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

Abstract

To provide a copper foil in which the formation of curls is prevented, an electrode containing the same, a secondary battery containing the same, and a manufacturing method thereof.SOLUTION: 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 disposed on the copper film, wherein the copper film includes copper and non-copper elements, and the non-copper elements include carbon (C), nitrogen (N), and oxygen (O).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 in which the generation of curl is prevented, an electrode containing the same, a secondary battery containing the same, and a method for manufacturing the same.

Background Art

[0002] A secondary battery is a type of energy conversion device that stores electrical energy by converting it into chemical energy and generates electricity by converting the chemical energy back into electrical energy when electricity is needed. It is used not only for portable household appliances such as mobile phones and notebook computers, but also as an energy source for electric vehicles. A secondary battery is also referred to as a rechargeable battery because it can be recharged.

[0003] Examples of secondary batteries that have economic and environmental advantages compared to disposable primary batteries include lead-acid batteries, nickel-cadmium secondary batteries, nickel-metal hydride secondary batteries, and lithium secondary batteries.

[0004] In particular, a lithium secondary battery can store relatively more energy compared to its size and weight when compared to other secondary batteries. Therefore, in the field of information and communication equipment where portability and mobility are important, lithium secondary batteries are preferably used, and their application scope is also expanding to energy storage devices for hybrid vehicles and electric vehicles.

[0005] A lithium secondary battery is repeatedly used with one charge and discharge cycle. When operating any device with a fully charged lithium secondary battery, in order to increase the operating time of the device, the lithium-ion secondary battery must have a high charge-discharge capacity. Therefore, research is continuously required to meet the increasingly high expectations (needs) of consumers for the charge-discharge capacity of lithium secondary batteries.

[0006] Such a secondary battery includes a negative electrode current collector made of copper foil, and among copper foils, electrolytic copper foil is widely used as the negative electrode current collector of the secondary battery. As the accommodation for secondary batteries increases and the demand for high-capacity, high-efficiency, and high-quality secondary batteries increases, an electrolytic copper foil that can improve the characteristics of the secondary battery is required. In particular, an electrolytic copper foil that can ensure high capacity, stable capacity retention, and performance of the secondary battery is required.

[0007] Note that the thinner the copper foil, the more the amount of active material that can be contained in the same space, the more the number of current collectors can increase, and the more the capacity of the secondary battery can increase. However, the thinner the copper foil, the more curl occurs, and defects such as tearing or wrinkling of the copper foil due to curl at the edge part occur during winding of the copper foil, so it is difficult to manufacture a copper foil in the form of a very thin film. Therefore, in order to manufacture a copper foil having a very thin thickness, curl of the copper foil must be prevented.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] Therefore, the present invention relates to a copper foil that can prevent problems caused by the limitations and disadvantages of the related art as described above, an electrode including the same, a secondary battery including the same, and a method for manufacturing the same.

[0009] In addition to the aspects of the present invention mentioned above, other features and merits 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

[0010] 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, wherein the copper film contains copper and non-copper elements, and the non-copper elements include carbon (C), nitrogen (N), and oxygen (O).

[0011] Another embodiment of the present invention includes the steps of manufacturing an electrolytic solution containing copper ions; forming a copper film; and forming a protective layer on the copper film. The step of forming the copper film includes 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 PPG derivative, and attempts to provide a method for manufacturing a copper foil.

[0012] According to still another embodiment of the present invention, 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 is provided.

[0013] According to still another embodiment of the present invention, a secondary battery including a cathode that provides lithium ions during charging; an anode that provides electrons and lithium ions during discharging; an electrolyte disposed between the cathode and the anode that provides an environment in which lithium ions can move; and a separator that electrically insulates the cathode and the anode is provided.

Advantages of the Invention

[0014] The copper foil according to the present invention prevents the occurrence of wrinkles or tears. By manufacturing intermediate parts and final products such as flexible printed circuit boards (FPCBs) and secondary batteries using such a copper foil, the productivity of not only the intermediate parts but also the final products can be improved.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0016] Hereinafter, examples of the present invention will be described in detail with reference to the accompanying drawings. However, the examples described below are only presented for illustrative purposes to assist in a clear understanding of the present invention and do not limit the scope of the present invention.

[0017] The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for explaining the examples of the present invention are exemplary, so the present invention is not limited to the matters illustrated in the drawings. The same components can be referred to by the same reference numerals throughout the specification. In describing the present invention, when it is determined that a specific description of related known technologies may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

[0018] When terms such as "including", "having", "consisting of", etc. are used in this specification, other parts can be added as long as the expression "only ~" is not used. When a component is expressed in the singular, it includes a plurality unless otherwise explicitly stated. Also, in the interpretation of components, it is interpreted to include an error range even without separate explicit description.

[0019] In the case of an explanation of a positional relationship, for example, when the positional relationship between both parts is explained by "above", "on the upper part of", "on the lower part of", "next to", etc., as long as the expressions "immediately" or "directly" are not used, one or more other parts can be located between both parts.

[0020] Spatially relative terms such as "below", "beneath", "above", "upper", etc. can be used to easily describe the correlation between one element or component and another element or component as shown in the drawings. Spatially relative terms should be understood as terms including different directions of elements relative to each other during use or operation in addition to the directions shown in the drawings. 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 below and above. Similarly, the exemplary terms "above" or "on" can include all directions of above and below.

[0021] In the case of an explanation of a temporal relationship, for example, when the temporal sequence is explained by "after", "subsequent to", "next", "before", etc., as long as the expressions "immediately" or "directly" are not used, non - continuous cases can also be included.

[0022] The first, second, etc. are used to describe various components, but these components are not limited by these terms. These terms are simply used to distinguish one component from another. Therefore, the first component mentioned below may be the second component within the technical idea of the present invention.

[0023] 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 two or more items that can be presented from the first item, the second item, and the third item.

[0024] Each feature 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.

[0025] FIG. 1 is a cross-sectional view of a copper foil 110 according to an embodiment of the present invention.

[0026] 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.

[0027] 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.

[0028] The protective layer 112 is formed by electrodepositing an anticorrosion material on the copper film 111. The anticorrosion material may include at least one of a chromium compound, a silane compound, and a nitrogen compound. The protective layer 112 prevents oxidation and corrosion of the copper film 111 and improves heat resistance, thereby extending the life of the copper foil 110 as well as the life of the final product including the same.

[0029] 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.

[0030] According to an embodiment of the present invention, the copper film 111 of the copper foil 110 may contain copper (Cu) and non - copper elements, and the non - copper elements may include carbon (C), nitrogen (N), and oxygen (O).

[0031] Specifically, according to an embodiment of the present invention, the copper film 111 of the copper foil 110 may contain 0.05 - 0.2 at% of carbon (C), 0.01 - 0.05 at% of nitrogen (N), 0.1 - 0.5 at% of oxygen (O), and less than 0.01 at% of sulfur (S).

[0032] At this time, when the contents of carbon (C), nitrogen (N), oxygen (O), and sulfur (S) in the copper film 111 satisfy the respective ranges, while forming the crystals of the copper film 111, the generation of curl in the copper foil 110 can be suppressed or prevented.

[0033] On the other hand, when the content of any one of carbon (C), nitrogen (N), and oxygen (O) in the copper film 111 is less than the above range, for example, when carbon (C) is contained less than 0.05 at%, nitrogen (N) is contained less than 0.01 at%, or oxygen (O) is contained less than 0.1 at%, it may be difficult to form the crystals of the copper film 111.

[0034] Also, when the content of any one of carbon (C), nitrogen (N), oxygen (O), and sulfur (S) in the copper film 111 is greater than the above range, for example, when carbon (C) exceeds 0.2 at%, nitrogen (N) exceeds 0.05 at%, oxygen (O) exceeds 0.5 at%, or sulfur (S) exceeds 0.01 at%, excessive impurities are added to the copper film 111, and curl may occur in the copper foil 110.

[0035] Therefore, in order to suppress the generation of curl of the copper foil 110 or form the crystal of the copper film 111, the copper film 111 of the copper foil 110 needs to contain 0.05 to 0.2 at% of carbon (C), 0.01 to 0.05 at% of nitrogen (N), 0.1 to 0.5 at% of oxygen (O), and less than 0.01 at% of sulfur (S).

[0036] According to an embodiment of the present invention, the copper film 111 of the copper foil 110 may not contain sulfur (S). Specifically, when the copper film 111 of the copper foil 110 does not contain sulfur (S), the generation of curl of the copper foil 110 can be suppressed or prevented.

[0037] On the other hand, when the copper film 111 of the copper foil 110 contains sulfur (S), sulfur (S) forms the surface characteristics of the copper film 111 unevenly compared to other non - copper elements excluding sulfur (S), thereby causing curl to occur in the copper foil 110.

[0038] Therefore, in order to suppress or prevent the generation of curl in the copper foil 110, the copper film 111 needs to contain no sulfur.

[0039] 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 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, the manufacture of the copper foil 110 having a thickness of less than 4 μm causes a decrease in workability.

[0040] 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.

[0041] 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.

[0042] FIG. 2 is a cross-sectional view of the electrode 100a for a secondary battery according to an embodiment of the present invention. FIG. 3 is a cross-sectional view of the electrode 100b for a secondary battery according to another embodiment of the present invention.

[0043] As shown in FIG. 2, the electrode 100a for a secondary battery 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 examples of the present invention.

[0044] FIG. 2 shows a configuration in which the active material layer 120 is formed on one surface of the copper foil 110. However, in an embodiment of the present invention, 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.

[0045] In a lithium secondary battery, an aluminum foil is generally used as a positive electrode current collector that binds to a positive electrode active material, and the copper foil 110 is generally used as a negative electrode current collector that binds to a negative electrode active material.

[0046] According to an 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.

[0047] In order to guarantee a 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.

[0048] FIG. 4 is a schematic cross-sectional view of a secondary battery according to an embodiment of the present invention.

[0049] Referring to FIG. 4, the secondary battery includes a cathode 370, an anode 340, an electrolyte 350 disposed between the cathode 370 and the anode 340 to provide an environment in which ions can move, and a separator 360 that electrically insulates the cathode 370 and the anode 340. Here, the ions moving between the cathode 370 and the anode 340 are, for example, lithium ions. The separator 360 separates the cathode 370 and the anode 340 to prevent the charge generated at one electrode from being wasted by moving through the interior of the secondary battery 105 to the other electrode. Referring to FIG. 4, the separator 360 is disposed within the electrolyte 350.

[0050] The cathode 370 includes a cathode current collector 371 and a cathode active material layer 372, and aluminum foil can be used as the cathode current collector 371.

[0051] The anode 340 includes an anode current collector 341 and an anode active material layer 342, and copper foil 110 can be used as the anode current collector 341.

[0052] According to an embodiment of the present invention, the copper foil 110 shown in FIG. 1 can be used as the anode current collector 341. Also, the electrodes 100a and 100b for secondary batteries shown in FIG. 2 or FIG. 3 can be used for the anode 340 of the secondary battery shown in FIG. 4.

[0053] Hereinafter, the manufacturing method of the copper foil 110 of the present invention will be specifically described with reference to FIGS. 5 and 6.

[0054] 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.

[0055] The method of the present invention includes a step of forming a copper film 111 on the rotating anode drum 40 by energizing a positive electrode plate 30 and a rotating anode drum 40 disposed apart from each other in the electrolytic solution 20 in the electrolytic cell 10.

[0056] 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.

[0057] The formation step of 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.

[0058] The current density provided by each of the first and second positive electrode plates 31 and 32 can be 30 to 130 ASD.

[0059] When the current density provided by each of 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.

[0060] On the other hand, when the current density provided by each of the first and second positive electrode plates 31 and 32 exceeds 130 ASD, the surface of the copper foil 110 becomes rough, and the coating of the active material may not be smooth.

[0061] The surface characteristics of the copper film 111 can be changed depending on the surface buff finish or polishing degree of the rotating negative electrode drum 40. For example, the surface of the rotating negative electrode drum 40 can be polished with a polishing brush having a grit size of #800 to #3000.

[0062] During the formation process of the copper film 111, the electrolytic solution 20 is maintained at a temperature of 40 to 60 °C. More specifically, the temperature of the electrolytic solution 20 can be maintained at 50 °C or higher. At this time, by adjusting the composition of the electrolytic solution 20, the physical, chemical, and electrical characteristics of the copper film 111 can be controlled.

[0063] According to an embodiment of the present invention, the electrolytic solution 20 may include copper ions, sulfuric acid, chlorine (Cl), and an organic additive.

[0064] To smooth the formation of the copper film 111 by electrodeposition of copper, the concentration of copper ions and sulfuric acid in the electrolytic solution 20 are adjusted to 70 - 150 g / L and 80 - 150 g / L, respectively.

[0065] In one 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 flow into the electrolytic solution 20 during the formation of the copper film 111. Specifically, chlorine (Cl) can precipitate silver (Ag) ions in the form of silver chloride (AgCl). Such silver chloride (AgCl) can be removed by filtration.

[0066] When the concentration of chlorine (Cl) is less than 15 ppm, the removal of silver (Ag) ions is not smooth. On the other hand, when the concentration of chlorine (Cl) exceeds 25 ppm, unnecessary reactions may occur due to excessive chlorine (Cl). Therefore, the concentration of chlorine (Cl) in the electrolytic solution 20 is controlled in the range of 15 - 25 ppm.

[0067] According to one embodiment of the present invention, the electrolytic solution 20 may contain an organic additive.

[0068] The organic additive contained in the electrolytic solution 20 includes a brightener (Component A), a retarder (Component B), and a leveling agent (Component C).

[0069] The brightener (Component A) includes a sulfonic acid or its metal salt. The brightener (Component A) can have a concentration of 1 - 20 ppm in the electrolytic solution 20.

[0070] 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, and if it exceeds 20 ppm, problems such as a change in the weight of the copper foil 110 after immersion or a change in surface roughness may occur.

[0071] The brightener may contain at least one of, for example, 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.

[0072] 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 electrolytic solution 20.

[0073] The retarder (Component B) reduces the electrodeposition rate of copper and prevents a rapid 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.

[0074] If the concentration of the retarder (Component B) is less than 0.1 ppm, there may occur a problem that the roughness of the copper foil 110 rapidly increases and the surface state of the copper foil 110 changes. On the other hand, even if the concentration of the retarder (Component B) exceeds 10 ppm, there are hardly any physical property changes such as the appearance, gloss, roughness, strength, elongation rate, etc. of the copper foil 110. Therefore, without the need to increase the manufacturing cost by unnecessarily increasing the concentration of the retarder (Component B) and wasting raw materials, the concentration of the retarder (Component B) can be adjusted to the range of 0.1 to 10 ppm.

[0075] The retarder (Component B) may contain at least one nonionic water-soluble polymer selected from, for example, polyethylene glycol (PEG), polypropylene glycol, polyethylene-polypropylene copolymer, polyglycerin, polyethylene glycol dimethyl ether, hydroxyethyl cellulose, polyvinyl alcohol, polyglycol stearate ether, and polyglycol stearyl alcohol ether. However, the type of the retarder is not limited thereto, and other nonionic water-soluble polymers that can be used in the production of the high-strength copper foil 110 can be used as the retarder.

[0076] 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 electrolytic solution 20.

[0077] The leveling agent (Component C) prevents the formation of excessively high peaks or excessively large protrusions on the copper film 111 and makes the copper film 111 macroscopically flat. The leveling agent (Component C) can have a concentration of 1 to 10 ppm in the electrolytic solution 11.

[0078] 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 contain at least one of an ethylene group, an acrylic group, and a bisphenol group. At this time, PEG means Polyethylene glycol.

[0079] Specifically, in the case of PEG, generally a hydroxyl group (-OH) is present in the terminal group, and the hydroxyl group (-OH) present in the terminal group can react with other additives added to the electrolytic solution and reduce the physical properties of the copper foil.

[0080] At this time, when the end group of the PEG derivative is substituted with a functional group containing at least one of a saturated hydrocarbon, an ethylene group, an acrylic group, and a bisphenol group, the end 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.

[0081] 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.

[0082] On the other hand, when the concentration of the leveling agent (Component C) exceeds 10 ppm, the surface roughness of the copper foil 110 excessively increases, the strength can be decreased, pinholes and curls may occur on the surface of the copper foil 110, and it may be difficult to separate from the winder (WR) after manufacturing the copper foil 110.

[0083] The leveling agent (Component C) may contain, for example, at least one of PEG-PPG-isodecyl ether, PEG-PPG-glyceryl ether, PEG-PPG-butyl ether, PEG-PPG-hexylene glycol, PEG-PPG-trimethylpropane, PEG-PPG-allyl ether, PEG-PPG-methacrylate, PEG-PPG-acrylate, and PEG-PPG-bisphenol A ether.

[0084] When the copper film 111 is formed, the flow rate of the electrolytic solution 20 supplied into the electrolytic cell 10 can be 41 - 45 m 3 / hour.

[0085] Figure 6 is a schematic diagram showing the circulation process of the electrolytic solution according to the present invention.

[0086] According to one embodiment of the present invention, the step of manufacturing the electrolytic solution may include filtering (C / F) the first electrolytic solution transferred from the storage tank using carbon to form a second electrolytic solution, and adding a leveling agent (C component) to the filtered second electrolytic solution to form the electrolytic solution.

[0087] Specifically, the first electrolytic solution transferred from the storage tank may contain copper ions, sulfuric acid, chlorine, organic additives, and the like.

[0088] The step of filtering (C / F) the first electrolytic solution using carbon means removing organic impurities and inorganic impurities present in the first electrolytic solution.

[0089] According to one embodiment of the present invention, the second electrolytic solution means the electrolytic solution obtained by filtering the first electrolytic solution using carbon.

[0090] According to one embodiment of the present invention, adding a leveling agent (C component) to the second electrolytic solution can form the electrolytic solution. Since the additives contained in the electrolytic solution have been described above, the description is omitted. Specifically, the leveling agent (C component) is added after the filtering (C / F) step.

[0091] For example, if the leveling agent (C component) is added before the filtering (C / F) step, the leveling agent (C component) may deteriorate and the physical properties of the copper foil may be reduced. On the other hand, if the leveling agent (C component) is added after the filtering (C / F) step, deterioration of the leveling agent (C component) can be prevented, which is effective for improving the physical properties according to the present invention.

[0092] The electrolytic solution formed by adding the leveling agent (C component) is contained in the electrolytic cell 10, and a copper foil is manufactured using a foil manufacturing machine including a rotating negative electrode drum 40 disposed in the electrolytic cell 10 and a positive electrode plate 30 disposed apart from the rotating negative electrode drum 40.

[0093] 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.

[0094] According to an embodiment of the present invention, the step of manufacturing the electrolytic solution 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 introducing the washed copper wire into sulfuric acid for the electrolytic solution.

[0095] 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 going through the process of washing the pickled copper wire with distilled water, copper for manufacturing the electrolytic solution 20 can be manufactured. The washed copper wire is administered to sulfuric acid for the electrolytic solution, and the electrolytic solution 20 can be manufactured.

[0096] 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.

[0097] The copper film 111 manufactured in this way can be washed in a washing tank.

[0098] 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 washing process may be omitted.

[0099] Next, a protective layer 112 is formed on the copper film 111.

[0100] 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.

[0101] As described above, the anticorrosion solution 60 may include at least one of a chromium compound, a silane compound, and a nitrogen compound. For example, the copper film 111 can be immersed in a potassium dichromate solution of 1 to 10 g / L at room temperature for 1 to 30 seconds.

[0102] In addition, the protective layer 112 can also contain a silane compound by silane treatment and can also contain a nitrogen compound by nitrogen treatment.

[0103] The copper foil 110 is manufactured by forming such a protective layer 112.

[0104] One or more negative electrode active materials selected from the group consisting of carbon; a metal (Me) such as Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe; an alloy containing the metal (Me); an oxide (MeOx) of the metal (Me); and a composite of the metal (Me) and carbon are coated on one or both sides of the copper foil 110 of the present invention manufactured through the above method, whereby the electrode for a secondary battery (i.e., the negative electrode) of the present invention can be manufactured.

[0105] For example, after mixing 1 to 3 parts by weight of styrene-butadiene rubber (SBR) and 1 to 3 parts by weight of carboxymethyl cellulose (CMC) with 100 parts by weight of carbon for the negative electrode active material carbon, a slurry is prepared using distilled water as a solvent. Next, the slurry is 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.

[0106] A secondary battery can be manufactured using a normal positive electrode, an electrolyte, and a separator together with the electrode (negative electrode) for the secondary battery of the present invention manufactured by the above method.

[0107] 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.

[0108] 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 apart from the rotating negative electrode drum 40. The electrolytic solution 20 was a copper sulfate solution. The copper ion concentration in the electrolytic solution 20 was set to 87 g / L, the sulfuric acid concentration was 110 g / L, the temperature of the electrolytic solution was 55°C, and the current density was 60 ASD.

[0109] In addition, the concentration of chlorine (Cl) contained in the electrolytic solution 20 was maintained at 20 ppm, and the concentration of the organic additive was as shown in Table 1 below. At this time, the leveling agent was added to the filtered electrolytic solution after filtering the electrolytic solution using carbon.

[0110] 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).

[0111] A current was applied between the rotating negative electrode drum 40 and the positive electrode plate 30 at a current density of 60 ASD to manufacture a copper film 111. Next, the copper film 111 was immersed in a rust preventive solution for about 2 seconds to perform chromate treatment on both surfaces of the copper film 111, and a copper foil was manufactured by forming a 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.

[0112] As a result, copper foils of Examples 1 to 4 and Comparative Examples 1 to 4 were manufactured. At this time, the thickness of the manufactured copper foil was 8 μm.

[0113]

Table 1

[0114]

Table 2

[0115] For the copper foils of Examples 1 to 4 and Comparative Examples 1 to 4 manufactured as described above, (i) the contents of non - copper components (carbon, nitrogen, oxygen, sulfur) and (ii) the presence or absence of curl generation were confirmed.

[0116] The copper foil was cut to obtain a 2 cm x 2 cm sample. The content of the non - copper component was measured after removing the protective layer on the copper film. At this time, in order to remove the protective layer on the copper film, it was immersed in a 10% sulfuric acid solution for 30 seconds, and for the removal of the acidic solution, water cleaning using distilled water was carried out for 30 seconds, followed by drying at room temperature for 24 hours.

[0117] (i) The contents of non - copper components (carbon, nitrogen, oxygen, sulfur) For the content of the non - copper component of the copper film, XPS [Product name: PHI 5000 VersaProbe (ULVAC PHI)] was used with respect to the matte surface of the copper film. Specifically, the content of the non - copper component means the content from the matte surface of the copper film to a sputter depth of 100 nm.

[0118] At this time, the specific conditions are as follows.

[0119] - X - ray beam size: 400μm - Neutralizer: off - Sputter source: Ar+ - Ion energy: 2Kv - Sputter area: 1mm x 1mm - Sputter rate: 0.5nm / sec (SiO2 standard) (ii) Presence or absence of Curl generation After 100 charge and discharge cycles, the secondary battery was disassembled, and it was observed whether wrinkles or tears occurred in the copper foil. When wrinkles or tears occurred in the copper foil, it was indicated as "occurred", and when they did not occur, it was indicated as "none".

[0120] Referring to Tables 1 to 2, the copper foils according to Examples 1 to 4 did not generate Curl, while the copper foils according to Comparative Examples 1 to 4 generated Curl.

[0121] The present invention described above is not limited by the foregoing examples and the attached drawings, and it will be apparent to those having ordinary knowledge in the technical field to which the present invention pertains that various substitutions, modifications, and changes are possible within the scope not departing from the technical matters of the present invention. Therefore, the scope of the present invention is represented by the 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 symbols

[0122] 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 contains copper and non-copper elements, The non-copper elements include carbon (C), nitrogen (N), and oxygen (O), a copper foil.

2. The copper film is 0.05 to 0.2 at% carbon (C), 0.01 to 0.05 at% nitrogen (N), 0.1 to 0.5 at% oxygen (O) and Less than 0.01 at% sulfur (S), the copper foil according to claim 1.

3. The copper film does not contain sulfur (S), the copper foil according to claim 1.

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

5. The step of manufacturing an electrolytic solution containing copper ions; The step of forming a copper film; and The step of forming a protective layer on the copper film; including, The step of forming the copper film is 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, including the step of forming a copper film on the rotating negative electrode drum, The electrolytic solution is 70 to 150 g / L of copper ions; 80 to 150 g / L of sulfuric acid; 15 to 25 ppm of chlorine (Cl); and An organic additive; including, The organic additive includes a brightener (Component A), a retarder (Component B), and a leveling agent (Component C), The leveling agent (Component C) includes a PPG derivative, a method for manufacturing a copper foil.

6. The brightener (Component A) includes a sulfonic acid or a metal salt thereof, The retarder (Component B) includes a non-ionic water-soluble polymer, the method for manufacturing a copper foil according to claim 5.

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

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

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

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