TW201825285A - Electrolytic copper foil substantially free of wrinkle defect, electrode including the same, secondary battery including the same, and method of manufacturing the same - Google Patents

Abstract

Provided are an electrolytic copper foil substantially free of a wrinkle defect, an electrode including the same, a secondary battery including the same, and a method of manufacturing the same. The electrolytic copper foil of the present invention has a first surface and a second surface opposite the first surface, each of the first and second surfaces has a profile maximum ratio (PMR) of 4.8 to 16.1, and the electrolytic copper foil has a texture coefficient [TC(220)] of a (220) plane of 0.49 to 1.28, a yield strength of 35 to 58 kgf/mm2, and a weight deviation of 3% or less.

Description

Electrolytic copper foil having substantially no wrinkle defect, electrode including the same, secondary battery including the same, and method for manufacturing the same

The present invention relates to an electrolytic copper foil having substantially no wrinkle defects, an electrode including the same, a secondary battery including the same, and a method for manufacturing the same.

Electrolytic copper foil is used to make various products, such as the negative electrode of secondary batteries and flexible printed circuit boards (FPCBs).

When the production conditions cannot be accurately controlled during the electrolytic copper foil manufacturing process, typical wrinkle defects cannot be prevented from being produced during the manufacture of the film.

An electrolytic copper foil having a wrinkle defect causes a decrease in the yield and quality of a secondary battery. Specifically, the surface of the electrolytic copper foil cannot be uniformly covered with the negative electrode active material due to unevenness of the surface of the electrolytic copper foil having a wrinkle defect. The uneven coating of the negative active material may cause a short circuit of the secondary battery or delamination of the negative active material. Therefore, the wrinkle defect of electrolytic copper foil is one of the reasons for consumer returns.

It is known that reducing the weight deviation of an electrolytic copper foil is a method of suppressing a wrinkle defect of the electrolytic copper foil. However, in order to increase the secondary battery capacity and increase the usage ratio, wrinkle defects still occur when the thickness of the electrolytic copper foil is 8 μm or less, even if the weight deviation is controlled to be very low.

The invention relates to providing an electrolytic copper foil, an electrode including the same, a secondary battery including the same, and a manufacturing method thereof, which can avoid the limitations and disadvantages of the prior art.

The present invention also relates to an electrolytic copper foil having substantially no wrinkle defects.

In addition, the present invention relates to an electrode manufactured by using an electrolytic copper foil having substantially no wrinkle defects, thereby ensuring high productivity.

Furthermore, the present invention relates to a secondary battery manufactured by using an electrolytic copper foil having substantially no wrinkle defects, which can ensure high productivity.

Moreover, this invention relates to the manufacturing method of the electrolytic copper foil which can prevent a wrinkle defect.

In addition to the above aspects of the present invention, other features and advantages of the present invention are described below; or, according to the following description, certain undescribed features and advantages of the present invention are conceivable to those skilled in the art.

An aspect of the present invention is to provide an electrolytic copper foil. The electrolytic copper foil may include a first surface, a second surface opposite to the first surface, a copper layer, and a first protective layer. A matte surface on one surface and a matte surface facing the second surface; a first protective layer on the matte surface of the copper layer, and a second protective layer on the glossy surface; wherein the first surface And the second surface each have a profile maximum ratio (PMR) of 4.8 to 16.1, wherein the maximum profile ratio is a ratio of a maximum height roughness (R _max ) and an arithmetic average roughness (R _a ) The ratio (R _max / R _a ); and the texture coefficient [TC (220)] of the (220) surface of the electrolytic copper foil ranges from 0.49 to 1.28, and the drop strength ranges from 35 kgf / mm ² to 58 kgf / mm ² , and the range of weight deviation is equal to or less than 3%.

The first surface and the second surface each have a maximum height roughness (R _max ) of 1.2 μm to 3.7 μm and an arithmetic average roughness (R _a ) of 0.15 μm to 0.45 μm.

The first protective layer and the second protective layer may each contain chromium (Cr).

The electrolytic copper foil has a thickness of 4 μm to 30 μm, and a preferred thickness is 4 μm to 8 μm.

Another aspect of the present invention is to provide a secondary battery electrode including an electrolytic copper foil including a first surface and a second surface opposite to the first surface; and a first active material layer, the first An active material layer is formed on the first surface, wherein the electrolytic copper foil includes a copper layer having a matte surface facing the first surface and a gloss surface facing the second surface, and a copper layer on the matte surface of the copper layer. The first protective layer and the second protective layer on the glossy surface, wherein the first surface and the second surface each have a profile maximum ratio (PMR) of 4.8 to 16.1, and the maximum profile ratio is one A ratio (R _max / R _a ) of the maximum height roughness (R _max ) to an arithmetic average roughness (R _a ); and a texture coefficient of the (220) plane of the electrolytic copper foil having 0.49 to 1.28 [TC (220)], a drop strength of 35 kgf / mm ² to 58 kgf / mm ² , and a weight deviation of 3% or less.

The first surface and the second surface each have a maximum height roughness (R _max ) of 1.2 μm to 3.7 μm and an arithmetic average roughness (R _a ) of 0.15 μm to 0.45 μm.

The first protective layer and the second protective layer may each contain chromium (Cr).

The electrolytic copper foil has a thickness of 4 μm to 30 μm, and a preferred thickness is 4 μm to 8 μm.

The secondary battery electrode further includes a second active material layer disposed on the second surface; wherein the first active material layer and the second active material layer each include at least one active material, and the at least one active material is selected from, for example, carbon , Silicon, germanium, tin, lithium, zinc, magnesium, cadmium, cerium, nickel, or iron or a metal containing the metal, an oxide of the metal, and a group consisting of the metal and carbon .

Another aspect of the present invention is to provide a secondary battery. The secondary battery includes a cathode, an anode including a secondary battery electrode, an electrolyte, and a separator. The electrolyte is configured to provide an environment, and lithium ions are in the environment. It can be moved between the cathode and the anode, and the separator is configured to electrically insulate the anode from the cathode.

Another aspect of the present invention is to provide a method for manufacturing an electrolytic copper foil for a secondary battery. The method includes forming a copper layer and forming a protective layer on the copper layer. The step of forming the copper layer includes preparing an electrolytic solution. The electrolyte contains 70 g / L to 90 g / L of copper ions, 50 g / L to 150 g / L of sulfuric acid, 2 mg / L to 20 mg / L of N-allyl thiourea (ATU), and 2 mg / L to 20 mg / L of bis- (3-sulfopropyl) disulfide (SPS); and the application of 40A / dm ² to from a electrode plate to a rotating electrode drum A current of 80 A / dm ² for electroplating; wherein a surface of the rotating electrode drum is polished using a polishing brush having a grit size of 800 to 3000; and when the electroplating step is performed, the The concentration of silver in the electrolyte was maintained at 50 mg / L or less.

The step of preparing the electrolytic solution may include heat treating a copper wire at a temperature range of 600 ° C to 900 ° C for 30 minutes to 60 minutes; pickling the heat-treated copper wire; and placing the acid-washed copper wire into the sulfuric acid. The copper wire; and adding ATU and SPS to the sulfuric acid placed in the copper wire.

When deposition was carried out, the electrolytic solution for a continuous filtration (Continuous Filtration); and when the continuous filtration, the flow rate of the electrolyte is 39m ³ / hr to 46m ³ / hr.

When plating is performed, the change in flow rate is equal to or less than 5% / sec.

The step of forming the copper layer further includes adding chloride ions that can react with silver to form a silver chloride precipitate to the electrolytic solution to prevent the concentration of silver in the electrolytic solution from exceeding 50 mg / L.

The step of forming the protective layer includes immersing the copper layer in a rust-proof solution containing 0.5 g / L to 1.5 g / L of chromium.

The general description of the invention as described above is only intended to illustrate or explain the invention and is not intended to limit the scope of the invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Various modifications and changes can be made to the present invention, and various modifications and changes are easily conceivable by those skilled in the art without departing from the spirit and scope of the present invention. Therefore, the present invention includes all modifications and changes that fall within the scope of the present invention as defined by the scope of the patents to which they belong and their equivalents.

A lithium ion secondary battery includes a cathode, an anode, an electrolyte, and a separator. The electrolyte provides an environment for lithium ions to move between the cathode and the anode. The separator can electrically isolate the cathode and the anode, thereby Avoid unnecessary consumption of electrons that move from one electrode to another electrode inside the secondary battery.

FIG. 1 is a cross-sectional view of a secondary battery electrode according to an embodiment of the present invention.

As shown in FIG. 1, the secondary battery electrode 100 according to the embodiment of the present invention includes: an electrolytic copper foil 110, the electrolytic copper foil 110 includes a first surface S1 and a second surface S2 opposite to the first surface S1; A first active material layer 120a on the first surface S1; and a second active material layer 120b provided on the second surface S2. In one embodiment of FIG. 1, the first active material layer 120 a and the second active material layer 120 b are respectively formed on the first surface S1 and the second surface S2 of the electrolytic copper foil 110, but the present invention is not limited thereto. In some embodiments, the secondary battery electrode 100 of the present invention may include only one of the first active material layer 120a and the second active material layer 120b as the active material layer.

Generally, in a lithium secondary battery, aluminum foil is used as a positive current collector, the positive current collector is connected to a positive active material, and electrolytic copper foil is used as a negative current collector, and the negative current collector is connected to the negative active material.

According to an embodiment of the present invention, the secondary battery electrode 100 is used as an anode of a lithium secondary battery, and its electrolytic copper foil 110 is used as a negative electrode current collector, and the first active material layer 120a and the second active material layer 120b each include a negative electrode. Active material.

As shown in FIG. 1, the electrolytic copper foil 110 of the present invention includes a copper layer 111, a first protective layer 112a, and a second protective layer 112b. The copper layer 111 includes a matte surface MS and a glossy surface SS. A first protective layer 112a is formed on the matte surface MS of the copper layer 111, and a second protective layer 112b is formed on the matte surface SS of the copper layer 111.

The matte surface MS is the surface of the copper layer 111 that faces the first surface S1 of the electrolytic copper foil 110, and the matte surface SS is the surface of the copper layer 111 that faces the second surface S2 of the electrolytic copper foil 110.

The copper layer 111 of the present invention can be formed on a rotating electrode drum by electroplating. The glossy surface SS refers to a surface in contact with the rotating electrode drum during the plating process, and the matte surface MS refers to a surface opposite the glossy surface SS.

Generally, the glossy surface SS has a ten-point average roughness (Rz) lower than the matte surface MS, but the present invention is not limited thereto, and the ten-point average roughness (Rz) of the glossy surface SS may be greater than or equal to the matte surface MS Surface roughness.

The first protective layer 112a and the second protective layer 112b may prevent corrosion of the copper layer 111 and may improve heat resistance of the copper layer 111, and may contain chromium (Cr).

According to an embodiment of the present invention, an adhesion amount of chromium (Cr) in the first surface S1 and the second surface S2 may be 1 mg / m ² to 5 mg / m ² .

As described above, the electrolytic copper foil 110 having a wrinkle defect may cause uneven coating of the negative electrode active material, and uneven coating of the negative electrode active material may cause short circuits in the secondary battery and delamination of the negative electrode active material. Therefore, all factors that cause the wrinkle defect of the electrolytic copper foil 110 should be considered in manufacturing the electrolytic copper foil 110.

According to the present invention, it has been found that factors such as the surface contour, the crystal structure of the surface, the yield strength, and the weight deviation of the electrolytic copper foil 110 can cause wrinkle defects in the electrolytic copper foil 110. Therefore, in order to minimize the wrinkle defect of the electrolytic copper foil 110, it is necessary to accurately control these important factors.

The surface profile closely related to the grain size can be represented by the arithmetic average roughness (R _a ) and the maximum height roughness (R _max ), and the crystal structure of the surface can be represented by the texture coefficient of the (220) plane [TC (220 )] Said.

According to the present invention, in order to minimize the wrinkle defect of the electrolytic copper foil 110, the first surface and the second surface have a profile maximum ratio (PMR) of 4.8 to 16.1. Texture coefficient of (220) plane of the electrolytic copper foil [the TC (220)] is 0.49 to 1.28, and having 35 kgf / mm ² to 58 kgf / mm ² yield strength, and less than or equal to 3% by weight deviation.

PMR is the ratio of the maximum height roughness (R _max ) to the arithmetic mean roughness (R _a ) (R _max / R _a ). In the present invention, the arithmetic average roughness (R _a ) and the maximum height roughness (R _max ) are measured according to the Japanese Industrial Standard (JIS) B 0601-2001 standard [measurement length: 4 mm (excluding cut-off portions)].

When the PMR is greater than 16.1, air is trapped between the electrolytic copper foils 110 when the electrolytic copper foil 110 manufactured by electrolytic plating is wound on a bobbin, thereby causing a wrinkle defect. On the other hand, when the PMR is less than 4.8, the electrolytic copper foil 110 may locally extend when wound on a roll in a roll-to-roll (RTR) process, thereby causing a wrinkle defect.

According to an embodiment of the present invention, the first surface S1 and the second surface S2 may each have a maximum height roughness (R _max ) of 1.2 μm to 3.7 μm and an arithmetic average roughness (R _a ) of 0.15 μm to 0.45 μm.

In the present invention, the texture coefficient of the (220) surface of the electrolytic copper foil 110 is measured and calculated as follows.

First, by performing X-ray diffraction (XRD) within a diffraction angle (2θ) of 30 ° to 95 ° [target: copper K α1, interval between 2θ: 0.01 °, and Scanning rate of 2θ: 3 ° / min] to obtain an XRD pattern of peaks corresponding to n crystal planes (for example, XRDs of peaks corresponding to planes (111), (200), (220), and (311) exist Figure). The XRD diffraction intensity [I (hkl)] of each crystal plane (hkl) is obtained from the XRD diagram. In addition, the XRD diffraction intensity [I ₀ (hkl)] of n crystal planes of a standard copper powder specified by the Joint Committee on Power Diffraction standards (JCPDS) was obtained. Next, get the arithmetic mean of I (hkl) / I ₀ (hkl) for n crystal planes, and then calculate by dividing the I (220) / I ₀ (220) of the (220) plane by the arithmetic mean Texture coefficient of the (220) plane [TC (220)]. That is, the texture coefficient [TC (220)] of the (220) plane will be calculated based on the following Equation 1.

[Equation 1]

When the texture coefficient [TC (220)] of the (220) plane is less than 0.49, the crystal structure of the electrolytic copper foil 110 is not dense enough, and the electrolytic copper foil 110 is easily deformed when wound on a bobbin, causing wrinkle defects. On the other hand, when the texture coefficient [TC (220)] of the (220) plane is greater than 1.28, the crystal structure of the electrolytic copper foil 110 becomes too dense and has high brittleness. As a result, the electrolytic copper foil 110 is damaged during the manufacturing process. Torn.

In the present invention, the drop-down strength is measured at a room temperature of 25 ° C using a universal testing machine (UTM) [sample width: 12.7mm, distance between clamps: 50mm, measurement speed: 50mm / min) .

When the drop strength of the electrolytic copper foil 110 is less than 35 kgf / mm ² , the electrolytic copper foil 110 may cause plastic deformation when it is wound on a bobbin, thereby causing acceleration of wrinkle defects. On the other hand, when the yield strength electrodeposited copper foil 110 is greater than 58kgf / mm ^2, the electrodeposited copper foil becomes brittle and 110 allow high compatibility decrease, and increase the risk of tearing of the electrolytic copper foil 110 in the manufacturing process.

In the present invention, the weight deviation means a weight deviation in the width direction, and is measured and calculated as follows.

After taking 5 cm × 5 cm samples from the left, middle, and right points in the width direction of the electrolytic copper foil 110, the weights of the three samples were measured. Use the measured values to calculate the arithmetic average weight and standard deviation, and then calculate the ratio (%) of the weight standard deviation to the average weight, which is [(weight standard deviation / average weight) × 100].

When the weight deviation of the electrolytic copper foil 110 is greater than 3%, the electrolytic copper foil 110 may partially extend when wound on a spool, thereby causing wrinkling.

The electrolytic copper foil 110 of the battery of the present invention has an elongation of 3% or more at room temperature (25 ° C). When the elongation of the electrolytic copper foil 110 is less than 3%, the electrolytic copper foil 110 will not be stretched by the force applied during the manufacturing of the electrolytic copper foil 110 or during the manufacturing of the secondary battery electrode 100, thereby increasing Risk of tearing of the electrolytic copper foil 110.

The electrolytic copper foil 110 of the present invention may have a thickness of 4 μm to 30 μm, and preferably a thickness of 4 μm to 8 μm. When the thickness of the electrolytic copper foil 110 is less than 4 μm, workability in the process of manufacturing a secondary battery may decrease. On the other hand, when the thickness of the electrolytic copper foil 110 is more than 30 μm, it is difficult to ensure a sufficient capacity of the lithium battery.

Specifically, since the electrolytic copper foil 110 having a thickness of 8 μm or less (the demand for manufacturing a high-capacity secondary battery is increasing) is difficult to prevent wrinkle defects only by reducing its weight deviation, it is necessary to further apply the present invention Technical characteristics.

The first active material layer 120a and the second active material layer 120b may each include at least one active material as a negative electrode active material, and the active material is selected from, for example, carbon, silicon, germanium, tin, lithium, zinc, magnesium, cadmium, cerium, nickel, Or a group consisting of a metal of iron, an alloy of the metal, an oxide of the metal, a composition of the metal and carbon.

In order to increase the charge and discharge capacity of the battery, the first active material layer 120a and the second active material layer 120b may be composed of a mixture of a predetermined amount of silicon.

Hereinafter, a method of manufacturing the electrolytic copper foil 110 according to an embodiment of the present invention will be described in detail.

The method of the present invention includes forming a copper layer 111, and forming a first protective layer 112a and a second protective layer 112b on the copper layer 111.

First, a preparation containing 70 g / L to 90 g / L of copper ions, 50 g / L to 150 g / L of sulfuric acid, 2 mg / L to 20 mg / L of N-allyl thiourea (ATU), and 2 mg / L to 20 mg / L An electrolyte of L's bis- (3-sulfopropyl) disulfide (SPS).

The drop strength of the electrolytic copper foil 110 can be controlled by adjusting the concentration of the ATU. As the ATU concentration increases, the drop strength of the electrolytic copper foil 110 also increases significantly.

The texture coefficient [TC (220)] of the (220) plane of the first surface S1 and the second surface S2 of the electrolytic copper foil 110 can be controlled by adjusting the concentration of SPS. The texture coefficient [TC (220)] of the (220) surface of the electrolytic copper foil 110 also increases significantly as the SPS concentration increases.

The high-purity copper wire is heat-treated at a temperature range of 600 ° C to 900 ° C for 30 minutes to 60 minutes to sinter organic substances, pickle the heat-treated copper wire, and place the acid-washed copper wire in sulfuric acid. In order to prepare an electrolyte with little or no impurities. Then, ATU and SPS were added to the electrolyte.

Subsequently, in the electrolyte between the electrode plates by 50 deg.] C to 60 deg.] C of each other and spaced apart from the rotating drum electrode generating a current 40 A / dm ² to 80 A / dm ² of current density in electroplating to the rotating electrode drum A copper layer 111 is formed thereon.

Effect of current density arithmetic mean roughness electrolytic copper foil 110 (R _a). The arithmetic mean roughness (R _a ) decreases significantly as the current density increases. In other words, as the current density decreases, the arithmetic mean roughness (R _a ) increases significantly.

A polishing brush having a grit size of 800 to 3000 is used to polish the surface of the rotary electrode drum (for example, the surface on which copper is deposited by performing electroplating). Preferably, while the water is spreading in the width direction, the surface of the rotating electrode drum is polished uniformly in the width direction by surface polishing the surface of the rotating electrode drum.

The degree of polishing of the surface of the rotating electrode drum (for example, a surface where copper is deposited by performing electroplating) affects the arithmetic average roughness (R _a ), the maximum height roughness (R _max ), and the like of the second surface S2 of the electrolytic copper foil 110.

According to the present invention, the concentration of silver (Ag) in the electrolytic solution is maintained at 50 mg / L or less when the plating is performed. The concentration of silver (Ag) affects the maximum height roughness (R _max ) of the electrolytic copper foil 110. The maximum height roughness (R _max ) of the electrolytic copper foil 110 significantly increases as the concentration of silver (Ag) decreases.

In order to prevent silver from flowing into the electrolyte during electroplating so that the concentration of silver (Ag) in the electrolyte exceeds 50 mg / L, a small amount of chloride ions (for example, 15 to 25 ppm) that can react with silver (Ag) to silver chloride (AgCl) may Add to electrolyte. As a result, silver (Ag) in the electrolytic solution may have a concentration of, for example, 1 mg / L to 50 mg / L.

Continuous (or cyclic) filtration can be performed at a flow rate of 39 m ³ / hr to 46 m ³ / hr to remove solid impurities from the electrolyte while performing electroplating. When the flow rate is less than 39 m ³ / hr, the flow velocity decreases, the overvoltage increases, and the copper layer 111 is unevenly formed. On the other hand, when the flow rate exceeds 46 m ³ / hr, the filter is damaged and foreign matter enters the electrolytic solution. The flow rate of the electrolyte also affects the drop strength of the electrolytic copper foil 110.

In order to manufacture the electrolytic copper foil 110 having a weight deviation of 3% or less, it is preferable to keep the variation in the flow rate during plating at 5% / sec or less. When the change in the flow rate of the electrolytic solution is greater than 5% / sec, the change in the copper plating efficiency in the width direction of the copper layer 111 increases, and the weight deviation of the electrolytic copper foil 110 exceeds 3%.

Then, the first protective layer 112a and the second protective layer on the copper layer 111 are formed by soaking the copper layer 111 manufactured as described above in a rust-proof solution (for example, soaking at room temperature for 2 seconds to 20 seconds). Layer 112b. The rust preventive solution contains 0.5 to 1.5 g / L of chromium. After soaking, the copper layer 111 is dried.

The antirust solution may further include at least one of a silane compound and a nitrogen compound. For example, the rust preventive solution may contain 0.5 g / L to 1.5 g / L of Cr and 0.5 g / L to 1.5 g / L of a silane compound.

The secondary battery electrode (that is, the anode) of the present invention can be manufactured by coating a negative electrode active material on the obtained electrolytic copper foil 110 of the present invention.

The negative electrode active material is selected from metals such as carbon, silicon, germanium, tin, lithium, zinc, magnesium, cadmium, cerium, nickel, or iron, alloys of the metal, oxides of the metal, and combinations of the metal and carbon. Group of people.

For example, by mixing 1 to 3 weight ratio of styrene-butadiene rubber (SBR. Styrene butadiene rubber) and 1 to 3 weight ratio of carboxymethyl cellulose (CMC. Carboxymethyl cellulose) and 100 weight ratio as the negative electrode Carbon of the active material, and then distilled water was used as a solvent to prepare a slurry. Subsequently, the electrolytic copper foil 110 is coated with a slurry having a thickness of 20 μm to 100 μm by a doctor blade, and pressurized at a temperature of 100 ° C. to 130 ° C. under a pressure of 0.5 ton / cm ² to 1.5 ton / cm ² .

The lithium secondary battery can be manufactured using a conventional cathode, an electrolyte and a separator, and a secondary battery electrode (or anode) manufactured as described above.

Hereinafter, the contents of the present invention will be described in detail with reference to examples and comparative examples. However, the following examples are merely examples to help understand the present invention, and the scope of the present invention is not limited to these examples.

Examples 1 to 6 and Comparative Examples 1 to 7

A current having a current density of 60 A / dm ² was generated between the electrode plate and the rotating electrode drum spaced apart from each other in the electrolytic solution to form a copper layer on the rotating electrode drum. The electrolyte contains 75 g / L of copper ions, 100 g / L of sulfuric acid, 100 g / L of ATU, and 100 g / L of SPS, and is maintained at a temperature of 55 ° C. The flow rate of the electrolytic solution was 42 m ³ / hr. The changes in the ATU concentration, SPS concentration, silver (Ag) concentration, and electrolyte flow rate used for electroplating, and the particle size of the polishing brush used to polish the surface of the rotating electrode drum are shown in Table 1 below. An electrolytic copper foil is prepared by soaking a copper layer formed by electroplating, and then drying the copper layer.

[Table 1]

The electrolytic copper foils of the examples and comparative examples described above were obtained with PMRs, a texture coefficient (TC (220)) of the (220) plane, a drop strength, and a weight deviation. The results are shown in Table 2. In addition, in the examples and comparative examples shown in Table 2, whether wrinkles and tears occurred during the manufacturing process of the electrolytic copper foil.

* Maximum profile ratio (PMR)

According to the JIS B 0601-2001 standard, using a SJ-310 light meter manufactured by Mitutoyo Co., the first surface (the surface on the copper layer adjacent to the matte surface) and the second surface (on the copper layer) were measured the surface adjacent to the shiny surface) of the arithmetic mean roughness (R _a) and a maximum height roughness (R _max) [measuring length: 4mm (not including the truncated portion)]. Next, the PMR of the first surface and the second surface is obtained by calculating the ratio (R _max / R _a ) of the maximum height roughness (R _max ) to the arithmetic mean roughness (R _a ).

* Texture coefficient of (220) plane [TC (220)]

By performing X-ray diffraction within a diffraction angle (2θ) of 30 ° to 95 ° [(i) target: copper K α1, (ii) interval between 2θ: 0.01 °, (iii) Scanning rate of 2θ: 3degree / min] An XRD pattern with peaks corresponding to n crystal planes is obtained, and the XRD diffraction (light) intensity of each crystal plane (hkl) is obtained from the XRD graph [I (hkl)] . In addition, the diffraction (light) intensity [I ₀ (hkl)] of the n crystal planes of the standard copper powder specified by JCPDS was obtained. Next, get the arithmetic mean of I (hkl) / I ₀ (hkl) for n crystal planes, and then divide the I (220) / I ₀ (220) of (220) plane by the arithmetic mean to Calculate the texture coefficient [TC (220)] of the (220) surface of the electrolytic copper foil 110. That is, the texture coefficient [TC (220)] of the (220) plane will be calculated based on Equation 1 below.

[Equation 1]

Falling strength (kgf / mm ² )

The drop strength of the electrolytic copper foil was measured using UTM at a room temperature of 25 ° C. The width of the sample is 12.7mm, the distance between the clamps is 50mm, and the measurement speed is 50mm / min.

* Weight deviation (%)

A 5 cm × 5 cm sample was taken from left, middle, and right points of the electrolytic copper foil in the width direction, and the weights of the three samples were measured. Calculate the arithmetic average weight and standard deviation using the measured values, and then calculate the ratio (%) of the weight standard deviation and the average weight, [ie, (weight standard deviation / average weight) × 100].

[Table 2]

Referring to Table 2 above, in the case where the electrolytic copper foil contains a surface with a PMR less than 4.8 (in Comparative Example 1); in the case where the electrolytic copper foil contains a surface with a PMR greater than 16.1 (in Comparative Example 2); When the foil contains a surface with a texture coefficient [TC (220)] of less than 0.49 (in Comparative Example 6); when the surface of the electrolytic copper foil contains a drop strength of less than 35 kgf / mm ² ( In Comparative Example 3), and in the case where the electrolytic copper foil contains a surface having a weight deviation of more than 3% (in Comparative Example 5), wrinkles occur during the manufacturing process of the electrolytic copper foil. FIG. 3 is a photograph of an electrolytic copper foil having a wrinkle defect in Comparative Example 1. FIG.

In addition, when the electrolytic copper foil includes a surface having a drop strength of more than 58 kgf / mm ² (in Comparative Example 4), tearing of the electrolytic copper foil occurs. FIG. 4 is a photograph of an electrolytic copper foil tearing during the manufacturing process of Comparative Example 4. FIG.

Specifically, when the electrolytic copper foil includes a surface having a texture coefficient [TC (220)] of (220) plane greater than 1.28 (in Comparative Example 7), wrinkling and tearing occur.

According to the present invention, an electrolytic copper foil having substantially no wrinkle defects can be manufactured. As a result, the electrolytic copper foil can be uniformly coated with a negative electrode active material when manufacturing a negative electrode of a secondary battery. Therefore, according to the present invention, it is possible to prevent a short circuit of the secondary battery and delamination of the negative electrode active material due to uneven coating of the negative electrode active material. As a result, according to the present invention, it is possible to improve the life and capacity retention rate of the secondary battery.

100‧‧‧ electrode

110‧‧‧electrolytic copper foil

111‧‧‧ Copper

112a‧‧‧First protective layer

112b‧‧‧Second protective layer

120a‧‧‧first active material layer

120b‧‧‧Second active material layer

S1‧‧‧First surface

S2‧‧‧Second surface

MS‧‧‧ Matte surface

SS‧‧‧Glossy

FIG. 1 is a cross-sectional view of a secondary battery electrode according to an embodiment of the present invention. FIG. 2 is an X-ray diffraction (XRD) diagram of an electrolytic copper foil. FIG. 3 is a photograph of an electrolytic copper foil having a wrinkle defect in Comparative Example 1. FIG. FIG. 4 is a photograph of tearing of electrolytic copper foil in the manufacturing process of Comparative Example 4. FIG.

Claims (16)

An electrolytic copper foil includes a first surface and a second surface opposite to the first surface. The electrolytic copper foil includes: a copper layer including a matte surface facing the first surface and facing the second surface A glossy surface; a first protective layer on the matte surface; and a second protective layer on the glossy surface; wherein the first surface and the second surface each have a maximum profile of 4.8 to 16.1 ratio (profile maximum ratio, PMR), wherein the maximum profile height ratio is a maximum roughness (R _max) with an arithmetic mean roughness (R _a) of a ratio (R _max / R _a); and the electrodeposited copper foil The texture coefficient [TC (220)] of the (220) plane ranges from 0.49 to 1.28, the drop strength ranges from 35 kgf / mm ² to 58 kgf / mm ² , and the weight deviation ranges from less than 3%. The electrolytic copper foil of claim 1, wherein the first surface and the second surface each have a maximum height roughness (R _max ) of 1.2 μm to 3.7 μm and an arithmetic average roughness (R of 0.15 μm to 0.45 μm) _a ). The electrolytic copper foil of claim 1, wherein the first protective layer and the second protective layer each contain chromium (Cr). The electrolytic copper foil of claim 1, wherein the electrolytic copper foil has a thickness of 4 μm to 30 μm. A secondary battery electrode includes: an electrolytic copper foil including a first surface and a second surface opposite to the first surface; and a first active material layer formed on the first surface; wherein the electrolytic copper The foil includes: a copper layer including a matte surface facing the first surface and a glossy surface facing the second surface; a first protective layer on the matte surface; and a second protective layer on the The glossy surface; wherein the first surface and the second surface each have a profile maximum ratio (PMR) of 4.8 to 16.1, the maximum profile ratio is a maximum height roughness (R _max ) and an arithmetic the average roughness (R _a) of a ratio (R _max / R _a); and a texture coefficient of 0.49 to 1.28 with a (220) surface of the electrodeposited copper foil [TC (220)], 35 kgf / mm A drop strength of ² to 58 kgf / mm ² and a weight deviation of 3% or less. The secondary battery electrode of claim 5, wherein the first surface and the second surface each have a maximum height roughness (R _max ) of 1.2 μm to 3.7 μm and an arithmetic average roughness (0.15 μm to 0.45 μm) ( R _a ). The secondary battery electrode of claim 5, wherein the first protective layer and the second protective layer each contain chromium (Cr). The secondary battery electrode of claim 5, wherein the electrolytic copper foil has a thickness of 4 μm to 30 μm. The secondary battery electrode of claim 5, further comprising a second active material layer disposed on the second surface; wherein the first active material layer and the second active material layer each include at least one active material, and the at least one An active material is selected from a metal such as carbon, silicon, germanium, tin, lithium, zinc, magnesium, cadmium, cerium, nickel, or iron, or an alloy containing the metal, an oxide of the metal, and a composition consisting of the metal and carbon A group of things. A secondary battery comprising: a cathode; an anode including the secondary battery electrode according to any one of claims 5 to 9; an electrolyte for providing lithium ions to the cathode and the anode An environment moving between; and an isolation film for electrically insulating the cathode and the anode. A method for manufacturing an electrolytic copper foil, the method includes: forming a copper layer; and forming a protective layer on the copper layer; wherein the step of forming the copper layer includes: preparing an electrolytic solution, the electrolytic solution contains 70 g / L to 90 g / L copper ion, 50 g / L to 150 g / L sulfuric acid, 2 to 20 mg / L N-allyl thiourea (ATU), and 2 mg / L to 20 mg / L bis (3-sulfopropyl) Disulfide (bis- (3-sulfopropyl) disulfide (SPS)); and by applying a current having a density of 40 A / dm ² to 80 A / dm ² from an electrode plate to a rotating electrode drum Electroplating; wherein a surface of the rotary electrode drum is polished using a polishing brush having a grit size of 800 to 3000; and when the electroplating step is performed, the concentration of silver in the electrolyte is maintained at less than or It is equal to 50 mg / L. The method for manufacturing an electrolytic copper foil according to claim 11, wherein the step of preparing the electrolyte comprises: heat treating a copper wire at a temperature ranging from 600 ° C to 900 ° C for 30 minutes to 60 minutes; Copper wire; placing the pickled copper wire into a sulfuric acid; and adding ATU and SPS to the sulfuric acid into the copper wire. The method for manufacturing an electrolytic copper foil according to claim 11, wherein: when electroplating is performed, the electrolytic solution is subjected to continuous filtration (Continuous Filtration); and when the continuous filtration is performed, the flow rate of the electrolytic solution is 39m ³ / hr To 46m ³ / hr. The method for manufacturing an electrolytic copper foil according to claim 13, wherein the change in the flow rate is less than or equal to 5% / sec when the electroplating is performed. The method of manufacturing an electrolytic copper foil according to claim 11, wherein the step of forming the copper layer further comprises adding chloride ions that can react with silver to form a silver chloride precipitate to the electrolytic solution to avoid the silver in the electrolytic solution. Concentrations exceed 50 mg / L. The method for manufacturing an electrolytic copper foil as claimed in claim 11, wherein the step of forming the protective layer includes immersing the copper layer in a rust-proof solution containing 0.5 g / L to 1.5 g / L of chromium.