WO2020256115A1 - Current collector for power storage device electrode, manufacturing method thereof, and power storage device - Google Patents

Abstract

A current collector for a power storage device electrode that increases output and excels in output characteristics while maintaining a high energy density, a method for manufacturing the current collector for a power storage device electrode, and a power storage device having the current collector for a power storage device electrode are provided. The current collector for a power storage device electrode according to the present invention includes an aluminum material and an amorphous carbon coating film formed on the aluminum material. The ratio of sp² bonded carbons to the total amount of sp² bonded carbons and sp³ bonded carbons in the amorphous carbon coating film (sp²/(sp³ + sp²)) is 0.35 or more. The ratio (sp²/(sp³ + sp²)) was measured by an X-ray absorption fine structure (XAFS) method.

Description

Current collector for electrode of power storage device, its manufacturing method, and power storage device

The present invention relates to a current collector for a power storage device electrode, a method for manufacturing the current collector for the power storage device electrode, and a power storage device using the current collector for the power storage device electrode.
The present application claims priority based on Japanese Patent Application No. 2019-113900 filed in Japan on June 19, 2019, the contents of which are incorporated herein by reference.

Conventionally, electric double layer capacitors (see, for example, Patent Document 1) and secondary batteries are known as techniques for storing electric energy. Electric double layer capacitors (EDLCs: Electric double-layer capacitors) are significantly superior to secondary batteries in terms of life, safety, and output density. However, the electric double layer capacitor has a problem that the energy density (volume energy density) is lower than that of the secondary battery.

Here, the energy (E) stored in the electric double layer capacitor is expressed as E = 1/2 × C × V ² using the capacitance (C) of the capacitor and the applied voltage (V), and the energy is It is proportional to the capacitance and the square of the applied voltage. Therefore, in order to improve the energy density of the electric double layer capacitor, a technique for improving the capacitance and the applied voltage of the electric double layer capacitor has been proposed.

As a technique for improving the capacitance of an electric double layer capacitor, a technique for increasing the specific surface area of activated carbon constituting the electrode of the electric double layer capacitor is known. Currently known activated carbons have a specific surface area of 1000 m ² / g to 2500 m ² / g. In the electric double layer capacitor using such activated carbon as an electrode, an organic electrolytic solution in which a quaternary ammonium salt is dissolved in an organic solvent, an aqueous electrolytic solution such as sulfuric acid, or the like is used as the electrolytic solution.
Since the organic electrolyte has a wide usable voltage range, the applied voltage can be increased and the energy density can be improved.

A lithium ion capacitor is known as a capacitor in which the applied voltage is improved by utilizing the principle of an electric double layer capacitor. A lithium ion capacitor is a capacitor that uses graphite or carbon that can intercalate and deintercalate lithium ions for the negative electrode and activated carbon that is equivalent to the electrode material of an electric double layer capacitor that can absorb and desorb electrolyte ions for the positive electrode. ing. For one of the positive electrode and the negative electrode, which uses the same activated carbon as the electrode material of the electric double layer capacitor, and which uses a metal oxide or a conductive polymer as the electrode at which the Faraday reaction occurs on the other electrode, It is called a hybrid capacitor. In the lithium ion capacitor, among the electrodes constituting the electric double layer capacitor, the negative electrode is made of graphite, hard carbon, soft carbon, etc., which are the negative electrode materials of the lithium ion secondary battery, and the inside of the graphite, hard carbon, soft carbon, etc. An electrode into which lithium ions are inserted. A lithium ion capacitor is characterized in that the applied voltage is larger than that of a general electric double layer capacitor, that is, one in which both electrodes are composed of activated carbon.

However, when graphite is used for the electrode, there is a problem that propylene carbonate, which is known as a solvent for the electrolytic solution, cannot be used. This is because when graphite is used for the electrode, propylene carbonate is electrolyzed and the decomposition product of propylene carbonate adheres to the surface of graphite, which reduces the reversibility of lithium ions. Propylene carbonate is a solvent that can operate even at low temperatures. When propylene carbonate is applied to an electric double layer capacitor, the electric double layer capacitor can also operate at −40 ° C. Therefore, in lithium ion capacitors, hard carbon and soft carbon, which are difficult to decompose propylene carbonate, are used as electrode materials. However, hard carbon and soft carbon have a lower capacity per volume of the electrode than graphite, and the voltage is also lower than that of graphite (becomes a noble potential). Therefore, there is a problem that the energy density of the lithium ion capacitor becomes low.

As a new concept capacitor, a capacitor using graphite as the positive electrode active material instead of activated carbon and using a reaction of inserting and removing electrolyte ions between the layers of graphite has been developed (see, for example, Patent Document 2). Patent Document 2 describes the following. In a conventional electric double layer capacitor that uses activated carbon as the positive electrode active material, when a voltage exceeding 2.5 V is applied to the positive electrode, the electrolytic solution is decomposed and gas is generated. On the other hand, a capacitor with a new concept that uses graphite as the positive electrode active material does not cause decomposition of the electrolytic solution even at a charging voltage of 3.5 V, and has a higher voltage than the conventional electric double layer capacitor that uses activated carbon as the positive electrode active material. Can work with. By using this technique, the energy density can be increased by about 2 to 3 times as compared with the conventional electric double layer capacitor. The cycle characteristics, low temperature characteristics, and output characteristics are also equal to or better than those of conventional electric double layer capacitors. The specific surface area of graphite is several hundredths of the specific surface area of activated carbon, and this difference in electrolytic solution decomposition action is due to this large difference in specific surface area.

A new concept capacitor that uses graphite as the positive electrode active material has insufficient durability, which has hindered its practical application. However, it has been found that high temperature durability can be improved to a practical level by a technique of using an aluminum material coated with an amorphous carbon film as a current collector (see Patent Document 3). The capacitor of this new concept is a capacitor that uses a reaction of inserting and removing electrolyte ions between layers of graphite on the positive electrode, and is not strictly an electric double layer capacitor, but in Patent Document 3, it is electric in a broad sense. It is called a double layer capacitor.

Further, in the negative electrode as well, a power storage device using a reaction of inserting and desorbing lithium ions between layers of lithium titanate by using a metal oxide such as lithium titanate or lithium-containing niobium oxide as the negative electrode active material instead of activated carbon. Proposed (see, eg, Patent Documents 2 and 4). In charging and discharging, the electrolyte anion and the lithium cation contained in the electrolyte move toward the positive electrode or the negative electrode in opposite directions, so that they are called a dual ion battery (DIB). It is expected that the DIB has excellent output characteristics and life as compared with a lithium ion secondary battery that moves only lithium ions, and it is not necessary to impose restrictions on the SOC (charge state: state of charge).

Japanese Unexamined Patent Publication No. 2011-046584 Japanese Unexamined Patent Publication No. 2010-040180 Japanese Patent No. 6167243 Japanese Patent No. 4465492

The hybrid capacitor and the dual ion battery, which are the above-mentioned two types of power storage devices, can improve the energy density several times or more as compared with the conventional electric double layer capacitor (EDLC). On the other hand, regarding the high output characteristics, which is a major feature of EDLC, hybrid capacitors and dual ion batteries also have high output characteristics like EDLC. However, there is a problem aiming at further high output.
The present invention has been made in view of the above circumstances, and focuses on a current collector used for an electrode of a power storage device such as a hybrid capacitor or a dual ion battery (a current collector for a power storage device electrode), and collects electricity for a power storage device electrode. It is an object of the present invention to provide a power storage device having excellent output characteristics while maintaining a high energy density by further increasing the output by enhancing the amorphous carbon film contained in the body. Another object of the present invention is to provide a method for manufacturing an electrode current collector for a power storage device having excellent output characteristics and an electrode current collector for a power storage device having excellent output characteristics.

The following means are provided to solve the above problems.
[1] A current collector for a power storage device electrode containing an aluminum material and an amorphous carbon film formed on the aluminum material.
In the amorphous carbon film, the ratio of sp ^2- bonded carbon to the total amount of sp ^2- bonded carbon and sp ^3- bonded carbon (sp ² / (sp ³ + sp ² )) is 0.35 or more.
A current collector for a power storage device electrode, characterized in that the ratio (sp ² / (sp ³ + sp ² )) is measured by the X-ray absorption fine structure (XAFS) method.
[2] The current collector for the power storage device electrode is a current collector for the positive electrode of the hybrid capacitor or a current collector for the positive electrode of the dual ion battery.
The current collector for a power storage device electrode according to [1], wherein the hybrid capacitor positive electrode or the dual ion battery positive electrode contains graphite as a positive electrode active material.
[3] The current collector for the electrode of the power storage device is a current collector for the negative electrode of the hybrid capacitor or a current collector for the negative electrode of the dual ion battery.
The collection for a power storage device electrode according to [1], wherein the hybrid capacitor negative electrode or the dual ion battery negative electrode includes one selected from the group consisting of activated carbon, graphite, hard carbon, soft carbon, and lithium titanate as the negative electrode active material. Electrode.
[4] A film forming process for forming an amorphous carbon film on an aluminum material, and
A method for manufacturing a current collector for a power storage device electrode, which comprises a heat treatment step of heat-treating an amorphous carbon film at a temperature of 400 ° C. or higher.
[5] The method for manufacturing a current collector for a power storage device electrode according to [4], wherein a heat treatment step is performed after the film forming step.
[6] A current collector for a power storage device electrode containing an aluminum material and an amorphous carbon film formed on the aluminum material.
A current collector for a power storage device electrode, wherein the amorphous carbon film is obtained by the production method according to [4] or [5].
[7] A power storage device composed of at least a positive electrode, a negative electrode, and an electrolyte.
The positive electrode contains a positive electrode active material, and the negative electrode contains a negative electrode active material.
The positive electrode active material contains graphite and
The current collector on the positive electrode side is the current collector for the power storage device electrode according to any one of [1] and [6].
A power storage device characterized in that the thickness of the amorphous carbon film is 60 nm or more and 300 nm or less.
[8] The power storage device according to [7], wherein graphite contains rhombohedral crystals.
[9] The negative electrode active material includes one selected from the group consisting of activated carbon, graphite, hard carbon, soft carbon, and lithium titanate.
The current collector on the negative electrode side is one selected from the group consisting of the current collector for the power storage device electrode described in [1] and [7], etched aluminum, and an aluminum material [7] or [8]. ] The power storage device described in.

According to the present invention, by improving the amorphous carbon film contained in the current collector for the electrode of the power storage device, the output can be further increased, the high energy density is maintained, and the output characteristics are excellent. A power storage device can be provided. Further, according to the present invention, it is possible to provide a method for manufacturing an electrode current collector of a power storage device having excellent output characteristics and an electrode current collector of a power storage device having excellent output characteristics.

It is a NEXAFS spectrum for explaining the XAFS measurement method.

The materials, dimensions, etc. exemplified in the following description are examples, and the present invention is not limited thereto, and can be appropriately modified without changing the gist thereof.

(Current collector for storage device electrode)
The current collector for a power storage device electrode of the present invention includes an aluminum material and an amorphous carbon film formed on the aluminum material. In the amorphous carbon film, the ratio of sp ^2- bonded carbon to the total amount of sp ^2- bonded carbon and sp ^3- bonded carbon (referred to as "sp ² / (sp ³ + sp ² ) ratio") is 0.35 or more. It is characterized by. The sp ² / (sp ³ + sp ² ) ratio was measured by the X-ray Absorption Fine Structure (XAFS: X-ray Absorption Fine Structure) method. The XAFS method will be described in detail later. Further, a conductive carbon layer may be formed between the amorphous carbon film and the positive electrode active material, or between the amorphous carbon film and the negative electrode active material.
Since the current collector for the electrode of the power storage device of the present invention can be particularly effective, it can be used for a hybrid capacitor positive electrode containing graphite as a positive electrode active material, or a dual ion battery positive current collector containing graphite as a positive electrode active material. It is preferably used on the body. Further, the current collector for the electrode of the power storage device of the present invention can be used for the current collector for the negative electrode of the hybrid capacitor, or can be used for the current collector for the negative electrode of the dual ion battery.

Here, the "hybrid capacitor" of the present invention uses the principle of an electric double layer of adsorption and desorption of the cation of the electrolyte for the negative electrode, and inserts and desorbs the electrolyte anion into graphite for the positive electrode (intercalation-deinter). It is a power storage device that uses the principle of cullation). For example, activated carbon is used for the negative electrode and graphite is used for the positive electrode.

Here, the "dual ion battery" of the present invention uses the principle of inserting and desorbing lithium ions into the negative electrode (intercalation-deintercalation), and the positive electrode also inserts and desorbs the electrolyte anion into graphite (intercalation). It is a power storage device that uses the principle of curation-deintercalation). Both the "hybrid capacitor" and the "dual ion battery" are storage devices in which the anions and cations of the electrolyte are inserted or adsorbed into the positive electrode and the negative electrode during charging, and desorbed or released during discharge. This is different from the principle that lithium ions move in the positive electrode during charging and discharging as in a lithium ion battery. More specifically, in a lithium ion battery, lithium ions in the positive electrode are moved to the negative electrode (lithium ion insertion reaction) and discharged (lithium ion desorption reaction) during charging.

The current collector for the electrode of the power storage device of the present invention is preferably obtained by the manufacturing method described later.

<Aluminum material>
As the aluminum material as the base material, an aluminum material generally used for current collector applications can be used.
The shape of the aluminum material can be a foil, a sheet, a film, a mesh, or the like. Aluminum foil can be preferably used as the current collector.
Further, in addition to a plain aluminum material, etched aluminum described later may be used.

The thickness when the aluminum material is a foil, sheet or film is not particularly limited, but if the size of the cell itself is the same, the thinner the aluminum material, the more active material can be enclosed in the cell case, but the strength is reduced. Therefore, select an appropriate thickness. The actual thickness is preferably 10 μm to 40 μm, more preferably 15 μm to 30 μm. If the thickness is less than 10 μm, the aluminum material may be broken or cracked during the step of roughening the surface of the aluminum material or another manufacturing process.

Etched aluminum may be used as the aluminum material.
Etched aluminum is roughened by etching. For etching, a method of immersing in an acid solution such as hydrochloric acid (chemical etching) or electrolysis (electrochemical etching) using aluminum as an anode in an acid solution such as hydrochloric acid is generally used. In electrochemical etching, the etching shape differs depending on the current waveform during electrolysis, the composition of the solution, the temperature, and the like, so it can be selected from the viewpoint of the performance of the power storage device.

As the aluminum material, either one having a passivation layer on the surface or one having no passivation layer can be used. When a passivation film which is a natural oxide film is formed on the surface of the aluminum material, an amorphous carbon film layer may be provided on the natural oxide film, or the natural oxide film may be provided, for example, argon sputtering. It may be provided after being removed by.
The natural oxide film on the aluminum material is a passivation film and has the advantage that it is not easily eroded by the electrolytic solution, but it leads to an increase in the resistance of the current collector, so from the viewpoint of reducing the resistance of the current collector. , It is preferable that there is no natural oxide film.

<Amorphous carbon film>
In the present specification, the term "amorphous carbon film" is an amorphous (amorphous structure) carbon film or a hydrogenated carbon film. It usually contains sp ^2- bonded carbon and sp ^3- bonded carbon in a constant ratio. The amorphous carbon film (hereinafter referred to as “the amorphous carbon film of the present invention”) used in the current collector for the power storage device electrode of the present invention is sp ² bonded to the total amount of sp ² bonded carbon and sp ³ bonded carbon. The carbon ratio (also referred to as sp ² / (sp ³ + sp ² ) ratio) is 0.35 or more. The (sp ² / (sp ³ + sp ² )) ratio was measured by the X-ray absorption fine structure (XAFS) method. The sp ² / (sp ³ + sp ² ) ratio is preferably 0.40 or more.
Further, from the viewpoint that higher conductivity can be obtained while maintaining high chemical resistance, and the higher the sp ² ratio, the softer the material and the better the adhesion to the active material layer, sp ² / (sp) ^{The 3} + sp ² ) ratio is preferably 0.6 or less, more preferably 0.5 or less.
The current collector using the current collector for the electrode of the power storage device having the amorphous carbon film of the present invention (hereinafter referred to as "the current collector for the electrode of the power storage device of the present invention") outputs while maintaining a high energy density. The characteristics can be improved. In particular, a current collector using the current collector for the electrode of the power storage device of the present invention as a positive current collector made of a graphite active material is suitable because the output characteristics can be further improved while maintaining a high energy density. Is.

Here, the XAFS method will be described.
In general, each element has a property of strongly absorbing X-rays having an energy corresponding to the binding energy of inner-shell electrons. Here, the portion of the substance in which the X-ray absorption coefficient greatly increases is referred to as an absorption end, and the X-ray energy corresponding to this absorption end is referred to as the X-ray absorption edge energy. Each element has different binding energies of inner-shell electrons, and when irradiated with X-rays having a higher energy, the absorption coefficient of X-rays increases with the emission of inner-shell electrons. Therefore, by measuring the X-ray absorption spectrum of a certain element and observing the absorption edge, information on the X-ray absorption fine structure (XAFS vibration) reflecting the environment and structure around the element can be obtained. By analyzing this XAFS vibration, the local structure around the element of interest can be known. Further, it is known that the position of the absorption edge shifts due to the change in the electronic state of the element, and the valence of the element of interest can be known by comparing the absorption edges. There are a transmission method and a fluorescence yield method as a measurement method for obtaining an average X-ray absorption spectrum in a sample as described above by using the XAFS method. The transmission method is a method of directly measuring the amount of X-ray absorption by measuring the X-ray intensity before and after the sample when the sample is irradiated with X-rays. The fluorescence yield method is a method of measuring fluorescent X-rays emitted from atoms that are excited by absorbing X-rays when the sample is irradiated with X-rays. With either method, the local structure and valence of the target element can be analyzed and similar results can be obtained.

XAFS is an X-ray absorption fine structure near the absorption edge that appears in the region of about 50 eV from the absorption edge (NEXAFS: Near Edge X-ray Absorption Fine Structure, or XANES: X-ray Absorption Near Edge Energy, More than that). It is divided into the wide-area X-ray absorption microstructure (EXAFS: Extended X-ray Absorption Fine Structure) that appears. On the other hand, the peak of NEXAFS appearing in the region in the range of about 50 eV from the absorption edge corresponds to the energy of transition of the inner shell electron to the empty orbital unoccupied orbital, and the spectral structure depends on the valence and coordination structure of the element of interest. I take the. It is a feature of NEXAFS that the excitation to the empty orbit can be observed in this way. In the XAFS measurement method of the present application, NEXAFS is used because the sp ² / (sp ² + sp ³ ) ratio of the diamond-like carbon (DLC) film can be determined with high accuracy as described later.

FIG. 1 shows a carbon atom K-end NEXAFS spectrum of a general DLC film. Since the ionization energy of carbon is 295 eV, photoelectrons generated by direct photoionization are included in the energy higher than this energy. The portion shown as Direct ionization in FIG. 1 includes photoelectrons, normal Auger electrons which are subsequent reactions thereof, and secondary electrons emitted by them. The broad peaks present at 290 to 310 eV reflect Auger electrons derived from the C1s-> σ ^* resonant Auger electron emission process and secondary electrons emitted thereby. The peak observed near 285.4 eV reflects Auger electrons derived from the 1s → π * resonance Auger electron emission process and secondary electrons emitted due to it. In the NEXAFS measurement method, the sp ² / (sp ² + sp ³ ) ratio can be determined with high accuracy by observing at a distance of 1s → π *. Actually, the ratio (I _{π *} / I _all ) of the integrated value (I _all ) of the absorption intensity in the defined region and the peak area (I _{π *} ) of 1s → π * is calculated, and the sp ² composition is 100%. The sp ² / (sp ² + sp ³ ) ratio is determined in comparison with I _{π *} / I _{all of} HOPG. Detailed measurement methods and analysis methods are described in Examples.

The amorphous carbon film of the present invention having an sp ² / (sp ³ + sp ² ) ratio of 0.35 or more is, for example, a diamond-like carbon (DLC) film, a carbon hard film, an amorphous carbon (a-C) film, or hydrogen. Includes a modified amorphous carbon (AC: H) film and the like.

Among the materials of the amorphous carbon film exemplified, a diamond-like carbon (DLC) film is preferable. Diamond-like carbon is a material having an amorphous structure in which both diamond bonds (sp ³ ) and graphite bonds (sp ² ) are mixed, and has high chemical resistance. The amorphous carbon film of the present invention having an sp ² / (sp ³ + sp ² ) ratio of 0.35 or more measured by the XAFS method is preferably a DLC film having a developed graphite structure.
Further, for use in a coating of a current collector, boron or nitrogen can be doped in order to increase conductivity.

The thickness of the amorphous carbon film is preferably 60 nm or more and 300 nm or less. If the thickness of the amorphous carbon film is less than 60 nm, the thickness of the amorphous carbon film is too thin and the coating effect of the amorphous carbon film becomes small, and corrosion of the current collector in the constant current constant voltage continuous charging test cannot be sufficiently suppressed. If the thickness of the amorphous carbon film exceeds 300 nm and is too thick, the amorphous carbon film becomes a resistor and the resistance between the amorphous carbon film and the active material layer increases. Therefore, an appropriate thickness is appropriately selected. The thickness of the amorphous carbon film is more preferably 80 nm or more and 300 nm or less, and further preferably 120 nm or more and 300 nm or less.

Since the current collector of the power storage device according to the embodiment of the present invention has an amorphous carbon film on the surface of the aluminum material, it prevents the aluminum material from coming into contact with the electrolytic solution and causes corrosion of the current collector by the electrolytic solution. Can be prevented. Further, since it is the amorphous carbon film of the present invention in which the sp ² / (sp ³ + sp ² ) ratio measured by the X-ray absorption fine structure (XAFS) method is 0.35 or more, it has a certain conductivity. The output characteristics are improved while maintaining high energy density.

The amorphous carbon film of the present invention is preferably obtained by the production method described later. For example, those obtained by the production method described below having a heat treatment temperature of 400 ° C. or higher, preferably 500 ° C. or higher are preferable. Further, from the viewpoint of mass production of a current collector for a power storage device electrode containing an amorphous carbon film of the present invention, for example, an aluminum foil having a DLC film (hereinafter referred to as "DLC coated Al foil"), it is amorphous. When the carbon film (DLC film) is formed by the roll-to-roll method, there is a problem that wrinkles are likely to occur if the heat treatment step of raising the temperature while forming the film is performed. Therefore, as a result of diligent studies, for example, after the film forming step at room temperature or the like, the amorphous carbon film (DLC film which has not been heat-treated) obtained in the film forming step is 400 ° C. or higher, preferably 500 ° C. or higher. A production method in which heat treatment is performed in the above is more preferable. This is because the amorphous carbon film (DLC film after heat treatment) of the present invention obtained by this production method has a sp ² / (sp ³ + sp ² ) ratio of 0.35 or more.

<Conductive carbon layer>
The current collector for the electrode of the power storage device according to the embodiment of the present invention has a conductive carbon layer between the amorphous carbon film and the positive electrode active material, or between the amorphous carbon film and the negative electrode active material. Is preferably formed. For example, the thickness of the conductive carbon layer is preferably 5 μm or less, and more preferably 3 μm or less, because it is exposed to a lower electrode potential for a longer time than the activated carbon negative electrode used in a conventional power storage device. This is because if the thickness exceeds 5 μm, the energy density becomes small when it becomes a cell or an electrode. The material of the conductive carbon layer may be any kind as long as it is carbon having high conductivity, but it is preferable that graphite is contained as carbon having high conductivity, and more preferably graphite alone.

The particle size of the material of the conductive carbon layer is preferably 1/10 or less of the size of graphite or the like as an active material. This is because if the particle size is within this range, the contact property at the interface where the conductive carbon layer and the active material layer are in contact is increased, and the interface (contact) resistance can be reduced. Specifically, the particle size of the carbon material of the conductive carbon layer is preferably 1 μm or less, and more preferably 0.5 μm or less.
By providing the conductive carbon layer, even if there are pinholes in the amorphous carbon film, the pinholes are sealed to prevent the aluminum material from coming into contact with the electrolytic solution, and the current collector by the electrolytic solution is provided. Corrosion can be prevented.
Further, by providing the conductive carbon layer, the contact resistance between the amorphous carbon film covering the current collector and the positive electrode active material or the amorphous carbon film and the negative electrode active material is reduced, and the discharge rate is increased. The output characteristics can be improved and the high temperature durability can be improved.

Also, when forming a conductive carbon layer, a binder is added together with a solvent to make a paint, and the coating is applied onto a DLC-coated aluminum foil. As a coating method, screen printing, gravure printing, a comma coater (registered trademark), a spin coater, or the like can be used. As the binder, cellulose, acrylic, polyvinyl alcohol, thermoplastic resin, rubber, or organic resin can be used. Polyethylene or polypropylene can be used as the thermoplastic resin, SBR (styrene-butadiene rubber) or EPDM can be used as the rubber, and phenol resin or polyimide resin can be used as the organic resin.

The conductive carbon layer preferably has few gaps between particles and low contact resistance. Further, there are two types of solvents for dissolving the binder for forming the conductive carbon layer, an aqueous solution and an organic solvent. If the binder for forming the electrode active material layer is one that dissolves in an organic solvent, it is preferable to use a binder that dissolves in an aqueous solution for the conductive carbon layer. On the contrary, when the binder for forming the electrode active material layer is an aqueous solution, it is preferable to use a binder that dissolves in an organic solvent for the conductive carbon layer. This is because when the same type of solvent is used for the electrode active material layer and the conductive carbon layer, the binder of the conductive carbon layer tends to dissolve and become non-uniform when the electrode active material layer is applied.

(Manufacturing method of current collector for power storage device electrode)
The method for producing a current collector for a power storage device electrode of the present invention includes a film forming step of forming an amorphous carbon film on an aluminum material and a heat treatment step of heat-treating the amorphous carbon film at a temperature of 400 ° C. or higher. It is characterized by including. The order of the film forming step and the heat treatment step may be arbitrary. For example, a manufacturing method in which a film forming step and a heat treatment step proceed at the same time (sometimes referred to as a direct film forming method), or a manufacturing method in which a heat treatment step is performed after the film forming step (post-heat treatment film forming). It may also be called a law.) Any of these is possible. The treatment temperature in the heat treatment step is preferably 300 ° C. or higher, preferably 600 ° C. or lower, and more preferably 500 ° C. or lower. It is preferable to raise the heating temperature because the sp ² / (sp ³ + sp ² ) ratio becomes higher and the resistance becomes smaller. On the other hand, the melting point of aluminum as a base material is 660 ° C. The closer to the melting point, the easier it is for the aluminum material to soften, the aluminum material becomes wrinkled, and the base material loses its flatness. Therefore, the temperature at which wrinkles are unlikely to occur becomes the upper limit. The upper limit temperature when another metal or aluminum alloy is used as the base material is different, and the upper limit temperature is the temperature at which wrinkles do not occur on the base material below the respective melting points.

A manufacturing method in which the film forming process and the heat treatment process proceed at the same time (direct film forming method) is a method in which an amorphous carbon film is formed on an aluminum material and the temperature of the aluminum material is increased to 400 ° C. or higher in the same atmosphere. This is a heat treatment method.

A manufacturing method in which a heat treatment step is performed after a film forming step (post-heat treatment film forming method) is an aluminum material in which an amorphous carbon film is formed on an aluminum material and then an amorphous carbon film is formed. This is a method of heat-treating or the like to 400 ° C. or higher. The atmosphere of the heat treatment may be, for example, an atmosphere in which the raw material gas is not supplied, preferably an argon atmosphere. This is a method in which an aluminum material having an amorphous carbon film obtained in a film forming step is heat-treated at 400 ° C. or higher in an atmosphere different from that in the film forming step, for example, in an atmosphere of nitrogen or argon. At that time, the processing temperature in the film forming step is preferably less than 200 ° C., more preferably 100 ° C. or lower, and even more preferably 50 ° C. or lower. Most preferably room temperature.

From the viewpoint of mass production, the post-heat treatment film forming method is preferable as the method for manufacturing the current collector for the electrode of the power storage device of the present invention. For example, when the current collector for the electrode of the power storage device of the present invention such as the DLC coated Al foil is carried out by the roll-to-roll method, there is a problem that wrinkles are likely to occur when the direct film forming method is used.

As a method for forming the amorphous carbon film, a known method such as a plasma CVD method using a hydrocarbon gas, a sputtering vapor deposition method, an ion plating method, or a vacuum arc vapor deposition method can be used. A plasma CVD method using a hydrocarbon gas is preferable. The amorphous carbon film preferably has enough conductivity to function as a current collector.
When an amorphous carbon film is formed by the plasma CVD method using a hydrocarbon gas, the thickness of the amorphous carbon film is controlled by the energy injected into the aluminum material, specifically, the applied voltage, the applied time, and the temperature. can do.

More specifically, in the current collector for the electrode of the power storage device of the present invention, when the amorphous carbon film of the present invention (for example, DLC coated Al foil) formed at a temperature of 400 ° C. or higher is used, the XAFS method can be used. The measured sp ² / (sp ³ + sp ² ) ratio is 0.35 or more. An amorphous carbon film (DLC film) having a developed graphite structure can be obtained. Further, from the viewpoint of mass production of the amorphous carbon film (DLC coated Al foil), when the amorphous carbon film (DLC coated Al foil) is performed by the roll-to-roll method, wrinkles are likely to occur when the film forming temperature is raised. There is a problem. On the other hand, in the case of room temperature film formation, the occurrence of wrinkles can be suppressed, but there is a problem that the graphite structure is difficult to develop. The unheated amorphous carbon film (DLC coated Al foil) has a sp ² / (sp ³ + sp ² ) ratio of 0.29 or less, and when applied to electrodes for hybrid capacitors and dual ion batteries, The interfacial resistance between the current collector and the active material layer may increase, and the output characteristics may deteriorate. Therefore, as a result of diligent studies, in the above-mentioned post-heat treatment film forming method, after the film was formed at room temperature, the amorphous carbon film (DLC-coated Al foil) was heat-treated at 400 ° C. or higher in an inert atmosphere. It was found that the sp ² / (sp ³ + sp ² ) ratio could be 0.35 or more by doing so. This was sp ² / (sp ³ + sp ² ) equal to or higher than that in the case of the direct film forming method in which the film was directly formed at 400 ° C. or higher. By using the obtained amorphous carbon film (DLC coated Al foil) as a current collector for a positive electrode made of graphite, the output characteristics can be further improved.

The wrinkles of the foil, which was a problem in the direct film formation by the roll-to-roll method, can be prevented by the post-heat treatment of the present invention. This is due to the fact that the temperature of the Al foil rises due to the energy of the plasma in addition to the film formation temperature (atmospheric temperature at the time of film formation) in the direct film formation by the roll-to-roll method, which is affected by the temperature exceeding the atmospheric temperature. It was. However, in the post-heat treatment film forming method of the present invention, since only the ambient temperature is applied to the film-formed foil, the occurrence of wrinkles can be suppressed.

(Power storage device)
The power storage device according to an embodiment of the present invention has a positive electrode, a negative electrode, a separator, and an electrolyte.
The power storage device of the present invention is preferably a hybrid capacitor or a dual ion battery.

(Hybrid capacitor)
Hereinafter, a hybrid capacitor according to an embodiment of the power storage device of the present invention will be described in detail.

It is preferable to use the above-mentioned current collector for the power storage device electrode of the present invention as at least one of the current collector on the negative electrode side and the current collector on the positive electrode side of the hybrid capacitor of the present embodiment. When the positive electrode contains graphite, it is preferable to use the above-mentioned current collector for the power storage device electrode of the present invention as the current collector on the positive electrode side at least. It is more preferable to use the above-mentioned current collector for the power storage device electrode of the present invention for both the current collector on the negative electrode side and the current collector on the positive electrode side.

<Positive electrode>
The positive electrode used in the hybrid capacitor of the present embodiment includes a current collector (current collector on the positive electrode side) and a positive electrode active material layer formed on the current collector. The positive electrode active material layer contains a positive electrode active material, a binder, and a conductive material.
The positive electrode active material layer is formed by applying a paste-like positive electrode material containing a positive electrode active material, a binder, and an required amount of a conductive material on the current collector on the positive electrode side, and drying the layer. be able to.

[Positive electrode active material]
The positive electrode active material used in the hybrid capacitor of the present embodiment contains graphite. As the graphite, either artificial graphite or natural graphite can be used. Further, as natural graphite, scaly and earth-like graphite are known. Natural graphite is obtained by crushing the mined raw ore and repeating beneficiation called flotation. Further, artificial graphite is produced, for example, through a graphitization step of calcining a carbon material at a high temperature. More specifically, for example, the raw material coke is molded by adding a binder such as pitch, heated to around 1300 ° C. for primary firing, then the primary fired product is impregnated with the pitch resin, and the temperature is further increased to 3000 ° C. It is obtained by secondary firing at a near high temperature. Further, those in which the surface of graphite particles is coated with carbon can also be used.

The crystal structure of graphite is roughly divided into hexagonal crystals with a layered structure consisting of ABAB and rhombohedral crystals with a layered structure consisting of ABCABC. Depending on the conditions, these structures may be in a single state or in a mixed state, but any crystal structure or a mixed state can be used. For example, the graphite of KS-6 (trade name) manufactured by Imerys GC Japan Co., Ltd. used in the examples described later has a rhombohedral crystal ratio of 26%, and is an artificial graphite manufactured by Osaka Gas Chemical Co., Ltd. Carbon microbeads (MCMB) have a ratio of graphite crystals of 0%.

The graphite used in other embodiments of the present invention has a different capacitance expression mechanism from the activated carbon used in the conventional EDLC. In the case of activated carbon, taking advantage of its large specific surface area, electrolyte ions are adsorbed and desorbed on the surface of the activated carbon to develop capacitance. On the other hand, in the case of graphite, the capacitance is developed by inserting and desorbing (intercalation-deintercalation) an anion which is an electrolyte ion between the layers. From such a difference, the electricity storage device using graphite according to the present embodiment was called an electric double layer capacitor in a broad sense in Patent Document 3, but can be called a hybrid capacitor and has an electric double layer. It is distinguished from EDLC using activated carbon.

[Current collector on the positive electrode side]
As the current collector on the positive electrode side used in the hybrid capacitor of the present embodiment, it is preferable to use an aluminum material coated with an amorphous carbon film which is an aluminum material having improved corrosion resistance, and the current collector for the storage device electrode of the present invention. It is more preferable to use an electric body.
Further, it is preferable that the current collector on the positive electrode side has a conductive carbon layer formed between the amorphous carbon film and the positive electrode active material.

<Negative electrode>
The negative electrode used in the hybrid capacitor of the present embodiment includes a current collector (current collector on the negative electrode side) and a negative electrode active material layer formed on the current collector. The negative electrode active material layer contains a negative electrode active material, a binder, and a conductive material.
The negative electrode active material layer is formed by applying a paste-like negative electrode material containing a negative electrode active material, a binder, and an required amount of a conductive material on the current collector on the negative electrode side, and drying the negative electrode material. be able to.

[Negative electrode active material]
The negative electrode active material used in the hybrid capacitor of the present embodiment is a carbonaceous material capable of adsorbing and desorbing cations, which are electrolyte ions, in order to obtain a power storage device having a high withstand voltage.
As the negative electrode active material, a material capable of absorbing and desorbing a cation which is an electrolyte ion can be used, and for example, a carbonaceous material selected from the group consisting of activated carbon, graphite, hard carbon, and soft carbon can be used. ..

[Current collector on the negative electrode side]
As the current collector on the negative electrode side used in the hybrid capacitor of the present embodiment, a known one can be used, but aluminum in which a conductive carbon layer is formed between the amorphous carbon film and the negative electrode active material. A material selected from the group consisting of a material, an aluminum material coated with an amorphous carbon film, etched aluminum, and an aluminum material can be used. An aluminum material in which a conductive carbon layer is formed between the amorphous carbon film and the negative electrode active material or an aluminum material coated with the amorphous carbon film is preferable. These aluminum materials are aluminum materials having improved corrosion resistance. When these aluminum materials are used, the current collector for the power storage device electrode of the present invention can be used, and the high temperature durability performance can be improved when the hybrid capacitor is operated at a high voltage.
When the hybrid capacitor of the present embodiment uses an aluminum material in which a conductive carbon layer is formed between the amorphous carbon film and the negative electrode active material or an aluminum material coated with the amorphous carbon film, the above-mentioned It is preferable to use the current collector for the storage device electrode of the present invention.

<Binder>
The electrodes used in the hybrid capacitor of this embodiment preferably further contain a binder.
As the binder, for example, fluororesin, rubber, acrylic resin, olephine resin, carboxymethyl cellulose (CMC) resin, and natural polymer can be used. Examples of the fluororesin include polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). Examples of rubber include fluororubber, ethylene propylene diene rubber, and styrene butadiene rubber. Examples of natural polymers include gelatin, chitosan and alginic acid. One of these binders may be used alone, or two or more of these binders may be used in combination.

<Conductive material>
The conductive material used in the hybrid capacitor of the present embodiment is not particularly limited as long as it improves the conductivity of the negative electrode active material layer or the positive electrode active material layer, and a known conductive material can be used. For example, carbon black and carbon fiber can be used. Examples of carbon fibers include carbon nanotubes (CNT) and VGCF®. The carbon nanotubes may be single-walled carbon nanotubes or multi-walled carbon nanotubes. One of these conductive materials may be used alone, or two or more of them may be used in combination.

<Electrolytic solution>
As the electrolyte used in the hybrid capacitor of the present embodiment, for example, an organic electrolytic solution using an organic solvent can be used. As long as it contains electrolyte ions, it is not limited to the organic electrolyte. Further, for example, a gel may be used. The electrolyte contains electrolyte ions that can be attached to and detached from the electrode. It is preferable that the electrolyte ion has an ion diameter as small as possible. Specifically, ammonium salts, phosphonium salts, ionic liquids, lithium salts and the like can be used.

As the ammonium salt, tetraethylammonium (TEA) salt, triethylammonium (TEMA) salt and the like can be used. Further, as the phosphonium salt, a spiro compound having two five-membered rings or the like can be used.

The type of ionic liquid is not particularly limited, but a material having a viscosity as low as possible and a high conductivity (conductivity) is preferable from the viewpoint of facilitating the movement of electrolyte ions. Examples of the cation constituting the ionic liquid include imidazolium ion and pyridinium ion. Examples of the imidazolium ion include 1-ethyl-3-methylimidazolium (EMIm) ion and 1-methyl-1-propylpyrrolidinium (1-methyl-1-propylpyrrolidinium). Examples thereof include (MPPy) ion, 1-methyl-1-propylpiperidinium (MPPi) ion and the like. Further, as the lithium salt, lithium tetrafluorobolate LiBF ₄ , lithium hexafluorophosphate LiPF _6, or the like can be used.

Examples of the pyridinium ion include 1-ethylpyridinium ion, 1-butylpyridinium ion and the like.

Examples of anions constituting the ionic liquid include BF ₄ ion, PF ₆ ion, [(CF ₃ SO ₂ ) ₂ N] ion, FSI (bis (fluorosulfonyl) imide, bis (fluorosulfonyl) imide) ion, and TFSI (bis Examples thereof include trifluoromethylsulfonyl) imide and bis (trifluoromethyl sulphonyl) ion.

As the solvent, acetonitrile, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl sulfone, ethyl isopropyl sulfone, ethyl carbonate, fluoroethylene carbonate, γ-butyrolactone, sulfolane, N, N-dimethylformamide, dimethyl sulfoxide and the like are used. Can be done. One of these solvents may be used alone, or two or more of these solvents may be used in combination.

<Separator>
The separator used in the hybrid capacitor of the present embodiment includes a cellulosic paper-like separator, a glass fiber separator, and a microporous polyethylene or polypropylene film for the purpose of preventing a short circuit between the positive electrode and the negative electrode and ensuring the electrolyte liquid retention property. Etc. are suitable.

As described above, in the hybrid capacitor of the present embodiment, the aluminum material coated with the amorphous carbon film of the present invention (the current collector for the electrode of the power storage device of the present invention) is used to collect current on the positive side containing graphite. Used as a body. As a result, the hybrid capacitor of the present embodiment aims to increase the output, maintain a high energy density, and improve the output characteristics.
Further, in the hybrid capacitor of another embodiment according to the hybrid capacitor of the present embodiment, the aluminum material coated with the amorphous carbon film of the present invention (the current collector for the storage device electrode of the present invention) is used on the negative side. Used as a current collector. As a result, the hybrid capacitor of the other embodiment related to the hybrid capacitor of the present embodiment has further improved output characteristics while maintaining high energy density by further increasing the output.

The aluminum material coated with the amorphous carbon film of the present invention (the current collector for the power storage device electrode of the present invention) is preferably used as an electrode current collector for a hybrid capacitor having a positive electrode containing graphite. Further, the aluminum material coated with the amorphous carbon film of the present invention (current collector for the electrode of the power storage device of the present invention) can also be used as a current collector for the electrode of the power storage device such as EDLC.

(Dual ion battery)
A dual ion battery (DIB), which is another embodiment of the power storage device of the present invention, includes a positive electrode including a positive electrode side current collector and a positive electrode active material layer formed on the positive electrode side current collector, and a negative electrode side current collector. It has a negative electrode including a negative electrode active material layer formed on the negative electrode. The positive electrode active material contains graphite, and the negative electrode active material contains a metal oxide that can occlude and release cations. The current collector on the positive electrode side and the current collector on the negative electrode side are made of an aluminum material coated with an amorphous carbon film.

Hereinafter, the dual ion battery will be described in detail as another embodiment of the power storage device of the present invention, but the configuration common to the above-mentioned hybrid capacitor will be omitted.

In the present embodiment, the negative electrode is changed from the activated carbon negative electrode of the conventional power storage device to the lithium-containing metal oxide or the lithium-free metal oxide of the dual ion battery of the present embodiment (hereinafter, simply referred to as “MO _X ”). As a result, the charge / discharge capacity of the negative electrode increased. Examples of the lithium-containing metal oxide include lithium titanate. The problem that the activated carbon of the negative electrode became the rate-determining factor in the conventional power storage device and hindered the improvement of the energy density was solved. Theoretically, the energy density could be increased by making the capacity of graphite of the positive electrode more usable, but this time, the problem of lowering the cycle life characteristic appeared. The cause of this problem is that when MO _X such as lithium titanate is used for the negative electrode, the electrode potential when activated charcoal is used decreases and changes diagonally and linearly, whereas the potential of MO _X such as lithium titanate decreases. The curve becomes flat. Therefore, the potential curve of the case of using the MO _X and lithium titanate as a negative electrode, than the potential curve of the activated carbon, time of exposure in a more lower potential becomes longer. As a result, the current collector on the negative electrode side of the dual ion battery of the present embodiment is more easily dissolved than the current collector on the negative electrode side of the conventional power storage device. As a result, the high temperature durability performance is deteriorated, and the charge / discharge cycle life characteristics are deteriorated. To solve this problem, it has been found that the dissolution of the current collector can be suppressed by using the current collector having improved corrosion resistance of the present embodiment as the current collector on the negative electrode side. That is, the energy density of the cell could be improved by using a negative electrode active material having a charge / discharge capacity larger than that of activated carbon, but the effect of melting the current collector on the negative electrode side became apparent. The problem can be solved by applying the current collector having improved corrosion resistance of the present embodiment.

It is preferable to use the above-mentioned current collector for the power storage device electrode of the present invention as at least one of the current collector on the negative electrode side and the current collector on the positive electrode side of the dual ion battery of the present embodiment. When the positive electrode contains graphite, it is preferable to use the above-mentioned current collector for the power storage device electrode of the present invention as the current collector on the positive electrode side at least. It is more preferable to use the above-mentioned current collector for the power storage device electrode of the present invention for both the current collector on the negative electrode side and the current collector on the positive electrode side.

<Negative electrode>
The negative electrode used in the dual ion battery of the present embodiment includes a current collector (current collector on the negative electrode side) and a negative electrode active material layer formed on the current collector. The negative electrode active material layer contains a negative electrode active material, a binder, and a conductive material.
The negative electrode active material layer is formed by applying a paste-like negative electrode material containing a negative electrode active material, a binder, and an required amount of a conductive material on the current collector on the negative electrode side, and drying the negative electrode material. be able to.

[Negative electrode active material]
The negative electrode active material of the dual ion battery of the present embodiment contains a metal oxide capable of occluding and releasing a cation which is an electrolyte ion contained in an electrolytic solution described later. That is, any material that can reversibly insert and remove cations can be used. As the cation, for example, alkali metal ions such as Li, Na and K, alkaline earth metal ions such as Mg and Ca and the like can be used.
Here, an example using lithium will be illustrated. For example, a metal oxide capable of inserting and removing lithium can be used. More specifically, a metal oxide containing lithium or a metal oxide not containing lithium can be used. As the metal of the metal oxide capable of inserting and removing lithium, groups 4, 5, and 6 of the 4, 5, and 6 periods of the periodic table can be used. Specifically, it is preferable to use transition metals such as titanium (Ti), vanadium (V), chromium (Cr), zirconium (Zr), niobium (Nb), and molybdenum (Mo). Examples of the lithium-containing metal oxide include Li ₄ Ti ₅ O ₁₂ , which is a lithium-containing titanium oxide, LiNbO ₂ , which is a lithium-containing niobium oxide, and Li _1.1 V _0.9, which is a lithium-containing vanadium oxide. O _{2 and the} like can be used. Further, as the lithium-free metal oxide, for example, TiO ₂ , NbO ₂ , V ₂ O _5, or the like can be used.

From the viewpoint of further improving the high temperature durability, the capacity of the negative electrode active material per unit weight is preferably higher than the capacity of the positive electrode active material (graphite) described later per unit weight. The theoretical capacity of graphite used for the positive electrode is 372 mAh / g. However, the capacity of the graphite positive electrode of the present invention for inserting and desorbing a larger anion than that of lithium ion is preferably 50 mAh / g to 100 mAh / g from the viewpoint of cycle life and the degree of expansion of the graphite positive electrode. On the other hand, the theoretical capacities of the active material used for the negative electrode are as follows. Li ₄ Ti ₅ O ₁₂ is 175 mAh / g, LiNbO ₂ is 203 mAh / g, Li _1.1 V _0.9 O ₂ is 313 mAh / g, TiO ₂ is 335 mAh / g, NbO ₂ is 214 mAh / g, V ₂ O ₅ is 147 mAh / g. Unlike the above-mentioned graphite positive electrode, the negative electrode using these negative electrode active materials can be charged and discharged to near the theoretical capacity. Therefore, the practical capacity of the negative electrode active material is larger than the practical capacity of the graphite positive electrode (50 mAh / g to 100 mAh / g). That is, the positive electrode active material of the present invention is graphite having a practical capacity of 50 mAh / g to 100 mAh / g, and the negative electrode active material of the present invention is preferably higher than the practical capacity of the graphite positive electrode. The positive electrode active material of the present invention is more preferably graphite having a practical capacity of 50 mAh / g to 100 mAh / g. The negative electrode active material of the present invention is at least one selected from the group consisting of Li ₄ Ti ₅ O ₁₂ , LiNbO ₂ , Li _1.1 V _0.9 O ₂ , TiO ₂ , NbO ₂ , and V ₂ O _5. Is more preferable. The positive electrode active material of the present invention is graphite having a practical capacity of 50 mAh / g to 100 mAh / g, and the negative electrode active material of the present invention is more preferably Li ₄ Ti ₅ O ₁₂ .

[Current collector on the negative electrode side]
As the current collector on the negative electrode side used in the dual ion battery of the present embodiment, it is preferable to use an aluminum material coated with an amorphous carbon film. The aluminum material coated with the amorphous carbon film is an aluminum material having improved corrosion resistance. Further, it is more preferable to use the current collector for the electrode of the power storage device of the present invention as the current collector on the negative electrode side used in the dual ion battery of the present embodiment.

It is preferable that the current collector on the negative electrode side further has a conductive carbon layer formed between the amorphous carbon film and the negative electrode active material.

<Positive electrode>
The positive electrode used in the dual ion battery of the present embodiment includes a current collector (current collector on the positive electrode side) and a positive electrode active material layer formed on the current collector. The positive electrode active material layer contains a positive electrode active material, a binder, and a conductive material.
The positive electrode active material layer is formed by applying a paste-like positive electrode material containing a positive electrode active material, a binder, and an required amount of a conductive material on the current collector on the positive electrode side, and drying the layer. be able to.

[Positive electrode active material]
The positive electrode active material used in the dual ion battery of the present embodiment contains graphite, which is a carbonaceous material capable of inserting and removing anions, which are electrolyte ions, in order to obtain a dual ion battery having a high withstand voltage.
The details of graphite are as described in [Positive electrode active material] of the hybrid capacitor which is the power storage device of one embodiment of the present invention described above.

[Current collector on the positive electrode side]
As the current collector on the positive electrode side used in the dual ion battery of the present embodiment, it is preferable to use an aluminum material coated with an amorphous carbon film, similarly to the current collector on the negative electrode side. The aluminum material coated with the amorphous carbon film is an aluminum material having improved corrosion resistance. Further, it is more preferable to use the current collector for the electrode of the power storage device of the present invention as the current collector on the positive electrode side used in the dual ion battery of the present embodiment.
Further, it is preferable that the current collector on the positive electrode side has a conductive carbon film formed between the amorphous carbon film and the positive electrode active material, similarly to the current collector on the negative electrode side.

<Binder>
The negative electrode or positive electrode used in the dual ion battery of the present embodiment preferably further contains a binder.
As the binder, a binder of the same type as the power storage device (hybrid capacitor) according to the embodiment of the present invention can be used.

<Conductive material>
The conductive material used in the dual ion battery of the present embodiment is not particularly limited as long as it improves the conductivity of the negative electrode active material layer or the positive electrode active material layer, and a known conductive material can be used. For example, a device of the same type as the power storage device (hybrid capacitor) according to the embodiment of the present invention described above can be used.

<Electrolytic solution>
As the electrolytic solution used in the dual ion battery of the present embodiment, for example, an organic electrolytic solution in which an electrolyte is dissolved in an organic solvent can be used. The electrolyte contains electrolyte ions that can be inserted and removed from the electrode. Specifically, a lithium salt or the like can be used.
Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate and trifluoropropylene carbonate; and chain carbonates such as diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate and dipropyl carbonate. One of these organic solvents may be used alone, or two or more of them may be mixed and used.
Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) _{2, and the} like.
Further, an additive may be used in the electrolytic solution in order to improve high temperature durability performance, charge / discharge cycle characteristics, input / output characteristics, and the like.

<Separator>
As the separator used in the dual ion battery of the present embodiment, the same type as the above-mentioned power storage device (hybrid capacitor) of the one embodiment of the present invention can be used.

(Production Example 1) Production of current collector Production of current collector made of DLC-coated aluminum foil The DLC-coated aluminum foil (sometimes referred to as "DLC-coated aluminum foil" or "DLC-coated Al foil") is on the positive electrode side. It is a current collector and a current collector on the negative electrode side, and corresponds to an aluminum material coated with an amorphous carbon film. The manufacturing method of the DLC coated aluminum foil is as follows. The natural oxide film on the surface of the aluminum foil was removed by argon sputtering on an aluminum foil having a purity of 99.99% (manufactured by UACJ Co., Ltd., thickness 20 μm). Then, a discharge plasma was generated in a mixed gas of methane, acetylene and nitrogen in the vicinity of the surface of the aluminum foil, and a negative bias voltage was applied to the aluminum material to form a DLC film.
The DLC-coated Al foil formed at an atmospheric temperature of 25 ° C. at the time of film formation was transferred to an argon atmosphere furnace, and the temperature was raised to 500 ° C., which is the heat treatment temperature, under an argon flow (500 mL / min). Then, after holding at this temperature for 1 hour, it was naturally cooled to room temperature to produce a DLC coated Al foil (A). Here, the thickness of the DLC film on the aluminum foil coated (coated) with DLC was measured using a stylus type surface shape measuring instrument DektakXT manufactured by Bruker Co., Ltd. and found to be 150 nm. As a result of measuring the DLC coated Al foil (A) by the XAFS method described later, the sp ² / (sp ³ + sp ² ) ratio was 0.43. The results are shown in Table 1.

<Evaluation method: XAFS method>
The NEXAFS analysis was performed at the Ritsumeikan University SR Center BL-2 ultra-soft X-ray spectroscopic line, and the spectrum was acquired by the total electron yield method (TEY: Total Electron Yield) by measuring the sample current. The measured NEXAFS spectrum is CK-edge (260-345 eV). The slit size was 25 × 25 μm, the angle of incidence of X-rays on the sample was 90 °, and the spectrum integration time was 30 minutes each.
The energy axis calibration was performed using the literature values of a standard sample, highly oriented pyrolytic graphite (HOPG). In addition, the sp ² / (sp ³ + sp ² ) ratio was calculated based on the HOPG spectrum measured on the same day.

(Manufacturing Examples 2 to 5)
DLC-coated Al foil (B), DLC-coated Al foil (C), by the same post-heat treatment method as in Production Example 1 except that the heat treatment temperatures are 100 ° C., 200 ° C., 300 ° C., and 400 ° C., respectively. A DLC coated Al foil (D) and a DLC coated Al foil (E) were produced, respectively. With respect to the obtained DLC-coated Al foil, the sp ² / (sp ³ + sp ² ) ratio was measured in the same manner as in Production Example 1. The results are shown in Table 1.

(Manufacturing Example 6)
The DLC-coated Al foil (F) was produced by the same method as in Production Example 1 except that the DLC-coated Al foil formed at an atmospheric temperature of 25 ° C. was not heat-treated and was naturally cooled to room temperature. .. With respect to the obtained DLC-coated Al foil, the ratio of sp ² / (sp ³ + sp ² ) was measured by the same method as in Production Example 1. The results are shown in Table 1.

(Synthesis Example 1) Synthesis of negative electrode active material Synthesis of lithium titanate Anatase-type titanium oxide and lithium hydroxide having an average particle size of 3 μm were weighed so that the chemical ratio of titanium to lithium was 5: 4 mol. They were placed in a crucible and placed in an electric atmosphere furnace. Lithium titanate (Li ₄ Ti ₅ O ₁₂ , LTO) was obtained by firing in the air at 800 ° C. for 5 hours.

"Manufacturing of hybrid capacitors"
(Example 1)
(1) Preparation of paste for power storage device electrode Graphite manufactured by Imeris GC Japan Co., Ltd. (trade name: KS-6, average particle size 6 μm), acetylene black (conductive material), polyvinylidene fluoride (organic solvent) as positive electrode active material The system binder) was weighed so that the weight percent concentration (wt%) ratio was 80:10:10. They were dissolved and mixed with N-methylpyrrolidone (organic solvent) to prepare a positive electrode paste of this example.
As the negative electrode active material, activated carbon YP-50F manufactured by Kuraray Co., Ltd., acetylene black (conductive material), carboxymethyl cellulose (aqueous solution binder 1), and polyacrylic acid (aqueous solution binder 2) are 85 wt%: 5 wt%: Weighed so that the ratio was 5 wt%: 5 wt%. Then, they were dissolved and mixed with pure water to prepare the negative electrode paste of this example.

(2) Preparation of Power Storage Device Electrode The DLC-coated Al foil (A) obtained in Production Example 1 was used as a current collector on the positive electrode side, and the prepared positive electrode paste was applied onto the current collector using a desktop coater. After that, it was dried at 100 ° C. for 1 hour to prepare a positive electrode of this example.
When the thickness of the positive electrode was measured using a micrometer, it was 68 μm.
An etched aluminum foil (thickness 20 μm) manufactured by Nippon Denki Kogyo Co., Ltd. is used as a current collector on the negative electrode side, and the prepared negative electrode paste is applied onto the current collector using a desktop coater, and then dried at 100 ° C. for 1 hour. Then, the negative electrode of this example was prepared.
When the thickness of the negative electrode was measured using a micrometer, it was 88 μm.

<Manufacturing of coin cell type hybrid capacitor>
Next, the obtained positive electrode was punched into a disk shape having a diameter of 16 mm and the obtained negative electrode having a diameter of 14 mm, and vacuum dried at 150 ° C. for 24 hours. After that, it was moved to the argon glove box. The dried positive electrode and negative electrode were laminated via a paper separator (trade name: TF4540) manufactured by Nippon Kodoshi Paper Industry Co., Ltd. Add 1 M of SBP-BF ₄ (5-azoniaspirotetrafluorate [4.4] nonane) to the electrolyte and 0.1 mL of the electrolyte solution using PC (propylene carbonate) to the solvent, and add the book in an argon glove box. A 2032 type coin cell, which is a hybrid capacitor of the example, was produced.
The obtained hybrid capacitor was evaluated for its discharge rate characteristics and discharge capacity improvement rate by the evaluation method described later. The results are shown in Table 2.

(Example 2)
The positive electrode of Example 2 was produced in the same manner as in Example 1 except that the DLC-coated Al foil (E) obtained in Production Example 5 was used. Further, a hybrid capacitor was produced by the same method as in Example 1 except that the positive electrode of Example 2 was used. The obtained hybrid capacitor was evaluated for its discharge rate characteristics and discharge capacity improvement rate by the evaluation method described later. The results are shown in Table 2.

(Comparative Example 1)
The positive electrode of Comparative Example 1 was produced in the same manner as in Example 1 except that the DLC-coated Al foil (F) obtained in Production Example 6 was used. Further, a hybrid capacitor was produced by the same method as in Example 1 except that this positive electrode was used. The obtained hybrid capacitor was evaluated for its discharge rate characteristics and discharge capacity improvement rate by the evaluation method described later. The results are shown in Table 2.

(Comparative Examples 2 to 4)
The same method as in Example 1 was used except that the DLC-coated Al foil (B), the DLC-coated Al foil (C), and the DLC-coated Al foil (D) obtained in Production Examples 2 to 4 were used. Positive electrodes of Comparative Examples 2 to 4 were prepared. Further, a hybrid capacitor was produced by the same method as in Example 1 except that this positive electrode was used. The obtained hybrid capacitor was evaluated for its discharge rate characteristics and discharge capacity improvement rate by the evaluation method described later. The results are shown in Table 2.

"Manufacturing dual-ion batteries"
(Example 3)
<Manufacturing of negative electrode>
Lithium titanate (Li ₄ Ti ₅ O ₁₂ , LTO), acetylene black (conductive material), and vinylidene polyfluoride (organic solvent-based binder) obtained in Synthesis 1 as the negative electrode active material are used in a weight percent concentration (wt%). Weighed so that the ratio was 80:10:10. The negative electrode paste obtained by dissolving and mixing these with N-methylpyrrolidone (organic solvent) was applied onto plain Al (manufactured by UACJ Foil Corporation, thickness 20 μm) using a doctor blade. Then, it was dried, and the negative electrode of this Example was obtained. When the thickness of the negative electrode was measured using a micrometer, it was 48 μm.

<Manufacturing of coin cell type dual ion battery>
A 2032 type coin cell, which is a dual ion battery of this example, was produced by the same method as in Example 1 except that 3-LiPF ₆ / EMC was used as the electrolytic solution using the prepared negative electrode of this example. .. The obtained dual ion battery was evaluated for its discharge rate characteristics and discharge capacity improvement rate by the evaluation method described later. The results are shown in Table 3.

(Example 4)
A coin cell was produced in the same manner as in Example 3 except that the DLC-coated Al foil (A) obtained in Production Example 1 was used as the current collector on the negative electrode side. The obtained dual ion battery was evaluated for its discharge rate characteristics and discharge capacity improvement rate by the evaluation method described later. The results are shown in Table 3.

(Comparative Example 5)
A coin cell was produced by the same method as in Example 3 except that the same positive electrode as in Comparative Example 1 was used. The obtained dual ion battery was evaluated for its discharge rate characteristics and discharge capacity improvement rate by the evaluation method described later. The results are shown in Table 3.

(Test 1) Evaluation of power storage device <Discharge rate characteristics>
The obtained cell was subjected to a constant current at a current density of 0.2 mA / cm ² or 14 mA / cm ² and a voltage of 3.5 V in a constant temperature bath at 25 ° C. using a charge / discharge test device BTS2004 manufactured by Nagano Co., Ltd. Constant voltage charging was performed. Then, a charge / discharge test was carried out in which a discharge current value of 0.2 mA / cm ² was used to discharge the battery to a predetermined final voltage. Here, the final discharge voltage of the hybrid capacitors of Examples 1 to 4 and Comparative Examples 1 to 4 is 0 V, and the final discharge voltage of the dual ion batteries of Examples 5 and 6 and Comparative Example 5 is 2 V. I went there. The ratio of the discharge capacity at 14 mA / cm ² to the discharge capacity when the charge / discharge test was performed at a current density of 0.2 mA / cm ² obtained as a result was calculated to obtain the discharge rate. The results are shown in Tables 2 and 3. In Table 2, the results of the discharge rate characteristics of Examples 1 and 2 and Comparative Examples 2 and 3 show standardized values with the discharge rate value of Comparative Example 1 as 100. For example, when the discharge rate of Comparative Example 1 is X and the discharge rate of Example 1 is Y, the discharge rate characteristic of Comparative Example 1 is 100, and the discharge rate characteristic of Example 1 is 100 Y / X. In Table 3, the results of the discharge rate characteristics of Examples 3 and 4 show the values standardized with Comparative Example 5 as 100.

(Test 2) Evaluation of power storage device <Discharge capacity improvement rate>
The obtained cell is charged with a constant current constant voltage at a current density of 0.2 mA / cm ² and a voltage of 3.5 V in a constant temperature bath at 25 ° C. using a charge / discharge test device BTS2004 manufactured by Nagano Co., Ltd. It was. Then, a charge / discharge test was carried out in which a discharge current value of 0.2 mA / cm ² was used to discharge the battery to a predetermined final voltage. In addition, the discharge capacity before the constant current / constant voltage continuous charging test was measured. Here, the final discharge voltage in the case of the hybrid capacitor was 0 V, and the final discharge voltage in the case of the dual ion battery was 2 V.
Next, using the charge / discharge test device BTS2004, a continuous charging test (constant current constant voltage continuous charging test) was performed in a constant temperature bath at 60 ° C. at a current density of 0.2 mA / cm ² and a voltage of 3.5 V. Specifically, during charging, charging is stopped at a predetermined time, the cell is moved to a constant temperature bath at 25 ° C., and then the current density is 0.2 mA / cm ² and the voltage is 3.5 V in the same manner as above. Current constant voltage charging was performed. Then, discharge was performed to a predetermined end voltage with a discharge current value of a current density of 0.2 mA / cm ² . The discharge capacity was obtained by performing this charge / discharge test 5 times. Here, the final discharge voltage in the case of the hybrid capacitor was 0 V, and the final discharge voltage in the case of the dual ion battery was 2 V. Then, the mixture was returned to a constant temperature bath at 60 ° C. and the continuous charging test was restarted, and the test was carried out until the total continuous charging test time reached 2000 hours. The discharge capacity at that time was measured.
The discharge capacity improvement rate is compared with the charge time when the discharge capacity maintenance rate after the constant current constant voltage continuous charge test is 80% or less of the discharge capacity before the start of the constant current constant voltage continuous charge test. It is a value standardized with the time at which the life reached in the target comparative example as 100.

In Table 2, the results of the discharge capacity improvement rates of Examples 1 and 2 and Comparative Examples 2 and 3 show the values standardized with the value of the discharge capacity improvement rate of Comparative Example 1 as 100. In Table 3, the results of the discharge capacity improvement rates of Examples 3 and 4 show the values standardized with the discharge capacity improvement rate of Comparative Example 5 as 100.

As shown in Table 2, Examples 1 and 2 using the current collector for the power storage device electrode of the present invention obtained excellent discharge rate characteristics and discharge capacity improvement rates as compared with Comparative Examples 1 to 4. Similarly, as shown in Table 3, Examples 3 and 4 using the current collector for the power storage device electrode of the present invention obtained excellent discharge rate characteristics and discharge capacity improvement rate as compared with Comparative Example 5. The DLC coated Al foil (A), the DLC coated Al foil (E), the DLC coated Al foil (F), and the DLC coated Al foil (G) formed at a temperature of 400 ° C. or higher were sp ² / measured by the XAFS method. The ratio (sp ³ + sp ² ) was 0.35 or more. Therefore, it was a DLC film having a developed graphite structure. When the current collector for the power storage device electrode including the DLC film is applied to the positive electrodes for the hybrid capacitors of Examples 1 to 4 and the dual ion batteries of Examples 5 and 6, the interfacial resistance between the current collector and the active material layer. It is considered that the output characteristics could be improved.

In the power storage device of Example 1, since the sp ² / (sp ³ + sp ² ) ratio of the DLC coated Al foil (A) obtained at a processing temperature of 500 ° C. or higher is 0.40 or more, the power storage device of Example 2 is stored. It was found that it showed even better characteristics than the device.

In Example 4, both the current collector on the negative electrode side and the current collector on the positive electrode side use the current collector for the electrode of the power storage device of the present invention (DLC coated Al foil (A). Example 3 uses the current collector on the positive electrode side. Only the current collector The current collector for the electrode of the power storage device of the present invention (DLC-coated Al foil (A) is used. Example 4 has the same discharge rate characteristics as Example 3, but the discharge capacity. The improvement rate was further improved. It was found that the current collector for the power storage device electrode of the present invention is effective even when applied to the negative electrode.

Claims (9)

1. With aluminum material
   The amorphous carbon film formed on the aluminum material and
   A current collector for the electrode of a power storage device including
   In the amorphous carbon film, the ratio of sp ^2- bonded carbon to the total amount of sp ^2- bonded carbon and sp ^3- bonded carbon (sp ² / (sp ³ + sp ² )) is 0.35 or more.
   The current collector for a power storage device electrode, characterized in that the ratio (sp ² / (sp ³ + sp ² )) is measured by the X-ray absorption fine structure (XAFS) method.
2. The current collector for the storage device electrode is a current collector for a hybrid capacitor positive electrode or a current collector for a dual ion battery positive electrode.
   The current collector for a power storage device electrode according to claim 1, wherein the hybrid capacitor positive electrode or the dual ion battery positive electrode contains graphite as a positive electrode active material.
3. The current collector for the storage device electrode is a current collector for a hybrid capacitor negative electrode or a current collector for a dual ion battery negative electrode.
   The power storage device electrode according to claim 1, wherein the hybrid capacitor negative electrode or the dual ion battery negative electrode includes one selected from the group consisting of activated carbon, graphite, hard carbon, soft carbon, and lithium titanate as the negative electrode active material. Collector.
4. A film forming process for forming an amorphous carbon film on an aluminum material,
   A method for manufacturing a current collector for a power storage device electrode, which comprises a heat treatment step of heat-treating the amorphous carbon film at a temperature of 400 ° C. or higher.
5. The method for manufacturing a current collector for a power storage device electrode according to claim 4, wherein the heat treatment step is performed after the film forming step.
6. With aluminum material
   The amorphous carbon film formed on the aluminum material and
   A current collector for the electrode of a power storage device including
   A current collector for a power storage device electrode, wherein the amorphous carbon film is obtained by the production method according to claim 4 or 5.
7. A power storage device composed of at least a positive electrode, a negative electrode, and an electrolyte.
   The positive electrode contains a positive electrode active material, and the negative electrode contains a negative electrode active material.
   The positive electrode active material contains graphite and contains graphite.
   The current collector on the positive electrode side is the current collector for the power storage device electrode according to claim 1 or 6.
   A power storage device characterized by this.
8. The power storage device according to claim 7, wherein the graphite contains rhombohedral crystals.
9. The negative electrode active material contains one selected from the group consisting of activated carbon, graphite, hard carbon, soft carbon, and lithium titanate.
   The current collector on the negative electrode side is one selected from the group consisting of the current collector for the power storage device electrode according to claims 1 and 6, etched aluminum, and an aluminum material, according to claim 7 or 8. Power storage device.

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