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

Abstract

To provide a copper foil having excellent adhesive strength, 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. 45≤[(average 60° gloss) / (G.U.)×(average peak density) / (count)] / 100≤70.[Equation 1] The average peak density in Equation 1 means an average value of peak densities of the first surface and the second surface, the peak density means a value acquired by dividing a peak count roughness (Rpc) by a surface area ratio, and the average 60° gloss in Equation 1 means an average value of 60° glosses 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 having excellent adhesion, an electrode containing the same, a secondary battery containing the same, and a method for manufacturing the same.

Background Art

[0002] Copper foil is used to manufacture various products such as the negative electrode of a secondary battery and a flexible printed circuit board (FPCB).

[0003] Copper foil can be manufactured by a roll-to-roll (RTR) process using electrolytic plating. Such copper foil is used for manufacturing the negative electrode for a secondary battery or a flexible printed circuit board (FPCB) through a roll-to-roll (RTR) process.

[0004] The negative electrode of a secondary battery generally includes a copper foil and an active material laminated on the copper foil. Since the active material expands or contracts in volume during charge and discharge, it may detach from the copper foil, and there is a problem that the life of the secondary battery is shortened due to such detachment of the active material. To solve this, it is necessary to increase the adhesion between the copper foil and the active material.

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)] 45 ≦ [(average 60° glossiness) / (G.U) × (average peak density) / (pieces)] / 100 ≦ 70. The average peak density in the formula (1) means the average value of the peak densities of the first surface and the second surface, the peak density means a value obtained by dividing the peak count roughness (Rpc) by the surface area ratio, and the average 60° glossiness in the formula (1) means the average value of the 60° glossinesses of the first surface and the second surface.

[0008] Another embodiment of the present invention provides a method for manufacturing a copper foil, including 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), and the leveling agent (Component C) includes a PEG derivative.

[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 and providing 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 have excellent adhesive strength. Therefore, when the copper foil according to an embodiment of the present invention is used for an electrode of a secondary battery, the adhesive strength between the copper foil and the active material is improved, and the life and reliability of the secondary battery are improved.

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 illustrative, and thus the present invention is not limited to the matters illustrated in the drawings. The same components throughout the specification may be referred to by the same reference numerals. In describing the present invention, if it is determined that a detailed 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. mentioned in this specification are used, unless the expression "only" is used, other parts can be added. 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 an explanation of a positional relationship, for example, when the positional relationship between both parts is explained by "on ~", "above ~", "below ~", "beside ~", etc., unless the expressions "immediately" or "directly" are used, one or more other parts can be located between both parts.

[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 drawing. Spatially relative terms should be understood as terms including different directions of elements during use or operation in addition to the direction shown in the drawing. For example, when an element shown in the drawing is turned over, an 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 of a time relationship, for example, when the time sequence relationship is explained by "after ~", "subsequent to ~", "next to ~", "before ~", etc., unless the expressions "immediately" or "directly" are used, it can include cases that are not continuous.

[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. Thus, the first component referred to 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" can mean not only each of the first item, the second item, or the third item alone, but also all combinations of items that can be presented from two or more of 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 wholly 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 the protective layer 112 is disposed on both sides of the copper film 111. However, an embodiment of the present invention is not limited thereto, and although not shown, the protective layer 112 may be disposed on one side of the copper film 111.

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

[0025] The protective layer 112 is formed by electrodepositing an anticorrosion material on 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 the oxidation and corrosion of the copper film 111 and improves the 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] 45 ≦ [(average 60° glossiness) / (G.U) x (average peak density) / (pieces)] / 100 ≦ 70

[0028] Specifically, when the copper foil 110 according to an embodiment of the present invention satisfies Formula 1, a sufficient active specific surface area is ensured in the fine regions of the copper foil 110, and at the same time, since the surface uniformity in the wide regions of the copper foil 110 is high, sufficient adhesion between the copper foil 110 and the active material can be ensured.

[0029] On the other hand, when the value of Formula 1 is less than 45, the average peak density may become excessively low, and thereby, since the active specific surface area in the fine regions of the copper foil 110 is too small, sufficient adhesion between the copper foil 110 and the active material cannot be ensured. Also, the average 60° glossiness may become excessively low, and thereby, the surface characteristics in the wide regions of the copper foil 110 become non-uniform, making it difficult to ensure sufficient adhesion between the copper foil 110 and the active material.

[0030] At this time, it is difficult to see that the value of the 60° glossiness necessarily becomes small just because the value of the peak density of the copper foil 110 increases.

[0031] In addition, when the value of Formula 1 exceeds 70, the average peak density may become excessively high, thereby reducing the coating uniformity with the active material, and thereby significantly reducing the adhesion between the copper foil 110 and the active material. Further, the average 60° glossiness may become excessively high, and thereby, since the active specific surface area is too small in a wide area of the copper foil 110, sufficient adhesion between the copper foil 110 and the active material cannot be ensured.

[0032] At this time, the 60° glossiness of Formula 1 was measured for the glossiness at a 60° incident angle of each of the first surface S1 and the second surface S2 using a gloss meter (Nippon Denshoku Co., Ltd., VG7000) according to the JIS Z 8741 standard.

[0033] In addition, the average peak density of Formula 1 means the average value of the peak densities of the first surface and the second surface, and the peak density means the value obtained by dividing the peak count roughness (Rpc) for the first surface S1 and the second surface S2 by the surface area ratio.

[0034] At this time, the peak count roughness (Rpc) is the average value of the peak count roughness (Rpc) at any three points, and the peak count roughness (Rpc) at each of the points means the number of effective peaks standing on the upper criteria line (C1) of 0.5 μm per unit sampling length of 4 mm in the surface roughness profile obtained according to the steel-iron test schedule (SEP 1940) standard. The surface area ratio means the ratio of the three-dimensional surface area to the two-dimensional surface area for each of the first surface S1 and the second surface S2.

[0035] According to an embodiment of the present invention, the difference between the peak density of the first surface S1 and the peak density of the second surface S2 can be 30 or less.

[0036] Specifically, when the difference between the peak density of the first surface S1 and the peak density of the second surface S2 is 30 or less, since the difference in surface characteristics between the first surface S1 and the second surface S2 is small, the coating uniformity of the active material is improved, and sufficient adhesion between the copper foil 110 and the active material can be ensured.

[0037] On the other hand, when the difference between the peak density of the first surface S1 and the peak density of the second surface S2 exceeds 30, the difference in surface characteristics between the first surface S1 and the second surface S2 becomes large, the coating uniformity of the active material decreases, and it may be difficult to ensure sufficient adhesion between the copper foil 110 and the active material.

[0038] The copper foil 110 according to an embodiment of the present invention has a thickness of 4 to 35 μm. When the copper foil 110 is used as a current collector of an electrode in a secondary battery, the thinner the thickness of the copper foil 110, the more current collectors can be accommodated in the same space, which is advantageous for increasing the capacity of the secondary battery. However, manufacturing the copper foil 110 having a thickness of less than 4 μm causes a decrease in workability. 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.

[0039] 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.

[0040] FIG. 2 is a cross-sectional view of a secondary battery electrode 100a according to an embodiment of the present invention. FIG. 3 is a cross-sectional view of a secondary battery electrode 100b according to another embodiment of the present invention.

[0041] As shown in FIG. 2, the secondary battery electrode 100a according to an 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.

[0042] FIG. 2 shows a configuration in which the active material layer 120 is formed on one surface of the copper foil 110. However, an embodiment of the present invention is not limited thereto, and referring to FIG. 3, the active material layer 120 can also be formed on both surfaces of the copper foil 110.

[0043] In a lithium secondary battery, as the positive electrode current collector that binds to the positive electrode active material, aluminum foil is generally used, and as the negative electrode current collector that binds to the negative electrode active material, copper foil 110 is generally used.

[0044] According to an embodiment of the present invention, the secondary battery electrode 100 is a negative electrode, the copper foil 110 is used as the negative electrode current collector, and the active material layer 120 contains a negative electrode active material.

[0045] 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 a 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.

[0046] FIG. 4 is a schematic cross-sectional view of a secondary battery according to an embodiment of the present invention.

[0047] Referring to FIG. 4, the secondary battery includes a positive electrode (cathode) 370, a negative electrode (anode) 340, an electrolyte 350 disposed between the positive electrode 370 and the negative electrode 340 to provide an environment in which ions can move, and a separator 360 that electrically insulates the positive electrode 370 and the negative electrode 340. Here, the ions moving between the positive electrode 370 and the negative electrode 340 are, for example, lithium ions. The separator 360 separates the positive electrode 370 and the negative electrode 340 in order 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.

[0048] 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.

[0049] The negative electrode 340 includes a negative electrode current collector 341 and a negative electrode active material layer 342, and a copper foil 110 can be used for the negative electrode current collector 341.

[0050] According to an embodiment of the present invention, the copper foil 110 shown in FIG. 1 can be used as the negative electrode current collector 341. Further, the electrodes 100a and 100b for secondary batteries shown in FIG. 2 or FIG. 3 can be used for the negative electrode 340 of the secondary battery shown in FIG. 4.

[0051] Hereinafter, with reference to FIGS. 5 and 6, the manufacturing method of the copper foil 110 of the present invention will be specifically described.

[0052] The manufacturing method of the copper foil 110 of the present invention includes a step of forming a copper film 111 and a step of forming a protective layer 112 on the copper film 111.

[0053] 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 arranged to be separated from each other in the electrolytic solution 20 in the electrolytic cell 10.

[0054] As shown in FIG. 5, the positive electrode plate 30 may include first and second positive electrode plates 31 and 32 that are electrically insulated from each other.

[0055] 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.

[0056] The current density provided by the first and second positive electrode plates 31 and 32 can be 30 to 130 ASD.

[0057] When the current density provided by the first and second positive electrode plates 31 and 32 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.

[0058] 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 able to be made smooth.

[0059] The surface characteristics of the copper film 111 can be changed by the surface buffing 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.

[0060] In the process of forming 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 characteristics of the copper film 111 can be controlled.

[0061] According to an embodiment of the present invention, the electrolytic solution 20 may contain copper ions, sulfuric acid, chlorine (Cl), and an organic additive.

[0062] In order to smooth the formation of the copper film 111 by electroplating of copper, the concentration of copper ions and the concentration of sulfuric acid in the electrolytic solution 20 are adjusted to 70 to 150 g / L and 80 to 150 g / L respectively.

[0063] 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 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.

[0064] When the concentration of chlorine (Cl) is less than 15 ppm, the removal of silver (Ag) ions does not proceed smoothly. On the other hand, when the concentration of chlorine (Cl) exceeds 25 ppm, unnecessary reactions may occur due to the excess chlorine (Cl). Therefore, the concentration of chlorine (Cl) in the electrolytic solution 20 is controlled in the range of 15 to 25 ppm.

[0065] According to one embodiment of the present invention, the electrolytic solution 20 may contain an organic additive.

[0066] The organic additive contained in the electrolytic solution 20 includes a brightener (Component A), a retarder (Component B), and a leveling agent (Component C).

[0067] The brightener (Component A) contains a sulfonic acid or a metal salt thereof. The brightener (Component A) can have a concentration of 1 to 20 ppm in the electrolytic solution 20.

[0068] 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.

[0069] 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.

[0070] The retarder (Component B) contains a nonionic water-soluble polymer. The retarder (Component B) can have a concentration of 0.1 to 10 ppm in the electrolyte 20.

[0071] The retarder (Component B) reduces the electrodeposition rate of copper and prevents 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.

[0072] If the concentration of the retarder (Component B) is less than 0.1 ppm, there may be 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 almost no physical property changes such as the appearance, gloss, roughness, strength, elongation rate, etc. of the copper foil 110. Therefore, without the need to unnecessarily increase the concentration of the retarder (Component B) to increase the manufacturing cost and waste raw materials, the concentration of the retarder (Component B) can be adjusted to the range of 0.1 to 10 ppm.

[0073] 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, stearic acid polyglycol 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 manufacture of the high-strength copper foil 110 can be used as retarders.

[0074] The leveling agent (Component C) contains a PEG derivative. The leveling agent (Component C) can have a concentration of 1 to 10 ppm in the electrolyte 20.

[0075] The leveling agent (Component C) prevents the generation 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 1 to 10 ppm in the electrolytic solution 11.

[0076] Specifically, in the PEG 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 include at least one of an ethylene group, an acrylic group, and a bisphenol group. At this time, PEG means Polyethylene glycol.

[0077] Specifically, in the case of PEG, 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 in the electrolytic solution and reduce the physical properties of the copper foil.

[0078] At this time, when the terminal group of the PEG derivative is substituted with a saturated hydrocarbon or a functional group containing at least one of an ethylene group, an acrylic group, and a bisphenol group, the terminal group of the PEG 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 derivative, there is an advantage that plating defects such as pinholes can be reduced.

[0079] If the concentration of the leveling agent (Component C) is less than 1 ppm, the strength of the copper foil 110 may decrease, and it may be difficult to manufacture the high-strength copper foil 110.

[0080] On the other hand, when the concentration of the leveling agent (Component C) exceeds 10 ppm, the surface roughness of the copper foil 110 may excessively increase, the strength can be reduced, pinholes or curls may occur on the surface of the copper foil 110, and it may be difficult to separate from the winder (WR) after manufacturing the copper foil 110.

[0081] The leveling agent (Component C) may contain at least one of, for example, 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.

[0082] 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.

[0083] Figure 6 is a schematic diagram showing the circulation process of the electrolytic solution according to the present invention.

[0084] According to an embodiment of the present invention, the step of manufacturing the electrolytic solution may include a step of filtering (C / F) the first electrolytic solution transferred from the storage tank using carbon to form a second electrolytic solution, and a step of adding a leveling agent (Component C) to the filtered second electrolytic solution to form an electrolytic solution.

[0085] Specifically, the first electrolytic solution transferred from the storage tank may contain copper ions, sulfuric acid, chlorine, organic additives, and the like.

[0086] The step of filtering (C / F) the first electrolytic solution using carbon means a step of removing organic impurities and inorganic impurities present in the first electrolytic solution.

[0087] 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.

[0088] According to an embodiment of the present invention, an electrolytic solution can be formed by adding a leveling agent (Component C) to the second electrolytic solution. Since the additives contained in the electrolytic solution have been described above, the description is omitted. Specifically, the leveling agent (Component C) is added after the step of filtering (C / F).

[0089] For example, when the leveling agent (Component C) is added before the filtration (C / F) step, the leveling agent (Component C) may deteriorate, which can reduce the physical properties of the copper foil. On the other hand, when the leveling agent (Component C) is added after the filtration (C / F) step, deterioration of the leveling agent (Component C) is prevented, which is effective in improving the physical properties according to the present invention.

[0090] The electrolytic solution formed by adding the leveling agent (Component C) 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.

[0091] Also, for the cleanliness of the electrolytic solution 20, the copper wire (Cu wire) used as a raw material for the electrolytic solution 20 can be washed.

[0092] According to an 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.

[0093] More specifically, in order to maintain the cleanliness of the electrolytic solution 20, a high-purity (99.9% or more) copper wire (Cu wire) 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 passing 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.

[0094] According to an 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.

[0095] The copper film 111 manufactured in this way can be cleaned in a cleaning tank.

[0096] 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 in the acid cleaning can be sequentially performed. The cleaning process may be omitted.

[0097] Next, a protective layer 112 is formed on the copper film 111.

[0098] 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.

[0099] 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.

[0100] In addition, the protective layer 112 can also contain a silane compound by silane treatment or a nitrogen compound by nitrogen treatment.

[0101] Such formation of the protective layer 112 manufactures the copper foil 110.

[0102] On one or both sides of the copper foil 110 of the present invention manufactured through the method as described above, 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, whereby an electrode (i.e., a negative electrode) for a secondary battery of the present invention can be manufactured.

[0103] For example, 1 to 3 parts by weight of styrene-butadiene rubber (SBR) and 1 to 3 parts by weight of carboxymethyl cellulose (CMC) are mixed with 100 parts by weight of carbon as a negative electrode active material carbon, and then a slurry is prepared using distilled water as a solvent. Next, the slurry is applied onto the copper foil 110 with a thickness of 20 to 60 μm using a doctor blade and pressed at a pressure of 0.5 to 1.5 ton / cm 2 at 110 to 130 °C.

[0104] A secondary battery can be manufactured using the electrode (negative electrode) for a secondary battery of the present invention manufactured by the above method together with a normal positive electrode, electrolyte, and separator.

[0105] 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.

[0106] 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 is 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.

[0107] Also, 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.

[0108] 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-methacrylate was used as the leveling agent (Component C).

[0109] 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 produce the copper film 111. Next, the copper film 111 was immersed in the rust preventive solution for about 2 seconds to perform chromate treatment on both sides of the copper film 111, and a copper foil was produced by forming the protective layer 112. 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.

[0110] As a result, the 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.

[0111]

Table 1

Table 2

Table 3

[0112] For the copper foils of Examples 1 to 4 and Comparative Examples 1 to 4 produced in this way, (i) the 60° gloss of the first and second surfaces, (ii) the peak count roughness of the first and second surfaces, (iii) the surface area ratio of the first and second surfaces, (iv) the average 60° gloss, (v) the peak density of the first and second surfaces, (vi) the peak density difference between the first surface / second surface, (vii) the average peak density, (viii) the value of Equation 1, and (ix) the presence or absence of adhesion of the active material were confirmed.

[0113] The copper foil was cut to obtain a 10 cm x 10 cm sample.

[0114] (i) 60° glossiness of the first and second surfaces The 60° glossiness was measured for both surfaces of the sample at a 60° incident angle using a gloss meter (Nippon Denshoku, VG7000) in accordance with JIS Z 8741 standard.

[0115] (ii) Peak count roughness of the first and second surfaces The peak count roughness (Rpc) is the average value of the peak count roughness (Rpc) at any three points. The peak count roughness (Rpc) at each of the said points means the number of effective peaks standing on the upper criteria line of 0.5 μm per unit sampling length of 4 mm in the surface roughness profile obtained in accordance with the steel - iron test schedule (SEP 1940) standard.

[0116] At this time, between adjacent effective peaks among the said effective peaks, there is at least one valley deeper than the lower criteria line of - 0.5 μm. If there is no valley deeper than the lower criteria line of - 0.5 μm between adjacent peaks standing on the upper criteria line, all of the adjacent peaks cannot be regarded as "effective peaks" used for the measurement of the peak count roughness (Rpc), and when determining the number of "effective peaks", relatively lower peaks among the said peaks are ignored.

[0117] (iii) Surface area ratio of the first and second surfaces The surface area ratio of the first side and the second side was measured using the VK-9710 of KEYENCE. At this time, the surface area ratio of the first side and the second side means the ratio of the three-dimensional surface area of the first side and the second side to the two-dimensional surface area of the first side and the second side, respectively. Specifically, a copper foil was cut into 1 cm x 1 cm to produce a test piece, and the copper foil test piece was observed at a magnification of 50 times using the color 3D laser microscope VK-9710 of KEYENCE, and the three-dimensional surface area was observed. The "surface area ratio of the first side and the second side" is the value obtained by dividing the three-dimensional surface area of the copper foil test piece measured in three dimensions by the two-dimensional planar area (1 cm 2 ) of the copper foil test piece. Here, the three-dimensional surface area is the area obtained by moving the lens of the microscope in the Z-axis direction to focus.

[0118] (iv) Average 60° gloss The average 60° gloss means the average value of the 60° gloss of the first side and the second side measured above. Specifically, it means half of the value obtained by adding the 60° gloss of the first side and the second side.

[0119] (v) Peak density of the first side and the second side The peak density of the first side and the second side means the value obtained by dividing the peak count roughness of the first side and the second side measured above by the surface area ratio of the first side and the second side.

[0120] (vi) Peak density difference between the first side / second side The peak density difference between the first side and the second side means the value obtained by subtracting the peak density value of the second side from the peak density value of the first side measured above.

[0121] (vii) Average peak density The average peak density means the average value of the peak densities of the first side and the second side measured above. Specifically, it means half of the value obtained by adding the peak densities of the first side and the second side.

[0122] (viii) Value of Equation 1 The value of Equation 1 is calculated by the following Equation 1.

[0123] [Formula 1] [(Average 60° gloss) / (G.U) x (Average peak density) / (pieces)] / 100

[0124] (ix) Adhesion of the active material The negative electrode active material was placed on the copper foils produced in Examples 1 to 4 and Comparative Examples 1 to 4 to form a negative electrode active material layer, and then the peel strength between the copper foil and the active material was measured using a universal testing machine (UTM).

[0125] (1) Production of the negative electrode 2 parts by weight of styrene-butadiene rubber (SBR) and 2 parts by weight of carboxymethyl cellulose (CMC) were mixed with 100 parts by weight of commercially available carbon for the negative electrode active material, and a slurry of the negative electrode active material was produced using distilled water as a solvent. The slurry of the negative electrode active material was applied to a copper foil (Examples and Comparative Examples) having a width of 10 cm with a thickness of 40 μm using a doctor blade, dried at 120 °C, and pressed at a pressure of 1 ton / cm 2 to produce a negative electrode for a secondary battery.

[0126] (2) Measurement method One side of the double-sided tape was attached to a slide glass, and the active material part of the negative electrode for the secondary battery was attached to the other side of the double-sided tape. After fixing the slide glass to the lower part of the universal testing machine (UTM), the adhesive force was measured while peeling the copper foil.

[0127] - Measuring test machine: Universal testing machine (UTM) - Width of the sample: 12.7 mm - Measurement Type: 180° Peel Test - Measurement speed: 50 mm / min

[0128] At this time, if the measured adhesive force is 27 N / m or more, the adhesion to the active material is excellent, and it is indicated as "good adhesion" in Table 3. If the measured adhesive force is less than 27 N / m, the adhesion to the active material is not good, so it is indicated as "poor adhesion" in Table 3.

[0129] Referring to Tables 1 to 3, the copper foils according to Examples 1 to 4 were excellent in adhesion to the active material, while the copper foils according to Comparative Examples 1 to 4 had poor adhesion to the active material.

[0130] The present invention described above is not limited by the aforementioned examples 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 that does not deviate from the technical matters of the present invention. Therefore, the scope of the present invention is represented by the claims described below, 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 Reference Signs

[0131] 100 Electrode for secondary battery 110 Copper foil 111 Copper film 111a Matt 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, The copper film has a first surface in the matte surface direction and a second surface in the shiny surface direction, A copper foil satisfying the following formula 1: [Formula 1] 45 ≤ [(average 60° gloss) / (G.U) x (average peak density) / (pcs)] / 100 ≤ 70 The average peak density in Formula 1 means the average value of the peak densities of the first surface and the second surface, The peak density means a value obtained by dividing the peak count roughness (Rpc) by the surface area ratio, The average 60° gloss in Formula 1 means the average value of the 60° glosses of the first surface and the second surface.

2. The copper foil according to Claim 1, wherein the difference between the peak density of the first surface and the peak density of the second surface is 30 pcs or less.

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

4. 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 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 the electrolytic cell, The electrolytic solution 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 brightener (Component A), a retarder (Component B), and a leveling agent (Component C), The leveling agent (Component C) includes a PEG derivative, a method for manufacturing a copper foil.

5. The brightener (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 4.

6. The PEG derivative in Claim 4, wherein the terminal group is substituted with a saturated hydrocarbon or a functional group, the method for manufacturing a copper foil according to Claim 4.

7. The functional group in Claim 6 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 6.

8. The step of manufacturing the electrolytic solution includes the step of filtering the first electrolytic solution transferred from the storage tank using carbon to form a second electrolytic solution; and The step of 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 4.

Images