WO2013002273A1

WO2013002273A1 - Lithium ion secondary cell, current collector constituting negative electrode of secondary cell, and electrolytic copper foil constituting negative-electrode current collector

Info

Publication number: WO2013002273A1
Application number: PCT/JP2012/066413
Authority: WO
Inventors: 鈴木　昭利; 健作篠崎
Original assignee: 古河電気工業株式会社
Priority date: 2011-06-28
Filing date: 2012-06-27
Publication date: 2013-01-03
Also published as: JPWO2013002273A1; TWI605627B; KR101606251B1; TW201312826A; JP5158918B2; KR20140023955A; CN103460462A

Abstract

Provided is an electrolytic copper foil having excellent coatability by an active material slurry, high cell capacity, minimal cell capacity loss even after repeated charge-discharge cycles, and nearly the same morphology on both sides thereof, such that an active material coating film does not peel away from the copper foil as a negative-electrode current collector. Also provided is a lithium ion secondary cell wherein the electrolytic copper foil is a current collector, an active material is deposited on the current collector to form a negative electrode, and the negative electrode is incorporated into the lithium ion secondary cell. The electrolytic copper foil constitutes a negative-electrode current collector of the lithium ion secondary cell, both sides of the electrolytic copper foil are formed by electrolytic deposition, and the electrolytic deposited sides have a granular crystalline structure. In the current collector comprising the electrolytic copper foil constituting the negative electrode of the lithium ion secondary cell, both sides of the electrolytic copper foil are formed by electrolytic deposition, and the electrolytic deposited sides are configured from a granular crystalline structure.

Description

Lithium ion secondary battery, current collector constituting the negative electrode of the secondary battery, and electrolytic copper foil constituting the negative electrode current collector

The present invention relates to a lithium ion secondary battery comprising a positive electrode, a negative electrode having a negative electrode active material layer formed on the surface of a negative electrode current collector, and a non-aqueous electrolyte, and a current collector constituting the negative electrode of the secondary battery And an electrolytic copper foil constituting the negative electrode current collector.

A lithium ion secondary battery comprising a positive electrode and a negative electrode current collector made of an electrolytic copper foil with smooth both surfaces coated with carbon particles as a negative electrode active material layer, dried and further pressed, and a non-aqueous electrolyte Currently, it is used for mobile phones and notebook computers. As the negative electrode current collector of the lithium ion secondary battery, a so-called “untreated copper foil” manufactured by electrolysis is subjected to rust prevention treatment.

As disclosed in Patent Document 1, the copper foil as the negative electrode current collector for a lithium ion secondary battery has a roughened surface and a surface roughness of a glossy surface and a rough surface (both surfaces of the copper foil). By using an electrolytic copper foil with a small difference, it is possible to suppress a decrease in charge / discharge efficiency of the battery.

Electrolytic copper foil with a smooth surface as described above and a small difference in surface roughness between glossy and rough surfaces is made of copper sulfate-sulfuric acid electrolyte, various water-soluble polymer substances, various surfactants, various organic substances. Using an electrolytic solution that has been appropriately selected and added with sulfur compounds, chloride ions, etc., copper is electrolytically deposited on a rotating titanium drum cathode, and when it reaches a predetermined thickness, it is peeled off and wound up. Is manufactured by.
For example, a technique for producing an electrolytic copper foil by adding a compound having a mercapto group, a chloride ion, a low molecular weight glue having a molecular weight of 10,000 or less, and a high molecular weight polysaccharide to a copper sulfate-sulfuric acid electrolytic solution has been proposed. (See Patent Document 1).
This electrolytic copper foil has a tensile strength of 300 to 350 N / mm ² and is a suitable material in combination with appropriate elongation when used as a negative electrode current collector (copper foil) using the carbon particles as an active material. is there.

In addition, electrolytic copper foils with a smooth rough surface have been proposed. For lithium-ion secondary batteries using carbon-based active materials, which are currently mainstream, this type of rough surface is smooth and glossy. A copper foil having a small difference in surface roughness between a rough surface and a rough surface is mainly used (see Patent Document 2 and Patent Document 3).

In recent years, for the purpose of increasing the capacity of lithium ion secondary batteries, lithium ion secondary batteries that use an alloy active material that is electrochemically alloyed with lithium during charging, such as aluminum, silicon, and tin, as the negative electrode active material. A secondary battery has been proposed (see Patent Document 4).

A negative electrode for a lithium ion secondary battery for the purpose of increasing the capacity is obtained by depositing, for example, silicon as an amorphous silicon thin film or a microcrystalline silicon thin film on a current collector such as a copper foil by a CVD method or a sputtering method. Forming. It has been found that the thin film layer of the active material produced by such a method is in close contact with the current collector, and thus exhibits good charge / discharge cycle characteristics (see Patent Document 5).
Recently, a forming method has also been developed in which powdered silicon or a silicon compound is slurried with an imide-based binder in an organic solvent, applied onto a copper foil, dried and pressed. (See Patent Document 6)

Regardless of whether the type of the negative electrode active material is carbon or alloy, the battery capacity is high, and even when the charge / discharge cycle is repeated, there is little deterioration of the battery capacity. There is a need for a copper foil that does not peel off.

Japanese Patent No. 3742144 JP 2004-263289 A JP 2004-162144 A JP-A-10-255768 Japanese Patent Laid-Open No. 2002-083594 JP 2007-227328 A

The present invention is excellent in coating properties of the active material slurry, has a high battery capacity, little deterioration of the battery capacity even after repeated charge / discharge cycles, and the active material coating layer does not peel from the copper foil as the negative electrode current collector. Provided is an electrolytic copper foil having the same shape, and uses the electrolytic copper foil as a current collector, a negative electrode in which an active material is deposited on the current collector, and a lithium ion secondary battery incorporating the negative electrode This is the issue.

The lithium ion secondary battery of the present invention is a lithium ion secondary battery comprising a positive electrode, a negative electrode in which an electrode constituent active material layer is formed on the surface of a current collector, and a non-aqueous electrolyte, The current collector constituting the negative electrode of the ion secondary battery is made of an electrolytic copper foil. Both surfaces of the electrolytic copper foil are formed by electrolytic deposition, and the electrolytic deposited surface has a crystalline structure of granular crystals.

The current collector for a lithium ion secondary battery of the present invention is a lithium ion secondary battery comprising a positive electrode, a negative electrode in which an electrode constituting active material layer is formed on the surface of the current collector, and a non-aqueous electrolyte. A current collector constituting a negative electrode, wherein the current collector is made of an electrolytic copper foil, both surfaces of the electrolytic copper foil are formed by electrolytic deposition, and the electrolytic deposited surface is a crystal structure of a granular crystal.

An electrolytic copper foil for a negative electrode current collector of a lithium ion secondary battery of the present invention is an electrolytic copper foil constituting the negative electrode current collector of a lithium ion secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, Both surfaces of the electrolytic copper foil are formed by electrolytic deposition, and the electrolytic deposition surface has a crystal structure of granular crystals.

A lithium ion secondary battery of the present invention is a lithium ion secondary battery comprising a negative electrode in which an electrode-constituting active material layer is formed on the surfaces of a positive electrode and a current collector, and a non-aqueous electrolyte, wherein the negative electrode The current collector constituting is an electrolytic copper foil formed by electrolytic deposition of copper, and the first surface of the electrolytic copper foil is a surface formed by copper electrodeposition of a crystal structure of granular crystals on the drum surface, The second surface opposite to the first surface is a surface formed by copper electrodeposition of a granular crystal structure on the back side of the first surface after the first surface film formation.

A negative electrode current collector for a lithium ion secondary battery of the present invention is a lithium ion secondary battery comprising a positive electrode, a negative electrode in which an electrode constituent active material layer is formed on the surface of the current collector, and a non-aqueous electrolyte. A negative electrode current collector constituting the secondary battery, wherein the negative electrode current collector is an electrolytic copper foil formed by electrolytic deposition of copper, and the first surface of the electrolytic copper foil is a granular crystal on a drum surface. The second surface opposite to the first surface is formed by copper electrodeposition of granular crystals on the back side of the first surface after the first surface film formation. It is the formed surface.

The electrolytic copper foil for a negative electrode current collector of a lithium ion secondary battery of the present invention is an electrolytic copper foil for a negative electrode current collector constituting the secondary battery of a lithium ion secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte. The electrolytic copper foil is an electrolytic copper foil formed by electrolytic deposition of copper, and the first surface of the electrolytic copper foil is a surface formed by copper electrodeposition of a granular crystal structure on the drum surface. The second surface opposite to the first surface is a surface formed by copper electrodeposition of a granular crystal structure on the back side of the first surface after the first surface film formation.

The present invention is excellent in coating properties of the active material slurry, has a high battery capacity, little deterioration of the battery capacity even after repeated charge / discharge cycles, and the active material coating layer does not peel from the copper foil as the negative electrode current collector. An electrolytic copper foil having the same shape can be provided.
Further, the present invention provides a negative electrode current collector by using the electrolytic copper foil as a current collector, depositing an active material on the current collector as a negative electrode, and forming a lithium ion secondary battery incorporating the negative electrode. A current collector in which the active material deposition layer does not peel from the copper foil can be provided, and the negative electrode is constituted by the current collector, so that the battery capacity is high, and the battery capacity is hardly deteriorated even after repeated charge / discharge cycles. An ion secondary battery can be provided.

FIG. 1 is an explanatory view showing an example of a process for producing an electrolytic copper foil having the same shape on both sides. FIG. 2 is an explanatory view of a conventional apparatus for producing an electrolytic copper foil. FIG. 3 shows a first example of the electrolytic copper foil of the present invention, wherein A1 is an electrolytic deposition surface formed first, and A2 is a micrograph (SEM) showing an electrolytic deposition surface formed next. FIG. 4 shows a second embodiment of the electrolytic copper foil of the present invention, wherein A1 is an electrolytic deposition surface formed first, and A2 is a micrograph (SEM) showing an electrolytic deposition surface formed next. FIG. 5 shows a third embodiment of the electrolytic copper foil of the present invention, wherein A1 is an electrolytic deposition surface formed first, and A2 is a micrograph (SEM) showing an electrolytic deposition surface formed next. FIG. 6 shows a fourth embodiment of the electrolytic copper foil of the present invention, in which A1 is an electrolytic deposition surface formed first, and A2 is a micrograph (SEM) showing an electrolytic deposition surface formed next. FIG. 7 is a micrograph (SEM) of a conventional electrolytic copper foil, where X1 represents a drum surface and Y1 represents a drum surface.

In this specification, the surface of the electrolytic copper foil that is in contact with the electrolytic solution is expressed as an “electrolytic deposition surface”.
The electrolytic copper foil of the present invention is “both electrolytic deposition surfaces on the first surface and the second surface opposite to the first surface”. Both sides of the electrolytic copper foil on the electrolytically deposited surface are constituted by a surface where both sides of the copper foil are in contact with the electrolytic solution so that the foil can be made by a foil making apparatus shown in FIG.

As shown in FIG. 2, the electrolytic copper foil generally has a rotating titanium drum 21 and an insoluble anode 22 (hereinafter referred to as DSA) disposed below the rotating titanium drum 21 and a copper sulfate-sulfuric acid solution between the titanium drum 21 and the DSA 22. A copper foil 24 is produced by flowing an electrolytic solution 23 and flowing a current between the titanium drum and the DSA with the titanium drum 21 as a cathode and the DSA 22 as an anode.
When a current is passed between the titanium drum 21 and the DSA 22, copper is electrolytically deposited on the titanium drum 21. The electrolytic copper foil 24 is manufactured by continuously peeling and winding it up at a predetermined thickness. Usually, the foil in this state is referred to as “untreated copper foil”.

The shape of the electrolytic copper foil 24 manufactured by the manufacturing method shown in FIG. 2 is different between the surface 241 in contact with the electrolytic solution 23 and the surface 242 in contact with the titanium drum 21.
The surface 241 that is normally in contact with the electrolytic solution 23 is referred to as a “rough surface”, and the surface 242 that is in contact with the titanium drum 21 is referred to as a “glossy surface”.

However, in the case of the electrolytic copper foil for the negative electrode current collector of the lithium ion secondary battery, as shown in Patent Documents 1 to 3, the surface in contact with the electrolytic solution is more in contact with the titanium drum, Rather, since a smooth electrolytic copper foil can be produced, the surface 241 that has been in contact with the electrolyte in the copper foil industry for lithium ion secondary batteries is referred to as an “electrolytic deposition surface” or “electrodeposition surface”, or a surface that has been in contact with a titanium drum. Reference numeral 242 is referred to as a “drum surface”. In this specification, “electrolytic deposition surface” and “drum surface”, which are generalized in the copper foil industry for lithium ion secondary batteries, are adopted, and the surface of the electrolytic copper foil in contact with the electrolytic solution as described above is “ It is expressed as “electrolytically deposited surface”.

The “drum surface” that was in contact with the titanium drum looks glossy and looks smooth at first glance, but when observed with an SEM, as shown in FIG. There are irregularities.
On the other hand, the “electrolytically deposited surface” shown in FIGS. 3 to 6 is smoother than the “drum surface” without any streaks.
This is because the “drum surface” is the surface in contact with the titanium drum. After the surface of the titanium drum is polished, it is set in an electrolytic cell 26 as shown in FIG.
At this time, since a copper sulfate-sulfuric acid electrolytic solution having a relatively high temperature of about 50 ° C. is used, the surface of the titanium drum 21 is gradually roughened and the copper foil 24 is hardly peeled off during the continuous production. In order to avoid this, after manufacturing the copper foil for a certain period, the titanium drum surface is periodically polished and the manufacturing is continued again.

Usually, the surface of the titanium drum is formed by a cylindrical polishing buff obtained by uniformly bonding and impregnating abrasive grains such as aluminum oxide and silicon carbide to a nylon nonwoven fabric.
The “drum surface” is a replica of the “polishing streaks” of the titanium drum that has been surface-polished by the buff as described above.
Therefore, in the normal manufacturing method, it is inevitable that streak-like irregularities as shown in FIG. 7 (Y1) exist in the MD direction (vertical direction) of the “drum surface”.

The copper foil shown in FIG. 7 has been used as a negative electrode current collector for consumer-use lithium ion secondary batteries such as notebook computers and mobile phones, but the shape of this “drum surface” and “electrolytic deposition surface” The difference has not caused any problems so far.
For example, the difference in applicability at the time of applying the active material or the difference in charge / discharge efficiency after becoming a battery has not been particularly problematic.

However, when electrolytic copper foil is used as the negative electrode current collector of lithium ion secondary batteries for automobiles such as HEV, EV, and PHEV, the lithium ion secondary on the “drum surface” and “electrolytic deposition surface” of the electrolytic copper foil The difference in charge and discharge efficiency after becoming a battery has been regarded as a problem.

The cause of the problem is that when manufacturing a negative electrode for a lithium ion secondary battery, a current collector (copper foil) is continuously run to apply a slurry-like active material, and then dried and wound up. Although the manufacturing is performed, it is considered that the speed of running the copper foil is much faster in the case of manufacturing a battery for automobiles than in the case of manufacturing a battery for consumer use.

In addition, the charge / discharge efficiency for automobiles needs to be higher than a certain level even after 10 years of decline in charge / discharge efficiency, while for consumer use, it is constant after about 1-2 years. A much stricter level of performance is required, such as the need for the above efficiency.

As described above, when comparing the charging / discharging efficiency after battery production on the `` drum surface '' and the `` electrolytic deposition surface '' of the electrolytic copper foil according to strict evaluation criteria required for lithium ion secondary batteries for automobiles, The “drum surface” tends to have a greater (faster) deterioration in charge / discharge efficiency than the “electrolytic deposition surface”.

This phenomenon also applies to lithium-ion secondary batteries that use an alloy-based active material that is electrochemically alloyed with lithium during charging, such as aluminum, silicon, or tin, as the negative electrode active material for the purpose of increasing capacity. It can be seen.

The decrease in charge / discharge efficiency of a lithium ion secondary battery using aluminum, silicon, tin, or the like as a negative electrode active material appears remarkably in fewer cycles, for example, about 50 to 100 cycles than when a carbon-based active material is used.
In this case as well, when comparing the “drum surface” and the “electrolytic deposition surface” of the electrolytic copper foil, in terms of charge / discharge efficiency, the “drum surface” tends to have a greater deterioration in charge / discharge efficiency than the “electrolytic deposition surface”. Is seen.

Furthermore, the present inventors analyzed this phenomenon in detail, and ascertained that the difference in surface shape between the “drum surface” and the “electrolytic deposition surface” was a major factor.
That is, it has been found that streaky irregularities on the “drum surface” are likely to cause deterioration in terms of charge / discharge efficiency. Although the cause of this is not clear, it is presumed that the contact area between the negative electrode active material and the electrolytic copper foil is larger on the “electrolytic deposition surface” than on the “drum surface”.

In order to make the surface shapes of the “drum surface” and the “electrolytic deposition surface” coincide with each other, the present inventors use the same electrolytic solution as that used when producing the electrolytic copper foil on the “drum surface” of the copper foil after production. Copper plating was made to remove the streaks on the “drum surface”, and the “drum surface” was made to have the same shape as the “electrolytic deposition surface” to make a cathode current collector for a lithium ion secondary battery.
As another embodiment, in order to eliminate the streaky irregularities on the “drum surface”, an electrolytic solution having a composition different from that of the electrolytic copper foil production may be used as long as the same shape as the “electrolytic deposition surface” is obtained. Was also considered effective.

A smooth and glossy surface is suitable for the surface of the electrolytic copper foil for the negative electrode current collector of the lithium ion secondary battery. This is as shown in Patent Examples 1 to 3. In order to obtain a smooth and glossy surface suitable as such a current collector for a lithium ion secondary battery, it is effective to make the crystal structure of copper granular.

The improved electrolytic copper foil for a negative electrode current collector of a lithium ion secondary battery for preventing deterioration of charge / discharge efficiency of the present invention is an “electrolytic precipitation surface (first surface)” formed in the previous foil-making process. It is a glossy surface with a texture, and the “drum surface (second surface)” side is the next step, and electrodeposits of granular crystal copper with a thickness that eliminates the streaks formed in the previous step. Both have a smooth and glossy copper foil as a surface shape composed of granular crystals similar to the “electrolytically deposited surface”.

An example of a specific method for producing the electrolytic copper foil is shown in FIG.
After producing the copper foil 1 having a crystal structure of granular crystals with the first drum 11, the copper foil 1 is peeled off, and copper electrodeposition of the crystal structure of granular crystals is performed on the drum surface 101 side of the copper foil 1 with the second drum 12. The surface of both surfaces is made the same as that of the electrolytic deposition surface 102 by filling the polishing surface of the drum 11 with the drum surface 101 as the electrolytic deposition surface 103.

In this case, it is more convenient in manufacturing that the

electrolytic solutions

13 and 18 in the first electrolytic tank 16 and the second electrolytic tank 17 are the same electrolytic solution, but the first electrolytic tank 16 and the second electrolytic tank 17 are liquid solutions. Even when electrolytic solutions having different compositions are used, the surface shapes on both sides can be made the same.
By performing copper electrodeposition of the crystalline structure of the granular crystals on the first drum 11 and using a copper electrolyte having a composition different from that of the first electrolytic cell 16, It is possible to make the shape of both sides the same.

In order to obtain a foil having the same shape on both sides, it is easy in manufacturing to make the thickness of the copper foil formed on the first drum the same as the thickness of the copper coating formed on the second drum. However, it is also possible to increase the thickness of the copper foil formed on the first drum and reduce the thickness of the copper coating formed on the second drum.
The former method is suitable for producing a foil having a thickness of about 35 μm, while the latter method is suitable for producing a thin foil having a thickness of about 6 μm.
For example, it is practically quite difficult to produce a 3 μm copper foil on the first drum and a 3 μm copper coating on the second drum. It is difficult to manufacture a copper foil having a thickness of 3 μm using the first drum and to cover the copper foil with 3 μm using the second drum because the foil is easily cut thinly on the first drum.
In contrast, the latter method, for example, producing 5.0 μm copper foil on the first drum and coating 1.0 μm copper on the second drum means that the tensile strength of the copper foil produced on the first drum is This is possible if the height is high enough.
From the above manufacturing method, it is considered that the foil thickness is preferably 6 to 35 μm.

Thus, by obtaining a foil having the same shape on both sides, when applying the active material slurry, the same wettability is obtained, the condition setting of the active material application process becomes easy, and the coating film structure on both sides becomes the same, The same charge / discharge characteristics are obtained, and it is considered that the battery exhibits extremely stable performance.

As described above, the present invention is a lithium ion secondary battery including a positive electrode and a negative electrode in which an electrode constituent active material layer is formed on the surface of the current collector. First, an electrolytic copper foil having a drum surface and an electrolytic deposition surface is formed.
Subsequently, copper electrodeposition of the crystalline structure of the granular crystals is performed to a thickness that eliminates the streaky irregularities formed on the drum surface in the previous step, and a copper layer serving as an electrolytic deposition surface is formed on the electrolytic copper foil. Provide. The electrolytic copper foil thus produced is used as a negative electrode current collector, an active material is deposited on the negative electrode current collector to form a negative electrode, and the negative electrode is incorporated into a lithium ion secondary battery.

Furthermore, the present invention relates to a lithium ion secondary battery including a positive electrode and a negative electrode in which an electrode-constituting active material layer is formed on the surface of a planar current collector. First, an electrolytic copper foil having a “drum surface” and an “electrolytic deposition surface” is formed.
Then, the copper foil which performed the copper electrodeposition of the crystal structure of a granular crystal as mentioned above on the "drum surface" of the said electrolytic copper foil is created. At least one surface of the electrolytic copper foil thus manufactured is subjected to a surface treatment for improving adhesion with the electrode-constituting active material layer to form a negative electrode current collector, and the active material is deposited on the negative electrode current collector to form the negative electrode And incorporating the negative electrode into a lithium ion secondary battery.

The above-mentioned foils are classified as “untreated foils” since no surface treatment is performed after the foil production. "Untreated foil" is an intermediate product that does not undergo any surface treatment. In order to use this as a battery foil, some surface treatment is applied.
Usually, the surface treatment is performed for the purpose of enhancing the adhesion to the electrode constituent active material layer together with the antirust function.

As the rust prevention treatment, an inorganic rust prevention treatment or an organic rust prevention treatment is performed. Chromate treatment or the like is performed as the inorganic rust prevention treatment. Examples of the organic rust preventive treatment include benzotriazole treatment and silane coupling agent treatment, and these can be performed singly or in combination.

The chromate treatment uses an aqueous solution containing dichromate ions, which may be acidic or alkaline, and is subjected to immersion treatment or cathodic electrolysis treatment. In this chromate treatment, the form of adhesion to the copper foil is an oxide or hydroxide of trivalent chromium reduced from hexavalent chromium.
Usual chemicals include chromium trioxide, potassium dichromate, sodium dichromate and the like.

Benzotriazoles as organic rust preventive treatments include benzotriazole, methylbenzotriazole, aminobenzotriazole, carboxybenzotriazole and the like, and are applied as an aqueous solution by immersion treatment or spray treatment.
There are various types of silane coupling agents such as those having an epoxy group, amino group, mercapto group, and vinyl group, but those having excellent adhesion to the electrode active material layer may be used, and an aqueous solution or solvent may be used. Apply by dipping or spraying.
The copper foil for lithium ion secondary battery negative electrode collectors is completed by the above process.

Hereinafter, the present invention will be described in more detail by way of examples, but these examples do not limit the present invention.

<Example 1>
An electrolytic copper foil was made using the apparatus shown in FIG. That is, a copper sulfate-sulfuric acid electrolyte solution 13 having the following composition is caused to flow between the titanium drum 11 and the DSA 14 by the first electrolytic cell 16 in which the rotating titanium drum 11 is used as a cathode and the DSA 14 is disposed on the lower side. An electrolytic copper foil 1 having a thickness of 6 μm was produced by passing an electric current between −DSA.
Electrolyte composition and electrolysis conditions;
Cu = 50 to 150 g / L
H ₂ SO ₄ = 20 to 200 g / L
Chloride ion = 1-60ppm
Sodium 3-mercapto-1-propanesulfonate = 0.5-10ppm
Hydroxyethyl cellulose = 1-30ppm
Low molecular weight gelatin (molecular weight 3,000) = 1-30ppm
Temperature = 30-70 ° C
Current density: 30 to 100 A / dm ²
The roughness of the electrolytic deposition surface 102 of this copper foil 1 was Rz = 1.3 μm and Ra = 0.3 μm, and the roughness of the drum surface 101 was Rz = 1.6 μm and Ra = 0.4 μm.

The copper foil 1 was guided to the second drum 12, and 6 μm of copper electrodeposition was performed on the drum surface side using the same electrolytic solution 18 as the first electrolytic solution to obtain a 12 μm foil 2. The roughness of the surface where copper electrodeposition was performed on the surface of the drum 101 was Rz = 1.3 μm and Ra = 0.3 μm, and it was possible to obtain a copper foil 2 having the shape of an “electrolytically deposited surface” on both sides. . The copper foil had a tensile strength of 310 MPa and an elongation of 8.0%.

Rz is the ten-point average roughness described in JIS B 0601-1994, and Ra is the arithmetic average roughness described in JIS B 0601-1994.

Next, this copper foil was subjected to cathodic electrolysis in a chromium trioxide 5 g / L solution on both sides at 0.3 A / dm ² for 10 seconds, washed with water and dried to obtain an electrolytic copper foil for a battery.
Also, an electron micrograph of this electrolytic copper foil is taken, and the electrolytic deposition surface by the first drum is shown in FIG. 3 (A1), and the copper is electroanalyzed by the second drum on the drum surface of the first drum in FIG. 3 (A2). Shown the raised surface.
It can be seen that both sides of the copper foil have an “electrolytic deposition surface” shape.

On the other hand, for the active material, silicon-based particles having an average particle diameter of 100 nm were used.

A slurry was prepared by mixing 74% active material, 16% acetylene black powder (AB), 5% styrene butadiene copolymer (SBR), 5% sodium carboxymethylcellulose (CMCNa) with water as a solvent. Next, the slurry is applied to the electrolytic copper foil, the coating film is made into a substantially uniform sheet, dried, compressed by a press machine to closely bond the active material layer on the current collector, and further dried under reduced pressure. A test electrode (negative electrode) was prepared. Thereafter, a negative electrode was punched out to 20φ.

1.3 mol of LiPF ₆ / ethylene carbonate (EC) + ethyl methyl carbonate (EMC) + dimethyl carbonate (DMC) (EC: EMC: DMC) using the above electrode as a negative electrode, a metal lithium foil as a counter electrode, and a reference electrode = 2: 5: 3 (volume ratio)) A triode cell was produced using the solution as an electrolyte.
The negative electrode in this test cell was evaluated at a temperature of 25 ° C. by the following method.

Charge / discharge test method;
C rate calculation The C rate was calculated as follows according to the amount of active material in the test electrode.
Si: 1C = 4,000 mAh / g
Initial condition charging: constant current charging at a current equivalent to 0.1 C, constant potential charging after reaching 0.02 V (vs. Li / Li +), and termination when charging current decreased to 0.05 C equivalent.
Discharge: A constant current was discharged at a current equivalent to 0.1 C, and the discharge was terminated when the voltage reached 1.5V.
Charging / discharging cycle conditions After conducting the initial charging / discharging test, charging / discharging was repeated up to 100 cycles at the same current equivalent to 0.1 C.

Table 1 shows the discharge capacity retention after 10 cycles of charge / discharge, 50 cycles, and 100 cycles for an electrode using this electrolytic copper foil as a negative electrode current collector material.

The post-cycle discharge capacity retention rate is given by the following equation.
(Discharge capacity retention after each cycle%) = [(Discharge capacity after each cycle) / (Maximum discharge capacity)] × 100

<Example 2>
An electrolytic copper foil having a thickness of 11 μm was produced using the first drum under the same conditions as in Example 1. This copper foil was guided to the second drum, and 1 μm of copper electrodeposition was performed on the drum surface side using the same electrolytic solution as that of the first drum to obtain a 12 μm foil.
The electrolytically deposited surface roughness of this copper foil was Rz = 1.2 μm, Ra = 0.3 μm, and the surface of the copper electrodeposited surface on the drum surface was Rz = 1.5 μm, Ra = 0.3 μm. It was. The copper foil has a tensile strength of 310 MPa and an elongation of 9.0%.
Also, an electron micrograph of this electrolytic copper foil is taken, and the electrolytic deposition surface by the first drum is shown in FIG. 4 (A1), and the copper is electroanalyzed by the second drum on the drum surface of the first drum in FIG. 4 (A2). Shown the raised surface.

Next, this copper foil was washed with water and then subjected to cathodic electrolysis on both sides in a chromium trioxide solution in the same manner as in Example 1, washed with water and dried to obtain an electrolytic copper foil for a battery current collector.

The same active material as in Example 1 was applied to this electrolytic copper foil, and a test cell was prepared and evaluated by the same method. The results are also shown in Table 1.

<Example 3>
A copper drum-sulfuric acid electrolyte having the following composition is passed between the titanium drum and the DSA, and a current is passed between the titanium drum and the DSA, with the rotating titanium drum serving as the cathode and a DSA disposed below the DSA. An electrolytic copper foil having a thickness of 11 μm was manufactured.
Electrolyte composition and electrolysis conditions;
Cu = 50 to 150 g / L
H ₂ SO ₄ = 20 to 200 g / L
Chloride ion = 1-60ppm
Sodium 3-mercapto-1-propanesulfonate = 0.5-10ppm
Hydroxyethyl cellulose = 1-30ppm
Low molecular weight gelatin (average molecular weight 3,000) = 1-30 ppm
Temperature = 30-70 ° C
Current density: 30 to 100 A / dm ²
The electrolytic deposition surface roughness of this copper foil was Rz = 1.2 μm, Ra = 0.3 μm, and the drum surface roughness was Rz = 1.4 μm, Ra = 0.4 μm.
This copper foil was guided to the second drum, and 1 μm of copper electrodeposition was performed on the drum surface side using the following electrolytic solution different from the first drum to obtain a 12 μm foil. A copper foil in which the surface of the electrodeposited copper on the drum surface had the shape of an “electrolytically deposited surface” on both surfaces having a roughness of Rz = 1.1 μm and Ra = 0.2 could be obtained. The copper foil has a tensile strength of 310 MPa and an elongation of 8.0%.
Electrolyte composition and electrolysis conditions;
Cu = 50 to 150 g / L
H ₂ SO ₄ = 20 to 200 g / L
Chloride ion = 1-60ppm
Sodium 3-mercapto-1-propanesulfonate = 0.5-10ppm
Polyethylene glycol (average molecular weight 1,000) = 1-30ppm
Temperature = 30-70 ° C
Current density: 30 to 100 A / dm ²
Also, an electron micrograph of this electrolytic copper foil is taken, and the electrolytic deposition surface by the first drum is shown in FIG. 5 (A1), and the copper is electroanalyzed by the second drum on the drum surface of the first drum in FIG. 5 (A2). Shown the raised surface.

Next, after washing this copper foil with water, both sides were subjected to cathodic electrolysis in a chromium trioxide solution in the same manner as in Example 1, washed with water and dried to obtain an electrolytic copper foil for batteries.

<Example 4>
A copper drum-sulfuric acid electrolyte having the following composition is passed between the titanium drum and the DSA, and a current is passed between the titanium drum and the DSA, with the rotating titanium drum serving as the cathode and a DSA disposed below the DSA. An electrolytic copper foil having a thickness of 11 μm was manufactured.
Electrolyte composition and electrolysis conditions;
Cu = 50 to 150 g / L
H ₂ SO ₄ = 20 to 200 g / L
Chloride ion = 1-60ppm
Sodium 3-mercapto-1-propanesulfonate = 0.5-10ppm
Polyethylene glycol (average molecular weight 1,000) = 1-30ppm
Temperature = 30-70 ° C
Current density: 30 to 100 A / dm ²
The electrolytic deposition surface roughness of this copper foil was Rz = 1.2 μm, Ra = 0.3 μm, and the drum surface roughness was Rz = 1.8 μm, Ra = 0.4 μm.
This copper foil was guided to the second drum, and 1 μm of copper electrodeposition was performed on the drum surface side using the following electrolytic solution different from the first drum to obtain a 12 μm foil. The surface of the drum electrode on which the copper electrodeposition was performed was able to obtain a copper foil having the shape of an “electrolytically deposited surface” on both surfaces with Rz = 1.5 μm and Ra = 0.2. The copper foil has a tensile strength of 310 MPa and an elongation of 8.0%.
Electrolyte composition and electrolysis conditions;
Cu = 50 to 150 g / L
H ₂ SO ₄ = 20 to 200 g / L
Chloride ion = 1-60ppm
Sodium 3-mercapto-1-propanesulfonate = 0.5-10ppm
Hydroxyethyl cellulose = 1-30ppm
Low molecular weight gelatin (average molecular weight 3,000) = 1-30 ppm
Temperature = 30-70 ° C
Current density: 30 to 100 A / dm ²
Also, an electron micrograph of this electrolytic copper foil is taken, and the electrolytic deposition surface by the first drum is shown in FIG. 6 (A1), and the copper is electroanalyzed by the second drum on the drum surface of the first drum in FIG. 6 (A2). Shown the raised surface.

<Comparative Example 1>
Using a rotating titanium drum as a cathode and a drum with DSA disposed below it, a copper sulfate-sulfuric acid electrolyte solution having the following composition is passed between the titanium drum and the DSA, and a current is passed between the titanium drum and the DSA to 12 μm. Thick electrolytic copper foil was produced.
Electrolyte composition and electrolysis conditions;
Cu = 50 to 150 g / L
H ₂ SO ₄ = 20 to 200 g / L
Chloride ion = 1-60ppm
Sodium 3-mercapto-1-propanesulfonate = 0.5-10ppm
Hydroxyethyl cellulose = 1-30ppm
Low molecular weight gelatin (molecular weight 3,000) = 1-30ppm
Temperature = 30-70 ° C
Current density: 30 to 100 A / dm ²
The electrolytic deposition surface roughness of this copper foil was Rz = 1.3 μm, Ra = 0.3 μm, and the drum surface roughness was Rz = 1.6 μm, Ra = 0.4 μm.
An electron micrograph of this electrolytic copper foil was taken, and the drum surface was shown in FIG. 7 (X1).

<Comparative example 2>
Using a rotating titanium drum as a cathode and a drum with DSA disposed below it, a copper sulfate-sulfuric acid electrolyte having the following composition is passed between the titanium drum and DSA, and an electric current is passed between the titanium drum and DSA to 12 μm. Thick electrolytic copper foil was produced.
Electrolyte composition and electrolysis conditions;
Cu = 50 to 150 g / L
H ₂ SO ₄ = 20 to 200 g / L
Chloride ion = 1-60ppm
Sodium 3-mercapto-1-propanesulfonate = 0.5-10ppm
Polyethylene glycol (average molecular weight 1,000) = 1-30ppm
Temperature = 30-70 ° C
Current density: 30 to 100 A / dm ²
The electrolytic deposition surface roughness of this copper foil was Rz = 1.3 μm, Ra = 0.3 μm, and the drum surface roughness was Rz = 1.8 μm, Ra = 0.4 μm.
An electron micrograph of this electrolytic copper foil was taken, and the drum surface was shown in FIG. 7 (Y1).

As shown in Table 1 and FIGS. 3 to 6, in the examples of the present invention, both surfaces of the copper foil showed the same surface shape, the electrolytic copper foil was used as a current collector, a negative electrode was manufactured, HEV, EV, It was excellent in satisfying battery performance as a lithium ion secondary battery for automobiles such as PHEV.
On the other hand, in Comparative Examples 1 and 2, since the drum surface is in direct contact with the active material, the charge / discharge efficiency is not preferable, and the results are not satisfactory as lithium ion secondary batteries for automobiles such as HEV, EV, and PHEV. .

The present copper foil is useful as a secondary battery copper foil, particularly as a negative electrode current collector for a lithium ion secondary battery.

11, 12 Titanium drum 14 DSA
16 First electrolytic cell 17 Second electrolytic cell

Claims

In a lithium ion secondary battery comprising a positive electrode, a negative electrode in which an electrode constituent active material layer is formed on the surface of the current collector, and a non-aqueous electrolyte, the current collector constituting the negative electrode is made of an electrolytic copper foil. Both surfaces of the electrolytic copper foil are formed by electrolytic deposition, and the electrolytic deposition surface is a lithium ion secondary battery having a granular crystal structure.
A current collector constituting the negative electrode of a lithium ion secondary battery comprising a positive electrode, a negative electrode having an electrode-constituting active material layer formed on the surface of the current collector, and a non-aqueous electrolyte, The body is made of electrolytic copper foil, and both surfaces of the electrolytic copper foil are formed by electrolytic deposition, and the electrolytic deposition surface is a current collector for a lithium ion secondary battery having a crystalline structure of granular crystals.
An electrolytic copper foil constituting the negative electrode current collector of a lithium ion secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein both sides of the electrolytic copper foil are formed by electrolytic deposition, and the electrolytic deposition surface Is an electrolytic copper foil for a negative electrode current collector of a lithium ion secondary battery, which has a granular crystal structure.
In a lithium ion secondary battery comprising a negative electrode in which an electrode-constituting active material layer is formed on the surfaces of a positive electrode and a current collector and a non-aqueous electrolyte, the current collector constituting the negative electrode is formed by electrolytically depositing copper. An electrolytic copper foil to be formed, wherein the first surface of the electrolytic copper foil is a surface formed by copper electrodeposition of a granular crystal structure on the drum surface, and the second surface opposite to the first surface is The lithium ion secondary battery which is the surface formed by the copper electrodeposition of the crystal structure of a granular crystal on the back side of the 1st surface after film-forming of the 1st surface.
A negative electrode current collector constituting the secondary battery of a lithium ion secondary battery comprising a positive electrode, a negative electrode in which an electrode-constituting active material layer is formed on the surface of the current collector, and a non-aqueous electrolyte, The negative electrode current collector is an electrolytic copper foil formed by electrolytic deposition of copper, and the first surface of the electrolytic copper foil is a surface formed by copper electrodeposition of a granular crystal structure on the drum surface; The second surface opposite to the first surface is a surface formed by copper electrodeposition of a granular crystal structure on the back side of the first surface after the first surface film formation. body.
An electrolytic copper foil for a negative electrode current collector constituting the secondary battery of a lithium ion secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, the electrolytic copper foil being formed by electrolytic deposition of copper A first surface of the electrolytic copper foil is a surface formed by copper electrodeposition of a granular crystal structure on a drum surface, and a second surface opposite to the first surface is a first surface An electrolytic copper foil for a negative electrode current collector for a lithium ion secondary battery, which is a surface formed by copper electrodeposition of a granular crystal structure on the back side of the first surface after surface film formation.