Electrolytic copper foil, manufacturing method therefor, and electrolyte composition and secondary battery including same

Abstract

The present invention relates to an electrolytic copper foil having a tensile strength of 64 kgf / mm2 or more as measured at room temperature (25±15℃), and an elongation of 3.0% or more.

Description

Electrolytic copper foil, method of manufacturing the same, electrolyte composition including the same, and secondary battery

[0001] The present invention relates to electrolytic copper foil. More specifically, it relates to a high-strength electrolytic copper foil that simultaneously achieves ultra-high strength characteristics at room temperature and excellent mechanical property retention after high-temperature heat treatment.

[0002] In addition, the present invention relates to a method for manufacturing an electrolytic copper foil in which the impurity content inside the copper foil is minimized and the microstructure of the crystal grains is thermally stabilized through an electrolyte composition using a specific organic additive alone, and to an electrolyte composition for the same.

[0003] Electrolytic copper foil is a thin copper foil manufactured by electrolyzing a copper sulfate electrolyte and electrodepositing copper onto a rotating cathode drum. As a fundamental material in the electronics industry, it has been widely used as a conductor to form circuits on printed circuit boards (PCBs); recently, its importance has been rapidly increasing as an anode current collector for lithium-ion secondary batteries used in electric vehicles (EVs) and energy storage systems (ESS).

[0004] Recently, efforts to maximize battery energy density have been ongoing to miniaturize and enhance the performance of electronic devices, as well as to improve the driving range of electric vehicles. Accordingly, 'thinning' technology, which involves reducing the thickness of electrolytic copper foil that supports active materials and transmits electrons within the battery, is emerging as a key challenge.

[0005] However, as the thickness of the copper foil decreases, its mechanical strength deteriorates, making it difficult to handle and prone to tearing or wrinkling during the manufacturing process. In particular, silicon (Si)-based anode materials, which are being introduced for next-generation high-capacity batteries, have the characteristic of expanding by 300–400% in volume during charging, thereby applying massive mechanical stress to the copper foil supporting them. If the copper foil cannot withstand this stress, it may fracture or delaminate from the electrode, shortening the battery's lifespan and posing a fire hazard.

[0006] A more serious problem is 'thermal stability'. The manufacturing process of products using electrolytic copper foil, particularly the battery electrode manufacturing process, involves high-temperature heat treatment processes such as slurry drying (approx. 110–130°C) and roll pressing / vacuum drying (approx. 150–190°C). Conventional high-strength copper foils exhibit high strength at room temperature, but when exposed to such high-temperature environments, they undergo a softening phenomenon in which the copper grains recrystallize or grow coarsely, causing a rapid drop in strength.

[0007] In conventional technology, to increase strength, complex organic additives with large molecular weights, such as gelatin, hydroxyethyl cellulose (HEC), polyethylene glycol (PEG), and 3-mercapto-1-propanesulfonic acid (MPS), have been mixed in a three-component system (brightener / leveler / inhibitor) or higher. However, these polymer additives, which contain a large amount of oxygen (O), are prone to entrapment as impurities within the copper during the electrodeposition process. Furthermore, when heated, they easily decompose to generate gas (void formation) or, conversely, promote grain growth, thereby impairing thermal stability. Additionally, managing a mixture of various additives has increased process complexity and caused quality variations.

[0008] Accordingly, the inventors completed the present invention by introducing a single additive system having a specific molecular structure and optimizing high current density film production conditions, thereby developing an electrolytic copper foil that simultaneously satisfies room temperature and high temperature properties even at ultra-thin film thicknesses.

[0009] The first objective of the present invention is to provide a high-strength electrolytic copper foil having a room-temperature tensile strength of 64 kgf / mm² or more even at a thin thickness, and in particular, a suppression of mechanical strength reduction even after high-temperature heat treatment at 130°C and 190°C.

[0010] The second objective of the present invention is to provide an electrolytic copper foil having optimal physical properties that, when applied as a negative electrode current collector of a lithium-ion secondary battery, prevent thermal deformation (wrinkling) in a process with a maximum temperature of 130°C, for example, an active material slurry drying process, and withstand volume expansion during a process with a maximum temperature of 190°C, for example, a pressing process and during charging and discharging.

[0011] The third objective of the present invention is to provide an electrolytic copper foil that minimizes oxygen impurities inside the copper foil by using a specific organic additive that does not contain oxygen (O) atoms, and effectively inhibits grain growth by ensuring that the additive does not decompose and remains even at high temperatures.

[0012] The fourth objective of the present invention is to provide a manufacturing method capable of stably manufacturing the electrolytic copper foil and an electrolyte composition for the same.

[0013] However, the technical problems that the present invention aims to solve are not limited to those described above, and other unmentioned problems will be clearly understood by a person skilled in the art from the description of the invention below.

[0014] To solve the above technical problem, the first aspect of the present invention is a tensile strength of 64 kgf / mm² measured at room temperature (25±15℃). 2 The present invention provides an electrolytic copper foil characterized by having an elongation rate of 3.0% or more.

[0015] This is compared to conventional general copper foil at 30~40 kgf / mm 2 Compared to having a level of strength, it has secured significantly improved strength, which fundamentally prevents tearing or wrinkling that may occur during the handling of copper foil, and at the same time, through excellent elongation, it has the effect of flexibly coping with tension or bending stress that occurs during the electrode manufacturing process.

[0016] In one embodiment of the present invention, the electrolytic copper foil may be characterized by including carbon (C), nitrogen (N), and sulfur (S) components.

[0017] By including the above carbon (C), nitrogen (N), and sulfur (S) components, the growth of crystal grains in the copper foil can be suppressed, thereby enabling efficient control in terms of tensile strength and elongation.

[0018] In one embodiment of the present invention, the electrolytic copper foil has a tensile strength of 59.8 kgf / mm² after heat treatment at 130°C for 10 minutes. 2 It may be characterized by having an elongation rate of 3.0% or more.

[0019] Through the above features, it means that the mechanical strength of the copper foil is not reduced in a process, for example, a slurry drying process, where the maximum temperature is 130℃, and there is an advantage of being able to maximize the quality of the electrode and production yield by preventing stretching or deformation (wrinkling) of the copper foil due to heat.

[0020]

[0021] In one embodiment of the present invention, the electrolytic copper foil has a tensile strength of 41.4 kgf / mm² after heat treatment at 190°C for 1 hour. 2 It may be characterized by having an elongation rate of 3.0% or more.

[0022] This high-temperature heat resistance suppresses the softening or increased brittleness of the copper foil due to thermal stress that may occur during the pressing and vacuum drying processes, thereby preventing web breakage accidents during the process and contributing to the enhancement of the battery's long-term reliability.

[0023]

[0024] In one embodiment of the present invention, the electrolytic copper foil may be characterized in that, as a result of secondary ion mass spectrometry (SIMS) at a depth of 1 μm to 3 μm from the surface at room temperature (25±15℃), the detection intensity of the carbon-nitrogen (CN) component is in the range of 123 to 391 and the detection intensity of the sulfur (S) component is in the range of 29 to 141.

[0025] Through these characteristics, organic additives that do not contain oxygen atoms are uniformly solidified between copper crystal lattices or grain boundaries throughout the copper foil, allowing for uniform mechanical properties in any region or in the thickness direction.

[0026] In addition, the composition of carbon-nitrogen (CN) and sulfur (S) components at room temperature can act as a chemical fingerprint and can be used as data to determine whether a product is normal or defective.

[0027]

[0028] In one embodiment of the present invention, the electrolytic copper foil may be characterized in that, after heat treatment at 130°C for 10 minutes, the secondary ion mass spectrometry (SIMS) results in a depth range of 1 μm to 3 μm from the surface show that the detection intensity of the carbon-nitrogen (CN) component is in the range of 112 to 418 and the detection intensity of the sulfur (S) component is in the range of 34 to 164.

[0029] This means that even in a process with a maximum temperature of 130℃, the framework of the organic additive does not decompose and remains at the grain boundaries, exhibiting a pinning effect that inhibits the movement of copper atoms, thereby achieving technical effects such as inhibiting high-temperature grain growth and maintaining mechanical strength.

[0030]

[0031] In one embodiment of the present invention, the electrolytic copper foil may be characterized in that, after heat treatment at 190°C for 1 hour, the secondary ion mass spectrometry (SIMS) results in a depth range of 1 μm to 3 μm from the surface show that the detection intensity of the carbon-nitrogen (CN) component is in the range of 73 to 421 and the detection intensity of the sulfur (S) component is in the range of 30 to 195.

[0032] This means that even in a process with a maximum temperature of 190℃, the framework of the organic additive does not decompose and remains at the grain boundaries, exhibiting a pinning effect that inhibits the movement of copper atoms, thereby achieving technical effects such as inhibiting high-temperature grain growth and maintaining mechanical strength.

[0033] In one embodiment of the present invention, the carbon, nitrogen, and sulfur components contained in the electrolytic copper foil are derived from the decomposition product of a single compound of ethylene thiourea (ETU) added to the electrolyte, and the electrolytic copper foil may be characterized in that it substantially does not contain components derived from gelatin, hydroxyethyl cellulose (HEC), and sulfonic acid compounds (SPS).

[0034] This not only facilitates the management of impurities in the electrolyte to increase production efficiency, but also minimizes the oxygen impurity content in the copper foil, thereby suppressing the generation of by-product gases during battery operation and improving electrochemical stability.

[0035]

[0036] In one embodiment of the present invention, the thickness of the electrolytic copper foil may be characterized as being in the range of 4 μm to 6 μm.

[0037] The present invention can maximize the energy density of a lithium-ion secondary battery by having an ultra-thin film thickness of 4 to 6 μm.

[0038] In one embodiment of the present invention, the electrolytic copper foil is used as an anode current collector of a lithium-ion secondary battery and may be characterized by preventing the rupture of the electrode in response to the volume expansion of the active material during charging and discharging.

[0039] Through this, even when carbon-based, silicon (Si)-based, or silicon oxide (SiOx)-based negative electrode active materials that undergo large volume expansion during charging and discharging are applied, the high strength and high elongation characteristics of the copper foil of the present invention effectively withstand expansion stress, thereby providing excellent current collector performance that prevents electrode breakage and delamination.

[0040]

[0041] To solve the above technical problem, a second aspect of the present invention provides an anode for a lithium-ion secondary battery comprising: the electrolytic copper foil; and a negative electrode active material layer formed on at least one surface of the electrolytic copper foil and comprising a carbon-based material or a silicon-based material.

[0042] The present invention can be optimized for the application of carbon-based materials, such as graphite, or silicon-based materials, such as silicon (Si)-based anode materials, which undergo significant volume expansion during charging and discharging. The high thermal stability and strength of the electrolytic copper foil of the present invention effectively withstand the expansion stress of the silicon anode, thereby significantly improving the battery's lifespan and safety.

[0043]

[0044] To solve the above technical problem, a third aspect of the present invention provides a lithium-ion secondary battery comprising: the cathode; the anode; a separator interposed between the cathode and the anode; and a non-aqueous electrolyte comprising a lithium salt.

[0045] The negative electrode and lithium-ion secondary battery including the electrolytic copper foil according to the present invention can significantly improve the lifespan characteristics and safety of the battery even when high-capacity active materials are applied, based on the excellent mechanical properties and thermal stability of the copper foil.

[0046]

[0047] To solve the above technical problem, a fourth aspect of the present invention relates to a method for manufacturing an electrolytic copper foil, comprising the steps of: preparing a base electrolyte comprising 80 to 100 g / L of copper ions, 70 to 90 g / L of sulfuric acid, and 0.1 to 1.0 ppm of chloride ions; adding to the electrolyte a compound having an imidazole-2-thione functional group as an organic additive at a concentration of 0.5 to 1.5 mg / L; and placing a cathode drum and an anode plate disposed in the electrolyte at a concentration of 70 to 85 A / dm 2 A method for manufacturing an electrolytic copper foil is provided, comprising the step of forming an electrolytic copper foil by applying a current density of (ASD); wherein the electrolyte temperature during the forming step is maintained at 40 to 48℃, and the thickness of the manufactured electrolytic copper foil is 6 μm or less.

[0048] The manufacturing method of the present invention is 70~85 A / dm 2 By optimizing and applying a high current density, specific temperature conditions of 40~48℃, and a single ETU additive (0.5~1.5mg / L), it provides technical advantages that enable stable mass production of high-quality, high-strength copper foil while ensuring high productivity.

[0049] In one embodiment of the present invention, the organic additive may be characterized as being composed solely of a compound having the imidazole-2-thione functional group and not including gelatin, hydroxyethyl cellulose (HEC), polyethylene glycol (PEG), and sulfur-containing gloss agents (SPS, MPS).

[0050] In one embodiment of the present invention, the compound having an imidazole-2-thione functional group is an ethylene thiourea (ETU) compound, the concentration of the ethylene thiourea (ETU) compound is in the range of 0.5 to 1.5 mg / L, and the concentration of the chloride ion is in the range of 0.3 to 0.8 ppm.

[0051]

[0052] To solve the above technical problem, the fifth aspect of the present invention comprises, in an electrolyte composition for manufacturing an electrolytic copper foil, 80 to 100 g / L of copper ions; 70 to 90 g / L of sulfuric acid; 0.1 to 1.0 ppm of chloride ions; and a single additive of ethylene thiourea (ETU) having a concentration of 0.5 to 1.5 mg / L, and 70 A / dm² 2 Tensile strength of 64 kgf / mm at room temperature under the above current densities 2 The present invention provides an electrolyte composition characterized by realizing the above physical properties.

[0053] In one embodiment of the present invention, the electrolyte composition may be characterized by being free of an additive containing oxygen (O) atoms within the molecule.

[0054] In one embodiment of the present invention, the additive containing an oxygen (O) atom within the molecule may be characterized by comprising one or more selected from polymer additives, gelatin, cellulose (HEC), and sulfonic acid-based glossing agents (SPS).

[0055]

[0056] To solve the above technical problem, the sixth aspect of the present invention provides a replenishing solution for manufacturing electrolytic copper foil, wherein the replenishing solution introduced into a plating bath to maintain the concentration of the electrolyte composition of claim 15 comprises ethylene thiourea (ETU) as an active ingredient and does not contain oxygen-containing organic material.

[0057]

[0058] The electrolyte composition and replenishment solution of the present invention are designed to exclude oxygen-containing organic matter and contain an ETU of a specific concentration, such that 70 A / dm² 2 Tensile strength of 64 kgf / mm² even under the above high-speed plating conditions 2 It enables the realization of copper foil with the above-mentioned high physical properties. This enhances the convenience of electrolyte management and prevents quality degradation caused by the accumulation of impurities, thereby providing an advantageous effect for long-term continuous production.

[0059] According to the present invention, the following significant effects can be obtained.

[0060] First, the present invention maximizes the refinement of copper grains by using a single additive, ethylene thiourea (ETU), which does not contain oxygen, and pins grain boundaries without the additive decomposing even at high temperatures, thereby securing excellent mechanical properties such as a room-temperature tensile strength of 64 kgf / mm² or more and an elongation of 3.0% or more, even at an ultra-thin film thickness of 6 μm or less. This provides ease of handling due to the thinning of copper foil, resulting from a revolutionary improvement in strength compared to conventional technology.

[0061]

[0062] Second, the electrolytic copper foil of the present invention maintains a tensile strength of 59.8 kgf / mm² or more even after heat treatment at 130°C, effectively suppressing thermal deformation and wrinkling during the slurry drying step in the secondary battery electrode manufacturing process. In addition, it maintains a tensile strength of 41.4 kgf / mm² or more and an elongation of 3.0% or more even after high-temperature heat treatment at 190°C, thereby preventing web breakage caused by stress during the press process and battery charging / discharging, and maximizing process yield.

[0063]

[0064] Third, the present invention achieves a pinning effect that suppresses grain growth by controlling the presence of additive components within a specific range (CN strength 73~421, S strength 30~195) inside the copper foil even after high-temperature heat treatment. Through this, it provides excellent thermal stability capable of withstanding volume expansion of high-capacity negative electrode active materials, such as silicon-based materials.

[0065]

[0066] Fourth, by applying a single additive system instead of a complex multi-component additive system and excluding oxygen-containing impurities, electrolyte management can be facilitated and manufacturing costs can be reduced, and the chemical purity of the copper foil can be increased to improve the long-term reliability and safety of the battery.

[0067]

[0068] However, the effects obtainable through the present invention are not limited to those described above, and other unmentioned technical effects will be clearly understood by a person skilled in the art from the description of the invention below.

[0069] Figure 1 is a diagram showing the TOF-SIMS analysis results for CN contained in a copper foil at room temperature according to one embodiment of the present invention.

[0070] FIG. 2 is a diagram showing the TOF-SIMS analysis results for S contained in a copper foil at room temperature according to one embodiment of the present invention.

[0071] FIG. 3 is a diagram showing the TOF-SIMS analysis results for CN contained in copper foil after heat treatment at 130°C for 10 minutes according to one embodiment of the present invention.

[0072] Figure 4 is a diagram showing the TOF-SIMS analysis results for S contained in the copper foil after heat treatment at 130°C for 10 minutes according to one embodiment of the present invention.

[0073] FIG. 5 is a diagram showing the TOF-SIMS analysis results for CN contained in copper foil after heat treatment at 190°C for 60 minutes according to one embodiment of the present invention.

[0074] FIG. 6 is a diagram showing the TOF-SIMS analysis results for S contained in copper foil after heat treatment at 190°C for 60 minutes according to one embodiment of the present invention.

[0075] Hereinafter, the present invention will be described in detail with reference to the attached drawings. However, this is merely illustrative and the present invention is not limited to the specific embodiments described illustratively.

[0076] Specific terms used in this specification are for convenience of explanation only and are not intended to limit the exemplified embodiments.

[0077] For example, expressions such as "identical" and "to be identical" indicate not only a strictly identical state, but also a state where tolerances or differences exist in the degree to which the same function is obtained.

[0078] The use of terms such as 'first, second, third' attached to the components mentioned below is intended solely to avoid confusion regarding the components being referred to, and is unrelated to the order, importance, or master-subordinate relationship between the components. For example, an invention including only the second component without the first component can be implemented.

[0079] The terms used herein are for the description of specific embodiments and are not intended to limit the claims. As used in the description of embodiments and the appended claims, the singular form is intended to include the plural form unless the context clearly indicates otherwise.

[0080] In this specification, when any layer is described as being located "on" or "between" another arbitrary layer, this includes not only cases where any layer is in contact with another arbitrary layer, but also cases where another layer or material, etc., exists between the two layers.

[0081] Where in this specification a quantity, concentration, or other value or parameter is given as an enumeration of a range, a preferred range, a preferred upper limit, and a preferred lower limit, it should be understood that any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether the range is disclosed separately, specifically discloses all ranges that may be formed. Where a range of numerical values ​​is mentioned in this specification, unless otherwise stated, for example, without limiting terms such as greater than or less than, the range is intended to include the endpoint value and all integers and fractions within that range. The scope of the invention is not intended to be limited to the specific value mentioned when defining the range.

[0082] Among the physical properties mentioned in this specification, if the measured temperature affects the property, the property is measured at room temperature unless specifically otherwise specified. The term "room temperature" refers to a natural temperature that has not been heated or cooled, and may mean, for example, any temperature within the range of about 10°C to 30°C, about 23°C, or about 25°C. Furthermore, unless specifically otherwise specified, the unit of temperature in this specification is °C.

[0083] In addition, among the physical properties mentioned in this specification, if the measured pressure affects the physical property, unless otherwise specifically defined, the physical property is measured at normal pressure, that is, atmospheric pressure (about 1 atmosphere).

[0084]

[0085] 1. Electrolytic Copper Foil (Product)

[0086] An electrolytic copper foil according to one embodiment of the present invention is characterized by having a tensile strength of 64 kgf / mm² or more and an elongation of 3.0% or more measured at room temperature (25±15℃). This secures a groundbreaking mechanical strength compared to conventional copper foil, which has a strength of 30 to 40 kgf / mm² at room temperature.

[0087] In addition, in one embodiment of the present invention, the electrolytic copper foil may be characterized by including carbon (C), nitrogen (N), and sulfur (S) components. By including the carbon (C), nitrogen (N), and sulfur (S) components, the growth of the crystal grains of the copper foil can be suppressed, thereby enabling efficient control in terms of tensile strength and elongation.

[0088]

[0089] In addition, the electrolytic copper foil of the present invention is characterized by maintaining excellent mechanical properties even after high-temperature heat treatment. Specifically, the tensile strength measured after heat treatment at 130°C for 10 minutes is 59.8 kgf / mm² or higher, and the elongation is maintained at 3.0% or higher. This means that thermal deformation and the occurrence of wrinkles during the slurry drying step in the secondary battery electrode manufacturing process can be effectively suppressed. Furthermore, even after heat treatment at 190°C for 1 hour, the tensile strength is 41.4 kgf / mm² or higher, and the elongation is maintained at 3.0% or higher. Such high-temperature heat resistance contributes to preventing web breakage caused by stress during the press process and battery charging and discharging.

[0090]

[0091] In terms of chemical composition and microstructure, when the electrolytic copper foil of the present invention is measured in the depth direction from the surface using Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS), carbon-nitrogen (CN) components and sulfur (S) components are continuously detected in the depth range of 1 μm to 3 μm (Bulk). Specifically, under room temperature conditions (25±15℃), the detection intensity of the CN component is in the range of 123 to 391, and the detection intensity of the sulfur (S) component is in the range of 29 to 141. In addition, after heat treatment at 130℃ for 10 minutes, the detection intensity of the CN component is maintained in the range of 112 to 418, and the detection intensity of the sulfur (S) component is maintained in the range of 34 to 164. In particular, even after heat treatment at 190℃ for 1 hour, the detection intensity of the CN component is maintained in the range of 73 to 421, and the detection intensity of the sulfur (S) component is maintained in the range of 30 to 195. This demonstrates that the framework of the organic additive does not decompose even at high temperatures but remains at the grain boundaries, exhibiting a pinning effect that inhibits the movement of copper atoms.

[0092]

[0093] The carbon, nitrogen, and sulfur components contained in the electrolytic copper foil of the present invention are derived from the decomposition products of a single compound of ethylene thiourea (ETU) added to the electrolyte, and substantially do not contain components derived from gelatin, hydroxyethyl cellulose (HEC), and sulfonic acid compounds (SPS).

[0094]

[0095] The above electrolytic copper foil is used as an anode current collector for lithium-ion secondary batteries and exhibits excellent characteristics that prevent electrode breakage even when silicon (Si)-based or silicon oxide (SiOx)-based anode active materials, which undergo volume expansion of more than 10% during charging and discharging, are applied.

[0096]

[0097] 2. Manufacturing Method of Electrolytic Copper Foil (Process)

[0098] The method for manufacturing electrolytic copper foil according to the present invention comprises the following steps. First, a base electrolyte is prepared containing 80 to 100 g / L of copper ions, 70 to 90 g / L of sulfuric acid, and 0.1 to 1.0 ppm of chloride ions. Second, a compound having an imidazole-2-thione functional group, specifically an ethylene thiourea (ETU) compound, is added to the electrolyte as an organic additive at a concentration of 0.3 to 1.8 mg / L, preferably 0.5 to 1.5 mg / L. At this time, other additives such as gelatin, HEC, and SPS are not included. Third, an electrolytic copper foil is produced by applying a current density of 70 to 85 A / dm² (ASD) between a cathode drum and an anode plate placed within the electrolyte. At this time, the electrolyte temperature is maintained at 40 to 48°C, and the thickness of the produced electrolytic copper foil is controlled to be 6 μm or less.

[0099]

[0100] 3. Electrolyte Composition

[0101] The electrolyte composition of the present invention comprises 80 to 100 g / L of copper ions, 70 to 90 g / L of sulfuric acid, 0.1 to 1.0 ppm of chloride ions, and a single additive of ethylene thiourea (ETU) having a concentration of 0.5 to 1.5 mg / L. The composition can achieve a tensile strength of 64 kgf / mm² or more at room temperature under a current density of 70 A / dm² or more. In addition, the electrolyte composition is characterized by being free of polymer additives containing oxygen (O) atoms within the molecule, gelatin, cellulose (HEC), and sulfonic acid-based polishing agents (SPS).

[0102]

[0103] The replenishing solution introduced into the plating bath to maintain the concentration of the electrolyte composition of the present invention contains ethylene thiourea (ETU) as an active ingredient and does not contain oxygen-containing organic matter.

[0104]

[0105] The present invention is described in more detail below through examples and comparative examples. However, the present invention is not limited to the examples.

[0106]

[0107]

[0108] Examples

[0109] (1) Manufacture of electrolytic copper foil

[0110] A rotating titanium drum (cathode) and an insoluble anode (DSA) were installed in a foil-making machine, and an electrolyte with the composition listed in [Table 1] below was supplied to manufacture electrolytic copper foils corresponding to the examples and comparative examples. The base electrolyte was prepared by dissolving copper wire in sulfuric acid, and the chloride ion concentration was strictly controlled to 0.5 ppm. The line speed was adjusted so that the thickness of the manufactured copper foil was 6 μm.

[0111] [Table 1] Electrolyte composition and manufacturing conditions of examples and comparative examples

[0112] Classification Cu (g / L) H₂SO₄ (g / L) Cl (ppm) Type of Additive Additive Concentration (mg / L) Current Density (ASD) Electrolyte Temperature (°C) Example 1 90 800.5 ETU 0.5 7841 Example 2 90 800.5 ETU 1.0 7841 Example 3 90 800.5 ETU 1.5 7841 Example 4 90 800.5 ETU 0.5 7845 Example 5 90 800.5 ETU 1.5 7845 Comparative Example 190 800.5 ETU 0.1 7841 Comparative Example 2 90 800.5 ETU 2.0 7841 Comparative Example 3 90 80303 Component System HEC (1.0) Gel (5.0) SPS (1.0) 7257 Comparative Example 490800.5ETU0.0567.245

[0113]

[0114]

[0115] (2) Items for evaluating physical properties

[0116] The physical properties of the electrolytic copper foil prepared in the embodiments and comparative examples of the present invention were measured under the following instruments and conditions.

[0117]

[0118] (1) Tensile Strength and Elongation

[0119] Measurement standard: Measured in accordance with IPC-TM-650 2.4.18 standard.

[0120] Specimen preparation: A specimen was prepared by cutting an electrolytic copper foil to a width of 12.7 mm (0.5 inch) and a length of 150 mm.

[0121] Measuring instrument: A Universal Testing Machine (UTM, Universal Testing Machine, Model name: Instron 5900 Series or equivalent) was used.

[0122] Measurement conditions: The gauge length was set to 50 mm, and the cross-head speed was set to 50 mm / min, and the specimen was tensile until fractured.

[0123] - Calculation method:

[0124] Tensile strength (kgf / mm²): Calculated by dividing the maximum load (kgf) at which the specimen fractures by the cross-sectional area of ​​the specimen (thickness × width, mm²).

[0125] Elongation (%): The length increased up to the point of fracture was divided by the initial gauge length (50 mm) and converted into a percentage.

[0126] - Heat treatment conditions:

[0127] 130℃ heat treatment: The specimen was held in an oven preheated to 130℃ for 10 minutes, then removed, cooled at room temperature, and measured.

[0128] 190℃ heat treatment: The specimen was held in a 190℃ oven for 1 hour (60 minutes), then removed, cooled to room temperature, and measured.

[0129]

[0130] (2) TOF-SIMS (additive distribution and intensity)

[0131] Measurement instrument: Time-of-flight secondary ion mass spectrometry was used.

[0132] - Analysis conditions:

[0133] Primary ion source: Bi + or Bi3 + 30 keV (maximum 30 keV)

[0134] Analysis ion beam current: 0.9 pA

[0135] Sample analysis area: 40 x 40 µm²

[0136] - Sputtering conditions :

[0137] Ion source: Cs +(Max. 2 keV)

[0138] Sputtering ion beam current: 125 nA

[0139] Sample area: 250 x 250 µm²

[0140] Data processing: Since oxides or process residues are present on the surface and do not accurately represent the actual internal composition of the copper foil, the average intensity value of secondary ions detected in the depth range of 1.0 μm to 3.0 μm (Bulk region) from the surface was used to exclude surface influences such as surface contamination layers and initial unstable regions.

[0141] Detectable: Carbon-nitrogen component is CN - (m / z 26) or CNO - (m / z 42), sulfur component is S - The ion counts of (m / z 32) were measured, and the values ​​of the carbon-nitrogen analysis results represent the detection intensity of secondary ions attributable to components containing carbon and nitrogen bonds.

[0142]

[0143] The results of the above physical property evaluation are shown in Tables 2 and 3 below.

[0144]

[0145] 3. Experimental Results and In-depth Analysis

[0146] 3.1. Results of Mechanical Property Evaluation (Strength & Elongation)

[0147] [Table 2] Changes in Tensile Strength and Elongation by Temperature

[0148] Classification Room Temperature (25℃) Strength (kgf / mm²) 130℃ Strength (kgf / mm²) 190℃ Strength (kgf / mm²) Room Temperature Elongation (%) 130℃ Elongation (%) 190℃ Elongation (%) Example 1 65.25 9.84 2.85.7 3.0 3.0 Example 2 65.36 3.34 5.85.15.0 3.0 Example 3 64.76 2.74 5.7 3.33.2 3.0 Example 4 64.26 0.34 1.43.0 3.0 3.0 Example 5 64.06 1.04 4.0 3.9 3.8 3.3 Comparative Example 1 56.55 4.65 1.16.75 66.1 Comparative Example 269.067.052.02.82.41.7 Comparative Example 336.433.329.46.17.010.0 Comparative Example 450.450.024.94.44.613.0

[0149]

[0150] [Analysis 1] Tensile Strength and Elongation at Room Temperature (25±15℃)

[0151] At room temperature (25℃), it exhibited a tensile strength of 64 kgf / mm² or more and an elongation of 3.0% or more, showing ultra-high strength characteristics that can solve handling issues caused by thin film formation.

[0152]

[0153] [Analysis 2] 130℃ Drying Process Stability

[0154] During the manufacturing of secondary battery negative electrodes, the slurry drying process is performed at approximately 130°C. At this time, if the strength of the copper foil is low, the copper foil stretches due to the tension of the roll-to-roll process, causing wrinkles to form.

[0155] Examples 1 to 5: Even after heat treatment at 130°C, the strength is maintained at a level of 60 kgf / mm², showing almost no change compared to room temperature. This means that it has excellent dimensional stability during the drying process.

[0156] Comparative Example 3 (General Purpose): The strength is very low at 33.3 kgf / mm², so there is a high risk of wrinkling and detachment of active material during the drying process.

[0157]

[0158] [Analysis 3] 190℃ Heat Resistance and Cause of Failure of Comparative Example 4

[0159] Example: Even at a high temperature of 190°C, the strength is maintained at 41.4 kgf / mm² or more and the elongation at 3.0% or more. This is because the ETU additive does not decompose even at high temperatures and inhibits grain growth.

[0160] Comparative Example 4 (small amount added): It was good at room temperature (50.4) and 130°C (50.0), but at 190°C the strength was reduced to about half at 24.9, and the elongation increased significantly to 13.0%. This shows that the ethylene thiourea (ETU) additive could not withstand 190°C and decomposed and disappeared, and as a result, the copper crystals were greatly softened.

[0161] Comparative Example 2 (excessive addition): Although the strength was high, the elongation at 190°C dropped sharply to 1.7%. This suggests that the copper foil has brittleness, and there is a very high risk of the electrode breaking (web breakage) during the press process.

[0162]

[0163]

[0164] 3.2. TOF-SIMS Analysis Results (Chemical Stability)

[0165] [Table 3] TOF-SIMS Analysis Results

[0166] Carbon-Nitrogen Sulfur RT1 30°C 10 min 190°C 60 min RT1 30°C 10 min 190°C 60 min Example 1 156~270 138~250 183~270 43~9 242~96 74~141 Example 2 253~377 243~347 243~349 62~128 78~129 100~166 Example 3 276~390 273~41 3268~42 171~14 186~158 102~195 Example 4 123~207 112~188 73~140 29~72 34~80 30~82 Example 5237~391269~418216~35755~12391~164115~191 Comparative Example 19~5318~464~292~274~2715~41 Comparative Example 2292~505291~443252~39299~15690~15593~173 Comparative Example 30~100~100~100~100~100~100~10 Comparative Example 40~100~100~100~100~100~10

[0167]

[0168] [Analysis 1] In-depth Analysis of TOF-SIMS: Identifying Internal Hiring and Pinning Effects

[0169] This analysis is intended to confirm the distribution of additives at a depth of 1–3 μm (Bulk region) after removing the surface contaminant layer using Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) and whether they remain after heat treatment.

[0170]

[0171] 1. Analysis of Carbon-Nitrogen (CN) Bond Strength: Maintenance of the Organic Molecular Framework

[0172] Examples 1 to 5 (structural stability): CN ions (mass numbers 26, 42, etc.) were continuously detected in depth ranges 1 to 3. Examples 1 to 5 showed detection intensities of carbon-nitrogen (CN) components ranging from 123 to 391 and detection intensities of sulfur (S) components ranging from 29 to 141 at room temperature. This range is the optimal additive content (Sweet Spot) for simultaneously achieving high strength and high elongation.

[0173] In particular, the CN detection intensity remained in the range of 70 to 430 (Counts / Normalized Intensity) even after heat treatment at 190°C. This suggests that the ring structure of the ETU or its core framework is not completely broken even at high temperatures and is firmly embedded in the copper grain boundaries in the form of a solid solution. This proves that the movement of copper atoms is inhibited through chemical bonding rather than simple physical adsorption.

[0174]

[0175] Comparative Example 3 (General ternary system): The CN intensity was very low, ranging from 0 to 10, or was not detected. This implies that the additives used (HEC, SPS, etc.) exhibited decomposition behavior different from that of ETU, or that they were carbonized at high temperatures, leaving no organic framework. Therefore, it is difficult to expect a pinning effect at high temperatures.

[0176] Comparative Example 2 (Excessive Addition): Although the strength was high, the elongation at 190°C dropped sharply to 1.7%. This suggests that the copper foil exhibits brittleness, indicating a very high risk of the electrode breaking (Web Breakage) during the press process. It is determined that the CN strength reached a maximum of 505, which caused the occurrence of brittleness due to excessive impurities.

[0177]

[0178]

[0179] 2. Sulfur (S) Intensity Analysis: The Key to Grain Boundary Pinning

[0180] Examples 1–5 (Uniform Distribution): The detection intensity of sulfur (S) components ranged from 29 to 141 (at room temperature) and 30 to 195 (after heat treatment at 190°C). Notably, after heat treatment at 190°C, the detection intensity of sulfur did not decrease but rather tended to slightly increase or remain constant. This indicates that when copper crystals are rearranged by heat treatment, sulfur atoms diffuse (segregate) to the grain boundaries, strongly exerting a 'Zener Pinning' effect that blocks grain growth. This plays a key role in suppressing the softening phenomenon—where the mechanical strength of the copper foil drops sharply even at high temperatures—and maintaining the elongation. Conversely, when the intensity falls outside this range (Comparative Examples), problems arise where the additive is lost, resulting in no pinning effect, or where brittleness increases due to excessive impurities.

[0181]

[0182] Comparative Example 4 (ETU): (Data Inference) Given that the carbon content in Comparative Example 4 decreased rapidly, it is highly likely that the sulfur component also volatilized in the form of gases such as CS2 or clumped together locally to form copper sulfide (CuS) foreign substances. Sulfur that is not uniformly distributed does not produce a pinning effect and instead acts as a crack initiation site, thereby degrading the physical properties.

[0183]

[0184] Meanwhile, FIG. 1 is a diagram showing the TOF-SIMS analysis results for CN contained in a copper foil at room temperature according to one embodiment of the present invention, and FIG. 2 is a diagram showing the TOF-SIMS analysis results for S contained in a copper foil at room temperature according to one embodiment of the present invention.

[0185] FIG. 3 is a diagram showing the TOF-SIMS analysis results for CN contained in copper foil after heat treatment at 130°C for 10 minutes according to one embodiment of the present invention, and FIG. 4 is a diagram showing the TOF-SIMS analysis results for S contained in copper foil after heat treatment at 130°C for 10 minutes according to one embodiment of the present invention.

[0186] FIG. 5 is a figure showing the TOF-SIMS analysis results for CN contained in copper foil after heat treatment at 190°C for 60 minutes according to one embodiment of the present invention, and FIG. 6 is a figure showing the TOF-SIMS analysis results for S contained in copper foil after heat treatment at 190°C for 60 minutes according to one embodiment of the present invention.

[0187] Referring to FIGS. 1 to 6, it was confirmed that in Examples 1 to 5, the intensity of CN and S elements showed a significant difference compared to Comparative Examples 1 to 5.

[0188] Specifically, under room temperature conditions, the intensity of the S element was measured to be about 20 to 150 in Examples 1 to 5, showing a clear difference from Comparative Example 1, and in particular, showed significantly higher values ​​compared to Comparative Examples 3 and 4, where the intensity of the S element was 0 to 10.

[0189] In addition, CN is an element constituting the organic material under room temperature conditions, and in Examples 1 to 5, it showed an intensity of about 123 to 391, showing a difference from Comparative Example 1, and was measured to be significantly higher than Comparative Examples 3 and 4, where the CN intensity was at a level of 0 to 10.

[0190] Meanwhile, a similar trend was confirmed even after heat treatment at 190°C for 1 hour. After heat treatment, the intensity of the S element in Examples 1 to 5 was measured to be approximately 20 to 200, showing a difference from Comparative Example 1, and maintained a higher value compared to Comparative Examples 3 and 4, where the intensity of the S element was 0 to 10.

[0191] In addition, the intensity of CN after heat treatment was measured to be approximately 70 to 430 in Examples 1 to 5, showing a difference distinct from Comparative Example 1, and exhibiting a significantly higher intensity compared to Comparative Examples 3 and 4.

[0192] From these results, it can be seen that the organic materials included in Examples 1 to 5 influence the grain size even after heat treatment, thereby contributing to the improvement of the tensile strength of the copper foil. In particular, when the intensity of the S element is less than 20, it is difficult to secure sufficient tensile strength, and when it exceeds 150, although the tensile strength increases, the elongation decreases, making it difficult to produce the copper foil stably. In addition, when the intensity of CN is less than 70, sufficient tensile strength is not secured, and when it exceeds 430, although the tensile strength is high, the elongation decreases, resulting in a problem of reduced productivity of the copper foil.

[0193]

[0194]

[0195] 3. Comprehensive Analysis (Discovery of Sweet Spot) As a result of data analysis, Examples 1 to 5 showed a detection intensity of carbon-nitrogen (CN) components ranging from 123 to 391 and a detection intensity of sulfur (S) components ranging from 29 to 141 at room temperature. Within this range, an optimal balance of physical properties was achieved, specifically [room temperature strength 64 or higher + high temperature strength 40 or higher + elongation 3% or higher], which is the performance of high strength and high elongation.

[0196]

[0197] If it is lower than this range (Comparative Examples 1 and 3), the strength is reduced due to insufficient pinning effect.

[0198] If it is higher than this range (high concentration in Comparative Example 2 and some Examples), the elongation rate decreases due to excessive impurities.

[0199]

[0200] Therefore, the above SIMS strength range can be defined as the 'chemical fingerprint' that copper foil for high-capacity secondary batteries must possess.

[0201]

[0202]

[0203] 4. Performance Evaluation of Secondary Battery Application

[0204] A pouch-type battery was manufactured and evaluated using the copper foil of Example 2 and Comparative Example 4 as a negative current collector.

[0205] The cathode slurry was composed of 90% artificial graphite, 5% silicon oxide (SiOx), 2.5% conductive material, and 2.5% binder.

[0206] Electrode manufacturing processability: The copper foil of Comparative Example 4 developed wrinkles at the edges due to tension after drying at 130°C, whereas the copper foil of Example 2 formed a flat electrode without wrinkles.

[0207] Lifespan characteristics: As a result of disassembling the battery after 300 charge-discharge cycles, the copper foil of Comparative Example 4 could not withstand the expansion of silicon and numerous microcracks were observed, whereas the copper foil of Example 2 remained sound. As a result, the capacity retention rate of the battery using Example 2 was more than 15% better than that of the Comparative Example.

[0208]

[0209]

[0210]

Claims

Tensile strength measured at room temperature (25±15℃) is 64 kgf / mm 2 Electrolytic copper foil characterized by having an elongation rate of 3.0% or more. In paragraph 1, The above electrolytic copper foil is characterized by containing carbon (C), nitrogen (N), and sulfur (S) components. In paragraph 1, After heat treating the above electrolytic copper foil at 130°C for 10 minutes, Tensile strength is 59.8 kgf / mm 2 Electrolytic copper foil characterized by having an elongation rate of 3.0% or more. In paragraph 1, After heat treating the above electrolytic copper foil at 190℃ for 1 hour, Tensile strength is 41.4 kgf / mm 2 Electrolytic copper foil characterized by having an elongation rate of 3.0% or more. In paragraph 1, The above electrolytic copper foil, based on the results of secondary ion mass spectrometry (SIMS) at room temperature (25±15℃) in the depth range of 1 μm to 3 μm from the surface, Electrolytic copper foil characterized by a detection intensity of carbon-nitrogen (CN) components in the range of 123 to 391 and a detection intensity of sulfur (S) components in the range of 29 to 141. In paragraph 1, After heat treatment of the above electrolytic copper foil at 130°C for 10 minutes, the results of secondary ion mass spectrometry (SIMS) at a depth of 1 μm to 3 μm from the surface, Electrolytic copper foil characterized by a detection intensity of carbon-nitrogen (CN) components in the range of 112 to 418 and a detection intensity of sulfur (S) components in the range of 34 to 164. In paragraph 1, After heat treatment of the above electrolytic copper foil at 190°C for 1 hour, the results of secondary ion mass spectrometry (SIMS) at a depth of 1 μm to 3 μm from the surface, Electrolytic copper foil characterized by a detection intensity of carbon-nitrogen (CN) components in the range of 73 to 421 and a detection intensity of sulfur (S) components in the range of 30 to 195. In paragraph 1, The carbon, nitrogen, and sulfur components contained in the above electrolytic copper foil originate from the decomposition products of a single compound, ethylene thiourea (ETU), added to the electrolyte, and The above electrolytic copper foil is characterized by substantially not containing components derived from gelatin, hydroxyethyl cellulose (HEC), and sulfonic acid compounds (SPS). In paragraph 1, Electrolytic copper foil characterized by the thickness of the electrolytic copper foil being in the range of 4 μm to 6 μm. In paragraph 1, The above electrolytic copper foil is used as an anode current collector for a lithium-ion secondary battery and is characterized by preventing electrode breakage in response to volume expansion of the active material during charging and discharging. Electrolytic copper foil described in any one of claims 1 to 10; and A negative electrode active material layer formed on at least one surface of the above electrolytic copper foil and comprising a carbon-based material or a silicon-based material; A negative electrode (Anode) for a lithium-ion secondary battery including The cathode of Clause 11; anode; A separator interposed between the above-mentioned cathode and anode; and Non-aqueous electrolyte containing lithium salt; A lithium-ion secondary battery including In a method for manufacturing electrolytic copper foil, A step of preparing a base electrolyte comprising 80 to 100 g / L of copper ions, 70 to 90 g / L of sulfuric acid, and 0.1 to 1.0 ppm of chloride ions; A step of adding a compound having an imidazole-2-thione functional group as an organic additive to the above electrolyte at a concentration of 0.5 to 1.5 mg / L; and 70 to 85 A / dm between the cathode drum and the anode plate placed in the above electrolyte 2 The method includes the step of producing an electrolytic copper foil by applying a current density of (ASD); The electrolyte temperature during the above-mentioned foil-making step is maintained at 40 to 48℃, and A method for manufacturing electrolytic copper foil characterized by the thickness of the manufactured electrolytic copper foil being 6 μm or less. In Paragraph 13, The above organic additive consists solely of a compound having the imidazole-2-thione functional group, A method for manufacturing electrolytic copper foil characterized by not including gelatin, hydroxyethyl cellulose (HEC), polyethylene glycol (PEG), and sulfur-containing gloss agents (SPS, MPS). In Paragraph 14, The compound having the imidazole-2-thione functional group is an ethylene thiourea (ETU) compound, and The concentration of the above ethylene thiourea (ETU) compound is in the range of 0.5 to 1.5 mg / L, and A method for manufacturing electrolytic copper foil characterized in that the concentration of the chloride ions is in the range of 0.3 to 0.8 ppm. In an electrolyte composition for manufacturing electrolytic copper foil, 80 to 100 g / L of copper ions; 70 to 90 g / L of sulfuric acid; 0.1 to 1.0 ppm of chloride ions; and A single ethylene thiourea (ETU) additive having a concentration of 0.5 to 1.5 mg / L; comprising, 70 A / dm 2 Tensile strength of 64 kgf / mm at room temperature under the above current densities 2 Electrolyte composition characterized by realizing the above physical properties. In Paragraph 16, The above electrolyte composition is characterized by being free of additives containing oxygen (O) atoms within the molecule. In Paragraph 16, An electrolyte composition characterized by comprising one or more additives selected from polymer additives, gelatin, cellulose (HEC), and sulfonic acid-based polishing agents (SPS), wherein the additive containing oxygen (O) atoms within the above molecule. A replenishing solution for manufacturing electrolytic copper foil, wherein the replenishing solution introduced into a plating bath to maintain the concentration of the electrolyte composition of claim 16 comprises ethylene thiourea (ETU) as an active ingredient and does not contain oxygen-containing organic material.

Images