KR20180083512A - Electrolytic Copper Foil of High Reliability, Electrode Comprising The Same, Secondary Battery Comprising The Same, and Method for Manufacturing The Same - Google Patents

Abstract

Disclosed are a high reliability electrolytic copper foil capable of preventing tearing and/or wrinkle generation during a roll-to-roll process, a manufacturing method thereof, and an electrode and a secondary battery which are manufactured by the electrolytic copper foil to be able to have guaranteed high productivity. The yield strength of the electrolytic copper foil of the present invention measured immediately after an overlapping heat treatment is 35 to 58 kgf/mm^2, and the rate of change of a ratio of yield strength (RYS) of the electrolytic copper foil according to a temperature at which the overlapping heat treatment is performed is -0.0012 to -0.0002.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high reliability electrolytic copper foil, an electrode including the same, a secondary battery including the electrode, and a method of manufacturing the same. BACKGROUND ART [0002] Electrolytic Copper Foil of High Reliability, Electrode Comprising The Same, Secondary Battery Comprising The Same,

The present invention relates to a highly reliable electrolytic copper foil with suppressed wrinkles or tears, an electrode including the same, a secondary battery comprising the same, and a method of manufacturing the same.

The electrolytic copper foil is used to manufacture various products such as a negative electrode of a secondary battery and a flexible printed circuit board (FPCB).

Generally, an electrolytic copper foil is manufactured not only by a roll to roll (RTR) process but also for manufacturing a secondary battery and a flexible printed circuit board (FPCB) through a roll-to-roll (RTR) process.

The roll-to-roll (RTR) process is known as a process suitable for mass production of products because it enables continuous production. However, in reality, due to the tearing and / or wrinkling of the electrolytic copper foil, which is frequently caused during the roll-to-roll (RTR) process, especially the wrinkles at the portion not coated with the negative electrode active material (uncoated portion) And the facility must be restarted after these problems have been solved. The repeated interruption and re-start of such process facilities cause serious problems such as lowered productivity and lowered yield.

In particular, the electrolytic copper foil is inevitably more susceptible to tearing and / or wrinkling since it typically undergoes a thermal history of 40 to 190 ° C during the secondary battery manufacturing process.

Accordingly, the present invention relates to an electrolytic copper foil capable of preventing problems caused by limitations and disadvantages of the related art, an electrode including the same, a secondary battery including the same, and a method of manufacturing the same.

One aspect of the present invention is to provide a highly reliable electrolytic copper foil that can prevent ripping and / or wrinkling during a roll-to-roll (RTR) process.

Another aspect of the present invention is to provide an electrode capable of securing high productivity by being manufactured from a highly reliable electrolytic copper foil that can prevent ripping and / or wrinkling during a roll-to-roll (RTR) process.

Another aspect of the present invention is to provide a secondary battery capable of securing high productivity by being manufactured from a highly reliable electrolytic copper foil that can prevent ripping and / or wrinkling during a roll-to-roll (RTR) process.

Another aspect of the present invention is to provide a method of manufacturing a highly reliable electrolytic foil that can prevent tearing and / or wrinkling during a roll-to-roll (RTR) process.

Other features and advantages of the invention will be set forth in the description which follows, or may be learned by those skilled in the art from the description.

According to an aspect of the present invention, there is provided an electrolytic copper foil having a first surface and a second surface opposite to the first surface, the electrolytic copper foil having a matte surface facing the first surface and a shiny surface facing the second surface, A copper layer; A first protective layer on the mat surface; And a second protective layer on the shiny surface, wherein the yield strength of the electrolytic copper foil measured immediately after the cumulative heat treatment is 35 to 58 kgf / mm ^2, and the superimposed heat treatment is performed at 40 ° C for 30 minutes 1 heat treatment, a second heat treatment at 90 占 폚 for 30 minutes, a third heat treatment at 140 占 폚 for 30 minutes, and a fourth heat treatment for 30 minutes at 190 占 폚, Wherein the rate of change of the ratio of yield strength (RYS) of the electrolytic copper foil to the temperature is from -0.0012 to -0.0002.

The surface roughness R _z of each of the first and second surfaces may be 3 탆 or less and the difference in surface roughness R _z of the first and second surfaces may be 0.3 탆 or less.

Each of the first and second protective layers may include chromium (Cr), and the chromium (Cr) deposition amount difference on the first and second surfaces may be 2.5 mg / m ² or less.

The electrolytic copper foil may have an elongation of 3% or more at room temperature of 25 ± 15 ° C.

The electrolytic copper foil may have a thickness of 4 to 30 탆.

According to another aspect of the present invention, there is provided an electrolytic copper foil having a first side and a second side opposite to the first side; And a first active material layer on the first surface, the electrolytic copper foil comprising: a copper layer including a matte surface facing the first surface and a shiny surface facing the second surface; A first protective layer on the mat surface; And a second protective layer on the shiny surface, wherein the yield strength of the electrolytic copper foil measured immediately after the cumulative heat treatment is 35 to 58 kgf / mm ^2, and the superimposed heat treatment is performed at 40 ° C for 30 minutes 1 heat treatment, a second heat treatment at 90 占 폚 for 30 minutes, a third heat treatment at 140 占 폚 for 30 minutes, and a fourth heat treatment for 30 minutes at 190 占 폚, And the rate of change of the yield strength ratio (RYS) of the electrolytic copper foil with respect to the temperature is -0.0012 to -0.0002.

The surface roughness R _z of each of the first and second surfaces may be 3 탆 or less and the difference in surface roughness R _z of the first and second surfaces may be 0.3 탆 or less, Each of the protective layers may include chromium (Cr), and the chromium (Cr) deposition amount difference on the first and second surfaces may be 2.5 mg / m ² or less.

And a second active material layer on the second surface, wherein the first and second active material layers are formed of a material selected from the group consisting of carbon; A metal of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; An alloy comprising the metal; An oxide of the metal; And at least one active material selected from the group consisting of a complex of the metal and carbon.

According to another aspect of the present invention, there is provided a fuel cell comprising: a cathode; An anode comprising the electrode for the secondary battery; An electrolyte for providing an environment in which lithium ions can move between the anode and the cathode; And a separator that electrically isolates the anode and the cathode from each other.

According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: forming a copper layer; And forming a protective layer on the copper layer, wherein the copper layer forming step comprises forming a copper layer comprising 70 to 90 g / L of copper ion, 50 to 150 g / L of sulfuric acid, 2 to 20 mg / L of N - an allylthiourea, and 2 ppm or less of chlorine (Cl); And performing electroplating by energizing the positive electrode plate and the rotating negative electrode drum, which are arranged to be spaced apart from each other, in the electrolyte at a current density of 40 to 80 A / dm < ² >.

During the electroplating, the concentration of the N-allyl thiourea in the electrolyte may be controlled such that the concentration change rate of the N-allyl thiourea defined by the following Equation 1 is 10% or less.

* 1: Change in concentration (%) = [(maximum concentration - minimum concentration) / maximum concentration] × 100

The method of the present invention may further comprise performing an inline analysis on the concentration of the N-allyl thiourea in the electrolyte solution.

Continuous filtration may be performed on the electrolyte while the electroplating is performed, and the flow rate of the electrolyte may be 39 to 46 m ³ / hr when the continuous filtration is performed.

The surface of the rotating cathode drum may be polished with an abrasive brush having a grain size of # 800 to # 3000.

The protective layer forming step may include immersing the copper layer in a rust preventive solution containing 0.5 to 1.5 g / L of Cr.

The foregoing general description of the present invention is intended to be illustrative of or explaining the present invention, but does not limit the scope of the present invention.

According to the present invention, when the intermediate parts such as the flexible printed circuit board (FPCB), the secondary battery, and the final products are manufactured through the roll-to-roll (RTR) process, the ripple of the electrolytic copper foil And as a result, the productivity and reliability of the intermediate parts as well as the final products can be greatly improved.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
1 is a cross-sectional view of an electrode for a secondary battery according to an embodiment of the present invention,
FIG. 2 is a graph illustrating the rate of change of the yield strength ratio (RYS) according to the superposition heat treatment temperature of the electrolytic copper foil,
3 is a photograph of an electrolytic copper foil of Example 1 in which a negative electrode active material is partially coated,
4 is a photograph of an electrolytic copper foil of Comparative Example 1 in which a negative electrode active material is partially coated,
5 is a photograph of electrolytic copper foils of comparative examples 2 and 4 torn in the process of manufacturing a negative electrode for a secondary battery.

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

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. Therefore, the present invention encompasses all changes and modifications that come within the scope of the invention as defined in the appended claims and equivalents thereof.

The lithium ion secondary battery includes a cathode, an anode, an electrolyte that provides an environment in which lithium ions can move between the anode and the cathode, and electrons generated from one electrode, And a separator electrically isolating the anode and the cathode from each other to prevent the electrode from being wasted by moving to the other electrode.

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

1, an electrode 100 for a secondary battery according to an embodiment of the present invention includes an electrolytic copper foil 110 having 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 on the second surface S2. 1 shows an example in which active material layers 120a and 120b are formed on both the first and second surfaces S1 and S2 of the electrolytic copper foil 110. However, the present invention is not limited thereto, The secondary battery electrode 100 may include only one of the first and second active material layers 120a and 120b as an active material layer.

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

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

1, the electrolytic copper foil 110 of the present invention includes a copper layer 111 including a matte surface MS and a shiny surface SS, a copper layer 111, A first protective layer 112a on the mat surface MS of the copper layer 111 and a second protective layer 112b on the shiny surface SS of the copper layer 111. [

The mat surface MS is a surface of the copper layer 111 facing the first surface S1 of the electrolytic copper foil 110. The shiny surface SS is formed on the second surface S2 of the electrolytic copper foil 110, Is the surface of the copper layer 111 facing the copper layer 111.

The copper layer 111 of the present invention may be formed on the rotating cathode drum through electroplating, which refers to the surface that has come into contact with the rotating cathode drum during the electroplating process, MS) refers to the opposite side of the shiny surface SS.

Although it is common that the shiny surface SS has a lower surface roughness R _z than the mat surface MS, the present invention is not limited to this, and the surface roughness R _z of the shiny surface SS is not limited to the mat surface May be equal to or higher than the surface roughness (R _z ) of the substrate (MS).

The first and second protective layers 112a and 112b may include chromium (Cr) for preventing corrosion of the copper layer 111 and improving heat resistance.

As described above, it is important for a manufacturer of an electrolytic copper foil to supply a secondary battery maker with a highly reliable electrolytic copper foil 110 having a low risk of tearing and / or wrinkling during a roll-to-roll (RTR) process for manufacturing secondary batteries. Therefore, it is an important task for the electrolytic copper foil manufacturer to grasp the properties related to the tearing and wrinkling of the electrolytic copper foil 110 and properly manage the properties.

As described above, the electrolytic copper foil 110 is typically subjected to a thermal history of 40 to 190 DEG C during the secondary battery manufacturing process. Therefore, although the yield strength reduction rate according to the temperature of the electrolytic copper foil 110 should be within an appropriate range within the above temperature range, the electrolytic copper foil 110 (particularly, the uncoated portion not coated with the negative electrode active material) / RTI > and / or wrinkles can be prevented.

That is, according to the present invention, the "rate of change of yield strength ratio (RYS) according to the superposition heat treatment temperature" of the electrolytic copper foil 110 is the ratio of the ripple of the electrolytic copper foil 110 generated during the roll- It was found that there was a close relationship with wrinkles. In order to provide a highly reliable electrolytic copper foil 110 capable of suppressing the occurrence of tearing and / or wrinkling as much as possible during the roll-to-roll (RTR) process for manufacturing a secondary battery, the yield strength of the electrolytic copper foil 110 Quot; rate of change of ratio RYS " is within the optimum range.

In the present invention, the " cumulative heat treatment " includes a first heat treatment at 40 DEG C for 30 minutes, a second heat treatment at 90 DEG C for 30 minutes, a third heat treatment at 140 DEG C for 30 minutes, Followed by a fourth heat treatment for 30 minutes in succession.

The term "rate of change of the yield strength ratio RYS according to the superposition heat treatment temperature" in the present invention means the rate of change of the yield strength ratio RYS according to the superposition heat treatment temperature in terms of the yield of the electrolytic copper foil according to the temperature at which the superposition heat treatment is performed (i.e., 40 ° C, 90 ° C, 140 ° C, The yield strength of the electrolytic copper foil is measured immediately after each heat treatment, and the ratio of the yield strength immediately after each heat treatment to the yield strength immediately after the first heat treatment (that is, the yield strength ratio RYS = αT + C (where T is the superposition heat treatment temperature, and RYS is the heat treatment temperature), based on the calculated values RYS ₄₀ , RYS ₉₀ , RYS ₁₄₀ , and RYS ₁₉₀ , C is the intrinsic characteristic constant of the electrolytic copper foil sample "), which is the slope of the linear regression equation (see the graph of FIG. 2). The yield strength is measured using a universal testing machine (UTM) with a sample width of 12.7 mm, a distance between grips of 50 mm, and a measurement speed of 50 mm / min.

According to the present invention, the rate of change of the yield strength ratio RYS according to the superposition heat treatment temperature of the electrolytic copper foil 110 is from -0.0012 to -0.0002.

If the " rate of change of the yield strength ratio RYS according to the superposition heat treatment temperature " is less than -0.0012, the yield strength change rate of the electrolytic copper foil 110 is excessively large within the temperature range of the thermal history experienced in the manufacturing process of the secondary battery, The risk is great.

On the other hand, when the " rate of change of the yield strength ratio RYS according to the superposition heat treatment temperature " exceeds -0.0002, the yield strength change rate of the electrolytic copper foil 110 is excessively high within the temperature range of the thermal history experienced in the manufacturing process of the secondary battery The brittleness is too strong even after experiencing the thermal history, so that the electrolytic copper foil 110 is easily torn during the anode active material pressing process.

According to the present invention, the yield strength of the electrolytic copper foil 110 measured immediately after the superposition heat treatment (i.e., measured immediately after the fourth heat treatment) is 35 to 58 kgf / mm ² .

If the yield strength of the electrolytic copper foil 110 measured after the fourth heat treatment is less than 35 kgf / mm ² , it is easily deformed by the force and / or heat applied by the equipment during the manufacturing process of the secondary battery, and wrinkles are generated.

On the other hand, if the yield strength of the electrolytic copper foil 110 measured after the fourth heat treatment exceeds 58 kgf / mm ² , the electrolytic copper foil 110 is too brittle and the electrolytic copper foil 110 tears easily during the negative electrode active material pressing process .

The difference between the first and second faces S1 and S2 of the electrolytic copper foil 110 with respect to factors such as the surface roughness R _z and the chromium (Cr) adherence is also related to the wrinkles of the electrolytic copper foil 110 Was discovered. That is, the difference between the first and second sides S1 and S2 with respect to the factors causes a stress difference in the first and second faces S1 and S2, Lt; / RTI > Therefore, in order to minimize the wrinkles of the electrolytic copper foil 110, it is necessary to minimize the difference between the first and second faces S1 and S2 with respect to the important factors.

According to the present invention, in order to minimize curling of the electrolytic copper foil 110, the difference in surface roughness R _z of the first and second surfaces S1 and S2 is 0.3 탆 or less.

The surface roughness (R _z ) can be measured in accordance with JIS B 0601-2001 (measuring length: 4 mm (excluding cut off section)). According to an embodiment of the present invention, the surface roughness R _z of each of the first and second surfaces S1 and S2 of the electrolytic copper foil 110 may be 3 탆 or less.

When the surface roughness R _z is more than 3 μm, the first and second faces S1 and S2 of the electrolytic copper foil 110 are excessively uneven and the coating uniformity of the negative electrode active material is deteriorated. As a result, 110 and the first and second active material layers 120a, 120b is remarkably lowered, resulting in a decrease in the capacity retention rate of the secondary battery.

Further, according to the present invention, the chromium (Cr) adhesion amount difference on the first and second surfaces S1 and S2 is 2.5 mg / m ² or less. The amount of chromium (Cr) deposited can be measured by AAS (Atomic Absorption Spectrometry) analysis.

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

The electrolytic copper foil 110 of the present invention may have an elongation of 3% or more at room temperature (25 占 15 占 폚). If the elongation percentage of the electrolytic copper foil 110 is less than 3%, the electrolytic copper foil 110 can not stretch due to the force applied during the manufacturing process of the electrode 100 and the secondary battery, and the risk of tearing increases.

The electrolytic copper foil 110 of the present invention may have a thickness of 4 to 30 占 퐉.

The first and second active material layers 120a and 120b may be formed of a material selected from the group consisting of carbon; A metal of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; An alloy comprising the metal; An oxide of the metal; And at least one active material selected from the group consisting of a composite of the metal and carbon may be included as a negative electrode active material.

In order to increase the charge / discharge capacity of the secondary battery, the first and second active material layers 120a and 120b may be formed of a mixture containing a predetermined amount of Si.

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 the steps of forming a copper layer 111 and forming a protective layer 112a, 112b on the copper layer 111.

First, an aqueous solution containing 70 to 90 g / L of copper ion, 50 to 150 g / L of sulfuric acid, 2 to 20 mg / L of N-allylthiourea of the following formula (1) Cl) is prepared.

* Formula 1:

For example, a high purity copper wire is heat treated at 600 to 900 DEG C for 30 to 60 minutes to pick up organic matter, pick up the heat-treated copper wire, and put the pickled copper wire into sulfuric acid to cause no or little impurities After preparing the plating solution, the electrolytic solution can be prepared by adding N-allyl thiourea and chlorine ions to the plating solution.

The rate of change of the yield strength ratio RYS according to the superposition heat treatment temperature of the electrolytic copper foil 110 is mainly determined by the kind and concentration of the additive of the electrolytic solution. According to the present invention, an electrolytic copper foil having an " rate of change of the yield strength ratio RYS according to the superposition heat treatment temperature " of -0.0012 to -0.0002 (inclusive) by containing the electrolyte in an amount of 2 to 20 mg / 110) can be produced.

The electrolytic copper foil 110 produced through the electrolytic solution containing less than 2 mg / L of N-allylthio urea as an additive has a "rate of change in the yield strength ratio RYS according to the superposition heat treatment temperature" of less than -0.0012, Wrinkles are caused in the battery manufacturing process.

On the other hand, the electrolytic copper foil 110 produced through an electrolytic solution containing an N-allylthio urea in an amount exceeding 20 mg / L as an additive has a rate of change in yield strength ratio RYS according to the superposition heat treatment temperature exceeding -0.0002 ) ". Such an electrolytic copper foil has an excessively high yield strength exceeding 58 kgf / mm < ² > even after undergoing a thermal history of 40 to 190 DEG C, so that it tears easily in the manufacturing process of the secondary battery.

By keeping the concentration of chlorine (Cl) in the electrolytic solution at 2 ppm or less, copper grain growth can be suppressed in the initial plating step and the rate of change of the yield strength ratio RYS according to the superimposed heat treatment temperature Quot; and " yield strength " can be manufactured.

By performing electroplating by the 50 to 60 ℃ the negative electrode a positive electrode plate and the rotation spaced apart from each other in the electrolyte drum of energization with a current density of 40 to 80 A / dm ² with the copper layer 111 on the rotating cathode drum .

If the current density is less than 40 A / dm < ^{2 &} gt ;, the first heat treatment at 40 DEG C for 30 minutes, the second heat treatment at 90 DEG C for 30 minutes, the third heat treatment at 140 DEG C for 30 minutes, Minute, the yield strength of the electrolytic copper foil 110 measured after sequentially and superimposingly performing the fourth heat treatment is less than 35 kgf / mm < ² > so that the force and / or heat applied by the equipment during the manufacturing process of the secondary battery The electrolytic copper foil 110 is easily deformed and wrinkles are generated.

On the other hand, when the current density exceeds 80 A / dm ² , the yield strength of the electrolytic copper foil 110 measured after the fourth heat treatment exceeds 58 kgf / mm ² , so that the negative electrode active material pressing process The electrolytic copper foil 110 tears easily.

Continuous (or circulating) filtration to remove solid impurities from the electrolyte during the electroplating may be performed at a flow rate of 39 to 46 m ³ / hr. If the flow rate is less than 39 m < ³ > / hr, the flow velocity is lowered, the overvoltage is increased, the copper layer 111 is formed unevenly, and the yield strength of the electrolytic copper foil 110 is affected. On the other hand, if the flow rate exceeds 46 m ³ / hr, the filter is damaged and foreign matter flows into the electrolytic solution.

According to an embodiment of the present invention, in order to ensure a uniform quality in the width direction and the longitudinal direction of the electrolytic copper foil 110, the concentration of the N-allyl thiourea defined by the following formula 1 during the electroplating The concentration of the N-allyl thiourea in the electrolyte can be controlled so that the rate of change is 10% or less.

* 1: Change in concentration (%) = [(maximum concentration - minimum concentration) / maximum concentration] × 100

In order to control the concentration of the N-allyl thiourea in the electrolyte so that the concentration change rate of the N-allyl thiourea is 10% or less, the method of the present invention is characterized by an inline And performing an inline analysis.

On the other hand, the degree of polishing of the rotating cathode drum surface (surface on which copper is precipitated by electroplating) is one element for controlling the surface roughness R _z of the second surface S2 of the electrolytic copper foil 110 and the chromium deposition amount. According to an embodiment of the present invention, the surface of the rotary cathode drum is polished with an abrasive brush having a grain size of # 800 to # 3000. The drum surface can be uniformly polished in the width direction by spraying water in the width direction of the drum when polishing the rotary cathode drum.

The copper layer 111 thus prepared is dipped (for example, at room temperature for 2 to 20 seconds) in a rust preventive solution containing 0.5 to 1.5 g / L of Cr and dried to form a copper layer 111 on the copper layer 111 Thereby forming the first and second protective layers 112a and 112b, respectively.

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

By coating the anode active material on the electrolytic copper foil 110 of the present invention thus manufactured, the electrode (i.e., cathode) for a secondary battery of the present invention can be manufactured.

The negative electrode active material may include carbon; A metal of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; An alloy comprising the metal; An oxide of the metal; And a complex of the metal and carbon.

For example, 1 to 3 parts by weight of styrene butadiene rubber (SBR) and 1 to 3 parts by weight of carboxymethyl cellulose (CMC) are mixed with 100 parts by weight of carbon for an anode active material, and distilled water is used as a solvent to prepare a slurry. Next, the slurry is coated on the electrolytic copper foil 110 with a doctor blade at a thickness of 20 to 100 mu m and pressed at 110 to 130 DEG C under a pressure of 0.5 to 1.5 ton / cm < ² >.

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

Hereinafter, the present invention will be described in detail with reference to examples and comparative examples. It is to be understood, however, that the present invention is not limited to the following embodiments, but the scope of the present invention is not limited to these embodiments.

Example 1

A positive electrode plate and a rotating negative electrode drum, which were arranged so as to be spaced apart from each other in the electrolyte solution, were energized at a current density of 60 A / dm ² to form a copper layer on the rotating negative electrode drum. The particle size of the polishing brush used for polishing the rotary cathode drum surface was # 2000. 75 g / L of copper ion, 100 g / L of sulfuric acid, and 1.1 ppm of chloride ion. And 2.8 mg / L of N-allyl thiourea (ATU). During the electroplating, the electrolyte was maintained at about 55 ° C. and the concentration change rate of N-allyl thiourea (ATU) was controlled to be within 7%. The copper layer formed through the electroplating was immersed in a rust preventive solution and then dried to complete an electrolytic copper foil.

Example 2

An electrolytic copper foil was completed in the same manner as in Example 1, except that the concentration of N-allyl thiourea (ATU) was 19.5 mg / L when preparing the electrolytic solution.

Example 3

The electrolytic solution was prepared in the same manner as in Example 1, except that the concentration of N-allyl thiourea (ATU) was 10.5 mg / L and electroplating was performed at a current density of 40 A / dm ² . Completed.

Example 4

The electrolytic solution was prepared in the same manner as in Example 1, except that the concentration of N-allyl thiourea (ATU) was 10.5 mg / L and electroplating was performed at a current density of 80 A / dm ² . Completed.

Comparative Example 1

An electrolytic copper foil was completed in the same manner as in Example 1, except that the concentration of N-allyl thiourea (ATU) was 1 mg / L when the electrolytic solution was prepared.

Comparative Example 2

An electrolytic copper foil was completed in the same manner as in Example 1, except that the concentration of N-allyl thiourea (ATU) was 21 mg / L when preparing the electrolytic solution.

Comparative Example 3

The electrolytic solution was prepared in the same manner as in Example 1, except that the concentration of N-allyl thiourea (ATU) was 10.5 mg / L and electroplating was performed at a current density of 30 A / dm ² . Completed.

Comparative Example 4

The electrolytic solution was prepared in the same manner as in Example 1 except that the concentration of N-allyl thiourea (ATU) was 10.5 mg / L and electroplating was performed at a current density of 90 A / dm ² . Completed.

The rate of change (?) Of the yield strength ratio (RYS) according to the superposition heat treatment temperature and the yield strength after superposition heat treatment of the electrolytic copper foils of the examples and comparative examples prepared above were respectively measured by the following methods, The results are shown in Table 1. The electrolytic copper foils of Examples and Comparative Examples were used to fabricate a secondary battery anode in the following manner, and whether or not wrinkles or tears were generated in the process was shown in Table 1.

* The yield strength ( kgf / mm ² ) and the rate of change of the yield strength ratio (RYS) according to the superposition heat treatment temperature (α)

The electrolytic copper foil was subjected to a first heat treatment at 40 占 폚 for 30 minutes, a second heat treatment at 90 占 폚 for 30 minutes, a third heat treatment at 140 占 폚 for 30 minutes, and a fourth heat treatment at 190 占 폚 for 30 minutes The superimposed heat treatment was carried out. The yield strength of the electrolytic copper foil was measured immediately after the first to fourth heat treatments (yield strength after superficial heat treatment = yield strength measured immediately after the fourth heat treatment), yield strength immediately after each heat treatment to the yield strength immediately after the first heat treatment (RYS = α · T + C (RYS)) based on the calculated values (RYS ₄₀ , RYS ₉₀ , RYS ₁₄₀ , and RYS ₁₉₀ ) (Where T is the superposition heat treatment temperature and C is the intrinsic property constant of the electrolytic copper foil sample) ", the ratio of the yield strength ratio RYS according to the superposition heat treatment temperature of the electrolytic copper foil The slope (?) Of the linear regression equation] "was obtained. The yield strength was measured using a universal testing machine (UTM), in which the width of the sample was 12.7 mm, the distance between the grips was 50 mm, and the measuring speed was 50 mm / min.

* Manufacture of cathode for secondary battery

2 parts by weight of SBR (styrene butadiene rubber) and 2 parts by weight of CMC (caroboxymethylcellulose) were mixed with 100 parts by weight of carbon commercially available as an anode active material. Then, a slurry was prepared by adding distilled water as a solvent to this mixture. The slurry was coated on the surface of the electrolytic copper foil to a thickness of about 60 mu m using a doctor blade, dried at 120 DEG C, and then subjected to a roll pressing process (pressure: 1 ton / cm < ² >) to prepare a negative electrode.

Current density
(A / dm ² ) ATU
(mg / L) alpha Yield strength after super heat treatment (kfg / mm ² ) effect wrinkle Tear Example 1 60 2.8 -0.0012 46.3 Good Good Example 2 60 19.5 -0.0002 45.9 Good Good Example 3 40 10.5 -0.0009 35.2 Good Good Example 4 80 10.5 -0.0009 57.6 Good Good Comparative Example 1 60 One -0.0014 46.3 Wrinkle Good Comparative Example 2 60 21 -0.0001 46.1 Good Tearing Comparative Example 3 30 10.5 -0.0009 34.2 Wrinkle Good Comparative Example 4 90 10.5 -0.0009 58.8 Good Tearing

As can be seen from the above Table 1, when the concentration of N-allyl thiourea in the electrolyte was less than 2 mg / L (Comparative Example 1), the rate of change of the yield strength ratio RYS according to the superposition heat treatment temperature α) "was less than -0.0012, and wrinkles of electrolytic copper foil occurred in the process of manufacturing negative electrode for secondary battery. That is, unlike the electrolytic copper foil of Example 1 (see the photograph of FIG. 3) in which no wrinkles were generated in both the coated portion and the uncoated portion coated with the negative electrode active material, the electrolytic copper foil of Example 1 In the electrolytic copper foil of Example 1, significant wrinkles were generated in the uncoated portion not coated with the negative electrode active material.

When the electric density applied during the electroplating was less than 40 A / dm ² (Comparative Example 3), the yield strength of the electrolytic copper foil after the superimposed heat treatment was less than 35 kgf / mm ² and wrinkles of the electrolytic copper foil were generated in the manufacturing process of the negative electrode for the secondary battery .

On the other hand, when the concentration of N-allyl thiourea in the electrolyte exceeds 20 mg / L (Comparative Example 2), the rate of change of the yield strength ratio RYS according to the superposition heat treatment temperature of the electrolytic copper foil is -0.0002 And tearing of the electrolytic copper foil occurred during the manufacturing process of the negative electrode for the secondary battery. Further, in the case where the electric density applied during electroplating exceeded 80 A / dm ² (Comparative Example 4), the "yield strength after superimposed heat treatment" of the electrolytic copper foil exceeded 58 kgf / mm ² . Tearing occurred. 5 is a photograph of electrolytic copper foils of comparative examples 2 and 4 torn in the process of manufacturing a negative electrode for a secondary battery.

100: secondary battery electrode 110: electrolytic copper foil
111: copper layer 112a: first protective layer
112b: second protective layer 120a: first active material layer
120b: second active material layer

Claims (15)

An electrolytic copper foil having a first surface and a second surface opposite to the first surface,
A copper layer comprising a matte surface facing the first surface and a shiny surface facing the second surface;
A first protective layer on the mat surface; And
And a second protective layer on the shiny surface,
The yield strength of the electrolytic copper foil measured immediately after the cumulative heat treatment is 35 to 58 kgf / mm ^2. The superficial heat treatment is performed by a first heat treatment at 40 캜 for 30 minutes, a second heat treatment at 90 캜 for 30 minutes , A third heat treatment at 140 占 폚 for 30 minutes, and a fourth heat treatment at 190 占 폚 for 30 minutes,
Wherein a rate of change of a ratio of yield strength (RYS) of the electrolytic copper foil to a temperature at which the superposition heat treatment is performed is from -0.0012 to -0.0002.
An electric boat. The method according to claim 1,
The surface roughness (R _z ) of each of the first and second surfaces is 3 μm or less,
Wherein a difference in surface roughness (R _z ) between the first and second surfaces is 0.3 탆 or less.
An electric boat. The method according to claim 1,
Wherein each of the first and second protective layers comprises chromium (Cr)
The first and of chromium (Cr) coating weight difference is 2.5 mg / m ² or less, wherein in the second surfaces,
An electric boat. The method according to claim 1,
And has an elongation of 3% or more at room temperature of 25 占 폚 to 15 占 폚.
An electric boat. The method according to claim 1,
Wherein the electrolytic copper foil has a thickness of 4 to 30 占 퐉.
An electric boat. An electrolytic copper foil having a first surface and a second surface opposite to the first surface; And
And a first active material layer on the first surface,
The electrolytic copper foil,
A copper layer including a mat surface facing the first surface and a shiny surface facing the second surface;
A first protective layer on the mat surface; And
And a second protective layer on the shiny surface,
The yield strength of the electrolytic copper foil measured immediately after the cumulative heat treatment is 35 to 58 kgf / mm ^2. The superficial heat treatment is performed by a first heat treatment at 40 캜 for 30 minutes, a second heat treatment at 90 캜 for 30 minutes , A third heat treatment at 140 占 폚 for 30 minutes, and a fourth heat treatment at 190 占 폚 for 30 minutes,
Wherein the rate of change of the yield strength ratio (RYS) of the electrolytic copper foil according to the temperature at which the superposition heat treatment is performed is from -0.0012 to -0.0002.
Electrode for secondary battery. The method according to claim 6,
The surface roughness (R _z ) of each of the first and second surfaces is 3 μm or less,
The difference in surface roughness (R _z ) between the first and second surfaces is 0.3 μm or less,
Wherein each of the first and second protective layers comprises chromium (Cr)
The first and of chromium (Cr) coating weight difference is 2.5 mg / m ² or less, wherein in the second surfaces,
Electrode for secondary battery. The method according to claim 6,
Further comprising a second active material layer on the second surface,
The first and second active material layers may be, independently from each other, carbon; A metal of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; An alloy comprising the metal; An oxide of the metal; And at least one active material selected from the group consisting of a complex of said metal and carbon.
Electrode for secondary battery. A cathode;
An anode comprising the electrode for a secondary battery according to any one of claims 6 to 8;
An electrolyte for providing an environment in which lithium ions can move between the anode and the cathode; And
And a separator for electrically insulating the anode and the cathode.
Secondary battery. Forming a copper layer; And
And forming a protective layer on the copper layer,
The copper layer forming step may include:
An electrolyte solution containing 70 to 90 g / L of copper ion, 50 to 150 g / L of sulfuric acid, 2 to 20 mg / L of N-allylthiourea, and 2 ppm or less of chlorine (Cl) ; And
And performing electroplating by energizing the positive electrode plate and the rotating negative electrode drum, which are arranged apart from each other in the electrolyte, at a current density of 40 to 80 A / dm < ² >.
Method of manufacturing electrolytic copper foil. 11. The method of claim 10,
Characterized in that the concentration of the N-allyl thiourea in the electrolyte is controlled such that the rate of change of the concentration of the N-allyl thiourea defined by the following formula 1 is 10% or less during the electroplating.
(%) = [(Maximum concentration - minimum concentration) / maximum concentration] × 100
Method of manufacturing electrolytic copper foil. 12. The method of claim 11,
Further comprising performing an inline analysis on the concentration of the N-allyl thiourea in the electrolyte.
Method of manufacturing electrolytic copper foil. 11. The method of claim 10,
Continuous filtration of the electrolyte is performed while the electroplating is performed,
Wherein the flow rate of the electrolytic solution when the continuous filtration is performed is 39 to 46 m ³ / hr.
Method of manufacturing electrolytic copper foil. 11. The method of claim 10,
Characterized in that the surface of the rotary cathode drum is polished with an abrasive brush having a grain size of # 800 to # 3000.
Method of manufacturing electrolytic copper foil. 11. The method of claim 10,
Wherein the forming of the protective layer comprises immersing the copper layer in an anticorrosive solution containing 0.5 to 1.5 g / L of Cr.
Method of manufacturing electrolytic copper foil.

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