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

Abstract

One embodiment of this disclosure provides a copper foil comprising a copper film having a matte surface and a glossy surface; and a protective layer disposed on the copper film; wherein, when a boundary with an orientation difference of 5° or greater between adjacent pixels is considered a grain boundary, the area ratio of grains (including twins) with a room temperature GOS value of 0° to less than 2° is 45% to 95% of the total cross-sectional area. The room temperature GOS value is measured on the cross-section of the copper foil at room temperature using an electron backscatter diffraction (EBSD) pattern analyzer.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2024-0201189, filed on December 30, 2024, and Korean Patent Application No. 10-2025-0049424, filed on April 16, 2025, the contents of which are hereby incorporated by reference in their entirety. Technical Field

[0003] This invention relates to a copper foil, an electrode comprising the same, a secondary battery comprising the same, and a method for manufacturing the same. More specifically, this disclosure relates to a copper foil that will not curl, wrinkle, or tear, an electrode comprising the same, a secondary battery comprising the same, and a method for manufacturing the same. Background Technology

[0004] A rechargeable battery is an energy conversion device that converts electrical energy into chemical energy, stores the chemical energy, and then converts the chemical energy back into electrical energy to generate electricity when needed. Rechargeable batteries are used as power sources for portable household appliances (such as mobile phones and laptops) and electric vehicles. Because rechargeable batteries can be repeatedly charged, they are also known as "rechargeable batteries."

[0005] Compared to primary batteries, secondary batteries, which offer economic and environmental advantages, include lead-acid batteries, nickel-cadmium secondary batteries, nickel-metal hydride secondary batteries, and lithium secondary batteries.

[0006] In particular, compared to other rechargeable batteries, lithium-ion batteries can store relatively more energy relative to their size and weight. Therefore, lithium-ion batteries are highly favored in the field of information and communication equipment where portability and mobility are crucial, and their applications are continuously expanding to energy storage devices for hybrid and electric vehicles.

[0007] These secondary batteries contain an anode current collector made of copper foil, and electrolytic copper foil has been widely used as the anode current collector in secondary batteries. With the increasing popularity of secondary batteries and the growing demand for high-capacity, high-efficiency, and high-quality batteries, there is a need for electrolytic copper foil capable of improving the performance of secondary batteries. Specifically, there is a need for electrolytic copper foil that can ensure high capacity, stable capacity retention, and performance of secondary batteries.

[0008] Simultaneously, as the thickness of the copper foil decreases, the amount of active material that can be accommodated in the same space increases, and the number of current collectors can also be increased, thereby improving the capacity of the secondary battery. However, as the copper foil becomes thinner, curling occurs. At this point, during the winding of the copper foil, defects such as tears or wrinkles will appear in the copper foil due to edge curling, making it difficult to manufacture very thin copper foil. Therefore, in order to manufacture very thin copper foil, it is necessary to prevent the copper foil from curling. Summary of the Invention

[0009] Therefore, this disclosure relates to a copper foil, an electrode therein, a secondary battery therein, and a method for manufacturing the same, which can prevent problems caused by the limitations and disadvantages of the aforementioned related technologies.

[0010] According to one embodiment of the present disclosure, a copper foil is provided that does not curl, wrinkle, or tear during manufacturing, wherein when the boundary with an orientation difference of 5° or more between adjacent pixels is considered a crystal grain boundary, the area of ​​grains (including twins) with a room temperature GOS value of 0° to less than 2° is 45% to 95% of the total cross-sectional area.

[0011] According to another embodiment of this disclosure, an electrode for a secondary battery comprising copper foil is provided, and a secondary battery comprising the electrode for the secondary battery is provided.

[0012] According to another embodiment of this disclosure, a method for manufacturing copper foil is provided, wherein the copper foil does not curl, wrinkle or tear during the manufacturing process.

[0013] In addition to the aspects of this disclosure described above, other features and advantages of this disclosure will be described below, or may be clearly understood by those skilled in the art to which this disclosure pertains.

[0014] One embodiment of the present invention provides a copper foil comprising a copper film having a matte surface and a glossy surface; and a protective layer disposed on the copper film, wherein, when a boundary with an orientation difference of 5° or more between adjacent pixels is considered a grain boundary, the area ratio of grains (including twins) with a room temperature GOS value of 0° to less than 2° is 45% to 95% of the total cross-sectional area. The room temperature GOS value is measured on the cross-section of the copper foil at room temperature using an electron backscatter diffraction (EBSD) pattern analyzer. Attached Figure Description

[0015] The accompanying drawings are included to provide a further understanding of this disclosure and form part of this application. The drawings illustrate embodiments of the disclosure and, together with the specification, serve to explain the principles of the disclosure. In the drawings: Figure 1 This is a cross-sectional view of a copper foil according to one embodiment of the present disclosure; Figure 2 This is a cross-sectional view of a copper foil according to another embodiment of this disclosure; Figure 3 This is a cross-sectional view of an electrode for a secondary battery according to another embodiment of this disclosure; Figure 4This is a cross-sectional view of an electrode for a secondary battery according to another embodiment of this disclosure; Figure 5 This is a schematic cross-sectional view of a secondary battery according to another embodiment of this disclosure; Figure 6 An apparatus for manufacturing copper foil according to another embodiment of the present disclosure is shown; and Figure 7 This is an EBSD GOS analysis image of a copper foil according to one embodiment of the present disclosure. Detailed Implementation

[0016] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. However, it should be understood that the embodiments described below are for illustrative purposes only to provide a clear understanding of this disclosure and are not intended to limit the scope of this disclosure.

[0017] The shapes, dimensions, scales, angles, numbers, etc., disclosed in the accompanying drawings for illustrating embodiments of this disclosure are illustrative, and therefore this disclosure is not limited to the details shown in the drawings. Throughout this specification, the same components may be indicated using the same reference numerals. In describing this disclosure, detailed descriptions of related known technologies will be omitted if it is determined that such detailed descriptions would unnecessarily obscure the essential points of this disclosure.

[0018] In this specification, when terms such as "comprising," "having," or "consisting of" are used, other components may be added unless the term "only" is used herein. When a component is expressed in the singular, the plural form shall be included unless otherwise specified. In interpreting a component, even if not explicitly stated, it shall be construed as including a range of tolerances.

[0019] When describing positional relationships, such as when the positional relationship between two parts is described as "on top of", "above", "below", "next to", etc., unless expressions such as "adjacent" or "direct" are used, one or more other parts may be located between these two parts.

[0020] This document uses spatially relative terms such as “below,” “under,” “lower,” “above,” and “upper” to describe the relationship between one element or component shown in the accompanying drawings and other elements or components. It should be understood that these spatially relative terms are intended to cover different orientations of the element during use or operation, other than those shown in the accompanying drawings. For example, when the element shown in the accompanying drawings is flipped, an element described as “above” or “upper” relative to another element will become “below” or “lower” relative to that other element. Therefore, the exemplary term “below” can encompass both above and below orientations. Similarly, the exemplary terms “above” or “upper” can also encompass both above and below orientations.

[0021] When describing temporal relationships, such as "after", "following", "next", "before", etc., discontinuous situations may be included unless expressions such as "immediately" or "directly" are used.

[0022] In describing the various components, terms such as "first" and "second" are used, but these components are not limited by these terms. These terms are only used to distinguish one component from another. Therefore, the first component described below can also be the second component within the technical spirit of this disclosure.

[0023] 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 the first, second, and third items" can mean not only any one of the first, second, or third items, but also all possible combinations of two or more of the first, second, and third items.

[0024] The corresponding features of the various embodiments of this disclosure may be combined or integrated with each other in whole or in part, and may be technically linked and driven in various ways. The various embodiments of this disclosure may be implemented independently of each other, or may be implemented together in a related relationship.

[0025] Figure 1 This is a cross-sectional view of copper foil 110a according to one embodiment of the present disclosure.

[0026] Reference Figure 1 The copper foil 110a of this disclosure includes a copper film 111 containing 99.9% by weight or more copper. (See also...) Figure 1 The copper foil 110a disclosed herein includes a copper film 111 and a protective layer 112 disposed on the copper film 111. Figure 1 This shows that a protective layer 112 is disposed on one surface of the copper film 111. One embodiment of this disclosure is not limited thereto; the protective layer 112 may be disposed on both surfaces of the copper film 111 (see [link]). Figure 2 ).

[0027] The copper film 111 can be formed on a rotating cathode roller by electroplating, and has a bright surface that is in direct contact with the rotating cathode roller during the electroplating process and a matte surface opposite to the bright surface.

[0028] The protective layer 112 can be formed by electrodepositing an anti-corrosion material onto the copper film 111. The anti-corrosion material may include 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 life of the copper foil 110 itself and the life of the final product containing the copper foil.

[0029] The copper foil 110 described below can correspond to Figure 1 and Figure 2 Copper foils 110a and 110b are included.

[0030] According to one embodiment of this disclosure, when a boundary with an orientation difference of 5° or more between adjacent pixels is considered a grain boundary, the copper foil 110 may include grains (including twins) with a room temperature GOS value of 0° to less than 2°, wherein the area of ​​the grains (including twins) is 45% to 95% of the total cross-sectional area. Specifically, when the area of ​​the grains (including twins) with a room temperature GOS value of 0° to less than 2° in the copper foil 110 is 45% to 95% of the total cross-sectional area, no wrinkles or tears will occur during the manufacturing process of the copper foil 110.

[0031] According to this disclosure, the room temperature GOS value refers to the GOS value measured on the copper foil 110 at room temperature (23 ± 2 °C). According to this disclosure, the grain orientation spread (GOS) value refers to the average value of the orientation differences between all pixels within a grain. For example, each grain may have one GOS value.

[0032] According to one embodiment of this disclosure, a twin refers to a crystal structure of a mirror target having twin boundaries (planes) as its boundaries. Specifically, a twin can refer to two or more symmetrically related crystals.

[0033] According to this disclosure, the room temperature GOS value is measured on the cross section of the copper foil 110 using an electron backscatter diffraction (EBSD) pattern analyzer at room temperature. Figure 7 This is an EBSD GOS analysis image of copper foil 100 according to one embodiment of this disclosure.

[0034] According to this disclosure, a pixel refers to the smallest data unit obtained by crystal analysis using EBSD. Specifically, the EBSD device is used to measure crystal orientation when scanning a cross-section of the copper foil 110 and records the crystal orientation as a pixel. Each pixel stores crystal orientation information at that location. Therefore, when measuring GOS, the orientation difference between pixels can be calculated to assess the uniformity of orientation within the grain.

[0035] According to this disclosure, the total cross-sectional area can refer to the area excluding regions where no diffraction pattern was observed in the entire cross-sectional region of the copper foil 110. Specifically, the total cross-sectional area can refer to the area of ​​the effective region where crystals exist in the entire cross-sectional region of the copper foil 110.

[0036] According to this disclosure, when the area ratio of grains (including twins) with a room temperature GOS value of 0° to less than 2° to the total cross-sectional area is less than 45%, this may mean that the copper foil grains do not have a uniform orientation. That is, due to the non-uniform grain structure in the copper foil, accidental deformation or twisting may occur, which can lead to wrinkles or tears in the copper foil.

[0037] Furthermore, when the area ratio of grains (including twins) with a room temperature GOS value of 0° to less than 2° to the total cross-sectional area is greater than 95%, this may indicate that the copper foil grains have an overly uniform orientation. When the copper foil grains have an overly uniform orientation, the copper foil may lack sufficient ductility. That is, when the copper foil undergoes a certain degree of mechanical deformation during manufacturing, its insufficient ductility makes it highly likely to tear before it can adequately absorb the mechanical deformation.

[0038] According to this disclosure, the area ratio of grains (including twins) with room temperature GOS values ​​of 0° to less than 2° to the total cross-sectional area may be referred to as the "first area ratio".

[0039] According to one embodiment of this disclosure, the area ratio of grains (including twins) with a room temperature GOS value of 4° or higher to the total cross-sectional area can be 3% to 12%.

[0040] According to this disclosure, when the area of ​​grains (including twins) with a room temperature GOS value of 4° or higher is 3% to 12% of the total cross-sectional area, no wrinkles or tears will occur in the copper foil 110 during the manufacturing process.

[0041] According to this disclosure, when the area ratio of grains (including twins) with a room temperature GOS value of 4° or higher to the total cross-sectional area is less than 3%, the area ratio of grains (including twins) with a room temperature GOS value of 4° or higher may be excessively increased due to the excessive reduction in the area ratio of grains (including twins) with a room temperature GOS value of 4° or higher. In other words, this may mean that the copper foil grains have an overly uniform orientation. When the copper foil grains have an overly uniform orientation, the copper foil may lack sufficient ductility. That is, when the copper foil undergoes a certain degree of mechanical deformation during manufacturing, its insufficient ductility makes it highly likely to tear before it can adequately absorb the mechanical deformation.

[0042] Furthermore, when the area ratio of grains (including twins) with a room temperature GOS value of 4° or higher to the total cross-sectional area is greater than 12%, the area ratio of grains with a room temperature GOS value of 4° or higher (including twins) may be excessively reduced due to the excessive increase in the area proportion of grains with a room temperature GOS value of 4° or higher (including twins). In other words, this means that the copper foil grains do not have a uniform orientation. This means that due to the non-uniform grain structure in the copper foil, accidental deformation or twisting may occur, leading to wrinkles or tears in the copper foil.

[0043] According to this disclosure, the area ratio of grains (including twins) with a room temperature GOS value of 4° or higher to the total cross-sectional area may be referred to as the "second area ratio".

[0044] According to one embodiment of this disclosure, the copper foil 110 has a thickness of 3 to 35 µm. When the copper foil 110 is used as a current collector in a secondary battery, the thinner the copper foil 110, the more current collector can be accommodated in the same space, which is beneficial for increasing the capacity of the secondary battery. However, manufacturing a copper foil 110 with a thickness of less than 3 µm will result in a decrease in processability.

[0045] On the other hand, when using copper foil 110 with a thickness greater than 35 µm to manufacture secondary batteries, it is difficult to achieve high capacity due to the thickness of copper foil 110.

[0046] The electrode 100 comprising the copper foil 110 of this disclosure and the secondary battery comprising the electrode 100 will be described in detail below.

[0047] Figure 3 This is a cross-sectional view of an electrode 100a for a secondary battery according to one embodiment of the present disclosure. Figure 4 This is a cross-sectional view of an electrode 100b for a secondary battery according to another embodiment of this disclosure.

[0048] like Figure 3 As shown, an electrode 100a for a secondary battery according to one embodiment of the present disclosure includes a copper foil 110 and an active material layer 120 as described above according to any embodiment of the present disclosure.

[0049] Figure 3 The illustration shows a configuration in which an active material layer 120 is formed on one surface of a copper foil 110, but one embodiment of this disclosure is not limited thereto. (See also...) Figure 4 The active material layer 120 can be formed on both surfaces of the copper foil 110.

[0050] In lithium secondary batteries, aluminum foil is typically used as the cathode current collector bonded to the cathode active material, and copper foil 110 is typically used as the anode current collector bonded to the anode active material.

[0051] According to one embodiment of this disclosure, the electrode 100 for the secondary battery is the anode, and copper foil 110 is used as the anode current collector. In this case, the active material layer 120 includes the anode active material.

[0052] To ensure high capacity of the secondary battery, the active material layer 120 of this disclosure may be formed of a composite material of carbon and metal. The metal may include at least one of, for example, Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni and Fe, preferably Si and / or Sn.

[0053] Figure 5 This is a schematic cross-sectional view of a secondary battery according to one embodiment of the present disclosure.

[0054] Reference Figure 5 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 configured to electrically insulate 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 unnecessarily being consumed by moving through the interior of the secondary battery 105 to the other electrode. (See reference...) Figure 5 The diaphragm 360 is disposed within the electrolyte 350.

[0055] The cathode 370 includes a cathode current collector 371 and a cathode active material layer 372. Here, aluminum foil can be used as the cathode current collector 371.

[0056] The anode 340 includes an anode current collector 341 and an anode active material layer 342. Here, copper foil 110 can be used as the anode current collector 341.

[0057] According to one embodiment of this disclosure, it can be used Figure 1 and Figure 2 The copper foil 110 shown serves as the anode current collector 341. Alternatively, it can be used... Figure 3 or Figure 4 The electrodes 100a or 100b shown for the secondary battery are as follows: Figure 5 The anode 340 of the secondary battery shown.

[0058] The following will refer to Figure 6 The method for manufacturing the copper foil 110 disclosed herein is described in detail.

[0059] The method of manufacturing the copper foil 110 of this disclosure includes: forming a copper film 111; and forming a protective layer 112 on the copper film 111.

[0060] The method disclosed herein includes forming a copper film 111 on a rotating cathode drum 40 by energizing an anode plate 30 and a rotating cathode drum 40 spaced apart from each other in an electrolyte 20 within an electrolytic cell 10.

[0061] like Figure 6 As shown, the anode plate 30 may include a first anode plate 31 and a second anode plate 32 that are electrically insulated from each other.

[0062] The copper film 111 can be formed by passing an electric current between the first anode plate 31 and the rotating cathode roller 40 to form a seed crystal layer, and then by passing an electric current between the second anode plate 32 and the rotating cathode roller 40 to grow the seed crystal layer.

[0063] The current density provided by each of the first anode plate 31 and the second anode plate 32 can be 40 to 130 ASD.

[0064] When the current density provided by each of the first anode plate 31 and the second anode plate 32 is less than 40 ASD, the adhesion strength between the copper foil 110 and the active material layer 120 may be insufficient due to the low surface roughness of the copper foil 110.

[0065] On the other hand, when the current density provided by each of the first anode plate 31 and the second anode plate 32 is greater than 130 ASD, the coating of the active material may not be able to be carried out smoothly due to the rough surface of the copper foil 110.

[0066] The surface properties of the copper film 111 can vary depending on the degree of surface grinding or polishing of the rotating cathode roller 40. For example, the surface of the rotating cathode roller 40 can be polished with a polishing brush with a grit size of #800 to #3000.

[0067] During the formation of the copper film 111, the temperature of the electrolyte 20 is maintained between 40 and 65°C. More specifically, the temperature of the electrolyte 20 can be maintained at 45°C or higher. At this time, the physical, chemical, and electrical properties of the copper film 111 can be controlled by adjusting the composition of the electrolyte 20.

[0068] According to one embodiment of this disclosure, electrolyte 20 may include copper ions, sulfuric acid, chlorine, and organic additives.

[0069] To facilitate the formation of a copper film 111 by copper electrodeposition, the concentrations of copper ions and sulfuric acid in the electrolyte 20 are adjusted to 70 to 150 g / L and 80 to 130 g / L, respectively.

[0070] According to one embodiment of this disclosure, chlorine (Cl) includes chloride ions (Cl-). -The chlorine atoms present in the molecule. For example, chlorine (Cl) can be used to remove silver (Ag) ions introduced into the electrolyte 20 during the formation of the copper film 111. Specifically, chlorine (Cl) can cause silver (Ag) ions to precipitate as silver chloride (AgCl). This silver chloride (AgCl) can be removed by filtration.

[0071] When the concentration of chlorine (Cl) is less than 15 ppm, the removal of silver (Ag) ions cannot proceed smoothly. On the other hand, when the concentration of chlorine (Cl) is greater than 25 ppm, unnecessary reactions caused by excess chlorine (Cl) may occur. Therefore, the concentration of chlorine (Cl) in electrolyte 20 is controlled within the range of 15 to 25 ppm.

[0072] According to one embodiment of this disclosure, electrolyte 20 may include organic additives.

[0073] The organic additives contained in electrolyte 20 include brightener (component A), slowing agent (component B), and roughness modifier (component C).

[0074] Brightener (component A) includes sulfonic acid or its metal salt. The concentration of brightener (component A) in electrolyte 20 can be from 1 to 15 ppm.

[0075] The brightener (component A) increases the charge in the electrolyte 20, thereby increasing the copper deposition rate, improving the coiling properties of the copper foil, and enhancing the gloss of the copper foil 110. When the concentration of the brightener (component A) is less than 1 ppm, the gloss of the copper foil 110 deteriorates. On the other hand, when the concentration of the brightener (component A) is greater than 15 ppm, the weight or surface roughness of the copper foil 110 after impregnation may change.

[0076] Brighteners may include, for example, at least one of the following: disodium bis-(3-sulfopropyl)-disulfide, 3-mercapto-1-propanesulfonic acid, sodium 3-(N,N-dimethylthiocarbamoyl)-thiopropanesulfonate, sodium 3-[(amino-iminomethyl)thio]-1-propanesulfonate, sodium O-ethyl dithiocarbonate-S-(3-sulfopropyl)-ester, sodium 3-(benzothiazolyl-2-mercapto)-propyl-sulfonate, and sodium ethylidene dithiodipropylsulfonate.

[0077] The decelerator (component B) comprises a nonionic water-soluble polymer. The concentration of the decelerator (component B) in electrolyte 20 can be from 0.1 to 15 ppm.

[0078] The moderator (component B) reduces the copper deposition rate to prevent a rapid increase in the roughness and a decrease in the strength of the copper foil 110. The moderator (component B) is also known as an inhibitor or suppressor.

[0079] When the concentration of the moderator (component B) is less than 0.1 ppm, the roughness of the copper foil 110 may increase rapidly, and changes in the surface condition of the copper foil 110 may occur. On the other hand, even when the concentration of the moderator (component B) is greater than 15 ppm, the physical properties of the copper foil 110 (such as appearance, gloss, roughness, strength, elongation, etc.) show almost no change. Therefore, the concentration of the moderator (component B) can be adjusted within the range of 0.1 to 15 ppm without unnecessarily increasing the concentration of the moderator (component B), as this would increase manufacturing costs and waste raw materials.

[0080] The decelerator (component B) may include at least one nonionic water-soluble polymer selected from, for example, polyethylene glycol (PEG), polypropylene glycol, polyethylene-polypropylene copolymer, polyglycerol, polyethylene glycol dimethyl ether, hydroxyethyl cellulose, polyvinyl alcohol, polyethylene glycol stearate, and polyethylene glycol stearate. However, the type of decelerator is not limited to this; other nonionic water-soluble polymers that can be used to manufacture high-strength copper foil 110 may also be used as decelerators.

[0081] Roughness modifiers (component C) include nitrogen-containing heterocyclic quaternary ammonium salts or their derivatives.

[0082] The roughness modifier (component C) improves the gloss and flatness of the copper foil 110. The concentration of the roughness modifier (component C) in the electrolyte 20 can be from 1 to 15 ppm.

[0083] When the concentration of the roughness modifier (component C) is less than 1 ppm, the gloss and flatness of the copper foil 110 cannot be improved. On the other hand, when the concentration of the roughness modifier (component C) is higher than 15 ppm, the surface gloss of the copper foil 110 may become uneven, and the surface roughness of the copper foil 110 may increase rapidly.

[0084] Roughness modifier (component C) may include any compound represented by the following chemical formulas 1 to 5.

[0085] [Chemical Formula 1]

[0086] [Chemical Formula 2]

[0087] [Chemical Formula 3]

[0088] [Chemical Formula 4]

[0089] [Chemical Formula 5]

[0090] In chemical formulas 1 to 5, 1 to 4. m1 to m4 and n1 to n5 each represent repeating units and are integers greater than or equal to 1. They can be the same as or different from each other.

[0091] According to one embodiment of this disclosure, each compound represented by chemical formulas 1 to 5 has a number-average molecular weight of 500 to 12,000.

[0092] When the number average molecular weight of the compounds represented by chemical formulas 1 to 5 used as roughness modifiers is less than 500, the monomer ratio may increase, resulting in an increase in the surface roughness of the copper foil 110. When the content of the roughness modifier is low, the surface roughness of the copper film 111 may increase, leading to a deterioration in gloss and flatness.

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

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

[0095] Compounds represented by chemical formula 1 include, for example, PAS-2451 (Mw: 30,000, Nittobo).

[0096] Compounds represented by chemical formula 2 include, for example, PAS-84 (Mw: 20,000, Nittobo).

[0097] Compounds represented by chemical formula 3 include, for example, PAS-2351 (Mw: 25,000, Nittobo).

[0098] Compounds represented by chemical formula 4 include, for example, PAS-A-1 (Mw: 5,000, Nittobo), PAS-A-5 (Mw: 4,000, Nittobo), etc.

[0099] Compounds represented by chemical formula 5 include, for example, PAS-J-81 (Mw: 180,000, Nittobo).

[0100] When the copper film 111 is formed, the flow rate of the electrolyte 20 supplied to the electrolytic cell 10 can be 41 to 45 m. 3 / Hour.

[0101] According to one embodiment of the present disclosure, before forming a copper film 111 on the rotating cathode roller 40 by immersing the rotating cathode roller 40 in the electrolyte 20 prepared as described above, a detergent may be used to rinse or wash the surface of the rotating cathode roller 40.

[0102] According to this disclosure, the detergent is an aqueous solution comprising 8% (w / w) to 12% (w / w) sulfuric acid and 0.1% (w / w) to 0.3% (w / w) brightener (component A). In this case, the brightener (component A) may comprise any of the types of brightener (component A) described above.

[0103] According to this disclosure, when the surface of the rotating cathode drum 40 is rinsed with detergent, the sulfuric acid in the detergent reacts with the oxides present on the surface of the rotating cathode drum 40 to effectively dissolve or remove the oxides.

[0104] Furthermore, titanium (Ti) may be present on the surface of the rotary cathode cylinder 40 after oxide removal. When the titanium (Ti) present on the surface of the rotary cathode cylinder 40 is exposed to air, an oxide film can form on the surface of the rotary cathode cylinder 40. Since this titanium oxide film has insulating properties, it may impede the flow of current, which may make it difficult to achieve a uniform current distribution during electroplating. Moreover, as the titanium oxide film thickens, the surface of the rotary cathode cylinder 40 becomes irregular, which may make it impossible to maintain the desired thickness and flatness during electroplating.

[0105] At this point, the brightener (component A) in the detergent can coat the surface of the rotating cathode roller 40 before the titanium (Ti) present on the surface of the rotating cathode roller 40 is exposed to air. Therefore, the formation of a titanium oxide film on the surface of the rotating cathode roller 40 can be prevented.

[0106] In other words, if the surface of the rotating cathode roller 40 is not rinsed or washed with detergent before immersing the rotating cathode roller 40 in the electrolyte 20 to form a copper film 111 on the rotating cathode roller 40, the surface of the manufactured copper foil may be irregular and there may be more defects in the copper foil. Therefore, the copper foil may have a first area ratio outside the range of 45% to 95%.

[0107] Therefore, in order to make the copper foil 110 have a first area ratio of 45 to 95%, the surface of the rotating cathode roller 40 must be rinsed or washed with detergent before immersing the rotating cathode roller 40 in the electrolyte 20 to form a copper film 111 on the rotating cathode roller 40.

[0108] According to this disclosure, in order to enable the copper foil 110 to have a first area ratio of 45% to 95%, the concentration of brightener (component A) in the detergent needs to be maintained in the range of 0.1% (w / w) to 0.3% (w / w).

[0109] When the concentration of brightener (component A) in the detergent is less than 0.1% (w / w), the pretreatment effect on the rotating cathode roller 40 may be insufficient due to the insufficient amount of brightener (component A) in the detergent. As a result, more defects may exist in the copper foil, and the copper foil may have a first area ratio outside the range of 45% to 95%.

[0110] Furthermore, when the concentration of brightener (component A) in the detergent is greater than 0.3% (w / w), brightener (component A) may be excessively adsorbed onto the rotating cathode roller 40. As mentioned above, when a large amount of brightener (component A) is adsorbed onto the rotating cathode roller 40, brightener (component A) will occupy the space where other organic additives are adsorbed onto the rotating cathode roller 40. Therefore, the chance of other organic additives adsorbing onto the rotating cathode roller 40 is reduced. In order to obtain the physical properties of the copper foil 110 according to this disclosure, an appropriate adsorption balance among the organic additives must be maintained. In this case, when brightener (component A) is excessively adsorbed onto the rotating cathode roller 40, this balance may be disrupted. That is, the gloss of the copper foil may be improved, but the depressant (component B) and roughness modifier (component C) that improve the surface properties of the copper foil may not be sufficiently adsorbed onto the rotating cathode roller 40, which may lead to problems such as deterioration of the surface properties of the copper foil. As a result, more defects may exist in the copper foil, and the copper foil may have a first area ratio outside the range of 45% to 95%.

[0111] According to this disclosure, in order to enable the copper foil 110 to have a first area ratio of 45% to 95%, the concentration of sulfuric acid in the detergent needs to be maintained in the range of 8% (w / w) to 12% (w / w).

[0112] When the concentration of sulfuric acid in the detergent is less than 8% (w / w), the sulfuric acid may not react sufficiently with the oxides present on the surface of the rotating cathode roller 40 to dissolve or remove these oxides. Therefore, the surface of the manufactured copper foil may be irregular, and more defects may be present in the copper foil. As a result, the copper foil may have a first area ratio outside the range of 45% to 95%.

[0113] Furthermore, when the concentration of sulfuric acid in the detergent exceeds 12% (w / w), sulfuric acid may be present at a high concentration on the surface of the rotating cathode roller 40, resulting in an excessive increase in current density, which may make it difficult to obtain copper foil of the desired quality. Additionally, when the concentration of sulfuric acid in the detergent is too high, uneven defects may appear on the surface of the copper foil, which may make it difficult to obtain the physical properties of the copper foil 110 of this disclosure. Therefore, the surface of the manufactured copper foil may be irregular, and more defects may exist within the copper foil. As a result, the copper foil may have a first area ratio outside the range of 45% to 95%.

[0114] According to this disclosure, even when the surface of the rotating cathode drum 40 is rinsed with detergent, the concentration of brightener (component A) in the electrolyte 20 can be 1 to 15 ppm, and the concentration of sulfuric acid can be 70 to 150 g / L.

[0115] To ensure the cleanliness of electrolyte 20, the copper wire (Cu wire) used as the raw material for electrolyte 20 can be cleaned.

[0116] According to one embodiment of this disclosure, the preparation of electrolyte 20 may include: heat-treating a copper wire; cleaning the heat-treated copper wire with an acid; cleaning the acid-cleaned copper wire with water; and introducing the water-cleaned copper wire into sulfuric acid for use as electrolyte.

[0117] More specifically, to maintain the cleanliness of electrolyte 20, high-purity (99.9% or higher) copper wire is heat-treated in an electric furnace at 750°C to 850°C to burn off various organic impurities. Then, the heat-treated copper wire is cleaned with a 10% sulfuric acid solution for 10 to 20 minutes, and the acid-treated copper wire is cleaned with distilled water. Through these sequential steps, copper for manufacturing electrolyte 20 can be prepared. Electrolyte 20 can be prepared by mixing water-cleaned copper wire with sulfuric acid for use in the electrolyte.

[0118] The copper film 111 manufactured in this way can be cleaned in a cleaning tank.

[0119] For example, acid cleaning can be performed sequentially to remove impurities (such as resin components or natural oxides) from the surface of the copper film 111, followed by water cleaning to remove the acid solution used in the acid cleaning. The cleaning process can be omitted.

[0120] Next, a protective layer 112 is formed on the copper film 111.

[0121] Reference Figure 6 The method disclosed herein may further include immersing the copper film 111 in the anti-corrosion solution 60. When the copper film 111 is immersed in the anti-corrosion solution 60, the copper film 111 may be guided by a guide roller disposed in the anti-corrosion solution 60.

[0122] As described above, the anti-corrosion solution 60 may include at least one of a chromium compound, a silane compound, and a nitrogen compound. For example, the copper film 111 may be immersed in a potassium dichromate solution with a concentration of 1 to 10 g / L for 1 to 30 seconds at room temperature.

[0123] Meanwhile, the protective layer 112 may contain silane compounds through silane treatment or nitrogen compounds through nitrogen treatment.

[0124] Copper foil 110 is made by forming such a protective layer 112.

[0125] The electrode (i.e., anode) for a secondary battery disclosed herein can be manufactured by coating one or more anode active materials selected from carbon; a metal (Me) of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; an alloy containing said metal (Me); an oxide (MeOx) of said metal (Me); and a composite material of said metal (Me) and carbon onto one or both surfaces of the copper foil 110 of this disclosure manufactured by the above method.

[0126] 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 for anode active materials, and then distilled water is added to the mixture as a solvent to prepare a slurry. The slurry is then coated onto copper foil 110 using a doctor blade to a thickness of 20 to 60 μm, and heated at 110 to 130°C at a rate of 0.5 to 1.5 tons / cm². 2 The pressure was suppressed.

[0127] The electrode (anode) of this disclosure, manufactured by the method described above, can be used to manufacture a secondary battery together with a conventional cathode, electrolyte, and separator.

[0128] The present disclosure will now be described in detail with reference to embodiments and comparative examples. However, it should be understood that the embodiments described below are provided only to aid in understanding the present disclosure and are not intended to limit the scope of the present disclosure.

[0129] Examples 1 to 4

[0130] Copper foil is manufactured using an electroplating machine comprising an electrolytic cell 10, a rotating cathode drum 40 disposed within the electrolytic cell 10, and an anode plate 30 spaced apart from the rotating cathode drum 40. The electrolyte 20 is a copper sulfate solution. The copper ion concentration in the electrolyte 20 is set to 87 g / L, the sulfuric acid concentration is set to 110 g / L, the electrolyte temperature is set to 55°C, and the current density is set to 60 ASD.

[0131] In addition, the concentration of chlorine (Cl) in electrolyte 20 is maintained at 20 ppm, and the concentration of organic additives is shown in Table 1 below.

[0132] In the organic additives, disodium bis-(3-sulfopropyl)-disulfide (SPS) is used as a brightener (component A), polyethylene glycol (PEG) is used as a moderator (component B), and triallyl methyl ethyl ammonium ethyl sulfide maleic acid copolymer (PAS-2451TM, Nittobo, Mw.: 30,000) is used as a roughness modifier (component C).

[0133] Before immersing the rotating cathode roller 40 into the electrolyte 20, the surface of the rotating cathode roller 40 is washed with a detergent. An aqueous solution containing sulfuric acid and a brightener (component A) is used as the detergent. Disodium bis-(3-sulfopropyl)-disulfide (SPS) is used as the brightener (component A) in the detergent. The concentrations of sulfuric acid and brightener (component A) in the detergent are shown in Table 1 below.

[0134] A copper film 111 is fabricated by applying a current at a current density of 60 ASD between a rotating cathode roller 40 and an anode plate 30. Next, the copper film 111 is immersed in an anti-corrosion solution for approximately 2 seconds, and both surfaces of the copper film 111 are treated with chromate to form a protective layer 112, thereby fabricating a copper foil. An anti-corrosion solution containing chromic acid as the main component is used, with a chromic acid concentration of 5 g / L.

[0135] As a result, copper foils of Examples 1 to 4 were manufactured. At this time, the thickness of the manufactured copper foil was 8 μm.

[0136] Comparative Examples 1 and 2

[0137] The concentrations of organic additives, whether the drum is washed, and the concentration of brighteners in the detergent are shown in Table 1 below.

[0138] Copper foils for Comparative Examples 1 and 2 were manufactured in the same manner as in Examples 1 to 4. The thickness of the manufactured copper foils was 8 μm.

[0139] Comparative Examples 3 and 4

[0140] The concentration of organic additives and whether or not the drum is washed are shown in Table 1 below.

[0141] The copper foil was manufactured in the same manner as in Examples 1 to 4, except that the surface of the rotating cathode roller 40 was not rinsed with detergent before immersing the rotating cathode roller 40 in the electrolyte 20 to form a copper film 111 on the rotating cathode roller 40. The thickness of the manufactured copper foil was 8 μm.

[0142] [Table 1]

[0143] [Table 2]

[0144] For the copper foils of Examples 1 to 4 and Comparative Examples 1 to 4 manufactured as described above, i) the first area ratio, ii) the second area ratio, and iii) whether wrinkles or tears occurred were confirmed.

[0145] i) First area ratio

[0146] The first area ratio can refer to the area ratio of the area of ​​the grains (including twins) with a room temperature GOS value of 0° to less than 2° in the copper foil to the total cross-sectional area.

[0147] The room-temperature GOS value of the cross-section of the copper foil was measured using electron backscatter diffraction (EBSD) imaging at room temperature (23±2℃).

[0148] The specific imaging conditions and imaging steps are as follows.

[0149] 1. Fix the specimen and heat-mount it on the cross-section of the specimen.

[0150] 2. Perform mechanical polishing.

[0151] 3. Mount the sample on the SEM equipment and measure the cross-section of the sample (accelerating voltage: 15 kV, step size: 0.06 μm, measurement location: random).

[0152] 4. Measure the first area ratio.

[0153] EBSD Imaging Equipment: JEOL JSM-7100F

[0154] Analysis program: TSL OIM analysis 8.0

[0155] Total cross-sectional area refers to the area of ​​the entire cross-sectional region of the copper foil, excluding areas where diffraction patterns were not identified.

[0156] The width of the entire cross-sectional area is 40 μm and the length is 8 μm (the thickness of the copper foil).

[0157] ii) Second area ratio

[0158] The second area ratio can refer to the ratio of the area of ​​the grains (including twins) in the copper foil with a room temperature GOS value of 4° or higher to the total cross-sectional area.

[0159] The second area ratio is measured using the same test method as the first area ratio.

[0160] iii) Are there any wrinkles or tears?

[0161] 1) Anode manufacturing

[0162] Two parts by weight of styrene-butadiene rubber (SBR) and two parts by weight of carboxymethyl cellulose (CMC) were mixed with 100 parts by weight of a commercially available silicon / carbon composite anode material for anode active materials, and distilled water was used as a solvent to prepare a slurry for the anode active material. The slurry for the anode active material was coated onto copper foils (10 cm wide) of Examples 1 to 4 and Comparative Examples 1 to 4 using a doctor blade to a thickness of 40 μm, dried at 120°C, and then subjected to a process at 1 ton / cm². 2 It is pressed under pressure to manufacture the anode for secondary batteries.

[0163] 2) Preparation of electrolytes

[0164] LiPF6, as a solute, was dissolved at a concentration of 1 M in a non-aqueous organic solvent composed of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a 1:2 ratio to prepare a basic electrolyte. 99.5% by weight of the basic electrolyte was mixed with 0.5% by weight of succinic anhydride to prepare a non-aqueous electrolyte.

[0165] 3) Cathode manufacturing

[0166] Lithium manganese oxide Li 1.1 Mn 1.85 Al 0.05 O4 and lithium manganese oxide o-LiMnO2 with an orthorhombic crystal structure were mixed at a weight ratio of 90:10 to prepare a cathode active material. This cathode active material, carbon black, and polyvinylidene fluoride (PVDF) as a binder were mixed at a weight ratio of 85:10:5, and the resulting mixture was mixed with NMP as an organic solvent to prepare a slurry. The prepared slurry was coated on both surfaces of an Al foil with a thickness of 20 μm and then dried to manufacture the cathode.

[0167] 4) Manufacturing of experimental lithium secondary batteries

[0168] A button-type lithium secondary battery is manufactured by placing the cathode and anode inside an aluminum can, insulated from the can, and placing a non-aqueous electrolyte and a separator between the cathode and anode. The separator used is polypropylene (Celgard 2325; thickness: 25 μm, average pore size: ...). (28 nm, porosity: 40%).

[0169] 5) Charging and discharging of secondary batteries

[0170] The lithium secondary battery manufactured as described above operates at a charging voltage of 4.3 V and a discharging voltage of 3.4 V, and undergoes 100 charge-discharge cycles at a high temperature of 50°C and a current rate of 0.2 C (C rate).

[0171] 6) Are there any wrinkles or tears?

[0172] After 100 charge-discharge cycles, the secondary battery is disassembled to observe whether wrinkles or tears appear in the copper foil. If wrinkles or tears appear in the copper foil, it is marked as "present"; if no wrinkles or tears appear, it is marked as "absent".

[0173] Referring to Tables 1 and 2, no wrinkles or tears occurred because the first area ratio of the copper foils according to Examples 1 to 4 met the range of 45% to 95%. However, wrinkles or tears occurred because the first area ratio of the copper foils according to Comparative Examples 1 to 4 did not meet the range of 45% to 95%.

[0174] According to this disclosure, wrinkles or tears can be prevented during the manufacturing process of copper foil. Furthermore, when copper foil is used to manufacture intermediate parts and final products (such as flexible printed circuit boards (FPCBs), secondary batteries, etc.), the productivity of both intermediate parts and final products can be improved.

[0175] It will be apparent to those skilled in the art to which this disclosure pertains that the present disclosure is not limited to the described embodiments and drawings, and that various substitutions, modifications, and variations can be made without departing from the spirit and scope of this disclosure. Therefore, the scope of this disclosure is defined by the appended claims, and it is intended that all variations and modifications derived from the meaning, scope, and equivalent concepts of the claims fall within the scope of this disclosure.

[0176] [Brief Description of Main Components]

[0177] 100: Electrode used in secondary batteries

[0178] 110, 110a, 110b: Copper foil

[0179] 111: Copper film

[0180] 112: Protective layer

[0181] 120: Active material layer

[0182] 10: Electrolytic cell

[0183] 20: Electrolytes

Claims

1. A copper foil comprising: Copper films with both matte and glossy surfaces; and A protective layer disposed on the copper film; Where boundaries with an orientation difference of 5° or greater between adjacent pixels are considered grain boundaries, the area of ​​grains (including twins) with a room temperature GOS value of 0° to less than 2° is 45% to 95% of the total cross-sectional area; and The room temperature GOS value was measured on the cross-section of the copper foil at room temperature using an electron backscatter diffraction (EBSD) pattern analyzer.

2. The copper foil of claim 1, wherein the area of ​​grains (including twins) with a room temperature GOS value of 4° or greater is 3% to 12% of the total cross-sectional area.

3. The copper foil of claim 1, wherein the protective layer comprises at least one selected from chromium compounds, silane compounds, and nitrogen compounds.

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