JP2017014608A - Electrolytic copper foil, lithium ion secondary battery negative electrode and lithium ion secondary battery, printed wiring board, and electromagnetic wave-shielding material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic copper foil that is excellent in handling property during manufacturing of secondary battery, and that does not exhibit decrease in tensile strength even when heated at 150°C for one hour; and to provide, by using said electrolytic copper foil as a current collector, a lithium ion secondary battery negative electrode with increased cycle life, and a lithium ion secondary battery incorporating said electrode.SOLUTION: Provided is an electrolytic copper foil having, on a matte surface, a glossiness Gs (60°) of 20 or more and 150 or less and a coefficient of dynamic friction of 0.11 or more and 0.39 or less, and having a tensile strength after heated at 150°C for one hour of 350 MPa or more; and a lithium ion secondary battery using said electrolytic copper foil as a current collector.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electrolytic copper foil, a negative electrode for a lithium (Li) ion secondary battery and a lithium ion secondary battery using the same.
Moreover, this invention relates to the printed wiring board and electromagnetic wave shielding material which used this invention electrolytic copper foil.

A lithium ion secondary battery includes, for example, a positive electrode, a negative electrode having a negative electrode active material layer formed on the surface of a negative electrode current collector (hereinafter abbreviated as a current collector), and a non-aqueous electrolyte. It is used in mobile phones and notebook computers.
As the negative electrode of the lithium ion secondary battery, a so-called “untreated copper foil” which has been manufactured by electrolysis and not subjected to a surface treatment or the like, is subjected to a rust prevention treatment. It is formed by applying carbon particles or the like as a negative electrode active material layer on the surface of the electric body, drying, and pressing.
In order for the lithium ion secondary battery to obtain sufficient battery characteristics, the distance between the active material particles and the distance between the active material and the current collector are reduced, and the shape of the current collector is deformed along the shape of the active material surface. This is very important. When the current collector is deformed along the shape of the active material surface, the contact between the active material and the current collector is further improved, the electric conductivity is further increased, and desirable battery characteristics can be obtained. When the current collector does not deform along the shape of the active material surface, the contact portion between the active material and the current collector is reduced, the electric conductivity is reduced, and desirable battery characteristics cannot be obtained.

  Moreover, when the unevenness | corrugation of the collector surface is large, there are few contact points of an active material and a collector, and contact resistance becomes high. Such an electrode having a large contact resistance, when repeated charging and discharging, due to stress due to expansion and contraction accompanying charging and discharging of the active material, dissolution of the binder as an adhesive in the electrolytic solution, and the like, As the distance increases gradually, the electrical conductivity of some active materials becomes an electrical conductivity that cannot be used for charging and discharging, resulting in a decrease in battery capacity. Therefore, a copper foil having a tensile strength equal to or higher than a predetermined value and smoother on both sides is preferably used for the negative electrode current collector (Patent Documents 1, 2, and 3).

  However, in recent years, from the viewpoint of productivity, it has been demanded to increase the conveyance speed in the battery manufacturing process. When an electrolytic copper foil having smoother surfaces is used as a negative electrode current collector of a lithium ion secondary battery, smooth copper In the active material coating line, the copper foil easily slips and slips on the transport roll, and the slip may cause wrinkles in the copper foil (current collector) or cause problems in the active material coating process. There is.

Further, in order to reduce the size and weight of the lithium ion secondary battery, the electrolytic copper foil as a current collector is required to be thin. When thinning the copper foil, it is necessary to be able to withstand the stress caused by the expansion and contraction of the active material during charging and discharging. If the current collector cannot withstand the expansion and contraction of the active material, the cycle characteristics of the battery Has the adverse effect of lowering. For this reason, increasing the strength of the copper foil is an important issue. When a conventional carbon-based negative electrode active material layer is formed on a current collector, a paste made of carbon as a negative electrode active material, polyvinylidene fluoride resin as a binder, and N-methylpyrrolidone as a solvent is prepared. Apply and dry on both sides of copper foil (current collector). In this case, since drying is performed at a temperature of about 150 ° C., it is desirable to evaluate the strength of the foil that can withstand the expansion and contraction of the active material during charging and discharging by the strength after the heat treatment at 150 ° C.
As such a countermeasure, it is necessary to set the tensile strength of the current collector to a predetermined value or more.

Also, recently, in printed wiring boards such as rigid printed wiring boards and flexible printed wiring boards, printed wiring boards that have higher adhesion strength between the copper foil and the film and have excellent high frequency characteristics required for circuit boards have been developed. It is requested.
In addition, there is a demand for copper foil that is thin and strong, and that is less likely to cause foil breakage, wrinkles, etc., particularly in the manufacturing process of flexible printed wiring boards.
In addition, a copper foil that maintains high strength is required even after a thermal history when manufacturing a printed wiring board.

Japanese Patent No. 3742144 Japanese Patent No. 5255229 JP2014-224321A

The present invention provides an electrolytic copper foil that is smooth on both sides, excellent in tensile strength, and does not decrease in tensile strength even when heated at 150 ° C. for 1 hour, and a lithium ion secondary battery using the electrolytic copper foil as a current collector An object is to provide a negative electrode and a lithium ion secondary battery.
The present invention is also required in printed wiring boards such as rigid printed wiring boards and flexible printed wiring boards, in addition to higher adhesion strength between copper foil and film, high frequency characteristics, strength in thin foil, An object of the present invention is to provide a copper foil that is less prone to foil breakage, wrinkles and the like in the manufacturing process of a flexible printed wiring board.
Another object of the present invention is to provide a copper foil that maintains high strength even after undergoing a thermal history when producing a printed wiring board.

The electrolytic copper foil of the present invention has a glossiness Gs (60 °) of 20 or more and 150 or less, a dynamic friction coefficient of 0.11 or more and 0.39 or less, and a tensile strength after heating for 1 hour at 150 ° C. Is 350 MPa or more and 900 MPa or less.
The glossiness Gs (60 °) indicates the glossiness measured at a light projecting / receiving angle of 60 °.

  The electrolytic copper foil of the present invention preferably has a tensile strength of 400 MPa or more after heat treatment at 150 ° C. for 1 hour.

  The negative electrode for a lithium ion secondary battery of the present invention uses the electrolytic copper foil of the present invention as a negative electrode current collector.

  Moreover, the lithium ion secondary battery of this invention is a secondary battery incorporating the negative electrode which made the said this invention copper foil the negative electrode electrical power collector.

  Moreover, the printed wiring board of this invention uses the said electrolytic copper foil as a conductor.

  Furthermore, the electromagnetic shielding material of the present invention uses the electrolytic copper foil as a shielding material.

  According to the present invention, the glossiness Gs (60 °) is 20 or more and 150 or less and the dynamic friction coefficient is 0.11 or more and 0.39 or less on the mat surface, and the copper foil is heated at 150 ° C. for 1 hour. An electrolytic copper foil characterized by a tensile strength of 350 MPa or more and 900 MPa or less can be provided.

Further, according to the present invention, by using the electrolytic copper foil as a negative electrode current collector, the contact between the active material and the current collector is improved, and the secondary battery having a high electric conductivity and a good cycle life is provided. can do.
Furthermore, the glossiness Gs (60 °) of the matte surface of the electrolytic copper foil constituting the current collector is 150 or less, so that fine irregularities on the surface of the current collector can be used as an anchor effect when closely contacting the active material particles. It is possible to provide a secondary battery having a good cycle life by suppressing the active material from dropping from the current collector during the expansion and contraction of the active material during the charge / discharge cycle.
In addition, the electrolytic copper foil constituting the current collector has a tensile strength of 350 MPa or more after heating at 150 ° C. for 1 hour, so that it can withstand the stress due to the volume expansion and contraction of the active material during charging and discharging, and is good A secondary battery having a sufficient cycle life can be provided.

  Furthermore, by attaching the electrolytic copper foil to the insulating film, the fine unevenness present on the surface of the copper foil has a higher adhesion strength between the copper foil and the insulating film, for example, when applying a high frequency signal It is possible to provide a printed wiring board (rigid printed wiring board, flexible printed wiring board, etc.) having excellent high frequency characteristics required for a circuit board, such as preventing an increase in resistance value due to the skin effect.

  In addition, the electrolytic copper foil of the present invention is strong even when it is a thin foil, and it can be preferably used, particularly in the process of manufacturing a flexible printed wiring board, in which foil breakage, wrinkles and the like are unlikely to occur. Moreover, high intensity | strength can be maintained even if it passes through the thermal history concerning the manufacture of a printed wiring board because the tensile strength after 1 hour heating at 150 degreeC of copper foil is 350 Mpa or more.

  The electrolytic copper foil of the present invention has low contact resistance and excellent high frequency characteristics, and has an excellent effect as an electromagnetic shielding material.

  Moreover, in any of the above-mentioned applications, the glossiness Gs (60 °) on the mat surface of the electrolytic copper foil is 150 or less, and the dynamic friction coefficient is 0.11 or more and 0.39 or less. Becomes anti-slip on the transport roll in the electrolysis apparatus, and the foil is prevented from slipping on the transport roll, so that the handling property is good.

It is a figure which shows the relationship between glossiness Gs (60 degrees) and a dynamic friction coefficient.

[Configuration of electrolytic copper foil]
One embodiment of the present invention will be described with respect to an electrolytic copper foil constituting a current collector for a lithium ion secondary battery. However, the electrolytic copper foil of the present invention is not used only for a current collector for a lithium ion secondary battery, and is appropriately used for other purposes as long as the gist of the printed wiring board, the electromagnetic conductor, etc. does not change its gist. Can be used.

  The electrolytic copper foil for the negative electrode current collector of the lithium ion secondary battery of this embodiment has a tensile strength of 350 MPa or more, particularly preferably 400 MPa or more after heat treatment at 150 ° C. for 1 hour. A secondary battery having a good cycle life can be provided, which can withstand the stress caused by the volume expansion and contraction of the substance.

For example, the electrolytic copper foil for a lithium ion secondary battery current collector of the present embodiment is provided with a rust-proofing layer on at least the surface on the side where the active material layer is provided on the electrolytic copper foil.
The antirust treatment layer is, for example, a chromate treatment layer, or a nickel or Ni alloy plating layer, a Co or Co alloy plating layer, a Zn or Zn alloy plating layer, a Sn or Sn alloy plating layer, or a chromate treatment on the above various plating layers. It is an inorganic rust preventive treatment such as one provided with a layer, or an organic rust preventive treatment layer such as benzotriazole.
Furthermore, a silane coupling agent treatment layer or the like may be formed.
The inorganic rust-proofing treatment, organic rust-proofing treatment, and silane coupling agent treatment serve to increase the adhesion strength between the negative electrode current collector and the active material and prevent the battery charge / discharge cycle efficiency from being lowered.

  Further, for example, the electrolytic copper foil for a lithium ion secondary battery current collector of the present embodiment is subjected to a roughening treatment on the surface of the electrolytic copper foil in which an active material layer is provided on the electrolytic copper foil, and the roughening treatment is performed. A rust preventive treatment layer is provided on the surface, and a silane coupling agent treatment layer is provided as necessary.

The electrolytic copper foil of this embodiment has a glossiness Gs (60 °) of 20 to 150 and a dynamic friction coefficient of 0.11 to 0.39 on the mat surface.
Gs (60 °) indicates the glossiness measured at a light projection / reception angle of 60 °.
The surface roughness Rz on the mat surface is more preferably 1.0 μm or more and 2.0 μm or less.

The surface roughness Rz on the matte surface of the electrolytic copper foil is set to 2.0 μm or less. If the surface roughness is 2.0 μm or more, the surface of the electrolytic copper foil (current collector) has large irregularities, and the contact point between the active material and the current collector And the electrode has a high contact resistance. Therefore, when charging / discharging is repeated, the distance between the negative electrode current collector and the active material gradually increases due to stress due to expansion / contraction associated with charging / discharging of the active material, dissolution of the binder as an adhesive in the electrolytic solution, This is because the electric conductivity of some active materials becomes an electric conductivity that cannot be used for charging and discharging, and the capacity of the secondary battery may decrease, which is not preferable.
On the other hand, the reason why the surface roughness Rz is 1.0 μm is to provide adhesion and an anchor effect.

Moreover, the electrolytic copper foil of this embodiment makes glossiness Gs (60 degrees) in a mat | matte surface 20 or more and 150 or less, and makes a dynamic friction coefficient 0.11 or more and 0.39 or less. When the surface roughness Rz of the copper foil is 2.0 μm or less and the glossiness Gs (60 °) is 20 or more, the contact between the active material and the current collector is improved, the electric conductivity is high, and the cycle is good. Life expectancy is obtained.
Moreover, the glossiness Gs (60 °) on the mat surface of the copper foil is 150 or less and the dynamic friction coefficient is 0.11 or more and 0.39 or less, so that the surface of the copper foil is fine in the active material coating line in the battery manufacturing process. The unevenness becomes slippery on the transport roll, the copper foil is prevented from slipping on the transport roll, wrinkles are not generated on the copper foil in the battery production line, and the handling property is improved. The fine irregularities also function as an anchor effect between the active material and the current collector, and are effective in improving the adhesion of the active material.
That is, the handling property is good when the glossiness Gs (60 °) on the mat surface is 150 or less and the dynamic friction coefficient is 0.11 or more and 0.39 or less, more preferably 0.15 or more and 0.35 or less. Is good when the glossiness Gs (60 °) is 20 or more and the tensile strength (before and after heating) is 350 MPa or more.
As for the shiny surface, it was possible to control the glossiness and the dynamic friction coefficient relatively easily in the past by controlling the surface shape of the electrolysis drum. The electrolytic copper foil having a predetermined glossiness and dynamic friction coefficient on both surfaces is realized by paying attention to the glossiness and dynamic friction coefficient on the mat surface, which is difficult to achieve.

[Method for producing electrolytic copper foil]
The electrolytic copper foil for the negative electrode current collector of the lithium ion secondary battery according to the present embodiment includes, for example, an insoluble anode made of titanium coated with a white metal element or an oxide element thereof using a sulfuric acid-copper sulfate aqueous solution as an electrolyte and the anode Copper is deposited on the surface of the cathode drum by supplying a direct current between both electrodes while supplying the electrolyte between the cathode cathode and a titanium cathode drum provided opposite to the cathode drum and rotating the cathode drum at a constant speed. The deposited copper is peeled off from the surface of the cathode drum and is continuously wound up.
A maximum tensile strength of 900 MPa is sufficient.

The electrolytic copper foil for a lithium ion secondary battery negative electrode current collector of the present embodiment can be produced, for example, by performing an electrolytic treatment using a sulfuric acid-copper sulfate electrolytic plating solution.
As a copper concentration of a sulfuric acid-copper sulfate electroplating solution, it is preferable to set it as the range of 40-120 g / L, for example, More preferably, it is the range of 60-100 g / L.
The sulfuric acid concentration of the sulfuric acid-copper sulfate electroplating solution is preferably in the range of 40 to 60 g / L.
Furthermore, the chlorine concentration of the sulfuric acid-copper sulfate electroplating solution is preferably in the range of 50 to 100 ppm.

  Moreover, the organic additives A, B, and C shown below can be used as an additive in an electrolytic (plating) solution.

  The organic additive A is, for example, in a molecular structure such as polyethylene glycol, polypropylene glycol, starch, polymer polysaccharides such as cellulose water-soluble polymer (carboxyl methyl cellulose, hydroxyethyl cellulose, etc.), polyethylene imine, polyallyl, polyacrylamide and the like. Among additives selected from water-soluble polymer compounds containing no S (sulfur), those having a molecular weight of 100,000 or more can be used.

  The organic additive B is, for example, in a molecular structure such as polyethylene glycol, polypropylene glycol, starch, a high molecular polysaccharide such as a cellulose-based water-soluble polymer (carboxyl methyl cellulose, hydroxyethyl cellulose, etc.), polyethylene imine, polyallyl, polyacrylamide, etc. Among additives selected from water-soluble polymer compounds not containing S (sulfur), those having a molecular weight of 10,000 or more and 50,000 or less can be used.

  The organic additive C is, for example, in a molecular structure such as polyethylene glycol, polypropylene glycol, starch, high molecular polysaccharides such as cellulose water-soluble polymer (carboxyl methyl cellulose, hydroxyethyl cellulose, etc.), polyethylene imine, polyallyl, polyacrylamide, etc. Among additives selected from water-soluble polymer compounds not containing S (sulfur), those having a molecular weight of 1000 or more and 5000 or less can be used.

Organic additives A (molecular weight 100,000 or more), B (molecular weight 10,000 or more, 50,000 or less) and C (molecular weight 1000 or more and 5000 or less) having different molecular weights are added in combination, and specific electrolysis (plating) By performing the foil production under the conditions, the tensile strength after heating at 150 ° C. for 1 hour is 350 MPa or more, the surface roughness Rz is 2.0 μm or less, the glossiness Gs (60 °) is 20 or more and 150 or less, the dynamic friction coefficient An electrolytic copper foil having a thickness of from 0.11 to 0.39, more preferably from 0.15 to 0.35 can be produced.
A polymer compound (additive C) having a molecular weight of 1000 or more and a molecular weight of 5000 or less and having a relatively small molecular weight is easily taken into the foil during foil formation, and these incorporated impurity components have a pinning effect at the grain boundaries. Thus, the strength of the foil is increased, and further, the foil is softened during heating and the strength is suppressed from being lowered. Patent Document 2 discloses an electrolytic copper foil having a normal tensile strength of 700 MPa or more and a glossiness Gs (60 °) of 80 or more. However, since the surface of such a foil is very smooth, the coefficient of dynamic friction is less than 0.11, and slipping of the foil occurs in the active material coating process, resulting in a problem in handling properties. I found out. Patent Document 3 discloses an electrolytic copper foil having a normal tensile strength of 700 MPa or more and a glossiness Gs (60 °) of 100 or more. However, as in the case of Patent Document 2, since the surface is very smooth, the coefficient of dynamic friction becomes less than 0.11, and slipping of the foil occurs in the active material coating process, which causes a problem in handling properties. Occurred. Generally, when the strength of the foil is increased, the crystal grains become finer and the smoothness of the surface increases, so that the coefficient of dynamic friction is lowered, and the handling property during active material coating tends to be difficult.
In this embodiment, in addition to the additive C, additives A and B having a larger molecular weight are used. These additives having a large molecular weight are adsorbed on the surface of the copper film during copper foil production, and have the effect of making the surface shape rougher by inhibiting the precipitation of copper. If only additive A having a molecular weight of 100,000 or more is added, the surface becomes too rough and the coefficient of dynamic friction exceeds 0.39. Therefore, the additive has a relatively low molecular weight and functions to suppress the effect of additive A. Addition of additive B that is relatively smaller than A and not larger than 10,000 and not larger than 50,000 makes the dynamic friction coefficient 0.11 or larger and 0.39 or smaller so that the handling during application of the active material becomes good. be able to.

The additives A, B and C can be used in the ranges of 30 mg / L, 10 to 20 mg / L and 5 to 20 mg / L, respectively.
For the produced electrolytic copper foil (untreated copper foil), for example, chromate treatment, Ni or Ni alloy plating, Co or Co alloy plating, Zn or Zn alloy plating, Sn or Sn alloy plating, the above various plating layers Further, an inorganic rust prevention treatment such as a chromate treatment or an organic rust prevention treatment such as benzotriazole.
Furthermore, for example, a silane coupling agent treatment or the like is performed to obtain an electrolytic copper foil for a negative electrode current collector of a lithium ion secondary battery.
The inorganic rust-proofing treatment, organic rust-proofing treatment, and silane coupling agent treatment serve to increase the adhesion strength between the negative electrode current collector and the active material and prevent the battery charge / discharge cycle efficiency from being lowered.

  Moreover, before performing said rust prevention process, it is also possible to perform a roughening process, for example to the electrolytic copper foil surface. As the roughening treatment, for example, a plating method or an etching method can be suitably employed.

  The plating method is a method of roughening the surface by forming a thin film layer having irregularities on the surface of the untreated electrolytic copper foil. As the plating method, an electrolytic plating method and an electroless plating method can be employed. As roughening by the plating method, it is preferable to form a plating film mainly composed of copper such as copper or copper alloy on the surface of the untreated electrolytic copper foil.

  As the roughening by the etching method, for example, a method by physical etching or chemical etching is suitable. For physical etching, there is a method of etching by sandblasting or the like, and for chemical etching, many liquids containing an inorganic or organic acid, an oxidizing agent, and an additive have been proposed.

[Configuration and production method of lithium ion secondary battery using current collector for lithium ion secondary battery]
The negative electrode of the lithium ion secondary battery of this embodiment uses the above-described electrolytic copper foil for the negative electrode current collector of the lithium ion secondary battery of the present embodiment as a negative electrode current collector, and the anticorrosion treatment layer of the current collector, etc. In this configuration, an active material layer is formed on the surface subjected to the surface treatment.

For example, the active material layer is obtained by applying a slurry obtained by kneading an active material, a binder, and a solvent to a negative electrode current collector, drying, and pressing.

  The active material in the present embodiment is a material that occludes / releases lithium, and is preferably an active material that occludes lithium by alloying. Examples of such an active material include group 14 elements such as carbon, silicon, germanium, and tin.

In the present embodiment, the current collector is preferably as thin as 4 to 10 μm, and the active material layer is formed on one side or both sides of the current collector. When the active material was applied only to the glossy surface of the copper foil having a surface roughness Rz of 1.0 μm or more and 2.0 μm or less formed from the drum, the surface was smooth and the adhesion with the active material was good.
If the thickness of the current collector is less than 4 μm, the foil is likely to break, and the production is difficult. If it is thicker than 10 μm, it is not preferable from the viewpoint of reducing the weight of the battery and increasing the energy density. Further, when the coefficient of dynamic friction is 0.11 or less, the surface is smooth, and therefore slips easily on the surface of the transport roll in the copper foil manufacturing process and the battery manufacturing process and becomes wrinkles. Therefore, for example, by making the dynamic friction coefficient within a range of 0.11 to 0.39 with a copper foil thickness of 4 to 10 μm, the current collector (which has good handling properties and is effective for reducing the weight and energy density of the battery) Copper foil).

When forming a carbon-based negative electrode active material layer, a paste made of carbon as a negative electrode active material, polyvinylidene fluoride resin as a binder, and N-methylpyrrolidone as a solvent is prepared, and the current collector (copper foil) Apply to one or both sides and dry.
For example, lithium may be occluded or added to the active material layer in this embodiment in advance. Lithium may be added when forming the active material layer. That is, lithium is contained in the active material layer by forming an active material layer containing lithium. Further, after forming the active material layer, lithium may be occluded or added to the active material layer. Examples of a method for inserting or adding lithium into the active material layer include a method for electrochemically inserting or adding lithium.

  Moreover, the lithium ion secondary battery of this embodiment is a lithium ion secondary battery provided with a positive electrode and a negative electrode, Comprising: A negative electrode is comprised by the lithium ion secondary battery negative electrode of said this embodiment.

[Configuration of printed wiring board]
The electrolytic copper foil of the embodiment of the present invention is a printed wiring board such as a rigid printed wiring board and a flexible printed wiring board (in this specification, the rigid printed wiring board and the flexible printed wiring board are collectively referred to as a printed wiring board). Can be used in various fields such as electromagnetic shielding materials.
Recent printed wiring boards are usually divided into two types. One is a three-layer printed wiring board in which a copper foil is attached to an insulating film (polyimide, polyester, etc.) with an adhesive resin and etched to give a pattern. On the other hand, another type is a two-layer printed wiring board in which an insulating film (polyimide, liquid crystal polymer, etc.) and a copper foil are directly laminated without using an adhesive.
The electrolytic copper foil of the embodiment of the present invention is laminated with an insulating film as a conductor of these printed wiring boards.

The main uses of printed wiring boards are for flat panel displays such as liquid crystal displays and plasma displays, or for internal wiring of cameras, AV equipment, personal computers, computer terminal equipment, HDDs, mobile phones, car electronics equipment, and the like. One of the important characteristics of these wirings is that they are bent and attached to equipment, or used in places where they can be bent repeatedly. is there.
The printed wiring board of the present invention uses the electrolytic copper foil of the embodiment, that is, the electrolytic copper foil having a surface roughness Rz of 1.0 μm to 2.0 μm and a glossiness Gs (60 °) of 20 or more as an insulating film. By sticking, it is possible to obtain a printed wiring board having excellent high-frequency characteristics required for a circuit board while having higher adhesion strength between the copper foil and the insulating film due to fine unevenness present on the surface of the copper foil. .
In addition, the tensile strength at room temperature of the copper foil to be bonded to the insulating film is preferably 450 MPa or more, so even thin foils are strong. It is hard to do.
In addition, since the tensile strength after heating at 150 ° C. for 1 hour of the copper foil to which the insulating film is laminated is 350 MPa or more, high strength can be maintained even after passing through a heat history when manufacturing a printed wiring board. it can.

  The excellent characteristics of the electrolytic copper foil of the present invention, such as high frequency characteristics and low resistance, are also excellent in the effect of electromagnetic shielding, and an excellent electromagnetic shielding material can be obtained by bonding to an insulating substrate.

  In any application, the copper foil has a gloss Gs (60 °) of 150 or less and a dynamic friction coefficient of 0.11 or more and 0.39 or less. Thus, since the foil is prevented from slipping on the roll, the handling property is improved.

  Hereinafter, the present invention will be described in more detail based on examples. However, the present invention is not limited to the following examples, and can be implemented with appropriate modifications within a range not changing the gist thereof. Is.

[Manufacture of untreated copper foil]
Examples 1-8
The electrolyte was adjusted to a copper concentration of 65 g / L, a sulfuric acid concentration of 45 g / L, and a chloride ion concentration of 25 ppm, and the additives A, B and C shown in Table 1 were used. An untreated copper foil having a thickness of 10 μm was produced by an electrolytic foil method under conditions of a current density of 30 A / dm ² and a bath temperature of 50 ° C. using a titanium rotating drum as an electrode and a cathode.

Comparative Examples 1-8
The untreated copper foil was manufactured so that thickness might be set to 10 micrometers with the installation similar to an Example by the electrolyte solution and electrolysis conditions of the comparative examples 1-8 shown in Table 2. Comparative Example 5 was produced by the method of Japanese Patent Application Laid-Open No. 2014-224321, Comparative Example 6 was produced by Japanese Patent No. 3742144, and Comparative Example 8 was produced by Japanese Patent No. 5255229.

[Measurement of tensile strength and elongation of electrolytic copper foil]
Table 3 shows the results of measuring the tensile strength (MPa) and the elongation rate (%) at room temperature of each of the electrolytic copper foils of Examples 1 to 8 and Comparative Examples 1 to 8.
The tensile strength (MPa) and elongation (%) were also measured after heat treatment at 150 ° C. for 1 hour, and the results are also shown in Table 3.
Tensile strength and elongation were measured at room temperature for tensile strength (MPa) and elongation (%) based on IPC-TM-650 using a tensile tester (Instron type 1122). The measurement was performed using a sample cut out in the longitudinal direction.
In this embodiment, “normal temperature” represents a normal humidity before the heat treatment at 150 ° C. for 1 hour as described above, for example, a temperature state of about 20 ° C.

[Measurement of surface roughness Rz]
Ten-point average surface roughness Rz (unit: μm) of the mat surface of each electrolytic copper foil of Examples 1 to 8 and Comparative Examples 1 to 8 was measured. The measurement was performed by the method defined in JIS B 0601-1994), and the results are shown in Table 3.

[Measurement of dynamic friction coefficient of electrolytic copper foil]
The dynamic friction coefficients of the mat surfaces of the electrolytic copper foils of Examples 1 to 8 and Comparative Examples 1 to 8 were measured using a surface weighing machine (HEIDON 14FW manufactured by Shinto Kagaku Co., Ltd.). The measurement conditions were as follows: a 10 mm diameter steel ball was used for the slider, a 50 gf load was applied, the sliding speed was 100 mm / min, and the sliding distance was 10 mm once per way. The results are shown in Table 3.

[Measurement of gloss of electrolytic copper foil]
The glossiness Gs (60 °) of the mat surface of each electrolytic copper foil of Examples 1 to 8 and Comparative Examples 1 to 8 is a gloss meter (VG2000 manufactured by Nippon Denshoku Industries Co., Ltd.) based on JIS Z8741. The measurement was made at a light projecting / receiving angle of 60 °. The measurement was carried out three times each in parallel to the longitudinal direction and in two orthogonal directions, and the average value of all these values was shown. The results are shown in Table 3.
FIG. 1 shows the relationship between the glossiness Gs (60 °) and the dynamic friction coefficient.

[Chromate treatment]
The surface of each electrolytic copper foil of Examples 1 to 8 and Comparative Examples 1 to 8 was subjected to chromate treatment to form a rust preventive treatment layer to obtain a current collector.
The conditions for the chromate treatment of the copper foil surface are as follows.
Chromate treatment conditions:
Potassium dichromate 1-10g / L
Immersion treatment time 2 to 20 seconds

[Evaluation of battery characteristics]
1. Production of positive electrode 90% by weight of LiCoO ₂ powder, 7% by weight of graphite powder and 3% by weight of polyvinylidene fluoride powder were mixed and a solution prepared by dissolving N-methylpyrrolidone in ethanol was added and kneaded to prepare a positive electrode agent paste. . After this paste was uniformly applied to a 15 μm thick aluminum foil, it was dried in a nitrogen atmosphere to evaporate ethanol, and then roll-rolled to prepare a sheet having a total thickness of 100 μm. The sheet was cut into a width of 43 mm and a length of 290 mm, and then an aluminum foil lead terminal was attached to one end thereof by ultrasonic welding to form a positive electrode.

2. Production of negative electrode:
90% by weight of natural graphite powder (average particle size: 10 μm) and 10% by weight of polyvinylidene fluoride powder were mixed, and a solution in which N-methylpyrrolidone was dissolved in ethanol was added and kneaded to prepare a paste. Next, this paste was applied to both surfaces of each of the copper foils of Examples and Comparative Examples. The coated copper foil was dried in a nitrogen atmosphere to evaporate ethanol, and then roll-rolled to form a sheet having an overall thickness of 110 μm. The sheet was cut to a width of 43 mm and a length of 285 mm, and then a nickel foil lead terminal was attached to one end thereof by ultrasonic welding to form a negative electrode.

3. Battery fabrication:
The whole was wound with a 25 μm thick polypropylene separator sandwiched between the positive electrode and negative electrode manufactured as described above, and this was accommodated in a nickel-plated battery can, and the lead terminal of the negative electrode was spotted on the bottom of the can Welded. Next, after placing the top cover of the insulating material and inserting the gasket, the lead terminal of the positive electrode and the aluminum safety valve were connected by ultrasonic welding, and a non-aqueous electrolyte consisting of propylene carbonate, diethyl carbonate and ethylene carbonate was added to the battery can. After injecting the inside, a lid was attached to the safety valve, and a sealed structure type lithium ion secondary battery having an outer shape of 14 mm and a height of 50 mm was assembled.

4). Measurement of Battery Characteristics A charge / discharge cycle test was performed on the above battery, in which the cycle of charging to 4.2 V at a charging current of 50 mA and discharging to 2.5 V at 50 mA was one cycle. Table 3 shows the battery capacity and cycle life at the first charge. The cycle life is the number of cycles when the discharge capacity of the battery is below 300 mAh.
5. Evaluation of good handling A foil that can be smoothly transported without any foil slip on the transport roll and without being caught on the transport roll in the coating process of 1000 m foil in the active material coating line. The results are shown in Table 3. The results are shown in Table 3 where the results indicate that the handling property is good and that the slip occurs or the foil is caught on the roll and the conveyance stops, and the handling property is poor. In addition, although a slight problem in conveyance occurred, a case where the problem did not occur in the application of the active material was marked with Δ.

From Table 3, Examples 1 to 8 have good battery characteristics with a cycle life of 500 cycles or more because the tensile strength before and after heating at 150 ° C. for 1 hour is 350 MPa or more and the glossiness Gs (60 °) is 20 or more. showed that. Furthermore, the dynamic friction coefficient was 0.11 or more and 0.39 or less, slippage with a roll during line production was suppressed, and handling properties were good.
However, in Example 1, the coefficient of dynamic friction was as high as 0.38, and although there was no hindrance to the coating of the active material, it was confirmed that the handling property was Δ because some catching was confirmed during transportation.
On the other hand, the foil of Example 8 had a low coefficient of dynamic friction of 0.12, and although some foil slip was confirmed on the transport roll, it did not hinder the coating of the active material. A triangle was attached in the same manner as in 1.

The copper foil of Comparative Example 1 has a very low Rz on the M-plane side of 2.0 or more and a glossiness Gs (60 °) of 20 or less, so that the contact between the active material and the current collector is poor and during charging and discharging. Since the active material layer formed on the mat surface side could not withstand the stress due to the expansion and contraction of the active material, the cycle life was very low, 500 cycles or less. Further, since the dynamic friction coefficient on the mat surface side is relatively high at 0.38, there is no problem in coating the active material although the foil may be caught on the transport roll.

The copper foil of Comparative Example 2 showed a preferable cycle life because the tensile strength after heating was 350 MPa or more and the glossiness Gs (60 °) on the mat surface side was 20 or more and 150 or less. Since the dynamic friction coefficient on the side was as low as 0.11 or less, a slip occurred during the conveyance of the foil in the active material coating process, resulting in poor handling.

  The copper foil of Comparative Example 3 is formed on the mat surface side because the tensile strength after heating is 350 MPa or more, the Rz on the mat surface side is 2.0 or less, and the glossiness Gs (60 °) is 20 or more. The contact property between the active material and the current collector was good, and the cycle life was 500 cycles or more. However, since the dynamic friction coefficient on the mat surface side is very high at 0.45, the handling property is not preferable because the foil is caught on the transport roll and stops, causing a problem in the coating of the active material. It was.

  In addition, the copper foil of Comparative Example 4 has a kinetic friction coefficient of 0.13 on the mat surface side, and has good handling properties when coated with an active material, but has a gloss Gs (60 °) of 150 or more. The active material exfoliated due to the expansion and contraction of the active material during charge and discharge, and the cycle life was less than 500 cycles.

Comparative Example 5 is a foil that was manufactured based on the manufacturing method of the example (sample 8) described in Patent Document 3.
Since the tensile strength after heating is 350 MPa or more and the glossiness Gs (60 °) on the mat surface side is 20 or more and 150 or less, a preferable cycle life is shown, but the dynamic friction coefficient on the mat surface side is 0.11 or less. Therefore, since the slip occurred during the conveyance of the foil in the active material coating process, the handling property was not preferable.

Moreover, the comparative example 6 is the foil manufactured by the method as described in the Example of patent document 1. FIG. Since the dynamic friction coefficient on the mat surface side is in the range of 0.11 to 0.39, handling in the active material coating process is preferable, and the glossiness Gs (60 °) is also in the range of 20 to 150. However, since the tensile strength after heating is as low as less than 350 MPa at 320 MPa, it cannot withstand the expansion and contraction of the active material during charge and discharge, and deformation of the foil occurs. As a result, the cycle characteristics were poor and the result was x.
Similarly, in Comparative Example 7, although the handling during active material coating was good, the tensile strength after heating was as low as less than 350 MPa. Therefore, the foil was deformed during charging and discharging, and the cycle characteristics were low.
Comparative Example 8 is a foil manufactured by the method described in the example of Patent Document 2, but the tensile strength after heating is 350 MPa or more, and the glossiness Gs (60 °) on the mat surface side is 20 or more and 150 or less. Therefore, although the preferable cycle life was shown, the mat frictional coefficient on the mat surface side was 0.11 or less, so that the slip during the conveyance of the foil in the active material coating process occurred and the handling property was poor. Met.

FIG. 1 shows the relationship between the glossiness and the dynamic friction coefficient of the copper foils shown in the comparative examples and examples. About the comparative example, even if it was the electrolytic copper foil whose active material adhesiveness and handling property were in the favorable range, since the intensity | strength after a 150 degreeC 1 hour heating was less than 350 Mpa, it became battery characteristic evaluation NG. On the other hand, the electrolytic copper foils of the examples showed good evaluation results for both handling properties and battery characteristics evaluation.

As described above, the electrolytic copper foil of the present invention has a tensile strength of 350 MPa or more, preferably 400 MPa or more after heating at 150 ° C. for 1 hour, a glossiness Gs (60 °) on the mat surface of 20 to 150, and dynamic friction. By using an electrolytic copper foil having a coefficient of 0.11 or more and 0.39 or less, preferably 0.15 or more and 0.35 or less, it is difficult to slip on the production line while exhibiting good lithium ion secondary battery characteristics. It is possible to provide an electrolytic copper foil having good handleability during production.
Moreover, the electrolytic copper foil of the embodiment of the present invention has a tensile strength of 350 MPa or more after heating at 150 ° C. for 1 hour, can withstand stress due to volume expansion / contraction of the active material during charge / discharge, and has a good cycle life. A secondary battery is obtained.

Furthermore, the electrolytic copper foil of the embodiment of the present invention has a gloss Gs (60 °) on the mat surface of 20 or more, so that the contact between the active material and the current collector is good, the electrical conductivity is high, and the good. Cycle life is obtained.
Furthermore, the electrolytic copper foil of the present invention has a gloss Gs (60 °) of 150 or less and a dynamic friction coefficient of 0.11 or more and 0.39 or less. Is suppressed from slipping on the roll, and handling properties are improved.

  Moreover, the lithium ion secondary battery negative electrode of the present invention becomes a lithium ion secondary battery negative electrode with improved cycle characteristics by using the electrolytic copper foil of the present invention as a current collector, and the lithium ion secondary battery incorporating the electrode. The secondary battery is a battery having an excellent cycle life.

[Creation and evaluation of printed wiring boards]
The electrolytic copper foil of Example 5 was laminated with a polyimide film to produce a three-layer printed wiring board, and the production process and the performance of the completed wiring board were evaluated.
(1) Adhesiveness between copper foil and film The adhesiveness between the copper foil and the film was such that the polyimide film bites into the fine irregularities present on the surface of the copper foil, and had satisfactory strength.
(2) High frequency characteristics The high frequency characteristics of the printed wiring board are as follows: the roughness Rz of the copper foil surface is 2.0 or less, the glossiness Gs (60 °) is 90 or more, and the unevenness of the copper foil surface is fine. It was satisfactory.
(3) Strength of copper foil and generation of wrinkles Since the tensile strength of copper foil at normal temperature is 668 MPa and is 450 MPa or more, the strength of bonding with an insulating film is sufficient even with a thin foil. There was no occurrence of foil breakage or wrinkles in the process.
(4) Thermal history There is almost no change in strength due to the thermal history in the copper foil during heating when the copper foil and the insulating film are bonded together, and even after passing through the thermal history when manufacturing a printed wiring board, the strength is high. Maintained.

As described above, the present invention is particularly excellent as a copper foil for a secondary battery current collector with a long cycle life, and in order to have excellent handling properties, no wrinkles are formed on the copper foil in the active material coating line, From these characteristics, it is possible to easily provide a negative electrode for a lithium ion secondary battery with improved cycle characteristics, and to provide a lithium ion secondary battery with a long cycle life incorporating the negative electrode for the lithium ion secondary battery. It is what you have.
In addition, as described above, the present invention has an excellent effect of providing a printed wiring board having excellent characteristics and an electromagnetic wave shielding material.

Claims (7)

  On the matte surface, electrolytic copper having a gloss Gs (60 °) of 20 or more and 150 or less, a dynamic friction coefficient of 0.11 or more and 0.39 or less, and a tensile strength after heating for 1 hour at 150 ° C. of 350 MPa or more and 900 MPa or less. Foil.   The electrolytic copper foil according to claim 1, wherein the tensile strength after heating at 150 ° C. for 1 hour is 400 MPa or more.   The electrolytic copper foil according to claim 1 or 2, wherein the thickness of the electrolytic copper foil is 4 µm or more and 10 µm or less.   The negative electrode for lithium ion secondary batteries which used the electrolytic copper foil in any one of Claims 1-3 as a collector.   The lithium ion secondary battery using the negative electrode for lithium ion secondary batteries made into the electrical power collector of Claim 4.   The printed wiring board formed by laminating | stacking the electrolytic copper foil and insulating film in any one of Claims 1-3.   The electromagnetic wave shielding material formed by laminating | stacking the electrolytic copper foil and insulating substrate in any one of Claims 1-3.

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