Surface treatment method for copper foil, anti-oxidation copper foil, and negative electrode of lithium battery

Abstract

To provide a surface treatment method of a copper foil, an antioxidant copper foil, and a cathode of a lithium battery.SOLUTION: An antioxidant copper foil includes a copper foil substrate and an antioxidant layer formed thereon. The antioxidant layer contains chromium elements derived from a chromic acid compound, and contains nitrogen elements at least partially derived from an aminotetrazole compound and a nitrogen-containing heterocyclic compound. The antioxidant copper foil satisfies the following characteristics: (a) the antioxidant layer has a chromium content of 5 μg / m2 to 35 μg / m2 determined by X-ray fluorescence analyzer (XRF); (b) the antioxidant layer has a nitrogen content of 0.1 to 10 mass% determined by X-ray photoelectron spectrometer (XPS); (c) the antioxidant layer has a C-N signal detected by headspace GC-MS; and (d) a color difference ΔE before and after baking the antioxidant copper foil at 250°C for 10 minutes is 8 or less.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to the technical field of copper foil, and in particular to a surface treatment method for copper foil, an oxidation-resistant copper foil, and a negative electrode for a lithium battery. [Background technology]

[0002] In the development of conventional copper foil technology, an anti-oxidation layer is formed on the surface of the copper foil to prevent the oxidation of the copper foil. If an anti-oxidation layer is not formed on the surface of the copper foil, the surface of the copper foil is easily oxidized at room temperature or in a high-temperature atmospheric environment, and the copper foil cannot be stored for a long time and is not suitable for high-temperature work (i.e., the heat resistance of the copper foil is poor).

[0003] Conventionally, an anti-oxidation layer is formed on the surface of copper foil by electrolysis to form a nickel (Ni) plating layer, a zinc (Zn) plating layer, or a nickel-zinc (Ni-Zn) alloy plating layer.

[0004] However, the copper foil having an antioxidant layer containing the metal elements (e.g., nickel, zinc) is not applicable to lithium batteries, and if the copper foil is applied to a lithium battery, the function and stability of the lithium battery may be reduced by the metal elements such as nickel and zinc.

[0005] In order to apply copper foil to lithium batteries, conventional technology uses chromic acid and glucose as the components of the oxidation-resistant layer, which makes the copper foil less susceptible to oxidation at room temperature, and the color difference ΔE of the copper foil before and after heating for 10 minutes at an operating temperature of 180°C can be less than 8. That is, the copper foil has a certain degree of heat resistance. However, when using chromic acid and glucose as the components of the oxidation-resistant layer, the color difference ΔE still exceeds 8 at higher temperatures (e.g., 250°C), limiting its application. Summary of the Invention [Problem to be solved by the invention]

[0006] The technical problem to be solved by the present invention is to provide a surface treatment method for copper foil and an oxidation-resistant copper foil to provide a better heat resistance in response to the shortcomings of the prior art. For example, even after the copper foil of the present invention is baked for 10 minutes at an operating temperature of 250°C, the color difference ΔE of the copper foil is still less than 8. That is, the copper foil of the present invention achieves a more remarkable heat resistance than the copper foil of the prior art that uses chromic acid and glucose as components of the oxidation-resistant layer. [Means for solving the problem]

[0007] In order to solve the above technical problems, one technical means adopted by the present invention provides a method for surface treating a copper foil, which includes providing a copper foil substrate, immersing the copper foil substrate in an antioxidant solution containing a chromate compound, an aminotetrazole compound, and a nitrogen-containing heterocyclic compound, and immersing the copper foil substrate in the antioxidant solution for a predetermined time or electrolyzing the copper foil substrate, thereby forming an antioxidant layer on at least one surface of the copper foil substrate to form an antioxidant copper foil.

[0008] The oxidation-resistant copper foil satisfies the following characteristics (a) to (d), and (a) the chromium content of the oxidation-resistant layer measured by an X-ray fluorescence analyzer (XRF) is 5 μg / m 2 ~35μg / m 2 and the chromium in the antioxidant layer is derived from the chromate compound, (b) the nitrogen content of the antioxidant layer measured by an X-ray photoelectron spectroscopy (XPS) is 0.1% by mass to 10% by mass, and at least a part of the nitrogen in the antioxidant layer is derived from the aminotetrazole compound and the nitrogen-containing heterocyclic compound, (c) a CN signal is detected by headspace GC / MS analysis of the antioxidant copper foil, and (d) the color difference ΔE of the antioxidant copper foil before and after firing at 250° C. for 10 minutes is 8 or less.

[0009] Preferably, in the antioxidant solution, the concentration of the chromate compound is 0.1 g / L to 5 g / L.

[0010] Preferably, the chromate compound is at least one selected from the group consisting of chromic acid, dichromic acid, and potassium dichromate.

[0011] Preferably, in the antioxidant liquid, the concentration of the aminotetrazole compound is 0.1 g / L to 10 g / L, the concentration of the nitrogen-containing heterocyclic compound is 0.1 g / L to 10 g / L, and the mass ratio of the aminotetrazole compound to the nitrogen-containing heterocyclic compound (the aminotetrazole compound:the nitrogen-containing heterocyclic compound) is 1:5 to 5:1.

[0012] Preferably, the aminotetrazole compound is 5-aminotetrazole, and the nitrogen-containing heterocyclic compound is a bicyclic nitrogen-containing heterocyclic compound.

[0013] Preferably, the nitrogen-containing heterocyclic compound is benzotriazole.

[0014] Preferably, the antioxidant liquid 2 further contains at least two selected from the group consisting of 1,5-diaminotetrazole, 2-amino-1,3,4-thiadiazole, and 3,5-diamino-1,2,4-triazole.

[0015] Preferably, the predetermined time for immersing the copper foil base material in the antioxidant solution or electrolyzing the copper foil base material is 0.1 to 10 seconds, and the current density of the electrolytic plating conditions is 0.1 to 5 ASD (A / dm 2 ).

[0016] In order to solve the above technical problems, another technical means adopted by the present invention provides an oxidation-resistant copper foil. The oxidation-resistant copper foil comprises a copper foil substrate and an oxidation-resistant layer formed on one side of the copper foil substrate, the oxidation-resistant layer containing chromium derived from a chromate compound, and the oxidation-resistant layer containing nitrogen at least partially derived from an aminotetrazole compound and a nitrogen-containing heterocyclic compound, and the oxidation-resistant copper foil satisfies the following properties (a) to (d), in which (a) the chromium content of the oxidation-resistant layer measured by an X-ray fluorescence analyzer (XRF) is 5 μg / m 2 ~35μg / m 2 (b) the nitrogen content of the oxidation-resistant layer is 0.1% by mass to 10% by mass as measured by an X-ray photoelectron spectroscopy (XPS); (c) a CN signal is detected from the oxidation-resistant copper foil by head space GC / MS analysis (head space-GC / MS); and (d) the color difference ΔE of the oxidation-resistant copper foil before and after firing at 250° C. for 10 minutes is 8 or less.

[0017] Preferably, the copper foil base has a thickness of 1 μm to 10 μm, and the antioxidant layer has a thickness of 1 nm to 100 nm.

[0018] In order to solve the above technical problems, another technical solution adopted by the present invention provides a negative electrode of a lithium battery, which comprises the above-mentioned oxidation-resistant copper foil. Effect of the Invention

[0019] As advantageous effects of the present invention, the surface treatment method for copper foil, the oxidation-resistant copper foil, and the negative electrode of a lithium battery according to the present invention have the following characteristics: "The oxidation-resistant copper foil comprises a copper foil base material and an oxidation-resistant layer formed on the copper foil base material. The oxidation-resistant layer contains chromium derived from a chromate compound, and the oxidation-resistant layer contains nitrogen at least partially derived from an aminotetrazole compound and a nitrogen-containing heterocyclic compound" and "The oxidation-resistant copper foil satisfies the following characteristics (a) to (d): (a) the chromium content of the oxidation-resistant layer measured by an X-ray fluorescence analyzer (XRF) is 5 μg / m 2 ~35μg / m 2(b) the nitrogen content of the oxidation-resistant layer measured by X-ray photoelectron spectroscopy (XPS) is 0.1% by mass to 10% by mass, (c) the oxidation-resistant copper foil detects CN signals by headspace GC / MS analysis, and (d) the color difference ΔE of the oxidation-resistant copper foil before and after baking at 250°C for 10 minutes is 8 or less," the copper foil of the present invention achieves a more remarkable degree of heat resistance than the copper foil of the prior art that uses chromic acid and glucose as the components of the oxidation-resistant layer. Thus, it is particularly suitable for use as a negative electrode material for lithium batteries, and the product can be applied more widely. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic diagram showing a surface treatment method for a copper foil according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing the formation of an antioxidant layer on the surface of the copper foil shown in FIG. 1. [Diagram 3] FIG. 2 is a schematic diagram showing an antioxidant layer formed on one surface of a copper foil according to an embodiment of the present invention. [Figure 4] FIG. 2 is a schematic diagram showing an antioxidant layer formed on both sides of a copper foil according to an embodiment of the present invention. [Diagram 5] FIG. 2 is a schematic diagram showing a modified example of a surface treatment method for a copper foil according to an embodiment of the present invention. [Figure 6] FIG. 2 is a schematic diagram showing another modified example of the surface treatment method for copper foil according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] In order to better understand the features and technical contents of the present invention, please refer to the following detailed description of the present invention and the accompanying drawings, which are provided for reference and explanation only and are not intended to limit the scope of the present invention.

[0022] Hereinafter, the embodiments of the present invention will be described in accordance with certain specific embodiments, and those skilled in the art can understand the advantages and effects of the present invention based on the contents disclosed in this specification. The present invention can be implemented or applied in other different specific embodiments, and various modifications and changes can be made to each detail in this specification based on different perspectives and applications without departing from the concept of the present invention. In addition, as described in advance, the accompanying drawings of the present invention are simple schematic illustrations and are not drawn based on actual size. The technical contents of the present invention will be described in more detail based on the following embodiments, but the disclosed contents do not limit the protection scope of the present invention.

[0023] It should be understood that although the present specification may use terms such as "first," "second," and "third" to describe various materials or parameters, these materials or parameters are not limited by these terms, and the term "or" as used herein may include any one or more combinations of the associated listed items, depending on the actual situation.

[0024] [Surface treatment method for copper foil] As shown in Figures 1 to 6, in an embodiment of the present invention, a copper foil surface treatment method is provided, which includes steps S110, S120, S130, S140, and S150. It should be noted that the order and operation method of each step in this embodiment can be adjusted according to needs, and is not limited thereto.

[0025] The step S110 includes providing a copper foil substrate 1 (copper foil).

[0026] The copper foil substrate 1 may be, for example, an electrolytic copper foil or a rolled copper foil. In one embodiment, the copper foil substrate 1 is an electrolytic copper foil, and the copper foil substrate 1 is suitable for manufacturing a negative electrode of a lithium battery, but the present invention is not limited thereto. The thickness of the copper foil substrate 1 is, for example, 1 to 10 μm, and preferably 3 to 8 μm.

[0027] In one embodiment of the present invention, the step S110 further includes rinsing the copper foil substrate 1 with water to remove impurities or chemical residues on the surface of the copper foil substrate 1.

[0028] The step S120 includes preparing an antioxidant liquid 2 in a liquid storage tank T and immersing the copper foil base material 1 in the antioxidant liquid 2 (see FIG. 1).

[0029] Here, the antioxidant liquid 2 contains at least the following compounds (1) to (3). (1) Chromate compounds. (2) Aminotetrazole compounds. (3) Nitrogen-containing heterocyclic compound.

[0030] Here, (1) the concentration of the chromate compound in the antioxidant solution is preferably 0.1 g / L to 5 g / L, and particularly preferably 0.1 g / L to 2 g / L.

[0031] In one embodiment of the present invention, the chromate compound is at least one selected from the group consisting of chromic acid, dichromic acid, and potassium dichromate.

[0032] Here, the chromate compound is preferably chromate.

[0033] The chemical formula for chromic acid is H 2 CrO 4and its chemical structure is as follows: [ka]

[0034] The chemical formula for dichromate is H 2 Cr 2 O 7 and its chemical structure is as follows: [ka]

[0035] The chemical formula for potassium dichromate is K 2 Cr 2 O 7 and its chemical structure is as follows: [ka]

[0036] To further explain, (2) the aminotetrazole compound is 5-aminotetrazole, whose chemical formula is HN 4 CNH 2 and its chemical structure is as follows: [ka]

[0037] Here, the concentration of the aminotetrazole compound in the antioxidant solution is preferably 0.1 g / L to 10 g / L, and particularly preferably 2 g / L to 8 g / L.

[0038] In further detail, (3) the nitrogen-containing heterocyclic compound is a bicyclic nitrogen-containing heterocyclic compound, and is preferably benzotriazole. The bicyclic nitrogen-containing heterocyclic compound may be, for example, indoline or 1,4-diazabicyclo[2.2.2]octane, but the present invention is not limited thereto.

[0039] Here, the chemical formula of benzotriazole is C 6 H 5 N 3 and its chemical structure is as follows: [ka]

[0040] Here, the concentration of the nitrogen-containing heterocyclic compound in the antioxidant solution is preferably 0.1 g / L to 10 g / L, and particularly preferably 2 g / L to 8 g / L.

[0041] Here, the mass ratio of the aminotetrazole compound to the nitrogen-containing heterocyclic compound (aminotetrazole compound:nitrogen-containing heterocyclic compound) is preferably 1:5 to 5:1, and particularly preferably 1:2 to 2:1, but the present invention is not limited thereto.

[0042] The antioxidant liquid 2 may further contain at least one of the following nitrogen-containing heterocyclic compounds (4) to (6).

[0043] (4) 1,5-diaminotetrazole. (5) 2-amino-1,3,4-thiadiazole. (6) 3,5-diamino-1,2,4-triazole (1H-1,2,4-Triazole-3,5-diamine).

[0044] Here, the chemical formula of 1,5-diaminotetrazole is CH 4 N 6 and its chemical structure is as follows: [ka]

[0045] The chemical formula for 2-amino-1,3,4-thiadiazole is C 2 H 3 N3 S and its chemical structure is as follows: [ka]

[0046] The chemical formula for 3,5-diamino-1,2,4-triazole is C 2 H 5 N 5 and its chemical structure is as follows: [ka]

[0047] In one embodiment of the present invention, the antioxidant solution 2 includes at least two selected from the group consisting of 1,5-diaminotetrazole, 2-amino-1,3,4-thiadiazole, and 3,5-diamino-1,2,4-triazole.

[0048] The total concentration of the nitrogen-containing heterocyclic compounds (4) to (6) in the antioxidant solution is 0.1 g / L to 100 g / L, and particularly preferably 1 g / L to 20 g / L.

[0049] Here, the concentration of 1,5-diaminotetrazole is 1 to 100 g / L, and preferably 1 to 10 g / L.

[0050] Here, the concentration of 2-amino-1,3,4-thiadiazole is 0.1 to 10 g / L.

[0051] Here, the concentration of 3,5-diamino-1,2,4-triazole is 0.1 to 10 g / L.

[0052] However, the present invention is not limited to the concentration ranges given in the above embodiments.

[0053] In this embodiment, the liquid component of the antioxidant liquid 2 is water, which may be, for example, deionized water (DI), reverse osmosis water (RO), or ultrapure water (MQ), but the present invention is not limited thereto.

[0054] The step S130 includes forming an antioxidant layer 1a (as shown in FIGS. 2 and 3) on at least one surface of the copper foil base material 1 by immersing the copper foil base material 1 in the antioxidant liquid 2 or by electrolysis. The antioxidant layer 1a has a thickness of 1 to 100 nm, and preferably 1 to 30 nm.

[0055] In another embodiment of the present invention, the copper foil substrate 1 is formed on both sides with an anti-oxidation layer 1a (as shown in FIG. 4).

[0056] More specifically, the copper foil substrate 1 is immersed in the antioxidant liquid 2 for a predetermined time or is electrolyzed, thereby forming the antioxidant layer 1a.

[0057] In one embodiment of the present invention, the predetermined time is 0.1 seconds to 10 seconds, and preferably 0.5 seconds to 5 seconds. For example, the predetermined time may be 0.3 seconds, 0.5 seconds, 1 second, 3 seconds, or 5 seconds.

[0058] The electrolytic plating conditions for the copper foil substrate 1 in the antioxidant solution are a current density of 0.1 ASD to 5 ASD (i.e., A / dm 2 , amperes per square centimeter). For example, the current density may be 0.5 ASD, 0.8 ASD, or 1 ASD.

[0059] It should be noted that, in this embodiment, the copper foil substrate 1 is described as a single copper foil immersed in the antioxidant liquid 2, but the present invention is not limited thereto.

[0060] 5, in one embodiment of the present invention, the copper foil substrate 1 is a bendable continuous sheet. The copper foil substrate 1 is placed inside a liquid storage tank T and guided to the antioxidant liquid 2 by a plurality of guide rollers R around the copper foil substrate 1.

[0061] The copper foil base material 1 is immersed in the antioxidant liquid 2 for a predetermined time by controlling the scroll speed of a plurality of guide rollers R.

[0062] 6, in another embodiment of the present invention, at least a pair of electrodes E are further installed in the storage tank T, and an electrolytic plating operation is performed on the copper foil substrate 1 immersed in the antioxidant solution 2 by energizing the electrodes E. However, the present invention is not limited thereto.

[0063] The step S140 includes removing the copper foil base material 1 on which the antioxidant layer 1a has been formed, and blowing air and drying it to remove excess liquid components (for example, moisture) from the antioxidant layer 1a.

[0064] The step S150 includes winding up the copper foil substrate 1 on which the oxidation-resistant layer 1a is formed, thereby completing the oxidation-resistant copper foil CF, but the present invention is not limited thereto.

[0065] [Antioxidant copper foil] 3 and 4, an oxidation-resistant copper foil CF according to an embodiment of the present invention includes a copper foil base material 1 and an oxidation-resistant layer 1a formed on one surface of the copper foil base material 1, as shown in Fig. 3. In another embodiment, an oxidation-resistant layer 1a is formed on both surfaces of the copper foil base material 1, as shown in Fig. 4.

[0066] The copper foil base 1 has a thickness of, for example, 1 μm to 10 μm, and preferably 5 μm to 8 μm. The antioxidant layer 1a has a thickness of, for example, 1 nm to 100 nm, and preferably 1 nm to 30 nm.

[0067] The oxidation-resistant copper foil CF is applied to the manufacture of a negative electrode (cathode) of a lithium battery, and has the following properties (a) to (d):

[0068] (a) The chromium content of the oxidation-resistant copper layer 1a of the oxidation-resistant copper foil CF measured by an X-ray fluorescence spectroscopy (XRF) is 5 μg / m 2 (micrograms / square meter) ~ 35μg / m 2 and 0 μg / m 2 ~30μg / m 2 Here, the chromium element in the antioxidant layer 1a is derived from a chromate compound (i.e., a chromate compound in the antioxidant solution, such as chromic acid, dichromate, and / or potassium dichromate). It is noteworthy that the X-ray fluorescence analyzer can be applied to elemental analysis and chemical analysis using high-energy X-rays or secondary X-rays excited by gamma rays that hit a material, and can also quantify the chromium content in a material.

[0069] (b) The nitrogen content of the oxidation-resistant layer 1a of the oxidation-resistant copper foil CF measured by an X-ray photoelectron spectroscopy (XPS) is 0.1% by mass to 10% by mass, preferably 0.1% by mass to 5% by mass, and more preferably 0.1% by mass to 2% by mass. At least a part of the nitrogen element in the oxidation-resistant layer 1a is derived from the aminotetrazole compound and the nitrogen-containing heterocyclic compound in the oxidation-resistant liquid, and the other part is derived from at least one selected from the group consisting of 1,5-diaminotetrazole, 2-amino-1,3,4-thiadiazole, and 3,5-diamino-1,2,4-triazole. It is worth noting that XPS is a quantitative energy spectroscopy method for measuring the elemental composition, empirical formula, and chemical and electronic states of the elements contained in a material. This technique involves irradiating the material to be analyzed with X-rays while simultaneously measuring the kinetic energy and number of electrons that escape within a range of 1 nm to 10 nm below the surface of the material to obtain an X-ray photoelectron spectrum.

[0070] (c) The oxidation-resistant copper foil CF was subjected to head space GC / MS analysis to detect a CN signal. For example, the oxidation-resistant copper foil CF was heated to 150°C to 250°C, and the gas generated from the sample was input to a mass spectrometer for analysis. The mass spectrum analysis result was output, and it was possible to evaluate whether or not there was a CN signal peak in the mass spectrum analysis result.

[0071] (d) The oxidation-resistant copper foil CF was placed in an oven and baked for 10 minutes at 250° C. Here, the color of the surface of the oxidation-resistant copper foil CF before and after baking was observed with a chroma meter, and the color difference ΔE was 8 or less.

[0072] Due to the above-mentioned constitution, the oxidation-resistant copper foil CF is resistant to oxidation at both room temperature and high temperature, and achieves a more remarkable heat resistance than the copper foil in the prior art that uses chromic acid and glucose as components of the oxidation-resistant layer.

[0073] It is worth noting that in the antioxidant liquid 2 for forming the antioxidant layer 1a, the nitrogen-containing heterocyclic compound (e.g., benzotriazole) is the main component for forming the antioxidant layer 1a, and can provide the antioxidant layer 1a with basic antioxidant properties and heat resistance. The aminotetrazole compound (e.g., 5-aminotetrazole) improves the density of the antioxidant layer 1a, thereby helping to improve the antioxidant properties and heat resistance. The excess amino-containing azole compound contained in the antioxidant liquid 2 forms a composite blend that can reinforce the antioxidant properties.

[0074] [Measurement of experimental data] The present invention will be described in detail below with reference to examples and comparative examples. However, these examples are provided for the purpose of understanding the present invention and are not intended to limit the present invention.

[0075] For Example 1, an aqueous solution of an antioxidant solution containing 0.6 g / L of chromic acid, 5 g / L of 5-aminotetrazole, 5 g / L of benzotriazole, 2 g / L of 1,5-diaminotetrazole, 5 g / L of 2-amino-1,3,4-thiadiazole, and 2 g / L of 3,5-diamino-1,2,4-triazole was prepared. A copper foil substrate (electrolytic copper foil, the thickness of which was about 6 μm) was washed with water, and the copper foil substrate was immersed in the antioxidant solution. The copper foil substrate was treated for 0.5 seconds under electrolytic plating conditions with a current density of 0.8 ASD to form an antioxidant layer on the surface of the copper foil substrate, thereby obtaining an antioxidant copper foil. The antioxidant copper foil was then removed from the antioxidant solution, air-dried, and wound up to complete the manufacture of the antioxidant copper foil.

[0076] Regarding the measurement results, the chromium content of the oxidation-resistant copper foil according to Example 1 was 20 μg / m 2 The nitrogen content by XPS analysis was 0.5% by mass, a CN signal was detected by headspace GC / MS analysis, and the color difference ΔE before and after firing for 10 minutes at 250° C. was 8 or less. The oxidation-resistant copper foil of Example 1 had excellent oxidation resistance and heat resistance.

[0077] For Example 2, an aqueous solution of an antioxidant solution containing 0.6 g / L of chromic acid, 5 g / L of 5-aminotetrazole, 5 g / L of benzotriazole, 2 g / L of 2-amino-1,3,4-thiadiazole, and 5 g / L of 3,5-diamino-1,2,4-triazole was prepared. A copper foil substrate (electrolytic copper foil, the thickness of which was about 6 μm) was washed with water, and the copper foil substrate was immersed in the antioxidant solution. The copper foil substrate was treated for 0.5 seconds under electrolytic plating conditions with a current density of 0.8 ASD to form an antioxidant layer on the surface of the copper foil substrate, thereby obtaining an antioxidant copper foil. The antioxidant copper foil was then removed from the antioxidant solution, air-dried, and wound up to complete the manufacture of the antioxidant copper foil.

[0078] Regarding the measurement results, the chromium content of the oxidation-resistant copper foil according to Example 2 was 20 μg / m 2 The nitrogen content by XPS analysis was 0.5% by mass, a CN signal was detected by headspace GC / MS analysis, and the color difference ΔE before and after firing for 10 minutes at 250° C. was 8 or less. The oxidation-resistant copper foil of Example 2 had excellent oxidation resistance and heat resistance.

[0079] For Reference Example 1, an aqueous solution of an antioxidant solution containing 0.6 g / L of chromic acid, 5 g / L of 5-aminotetrazole, 5 g / L of 1,5-diaminotetrazole, 2 g / L of 2-amino-1,3,4-thiadiazole, and 2 g / L of 3,5-diamino-1,2,4-triazole was prepared, and the antioxidant solution did not contain benzotriazole. A copper foil substrate (electrolytic copper foil, the thickness of which was about 6 μm) was washed with water, and the copper foil substrate was immersed in the antioxidant solution. The copper foil substrate was treated for 0.5 seconds under electrolytic plating conditions with a current density of 0.8 ASD to form an antioxidant layer on the surface of the copper foil substrate, thereby obtaining an antioxidant copper foil. Thereafter, the antioxidant copper foil was taken out of the antioxidant solution, air-dried, and wound up to complete the production of the antioxidant copper foil.

[0080] As a result of the measurement, the chromium content of the oxidation-resistant copper foil according to Reference Example 1 was 20 μg / m2 The nitrogen content by XPS analysis was 0.5% by mass, a CN signal was detected by headspace GC / MS analysis, and the color difference ΔE before and after firing at 250° C. for 10 minutes exceeded 10. The oxidation-resistant copper foil of Reference Example 1 had slightly inferior oxidation resistance and heat resistance to those of Examples 1 and 2. The reason for this is presumed to be that the density of the oxidation-resistant layer was relatively inferior.

[0081] For Reference Example 2, an aqueous solution of an antioxidant solution containing 0.6 g / L chromic acid, 5 g / L benzotriazole, 2 g / L 1,5-diaminotetrazole, 5 g / L 2-amino-1,3,4-thiadiazole, and 2 g / L 3,5-diamino-1,2,4-triazole was prepared, and 5-aminotetrazole was not contained in the antioxidant solution. A copper foil substrate (electrolytic copper foil, the thickness of which was about 6 μm) was washed with water, and the copper foil substrate was immersed in the antioxidant solution. The copper foil substrate was treated for 0.5 seconds under electrolytic plating conditions of a current density of 0.8 ASD to form an antioxidant layer on the surface of the copper foil substrate, thereby obtaining an antioxidant copper foil. Thereafter, the antioxidant copper foil was taken out of the antioxidant solution, air-dried, and wound up to complete the production of the antioxidant copper foil.

[0082] As a result of the measurement, the chromium content of the oxidation-resistant copper foil according to Reference Example 2 was 20 μg / m 2 The nitrogen content by XPS analysis was 0.5% by mass, a CN signal was detected by headspace GC / MS analysis, and the color difference ΔE before and after firing at 250° C. for 10 minutes exceeded 10. The oxidation-resistant copper foil of Reference Example 2 was slightly inferior in oxidation resistance and heat resistance to those of Examples 1 and 2. The reason for this was that the density of the oxidation-resistant layer was relatively poor.

[0083] For Comparative Example 1, an aqueous solution containing 0.6 g / L of chromic acid and 2 g / L of 3,5-diamino-1,2,4-triazole was prepared as an antioxidant solution, and the antioxidant solution did not contain 5-aminotetrazole or benzotriazole. A copper foil substrate (electrolytic copper foil having a thickness of about 6 μm) was washed with water and immersed in the antioxidant solution. The copper foil substrate was treated for 0.5 seconds under electrolytic plating conditions with a current density of 0.8 ASD to form an antioxidant layer on the surface of the copper foil substrate, thereby obtaining an antioxidant copper foil. Thereafter, the antioxidant copper foil was taken out of the antioxidant solution, air-dried, and wound up to complete the manufacture of the antioxidant copper foil. As a result of the measurement, the chromium content of the antioxidant copper foil according to Comparative Example 1 was 20 μg / m 2 The nitrogen content by XPS analysis was 0 mass% (undetectable), a CN signal was detected by headspace GC / MS analysis, and the color difference ΔE before and after firing at 250° C. for 10 minutes exceeded 20. The oxidation-resistant copper foil of Comparative Example 1 was far inferior in oxidation resistance and heat resistance to those of Examples 1 and 2.

[0084] For Comparative Example 2, an aqueous solution containing 0.6 g / L of chromic acid and 2 g / L of 2-amino-1,3,4-thiadiazole was prepared as an antioxidant solution, and the antioxidant solution did not contain 5-aminotetrazole or benzotriazole. A copper foil substrate (electrolytic copper foil having a thickness of about 6 μm) was washed with water and immersed in the antioxidant solution. The copper foil substrate was treated for 0.5 seconds under electrolytic plating conditions with a current density of 0.8 ASD to form an antioxidant layer on the surface of the copper foil substrate, thereby obtaining an antioxidant copper foil. Thereafter, the antioxidant copper foil was taken out of the antioxidant solution, air-dried, and wound up to complete the manufacture of the antioxidant copper foil. As a result of the measurement, the chromium content of the antioxidant copper foil according to Comparative Example 2 was 20 μg / m 2 The nitrogen content by XPS analysis was 0 mass% (undetectable), a CN signal was detected by headspace GC / MS analysis, and the color difference ΔE before and after firing at 250° C. for 10 minutes exceeded 20. The oxidation-resistant copper foil of Comparative Example 2 was far inferior in oxidation resistance and heat resistance to those of Examples 1 and 2.

[0085] The above-mentioned methods of analyzing the chromium content by XRF, the nitrogen content by XPS analysis, and the CN signal by headspace GC / MS analysis, and the analysis method of the color difference ΔE have been explained above, so they will not be explained here again.

[0086] [Table 1]

[0087] According to the above experimental results, the color difference ΔE of the antioxidant copper foils produced in Examples 1 and 2 before and after firing at 250°C for 10 minutes was all 8 or less, proving that the antioxidant layer formed from the antioxidant solution simultaneously containing 5-aminotetrazole and benzotriazole (i.e., a nitrogen-containing heterocyclic compound) provides the copper foil with excellent antioxidant properties and heat resistance.

[0088] [Advantageous Effects of the Embodiments] As advantageous effects of the present invention, the surface treatment method for copper foil, the oxidation-resistant copper foil, and the negative electrode of a lithium battery according to the present invention include the following: "The oxidation-resistant copper foil comprises a copper foil base material and an oxidation-resistant layer formed on the copper foil base material. The oxidation-resistant layer contains chromium derived from a chromate compound, and the oxidation-resistant layer contains nitrogen at least partially derived from an aminotetrazole compound and a nitrogen-containing heterocyclic compound" and "The oxidation-resistant copper foil satisfies the following properties (a) to (d): (a) the chromium content of the oxidation-resistant layer measured by an X-ray fluorescence analyzer (XRF) is 5 to 35 μg / m 2 (b) the nitrogen content of the oxidation-resistant layer measured by an X-ray fluorescence analyzer (XRF) is 0.1-10 mass%, (c) the oxidation-resistant copper foil detects CN signals by headspace GC / MS analysis, and (d) the color difference ΔE of the oxidation-resistant copper foil before and after baking at 250°C for 10 minutes is 8 or less" due to the above technical features, the copper foil of the present invention achieves a more remarkable degree of heat resistance than the copper foil of the prior art that uses chromic acid and glucose as the components of the oxidation-resistant layer. Thus, it is particularly suitable for use as a negative electrode material for lithium batteries, and the product can be applied more widely.

[0089] The above disclosure is merely a preferred embodiment of the present invention, and the scope of the claims of the present invention is not limited thereto. Therefore, all equivalent technical modifications made by utilizing the specification and drawings of the present invention are included in the scope of the claims of the present invention. [Explanation of symbols]

[0090] CF, CF'...Antioxidant copper foil 1...Copper foil base material 1a...Antioxidant layer 2. Antioxidant T...Storage tank R...Guide roller E...electrode

Claims

1. Providing a copper foil substrate; Immersing the copper foil substrate in an antioxidant solution containing a chromic acid compound, an aminotetrazole compound such as 5-aminotetrazole, and a nitrogen-containing heterocyclic compound such as benzotriazole; and forming an oxidation-resistant copper foil by immersing the copper foil substrate in the oxidation-resistant liquid for a predetermined time or by electrolysis, thereby forming an oxidation-resistant layer on at least one surface of the copper foil substrate, The oxidation-resistant copper foil satisfies the following properties (a) to (d): (a) The chromium content of the antioxidant layer measured by an X-ray fluorescence analyzer (XRF) is 5 μg / m ２ ~35 μg / m ２ and the chromium in the antioxidant layer is derived from the chromate compound; (b) the nitrogen content of the antioxidant layer measured by an X-ray photoelectron spectroscopy (XPS) is 0.1% by mass to 10% by mass, and at least a part of the nitrogen in the antioxidant layer is derived from the aminotetrazole compound and the nitrogen-containing heterocyclic compound; (c) the antioxidant layer is analyzed by headspace GC / MS to detect a C—N signal; (d) A method for surface treatment of a copper foil, characterized in that the color difference ΔE of the oxidation-resistant copper foil before and after baking at 250° C. for 10 minutes is 8 or less.

2. In the antioxidant solution, the concentration of the chromate compound is 0.1 g / L to 5 g / L; 2. The method for treating a copper foil surface according to claim 1, wherein the chromate compound is at least one selected from the group consisting of chromic acid, dichromic acid, and potassium dichromate.

3. 2. The method for surface treating a copper foil according to claim 1, wherein, in the antioxidant solution, a concentration of the aminotetrazole compound is 0.1 g / L to 10 g / L, a concentration of the nitrogen-containing heterocyclic compound is 0.1 g / L to 10 g / L, and a mass ratio of the aminotetrazole compound to the nitrogen-containing heterocyclic compound (the aminotetrazole compound:the nitrogen-containing heterocyclic compound) is 1:5 to 5:

1.

4. 2. The method for treating a copper foil surface according to claim 1, wherein the antioxidant solution further comprises at least two selected from the group consisting of 1,5-diaminotetrazole, 2-amino-1,3,4-thiadiazole, and 3,5-diamino-1,2,4-triazole.

5. The predetermined time for immersing the copper foil base material in the antioxidant solution or electrolyzing the copper foil base material is 0.1 to 10 seconds, and the current density of the electrolytic plating conditions is 0.1 to 5 ASD (A / dm ２ 2. The method for treating the surface of copper foil according to claim 1 .

6. A copper foil substrate; An oxidation-resistant copper foil comprising an oxidation-resistant layer formed on one surface of the copper foil base material, the oxidation-resistant layer includes chromium derived from a chromate compound, the oxidation-resistant layer includes nitrogen at least partially derived from an aminotetrazole compound, 5-aminotetrazole, and a nitrogen-containing heterocyclic compound, benzotriazole; The oxidation-resistant copper foil satisfies the following characteristics (a) to (d): (a) The chromium content of the antioxidant layer measured by an X-ray fluorescence analyzer (XRF) is 5 μg / m ２ ~35 μg / m ２ and (b) the nitrogen content of the antioxidant layer is 0.1% by mass to 10% by mass as measured by an X-ray photoelectron spectroscopy (XPS); (c) the antioxidant layer is analyzed by headspace GC / MS to detect a C—N signal; (d) An oxidation-resistant copper foil, characterized in that the color difference ΔE of the oxidation-resistant copper foil before and after baking at 250° C. for 10 minutes is 8 or less.

7. The oxidation-resistant copper foil according to claim 6, wherein the thickness of the copper foil base is 1 μm to 10 μm, and the thickness of the oxidation-resistant layer is 1 nm to 100 nm.

8. A negative electrode of a lithium battery, comprising the oxidation-resistant copper foil according to claim 6 or 7.

Images