KR102473557B1 - Electrolytic Copper Foil, Electrode Comprising The Same, Secondary Battery Comprising The Same, and Method for Manufacturing The Same - Google Patents

Abstract

Disclosed are a high-strength electrodeposited copper foil that prevents folding/wrinkling during a roll-to-roll (RTR) process, a method for manufacturing the same, and an electrode and a secondary battery that can secure high productivity by being manufactured with the electrodeposited copper foil. The electrodeposited copper foil of the present invention includes a copper film containing 99% by weight or more of copper and a protective layer on the copper film, and has a tensile strength of 45 kgf/mm ² or more.

Description

Electrolytic copper foil, an electrode including the same, a secondary battery including the same, and a manufacturing method thereof

The present invention relates to an electrodeposited copper foil, an electrode including the same, a secondary battery including the same, and a manufacturing method thereof.

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

In general, electrodeposited copper foil is not only manufactured through a roll-to-roll (RTR) process, but is also used in the manufacture of a negative current collector of a secondary battery, a flexible printed circuit board (FPCB), etc. 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 folding and/or wrinkles of the electrodeposited copper foil frequently occurring during the roll-to-roll (RTR) process, the roll-to-roll process equipment must be stopped and the equipment restarted after solving these problems, and such process equipment A serious problem of reduced productivity is caused by repetition of interruption and restart of operation.

That is, the folding and wrinkles of the electrodeposited copper foil caused during the roll-to-roll (RTR) process make it impossible to continuously produce products, thereby damaging the inherent merits of the roll-to-roll (RTR) process, resulting in a decrease in product productivity.

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

One aspect of the present invention is to provide a high-strength electrodeposited copper foil that has a high tensile strength of 45 kgf/mm ² or more, thereby preventing folding or wrinkles during a roll-to-roll (RTR) process.

Another aspect of the present invention is to provide an electrode capable of ensuring high productivity by being made of a high-strength electrodeposited copper foil that is prevented from being folded or wrinkled during a roll-to-roll (RTR) process.

Another aspect of the present invention is to provide a secondary battery capable of ensuring high productivity by being made of a high-strength electrodeposited copper foil preventing folding or wrinkles during a roll-to-roll (RTR) process.

Another aspect of the present invention is to provide a method for manufacturing a high-strength electrodeposited copper foil that can prevent folding or wrinkles during a roll-to-roll (RTR) process by having a high tensile strength of 45 kgf/mm ² or more.

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

According to one aspect of the present invention as above, a copper film containing 99% by weight or more of copper; and a protective layer on the copper film, and having a tensile strength of 45 kgf/mm ² or more, an electrodeposited copper foil is provided.

According to another aspect of the present invention, an electrodeposited copper foil including a copper film containing 99% by weight or more of copper and a protective layer on the copper film, and having a tensile strength of 45 kgf/mm ² or more; and an active material layer on the electrodeposited copper foil, wherein the active material layer includes carbon; a metal (Me) of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; an alloy containing the metal (Me); an oxide (MeO _x ) of the metal (Me); and at least one active material selected from the group consisting of a composite of the metal (Me) and carbon.

According to another aspect of the present invention, a cathode for providing lithium ions during charging; an anode that provides electrons and lithium ions upon discharge; an electrolyte providing an environment in which lithium ions can move between the positive electrode and the negative electrode; and a separator that electrically insulates the anode and the cathode, wherein the cathode includes a copper film containing 99% by weight or more of copper and a protective layer on the copper film, and has a thickness of 45 kgf/mm ² or more. Electrolytic copper foil having tensile strength; and an active material layer on the electrodeposited copper foil, wherein the active material layer includes carbon; a metal (Me) of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; an alloy containing the metal (Me); an oxide (MeO _x ) of the metal (Me); and at least one active material selected from the group consisting of a composite of the metal (Me) and carbon.

According to another aspect of the present invention, a step of forming a copper film on the rotating cathode drum by energizing a cathode plate and a rotating cathode drum spaced apart from each other in an electrolyte solution in an electrolytic cell, wherein the electrolyte solution is 50 to 100 g/L Electrodeposited copper foil (110 ) is provided.

The divalent cerium compound may be CeSO ₄ .

The electrolyte solution is maintained at 40 to 60 °C, and the current density provided by the positive electrode plate may be 40 to 80 A/dm ² .

When the copper layer is formed, a flow rate of the electrolyte solution supplied into the electrolytic bath may be 30 to 50 m ³ /hour.

The total organic carbon (TOC) content in the electrolyte may be maintained at 30 ppm or less.

The method of the present invention may further include injecting 20 to 80 mg/L of activated carbon into the electrolyte solution at predetermined intervals when the copper film is formed.

The method of the present invention may further include immersing the copper film in an anticorrosion solution 60 .

The general description of the present invention as above is only for exemplifying or explaining the present invention, and does not limit the scope of the present invention.

According to the present invention, it is possible to produce a high-strength electrodeposited copper foil capable of preventing folding or wrinkles during a roll-to-roll (RTR) process. By manufacturing final products, the productivity of the intermediate parts as well as the final products can be improved.

The accompanying drawings are intended to aid understanding of the present invention and constitute a part of this specification, illustrate embodiments of the present invention, and explain the principles of the present invention together with the detailed description of the present invention.
1 is a cross-sectional view of an electrodeposited copper foil according to an embodiment of the present invention;
2 is a cross-sectional view of an electrode for a secondary battery according to an embodiment of the present invention;
3 shows an apparatus for manufacturing an electrodeposited copper foil according to an embodiment of the present invention.

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 changes and modifications of the present invention are possible without departing from the spirit and scope of the present invention. Accordingly, the present invention includes all modifications and variations falling within the scope of the invention described in the claims and equivalents thereof.

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

As illustrated in FIG. 1 , the electrodeposited copper foil 110 of the present invention includes a copper film 111 containing 99% by weight or more of copper and a protective layer 112 on the copper film 111 . In the electrodeposited copper foil 110 illustrated in FIG. 1, the protective layer 112 is formed on both surfaces of the copper film 111, but the present invention is not limited thereto and one surface of the copper film 111 The protective layer 112 may be formed only on the top.

The electrodeposited copper foil 110 according to an embodiment of the present invention has a thickness of 4 to 35 μm. Manufacturing of the electrodeposited copper foil 110 having a thickness of less than 4 μm causes deterioration in workability. On the other hand, when a secondary battery is manufactured with the electrodeposited copper foil 110 exceeding 35 μm, it is difficult to realize high capacity due to the thick electrodeposited copper foil 110 .

The copper film 111 may be formed on the rotating cathode drum through electroplating, and has a shiny surface directly contacting the rotating cathode drum and a matte surface opposite thereto during the electroplating process.

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 chromate, benzotriazole (BTA), and a silane compound. The protective layer 112 prevents oxidation and corrosion of the copper film 111 and improves heat resistance, thereby extending the lifespan of the electrodeposited copper foil 110 itself and the lifespan of a final product including the same.

In order to suppress folding and curling (ie, wrinkles) of the electrodeposited copper foil 110, the electrodeposited copper foil 110 of the present invention has a high tensile strength of 45 kgf/mm ² or more. If the tensile strength of the electrodeposited copper foil 110 is less than 45 kgf/mm ² , folding of the electrodeposited copper foil 110 occurs between two adjacent rolls during the roll-to-roll manufacturing process, or the left and right ends of the electrodeposited copper foil 110 during the roll-to-roll manufacturing process. causes wrinkles in

On the other hand, when the tensile strength of the electrodeposited copper foil 110 exceeds 50 kgf/mm ² , the electrodeposited copper foil 110 has a low elongation, thereby manufacturing final products such as a negative electrode current collector of a secondary battery and a flexible printed circuit board (FPCB). During the process, there is a risk of breakage of the electrodeposited copper foil 110. Therefore, preferably, the electrodeposited copper foil 110 of the present invention has a tensile strength of 45 to 50 kgf/mm ² and an elongation of 3 to 13%.

Hereinafter, only for convenience of description, an example in which the electrodeposited copper foil 110 of the present invention is used for manufacturing a secondary battery will be described in detail. However, as described above, the electrodeposited copper foil 110 of the present invention is also used in the manufacture of various other products that can be manufactured through a roll-to-roll (RTR) process using copper foil, for example, a flexible printed circuit board (FPCB). could be used similarly.

A lithium ion secondary battery includes a cathode providing electrons and lithium ions during charging, an anode providing electrons and lithium ions during discharging, and an environment in which lithium ions can move between the anode and the cathode. It includes an electrolyte and a separator that electrically insulates the anode and the cathode in order to prevent the electrons generated from one electrode from being unprofitably consumed by moving to the other electrode through the inside of the secondary battery.

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

As illustrated in FIG. 2 , the electrode 100 for a secondary battery according to an embodiment of the present invention includes the electrodeposited copper foil 110 and the active material layer 120 of any one of the above-described embodiments of the present invention.

2 illustrates the active material layer 120 formed on both sides of the electrodeposited copper foil 110, but the present invention is not limited thereto, and the active material layer 120 is formed only on one side of the electrodeposited copper foil 110. may be formed.

In a lithium secondary battery, it is common to use an aluminum foil as a cathode current collector combined with a cathode active material and an electrodeposited copper foil 110 as a cathode current collector coupled with a cathode active material.

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

The active material layer 120 may include carbon; a metal (Me) of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; an alloy containing the metal (Me); an oxide (MeO _x ) of the metal (Me); and at least one active material selected from the group consisting of a composite of metal (Me) and carbon as an anode active material.

In order to increase the charge/discharge capacity of the secondary battery, the active material layer 120 may be formed of a mixture of negative active materials including a predetermined amount of Si.

Meanwhile, contraction and expansion of the active material layer 120 occur alternately as charging and discharging of the secondary battery is repeated, which causes separation between the active material layer 120 and the electrodeposited copper foil 110, thereby improving the charging and discharging efficiency of the secondary battery. lower it Therefore, in order for the secondary battery to secure the capacity retention rate and lifespan of a certain level or higher (ie, to suppress the deterioration of the charging and discharging efficiency of the secondary battery), the electrodeposited copper foil 110 has excellent coating properties with respect to the active material, so that the electrodeposited copper foil The adhesive strength between (110) and the active material layer 120 should be high.

From a macroscopic point of view, the smaller the 10-point average roughness (R _zJIS ) of the surface of the electrodeposited copper foil 110 is, the less the charge/discharge efficiency of the secondary battery tends to decrease.

Therefore, the surface of the electrodeposited copper foil 110 according to an embodiment of the present invention has a 10-point average roughness (R _zJIS ) of 3.5 μm or less. If the surface of the electrodeposited copper foil 110 has a 10-point average roughness (R _zJIS ) exceeding 3.5 μm, the contact uniformity between the electrodeposited copper foil 110 and the active material layer 120 will not reach a certain level, and therefore secondary The battery will not be able to satisfy the capacity retention rate of 90% or more required by the industry.

Hereinafter, a method of manufacturing the electrodeposited copper foil 110 of the present invention will be described in detail with reference to FIG. 3 .

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

As illustrated in FIG. 3 , the positive electrode plate 30 may include first and second positive electrode plates 31 and 32 electrically insulated from each other.

In the step of forming the copper film 111, a seed layer is formed by energization between the first positive electrode plate 31 and the rotating cathode drum 40, and then the second positive electrode plate 32 and the rotating cathode drum ( 40) by growing the seed layer by current.

A current density respectively provided by the first and second positive electrode plates 31 and 32 may be 40 to 80 A/dm ² .

According to one embodiment of the present invention, by setting the current density provided by the first positive electrode plate 31 higher than the current density provided by the second positive electrode plate 32 (ie, relatively high when forming the seed layer) By applying a current density), the grain size of the seed layer is reduced, and as a result, the grain size of the shiny surface and the matte surface of the copper layer 111 may be made the same or similar.

Since the shiny surface and the matte surface of the copper film 111 have the same or similar grain size, folding/curling of the electrodeposited copper foil 110 of the present invention can be further suppressed.

According to the present invention, the electrolyte solution 20 is prepared by adding a compound of bivalent cerium to a mixture containing 50 to 100 g/L of copper ions and 50 to 150 g/L of sulfuric acid.

The divalent cerium compound is an additive that makes an important contribution to the electrodeposited copper foil 110 of the present invention having a high tensile strength of 45 kgf/mm ² or more, and may be, for example, CeSO ₄ .

The content of cerium ions (Ce ²⁺ ) in the electrolyte solution 20 of the present invention is 3 ppm or more, preferably 3 to 15 ppm.

When the content of the cerium ion is less than 3 ppm, the tensile strength of the electrodeposited copper foil 110 does not reach 45 kgf / mm ² , and when a final product is manufactured with the electrodeposited copper foil 110 through a roll-to-roll process, folding / curling ( That is, the risk of causing wrinkles) problems increases.

When the content of the cerium ion exceeds 15 ppm, the effect of increasing the tensile strength is insignificant compared to the increase in the cerium ion content. Therefore, by adjusting the cerium ion content in the electrolyte solution 20 to 3 to 15 ppm or less, it is possible to maximize the performance of the electrodeposited copper foil 110 compared to the manufacturing cost.

The electrolyte solution 20 is maintained at 40 to 60 °C, and the current density provided by the positive electrode plate 30 may be 40 to 80 A/dm ² . When the copper layer 111 is formed, the flow rate of the electrolyte solution 20 supplied into the electrolytic bath 10 may be 30 to 50 m ³ /hour.

When the copper film 111 is formed, the total organic carbon (TOC) content in the electrolyte 20 is preferably maintained at 30 ppm or less. When the total organic carbon (TOC) content exceeds 30 ppm, organic matter adsorbs to the active point of copper plating crystal growth, so that the growth of crystal grains of the copper film 111 cannot be suppressed, and as a result, 45 kgf/ It becomes impossible to manufacture the electrodeposited copper foil 110 having a high tensile strength of mm ² or more.

According to one embodiment of the present invention, in order to maintain the total organic carbon (TOC) content in the electrolyte solution 20 to 30 ppm or less, activated carbon is injected into the electrolyte solution 20 .

Since the electrolyte 20 is supplied into the electrolytic bath 10 at a flow rate of 30 to 50 m ³ /hour when the copper film 111 is formed, the total organic carbon (TOC) content in the electrolyte 20 is 30 In order to keep it below ppm, a predetermined amount of activated carbon must be repeatedly injected at predetermined intervals.

According to an embodiment of the present invention, when the copper film 111 is formed, 20 to 80 mg/L of activated carbon may be repeatedly injected into the electrolyte solution 20 at intervals of about 8 hours. The input amount of activated carbon refers to the weight (mg) of activated carbon added per unit volume (L) of the electrolyte 20.

When the amount of activated carbon injected into the electrolyte 20 is less than 20 mg/L, the concentration of organic matter (ie, TOC) in the electrolyte 20 is high (eg, greater than 30 ppm), and the organic matter is at the active point of copper plating crystal growth. Due to this adsorption, the grain growth of the copper film 111 cannot be suppressed, and as a result, the electrodeposited copper foil 110 having a high tensile strength of 45 kgf/mm ² or more cannot be manufactured.

On the other hand, if the amount of activated carbon injected into the electrolyte solution 20 exceeds 80 mg/L, cerium ions are also adsorbed to the excess activated carbon, so that cerium ions cannot be sufficiently adsorbed to the active point of copper plating crystal growth. As a result, It becomes impossible to manufacture the electrodeposited copper foil 110 having a high tensile strength of 45 kgf/mm ² or more.

The surface of the rotating cathode drum 40 affects the 10-point average roughness (R _zJIS ) of the shiny surface of the copper film 111 . According to one embodiment of the present invention, the surface of the rotating cathode drum 40 may be polished with a polishing brush having a grit of #800 to #1500.

The method of the present invention may further include immersing the copper film 111 in an anticorrosion solution 60 . When the copper film 111 is immersed in the anticorrosive liquid 60, it may be guided by a guide roll 70 disposed in the anticorrosive liquid 60.

As described above, the anti-rust solution 60 may include chromate, benzotriazole, and/or a silane-based compound. For example, the copper film 111 may be immersed in a 1 to 10 g/L potassium dichromate solution at room temperature for 2 to 20 seconds.

Carbon; a metal (Me) of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; an alloy containing the metal (Me); an oxide (MeO _x ) of the metal (Me); And by coating at least one negative electrode active material selected from the group consisting of a composite of metal (Me) and carbon, the electrode (ie, negative electrode) for a secondary battery of the present invention can be manufactured.

For example, after mixing 1 to 3 parts by weight of styrene-butadiene rubber (SBR) and 1 to 3 parts by weight of carboxymethyl cellulose (CMC) with 100 parts by weight of carbon for negative electrode active material, a slurry is prepared using distilled water as a solvent. . Subsequently, the slurry is applied to a thickness of 20 to 60 μm on the electrodeposited copper foil 110 using a doctor blade, and pressed at a pressure of 0.5 to 1.5 ton/cm ² at 110 to 130° C.

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

Hereinafter, the present invention will be specifically described through Examples and Comparative Examples. However, the following examples are only for helping understanding of the present invention, and the scope of the present invention is not limited to these examples.

Example 1

A copper film was formed on the rotating cathode drum by energizing the cathode plate and the rotating cathode drum spaced apart from each other in the electrolyte solution in the electrolytic cell. The electrolyte solution contained 88 g/L of copper ions, 105 g/L of sulfuric acid, and 3.2 ppm of cerium ions (Ce ²⁺ ). During the copper film forming step, the electrolyte solution was maintained at about 50°C. The flow rate of the electrolyte solution supplied into the electrolytic cell was 40 m ³ /hour, and 22 mg/L of activated carbon was repeatedly added to the electrolyte solution at 8-hour intervals. The current density provided for forming the copper film was 55 A/dm ² . After immersing the copper film in a 5 g/L potassium dichromate solution at room temperature for 10 seconds, a drying process was performed to form protective layers on both sides of the copper film, thereby completing an electrodeposited copper foil having a thickness of 4 μm.

Example 2

An electrodeposited copper foil was manufactured in the same manner as in Example 1, except that 77 mg/L of activated carbon was repeatedly added to the electrolyte at an interval of 8 hours.

Example 3

An electrodeposited copper foil was manufactured in the same manner as in Example 1, except that the content of cerium ions (Ce ²⁺ ) in the electrolyte solution was 14.9 ppm.

Example 4

An electrodeposited copper foil was manufactured in the same manner as in Example 3, except that 77 mg/L of activated carbon was repeatedly added to the electrolyte at an interval of 8 hours.

Example 5

An electrodeposited copper foil was manufactured in the same manner as in Example 1, except that the content of cerium ions (Ce ²⁺ ) in the electrolyte solution was 15.6 ppm.

Example 6

An electrodeposited copper foil was manufactured in the same manner as in Example 5, except that 77 mg/L of activated carbon was repeatedly added to the electrolyte at an interval of 8 hours.

Comparative Example 1

An electrodeposited copper foil was manufactured in the same manner as in Example 1, except that the content of cerium ions (Ce ²⁺ ) in the electrolyte solution was 2.9 ppm.

Comparative Example 2

An electrodeposited copper foil was manufactured in the same manner as in Comparative Example 1, except that 77 mg/L of activated carbon was repeatedly added to the electrolyte at an interval of 8 hours.

Comparative Example 3

An electrodeposited copper foil was manufactured in the same manner as in Example 1, except that the electrolyte solution did not contain cerium ions (Ce ²⁺ ) and activated carbon was not added to the electrolyte solution.

The tensile strength and wrinkle/breakage of the electrodeposited copper foils prepared in the above Examples and Comparative Examples were measured as follows, and the results are shown in Table 1.

* Tensile strength and elongation of electrodeposited copper foil

The tensile strength and elongation of the electrodeposited copper foils were respectively measured through the method specified in the IPC-TM-650 Test Method Manual.

* Wrinkles/breaks

In the process of manufacturing a secondary battery electrode with electrodeposited copper foil through a roll-to-roll (RTR) process, whether wrinkles or breaks were observed was observed.

electrolyte The tensile strength
(kgf/mm ² ) Whether wrinkles/breaks occur Cu
(g/L) sulfuric acid
(g/L) Ce ²⁺
(ppm) activated carbon
(mg/L) Example 1 88 105 3.2 22 45.9 × Example 2 88 105 3.2 77 45.2 × Example 3 88 105 14.9 22 49.8 × Example 4 88 105 14.9 77 48.5 × Example 5 88 105 15.6 22 49.6 × Example 6 88 105 15.6 77 49.3 × Comparative Example 1 88 105 2.9 22 44.5 ○ Comparative Example 2 88 105 2.9 77 43.8 ○ Comparative Example 3 88 105 0 0 32.7 ○

As can be seen from Table 1 above, even in cases where the electrolyte does not contain cerium ions at all (Comparative Example 3) and when the content is less than 3 ppm (Comparative Example 1 and Comparative Example 2), the electrodeposited copper foil The tensile strength of was less than 45 kgf/mm ² , and as a result, wrinkles occurred during the roll-to-roll process.

100: secondary battery electrode 110: electrodeposited copper foil
111: copper film 112: protective layer
120: active material layer

Claims (13)

delete delete delete delete delete delete Forming a copper film 111 on the rotating cathode drum 40 by energizing the cathode plate 30 and the rotating cathode drum 40 spaced apart from each other in the electrolyte solution 20 in the electrolytic cell 10, ,
The electrolyte 20 is prepared by adding a compound of bivalent cerium to a mixture containing 70 to 100 g/L of copper ions and 70 to 130 g/L of sulfuric acid,
The electrolyte solution contains 3 to 15 ppm of cerium ions,
The total organic carbon (TOC) content in the electrolyte 20 is maintained at 30 ppm or less,
Further comprising the step of repeatedly injecting 20 to 80 mg/L of activated carbon into the electrolyte solution 20 at intervals of 8 hours,
Manufacturing method of electrodeposited copper foil (110). According to claim 7,
The divalent cerium compound is CeSO ₄ ,
Manufacturing method of electrodeposited copper foil (110). According to claim 7,
The electrolyte solution 20 is maintained at 40 to 60 ° C,
The current density provided by the positive plate 30 is 40 to 80 A / dm ² ,
Manufacturing method of electrodeposited copper foil (110). According to claim 7,
When the copper film 111 is formed, the flow rate of the electrolyte 20 supplied into the electrolytic bath 10 is 30 to 50 m ³ /hour,
Manufacturing method of electrodeposited copper foil (110). delete delete According to claim 7,
Further comprising immersing the copper film 111 in an anticorrosion solution 60,
Manufacturing method of electrodeposited copper foil (100).

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