Copper foil, electrodes containing the same, a secondary battery containing the same, and a method for 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 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 copper foil that prevents slippage during the manufacturing process while simultaneously having excellent strength, an electrode containing the same, a secondary battery containing the same, and a method for manufacturing the same. [Background technology]

[0002] Copper foil is used in the manufacture of various products, such as the negative electrode of secondary batteries and flexible printed circuit boards (FPCBs).

[0003] Generally, copper foil is produced in a roll-to-roll process in foil manufacturing equipment, and the process of coating the active material during the manufacturing of the negative electrode of a secondary battery is also carried out in a roll-to-roll process. Recently, ultra-thin copper foil is used to increase the capacity of secondary batteries, but when the thickness of the copper foil becomes 10 μm or less, a slip phenomenon frequently occurs between the roll and the copper foil. When a slip phenomenon occurs, wrinkles or tears occur in the copper foil, making continuous processing impossible, which reduces the workability or handleability of the electrode formation process for secondary batteries, and in severe cases, makes the manufacture of electrodes itself impossible.

[0004] Therefore, it is necessary to suppress copper foil slippage and prevent or suppress the occurrence of wrinkles or tears in the copper foil. [Overview of the project] [Problems that the invention aims to solve]

[0005] Therefore, the present invention relates to copper foil, an electrode containing the same, a secondary battery containing the same, and a method for manufacturing the same, which can prevent problems arising from the limitations and disadvantages of the above-mentioned related technologies.

[0006] In addition to the embodiments of the present invention mentioned above, other features and advantages of the present invention are described below or can be clearly understood from such description by a person with ordinary skill in the art to which the present invention pertains. [Means for solving the problem]

[0007] One embodiment of the present invention provides a copper foil comprising a copper film having a matte surface and a shiny surface; and a protective layer on the copper film, wherein the copper film has a first surface in the direction of the matte surface and a second surface in the direction of the shiny surface, and satisfies the following formula 1: [Formula 1] 3.0 kgf / mm 2 ≤Tensile strength x Average coefficient of dynamic friction ≤8.0 kgf / mm 2 The average coefficient of kinetic friction in Equation 1 refers to the average value of the coefficients of kinetic friction of the first and second surfaces.

[0008] Another embodiment of the present invention provides a method for producing copper foil, comprising the steps of: producing an electrolyte containing copper ions; forming a copper film; and forming a protective layer on the copper film, wherein the step of forming the copper film includes 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 that are spaced apart from each other in the electrolyte in an electrolytic cell, the electrolyte comprising 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, wherein the organic additive comprises at least one of a brightener (component A), a moderator (component B), and a leveling agent (component C), and the leveling agent (component C) comprises a PEG-PPG derivative.

[0009] According to yet another embodiment of the present invention, an electrode for a secondary battery is provided, comprising a copper foil and an active material layer disposed on at least one surface of the copper foil.

[0010] According to yet another embodiment of the present invention, a secondary battery is provided comprising: a cathode that provides lithium ions during charging; an anode that provides electrons and lithium ions during discharge; 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. [Effects of the Invention]

[0011] The copper foil according to the present invention is able to prevent slippage during the manufacturing process, prevent wrinkles or tears from occurring in the copper foil, and at the same time possess excellent tensile strength. Therefore, the copper foil according to one embodiment of the present invention can have excellent roll-to-roll processability, workability, or handling properties. [Brief explanation of the drawing]

[0012] [Figure 1] This is a cross-sectional view of copper foil according to one embodiment of the present invention. [Figure 2] This is a cross-sectional view of an electrode for a secondary battery according to another embodiment of the present invention. [Figure 3] This is a cross-sectional view of an electrode for a secondary battery according to yet another embodiment of the present invention. [Figure 4] This is a schematic cross-sectional view of a secondary battery according to yet another embodiment of the present invention. [Figure 5] This is a copper foil manufacturing apparatus according to yet another embodiment of the present invention. [Figure 6] This is a schematic diagram showing the electrolyte circulation process according to the present invention. [Modes for carrying out the invention]

[0013] The embodiments of the present invention will be described in detail below with reference to the attached drawings. However, the embodiments described below are presented only for illustrative purposes to aid in a clear understanding of the present invention and do not limit the scope of the invention.

[0014] The shapes, sizes, ratios, angles, numbers, 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 illustrated in the drawings. Throughout the specification, the same components may be referred to by the same reference numerals. In the description of the present invention, if it is determined that a specific description of related known technologies may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

[0015] When terms such as "comprising", "having", "consisting of", etc. referred to 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 an error range even without separate explicit description.

[0016] In the case of descriptions of positional relationships, for example, when the positional relationships between both parts are described by expressions such as "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 illustrated 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 illustrated in the drawings. For example, when an element illustrated in the drawings is turned over, an element described as "below" or "beneath" another element may be placed "above" the other element. Therefore, the exemplary term "below" can include all directions of below and above. Similarly, the exemplary terms "above" or "on" can include all directions of above and below.

[0018] In the case of an explanation regarding the time relationship, for example, when the time sequence relationship is explained by "after ~", "subsequent to ~", "next to ~", "before ~", etc., the expressions "immediately" or "directly" are not used, and even non - continuous cases can be included as long as they are not used.

[0019] The terms such as "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 concept 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 presented from the first item, the second item, and the third item.

[0021] The respective features of various embodiments of the present invention can be partially or wholly combined or combined with each other, enabling various technical linkages and drives. 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 sides 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 side of the copper film 111.

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

[0025] The protective layer 112 is formed by electrodepositing an anticorrosion material onto the copper film 111. The anticorrosion material may contain 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 its heat resistance, thereby extending the lifespan of the copper foil 110, as well as the lifespan of the final product containing it.

[0026] According to one 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. In this case, the copper foil 110 according to one 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 dynamic friction ≤8.0 kgf / mm 2 Specifically, if the copper foil 110 according to one embodiment of the present invention satisfies the above formula 1, slippage during the manufacturing process is prevented, wrinkles or tears in the copper foil are prevented, and at the same time, it can have excellent tensile strength.

[0028] On the other hand, the value of Equation 1 is 3.0 kgf / mm². 2 If the value is less than [value missing], the tensile strength may become excessively low, which can degrade the mechanical properties of the copper foil. The mean coefficient of kinetic friction may also become excessively low, which can cause slippage during the manufacturing process of the copper foil, resulting in wrinkles or tears in the copper foil.

[0029] Furthermore, the value of Equation 1 is 8.0 kgf / mm². 2If the coefficient of dynamic friction is exceeded, it is possible to prevent or suppress the occurrence of slippage of the copper foil, but the surface of the copper foil may become excessively rough, and when the active material is coated onto the copper foil, the coating may become uneven. Also, even if the coefficient of dynamic friction is maintained at a constant value, if the tensile strength is excessively high, the brittleness of the copper foil 110 increases, and the copper foil 110 does not stretch in response to the force applied to the copper foil 110 during the roll-to-roll process, which may cause tearing of the copper foil 110.

[0030] In this case, the tensile strength in Equation 1 was measured using a universal tester (UTM) in accordance with the IPC-TM-650 Test Method Manual. Specifically, the tensile strength of copper foil 110 at room temperature (25±3℃) was measured using an Instron universal tester. The sample width was 12.7 mm, the distance between grips was 50 mm, and the measurement speed was 50 mm / min.

[0031] Furthermore, the average kinetic friction coefficient in Equation 1 represents the average value of the kinetic friction coefficients of the first surface S1 and the second surface S2 of the copper foil 110. Specifically, it represents half the value of the sum of the kinetic friction coefficients of the first surface S1 and the second surface S2.

[0032] In this case, the coefficients of dynamic friction of the first surface S1 and the second surface S2 of the copper foil 110 can be measured using a Withlab WL2100C according to the provisions of ASTM D1894. Specifically, the coefficient of dynamic friction of the copper foil 110 can be measured by bringing a stainless steel ball (SUS ball) into contact with the copper foil 110 and moving the stainless steel ball (SUS ball) relative to the copper foil while applying a load to it. In this case, a stainless steel ball (SUS ball) with a diameter of 10 mm is used, and the coefficient of dynamic 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 dynamic friction is measured three times, and the average value is used.

[0033] According to one embodiment of the present invention, the coefficient of dynamic friction of the first surface S1 of the copper foil 110 may be 0.05 to 0.15, and the coefficient of dynamic friction of the second surface S2 may be 0.1 to 0.2. Specifically, when the coefficients of dynamic friction of the first surface S1 and the second surface S2 of the copper foil 110 satisfy the above range, it is possible to prevent slippage during the manufacturing process of the copper foil and prevent wrinkles or tears from occurring in the copper foil.

[0034] On the other hand, if the coefficient of dynamic friction of the first surface S1 is less than 0.05, or the coefficient of dynamic friction of the second surface S2 is less than 0.1, slip may occur during the manufacturing process of the copper foil 110, causing wrinkles or tears in the copper foil 110.

[0035] Furthermore, if the coefficient of dynamic friction of the first surface S1 exceeds 0.15, or the coefficient of dynamic 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 may become excessively rough, and when the active material is coated onto the copper foil, the coating may become uneven.

[0036] According to one embodiment of the present invention, the difference in the coefficient of dynamic 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 dynamic 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 properties between the first surface S1 and the second surface S2 is small, which makes it possible to coat both sides of the copper foil 110 with a uniform active material.

[0037] On the other hand, if the difference in the coefficient of dynamic friction between the first surface S1 and the second surface S2 of the copper foil 110 exceeds 0.1, the difference in surface properties between the first surface S1 and the second surface S2 becomes large, making it difficult to uniformly coat both sides of the copper foil 110 with the active material.

[0038] A copper foil 110 according to one embodiment of the present invention has a thickness of 4 to 35 μm. When the copper foil 110 is used as a current collector for electrodes in a secondary battery, the thinner 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 copper foil 110 with a thickness of less than 4 μm leads to a decrease in workability.

[0039] On the other hand, when manufacturing secondary batteries with copper foil 110 exceeding 35 μm in thickness, achieving high capacity becomes difficult due to the thickness of the copper foil 110.

[0040] The following describes in detail the electrode 100 containing the copper foil 110 of the present invention and the secondary battery containing the electrode 100.

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

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

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

[0044] In lithium secondary batteries, aluminum foil is commonly used as the positive electrode current collector that bonds with the positive electrode active material, and copper foil 110 is commonly used as the negative electrode current collector that bonds with the negative electrode active material.

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

[0046] To ensure the high capacity of the secondary battery, the active material layer 120 of the present invention can be formed from a carbon-metal composite. 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] Figure 4 is a schematic cross-sectional view of a secondary battery according to one embodiment of the present invention.

[0048] Referring to Figure 4, the secondary battery includes a cathode 370, a negative electrode 340, an electrolyte 350 placed between the cathode 370 and the negative electrode 340 to provide an environment in which ions can move, and a separator 360 that electrically insulates the cathode 370 and the negative electrode 340. Here, the ions moving between the cathode 370 and the negative electrode 340 are, for example, lithium ions. The separator 360 separates the cathode 370 and the negative electrode 340 to prevent the charge generated at one electrode from being wasted by moving to the other electrode through the interior of the secondary battery 105. Referring to Figure 4, the separator 360 is placed within the electrolyte 350.

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

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

[0051] According to one embodiment of the present invention, the copper foil 110 shown in Figure 1 can be used as the negative electrode current collector 341. In addition, the secondary battery electrodes 100a and 100b shown in Figure 2 or Figure 3 can be used as the negative electrode 340 of the secondary battery shown in Figure 4.

[0052] The method for manufacturing the copper foil 110 of the present invention will be specifically described below with reference to Figures 5 and 6.

[0053] The method for manufacturing copper foil 110 of the present invention includes the steps of forming a copper film 111 and forming a protective layer 112 on the copper film 111.

[0054] The method of the present invention includes the 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 spaced apart from each other in an electrolyte 20 within an electrolytic cell 10.

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

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

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

[0058] If the current densities provided by the first and second positive electrode plates 31 and 32, respectively, are less than 30 ASD, the adhesion between the copper foil 110 and the active material layer 120 may be insufficient due to the low surface roughness of the copper foil 110.

[0059] On the other hand, if the current densities provided by the first and second positive electrode plates 31 and 32, respectively, exceed 130 ASD, the surface of the copper foil 110 may become rough, making it difficult to coat the active material smoothly.

[0060] The surface properties of the copper film 111 can be varied depending on the degree of surface buffing or polishing of the rotating anode drum 40. For example, the surface of the rotating anode drum 40 can be polished with an abrasive brush having a grit size of #800 to #3000.

[0061] During the formation of the copper film 111, the electrolyte 20 is maintained at a temperature of 40-60°C. More specifically, the temperature of the electrolyte 20 can be maintained at 50°C or higher. In this process, the physical, chemical, and electrical properties of the copper film 111 can be controlled by adjusting the composition of the electrolyte 20.

[0062] According to one embodiment of the present invention, the electrolyte 20 may contain copper ions, sulfuric acid, chlorine (Cl), and organic additives.

[0063] To facilitate the formation of the copper film 111 by copper electrodeposition, the concentrations of copper ions and sulfuric acid in the electrolyte 20 are adjusted to 70-150 g / L and 80-150 g / L, respectively.

[0064] In one embodiment of the present invention, chlorine (Cl) is a chloride ion (Cl - This includes all chlorine atoms present in the molecule. Chlorine (Cl) can be used, for example, to remove silver (Ag) ions that have flowed into the electrolyte 20 during the process of forming 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] If the chlorine (Cl) concentration is less than 15 ppm, the removal of silver (Ag) ions will not proceed smoothly. On the other hand, if the chlorine (Cl) concentration exceeds 25 ppm, unwanted reactions may occur due to an excess of chlorine (Cl). Therefore, the chlorine (Cl) concentration in the electrolyte 20 is controlled within the range of 15 to 25 ppm.

[0066] According to one embodiment of the present invention, the electrolyte 20 may contain organic additives.

[0067] The organic additives contained in the electrolyte 20 include a brightener (component A), a moderator (component B), and a leveling agent (component C).

[0068] The glossing agent (component A) contains sulfonic acid or a metal salt thereof. The glossing agent (component A) can have a concentration of 1 to 20 ppm in the electrolyte 20.

[0069] The brightener (component A) increases the charge of the electrolyte 20, thereby increasing the electrodeposition rate of copper, improving the curl characteristics of the copper foil, and enhancing the gloss of the copper foil 110. If the concentration of the brightener (component A) is less than 1 ppm, the gloss of the copper foil 110 decreases, and if it exceeds 20 ppm, problems may occur where the weight of the copper foil 110 changes after immersion or the surface roughness changes.

[0070] The glossing agent may include, for example, at least one of the following: 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-sulfonate sodium salt, and ethylenedithiodipropylsulfonic acid sodium salt.

[0071] The moderator (component B) contains a nonionic water-soluble polymer. The moderator (component B) can have a concentration of 1 to 10 ppm in the electrolyte 20.

[0072] The moderator (component B) reduces the electrodeposition rate of copper, preventing a rapid increase in the roughness and decrease in strength of the copper foil 110. Such a moderator (component B) is also called an inhibitor or suppressor.

[0073] If the concentration of the moderator (component B) is less than 1 ppm, the roughness of the copper foil 110 increases rapidly, which can cause problems with the surface condition of the copper foil 110. On the other hand, even if the concentration of the moderator (component B) exceeds 10 ppm, there is almost no change in the physical properties of the copper foil 110, such as appearance, gloss, roughness, strength, and elongation. Therefore, the concentration of the moderator (component B) can be adjusted within the range of 1 to 10 ppm without unnecessarily increasing the concentration of the moderator (component B), thereby increasing manufacturing costs and wasting raw materials.

[0074] The moderator (component B) may include, for example, at least one nonionic water-soluble polymer selected from polyethylene glycol (PEG), polypropylene glycol, polyethylene polypropylene copolymer, polyglycerin, polyethylene glycol dimethyl ether, hydroxyethylene cellulose, polyvinyl alcohol, polyglycol stearate ether, and stearyl alcohol polyglycol ether. However, the type of moderator is not limited thereto, and other nonionic water-soluble polymers that can be used in the manufacture of high-strength copper foil 110 can be used as moderators.

[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 electrolyte 20.

[0076] The leveling agent (component C) prevents the formation of excessively high peaks or excessively large protrusions on the copper film 111, ensuring that the copper film 111 is macroscopically flat. The leveling agent (component C) can have a concentration of 0.1 to 10 ppm in the electrolyte (11).

[0077] Specifically, a PEG-PPG derivative according to one embodiment of the present invention may have its terminal group substituted with a saturated hydrocarbon or with a functional group. In this case, the functional group may include at least one of an ethylene group, an acrylic group, and a bisphenol group. Herein, PEG means polyethylene glycol and PPG means polyethylene glycol.

[0078] Specifically, in the case of PEG-PPG copolymers, hydroxyl groups (-OH) are generally present at the terminal groups, and these hydroxyl groups (-OH) at the terminal groups react with other additives added to the electrolyte, which can degrade the physical properties of the copper foil.

[0079] In this case, if the terminal group of the PEG-PPG derivative is substituted with a functional group containing at least one saturated hydrocarbon, ethylene group, acrylic group, or bisphenol group, the terminal group of the PEG-PPG derivative is stabilized, and the effects of various by-products in the electrolyte during long-term use are reduced. Specifically, compared to unsubstituted PEG-PPG derivatives, it has the advantage of reducing plating defects such as pinholes.

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

[0081] On the other hand, if the concentration of the leveling agent (component C) exceeds 10 ppm, the surface roughness of the copper foil 110 may increase excessively, reducing its strength. Pinholes and curls may also occur on the surface of the copper foil 110, making it difficult to separate the copper foil 110 from the winder (WR) after manufacturing.

[0082] The leveling agent (component C) may include, for example, at least one of the following: 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 electrolyte 20 supplied into the electrolytic cell 10 is 41-45 m / s. 3 It could be / hour

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

[0085] According to one embodiment of the present invention, the steps for producing the electrolyte may include filtering (C / F) the first electrolyte transferred from the storage tank using carbon to form a second electrolyte, and adding a leveling agent (component C) to the filtered second electrolyte to form the electrolyte.

[0086] Specifically, the first electrolyte transferred from the storage tank may contain copper ions, sulfuric acid, chlorine, organic additives, etc.

[0087] The process of filtering the first electrolyte using carbon (C / F) refers to the step of removing organic and inorganic impurities present in the first electrolyte.

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

[0089] According to one embodiment of the present invention, an electrolyte can be formed by adding a leveling agent (component C) to the second electrolyte. The additives contained in the electrolyte have been described above, so their explanation will be omitted. Specifically, the leveling agent (component C) is added after the filtration (C / F) step.

[0090] For example, if the leveling agent (component C) is added before the filtration (C / F) process, the leveling agent (component C) may deteriorate, reducing the physical properties of the copper foil. On the other hand, if the leveling agent (component C) is added after the filtration (C / F) process, deterioration of the leveling agent (component C) is prevented, which is effective in improving the physical properties according to the present invention.

[0091] The electrolyte formed by adding a leveling agent (component C) is contained within the electrolytic cell 10, and copper foil is manufactured using a foil-making machine that includes a rotating negative electrode drum 40 located in the electrolytic cell 10 and a positive electrode plate 30 located away from the rotating negative electrode drum 40.

[0092] Furthermore, to ensure the cleanliness of the electrolyte 20, the copper wire (Cu wire) that serves as the raw material for the electrolyte 20 can be washed.

[0093] According to one embodiment of the present invention, the steps for producing the electrolyte 20 may include the steps of heat-treating a copper wire, pickling the heat-treated copper wire, washing the pickled copper wire with water, and immersing the washed copper wire in sulfuric acid for the electrolyte.

[0094] More specifically, in order to maintain the cleanliness of the electrolyte 20, copper for the production of the electrolyte 20 can be produced by sequentially following the steps of: heat-treating high-purity (99.9% or higher) copper wire (Cu wire) in an electric furnace at 750°C to 850°C to burn off various organic impurities attached to the copper wire; pickling the heat-treated copper wire with a 10% sulfuric acid solution for 10 to 20 minutes; and rinsing the pickled copper wire with distilled water. The rinsed copper wire can then be added to sulfuric acid for the electrolyte to produce the electrolyte 20.

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

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

[0097] For example, acid cleaning can be performed sequentially to remove impurities on the surface of the copper film 111, such as resin components or natural oxide films, followed by water cleaning to remove the acidic solution used in acid cleaning. The cleaning step 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 1 - 10 g / L potassium dichromate solution at room temperature for 1 - 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) such as 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, thereby manufacturing the electrode (i.e., the negative electrode) for the secondary battery of the present invention.

[0104] For example, after mixing 1 - 3 parts by weight of styrene - butadiene rubber (SBR) and 1 - 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 - 60 μm using a doctor blade and pressed at a pressure of 0.5 - 1.5 ton / cm 2 at 110 - 130 °C.

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

[0106] The present invention will be described in detail below based on examples and comparative examples. However, the following examples are provided solely to aid in understanding the present invention, and the scope of the present invention is not limited to these examples.

[0107] Examples 1-4 and Comparative Examples 1-4 Copper foil was manufactured using a foil-making machine that included an electrolytic cell 10, a rotating negative electrode drum 40 positioned in the electrolytic cell 10, and a positive electrode plate 30 positioned away from the rotating negative electrode drum 40. The electrolyte 20 was a copper sulfate solution. The copper ion concentration in the electrolyte 20 was set to 87 g / L, the sulfuric acid concentration to 110 g / L, the electrolyte temperature to 55°C, and the current density to 60 ASD.

[0108] Furthermore, the concentration of chlorine (Cl) in the electrolyte 20 was maintained at 20 ppm, and the concentrations of the organic additives were as shown in Table 1 below. In this process, the leveling agent was added to the filtered electrolyte after filtering it using carbon.

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

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

[0111] As a result, copper foils for Examples 1-4 and Comparative Examples 1-4 were manufactured. The thickness of the manufactured copper foil was 8 μm.

[0112] [Table 1]

[0113] [Table 2]

[0114] For the copper foils of Examples 1-4 and Comparative Examples 1-4 manufactured in this manner, (i) tensile strength, (ii) coefficient of dynamic friction of the first and second surfaces, (iii) average coefficient of dynamic friction, (iv) Equation 1, and (v) presence or absence of wrinkles or tears were confirmed.

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

[0116] (i) Tensile strength Tensile strength was measured using a universal tester (UTM) in accordance with the IPC-TM-650 Test Method Manual. Specifically, tensile strength was measured at room temperature (25±3℃) using an Instron universal tester. The sample width 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 and second surfaces The coefficients of dynamic friction of the first and second surfaces can be measured using a WITHLAB WL2100C according to ASTM D1894. Specifically, a stainless steel ball (SUS ball) is brought into contact with the sample, and the coefficients of dynamic friction of both sides of the sample can be measured by moving the stainless steel ball (SUS ball) back and forth while applying a load to it. In this case, a stainless steel ball (SUS ball) with a diameter of 10 mm is used, and the coefficient of dynamic 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 dynamic friction is measured three times, and the average value is used.

[0118] (iii) Mean coefficient of kinetic friction The average coefficient of kinetic friction refers to the average value of the coefficients of kinetic friction of the first and second surfaces measured as described above. Specifically, it refers to half the value of the sum of the coefficients of kinetic friction of the first and second surfaces.

[0119] (iv) Presence or absence of wrinkles or tears After 100 charge-discharge cycles, the secondary batteries were disassembled, and the presence or absence of wrinkles or tears in the copper foil was observed. If wrinkles or tears occurred in the copper foil, it was indicated as "occurred," and if they did not occur, it was indicated as "none."

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

[0121] The present invention, as described above, is not limited by the embodiments and accompanying drawings, and it will be apparent to those with ordinary skill in the art to which the present invention pertains that various substitutions, modifications, and alterations are possible within the scope of the technical matters of the present invention. Accordingly, the scope of the present invention is expressed by the claims described below, and it should be understood that all modified or altered forms derived from the meaning, scope, and equivalent concepts of the claims are included within 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 foil for a current collector of a secondary battery, Copper films having a matte surface and a shiny surface; and The protective layer on the copper film is included, The copper foil has a thickness of 4 μm to 35 μm. The copper film has a first surface in the matte surface direction and a second surface in the shiny surface direction, The following equation 1 is satisfied, Copper foil with a tensile strength of 42 kgf / mm² to 53 kgf / mm²: [Formula 1] 3.0 kgf / mm ２ ≤Tensile strength x Average coefficient of dynamic friction ≤ 8.0 kgf / mm ２ The average coefficient of kinetic friction of the first and second surfaces refers to the average value of the coefficients of kinetic friction of the first and second surfaces. The coefficients of dynamic friction of the first and second surfaces are measured by bringing a 10 mm diameter stainless steel ball (SUS ball) into contact with the copper foil and moving it while applying a load under the conditions of a sliding speed of 150 mm / min, a vertical load of 1.96 N (200 g), and a load cell of 29 N.

2. The coefficient of kinetic friction of the first surface is 0.05 to 0.

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

2.

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

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

5. A method for manufacturing copper foil for a current collector of a secondary battery, The step of producing an electrolyte solution containing copper ions; The step of forming a copper film; and The step of forming a protective layer on the copper film; The step of forming the copper film is: The step includes applying current to a positive electrode plate and a rotating negative electrode drum, which are arranged in the electrolyte within the electrolytic cell so as to be spaced apart from each other, thereby forming a copper film on the rotating negative electrode drum. The aforementioned electrolyte is 70-150 g / L of copper ions; 80-150 g / L sulfuric acid; 15-25 ppm chlorine (Cl); and Contains organic additives; The aforementioned organic additive comprises a brightener (component A), a speed reducer (component B), and a leveling agent (component C). The glossing agent (component A) is bis-(3-sulfopropyl)-disulfide disodium salt (SPS) at a concentration of 1 to 10 ppm. The aforementioned moderator (component B) is polyethylene glycol (PEG) at a concentration of 5 to 12 ppm. The leveling agent (component C) is PEG-PPG-isodecyl ether at a concentration of 3 to 10 ppm. The copper foil having a thickness of 4 μm to 35 μm, and a method for manufacturing copper foil.

6. The step of manufacturing the aforementioned electrolyte is: A step of filtering the first electrolyte transferred from the storage tank using carbon to form a second electrolyte; and A method for producing copper foil according to claim 5, comprising the step of adding the leveling agent (component C) to the second electrolyte to form the electrolyte.

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