KR20190003451A - Electrolytic copper foil, lithium ion secondary cell negative electrode, lithium ion secondary cell, and printed wiring board - Google Patents

Abstract

The present invention provides an electrolytic copper foil having high strength, high heat resistance, and small anisotropic elongation, a negative electrode for a lithium ion secondary battery, a lithium ion secondary battery, and a printed wiring board. The surface-treated copper foil of the present invention contains carbon in an amount of 0.001 to 0.020 mass%, wherein the electrolytic copper foil has a 10-point average roughness (Rz) of 1.8 탆 or less and the electrolytic copper foil is heated at 150 캜 for 1 hour The tensile strength of the copper foil measured at room temperature is preferably 400 MPa or more and the elongation in the width direction (TD) of the copper foil is 2% or more, and the elongation of the copper foil in the longitudinal direction (MD) TD is a parameter representing a difference in elongation of the kidney (TD (TD) / (TD) / MD) x 100} is 50% or less.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic copper foil, a negative electrode for a lithium ion secondary battery, a lithium ion secondary battery, and a printed circuit board,

The present invention relates to an electrolytic copper foil and a negative electrode for a lithium ion secondary battery having the electrolytic copper foil, a lithium ion secondary battery and a printed wiring board.

In recent years, in order to reduce the size and weight of a lithium ion secondary battery, studies have been made on thinning a copper foil used as a current collector, and accordingly, stress and deformation acting on the copper foil Tend to increase. Further, in order to increase the capacity of the lithium ion secondary battery, an attempt has been made to add the active material to the conventional carbon system to mix the silicon system to increase the theoretical capacity, to increase the capacity per volume by filling the active material layer with high density , The development of a next-generation lithium ion secondary battery has been in full swing. As a result, the stress acting on the copper foil as a current collector becomes higher and the restraint condition becomes stronger. As a result, wrinkles and tearing of the electrolytic copper foil Foil cutting) has become more current than ever, and there is a concern that the battery characteristics will deteriorate accordingly.

As a conventional means for realizing the thinning of the copper foil, for example, improvement in properties (high internal resistance) which is less liable to cause deterioration of characteristics such as softening even in the case of high strength of the electrolytic copper foil and heat treatment in a battery manufacturing process For example, Patent Documents 1 to 4).

The high strength and high internal resistance of the electrolytic copper foil can be attained by adding an additive to the electrolytic solution and injecting the additive component into the crystal grains or grain boundaries of the mother phase during electrodeposition to increase the strength due to the refining effect of the crystal grains, It is common.

However, even in the case where high strength and high internal resistance can be realized, it is difficult to completely prevent wrinkles and tears in the next-generation lithium ion secondary battery, and it is necessary to further improve the characteristics from a viewpoint different from the conventional design did.

Japanese Patent Publication No. 5771392 Japanese Patent Application Laid-Open No. 2008-285727 Japanese Laid-Open Patent Publication No. 2014-224321 Japanese Patent Publication No. 5598700 Japanese Patent Publication No. 3850155

An object of the present invention is to provide an electrolytic copper foil having a high strength, a high heat resistance and a small elongation anisotropy, a negative electrode for a lithium ion secondary battery, a lithium ion secondary battery and a printed wiring board.

The inventors of the present invention have studied the development of a new electrolytic copper foil based on the above design guidelines and found that in an electrolytic copper foil having high strength and high heat resistance, the elongation anisotropy (phenomenon that the elongation value differs depending on the direction in which the tensile test is performed) As described later in detail, it has been found that reduction in the anisotropy of the elongation can effectively reduce occurrence of wrinkles and tears after charging and discharging, and occurrence of wrinkles and tears after pressing.

The electrolytic copper foil is generally produced by depositing copper on the surface of a negative electrode drum made of titanium, peeling it off continuously, and winding it to produce a long product (electrolytic copper foil). At this time, the rotational direction of the drum, that is, the longitudinal direction of the elongated product is denoted by MD, and the direction orthogonal to the MD direction, that is, the width direction of the copper foil, is denoted by TD.

Test pieces cut in the MD and TD directions were prepared for a conventional general electrolytic copper foil and a conventional high-strength and high-heat-resistance electrolytic copper foil, and a stress-strain curve (SS curve) obtained by measuring stress and strain with a tensile tester A representative example is shown in Fig. As apparent from Fig. 1, in the conventional high strength and high heat resistance foil, the elongation in the MD direction was 5.8%, the elongation in the TD direction was 2.0%, and the elongation anisotropy was about 65.5% (5.8-2.0) /5.8x100%), and it can be seen that it is being changed. However, all of Patent Documents 1 to 4 do not pay much attention to the elongation anisotropy of the high-strength and high-heat-resistance electrolytic copper foil, and in such a configuration, the generation of wrinkles and tears in the next- Can not. In addition, even in the conventional general electrolytic copper foil, the elongation anisotropy is as small as about 11.1%, which is considered to be due to the surface irregularities generated by transferring the buff line existing in the electrolytic drum, It is difficult to cause wrinkles or tearing.

Considering that the development of a next-generation lithium ion secondary battery will be developed in the future, development of a high strength and high heat resistance foil is considered to be essential, and reduction of the anisotropy of the elongation that is currently attained is an important task. That is, in the current collector use of a high capacity lithium ion secondary battery, it is desired to develop a copper foil having high strength, high heat resistance, and small anisotropic elongation.

Also, in the case of a printed wiring board, considering that an isotropic stress is given at the time of bonding with a resin, it is considered that a smaller anisotropy of the elongation is preferable, and development of a copper foil with a small anisotropic elongation is desired.

The inventors of the present invention have found a method for solving the above problems by examining the examples to complete the present invention. That is, the structure of the present invention is as follows.

(1) An electrolytic copper foil containing 0.001 to 0.020% by mass of carbon, wherein the electrolytic copper foil has a 10-point average roughness (Rz) of 1.8 占 퐉 or less and the electrolytic copper foil is heated at 150 占 폚 for 1 hour and then measured at room temperature Is characterized in that the tensile strength of the copper foil is 400 MPa or more and the elongation of the copper foil in the width direction (TD) is 2% or more and the elongation of the copper foil in the longitudinal direction (MD) Wherein the elongation anisotropy {(MD elongation - TD elongation) / MD elongation] x 100}, which is a parameter representing a difference, is 50% or less.

(2) The electrolytic copper foil according to (1), wherein the elongation anisotropy {(MD elongation - TD elongation) / MD elongation] x 100} is 30%

(3) The electrolytic copper foil according to (1) or (2), wherein the tensile property is obtained in the form of an electrolytic copper foil (original foil) in which no roughened layer is formed on both sides.

(4) A negative electrode for a lithium ion secondary battery having the electrolytic copper foil according to any one of (1) to (3) as a current collector.

(5) A lithium ion secondary battery comprising a negative electrode for a lithium ion secondary battery having the electrolytic copper foil according to any one of (1) to (3) as a current collector.

(6) A printed wiring board comprising the electrolytic copper foil according to any one of (1) to (3) and an insulating film laminated.

According to the present invention, there is provided an electrolytic copper foil containing 0.001 to 0.020 mass% of carbon, wherein the electrolytic copper foil has a 10-point average roughness (Rz) of 1.8 탆 or less and the electrolytic copper foil is heated at 150 캜 for 1 hour, , The tensile strength of the copper foil is 400 MPa or more and the elongation of the copper foil in the width direction (TD) is 2% or more and the elongation of the copper foil in the longitudinal direction (MD) It is possible to provide an electrolytic copper foil having high strength, high heat resistance and low anisotropic elongation because the elongation anisotropy {[(MD elongation - TD elongation) / MD elongation] x 100} .

Further, when the electrolytic copper foil of the present invention is used for a lithium ion secondary battery having a negative electrode for a lithium ion secondary battery, for example, as a current collector, it is possible to prevent tearing and wrinkling during charging and discharging, Cycle characteristics and safety, it is suitable for use in next-generation lithium ion secondary batteries. Further, when the electrolytic copper foil of the present invention is used for a printed wiring board formed by lamination of an electrolytic copper foil together with an insulating film, it is possible to prevent generation of tears and wrinkles at the time of pressing, and also to improve dimensional stability.

Fig. 1 is a graph showing the relationship between a typical stress-strain curve obtained by preparing a test piece cut out in the MD direction and the TD direction for a conventional general electrolytic copper foil and a conventional high-strength and high-heat-resistance electrolytic copper foil, (SS curve).
2 is a conceptual diagram for explaining main parts of a manufacturing apparatus for manufacturing an electrolytic copper foil of the present invention.

(Mode for carrying out the invention)

Next, an embodiment of the present invention will be described below.

The electrolytic copper foil of the present invention contains carbon in an amount of 0.001 to 0.020 mass%, wherein the electrolytic copper foil has a 10-point average roughness (Rz) of 1.8 占 퐉 or less and the electrolytic copper foil is heated at 150 占 폚 for 1 hour, (20 占 폚 占 15 占 폚), the tensile strength of the copper foil is not less than 400 MPa, the elongation of the copper foil in the width direction (TD) is not less than 2%, and the tensile strength of the copper foil in the longitudinal direction (MD elongation - TD elongation) / MD elongation] x 100}, which is a parameter indicating a difference between the elongation in the elongation direction and the elongation in the transverse direction (TD), is 50% or less.

≪ Carbon content in copper foil &

In the present invention, it is necessary to set the content of carbon (C) in the electrolytic copper foil to 0.001 to 0.020 mass%. If the carbon content is less than 0.001 mass%, sufficient strength and heat resistance can not be obtained. If the carbon content is more than 0.020 mass%, ductility tends to decrease and tearing tends to occur at the time of handling or charging / discharging . Therefore, the carbon content is set to 0.001 to 0.020 mass%. The carbon content in the copper foil can be measured, for example, by combustion (tubular electric furnace method) -infrared absorption method in an oxygen flow using a carbon-sulfur analyzer EMIA-810W (manufactured by Horiba Seisakusho) have.

<10-point average roughness (Rz) of copper surface>

Further, in the present invention, it is necessary that the electrolytic copper foil has a 10-point average roughness (Rz) of 1.8 탆 or less. When the 10-point average roughness (Rz) is more than 1.8 占 퐉, the elongation anisotropy due to the surface irregularities of the electrolytic copper foil becomes large and becomes present, and the copper foil after charging / discharging test is likely to wrinkle remarkably. For this reason, the ten-point average roughness (Rz) of the electrolytic copper foil was set to 1.8 μm or less. The 10-point average roughness (Rz) of the electrolytic copper foil was measured in accordance with JIS B0601: 1994. The measurement plane is the S plane (the surface on the negative electrode (Ti) drum side) of the untreated electrolytic copper foil (original plate) on which the harmonized treatment layer is not formed, and the measurement direction is the (= TD direction).

&Lt; Tensile properties of copper foil measured at room temperature after heating at 150 占 폚 for 1 hour>

The electrodeposited copper foil of the present invention satisfies the following characteristics when measured at room temperature after heating at 150 占 폚 for 1 hour. That is, a parameter indicating a difference between elongation in the longitudinal direction (MD) of the copper foil and elongation in the transverse direction (TD) of the copper foil, wherein the tensile strength of the copper foil is 400 MPa or more and the elongation of the copper foil in the width direction It is necessary that the inhaled anisotropy {[(MD elongation - TD elongation) / MD elongation] x 100} is 50% or less.

Conventional general electrolytic copper foils have been demanded less for high strength and high thermal resistance, and electrolytic copper foil (for example, Patent Document 5) which does not use additives and has high purity (for example, Patent Document 5) An electrolytic copper foil (for example, NC-WS, manufactured by Furukawa Electric Co., Ltd.) in which the additive is hardly blown into the copper foil during the process is common. However, the demand for electrolytic copper foils having high strength and high heat resistance has been increased along with high capacity, miniaturization and light weight of batteries, so that cases of positively using additive species injected into foil during electrochemical processes have increased (for example, Patent Documents 1 to 4, etc.).

The present inventors have found that an electrolytic copper foil using various additives is prepared on the premise that it has high strength and high heat resistance suitable for use in a battery or printed wiring board and a lithium ion secondary battery of the next generation type containing a Si- As a result, it was found that the wrinkles of the copper foil after charging and discharging could not be sufficiently suppressed only by improvement of the characteristics that had been required in the past, such as strength, elongation, and heat resistance. Therefore, as a result of intensive investigations directed toward further suppression of wrinkles, it has been found that in the electrolytic copper foil having high strength and high internal resistance, the kidney anisotropy becomes effective and the anisotropy of elongation is reduced, . Hereinafter, the stretch anisotropy will be described.

The term &quot; stretch anisotropy &quot; refers to a property that a stretch value differs depending on a tensile direction in a tensile test. The present inventors have found that when anisotropic elongation of a plurality of high-strength and high-heat-resistance electrolytic copper foils is examined, the value of elongation when the copper foil is stretched in the longitudinal direction (MD direction) Direction), the value of the elongation was found to be the smallest. Therefore, in the present invention, as a value indicating the magnitude of the elongation anisotropy, the elongation anisotropy, which is a parameter indicating the difference between elongation in the longitudinal direction (MD) of the copper foil and elongation in the transverse direction (TD) Elongation) / MD height] × 100}. Hereinafter, the relationship between the anisotropy of the kidney and the wrinkles will be described.

When an isotropic stress is applied to the electrolytic copper foil due to charging or discharging of the battery or pressing with a resin or the like, when the elongation anisotropy is large, in a direction in which the elongation value is low (for example, in the width direction TD of the copper foil) (Equivalent to the necking area referred to in the single tensile test), the uniform strain region and the non-uniform strain region are mixed according to the direction, and the local strain of the strain is generated. As a result, the copper foil is prone to wrinkles. On the other hand, in the case where the elongation anisotropy is small, since the uniform strain region and the non-uniform strain region as described above are hardly mixed, it is considered that wrinkles are unlikely to occur as a result of suppressing the bias of strain.

Therefore, the electrolytic copper foil of the present invention suppresses the tensile strength from being maintained at 400 MPa or higher or lower than 400 MPa when measured at room temperature after being heated at 150 占 폚 for 1 hour, And the elongation in the width direction (TD) of the copper foil is 2% or more, and the elongation anisotropy of the copper foil is 50% or less, preferably 30% or less. If the tensile strength after heating is less than 400 MPa, the strength of the thinned copper foil becomes insufficient and tear easily occurs. If the elongation in the width direction (TD) of the copper foil after heating is less than 2%, tearing easily occurs. When the anisotropic elongation of the copper foil after heating is more than 50%, the homogeneous strain region and the heterogeneous strain region are mixed together, and the local strain of the strain is generated. As a result, the copper foil is easily wrinkled.

Therefore, the electrodeposited copper foil of the present invention suppresses the tensile strength from being maintained at or lower than 400 MPa when heated at 150 캜 for 1 hour and then measured at room temperature, and has high strength and high heat resistance Tensile elongation in the width direction (TD) of the copper foil was 2% or more, and the elongation anisotropy of the copper foil was 50% or less.

The tensile strength (initial strength) measured at room temperature before heating is preferably in the range of 400 to 900 MPa. If the tensile strength is less than 400 MPa, the initial strength is insufficient, and the tensile strength when measured at room temperature after heating at 150 캜 can not be 400 MPa or more, and tearing tends to occur easily. If the tensile strength is more than 900 MPa, elongation is insufficient and elongation in the width direction (TD) of the copper foil measured at room temperature after heating at 150 캜 can not be made 2% or more, It tends to be easier to do.

In particular, the electrolytic copper foil used for forming the printed wiring board is a post-treatment of the produced electrolytic copper foil (original foil) for the purpose of ensuring the adhesion with the resin constituting the printed wiring board, There are many cases. The coarsening plating generally forms copper particles having a particle shape on the order of 0.1 to 1 mu m on the electrolytic copper foil surface by electrolysis in a sulfuric acid-copper sulfate copper plating solution in a relatively short time and at a high current density. On the other hand, the electrodeposited copper foil of the present invention is characterized by the tensile characteristics when measured in the state of the untreated electrolytic copper foil (original foil) where the roughened layer is not formed on both sides. The roughness of the surface of the electrolytic copper foil becomes coarse because of the existence of the coarsened plating layer on the surface of the electrolytic copper foil, depending on the thickness of the coarsened layer. In addition, the electrolysis conditions of the coarsened plating generally differ significantly from the electrolysis conditions for producing the untreated electrolytic copper foil (original foil). Therefore, the crystal structure and structure of the copper particles formed by co-plating are different from the crystal structure and structure of the untreated electrolytic copper foil (original foil).

Although the detailed mechanism is not clear, the electrolytic copper foil having the roughened plating layer by the plurality of factors has a problem that the elongation anisotropy is apparently larger or smaller than the electrolytic copper foil (original foil) having no roughened plating layer . Therefore, it is preferable that the electrolytic copper foil of the present invention does not have a roughened layer formed by roughened plating when accurately measuring (evaluating) the aforementioned tensile properties.

The tensile test was carried out in accordance with the IPC standard (IPC-TM-650). After 10 measurements for each sample, numerical values obtained by averaging their tensile strength and elongation were employed as the values of strength and elongation. The numerical values of the tensile strengths show that the test pieces cut along the length direction of the copper foil and the test pieces cut along the width direction of the copper foil did not show a significant anisotropy. In the present invention, the tensile strength was measured along the length direction of the copper foil And the tensile test speed was set at 50 mm / min.

[Manufacturing method of electrolytic copper foil]

The inventors of the present invention have made intensive investigations on a method of reducing the anisotropy of the elongation. As a result, they found that the flow rate of the electrolytic solution in the copper electrolytic bath is reduced, and ideally, the foil is formed in a non-crosslinked state to significantly reduce the anisotropic elongation. Various analyzes have been made on the mechanism, but a clear difference in the metal structure due to the presence or absence of the anisotropy of the kidney has not been confirmed, and the mechanism has not been elucidated. However, the anisotropy of the elongation is considered to be a phenomenon peculiar to an electrolytic copper foil having high strength and high heat resistance, which can not be confirmed in an electrolytic copper foil having almost no blowing of an additive such as a conventional foil (see Fig. 1). The adsorption of the additive component and the subsequent blowing of the additive component into the copper foil are generally known to be influenced by the flow rate of the electrolytic solution and therefore the electrolytic solution at the time of producing the electrolytic copper foil flows at a high rate It is presumed that the effect of the additive is something different and the anisotropy of the elongation of the copper foil is expressed.

Next, an example of a typical manufacturing method of the electrolytic copper foil according to the present invention will be described below.

2 is a schematic view showing a main part of a typical manufacturing apparatus 1 used for manufacturing the electrolytic copper foil M of the present invention. The electrolytic copper foil M is an electrolytic bath 3 filled with an electrolytic solution 2, A cathode drum 4, and an anode 5 positioned opposite to the cathode drum 4. The cathode drum 4 is made up of an anode 5, The electrolytic solution (2) is preferably an aqueous solution of sulfuric acid-copper sulfate. The anode 5 is preferably made of an insoluble anode made of titanium covered with a white metal element or an oxide thereof.

The electrolytic copper foil M is formed on the surface of the negative electrode drum 5 in such a state that the electrolytic solution 2 is filled between the insoluble positive electrode 5 and the negative electrode drum 4 made of titanium and opposed to the positive electrode 5, 4) is rotated at a constant speed, copper is precipitated on the surface of the negative electrode drum 4 by passing a direct current between the two poles 4, 5, and the precipitated copper is peeled from the surface of the negative electrode drum 4 The electrolytic copper foil M is formed and the formed electrolytic copper foil is wound by a winding roll 6.

The electrolytic solution 2 is supplied from the portion called the distributor 7 formed at the bottom of the electrolytic bath 3 so that the direction of flow of the electrolytic solution 2 flows from the distributor 7 to both sides of the top of the electrolytic bath 3 Is directed in the same direction as the longitudinal direction of the copper foil formed on the surface of the negative electrode drum 4 as the direction toward the overflow portion 8 formed. The flow rate of the electrolytic solution 2 can be suitably changed by the pump output or the like. However, when the electrolytic solution 2 is produced under the electrolytic conditions of the limit current density or more, so-called plating burning occurs. It is necessary to appropriately adjust the electrolytic bath composition, the bath temperature, the current density, and the like so that the electrolysis condition is less than the density. Suitable electrolysis conditions for producing the electrolytic copper foil of the present invention are shown below.

Copper concentration: 120 ~ 155g / L

Sulfuric acid concentration: 30 to 100 g / L

Chlorine concentration: 60 to 140 mg / L

Additive concentration: 2 to 20 mg / L

Bath temperature: 65 ~ 80 ℃

Current density: 10 to 35 A / dm ²

Flow rate: 0.02 to 0.05 t

In order to obtain an electrolytic copper foil having high strength and high heat resistance, it is necessary to add an additive to the electrolytic solution. As the method of selecting the additive, it is possible to appropriately select and use the effect of adsorbing on the copper surface to refine the crystal grains and having the heat-resistant effect blown into the particles. There is no particular problem in using a plurality of additives, but it is preferable that the additive is as small as possible in view of economical efficiency, manufacturing stability, and ease of concentration control. It is known that an additive having the above effect is generally effective to have a functional group having a pair of non-covalent electrons such as S, N, and O. In this embodiment, at least one of S, N, and O is included, And an additive that combines heat resistance. In addition, the higher the additive concentration, the more the blowing of the additive into the copper foil increases, the higher the strength and the heat resistance. On the other hand, the ductility tends to decrease, and therefore tearing tends to occur at the time of handling or charging / discharging. Thus, there is an optimum concentration range. As the additive, for example, polyethylene glycol (PEG), hydroxyethyl cellulose (HEC), thiourea and the like are preferably used.

In the present invention, the copper concentration and the bath temperature are significantly increased and the current density is lowered compared to the conventional general manufacturing conditions, so that electrolytic conditions of less than the critical current density are devised so as to meet the extremely low flow rate and ideally even in the non-copper layer. The flow rate of the electrolytic solution in the electrolytic cell was measured by using a small anemometer CM-1SX type (manufactured by Toyo Denka Kogyo Co., Ltd.) and measuring the flow rate of the electrolyte from the distributor 7 of the electrolytic cell to the overflow portion 8 And the measurement was carried out. The electrolytic copper foil of the present invention can be produced by the above-mentioned method.

Further, when the electrolytic copper foil of the present invention is used for a lithium ion secondary battery having a negative electrode for a lithium ion secondary battery, for example, as a current collector, it is possible to prevent tearing and wrinkling during charging and discharging, Cycle characteristics and safety can be improved. Further, when the electrolytic copper foil of the present invention is used for a printed wiring board formed by lamination of an electrolytic copper foil together with an insulating film, it is possible to prevent the occurrence of tearing, wrinkling and dimensional stability at the time of pressing.

The above description is merely an example of an embodiment of the present invention, and various modifications can be added in the claims.

Example

(Examples 1 to 7 and Comparative Examples 1 to 8)

In Examples 1 to 7 and Comparative Examples 1 to 8, the insoluble positive electrode 5 and the negative electrode drum 4 made of titanium formed opposite to the positive electrode 5 were produced by using the electrolytic copper foil production apparatus shown in Fig. Copper is deposited on the surface of the negative electrode drum 4 by supplying a direct current between the two electrodes 4 and 5 while rotating the negative electrode drum 4 at a constant speed while satisfying the electrolytic solution 2 between the electrodes 2, And the precipitated copper was peeled from the surface of the cathode drum 4 to prepare an electrolytic copper foil M having a thickness of 8 탆. Table 1 shows the bath composition of the electrolytic solution, the kind and addition amount of the additive, the bath temperature, the current density and the flow rate of the electrolytic solution. In addition, in Examples 1 to 5 and 7, the reason why the flow velocity is set to 0.02 kPa instead of the non-crosslinked bar is to prevent the concentration fluctuation due to the retention of the bath at the time of manufacturing the continuous film. The roughness Rz of the negative electrode drum 4 measured in the direction perpendicular to the polishing direction (buff line direction) is equivalent to the roughness Rz of the electrolytic copper foil (S side) shown in Table 2 Until then, the surface was buffed.

(Comparative Examples 9 to 13)

In Comparative Examples 9 to 13, an electrolytic copper foil M having a thickness of 8 탆 was produced under the conditions corresponding to Example 1 of Patent Documents 1 to 5, respectively. In addition, since there was no description about the flow rate, in all of Comparative Examples 9 to 13, the flow rate of the electrolytic solution was set to 0.5 인, which is a general flow rate condition range of the conventional electrolytic copper foil. The roughness Rz of the negative electrode drum 4 measured in the direction perpendicular to the polishing direction (buff line direction) is equivalent to the roughness Rz of the electrolytic copper foil (S side) shown in Table 2 Until then, the surface was buffed.

(Comparative Example 14)

NC-WS &quot; manufactured by Furukawa Electric Kogyo Co., Ltd., which is an electrolytic copper foil in which the additive is hardly blown into the copper foil in the course of electroplating, although the additive is added to the electrolytic solution for smoothing. ".

<Evaluation method>

1. Measurement of carbon content in copper foil

The amount of carbon contained in the copper foil was measured by burning a sample of about 0.5 g using a carbon / sulfur analyzer EMIA-810W (manufactured by Horiba Seisakusho Co., Ltd.), burning in an oxygen flow (tubular electric furnace system) Measurement was carried out by the method. The measured carbon contents are shown in Table 2. In the measurement, the copper foil was handled with sufficient caution so that the surface was not contaminated, and pretreatment such as acetone degreasing was performed as necessary.

2. Measurement of 10 point average roughness Rz of copper surface

The 10-point average roughness Rz was measured according to JIS B0601: 1994. The measuring surface was a S face (copper foil surface on the negative electrode drum side) of the copper foil and a measuring direction was a direction (= TD direction) perpendicular to the buff line direction (= MD direction).

3. Battery performance test

(1) Fabrication of negative electrode for lithium secondary battery

A carbon material-based active material (containing 20 mass% of a silicon-based alloy active material) and acetylene black were pulverized and mixed using a ball mill so as to have a mass ratio of 8: 1, thereby producing a negative electrode material. The negative electrode material was mixed with 80 mass% of the negative electrode material and 20 mass% of polyvinylidene fluoride (PVDF) as a binder to prepare a negative electrode material mixture. The negative electrode material mixture was dispersed in N-methylpyrrolidone (solvent) Slurry. Subsequently, the active material slurry was coated on both surfaces of an electrolytic copper foil having a thickness of 8 mu m (parallel to the direction of the copper foil MD), which had been produced under the above conditions, and dried, After heating for 1 hour, the negative electrode mixture was compressed and formed into a negative electrode mixture having a thickness of 120 mu m on both sides by a roller press machine to obtain a negative electrode for a lithium secondary battery.

(2) Fabrication of positive electrode for lithium secondary battery

A mixture of lithium carbonate 0.5 molar and cobalt carbonate 1 mol and, 900 ℃ in air and calcined 5 hours to a positive electrode active material (LiCoO _2). The positive electrode active material (LiCoO ₂₎ the 91% by weight, 6% by weight of graphite as a conductive agent, a mixture of PVDF as a binding agent in a proportion of 3 mass% to prepare a positive electrode laminated material, this N- methyl-2-pyrrolidone ( NMP) to form a slurry. Next, this slurry was uniformly applied to both surfaces of a positive electrode current collector made of a strip-shaped aluminum having a thickness of 20 mu m, followed by drying so as to have a thickness of 95 mu m on the surface of the positive electrode mixture after molding, Thereby obtaining a positive electrode for a lithium secondary battery.

(3) Production of lithium ion secondary battery

As a kind of non-aqueous electrolyte secondary battery, a lithium ion secondary battery was produced. The positive electrode and the negative electrode fabricated as described above and a separator made of a microporous polypropylene film were laminated to obtain a laminated electrode body. This laminated electrode body was wound several times in a vortex shape with the negative electrode inward along the longitudinal direction thereof, and the terminal end of the separator was fixed to the outermost periphery with a tape to form a swirling electrode body. The spirally wound electrode body thus manufactured was housed in a nickel-plated steel battery can with an insulating plate provided on both the upper and lower surfaces thereof. In order to collect the positive and negative electrodes, And the negative electrode lead made of nickel was led out from the negative electrode collector and connected to the battery can.

A nonaqueous electrolytic solution obtained by dissolving LiPF6 in a molar ratio of 1 mol / L into a mixed solvent of equal volume of propylene carbonate and diethyl carbonate was injected into the battery can containing the spirally wound electrode body. Then, the battery can was caulked through an insulating sealing gasket having a surface coated with asphalt to fix the battery cover, and the airtightness in the battery can was preserved and maintained. Thus, a cylindrical lithium secondary battery having a diameter of 18 mm and a height of 65 mm was produced.

The evaluation of the battery in this lithium ion secondary battery was carried out at a temperature of 25 占 폚 by the following method.

(Conditions of charge-discharge test)

Charging: Constant current charging was performed at a current equivalent to 1 C, and after reaching 4.2 V, switching to constant voltage charging was terminated when the charging current decreased to 0.05 C or equivalent.

Discharge: Constant current was discharged at a current equivalent to 1 C, and the process was terminated when the voltage reached 3.0 V.

C is the C rate and refers to the amount of current that discharges the entire capacity of the cell in one hour.

(Evaluation of wrinkles and tears after charging / discharging)

The evaluation of the tear after charging and discharging was repeated by charging and discharging up to 1000 cycles under the above conditions. After completion of the cycle test, the battery was disassembled, and wrinkles and tears of the copper foil were visually observed. The evaluation of the wrinkles and the tear in Table 2 were evaluated as "⊚" when no wrinkles or tears were present, "◯" when wrinkles were slightly generated, and when " Quot ;, and &quot; peel-off &quot;, respectively, and the case where both of the significant wrinkles and the tearing are generated is referred to as &quot;

The electrodeposited copper foil produced under the above conditions was subjected to a rustproofing treatment under the following chromate conditions, and the surface-treated copper foil was used as a tensile test, a roughness measurement, a gas analysis, and a battery evaluation sample.

&Lt; Chromate treatment conditions >

Potassium dichromate 1 to 10 g / L

Temperature (℃) 25 ℃

Immersion time 2 to 20 seconds

Table 2 shows the evaluation results.

From the results shown in Table 2, it can be seen that in all of Examples 1 to 7, the amount of carbon contained in the copper foil is 0.0015 to 0.018 mass%, the preferred range of the present invention (0.001 to 0.020 mass%) and Rz is 1.0 to 1.7 m (Tensile strength) of 420 to 653 MPa in a suitable range (400 MPa or more) of the present invention when measured at room temperature after heating at 150 占 폚 for one hour, (2% or more) and a tensile anisotropy of 6.2 to 47.5% in the range of the present invention (50% or less) in terms of the width-direction elongation (TD) of 2.1 to 6.1% After the test, remarkable wrinkles and tears were hardly observed, and in Examples 1 to 4 in particular, the elongation anisotropy was 30% or less and no wrinkles were generated at all.

On the other hand, in Comparative Examples 1 to 4, the elongation anisotropy was 57.1 to 63.9%, which exceeded the upper limit (50%) of the appropriate range of the present invention, and remarkable wrinkles were observed in the copper foil after the charge and discharge test. In addition, in Comparative Examples 3 and 4, since the value of the elongation (TD) in the width direction of the copper foil was 1.3 to 1.8%, which was smaller than the lower limit (2%) of the appropriate range of the present invention, a foil tear was also observed in the copper foil after the charge- . In Comparative Example 5, since the carbon content was 0.023 mass%, which was higher than the upper limit value (0.02 mass%) in the appropriate range of the present invention, the copper foil after the charge and discharge test was confirmed to be torn. In Comparative Example 6, since the carbon content is less than the lower limit value (0.001 mass%) of the appropriate range of the present invention as 0.0008 mass%, the tensile strength after heating at 150 占 폚 is 370 MPa, which is lower than the lower limit value (400 MPa) And was markedly softened by the heat treatment, and tearing was confirmed in the copper foil after the charge-discharge test. In Comparative Example 7, the elongation in the width direction (TD) of the copper foil was 1.3%, which is smaller than the lower limit value (2%) of the appropriate range of the present invention, so that tearing was confirmed in the copper foil after the charge and discharge test. In Comparative Example 8, the anisotropy of the elongation due to the surface irregularities became present and remarkable wrinkles were confirmed in the copper foil after the charge / discharge test because Rz was 2.0 탆 which was larger than the upper limit (1.8 탆) of the appropriate range of the present invention . In addition, since the value of the elongation (TD) in the width direction of the copper foil was 1.8%, which is smaller than the upper limit value of the appropriate range of the present invention, the copper foil after the charge and discharge test was also confirmed to be torn. In all of Comparative Examples 9 to 12, the elongation anisotropy was 53.6 to 70.0%, which is larger than the upper limit value of the appropriate range of the present invention, and therefore, remarkable wrinkles were observed in the copper foil after the charge and discharge test. In addition, in Comparative Examples 9 and 10, since the value of the elongation (TD) in the width direction of the copper foil was 0.9 to 1.3%, which is smaller than the lower limit value of the appropriate range of the present invention, peeling was simultaneously confirmed. In all of Comparative Examples 13 and 14, the tensile strength after heating at 150 占 폚 was 251 to 273 MPa, which is lower than the lower limit value of the appropriate range of the present invention, so that tearing was confirmed in the copper foil after the charge and discharge test.

From the above results, it was found that when the electrolytic copper foil contains 0.001 to 0.020% by mass of carbon, the 10-point average roughness (Rz) of the electrolytic copper foil is 1.8 占 퐉 or less and the electrolytic copper foil is heated at 150 占 폚 for 1 hour, That is, the tensile strength of the copper foil is 400 MPa or more, the elongation of the copper foil in the width direction (TD) is 2% or more, and the difference between elongation in the longitudinal direction (MD) The electrolytic copper foil satisfying a parameter of a tensile anisotropy {[(MD elongation-TD elongation) / MD elongation] x 100} of 50% or less, preferably 30% or less, Wrinkles and tears are suppressed at the time of discharging and it is very suitable for long life of the battery. It has also been confirmed that, in the use of a printed board, the copper foil satisfying the above characteristics is effective for suppressing wrinkles and tearing in the copper foil after pressing.

Further, the strength after heating and the anisotropy of elongation are characteristics provided in the untreated electrolytic copper foil, and even if the surface treatment such as the rust-preventive treatment and the silane coupling treatment is performed, the above characteristics are not affected.

[Industrial applicability]

According to the present invention, it has become possible to provide an electrolytic copper foil having high strength, high heat resistance, and small anisotropic elongation. Further, when the electrolytic copper foil of the present invention is used for a lithium ion secondary battery having a negative electrode for a lithium ion secondary battery, for example, as a current collector, it is possible to prevent tearing and wrinkling during charging and discharging, Cycle characteristics and safety can be improved. Further, when the electrolytic copper foil of the present invention is used for a printed wiring board formed by lamination of an electrolytic copper foil together with an insulating film, it is possible to prevent generation of tears and wrinkles at the time of pressing, and also to improve dimensional stability.

1: Electrolytic copper foil manufacturing apparatus
2: electrolyte
3: electrolytic bath
4: cathode drum
5: anode
6: Winding roll
7: Distributor
8: Overflow section

Claims (6)

An electrolytic copper foil containing 0.001 to 0.020 mass% of carbon,
The electrolytic copper foil has a 10-point average roughness (Rz) of 1.8 占 퐉 or less,
The tensile strength of the copper foil is 400 MPa or more and the elongation of the copper foil in the width direction (TD) is 2% or more, and the tensile strength of the copper foil (MD elongation - TD elongation) / MD elongation] x 100}, which is a parameter indicating the difference between elongation in the longitudinal direction (MD) and elongation in the transverse direction (TD) . The method according to claim 1,
Wherein the elongation anisotropy {(MD elongation - TD elongation) / MD elongation] x 100} is 30% or less. 3. The method according to claim 1 or 2,
Wherein the tensile properties are obtained in the form of an electrolytic copper foil (original foil) in which no roughening treatment layer is formed on both sides of the copper foil. A negative electrode for a lithium ion secondary battery, comprising the electrolytic copper foil according to any one of claims 1 to 3 as a current collector. A lithium ion secondary battery comprising a negative electrode for a lithium ion secondary battery having the electrolytic copper foil according to any one of claims 1 to 3 as a current collector. A printed wiring board comprising the electrolytic copper foil according to any one of claims 1 to 3 and an insulating film laminated.

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