WO2020195724A1

WO2020195724A1 - Active material for electricity storage device positive electrodes, positive electrode for electricity storage devices, and electricity storage device

Info

Publication number: WO2020195724A1
Application number: PCT/JP2020/009805
Authority: WO
Inventors: 健吾山内; 弘義武; 矢野　雅也
Original assignee: 日東電工株式会社
Priority date: 2019-03-27
Filing date: 2020-03-06
Publication date: 2020-10-01
Also published as: JP2020161737A

Abstract

This active material for electricity storage device positive electrodes contains at least one of a polyaniline and a polyaniline derivative, which has an oxidant and a reductant. With respect to this active material for positive electrodes, the ratio of the peak intensity at a mass number m/z of 292.1 to the peak intensity at a mass number m/z of 77.0 as determined by time-of-flight secondary ion mass spectrometry (TOF-SIMS) is 0.080 or less.

Description

Active material for power storage device positive electrode, positive electrode for power storage device, and power storage device

The present invention relates to an active material for a positive electrode of a power storage device, a positive electrode for a power storage device, and a power storage device.

Conventionally, a technique of using an electrochemically active polymer such as polyaniline as an active material in the positive electrode of a power storage device has been known.

For example, Patent Document 1 describes a positive electrode for a power storage device containing polyaniline or a derivative thereof as an active material. Polyaniline in a reduction dedoping state is used for producing a positive electrode for a power storage device.

Japanese Unexamined Patent Publication No. 2014-53297

In Patent Document 1, no attempt has been made to produce a positive electrode for a power storage device using polyaniline in a semi-oxidized state having an oxidized body and a reduced body. Therefore, the present invention provides an active material for a positive electrode which is advantageous from the viewpoint of increasing the initial discharge capacity of a power storage device while containing at least one of a semi-oxidized polyaniline and a polyaniline derivative having an oxidant and a reducer.

The present invention
Containing at least one of a polyaniline and a polyaniline derivative having an oxidant and a reduced form,
The ratio of the peak intensity of mass number m / z: 292.1 to the peak intensity of mass number m / z: 77.0 determined by time-of-flight secondary ion mass spectrometry (TOF-SIMS) is 0. 080 or less,
Provided is an active material for a positive electrode of a power storage device.

The present invention
Containing at least one of a polyaniline and a polyaniline derivative having an oxidant and a reduced form,
Of the peak intensities of mass number m / z: 77.0 determined by time-of-flight secondary ion mass spectrometry (TOF-SIMS), the mass number m / z relative to the peak intensity derived from the aromatic hydrocarbon structure. Among the peak intensities of z: 292.1, the ratio of the peak intensities derived from oligomers containing oxygen atoms is 0.080 or less.
Provided is an active material for a positive electrode of a power storage device.

The present invention
Containing at least one of a polyaniline and a polyaniline derivative having an oxidant and a reduced form,
Of the peak intensities of mass number m / z: 77.0 determined by time-of-flight secondary ion mass spectrometry (TOF-SIMS), the mass number m / z with respect to the peak intensity derived from C ₆ H ₅ ^+. Of the peak intensities of z: 292.1, the ratio of the peak intensities derived from C ₁₈ H ₁₈ N ₃ O ⁺ or C ₁₈ H ₁₆ N ₂ O ₂ ⁺ is 0.080 or less.
Provided is an active material for a positive electrode of a power storage device.

The present invention also provides a positive electrode for a power storage device provided with an active material layer containing the above-mentioned active material for a positive electrode for a power storage device.

In addition, the present invention
With the electrolyte layer,
A negative electrode arranged in contact with the first main surface of the electrolyte layer,
The positive electrode for a power storage device, which is arranged in contact with the second main surface of the electrolyte layer, is provided.
Provides a power storage device.

The above-mentioned active material for the positive electrode of the power storage device is advantageous from the viewpoint of increasing the initial discharge capacity of the power storage device.

FIG. 1 is a cross-sectional view showing an example of a positive electrode for a power storage device according to the present invention. FIG. 2 is a cross-sectional view showing an example of a power storage device according to the present invention. FIG. 3 is a graph showing the relationship between the ratio of the amount of substance of APS to the amount of substance of aniline used for preparing the active material for the positive electrode and It / Ia. FIG. 4 is a graph showing the relationship between the initial discharge capacity Ai of the power storage device and It / Ia in the positive electrode active material.

When polyaniline in a reduction dedoping state is used in the production of a positive electrode for a power storage device as in the technique described in Patent Document 1, it is difficult to improve the durability of the power storage device. Therefore, in order to eliminate the drawbacks of polyaniline in the reduction-dedoped state, it is possible to fabricate a storage device using a positive electrode active material containing at least one of a semi-oxidized polyaniline having an oxide and a reduced body and a polyaniline derivative. Conceivable. As a result of repeated studies on the positive electrode active material from this point of view, the present inventors have newly found that the amount of a predetermined mass number of substances in the positive electrode active material affects the initial discharge capacity of the power storage device. Found in. Based on this new finding, the present inventors have devised an active material for a positive electrode of a power storage device according to the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments.

The active material for the positive electrode of the power storage device according to the present invention (hereinafter, may be referred to as "active material for the positive electrode") includes at least one of a polyaniline and a polyaniline derivative having an oxidized body and a reduced body. In other words, the positive electrode active material contains at least one of a polyaniline and a polyaniline derivative in a semi-oxidized state. In addition, the positive electrode active material is the ratio of the peak intensity It of mass number m / z: 292.1 to the peak intensity Ia of mass number m / z: 77.0 determined by TOF-SIMS (It / Ia) is 0.080 or less.

When It / Ia of the positive electrode active material is 0.080 or less, the initial discharge capacity of the power storage device manufactured using this positive electrode active material tends to increase.

In the positive electrode active material, It / Ia is preferably 0.070 or less, and more preferably 0.060 or less.

In the positive electrode active material, the peak intensity of mass number m / z: 77.0 determined by TOF-SIMS has a mass number of m / z: 292.1 with respect to the peak intensity derived from the aromatic hydrocarbon structure. The ratio of the peak intensities derived from the oligomer containing oxygen atoms to the peak intensities can be 0.080 or less. In this case, the amount of the oligomer containing an oxygen atom having a mass number of m / z: 292.1 is likely to be kept low. As a result, it is considered that the initial discharge capacity of the power storage device manufactured by using this positive electrode active material is likely to increase.

In the positive electrode active material, the mass number m / z: 292.1 with respect to the peak intensity derived from C ₆ H ₅ ⁺ among the peak intensities of mass number m / z: 77.0 determined by TOF-SIMS. Of the peak intensities, the ratio of the peak intensities derived from C ₁₈ H ₁₈ N ₃ O ⁺ or C ₁₈ H ₁₆ N ₂ O ₂ ⁺ can be 0.080 or less. In this case, the amount of C ₁₈ H ₁₈ N ₃ O ⁺ or C ₁₈ H ₁₆ N ₂ O ₂ ⁺ having a mass number m / z: 292.1 tends to be kept low. As a result, it is considered that the initial discharge capacity of the power storage device manufactured by using this positive electrode active material is likely to increase.

The polyaniline compound contains, for example, 35 to 60% of an oxide by weight. In this case, the storage stability of the polyaniline compound is good, and the durability of the power storage device can be more reliably increased. The chemical structures of the oxidized form Ox and the reduced form Red of polyaniline are shown in the following formula (a). In the formula (a), each of x and y is an integer of 0 or more.

The content of the oxidant in the polyaniline compound can be determined, for example, from the solid ¹³ CNMR spectrum. The content of the oxidant in the polyaniline compound is the degree of oxidation represented by the ratio A640 / A340 of the maximum absorption A640 near 640 nm and the maximum absorption A340 near 340 nm in the electron spectrum of the spectrophotometer. It can also be calculated from the index. The content of the oxidant (ratio of the oxidant) in the polyaniline compound can be determined, for example, according to the method described in paragraphs 0040 to 0051 of JP-A-2018-26341.

The semi-oxidized polyaniline is typically obtained by electrolytic polymerization or chemical oxidation polymerization of aniline. The semi-oxidized polyaniline derivative is typically obtained by electrolytic or chemical oxidative polymerization of the aniline derivative. The aniline derivative has, for example, at least one substituent such as an alkyl group, an alkenyl group, an alkoxy group, an aryl group, an aryloxy group, an alkylaryl group, an arylalkyl group, and an alkoxyalkyl group at a position other than the 4-position of aniline. Have. The aniline derivative is, for example, (i) o-substituted aniline such as o-methylaniline, o-ethylaniline, o-phenylaniline, o-methoxyaniline, and o-ethoxyaniline, or (ii) m-methylaniline. , M-Ethylaniline, m-methoxyaniline, m-ethoxyaniline, m-phenylaniline and the like can be m-substituted anilines. In the synthesis of the polyaniline derivative, only one kind of aniline derivative may be used, or two or more kinds of aniline derivatives may be used in combination.

When a semi-oxidized polyaniline compound is obtained by chemical oxidative polymerization of aniline or an aniline derivative, for example, a predetermined oxidizing agent is used. The oxidant is not limited to a specific oxidant as long as It / Ia can be adjusted to 0.080 or less in the positive electrode active material. The oxidizing agent is selected from the group consisting of, for example, ammonium peroxodisulfate (APS), hydrogen peroxide, potassium dichromate, potassium permanganate, sodium chlorate, ammonium cerium nitrate, sodium iodate, iron chloride, and manganese dioxide. At least one.

For example, in the chemical oxidative polymerization of aniline or an aniline derivative, by adjusting the ratio (No / Na) of the substance amount No of the oxidizing agent to the substance amount Na of the aniline or the aniline derivative, It / Ia is set to 0 in the positive electrode active material. Easy to adjust to .080 or less. For example, when APS is used as an oxidizing agent in the chemical oxidative polymerization of aniline or an aniline derivative, No / Na is, for example, 0.725 to 1.40. No / Na may be 0.825 to 1.30 or 0.875 to 1.25.

Dopants such as protonic acid may be doped into polyaniline compounds in order to impart conductivity. On the other hand, the polyaniline and the polyaniline derivative contained in the positive electrode active material are preferably dedoping at the time of producing the positive electrode for the power storage device. Specifically, the polyaniline compound contained in the active material for the positive electrode is in a state in which a dopant such as a protonic acid is dedoping. In this case, the positive electrode active material is likely to be appropriately dispersed in the active material layer, and the energy density of the power storage device is likely to increase. This is because the dedoping polyaniline compound disperses well in the slurry even if the dispersion medium of the slurry for forming the active material layer is water. On the other hand, it may be difficult to satisfactorily disperse the doped polyaniline compound using water as a dispersion medium.

The polyaniline compound contained in the active material for the positive electrode is preferably dedoping at the time of assembling the power storage device. When the power storage device is in a charged state, the polyaniline compound contained in the positive electrode active material is in a doped state. It is conceivable to assemble a power storage device by combining a positive electrode chemically doped in advance and a negative electrode that has not been charged. In this case, in the initial charge of the power storage device, only the chemically undoped polyaniline compound at the positive electrode contributes to the charge. Therefore, the initial charge capacity of the power storage device is significantly reduced, which is not preferable for the power storage device. It is also conceivable to assemble a power storage device by combining a positive electrode chemically doped in advance and a negative electrode such as a lithium pre-doped negative electrode. In this case, it is possible to discharge immediately after assembling the power storage device, but the chemically doped positive electrode is difficult to be electrochemically doped and dedoping, resulting in a decrease in the capacity of the power storage device. Therefore, it is difficult to obtain a desired power storage device. Even if the polymer is electrochemically active in a dedoping state when the positive electrode is manufactured or when the power storage device is assembled, it is electrochemically doped from the time when charging is started after the power storage device is assembled. After that, the polyaniline compound contained in the active material for the positive electrode is repeatedly doped and dedoping, so that it can be used as a power storage device.

In order to adjust It / Ia to 0.080 or less in the positive electrode active material, the semi-oxidized polyaniline compound obtained as described above may be washed, classified, or pulverized. .. The classification method is not limited to a specific method, and a known classification method can be applied. The method of pulverization is not limited to a specific method. The pulverization method is at least one selected from the group consisting of, for example, a ball mill, a bead mill, a sand mill, a jet mill, and a roll mill.

The positive electrode active material has, for example, an average particle size of more than 0.5 μm and 20 μm or less. As a result, the initial discharge capacity of the power storage device tends to increase more reliably. The average particle size of the positive electrode active material is the maximum of 50 or more positive electrode active materials when observing 50 or more positive electrode active materials using an electron microscope such as a scanning electron microscope (SEM). It can be determined by measuring the diameter. Alternatively, the average particle size of the active material for the positive electrode may be determined using a particle image analyzer that images the shape of the particles using a microscope and analyzes them by image analysis. As used herein, the "average particle size" refers to the median diameter (D50). The median diameter is a particle size such that the number of particles having a particle size larger than that value is equal to the number of particles having a particle size smaller than that value.

In the positive electrode active material, the ratio (D90 / D10) of the 90% particle diameter (D90) to the 10% particle diameter (D10) in the number-based particle diameter distribution is, for example, 20 or less. As a result, the initial discharge capacity of the power storage device tends to increase more reliably. The positive electrode active materials D10 and D90 can be determined using, for example, the above-mentioned particle image analyzer.

The positive electrode for a power storage device can be provided by using the above-mentioned active material for a positive electrode. As shown in FIG. 1, the positive electrode 1 for a power storage device includes an active material layer 10. The active material layer 10 contains the above-mentioned positive electrode active material (positive electrode active material 12). As a result, the initial discharge capacity of the power storage device manufactured by using the positive electrode 1 tends to increase.

The content of the positive electrode active material 12 in the active material layer 10 is, for example, 1% or more, preferably 5% or more, more preferably 20% or more, and further preferably 40% or more on a weight basis. Yes, especially preferably 60% or more. As a result, the energy density of the power storage device tends to increase.

As shown in FIG. 1, the active material layer 10 further contains, for example, a conductive additive 14. The conductive auxiliary agent 14 is typically made of a conductive material having properties that do not change with the voltage applied for charging and discharging the power storage device. The conductive auxiliary agent 14 can be a conductive carbon material or a metallic material. The conductive carbon material is, for example, conductive carbon black such as acetylene black and Ketjen black, or fibrous carbon material such as carbon fiber and carbon nanotube. The conductive carbon material is preferably conductive carbon black.

The content of the conductive additive 14 in the active material layer 10 is, for example, 1 to 30%, preferably 4 to 25%, and more preferably 4 to 19% on a weight basis. As a result, the positive electrode active material 12 can be activated more reliably while suppressing the content of the conductive auxiliary agent 14. As a result, it is easy to increase the energy density of the power storage device.

As shown in FIG. 1, the active material layer 10 further contains, for example, a binder 15. The binder 15 contains, for example, an elastomer. The elastomer can be natural rubber, synthetic rubber, or thermoplastic elastomer. The binder 15 is typically in contact with the outer surface of the positive electrode active material 12 and the outer surface of the conductive additive 14. The binder 15 binds the positive electrode active material 12 and the conductive auxiliary agent 14. The binder 15 binds the positive electrode active material 12 and the conductive auxiliary agent 14. As shown in FIG. 1, the active material layer 10 has, for example, pores 16. The pores 16 are formed so as to be continuous from one main surface of the active material layer 10 to the other main surface, for example. In the power storage device manufactured by using the positive electrode 1, the pores 16 are impregnated with the electrolytic solution. Since the binder 15 contains an elastomer, the binder 15 is easily deformed without generating a large stress according to the dimensional change of the electrochemically active polymer particles accompanying the charging and discharging of the power storage device. As a result, it is considered that the desired characteristics related to rapid charging / discharging are likely to be exhibited in the power storage device.

The binder 15 contains, for example, a rubber material. In this case, the rubber material can be, for example, a styrene-butadiene copolymer, an acrylonitrile-butadiene copolymer, or a methyl methacrylate-butadiene copolymer.

The total of the polar term and the hydrogen bond term in the Hansen solubility parameter of the binder 15 is, for example, 20 MPa ^1/2 or less. In this case, the binder 15 and the positive electrode active material 12 have a good affinity, and the conductive auxiliary agent 14 easily comes into contact with the positive electrode active material 12. The calculation for determining the Hansen solubility parameter can be performed according to the method described in Charles M. Hansen, Hansen Solubility Parameters: A Users Handbook (CRC Press, 2007). In addition, the Hansen Solubility Parameters in Practice (HSPiP), a computer software, can be used to calculate the Hansen solubility parameter from the chemical structure. Further, the total of the polarity term and the hydrogen bond term in the Hansen solubility parameter of the binder made of the composite material is determined by summing the product of the Hansen solubility parameter of each component constituting the binder and the mass-based composition ratio of each component. it can. The sum of the polar term and the hydrogen bond term in the Hansen solubility parameter of the binder 15 is preferably 19 MPa ^1/2 or less, more preferably 12 MPa ^1/2 or less, and further preferably 8 MPa ^1/2 or less. ..

The content of the binder 15 in the active material layer 10 is, for example, 1 to 30%, preferably 4 to 25%, and more preferably 4 to 18% on a weight basis. As a result, the positive electrode active material 12 can be appropriately dispersed in the active material layer 10 while suppressing the content of the binder 15. As a result, it is easy to increase the energy density in the power storage device.

The active material layer 10 may contain an active material other than the positive electrode active material 12, if necessary. The active material other than the positive electrode active material 12 is, for example, a carbon material such as activated carbon. The activated carbon can be an alkaline activated carbon, a steam activated carbon, a gas activated carbon, or a zinc chloride activated carbon.

The active material layer 10 may further contain an additive such as a thickener, if necessary. Thickeners are, for example, methyl cellulose, hydroxyethyl cellulose, polyethylene oxide, carboxymethyl cellulose, derivatives thereof, or salts thereof. Among them, carboxylmethyl cellulose, a derivative thereof, or a salt thereof is preferably used as a thickener.

The content of the thickener in the active material layer 10 is, for example, 1 to 20%, preferably 1 to 10%, and more preferably 1 to 8% on a weight basis.

As shown in FIG. 1, the positive electrode 1 further includes, for example, a current collector 20 and a conductive layer 30. The conductive layer 30 is arranged between the active material layer 10 and the current collector 20. The conductive layer 30 is in contact with the active material layer 10 and the current collector 20. Due to the conductive layer 30, peeling or the like is unlikely to occur between the active material layer 10 and the current collector 20. The conductive layer 30 may be omitted, and the active material layer 10 may be in direct contact with the current collector 20.

The conductive layer 30 is not limited to a specific embodiment. The conductive layer 30 contains, for example, conductive particles 32 made of a carbon material such as graphite, and a binder 35 in contact with the outer surface of the conductive particles 32. In this case, the conductive layer 30 easily adheres to the active material layer 10 and the current collector 20.

The thickness of the conductive layer 30 has a thickness of, for example, 0.1 μm to 20 μm. The conductive layer 30 may have a thickness of 0.1 μm to 10 μm, or may have a thickness of 0.1 μm to 5 μm.

The contact angle of water droplets on the surface formed by the conductive layer 30 is, for example, 100 ° or less. The contact angle of water droplets on the surface of the conductive layer 30 can be measured, for example, according to the static droplet method in Japanese Industrial Standards JIS R 3257: 1999 before forming the active material layer 10. The measurement temperature of the contact angle of the water droplet is 25 ° C. The contact angle of water droplets on the surface of the conductive layer 30 is determined by, for example, forming the active material layer 10 and then removing at least a part of the active material layer 10 by a method such as polishing or cutting to expose the conductive layer 30. It may be measured on the surface of the conductive layer 30. In addition, at least a part of the current collector 20 may be removed by a method such as polishing or cutting to expose the conductive layer 30, and measurement may be performed on the surface of the exposed conductive layer 30.

The small contact angle of water droplets on the main surface of the conductive layer 30 is advantageous from the viewpoint of enhancing the adhesion between the conductive layer 30 and the active material layer 10. The contact angle of the water droplets is preferably 90 ° or less, more preferably 80 ° or less, and even more preferably 70 ° or less. The contact angle of the water droplet is, for example, 10 ° or more.

The peel strength P of the active material layer 10 with respect to the conductive layer 30 measured by the Surface And Interfacial Cutting Analysis System (SAICAS) is, for example, 0.15 kN / m or more. The peel strength P is determined by, for example, the following formula (1). The measurement mode of SAICAS is the constant speed mode. The cutting speed is 10 μm / sec. FH is the horizontal cutting stress [N] when the SAICAS diamond cutting edge (manufactured by Daipla, rake angle: 10 °) is horizontally moved at the interface between the active material layer 10 and the conductive layer 30. W is the blade width [m] of the cutting blade of SAICAS. SAICAS is a registered trademark of Daipla Co., Ltd.
P = FH / W (1)

The larger the peel strength P, the higher the adhesion between the conductive layer 30 and the active material layer 10. The peel strength P is preferably 0.15 kN / m or more, more preferably 0.17 kN / m or more, and further preferably 0.23 kN / m or more.

The binder 35 of the conductive layer 30 is not limited to a specific binder as long as the discharge capacity of the power storage device at low temperature can be increased. The binder 35 contains, for example, at least one selected from the group consisting of methyl cellulose, hydroxyethyl cellulose, polyethylene oxide, carboxymethyl cellulose, derivatives thereof, salts thereof, polyolefins, natural rubbers, synthetic rubbers, and thermoplastic elastomers. In this case, the conductive layer 30 easily adheres to the active material layer 10 and the current collector 20. In particular, when the total of the polar term and the hydrogen bond term in the Hansen solubility parameter of the binder 15 is 20 MPa ^1/2 or less, and the binder 35 of the conductive layer 30 contains the above components, the active material layer 10 and Adhesion with the conductive layer 30 tends to be high.

As the synthetic rubber or thermoplastic elastomer, for example, a styrene-butadiene copolymer, an acrylonitrile-butadiene copolymer, or a methyl methacrylate-butadiene copolymer can be used.

The binder 35 may contain at least one selected from the group consisting of polyolefin, carboxymethyl cellulose, and styrene-butadiene copolymer. In this case, the adhesion between the conductive layer 30 and the active material layer 10 or the current collector 20 tends to increase more reliably.

The binder 35 preferably contains at least one of carboxymethyl cellulose and a styrene-butadiene copolymer. In this case, the adhesion between the conductive layer 30 and the active material layer 10 tends to increase.

The current collector 20 is a foil or mesh made of a metal material such as nickel, aluminum, and stainless steel.

An example of a method for manufacturing the positive electrode 1 will be described. First, the current collector 20 is prepared, and the conductive layer 30 is formed on the main surface of the current collector 20. The conductive layer 30 is formed, for example, by coating, sputtering, vapor deposition, ion plating, or CVD using a predetermined raw material. Desirably, the conductive layer 30 is formed by applying a slurry prepared by dispersing the conductive particles 32 and the binder 35 in a dispersion medium to the main surface of the current collector 20 to form a coating film, and the coating film is dried. It can be formed by that. Then, a slurry prepared by dispersing the positive electrode active material 12, the conductive auxiliary agent 14, and the binder 15 in a dispersion medium is applied to the surface of the conductive layer 30 to form a coating film, and the coating film is dried. The active material layer 10 can be formed by. In this way, the positive electrode 1 can be manufactured. If necessary, an active material other than the positive electrode active material 12 and an additive such as a thickener are added to the slurry for forming the active material layer 10.

As shown in FIG. 2, the power storage device 5 can be provided by using the positive electrode 1. The power storage device 5 includes an electrolyte layer 3, a negative electrode 2, and a positive electrode 1. The negative electrode 2 is arranged in contact with the first main surface of the electrolyte layer 3. The positive electrode 1 is arranged in contact with the second main surface of the electrolyte layer 3. The active material layer 10 of the positive electrode 1 is in contact with the second main surface of the electrolyte layer 3. The electrolyte layer 3 is arranged between the positive electrode 1 and the negative electrode 2. Since the power storage device 5 includes the positive electrode 1, it is easy to exhibit a high initial discharge capacity.

The electrolyte layer 3 is composed of an electrolyte. The electrolyte layer 3 is, for example, a sheet in which a separator is impregnated with an electrolytic solution or a sheet made of a solid electrolyte. When the electrolyte layer 3 is a sheet made of a solid electrolyte, the electrolyte layer 3 itself may also serve as a separator.

The above electrolyte contains a solute and, if necessary, a solvent and various additives. In this case, the solute is, for example, a combination of a metal ion such as lithium ion and a predetermined counter ion for the metal ion. Counter ions include, for example, sulfonic acid ion, perchlorate ion, tetrafluoroborate ion, hexafluorophosphate ion, hexafluoroarsenic ion, bis (trifluoromethanesulfonyl) imide ion, bis (pentafluoroethanesulfonyl) imide ion, and bis. (Fluorosulfonyl) imide or halogen ion. Specific examples of electrolytes include LiCF ₃ SO ₃ , LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ), LiN (SO ₂ F) ₂ , And LiCl.

The solvent in the electrolyte is, for example, a non-aqueous solvent (organic solvent) such as a carbonate compound, a nitrile compound, an amide compound, and an ether compound. Specific examples of the solvent include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, acetonitrile, propyronitrile, N, N'-dimethylacetamide, N-methyl-2-pyrrolidone, dimethoxyethane, and the like. Diethoxyethane and γ-butyrolactone. As the solvent in the electrolyte, one kind of solvent may be used alone, or two or more kinds of solvents may be used in combination. A solution in which a solute is dissolved in the above solvent may be referred to as an "electrolyte solution".

The electrolytic solution may contain additives as needed. Additives are, for example, vinylene carbonate or fluoroethylene carbonate.

The negative electrode 2 includes, for example, an active material layer 60 and a current collector 70. The active material layer 60 contains a negative electrode active material. The negative electrode active material is a substance capable of inserting and removing a metal or ions. As the negative electrode active material, metallic lithium, a carbon material capable of inserting and removing lithium ions by a redox reaction, a transition metal oxide, silicon, and tin are preferably used. The active material layer 60 is in contact with the first main surface of the electrolyte layer 3.

Carbon materials capable of inserting and removing lithium ions include, for example, (i) activated carbon, (ii) coke, (iii) pitch, (iv) phenolic resin, polyimide, and a calcined product of cellulose, and (v) artificial graphite. , (Vi) natural graphite, (vii) hard carbon, or (vii) soft carbon.

A carbon material capable of inserting and removing lithium ions is preferably used as the main component of the negative electrode. In the present specification, the principal component means the component contained most in terms of weight.

The current collector 70 is a foil or mesh made of a metal material such as nickel, aluminum, stainless steel, and copper.

As the negative electrode 2, it is also possible to use a lithium pre-doped negative electrode in which lithium ions are pre-doped into a carbon material such as graphite, hard carbon, or soft carbon.

In the power storage device 5, a separator is typically arranged between the positive electrode 1 and the negative electrode 2. The separator prevents an electrical short circuit between the positive electrode 1 and the negative electrode 2. The separator is, for example, a porous sheet that is electrochemically stable and has high ion permeability, desired mechanical strength, and insulating properties. The material of the separator is preferably a porous film made of a resin such as (i) paper, (ii) non-woven fabric, (iii) polypropylene, polyethylene, and polyimide.

An example of a manufacturing method of the power storage device 5 will be described. A separator is arranged between the positive electrode 1 and the negative electrode 2 to obtain a laminated body. This laminate is placed in a package made of an aluminum laminate film and vacuum dried. Next, the electrolytic solution is injected into the vacuum-dried package, the package is sealed, and the power storage device 5 is assembled. The assembly step of the power storage device 5, such as injecting the electrolytic solution into the package, is preferably performed in an inert gas atmosphere such as ultra-high purity argon gas using a glove box.

The power storage device 5 may be manufactured in a film type, a sheet type, a square type, a cylindrical type, a button type, or the like by using a package other than the package made of the aluminum laminated film.

Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention is not limited to the examples shown below.

<Example 1>
(Preparation of active material for positive electrode)
165.3 g of ion-exchanged water, 54.69 g of hydrochloric acid (concentration: 36% by weight), and 41.9 g of aniline were added to a 500 ml separable flask, and the mixture was stirred while cooling to 10 ° C. The aniline-containing liquid according to Example 1 was prepared. 166.9 g of ion-exchanged water and 89.9 g of ammonium peroxodisulfate (APS) were mixed to obtain an APS solution according to Example 1. The APS solution according to Example 1 was added dropwise to the aniline-containing solution according to Example 1. At this time, the temperature of the reaction solution was adjusted to 20 ° C. After completion of dropping the APS solution, suction filtration was performed on the reaction solution to obtain a black-green powder. Table 1 shows the ratio [% by weight] of the remaining amount of aniline after the completion of dropping the APS solution to the total amount of aniline added. The powder was washed with ion-exchanged water, the obtained powder was placed in a flask, an aqueous sodium hydroxide solution was further added, and the mixture was stirred to perform dedoping. Next, the powder obtained by filtering the solution was filtered by suction filtration. Then, the powder was washed with ion-exchanged water until the filtrate became neutral. Then, the powder was vacuum dried at 60 ° C. for 10 hours to obtain an active material for a positive electrode according to Example 1.

The proportion of the oxidized substance in the polyaniline of the positive electrode active material according to Example 1 determined from the solid-state NMR spectrum was 40% by weight. The polyaniline contained in the positive electrode active material according to Example 1 was in a semi-oxidized state and in a de-doping state.

10 g (67 parts by weight) of the positive electrode active material according to Example 1, 2.678 g (18 parts by weight) of conductive carbon black powder (Denka Black, manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive auxiliary agent, and styrene as a binder. -Conversion and revolution vacuum mixer (manufactured by Shinky) by adding 1.765 g (12 parts by weight) of butadiene copolymer, 22.04 g (3 parts by weight) of sodium carboxymethyl cellulose diluted to 2% by weight, and 13.13 g of water. , Awatori Rentaro ARV-310), stirred at 2000 rpm for 10 minutes, and defoamed for 3 minutes. In this way, the slurry for the active material layer according to Example 1 was obtained. In the styrene-butadiene copolymer, the copolymerization ratio of styrene: butadiene [1,4 bodies]: butadiene [1,2 bodies] was 61:31: 8. The solid content concentration in the slurry for the active material layer according to Example 1 was 30% by weight.

An aluminum foil having a thickness of 20 μm was prepared as a current collector. Using a tabletop automatic coating device (manufactured by Tester Sangyo Co., Ltd.), a slurry for the active material layer according to Example 1 was applied onto the current collector at a coating speed of 10 mm / sec by a doctor blade type applicator with a micrometer. It was applied to form a coating film. Next, this coating film was left at room temperature (25 ° C.) for 45 minutes and then dried on a hot plate at a temperature of 100 ° C. to form the active material layer according to Example 1. In this way, the positive electrode according to Example 1 was produced. The thickness of the active material layer was 102.4 μm.

<Manufacturing of power storage device>
Inside a glove box kept in an environment with a dew point of -60 ° C or less and an oxygen concentration of 1 ppm or less, a separator (manufactured by Nippon Kodoshi Kogyo Co., Ltd., product name: TF40-) is attached to a graphite negative electrode sheet with a current collector tab attached. 50) was piled up. Next, an electrode having a metal lithium foil attached to a stainless steel mesh to which a current collector tab was attached was placed on the separator. At this time, the metallic lithium foil was brought into contact with the separator. This laminate was placed inside a bag-shaped package made of an aluminum laminate film. In this package, the three sides of the pair of square aluminum laminate films were sealed, and the other sides were separated from each other to form an opening. Next, a LiPF ₆ carbonate solution having a concentration of 1.2 M (mol / dm ³ ) was injected into the inside of this package as an electrolytic solution. This carbonate solution contained ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) as carbonates. Next, the opening of the package was sealed with the current collector tab protruding from the opening of the package. In this way, a laminated cell for producing a lithium pre-doped negative electrode was obtained. Next, this laminated cell is taken out from the glove box, and inside a constant temperature bath kept at 25 ° C., in a potential range of 2.0 V to 0.01 V, it corresponds to 0.2 C with respect to the capacity of the graphite negative electrode sheet. Charging and discharging were carried out for 3 cycles with the current value to be applied, and finally, a reaction of inserting lithium ions into graphite up to a capacity of 75% of the capacity of the graphite negative electrode sheet was carried out. In this way, a laminated cell containing a lithium-predoped negative electrode sheet was produced.

The laminate cell containing the lithium pre-doped negative electrode sheet was reinserted into the glove box. The sealed portion of the laminate cell was cut off, and the lithium-predoped negative electrode sheet was taken out. Next, these were stacked so that the separator was located between the positive electrode according to Example 1 and the negative electrode sheet predoped with lithium. A non-woven fabric (manufactured by Nippon Kodoshi Kogyo Co., Ltd., product name: TF40-50) was used as the separator. A current collector tab was attached to the positive electrode. Next, the laminate of the positive electrode, the separator, and the negative electrode sheet was placed inside a bag-shaped package made of an aluminum laminate film. In this package, the three sides of the pair of square aluminum laminate films were sealed, and the other sides were separated from each other to form an opening. Next, a LiPF ₆ carbonate solution having a concentration of 1.2 M (mol / dm ³ ) was injected into the package as an electrolytic solution. This carbonate solution contained ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) as carbonates. Next, the opening of the package was sealed with the current collector tab of the positive electrode and the current collector tab of the negative electrode sheet protruding from the opening of the package. In this way, the lithium ion capacitor according to Example 1 was obtained.

<Examples 2 and 3>
The active material for the positive electrode according to Examples 2 and 3 was obtained in the same manner as in Example 1 except that the amount of each component of the aniline-containing solution and the amount of each component in the APS solution were adjusted as shown in Table 1. ..

A positive electrode according to Example 2 was obtained in the same manner as in Example 1 except that the positive electrode active material according to Example 2 was used instead of the positive electrode active material according to Example 1. A positive electrode according to Example 3 was obtained in the same manner as in Example 1 except that the positive electrode active material according to Example 3 was used instead of the positive electrode active material according to Example 1. A lithium ion capacitor according to Example 2 was obtained in the same manner as in Example 1 except that the positive electrode according to Example 2 was used instead of the positive electrode according to Example 1. A lithium ion capacitor according to Example 3 was obtained in the same manner as in Example 1 except that the positive electrode according to Example 3 was used instead of the positive electrode according to Example 1.

<Comparison example>
An active material for a positive electrode according to a comparative example was obtained in the same manner as in Example 1 except that the amount of each component of the aniline-containing solution and the amount of each component in the APS solution were adjusted as shown in Table 1. A positive electrode according to Comparative Example was obtained in the same manner as in Example 1 except that the positive electrode active material according to Comparative Example was used instead of the positive electrode active material according to Example 1. A lithium ion capacitor according to Comparative Example was obtained in the same manner as in Example 1 except that the positive electrode according to Comparative Example was used instead of the positive electrode according to Example 1.

<Reference example>
The positive electrode active material prepared in the same manner as in Example 3 was placed in an aqueous methanol solution of phenylhydrazine, and the positive electrode active material was reduced for 30 minutes while stirring the dispersion. Then, the active material for the positive electrode after reduction was washed with methanol and acetone, and the powder obtained by filtration was vacuum dried at room temperature to obtain the active material for the positive electrode according to the reference example. The polyaniline contained in the positive electrode active material according to the reference example was in a reduced state and in a dedoping state.

<Particle size measurement>
Using a particle image analyzer (manufactured by Marballoon Co., Ltd., product name: Morphologi G3), the particle size distribution based on the number of positive electrode active materials according to each example was measured, and the average particle size (D50) was measured from the measurement results. ), D10, and D90 were determined. The results are shown in Table 2.

<TOF-SIMS>
A sample for TOF-SIMS was prepared from the positive electrode active material according to each example, the positive electrode active material according to the comparative example, and the positive electrode active material according to the reference example. TOF-SIMS was performed on each sample using a TOF-SIMS device (manufactured by ULVAC-PHI, product name: TRIFT V). With Bi ₃ ⁺ as primary ion in this analysis, to adjust the primary ion acceleration voltage 30 kV, to adjust the measurement area 100μm square. From the analysis results, the peak intensity of mass number m / z: 77.0 and the peak intensity of mass number m / z: 292.1 were obtained. Next, these peaks were assigned. The peak with a mass number of m / z: 77.0 was assigned to the ion C ₆ H ₅₊ derived from the aromatic hydrocarbon structure. Further, the peak of mass number m / z: 292.1 was assigned to be the cation C ₁₈ H ₁₈ N ₃ O ⁺ or C ₁₈ H ₁₆ N ₂ O ₂ ⁺ of the polyaniline trimer. Next, the polyaniline trimer cation C ₁₈ H ₁₈ N ₃ O ^{+ with} respect to the peak intensity (Ia) of the ion C ₆ H ₅ ⁺ (mass number m / z: 77.0) derived from the aromatic hydrocarbon structure. Alternatively, the ratio (It / Ia) of the peak intensities (It) of C ₁₈ H ₁₆ N ₂ O ₂ ⁺ (m / z: 292.1) was determined. FIG. 3 shows the relationship between the ratio of the amount of substance of APS to the amount of substance of aniline used for preparing the active material for the positive electrode and It / Ia. It / Ia in the positive electrode active material according to the reference example was 0.26.

<Initial discharge capacity>
The lithium-ion capacitors according to Examples and Comparative Examples are taken out from the glove box, and inside a constant temperature bath kept at 25 ° C., they are charged for 10 cycles with a current value corresponding to 1C in a voltage range of 3.8V to 2.2V. Discharging was performed, and the discharge capacity [mAh / g] in the first cycle was determined to be the initial discharge capacity Ai [mAh / g] of the lithium ion capacitors according to Examples and Comparative Examples. FIG. 4 shows the relationship between the initial discharge capacity Ai and It / Ia in the positive electrode active material.

As shown in FIG. 4, the lithium ion capacitors according to Examples 1 to 3 showed a higher initial discharge capacity Ai than the lithium ion capacitors according to Comparative Example. It was suggested that a small It / Ia in the positive electrode active material is advantageous in increasing the initial discharge capacity Ai of the lithium ion capacitor.

Claims

Containing at least one of a polyaniline and a polyaniline derivative having an oxidant and a reduced form,
The ratio of the peak intensity of mass number m / z: 292.1 to the peak intensity of mass number m / z: 77.0 determined by time-of-flight secondary ion mass spectrometry (TOF-SIMS) is 0. 080 or less,
Active material for positive electrode of power storage device.
Containing at least one of a polyaniline and a polyaniline derivative having an oxidant and a reduced form,
Of the peak intensities of mass number m / z: 77.0 determined by time-of-flight secondary ion mass spectrometry (TOF-SIMS), the mass number m / z relative to the peak intensity derived from the aromatic hydrocarbon structure. Among the peak intensities of z: 292.1, the ratio of the peak intensities derived from oligomers containing oxygen atoms is 0.080 or less.
Active material for positive electrode of power storage device.
Containing at least one of a polyaniline and a polyaniline derivative having an oxidant and a reduced form,
Of the peak intensities of mass number m / z: 77.0 determined by time-of-flight secondary ion mass spectrometry (TOF-SIMS), the mass number m / z with respect to the peak intensity derived from C 6 H 5 +. Of the peak intensities of z: 292.1, the ratio of the peak intensities derived from C 18 H 18 N 3 O + or C 18 H 16 N 2 O 2 + is 0.080 or less.
Active material for positive electrode of power storage device.
The active material for a positive electrode of a power storage device according to any one of claims 1 to 3, wherein the polyaniline and the polyaniline derivative contain 35 to 60% of an oxidant on a weight basis.
The active material for a positive electrode of a power storage device according to any one of claims 1 to 4, which has an average particle size of more than 0.5 μm and 20 μm or less.
The active material for a positive electrode of a power storage device according to any one of claims 1 to 5, wherein the ratio of the 90% particle diameter (D90) to the 10% particle diameter (D10) in the number-based particle diameter distribution is 20 or less.
A positive electrode for a power storage device provided with an active material layer containing the active material for the positive electrode for the power storage device according to any one of claims 1 to 6.
With the electrolyte layer,
A negative electrode arranged in contact with the first main surface of the electrolyte layer,
The positive electrode for a power storage device according to claim 7, which is arranged in contact with the second main surface of the electrolyte layer.
Power storage device.