Surface-treated copper foil for lithium-ion secondary battery, current collector, and lithium-ion secondary battery

Abstract

To provide a surface-treated copper foil for a lithium ion secondary battery, a current collector for the lithium ion secondary battery, and a lithium ion secondary battery.SOLUTION: A surface-treated copper foil for a lithium-ion secondary battery includes a copper layer having a first surface and an opposite second surface, and nickel-containing treatment layers disposed on the first and second surfaces of the copper layer, and each treatment layer has a nickel coating weight of 3.0×104 μg / dm2 or more, and each treatment layer provides a treated surface, and the treated surface has a chromaticity L* value of 30 to 60 and a protruding valley depth Svk of 0.10 to 0.65 μm.SELECTED DRAWING: Figure 2-2

Description

[Technical Field]

[0001] The present disclosure relates to a surface-treated copper foil, and more particularly to a surface-treated copper foil used in a lithium-ion secondary battery containing a solid electrolyte. [Background technology]

[0002] Lithium-ion secondary batteries are widely used in various electronic devices, electric vehicles, and energy storage systems due to their small size, high energy density, long life, fast charging, small memory effect, and low cost, making them indispensable in modern life. To achieve the goal of higher energy density, small volume, and high energy, technologies to improve the performance of lithium-ion secondary batteries are still being developed and innovated.

[0003] Most lithium-ion secondary batteries on the market today primarily use liquid electrolytes containing various organic compounds, but these have drawbacks such as flammability and insufficient stability at high temperatures. Therefore, solid-state batteries (SSBs), which offer safer, more durable, faster charging, and higher capacity, have consistently attracted the most attention. Solid-state electrolytes (SSEs) are used in solid-state batteries and are primarily classified into three types: sulfide, oxide, and organic polymer. Among these, sulfide solid electrolytes offer advantages such as high energy density, high ionic conductivity, low processing temperature, and better thermal stability, and have attracted considerable attention due to their potential for development. However, such batteries are difficult to manufacture, and much research is needed to overcome the commercial challenges of large-scale production and application.

[0004] For example, stainless steel is often used as the negative electrode current collector material for all-solid-state batteries, but its thin film processing is difficult, making it disadvantageous for making batteries smaller and thinner. Furthermore, the electrical conductivity of stainless steel is not sufficiently high, being much lower than that of copper. If copper is used as the negative electrode current collector material to improve electrical conductivity, the copper reacts with sulfur in the solid electrolyte to form copper sulfide, which increases the battery's internal resistance, reduces cycle performance, and increases battery temperature, raising safety concerns and potentially shortening the lifespan of the all-solid-state battery.

[0005] Research has shown that nickel is highly stable in air, and that forming a thin protective film on the surface of copper foil through surface treatments such as nickel plating can improve the abrasion resistance, corrosion resistance, and rust prevention of the copper foil, thereby chemically stabilizing the copper foil within the battery. However, although the nickel-plated protective layer has strong adhesion and is difficult to peel off, the surface-treated copper foil is bent many times during the roll-to-roll production process of lithium-ion secondary batteries, and even small bends (also known as folds) occur near the roll core. This can cause cracks and wrinkles in the nickel-plated protective layer, causing it to lose its functionality and making it difficult to protect the copper foil from corrosion by the solid electrolyte. Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above, the present disclosure provides a surface-treated copper foil for lithium-ion secondary batteries having excellent processability and sulfide corrosion resistance. [Means for solving the problem]

[0007] The surface-treated copper foil for lithium-ion secondary batteries of the present disclosure includes a copper layer and at least one treatment layer. The copper layer has a first surface and an opposite second surface. The treatment layer is formed on the first surface and / or the second surface of the copper layer, and the treatment layer contains nickel. Here, the nickel deposition amount of the treatment layer is 3.0 × 10 4μg / dm 2 The above, the treatment layer provides a treatment surface, and the chromaticity L * The value is 30 to 60, and the protruding valley depth Svk of the treated surface is 0.10 to 0.65 μm.

[0008] In one specific embodiment, the surface-treated copper foil comprises separate treatment layers, each treatment layer formed on a first surface and a second surface of the copper layer, respectively.

[0009] In one specific embodiment, the nickel deposition amount of each treatment layer of the surface-treated copper foil is 3.0×10 4 ~21.5×10 4 μg / dm 2 is.

[0010] In one specific embodiment, the nickel deposition amount of each treatment layer of the surface-treated copper foil is 4.0×10 4 ~20.0×10 4 μg / dm 2 is.

[0011] In one specific embodiment, the nickel deposition amount of each treatment layer of the surface-treated copper foil is 4.5×10 4 ~18.5×10 4 μg / dm 2 is.

[0012] In one specific embodiment, the protruding valley depth Svk of the treated surface of the surface-treated copper foil is 0.10 to 0.45 μm.

[0013] In one specific embodiment, the color of the treated surface of the surface-treated copper foil is * The value is between -5 and 5.

[0014] In one specific embodiment, the color b of the treated surface of the surface-treated copper foil * The value is between -5 and 5.

[0015] In one specific embodiment, the conductivity of the surface-treated copper foil is 3.2×10 7 S / m or more.

[0016] In one specific embodiment, the copper layer of the surface-treated copper foil is an electrolytic copper foil or a rolled copper foil.

[0017] The present disclosure also provides a current collector for a lithium ion secondary battery, comprising the surface-treated copper foil described in the present disclosure.

[0018] The present disclosure also provides a lithium ion secondary battery comprising the current collector described herein. In one specific embodiment, the lithium ion secondary battery comprises a solid electrolyte. [Effects of the Invention]

[0019] The present disclosure relates to the nickel deposition amount of the treatment layer of the surface-treated copper foil, the color L of the treatment surface, and * By controlling the value and the protruding valley depth Svk within a specific range, the problem of cracks occurring after the surface-treated copper foil is bent can be alleviated, and the surface-treated copper foil can be made corrosion-resistant.

[0020] The above summary is not intended to represent every particular embodiment or every aspect of the present disclosure, but rather, the above summary merely provides examples of novel aspects and features of the present disclosure. [Brief explanation of the drawings]

[0021] The accompanying drawings, for illustrative reference, illustrate embodiments of the present invention. [Figure 1] FIG. 1 is a flow diagram of the raw foil preparation and nickel plating process of the present disclosure. [Figure 2-1] FIG. 1 is a schematic diagram of the flex crack test method of the present disclosure. [Figure 2-2] FIG. 1 is a diagram showing that no cracks appear in the nickel plating layer under a scanning electron microscope (SEM). [Figure 2-3] FIG. 1 shows cracks appearing in the nickel plating layer under a scanning electron microscope (SEM). [Figure 3]FIG. 2 is a comparison diagram of the surface-treated copper foil of the present disclosure before and after a corrosion resistance test in a scanning electron microscope (SEM). DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present disclosure will be described with reference to specific specific embodiments, but those skilled in the art will easily understand other benefits and effects of the present disclosure from the disclosure of this specification.

[0023] It should be understood that all ranges and numerical values ​​described herein are inclusive and combinable. When a numerical range is provided, all numerical values ​​between the upper and lower limits of that range, as well as the upper and lower limits of that range, are considered to be disclosed herein. It should be understood that any numerical range described herein is intended to include all subranges subsumed within that range. For example, a range of "1 to 10" is intended to include all subranges between the stated minimum value of 1 and the stated maximum value of 10, i.e., having a minimum value of 1 or greater and a maximum value of 10 or less. Because the disclosed numerical ranges are continuous, they are intended to include every value between the minimum and maximum values.

[0024] Unless otherwise specified, the terms "comprise," "include," "contain," or "have" used herein may further include other elements, such as components, structures, regions, parts, devices, systems, steps, and connections, and do not exclude other elements. In other words, the claimed invention "comprises," "includes," "contains," or "has" a particular element and in fact allows for other unspecified elements, whether or not those elements are required.

[0025] Terms such as "upper" and "lower" used in this specification are not intended to limit the scope of the present invention, but are intended to facilitate the description of specific embodiments of the present invention. As long as the adjustment, replacement, and modification of the relative positions and relationships thereof, and the technical content of the present invention are not substantially changed, they should all be considered to be within the scope of the present invention.

[0026] Unless expressly stated otherwise herein, the singular forms "a," "an," and "the" as used herein can include the plural forms and the term "or" as used herein can be used interchangeably with "and / or."

[0027] The surface-treated copper foil of the present disclosure is a copper layer that has been surface-treated, and therefore includes at least a copper layer and a treatment layer thereon. This copper layer refers to bare copper foil, which may be a rolled copper foil or an electrolytic copper foil. The bare foil is substantially made of copper (e.g., more than 99% by weight of copper). At least one of the first surface and the opposite second surface of the bare foil is surface-treated (e.g., coated), and both the first surface and the second surface may be surface-treated. The treatment layer is formed on the first surface or the second surface of the copper layer in a thickness of 3.0 × 10 4 μg / dm 2 The treatment layer provides a treated surface, and the color of the treated surface is L * The value is 30 to 60, and the protruding valley depth Svk of the treated surface is 0.10 to 0.65 μm.

[0028] In some specific embodiments, raw foil can be produced by electrodeposition (also known as electrolysis, electrolytic deposition, or electroplating) using a foil-forming machine to provide raw foil having a roller surface and a deposition surface. As shown in FIG. 1 , the foil-forming machine can include at least a roller 1 as a cathode, a pair of insoluble metal anode plates 2, and an electrolyte 3 and its supply pipe (not shown). The roller 1 is a rotatable metal roller with a mirror-polished surface. The metal anode plate 2 can be fixedly installed below the roller so as to surround the lower part of the roller. The supply pipe can be fixedly installed directly below the roller 1 and located between the two metal anode plates 2. The roller surface 4a of the copper layer 4 is the surface of the copper layer 4 that contacts the roller 1 used in the electrodeposition process, and the deposition surface 4b is the surface opposite to the roller surface 4a or the surface of the copper layer 4 that contacts the electrolyte 3 in the electrodeposition process to form the copper layer 4. The method for producing raw foil involves partially immersing a rotating roller 1 in an electrolyte 3 containing copper ions. Thus, under the action of an electric current, the copper ions are attracted to the roller 1 and reduced, plating metallic copper onto the surface of the roller 1 and forming an electrolytic copper layer 4 on the surface of the roller 1. In a continuous process, the roller 1 is rotated, and the formed copper layer 4 is removed as the roller 1 and the roller 1 are both removed from the electrolyte 3. For example, in a continuous process, the copper layer 4 can be pulled away from the roller 1 as it forms and move on or through the roller. In a specific embodiment, the roller surface 4a corresponds to the first surface, and the deposition surface 4b corresponds to the second surface.

[0029] To meet the need for high battery capacity, the thickness of the copper layer should not be too thick. In some specific embodiments, the thickness of the raw foil may be 4 μm to 10 μm. The surface condition of the raw foil may affect the morphology of the treatment layer, and in some specific embodiments, a raw foil having a protruding valley depth Svk of 1 μm or less may be selected as the copper layer.

[0030] The surface-treated copper foil of the present disclosure is obtained by surface-treating a raw foil, and therefore the surface-treated copper foil further comprises a treatment layer located on the first or second surface in addition to the raw foil. The treatment layer contains nickel and can protect the raw foil from deterioration such as corrosion. The nickel-containing treatment layer can be prepared by any known method, including immersing or passing the formed raw foil through a nickel-containing solution or plating nickel metal on the formed raw foil (e.g., using an electroplating bath). The process can be continuous or part of the overall process for preparing the surface-treated copper foil. The treatment layer can be formed as two layers on the first and second surfaces, respectively, as needed, or on only one of the surfaces. Depending on the application needs, for example, in button batteries, where only one side of the surface-treated copper foil comes into contact with the electrolyte, forming a treatment layer on that side can prevent corrosion of the surface-treated copper foil.

[0031] The present disclosure has found that the nickel coverage affects the performance of surface-treated copper foil. Nickel slowly oxidizes at room temperature and is generally considered corrosion-resistant. Its atomic size (0.125 nm) is close to that of copper (0.128 nm). Furthermore, the deposition method of nickel atoms is similar to copper's face-centered cubic (FCC) lattice, so nickel has good atomic compatibility with copper. However, nickel has a much lower electrical conductivity than copper. Therefore, if the nickel coverage is too low, e.g., 30,000 μg / dm 2 If the nickel deposition amount is less than 30,000 μg / dm, the effect on conductivity is small, but the corrosion resistance is poor and there is a risk that the copper layer will be corroded by sulfides, which will increase the internal resistance of the battery, raise the battery temperature, reduce the charge / discharge efficiency, and increase the risk of failure or thermal runaway in the all-solid-state battery. 2 If the amount of coating is more than this, corrosion of the copper layer by sulfides can be effectively prevented. Furthermore, if the surface-treated copper foil has the above-mentioned coating amount, it has the property of being resistant to oxidation, and can be applied to all-solid-state batteries (e.g., oxide-based solid electrolyte batteries) that use high-temperature processes.

[0032] Increasing the amount of nickel deposited improves corrosion resistance, but it also reduces the electrical conductivity of the surface-treated copper foil, increasing the internal resistance of the battery and slowing down the charge / discharge rate of the battery. Thus, when trying to control the electrical conductivity of the surface-treated copper foil, it is recommended to keep the amount of nickel deposited at 215,000 μg / dm 2 In the present disclosure, the nickel coating weight of the nickel-containing treatment layer of the surface-treated copper foil must be controlled to 30,000 to 215,000 μg / dm 2 By controlling the thickness within this range, the surface-treated copper foil can have sufficient corrosion resistance against sulfides and maintain the required electrical conductivity. When a nickel-containing treatment layer is provided on a raw foil, the total thickness of the surface-treated copper foil of the present disclosure is about 4.3 μm or more, for example, 4.3 μm to 16 μm, or 5 μm to 15 μm, but is not limited thereto.

[0033] The nickel deposition amount of the treatment layer of the surface-treated copper foil can be controlled by adjusting the electroplating time, current density, and temperature of the plating solution. In one specific embodiment, the electroplating time for nickel plating is 100 to 600 seconds, for example, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, and 600 seconds. In one specific embodiment, the current density for nickel plating is 5 to 20 A / dm 2 , e.g., 5, 10, 15 and 20 A / dm 2 In one specific embodiment, the nickel plating temperature is 40 to 60°C, for example, 40, 45, 50, 55, and 60°C.

[0034] In one specific embodiment, the nickel deposition amount of each treatment layer of the surface-treated copper foil is 3.0×10 4 That's it, 3.0 x 10 4 ~21.5×10 4 μg / dm 2 , 4.0×10 4 ~20.0×10 4 μg / dm 2 , or 4.5 × 10 4 ~18.5×10 4and 210,000 μg / dm 2 , as well as any value between the values ​​exemplified above.

[0035] "Chromaticity" as used herein refers to the CIE color space (L * a * b * The CIE color space is a commonly used international color measurement standard defined by the International Commission on Illumination (CIE). The CIE color space represents color using three values: * " represents the lightness of the color, and L * A value of 0 is defined as black, and a value of 100 indicates white, i.e., L * The larger the value, the closer it is to white. * The smaller the value, the closer to black. * " represents the position between the two opposing colors red / magenta-green in human vision, and a * Positive values ​​indicate a red / magenta color, negative values ​​indicate a green color. * " represents the position between the two opposing colors blue and yellow in human vision, and b * Positive values ​​indicate yellow, negative values ​​indicate blue. The CIE color space is the most complete color model available for representing all colors visible to the human eye, among which L * , a * , b * These three values ​​can detect subtle differences between similar colors. * value, a * value, b * The value conforms to JIS Z 8729 and can be obtained based on the method described in JIS Z 8722 using values ​​measured with a spectrophotometer.

[0036] This disclosure provides chromaticity L * It was found that the L value indicates the surface properties of the surface-treated copper foil. * If the value is 65 to 80, cracks will occur on the surface after bending, and the nickel plating layer will not be able to adequately protect the copper layer in a bending process such as roll-to-roll, and the copper layer will come into contact with the solid electrolyte, causing the all-solid-state battery to fail. * By controlling the value to within the range of 30 to 60, the problem of cracks occurring on the surface after the nickel-plated copper layer is bent can be alleviated.

[0037] L of the treated surface of surface-treated copper foil * The value can be controlled by adjusting the total organic carbon (TOC) concentration in the nickel plating solution, the electroplating time, the current density, and the temperature. In one specific embodiment, the total organic carbon concentration can be achieved by adjusting the concentration of additives such as brighteners. In one specific embodiment, the brightener may be saccharin and / or polyethylene glycol (PEG), and the content thereof may be 30 to 100 ppm. In one specific embodiment, the brightener is a 1:1 ratio of saccharin to PEG. In one specific embodiment, the electroplating time for nickel plating is 100 to 600 seconds. In one specific embodiment, the current density for nickel plating is 5 to 20 A / dm 2 In one specific embodiment, the nickel plating temperature is 40 to 60°C.

[0038] In one specific embodiment, the color L of the treated surface of the surface-treated copper foil * Values ​​range from 30 to 60, for example, 30, 35, 40, 45, 50, 55 and 60, and any value between the above exemplified values.

[0039] In one specific embodiment, the color of the treated surface of the surface-treated copper foil is *The value ranges from -5 to 5, for example, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4 and 5, and any value between the above exemplified values.

[0040] In one specific embodiment, the color b of the treated surface of the surface-treated copper foil * The value ranges from -5 to 5, for example, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4 and 5, and any value between the above exemplified values.

[0041] As used herein, "protruding valley depth" and "Svk" are the same term and are used as a parameter to describe the surface profile, representing the average depth of the protruding valleys below the core in the surface profile. Protruding valley depth Svk is based on ISO 25178-2:2012 and can be measured using a laser microscope.

[0042] The present disclosure has found that the depressions (related to the protruding valley depth Svk) on the surface of a surface-treated copper foil affect the flex resistance of the surface-treated copper foil, as well as the adhesion and coating uniformity of a negative electrode material. From the viewpoint of flex resistance, if the protruding valley depth Svk value is too small, the surface becomes too smooth and is poorly able to withstand elongation stress. When bent, the outer edge of the bent portion undergoes significant deformation, which presumably causes cracks to occur at the bent portion and ultimately makes the foil more susceptible to fracture. On the other hand, if the protruding valley depth Svk is too large, the depressions on the surface of the surface-treated copper foil become too deep, resulting in insufficient mechanical strength at the depressions and making cracks more likely to occur even after bending. In the present disclosure, the problem of cracks occurring after bending of the surface-treated copper foil can be improved by controlling the protruding valley depth Svk value of the surface (i.e., the treated surface) of the surface-treated copper foil to a range of 0.10 to 0.65 μm. Regarding coating uniformity, if the value of the protruding valley depth Svk is too large, the negative electrode material will be unevenly coated, for example, resulting in excessive deposition in the recesses. By controlling the value of the protruding valley depth Svk within an appropriate range, for example, 0.65 μm or less, the coating uniformity of the negative electrode material will be good, and by controlling it to 0.45 μm or less, the coating uniformity of the negative electrode material will be even better.

[0043] The protruding valley depth (Svk) of the surface-treated copper foil can be controlled by adjusting the total organic carbon (TOC) concentration in the nickel plating solution, the electroplating time, the current density, and the temperature. In one specific embodiment, the total organic carbon concentration can be achieved by an additive such as a brightener. The addition of a brightener to the electroplating process can improve the porosity, brightness, dispersibility of the plating solution, and the ability to plate deeply. Brighteners are typically stable and provide high stretchability within a wide range of current densities, making the deposited metal layer bright, flat, and easy to stretch. Examples of brighteners include, but are not limited to, combinations of metal salts, 2-butyne-1,4-diol, saccharin, polycondensates of epoxy compounds, pyridine derivatives, acetylene amine compounds, and propargyl alcohol derivatives. In one specific embodiment, the brightener is saccharin and / or polyethylene glycol (PEG). In one specific embodiment, the brightener is a 1:1 ratio of saccharin to PEG. In one specific embodiment, the concentration of the brightener is 30 to 100 ppm. In one specific embodiment, the electroplating time for nickel plating is 100 to 600 seconds. In one specific embodiment, the current density for nickel plating is 5 to 20 A / dm 2 In one specific embodiment, the nickel plating temperature is 40 to 60°C.

[0044] In one specific embodiment, the protruding valley depth Svk of the treated surface of the surface-treated copper foil is in the range of 0.10 to 0.65 μm, for example, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, and 0.65 μm, and any value between the values ​​exemplified above.

[0045] In one specific embodiment, the conductivity of the surface-treated copper foil is 3.2×10 7 S / m or more.

[0046] In one specific embodiment, the surface-treated copper foil can be a current collector in a battery, such as a lithium-ion secondary battery, and the current collector can be a positive electrode current collector and / or a negative electrode current collector. In one specific embodiment, the battery includes, for example, a laminated structure of a copper negative electrode current collector, a negative electrode active material, a separator, a positive electrode active material, and a positive electrode current collector. At least one side of the surface-treated copper foil of the present disclosure is coated with an active material. By way of example, the active material may include, but is not limited to, carbon, silicon, germanium, and combinations or mixtures thereof.

[0047] The present disclosure also provides a lithium ion secondary battery including the current collector of the present disclosure.

[0048] The electrolyte solution of the lithium-ion secondary battery of the present disclosure may include a solid electrolyte. The solid electrolyte may be, but is not limited to, a crystalline electrolyte, a glass electrolyte, a glass ceramic electrolyte, or a polymer electrolyte. Specifically, the crystalline electrolyte may be, but is not limited to, a sulfide solid electrolyte such as a lithium superionic conductor (LISICON) type or an argyrodite type, or an oxide solid electrolyte such as a garnet type, a perovskite type, or a NASICON structure type. The glassy electrolyte may be, but is not limited to, a glassy solid electrolyte such as an oxide or a sulfide. The polymer electrolyte may be a pure solid polymer electrolyte such as a polyethylene oxide-based (PEO-based) or polypropylene oxide-based (PPO-based) electrolyte, or a gel-type polymer electrolyte such as a polyacrylonitrile-based (PAN-based) electrolyte, a poly(methyl methacrylate)-based (PMMA-based) electrolyte, a poly(vinyl chloride)-based (PVC-based) electrolyte, or a poly(vinylidene fluoride)-based (PVDF-based) electrolyte, but is not limited to these.

[0049] The surface-treated copper foils in specific embodiments disclosed herein can be used in devices, such as any article or component that requires electricity for its operation. For example, independent, separate, or mobile components and devices require small, lightweight batteries. Examples of such devices include, but are not limited to, vehicles (e.g., automobiles, trains, buses, trucks, ships, submarines, and airplanes), computers (e.g., microcontrollers, laptops, and tablet computers), phones (e.g., smartphones and walkie-talkies), personal health monitoring and maintenance devices (e.g., blood glucose monitors and heart rate monitors), tools (e.g., drills and chainsaws), lighting devices (e.g., flashlights, emergency lights, and signs), handheld measuring devices (e.g., pH meters and air quality monitoring devices), and dwelling units (e.g., spacecraft, trailers, homes, airplanes, and submarines).

[0050] In one specific embodiment, the lithium ion secondary battery may be, but is not limited to, a stacked lithium ion secondary battery including a negative electrode and a positive electrode stacked with a separator film interposed therebetween, or a spirally wound stacked lithium ion secondary battery including continuous electrodes and a separator film wound together in a spiral shape. The lithium ion secondary battery of the present disclosure can be manufactured as, for example, but not limited to, a laminated secondary battery, a cylindrical secondary battery, a prismatic secondary battery, a pouch-type secondary battery, or a button-type secondary battery according to different application devices. [Example]

[0051] Further, the present invention will be described in more detail in the following examples. However, the interpretation of the present disclosure should not be limited to the description of the following examples. It should be understood that within the scope of the present disclosure, the technical features mentioned above and below (e.g., examples) can be freely combined with each other to form new or preferred technical solutions, and are omitted for brevity.

[0052] Examples and Comparative Examples

[0053] A. Preparation of Raw Foil

[0054] The copper wire was dissolved in a 50 wt% aqueous sulfuric acid solution to prepare an electrolyte. The copper sulfate electrolyte contained 320 g / L of copper sulfate (CuSO4·5H2O) and 85 g / L of sulfuric acid. The chloride ion concentration in the copper sulfate electrolyte was 35 ppm.

[0055] The raw foil was produced by electrodeposition on a rotating roller, which was partially immersed in the copper sulfate electrolyte described above. The roller was the cathode opposite the anode electrode, and copper ions in the electrolyte were continuously deposited on the roller. 10 A / dm 2 The temperature of the electrolyte was controlled at 48°C using a current density of 1000 kJ / cm, and raw foils with a thickness of 4 to 10 μm were produced.

[0056] B. Nickel plating

[0057] Next, an electroplating solution containing 350 g / L of nickel sulfate (NiSO4), 80 g / L of boric acid, and 15 g / L of sodium hypochlorite was placed, in which the chloride ion concentration was 15 ppm and the concentration of the brightener (saccharin:PEG = 1:1) was 10 to 300 ppm.

[0058] As shown in Figure 1, the raw foil was passed through a series of guide rollers and transported to a nickel plating device, where it was subjected to nickel plating. The raw foil was immersed in a treatment tank containing the electroplating solution 5, and nickel plating layers were formed on the first and second surfaces of the raw foil by electrodeposition using two pairs of electrode plates 6. The nickel plating layers were formed at a current of 5 to 30 A / dm 2 The temperature of the electroplating solution was controlled to 20 to 80°C using a current density of 1000 kJ / min, and electroplating was carried out for 60 to 600 seconds to produce a nickel-plated surface-treated copper foil.

[0059] After the nickel plating process was completed, the nickel-plated surface-treated copper foil was guided through a series of guide rollers, and an air knife 7 was used to remove excess electroplating solution and other substances from the surface. The foil was then dried and wound up to obtain a surface-treated copper foil. The parameters for producing the surface-treated copper foil are shown in Table 1 below.

[0060] [Table 1]

[0061] C. Measurement

[0062] (I) Chromaticity (CIE L * a * b * ) The surface-treated copper foils produced in the examples and comparative examples were analyzed for color, and the L * value, a * The b* and b* values ​​were measured. Standard: L listed in JIS Z 8729 (2004) * Value a * Value b * Color value system Measurement equipment: Spectrophotometer (Konica Minolta, CM2500c). Measured values ​​are based on the method of JIS Z 8722 (2000). Lighting and receiving method: 45 / 0 (45° ring lighting, vertical receiving) Observation angle (observer): 2° Wavelength range: 360~740nm Wavelength spacing: 10nm Reflectance range: 0-175%, resolution 0.01% Measurement time: 1.5 seconds Measurement / Irradiation diameter: Φ7mm / Φ11mm Light source (illuminator): D65 daylight

[0063] (II) Protrusion valley depth Svk The surface profile of the surface-treated copper foils produced in the examples and comparative examples was analyzed, and the protruding valley depth Svk of the surface-treated copper foils was measured. Standard:ISO 25178-2(2012) Equipment: Laser microscope (LEXT OLS5000-SAF, Olympus) Light source wavelength: 405nm Objective lens magnification: 100x objective lens (MPLAPON-100x LEXT, Olympus) Optical zoom: 1.0x Observation area: 129 μm x 129 μm Resolution: 1024 pixels x 1024 pixels Condition: Enable the automatic tilt removal function of the laser microscope (Auto tilt removal) Filter: Unfiltered Air temperature: 24±3℃ Relative humidity: 63±3%

[0064] (III) Nickel deposition amount The surface-treated copper foils produced in the examples and comparative examples were analyzed by inductively coupled plasma (ICP) to measure the amount of nickel deposited on the surface-treated copper foils. Sample preparation: Cut the surface-treated copper foil into a size of 150 x 150 mm, apply tape to one side of the surface-treated copper foil to prevent it from dissolving, and then cut the surface-treated copper foil into a size of 100 mm x 100 mm (area = 1 dm 2 ) and used as test samples. 20 mL of 18% HCl was placed in a rectangular container with a bottom side length of 120 x 120 mm. The sample was immersed in the container, with the tape side of the sample facing the bottom of the container. During the immersion process, the container was continuously rocked from side to side, with a rocking distance of approximately 5 cm on each side. This was counted as one rocking motion, and the rocking frequency was 6 times per minute. After 7.5 minutes of immersion, an additional 2 mL of 30% hydrogen peroxide solution was added to the rectangular container, and the container was shaken repeatedly until the nickel layer on the side not protected by tape had completely dissolved and the original color of the surface-treated copper foil was revealed. The container was then stopped and the sample removed. The solution was then poured into a 50 mL measuring flask and filled with deionized water to a liquid level of 50 mL. Analysis: The nickel content of the above 50 mL solution was measured using an inductively coupled plasma atomic emission spectrometer (ICP-AES), where argon was used as the carrier gas and the nebulizer flow rate was 0.5 L / min. Equipment: Thermo Scientific TM iCAP TM7400 ICP-OES Duo MFC

[0065] (IV) Flexural cracks Each surface-treated copper foil was tested for the occurrence of cracks or wrinkles after bending. Test method: As shown in Figure 2-1, a surface-treated copper foil sample of 80 mm (TD) x 200 mm (MD) was taken and first bent in the front using a PVC pipe 91 with a nominal pipe diameter of 1 / 2" (outside diameter 1 / 2 mm). A 100 g weight 92 was applied to each end of the surface-treated copper foil and held for 10 seconds, after which the reverse side was bent. This front-to-reverse bending was counted as one bending, and a total of 10 bendings were performed. The surface condition of the nickel plating layer was then observed at 800x magnification using a scanning electron microscope (SEM). The results of no cracks being apparent are shown in Figure 2-2. The results of crack appearance are shown in Figure 2-3.

[0066] (V) Coating uniformity of negative electrode material The coating uniformity of the negative electrode material on each surface-treated copper foil was tested. The negative electrode materials, test methods, and test standards used were as follows: In preparing the negative electrode material, water was used as a solvent, and a negative electrode material with a liquid-solid ratio of 73% (100 g of negative electrode material: 73 g of water) was used as shown in the table below. [Table A] After mixing the components of the negative electrode material formulation, the negative electrode material was applied to the surface of the surface-treated copper foil at a speed of 5 m / min to a thickness of 200 μm and then dried in an oven at 120°C for 1 hour. The negative electrode (surface-treated copper foil + negative electrode material) was then pressed using a press. The roller size of the press was φ250 mm x 250 mm, with a hardness of 62-65 HRC, and the roller material was high-carbon chromium bearing steel (SUJ2). The negative electrode was produced by pressing at a pressing (rolling) speed of 1 m / min and a pressure of 3000 psi. The negative electrode was cut into multiple test pieces of 50 x 50 mm, a total of 10 test pieces were taken, and these were weighed on an electronic balance to confirm the deviation between each weight value and the average weight value. If the weight deviation is less than 0.3%, it is considered very uniform (◎). If the weight deviation is 0.3 to 0.5%, it is considered uniform (◯). If the weight deviation is 0.5-1.5%, it is considered non-uniform (△); If the weight deviation is more than 1.5%, it is considered very non-uniform (x).

[0067] (VI) Electrical conductivity The conductivity of each surface-treated copper foil was tested, and the test methods, standards, and parameters used were as follows: Method: Conductivity was measured using the four-probe method, where measurements were taken at three random locations, and the conductivity value of the surface-treated copper foil was calculated from the measured surface resistance value. The arithmetic mean value of the conductivity at the three locations was calculated and used as the conductivity value. Standard: IPC TM650 2.5.14 Equipment: LRS4-TG2 (KeithLink) Probe diameter: 100μm Needle pitch: 1.6 mm Pressure: 100g Volume resistivity conversion factor: 4.532 Sample size: 100mm x 100mm Environmental temperature: 25℃

[0068] (VII) Sulfur corrosion resistance (FoS) The sulfur corrosion resistance of each surface-treated copper foil was tested using the following test method. Method: A typical wet sulfur vapor test method in which the sample is exposed to sulfur vapor. Standard: ASTM B809-95 1. First, the surface morphology of the surface-treated copper foil was observed and confirmed using a scanning electron microscope (SEM). 2. After the surface-treated copper foil was subjected to a flex crack test, it was cut into a 50 mm x 50 mm sample. 3. Nitrogen pre-bake was performed, in which the samples were first placed in a nitrogen oven at 50°C for 24 hours (nitrogen injection pressure 10 psi, nitrogen flow rate 1 liter / min) to prevent organic volatile gases from being generated during the test and affecting the FoS test results. 4. Excess sulfur was placed in a sealed glass container, and the sample was suspended in the glass container and maintained at 50°C and a relative humidity of 82%. The sample was exposed to a saturated sulfur vapor environment and then removed after 24 hours. 5. As shown in Figure 3, the surface morphology of the surface-treated copper foil in the wet sulfur vapor test was observed with a scanning electron microscope (SEM), and if copper sulfide particles appeared on the surface, it was deemed to have failed.

[0069] The color of each surface-treated copper foil obtained by the above test method (L * a * b * ), protruding valley depth Svk, nickel coating weight, presence or absence of cracks after bending, coating uniformity, conductivity, and corrosion resistance are shown in Table 2 below.

[0070] [Table 2-1] [Table 2-2]

[0071] From the above results, the surface-treated copper foil of the present disclosure has a nickel coating amount in the treatment layer, a color index L * It has been found that by controlling the value of the surface roughness and the protruding valley depth Svk, the problem of cracks occurring on the surface after bending can be improved and good corrosion resistance can be achieved. Furthermore, the surface-treated copper foil of the present disclosure also exhibits better coating uniformity when applying a negative electrode material.

[0072] Specifically, in the corrosion resistance test, the surface-treated copper foils of Examples 1 to 16 of the present disclosure had a nickel coating amount in the treatment layer, a color index L *By controlling the value of σ and the protruding valley depth Svk, the treatment layer exhibits a protective effect and good corrosion resistance is obtained, whereas the surface-treated copper foils of Comparative Examples 1 to 9 have poor protection of the treatment layer and are not resistant to corrosion, so the copper on the surface reacts with wet sulfur vapor to form copper sulfide. * If the value and the protruding valley depth Svk are too high or too low, cracks are likely to occur after bending the surface-treated copper foil, and the color L * It was found that by controlling the value within an appropriate range (e.g., between 30 and 60) and the protruding valley depth Svk within an appropriate range (e.g., between 0.10 and 0.65 μm), the treatment layer can be stabilized against bending, making it less susceptible to cracking. A coating uniformity test of the negative electrode material showed that the coating uniformity worsens as the protruding valley depth Svk increases, and that when the protruding valley depth Svk exceeds 0.65 μm, the coating of the negative electrode material becomes uneven.

[0073] Furthermore, the above results indicate that the amount of nickel deposited in the treatment layer affects the conductivity of the surface-treated copper foil. If the amount of nickel deposited is too high, for example, in Examples 15 and 16, the amount of nickel deposited was 21.5 × 10 4 μg / dm 2 If the nickel deposition amount exceeds 3.0×10, the conductivity may decrease. 4 ~21.5×10 4 μg / dm 2 ) can further improve the conductivity.

[0074] Furthermore, the above results also revealed that the application uniformity of the negative electrode material can be further improved by adjusting the protruding valley depth Svk. For example, if the protruding valley depth Svk is 0.65 μm or less, the application uniformity of the negative electrode material meets the requirements, but if the protruding valley depth Svk is further controlled to 0.45 μm or less, the application uniformity of the negative electrode material can be further improved. [Explanation of symbols]

[0075] 1: Laura 2: Metal anode plate 3: Electrolyte 4: Copper layer 4a: Roller surface 4b: Deposition surface 5: Electroplating solution 6: Electrode plate 7: Air knife 91: PVC pipe 92: Weight

Claims

1. a copper layer having a first surface and an opposing second surface; a treatment layer formed on the first surface or the second surface of the copper layer; A surface-treated copper foil for a lithium ion secondary battery, comprising: the treatment layer contains nickel, The amount of nickel deposited in the treatment layer is 3.0 × 10 ４ μg / dm ２ That's all, the treatment layer provides a treatment surface; The chromaticity L of the treated surface ＊ value is 30 to 60, and the protruding valley depth Svk of the treated surface is 0.10 to 0.65 μm; A surface-treated copper foil characterized by:

2. The surface-treated copper foil includes another treatment layer, Each treatment layer is formed on a first surface and a second surface of the copper layer, respectively. The surface-treated copper foil according to claim 1.

3. The amount of nickel deposited in the treatment layer is 3.0 × 10 ４ ~21.5 x 10 ４ μg / dm ２ The surface-treated copper foil according to claim 1,

4. The amount of nickel deposited in the treatment layer is 4.0 × 10 ４ ~20.0 x 10 ４ μg / dm ２ The surface-treated copper foil according to claim 1,

5. The amount of nickel deposited in the treatment layer is 4.5 × 10 ４ ~18.5 x 10 ４ μg / dm ２ The surface-treated copper foil according to claim 1,

6. 2. The surface-treated copper foil according to claim 1, wherein the protruding valley depth Svk of the treated surface is 0.10 to 0.45 μm.

7. Chromaticity a of the treated surface ＊ The surface-treated copper foil according to claim 1, wherein the value is −5 to 5.

8. The surface-treated copper foil according to claim 1, wherein the chromaticity b* value of the treated surface is −5 to 5.

9. The conductivity of the surface-treated copper foil is 3.2 × 10 ７ The surface-treated copper foil according to claim 1, wherein the surface roughness is S / m or more.

10. The surface-treated copper foil according to claim 1, wherein the copper layer is an electrolytic copper foil or a rolled copper foil.

11. A current collector for a lithium ion secondary battery, comprising the surface-treated copper foil according to any one of claims 1 to 10.

12. A lithium ion secondary battery comprising the current collector according to claim 11.

13. 13. The lithium ion secondary battery of claim 12, wherein the lithium ion secondary battery comprises a solid electrolyte.

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