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 including a matte surface and a shiny surface, wherein a hydrogen co-precipitation amount at a depth of 30 nm to 45 nm from the matte surface ranges from 80 to 250 counts, the hydrogen co-precipitation amount at a depth of 30 nm to 45 nm from the shiny surface ranges from 3 to 20 counts. The hydrogen co-precipitation amount refers to the number of hydrogen ions measured at a certain sputter depth from each of the matte surface and the shiny surface using time of flight-secondary ion mass spectrometry (TOF-SIMS).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 in 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, lithium secondary batteries can store relatively more energy compared to their size and weight compared to other secondary batteries. Therefore, lithium secondary batteries are preferably used in the field of information and communication devices where portability and mobility are important, and their application range 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, the lithium-ion secondary battery must have a high charge-discharge capacity in order to increase the operating time of the device. Therefore, research is continuously required to meet the increasing expected values (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. Among copper foils, electrolytic copper foil is widely used as the negative electrode current collector of secondary batteries. As the accommodation for secondary batteries increases and the demand for high-capacity, high-efficiency, and high-quality secondary batteries increases, there is a need for electrolytic copper foil that can improve the characteristics of secondary batteries. In particular, there is a need for electrolytic copper foil that can ensure high capacity, stable capacity retention, and performance of secondary batteries.

[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 be increased, and the more the capacity of the secondary battery can be increased. However, the thinner the copper foil, the more curl occurs, and when the copper foil is wound, defects such as tearing or wrinkling of the copper foil due to curl at the edge part occur, 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, it is necessary to prevent curl of the copper foil. 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 manufacturing method thereof.

[0009] One embodiment of the present invention provides a copper foil having a hydrogen eutectoid amount of 80 to 250 counts at a depth of 30 nm to 45 nm on the matte surface, a hydrogen eutectoid amount of 3 to 20 counts at a depth of 30 nm to 45 nm on the shiny surface, and wrinkles or tears prevented.

[0010] One embodiment of the present invention provides a copper foil having a hydrogen eutectoid amount of 15 to 60 counts at a depth of 60 nm to 75 nm on the matte surface, a hydrogen eutectoid amount of 1.0 to 10 counts at a depth of 60 nm to 75 nm on the shiny surface, and wrinkles or tears prevented.

[0011] Another embodiment of the present invention provides an electrode for a secondary battery including such a copper foil and a secondary battery including such an electrode for a secondary battery.

[0012] Yet another embodiment of the present invention provides a method for manufacturing a copper foil in which the occurrence of curl, wrinkle, or tear is prevented.

[0013] In addition to the aspects of the present invention mentioned above, other features and advantages of the present invention will be described below or will be clearly understood by those having ordinary knowledge in the technical field to which the present invention pertains from such description.

Means for Solving the Problems

[0014] One embodiment of the present invention provides a copper foil having a matte surface and a shiny surface; the amount of hydrogen eutectic at a depth of 30 nm to 45 nm on the matte surface is 80 to 250 counts, and the amount of hydrogen eutectic at a depth of 30 nm to 45 nm on the shiny surface is 3 to 20 counts. The amount of hydrogen eutectic means the number of hydrogen ions measured from the matte surface and the shiny surface at a certain sputter depth using TOF-SIMS (Time Of Flight-Secondary Ion Mass Spectrometry).

[0015] Another embodiment of the present invention includes the steps of manufacturing an electrolytic solution containing copper ions; forming a copper film; and forming a protective layer on the copper film. The step of forming the copper film includes the step of forming a copper film on the rotating negative electrode drum by energizing a positive electrode plate and a rotating negative electrode drum arranged to be separated from each other in the electrolytic solution in an electrolytic cell. The electrolytic solution contains 70 to 150 g / L of copper ions; 80 to 150 g / L of sulfuric acid; 15 to 25 ppm of chlorine (Cl); 1 to 15 ppm of collagen; 0.1 to 5 ppm of gelatin; and an organic additive. The organic additive includes at least one of a brightening agent (Component A) and a retarder (Component B). The brightening agent (Component A) includes a sulfonic acid or a metal salt thereof. The retarder (Component B) includes a nonionic water-soluble polymer, and provides a method for manufacturing a copper foil.

Advantages of the Invention

[0016] According to the present invention, the amount of hydrogen eutectic at a depth of 30 nm to 45 nm on the matte surface of the copper foil is 80 to 250 counts, and the amount of hydrogen eutectic at a depth of 30 nm to 45 nm on the shiny surface is 3 to 20 counts. Thus, the occurrence of wrinkles or tears is prevented during the manufacturing process of the copper foil. By using such a copper foil to manufacture intermediate parts and final products such as flexible printed circuit boards (FPCBs) and secondary batteries, the productivity of not only the intermediate parts but also the final products can be improved.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode 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 assist in 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 illustrated in the drawings. The same components throughout the specification may be referred to by the same reference numerals. In explaining the present invention, if it is determined that a specific description of related known technologies may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

[0020] When terms such as "including", "having", "consisting of", etc. mentioned in this specification are used, other parts may be added as long as the expression "only" is not used. When a component is expressed in the singular, it includes a plurality unless otherwise explicitly stated. Also, in the interpretation of components, it is interpreted to include an error range even without separate explicit description.

[0021] In the case of an explanation of a positional relationship, for example, when the positional relationship between both parts is explained by "on ~", "above ~", "below ~", "beside ~", etc., as long as the expressions "immediately" or "directly" are not used, one or more other parts can be located between both parts.

[0022] 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 as illustrated 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 illustrated in the drawings. For example, when an element illustrated in the drawings is turned over, an element described as "below" or "beneath" another element can be placed "above" the other element. Thus, the exemplary term "below" can include all directions of below and above. Similarly, the exemplary terms "above" or "upper" can include all directions of above and below.

[0023] In the case of descriptions regarding temporal relationships, for example, when temporal front-back relationships are described with expressions such as "after," "subsequent to," "next to," "before," etc., cases where it is not continuous can also be included as long as the expressions "immediately" or "directly" are not used.

[0024] The first, second, etc. are used to describe various components, but these components are not limited by these terms. These terms are merely used to distinguish one component from another. Thus, the first component referred to below may be the second component within the technical idea of the present invention.

[0025] 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 presented from the first item, the second item, and the third item.

[0026] Each feature of various embodiments of the present invention can be partially or wholly combined or combined with each other, enabling various technical linkages and drives. Each embodiment may be implemented independently of each other or may be implemented together in a related relationship.

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

[0028] 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. 2, the copper foil 110a of the present invention includes a copper film 111 and a protective layer 112 on the copper film 111. FIG. 2 shows a configuration in which the protective layer 112 is disposed on one side of the copper film 111. However, an embodiment of the present invention is not limited thereto, and the protective layer 112 may be disposed on both sides of the copper film 111 (see FIG. 3).

[0029] The copper film 111 may be formed on a rotating negative electrode drum through electroplating, and may have a shiny surface that directly contacts the rotating negative electrode drum and a matte surface on the opposite side during the electroplating process.

[0030] 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.

[0031] The copper foil 110 described later can correspond to the copper foils 110a, 110b, and 110c according to FIGS. 1 to 3.

[0032] According to an embodiment of the present invention, the copper foil 110 includes a copper film 111 having a matte surface 111a and a shiny surface 111b, the amount of hydrogen eutectic at a depth of 30 nm to 45 nm on the matte surface 111a is 80 to 250 counts, and the amount of hydrogen eutectic at a depth of 30 nm to 45 nm on the shiny surface 111b can be 3 to 20 counts.

[0033] At this time, the amount of hydrogen eutectic means the number of hydrogen ions measured from the matte surface and the shiny surface at a certain sputtering depth using TOF-SIMS (Time Of Flight-Secondary Ion Mass Spectrometry).

[0034] Specifically, when the amount of hydrogen eutectic at a depth of 30 nm to 45 nm on the matte surface 111a is 80 to 250 counts, and the amount of hydrogen eutectic at a depth of 30 nm to 45 nm on the shiny surface 111b is 3 to 20 counts, the surface characteristics of the matte surface 111a and the shiny surface 111b of the copper film 111 are stable, wrinkles or tears are prevented from occurring in the copper foil 110, and curl is prevented.

[0035] On the other hand, when the amount of hydrogen eutectic at a depth of 30 nm to 45 nm on the matte surface 111a is outside the range of 80 to 250 counts, or the amount of hydrogen eutectic at a depth of 30 nm to 45 nm on the shiny surface 111b is outside the range of 3 to 20 counts, the difference in surface characteristics between the matte surface 111a and the shiny surface 111b becomes large, a problem of severe warping occurs during the manufacturing process, wrinkles or tears may occur in the copper foil 110, and curl may occur.

[0036] Also, according to an embodiment of the present invention, the amount of hydrogen eutectic at a depth of 60 nm to 75 nm on the matte surface 111a is 15 to 60 counts, and the amount of hydrogen eutectic at a depth of 60 nm to 75 nm on the shiny surface 111b can be 1.0 to 10 counts.

[0037] Specifically, when the amount of hydrogen eutectoid at a depth of 60 nm to 75 nm on the matte surface 111a is 15 to 60 counts, and the amount of hydrogen eutectoid at a depth of 60 nm to 75 nm on the shiny surface 111b is 1.0 to 10 counts, the generation of wrinkles or tears in the copper foil 110 is prevented, and curl is prevented.

[0038] On the other hand, when the amount of hydrogen eutectoid at a depth of 60 nm to 75 nm on the matte surface 111a is outside the range of 15 to 60 counts, or the amount of hydrogen eutectoid at a depth of 60 nm to 75 nm on the shiny surface 111b is outside the range of 1.0 to 10 counts, the difference in surface characteristics between the matte surface 111a and the shiny surface 111b becomes large, a very warping problem occurs during the manufacturing process, wrinkles or tears may occur in the copper foil 110, and curl may occur.

[0039] According to an embodiment of the present invention, the depth of the hydrogen component on the matte surface 111a of the copper film 111 can be 35 nm or less.

[0040] At this time, the depth of the hydrogen component means the depth of a point where the number of hydrogen ions measured using TOF - SIMS on the matte surface 111a is 200 counts or more. Specifically, it means the distance between points where the number of hydrogen ions measured from the surface of the matte surface 111a is 200 counts or more.

[0041] When the depth of the hydrogen component on the matte surface 111a of the copper film 111 is 35 nm or more, hydrogen penetrates to a deep region based on the matte surface 111a of the copper film 111, and the difference in surface characteristics between the matte surface 111a and the shiny surface 111b can be induced, thereby causing a very warping problem during the manufacturing process, wrinkles or tears may occur in the copper foil 110, and curl may occur.

[0042] According to one embodiment of the present invention, the copper foil 110 has a thickness of 4 to 35 μm. When the copper foil 110 is used as a current collector of an electrode in a secondary battery, the thinner the thickness of the copper foil 110, the more current collectors can be accommodated in the same space, which is advantageous for increasing the capacity of the secondary battery. However, the production of the copper foil 110 having a thickness of less than 4 μm causes a decrease in workability.

[0043] On the other hand, when manufacturing a secondary battery using 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.

[0044] 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.

[0045] FIG. 4 is a cross-sectional view of the secondary battery electrode 100a according to one embodiment of the present invention. FIG. 5 is a cross-sectional view of the secondary battery electrode 100b according to another embodiment of the present invention.

[0046] As shown in FIG. 4, the secondary battery electrode 100a according to one embodiment of the present invention includes any one of the copper foils 110 and the active material layer 120 of the above-described embodiments of the present invention.

[0047] FIG. 4 shows a configuration in which the active material layer 120 is formed on one surface of the copper foil 110. However, one embodiment of the present invention is not limited thereto. Referring to FIG. 5, the active material layer 120 can also be formed on both surfaces of the copper foil 110.

[0048] 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 a copper foil 110 is generally used as a negative electrode current collector that binds to a negative electrode active material.

[0049] According to one embodiment of the present invention, the secondary battery electrode 100 is a negative electrode, the copper foil 110 is used as a negative electrode current collector, and the active material layer 120 includes a negative electrode active material.

[0050] In order to guarantee the high capacity of the secondary battery, the active material layer 120 of the present invention can be formed of a composite of carbon and metal. The metal may include, for example, at least one of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni, and Fe, preferably Si and / or Sn.

[0051] FIG. 6 is a schematic cross-sectional view of a secondary battery according to an embodiment of the present invention.

[0052] Referring to FIG. 6, the secondary battery includes a cathode 370, an anode 340, an electrolyte 350 disposed between the cathode 370 and the anode 340 to provide an environment in which ions can move, and a separator 360 that electrically insulates the cathode 370 and the anode 340. Here, the ions moving between the cathode 370 and the anode 340 are, for example, lithium ions. The separator 360 separates the cathode 370 and the anode 340 to prevent the charge generated at one electrode from being wasted by moving to the other electrode through the inside of the secondary battery 105. Referring to FIG. 6, the separator 360 is disposed in the electrolyte 350.

[0053] 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.

[0054] 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.

[0055] According to an embodiment of the present invention, the copper foil 110 shown in FIGS. 1 to 3 can be used as the anode current collector 341. Further, the electrodes 100a and 100b for secondary batteries shown in FIGS. 4 or 5 can be used for the anode 340 of the secondary battery shown in FIG. 6.

[0056] Hereinafter, the manufacturing method of the copper foil 110 of the present invention will be specifically described with reference to FIGS. 7 and 8.

[0057] 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.

[0058] The method of the present invention includes a step of forming a copper film 111 on the rotating negative electrode drum 40 by energizing a positive electrode plate 30 and a rotating negative electrode drum 40 which are arranged so as to be separated from each other in the electrolytic solution 20 in the electrolytic cell 10.

[0059] As shown in FIG. 7, the positive electrode plate 30 may include first and second positive electrode plates 31 and 32 which are electrically insulated from each other.

[0060] The step of forming the copper film 111 may 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.

[0061] The current density provided by the first and second positive electrode plates 31 and 32 respectively may be 30 to 130 ASD.

[0062] When the current density provided by the first and second positive electrode plates 31 and 32 respectively is less than 30 ASD, since the surface roughness of the copper foil 110 is low, the adhesion between the copper foil 110 and the active material layer 120 may not be sufficient.

[0063] On the other hand, when the current density provided by the first and second positive electrode plates 31 and 32 respectively exceeds 130 ASD, the surface of the copper foil 110 becomes rough, and the coating of the active material may not be smooth.

[0064] The surface characteristics of the copper film 111 can be changed by the surface buff finish or the polishing degree of the rotating negative electrode drum 40. For example, the surface of the rotating negative electrode drum 40 can be polished with a polishing brush having a particle size (Grit) of #800 to #3000.

[0065] During the formation process of the copper film 111, the electrolytic solution 20 is maintained at a temperature of 40 to 60 °C. More specifically, the temperature of the electrolytic solution 20 can be maintained at 50 °C or higher. At this time, by adjusting the composition of the electrolytic solution 20, the physical, chemical, and electrical properties of the copper film 111 can be controlled.

[0066] According to an embodiment of the present invention, the electrolytic solution 20 may contain copper ions, sulfuric acid, chlorine (Cl), collagen, gelatin, and an organic additive.

[0067] In order to facilitate the formation of the copper film 111 by electroplating of copper, the concentration of copper ions and the concentration of sulfuric acid in the electrolytic solution 20 are adjusted to 70 to 150 g / L and 80 to 150 g / L, respectively.

[0068] In one embodiment of the present invention, chlorine (Cl) includes all chloride ions (Cl - ) and chlorine atoms present in the molecule. Chlorine (Cl) can be used, for example, to remove silver (Ag) ions that have flowed into the electrolytic solution 20 during the formation 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.

[0069] When the concentration of chlorine (Cl) is less than 15 ppm, the removal of silver (Ag) ions is not smoothly carried out. On the other hand, when the concentration of chlorine (Cl) exceeds 25 ppm, unnecessary reactions due to excessive chlorine (Cl) may occur. Therefore, the concentration of chlorine (Cl) in the electrolytic solution 20 is controlled in the range of 15 to 25 ppm.

[0070] According to an embodiment of the present invention, the electrolytic solution 20 may contain collagen and gelatin. Specifically, the electrolytic solution 20 may contain 1 to 15 ppm of collagen and 0.1 to 5 ppm of gelatin.

[0071] According to an embodiment of the present invention, the collagen and gelatin are added to adjust the amount of hydrogen eutectoid on the matte surface and the shiny surface of the copper film according to the present invention. In order to obtain the physical properties of the amount of hydrogen eutectoid according to the present invention, the electrolytic solution 20 needs to contain 1 to 15 ppm of collagen and 0.1 to 5 ppm of gelatin.

[0072] More preferably, the collagen and gelatin contained in the electrolytic solution 20 need to be added at a concentration ratio of 10:1 to 3:1. At this time, the collagen can have a molecular weight of 2,000 to 10,000, and the gelatin can have a molecular weight of 10,000 to 100,000.

[0073] When the concentration ratio of the collagen and gelatin contained in the electrolytic solution 20 is outside the above range, there may be a problem that the gelatin with a large molecular weight becomes excessively large and the strength is too high, or there may be a problem that the collagen with a small molecular weight becomes excessively large compared to the gelatin and the strength is too low.

[0074] According to an embodiment of the present invention, the electrolytic solution 20 may contain an organic additive.

[0075] The organic additive contained in the electrolytic solution 20 contains at least one of a brightener (component A) and a retarder (component B).

[0076] The organic additive may contain one or more of a brightener (component A) and a retarder (component B), or may contain both components.

[0077] The brightener (component A) contains sulfonic acid or its metal salt. The brightener (component A) can have a concentration of 1 to 15 ppm in the electrolytic solution 20.

[0078] The brightener (Component A) can increase the charge amount of the electrolytic solution 20 to increase the copper electrodeposition rate, improve the curl characteristics of the copper foil, and enhance the gloss of the copper foil 110. If the concentration of the brightener (Component A) is less than 1 ppm, the gloss of the copper foil 110 will decrease. If it exceeds 15 ppm, problems may occur such as a change in the weight of the copper foil 110 after immersion or a change in the surface roughness.

[0079] The brightener may contain, for example, at least one of bis-(3-sulfopropyl)-disulfide disodium salt, 3-mercapto-1-propanesulfonic acid, 3-(N,N-dimethylthiocarbamoyl)-thiopropanesulfonate sodium salt, 3-[(amino-iminomethyl)thio]-1-propanesulfonate sodium salt, o-ethyldithiocarbonate-S-(3-sulfopropyl)-ester sodium salt, 3-(benzothiazolyl-2-mercapto)-propyl-sulfonic acid sodium salt, and ethylenedithiodipropylsulfonic acid sodium salt.

[0080] The retarder (Component B) contains a nonionic water-soluble polymer. The retarder (Component B) can have a concentration of 0.1 to 15 ppm in the electrolytic solution 20.

[0081] The retarder (Component B) reduces the copper electrodeposition rate to prevent a sharp increase in the roughness and a decrease in the strength of the copper foil 110. Such a retarder (Component B) is also called an inhibitor or a suppressor.

[0082] If the concentration of the retarder (Component B) is less than 0.1 ppm, problems may occur such as a sharp increase in the roughness of the copper foil 110 and a change in the surface state of the copper foil 110. On the other hand, even if the concentration of the retarder (Component B) exceeds 15 ppm, there are almost no physical property changes such as the appearance, gloss, roughness, strength, and elongation rate of the copper foil 110. Therefore, without the need to unnecessarily increase the concentration of the retarder (Component B) to increase the manufacturing cost and waste raw materials, the concentration of the retarder (Component B) can be adjusted within the range of 0.1 to 15 ppm.

[0083] The retarder (Component B) may contain, for example, at least one nonionic water-soluble polymer selected from polyethylene glycol (PEG), polypropylene glycol, polyethylene polypropylene copolymer, polyglycerin, polyethylene glycol dimethyl ether, hydroxyethyl cellulose, polyvinyl alcohol, polyglycol ether stearate, and polyglycol ether stearyl alcohol. However, the types of retarders are not limited to this, and other nonionic water-soluble polymers that can be used in the production of the high-strength copper foil 110 can be used as retarders.

[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] FIG. 8 is a schematic diagram showing the circulation process of the electrolytic solution according to the present invention.

[0086] According to an embodiment of the present invention, the step of manufacturing the electrolytic solution may include a step of filtering (C / F) the first electrolytic solution transferred from the storage tank using carbon to form a second electrolytic solution, and a step of adding collagen and gelatin 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 an 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 an embodiment of the present invention, collagen and gelatin can be added to the second electrolytic solution to form an electrolytic solution. Additives contained in the electrolytic solution have been described above, so the description is omitted. Specifically, collagen and gelatin are added after the filtration (C / F) step. When collagen and gelatin are added after the filtration (C / F) step, deterioration of collagen and gelatin is prevented, which is effective in improving the physical properties according to the present invention.

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

[0092] Also, for the cleanliness of the electrolytic solution 20, the copper wire used as a raw material for the electrolytic solution 20 can be washed.

[0093] 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 putting the washed copper wire into sulfuric acid for the electrolytic solution.

[0094] More specifically, in order to maintain the cleanliness of the electrolytic solution 20, a 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. Through the process of sequentially 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 to manufacture the electrolytic solution 20.

[0095] 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.

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

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

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

[0099] Referring to FIG. 7, it may further include the step of immersing the copper film 111 in an anticorrosion solution 60. When the copper film 111 is immersed in the anticorrosion solution 60, it can be guided by a guide roll disposed in the anticorrosion solution 60.

[0100] As described above, the anticorrosion solution 60 may 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.

[0101] Note that the protective layer 112 can also contain a silane compound by silane treatment and can also contain a nitrogen compound by nitrogen treatment.

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

[0103] On one or both sides of the copper foil 110 of the present invention manufactured through the method as described above, one or more negative electrode active materials selected from the group consisting of carbon; a metal (Me) 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, whereby an electrode (i.e., a negative electrode) for a secondary battery of the present invention can be manufactured.

[0104] For example, 1 to 3 parts by weight of styrene-butadiene rubber (SBR) and 1 to 3 parts by weight of carboxymethyl cellulose (CMC) are mixed with 100 parts by weight of carbon as a negative electrode active material carbon, and then a slurry is prepared using distilled water as a solvent. Next, the slurry is applied onto the copper foil 110 with a thickness of 20 to 60 μm using a doctor blade, and pressed at a pressure of 0.5 to 1.5 ton / cm 2 at 110 to 130 °C.

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

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

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

[0108] In addition, the concentration of chlorine (Cl) contained in the electrolytic solution 20 is maintained at 20 ppm, and the concentrations of collagen, gelatin, and the organic additive are as shown in Table 1 below. At this time, collagen and gelatin were added to the filtered electrolytic solution after filtering the electrolytic solution using carbon.

[0109] Among the organic additives, bis-(3-sulfopropyl)-disulfide disodium salt (SPS) is used as the brightening agent (Component A), polyethylene glycol (PEG) is used as the retarder (Component B), and the molecular weights of collagen and gelatin are 3,500 and 10,000, respectively.

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

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

[0112]

Table 1

Table 2

Table 3

Table 4

Table 5

Table 6

[0113] The copper foil was cut to obtain a 2 cm x 2 cm sample. The amount of hydrogen eutectic and the depth of the hydrogen component were measured on the matte surface and the shiny surface of the copper film, respectively, 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 after proceeding with water cleaning using distilled water for 30 seconds for the removal of the acidic solution, drying was carried out.

[0114] (i) Measurement of the amount of hydrogen eutectic by the depth of the matte surface and the shiny surface The amount of hydrogen eutectic by the depth of the matte surface and the shiny surface means the number of hydrogen ions measured from the matte surface and the shiny surface at a certain sputter depth using TOF-SIMS (Time Of Flight-Secondary Ion Mass Spectrometry) for each of the matte surface and the shiny surface of the copper film.

[0115] At this time, the amount of hydrogen eutectic can be measured for each depth to obtain a graph.

[0116] The specific sputter conditions and analysis conditions are as follows.

[0117] Sputter conditions - SpI (sputter ion): Cs - Energy: 3 keV - Current: 26.0 nA - Area: 300 x 300 μm 2 - SpIDD: 5.41E+16 Ion / cm 2 Analysis conditions - PI (primary ion): Bi3 - Energy: 25 keV -Current: 0.300 PA -Area: 100 x 100 μm 2 -PIDD: 3.83E+12 Ion / cm 2 (ii) Depth of hydrogen component on the matte surface The depth of the hydrogen component on the matte surface means the depth at a point where the number of hydrogen ions measured using TOF - SIMS on the matte surface is 200 counts or more.

[0118] Specifically, in the graph of the hydrogen eutectoid amount measured in (i), the depth up to the point where the number of hydrogen ions (counts) is 200 counts or more was calculated.

[0119] In the case of "not measurable" indicated in Table 6, it means that the measurement was impossible because the point where the number of hydrogen ions is 200 counts or more is too deep from the matte surface.

[0120] (iii) Presence or absence of curl generation After 100 charge - discharge cycles, the secondary battery was disassembled, and it was observed whether wrinkles or tears occurred on the copper foil. The case where wrinkles or tears occurred on the copper foil was indicated as "occurred", and the case where they did not occur was indicated as "none".

[0121] Referring to Tables 1 - 2, for the copper foils according to Examples 1 - 4, curl did not occur, and for the copper foils according to Comparative Examples 1 - 4, curl occurred.

[0122] The present invention described above is not limited by the foregoing examples and the accompanying 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

[0123] 100 Electrode for secondary battery 110, 110a, 110b, 110c Copper foil 111 Copper film 111a Matt surface 111b Shiny 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; including, On the matte surface, the amount of hydrogen eutectic at a depth of 30 nm to 45 nm is 80 to 250 counts, On the shiny surface, the amount of hydrogen eutectic at a depth of 30 nm to 45 nm is 3 to 20 counts, a copper foil: The amount of hydrogen eutectic means the number of hydrogen ions measured from the matte surface and the shiny surface at a certain sputtering depth using TOF-SIMS (Time Of Flight-Secondary Ion Mass Spectrometry).

2. On the matte surface, the amount of hydrogen eutectic at a depth of 60 nm to 75 nm is 15 to 60 counts, On the shiny surface, the amount of hydrogen eutectic at a depth of 60 nm to 75 nm is 1.0 to 10 counts, the copper foil according to Claim 1.

3. The depth of the hydrogen component on the matte surface is 35 nm or less, the copper foil according to Claim 1: The depth of the hydrogen component on the matte surface means the depth of the point where the number of hydrogen ions measured using TOF-SIMS on the matte surface is 200 counts or more.

4. The copper foil according to Claim 1, further including a protective layer disposed on the copper film.

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

6. 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 disposed separately from each other in the electrolytic solution in an electrolytic cell, the step of forming a copper film on the rotating negative electrode drum is included, 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); 1 to 15 ppm of collagen; 0.1 to 5 ppm of gelatin; and An organic additive; including, The organic additive includes at least one of a brightener (Component A) and a retarder (Component B), The brightener (Component A) includes a sulfonic acid or a metal salt thereof, The retarder (Component B) includes a nonionic water-soluble polymer, a method for manufacturing a copper foil.

7. The collagen and the gelatin are added at a ratio of 10:1 to 3:1 based on the concentration, the method for manufacturing a copper foil according to Claim 6.

8. The step of manufacturing the electrolytic solution is Filtering the first electrolyte transferred from the storage tank using carbon to form a second electrolyte; and Adding the collagen and the gelatin to the second electrolyte to form the electrolyte; The method for manufacturing a copper foil according to claim 6, comprising:

9. The collagen has a molecular weight of 2,000 to 10,000, The gelatin has a molecular weight of 10,000 to 100,000, and the method for manufacturing a copper foil according to claim 6.

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