WO2014017449A1

WO2014017449A1 - Surface-treated copper foil, method for manufacturing same, electrode for lithium ion secondary battery, and lithium ion secondary battery

Info

Publication number: WO2014017449A1
Application number: PCT/JP2013/069832
Authority: WO
Inventors: 隆宏鶴田; 健作篠崎
Original assignee: 古河電気工業株式会社
Priority date: 2012-07-23
Filing date: 2013-07-22
Publication date: 2014-01-30
Also published as: JPWO2014017449A1; KR101579489B1; KR20150035502A; CN104204299B; JP5554455B1; TW201405925A; TWI508359B; CN104204299A

Abstract

Provided are a surface-treated copper foil that has an improved suitability for welding resistance so as to achieve an enhanced productivity, a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery. The surface-treated copper foil is characterized in that: the sum (atomic %) of the carbon element content and nitrogen element content, said element contents being measured in the depth direction of the copper foil by X-ray photoelectron spectroscopy (XPS), attains the maximum value on the outermost surface; at the depth at which the sum (atomic %) of the carbon element content and nitrogen element content is halved compared to the maximum value thereof on the outermost surface, the decreasing rate of the sum (atomic %) of the carbon element content and nitrogen element content in the depth direction of the copper foil is 50%/nm or greater; and the surface resistivity that is defined in JIS-K7194:1994 is 2.5-40 mΩ.

Description

Surface-treated copper foil and method for producing the same, electrode for lithium ion secondary battery and lithium ion secondary battery

The present invention is a surface-treated copper foil excellent in resistance weldability, particularly a copper foil mutually welded, or copper foil to each other, or a copper foil and another metal material welded by resistance welding, a method for producing the same, and The present invention relates to an electrode for a lithium ion secondary battery and a lithium ion secondary battery used.

In the case of electronic parts used in automobiles and the like, with the recent increase in density, the electrical connection portion is required to be more reliable, and in particular, in connection portions between terminals and dissimilar metals such as copper foil, It is required to be more reliably joined.
Also, in recent years, as a negative electrode current collector of a non-aqueous solvent secondary battery such as a lithium ion secondary battery, a strong bonding strength or a highly reliable bonding state is required to connect copper foils or copper foil and tab terminals. It is done.

One of the welding methods that satisfy such requirements is resistance welding.
In this resistance welding method, in the joining of dissimilar metals, a fused part called nugget is formed in the joining part, and stable joining where peeling of the joining part is hard to occur is possible, especially large metal parts such as automobile bodies. Are often used in the bonding of
In the field of lithium ion secondary batteries, not only a strong and reliable bonding state can be obtained, but unlike ultrasonic welding, friction between copper foils for current collectors and tab plates for copper foils-terminals is different. Therefore, by appropriately adjusting the current, pressure, and welding time and selecting the condition that does not generate spatter, generation of copper particulates and mixing in the battery cell can be prevented, and the safety of the lithium ion secondary battery It also contributes to securing.

The ultrasonic weldability of the copper foil is better if the surface is not subjected to anti-corrosion treatment when pretreatment such as heat drying is not performed. However, since the surface of the copper foil is easily oxidized in the air if it is not subjected to antirust treatment, it is not suitable for practical use regardless of the presence or absence of pretreatment such as heat drying. In order to prevent oxidation of the copper foil surface, chromate treatment is carried out in an acidic bath (pH 1 to 2) to form a chromium hydrate oxide film called a chromate film, and immersion in a solution containing a triazole compound and tetrazole compound Methods are known for forming organic rustproof coatings.
The copper foil coated with the rustproof film in this way is difficult to discolor in the atmosphere, but on the other hand, if the thickness of the rustproof film is thick, the surface is difficult to be cleaned even when ultrasonic vibration is applied, and pure copper Since it is hard to be exposed to the surface, atomic diffusion is unlikely to occur and it is considered that the bonding strength is weakened.

With regard to copper foils for which such improvement in ultrasonic weldability is a subject, copper foils having thin chromium hydrate oxides formed by the present inventors on copper foils (see Patent Document 1), triazole compounds and the like The copper foil (refer patent document 2) which performed the rustproofing process by the solution with which the silane coupling agent was mixed is proposed.

JP, 2009-68042, A JP 2011-23303 A

Thus, with regard to the weldability of copper foils used as current collectors for lithium ion batteries, many studies have been conducted to improve the characteristics for ultrasonic welding, but copper foils that exhibit good resistance weldability It is not yet known about the examination of and its method. For this reason, in the present invention, the development of a copper foil excellent in resistance weldability, which is expected to increase the introduction of a lithium ion battery for automobiles into a current collector, is a subject in the present invention.

As a result of intensive studies to solve this problem, the present inventors have found a clue to the prevention of corrosion by the organic component centering on triazole compounds and the control of the surface resistance. Therefore, as a result of examining the antirust treatment conditions, the total content of nitrogen and carbon contained in the antirust film is obtained by treating with an antirust solution in which a triazole compound and a predetermined ratio of carboxylic anhydride are mixed. Based on JIS K · 7194: 1994, it forms the rustproof film which is the highest on the outermost surface and is characterized by changes in the total content of nitrogen and carbon in the depth direction, and controls the concentration of triazole compounds. By making the measured surface resistance value into a fixed range, it discovered that an electrolytic copper foil with a good resistance welding characteristic was obtained.

The surface-treated copper foil of the present invention is the sum of the elemental content (atomic%) of carbon and nitrogen in the depth direction of the copper foil measured by XPS (X-ray photoelectron spectroscopy) on at least one surface of the copper foil. Is the largest at the outermost surface of the copper foil, and at a depth at which the sum of the elemental contents (atomic%) of carbon and nitrogen is half the value relative to the outermost surface, carbon in the depth direction of the copper foil A surface-treated film is formed which has a total reduction of the element content (atomic%) of nitrogen of 50% / nm or more and a surface resistance of 2.5 to 40 mΩ as defined in JIS-K7194: 1994. It is characterized by

Further, the method for producing a surface-treated copper foil according to the present invention contains 50 to 700 ppm of a triazole compound such that the concentration ratio of the carboxylic anhydride to the total concentration of the triazole compound is 0.05 or more. By applying the anticorrosion treatment solution prepared in the above to copper foil, at least one surface of the copper foil, containing carbon and nitrogen elements in the depth direction of copper foil measured by XPS (X-ray photoelectron spectroscopy) The copper foil at such a depth that the sum of the percentage (atomic%) is the largest on the outermost surface of the copper foil, and the sum of the elemental contents (atomic%) of carbon and nitrogen is half of the outermost surface. The total reduction of the elemental content (atomic%) of carbon and nitrogen in the direction of depth is 50% / nm or more, and the surface resistance specified in JIS-K7194: 1994 is 2.5 to 40 mΩ Surface treatment And forming a film.

ADVANTAGE OF THE INVENTION By this invention, the surface-treated copper foil excellent in the weldability of copper foils by resistance welding, or copper foil and other metals can be provided.
Moreover, the surface treatment method of the copper foil excellent in resistance weldability of the present invention easily produces a surface-treated copper foil excellent in weldability between copper foils by resistance welding or between copper foil and another metal. Can.

FIG. 1 is a graph showing the sum of the elemental content (atomic%) of carbon and nitrogen in the depth direction of a copper foil measured by XPS (X-ray photoelectron spectroscopy) according to an example. FIG. 2 is an explanatory view schematically showing resistance welding.

In the surface-treated copper foil of the present invention, at least one surface of the copper foil (in the present invention, when the electrolytic copper foil and the rolled copper foil need not be individually expressed, they are collectively referred to as copper foil) The elemental content (atomic%) of carbon and nitrogen in the depth direction of the copper foil is the largest at the outermost surface by XPS (X-ray photoelectron spectroscopy), and the total elemental content (atomic%) of carbon and nitrogen is the outermost surface The reduction rate of the total of the elemental content (atomic%) of carbon and nitrogen in the depth direction of the copper foil is 50% / nm or more, and the resistance value on the copper foil surface is 2 An organic anticorrosion coating comprising a triazole compound or a complex compound thereof having a mixture of 5 to 40 mΩ or a mixture of these two compounds (herein, an organic anticorrosion coating comprising a triazole compound or a complex compound thereof or a mixture of both of them; Triazole compound, and / or to as organic anti-rust compounds "consisting of the complex compounds) are formed.
The resistance value on the copper foil surface is measured in accordance with JIS-K7194: 1994.

In this embodiment, X-ray photoelectron spectroscopy (XPS) and argon sputtering are combined to perform elemental analysis in the depth direction, thereby detecting and quantifying carbon and nitrogen of a rust preventive film formed on the surface of a copper foil. Do.

The anticorrosive film is a complex of copper and a triazole compound and a mixture of a pure triazole compound, and the volume resistivity of the copper foil body is on the order of 10 ⁵ to 10 ⁶ times. In general, when the insulating film on the metal surface is attached, the resistance value becomes higher as the thickness of the insulating film becomes larger. For this reason, a measured value of surface resistance of one copper foil based on JIS-K7194: 1994 is adopted as an index of the thickness of the antirust film.

As a method to confirm the carbon and nitrogen content of the antirust film, measure the elemental content (atomic%) of carbon and nitrogen in the depth direction of the copper foil by XPS (X-ray photoelectron spectroscopy), The reduction rate [% / nm] of the sum of the elemental content of carbon and nitrogen at the depth position where the sum of the elemental content of nitrogen is half of the outermost surface is used.
The thickness of the anticorrosive film and the adhesion amount of the triazole compound, that is, the total amount of carbon and nitrogen derived from the triazole compound are determined by the treatment concentration and treatment temperature of the triazole compound used for the antirust treatment. In addition, the sum of carbon and nitrogen contents takes a maximum value near the outermost surface of the film, and decreases to draw an asymptotic line as it proceeds in the depth direction, and finally becomes 0%.
That is, if the reduction in the element content [% / nm] at the depth position where the sum of the element contents of carbon and nitrogen is half of the outermost surface is large, most of the carbon and nitrogen derived from the triazole compound It can be considered that it exists on the outermost surface of the antirust film, and the anticorrosive component is densely present on the outermost surface of the antirust film. On the other hand, if this value is small, not only the difference between the outermost surface and the central part of the film is small, but the abundance of carbon and nitrogen near the outermost surface is also small. It can be considered that the anticorrosion component is not present in a dense state.
From the above points, the reduction rate [% / nm] of the total of the elemental contents of carbon and nitrogen at the depth position where the sum of the elemental contents of carbon and nitrogen is the half value of the outermost surface It becomes a measure of whether carbon and nitrogen derived from the triazole compound near the outermost surface are abundantly and densely present.
If this value is less than 50% / nm, carbon and nitrogen derived from the triazole compound near the surface of the rustproof coating are insufficient, and the air and moisture heated in the heating step of the welding pretreatment are in contact with the copper foil As a result, the oxide film thickness tends to increase without satisfying the above, and there is a possibility that a satisfactory weldability can not be obtained.

The resistance value on the copper foil surface of this embodiment is 0.25 to 40 mΩ. If it is smaller than 0.25 mΩ, the ability to protect the copper foil surface from air or moisture at room temperature is poor, and surface oxidation or discoloration tends to occur during storage and transportation. In addition, in a high temperature environment of 100 to 160 ° C such as the drying step in the production of the negative electrode current collector of the non-aqueous solvent secondary battery, the strength of the antirust film is insufficient to prevent oxidation, and the oxide film thickness becomes too thick. This is because the weldability is extremely reduced due to an excessive increase. In addition, when the resistance value on the copper foil surface is larger than 40 mΩ, the thickness of the anticorrosion film itself is excessive, so the thermal energy at the time of welding is consumed excessively for the removal of the anticorrosion film, which is sufficient. It is because there is a possibility that a strong welding state can not be obtained.
The resistance value on the copper foil surface is more preferable in the range of 0.25 to 20 mΩ than in the range of 20 to 40 mΩ because the anticorrosive film is easily removed during welding.

In the method for producing a surface-treated copper foil of the present embodiment, for example, the compound contains 50 to 700 ppm of a triazole compound, and the concentration ratio of the carboxylic anhydride to the total concentration of the triazole compound is 0.05 or more. The anticorrosive treatment solution prepared as described above is applied to the copper foil to form an anticorrosive coating on at least one surface of the copper foil.

Examples of the triazole compounds include benzotriazole, tolyltriazole, carboxybenzotriazole, chlorobenzotriazole, ethylbenzotriazole, naphthotriazole and the like, and complex compounds thereof. Further, examples of the carboxylic acid anhydride include acetic anhydride, succinic anhydride, maleic anhydride, propionic anhydride, and phthalic anhydride.
The concentration of the triazole compound in the antirust treatment solution is desirably 50 to 700 ppm. If it is less than 50 ppm, the surface resistance value is less than 2.5 mΩ, and oxidation or discoloration of the surface is likely to occur during heating during storage, transport and drying steps. On the other hand, if it exceeds 700 ppm, the surface resistance value exceeds 40 mΩ, the thickness of the anticorrosion coating itself becomes excessive, and the thermal energy at the time of welding is excessively consumed for removing the anticorrosion coating, and sufficient There is a possibility that a strong welding condition can not be obtained.
Further, the concentration ratio of carboxylic anhydrides to triazole compounds is desirably 0.05 or more. When the concentration ratio of carboxylic anhydrides to triazole compounds is lower than 0.05, the sum of the elemental contents of carbon and nitrogen at a depth position at which the sum of the elemental contents of carbon and nitrogen is a half value with respect to the outermost surface Less than 50% / nm. As a result, the difference between the contents of carbon and nitrogen between the outermost surface of the anticorrosive film and the inside becomes smaller, and the anticorrosive component is insufficient near the outermost surface of the anticorrosive film, and the oxide film is generated in the heating process of the welding pretreatment. The thickness tends to increase, and satisfactory weldability may not be obtained.
Further, in order to secure the stability of the triazole component, it is preferable to set the temperature of the solution to 35 to 55 ° C. and the pH to 6.5 to 8.0. In addition, the immersion time may be usually about 0.5 to 30 seconds.
However, the conditions of the manufacturing method of the surface-treated copper foil of this embodiment are not limited above.

In the method of producing an electrolytic copper foil, for example, immediately after making the foil, it is dipped in an organic rust inhibitor solution to form a rust coating.
If corrosion prevention can not be carried out immediately after foil production, it is effective to use an acid pickling method in which it is immersed in dilute sulfuric acid with H ₂ SO ₄ = 5 to 200 g / l and temperature = 10 ° C. to 80 ° C. as pretreatment. In the case of degreasing, the current density is 1 to 10 A / dm ² in an aqueous solution of NaOH = 5 to 200 g / l and the temperature is 10 ° C. to 80 ° C., and the cathode or / and anode is 0.1 to 5 minutes. It is effective to carry out electrolytic degreasing.

It is more preferable that the heat energy at the time of welding be easily transmitted between the foils if the 10-point average surface roughness Rz of the copper foil is 2.5 μm or less.

[Fabrication of copper foil (common to Examples 1 to 9 and Comparative Examples 1 to 10)]
An electrolytic solution of the composition shown below was prepared, and a noble metal oxide-coated titanium electrode was used for the anode, and a titanium rotating drum for the cathode, and an electrolytic copper foil of 10 μm thickness at a current density of 50 to 100 A / dm ^2. Manufactured.
Copper: 70 to 130 g / l
Sulfuric acid: 80 to 140 g / l
Additive: Sodium 3-mercapto 1-propanesulfonate = 1 to 10 ppm
Hydroxyethyl cellulose = 1 to 100 ppm
Low molecular weight glue (molecular weight 3,000) = 1 to 50 ppm
Chloride ion concentration = 10 to 50 ppm
Temperature: 50 to 60 ° C

[Antirust film formation]
[Examples 1 to 9]
Immediately after the electrolytically produced foil, the triazole compound is benzotriazole (1,2,3-benzotriazole: BTA), tolyltriazole (5-methyl-1H-benzotriazole: TTA), ethylbenzotriazole 5-ethyl-1H-benzotriazole: 1 to 3 selected from the following EBTA to give a total concentration of 50 to 700 ppm, and carboxylic acid anhydrides selected from succinic anhydride, maleic anhydride and propionic anhydride The steel sheet was immersed in a rustproofing solution prepared so that the concentration ratio to the total concentration of the triazole compound was in the range of 0.05 or more to apply a rustproof film to the surface of the copper foil. The liquid temperature was 35 to 55 ° C., and the pH was 6.5 to 8.0.

[Comparative Examples 1 to 4]
The electrolytic copper foil was immediately selected, and one to three triazole compounds were selected from BTA, TTA, EBTA, and the total concentration was less than 50 ppm, and carboxylic anhydrides were succinic anhydride, maleic anhydride, propion anhydride It was immersed in the antirust processing solution prepared so that it might become an arbitrary density | concentration from 1 type of acid, and the antirust film was given to the copper foil surface. The liquid temperature was 35 to 55 ° C., and the pH was 6.5 to 8.0.
[Comparative Examples 5 to 6]
The electrolytic copper foil is immediately selected, and one to three triazole compounds are selected from BTA, TTA, and EBTA, and the total concentration is 50 to 700 ppm, and carboxylic anhydrides are succinic anhydride, maleic anhydride, anhydride One kind of propionic acid was selected, and it was immersed in an antirust treatment solution prepared so that the concentration ratio to the total concentration of the triazole compound was in the range of less than 0.05, to give an antirust film on the copper foil surface. The liquid temperature was 35 to 55 ° C., and the pH was 6.5 to 8.0.
[Comparative Examples 7 to 9]
The electrolytic copper foil was immediately selected, and one to three triazole compounds were selected from BTA, TTA, and EBTA, and the total concentration exceeded 700 ppm, and carboxylic anhydrides were succinic anhydride, maleic anhydride, propion anhydride It was immersed in the antirust processing solution prepared so that it might become an arbitrary density | concentration from 1 type of acid, and the antirust film was given to the copper foil surface. The liquid temperature was 35 to 55 ° C., and the pH was 6.5 to 8.0.
Comparative Example 10
With respect to the electrolytically produced copper foil, the anticorrosion agent was not applied, and it was left as it is.

[Determination of nitrogen and carbon in the depth direction]
The element content (atomic%) in the depth direction of nitrogen and carbon was measured under the following conditions using an XPS measurement apparatus 5600 MC manufactured by ULVAC-PHI, Inc.
Ultimate vacuum degree 1 × 10 ^-10 Torr (1 × 10 ^-8 Torr when Ar gas introduced),
X-ray: X-ray type monochromatized Al-k α ray, output 300 W, detection area 800 μmφ,
Ion beam: ion species Ar +, acceleration voltage 3 kV, sweep area 3 × 3 mm ² ,
Sample incident angle 45 ° (angle between sample and detector),
Sputtering rate 2.3 nm / min (SiO ₂ equivalent)
A curve is created by adding the contents of nitrogen and carbon, with the element content (atomic%) on the vertical axis and the depth direction on the horizontal axis, and a tangent at the depth position that is half the content of the outermost surface The concentration reduction degree [% / nm] was calculated from the slope of this tangent line.

FIG. 1 is a graph showing the sum of the elemental content (atomic%) of carbon and nitrogen in the depth direction of a copper foil measured by XPS (X-ray photoelectron spectroscopy) according to an example.
The solid line a in FIG. 1 shows an example of the total element content (atomic%) of carbon and nitrogen in the depth direction in Examples 1 to 12.
The broken line b in FIG. 1 shows an example of the total element content (atomic%) of carbon and nitrogen in the depth direction in Comparative Examples 1-9.
In both the solid line a and the broken line b, the sum of the elemental content of carbon and nitrogen in the depth direction of the copper foil is the largest at the outermost surface. Here, the reduction rate of the total of the carbon and nitrogen elemental contents in the depth direction of the copper foil at the depth at which the sum of the carbon and nitrogen elemental contents is half with respect to the outermost surface is the solid line a. The slope of the tangent line Sa of the graph indicated by the solid line a at the half value depth is indicated by a broken line b, and the inclination of the tangent line Sb of the graph indicated by the broken line b at the half value value is indicated.
The area of the region sandwiched by the solid line a and the x axis according to the example corresponds to the elemental content of carbon and nitrogen in the rustproof coating of the example. Similarly, the area of the region sandwiched by the broken line b and the x axis according to the comparative example corresponds to the elemental content of carbon and nitrogen in the rustproof coating of the comparative example. In the case of the same rust prevention film thickness, the element content of carbon and nitrogen is equivalent in the example and the comparative example, and the area between the solid line a and the x axis and the area between the dashed line b and x axis The area of is equal.

[Measurement of surface resistance]
The surface resistance of the copper foil was measured by a four-terminal method based on JIS-K7194: 1994, using a resistance meter RM3544 manufactured by Nitoki Denki.

[Resistance welding test]
As pretreatment, the copper foil was dried under reduced pressure at a temperature of 140 ° C. for 1 hour at a pressure of 100 Pa in a vacuum dryer (ADP 200 manufactured by Yamato Scientific Co., Ltd.).
FIG. 2 is an explanatory view schematically showing resistance welding. A tab copper plate 2 having a thickness of 200 μm is disposed on the lower electrode (copper stage-like electrode) 1, and 20 sample copper foils 3 are disposed in a stacked manner on the tab copper plate 2. The upper electrode (copper alumina alloy rod-shaped electrode, φ 3.2 mm) 4 is pressed to the welded portion of the sample copper foil 3, current I flows between the upper electrode 4 and the lower electrode 1, and resistance welding is performed.
As a welder, using NRW-200A made by Nippon Avionics, applying a pulse current of peak value 2400A, energizing time 4.9ms, and pressure of 33N, as shown in FIG. 2, 20 copper foils of 10 μm thickness 200 μm thick Welded to the tab copper plate.
After welding under the above conditions, the welded portion of the outermost copper foil in contact with the upper electrode is observed with an optical microscope at a magnification of 20 times to confirm that no cracks have occurred, and the welded copper foil Were peeled off one by one in order from the outermost copper foil. When 15 or more copper foils were torn at welds ○, when 10 to 14 copper foils were torn at welds, ○, no more than 9 copper foils torn at welds, or If not, it was x.

In Examples 1 to 12, the surface resistance and the content ratio of nitrogen to carbon to copper were all appropriate, and the welding condition was good.

In Comparative Examples 1 to 4, the surface resistance is too small. For this reason, the thickness of the antirust film is too small, and the copper foil surface is excessively oxidized in the drying heating step of the pretreatment for welding, and the welding energy is consumed excessively for removing the oxide film, which is satisfactory. The welding condition could not be obtained.

In Comparative Examples 5 to 6, at the depth position where the sum of the elemental contents of carbon and nitrogen is a half value with respect to the outermost face, the reduction degree of the total of the elemental contents of carbon and nitrogen near the outermost face in the depth direction Is less than 50% / nm, and there is a lack of antirust components near the outermost surface. For this reason, although the thickness of the anticorrosive film is in a sufficient range, the anticorrosive film is easily destroyed from the outermost surface during heating, and the oxidation resistance is poor. For this reason, the copper foil surface was excessively oxidized in the drying and heating step of the pretreatment for welding, and excessive welding energy was consumed for removing the oxide film, and a satisfactory welding state was not obtained.

In Comparative Examples 7 to 9, the surface resistance is excessive. For this reason, since the thickness of the anticorrosion coating becomes excessive, cleaning of the surface by the current at the time of welding is insufficient, and a satisfactory welding state can not be obtained.

In Comparative Example 10, the rust preventive film is not formed on the copper foil surface, and an oxide film is easily generated by heating. For this reason, the copper foil surface was excessively oxidized in the drying and heating step of the pretreatment for welding, and excessive welding energy was consumed for removing the oxide film, and a satisfactory welding state was not obtained.

Examples 1 to 12 are excellent in resistance weldability to facilitate assembly of electronic parts and the like, and are excellent even if this copper foil is used as a current collector for non-aqueous secondary batteries such as Li batteries. Brought an effect.

As described above, the present invention can provide a surface-treated copper foil excellent in weldability between copper foils by resistance welding or between the copper foil and another metal.
Moreover, the surface treatment method of copper foil excellent in resistance welding according to the present invention can easily produce a surface-treated copper foil excellent in weldability between copper foils by resistance welding or between copper foil and another metal. it can.
The surface-treated copper foil of the present invention can be preferably applied to an electrode for a lithium ion secondary battery using the negative electrode current collector.
Furthermore, it can be preferably applied to a lithium ion secondary battery using the lithium ion secondary battery electrode as a negative electrode.

Claims

In at least one surface of the copper foil, the sum of the elemental content (atomic%) of carbon and nitrogen in the depth direction of the copper foil measured by XPS (X-ray photoelectron spectroscopy) is the most on the outermost surface of the copper foil. Elemental content (atomic%) of carbon and nitrogen with respect to the depth direction of the copper foil at a depth where the sum of the elemental content (atomic%) of carbon and nitrogen is a half value relative to the outermost surface A surface-treated film having a total reduction degree of at least 50% / nm and a surface resistance of 2.5 to 40 mΩ as defined in JIS-K 7194: 1994, Treated copper foil.
In at least one surface of the copper foil, the sum of the elemental content (atomic%) of carbon and nitrogen in the depth direction of the copper foil measured by XPS (X-ray photoelectron spectroscopy) is the most on the outermost surface of the copper foil. Elemental content (atomic%) of carbon and nitrogen with respect to the depth direction of the copper foil at a depth where the sum of the elemental content (atomic%) of carbon and nitrogen is a half value relative to the outermost surface A surface-treated film having a total reduction degree of at least 50% / nm and a surface resistance defined in JIS-K 7194: 1994 of 2.5 to 20 mΩ is formed. Treated copper foil.
The surface-treated copper foil according to claim 1 or 2, which is used as a negative electrode current collector of a lithium ion secondary battery.
A step of applying an antirust treatment solution containing 50 to 700 ppm of a triazole compound and prepared so that the concentration ratio of the carboxylic acid anhydride to the total concentration of the triazole compound is 0.05 or more on a copper foil A method for producing a surface-treated copper foil, comprising the step of producing a surface-treated copper foil according to any one of claims 1 to 3.
An electrode for a lithium ion secondary battery, wherein the surface-treated copper foil according to any one of claims 1 to 3 is used as a negative electrode current collector.
A lithium ion secondary battery using the lithium ion secondary battery electrode according to claim 4 as a negative electrode.