KR102429088B1 - Copper foil with enhanced adhesion property by having imidazole compound layer, electrode comprisng the same, secondary battery comprising the same and method for manufacturing the same - Google Patents

Abstract

An embodiment of the present invention includes a copper layer, an anti-rust film disposed on the copper layer, and an imidazole compound layer disposed on the anti-rust film, wherein the imidazole compound layer has a mercapto group. A copper foil containing a dazole compound is provided.

Description

Copper foil having excellent adhesion including an imidazole compound layer, an electrode including the same, a secondary battery including the same, and a method for manufacturing the same SAME AND METHOD FOR MANUFACTURING THE SAME}

The present invention relates to a copper foil having an imidazole compound layer and having excellent adhesion, an electrode including the same, a secondary battery including the same, and a manufacturing method thereof.

Copper foil is used to manufacture various products such as anodes of secondary batteries and flexible printed circuit boards (FPCBs).

The copper foil may be manufactured by a Roll To Roll (RTR) process using electroplating. A copper foil manufactured by electroplating is called an electrolytic copper foil. This electrolytic copper foil is used for manufacturing a negative electrode for a secondary battery through a roll-to-roll (RTR) process or for manufacturing a flexible printed circuit board (FPCB).

A negative electrode of a secondary battery generally includes a copper foil and an active material laminated on the copper foil. Since the active material expands or contracts during charging and discharging, it is also detached from the copper foil. Due to the desorption of the active material, the lifespan of the secondary battery may be shortened and the capacity retention rate may be reduced. Therefore, in order to prevent detachment of the copper foil and the active material, it is necessary to increase the adhesive force between the copper foil and the active material.

As a method of increasing the adhesion between the copper foil and the active material, there is a method of changing the surface roughness of the copper foil or chemically treating the surface of the copper foil with a silane coupling agent. However, there is a limit to increasing the adhesion between the copper foil and the active material in this way.

The present invention relates to a copper foil capable of solving the above problems, an electrode including the same, a secondary battery including the same, and a method for manufacturing the same.

An embodiment of the present invention is to provide a copper foil having an imidazole compound layer having excellent adhesion.

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

Another embodiment of the present invention is to provide a method for manufacturing a copper foil having an imidazole compound layer and having excellent adhesion.

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.

In order to solve this problem, an embodiment of the present invention includes a copper layer, a rust preventive film disposed on the copper layer, and an imidazole compound layer disposed on the rust preventive film, wherein the imidazole compound layer is a mercapto group It provides a copper foil comprising an imidazole compound having a (mercapto group).

The imidazole compound is 2-mercaptobenzimidazole (2-mercaptobenzimidazole), 2-mercaptoimidazole (2-mercaptoimidazole), 2-mercapto-1-methylimidazole (2-mercapto-1- methylimidazole), 2-mercapto-5-methylimidazole (2-mercapto-5-methylimidazole), 5-amino-2-mercaptobenzimidazole (5-amino-2-mercaptobenzimidazole), 2-mercapto- 5-nitrobenzimidazole (2-mercapto-5-nitrobenzimidazole), 2-mercapto-5-methoxybenzimidazole (2-mercapto-5-methoxybenzimidazole) and 2-mercaptobenzimidazole-5-carboxylic acid (2-mercaptobenzimidazole-5-carboxylic acid) includes at least one selected from the group consisting of.

The imidazole compound layer has a thickness of 0.01 to 1.0 μm.

The copper foil has a surface roughness (Rz) of 1 μm or less.

The rust preventive film includes at least one of chromium, a silane compound, and a nitrogen compound.

Another embodiment of the present invention includes a copper foil and an active material layer disposed on the copper foil, wherein the copper foil includes a copper layer, a rust preventive film disposed on the copper layer, and an imidazole compound layer disposed on the rust preventive film and, the imidazole compound layer includes an imidazole compound having a mercapto group.

The adhesive force between the copper foil and the active material layer is 15 to 25N/m.

The active material layer is in contact with the imidazole compound layer.

Another embodiment of the present invention is a positive electrode (cathode), a negative electrode (anode) disposed opposite to the positive electrode (electrolyte) disposed between the positive electrode and the negative electrode to provide an environment in which lithium ions can move and and a separator for electrically insulating the positive electrode and the negative electrode, wherein the negative electrode provides a secondary battery including the above-described copper foil and an active material layer disposed on the copper foil.

Another embodiment of the present invention includes the steps of forming a copper layer by energizing a positive electrode plate and a rotating negative electrode drum disposed to be spaced apart from each other in an electrolyte containing copper ions, forming a rust preventive film on the copper layer, the rust prevention Forming a coating layer by applying a composition for forming an imidazole compound layer on a film and drying the coating layer to form an imidazole compound layer, wherein the composition for forming an imidazole compound layer comprises a mercapto group It provides a method for producing a copper foil comprising an imidazole compound having

The composition for forming the imidazole compound layer includes 0.1 to 1.0 wt% of the imidazole compound and 99.0 to 99.9 wt% of the solvent.

The solvent includes water.

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

The copper foil according to an embodiment of the present invention has an imidazole compound layer and thus has excellent adhesion. Therefore, when the copper foil according to an embodiment of the present invention is used for the electrode for a secondary battery, the adhesion between the copper foil and the active material is improved, so that separation between the copper foil and the active material is prevented. Accordingly, a decrease in the capacity retention rate of the secondary battery is prevented, and the lifespan and reliability of the secondary battery are improved.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are intended to aid the understanding of the present invention and constitute a part of this specification, illustrate embodiments of the present invention, and together with the description, explain the principles of the present invention.
1 is a schematic cross-sectional view of a copper foil according to an embodiment of the present invention.
2 is a schematic cross-sectional view of a copper foil according to another embodiment of the present invention.
3 is a schematic cross-sectional view of a copper foil according to another embodiment of the present invention.
4 is a schematic cross-sectional view of an electrode for a secondary battery according to another embodiment of the present invention.
5 is a schematic cross-sectional view of an electrode for a secondary battery according to another embodiment of the present invention.
6A and 6B are schematic diagrams for the arrangement of copper foil and graphite particles.
7 is a schematic cross-sectional view of a secondary battery according to still another embodiment of the present invention.
8A to 8D are schematic views of a manufacturing process of a copper foil.

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 within the scope of the invention described in the claims and their equivalents.

Since the shapes, sizes, proportions, angles, numbers, etc. disclosed in the drawings for explaining the embodiments of the present invention are exemplary, the present invention is not limited by the matters shown in the drawings. Like elements may be referred to by the same reference numerals throughout the specification.

When 'including', 'having', 'consisting', etc. mentioned in this specification are used, other parts may be added unless the expression 'only' is used. When a component is expressed in the singular, the plural is included unless specifically stated otherwise. In addition, in interpreting the components, it is interpreted as including an error range even if there is no separate explicit description.

In the case of a description of the positional relationship, for example, when the positional relationship of two parts is described as 'on', 'on', 'on', 'beside', etc., 'right' Alternatively, unless the expression 'directly' is used, one or more other parts may be positioned between the two parts.

In the case of a description of a temporal relationship, for example, 'immediately' or 'directly' when a temporal relationship is described as 'after', 'following', 'after', 'before', etc. It may include cases that are not continuous unless the expression "

To describe various elements, expressions such as 'first', 'second', etc. are used, but these elements are not limited by these terms. These terms are only used to distinguish one component from another. Accordingly, the first component mentioned below may be the second component within the spirit of the present invention.

The term “at least one” should be understood to include all possible combinations from one or more related items.

Each feature of the various embodiments of the present invention may be partially or wholly combined or combined with each other, technically various interlocking and driving are possible, and each of the embodiments may be implemented independently of each other or may be implemented together in a related relationship. may be

1 is a schematic cross-sectional view of a copper foil 100 according to an embodiment of the present invention.

Referring to FIG. 1 , the copper foil 100 includes a copper layer 110 , a rust preventive film 210 disposed on the copper layer 110 , and an imidazole compound layer 215 disposed on the rust preventive film 210 . .

The copper layer 110 according to an embodiment of the present invention has a matte surface MS and a shiny surface SS opposite thereto.

The copper layer 110 may be formed on the rotating cathode drum through, for example, electroplating (see FIG. 8A ). At this time, the shiny surface SS refers to the surface that has been in contact with the rotating cathode drum during the electroplating process, and the matte surface MS refers to the opposite surface of the shiny surface SS.

It is common for the shiny surface (SS) to have a lower surface roughness (Rz) than the matte surface (MS). However, one embodiment of the present invention is not limited thereto, and the surface roughness Rz of the shiny surface SS may be equal to or higher than the surface roughness Rz of the mat surface MS.

The rust prevention film 210 may be disposed on at least one of the mat surface MS and the shiny surface SS of the copper layer 110 . Referring to FIG. 1 , the anti-rust film 210 is disposed on the mat surface MS. However, one embodiment of the present invention is not limited thereto, and the rust prevention film 210 may be disposed only on the shiny surface SS, or may be disposed on both the mat surface MS and the shiny surface SS.

The rust prevention film 210 protects the copper layer 110 . The rust prevention film 210 may prevent the copper layer 110 from being oxidized or deteriorated during storage or distribution. Accordingly, the anti-rust film 210 is also referred to as a protective layer.

According to an embodiment of the present invention, the rust preventive film 210 may include at least one of chromium (Cr), a silane compound, and a nitrogen compound. For example, the rust preventive film 210 may be made by a rust preventive liquid containing chromium (Cr), that is, a rust preventive liquid containing a chromic acid compound.

The imidazole compound layer 215 includes an imidazole compound having a mercapto group. The imidazole compound according to an embodiment of the present invention is, for example, 2-mercaptobenzimidazole (2-mercaptobenzimidazole), 2-mercaptoimidazole (2-mercaptoimidazole), 2-mercapto-1- Methylimidazole (2-mercapto-1-methylimidazole), 2-mercapto-5-methylimidazole (2-mercapto-5-methylimidazole), 5-amino-2-mercaptobenzimidazole (5-amino -2-mercaptobenzimidazole), 2-mercapto-5-nitrobenzimidazole (2-mercapto-5-nitrobenzimidazole), 2-mercapto-5-methoxybenzimidazole (2-mercapto-5-methoxybenzimidazole) and 2 -Mercaptobenzimidazole-5-carboxylic acid may include at least one selected from the group consisting of (2-mercaptobenzimidazole-5-carboxylic acid). However, an embodiment of the present invention is not limited thereto, and other imidazole compounds having a mercapto group may be used in the preparation of the imidazole compound layer 215 according to an embodiment of the present invention.

The imidazole compound may be dissolved or dispersed in water (H ₂ O) to become a component of the composition for forming the imidazole compound layer.

The imidazole compound according to an embodiment of the present invention has a mercapto group (-SH). The sulfur (S) atom of the mercapto group (-SH) has affinity with copper (Cu). For example, a portion of the copper layer 210 exposed from the rust preventive film 210 may be combined with a mercapto group (-SH) of the imidazole compound, or the copper layer 210 through the rust preventive film 210 . It can bond with the mercapto group (-SH) of this imidazole compound. Accordingly, the bonding strength between the copper layer 110 or the rust preventive film 210 and the imidazole compound layer may be improved.

In addition, the imidazole group has excellent adhesion to the active material used in the manufacture of electrodes for secondary batteries. In particular, an imidazole group having a hydrocarbon group, a phenyl group, or a benzyl group may have excellent adhesion to the active material.

As such, since the mercapto group (-SH) has excellent affinity with the copper layer 110 or the rust preventive film 210, and the imidazole group has excellent adhesion with the active material, the The adhesion between the copper foil 100 and the active material may be improved by the dazole compound layer 215 .

That is, the copper foil 100 according to an embodiment of the present invention including the imidazole compound 100 has excellent adhesion to the active material.

According to an embodiment of the present invention, the imidazole compound layer 215 may further include an additive for enhancing adhesion.

According to one embodiment of the present invention, the imidazole compound layer 215 has a thickness of 0.01 to 1.0㎛. When the thickness of the imidazole compound layer 215 is less than 0.01 μm, it is difficult for the imidazole compound layer 215 to have sufficient adhesion. On the other hand, when the thickness of the imidazole compound layer 215 exceeds 1.0 μm, the surface resistance of the imidazole compound layer 215 increases, so that when the copper foil 100 is used as a current collector of an electrode for a secondary battery, the secondary battery due to the increase in resistance The efficiency of the cell may be reduced.

When the thickness of the imidazole compound layer 215 exceeds 1.0 μm, for example, the surface resistance of the copper foil 100 may exceed 10 mΩ based on a 4 mm x 4 mm sample. When the surface resistance of the copper foil 100 exceeds 10 mΩ based on the 4 mm x 4 mm sample, the efficiency of the secondary battery in which the copper foil 100 is used may decrease due to an increase in resistance.

More specifically, the imidazole compound layer 215 may have a thickness of 0.01 to 0.5 μm. Alternatively, the imidazole compound layer 215 may have a thickness of 0.05 to 0.5 μm. Alternatively, the imidazole compound layer 215 may have a thickness of 0.05 to 0.1 μm.

According to an embodiment of the present invention, the copper foil 100 may have a thickness of 4㎛ to 30㎛. When the thickness of the copper foil 100 is less than 4 μm, workability is reduced in the manufacturing process of an electrode for a secondary battery or a secondary battery using the copper foil 100 . When the thickness of the copper foil 100 exceeds 30 μm, the thickness of the electrode for a secondary battery using the copper foil 100 increases, and due to such a large thickness, it may be difficult to realize a high capacity of the secondary battery.

2 is a schematic cross-sectional view of a copper foil 200 according to another embodiment of the present invention. Hereinafter, descriptions of the already described components will be omitted to avoid duplication.

Referring to FIG. 2 , a copper foil 200 according to another embodiment of the present invention has a copper layer 110 and two anti-rust surfaces disposed on the mat surface MS and the shiny surface SS of the copper layer 110 , respectively. and two imidazole compound layers 215 and 225 respectively disposed on the membranes 210 and 220 and the two rust-preventing membranes 210 and 220 . Compared with the copper foil 100 illustrated in FIG. 1 , the copper foil 200 illustrated in FIG. 2 includes a rust preventive film 220 and an imidazole compound layer 225 disposed in the shiny surface SS direction of the copper layer 110 . further includes

Among the two anti-rust films 210 and 220 , the anti-rust film 210 disposed on the mat surface MS of the copper layer 110 is referred to as a first protective layer, and the rust-preventive film 220 disposed on the shiny surface SS. may be referred to as a second protective layer. In addition, the imidazole compound layer 215 disposed on the mat side (MS) side of the two imidazole compound layers 215 and 225 is referred to as a first imidazole compound layer, and the imidazole compound layer 225 disposed on the shiny side (SS) side. may be referred to as the second imidazole compound layer.

Each of the two anti-rust films 210 and 220 may include at least one of chromium (Cr), a silane compound, and a nitrogen compound.

The two imidazole compound layers 215 and 225 may have the same composition as each other, and may be made of the same material by the same method. However, one embodiment of the present invention is not limited thereto, and the two imidazole compound layers 215 and 225 may have different compositions.

In addition, the imidazole compound layer 225 on the shiny side SS side may also have a thickness of 0.01 to 1.0 μm, and a surface roughness Rz of 1 μm or less.

The copper foil 200 according to another embodiment of the present invention may have a thickness of 4 μm to 30 μm.

3 is a schematic cross-sectional view of a copper foil 300 according to another embodiment of the present invention.

Referring to FIG. 3 , the copper foil 300 according to another embodiment of the present invention has two copper layers 110 , respectively, disposed on the mat surface MS and the shiny surface SS of the copper layer 110 . and an imidazole compound layer 215 disposed on the anti-rust film 210 and 220 and the anti-rust film 210 on the mat surface MS. The copper foil 300 illustrated in FIG. 3 does not include the imidazole compound layer 225 disposed on the shiny surface SS side, compared to the copper foil 200 illustrated in FIG. 2 .

On the other hand, a portion including the copper layer 110 and the two rust-preventing films 210 and 220 disposed on both surfaces of the copper layer 110, respectively, is also referred to as the original foil 201.

4 is a schematic cross-sectional view of an electrode 400 for a secondary battery according to another embodiment of the present invention. The electrode 400 for a secondary battery shown in FIG. 4 may be applied to the secondary battery 600 shown in FIG. 7 , for example.

Referring to FIG. 4 , an electrode 400 for a secondary battery according to another embodiment of the present invention includes a copper foil 100 and an active material layer 310 disposed on the copper foil 100 . Here, the copper foil 100 includes a copper layer 110 , a rust preventive film 210 disposed on the copper layer 110 , and an imidazole compound layer 215 disposed on the rust preventive film 210 . The imidazole compound layer 215 is in contact with the active material layer 310 . In the electrode 400 for a secondary battery shown in FIG. 4 , the copper foil 100 is used as a current collector.

4 shows that the copper foil 100 of FIG. 1 is used as a current collector. However, another embodiment of the present invention is not limited thereto, and the copper foils 200 and 300 shown in FIG. 2 or 3 may be used as a current collector of the electrode 400 for a secondary battery.

In addition, although the structure in which the active material layer 310 is disposed only on the first surface S1 of the surfaces S1 and S2 of the copper foil 100 is shown in FIG. 4 , another embodiment of the present invention is limited thereto The active material layer 310 may be disposed on both the first surface S1 and the second surface S2 of the copper foil 100 , and the active material layer 310 only on the second surface S2 of the copper foil 100 . ) may be placed.

The active material layer 310 shown in FIG. 4 is made of an electrode active material, and in particular, may be made of an anode active material. That is, the electrode 400 for a secondary battery shown in FIG. 4 may be used as a negative electrode.

The active material layer 310 may include at least one active material selected from carbon, a metal, an oxide of a metal, and a composite of a metal and carbon. As the metal, at least one of Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni, and Fe may be used. In addition, in order to increase the charge/discharge capacity of the secondary battery, the active material layer 310 may include silicon (Si).

As the charging and discharging of the secondary battery is repeated, contraction and expansion of the active material layer 310 occur alternately, which causes separation of the active material layer 310 and the copper foil 100, thereby reducing the charging and discharging efficiency of the secondary battery. have. In particular, when the active material layer 310 includes silicon (Si), since the degree of contraction and expansion of the active material layer 310 due to charging and discharging is large, separation of the active material layer 310 and the copper foil 100 is more frequent. can happen

According to another embodiment of the present invention, the adhesion between the copper foil 100 and the active material layer 310 is improved by the imidazole compound layer 215 . As a result, separation of the copper foil 100 and the active material layer 310 or separation of the active material layer 310 can be prevented. Accordingly, the secondary battery including the electrode 400 for a secondary battery according to another embodiment of the present invention has excellent charge/discharge efficiency and capacity retention, and has a long lifespan and driving stability.

According to another embodiment of the present invention, the adhesive force between the copper foil 100 and the active material layer 310 is 15 to 25N/m. That is, the adhesive force between the imidazole compound layer 215 and the active material layer 310 of the copper foil 100 is in the range of 15 to 25 N/m.

When the adhesive force between the copper foil 100 and the active material layer 310 is less than 15N/m, separation of the active material layer 310 and the imidazole compound layer 215 occurs frequently, and the capacity retention rate of the secondary battery may be reduced. . On the other hand, when the adhesive force between the copper foil 100 and the active material layer 310 exceeds 25 N/m, the adhesion between the active material layer 310 and the imidazole compound layer 215 is excellent, but the active material layer 310 itself. Desorption of the active material may occur non-uniformly, thereby reducing the capacity retention rate of the secondary battery.

5 is a schematic cross-sectional view of an electrode 500 for a secondary battery according to another embodiment of the present invention.

The electrode 500 for a secondary battery according to another embodiment of the present invention includes a copper foil 200 and active material layers 310 and 320 disposed on both surfaces of the copper foil 200 . Copper foil 200 is a copper layer 110, the two imidazole compound layers disposed on the anti-rust films 210 and 220 and the anti-rust films 210 and 220 disposed on both surfaces (MS, SS) of the copper layer 110 . (215, 225). The two imidazole compound layers 215 and 225 are in contact with the two active material layers 310 and 320, respectively.

More specifically, the electrode 500 for a secondary battery shown in FIG. 5 includes two active material layers 310 and 320 respectively disposed on the first surface S1 and the second surface S2 of the copper foil 200 . . Here, the active material layer 310 disposed on the first surface S1 of the copper foil 200 is referred to as a first active material layer, and the active material layer 320 disposed on the second surface S2 of the copper foil 200 is formed. It may be referred to as the second active material layer. The two active material layers 310 and 320 may be made of the same material by the same method, or may be made of different materials or different methods.

6A and 6B are schematic diagrams for the arrangement of the copper foil and the graphite particles 315 .

Specifically, FIG. 6a is a schematic diagram of a state in which graphite particles 315 are disposed on a copper foil 101 having a copper layer 110 and a rust preventive film 210, and FIG. 6b is a copper layer 110, a rust preventive film ( 210) and a schematic diagram of a state in which the graphite particles 315 are disposed on the copper foil 100 having the imidazole compound layer 215 .

The graphite particles 315, which are components of the active material, have a particle size of about 15 to 30 μm. Therefore, when the surface roughness of the copper foil is higher than necessary, the contact area between the copper foil 101 and the graphite particles 315 is reduced, as shown in FIG. 6a, so that the adhesion between the copper foil 101 and the graphite particles 315 is reduced can be reduced.

On the other hand, the copper foil 100 shown in FIG. 6B according to an embodiment of the present invention has an imidazole compound layer 215 disposed on the rust preventive film 210 . In this case, since a portion of the graphite particles 315 may be depressed in the imidazole compound layer 215 , the contact area between the graphite particles 315 and the imidazole compound layer 215 increases. In addition, the imidazole compound layer 215 surrounds a portion of the graphite particles 315, and since the imidazole group of the imidazole compound layer 215 and the graphite particles 315 have excellent adhesion, the adhesion of the imidazole compound layer 215 is excellent. This can be improved.

Therefore, according to an embodiment of the present invention, the surface roughness of the upper portion of the copper layer 110 or the antirust film 210 is relieved due to the planarization action of the imidazole compound layer 215, so that the copper foil 100 has a thickness of 1 μm or less. Even with the surface roughness Rz, the graphite particles 315 constituting the negative active material may be stably attached to the copper foil 100 .

As such, according to an embodiment of the present invention, the copper foil 100 may have a surface roughness Rz of 1 μm or less. Here, "surface roughness (Rz)" means ten-point mean roughness. The surface roughness (Rz) may be measured from a sample of 4 mm x 4 mm by a surface roughness meter (MahrSurf M300) according to JIS B 0601-1994 standard.

More specifically, the copper foil 100 has a first surface S1, which is a surface in the matte surface (MS) direction, and a second surface S2, which is a surface in the shiny surface (SS) direction with respect to the copper layer 110, , the surface roughness (Rz) of the copper foil 100 is the surface roughness (Rz) of the first surface (S1) or the second surface (S2). Accordingly, according to an embodiment of the present invention, the surface of the imidazole compound layer 215 and the shiny surface SS of the copper layer 110 may each have a surface roughness Rz of 1 μm or less ( FIGS. 1 and 1 ). 6b).

More specifically, the copper foil 100 may have a surface roughness Rz of 0.3 to 1 μm. Alternatively, the copper foil 100 may have a surface roughness Rz of 0.3 to 0.7 μm.

7 is a schematic cross-sectional view of a secondary battery 600 according to another embodiment of the present invention. The secondary battery 600 illustrated in FIG. 7 is, for example, a lithium secondary battery.

Referring to FIG. 7 , the secondary battery 600 has a positive electrode 370 , an anode 340 disposed opposite to the positive electrode 370 , and ions between the positive electrode 370 and the negative electrode 340 . It includes an electrolyte 350 that provides a movable environment, and a separator 360 that electrically insulates the positive electrode 370 and the negative electrode 340 from each other. Here, ions moving between the positive electrode 370 and the negative electrode 340 are lithium ions. The separator 360 separates the positive electrode 370 and the negative electrode 340 to prevent the charge generated from one electrode from moving to the other electrode through the interior of the secondary battery 600 and being useless. Referring to FIG. 7 , the separator 360 is disposed in the electrolyte 350 .

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

The negative electrode 340 includes a negative electrode current collector 341 and an active material layer 342 . The active material layer 342 of the negative electrode 340 includes an anode active material.

As the negative electrode current collector 341 , one of the copper foils 100 , 200 , and 300 illustrated in FIGS. 1 , 2 and 3 may be used. In addition, any one of the electrodes 400 and 500 for secondary batteries shown in FIGS. 4 and 5 may be used as the negative electrode 340 of FIG. 7 .

Hereinafter, a method of manufacturing the copper foil 300 according to another embodiment of the present invention will be described in detail with reference to FIGS. 8A to 8D .

8A to 8D are schematic views of a manufacturing process of the copper foil 300 .

Referring to FIG. 8A , an original foil 201 is manufactured according to a method of manufacturing an electrolytic copper foil.

Specifically, the positive electrode plate 13 and the rotating negative electrode drum 12 disposed to be spaced apart from each other in the electrolyte 11 containing copper ions are energized to form the copper layer 110 . At this time, a current may be applied between the positive electrode plate 13 and the rotating negative electrode drum 12 at a current density of 20 to 80 ASD (A/dm ² ).

For example, the positive electrode plate 13 and the rotating negative electrode drum 12 disposed to be spaced apart from each other in the electrolyte 11 contained in the electrolytic cell 10 are energized at a current density of 20 to 80 ASD (A/dm ² ), and the rotating negative electrode Copper layer 110 may be formed by electrodepositing copper on drum 12 . The distance between the positive electrode plate 13 and the rotating negative electrode drum 12 may be adjusted in the range of 8 to 13 mm.

The electrolyte solution 11 contains 60 to 100 g/L of copper ions and 50 to 150 g/L of sulfuric acid. In addition, the electrolyte 11 may include an additive. As the additive, for example, at least one selected from hydroxyethyl cellulose (HEC), organic sulfide, organic nitride, and thiourea may be used.

The higher the current density applied between the positive electrode plate 13 and the rotating negative electrode drum 12, the more uniform plating is made, so that the surface roughness of the mat surface MS of the copper layer 110 decreases, and the lower the current density, the more non-uniform. The plating is performed to increase the surface roughness of the mat surface MS of the copper layer 110 .

The surface roughness of the shiny surface SS of the copper layer 110 may vary depending on the degree of polishing of the surface of the rotating cathode drum 12 . For controlling the surface roughness of the shiny surface SS, for example, the surface of the rotating cathode drum 12 may be polished with a polishing brush having a grit of #800 to #3000.

In the process of forming the copper layer 110 , the electrolyte 11 may be maintained at a temperature of 40 to 65°C.

In order to remove the solid impurities present in the electrolyte solution 11 while the electroplating is performed, circulation filtration may be performed. The cleanliness of the electrolyte 11 may be maintained or improved by treating the electrolyte 11 with ozone or injecting hydrogen peroxide and air into the electrolyte 11 .

Next, the copper layer 110 is cleaned in the cleaning tank 20 .

For example, acid cleaning for removing impurities on the surface of the copper layer 110 , for example, a resin component or natural oxide, and water cleaning for removing an acid solution used for pickling ) may be sequentially performed. The cleaning process may be omitted.

Next, rust-preventive films 210 and 220 are formed on the copper layer 110 .

The step of forming the rust-preventive films 210 and 220 may include, for example, treating the surface of the copper layer 110 with chromium (Cr) using the rust-preventing liquid 31 contained in the rust-preventing tank 30 . . The anti-rust films 210 and 220 containing chromium are formed by chromium treatment. Referring to FIG. 8A , the copper layer 110 is immersed in the rust preventive solution 31 to form the rust preventive films 210 and 220 on the copper layer 110 .

In addition, the rust preventive films 210 and 220 may include a silane compound by silane treatment or a nitrogen compound by nitrogen treatment. The original foil 201 is made by the formation of the rust prevention films 210 and 220 .

The original foil 201 is washed in the washing tank 40 . This cleaning process may be omitted. Next, after the drying process is performed, the original foil 201 is wound on the winder WR.

Referring to FIG. 8B , the composition 211 for forming an imidazole compound layer is applied on the original foil 201 to form a coating layer 212 . Specifically, the composition 211 for forming the imidazole compound layer may be applied to the entire surface of the original foil 201 by coating using the bar coater 250 to form the coating layer 212 .

As the bar coater 250, for example, Mayer bar No. 3 (Gap 6.86 μm) may be used. The bar coater 250 of FIG. 8b is a wire type, and the thickness of the coating layer 212 is controlled by the size of the gap between the wires according to the thickness of the wire. However, the type of the bar coater 250 is not limited thereto, and other bar coaters or other coating means may be used as needed.

The composition 211 for forming the imidazole compound layer includes an imidazole compound and a solvent. More specifically, the composition for forming the imidazole compound layer may include 0.1 to 1.0 wt% of the imidazole compound and 99.0 to 99.9 wt% of the solvent. When the content of the imidazole compound is less than 0.1% by weight and the content of the solvent exceeds 99.9% by weight, the imidazole compound layer 215 prepared by the composition 211 for forming the imidazole compound layer due to excessive use of the solvent has sufficient adhesive strength. may not have On the other hand, when the content of the imidazole compound exceeds 1% by weight and the content of the solvent is less than 99.0%, the coating property of the composition 211 for forming the imidazole compound layer is lowered, so that a uniform and thin imidazole compound layer 215 is difficult to prepare. Difficulty may arise, and the thickness of the imidazole compound layer 215 may be excessively thick.

Water (H ₂ O) may be used as a solvent. A solvent other than water (H ₂ O) may be used as the solvent, and water (H ₂ O) and another solvent may be mixed and used as the solvent.

Here, the imidazole compound has a mercapto group. Such imidazo compounds are 2-mercaptobenzimidazole (2-mercaptobenzimidazole), 2-mercaptoimidazole (2-mercaptoimidazole), 2-mercapto-1-methylimidazole (2-mercapto-1- methylimidazole), 2-mercapto-5-methylimidazole (2-mercapto-5-methylimidazole), 5-amino-2-mercaptobenzimidazole (5-amino-2-mercaptobenzimidazole), 2-mercapto- 5-nitrobenzimidazole (2-mercapto-5-nitrobenzimidazole), 2-mercapto-5-methoxybenzimidazole (2-mercapto-5-methoxybenzimidazole) and 2-mercaptobenzimidazole-5-carboxylic acid (2-mercaptobenzimidazole-5-carboxylic acid) may include one selected from the group consisting of.

The composition 211 for forming the imidazole compound layer may include an additive for enhancing adhesion.

Referring to FIG. 8c , the coating layer 212 is dried. The coating layer 212 may be heated to dry the coating layer 212 . For example, the coating layer 212 applied to the original foil 201 may be heated and dried in a convection oven at 100°C.

Referring to FIG. 8D , the coating layer 212 is dried to form the imidazole compound layer 215 . Accordingly, the copper foil 300 is made.

Hereinafter, the present invention will be described in detail through Preparation Examples and Comparative Examples. However, the following preparations or comparative examples are only for helping the understanding of the present invention, and the scope of the present invention is not limited by these preparations or comparative examples.

Preparation Example 1-3 and Comparative Example 1-2

The copper layer 110 was manufactured using a papermaking machine including an electrolytic cell 10, a rotating cathode drum 12 disposed in the electrolytic cell 10, and a positive electrode plate 13 disposed to be spaced apart from the rotating cathode drum 12. . The electrolyte solution 11 was a copper sulfate solution, and the copper ion concentration of the copper sulfate solution was 75 g/L, and the sulfuric acid concentration was 100 g/L. The temperature of the electrolyte 11 was maintained at 55°C. A current density of 40 ASD was applied between the rotating cathode drum 12 and the anode plate 13 .

Next, the copper layer 110 was washed using the washing tank 20 .

Next, the copper layer 110 was immersed in the rust prevention solution 31 contained in the rust prevention tank 30 to form the rust prevention films 210 and 220 containing chromium on the surface of the copper layer 110 . The rust preventive solution 31 contained 2.2 g/L of chromium (Cr) and was maintained at a temperature of 30°C. Accordingly, the original foil 201 was manufactured.

Next, a composition for coating was prepared according to the composition of Table 1.

Specifically, a coating composition was prepared by dispersing and dissolving the coating components disclosed in Table 1 in water (H ₂ O) as a solvent. The coating composition prepared in Preparation Examples 1 to 3 is a composition for forming an imidazole compound layer including an imidazole compound as a coating component. In Comparative Example 1, pyridine was used as a coating component, and in Comparative Example 2, a coating component was not used.

A coating layer was formed by applying a coating composition on the original foil 201 using a bar coater 250 . As the bar coater 250, Mayer bar No. 3 (Gap 6.86 μm) was used. Next, the coating was dried in a convection oven at 100° C. for 10 minutes to prepare a copper foil.

The copper foils according to Preparation Example 1-3 and Comparative Example 1-2 prepared as described above were measured as follows.

(i) Adhesion evaluation (N/m)

After the anode active material was disposed on the coating layer of the copper foil prepared in Preparation Examples 1-3 and Comparative Example 1-2 to form an anode active material layer, the peel strength between the copper foil and the active material was measured using a universal tester (UTM).

1) Preparation of anode

2 parts by weight of styrene-butadiene rubber (SBR) and 2 parts by weight of carboxymethyl cellulose (CMC) were mixed with 100 parts by weight of commercially available carbon for negative active material, and distilled water was used as a solvent to prepare a slurry of the negative active material. A slurry of the negative electrode active material was applied to a thickness of 175 μm on the coating layer of the copper foil having a width of 20 cm (Manufacturing Examples and Comparative Examples) using a doctor blade, dried at 120° C., and at a pressure of 1 ton/cm 2 By pressing, a negative electrode for a secondary battery including an active material layer was prepared.

2) How to measure

The prepared negative electrode for secondary battery was cut to a length of 150 mm and a width of 12.7 mm, and attached to a slide glass to which a double-sided tape (Tesa double-sided tape) was attached so that the copper foil was visible. At this time, the double-sided tape and the active material layer were attached to each other. Next, the slide glass to which the negative electrode for secondary battery was attached was put into the laminating machine so that the double-sided tape and the negative electrode for secondary battery were evenly attached to prepare a sample for measuring the adhesive force. Next, after fixing the slide glass at the bottom of the universal testing machine (UTM), the adhesive force was measured while peeling the copper foil.

- Measurement tester: universal tester (UTM)

- Width of sample: 12.7 mm

- Measurement Type: 180˚ Peel Test

- Measuring speed: 50mm/min

(ii) capacity retention rate evaluation

1) Cathode manufacturing

2 parts by weight of styrene butadiene rubber (SBR) and 2 parts by weight of carboxymethyl cellulose (CMC) were mixed with 100 parts by weight of commercially available carbon for negative active material, and distilled water was used as a solvent to prepare a slurry for negative active material. Using a doctor blade, the slurry for the negative electrode active material was applied to a thickness of 40 μm on the copper foils of Preparation Examples 1-3 and Comparative Examples 1-2 having a width of 10 cm, dried at 120° C., and a pressure of 1 ton/cm 2 A negative electrode for a secondary battery including an active material layer was prepared by pressing in.

2) Preparation of electrolyte

A basic electrolyte was prepared by dissolving LiPF ₆ as a solute at a concentration of 1M in a non-aqueous organic solvent in which ethylene carbonate (EC) and ethylmethyl carbonate (EMC) were mixed in a ratio of 1:2. A non-aqueous electrolyte was prepared by mixing 99.5% by weight of the basic electrolyte and 0.5% by weight of succinic anhydride.

3) Anode manufacturing

A cathode active material was prepared by mixing lithium manganese oxide of Li _1.1 Mn _1.85 Al _0.05 O ₄ and lithium manganese oxide of orthorhombic crystal structure of o-LiMnO ₂ in a ratio of 90:10 (weight ratio). A cathode active material, carbon black, and PVDF [Poly (vinylidenefluoride)] as a binder were mixed in a ratio of 85:10:5 (weight ratio), and this was mixed with NMP (N-methyl-2-pyrrolidone) as an organic solvent to prepare a slurry . The slurry thus prepared was coated on both sides of an Al foil having a thickness of 20 μm, and then dried to prepare a positive electrode.

4) Manufacture of lithium secondary battery for testing

Inside the aluminum can, a positive electrode and a negative electrode were disposed to be insulated from the aluminum can, and a non-aqueous electrolyte and a separator were disposed between them, thereby manufacturing a coin-type lithium secondary battery. The separator used was polypropylene (Celgard 2325; thickness 25㎛, average poresize φ28 nm, porosity 40%).

5) Measurement of capacity retention rate

Using the lithium secondary battery prepared as described above, the capacity per g of the positive electrode was measured by driving the battery with a 4.3V charging voltage and 3.4V discharging voltage, and 0.5C rate (current rate, C-rate) at a high temperature of 50°C After 500 charge/discharge experiments were performed with the furnace, the capacity retention rate per g was measured, and the capacity retention rate was calculated using the measured capacity values per g.

The capacity retention rate can be calculated by Equation 1 below.

[Equation 1]

Capacity retention rate (%) = [(Capacity after 500 charge/discharge)/(Capacity after one charge/discharge)] x 100

When the capacity retention ratio was 80% or less, it was determined that the copper foil was unsuitable as a negative electrode current collector for a lithium ion battery.

Table 1 shows the above measurement and test results.

division coating ingredients Adhesion (N/m) Capacity retention rate (%) Preparation Example 1 2-Mercaptoimidazole 25 88 Preparation 2 2-mercaptobenzimidazole 15 84 Preparation 3 2-mercapto-1-methylimidazole 19 85 Comparative Example 1 Pyridine 9 73 Comparative Example 2 - 8 63

Referring to Table 1, in the case of the negative electrode manufactured using the copper foils of Comparative Examples 1 and 2, the adhesion between the copper foil and the active material is not good. In addition, the secondary battery including the negative electrode manufactured using the copper foil of Comparative Examples 1 and 2 has a capacity retention rate of 80% or less. Therefore, it is determined that the copper foils according to Comparative Examples 1 and 2 are not suitable as negative electrode current collectors for lithium ion batteries.

On the other hand, in the case of the negative electrode for a lithium secondary battery prepared by using the copper foil of Preparation Examples 1 to 3 prepared in the condition range according to the embodiments of the present invention, the adhesion between the copper foil and the active material is excellent at 15N/m or more. In addition, a secondary battery manufactured using such a negative electrode for a lithium secondary battery has an excellent capacity retention rate of more than 80%.

The present invention described above is not limited by the above-described embodiments and the accompanying drawings, and it is a technical field to which the present invention pertains that various substitutions, modifications and changes are possible without departing from the technical matters of the present invention. It will be clear to those of ordinary skill in the art. Therefore, the scope of the present invention is expressed by the following claims, and all changes or modifications derived from the meaning, scope, and equivalent concept of the claims should be construed as being included in the scope of the present invention.

100, 200, 300: copper foil 210, 220: anti-rust film
215, 225: imidazole compound layer 310, 320: active material layer
400, 500: electrode for secondary battery 340: negative electrode for secondary battery
370: positive electrode for secondary battery MS: matte side
SS: Shiny noodles

Claims (12)

delete delete delete delete delete copper foil; and
and an active material layer disposed on the copper foil;
The copper foil is
copper layer;
a rust preventive film disposed on the copper layer; and
and an imidazole compound layer disposed on the rust-preventing film;
The imidazole compound layer includes an imidazole compound having a mercapto group,
The imidazole compound layer has a thickness of 0.01 to 1.0 μm,
The adhesive force between the copper foil and the active material layer is 15 to 25N/m, the electrode for a secondary battery. delete anode;
a cathode disposed opposite to the anode;
an electrolyte disposed between the positive electrode and the negative electrode to provide an environment in which lithium ions can move; and
a separator that electrically insulates the anode and the cathode;
The negative electrode is an electrode for a secondary battery according to claim 6, a secondary battery.
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