Copper foil, electrodes containing the same, a secondary battery containing the same, and a method for manufacturing the same.

Abstract

The present invention relates to copper foil, electrodes containing the same, secondary batteries containing the same, and methods for manufacturing the same, which can prevent problems arising from the limitations and shortcomings of related technologies. [Solution] One embodiment of the present invention provides a copper foil comprising a copper film having a first surface and a second surface, with a matte surface facing the first surface and a shiny surface facing the second surface, and a protective layer on the copper film, wherein the specular reflectance on the first surface is 1.0 to 30.0. The specular reflectance means the value obtained by subtracting the lightness index measured in SCE (Specular component excluded) mode from the lightness index measured in SCI (Specular component included) mode, and is measured using a colorimeter.

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. [Background technology]

[0002] Secondary batteries are a type of energy conversion device that stores electrical energy as chemical energy and generates electricity by converting the chemical energy back into electrical energy when needed. They are used in portable electronic devices such as mobile phones and laptops, as well as as an energy source for electric vehicles. Because secondary batteries can be recharged, they are also called rechargeable batteries.

[0003] Compared to disposable primary batteries, secondary batteries offer economic and environmental advantages, including lead-acid batteries, nickel-cadmium secondary batteries, nickel-metal hydride secondary batteries, and lithium-ion secondary batteries.

[0004] In particular, lithium-ion batteries can store a relatively large amount of energy relative to their size and weight compared to other rechargeable batteries. Therefore, lithium-ion batteries are suitably used in the field of information and communication equipment where portability and mobility are important, and their application range is expanding to energy storage devices for hybrid and electric vehicles.

[0005] Lithium-ion batteries are used repeatedly, with each cycle consisting of charging and discharging. To power any device using a fully charged lithium-ion battery, the battery must have a high charge / discharge capacity to increase the device's operating time. Therefore, research is constantly needed to meet the ever-increasing expectations (needs) of consumers regarding the charge / discharge capacity of lithium-ion batteries.

[0006] In lithium-ion secondary batteries, the characteristics of the battery vary greatly depending on the surface condition of the copper foil used in the current collector. Therefore, improving the surface characteristics of the copper foil is extremely important for improving yield.

[0007] In particular, if the surface shape of the copper foil is uneven, the active material coating will not be uniform. When the active material is unevenly coated on the surface of the copper foil, short circuits may occur during charging or discharging, or the active material may peel off from the copper foil, resulting in a decrease in yield. [Overview of the project] [Problems that the invention aims to solve]

[0008] 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 drawbacks of the aforementioned related technologies.

[0009] One embodiment of the present invention aims to provide a copper foil having a specular reflectance of 1.0 to 30.0 on its first surface and improved adhesion to the active material.

[0010] One embodiment of the present invention aims to provide a copper foil having a specular reflectance of 0.5 to 10.0 on its second surface and improved adhesion to the active material.

[0011] Another embodiment of the present invention aims to provide an electrode for a secondary battery containing such copper foil, and a secondary battery containing such an electrode for a secondary battery.

[0012] Yet another embodiment of the present invention aims to provide a method for manufacturing copper foil with improved adhesion to an active material.

[0013] In addition to the aspects 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 to a person with ordinary skill in the art to which the present invention pertains. [Means for solving the problem]

[0014] One embodiment of the present invention provides a copper foil comprising a copper film having a first surface and a second surface, with a matte surface facing the first surface and a shiny surface facing the second surface, and a protective layer on the copper film, wherein the specular reflectance on the first surface is 1.0 to 30.0. The specular reflectance means the value obtained by subtracting the lightness index measured in SCE (Specular component excluded) mode from the lightness index measured in SCI (Specular component included) mode, and is measured using a colorimeter. [Effects of the Invention]

[0015] A copper foil according to one embodiment of the present invention can improve adhesion to an active material by having a specular reflectance of 1.0 to 30.0 on its first surface.

[0016] A copper foil according to one embodiment of the present invention can improve adhesion to an active material by having a specular reflectance of 0.5 to 10.0 on its first surface. [Brief explanation of the drawing]

[0017] [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. [Modes for carrying out the invention]

[0018] 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 facilitate a clear understanding of the present invention and do not limit the scope of the present invention.

[0019] The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for explaining the embodiments of the present invention are illustrative, so the present invention is not limited to the matters shown in the drawings. The same components throughout the specification can be referred to by the same reference numerals. When explaining the present invention, if it is determined that a specific explanation of related known technologies may unnecessarily obscure the gist of the present invention, the detailed explanation thereof will be omitted.

[0020] When terms such as "comprising", "having", "consisting of", etc. mentioned in this specification are used, other parts may be added unless the expression "only" is used. When a component is expressed in the singular, it includes a plurality unless otherwise explicitly stated. Also, in the interpretation of components, even without a separate explicit description, it is interpreted to include the error range.

[0021] In the case of an explanation of a positional relationship, for example, when the positional relationship between two parts is explained by "on ~", "above ~", "below ~", "beside ~", etc., unless the expressions "immediately" or "directly" are used, one or more other parts may be located between the two parts.

[0022] Spatially relative terms such as "below" or "beneath," "lower," "above," and "upper" can be used to easily describe the correlation between one element or component and another, as shown in the drawing. Spatially relative terms should be understood as terms that include different directions of elements in use or operation, in addition to the directions shown in the drawing. For example, if elements shown in the drawing are flipped over, an element described as "below" or "beneath" of another element may be positioned "above" of the other element. Thus, the exemplary term "below" may include both the downward and upward directions. Similarly, the exemplary terms "up" or "above" may include both the upward and downward directions.

[0023] When describing temporal relationships, for example, when a temporal sequence is described using phrases such as "after," "following," "next," or "before," it may include non-continuous events unless expressions like "immediately" or "directly" are used.

[0024] While terms such as "first," "second," etc., are used to describe various components, these components are not limited by these terms. These terms are simply used to distinguish one component from others. Therefore, the first component referred to below may be the second component within the technical concept of the present invention.

[0025] The term "at least one" should be understood to include all possible combinations of one or more related items. For example, "at least one of items 1, 2, and 3" could mean not just each of items 1, 2, or 3 individually, but all possible combinations of items that could be presented from two or more of items 1, 2, and 3.

[0026] Each of the various embodiments of the present invention is partially or entirely combinable or combined with one another, enabling a variety of technically diverse interlocking and driving processes. Each embodiment may be implemented independently of the others or together in relation to one another.

[0027] Figure 1 is a cross-sectional view of a copper foil 110 according to one embodiment of the present invention.

[0028] Referring to Figure 1, the copper foil 110 of the present invention includes a copper film 111 containing 99.9% by weight or more of copper. Referring to Figure 1, the copper foil 110 of the present invention includes the copper film 111 and a protective layer 112 on the copper film 111. Figure 1 shows a configuration in which the protective layer 112 is disposed on both sides of the copper film 111. However, the present invention is not limited to this, and the protective layer 112 may be disposed on one side of the copper film 111.

[0029] 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.

[0030] 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 chromium compounds, silane compounds, and nitrogen compounds. The protective layer 112 prevents oxidation and corrosion of the copper film 111 and improves heat resistance, thereby extending the lifespan of the copper foil 110 itself, as well as the lifespan of the final product containing it.

[0031] 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.

[0032] According to one embodiment of the present invention, the copper foil 110 may have a specular reflectance on its first surface S1 ranging from 1.0 to 30.0. Specifically, when the specular reflectance on the first surface S1 of the copper foil 110 is between 1.0 and 30.0, the copper foil 110 may have uniform surface characteristics and excellent adhesion to the active material.

[0033] According to the present invention, specular reflectance means the value obtained by subtracting the lightness index measured in SCE (Specular component excluded) mode from the lightness index measured in SCI (Specular component included) mode.

[0034] According to the present invention, specular reflectance is measured using a colorimeter, specifically a CM-5 Model manufactured by Konica Minolta, in accordance with ASTM E1164.

[0035] The specific measurement conditions for specular reflectance are as follows:

[0036] Light source: xenon lamp(D65) Viewing angle: 10 degrees Wavelength range: 220~850nm Wavelength spacing: 10nm Reference: air

[0037] SCI (Specular component included) mode measures the color of an object including its specularly reflected light, while SCE (Specular component excluded) mode measures the color of the diffusely reflected light (light excluding the specularly reflected light) from the object.

[0038] If the specular reflectance of the first surface S1 of the copper foil is less than 1.0, the surface of the copper foil may become excessively non-uniform. Specifically, a low specular reflectance of the copper foil can mean that light is scattered and reflected in various directions. As a result, the active material may be unevenly coated on the surface of the copper foil, which can lead to short circuits during charging or discharging, or the active material peeling off from the copper foil. In other words, the adhesion between the copper foil and the active material may decrease.

[0039] If the specular reflectance of the first surface S1 of the copper foil exceeds 30.0, the surface of the copper foil may become excessively smooth. A high specular reflectance of copper foil can mean that light is reflected almost entirely in one direction. If the surface of the copper foil is excessively smooth, the active material may not spread easily across the surface of the copper foil, and the adhesion between the copper foil and the active material may decrease.

[0040] According to one embodiment of the present invention, the copper foil 110 may have a specular reflectance on its second surface S2 of 0.5 to 10.0. Specifically, when the specular reflectance on the second surface S2 of the copper foil 110 is 0.5 to 10.0, the copper foil 110 may have uniform surface characteristics and may have excellent adhesion to the active material.

[0041] If the specular reflectance of the second surface S2 of the copper foil is less than 0.5, the surface of the copper foil may become excessively non-uniform. Specifically, a low specular reflectance of the copper foil can mean that light is scattered and reflected in various directions. As a result, the active material may be unevenly coated on the surface of the copper foil, which can lead to short circuits during charging or discharging, or the active material peeling off from the copper foil. In other words, the adhesion between the copper foil and the active material may decrease.

[0042] If the specular reflectance of the second surface S2 of the copper foil exceeds 10.0, the surface of the copper foil may become excessively smooth. A high specular reflectance of copper foil can mean that light is reflected almost entirely in one direction. If the surface of the copper foil is excessively smooth, the active material may not spread easily across the surface of the copper foil, and the adhesion between the copper foil and the active material may decrease.

[0043] A copper foil 110 according to one embodiment of the present invention has a thickness of 3 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 3 μm causes a decrease in workability.

[0044] On the other hand, when manufacturing secondary batteries with copper foil 110 exceeding 35 μm in thickness, the thick copper foil 110 makes it difficult to achieve high capacity.

[0045] 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.

[0046] Figure 2 is a cross-sectional view of electrode 100a for a secondary battery according to one embodiment of the present invention. Figure 4 is a cross-sectional view of electrode 100b for a secondary battery according to another embodiment of the present invention.

[0047] 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 from the embodiments of the present invention described above.

[0048] 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.

[0049] 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.

[0050] According to one embodiment of the present invention, the electrode 100 for the secondary battery is a negative electrode, the copper foil 110 is used as a negative electrode current collector, and the active material layer 120 contains a negative electrode active material.

[0051] To ensure the high capacity of the secondary battery, the active material layer 120 of the present invention may be formed of 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.

[0052] Figure 4 is a schematic cross-sectional view of a secondary battery according to one embodiment of the present invention.

[0053] 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 that move 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. Referring to Figure 4, the separator 360 is placed within the electrolyte 350.

[0054] 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.

[0055] 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 as the negative electrode current collector 341.

[0056] 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.

[0057] The method for manufacturing the copper foil 110 of the present invention will be specifically described below with reference to Figure 5.

[0058] The present invention provides a method for manufacturing copper foil 110, which includes the steps of forming a copper film 111 and forming a protective layer 112 on the copper film 111.

[0059] The method of the present invention includes the step of forming a copper film 111 on a rotating negative electrode drum 40 by energizing a positive electrode plate 30 and a rotating negative electrode drum 40 that are arranged spaced apart from each other in an electrolyte 20 in an electrolytic cell 10.

[0060] 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.

[0061] The copper film 111 formation step 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 subsequently growing the seed layer by energizing the second positive electrode plate 32 and the rotating negative electrode drum 40.

[0062] The current densities provided by the first and second positive plates 31 and 32, respectively, may be 40 to 130 ASD.

[0063] If the current densities provided by the first and second positive electrode plates 31 and 32, respectively, are less than 40 ASD, the surface roughness of the copper foil 110 may be low, and the adhesion between the copper foil 110 and the active material layer 120 may not be sufficient.

[0064] On the other hand, if the current densities provided by the first and second positive plates 31 and 32, respectively, exceed 130 ASD, the surface of the copper foil 110 may become rough, and the coating of the active material may not be carried out smoothly.

[0065] The surface properties of the copper film 111 can be altered by the degree of 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.

[0066] During the formation of the copper film 111, the electrolyte 20 is maintained at a temperature of 40-65°C. More specifically, the temperature of the electrolyte 20 can be maintained at 45°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.

[0067] According to one embodiment of the present invention, the electrolyte 20 may contain copper ions, sulfuric acid, chlorine, and organic additives.

[0068] 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 80-130 g / L, respectively.

[0069] 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 flow 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.

[0070] 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.

[0071] According to one embodiment of the present invention, the electrolyte 20 may contain organic additives.

[0072] The organic additives contained in the electrolyte 20 include a brightener (component A), a moderator (component B), and a roughness modifier (component C).

[0073] The glossing agent (component A) contains a sulfonic acid or a metal salt thereof. The glossing agent (component A) may have a concentration of 1 to 20 ppm in the electrolyte 20. The glossing agent (component A) may also contain an alcohol ether structure or a thiocarbonyl bond structure (C=S).

[0074] 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 increasing the gloss of the copper foil 110. If the concentration of the brightener (component A) is less than 1 ppm, the gloss of the copper foil 110 decreases, and if it exceeds 20 ppm, problems such as changes in weight or surface roughness of the copper foil 110 after immersion may occur.

[0075] The glossing agent may include, for example, at least one of the following: bis-(3-sulfopropyl)-disulfide disodium salt, 3-mercapto-1-propanesulfonic acid and 3-(N,N-dimethylthiocarbamoyl)-thiopropanesulfonate sodium salt, thioglycolic acid, 3,3-thiobis-(1-propyonic acid, disodium salts), 3-(Benzthiazolyl-2-thio)-propanesulfonic acid, sodium salt, or bis-(p-sulfophenyl)disulfide, disodium salt.

[0076] The moderator (component B) contains a nonionic water-soluble polymer. The moderator (component B) may have a concentration of 0.1 to 10 ppm in the electrolyte 20.

[0077] 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.

[0078] If the concentration of the moderator (component B) is less than 0.1 ppm, the roughness of the copper foil 110 increases rapidly, which can cause problems with changes in 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 0.1 to 10 ppm without unnecessarily increasing the concentration of the moderator (component B), thereby increasing manufacturing costs and wasting raw materials.

[0079] 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 to these, and other nonionic water-soluble polymers that can be used in the manufacture of high-strength copper foil 110 can be used as moderators.

[0080] The roughness modifier (component C) includes nitrogen-containing heterocyclic quaternary ammonium salts or their derivatives. Specifically, the roughness modifier (component C) may include compounds of the type of primary amine, secondary amine, or tertiary amine, and may also include either collagen or gelatin.

[0081] For example, the roughness modifier (component C) may contain one or more of the following: urea, thiourea, ethylene thiourea, diethylthiourea, polyethyleneimine, and dimethyl acrylamide.

[0082] The roughness modifier (component C) improves the glossiness and flatness of the copper foil 110. The roughness modifier (component C) can have a concentration of 1 to 10 ppm in the electrolyte 20.

[0083] If the concentration of the roughness modifier (component C) is less than 1 ppm, a problem occurs where the improvement in gloss and flatness of the copper foil 110 does not occur. On the other hand, if the concentration of the roughness modifier (component C) exceeds 10 ppm, a problem occurs where the surface gloss of the copper foil 110 becomes uneven and the surface roughness increases rapidly.

[0084] The roughness modifier (component C) may also contain at least one of the compounds represented by the following chemical formulas 1 to 5.

[0085] [Chemical formula 1] [ka]

[0086] [Chemical formula 2] [ka]

[0087] [Chemical formula 3] [ka]

[0088] [Chemical formula 4] [ka]

[0089] [Chemical formula 5] [ka]

[0090] In chemical formulas 1-5, l1-l4, m1-m4, and n1-n5 each represent repeating units, are integers greater than or equal to 1, and may be the same or different from one another.

[0091] According to one embodiment of the present invention, the compounds represented by chemical formulas 1 to 5 each have a number average molecular weight of 500 to 12,000.

[0092] If the number-average molecular weight of the compounds represented by chemical formulas 1-5 used as roughness modifiers is less than 500, the monomer ratio is high, resulting in high surface roughness of the copper foil 110. If the roughness modifier content is low, the surface roughness of the copper film 111 increases, and its gloss and flatness may decrease.

[0093] When the number-average molecular weight of the compounds represented by chemical formulas 1-5 exceeds 12,000, the deviation in the surface roughness of the copper foil 110 increases. In this case, even by adjusting the concentrations of other additives, it is difficult to suppress the increase in the deviation in the surface roughness of the copper foil 110.

[0094] Compounds represented by chemical formulas 1-5 can be prepared, for example, by polymerization or copolymerization using DDAC (Diallyl dimethyl ammonium chloride).

[0095] Examples of compounds represented by chemical formula 1 include PAS-2451 (Mw 30,000, Nittobo).

[0096] Examples of compounds represented by chemical formula 2 include PAS-84 (Mw20,000, Nittobo).

[0097] Examples of compounds represented by chemical formula 3 include PAS-2351 (Mw 25,000, Nittobo).

[0098] Examples of compounds represented by chemical formula 4 include PAS-A-1 (Mw 5,000, Nittobo) and PAS-A-5 (Mw 4,000, Nittobo).

[0099] Examples of compounds represented by chemical formula 5 include PAS-J-81 (Mw 180,000, Nittobo).

[0100] 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 / hour is also acceptable.

[0101] According to one embodiment of the present invention, the electrolyte 20 can be used by mixing a first organic additive and a second organic additive. For example, the first organic additive means an additive obtained by forcibly electrolyzing one or two of the moderator (component B) and roughness modifier (component C). The second organic additive means an additive that is not electrolyzed, excluding the first organic additive. For example, the second organic additive may include a brightener (component A), a moderator (component B), and a roughness modifier (component C) among the organic additives.

[0102] In the following, the first organic additive can be referred to as a degradation additive, and the second organic additive can be referred to as a fresh additive.

[0103] According to the present invention, the forced electrolysis conditions are as follows:

[0104] -Current: 50A - Time: 10-100 hours - Rectifier manufacturer: UNICORN TMI - Rectifier model name: MRI-20150A

[0105] Forced electrolysis can be carried out by adding one or two of either a moderator (component B) or a roughness modifier (component C) to an acid-resistant container to produce a 1 wt% to 10 wt% aqueous solution, and then applying electricity.

[0106] According to one embodiment of the present invention, the first organic additive and the second organic additive can be added in a weight ratio (weight percent, wt%) of 3:1 to 10:1.

[0107] When the first organic additive and the second organic additive are added in a weight ratio of less than 3:1, for example, when the first organic additive and the second organic additive are added in a weight ratio of 2:1, the amount of the first organic additive added is smaller and the amount of the second organic additive added is larger than the amount targeted in this invention. Although the copper foil exhibits excellent properties such as strength when a small amount of the first organic additive is added, the adsorption force of the second organic additive is stronger than that of the second organic additive, so a problem may arise where the stretchability of the copper foil decreases when the ratio of the second organic additive increases. Therefore, the physical properties to be obtained in this invention may not be achieved.

[0108] When the first organic additive and the second organic additive are added in a weight ratio greater than 3:1, for example, when the first organic additive and the second organic additive are added in a weight ratio of 4:1 or 5:1, the amount of the first organic additive is added in a larger quantity and the amount of the second organic additive in a smaller quantity than the amount targeted in this invention. In this case, the electrolyzed first organic additive may have a small number average molecular weight, and the strength properties of the copper foil produced by the electrolyte to which an excess amount of the first organic additive with a small number average molecular weight is added may decrease. Therefore, the physical properties to be obtained in this invention may not be obtained.

[0109] Furthermore, the first organic additive may have a number average molecular weight in the range of 60 to 800, and the second organic additive may have a number average molecular weight in the range of 5,000 to 20,000.

[0110] Generally, when only an unelectrolyzed additive (second organic additive) is added to the electrolyte 20 for manufacturing copper foil 110, a problem may occur where the second organic additive rapidly deteriorates the moment it is introduced into the electrolytic cell 10. As a result, uneven current density occurs, and the quality of the copper foil 110 may become unstable.

[0111] On the other hand, according to the present invention, when an electrolyzed additive (first organic additive) and an unelectrolyzed additive (second organic additive) are mixed and used in the electrolyte 20 for manufacturing copper foil 110, the electrolyzed additive (first organic additive) increases the linkage and reactivity of polymer chains, while also diversifying the length of the polymer chains. As a result, the dispersion of polymer molecular weights can be broadened. When the dispersion of polymer molecular weights is broadened, electrodeposition defects that occur during the manufacture of copper foil 110 can be reduced, and the occurrence of wrinkles or tears in the copper foil 110 can be suppressed.

[0112] For example, if the molecular weight distribution of polymers is narrow, the adsorption strength of organic additives will be strong, which can cause defects during electrodeposition of the copper film. Also, the current distribution at the negative electrode becomes relatively high in the etched area, increasing the migration speed and quantity of organic additives. As a result, the adsorption strength of organic additives increases, which can cause wrinkles or tears in the copper foil.

[0113] Furthermore, if the molecular weight of the organic additive is too large, the uniform adsorption of the organic additive decreases, resulting in differences in the amount of electrodeposition. As a result, wrinkles or tears may occur in the copper foil.

[0114] Therefore, in order to prevent wrinkles or tears in the copper foil 110, it is necessary to reduce the molecular weight of the organic additive and spread it widely.

[0115] According to the present invention, when the electrolyte 20 is used by mixing the first organic additive and the second organic additive, the concentration of the brightener (component A) in the electrolyte 20 can be maintained at 1 to 20 ppm, the concentration of the moderator (component B) can be maintained at 0.1 to 10 ppm, and the concentration of the roughness modifier (component C) can be maintained at 1 to 10 ppm.

[0116] To ensure the cleanliness of the electrolyte 20, the copper wire (Cu wire) that is the raw material for the electrolyte 20 can be washed.

[0117] According to one embodiment of the present invention, the steps for producing the electrolyte 20 may include a step of heat-treating a 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 electrolyte.

[0118] 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 copper wire that has been heat-treated 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.

[0119] The copper film 111 manufactured in this manner can be washed in a washing tank.

[0120] 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 for acid cleaning. The cleaning step can also be omitted.

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

[0122] Referring to Figure 5, the step may further include 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 placed in the anticorrosion solution 60.

[0123] As mentioned above, the rust-preventive solution 60 may contain at least one of a chromium compound, a silane compound, and a nitrogen compound. For example, the copper film 111 can be immersed in a 1-10 g / L potassium dichromate solution at room temperature for 1-30 seconds.

[0124] Furthermore, the protective layer 112 may contain silane compounds obtained by silane treatment, or nitrogen compounds obtained by nitrogen treatment.

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

[0126] The electrode for a secondary battery (i.e., a negative electrode) of the present invention can be manufactured by coating one or more negative electrode active materials selected from the group consisting of carbon; metal (Me) of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe; alloys containing metal (Me); oxides of metal (Me) (MeOx); and composites of metal (Me) and carbon onto one or both sides of the copper foil 110 of the present invention manufactured by the method described above.

[0127] For example, 100 parts by weight of carbon for the negative electrode active material is mixed with 1 to 3 parts by weight of styrene-butadiene rubber (SBR) and 1 to 3 parts by weight of carboxymethylcellulose (CMC), and then a slurry is prepared using distilled water as a solvent. Next, the slurry is applied to the copper foil 110 to a thickness of 20 to 60 μm using a doctor blade, and heated at 110 to 130°C for 0.5 to 1.5 ton / cm². 2 Press with this pressure.

[0128] 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.

[0129] The present invention will be described in detail below with reference to examples and comparative examples. However, the following examples are provided to aid in understanding the present invention, and the scope of the present invention is not limited to these examples.

[0130] Examples 1-6 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 concentration of copper ions in the electrolyte 20 was set to 87 g / L, the concentration of sulfuric acid to 110 g / L, the temperature of the electrolyte to 55°C, and the current density to 60 ASD.

[0131] Furthermore, the concentration of chlorine (Cl) in the electrolyte solution 20 was maintained at 20 ppm, and the concentrations of the organic additives were as shown in Table 1 below.

[0132] Among the organic additives, bis-(3-sulfopropyl)-disulfide disodium salt (SPS) is used as the brightener (component A), polyethylene glycol (PEG) is used as the moderator (component B), and diallylmethylethylammonium ethyl sulfate maleic acid copolymer (PAS-2451) is used as the roughness modifier (component C). TM Nittobo (MW30,000) was used.

[0133] The organic additives used were a mixture of a first organic additive and a second organic additive. The first organic additive was electrolyzed polyethylene glycol (PEG), and the second organic additive was bis-(3-sulfopropyl)-disulfide disodium salt (SPS), polyethylene glycol (PEG), and diallylmethylethylammonium ethyl sulfate maleic acid copolymer (PAS-2451). TM This includes Nittobo Inc. (Mw30,000).

[0134] The number-average molecular weight of the first organic additive is in the range of 62 to 500, and the number-average molecular weight of the second organic additive is in the range of 5,000 to 20,000.

[0135] Electrolysis was carried out under the following conditions:

[0136] -Current: 50A -Time: 50hr

[0137] The weight ratio of the first organic additive to the second organic additive is as shown in Table 1 below.

[0138] A copper film 111 was manufactured 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 manufacturing copper foil. A rust-preventive solution mainly composed of chromic acid was used, with a chromic acid concentration of 5 g / L.

[0139] As a result, copper foils of Examples 1 to 6 were manufactured. The thickness of the manufactured copper foil was 7 μm.

[0140] Comparative Examples 1-2 The concentrations of the organic additives are as shown in Table 1 below.

[0141] Copper foil was manufactured in the same manner as in Examples 1-6, except that a first organic additive was added. The thickness of the manufactured copper foil was 7 μm.

[0142] Comparative Examples 3-4 The concentrations of the organic additives and the weight ratios of the first and second organic additives are as shown in Table 1 below.

[0143] Copper foil was manufactured using the same method as in Examples 1-6. The thickness of the manufactured copper foil was 7 μm.

[0144] [Table 1]

[0145] [Table 2]

[0146] [Table 3]

[0147] For the copper foils of Examples 1-6 and Comparative Examples 1-4 manufactured in this manner, (i) brightness index, (ii) specular reflectance, (iii) peel strength, and (iv) capacity retention rate were confirmed.

[0148] The copper foil was cut to obtain a 10cm x 10cm sample.

[0149] (i) Lightness index (SCI, SCE) SCI (Specular component included) mode measures the color of an object including its specularly reflected light, while SCE (Specular component excluded) mode measures the color of the diffusely reflected light (light excluding the specularly reflected light) from the object.

[0150] The lightness index (SCI, first surface) refers to the lightness index measured in SCI (Specular component included) mode on the first surface of the copper foil according to the present invention.

[0151] The lightness index (SCE, first surface) refers to the lightness index measured in SCE (Specular component excluded) mode on the first surface of the copper foil according to the present invention.

[0152] The lightness index (SCI, second surface) refers to the lightness index measured in SCI (Specular component included) mode on the second surface of the copper foil according to the present invention.

[0153] The lightness index (SCE, second surface) refers to the lightness index measured in SCE (Specular component excluded) mode on the second surface of the copper foil according to the present invention.

[0154] The lightness index is measured using a colorimeter, specifically the CM-5 Model manufactured by Konica Minolta, in accordance with ASTM E1164.

[0155] The specific measurement conditions are as follows:

[0156] Light source: xenon lamp(D65) Viewing angle: 10 degrees Wavelength range: 220~850nm Wavelength spacing: 10nm Reference: air

[0157] (ii) Specular reflectance Specular reflectance is the value obtained by subtracting the light index measured in SCE (Specular component excluded) mode from the light index measured in SCI (Specular component included) mode.

[0158] (iii) Peel strength For the negative electrode active material, 100 parts by weight of commercially available carbon was mixed with 2 parts by weight of SBR (styrene-butadiene rubber) and 2 parts by weight of CMC (carboxymethylcellulose). Next, distilled water was added to this mixture as a solvent to produce a slurry. Using a doctor blade, the slurry was applied to the surface of copper foil (width: 10 cm) to a thickness of approximately 60 μm, dried at 120°C for 10 minutes, and then subjected to a pressing process (pressure: 1 ton / cm²). 2 The negative electrode was manufactured by performing the following procedure.

[0159] After attaching the active material-laid surface of the negative electrode sample (width: 12.7 mm) with double-sided tape, the peel strength between the copper foil and the active material was measured using a universal testing machine (UTM) while peeling the copper foil at a 90° angle according to the IPC-TM-650 standard (measurement speed: 50 mm / min).

[0160] (iv) Capacity retention rate To 100 parts by weight of commercially available carbon for the negative electrode active material, 2 parts by weight of SBR (styrene-butadiene rubber) and 2 parts by weight of CMC (carboxymethyl cellulose) were mixed. Next, a slurry was produced by adding distilled water as a solvent to this mixture. The slurry was applied onto the surface of an electrolytic copper foil (width: 10 cm) with a thickness of about 60 μm using a doctor blade, dried at 120 °C for 10 minutes, and then a pressing process (pressure: 1 ton / cm 2 ) was carried out to produce a negative electrode.

[0161] Lithium manganese oxide (Li 1.1 Mn 1.85 Al 0.05 O4) and orthorhombic crystal structure lithium manganese oxide (o-LiMnO2) were mixed at a weight ratio of 90:10 to produce a positive electrode active material. The positive electrode active material, carbon black, and polyvinylidene fluoride (PVDF) were mixed with NMP as an organic solvent at a weight ratio of 85:10:5 to produce a slurry. After the slurry was applied to both sides of an aluminum foil with a thickness of 20 μm and then dried, a positive electrode was produced.

[0162] Also, a basic electrolyte solution was prepared by dissolving 1 M of LiPF6 as a solute in a non-aqueous organic solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a weight ratio of 1:2. An electrolyte solution was produced by mixing 99.5% by weight of this basic electrolyte solution and 0.5% by weight of succinic anhydride.

[0163] A secondary battery was produced using the negative electrode, positive electrode, and electrolyte solution thus produced.

[0164] Next, for the secondary battery thus produced, the capacity per gram of the positive electrode was measured at a charging operating voltage of 4.3 V and a discharging operating voltage of 3.4 V, and a charge-discharge experiment was carried out 50 times at a charge-discharge rate of 0.2 C at 50 °C, and the capacity retention rate of the secondary battery was calculated by the following formula 1.

[0165] [Formula 1] Capacity retention rate (%) = (Discharge capacity at 50th discharge / Discharge capacity at 1st discharge) × 100

[0166] Referring to Tables 1 to 3, the copper foils from Examples 1 to 6 met the range of 1.0 to 30.0 for specular reflectivity on the first surface and achieved a secondary battery capacity retention rate of 90% or more. However, the copper foils from Comparative Examples 1 to 4 did not meet the range of 1.0 to 30.0 for specular reflectivity on the first surface and did not achieve the 90% capacity retention rate required by the industry for secondary batteries.

[0167] The present invention, as described above, is not limited by the embodiments and examples 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 without departing from 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]

[0168] 100 Electrodes for secondary batteries 110 Copper foil 111 Copper film 112 Protective layer 120 Active material layer 10 Electrolytic cell 20 Electrolyte

Claims

1. It has a first surface and a second surface, A copper film having a matte surface facing the first surface and a shiny surface facing the second surface, A copper foil comprising a protective layer on the copper film, The specular reflectance of the first surface is 1.0 to 30.

0. The specular reflectance refers to the value obtained by subtracting the lightness index measured in SCE (Specular component excluded) mode from the lightness index measured in SCI (Specular component included) mode, and is measured using a colorimeter for copper foil.

2. The copper foil according to claim 1, wherein the specular reflectance on the second surface is 0.5 to 10.

0.

3. 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.

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