The organic additive contained in the electrolytic solution 20 includes a brightener (component A), a retarder (component B), and a leveling agent (component C).

[0068] The brightener (Component A) contains sulfonic acid or its metal salt. The brightener (Component A) can have a concentration of 1 to 20 ppm in the electrolytic solution 20.

[0069] The brightener (Component A) can increase the charge amount of the electrolytic solution 20 to increase the copper electrodeposition rate, improve the curl characteristics of the copper foil, and 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 will decrease. If it exceeds 20 ppm, problems may occur such as a change in the weight of the copper foil 110 after immersion or a change in the surface roughness.

[0070] The brightener may include, for example, at least one of bis-(3-sulfopropyl)-disulfide disodium salt, 3-mercapto-1-propanesulfonic acid, 3-(N,N-dimethylthiocarbamoyl)-thiopropanesulfonate sodium salt, 3-[(amino-iminomethyl)thio]-1-propanesulfonate sodium salt, o-ethyldithiocarbonate-S-(3-sulfopropyl)-ester sodium salt, 3-(benzothiazolyl-2-mercapto)-propyl-sulfonic acid sodium salt, and ethylenedithiodipropylsulfonic acid sodium salt.

[0071] The retarder (Component B) contains a nonionic water-soluble polymer. The retarder (Component B) can have a concentration of 1 to 10 ppm in the electrolytic solution 20.

[0072] The retarder (Component B) reduces the copper electrodeposition rate to prevent a sharp increase in the roughness and a decrease in the strength of the copper foil 110. Such a retarder (Component B) is also called an inhibitor or a suppressor.

[0073] If the concentration of the retarder (Component B) is less than 1 ppm, there may occur a problem that the roughness of the copper foil 110 sharply increases and the surface state of the copper foil 110 changes. On the other hand, even if the concentration of the retarder (Component B) exceeds 10 ppm, there are hardly any physical property changes such as appearance, gloss, roughness, strength, elongation, etc. of the copper foil 110. Therefore, without the need to unnecessarily increase the manufacturing cost by increasing the concentration of the retarder (Component B) and wasting raw materials, the concentration of the retarder (Component B) can be adjusted to the range of 1 to 10 ppm.

[0074] The retarder (Component B) may contain at least one nonionic water-soluble polymer selected from, for example, polyethylene glycol (PEG), polypropylene glycol, polyethylene polypropylene copolymer, polyglycerin, polyethylene glycol dimethyl ether, hydroxyethyl cellulose, polyvinyl alcohol, polyglycol stearate ether and stearyl alcohol polyglycol ether. However, the types of retarders are not limited to this, and other nonionic water-soluble polymers that can be used in the production of the high-strength copper foil 110 can be used as retarders.

[0075] The leveling agent (Component C) contains a PEG-PPG derivative. The leveling agent (Component C) can have a concentration of 0.1 to 10 ppm in the electrolytic solution 20.

[0076] The leveling agent (Component C) prevents the formation of excessively high peaks or excessively large protrusions on the copper film 111 and makes the copper film 111 macroscopically flat. The leveling agent (Component C) can have a concentration of 0.1 to 10 ppm in the electrolytic solution (11).

[0077] Specifically, in a PEG-PPG derivative according to an embodiment of the present invention, the terminal group may be substituted with a saturated hydrocarbon or a functional group. At this time, the functional group may contain at least one of an ethylene group, an acrylic group and a bisphenol group. At this time, PEG means Polyethylene glycol and PPG means Polypropylene glycol.

[0078] Specifically, in the case of a PEG-PPG copolymer, generally, a hydroxyl group (-OH) is present at the terminal group, and the hydroxyl group (-OH) present at the terminal group can react with other additives added into the electrolytic solution, reducing the physical properties of the copper foil.

[0079] At this time, when the terminal group of the PEG-PPG derivative is substituted with a functional group containing at least one of a saturated hydrocarbon, an ethylene group, an acrylic group, and a bisphenol group, the terminal group of the PEG-PPG derivative is stabilized, and the influence of various by-products in the electrolytic solution due to long-term use is small. Specifically, compared with an unsubstituted PEG-PPG derivative, there is an advantage that defects in plating such as pinholes can be reduced.

[0080] If the concentration of the leveling agent (component C) is less than 0.1 ppm, the strength of the copper foil 110 may decrease, and it may be difficult to manufacture the high-strength copper foil 110.

[0081] On the other hand, when the concentration of the leveling agent (component C) exceeds 10 ppm, the surface roughness of the copper foil 110 excessively increases, the strength can be reduced, pinholes and curls may occur on the surface of the copper foil 110, and it may be difficult to separate from the winder (WR) after the manufacture of the copper foil 110.

[0082] 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-trimethylpropane, PEG-PPG-allyl ether, PEG-PPG-methacrylate, PEG-PPG-acrylate, and PEG-PPG-bisphenol A ether.

[0083] When the copper film 111 is formed, the flow rate of the electrolytic solution 20 supplied into the electrolytic cell 10 can be 41 to 45 m 3 / hour.

[0084] Figure 6 is a schematic diagram showing the circulation process of the electrolytic solution according to the present invention.

[0085] According to an embodiment of the present invention, the step of manufacturing the electrolytic solution may include filtering (C / F) the first electrolytic solution transferred from the storage tank using carbon to form a second electrolytic solution, and adding a leveling agent (C component) to the filtered second electrolytic solution to form an electrolytic solution.

[0086] Specifically, the first electrolytic solution transferred from the storage tank may contain copper ions, sulfuric acid, chlorine, organic additives, and the like.

[0087] The step of filtering (C / F) the first electrolytic solution using carbon means removing organic impurities and inorganic impurities present in the first electrolytic solution.

[0088] According to an embodiment of the present invention, the second electrolytic solution means the electrolytic solution obtained by filtering the first electrolytic solution using carbon.

[0089] According to an embodiment of the present invention, a leveling agent (C component) can be added to the second electrolytic solution to form an electrolytic solution. Since the additives contained in the electrolytic solution have been described above, the description is omitted. Specifically, the leveling agent (C component) is added after the filtering (C / F) step.

[0090] For example, when the leveling agent (C component) is added before the filtering (C / F) step, the leveling agent (C component) may deteriorate and the physical properties of the copper foil may be reduced. On the other hand, when the leveling agent (C component) is added after the filtering (C / F) step, deterioration of the leveling agent (C component) can be prevented, which is effective for improving the physical properties according to the present invention.

[0091] The electrolytic solution formed by adding the leveling agent (C component) is contained in the electrolytic cell 10, and a copper foil is manufactured using a foil manufacturing machine including a rotating negative electrode drum 40 disposed in the electrolytic cell 10 and a positive electrode plate 30 disposed apart from the rotating negative electrode drum 40.

[0092] In addition, for the cleanliness of the electrolytic solution 20, the copper wire (Cu wire) used as the raw material of the electrolytic solution 20 can be washed.

[0093] According to one embodiment of the present invention, the step of manufacturing the electrolytic solution 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 with water, and a step of putting the washed copper wire into sulfuric acid for the electrolytic solution.

[0094] More specifically, in order to maintain the cleanliness of the electrolytic solution 20, a copper wire (Cu wire) of high purity (99.9% or more) is heat-treated in an electric furnace at 750°C to 850°C to burn various organic impurities adhering to the copper wire, and then the heat-treated copper wire is pickled with a 10% sulfuric acid solution for 10 to 20 minutes. After sequentially going through the process of washing the pickled copper wire with distilled water, copper for manufacturing the electrolytic solution 20 can be manufactured. The washed copper wire is administered to sulfuric acid for the electrolytic solution, and the electrolytic solution 20 can be manufactured.

[0095] According to one embodiment of the present invention, in order to satisfy the characteristics of the copper foil 110, the concentration of total organic carbon (TOC) in the electrolytic solution 20 is controlled to be 300 ppm or less. That is, the electrolytic solution 20 can have a concentration of total organic carbon (TOC) of 300 ppm or less.

[0096] The copper film 111 manufactured in this way can be washed in a washing tank.

[0097] For example, acid cleaning for removing impurities on the surface of the copper film 111, such as resin components or natural oxide, and water cleaning for removing the acidic solution used for acid cleaning can be sequentially performed. The cleaning process may be omitted.

[0098] Next, a protective layer 112 is formed on the copper film 111.

[0099] Referring to FIG. 5, 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.

[0100] As described above, the anticorrosion solution 60 may include at least one of a chromium compound, a silane compound, and a nitrogen compound. For example, the copper film 111 can be immersed in a potassium dichromate solution of 1 to 10 g / L at room temperature for 1 to 30 seconds.

[0101] In addition, the protective layer 112 can also contain a silane compound by silane treatment and can also contain a nitrogen compound by nitrogen treatment.

[0102] The copper foil 110 is manufactured by forming such a protective layer 112.

[0103] One or more negative electrode active materials selected from the group consisting of carbon; a metal (Me) of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe; an alloy containing the metal (Me); an oxide (MeOx) of the metal (Me); and a composite of the metal (Me) and carbon are coated on one or both surfaces of the copper foil 110 of the present invention manufactured through the above method, whereby the electrode for a secondary battery (i.e., the negative electrode) of the present invention can be manufactured.

[0104] 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) with 100 parts by weight of carbon for the negative electrode active material carbon, a slurry is prepared using distilled water as a solvent. Next, the slurry is coated on 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.

[0105] A secondary battery can be manufactured using a normal positive electrode, electrolyte, and separator together with the electrode (negative electrode) for a secondary battery of the present invention manufactured by the above method.

[0106] Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples. However, the following Examples are only for helping the understanding of the present invention, and the scope of rights of the present invention is not limited to these Examples.

[0107] Examples 1 to 4 and Comparative Examples 1 to 4 A copper foil was manufactured using a foil manufacturing machine including an electrolytic cell 10, a rotating negative electrode drum 40 disposed in the electrolytic cell 10, and a positive electrode plate 30 disposed separately from the rotating negative electrode drum 40. The electrolytic solution 20 was a copper sulfate solution. The copper ion concentration in the electrolytic solution 20 was set to 87 g / L, the sulfuric acid concentration was 110 g / L, the temperature of the electrolytic solution was 55°C, and the current density was 60 ASD.

[0108] 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, the leveling agent was added to the filtered electrolytic solution after filtering the electrolytic solution using carbon.

[0109] Among the organic additives, bis-(3-sulfopropyl)-disulfide disodium salt (SPS) was used as the brightening agent (Component A), polyethylene glycol (PEG) was used as the retarder (Component B), and PEG-PPG-isodecyl ether was used as the leveling agent (Component C).

[0110] A current was applied between the rotating negative electrode drum 40 and the positive electrode plate 30 at a current density of 60 ASD to manufacture a copper film 111. Next, the copper film 111 was immersed in a rust preventive solution for about 2 seconds, and a chromate treatment was performed on both sides of the copper film 111 to form a protective layer 112, thereby manufacturing a copper foil. A rust preventive solution mainly composed of chromic acid was used as the rust preventive solution, and the concentration of chromic acid was 5 g / L.

[0111] As a result, copper foils of Examples 1 to 4 and Comparative Examples 1 to 4 were produced. At this time, the thickness of the produced copper foil was 8 μm.

[0112] [Table 1]

[0113] [Table 2]

[0114] With respect to the copper foils of Examples 1 to 4 and Comparative Examples 1 to 4 produced in this way, (i) tensile strength, (ii) coefficient of kinetic friction of the first surface and the second surface, (iii) average coefficient of kinetic friction, (iv) Equation 1, and (v) the presence or absence of wrinkles or tears were confirmed.

[0115] The copper foil was cut to obtain a 15 cm x 15 cm sample.

[0116] (i) Tensile strength The tensile strength was measured by a universal testing machine (UTM) according to the provisions of the IPC-TM-650 Test Method Manual. Specifically, the tensile strength at room temperature (25 ± 3 °C) was measured using a universal testing machine manufactured by Instron. The width of the sample was 12.7 mm, the distance between grips was 50 mm, and the measurement speed was 50 mm / min.

[0117] (ii) Coefficient of kinetic friction of the first surface and the second surface The coefficient of kinetic friction of the first surface and the second surface can be measured by WL2100C of WITHLAB according to the provisions of ASTM D1894. Specifically, a stainless steel ball (SUS ball) is brought into contact with the sample, and while applying a load to the stainless steel ball (SUS ball), they are moved relative to each other to measure the coefficient of kinetic friction of both surfaces of the sample. At this time, a stainless steel ball (SUS ball) with a diameter of 10 mm is used, and the coefficient of kinetic friction can be measured under the conditions of a speed of 150 mm / min, a vertical load of 1.96 N (200 g), and a load cell of 29 N. The coefficient of kinetic friction is measured three times, and the average value is used.

[0118] (iii) Average coefficient of kinetic friction The average coefficient of kinetic friction means the average value of the coefficients of kinetic friction of the first surface and the second surface measured above. Specifically, it means half of the sum of the coefficients of kinetic friction of the first surface and the second surface.

[0119] (iv) Presence or absence of wrinkles or tears After 100 charge and discharge cycles, the secondary battery was disassembled, and it was observed whether wrinkles or tears occurred on the copper foil. The case where wrinkles or tears occurred on the copper foil was indicated as "occurred", and the case where they did not occur was indicated as "none".

[0120] Referring to Table 1 and Table 2, no wrinkles or tears occurred in the copper foils according to Examples 1 to 4, while wrinkles or tears occurred in the copper foils according to Comparative Examples 1 to 4.

[0121] The present invention described above is not limited by the foregoing embodiments and the accompanying drawings, and it will be apparent to those of ordinary skill in the technical field to which the present invention pertains that various substitutions, modifications, and changes are possible within the scope not departing from the technical matters of the present invention. Therefore, the scope of the present invention is represented by the following claims, and it should be understood that all changes or modified forms derived from the meaning, scope, and equivalent concepts of the claims are included in the scope of the present invention.

Explanation of symbols

[0122] 100 Electrode for secondary battery 110 Copper foil 111 Copper film 111a Matte surface 111b Shiny surface S1 First surface S2 Second surface 112 Protective layer 120 Active material layer 10 Electrolytic cell 20 Electrolyte

Claims

1. A copper film having a matte surface and a shiny surface; and A protective layer on the copper film, Having a first surface in the matte surface direction and a second surface in the shiny surface direction of the copper film, A copper foil satisfying the following formula 1: 【Formula 1】 3.0 kgf / mm ２ ≤ Tensile strength x Average coefficient of kinetic friction ≤ 8.0 kgf / mm ２ The average coefficient of kinetic friction in Formula 1 means the average value of the coefficients of kinetic friction of the first surface and the second surface.

2. The coefficient of kinetic friction of the first surface is 0.05 to 0.15, The coefficient of kinetic friction of the second surface is 0.1 to 0.2, the copper foil according to Claim 1.

3. The difference in the coefficients of kinetic friction of the first surface and the second surface is 0.1 or less, the copper foil according to Claim 1.

4. The protective layer contains at least one of a chromium compound, a silane compound, and a nitrogen compound, the copper foil according to Claim 1.

5. The step of manufacturing an electrolytic solution containing copper ions; The step of forming a copper film; and The step of forming a protective layer on the copper film; including The step of forming the copper film is Including the step of forming a copper film on the rotating negative electrode drum by energizing a positive electrode plate and a rotating negative electrode drum arranged to be separated from each other in the electrolytic solution in the electrolytic cell, The electrolytic solution is 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; including The organic additive includes a brightening agent (Component A), a retarder (Component B), and a leveling agent (Component C), The leveling agent (Component C) includes a PEG-PPG derivative, a method for manufacturing a copper foil.

6. The brightening agent (Component A) includes a sulfonic acid or a metal salt thereof, The retarder (Component B) includes a nonionic water-soluble polymer, the method for manufacturing a copper foil according to Claim 5.

7. The PEG-PPG derivative has a terminal group substituted with a saturated hydrocarbon or a functional group, the method for manufacturing a copper foil according to Claim 5.

8. The functional group is at least one of an ethylene group, an acrylic group, and a bisphenol group, the method for manufacturing a copper foil according to Claim 7.

9. The step of manufacturing the electrolytic solution is Filtering a first electrolytic solution transferred from a storage tank using carbon to form a second electrolytic solution; and Adding the leveling agent (Component C) to the second electrolytic solution to form the electrolytic solution; the method for manufacturing a copper foil according to Claim 5.

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