KR20210133270A - Aluminum foil, manufacturing method of aluminum foil, current collector, lithium ion capacitor, and lithium ion battery - Google Patents

Abstract

It makes it a subject to provide the aluminum foil which can make low the electrical resistance by the oxide film of the surface, the manufacturing method of aluminum foil, a collector, a lithium ion capacitor, and a lithium ion battery. An aluminum foil having a plurality of through holes penetrating in a thickness direction, wherein the aluminum foil has an oxide film on its surface, and the oxide film has an intermetallic compound having an element ratio of oxygen to aluminum O/Al of 2 or more and 4 or less, density of 500 pieces/mm ² or more.

Description

Aluminum foil, manufacturing method of aluminum foil, current collector, lithium ion capacitor, and lithium ion battery

This invention relates to an aluminum foil, the manufacturing method of this aluminum foil, and the electrical power collector using this aluminum foil, a lithium ion capacitor, and a lithium ion battery.

In recent years, with the development of portable devices such as personal computers and mobile phones, hybrid vehicles, electric vehicles, etc., the demand for power storage devices as power sources, particularly lithium ion capacitors, lithium ion secondary batteries, and electric double layer capacitors, is increasing. .

It is known that an aluminum plate is used as the current collector for electrodes used for the positive electrode or the negative electrode of such an electrical storage device (hereinafter, simply referred to as a “current collector”). Moreover, it is known to apply|coat an active material, activated carbon, etc. to the surface of the electrical power collector which consists of this aluminum plate as an electrode material, and to use it as an electrode of a positive electrode or a negative electrode.

In a high-capacity next-generation secondary battery, depending on the material of the electrode material, doping the electrode with a large amount of Li (lithium) ions is performed in advance for the purpose of securing the capacity. As the doping method of Li ions, there is known a method in which Li metal is placed in a battery cell and dissolution is promoted in the battery cell, thereby spreading excess Li ions to the electrode. The electrode material is originally a porous material that permeates Li ions. On the other hand, a metal foil is usually used as the current collector serving as a support for the electrode material and as a conductive plate for electric entry and exit during charging and discharging, and allows electricity to pass through but does not pass ions. Therefore, in order to spread Li ions to every corner of the electrode material in a battery cell, the through-foil which provided the metal foil with many through-holes for allowing Li ions to pass is used.

For example, in Patent Document 1, an aluminum substrate and an oxide film laminated on at least one main surface of the aluminum substrate, the density of the oxide film is 2.7 to 4.1 g/cm ³ , and a thickness of 5 nm or less for electrodes An aluminum member is described. It is described that this aluminum member for electrodes has a plurality of through holes penetrating in the thickness direction.

Patent Document 2 discloses an aluminum plate having a plurality of through-holes penetrating in the thickness direction, wherein the average opening diameter of the plurality of through-holes is 0.1 µm or more and 100 µm or less, and the average opening ratio of the plurality of through-holes is 2% or more and 40% or less wherein, among the plurality of through holes, the ratio of through holes having an opening diameter of 5 μm or less is 40% or less, and among the plurality of through holes, the ratio of through holes having an opening diameter of 40 μm or more is 40% or less, and among the plurality of through holes, An aluminum plate in which the ratio S ₁ /S ₀ of the area S _{1 of the through hole to the area S 0} of a circle having the major axis of the through hole as the diameter is 0.1 or more and 1 or less is 50% or more.

Patent Document 1: International Publication No. 2018/062046 Patent Document 2: International Publication No. 2017/018462

Here, the current collector made of aluminum always has an oxide film because the surface is easily oxidized and is oxidized when exposed to the atmosphere. Since the oxide film has high insulating properties, the presence of a thick oxide film on the surface of the current collector increases the electrical resistance.

Then, this invention makes it a subject to provide the aluminum foil which can make low the electrical resistance by the oxide film of the surface, the manufacturing method of aluminum foil, an electrical power collector, a lithium ion capacitor, and a lithium ion battery.

MEANS TO SOLVE THE PROBLEM This invention solves the subject by the following structures.

[1] An aluminum foil having a plurality of through holes penetrating in a thickness direction,

The aluminum foil has an oxide film on the surface,

The oxide film has an intermetallic compound in which the elemental ratio of oxygen to aluminum O/Al is 2 or more and 4 or less,

Aluminum foil with an intermetallic compound density of 500 pieces/mm ^{2 or more.}

[2] The aluminum foil according to [1], wherein the equivalent circle diameter of the intermetallic compound is 1 µm or less.

[3] The aluminum foil according to [1] or [2], wherein the oxide film contains 70% by mass or more of aluminum oxide.

[4] The aluminum foil according to any one of [1] to [3], wherein the surface contact angle of the oxide film is 20° to 80°.

[5] The aluminum foil according to any one of [1] to [4], wherein the through-holes have an average opening diameter of 0.1 µm to 100 µm.

[6] having an unperforated concave having an average opening diameter of 0.1 μm to 100 μm,

The aluminum foil according to any one of [1] to [5], wherein the occupancy of the recess is 1% or more.

[7] A method for producing an aluminum foil for producing the aluminum foil according to any one of [1] to [6],

A through-hole forming step of forming a through-hole in an aluminum substrate;

An alkali treatment step of dissolving the outermost layer by contacting the aluminum substrate with an alkaline aqueous solution;

The manufacturing method of the aluminum foil which has an acid treatment process which makes the said aluminum base material after the said alkali treatment process contact an acidic aqueous solution, and forms an oxide film on the surface of the said aluminum base material.

[8] A current collector using the aluminum foil according to any one of [1] to [6].

[9] A lithium ion capacitor using the current collector according to [8].

[10] A lithium ion battery using the current collector according to [8].

ADVANTAGE OF THE INVENTION According to this invention, the aluminum foil which can make low the electrical resistance by the oxide film of the surface, the manufacturing method of aluminum foil, a collector, a lithium ion capacitor, and a lithium ion battery can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows typically an example of the aluminum foil of this invention.
It is a top view of the aluminum foil shown in FIG.
It is a schematic sectional drawing for demonstrating an example of the suitable manufacturing method of the aluminum foil of this invention.
It is a schematic sectional drawing for demonstrating an example of the suitable manufacturing method of the aluminum foil of this invention.
It is a schematic sectional drawing for demonstrating an example of the suitable manufacturing method of the aluminum foil of this invention.
It is a schematic sectional drawing for demonstrating an example of the suitable manufacturing method of the aluminum foil of this invention.
It is a figure which shows typically the apparatus which measures resistance.
It is an SEM image of the aluminum foil of Example 1. FIG.
9 is a graph showing the relationship between depth and element composition ratio.
10 is a graph showing the relationship between depth and element composition ratio.
11 is a graph showing the relationship between depth and element composition ratio.
12 is a graph showing the relationship between depth and element composition ratio.
13 is an SEM image of the aluminum foil of Comparative Example 3. FIG.
14 is a graph showing the relationship between depth and element composition ratio.
15 is a graph showing the relationship between depth and element composition ratio.
16 is a graph showing the relationship between depth and element composition ratio.

Hereinafter, the present invention will be described in detail.

Although description of the structural requirements described below may be made based on the typical embodiment of this invention, this invention is not limited to such an embodiment.

In addition, in this specification, the numerical range shown using "-" means the range which includes the numerical value described before and after "-" as a lower limit and an upper limit.

[Aluminum Foil]

The aluminum foil of the present invention is

An aluminum foil having a plurality of through holes penetrating in a thickness direction, the aluminum foil comprising:

The aluminum foil has an oxide film on the surface,

The oxide film has an intermetallic compound in which the elemental ratio of oxygen to aluminum O/Al is 2 or more and 4 or less,

It is an aluminum foil in which the density of an intermetallic compound is 500 pieces/mm<^{2> or more.}

Next, the structure of the aluminum foil of this invention is demonstrated using FIG.1 and FIG.2.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing which shows an example of preferable embodiment of the aluminum foil of this invention. FIG. 2 : is a top view of the aluminum foil shown in FIG.

As shown in FIG. 1 , in the aluminum foil 10 , an oxide film 14 is formed on both main surfaces (maximum surfaces) of the aluminum substrate 3 . The oxide film is an aluminum oxide film containing aluminum oxide such as aluminum oxide _{(Al 2} O _{3 ).} Moreover, the aluminum foil 10 has the some through-hole 5 which penetrates the aluminum base material 3 and the oxide film 14 in the thickness direction. That is, the aluminum foil 10 has a structure in which an aluminum substrate 3 having a through hole penetrating in the thickness direction and an oxide film 14 having a through hole penetrating in the thickness direction are laminated.

In addition, in the example shown in FIG. 1, although it was set as the structure formed in the both main surfaces of the aluminum base material 3, the oxide film 14 is not limited to this, The structure formed only in one main surface may be sufficient.

The aluminum foil of this invention is used as a collector, an active material (electrode material) is apply|coated on the surface, and is used as a positive electrode or a negative electrode of an electrical storage device.

When the aluminum foil has a plurality of through holes penetrating in the thickness direction, when used as a current collector, the movement of lithium ions can be facilitated. Moreover, by having a large number of through-holes, adhesiveness with an active material can be improved.

Here, as shown in Fig. 2, in the present invention, the oxide film 14 has a large number of granular intermetallic compounds 16 dispersed in the film. This intermetallic compound 16 has an element ratio of oxygen to aluminum O/Al of 2 or more and 4 or less. Moreover, the density of the intermetallic compound 16 is 500 pieces/mm<^2> or more.

As described above, aluminum is easily oxidized and is oxidized when exposed to the atmosphere, so it always has an oxide film. Since an oxide film has high insulating property, when a thick oxide film exists on the surface of an aluminum base material, there existed a problem that the electrical resistance between an aluminum base material and an active material might increase.

Moreover, although it is conceivable to reduce the electrical resistance by making the thickness of an oxide film thin, there exists a limit also in the reduction of the electrical resistance by thinning of an oxide film, and there existed a problem that it was difficult to further reduce electrical resistance.

On the other hand, in the aluminum foil of the present invention, the oxide film 14 has a large number of granular intermetallic compounds dispersed in the film. The intermetallic compound has an elemental ratio of oxygen to aluminum O/Al of 2 or more and 4 or less. Moreover, the density of an intermetallic compound is 500 pieces/mm<^2> or more.

According to the study of the present inventors, it was found that the intermetallic compound having the element ratio O/Al of 2 or more and 4 or less serves as a starting point for lowering the insulation in the oxide film. By having the intermetallic compound serving as a starting point for lowering the insulating property at a ^{density of 500 pieces/mm 2} or more, the insulating property of the oxide film can be lowered and the electrical resistance of the oxide film can be lowered.

A method of forming an oxide film having an intermetallic compound having an element ratio O/Al of 2 or more and 4 or less ^{at a density of 500/mm 2 or more will be described in detail later.}

Here, the intermetallic compound in this invention is a compound containing aluminum element (Al) and at least 1 sort(s) chosen from Fe, Si, Mn, Mg, Ti, B, etc. Specific examples of the intermetallic compound include Al ₃ Fe, Al ₆ Fe, αAlFeSi, AlFeMnSi, Mg ₂ Si, and TiB ₂ . Among them, since the intermetallic compound containing Al contains Al, a natural oxide film of aluminum is formed on the surface.

Therefore, the surface layer of the intermetallic compound containing Al contains elemental oxygen (O).

Further, in the aluminum foil of the present invention, if the oxide film on the surface of the intermetallic compound has an intermetallic compound having an oxide film having an element ratio O/Al of 2 or more and 4 or less at a ^{density of 500 pieces/mm 2} or more, the oxide film of the outermost layer is an element The ratio O/Al may have an intermetallic compound other than 2 or more and 4 or less. That is, the oxide film of the outermost layer may have an intermetallic compound whose element ratio O/Al is less than 2 or more than 4.

In the following description, the intermetallic compound having an element ratio O/Al of 2 or more and 4 or less in the oxide film of the outermost layer is referred to as the intermetallic compound A, and, similarly, the element ratio O/Al in the oxide film of the outermost layer is less than 2 or more than 4 Let the phosphorus intermetallic compound be intermetallic compound B. Moreover, when it is not necessary to distinguish between the intermetallic compound A and the intermetallic compound B, it is collectively called an intermetallic compound.

In addition, when the oxide film has aluminum oxide (Al ₂ O ₃ ) as a main component and does not contain a hydrate, the element ratio O/Al in the portion other than the intermetallic compound of the oxide film is less than 2, about 1.3 to 1.5 am.

From the viewpoint of lowering the electrical resistance of the aluminum foil, etc., the average value of the element ratio O/Al of the oxide film of the surface layer of the intermetallic compound A is preferably 2 or more and 4 or less, and more preferably 2.5 or more and 3.5 or less. .

In addition, the element ratio O/Al of the outermost layer of an intermetallic compound is measured as follows.

Intermetallic compounds (intermetallic compound A and intermetallic compound B) can be visually recognized by distinguishing from parts other than the intermetallic compound of the oxide film when the surface of the oxide film is observed with a high-resolution scanning electron microscope (SEM). (see FIGS. 8 and 13).

Therefore, first, from the surface of the oxide film, using a high-resolution scanning electron microscope (SEM), the surface of the oxide film is photographed at a magnification of 5000, and in the obtained SEM photograph, at least 20 intermetallic compounds are extracted.

Next, elemental analysis is performed using field emission Auger electron spectroscopy (FE-AES) in the depth direction from the outermost surface at the position of the extracted intermetallic compound. The analysis in the depth direction is performed by repeating measurement and surface removal by sputtering. From the result of the element distribution in the depth direction by FE-AES (refer FIG. 9 etc.), the element ratio O/Al in the outermost layer is calculated|required.

Density in view of which can be lower than the electric resistance of the aluminum foil, the intermetallic compound A is 1000 / mm ² ~ 300000 pieces / mm ² is preferred, and 5000 / mm ² ~ 200000 pieces / mm ² is more preferable.

In addition, the density of the intermetallic compound A is measured as follows.

First, using a high-resolution scanning electron microscope (SEM), the surface of the aluminum foil is photographed from directly above at a magnification of 5000, and the intermetallic compound is extracted with respect to the 1.2 mm × 1.2 mm field of view (5 places) of the obtained SEM photograph. .

Next, the element ratio O/Al of each intermetallic compound extracted by elemental analysis using FE-AES is obtained. By counting the number of intermetallic compounds A having an element ratio O/Al of 2 or more and 4 or less, the number density is calculated from the number of intermetallic compounds A in the field of view and the area (geometric area) of the field of view, and the average value of the field of view in 5 places is calculated as the density.

Here, it is preferable that the equivalent circle diameter of the intermetallic compound A shall be 1 micrometer or less. Intermetallic compounds having an equivalent circle diameter of 1 µm or less are likely to appear on the surface of the aluminum foil. When a small intermetallic compound is expressed on the surface of an aluminum foil, the surface area with respect to the volume of an intermetallic compound becomes large. As a result, it is thought that water molecules are easily adsorbed locally, and the element ratio O/Al of the oxidized intermetallic compound tends to be 2 or more.

In addition, the equivalent circle diameter of intermetallic compound A is obtained by extracting at least 20 intermetallic compounds A whose element ratio O/Al is measured as described above, and using image analysis software or the like to determine the surface of the oxide film of intermetallic compound A. The area is calculated|required, the equivalent circle diameter is calculated|required from this area, and these average values are computed as an equivalent circle diameter.

The oxide film of the outermost layer _{preferably contains 70 mass% or more of aluminum oxide (Al 2} O ₃ ), more preferably contains 80 mass% to 100 mass%, and further contains 90 mass% to 100 mass% desirable.

When the content of the non-hydrate aluminum oxide (Al ₂ O ₃ ) in the oxide film is 70 mass % or more, the density of the oxide film can be made high, so that the oxide film can be suppressed from thickening with time. Therefore, it is preferable at the point which can suppress that an oxide film becomes thick and an electrical resistance increases.

The ratio of aluminum oxide (Al ₂ O ₃ ) in the oxide film can be calculated by measuring the film density of the oxide film as follows.

The film density of the oxide film is measured using a high resolution RBS analyzer HRBS500 (High Resolution Rutherford Backscattering Spectrometry; HR-RBS) manufactured by Kobe Seikosho Corporation. He+ ions with an energy of 450 keV are incident on the sample at 62.5 degrees with respect to the normal of the sample surface (the surface of the oxide film of the aluminum member for electrode), and the scattered He+ ions are detected by a deflection magnetic field energy analyzer at a scattering angle of 55 degrees. get density. The obtained areal density (atoms/cm ² ) is converted into a mass areal density (g/cm ^{2 ), and the oxide film density (g/cm 3} ) is calculated from this value and the film thickness measured with a transmission electron microscope (TEM). do.

The aluminum oxide film is made of non-hydrate aluminum oxide and hydrate aluminum oxide (monohydrate and trihydrate exist), and since the densities are different from each other, the density of the hydrate is conveniently taken as the average of the monohydrate and the trihydrate. The weighted average with the density of , non-hydrate is considered to be the density calculated|required above, and the ratio of non-hydrate aluminum oxide is calculated|required from it.

From the viewpoint of reducing electrical resistance, the thickness of the oxide film is preferably 5 nm or less, more preferably 4.5 nm or less, and still more preferably 4 nm or less.

The average opening diameter of the through-holes is preferably 0.1 µm or more and less than 100 µm, more preferably more than 1 µm and 80 µm or less, still more preferably more than 3 µm and 40 µm or less, and particularly preferably 5 µm or more and 30 µm or less.

By making the average opening diameter of a through hole into the said range, when apply|coating an active material etc. to aluminum foil, it can prevent that a leak etc. generate|occur|produce, and adhesiveness with the apply|coated active material can be improved. Moreover, even when the aluminum foil is set as having a large number of through holes, it can be set as what has sufficient tensile strength.

In addition, the average opening diameter of the through hole is taken from one surface of the aluminum foil using a high-resolution scanning electron microscope (SEM) to photograph the surface of the aluminum foil at a magnification of 200 times. In the SEM photograph obtained, At least 20 through-holes to which the periphery is connected annularly are extracted, the opening diameter is read, and these average values are computed as an average opening diameter.

In addition, the opening diameter measured the maximum value of the distance between the ends of a through-hole part. That is, since the shape of the opening of the through-hole is not limited to a substantially circular shape, when the shape of the opening is non-circular, the maximum value of the distance between the ends of the through-hole portion is the opening diameter. Therefore, for example, even in the case of a through hole having a shape in which two or more through holes are integrated, this is regarded as one through hole, and the maximum value of the distance between the ends of the through hole portions is defined as the opening diameter.

Moreover, it is preferable that it is 0.5 % - 30 %, and, as for the average opening ratio of a through hole, 1 % - 30 % are more preferable, 2 % - 20 % are still more preferable, and 3 % - 10 % are especially preferable.

By making the average opening ratio of the through-holes into the above range, it is possible to prevent leakage or the like from occurring when the active material is applied to the aluminum foil, and the adhesion to the applied active material can be improved. Moreover, even when the aluminum foil is set as having a large number of through holes, it can be set as what has sufficient tensile strength.

In addition, the average aperture ratio of the through-holes is a 30 mm x 30 mm field of view (5 places) of the SEM photograph obtained by photographing the surface of the aluminum foil from directly above using a high-resolution scanning electron microscope (SEM) at a magnification of 200 times. By binarizing with analysis software, etc., the through-hole portion and the non-through-hole portion are observed, and calculated from the ratio (opening area/geometric area) of the sum of the opening areas of the through-holes and the area of the field of view (geometric area), each field of view ( The average value in 5 places) was computed as an average aperture ratio.

Moreover, it is preferable that the aluminum foil has in the surface (oxide film) the recessed part which is not penetrated whose average opening diameter is 0.1 micrometer - 100 micrometers. Moreover, it is preferable that the occupancy (area ratio) of the recessed part in the surface of aluminum foil is 1 % or more.

By having a recessed part, a surface area increases and adhesiveness improves more because the area which closely_contact|adheres to an active material layer increases.

From an adhesive viewpoint, 0.1 micrometer - 100 micrometers are preferable, as for the average opening diameter of a recessed part, 1 micrometer - 50 micrometers are more preferable, 2 micrometers - 30 micrometers are still more preferable.

In addition, the average opening diameter of a recessed part is image|photographed at 200 times magnification of the surface of aluminum foil using a high-resolution scanning electron microscope (SEM) from one surface of aluminum foil, In the SEM photograph obtained, the circumference|surroundings are annular At least 20 concave portions (pits) of the concave-convex structure connected by . were extracted, the maximum diameter was read, and it was set as the opening diameter, and these average values were computed as an average opening diameter. Let the maximum diameter be the largest value among the linear distances between one edge part which comprises the opening part of a recessed part. For example, when the concave portion is circular, it refers to the diameter, when the concave portion is elliptical, refers to the long diameter. It is the maximum value of the distance.

Moreover, it is preferable that it is 1 % or more, and, as for the occupancy of a recessed part from an adhesive viewpoint, it is more preferable that it is 2 % - 5 %, It is more preferable that it is 5 % - 10 %.

In addition, the occupancy of the concave part was taken from directly above the surface of the aluminum foil at a magnification of 200 times using a high-resolution scanning electron microscope (SEM), and 30 mm × 30 mm field of view (5 places) of the obtained SEM photograph, image analysis software Observe the concave portion and the non-recessed portion by binarizing it with the following method, and calculate the ratio (open area/geometric area) of the sum of the opening areas of the concave and the area of the field of view (geometric area), and each field of view (5 places) The average value in , was calculated as the occupancy rate.

Moreover, it is preferable that the water contact angle of the surface of aluminum foil, ie, the surface of an oxide film, is 20 degrees - 80 degrees.

An electrode material is applied to the surface of the aluminum foil used as an electrical power collector, and it is used as an electrode. Usually, an electrode material makes an aqueous solvent into a slurry form, and is apply|coated to an electrical power collector. When a water-based electrode material is applied, in order to suppress aggregation of the electrode material and improve the applicability, the surface is subjected to a hydrophilic treatment to make it hydrophilic (that is, to reduce the water contact angle) (e.g., reducing the water contact angle). For example, International Publication No. 2011/089722).

However, according to the studies of the present inventors, when the water contact angle on the surface of the aluminum foil is excessively small, that is, when the affinity with water is high, moisture in the air is easily adsorbed, so that moisture is easily supplied to the oxide film. . When moisture is supplied to the oxide film, the oxide film tends to grow, and as a result, it has been found that the electrical resistance tends to deteriorate with time.

On the other hand, by setting the water contact angle on the surface of the aluminum foil (the surface of the oxide film) to 20° or more, the growth of the oxide film by adsorption of moisture can be suppressed, and deterioration of electrical resistance with time can be suppressed. The water contact angle of the surface of the aluminum foil (the surface of the oxide film) is preferably 40° or more, and more preferably 50° or more.

Moreover, when the water contact angle of the surface (surface of an oxide film) of aluminum foil is too high, when a water-based electrode material is apply|coated, there exists a possibility that the problem that aggregation on the surface cannot perform uniform application|coating may arise. On the other hand, when the water contact angle of the surface (surface of an oxide film) of aluminum foil shall be 80 degrees or less, the applicability|paintability of an electrode material can be improved. The water contact angle of the surface of the aluminum foil (the surface of the oxide film) is preferably 70° or less.

The water contact angle is measured by the droplet method in which water droplets are attached in the air to obtain the water contact angle. A static contact angle is good for the measuring method of a water contact angle, and in the case of a measuring method of a static contact angle, a droplet method can be used.

As an example, the static method described in "JISR3257:1999 Wettability Test Method of Substrate Glass Surface" can be used for the measurement of the water contact angle. The water contact angle can be measured, for example, by a portable contact angle meter PCA-1 (Kyowa Kaimen Chemical Co., Ltd.).

<Aluminum base material>

The aluminum base material used as the base material of aluminum foil is not specifically limited, For example, well-known aluminum base materials, such as alloy number 1N30 and 3003 described in JIS standard H4000, can be used. Although aluminum containing many intermetallic compounds is preferable, this application is not limited to an aluminum material. In addition, an aluminum base material has aluminum as a main component, and is an alloy plate containing a trace amount of two elements.

In order for the density of the intermetallic compound A having an element ratio O/Al of 2 or more and 4 or less in the oxide film formed on the surface of the aluminum substrate to be 500/mm ² or more, the aluminum substrate contains 500 intermetallic compounds/mm ² more than that, it is more desirable to have preferable, and 1000 / mm ² or more pieces 200,000 / mm ² or less, and more preferably has, 3000 / mm ² or more pieces 300,000 / mm ² or less with.

The equivalent circle diameter of the intermetallic compound having an element ratio O/Al of 2 or more and 4 or less contained in the aluminum substrate is preferably 1 µm or less.

Although there is no limitation as thickness of an aluminum base material, 5 micrometers - 100 micrometers are preferable, and 10 micrometers - 30 micrometers are more preferable.

[Method for producing aluminum foil]

Next, the manufacturing method of the aluminum foil of this invention is demonstrated.

The manufacturing method of the aluminum foil of this invention,

a through-hole forming step of forming a through-hole;

An alkali treatment step of dissolving the outermost surface by contacting the aluminum substrate after the film forming step with an alkaline aqueous solution;

It is a manufacturing method of aluminum foil which has an acid treatment process in which the aluminum base material after an alkali treatment process is made to contact with an acidic aqueous solution, the residue on the surface of an aluminum base material is removed, and the natural oxide film which generate|occur|produces after that turns into a non-hydrate.

By the acid treatment process, a film mainly composed of aluminum oxide having an element ratio of O/Al of 1 to 2 is formed on most of the surface of the aluminum substrate, and an oxide film having an element ratio of O/Al of 2 or more and 4 or less is formed on the surface of the intermetallic compound this is formed In addition, during the acid treatment process, by using an acidic aqueous solution containing nitric acid as the acidic aqueous solution, a film mainly composed of aluminum oxide having an element ratio of 1 to 2 O/Al on the surface of the aluminum substrate is formed, while intermetallic compounds An oxide film having an element ratio O/Al of 2 or more and 4 or less can be suitably formed on the surface of .

In addition, the alkali treatment process removes unnecessary film, oil, etc. before the acid treatment process, exposes the aluminum substrate, and facilitates the formation of an oxide film.

In the through-hole forming step, a known method such as a method using electrolysis or a method of forming a hole mechanically can be applied.

Moreover, it is preferable to have a water washing process which performs a water washing process after completion|finish of each process of an alkali treatment process, an acid treatment process, and a through-hole formation process.

Moreover, it is preferable to have a drying process of performing a drying process after the water washing process after each process.

Here, it is preferable to perform the drying process after the water washing process after an acid treatment process using high temperature wind of more than 200 degreeC and 350 degrees C or less for an aluminum base material. By carrying out the drying step after the acid treatment step under these conditions, the element ratio O/Al of most oxide films of the aluminum substrate becomes 1 or more and less than 2, and an oxide film having an element ratio O/Al of 2 or more and 4 or less on the surface of the intermetallic compound. It is preferable because it becomes easy to form.

Hereinafter, taking the aluminum foil which has a through hole shown in FIG. 1 as an example, and after demonstrating each process of the manufacturing method of an aluminum foil using FIGS. 3-6, each process is demonstrated in detail.

3-6 are schematic cross-sectional views which show an example of suitable embodiment of the manufacturing method of an aluminum foil.

In the method for manufacturing an aluminum foil, as shown in Figs. 3 to 6, a film forming process is performed on both main surfaces of the aluminum substrate 1 to form a film 2 such as aluminum hydroxide ( 3 and 4 ) and an electrolytic dissolution treatment after the film forming step to form a through hole 5 , and a through hole for forming the aluminum substrate 3 having the through hole and the coating film 4 having the through hole The forming process (FIGS. 4 and 5), the alkali treatment process process (FIG. 5 and FIG. 6) of dissolving and removing the outermost layer including the film 4 having the through-holes after the through-hole forming process (FIGS. 5 and 6), and alkali treatment It is a manufacturing method which has an acid treatment process (FIG. 6 and FIG. 1) of performing acid treatment after a process and forming oxide films on both main surfaces of the aluminum base material 3 which has a through hole.

[Through hole forming process]

The through hole forming step is a step of forming a through hole in the aluminum substrate.

There is no restriction|limiting in particular in the formation method of the through-hole in a through-hole forming process, A mechanical method, such as a punching process, or an electrochemical method, such as an electrolytic dissolution process, can be used.

Since the through-holes with an average opening diameter of 0.1 micrometer - 100 micrometers can be formed easily, the formation method of the through-hole by electrolytic dissolution treatment is suitable.

In the through-hole forming step of performing electrolytic dissolution treatment, after the pre-film forming step of forming a heterogeneous film, an aluminum substrate is used as an anode, and an electrolytic treatment (electrolytic dissolution treatment) is performed with a third acidic aqueous solution (electrolytic dissolution treatment), the aluminum substrate and This is a process of forming a through hole in the aluminum hydroxide film. The kind of the film is not particularly limited as long as it can form a difference between a place that is easily penetrated and a place that is easily penetrated by dissolving during the electrolytic treatment.

<Electrolytic dissolution treatment>

The electrolytic dissolution treatment is not particularly limited, and direct current or alternating current may be used, and an acidic solution (second acidic aqueous solution) may be used as the electrolytic solution. Among them, it is preferable to perform the electrochemical treatment using at least one or more acids of nitric acid and hydrochloric acid, and in addition to these acids, it is more preferable to perform the electrochemical treatment using a mixed acid of at least one or more of sulfuric acid, phosphoric acid and oxalic acid. do.

In the present invention, as an acidic solution that is an electrolyte, in addition to the above acids, U.S. Patent Nos. 4,671,859, 4,661,219, 4,618,405, 4,600,482, 4,566,960, 4,566,958, 4,566,959 The electrolytes described in the specifications of Nos. 4,416,972, 4,374,710, 4,336,113, and 4,184,932 can also be used.

It is preferable that it is 0.1-2.5 mass %, and, as for the density|concentration of an acidic solution, it is especially preferable that it is 0.2-2.0 mass %. Moreover, it is preferable that it is 20-80 degreeC, and, as for the liquid temperature of an acidic solution, it is more preferable that it is 30-60 degreeC.

The above-mentioned acid-based aqueous solution is an aqueous solution of an acid having a concentration of 1 to 100 g/L, a nitrate compound having nitrate ions such as aluminum nitrate, sodium nitrate, ammonium nitrate, or aluminum chloride, sodium chloride, ammonium chloride, etc. At least one of a hydrochloric acid compound having a hydrochloric acid ion and a sulfuric acid compound having a sulfate ion such as aluminum sulfate, sodium sulfate, and ammonium sulfate can be added and used in a range from 1 g/L to saturation.

Moreover, the metal contained in aluminum alloys, such as iron, copper, manganese, nickel, titanium, magnesium, and a silica, may be melt|dissolved in the aqueous solution which has the said acid as a main body. Preferably, it is preferable to use the liquid which added aluminum chloride, aluminum nitrate, aluminum sulfate, etc. so that the aluminum ion might become 1-100 g/L to the aqueous solution with an acid concentration of 0.1-2 mass %.

Although direct current is mainly used for electrochemical dissolution treatment, when alternating current is used, the alternating current power wave is not specifically limited, A sine wave, a rectangular wave, trapezoid wave, a triangular wave, etc. are used, Among them, a rectangular wave or trapezoid wave is preferable, and a trapezoidal wave is particularly preferable.

(Nitrate electrolysis)

In the present invention, through-holes having an average opening diameter of 0.1 µm to 100 µm can be easily formed by electrochemical dissolution treatment (hereinafter also abbreviated as “nitric acid dissolution treatment”) using an electrolyte solution mainly composed of nitric acid. can

Here, the nitric acid dissolution treatment uses a direct current for the reason that it is easy to control the dissolution point of the through hole formation, an average current density of 5 A/dm ² or more, and an electric quantity of 50 C/dm ² or more. It is preferable that it is an electrolytic treatment performed under conditions. In addition, the average current density ^{is preferably 100 A/dm 2} or less, and the amount of electricity is preferably 10000 C/dm ² or less.

The concentration and temperature of the electrolyte in the nitric acid electrolysis are not particularly limited, and the electrolysis is performed at 30 to 60°C using a high concentration, for example, a nitric acid electrolyte having a nitric acid concentration of 15 to 35% by mass, or a nitric acid concentration of 0.7 Electrolysis can be performed at a high temperature, for example, 80° C. or higher, using ˜2 mass % of a nitric acid electrolyte.

In addition, electrolysis may be performed using an electrolyte in which at least one of sulfuric acid, oxalic acid, and phosphoric acid having a concentration of 0.1 to 50% by mass is mixed with the nitric acid electrolyte.

(hydrochloric acid electrolysis)

In the present invention, even by electrochemical dissolution treatment (hereinafter, also abbreviated as "hydrochloric acid dissolution treatment") using an electrolytic solution mainly containing hydrochloric acid, through-holes having an average opening diameter of 0.1 µm to 100 µm can be easily formed. can

Here, the hydrochloric acid dissolution treatment uses direct current for the reason that it is easy to control the dissolution point of through-hole formation, the average current density is 5 A/dm ² or more, and the electric quantity is 50 C/dm ² or more. It is preferable that it is an electrolytic treatment performed under conditions. In addition, the average current density ^{is preferably 100 A/dm 2} or less, and the amount of electricity is preferably 10000 C/dm ² or less.

In addition, the concentration and temperature of the electrolytic solution in the hydrochloric acid electrolysis are not particularly limited, and electrolysis is performed at 30 to 60°C using a hydrochloric acid electrolytic solution having a high concentration, for example, a hydrochloric acid concentration of 10 to 35 mass%, or a hydrochloric acid concentration of 0.7 Electrolysis can be performed at a high temperature, for example, 80° C. or higher, using ˜2% by mass of hydrochloric acid electrolyte.

In addition, the electrolysis may be performed using an electrolyte in which at least one of sulfuric acid, oxalic acid, and phosphoric acid having a concentration of 0.1 to 50% by mass is mixed with the hydrochloric acid electrolyte.

[Alkali treatment process]

The alkali treatment step is a step of dissolving (removing) the outermost layer of the aluminum substrate by performing a chemical dissolution treatment using an alkaline aqueous solution. In addition, when the through-hole is formed in the electrolytic treatment, the residue or film remaining on the surface is temporarily removed. At that time, since the dissolution rate of the intermetallic compound in the surface layer of the aluminum substrate in alkaline aqueous solution is slower than that in the aluminum substrate, by appropriately selecting the treatment conditions, the intermetallic compound is slightly raised on the surface layer of the aluminum substrate. can be left on the surface.

The said alkali treatment process can melt|dissolve (remove) the outermost layer of an aluminum base material by performing the alkali etching process mentioned later, for example.

<Alkaline etching treatment>

The alkali etching treatment is a treatment for dissolving the surface layer by bringing the aluminum substrate into contact with an aqueous alkaline solution.

As an alkali used for alkaline aqueous solution, caustic alkali and alkali metal salt are mentioned, for example. Specific examples of the caustic alkali include sodium hydroxide (caustic soda) and caustic potassium. Moreover, as an alkali metal salt, For example, alkali metal silicates, such as sodium metasilicate, sodium silicate, potassium metasilicate, and potassium silicate; alkali metal carbonates such as sodium carbonate and potassium carbonate; alkali metal aluminates, such as sodium aluminate and potassium aluminate; alkali metal aldonic acid salts such as sodium gluconate and potassium gluconate; and alkali metal hydrogen phosphate salts such as sodium dibasic, potassium dibasic, sodium triphosphate, and potassium triphosphate. Among them, a solution of caustic alkali and a solution containing both caustic alkali and alkali metal aluminate are preferable from the viewpoint of a high etching rate and low cost. In particular, an aqueous solution of sodium hydroxide is preferred.

It is preferable that it is 0.1-50 mass %, and, as for the density|concentration of alkaline aqueous solution, it is more preferable that it is 0.2-10 mass %. When aluminum ion is melt|dissolving in alkaline aqueous solution, it is preferable that it is 0.01-10 mass %, and, as for the density|concentration of aluminum ion, it is more preferable that it is 0.1-3 mass %. It is preferable that the temperature of an alkali solution is 10-90 degreeC. It is preferable that processing time is 1-120 second.

As a method of bringing the aluminum substrate into contact with the alkali solution, for example, a method of passing the aluminum substrate through a tank containing an alkali solution, a method of immersing the aluminum substrate in a bath containing an alkali solution, and an alkali solution of the aluminum substrate The method of spraying on the surface is mentioned.

[acid treatment process]

In the acid treatment step, an aluminum substrate is brought into contact with an acidic aqueous solution (a first acidic aqueous solution) to form an oxide film having an element ratio O/Al of 1 or more and less than 2 on the surface to the back surface of the aluminum substrate, and an element is formed on the surface of the intermetallic compound. This is a step of forming an oxide film having a ratio O/Al of 2 or more and 4 or less.

As described above, an oxide film having an element ratio O/Al of 1 or more and less than 2 is formed on most of the surface of the aluminum substrate, and on the surface of the ^{intermetallic compound present at 500 pieces/mm 2} or more, the element ratio O/Al is 2 By forming an oxide film of 4 or less, the insulating property of the oxide film can be lowered using this intermetallic compound as a starting point, and the electrical resistance of the oxide film can be reduced.

In the acid treatment process, by washing the surface of the aluminum substrate with an acidic aqueous solution, the residue formed in the alkali treatment process is removed, and the natural oxide film formed on the surface of the aluminum substrate is made a passivation film mainly composed of aluminum oxide. can

Here, since the intermetallic compound which consists of aluminum, Fe, Si, etc. which the aluminum base material contains contains an aluminum element, an oxide film is formed. In that case, as described above, since the intermetallic compound is in a state in which the intermetallic compound is slightly raised on the surface layer of the aluminum substrate by the alkali treatment step, the ratio of the area exposed to the volume of the intermetallic compound becomes large. As a result, it was found that in the oxide film formed on the surface of the intermetallic compound, the element ratio of oxygen O to aluminum Al = O/Al becomes large. This is considered to be because the surface area of the intermetallic compound is large, so that it does not become a uniform passivation of aluminum oxide over the entire surface, and for example, water molecules are easily adsorbed locally. Therefore, an oxide film having ^{500 pieces/mm 2} or more of the intermetallic compound A having an element ratio O/Al of 2 or more and 4 or less can be formed.

As the acidic aqueous solution (first acidic aqueous solution) used in the acid treatment step, it is preferable to use nitric acid, sulfuric acid, phosphoric acid, oxalic acid, or a mixed acid of two or more thereof, and it is more preferable to use an acidic aqueous solution containing nitric acid.

It is preferable that it is 0.01-10 mass %, and, as for the density|concentration of an acidic aqueous solution, it is especially preferable that it is 0.1-5 mass %. Moreover, it is preferable that it is 25-70 degreeC, and, as for the liquid temperature of an acidic aqueous solution, it is more preferable that it is 30-55 degreeC.

Moreover, the method of making an aluminum base material contact an acidic aqueous solution is not specifically limited, For example, the immersion method and the spray method are mentioned. The spray method is preferable because liquid replacement on the aluminum surface is easy.

The immersion method is a process in which an aluminum base material is immersed in the acidic solution mentioned above. When stirring is performed at the time of an immersion process, since the process without non-uniformity is performed, it is preferable.

It is preferable that it is 15 second or more, as for the time of an immersion process, it is more preferable that it is 30 second or more, It is more preferable that it is 40 second or more.

[Washing process]

As described above, in the present invention, it is preferable to have a water washing step of performing a water washing treatment after each step of the alkali treatment step, the acid treatment step, and the through hole forming step is completed. For washing with water, pure water, well water, tap water, or the like can be used. In order to prevent carrying-in to the next process of a processing liquid, you may use a nip apparatus.

[drying process]

As mentioned above, it is preferable to have a drying process of performing a drying process after the water washing process after each process.

There is no limitation in the method of drying, Well-known drying methods, such as the method by which water|moisture content is blown off with an air knife etc., and the method by heating, can be used suitably. Moreover, you may perform a some drying method.

Here, it is preferable to have a water washing process of washing an aluminum base material with water after an acid treatment process, and it is preferable to have a drying process after the water washing process after an acid treatment process. In that case, it is preferable that a drying process is a process of heating by hitting the hot air of more than 200 degreeC and 350 degrees C or less on the surface of an aluminum base material.

After forming an oxide film on the surface of the aluminum substrate in the acid treatment step, a water washing step is performed to remove the acidic aqueous solution remaining on the surface of the aluminum substrate (oxide film), and further, in the drying step of removing the water film attached in the water washing step In this, by heating the aluminum substrate to more than 200 ° C. to 350 ° C. or less, an oxide film having an element ratio O / Al of 1 or more and less than 2 is formed on the surface of the aluminum substrate, and on the surface of the intermetallic compound, an element ratio O / Al is 2 or more An oxide film of 4 or less can be suitably formed.

Hot air temperature has preferable 180 degreeC - 350 degreeC, and, as for the heating temperature in the drying process after an acid treatment process, 240 degreeC - 300 degreeC are more preferable. Moreover, 1 to 30 second is preferable and, as for drying time, 3 to 10 second is more preferable.

Here, the water contact angle of the surface (surface of an oxide film) of the aluminum foil produced in the manufacturing method of this invention receives the influence of the formation method of a through hole. Therefore, you may implement the process of adjusting a water contact angle according to the water contact angle of the surface (surface of an oxide film) of the aluminum foil after preparation (after an acid treatment process). In addition, when the water contact angle of the surface (the surface of the oxide film) of the aluminum foil after production (after the acid treatment step) is 20° to 80°, the hydrophilization treatment is performed after the formation of the oxide film (after the acid treatment step). It is preferable not to Moreover, it is preferable not to perform a hydrophilization process after preparation of an aluminum foil until apply|coating an electrode material.

[Current collector]

As described above, the aluminum foil of the present invention can be used as a current collector for an electrical storage device (hereinafter, also referred to as a “current collector”).

In the current collector, since the aluminum foil has a plurality of through holes in the thickness direction, for example, when used for a lithium ion capacitor, lithium pre-doping in a short time is possible, and lithium can be more uniformly dispersed. becomes Moreover, adhesiveness with an active material layer and activated carbon becomes favorable, and the electrical storage device excellent in productivity, such as cycling characteristics, an output characteristic, and application|coating suitability, can be produced.

Moreover, since the electrical resistance of an oxide film is low in the electrical power collector using the aluminum foil of this invention, the electrical resistance between an active material layer becomes low, and an efficient electrical storage device can be produced.

<Active material layer>

There is no limitation in particular as an active material layer, The well-known active material layer used in the conventional electrical storage device can be used.

Specifically, in the case of using an aluminum foil as a current collector of a positive electrode, the active material and the conductive material, binder, solvent, etc. which may be contained in the active material layer are disclosed in Japanese Patent Application Laid-Open No. 2012-216513 [0077] to [0088] Materials described in the paragraphs may be appropriately employed, the content of which is incorporated herein by reference.

In addition, for the active material in the case of using aluminum foil as a collector of a negative electrode, the material described in the paragraph of Unexamined-Japanese-Patent No. 2012-216513 can be suitably employ|adopted, The content is incorporated by reference in this specification. .

[Power storage device]

The electrode using the aluminum foil of this invention as an electrical power collector can be used as a positive electrode or a negative electrode of electrical storage devices, such as a lithium ion battery and a lithium ion capacitor.

Here, for the specific configuration and application of the electrical storage device (especially the secondary battery), the materials and uses described in paragraphs [0090] to [0123] of Japanese Patent Application Laid-Open No. 2012-216513 can be appropriately employed, and the The content is incorporated herein by reference.

[Positive Pole]

The positive electrode using the aluminum foil of the present invention as a current collector is a positive electrode having a positive electrode current collector using an aluminum foil as a positive electrode, and a layer (positive electrode active material layer) containing a positive electrode active material formed on the surface of the positive electrode current collector.

Here, for the positive electrode active material, the conductive material, binder, solvent, etc. that may be contained in the positive electrode active material layer, the materials described in paragraphs [0077] to [0088] of Japanese Patent Application Laid-Open No. 2012-216513 may be appropriately employed. , the contents of which are incorporated herein by reference.

[Negative pole]

The negative electrode using the aluminum foil of the present invention as a current collector is a negative electrode having a negative electrode current collector using an aluminum foil as a negative electrode, and a layer containing a negative electrode active material formed on the surface of the negative electrode current collector.

Here, for the said negative electrode active material, the material described in the paragraph of Unexamined-Japanese-Patent No. 2012-216513 can be employ|adopted suitably, The content is integrated in this specification as a reference.

[Other uses]

The aluminum foil of the present invention can also be used as a current collector for an electrolytic capacitor.

Example

The present invention will be described in more detail below based on examples. Materials, amounts of use, ratios, processing contents, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Accordingly, the scope of the present invention should not be construed as being limited by the Examples shown below.

[Examples 1 and 2 and Comparative Examples 1-3]

<Preparation of aluminum substrate>

Aluminum substrates A1 and A2 containing an intermetallic compound with an equivalent circle diameter of 1 µm or less, and an aluminum substrate B containing no intermetallic compound with an equivalent circle diameter of 1 µm or less were prepared.

Aluminum base A1 is made by dissolving aluminum metal of 99.90% purity of Al, casting aluminum with 2% Fe added by DC (Direct Chill) casting method, and then hot rolling and cold rolling to a final plate thickness of 20 μm. It is an aluminum base. In order to adjust intensity|strength, it heat-processed when the plate|board thickness was 2 mm in the middle of cold rolling.

Aluminum base A2 is an aluminum base material which melt|dissolved the aluminum metal of 99.90% of Al purity, cast aluminum to which 0.5% of Fe was added by continuous casting method, and finished cold rolling to the final plate|board thickness of 20 micrometers. In order to adjust intensity|strength, it heat-processed when the plate|board thickness was 2 mm in the middle of cold rolling.

The aluminum base B is an aluminum base which is finished to a final plate thickness of 20 µm by hot rolling and cold rolling in the same manner as in the aluminum base A1 after casting an aluminum metal having an Al purity of 99.90% by a DC casting method.

Each of the aluminum substrates was subjected to the through-hole forming process 1 and/or the through-hole forming process 2 shown below to form a through-hole.

<Processing of forming a through hole 1>

(a-1) Heterogeneous film formation process

As a pretreatment, electrolysis was performed with an acidic solution containing aluminum ions in the liquid to precipitate aluminum hydroxide having a thickness of 1 µm or more. This results in an inhomogeneous film.

(b-1) Electrolytic dissolution treatment (through hole formation step)

Next, using an electrolyte solution kept at 50°C (nitric acid concentration 2%, sulfuric acid concentration 2%, aluminum concentration 1%), the aluminum substrate is used as an anode and electrolytic treatment is performed, and the through-holes are formed in the aluminum substrate and the aluminum hydroxide film. has formed In addition, the electrolytic treatment was performed with a DC power supply. The current density was adjusted so that the aperture ratio was about 4%.

After formation of the through hole, water washing by spraying was performed.

(c-1) alkali treatment process

Next, the aluminum substrate after electrolytic dissolution treatment was sprayed with an aqueous solution (solution temperature of 37°C) having a sodium hydroxide concentration of 10% by mass and an aluminum ion concentration of 5% by mass to remove residues.

After removal of the aluminum film, water washing by spraying was performed.

(d-1) acid treatment process

Next, the aluminum substrate after the alkali treatment step was sprayed with an aqueous solution having a nitric acid concentration of 10% and an aluminum ion concentration of 5% by mass (solution temperature of 50°C) for 5 seconds to form an oxide film on the surface of the aluminum substrate.

Then, water washing by spraying was performed.

(e-1) drying process

Next, the water remaining on the surface of the aluminum substrate washed with water while forming an oxide film was removed with an air knife, and dried again by heating with hot air at a drying temperature of 300°C to prepare an aluminum foil.

In addition, the through-holes formed in the through-hole formation process 1 are generally formed with an opening ratio of 4.0%, an average hole diameter of 10 micrometers, and a density of ^{100 pieces/mm<2>.}

<Processing of forming a through hole 2>

A through hole having an opening ratio of 10% and an average hole diameter of 250 µm was formed on the surface mechanically. An oxide film by natural oxidation is formed on the surface of the aluminum substrate in which the through-holes are formed by the through-hole forming process 2 .

Table 1 shows the type of the aluminum substrate and the type of the through-hole forming treatment used in each of Examples and Comparative Examples.

[evaluation]

<Initial resistance value>

On one surface of the aluminum foil 10 produced in each Example and Comparative Example, a conductive material "Varny Height" in which carbon particles are dispersed in an aqueous solvent is applied with an applicator, and dried at 130° C. for 15 minutes to form a carbon layer ( 106) was formed. Next, as shown in FIG. 7, the aluminum foil 100 in which the carbon layer 106 is formed is sandwiched between the pressurized conductive-only terminal 102 and the pressurized insulated terminal 104, and the resistance measuring instrument 100 (hi Resistance was measured with 1 sample N=7 using HIOKI3541 by Oki Corporation.

The initial resistance value determined A, 20 mΩ or more and less than 30 mΩ as A, B, 30 mΩ or more and less than 35 mΩ as C, and 35 mΩ or more as D.

<Evaluation of resistance over forced passage>

The aluminum foils prepared in Examples and Comparative Examples were stored in an environment of 30°C and 80% humidity, and the resistance after 1 week, 2 weeks, 3 weeks, and 4 weeks was measured by the above resistance value measurement method, respectively. did.

Forced aging resistance is A if the resistance value after 4 weeks of maintenance is within 50mΩ, within 50mΩ after 3 weeks of maintenance, B if it exceeds 50mΩ after 4 weeks of maintenance, and within 50mΩ after 2 weeks of maintenance C, 2 if it exceeds 50mΩ after 3 weeks of maintenance If it exceeded 50 mΩ after weekly maintenance, it was determined as D.

A result is shown in Table 1.

[Table 1]

In the following, the surface (the surface of the oxide film) of the portion in which the through-holes are not formed in Examples 1 and 3 is SEM observation using FE-AES (manufactured by Nippon Electronics Co., Ltd.), and The result of performing element distribution from the surface toward the depth direction is illustrated.

An example of the SEM image of Example 1 is shown in FIG. 8, the oxide film has many granular intermetallic compounds. In Fig. 8, intermetallic compounds are denoted by IMC1 and IMC2, and portions other than the intermetallic compound are denoted by A11 and A12.

9 to 12 show the results of elemental analysis in the depth direction for portions of IMC1, IMC2, A11 and A12 in FIG. 8, respectively.

Fig. 9 is a result of elemental analysis of a portion of IMC1. This intermetallic compound had an equivalent circle diameter of 3 μm or more. 10 is a result of elemental analysis of a portion of IMC2. This intermetallic compound had an equivalent circle diameter of 1 μm or less. 11 is a result of elemental analysis of Al1. 12 is a result of elemental analysis of a portion of Al2.

9-12, it turns out that there is no big difference in the thickness of an oxide film in any position.

It turns out that the element ratio O/Al of the outermost layer in the part of IMC1 of FIG. 9, the part of Al1 of FIG. 11, and the part of Al2 of FIG. 12 is 2 or less. On the other hand, it turns out that the element ratio O/Al of the outermost layer in the part of IMC2 of FIG. 10 is 2 or more and 4 or less. That is, in the example of the SEM image shown in FIG. 8, the part of IMC1 corresponds to the intermetallic compound B, and the part of IMC2 corresponds to the intermetallic compound A.

As a result of performing such elemental analysis and finding the density of the intermetallic compound A by the method described above, it was 110000 pieces/mm ² .

The example of the SEM image of the comparative example 3 is shown in FIG. 13, the oxide film has a granular intermetallic compound. In Fig. 13, the intermetallic compound is denoted by IMC3, and portions other than the intermetallic compound are denoted by A13 and A14.

14 to 16 show the results of elemental analysis in the depth direction for portions of IMC3, A13, and A14 in FIG. 13, respectively.

Fig. 14 is a result of elemental analysis of a portion of IMC3. This intermetallic compound had an equivalent circle diameter of 1 µm or more. 15 is a result of elemental analysis of a portion of Al3. 16 is a result of elemental analysis of a portion of Al4.

14-16, it turns out that there is no large difference in the thickness of an oxide film in any position.

It turns out that the element ratio O/Al of the outermost layer in the part of IMC3 of FIG. 14, the part of Al3 of FIG. 15, and the part of Al4 of FIG. 16 is 2 or less all. That is, in the example of the SEM image shown in FIG. 13, the part of IMC3 corresponds to the intermetallic compound B. In Comparative Example 3, the intermetallic compound A having an element ratio O/Al of 2 or more and 4 or less in the outermost layer could not be observed.

Table 2 shows the results of elemental analysis.

[Table 2]

^{From Tables 1 and 2, the aluminum foil of the present invention having an oxide film having 500 pieces/mm 2} or more of intermetallic compound A having an element ratio of O/Al of 2 or more and 4 or less, compared with Comparative Example, the initial resistance and resistance over time It can be seen that the low

[Comparative Examples 4 and 5]

An aluminum foil was produced using the method described in Example 5 and Example 11 of International Publication No. 2017/018462, respectively.

Comparative Example 4 is an example in which an aluminum substrate containing a small amount of intermetallic compound is used, and Comparative Example 5 is an example in which an aluminum substrate containing a small intermetallic compound is used.

[Example 3]

An aluminum foil was produced in the same manner as in Example 1, except that the treatment conditions of the through-hole forming step were changed in order to have substantially the same through-hole physical properties (average opening diameter and average opening ratio) as those of Comparative Examples 4 and 5.

[evaluation]

It carried out similarly to the above, and the initial resistance value and the resistance value after forced aging for 4 weeks were measured. In the same manner as above, using FE-AES, SEM observation and element distribution were performed from the outermost surface of the surface oxide film toward the depth direction to determine the density of the intermetallic compound A. In addition, with respect to the film thickness of the oxide film, the initial value and the value after forced aging for 4 weeks were obtained. In addition, the density (initial value) of the oxide film was also obtained.

Table 3 shows the treatment conditions and the like, and Table 4 shows the results.

[Table 3]

[Table 4]

As shown in Table 3, Comparative Example 4 and Comparative Example 5 differ in the type of the aluminum substrate, the type of acid used in the acid treatment step, and the temperature in the drying step. As shown in Table 4, in Comparative Examples 4 and 5 in which aluminum foil was produced under such conditions, intermetallic compound A was not observed in the oxide film. In Comparative Example 4, the element ratio O/Al of the intermetallic compound was 1.3 at the maximum. In Comparative Example 5, the element ratio O/Al of the intermetallic compound was 1.9 at the maximum. On the other hand, in Example 3, the element ratio O/Al of the intermetallic compound was 3.0 on average.

As can be seen from Tables 3 and 4, the initial resistance values of Comparative Examples 4 and 5 are as low as those of Example 3, but it is understood that the resistance value increases as the film thickness increases with time. On the other hand, in Example 3 of the present invention, although the initial thickness of the oxide film is thick, it can be seen that the increase in the resistance value with time is small. This uses an aluminum substrate containing a large amount of small intermetallic compounds as the aluminum substrate, and by setting the element ratio O/Al of the small intermetallic compounds in the oxide film within a predetermined range, this intermetallic compound A becomes a conduction point, Because resistance can be maintained.

[Comparative Example 6]

An aluminum foil was produced using the method described in Example 1 of International Publication No. 2018/062046.

Comparative Example 6 is an example of using an aluminum substrate having many small intermetallic compounds.

[Example 4]

An aluminum foil was produced in the same manner as in Example 1 except that the treatment conditions of the through hole forming step were changed in order to have substantially the same through-hole physical properties (average opening diameter and average opening ratio) as those of Comparative Example 6.

[evaluation]

It carried out similarly to the above, and measured the initial resistance value, the resistance value after forced aging for 3 weeks, and forced aging for 8 weeks. In the same manner as described above, using FE-AES, SEM observation and element distribution were performed from the outermost surface of the surface oxide film toward the depth direction to determine the density of the intermetallic compound A. In addition, with respect to the film thickness of the oxide film, the initial value, the value after the forced aging for 3 weeks, and the value after the forced aging for 8 weeks were obtained. In addition, the density (initial value) of the oxide film was also obtained.

Table 5 shows the treatment conditions and the like, and Table 6 shows the results.

[Table 5]

[Table 6]

As shown in Table 5, Comparative Example 6 differs in the type of the aluminum substrate, the type of acid used in the acid treatment step, and the temperature in the drying step. As shown in Table 6 in Comparative Example 6 in which an aluminum foil was produced under such conditions, intermetallic compound A was not observed in the oxide film. In Comparative Example 6, the element ratio O/Al of the intermetallic compound was 1.8 at the maximum. On the other hand, in Example 4, the element ratio O/Al of the intermetallic compound was 3.0 on average.

In Comparative Example 6, by controlling the film quality of the oxide film, it is possible to suppress the increase in the film thickness of the oxide film with time and to keep the film thickness thin. On the other hand, in Example 4 of the present invention, although the increase in the film thickness of the oxide film with time was larger than that of the comparative example, it was found that the resistance value could be kept low. This is because, by setting the element ratio O/Al of the small intermetallic compound in the oxide film to a predetermined range, the intermetallic compound A becomes a conduction point and low resistance can be maintained even when the overall oxide film thickness is increased.

[Example 5]

After carrying out similarly to Example 2 and producing an aluminum foil, it wash|cleaned with the solvent (MEK (methyl ethyl ketone)), and produced the aluminum foil.

[Example 6]

After producing an aluminum foil in the same manner as in Example 2, it was washed with a solvent (MEK (methyl ethyl ketone)), and then packed with an untreated aluminum foil (A1085 material, untreated, uncleaned) for one week. . That is, the aluminum foil produced in the same manner as in Example 5 was packed with an untreated aluminum foil for one week.

Here, packing and storage with an untreated aluminum foil increases the water contact angle because a trace amount of rolling oil remaining on the surface of the untreated aluminum foil is transferred to the surface of the aluminum foil. Using this point, Examples 6, 7, and 10 were each produced as an example with a large contact angle.

[Example 7]

After carrying out similarly to Example 2 and producing aluminum foil, it packed with unprocessed aluminum foil for 1 week.

[Example 8]

After carrying out similarly to Example 2 and producing an aluminum foil, it corona-treated once, it hydrophilized, and produced the aluminum foil. For the corona treatment, a processing apparatus manufactured by Kasuga Denki Co., Ltd. was used. The output of the corona treatment was 600 W.

[Example 9]

After carrying out similarly to Example 2 and producing an aluminum foil, it corona-treated twice, it hydrophilized, and produced the aluminum foil.

[Example 10]

After carrying out similarly to Example 2 and producing an aluminum foil, it packed with the unprocessed aluminum foil for 2 weeks.

About the aluminum foil of Examples 2 and 5-10, the water contact angle was measured. The water contact angle was measured using a portable contact angle meter PCA-1 (Kyowa Kaimen Chemical Co., Ltd.) according to the static method described in "JISR3257:1999 Wettability Test Method of Substrate Glass Surface". Measurement conditions were as follows.

Latency to measurement 2000 ms

Prepared liquid volume 1.8μL

Table 7 shows the measurement results of the water contact angle.

[evaluation]

<Initial resistance and forced aging resistance>

About the aluminum foil of Examples 2 and 5-10, it carried out similarly to the above, initial resistance and forced aging resistance were measured, and the same reference|standard evaluated. In addition, as in Examples 6, 7, and 10, for Examples packed and stored with untreated aluminum, in order to minimize the effect of aging during packing and storage, after storage for a predetermined period in a low-humidity environment, take out from the packaging, Resistance and forced aging resistance were measured.

<Applicability>

For the aluminum foil of Examples 2 and 5-10, when apply|coating an electrode material for the measurement of initial stage resistance, it confirmed visually whether it could apply|coat uniformly.

A result is shown in Table 7.

[Table 7]

From Table 7, it turns out that applicability|paintability becomes non-uniform|heterogenous when the water contact angle of the surface exceeds 80 degrees. It is thought that this is because the water-based electrode material partially aggregated and it became impossible to apply|coat uniformly because the surface became close to water repellency.

Here, Examples 6 and 7 packed and stored with untreated aluminum foil had a large water contact angle compared to Examples 2 and 5 prepared under the same conditions, respectively. By packing and storing this with an untreated aluminum foil, a trace amount of rolling oil remaining on the surface of the untreated aluminum foil is transferred to the aluminum foil, and the water contact angle is increasing compared to the original state (before packing and storage). In addition, Example 10 is packed and stored for a longer period than Example 8. In Example 10, since the packing storage period is long, the water contact angle becomes larger and exceeds 80 degrees. As a result, Example 10 became non-uniform in applicability|paintability compared with the other Example.

Moreover, it turns out from Table 7 that initial resistance and forced aging resistance deteriorate when the surface water contact angle is less than 20 degrees. In Examples 8 and 9, the surfaces were forcibly hydrophilized by corona treatment. As described above, when the water contact angle is lowered by performing the corona treatment, it can be seen that the resistance deteriorates.

Moreover, in Example 10, since applicability|paintability is non-uniform|heterogenous, the contact state of an electrode material and aluminum foil became inadequate, and it is thought that initial stage resistance deteriorated compared with Example 2. On the other hand, since the forced aging resistance of Example 10 was close to water repellency due to a large surface water contact angle, it did not deteriorate so much and was the same level as Example 2.

From the above, the effect of this invention is clear.

1 Aluminum base
2 Aluminum hydroxide film
3 Aluminum base with through hole
4 Aluminum hydroxide film with through hole
5 through hole
10 aluminum foil
14 oxide film
16 Intermetallic Compounds
100 resistance meter
102 Pressurized conductive terminal
104 Pressurized Insulated Terminals
106 carbon layer

Claims (10)

An aluminum foil having a plurality of through holes penetrating in a thickness direction, the aluminum foil comprising:
The aluminum foil has an oxide film on the surface,
The oxide film has an intermetallic compound having an element ratio of oxygen to aluminum O/Al of 2 or more and 4 or less,
An aluminum foil having a density of 500 pieces/mm ^{2 or more of the intermetallic compound.} The method according to claim 1,
An aluminum foil having an equivalent circle diameter of the intermetallic compound of 1 μm or less. The method according to claim 1 or 2,
The aluminum foil in which the said oxide film contains 70 mass % or more of aluminum oxide. 4. The method according to any one of claims 1 to 3,
An aluminum foil having a water contact angle of 20° to 80° on the surface of the oxide film. 5. The method according to any one of claims 1 to 4,
The aluminum foil whose average opening diameter of the said through-hole is 0.1 micrometer - 100 micrometers. 6. The method according to any one of claims 1 to 5,
having non-perforated recesses with an average aperture diameter of 0.1 μm to 100 μm,
An aluminum foil in which the occupancy of the concave portion is 1% or more. As a manufacturing method of the aluminum foil which manufactures the aluminum foil of any one of Claims 1-6,
A through-hole forming step of forming a through-hole in an aluminum substrate;
An alkali treatment step of dissolving the outermost layer by contacting the aluminum substrate with an alkaline aqueous solution;
The manufacturing method of the aluminum foil which has an acid treatment process which makes the said aluminum base material after the said alkali treatment process contact an acidic aqueous solution, and forms an oxide film on the surface of the said aluminum base material. The current collector using the aluminum foil in any one of Claims 1-6. A lithium ion capacitor using the current collector according to claim 8 . A lithium ion battery using the current collector according to claim 8 .

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