KR20150068386A - Surface-treated copper foil, method for manufacturing surface-treated copper foil, and negative electrode material for negative electrode current collector and nonaqueous secondary cell - Google Patents

Abstract

Disclosure of the Invention A problem to be solved by the present invention is to provide a surface-treated copper foil having less deterioration in tensile strength, a method for producing a surface-treated copper foil, a current collector using the surface- Thereby providing an anode material. In order to solve the above problems, a copper foil having a total amount of at least one kind of trace components selected from carbon, sulfur, chlorine and nitrogen in an amount of not less than 100 ppm, Treated copper foil having a surface treatment layer containing zinc of the following formula: wherein the surface treated copper foil is subjected to a pre-annealing treatment for heating in a temperature range of 200 ° C to 280 ° C.

Description

SURFACE-TREATED COPPER FOIL, METHOD FOR MANUFACTURING SURFACE-TREATED COPPER FOIL, AND NEGATIVE ELECTRODE MATERIAL FOR NEGATIVE ELECTRODE CURRENT COLLECTOR AND AND METHOD FOR MANUFACTURING SURFACE-TREATED COPPER FOIL NONAQUEOUS SECONDARY CELL}

The present invention relates to a surface-treated copper foil, a method for producing a surface-treated copper foil, a negative electrode collector, and an anode material of a non-aqueous secondary battery. Particularly, a surface treated copper foil used for a negative electrode current collector such as a lithium ion secondary battery in which a decrease in tensile strength is small even when it is heated at a high temperature for a long time, a production method thereof, a negative electrode collector using the surface- It is about ashes.

BACKGROUND ART Conventionally, copper foil has been used as a circuit forming material for various electronic parts including printed wiring boards. Further, in recent years, copper foil is not limited to these circuit forming materials, but is also used as a negative electrode current collector of a non-aqueous secondary battery such as a lithium ion secondary battery.

Generally, the negative electrode material of a lithium ion secondary battery comprises a negative electrode mixture layer containing a negative electrode active material, a conductive material, and a binder (binder) on the surface of a current collector made of a conductive material. When the negative electrode active material occludes and releases lithium in the charging and discharging of the lithium ion secondary battery, the negative electrode material mixture layer expands and contracts with this. Since the negative electrode mixture layer is in close contact with the surface of the current collector, repetitive stress is applied between the negative electrode mixture layer and the current collector by repeating the charge / discharge cycle of the lithium ion secondary battery. Therefore, if the tensile strength of the current collector is low, there is a fear that the current collector is elongated due to a change in the volume of the negative electrode mixture, causing deformation such as wrinkles or breaking. When the current collector is elongated to cause deformation such as wrinkles, a short circuit may occur between the positive electrode and the negative electrode, or a distance between the positive electrode and the negative electrode may change, which may hinder uniform electrode reaction and decrease the durability of the charge- have. Further, when the current collector is broken, the capacity per unit volume decreases and the battery characteristics of the lithium ion secondary battery deteriorate. Therefore, when a copper foil is used as a current collector, the copper foil is required to have a high tensile strength.

Incidentally, in the step of manufacturing the negative electrode material, when the negative electrode material mixture layer is formed on the surface of the current collector, high-temperature heat is applied to the current collector. In the case of general copper foil, when high-temperature heat is applied, crystal grains are coarsened by recrystallization of copper, and mechanical strength such as tensile strength is lowered. Therefore, it is required that the copper foil to be used for the current collector application maintain a high tensile strength even after the heat treatment at a high temperature is performed. As such copper foils, for example, Patent Documents 1 and 2 can maintain a tensile strength of 35 kgf / mm < 2 > or more even after heating at 350 DEG C for 60 minutes and then heating at 400 DEG C for 60 minutes. A surface treated copper foil having a surface treatment is disclosed.

International Publication No. 2012/070589 International Publication No. 2012/070591

However, when the negative electrode material of the lithium ion secondary battery is produced, the current collector may be heated in a temperature range of 350 占 폚 to 400 占 폚 for more than one hour. In this case, the tensile strength of the surface treated copper foil disclosed in Patent Document 1 or Patent Document 2 was lowered, and a sufficient level of tensile strength could not be maintained depending on the heating time.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a surface-treated copper foil having less decrease in tensile strength, a method for producing a surface-treated copper foil, a current collector using the surface- Thereby providing a negative electrode material for a battery.

As a result of intensive studies, the inventors of the present invention have found that even when a heat treatment at a high temperature is performed for a long time, the surface treated copper foil has less decrease in tensile strength.

The surface-treated copper foil according to the present invention is a copper foil having a copper foil containing at least 100 ppm of at least one kind of trace elements selected from carbon, sulfur, chlorine and nitrogen in a total amount of 20 mg / / M < 2 >, and is subjected to a pre-annealing treatment for heating in a temperature range of 200 DEG C to 280 DEG C.

The surface treated copper foil according to the present invention exhibits a tensile strength of 45 kgf / mm 2 or more after being heated at 350 ° C for 5 hours.

In the surface treated copper foil according to the present invention, it is preferable that the surface treatment layer includes a metal element other than zinc and having a diffusion rate in copper and / or copper that is higher than zinc.

In the surface-treated copper foil according to the present invention, it is preferable that the metal element is tin.

In the surface-treated copper foil of the present invention, it is preferable that the surface treatment layer contains tin of 1 mg / m 2 to 200 mg / m 2 per one side.

In the surface-treated copper foil of the present invention, it is preferable that the average crystal grain diameter of copper constituting the copper foil is 1.0 탆 or less.

In the surface-treated copper foil of the present invention, the tensile strength of the copper foil in the normal state is preferably 50 gf / mm 2 or more.

In the surface-treated copper foil of the present invention, it is preferable that the pre-annealing is performed at a temperature within the above temperature range for 2 hours to 25 hours.

The surface-treated copper foil according to the present invention is a copper foil having a copper foil containing at least 100 ppm of at least one kind of trace elements selected from carbon, sulfur, chlorine and nitrogen in a total amount of 20 mg / / M < 2 > and a tensile strength of 50 kgf / mm < 2 > or more after heating at 350 DEG C for 5 hours.

The method for producing a surface-treated copper foil according to the present invention is a method for producing a surface-treated copper foil having a copper foil containing at least 100 ppm of at least one kind of trace elements selected from carbon, sulfur, chlorine and nitrogen, M 2 to 1000 mg / m 2, and a pre-annealing step of heating the substrate at a temperature in the range of 200 ° C to 280 ° C after the surface treatment step.

In the method for producing a surface-treated copper foil according to the present invention, it is preferable that the heating time in the pre-annealing step is 2 hours or more and 25 hours or less.

The negative electrode current collector according to the present invention is characterized by using the surface treated copper foil described in any one of the above.

The negative electrode material of the non-aqueous secondary battery according to the present invention is characterized by using the negative electrode collector.

The surface-treated copper foil according to the present invention can be produced easily by forming the surface treatment layer containing zinc on both surfaces of the copper foil and performing the pre-annealing treatment. Further, after the high temperature heat treatment is performed for a long time It is possible to provide a copper foil with less deterioration in tensile strength.

Fig. 1 is an FIB-SIM image showing an example of a cross-section crystal structure of a sample 1 subjected to a pre-annealing treatment at 200 占 폚 for 8 hours and then at 350 占 폚 for 5 hours.
2 is an FIB-SIM image showing an example of a cross-section crystal structure of the comparative sample 1 after heating at 350 ° C for 5 hours.

Hereinafter, embodiments of the surface-treated copper foil, the method of producing the surface-treated copper foil, the negative electrode collector, and the negative electrode material of the non-aqueous secondary battery according to the present invention will be described in order.

1. Surface treated copper foil

First, an embodiment of the surface treated copper foil according to the present invention will be described. The surface-treated copper foil according to the present invention has a surface treatment layer (referred to as a zinc adhesion layer in this embodiment) containing zinc on both surfaces of a copper foil. After the zinc adhesion layer is formed, a pre- The lowering of the tensile strength can be suppressed even after the high-temperature heat treatment is performed for a long time. In the present specification, the term "high temperature" refers to a temperature equal to or higher than a temperature at which recrystallization of copper occurs, and refers to a temperature mainly within a range of about 300 ° C to 400 ° C. Further, the term long time means a time exceeding one hour, and mainly means a time of five hours or more. Hereinafter, in the present embodiment, a case is explained in which the surface-treated copper foil is used as a negative electrode collector of a non-aqueous secondary battery such as a lithium ion secondary battery. However, the surface-treated copper foil according to the present invention, It is needless to say that the negative electrode current collector is not limited to the negative electrode current collector of a non-aqueous secondary battery such as a battery and can be used as a material for producing a printed wiring board.

(1) Copper foil

First, the copper foil will be described. In the present invention, the zinc adhesion layer is formed on both sides of a copper foil containing at least 100 ppm of a total of at least one trace component selected from carbon, sulfur, chlorine, and nitrogen.

Here, in the present invention, the term "copper foil" refers to an untreated copper foil to which various treatments such as the surface treatment are not applied, and the term "surface-treated copper foil" Zinc annealing for forming a copper foil, and free annealing, as well as copper foil after various surface treatments. The copper foil may be an electrolytic copper foil or a rolled copper foil, but it is preferably an electrolytic copper foil from the viewpoint that it is easy to obtain a copper foil having a fine grain size and high tensile strength and excellent mechanical properties. Hereinafter, an electrolytic copper foil will be mainly described as an example. In the following description, when describing simply "copper foil", the copper foil includes not only "electrolytic copper foil" but also "rolled copper foil".

Trace element: In the present invention, as described above, the copper foil contains at least 100 ppm of a total of one or more trace components selected from carbon, sulfur, chlorine and nitrogen. When the content of these trace components is 100 ppm or more in total, the crystal structure (crystal grains) of the copper constituting the copper foil is easily miniaturized, and a copper foil having a high tensile strength and excellent mechanical strength is easily obtained.

Here, the copper foil used in the present invention contains not less than 100 ppm of the minor component in total, and contains 20 ppm to 470 ppm of carbon, 5 ppm to 600 ppm of sulfur, 15 ppm to 600 ppm of chlorine and 5 ppm to 600 ppm of nitrogen . By containing only such an appropriate amount of these minor components in the crystalline structure of the copper foil, it is possible to make the crystal structure of the copper more easily and to make the copper foil having higher mechanical strength with higher tensile strength. Concretely, by containing each of the minor components in the above-mentioned range, the copper foil has an average crystal grain size of 1.0 탆 or less, a state tensile strength of 50 kgf / mm 2 or more and a state elongation of 3% to 15% It can be made of excellent copper foil.

Here, when the content of each minor component is less than the lower limit value, it is difficult to obtain an extremely fine crystal structure having an average grain diameter of 1.0 占 퐉 or less, for example, and a copper foil having a higher tensile strength can not be obtained. On the other hand, when the content of each trace component in the copper foil exceeds the upper limit value, it is not preferable from the viewpoints described below. When the carbon content exceeds 470 ppm, graphite is coarsened and cracks tend to occur, which is not preferable. When the sulfur content is more than 600 ppm, the tensile strength of the copper foil is increased, but the elongation is lowered and the brittle is not preferable. When the chlorine content exceeds 600 ppm, in the case of electrolytic copper foil, the precipitation surface becomes rough. In this case, it is difficult to uniformly adhere the negative electrode active material or the like to the surface thereof, and the amount of volume change when the charge / discharge is repeated is not uniform in the plane and is locally broken. On the other hand, if the nitrogen content exceeds 180 ppm, the nitrogen compound becomes excessive, the effect of making the copper foil micro-fine is saturated, and the significance of increasing the nitrogen content is undesirably deteriorated.

In the present invention, the unit of "ppm" used for indicating the content of the minor component in the copper foil is the same as "mg / kg", and the term "containing the minor component in an amount of 100 ppm or more" Means that the total amount of the minor component contained in 1 kg of the copper foil is 100 mg or more.

Average Grain Size: Next, the average grain size of the grains of copper constituting the crystal structure of the copper foil will be described. First, the average grain diameter is preferably 1.0 탆 or less, and more preferably 0.8 탆 or less. When the average grain size exceeds 1.0 탆, it is not preferable because it becomes difficult to maintain the tensile strength at a required level as the negative electrode collector of the non-aqueous secondary battery such as a lithium ion secondary battery. In addition, the crystal grains of copper constituting the copper foil are preferably fine and uniform. The grain boundaries are uniformly distributed in the copper foil so that the load applied to the copper foil is dispersed without being biased to a specific crystal grain and a copper foil having excellent tensile strength and excellent mechanical strength can be obtained. Here, the average grain diameter referred to herein refers to the average grain diameter in the state of the copper foil (normal state), and can be obtained based on the grain size of the grain appearing on the cross section when the cross section of the copper foil is observed.

State tensile strength: The state tensile strength of the copper foil is preferably 50 kgf / mm < 2 > In the present invention, the term " state " refers to a state that is controlled at room temperature or a state before heat treatment. By using a copper foil having a state tensile strength of 50 kgf / mm < 2 > or more, it is possible to obtain a surface treated copper foil exhibiting a high tensile strength even after high temperature heat treatment. However, even in the case of a copper foil having a high state tensile strength, a decrease in tensile strength after heat treatment may be remarkable. Therefore, in the present invention, it is not preferable that the state tensile strength of the copper foil itself is higher, and regardless of the value of the state tensile strength, the tensile strength of the surface treated copper foil after the heat treatment is higher desirable.

Thickness: The thickness of the copper foil is not particularly limited. Depending on the use of the surface treated copper foil, a copper foil having an appropriate thickness may be employed. For example, when the surface-treated copper foil according to the present invention is used as a negative electrode current collector of a non-aqueous secondary battery such as a lithium ion secondary battery, the thickness of the copper foil is preferably in the range of 5 mu m to 35 mu m There are a lot of cases. Further, when the surface-treated copper foil is used for producing a printed wiring board, the thickness of the copper foil is often set within a range of 5 to 120 탆 (gauge thickness). The surface-treated copper foil according to the present invention has a tensile strength at a level required in the market as a negative electrode current collector of a lithium ion secondary battery, even if it is a thin copper foil having a thickness of 5 to 35 m.

(2) Zinc adhesion layer (surface treatment layer)

Next, the zinc adhesion layer will be described. The surface treated copper foil of the present invention has a zinc adhesion layer containing zinc of 20 mg / m 2 to 1000 mg / m 2 per side on both surfaces of the copper foil. Zinc in the zinc adhesion layer formed on both sides of the copper foil diffuses into the copper foil with the lapse of time and reacts with the trace components in the crystal structure. The zinc and the compound of the minor component are precipitated in the grain boundaries and when the heat is applied to the copper foil, the growth of the grains is disturbed, and the effect of suppressing coarsening of the grains is exerted. According to the present invention, zinc is deposited on both surfaces of a copper foil and then subjected to a pre-annealing treatment described later so that zinc is deposited not only in the surface layer portion of the copper foil but also in the inside Can be diffused. Therefore, according to the present invention, even when the surface-treated copper foil is subjected to a heat treatment for a longer time at a high temperature in the subsequent use process, the fine crystal structure can be maintained even after the heat treatment, and the tensile strength of the copper foil Can be suppressed.

Here, when the zinc content in the zinc adhesion layer, that is, the adhesion amount of zinc to the surface of the copper foil is less than 20 mg / m 2 per one side, the amount of zinc diffused into the copper foil is small, And it is not preferable because it is difficult to maintain a fine crystal structure. From this viewpoint, the adhesion amount of zinc is preferably 25 mg / m 2 or more, more preferably 50 mg / m 2 or more. On the other hand, when the adhesion amount of zinc exceeds 1000 mg / m < 2 >, an effect depending on the deposition amount is not obtained even if the adhesion amount of zinc is increased, From this viewpoint, the adhesion amount of zinc is preferably 500 mg / m 2 or less, more preferably 300 mg / m 2 or less, and still more preferably 200 mg / m 2 or less.

Here, since the zinc adhesion layer contains zinc within the above range per one side of the copper foil, the total adhesion amount of zinc to the copper foil falls within the range of 40 mg / m 2 to 2000 mg / m 2. The total adhesion amount of the zinc is preferably 50 mg / m 2 or more, more preferably 100 mg / m 2 or more from the same viewpoint as described above. The upper limit value is preferably 1000 mg / m 2 or less, and more preferably 600 mg / m 2 or less. However, the amount of zinc adhered is determined as the adhered amount (converted amount) of zinc per unit area on the assumption that the surface of the copper foil is completely flat.

The zinc adhesion layer may be a zinc layer containing zinc and may be a zinc alloy layer containing a metal element having a diffusion rate in copper and / or copper higher than zinc in addition to zinc. For example, Bi, Cd, Sn, Pb, Sb, In, Al, As, Ga, or the like is used as a metal element (hereinafter referred to as " dissimilar metal element ") whose diffusion rate in copper is higher than zinc , And Ge. Further, the zinc adhesion layer may be a zinc-based composite layer obtained by laminating a zinc layer and a dissimilar metal layer containing at least one kind or two or more kinds of the dissimilar metal elements. In this case, the order of stacking the zinc layer and the dissimilar metal layer is not limited. The zinc layer and the dissimilar metal layer may be stacked in this order on the surface of the copper foil, and the dissimilar metal layer and the zinc layer may be stacked in this order on the surface of the copper foil do. The dissimilar metal element can be diffused together with zinc in the copper foil by making the zinc adhesion layer contain the dissimilar metal element together with zinc. Since the dissimilar metal element diffusion rate is faster than zinc, these dissimilar metal elements reach deeper positions faster than zinc in the thickness direction of the copper foil. These dissimilar metal elements react with the trace components similarly to zinc to form a compound to suppress coarsening of the crystal grains of copper. Therefore, by making the zinc-clad layer contain a dissimilar metal element together with zinc, even if a heat treatment for a longer time is performed at a high temperature, the coarsening of the crystal grains of copper Can be effectively suppressed. Also, zinc refers to zinc having a purity of 99% or more. The zinc alloy refers to a mixture, solid solution, process, compound or the like of zinc and other elements.

In the present invention, when the zinc adhesion layer is a zinc alloy layer or a zinc-based composite layer, it is particularly preferable to use tin among the dissimilar metal elements. In this case, it is preferable that, in the conversion amount, the surface treatment is performed so that the adhesion amount of the tin per one surface becomes 1 mg / m 2 to 200 mg / m 2. In this case, it is preferable that the zinc content ratio calculated as {[zinc adhesion amount] / [zinc-tin alloy adhesion amount]} x 100 is 30 mass% or more. Even if the adhesion amount of zinc to the surface of the copper foil is within the above range, when the zinc content ratio in the zinc adhesion layer is less than 30 mass%, the tin amount with respect to the zinc amount becomes excessive. As a result, the presence of tin inhibits the diffusion of zinc into the copper foil, which makes it difficult to sufficiently diffuse zinc into the inside of the copper foil, and the above-mentioned effect can not be obtained. The zinc adhesion layer can be formed using, for example, a rust inhibitor containing zinc or zinc-tin, and exhibits a function as an anti-rust treatment layer.

(3) Other layer composition

The surface-treated copper foil according to the present invention may optionally include other surface-treated layers such as a roughened layer, a chromate treated layer, and an organic treated layer, if necessary, in addition to the zinc-coated layer.

For example, when the surface-treated copper foil is used as a negative electrode current collector of a lithium ion secondary battery by forming a roughened treatment layer, adhesion between the surface of the surface-treated copper foil and the negative electrode active material can be improved.

Further, by providing the chromate treatment layer and / or the organic treatment layer, it is possible to inhibit oxidation of the copper foil surface by these layers together with the zinc adhesion layer. In addition, the adhesion of the lithium ion secondary battery to the negative electrode active material can be further improved. Examples of the organic-treated layer include a silane coupling agent-treated layer and an organic anti-corrosive layer.

(4) Pre-annealing

The surface-treated copper foil according to the present invention is obtained by subjecting the both surfaces of the copper foil to the above-mentioned surface treatment and then subjecting to a pre-annealing treatment in which the copper foil is heated in a temperature range of 200 ° C to 280 ° C. By performing the pre-annealing treatment, zinc can be diffused into the copper foil in a state in which recrystallization of copper is suppressed. As a result, when the surface-treated copper foil is loaded with heat at a temperature higher than the temperature at which recrystallization of copper occurs, the compound precipitated at the grain boundaries prevents the growth of the grains and suppresses coarsening of the grains . The pre-annealing process will be described later. In the following, the copper foil after each surface treatment described above and before the pre-annealing treatment may be referred to as " copper foil after completion of surface treatment ".

(5) Mechanical properties

The surface-treated copper foil according to the present invention exhibits a tensile strength of 45 kgf / mm 2 or more after being subjected to the pre-annealing treatment on the surface-treated copper foil after heating at 350 ° C for 5 hours under an inert gas atmosphere, The tensile strength after the heat treatment is 50 kg / mm < 2 > or more by adjusting the conditions of the treatment under appropriate conditions depending on the amount of copper foil and the amount of zinc (and tin) adhered. In the present invention, it is particularly preferable that the tensile strength after heating at 350 DEG C for 5 hours is 50 kgf / mm < 2 > or more by adjusting the condition of the pre-annealing treatment.

The surface-treated copper foil according to the present invention preferably has a tensile strength retention ratio of 90% to 100% after heating at 350 占 폚 for 5 hours to tensile strength at the time of state, and the retention ratio of the tensile strength is 95% And more preferably in the range of 100% to 100%. According to the present invention, by performing the pre-annealing treatment, the retention ratio of the tensile strength after the heat treatment can be improved as compared with the case where the pre-annealing treatment is not performed.

2. Manufacturing method of surface-treated copper foil according to the present invention

Next, an embodiment of a method for producing a surface-treated copper foil according to the present invention will be described. The surface-treated copper foil according to the present invention can be obtained by producing the surface-treated copper foil by the following method. Each step will be described below.

(1) Preparation of Copper foil

In the present invention, a copper foil containing at least 100 ppm of a total of at least one minor component selected from carbon, sulfur, chlorine, and nitrogen is prepared. Here, it is preferable that the contents of the respective minor component are within the above respective ranges. The average grain size of copper constituting the copper foil is preferably 1.0 占 퐉 or less, and more preferably 0.8 占 퐉 or less. It is also as described above that it is more preferable to use a copper foil having a state tensile strength of 50 kgf / mm 2 or more. From the viewpoint that it is easy to obtain a copper foil satisfying the above conditions by adjusting various additives and the like in the electrolytic solution as long as copper foils satisfying these conditions can be obtained, It is preferable to produce a foil.

(2) Harmonious treatment process

Next, when the roughening treatment layer is formed on the surface of the copper foil, the surface of the copper foil is roughened. In the present invention, the roughening treatment layer has an arbitrary layer structure, and there is no particular limitation on the roughening treatment method and the roughening treatment conditions. It goes without saying that the pretreatment such as pickling treatment of the surface of the copper foil may be performed before the roughening treatment. However, the roughening treatment method and roughening treatment conditions are not limited to these, and appropriately appropriate methods and conditions may be adopted according to the surface characteristics required for the copper foil in the conventionally known method.

(3) Zinc adhering process (surface treatment process)

Next, a surface treatment (hereinafter referred to as " zinc adhesion treatment ") is performed on the surface of the copper foil using a surface treatment agent containing zinc to form a zinc adhesion layer containing zinc. In the zinc adhesion treatment step, any method may be used as long as the zinc adhesion layer can be formed on the surface of the copper foil so that the adhesion amount of zinc falls within the above range. For example, electrochemical methods such as electrolytic plating or electroless plating, physical vapor deposition methods such as sputter deposition or chemical vapor phase reaction can be used. However, considering the production cost, it is preferable to employ an electrochemical method. The surface treatment agent may contain other metal elements other than zinc as described above, and tin as the other metal element is also as described above.

Electrolytic plating method: When a zinc plating treatment is applied to the surface of a copper foil by an electrolytic plating method, a zinc pyrophosphate bath, a zinc cyanide plating bath, a zinc sulfate plating bath, or the like can be used as the zinc plating solution. For example, in the case of employing a zinc pyrophosphate bath, specifically, a bath composition of zinc concentration of 5 g / l to 30 g / l, potassium pyrophosphate concentration of 50 g / l to 500 g / l and pH 9 to pH 12 is adopted , The zinc foil layer can be formed on the surface of the copper foil by electrolyzing the copper foil itself in a solution at a liquid temperature of 20 to 50 占 폚 at a cathode under the conditions of a current density of 0.3 A / dm 2 to 10 A / dm 2 A .

(4) Chromate treatment

The surface of the zinc adhesion layer may optionally be subjected to a chromate treatment. The chromate treatment includes electrolytic chromate treatment and immersion chromate treatment, but any method may be used. However, it is preferable to employ an electrolytic chromate treatment in consideration of the thickness variation of the chromate film, the stability of the deposition amount, and the like. The electrolytic conditions in the case of the electrolytic chromate treatment are not particularly limited, and suitable conditions can be appropriately employed.

(5) Organic treatment

Further, the surface of the zinc adhesion layer may be subjected to an organic treatment. Examples of the organic agent treatment include a silane coupling agent treatment and an organic rust inhibitive treatment.

Silane coupling agent treatment: In the present invention, the treatment with the silane coupling agent is not essential but is carried out appropriately in consideration of the adhesion property of the insulating resin base material or the lithium ion secondary battery to the negative electrode active material required for the copper foil, Appropriate conditions and methods can be employed as appropriate.

Organic anti-rust treatment: In order to further improve the anti-rust effect, in the case of performing the organic anti-rust treatment, for example, methyl benzotriazole (tolyl triazole) of benzotriazoles, aminobenzotriazole, The surface treatment can be carried out using an organic agent such as sol or benzotriazole. As other organic agents, aliphatic carboxylic acids, alkyl amines, benzoic acids, imidazoles, triazine thiols and the like may be used. The organic rust preventive treatment is not particularly limited, and appropriate conditions and methods can be appropriately employed.

(6) Drying process

When the copper foil is subjected to the various surface treatments, a drying step is performed to dry the copper foil in a wet state in the various surface treatment steps. The drying conditions are not particularly limited. However, in the case where the organic treatment is carried out, it is preferable to prevent thermal decomposition or the like of the silane coupling agent and / or the organic rust inhibitor adhering to the surface of the copper foil, and to heat treat the copper foil surface in a satisfactory condition, Time, etc.) may be employed.

(7) Pre-annealing process

Next, the pre-annealing process will be described. In the pre-annealing step, the copper foil subjected to the processes up to the drying step is subjected to heat treatment in a temperature range of 200 ° C to 280 ° C to diffuse zinc from the zinc adhesion layer side into the copper foil, It is a process to obtain foil.

Temperature: In the present invention, the coarse grains of the copper foil are hardly coarsened even when the copper foil is heated in the temperature range of 200 ° C to 280 ° C due to the existence of the trace component. When the copper foil having the zinc adhesion layer on its surface is heated within the above temperature range, compared with the case where the copper foil is stored at room temperature, zinc is diffused into the copper foil at a speed suitable for industrial production efficiency So that the distribution of zinc in the copper foil can be made uniform. Thus, by performing the pre-annealing treatment, even when high-temperature heat is applied to the surface treated copper foil for a long time, the effect of suppressing the coarsening of the crystal grains of copper can be enhanced, The decrease in tensile strength can be suppressed sufficiently.

Processing time: Next, the time for performing the pre-annealing process (hereinafter referred to as " processing time ") will be described. By subjecting the surface-treated copper foil to the pre-annealing treatment, it is possible to increase the amount of zinc diffusion into the copper foil as compared with the case where the copper foil is stored at room temperature, and suppress the decrease in tensile strength even after the heat treatment at a high temperature . However, from the viewpoint that a sufficient amount of zinc is diffused not only in the surface layer portion of the copper foil but also inside the copper foil, the treatment time is preferably from 2 hours to 25 hours. Further, from the viewpoint that the zinc is more sufficiently diffused into the copper foil and the distribution of zinc in the copper foil is more uniform, the treatment time is preferably 8 hours or more and 25 hours or less. On the other hand, when the treatment time is less than 2 hours, the amount of zinc diffusion into the copper foil is small, and if the heat treatment at a high temperature is performed for a long time, there is a possibility that crystal grains are coarsened in the inside of the copper foil, Can not be sufficiently suppressed. When the pre-annealing time is 25 hours or more, the effect of suppressing the coarsening of the crystal grains of copper is saturated even if the pre-annealing treatment is further performed. In addition, the cost related to the heat treatment also increases. Therefore, from these viewpoints, the pre-annealing time is preferably set to be within 25 hours.

However, the optimum annealing temperature and / or time suitable for the diffusion of zinc differs depending on the crystal structure of the copper foil, the content of trace components in the copper foil, the amount of zinc adhered to the copper foil, and the like. Accordingly, it is preferable to appropriately set the appropriate pre-annealing conditions within the above-mentioned range within the temperature and time.

≪ Embodiment of negative electrode current collector according to the present invention &

Next, an embodiment of the negative electrode current collector according to the present invention will be described. The negative electrode current collector according to the present invention is characterized by using the above-described surface-treated copper foil according to the present invention. In a non-aqueous secondary battery such as a lithium ion secondary battery, a current collector Can be used. The current collector according to the present invention is not particularly limited except that the surface-treated copper foil is used. Since the current collector according to the present invention uses the above-mentioned surface-treated copper foil, it has excellent mechanical properties such as tensile strength.

<Embodiment of negative electrode material of non-aqueous secondary battery according to the present invention>

Next, an embodiment of the negative electrode material of the non-aqueous secondary battery according to the present invention will be described. Here, the non-aqueous secondary battery is a generic term of a secondary battery using an electrolyte other than an aqueous solution, and refers to a secondary battery using an organic electrolyte, a polymer gel electrolyte, a solid electrolyte, a polymer electrolyte, a molten salt electrolyte and the like. The negative electrode material according to the present invention is not particularly limited as far as it uses the current collector. For example, the negative electrode material mixture layer may be provided on the surface of the current collector like the negative electrode material of the lithium ion secondary battery. In this case, the negative electrode material mixture layer may include, for example, a negative electrode active material, a conductive agent, and a binder.

As described above, the surface treated copper foil according to the present invention has a higher effect of suppressing lowering of the tensile strength and higher retention ratio of the tensile strength after the heat treatment as compared with the case where the pre-annealing treatment is not performed. As a result, even after heating at 350 DEG C for 5 hours in an inert gas atmosphere, it becomes possible to maintain a tensile strength of 45 kgf / mm2 or more, preferably 50 kgf / mm2 or more. Therefore, even if a repetitive stress is applied to the current collector by repeating a charge-discharge cycle in a lithium ion secondary battery or the like, there is little fear that deformation such as wrinkling or the like will occur in the current collector, Electrical characteristics can be maintained. Further, when the negative electrode material of the lithium ion secondary battery is manufactured, high temperature heat is applied to the current collector in the step of forming the negative electrode material mixture layer on the surface of the current collector. Even in this case, it has a sufficient level of tensile strength.

Hereinafter, the surface treated copper foil according to the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Example 1

In Example 1, copper foil according to the present invention was produced and compared with Comparative Example 1 described later. Hereinafter, explanation will be given in the order of the process.

Preparation of copper foil: First, an electrolytic copper foil having a total amount of the above trace elements in copper foil of 100 ppm or more (carbon: 44 ppm, sulfur: 14 ppm, chlorine: 54 ppm, nitrogen: 11 ppm, average crystal grain diameter: 0.64 μm) was prepared. Specifically, an electrolytic copper foil having a thickness of 12 mu m and not subjected to a surface treatment used for the production of VLP copper foil manufactured by Mitsui Kinzoku Kogyo Co., Ltd. was prepared.

The copper foil was immersed in a copper plating solution having a free sulfuric acid concentration of 200 g / l, a copper concentration of 8 g / l, and a liquid temperature of 35 캜 to polarize the copper foil itself to the cathode, and the current density was 25 A / Under the conditions of burning copper plating, so that fine copper particles were deposited and deposited on the surface of the copper foil on the cathode surface side. Next, in order to prevent the fine copper particles from falling off, the copper foil itself was polarized to the cathode in a copper plating solution having a free sulfuric acid concentration of 110 g / l, a copper concentration of 70 g / l and a liquid temperature of 50 캜, dm &lt; 2 &gt; to smooth the cathode surface side.

Zinc Adhesion Treatment Step: A zinc coating layer containing zinc-tin alloy was formed on both sides of a copper foil by using a surface treatment agent containing zinc and tin on both surfaces of the copper foil after the roughening treatment. First, a method of forming the zinc adhesion layer will be described.

In this embodiment, a zinc-tin alloy layer was formed as a zinc-adhered layer on both sides of a copper foil using a zinc pyrophosphate-tin plating bath. The bath composition of the zinc pyrophosphate-tin plating bath was such that the zinc concentration was 1 g / l to 6 g / l, the tin concentration was 1 g / l to 6 g / l, the potassium pyrophosphate concentration was 100 g / l and the pH was 10.6. The copper foil itself was polarized to the cathode at a solution temperature of 30 占 폚 in a zinc pyrophosphate-tin plating bath of this composition to appropriately adjust the current density and the electrolysis time so that the adhesion amount of zinc per one side of the copper foil was 50 mg / To obtain a copper foil having an adhesion amount of tin of 5 mg / m &lt; 2 &gt;

Free annealing process: Next, sample 1 was subjected to pre-annealing under the conditions shown in Table 1, and it was designated as sample 1 for practical use. At the time of pre-annealing, each sample was placed in an oven and the temperature in the furnace was raised to 5 占 폚 / min. In Table 1, the sample 1 was heated under the corresponding treatment conditions. In Table 1, the column indicated by &quot;? &Quot; means that the pre-annealing process was performed on the sample of the number indicated in the parenthesis of the column under the condition (temperature, treatment time).

Example 2

In Example 2, a sample 2 was prepared in the same manner as in Example 1 except that the adhesion amount per one surface of tin was 15 mg / m &lt; 2 &gt;, subjected to pre-annealing under the conditions shown in Table 1, Respectively.

Example 3

In Example 3, a sample 3 was prepared in the same manner as in Example 1 except that the adhesion amount per one surface of tin was 30 mg / m 2. Thereafter, the sample was subjected to pre-annealing under the conditions shown in Table 1, Respectively.

Example 4

In Example 4, Sample 4 was produced in the same manner as in Example 1, except that the adhesion amount per one surface of tin was 15 mg / m 2 and the total adhesion amount of zinc was 100 mg / Subjected to pre-annealing treatment, and used as sample sample 4.

Example 5

In Example 5, Sample 5 was produced in the same manner as in Example 1 except that the adhesion amount per one surface of tin was 15 mg / m 2 and the total adhesion amount of zinc was 150 mg / Subjected to pre-annealing treatment and used as sample sample 5.

Example 6

Next, a sixth embodiment will be described. In Example 6, another copper foil according to the present invention was produced as follows. Hereinafter, explanation will be given in the order of the process.

Preparation of copper foil: In Example 6, an electrolytic copper foil produced under the following conditions was used. First, an electrolytic solution (50 占 폚) containing copper ion at a concentration of 80 g / l and sulfuric acid at a concentration of 250 g / l and chlorine ion at 2.7 ppm and gelatin at a concentration of 2 ppm was used as a sulfuric acid- , And electrolysis was performed at a current density of 50 A / dm 2 to obtain an electrolytic copper foil having a thickness of 12 탆. The contents of trace components in the electrolytic copper foil were 49 ppm of carbon, 26 ppm of sulfur, 24 ppm of chlorine, 11 ppm of nitrogen, and an average grain diameter of 0.58 탆.

Harmonious treatment process: The copper foil was subjected to a roughening treatment in the same manner as in Example 1.

Zinc adhering step: In the same manner as in Example 1 except that the electrolytic copper foil after the coarsening treatment had an adhesion amount of tin per side of 25 mg / m2 and an adhesion amount of zinc of 150 mg / An adhesive layer was formed and a sample 6 was prepared. Then, in the same manner as in Example 1, the pre-annealing treatment was performed under the conditions shown in Table 1, and the sample after each pre-annealing treatment was used as sample 6.

Example 7

In Example 7, a surface-treated copper foil was produced in the same manner as in Example 1 except that a zinc layer was formed as a zinc-adhered layer. The zinc layer was formed using a zinc pyrophosphate plating bath. The bath composition of the zinc pyrophosphate plating bath was electrolytic in the same manner as in Example 1 except that a bath composition having a zinc concentration of 6 g / l, a potassium pyrophosphate concentration of 125 g / l and a pH of 10.5 was employed, Copper foil having an adhered amount of zinc per 50 mg / m &lt; 2 &gt; was obtained. Thereafter, in the same manner as in Example 1, the pre-annealing treatment was performed under the conditions shown in Table 1, and the sample after each pre-annealing was used as Sample 7.

Comparative Example

In the comparative examples, samples were prepared in the same manner as in Examples 1 to 7 except that the pre-annealing treatment was not carried out, and Comparative Examples 1 to 7 were respectively prepared.

Table 2 shows the total amount of tin and zinc deposited and the type of copper foil in each sample in order to facilitate comparison of the conditions of the samples prepared in each of the examples and the comparative examples. Table 2 shows the tensile strength of each copper foil (A or B) measured by a method described later. In Table 2, the type A of the copper foil refers to the electrolytic copper foil used in Examples 1 to 5 and Example 7, and the type B of copper foil refers to the electrolytic copper foil used in Examples 1 to 5 and Example 7 And the like.

[evaluation]

1. Evaluation Method

(1) Trace element content

The contents of trace elements in the respective copper foils used in Examples 1 to 6 and Comparative Examples were measured as follows. First, the content of carbon and sulfur in the copper foil was analyzed using a carbon-sulfur analyzer (EMIA-920V) manufactured by Horiba Seisakusho Co., Ltd. The content of nitrogen in the copper foil was analyzed using an oxygen / nitrogen analyzer (EMGA-620) manufactured by Horiba Seisakusho Co., Ltd. The content of chlorine in the copper foil was analyzed by a silver chloride plating method using a spectrophotometer (U-3310) manufactured by Hitachi High-Tech Filing Co., Ltd.

(2) Tensile strength

Each of the samples obtained in Examples 1 to 6 and Comparative Example was heated at 350 占 폚 for 5 hours under an inert gas atmosphere and the tensile strength of each sample after heating was measured.

In the present invention, the &quot; tensile strength &quot; was measured using a rectangular copper foil sample of 100 mm x 10 mm (distance between marks: 50 mm) according to IPC-TM-650 at a tensile speed of 50 mm / min. &lt; / RTI &gt;

(3) Crystal structure

The untreated copper foils A and B before carrying out the respective samples obtained in Examples 1 and 5 and Comparative Examples 1 and 5 and the zinc treatment and the like were subjected to heat treatment under an inert gas atmosphere, The crystal grain size after heating at 350 DEG C for 5 hours was measured by the following method. The sample 1 and sample 5 obtained in Example 1 and Example 5 were subjected to a pre-annealing treatment under the treatment condition (1) (200 ° C) for 8 hours.

The measurement of the grain diameter of the copper foil was carried out by using an FE-type scanning electron microscope (SUPRA 55VP, manufactured by Carl Zeiss Co.) equipped with an EBSD evaluation device (OIM Analysis, manufactured by TSL Solutions Co., Ltd.) Respectively. Using this apparatus, image data of a pattern of a crystalline state of a cross section of a copper foil was obtained for the appropriately cross-sectioned sample according to the EBSD method, and this image data was analyzed by an EBSD analysis program (OIM Analysis, The average crystal grain size was numerically expressed by an analysis menu of TSL Solutions Co., Ltd., Japan. In this evaluation, the orientation difference of 5 degrees or more was regarded as a grain boundary system. The conditions of the scanning electron microscope at the time of observation were an acceleration voltage of 20 kV, an aperture diameter of 60 mm, a high current mode and a sample angle of 70 DEG. In addition, the observation magnification, the measurement area, and the step size were measured by appropriately changing the conditions according to the grain size.

2. Evaluation results

(1) Tensile strength

Tables 3 to 7 show the tensile strengths of the test samples and the comparative samples after heat treatment at 350 占 폚 for 5 hours. Table 7 shows the tensile strengths of Comparative Sample 5 and Comparative Sample 6 after heating at 350 占 폚 for 1 hour. In each table, the percent retention of tensile strength after heat treatment of each sample with respect to the state tensile strength is shown.

As shown in Tables 3 to 6, the test samples 1 to 7 according to the present invention had a tensile strength of 45 kgf / cm &lt; 2 &gt; after heating at 350 DEG C for 5 hours regardless of the treatment conditions at the time of performing the pre- Mm &lt; 2 &gt; and a tensile strength of 79% to 102% of the state tensile strength was maintained. Further, it is possible to adjust the tensile strength of 50 kgf / mm &lt; 2 &gt; or more even after heating at 350 DEG C for 5 hours by adjusting the adhesion amount of zinc, the amount of tin adhered, It is possible to keep the rate of decrease of the tensile strength within 10%, more preferably within 5%.

Comparing the examples 1 to 6 and the example 7, it was found that the use of the zinc-adhered layer as the zinc-tin alloy layer makes it possible to improve the tensile strength after heat treatment, as compared with the case where the zinc- It was confirmed that the value was high and the retention ratio was also improved.

On the other hand, as shown in Table 7, the tensile strength after heating at 350 DEG C for 5 hours was 45 kgf / mm &lt; 2 &gt; or more, but the tensile strength retention was 65% to 87% , It was confirmed that the tensile strength was lowered by 10% or more. For example, the comparative samples 5 and 6 had a tensile strength of 51.5 kgf / mm &lt; 2 &gt; and 58.8 kgf / mm &lt; 2 &gt; after heating at 350 DEG C for 1 hour, respectively. 40 kgf / mm &lt; 2 &gt;. On the other hand, with respect to the working samples 5 and 6, even when the pre-annealing treatment was performed for 8 hours at the lowest temperature treatment condition (1) (200 占 폚) as shown in Table 3, , And a tensile strength of 46.9 kgf / mm &lt; 2 &gt; is maintained. As shown in Table 5, when the treatment time was set to, for example, 2 hours and the treatment conditions (3) (250 ° C), the tensile strengths of the test samples 5 and 6 were 50.7 kgf / And 50.9 kgf / mm 2 and 49.2 kgf / mm 2 respectively under the treatment condition (5) (275 ° C). Therefore, it has been confirmed that by performing the pre-annealing treatment even at a low temperature or for a short time, an effect of suppressing the decrease of the tensile strength even after being heated at a high temperature for a long time is obtained.

(2) Crystal structure

Next, with reference to Fig. 1 and Fig. 2, the crystal structure of the sample 1 and the sample 1 is prepared. Figs. 1 and 2 are FIB-SIM images showing crystal structures of sample 1 and comparative sample 1 after heating at 350 deg. C for 5 hours, respectively. Table 8 shows the average crystal grain diameters of the sample 1, sample 5, comparative sample 1 and comparative sample 5 after heating at 350 占 폚 for 5 hours, respectively. As described above, the sample 1 and the sample 5 were subjected to pre-annealing (heating under the treatment condition (1) (200 ° C) for 8 hours) before heating at 350 ° C for 5 hours. As shown in Fig. 1 and Fig. 2, it can be confirmed that the crystal structure of the conducting sample 1 is entirely fine as compared with the crystal structure of the comparative sample 1. As shown in Table 8, Sample 1 and Sample 5 had an average grain size of 1.0 mu m or less in any of the surface layer portion and the central portion of the copper foil, and even after heating at 350 DEG C for 5 hours, It can be confirmed that a fine crystal structure is maintained. On the other hand, when the comparative sample 1 and the comparative sample 5 were heated at 350 占 폚 for 5 hours, the average crystal grain diameter exceeded 1.0 占 퐉 in any region, and the crystal grains in the center portion of the copper foil tended to be coarse . Therefore, zinc (and dissimilar metal element) can be diffused not only in the surface layer portion of the copper foil but also in the central portion of the copper foil by performing the pre-annealing treatment on each sample, and even when high temperature heat is loaded for a long time, It was confirmed that it is possible to suppress coarsening.

The surface copper foil according to the present invention can be easily manufactured by subjecting the surface of the copper foil to the above-described surface treatment and then performing the pre-annealing treatment, and even after a long heat treatment at a high temperature is performed, It is possible to provide a copper foil with less decrease in strength. Therefore, it can be suitably used for applications exposed to a high-temperature atmosphere at the time of production, and can be particularly preferably used as a negative electrode collector of a non-aqueous secondary battery such as a lithium ion secondary battery or a material for producing a printed wiring board.

Claims (13)

Surface treatment comprising zinc of 20 mg / m 2 to 1000 mg / m 2 per side on both sides of a copper foil containing at least 100 ppm of at least one minor component selected from carbon, sulfur, chlorine and nitrogen Treated copper foil,
Characterized in that a pre-annealing treatment is carried out in which the copper foil is heated in a temperature range of 200 ° C to 280 ° C. The surface treated copper foil according to claim 1, which has a tensile strength of 45 kgf / mm &lt; 2 &gt; or more after being heated at 350 DEG C for 5 hours. The surface treated copper foil of claim 1 or 2, wherein the surface treatment layer comprises a metal element other than zinc, the diffusion rate of copper and / or copper being higher than that of zinc. The surface-treated copper foil according to claim 3, wherein the metal element is tin. The surface-treated copper foil according to claim 4, wherein the surface treatment layer contains tin of 1 mg / m 2 to 200 mg / m 2 per one side. The surface-treated copper foil according to any one of claims 1 to 5, wherein an average crystal grain size of copper in the state of the copper foil is 1.0 탆 or less. 7. The surface-treated copper foil according to any one of claims 1 to 6, wherein the copper foil has a tensile strength of 50 gf / mm &lt; 2 &gt; The surface treated copper foil according to any one of claims 1 to 7, wherein in the pre-annealing treatment, the surface treated copper foil is heated for 2 hours to 25 hours at a temperature within the temperature range. Surface treatment comprising zinc of 20 mg / m 2 to 1000 mg / m 2 per side on both sides of a copper foil containing at least 100 ppm of at least one minor component selected from carbon, sulfur, chlorine and nitrogen Treated copper foil,
And a tensile strength of 50 kgf / mm &lt; 2 &gt; or more after heating at 350 DEG C for 5 hours. Surface treatment comprising zinc of 20 mg / m 2 to 1000 mg / m 2 per side on both sides of a copper foil containing at least 100 ppm of at least one minor component selected from carbon, sulfur, chlorine and nitrogen A surface treatment step of forming a layer,
And a pre-annealing step of heating the copper foil after the surface treatment step in a temperature range of 200 ° C to 280 ° C. The method for producing a surface-treated copper foil according to claim 10, wherein the heating time in the pre-annealing process is from 2 hours to 25 hours. A negative electrode current collector characterized by using the surface treated copper foil according to any one of claims 1 to 9. A negative electrode material for a nonaqueous secondary battery, comprising the negative electrode collector according to claim 12.

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