KR20240078586A - Copper Foil, Electrode Comprising The Same, Secondary Battery Comprising The Same, and Method for Manufacturing The Same - Google Patents

Abstract

One embodiment of the present invention is a copper foil that includes a copper film containing 99.9% by weight or more of copper and has an R value in the range of 2.0 to 3.5. The R is calculated using Equation 1 below, [Equation 1] R = log(WA/WB)/log(tA/tB)
WA in Equation 1 is calculated by Equation 2 below, [Equation 2] WA = [XA0+(XA45)X2+XA90]/4 WB in Equation 1 is calculated by Equation 3 below, [Equation 3] WB = [ XB0 + (XB45) , It refers to the width of the central part in the tensile direction after tensioning of the test specimen.

Description

Copper foil, electrode containing the same, secondary battery containing the same, and method for manufacturing the same {Copper Foil, Electrode Comprising The Same, Secondary Battery Comprising The Same, and Method for Manufacturing The Same}

The present invention relates to copper foil, an electrode containing it, a secondary battery containing it, and a method of manufacturing the same.

A secondary battery is a type of energy conversion device that generates electricity by converting electrical energy into chemical energy, storing it, and then converting the chemical energy back into electrical energy when electricity is needed. It is used in portable home appliances such as mobile phones and laptops, as well as electric vehicles. It is used as an energy source. Secondary batteries are also referred to as rechargeable batteries because they can be recharged.

Secondary batteries that have economical and environmental advantages over disposable primary batteries include lead acid batteries, nickel cadmium secondary batteries, nickel hydride secondary batteries, and lithium secondary batteries.

In particular, lithium secondary batteries can store a relatively large amount of energy relative to their size and weight compared to other secondary batteries. Therefore, lithium secondary batteries are preferred in the field of information and communication devices where portability and mobility are important, and their application range is also expanding to energy storage devices for hybrid vehicles and electric vehicles.

Lithium secondary batteries are used repeatedly through charging and discharging in one cycle. When operating a device with a fully charged lithium secondary battery, the lithium ion secondary battery must have a high charge/discharge capacity in order to increase the operation time of the device. Therefore, research is continuously required to meet consumers' ever-increasing expectations (needs) regarding the charge/discharge capacity of lithium secondary batteries.

These secondary batteries include a negative electrode current collector made of copper foil. Among copper foils, electrolytic copper foil is widely used as a negative electrode current collector for secondary batteries. As the acceptance of secondary batteries increases and the demand for high-capacity, high-efficiency, and high-quality secondary batteries increases, electrolytic copper foil that can improve the characteristics of secondary batteries is required. In particular, there is a demand for electrolytic copper foil that can increase the capacity of secondary batteries and ensure stable capacity maintenance and performance.

Meanwhile, as the thickness of the copper foil increases, the amount of active material that can be contained in the same space increases, and the number of current collectors can increase, thereby increasing the capacity of the secondary battery. However, the thinner the copper foil is, the more curls occur, which causes defects such as tears or wrinkles in the copper foil due to curling of the edges when winding the copper foil, so it is in the form of a very thin film. There are difficulties in manufacturing copper foil. Therefore, in order to manufacture copper foil having a very thin thickness, curling of the copper foil must be prevented.

Accordingly, the present invention relates to copper foil, an electrode containing the same, a secondary battery containing the same, and a manufacturing method thereof that can prevent problems caused by the limitations and disadvantages of the related technology as described above.

One embodiment of the present invention is to provide a copper foil that does not curl, wrinkle, or tear during the manufacturing process by having an R value in the range of 2.0 to 3.5.

Another embodiment of the present invention seeks to provide an electrode for a secondary battery including such copper foil, and a secondary battery including the electrode for such a secondary battery.

Another embodiment of the present invention seeks to provide a method of manufacturing copper foil that prevents curling, wrinkling, or tearing.

In addition to the aspects of the present invention mentioned above, other features and advantages of the present invention will be described below, or may be clearly understood by those skilled in the art from such description.

One embodiment of the present invention provides a copper foil that includes a copper film containing 99.9% by weight or more of copper and has an R value in the range of 2.0 to 3.5. The R is calculated using Equation 1 below, [Equation 1] R = log(WA/WB)/log(tA/tB) WA in Equation 1 is calculated using Equation 2 below, [Equation 2] WA = [XA0+ (XA45) refers to the thickness, tB in Equation 1 refers to the thickness of the test specimen after the tensile test, and XA0, XA45, and Means the width of, and XB0, XB45, and

Another embodiment of the present invention includes preparing an electrolyte solution containing copper ions, forming a copper film, and forming a protective layer on the copper film, wherein the step of forming the copper film includes, A step of forming a copper film on the rotating cathode drum by energizing a positive electrode plate and a rotating cathode drum disposed spaced apart from each other in an electrolyte solution in an electrolytic cell, wherein the electrolyte solution contains 70 to 100 g/L of copper ions and 70 to 150 g of copper ions. /L sulfuric acid, 15 to 25 ppm chlorine (Cl), 1 to 100 ppm lead (Pb), 0.3 to 5 ppm tungsten (W), 1 to 10 ml/L hydrogen peroxide and organic additives, The organic additive includes at least one of a brightener (component A), a moderator (component B), and a leveling agent (component C), the brightener (component A) contains sulfonic acid or a metal salt thereof, and the moderator (B component) includes a nonionic water-soluble polymer, and the leveling agent (component C) includes at least one of nitrogen (N) and sulfur (S).

According to another embodiment of the present invention, copper foil; and an active material layer disposed on at least one surface of the copper foil.

According to another embodiment of the present invention, a cathode that provides lithium ions when charging; A cathode (anode) that provides electrons and lithium ions during discharge; an electrolyte disposed between the anode and the cathode to provide an environment in which lithium ions can move; and a separator that electrically insulates the positive electrode and the negative electrode.

According to the present invention, the occurrence of wrinkles or tears during the manufacturing process of copper foil is prevented, and by using this copper foil to manufacture intermediate parts and final products such as flexible printed circuit boards (FPCB) and secondary batteries, the intermediate parts are Of course, the productivity of final products can be improved.

1 is a cross-sectional view of a copper foil according to an embodiment of the present invention.
Figure 2 is a cross-sectional view of copper foil according to another embodiment of the present invention.
Figure 3 is a cross-sectional view of an electrode for a secondary battery according to another embodiment of the present invention.
Figure 4 is a cross-sectional view of an electrode for a secondary battery according to another embodiment of the present invention.
Figure 5 is a schematic cross-sectional view of a secondary battery according to another embodiment of the present invention.
Figure 6 shows a copper foil manufacturing apparatus according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. However, the embodiments described below are provided for illustrative purposes only to facilitate a clear understanding of the present invention, and do not limit the scope of the present invention.

The shape, size, ratio, angle, number, etc. shown in the drawings for explaining embodiments of the present invention are illustrative, and the present invention is not limited to the matters shown in the drawings. Like components may be referred to by the same reference numerals throughout the specification. In describing the present invention, if it is determined that a detailed description of related known technology may unnecessarily obscure the gist of the present invention, the detailed description is omitted.

When 'includes', 'has', 'consists of', etc. mentioned in this specification are used, other parts may be added unless the expression 'only' is used. If a component is expressed in the singular, the plural is included unless specifically stated otherwise. In addition, when interpreting components, it is interpreted to include the margin of error even if there is no separate explicit description.

In the case of a description of a positional relationship, for example, if the positional relationship of two parts is described as 'on top', 'on the top', 'on the bottom', 'next to', etc., 'immediately' Alternatively, one or more other parts may be placed between the two parts, unless the expression 'directly' is used.

Spatially relative terms such as “below, beneath,” “lower,” “above,” and “upper” refer to one element or component as shown in the drawing. It can be used to easily describe the correlation with other elements or components. Spatially relative terms should be understood as terms that include different directions of the element during use or operation in addition to the direction shown in the drawings. For example, if an element shown in the drawings is turned over, an element described as “below” or “beneath” another element may be placed “above” the other element. Accordingly, the illustrative term “down” may include both downward and upward directions. Likewise, the illustrative terms “up” or “on” can include both up and down directions.

In the case of a description of a temporal relationship, for example, if a temporal relationship is described as 'after', 'successfully after', 'after', 'before', etc., 'immediately' or 'directly' Unless the expression is used, non-continuous cases may also be included.

Although first, second, etc. are used to describe various components, these components are not limited by these terms. These terms are merely used to distinguish one component from another. Accordingly, the first component mentioned below may also be the second component within the technical spirit of the present invention.

The term “at least one” should be understood to include all possible combinations from one or more related items. For example, “at least one of the first, second, and third items” means each of the first, second, or third items, as well as two of the first, second, and third items. It can mean a combination of all items that can be presented from more than one.

Each feature of the various embodiments of the present invention can be combined or combined with each other, partially or entirely, and various technological interconnections and operations are possible, and each embodiment may be implemented independently of each other or may be implemented together in a related relationship. It may be possible.

Figure 1 is a cross-sectional view of copper foil 110 according to an embodiment of the present invention.

Referring to FIG. 1, the copper foil 110 of the present invention includes a copper film 111 containing 99.9% by weight or more of copper and a protective layer 112 on the copper film 111. In the copper foil 110 shown in FIG. 1, the protective layer 112 is formed on one surface of the copper film 111, but embodiments of the present invention are not limited thereto. Referring to FIG. 2, a protective layer 112 may be formed on both sides of the copper film 111.

The copper film 111 can be formed on a rotating cathode drum through electroplating, and has a shiny side that directly contacts the rotating cathode drum during the electroplating process and a mat side on the opposite side.

The protective layer 112 is formed by electrodepositing an anticorrosion material on the copper film 111. The rust preventive material may include at least one of a chromium compound, a silane compound, and a nitrogen compound. The protective layer 112 prevents oxidation and corrosion of the copper film 111 and improves heat resistance, thereby extending the lifespan of the copper foil 110 itself as well as the lifespan of the final product containing it.

According to one embodiment of the present invention, the copper foil 110 has an R value in the range of 2.0 to 3.5. The R value can be obtained by measuring and calculating WA, WB, tA, and tB, respectively, and calculating the measured and calculated values of WA, WB, tA, and tB according to Equation 1 below.

[Equation 1]

R = log(WA/WB)/log(tA/tB)

tA in Equation 1 refers to the thickness of the test piece before the tensile test, and tB in Equation 1 refers to the thickness of the test piece after the tensile test.

The WA and WB can be obtained by calculating according to Equations 2 and 3 below. First, the copper foil 110 is sampled in three directions of 0°, 45°, and 90° in the MD direction, and a tensile test in the axial direction is performed on each of the collected copper foils under the condition of a UTM tensile test speed of 5 mm/min. At this time, the tensile test is conducted until the copper foil collected with a universal testing machine (UTM) grows by 15% after tensioning compared to before tensioning. In addition, by measuring the width of the central portion in the tensile direction before and after the tensile test of the collected copper foil, XA0, XA45, XA90, XB0, XB45, and

[Equation 2]

WA = [XA0+(XA45)X2+XA90]/4

[Equation 3]

WB = [XB0+(XB45)X2+XB90]/4

XA0, XA45, and

XB0, XB45, and

According to one embodiment of the present invention, the copper foil 110 may have an R value in the range of 2.0 to 3.5.

If the R value of the copper foil 110 is less than 2.0, the change in thickness of the copper foil 110 is large compared to the change in the width of the copper foil 110, so wrinkles or tears may occur during the manufacturing process of the copper foil 110, resulting in work Performance decreases and the defect rate of secondary batteries increases.

On the other hand, when the R value of the copper foil 110 is greater than 3.5, the change in the width of the copper foil 110 is large compared to the change in the thickness of the copper foil 110, so wrinkles or tears may occur during the manufacturing process of the copper foil 110. As a result, workability deteriorates and the defect rate of secondary batteries increases.

Copper foil 110 according to an embodiment of the present invention may have a thickness of 4 to 35 ㎛. When copper foil 110 is used as a current collector for an electrode in a secondary battery, the thinner the copper foil 110 is, the more current collectors can be accommodated in the same space, which is advantageous for increasing the capacity of the secondary battery. However, manufacturing copper foil 110 with a thickness of less than 4 μm causes a decrease in workability.

On the other hand, when a secondary battery is manufactured with copper foil 110 exceeding 35 ㎛, it becomes difficult to implement high capacity due to the thick copper foil 110.

Copper foil 110 according to an embodiment of the present invention may have a tensile strength of 45 kg/mm ² or more. In order to suppress wrinkles and tears of the copper foil 110, the copper foil 110 of the present invention has a high tensile strength of 45 kg/mm2 or more. If the tensile strength of the copper foil 110 is less than 45 kg/mm2, the copper foil 110 may be folded between two adjacent rolls during the roll-to-roll manufacturing process, or wrinkles may occur on the left and right end portions of the copper foil 110 during the roll-to-roll manufacturing process. It is caused.

Copper foil 110 according to an embodiment of the present invention may have an elongation of 3 to 13%.

If the elongation of the copper foil 110 is less than 3%, when the copper foil 110 is used as a current collector for a secondary battery, there is a high risk that the copper foil 110 will not be sufficiently stretched and torn in response to the large volume expansion of the high-capacity active material.

On the other hand, if the elongation of the copper foil 110 is greater than 13%, the copper foil 110 may easily be stretched during the manufacturing process of electrodes for secondary batteries, resulting in deformation of the electrode.

According to one embodiment of the present invention, the copper foil 110 may have a 10-point average roughness (Rz) of 0.7 to 0.9 ㎛.

As charging and discharging of the secondary battery is repeated, contraction and expansion of the active material layer occur alternately, which causes separation of the active material layer and the copper foil 110, thereby lowering the charging and discharging efficiency of the secondary battery. Therefore, in order for the secondary electrode to secure a capacity retention rate and lifespan above a certain level (i.e., to suppress a decrease in charging and discharging efficiency of the secondary battery), the copper foil 110 has excellent coating properties with respect to the active material. The adhesive strength of the active material layer must be high.

Specifically, as the 10-point average roughness (Rz) of the copper foil 110 is smaller, the charge/discharge efficiency of the secondary battery including the copper foil 110 tends to decrease to a lesser extent. Therefore, according to one embodiment of the present invention, the copper foil 110 has a 10-point average roughness (Rz) of 0.7 to 0.9㎛.

When the 10-point average roughness (Rz) of the copper foil 110 is less than 0.7, the surface area of the copper foil 110 is relatively small, so the active material is easily separated from the copper foil 110, and as a result, the secondary battery is damaged due to repeated charging and discharging. This causes a rapid decrease in lifespan.

On the other hand, when the 10-point average roughness (Rz) of the copper foil 110 is greater than 0.9, the uniformity of contact between the copper foil 110 and the active material layer does not reach a certain level, resulting in a large number of spaces between the copper foil 110 and the active material layer. exist (i.e., the coating itself is partially not completed), and as a result, the lifespan of the secondary battery is drastically reduced due to repeated charging and discharging.

Below, the electrode 100 including the copper foil 110 of the present invention and the secondary battery including the electrode 100 will be described in detail.

Figure 3 is a cross-sectional view of an electrode for a secondary battery according to an embodiment of the present invention.

As illustrated in FIG. 3, the electrode 100 for a secondary battery according to an embodiment of the present invention includes the copper foil 110 and the active material layer 120 of any one of the above-described embodiments of the present invention.

FIG. 3 shows a configuration in which the active material layer 120 is formed on one side of the copper foil 110. However, the present invention is not limited to this embodiment, and referring to FIG. 4, the active material layer 120 may be formed on both sides of the copper foil 110.

In a lithium secondary battery, aluminum foil is generally used as a positive electrode current collector combined with the positive electrode active material, and copper foil 110 is generally used as a negative electrode current collector combined with the negative electrode active material.

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

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

Figure 5 is a schematic cross-sectional view of a secondary battery according to an embodiment of the present invention.

Referring to FIG. 5, the secondary battery includes a cathode 370, a cathode 340, and an electrolyte disposed between the anode 370 and the cathode 340 to provide an environment in which ions can move. It includes an electrolyte (350), and a separator (360) that electrically insulates the anode (370) and the cathode (340). Here, the ions moving between the anode 370 and the cathode 340 are, for example, lithium ions. The separator 360 separates the positive electrode 370 and the negative electrode 340 to prevent charges generated in one electrode from being wasted in vain by moving to the other electrode through the interior of the secondary battery 105. Referring to FIG. 5 , the separator 360 is disposed within the electrolyte 350.

The positive electrode 370 includes a positive electrode current collector 371 and a positive electrode active material layer 372, and aluminum foil may be used as the positive electrode current collector 371.

The negative electrode 340 includes a negative electrode current collector 341 and a negative electrode active material layer 342, and copper foil 110 may be used as the negative electrode current collector 341.

According to one embodiment of the present invention, the copper foil 110 shown in Figure 1 or Figure 2 may be used as the negative electrode current collector 341. Additionally, the electrode 100 for a secondary battery shown in FIG. 3 or 4 may be used as the cathode 340 for the secondary battery shown in FIG. 5.

Hereinafter, the manufacturing method of the copper foil 110 of the present invention will be described in detail with reference to FIG. 6.

The method of manufacturing copper foil 110 of the present invention includes forming a copper film 111 and forming a protective layer 112 on the copper film 111.

In the method of the present invention, the copper film 111 is formed on the rotating cathode drum 40 by energizing the positive electrode plate 30 and the rotating cathode drum 40 spaced apart from each other in the electrolyte 20 in the electrolytic cell 10. Including forming steps.

As illustrated in FIG. 6 , the positive electrode plate 30 may include first and second positive electrode plates 31 and 32 that are electrically insulated from each other.

In the step of forming the copper film 111, a seed layer is formed by passing electricity between the first anode plate 31 and the rotating cathode drum 40, and then forming a seed layer by passing electricity between the second positive electrode plate 32 and the rotating cathode drum 40. It can be performed by growing the seed layer.

The current density provided by the first and second anode plates 31 and 32, respectively, may be 30 to 130 ASD.

When the current density provided by each of the first and second positive electrode plates 31 and 32 is less than 30 ASD, the surface roughness of the copper foil 110 is low and the adhesive force between the copper foil 110 and the active material layer 120 may not be sufficient. You can.

On the other hand, when the current density provided by the first and second positive electrode plates 31 and 32 respectively exceeds 130 ASD, the surface of the copper foil 110 is rough and the active material may not be coated smoothly.

The surface properties of the copper film 111 may vary depending on the degree of surface buffing or polishing of the rotating cathode drum 40. For example, the surface of the rotating cathode drum 40 may be polished with a polishing brush having a grit size of #800 to #3000.

During the process of forming the copper film 111, the electrolyte solution 20 is maintained at a temperature of 48 to 60°C. More specifically, the temperature of the electrolyte solution 20 may be maintained at 50°C or higher. At this time, the physical, chemical, and electrical properties of the copper film 111 can be controlled by adjusting the composition of the electrolyte solution 20.

According to one embodiment of the present invention, the electrolyte solution 20 contains 70 to 100 g/L of copper ions, 70 to 150 g/L of sulfuric acid, 15 to 25 ppm of chlorine (Cl), and 1 to 10 ml/L of hydrogen peroxide. (H2O2) and organic additives.

In order to facilitate the formation of the copper film 111 by electrodeposition of copper, the copper ion concentration and the sulfuric acid concentration in the electrolyte solution 20 are adjusted to 70 to 100 g/L and 70 to 150 g/L, respectively. .

In one embodiment of the present invention, chlorine (Cl) includes both a chlorine ion (Cl-) and a chlorine atom present in the molecule. Chlorine (Cl) may be used, for example, to remove silver (Ag) ions introduced into the electrolyte solution 20 during the process of forming the copper film 111. Specifically, chlorine (Cl) can precipitate silver (Ag) ions in the form of silver chloride (AgCl). This silver chloride (AgCl) can be removed by filtration.

If the concentration of chlorine (Cl) is less than 15 ppm, removal of silver (Ag) ions does not occur smoothly. On the other hand, if the concentration of chlorine (Cl) exceeds 25 ppm, unnecessary reactions may occur due to excess chlorine (Cl). Accordingly, the chlorine (Cl) concentration in the electrolyte solution 20 is managed in the range of 15 to 25 ppm.

According to one embodiment of the present invention, the electrolyte solution 20 containing an organic additive may further include lead ions (Pb ²⁺ ). Specifically, the electrolyte solution 20 may contain 1 to 100 ppm of lead ions (Pb ²⁺ ). When the lead ion (Pb ²⁺ ) is maintained at 1 to 100 ppm, the R value according to the present invention can be maintained in the range of 2.0 to 3.5.

On the other hand, when the concentration of lead ions (Pb ²⁺ ) is less than 1 ppm, a problem may occur in which the effectiveness of the present invention is reduced in terms of maintaining its physical properties. As a result, a problem may occur where the R value is outside the range of 2.0 to 3.5.

In addition, when the concentration of lead ions (Pb ²⁺ ) exceeds 100 ppm, copper precipitates unevenly, which may cause rapid changes in the thickness and width of the copper foil before and after the tensile test, so the R value is 2.0 to 3.5. Problems that go beyond the scope may occur.

Additionally, according to one embodiment of the present invention, the electrolyte solution 20 containing an organic additive may further include tungsten (W). Specifically, the electrolyte solution 20 may contain 0.3 to 5 ppm of tungsten (W). When tungsten (W) is maintained at 0.3 to 5 ppm, the R value according to the present invention can be maintained in the range of 2.0 to 3.5.

On the other hand, when the concentration of tungsten (W) is less than 0.3 ppm, the average crystalline particle size of the copper film 111 does not become constant, and as a result, rapid changes may occur in the thickness and width of the copper foil before and after the tensile test, Problems may arise where the R value is outside the range of 2.0 to 3.5.

In addition, when the concentration of tungsten (W) is more than 5ppm, impurities increase, and as a result, rapid changes may occur in the thickness and width of the copper foil before and after the tensile test, causing the R value to be outside the range of 2.0 to 3.5. may occur.

According to one embodiment of the present invention, the electrolyte solution 20 containing an organic additive may further include hydrogen peroxide (H2O2). Organic impurities are present in the electrolyte solution 20 for continuous plating due to organic additives. By treating with hydrogen peroxide (H2O2), the organic impurities can be decomposed and the carbon (C) content inside the copper foil can be appropriately adjusted. As the TOC concentration in the electrolyte solution 20 increases, the amount of carbon (C) element flowing into the copper film 111 increases, and accordingly, the total amount of elements released from the copper film 111 during heat treatment increases. This causes the strength of the copper foil 110 to decrease.

The amount of hydrogen peroxide (H2O2) added is 1 to 10 ml of hydrogen peroxide (H2O2) per L of electrolyte. Specifically, it is preferable to add 2 to 8 ml of hydrogen peroxide (H2O2) per L of electrolyte solution. If the amount of hydrogen peroxide (H2O2) added is less than 1 ml/L, it is meaningless because there is almost no effect on decomposing organic impurities. When the amount of hydrogen peroxide (H2O2) added exceeds 10 ml/L, organic impurities are excessively decomposed, and the effects of organic additives such as brighteners, moderators, and leveling agents are suppressed.

The organic additive contained in the electrolyte solution 20 includes at least one of a brightener (component A), a moderator (component B), and a leveling agent (component C). The organic additive in the electrolyte solution 20 has a concentration of 1 to 100 ppm.

The organic additive may include two or more of a brightener (component A), a moderator (component B), and a leveling agent (component C), or may include all three components. Even in this case, the concentration of organic additives is 100 ppm or less. If the organic additive includes all a brightener (component A), a moderator (component B), and a leveling agent (component C), the organic additive may have a concentration of 10 to 100 ppm.

The brightener (component A) contains sulfonic acid or a metal salt thereof. The brightener (component A) may have a concentration of 1 to 25 ppm in the electrolyte solution 20.

The brightener (component A) increases the amount of charge in the electrolyte 20, thereby increasing the electrodeposition rate of copper, improving the curl characteristics of the copper foil, and enhancing the gloss of the copper foil 110. If the concentration of the brightener (component A) is less than 1 ppm, the gloss of the copper foil 110 may decrease and surface defects of the copper foil 110 may occur, causing the R value to be outside the range of 2.0 to 3.5. In addition, if the concentration of the brightener (component A) exceeds 25 ppm, the roughness of the copper foil 110 may increase and the strength may decrease, and as a result, a rapid change may occur in the thickness and width of the copper foil before and after the tensile test. , a problem may occur where the R value is outside the range of 2.0 to 3.5.

More specifically, the brightener (component A) may have a concentration of 5 to 20 ppm in the electrolyte solution 20.

Brightening agents include, for example, bis-(3-sulfopropyl)-disulfide disodium salt, 3-mercapto-1-propanesulfonic acid, 3-(N,N-dimethylthiocarbamoyl)-thiopropanesulfonate sodium salt. , 3-[(amino-iminomethyl)thio]-1-propanesulfonate sodium salt, o-ethyldithiocarbonato-S-(3-sulfopropyl)-ester sodium salt, 3-(benzothiazolyl- It may include at least one of 2-mercapto)-propyl-sulfonic acid sodium salt and ethylenedithiiodipropylsulfonic acid sodium salt.

The moderator (component B) contains a nonionic water-soluble polymer. The moderator (component B) may have a concentration of 1 to 10 ppm in the electrolyte solution 20.

The moderator (component B) reduces the electrodeposition rate of copper and prevents a rapid increase in roughness and a decrease in strength of the copper foil 110. This moderator (component B) is also called an inhibitor or suppressor.

If the concentration of the moderator (component B) is less than 1 ppm, the roughness of the copper foil 110 increases rapidly, and a problem may occur in which the strength of the copper foil 110 decreases, and as a result, the thickness of the copper foil before and after the tensile test Because rapid changes may occur in the width and width, a problem may occur where the R value is outside the range of 2.0 to 3.5. On the other hand, even if the concentration of the moderator (component B) exceeds 10 ppm, there is little change in the physical properties of the copper foil 110, such as appearance, gloss, roughness, strength, and elongation. Therefore, the concentration of the moderator (component B) can be adjusted to the range of 1 to 10 ppm without the need to increase the manufacturing cost and waste raw materials by unnecessarily increasing the concentration of the moderator (component B).

The moderator (component B) is, for example, polyethylene glycol (PEG), polypropylene glycol, polyethylenepolypropylene copolymer, polyglycerin, polyethylene glycol dimethyl ether, hydroxyethylenecellulose, polyvinyl alcohol, stearic acid polyglycol. It may include at least one nonionic water-soluble polymer selected from ethers and stearyl alcohol polyglycol ethers. However, the type of moderator is not limited to this, and other nonionic water-soluble polymers that can be used in the production of the high-strength copper foil 110 can be used as a moderator.

The leveling agent (component C) contains at least one of nitrogen (N) and sulfur (S). That is, the leveling agent (component C) may contain one or more nitrogen atoms (N) or one or more sulfur atoms (S) in one molecule, and may contain one or more nitrogen atoms (N) and one or more sulfur atoms (S). It may also include . For example, the leveling agent (component C) is an organic compound containing at least one of nitrogen (N) and sulfur (S).

The leveling agent (component C) prevents excessively high peaks or excessively large protrusions from being generated in the copper film 111 and makes the copper film 111 macroscopically flat. The leveling agent (component C) may have a concentration of 1 to 10 ppm in the electrolyte solution 11.

When the concentration of the leveling agent (component C) is less than 1 ppm, the strength of the copper foil 110 decreases, making it difficult to manufacture the high-strength copper foil 110, and as a result, the thickness and width of the copper foil before and after the tensile test Because rapid changes may occur, a problem may occur where the R value is outside the range of 2.0 to 3.5. On the other hand, if the concentration of the leveling agent (component C) exceeds 10 ppm, the surface roughness of the copper foil 110 may increase excessively, resulting in a decrease in strength, and pinholes or curls may appear on the surface of the copper foil 110. This may result in difficulty in separating the copper foil 110 from the winder WR after manufacturing. As a result, rapid changes may occur in the thickness and width of the copper foil before and after the tensile test, which may cause the R value to be outside the range of 2.0 to 3.5.

The leveling agent (component C) is, for example, diethylthiourea, ethylenethiourea, acetylenethiourea, dipropylthiourea, dibutylthiourea, N-trifluoroacetylthiourea, N -Ethylthiourea, N-cyanoacetylthiourea, N-allylthiourea, o-tolylthiourea, N,N'-butylene N,N'-butylene thiourea, thiazolidinethiol, 4-thiazolinethiol, 4-methyl-2-pyrimidinethiol, 2-thiouracil, 3-(benzotriazole-2-mercapto)-prosulfonic acid), 2-mercaptopyridine, 3(5-mercapto 1H-tetrazole)benzenesulfonate, 2 -Mercaptobenzothiazole, dimethylpyridine, 2,2'-bipyridine, 4.4'-bipyridine, pyrimidine, pyridazine, pyrimidine, pyrinoline, oxazole, thiazole, 1-methylimidazole, 1-benzylimidazole, 1-methyl-2methylimidazole, 1-benzyl-2-methylimidazole, 1-ethyl-4-methylimidazole, 1-ethyl-2-ethyl-4-methyl All, N-methylpyrrole, N-ethylpyrrole, N-butylpyrrole, N-methylpyrroline, N-ethylpyrroline, N-butylpyrroline, pyrimidine, purine, quinoline, isoquinoline, N-methylcarbazole , N-ethylcarbazole, and N-butylcarbazole.

When the copper film 111 is formed, the flow rate of the electrolyte solution 20 supplied into the electrolytic cell 10 may be 41 to 45 m ³ /hour.

The step of forming the copper film 111 includes filtering the electrolyte solution 20 using activated carbon, filtering the electrolyte solution 20 using diatomaceous earth, and treating the electrolyte solution 20 with ozone (O ₃ ). It may include at least one of the following steps:

Specifically, for filtration of the electrolyte solution 20, the electrolyte solution 20 may be circulated at a flow rate of 35 to 45 m3/hour. That is, in order to remove solid impurities present in the electrolyte 20 while electroplating to form the copper film 111 is performed, filtration may be performed at a flow rate of 35 to 45 m3/hour. At this time, activated carbon or diatomaceous earth may be used.

In order to maintain the cleanliness of the electrolyte 20, the electrolyte 20 may be treated with ozone (O3).

Additionally, in order to ensure the cleanliness of the electrolyte 20, the copper wire (Cu wire), which is a raw material of the electrolyte 20, may be cleaned.

According to one embodiment of the present invention, the steps of preparing the electrolyte 20 include heat-treating the copper wire, pickling the heat-treated copper wire, washing the pickled copper wire, and placing the washed copper wire in the electrolyte solution. It may include the step of adding sulfuric acid.

More specifically, in order to maintain the cleanliness of the electrolyte 20, high purity (99.9% or more) copper wire (Cu wire) is heat treated in an electric furnace at 750°C to 850°C to burn off various organic impurities on the copper wire. , Copper for producing the electrolyte solution 20 can be manufactured by sequentially going through the process of pickling the heat-treated copper wire for 10 to 20 minutes using a 10% sulfuric acid solution and washing the pickled copper wire with distilled water. The electrolyte solution 20 can be prepared by combining the washed copper wire with sulfuric acid for electrolyte solution.

According to one embodiment of the present invention, in order to satisfy the characteristics of the copper foil 110, the concentration of total organic carbon (TOC) in the electrolyte solution 20 is managed to be 50 ppm or less. That is, the electrolyte solution 20 may have a total organic carbon (TOC) concentration of 50 ppm or less.

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

For example, acid cleaning to remove impurities on the surface of the copper film 111, such as resin components or natural oxide, and water cleaning to remove the acid solution used in the acid cleaning. ) can be performed sequentially. The cleaning process may be omitted.

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

Referring to FIG. 6 , the step of immersing the copper film 111 in an anticorrosion solution 60 may be further included. When the copper film 111 is immersed in the rust preventive liquid 60, it may be guided by a guide roll 70 disposed in the rust preventive liquid 60.

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

Meanwhile, the protective layer 112 may include a silane compound obtained by silane treatment or a nitrogen compound obtained by nitrogen treatment.

Copper foil 110 is created by forming this protective layer 112.

On one or both sides of the copper foil 110 of the present invention manufactured through the above method, carbon; metal (Me) of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; an alloy containing the metal (Me); Oxide (MeOx) of the metal (Me); The electrode (i.e., negative electrode) for a secondary battery of the present invention can be manufactured by coating one or more negative electrode active materials selected from the group consisting of a composite of metal (Me) and carbon.

For example, 100 parts by weight of carbon for a negative electrode active material is mixed with 1 to 3 parts by weight of styrenebutadiene rubber (SBR) and 1 to 3 parts by weight of carboxymethyl cellulose (CMC), and then a slurry is prepared using distilled water as a solvent. . Next, the slurry is applied to a thickness of 20 to 60 μm on the copper foil 110 using a doctor blade, and pressed at a temperature of 110 to 130° C. at a pressure of 0.5 to 1.5 ton/cm2.

A secondary battery can be manufactured using a conventional positive electrode, electrolyte, and separator along with the secondary battery electrode (negative electrode) of the present invention manufactured by the above method.

Below, the present invention will be described in detail through examples and comparative examples. However, the following examples are only intended to aid understanding of the present invention, and the scope of the present invention is not limited to these examples.

Examples 1-4 and Comparative Examples 1-7

Copper foil was manufactured using a making machine including an electrolytic cell 10, a rotating cathode drum 40 disposed in the electrolytic cell 10, and a positive electrode plate 30 disposed spaced apart from the rotating cathode drum 40. The electrolyte solution 20 is a copper sulfate solution. The concentration of copper ions in the electrolyte 20 was set to 87 g/L, the concentration of sulfuric acid was 110 g/L, the temperature of the electrolyte was set to 55°C, and the current density was set to 60ASD.

In addition, the concentrations of chlorine (Cl), lead (Pb ²⁺ ), tungsten (W) and organic additives contained in the electrolyte solution 20 are shown in Table 1 below.

Among the organic additives, bis-(3-sulfopropyl)-disulfide disodium salt (SPS) was used as a brightener (component A), polyethylene glycol (PEG) was used as a moderator (component B), and a leveling agent (C Ethylene thiourea (ETU) was used as an ingredient.

A copper film 111 was manufactured by applying a current at a current density of 60 ASD between the rotating cathode drum 40 and the anode plate 30. Next, the copper foil 110 was manufactured by immersing the copper film 111 in a rust preventive solution for about 2 seconds and chromating the surface of the copper film 111 to form a protective layer 112. A rust preventive liquid containing chromic acid as the main ingredient was used, and the concentration of chromic acid was 5 g/L.

As a result, copper foils of Examples 1-4 and Comparative Examples 1-7 were manufactured.

SPS
(Component A)
(ppm) PEG
(Component B)
(ppm) ETU
(C component)
(ppm) Goat
(ppm) Lead (Pb ²⁺ )
(ppm) tungsten
(ppm) hydrogen peroxide
(ml/L) current density
(ASD) Example 1 5 2 3 20 30 1.0 2 50 Example 2 10 4 5 20 30 1.5 5 50 Example 3 15 6 7 20 50 1.5 7 50 Example 4 20 8 9 20 70 2.0 7 50 Comparative Example 1 55 5 5 20 0.1 0.1 9 50 Comparative example 2 10 50 7 20 0.1 0.1 7 50 Comparative example 3 15 7 55 20 0.1 0.1 5 50 Comparative example 4 0.5 5 5 20 130 7 15 50 Comparative Example 5 10 0.5 7 20 130 10 0.1 50 Comparative Example 6 15 7 0.5 20 150 15 5 50 Comparative example 7 0.5 15 15 20 50 0.1 5 50

WA WB tA tB R tensile strength
(kgf/ ^mm2 ) elongation
(%) Rz Wrinkles/Tears
Occurred or not Example 1 12.7 12.3 8 7.92 3.18 56.2 10.2 0.8 doesn't exist Example 2 12.7 12.5 8 7.95 2.53 51.3 7.5 0.8 doesn't exist Example 3 12.7 12.5 8 7.94 2.10 58.5 8.6 0.8 doesn't exist Example 4 12.7 12.4 8 7.94 3.17 57.6 11.2 0.8 doesn't exist Comparative Example 1 12.7 12.1 8 7.80 1.91 35.2 10.5 2.7 generation Comparative example 2 12.7 12.1 8 7.78 1.73 45.6 10.5 0.75 generation Comparative example 3 12.7 12.2 8 7.84 1.98 32.7 10.3 3.1 generation Comparative example 4 12.7 12.3 8 7.85 1.6 51.0 10.6 0.8 generation Comparative Example 5 12.7 12.2 8 7.82 1.7 34.5 11.1 2.8 generation Comparative Example 6 12.7 12.4 8 7.88 1.5 34.6 9.5 2.7 generation Comparative Example 7 12.7 12 8 7.89 4.0 50.6 15.0 0.8 generation

For the copper foils of Examples 1-4 and Comparative Examples 1-7 manufactured in this way, i) WA, ii) WB, iii) tA, iv) tB, v) R value, vi) tensile strength, vii) elongation, and viii) Rz value was measured and calculated, and ix) the occurrence of wrinkles/tearing was checked. i) WA, ii) WB measurement

WA and WB of the copper foil 110 are calculated through Equations 2 and 3 below.

[Equation 2]

WA = [XA0+(XA45)X2+XA90]/4

[Equation 3]

WB = [XB0+(XB45)X2+XB90]/4

Copper foil 110 is sampled in three directions of 0°, 45°, and 90° in the MD direction, and a tensile test in the axial direction is performed on each of the collected copper foils under the condition of a UTM tensile test speed of 5 mm/min. At this time, the tensile test is conducted until the collected copper foil grows 15% after tension compared to before tension. In addition, by measuring the width of the central portion in the tensile direction before and after the tensile test of the collected copper foil, XA0, XA45, XA90, XB0, XB45, and

At this time, XA0, XA45, and XB0, XB45, and

iii) tA, iv) tB measurements

tA is the measurement of the thickness of the test piece before the tensile test, and tB is the measurement of the thickness of the test piece after the tensile test.

At this time, the tensile test was conducted using a universal testing machine (UTM).

v) Calculate R

The R value can be obtained by calculating the measured i) WA, ii) WB, iii) tA and iv) tB values according to Equation 1 below.

[Equation 1]

R = log(WA/WB)/log(tA/tB)

vi) Tensile strength measurement

Tensile strength is measured using a universal testing machine (UTM). At this time, the width of the sample is 12.7mm, the distance between grips is 50mm, and the test speed is 50mm/min.

vii) Elongation measurement

Elongation was measured by a universal testing machine (UTM) according to the specifications of the IPC-TM-650 Test Method Manual. Specifically, the elongation was measured using a universal testing machine from Instron. The width of the sample for measuring elongation is 12.7 mm, the distance between grips is 50 mm, and the measurement speed is 50 mm/min.

viii) 10-point surface roughness (Rz) measurement

The 10-point surface roughness (Rz) of the copper foil was measured using a surface roughness measuring device (M300, Mahr) according to the JIS B 0601-2001 standard.

ix) Whether wrinkles/tears occur?

After charging and discharging 100 times, the secondary battery was disassembled and observed whether wrinkles or tears occurred in the copper foil. Cases where wrinkles or tears occurred in the copper foil were marked as “occurrence,” and cases where they did not occur were marked as “none.”

Referring to Table 1 and Table 2, you can see the following results.

Tears/wrinkles occurred in the copper foil of Comparative Example 1, which was manufactured with an electrolyte solution containing an excessive amount of brightener (component A) and trace amounts of lead ions (Pb ²⁺ ) and tungsten (W).

Tears/wrinkles occurred in the copper foil of Comparative Example 2, which was manufactured with an electrolyte solution containing an excessive amount of a moderator (component B) and trace amounts of lead ions (Pb ²⁺ ) and tungsten (W).

Tears/wrinkles occurred in the copper foil of Comparative Example 3, which was manufactured with an electrolyte solution containing an excessive amount of a leveling agent (component C) and trace amounts of lead ions (Pb ²⁺ ) and tungsten (W).

Tearing/wrinkling occurred in the copper foil of Comparative Example 4 prepared with an electrolyte solution containing a trace amount of brightener (component A), an excessive amount of lead ions (Pb ²⁺ ) and tungsten (W), and an excessive amount of hydrogen peroxide. occurred.

Tears/wrinkles in the copper foil of Comparative Example 5 prepared with an electrolyte solution containing a trace amount of a moderator (component B), an excessive amount of lead ions (Pb ²⁺ ), tungsten (W), and a trace amount of hydrogen peroxide. This occurred.

Tears/wrinkles occurred in the copper foil of Comparative Example 6, which was manufactured with an electrolyte solution containing a trace amount of a leveling agent (component C) and an excessive amount of lead ions (Pb ²⁺ ) and tungsten (W).

Tears/wrinkles occurred in the copper foil of Comparative Example 7, which was manufactured with an electrolyte solution containing a trace amount of a brightener (component A) and tungsten (W) and an excessive amount of a moderator (component B) and a leveling agent (component C). did.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible without departing from the technical details of the present invention. It will be clear to a person with ordinary knowledge. Therefore, the scope of the present invention is expressed by the claims described later, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

100: Electrode for interest cell
110: copper foil
111: copper film
120: Active material layer
10: Electrolyzer
20: electrolyte

Claims (10)

It includes a copper film containing 99.9% by weight or more of copper,
Copper foil with an R value ranging from 2.0 to 3.5:
The R is calculated by the following equation 1,
[Equation 1]
R = log(WA/WB)/log(tA/tB)
WA in Equation 1 is calculated using Equation 2 below,
[Equation 2]
WA = [XA0+(XA45)X2+XA90]/4
WB in Equation 1 is calculated using Equation 3 below,
[Equation 3]
WB = [XB0+(XB45)X2+XB90]/4
tA in Equation 1 refers to the thickness of the test specimen before the tensile test,
tB in Equation 1 refers to the thickness of the test specimen after the tensile test,
XA0, XA45, and
XB0, XB45, and According to paragraph 1,
Copper foil having a tensile strength of 45 kgf/mm ² or more. According to paragraph 1,
Copper foil, with an elongation of 3 to 13%. According to paragraph 1,
Copper foil having a 10-point average roughness (Rz) of 0.7 to 0.9 μm. According to paragraph 1,
Copper foil further comprising a protective layer on the copper film. According to clause 5,
The protective layer includes at least one of a chromium compound, a silane compound, and a nitrogen compound. Preparing an electrolyte solution containing copper ions;
forming a copper film; and
Including forming a protective layer on the copper film,
The step of forming the copper film is,
Comprising the step of forming a copper film on the rotating cathode drum by energizing the positive electrode plate and the rotating cathode drum spaced apart from each other in the electrolyte solution in the electrolytic cell,
The electrolyte is,
70 to 100 g/L of copper ions;
70 to 150 g/L sulfuric acid;
15 to 25 ppm chlorine (Cl);
1 to 100 ppm of lead ions (Pb ²⁺ );
0.3 to 5 ppm tungsten (W);
1 to 10 ml/L of hydrogen peroxide; and
Contains organic additives;
The organic additive includes at least one of a brightener (component A), a reducer (component B), and a leveling agent (component C),
The polishing agent (component A) contains sulfonic acid or a metal salt thereof,
The moderator (component B) includes a nonionic water-soluble polymer,
The leveling agent (component C) contains at least one of nitrogen (N) and sulfur (S),
Manufacturing method of copper foil. In clause 7,
A method of manufacturing copper foil, wherein the brightener (component A) has a content of 1 to 25 ppm. In clause 7,
The method of manufacturing copper foil, wherein the moderator (component B) has a content of 1 to 10 ppm. In clause 7,
The leveling agent (component C) has a content of 1 to 10 ppm.